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Research ArticleGASTROINTESTINAL, HEPATIC, PULMONARY, AND RENAL

Specific Type IV Phosphodiesterase Inhibitor Rolipram Mitigates Experimental Colitis in Mice

Gunther Hartmann, Christoph Bidlingmaier, Britta Siegmund, Stefan Albrich, Johannes Schulze, Katharina Tschoep, Andreas Eigler, Hans Anton Lehr and Stefan Endres
Journal of Pharmacology and Experimental Therapeutics January 2000, 292 (1) 22-30;

Abstract

The specific type IV phosphodiesterase inhibitor rolipram is a potent suppressor of tumor necrosis factor-α (TNF) synthesis. We examined the efficacy of rolipram for the prevention and treatment of experimental colitis. To induce colitis, BALB/c mice received 5% dextran sulfate sodium in their drinking water continuously for up to 11 days. Colitis was quantified by a clinical activity score assessing weight loss, stool consistency, and rectal bleeding (range from 0 to 4); by colon length; by a semiquantitative histologic score (range from 0 to 6); and by detecting TNF concentration in colonic tissue by enzyme-linked immunosorbent assay. In a first protocol, rolipram (10 mg/kg b.wt./day i.p.) was started on the same day as dextran sulfate sodium. Rolipram reduced the clinical activity of colitis (score 1.1 ± 0.3) compared with mice that did not receive rolipram (2.4 ± 0.4; P = .041). Rolipram also partially reversed the reduction of colon length (without rolipram, 12.4 ± 0.3 cm; with rolipram, 15.4 ± 0.7 cm;P = .004) and improved the histologic score (1.5 ± 0.6 in rolipram-treated mice versus 4.6 ± 0.5;P = .020). Rolipram suppressed colonic tissue TNF concentrations. The beneficial effect of rolipram was confirmed in a second protocol in which dextran sulfate sodium exposure was discontinued on day 7 and rolipram was administered from day 8 through day 15. These three series of experiments on a total of 153 mice documented the efficacy of rolipram in both the prevention and treatment of experimental colitis.

In several diseases, the proinflammatory cytokine tumor necrosis factor-α (TNF) forms a necessary element in the chain of pathophysiologic events leading to inflammation. Successful treatment with anti-TNF-antibodies in patients with Crohn's disease (van Dullemen et al., 1995; Stack et al., 1997; Targan et al., 1997; Present et al., 1999), with rheumatoid arthritis (Elliott et al., 1994), and with Jarisch-Herxheimer reaction (Fekade et al., 1996) illustrate anti-inflammatory strategies based on the specific blockade of TNF (Eigler et al. 1997). Among the agents known to inhibit TNF production rather than block its function, attention has focused on cAMP-elevating phosphodiesterase (PDE) inhibitors. The predominant PDE isoenzyme family in monocytes, a main source of TNF production, is the PDEs of type IV. Compared with the nonspecific PDE inhibitor pentoxifylline (Strieter et al., 1988), the specific type IV PDE inhibitor rolipram is a 500-fold more potent inhibitor of TNF synthesis in human mononuclear cells (Semmler et al., 1993).

Rolipram has initially been developed and studied in clinical trials as an antidepressant (Wachtel 1983). Recently, the potential therapeutic use of rolipram in TNF-dependent disease has been demonstrated in several animal models. Rolipram mitigated experimental autoimmune encephalomyelitis in rats (Sommer et al., 1995) and in nonhuman primates (Genain et al., 1995) and decreased clinical activity of experimental arthritis in rats (Nyman et al., 1997; Ross et al., 1997). In mice, rolipram decreased lipopolysaccharide-induced TNF plasma levels (Fischer et al., 1993) and protected from T-cell-mediated liver failure (Gantner et al., 1997).

In humans, the majority of inflammatory bowel disease occurs in two related, albeit clinically and histologically distinct disorders, ulcerative colitis and Crohn's disease. Both diseases are characterized by chronically relapsing inflammation of the bowel of unknown cause. Crohn's disease is characterized by a granulomatous, transmural inflammation of the bowel wall, predominantly in the distal ileum. In contrast, ulcerative colitis is defined by crypt abscesses and ulcerations limited to mucosa and submucosa, associated with a prominent inflammatory infiltrate. The mainstay of therapy for inflammatory bowel disease is aminosalicylates and topical and systemic glucocorticoids. Both provide therapeutic benefit and improve quality of life in many patients, but others suffer from recurrent disease despite systemic glucocorticoid therapy. More specific and more effective therapeutic agents with fewer side effects are needed for the permanent control of inflammatory bowel disease.

Several experimental models of inflammatory bowel disease have been described (Kim and Berstad, 1992; Dieleman et al., 1994; Elson et al., 1995). The dextran sulfate sodium (DSS) model of colitis has been recommended for preclinical testing of new pharmacologic compounds for therapy of chronic inflammatory bowel disease (Cooper et al., 1993;Elson et al., 1995). DSS-induced colitis has a number advantages, including its simplicity, the ability to induce inflammatory lesions, and the reproducibility in respect to both time course and severity among individual mice of a given inbred strain. As in Crohn's disease, macrophage activation and TNF production play a key role in DSS-induced colitis. Elevated levels of TNF have been found in the inflamed colons of DSS-treated mice (Dieleman et al., 1994).

Several studies pointed to a necessary mediator function of TNF, particularly in Crohn's disease (Targan et al., 1997; van Deventer, 1997; Present et al., 1999). TNF elevation was more pronounced in Crohn's disease than in ulcerative colitis both in plasma (Murch et al., 1991) and mucosal samples (Murch et al., 1993; Breese et al., 1994). In the present article, we extend our previous in vitro studies on TNF inhibition by rolipram (Semmler et al., 1993; Siegmund et al., 1997; Eigler et al., 1998) to demonstrate that rolipram attenuates the development of experimental colitis and improves recovery of animals with established colitis.

Materials and Methods

Animals and Induction of Colitis.

Female BALB/c mice (∼6 weeks of age, mean body weight 20 g) were purchased from Harlan Winkelmann GmbH (Borchen, Germany). Mice were kept under standard laboratory conditions at the animal facility at the Medizinische Klinik, Klinikum Innenstadt. Drinking water and food were provided ad libitum. Mice were sacrificed by cervical dislocation under isoflurane anesthesia (Forene; Abbott GmbH, Wiesbaden, Germany). All experiments were approved by the regional animal study committee and are in agreement with the guidelines for the proper use of animals in biomedical research. Animal handling and scoring of colitis were performed in a consequently blinded experimental design.

DSS (molecular mass 40,000 Da) was obtained from ICN Biomedicals GmbH (Eschwege, Germany) and dissolved in distilled water. Colitis was induced by providing drinking water containing 5% DSS (w/v) for 7 to 11 days as indicated. Control mice received distilled water.

Clinical Activity Score.

Colitis was quantified with a clinical score assessing weight loss, stool consistency, and bleeding (measured by guaiac reaction, hemoccult) as described previously (Cooper et al., 1993). No weight loss was counted as 0 points, weight loss of 1 to 5% as 1 point, 5 to 10% as 2 points, 10 to 20% as 3 points, and >20% as 4 points. For stool consistency, 0 points were given for well formed pellets, 2 points for pasty and semiformed stools that did not stick to the anus, and 4 points for liquid stools that did stick to the anus. Bleeding was scored 0 points for no blood in hemoccult, 2 points for positive hemoccult, and 4 points for gross bleeding. These scores were added and divided by 3, forming a total clinical score that ranged from 0.0 (healthy) to 4.0 (maximal activity of colitis).

Colon Length, Histologic Scoring, and Mean Cross-Sectional Area.

Postmortem, the entire colon was removed from the cecum to the anus and placed without tension on cellulose. Colon length was measured as an indirect marker of inflammation.

Rings of the ascending, transverse, and descending part of the colon were fixed in 10% formalin and embedded in paraffin for histologic analysis. Sections were stained with hematoxylin/eosin. Histologic scoring was performed by a pathologist (0 to 3 points for infiltration of inflammatory cells plus 0 to 3 points for the degree of tissue damage). For infiltration of inflammatory cells, rare inflammatory cells in the lamina propria were counted as 0; increased numbers of inflammatory cells in the lamina propria as 1; confluence of inflammatory cells, extending into the submucosa as 2; and a score of 3 was given for transmural extension of the infiltrate. For tissue damage, no mucosal damage was counted as 0, discrete lymphoepithelial lesions were counted as 1, surface mucosal erosion was counted as 2, and a score of 3 was given for extensive mucosal damage and extension through deeper structures of the bowel wall. The combined histologic score ranged from 0 (no changes) to 6 (extensive cell infiltration and tissue damage).

For the image analysis of cross-sectional areas, glass slides were imported into Photoshop (Adobe Systems Incorporated, San Jose, CA) on an Apple computer (G3; Apple Computer, Inc., Cupertino, CA) with a kodachrome slide scanner (Nikon LS 1000). Kodachrome frames were opened on one side to allow introduction of the glass slide. Three entire cross sections of each colon part were selected with the “magic wand tool” in the Photoshop toolbox (Lehr et al., 1997). The cross-sectional area of the three bowel sections was quantified with the “histogram tool” (in number of pixels) and was transformed into square millimeters with comparative measurements of a micrometer slide.

Treatment with Rolipram.

Rolipram (0.5 mg), kindly supplied by Schering AG (Berlin, Germany), was diluted in 1 ml of distilled water by heating the solution for 30 s at 60°C and then cooling it at room temperature for 2 min. This was repeated until rolipram was totally dissolved. The solution was then frozen into aliquots of 2 ml at −80°C. This proved to be the most reliable protocol to dissolve a relatively high concentration of rolipram for a low total injection volume of 200 μl. Rolipram (5 mg/kg b.wt. b.i.d.) was injected two times per day i.p. with a total injection volume of 200 μl each. Control mice were injected with 200 μl of 0.9% NaCl. To test the therapeutic efficacy of rolipram, two protocols were used: 1) in the concurrent treatment protocol (prevention of colitis), DSS was administered for up to 11 days with rolipram therapy starting the same day as DSS; and 2) in the delayed treatment protocol (treatment of established colitis), colitis was first induced by DSS administration from day 1 to day 7, rolipram therapy was then started at day 8, and was continued up to day 15.

Colon Cytokine Extraction.

Strips (∼4 cm) of colon from DSS-exposed mice with or without rolipram treatment were weighed, vigorously vortexed for 1 min in 100 μl of 0.01 M PBS (Boehringer Mannheim, Ingelheim, Germany), and centrifuged at 10,000g at 4°C for 15 min. TNF was quantified in the eluate with a commercial enzyme-linked immunosorbent assay (ELISA) kit (Endogen, Woburn, MA) according to the manufacturer's instructions. The lower limit of detection of the assay is 50 pg/ml.

Statistical Analysis.

All data are expressed as means ± S.E. Statistical significance of differences between treatment and control groups was determined by the unpaired two-tailed Student'st test. Where applicable, P values were corrected by the Bonferroni method for three independent comparisons (clinical score, colon length, and histologic degree of inflammation). Differences were considered statistically significant forP < .050. Statistical analyses were performed with StatView 512 software (Abacus Concepts, Berkeley, CA).

Results

Characteristics of Colitis.

Treatment of BALB/c mice with 5% DSS in drinking water for 7 or 11 days resulted in clinical, gross, and histologic signs of colitis that resolved gradually when DSS administration was discontinued (Figs. 1-5). Mice produced loose stool or diarrhea, occult or gross rectal bleeding, and lost weight. After 11 days, the colon length of DSS-treated mice was 12.4 ± 0.3 cm (n = 5) compared with 17.4 ± 0.3 cm (n = 4; P < .001) in healthy controls. This has been described as a morphologic parameter of colon inflammation (Okayasu et al., 1990).

Histologic examination of colon sections from control mice showed no signs of inflammation (Figs. 1A and 2A). Histology of colon sections of DSS-treated mice revealed multiple erosive lesions and inflammatory cell infiltration composed mainly of macrophages with fewer lymphocytes and occasional eosinophils and neutrophils (Fig. 1, B and C). In some colon sections, particularly of advanced lesions, regeneration of epithelium were noted in the mucosa. The histologic score (assessing the extent of infiltration of inflammatory cells and the degree of tissue damage, range from 0 to 6) was determined as the mean score of sections of the ascending colon, transverse colon, and descending colon, each section evaluated separately. The most severe lesions were observed in the transverse and the descending colon. After 11 days of continuous DSS administration, a histologic severity score of 4.6 ± 0.5 (n = 14) was reached (Fig.6).

Figure 1
Figure 1

Histologic characteristics of DSS-induced colitis. A, normal colonic mucosa with regularly formed colonic folds covered by intact mucosa. Only occasional leukocytes are present in the lamina propria of the mucosa. B, a focal accumulation of lymphocytes, histiocytes, and fewer neutrophils compared with (A). Although the surface layer of the mucosa is still intact, there is marked crypt destruction by the inflammatory infiltrate. The inflammatory process is limited to the mucosa and submucosa. C, severe colonic inflammation, characterized by a dense inflammatory cell infiltrate in all colonic wall structures and widespread mucosal sloughing. Note the circumscription of the destructive process, immediately adjacent to normal appearing mucosa. Magnification of the images is 130-fold for (A) and (C), and 325-fold for (B).

Figure 6
Figure 6

Reduction of histologic signs of colon inflammation by rolipram. Mice were treated with 5% DSS in drinking water for 11 days and were given rolipram (10 mg/kg b.wt./day i.p.;n = 5) or 0.9% NaCl (n = 5). At day 11, mice were sacrificed and colon sections were stained and the histologic score (degree of inflammation: 0, no changes, to 6, extensive cell infiltration and tissue damage) was determined in a blinded fashion by a pathologist. In the rolipram-treated group, the histologic score was lower compared with mice given 0.9% NaCl (P = .020; unpaired t test). Control mice without administrating DSS developed no colitis. Scores are depicted as means ± S.E.

Mice studied at different time points during DSS treatment (days 0 to 7) and after DSS discontinuation (days 8 to 15) developed increasing histologic signs of colitis over time (Fig.3). Although mice improved clinically after discontinuation of DSS administration at day 7 (clinical score at day 8 was 2.1 (n = 2) compared with 0.8 at day 15 (n = 7; P = .008; data not shown), on the histologic level no decrease of cellular infiltration and tissue damage could be found until day 15 (Fig. 3). The apparent lack of improvement on the histologic level may be due to cellular infiltration involved in tissue regeneration during the first days of recovery.

Figure 3
Figure 3

Time course of DSS-induced colitis at the histologic level. Mice were treated with 5% DSS in drinking water for 8 days. At the indicated time points, mice were sacrificed and sections of the ascending, transverse, and descending colon were examined and scored for cellular infiltration and tissue damage. The magnitude of the histologic score reflects the degree of colitis (0, no changes, to 6, severe tissue damage and cell infiltration). Data represent the mean ± S.E. histologic score (average of the scores of a ascending, transverse, and descending section) of two mice (days 1 to 13) or of seven mice (day 15). Mice without DSS treatment had no signs of colitis (histologic score 0).

Prevention of Colitis with Rolipram.

In the concurrent treatment protocol, we tested the effect of rolipram on the prevention of DSS-induced colitis. Mice were administered 5% DSS in their drinking water and were injected i.p. with rolipram or with 0.9% NaCl for a total of 11 days. This protocol was studied in two independent experimental series. The first series comprised 14 mice. Mice fed with DSS developed clinical signs of colitis expressed by an activity score >0.5 starting from day 4 (Fig. 7). Intraperotineal injection of rolipram in a dose of 10 mg/kg b.wt. daily did not retard onset of colitis during the first 6 days of DSS administration. After that, it significantly reduced the progression of colitis as expressed by a lower clinical activity score (1.1 ± 0.3; n = 5 in rolipram-treated mice compared with 2.4 ± 0.4; n = 5 in NaCl controls;P = .041; day 11) (Fig. 7). Each of the three clinical parameters assessed in the clinical score was beneficially influenced by rolipram (body weight, 19.5 g ± 1.5 g in rolipram-treated mice versus 18.0 ± 0.9 g in NaCl-treated controls; stool consistency score, 0.0 ± 0.0 versus 1.2 ± 0.5; rectal bleeding score, 0.8 ± 0.8 versus 2.4 ± 1.0). Control mice (without DSS) treated with 0.9% NaCl or rolipram i.p. developed no signs of colitis (Fig. 7). At day 11, all mice were sacrificed. Of the DSS-treated mice, those with rolipram therapy had a longer colon (15.4 ± 0.7 cm) than NaCl controls (12.4 ± 0.3 cm;P = .004). Thus, rolipram had partially reversed the colon shortening induced by DSS compared with mice with normal drinking water (17.4 ± 0.3 cm). This argued for a lower extent of inflammation, which was confirmed by histologic examination in the rolipram group (Fig. 2C) compared with the NaCl group (Fig. 2B). In DSS-treated mice, rolipram decreased the histologic score compared with NaCl-treated control mice (1.5 ± 0.6 versus 4.6 ± 0.5;P = .020; Fig. 6).

Figure 7
Figure 7

Mitigation of DSS-induced colitis by rolipram. Mice were treated with 5% DSS in drinking water for 11 days. The degree of colitis was quantified by the clinical score assessing weight loss, stool consistency, and bleeding (range from 0, healthy, to 4, maximal activity; see Materials and Methods). Rolipram treatment (10 mg/kg b. wt. b.i.d. i.p.; ●; n = 5) beginning the same day as DSS administration reduced the development of colitis compared with mice 0.9% NaCl treatment (gray circles;n = 5; one mouse died on day 8;P = .041; unpaired t test). Control mice (n = 2) without DSS treatment but injection of rolipram (○; n = 2) or of 0.9% NaCl (data not shown; n = 2) showed no clinical signs of colitis. Scores are depicted as means ± S.E.

Figure 2
Figure 2

Influence of rolipram on the histologic manifestation of DSS-induced colitis. Shown are representative cross sections of the transversal colon in control mice without DSS (A) and in DSS-treated mice treated with i.p. injections of 0.9% NaCl (B) or rolipram [10 mg/kg b.wt., (C)] at day 11. Note the regional mucosal destruction in DSS-treated mice (B), which is effectively reversed by rolipram (C). In rolipram-treated mice, there is still some degree of edema, but no cross-mucosal damage. Also note the difference in colon cross-sectional area, which is partially reversed by rolipram. Magnification of the images is 52-fold.

The second experimental series studied with concurrent rolipram treatment comprised 36 animals. The beneficial effect of rolipram was confirmed by clinical [1.8 ± 0.6 in rolipram-treated mice (n = 14) versus 3.7 ± 0.3 in control mice (n = 14; P = .021; day 11; data not shown] and histologic scoring (1.9 ± 0.6 versus 4.3 ± 0.4;P = .014). The colon lengths in this series were 12.8 ± 0.4 versus 10.0 ± 0.3 cm; P < .001). In this experimental series, a further indicator of inflammation, the mean cross-sectional area of the colon wall was assessed with computer-based image analysis in nine colonic sections from each colon (Lehr et al., 1997). The mean area was higher in DSS-exposed mice (2.1 ± 0.2 mm2) compared with mice with normal drinking water (1.3 ± 0.2 mm2; P = .011). In the rolipram-treated DSS-exposed mice, this increased colon wall thickness was completely reversed (1.2 ± 0.1 mm2;P < .001; Fig. 2).

For measurement of colonic TNF concentration, the colon from 15 mice of a third experimental series treated as described above was obtained at day 11 (Fig. 8). Eluate from colonic tissue of DSS-exposed mice without rolipram treatment had the highest TNF concentration of 201 ± 39 pg/mg (wet weight) colonic tissue (n = 4) compared with 115 ± 25 pg/mg colonic tissue (n = 7) in rolipram-treated mice. In the noninflamed colon of control mice receiving rolipram alone, TNF was 97 pg/mg colonic tissue (n = 2) and in mice receiving 0.9% NaCl TNF was 97 pg/mg colonic tissue (n = 2).

Figure 8
Figure 8

Suppression of colonic TNF concentration by rolipram. Mice were treated with 5% DSS in drinking water for 11 days. At day 11, the colon was removed, weighed, vortexed for 1 min in 100 μl of PBS, and centrifuged at 10,000g for 15 min as described in Materials and Methods. TNF was quantified in the eluate by ELISA. Maximal TNF concentration could be measured in colonic tissue of DSS-treated mice (201 ± 39 pg/mg colonic tissue;n = 4) compared with rolipram-treated mice (115 ± 25 pg/mg colonic tissue; n = 7). In control mice colon, we observed the lowest concentrations, respectively (97 pg/mg colonic tissue; n = 2 in each control group).

Treatment of Established Colitis with Rolipram.

To further evaluate the therapeutic value of rolipram, we studied the effect of rolipram on preexisting colitis (delayed treatment protocol). Colitis was induced by the administration of DSS for 7 days. On day 8, after discontinuing DSS administration, rolipram therapy was started. A total of 88 mice was included in two independent series of studies. The first series was designed to assess clinical score and postmortem morphologic parameters at defined time points during resolution of colitis. In the second series, clinical parameters were followed until complete resolution of clinical colitis in treatment and control groups.

The first study included 54 mice, with 7 or 3 mice in each of the four treatment groups available for morphologic examination at the end of the study. The other mice were sacrificed at the indicated time points during the study.

On the first day of treatment (day 8), the groups designated to receive rolipram or 0.9% NaCl, respectively, had developed similar clinical activity of colitis (2.8 ± 0.2 in the rolipram group; 2.5 ± 0.2 in the NaCl group; N.S.; Fig. 4). After discontinuation of DSS administration, the clinical score in the control group declined gradually until day 15 (1.4 ± 0.3;n = 7). The rolipram-treated mice recovered faster as demonstrated by an earlier decrease and a lower clinical score at day 15 (0.3 ± 0.1; n = 7; P = 0.003).

Figure 4
Figure 4

Accelerated remission of established colitis by rolipram. Mice were treated with DSS in drinking water for 7 days. Rolipram treatment (10 mg/kg b.wt. daily) was started at day 8 after discontinuation of DSS. The degree of colitis was quantified by the clinical score (assessing weight loss, stool consistency, and bleeding; see Materials and Methods). Mice with rolipram treatment (●) recovered earlier than mice without rolipram treatment (gray circles; P = .022 at day 15; unpairedt test). Control mice without DSS exposure injected with either rolipram or 0.9% NaCl developed no signs of colitis. Scores are depicted as means ± S.E. DSS groups, n = 14; control groups, n = 6).

Changes of the colon length reflected the clinical course (Fig.5). At the indicated time points, two mice in each group were sacrificed. Beginning at day 10, the colon length in the rolipram group showed an earlier increase (indication of decreased inflammation) compared with the control group. From day 0 to 13, the variation is due to the low number of mice at each time point (two mice in each group). At day 15, all remaining mice were sacrificed (seven mice each in groups with DSS, three mice each in both groups without DSS). The colon length in the rolipram group was significantly longer than in DSS-fed mice given 0.9% NaCl (14.4 ± 0.4 versus 11.9 ± 0.3 cm; P < .001). In the control groups without DSS exposure, the colon length in mice treated with rolipram (17.8 ± 0.2 cm) was unchanged compared with mice injected with 0.9% NaCl (17.5 ± 0.5 cm; data not shown).

Figure 5
Figure 5

Reduction of colon length in DSS-induced colitis with and without rolipram treatment. Mice were treated with DSS in drinking water for 7 days. Rolipram treatment (10 mg/kg b.wt. daily) was started at day 8 after discontinuation of DSS. At the indicated time points, two mice of both DSS groups and one mouse of both control groups (with or without rolipram, respectively) were sacrificed and the length of the colon was measured. At day 15, the remaining 7 mice of both DSS groups and the remaining 3 mice of both control groups were examined. DSS-induced colitis lead to shortening of the colon as a marker of inflammation. Rolipram treatment partially reversed this shortening (P < .001 at day 15; unpaired ttest). Values are depicted as the mean length of the colon in each group. Error bars indicate S.E.M.

On the histologic level, no differences between rolipram-treated mice and the control group were found (histologic score 4.1 ± 1.1 in the rolipram group versus 4.3 ± 0.7 in the control group). For the mean cross-sectional area of the colon, there was only a trend to lower values in the rolipram group (2.8 ± 0.3 mm2) compared with the control group (3.4 ± 0.3 mm2; P = .195). Both were markedly higher than in mice without DSS treatment (1.8 ± 0.1 mm2; P = .010), reflecting inflammation in the DSS-treated mice.

In the second series with the delayed treatment protocol, clinical parameters were followed until complete resolution of clinical signs of colitis. This study included 34 mice, 14 in both DSS-exposed groups and 3 mice in both groups without DSS. After 7 days, the groups designated to receive rolipram or 0.9% NaCl, respectively, had developed the same extent of colitis as in the first series (clinical activity score of the rolipram group, 2.1 ± 0.3, and for the NaCl group, 2.3 ± 0.3; data not shown). Confirming the results of the first series, rolipram-treated mice recovered earlier than control mice. The difference in the clinical activity score between both groups was maximal at day 11 (rolipram group, 1.3 ± 0.3; NaCl group, 2.4 ± 2.1; P = .005) and declined to nonsignificance until day 15 (rolipram group, 0.5 ± 0.2; NaCl group, 0.9 ± 0.3; P = .301). At day 15, the colon length of the rolipram-treated mice was significantly longer (15.2 ± 0.4 cm) than the colon length of untreated mice (13.0 ± 0.3 cm, P < .001; controls without DSS, 17.5 ± 0.3 cm). Differences in the individual scores of body weight, rectal bleeding, and stool consistency between both groups are summarized in Fig. 9B. Rolipram significantly decreased rectal bleeding and the appearance of loose stool. There was a nonsignificant trend to higher body weight in the rolipram group (P = .18). The results are in accordance with the findings of the first series regarding individual clinical parameters (Fig. 9A).

Figure 9
Figure 9

Beneficial effect of rolipram on weight loss, stool consistency, and bleeding. Clinical parameters in two independent series of experiments with 54 mice (A) and 34 mice (B) examining the effect of rolipram in the model of established colitis. Mice were treated with 5% DSS for 7 days before starting therapy with rolipram (10 mg/kg b.wt./day) on day 8. Clinical signs of colitis are summarized for the final day of the first series [day 15 (A), time course of composite clinical score of this study shown in Fig. 8] and for the day of maximal difference between treatment groups in the second series [day 11 (B); in this series, no significant differences at day 15]. Loss of body weight, stool consistency, and bleeding were semiquantified by scores (see Materials and Methods). In the first series, one mouse in the DSS group without rolipram died at day 8 for unknown reasons. Data are shown as means ± S.E. Statistical evaluation was performed using the unpairedt test and P values were Bonferroni corrected.

Discussion

Summary of Results.

Type IV PDE inhibitors have been identified as a potential therapeutic principle for asthma (Turner et al., 1994) and multiple sclerosis (Genain et al., 1995; Sommer et al., 1995) because they are potent inhibitors of diverse leukocyte functions. In this study, we present evidence that the specific type IV PDE inhibitor rolipram abrogates experimental colitis in mice. A total of 138 female BALB/c mice was included in our studies. Administration of DSS in drinking water induced clinical and histologic signs of colitis. In agreement with published studies, we found reproducible and interindividually similar degrees of colitis in DSS-treated mice.

Rolipram therapy was effective for both prevention of colitis (Figs. 6and 7) and therapy of established colitis (Figs. 4 and 5). In the prevention model, rolipram administered in parallel with DSS did not inhibit or delay onset (∼day 4) but decreased aggravation of colitis at later time points (between days 5 and 11; Fig. 7). In accordance with the clinical and histologic results, rolipram suppressed TNF synthesis in the colon of DSS-fed mice. The model of delayed treatment was designed to test the efficacy of rolipram as therapy of preexisting colitis. Rolipram improved recovery of mice from established colitis after discontinuation of DSS treatment. Signs of colitis decreased earlier in rolipram-treated mice than in mice without therapy (Fig. 4).

DSS Model.

Several experimental models of inflammatory bowel disease have been described (for review, see Elson et al., 1995). The DSS model of colitis has been recommended for preclinical testing of new pharmacologic compounds for therapy of chronic inflammatory bowel disease (Cooper et al., 1993; Elson et al., 1995). DSS-induced colitis has a number of advantages, including its simplicity, the ability to induce both acute and chronic inflammatory lesions, the high degree of uniformity of the lesions, and the reproducibility in respect to both time course and severity among individual mice of a given inbred strain. This uniformity and reproducibility is not achieved in several other experimental models of inflammatory bowel disease (Elson et al., 1995).

Side Effects of Rolipram.

In general, therapy with rolipram at a dose of 10 mg/kg b.wt./day was well tolerated by the mice. Immediately after injection of rolipram, mice showed reduced motility, but they returned to normal motoric behavior after a few minutes. These changes could not be attributed to the i.p. injection of fluid because changes in the behavior did not occur in control mice injected with 0.9% NaCl. In agreement with previous in vivo studies (Turner et al., 1994; Genain et al., 1995; Gantner et al., 1997; Nyman et al., 1997;Ross et al., 1997) with the same (10 mg/kg b.wt./day) or lower doses of rolipram, we observed no major side effects. For higher doses, side effects in nonhuman primates include vomiting, salivation, and mouth scratching, none of which was observed in the present study (Genain et al., 1995).

Fasting has recently been described to have some protective effect during development of DSS-induced colitis (Savendahl et al., 1997). In our study, in control mice without DSS, injection of rolipram did not influence body weight. In contrast, rolipram-treated DSS mice had higher body weight compared with mice without rolipram. Therefore, it is unlikely that rolipram exerts anti-inflammatory activity by decreasing food intake as a possible mechanism of action.

Cellular Effects of Rolipram.

The anti-inflammatory activity of rolipram depends on its direct action on leukocytes. We and others have shown that rolipram strongly inhibits TNF production in monocytes and macrophages (Schade and Schudt, 1993; Semmler et al., 1993;Prabhakar et al., 1994; Seldon et al., 1995; Barnette et al., 1996). We have demonstrated that the synthesis of the anti-inflammatory cytokine interleukin (IL)-10 is enhanced by rolipram (Eigler et al., 1998) and that exogenous IL-10 acts synergistically with rolipram in decreasing TNF production (Siegmund et al., 1997). Furthermore, rolipram inhibits IL-2-mediated proliferation of primary T cells but not IL-2 production itself (Essayan et al. 1994) and inhibits γ-interferon synthesis of T cells (Essayan et al., 1994; Sommer et al., 1995). These anti-inflammatory characteristics of rolipram act in concert to effectively inhibit the inflammatory response in vivo (Turner et al., 1994; Genain et al., 1995; Sommer et al., 1995; Gantner et al., 1997).

Determination of Endpoints in Colitis Model.

We quantified clinical activity with a scoring system that has been described to be a reliable marker of pathologic changes (Cooper et al., 1993). The clinical score was determined in a blinded fashion to exclude bias by the examining person. Shortening of the colon as a morphologic parameter for the degree of inflammation correlates well with pathologic changes (Okayasu et al., 1990). In our studies, the length of the colon proved to be an easily determined and consistent marker of colitis. Histologic examination was performed blinded and included the degree of infiltration by inflammatory cells in the mucosa and the degree of tissue damage. In our study, a histologic score calculated from these two markers was found to parallel clinical changes during induction of colitis.

TNF-α and Colitis.

There is evidence that TNF plays a central role in inflammatory bowel disease (for review, see van Deventer, 1997; Sandborn and Hanauer, 1999). The therapeutic benefit of TNF inhibition in Crohn's disease has been shown in clinical studies with chimeric anti-TNF antibodies (van Dullemen et al., 1995; Stack et al., 1997; Targan et al., 1997; Present et al., 1999). Although proving the principle of targeting TNF in inflammatory bowel disease, efficacy of anti-TNF antibody therapy may decrease with time because of the formation of anti-idiotype antibodies. Furthermore, the development of antinuclear antibodies has been observed with prolonged anti-TNF antibody therapy in patients with rheumatoid arthritis (Elliott et al., 1994).

Anti-TNF antibodies also have been tested in DSS-induced colitis. Neutralization of TNF but not of IL-1 reduced inflammation in the chronic model of DSS-induced colitis in mice (Kojouharoff et al., 1997). In another study, treatment with anti-TNF antibody failed to prevent onset of colitis in the acute model of DSS-induced colitis (Olson et al., 1995). These primarily contradictory results may be due to the protective effect of TNF against bacterial invasion in intact mucosa.

PDE Inhibition and TNF-α.

Intracellular concentrations of cAMP increase either as a consequence of receptor-triggered adenylyl cyclase activation or by decreased activity of PDEs. Cyclic nucleotide PDEs have been classified into nine distinct families with several subgroups (Beavo, 1995). Because the predominant PDE family in monocytes, the main source of TNF, is PDE IV (Seldon et al., 1995;Souness et al., 1997), specific type IV PDE inhibitors such as rolipram have proven high potency in suppressing TNF synthesis. Activators of adenylyl cyclase, such as prostaglandin E2 and prostacyclin analogs, synergize with PDE inhibitors both in increasing cAMP levels and in suppressing TNF synthesis (Sinha et al., 1995). One may speculate that PDE inhibitors given systemically may exert their maximal TNF-suppressing effect in tissue containing prostaglandin E2 such as the inflamed mucosa of inflammatory bowel disease.

Rolipram In Vivo.

In humans, the specific type IV PDE inhibitor rolipram has been extensively studied as an antidepressant. However, it has not been marketed because of the lack of an additional therapeutic benefit compared with established drugs. Several studies have revealed a beneficial effect of rolipram in inflammatory disease in vivo. In the rat model of experimental autoimmune encephalomyelitis, where TNF synthesis forms a central pathogenetic link, rolipram decreased disease activity (Sommer et al., 1995). In nonhuman primates, rolipram protected against autoimmune demyelinating disease even when administered after sensitization to central nervous system antigens (Genain et al., 1995). In rats, rolipram decreased clinical activity of experimental arthritis (Nyman et al., 1997; Ross et al., 1997). Additionally, LPS-induced TNF synthesis in mice could be suppressed by rolipram (Griswold et al., 1998). Rolipram reduced airway hyper-responsiveness in response to acute and chronic antigen exposure in monkeys (Turner et al., 1994). In this study, antigen-induced increases of TNF but not of IL-1 concentration were inhibited in bronchoalveolar lavage. This is in agreement with our in vitro findings of selective inhibition of TNF but not IL-1 synthesis by rolipram (Semmler et al., 1993).

Phosphodiesterase Inhibition and Inflammatory Bowel Disease.

To date, specific type IV PDE inhibition has not been tested as a therapeutic strategy for inflammatory bowel disease. However, there are reports on the use of the nonspecific PDE inhibitor pentoxifylline for this indication. In the trinitrobenzene sulfonic acid model of colitis in rats, pentoxifylline treatment reduced the pathologic changes (Peterson and Davey, 1997). Yet, in a small clinical study with 16 patients with corticosteroid-dependent Crohn's disease, the administration of 400 mg of pentoxifylline administered four times a day did not improve clinical or histologic activity of disease (Bauditz et al., 1997). In vitro studies by the same research group revealed that a high concentration of pentoxifylline (IC50= 25 μg/ml) was necessary to inhibit TNF synthesis in organ cultures of inflamed mucosa (Reimund et al., 1997). Nonspecific PDE inhibitors are less selective than rolipram and require a 500-fold higher concentration for inhibition of TNF synthesis. In human mononuclear cells, the concentration that inhibits TNF synthesis by 50% (IC50) is 70 μM for pentoxifylline and 130 nM for rolipram (Semmler et al., 1993). This limits the therapeutic use of compounds such as pentoxifylline as anti-inflammatory agents. In the present study, we could demonstrate the suppression of colonic TNF concentrations by rolipram close to TNF concentrations observed in control mice. This emphasizes the mediatory function of TNF in this model.

The present study has some limitations. First, although DSS-induced colitis serves as a model for human disease, the cause of colitis in humans is not known and therefore other pathogenetic mechanisms may be at active. Second, due to the species studied and the particular situation of the animal model, we have examined a short disease course of 11 to 15 days, whereas inflammatory bowel disease in humans is chronic, extending over months and years. And third, i.p. administration is not a practicable route clinically and oral i.v. or topical formulations will have to be tested before the use in humans for this indication.

Acknowledgments

We thank Dr. Helmut Wachtel, Schering AG, Berlin, for providing rolipram; Prof. Elmar Richter for reviewing the animal study proposal; Prof. Klaus Loeschke, Dr. Ulrich Hacker, Dr. Jochen Moeller, Dr. Christoph Brunner, Katrin Wolf, Anne Krug, Simon Erhardt, Bernd Jahrsdoerfer, and Uta Emmerich for helpful discussion; and Angela Hackl and Oliver Blank for excellent technical assistance.

Footnotes

  • Send reprint requests to: Stefan Endres, M.D., Clinical Pharmacology, Medizinische Klinik, University of Munich, Ziemssenstraße 1, 80336 München, Germany. E-mail:EndresS{at}lrz.uni-muenchen.de

  • ↵1 This work was supported by the Deutsche Forschungsgemeinschaft (En 169/3), the German-Israeli Foundation for Scientific Research and Development (021-203.05/96), and the Wilhelm Sander-Stiftung (93.042.3). These data are part of the dissertation of Christoph Bidlingmaier, cand. med. and Stefan Albrich, cand. med. (Medizinische Klinik, Klinikum Innenstadt, Ludwig-Maximilians-University of Munich, in preparation). Parts of these studies have been presented in abstract form during the American Gastroenterology Association meeting, New Orleans, May 17–20, 1998.

  • ↵2 G.H. and C.B. contributed equivalently to the work.

  • ↵3 Current address: Department of Pathology, University of Mainz, Germany.

  • Abbreviations:
    TNF
    tumor necrosis factor-α
    PDE
    phosphodiesterase
    DSS
    dextran sulfate sodium
    ELISA
    enzyme-linked immunosorbent assay
    IL
    interleukin
    • Received December 7, 1998.
    • Accepted September 13, 1999.

References

  1. ↵
    1. Barnette MS,
    2. Bartus JO,
    3. Burman M,
    4. Christensen SB,
    5. Cieslinski LB,
    6. Esser KM,
    7. Prabhakar US,
    8. Rush JA,
    9. Torphy TJ
    (1996) Association of the anti-inflammatory activity of phosphodiesterase 4 (PDE4) inhibitors with either inhibition of PDE4 catalytic activity or competition for [3H]rolipram binding. Biochem Pharmacol 51:949–956.
    OpenUrlCrossRefPubMed
  2. ↵
    1. Bauditz J,
    2. Haemling J,
    3. Ortner M,
    4. Lochs H,
    5. Raedler A,
    6. Schreiber S
    (1997) Treatment with tumour necrosis factor inhibitor oxpentifylline does not improve corticosteroid dependent chronic active Crohn's disease. Gut 40:470–494.
    OpenUrlAbstract/FREE Full Text
  3. ↵
    1. Beavo JA
    (1995) Cyclic nucleotide phosphodiesterases: Functional implications of multiple isoforms. Physiol Rev 75:725–748.
    OpenUrlAbstract/FREE Full Text
  4. ↵
    1. Breese EJ,
    2. Michie CA,
    3. Nicholls SW,
    4. Murch SH,
    5. Williams CB,
    6. Domizio P,
    7. Walker-Smith JA,
    8. MacDonald TT
    (1994) Tumor necrosis factor α-producing cells in the intestinal mucosa of children with inflammatory bowel disease. Gastroenterology 106:1455–1466.
    OpenUrlPubMed
  5. ↵
    1. Cooper HS,
    2. Murthy SN,
    3. Shah RS,
    4. Sedergran DJ
    (1993) Clinicopathologic study of dextran sulfate sodium experimental murine colitis. Lab Invest 69:238–249.
    OpenUrlPubMed
  6. ↵
    1. Dieleman LA,
    2. Ridwan BU,
    3. Tennyson GS,
    4. Beagley KW,
    5. Bucy RP,
    6. Elson CO
    (1994) Dextran sulfate sodium-induced colitis occurs in severe combined immunodeficient mice. Gastroenterology 107:1643–1652.
    OpenUrlPubMed
  7. ↵
    1. Eigler A,
    2. Siegmund B,
    3. Emmerich U,
    4. Baumann KH,
    5. Hartmann G,
    6. Endres S
    (1998) Anti-inflammatory activities of cAMP-elevating agents: Enhancement of IL-10 synthesis and concurrent suppression of TNF production. J Leukocyte Biol 63:101–107.
    OpenUrlAbstract
  8. ↵
    1. Eigler A,
    2. Sinha B,
    3. Hartmann G,
    4. Endres S
    (1997) Taming TNF: Strategies to restrain this proinflammatory cytokine. Immunol Today 18:487–492.
    OpenUrlCrossRefPubMed
  9. ↵
    1. Elliott MJ,
    2. Maini RN,
    3. Feldmann M,
    4. Kalden JR,
    5. Antoni C,
    6. Smolen JS,
    7. Leeb B,
    8. Breedveld FC,
    9. Macfarlane JD,
    10. Bijl H,
    11. Woody JN
    (1994) Randomised double-blind comparison of chimeric monoclonal antibody to tumour necrosis factor-α (cA2) versus placebo in rheumatoid arthritis. Lancet 344:1105–1110.
    OpenUrlCrossRefPubMed
  10. ↵
    1. Elson CO,
    2. Sartor RB,
    3. Tennyson GS,
    4. Riddell RH
    (1995) Experimental models of inflammatory bowel disease. Gastroenterology 109:1344–1367.
    OpenUrlCrossRefPubMed
  11. ↵
    1. Essayan DM,
    2. Huang SK,
    3. Undem BJ,
    4. Kagey-Sobotka A,
    5. Lichtenstein LM
    (1994) Modulation of antigen- and mitogen-induced proliferative responses of peripheral blood mononuclear cells by nonselective and isozyme selective cyclic nucleotide phosphodiesterase inhibitors. J Immunol 153:3408–3416.
    OpenUrlAbstract
  12. ↵
    1. Fekade D,
    2. Knox K,
    3. Hussein K,
    4. Melka A,
    5. Lalloo DG,
    6. Coxon RE,
    7. Warrell DA
    (1996) Prevention of Jarisch-Herxheimer reactions by treatment with antibodies against tumor necrosis factor alpha. N Engl J Med 335:311–315.
    OpenUrlCrossRefPubMed
  13. ↵
    1. Fischer W,
    2. Schudt C,
    3. Wendel A
    (1993) Protection by phosphodiesterase inhibitors against endotoxin-induced liver injury in galactosamine-sensitized mice. Biochem Pharmacol 45:2399–2404.
    OpenUrlCrossRefPubMed
  14. ↵
    1. Gantner F,
    2. Kusters S,
    3. Wendel A,
    4. Hatzelmann A,
    5. Schudt C,
    6. Tiegs G
    (1997) Protection from T cell-mediated murine liver failure by phosphodiesterase inhibitors. J Pharmacol Exp Ther 280:53–60.
    OpenUrlAbstract/FREE Full Text
  15. ↵
    1. Genain CP,
    2. Roberts T,
    3. Davis RL,
    4. Nguyen MH,
    5. Uccelli A,
    6. Faulds D,
    7. Li Y,
    8. Hedgpeth J,
    9. Hauser SL
    (1995) Prevention of autoimmune demyelination in non-human primates by a cAMP-specific phosphodiesterase inhibitor. Proc Natl Acad Sci USA 92:3601–3605.
    OpenUrlAbstract/FREE Full Text
  16. ↵
    1. Griswold DE,
    2. Webb EF,
    3. Badger AM,
    4. Gorycki PD,
    5. Levandoski PA,
    6. Barnette MA,
    7. Grous M,
    8. Christensens S,
    9. Torphy TJ
    (1998) SB 207499 (Ariflo), a second generation phosphodiesterase 4 inhibitor, reduces tumor necrosis factor-α and interleukin-4 production in vivo. J Pharmacol Exp Ther 287:705–711.
    OpenUrlAbstract/FREE Full Text
  17. ↵
    1. Kim HS,
    2. Berstad A
    (1992) Experimental colitis in animal models. Scand J Gastroenterol 27:529–537.
    OpenUrlCrossRefPubMed
  18. ↵
    1. Kojouharoff G,
    2. Hans W,
    3. Obermeier F,
    4. Mannel DN,
    5. Andus T,
    6. Scholmerich J,
    7. Gross V,
    8. Falk W
    (1997) Neutralization of tumour necrosis factor (TNF) but not of IL-1 reduces inflammation in chronic dextran sulphate sodium-induced colitis in mice. Clin Exp Immunol 107:353–358.
    OpenUrlCrossRefPubMed
  19. ↵
    1. Lehr HA,
    2. Mankoff DA,
    3. Corwin D,
    4. Santeusanio G,
    5. Gown AM
    (1997) Application of photoshop-based image analysis to quantification of hormone receptor expression in breast cancer. J Histochem Cytochem 45:1559–1565.
    OpenUrlAbstract/FREE Full Text
  20. ↵
    1. Murch SH,
    2. Braegger CP,
    3. Walker-Smith JA,
    4. MacDonald TT
    (1993) Location of tumour necrosis factor α by immunohistochemistry in chronic inflammatory bowel disease. Gut 34:1705–1709.
    OpenUrlAbstract/FREE Full Text
  21. ↵
    1. Murch SH,
    2. Lamkin VA,
    3. Savage MO,
    4. Walker-Smith JA,
    5. MacDonald TT
    (1991) Serum concentrations of tumour necrosis factor-α in childhood chronic inflammatory bowel disease. Gut 32:913–917.
    OpenUrlAbstract/FREE Full Text
  22. ↵
    1. Nyman U,
    2. Mussener A,
    3. Larsson E,
    4. Lorentzen J,
    5. Klareskog L
    (1997) Amelioration of collagen II-induced arthritis in rats by the type IV phosphodiesterase inhibitor Rolipram. Clin Exp Immunol 108:415–419.
    OpenUrlCrossRefPubMed
  23. ↵
    1. Okayasu I,
    2. Hatakeyama S,
    3. Yamada M,
    4. Ohkusa T,
    5. Inagaki Y,
    6. Nakaya R
    (1990) A novel method in the induction of reliable experimental acute and chronic ulcerative colitis in mice. Gastroenterology 98:694–702.
    OpenUrlPubMed
  24. ↵
    1. Olson AD,
    2. DelBuono EA,
    3. Bitar KN,
    4. Remick DG
    (1995) Antiserum to tumor necrosis factor and failure to prevent murine colitis. J Pediatr Gastroenterol Nutr 21:410–418.
    OpenUrlCrossRefPubMed
  25. ↵
    1. Peterson TC,
    2. Davey K
    (1997) Effect of acute pentoxifylline treatment in an experimental model of colitis. Aliment Pharmacol Ther 11:575–580.
    OpenUrlCrossRefPubMed
  26. ↵
    1. Prabhakar U,
    2. Lipshutz D,
    3. Bartus JO,
    4. Slivjak MJ,
    5. Smith EFr,
    6. Lee JC,
    7. Esser KM
    (1994) Characterization of cAMP-dependent inhibition of LPS-induced TNF-α production by rolipram, a specific phosphodiesterase IV (PDE IV) inhibitor. Int J Immunopharmacol 16:805–816.
    OpenUrlCrossRefPubMed
  27. ↵
    1. Present DH,
    2. Rutgeerts P,
    3. Targan S,
    4. Hanauer SB,
    5. Mayer L,
    6. Van Hozegand RA,
    7. Podolsky DK,
    8. Sands BE,
    9. Braakman T,
    10. DeWoody KL,
    11. Schaible TF,
    12. Van Deventer SJ
    (1999) Infliximab for the treatment of fistulas in patients with Crohn's disease. N Engl J Med 340:1398–1405.
    OpenUrlCrossRefPubMed
  28. ↵
    1. Reimund JM,
    2. Dumont S,
    3. Muller CD,
    4. Kenney JS,
    5. Kedinger M,
    6. Baumann R,
    7. Poindron P,
    8. Duclos B
    (1997) In vitro effects of oxpentifylline on inflammatory cytokine release in patients with inflammatory bowel disease. Gut 40:475–480.
    OpenUrlAbstract/FREE Full Text
  29. ↵
    1. Ross SE,
    2. Williams RO,
    3. Mason LJ,
    4. Mauri C,
    5. Marinova-Mutafchieva L,
    6. Malfait AM,
    7. Maini RN,
    8. Feldmann M
    (1997) Suppression of TNF-α expression, inhibition of Th1 Activity, and amelioration of collagen-induced arthritis by rolipram. J Immunol 159:6253–6259.
    OpenUrlAbstract
  30. ↵
    1. Sandborn WJ,
    2. Hanauer SB
    (1999) Antitumor necrosis factor therapy for inflammatory bowel disease: A review of agents, pharmacology, clinical results and safety. Inflamm Bowel Dis 5:119–133.
    OpenUrlCrossRefPubMed
  31. ↵
    1. Savendahl L,
    2. Underwood LE,
    3. Haldeman KM,
    4. Ulshen MH,
    5. Lund PK
    (1997) Fasting prevents experimental murine colitis produced by dextran sulfate sodium and decreases interleukin-1β and insulin-like growth factor I messenger ribonucleic acid. Endocrinology 138:734–740.
    OpenUrlCrossRefPubMed
  32. ↵
    1. Schade FU,
    2. Schudt C
    (1993) The specific type III and IV phosphodiesterase inhibitor zardaverine suppresses formation of tumor necrosis factor by macrophages. Eur J Pharmacol 230:9–14.
    OpenUrlCrossRefPubMed
  33. ↵
    1. Seldon PM,
    2. Barnes PJ,
    3. Meja K,
    4. Giembycz MA
    (1995) Suppression of lipopolysaccharide-induced tumor necrosis factor-α generation from human peripheral blood monocytes by inhibitors of phosphodiesterase 4: Interaction with stimulants of adenylyl cyclase. Mol Pharmacol 48:747–457.
    OpenUrlAbstract
  34. ↵
    1. Semmler J,
    2. Wachtel H,
    3. Endres S
    (1993) The specific type IV phosphodiesterase inhibitor rolipram suppresses tumor necrosis factor-α production by human mononuclear cells. Int J Immunopharmacol 15:409–413.
    OpenUrlCrossRefPubMed
  35. ↵
    1. Siegmund B,
    2. Eigler A,
    3. Moeller J,
    4. Greten TF,
    5. Hartmann G,
    6. Endres S
    (1997) Suppression of tumor necrosis factor-α production by interleukin-10 is enhanced by cAMP-elevating agents. Eur J Pharmacol 321:231–239.
    OpenUrlCrossRefPubMed
  36. ↵
    1. Sinha B,
    2. Semmler J,
    3. Eisenhut T,
    4. Eigler A,
    5. Endres S
    (1995) Enhanced tumor necrosis factor suppression and cyclic adenosine monophosphate accumulation by combination of phosphodiesterase inhibitors and prostanoids. Eur J Immunol 25:147–153.
    OpenUrlPubMed
  37. ↵
    1. Sommer N,
    2. Loschmann PA,
    3. Northoff GH,
    4. Weller M,
    5. Steinbrecher A,
    6. Steinbach JP,
    7. Lichtenfels R,
    8. Meyermann R,
    9. Riethmuller A,
    10. Fontana A,
    11. Dichgans J,
    12. Martin R
    (1995) The antidepressant rolipram suppresses cytokine production and prevents autoimmune encephalomyelitis. Nat Med 1:244–248.
    OpenUrlCrossRefPubMed
  38. ↵
    1. Souness JE,
    2. Houghton C,
    3. Sardar N,
    4. Withnall MT
    (1997) Evidence that cyclic AMP phosphodiesterase inhibitors suppress interleukin-2 release from murine splenocytes by interacting with a 'low-affinity' phosphodiesterase 4 conformer. Br J Pharmacol 121:743–750.
    OpenUrlCrossRefPubMed
  39. ↵
    1. Stack WA,
    2. Mann SD,
    3. Roy AJ,
    4. Heath P,
    5. Sopwith M,
    6. Freeman J,
    7. Holmes G,
    8. Long R,
    9. Forbes A,
    10. Kamm MA,
    11. Hawkey CJ
    (1997) Randomised controlled trial of CDP571 antibody to tumour necrosis factor-α in Crohn's disease. Lancet 349:521–524.
    OpenUrlCrossRefPubMed
  40. ↵
    1. Strieter RM,
    2. Remick DG,
    3. Ward PA,
    4. Spengler RN,
    5. Lynch JPd,
    6. Larrick J,
    7. Kunkel SL
    (1988) Cellular and molecular regulation of tumor necrosis factor-α production by pentoxifylline. Biochem Biophys Res Commun 155:1230–1236.
    OpenUrlCrossRefPubMed
  41. ↵
    1. Targan SR,
    2. Hanauer SB,
    3. van Deventer SJ,
    4. Mayer L,
    5. Present DH,
    6. Braakman T,
    7. DeWoody KL,
    8. Schaible TF,
    9. Rutgeerts PJ
    (1997) A short-term study of chimeric monoclonal antibody cA2 to tumor necrosis factor α for Crohn's disease. Crohn's Disease cA2 Study Group. N Engl J Med 337:1029–1035.
    OpenUrlCrossRefPubMed
  42. ↵
    1. Turner CR,
    2. Andresen CJ,
    3. Smith WB,
    4. Watson JW
    (1994) Effects of rolipram on responses to acute and chronic antigen exposure in monkeys. Am J Respir Crit Care Med 149:1153–1159.
    OpenUrlPubMed
  43. ↵
    1. van Deventer SJ
    (1997) Tumour necrosis factor and Crohn's disease. Gut 40:443–448.
    OpenUrlFREE Full Text
  44. ↵
    1. van Dullemen HM,
    2. van Deventer SJ,
    3. Hommes DW,
    4. Bijl HA,
    5. Jansen J,
    6. Tytgat GN,
    7. Woody J
    (1995) Treatment of Crohn's disease with anti-tumor necrosis factor chimeric monoclonal antibody (cA2). Gastroenterology 109:129–135.
    OpenUrlCrossRefPubMed
  45. ↵
    1. Wachtel H
    (1983) Potential antidepressant activity of rolipram and other selective cyclic adenosine 3′,5′-monophosphate phosphodiesterase inhibitors. Neuropharmacology 22:267–272.
    OpenUrlCrossRefPubMed
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Research ArticleGASTROINTESTINAL, HEPATIC, PULMONARY, AND RENAL

Specific Type IV Phosphodiesterase Inhibitor Rolipram Mitigates Experimental Colitis in Mice

Gunther Hartmann, Christoph Bidlingmaier, Britta Siegmund, Stefan Albrich, Johannes Schulze, Katharina Tschoep, Andreas Eigler, Hans Anton Lehr and Stefan Endres
Journal of Pharmacology and Experimental Therapeutics January 1, 2000, 292 (1) 22-30;
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