Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to cause gastric mucosal damage as a side effect. Acetaminophen, widely used as an analgesic and antipyretic drug, has gastroprotective effects against gastric lesions induced by absolute ethanol and certain NSAIDs. However, the mechanisms that underlie the gastroprotective effects of acetaminophen have not yet been clarified. In the present study, we examined the role and protective mechanism of acetaminophen on ibuprofen-induced gastric damage in rats. Ibuprofen and acetaminophen were administered orally, and the gastric mucosa was macroscopically examined 4 hours later. Acetaminophen decreased ibuprofen-induced gastric damage in a dose-dependent manner. To investigate the mechanisms involved, transcriptome analyses of the ibuprofen-damaged gastric mucosa were performed in the presence and absence of acetaminophen. Ingenuity pathway analysis (IPA) software revealed that acetaminophen suppressed the pathways related to cellular assembly and inflammation, whereas they were highly activated by ibuprofen. On the basis of gene classifications from the IPA Knowledge Base, we identified the following five genes that were related to gastric damage and showed significant changes in gene expression: interleukin-1β (IL-1β), chemokine (C–C motif) ligand 2 (CCL2), matrix metalloproteinase-10 (MMP-10), MMP-13, and FBJ osteosarcoma oncogene (FOS). Expression of these salient genes was confirmed using real-time polymerase chain reaction. The expression of MMP-13 was the most reactive to the treatments, showing strong induction by ibuprofen and suppression by acetaminophen. Moreover, MMP-13 inhibitors decreased ibuprofen-induced gastric damage. In conclusion, these results suggest that acetaminophen decreases ibuprofen-induced gastric mucosal damage and that the suppression of MMP-13 may play an important role in the gastroprotective effects of acetaminophen.
Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (IBP), loxoprofen, and aspirin have been widely used for treatment of acute and chronic pain. The analgesic mechanism of NSAIDs involves inhibition of cyclooxygenase (COX) and suppression of prostaglandin production. However, it has been documented that NSAIDs cause gastrointestinal damage as an adverse effect; the annual incidence of upper gastrointestinal bleeding has been reported to range from 43 to 140 per 100,000 people (Hernandez-Diaz and Rodriguez, 2002).
One of the important factors in gastric damage induced by NSAIDs is endogenous prostaglandin (PG) deficiency caused by inhibition of COX-1 and COX-2 (Takeuchi, 2012; Okada et al., 1989). PGs protect the gastric mucosa against necrosis induced by NSAIDs or ethanol (Okada et al., 1989; Takeuchi, 2012). COX-1 is constitutively expressed in various tissues, including the stomach, as a housekeeping protein whereas COX-2 is expressed in response to cytokines in most tissues under pathologic conditions such as inflammation (O’Neill and Ford-Hutchinson, 1993). Studies using selective COX-1 or COX-2 inhibitors have indicated that the gastric ulcerogenic properties of NSAIDs are caused by inhibition of both COX-1 and COX-2 (Wallace et al., 2000; Tanaka et al., 2001). However, several reports suggest that other elements such as free radicals, disturbances of microcirculation, and hypermotility may be involved in the pathogenic mechanisms (Naito and Yoshikawa, 2006; Funatsu et al., 2007; Takeuchi, 2012). Furthermore, it has been reported that other risk factors, including diabetes and concomitant use of other agents, aggravate gastric lesions induced by NSAIDs (Pradeepkumar Singh et al., 2011; Takeuchi et al., 2011; Kwiecien et al., 2012). Taken together, although PG deficiencies due to inhibition of COX-1 and COX-2 play an important role in gastric side effects, the mechanisms by which NSAIDs induce gastric damage remain elusive.
Acetaminophen (APAP) is another analgesic and antipyretic drug. However, unlike NSAIDs, it does not cause gastric mucosal damage (Lanza et al., 1998; Yoon et al., 2012). Although the analgesic mechanism of APAP remains unclear and requires further elucidation, it is suggested that APAP may act centrally and be a weak inhibitor of PG synthesis (Anderson, 2008).
APAP reportedly reduces gastric lesions induced by absolute ethanol, acidic aspirin, IBP, and indomethacin in rats (Seegers et al., 1980; Konturek et al., 1982; Van Kolfschoten et al., 1983; Stern et al., 1984). However, the effects on IBP-induced gastric damage were limited because the suppression by APAP was examined in a fixed dose (Van Kolfschoten et al., 1983). Various theories have been proposed to explain the gastroprotective effects of APAP, such as activation of PG synthesis and scavenging of free radicals (van Kolfschoten et al., 1981). However, the precise mode of action has not yet been completely elucidated.
Our present study examined the protective effects of APAP on IBP-induced gastric mucosal damage using various APAP doses. In addition, transcriptome analyses were performed on the IBP-damaged gastric mucosa in the presence and absence of APAP. The gene expression profiles were analyzed using Ingenuity Pathway Analysis (IPA) software (QIAGEN/Ingenuity Systems, Redwood City, CA) to assess the involvement of gene expression changes in gastric protection by APAP. To the best of our knowledge, this is the first study to show gene expression profiling after oral administration of NSAIDs and APAP in rats.
Materials and Methods
IBP (Shiratori Pharmaceutical, Chiba, Japan), APAP (Iwaki Pharmaceutical, Tokyo, Japan), and the matrix metalloproteinase-13 (MMP-13) inhibitor N-[4-(4-morpholinyl)butyl]-2-benzofurancarboxamide (CL-82198; Sigma-Aldrich, St. Louis, MO) were purchased from each manufacturer.
Male Sprague-Dawley rats (6 weeks old) were purchased from Charles River Japan (Kanagawa, Japan). The animals were fed standard rat chow and tap water ad libitum. They were housed in stainless steel cages with wire bottoms and maintained on a 12-hour light/dark cycle with the temperature and relative humidity of the animal room controlled at 21–23°C and 40%–60%, respectively. All experimental procedures were performed in accordance with the Declaration of Helsinki and approved by the Animal Care and Use Committee of LION Corporation.
Induction of Gastric Mucosal Damage by IBP.
Gastric mucosal damage was induced by oral administration of 200 mg/kg IBP suspended in a 5% gum arabic solution. Rats were divided into the following treatment groups (n = 9–10 individuals per group): 1) 200 mg/kg IBP, 2) 200 mg/kg IBP and 100 mg/kg APAP, 3) 200 mg/kg IBP and 125 mg/kg APAP, 4) 200 mg/kg IBP and 150 mg/kg APAP, 5) 200 mg/kg IBP and 175 mg/kg APAP, 6) 200 mg/kg IBP and 200 mg/kg APAP, and 7) 200 mg/kg IBP and 400 mg/kg APAP. IBP and APAP were administered at the same time in groups 2 to 7. Before the experiments, the animals were deprived of food overnight. They were euthanized 4 hours after drug administration under isoflurane anesthesia, and the gastric tissues were collected.
Measurement of Gastric Damage.
The stomachs were removed, inflated by injecting 10 ml of saline, immersed in 1% formalin for 1 hour to fix the gastric tissue, and opened along the greater curvature. Subsequently, the lengths of hemorrhagic lesions were measured using a dissecting microscope with a ruler. The sum of the lesion lengths per stomach was used as a score of damage (Wallace et al., 1993).
The gastric mucosa was examined with a microscope after the administration of 200 mg/kg IBP with or without 200 mg/kg APAP. The animals were euthanized 4 hours after the drug administration under isoflurane anesthesia, and the stomachs were excised, immersed in 10% neutralized formalin, and embedded in paraffin. The sections (8 μm) were cut using microtome and stained with hematoxylin and eosin.
RNA Extraction and Microarray Analysis.
The rats were divided into the following three treatment groups: 1) 200 mg/kg IBP (n = 5); 2) 200 mg/kg IBP and 200 mg/kg APAP (n = 5); and 3) 5% gum arabic solution (control; n = 5). Before the experiments, the animals were deprived of food overnight. They were euthanized 2 hours or 4 hours after drug administration under isoflurane anesthesia, and the stomachs were removed and incised along the greater curvature. The corpus mucosa was scraped using two glass slides, and the samples were stored in RNAlater (Ambion, Austin, TX) until RNA extraction. Total RNA was extracted from each sample using a QIAGEN RNeasy kit (Valencia, CA) according to the manufacturer’s protocol. Subsequently, total RNA from five samples was pooled for each group.
The microarray analysis was performed using a SurePrint G3 Rat GE 8×60K Microarray (Agilent Inc., Santa Clara, CA) at Takara Biochemicals. A total of 100 ng of RNA was labeled using the fluorescent probe Cy3, and 0.6 μg of the labeled RNA was used for hybridization. The cDNA microarray was scanned using an Agilent DNA Microarray Scanner (G2565CA), and the images were analyzed using Agilent Feature Extraction Software v10.7 for background subtraction, normalization, and assessment of quality control. Signal evaluation was also performed with the Agilent Feature Extraction Software v10.7 to assess the reliability of the transcripts of each spot using the following three levels: 0 = not detected; 1 = detected but insufficient for analysis; and 2 = detected sufficiently for analysis. Subsequently, fold changes in mRNA expression were calculated relative to the control samples.
Ingenuity Pathway Analysis.
Probes were excluded from the analysis of gene expression using IPA software under any of the following conditions: 1) if signal evaluation values were 0 or 1 in every group or 2) if fold changes between two groups were greater than 0.5 or less than 2. Genes that met these criteria were uploaded into the IPA website (http://www.ingenuity.com/) to annotate biofunctions and construct molecular interaction networks. In our study, two major methods of pathway analysis were used: network analysis and canonical pathway analysis.
In network analysis, the significance and specificity of IPA-generated networks were based on the scores of each network. High scores indicated that gene networks are highly specific to each cluster. For example, a molecular network score of 3 indicates a 1 in 103 chance of getting a network containing the same number of network eligible molecules, with the same number of molecules randomly picked from the IPA Knowledge Base. That is, a score of 3 indicates 99.9% confidence of not being generated by random chance alone.
In canonical pathway analysis, the significance of the association between the data set and a canonical pathway was measured as follows. 1) The ratio of the number of identified genes in a particular pathway to the total number of genes that constitute the pathway was calculated. 2) Fisher’s exact test was used to calculate the probability (P) of the association between genes in the data set and the canonical pathway occurring due to chance alone.
Quantitative Real-Time Polymerase Chain Reaction Confirmation.
The expression of salient genes was confirmed by real-time polymerase chain reaction (PCR). Total RNA was extracted as described earlier. Aliquots (1 μg) of extracted RNA were reverse transcribed into cDNA at 37°C for 15 minutes using reverse transcriptase (Takara Biochemicals, Otsu, Japan). Real-time PCR was performed using a CFX96 Real-Time System and C1000 Thermal Cycler (Bio-Rad Laboratories, Hercules, CA), and the products were detected using the DNA-binding dye SYBR green II. Primer sequences used in this study are summarized in Table 1. The PCR settings were as follows: initial denaturation at 95°C for 30 seconds followed by 40 cycles of amplification at 95°C for 5 seconds and 60°C for 30 seconds, and subsequent melting curve analysis increasing the temperature from 60°C to 95°C. The values obtained were normalized to those of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA.
MMP-13 Inhibitor Assay on IBP-Induced Gastric Damage.
CL-82198 is a selective inhibitor of MMP-13 (IC50 = 10 µM) that does not inhibit MMP-1, MMP-9, or tumor necrosis factor α–converting enzyme (TACE) (Chen et al., 2000). Rats were divided into the following five treatment groups: 1) 5% gum arabic solution (n = 4), 2) 200 mg/kg IBP (n = 8), 3) 200 mg/kg IBP and 200 mg/kg APAP (n = 8), 4) 200 mg/kg IBP and 0.2 mg/kg CL-82198 (n = 8), and 5) 200 mg/kg IBP and 1.0 mg/kg CL-82198 (n = 8). APAP or CL-82198 was administered to rats with IBP at the same time in groups 3 to 5. They were killed 4 hours after drug administration under isoflurane anesthesia, the gastric tissue was collected, and gastric lesions were measured as mentioned earlier.
Gastric damage data and real-time PCR results are presented as mean ± S.E. with 4 to 10 rats per group. Statistical analyses were performed using a two-tailed unpaired t test or Dunnett’s multiple comparison test. P < 0.05 was considered statistically significant.
Effects of APAP on IBP-Induced Gastric Damage.
To investigate the effects of APAP on IBP-induced gastric damage, the lengths of the hemorrhagic lesions were measured. Cotreatment with APAP at 100, 125, 150, 175, 200, and 400 mg/kg led to a 35.0%, 81.0%, 98.7%, 98.6%, 97.0%, and 98.0% decrease in gastric lesions, respectively, compared with IBP treatment (200 mg/kg) alone (Fig. 1A). APAP significantly suppressed IBP-induced gastric damage in a dose-dependent manner. Histologic analysis revealed that IBP administration caused epithelial cell damage, whereas the combination of IBP and APAP prevented the mucosal tissue damage (Fig. 1B).
Microarray Analysis for Gene Expression Induced by IBP and APAP.
Expression profiles of differentially regulated transcripts were generated at two time points: 2 hours and 4 hours after drug administration. Of the 30,003 probes studied, 222 were up-regulated at least 2.0-fold by IBP compared with the control group and down-regulated at least 2.0-fold by IBP and APAP cotreatment compared with IBP alone at 2 hours after drug administration. In contrast, 160 probes were down-regulated by IBP compared with the control group and up-regulated by IBP and APAP cotreatment compared with IBP alone by at least 2.0-fold. In total, 382 probes were selected at 2 hours after drug administration, and 370 of these were mapped to IPA-defined genetic networks. Similarly, 525 probes were up-regulated by IBP and down-regulated by IBP and APAP cotreatment, and 55 probes were down-regulated by IBP and up-regulated by IBP and APAP cotreatment by at least 2.0-fold at 4 hours after drug administration. In total, 580 probes were selected at this time point, and 566 of these were mapped to IPA-defined genetic networks.
Selected genes were analyzed using IPA to identify the major functional molecular networks (Table 2). By network analysis, the following five top molecular networks were significantly activated with IBP and APAP cotreatment compared with IBP alone at 2 hours after drug administration: 1) lipid metabolism, molecular transport, small molecule biochemistry; 2) after translational modification, embryonic development, organ development; 3) carbohydrate metabolism, lipid metabolism, small molecule biochemistry; 4) embryonic development, organismal development, tissue development; and 5) molecular transport, cell cycle, DNA replication, recombination, and repair. At 4 hours after drug administration, the following five top molecular networks were significantly activated: 1) cellular assembly and organization, cellular movement, hematologic system development and function; 2) inflammatory disease, inflammatory response, ophthalmic disease; 3) organismal development, dermatologic diseases and conditions, cellular assembly and organization; 4) carbohydrate metabolism, small molecule biochemistry, cellular growth and proliferation; and 5) drug metabolism, nucleic acid metabolism, small molecule biochemistry. As shown in Table 2, the top scores at 4 hours were greater than those at 2 hours.
Further, canonical pathway analysis identified other major pathways related to inflammatory disease (Table 3). Among these, the liver X receptor/retinoid X receptor (LXR/RXR) activation pathway was highly activated at 2 hours after drug administration and pathways involving P450 genes were highly activated at 4 hours after drug administration. Genes involved in the LXR/RXR activation pathway included CD14, interleukin-6 (IL-6), and prostaglandin endoperoxide synthase 2 (PTGS2). Although the expression of the PTGS2 gene was up-regulated by IBP and down-regulated by IBP and APAP cotreatment, the expression pattern of prostaglandin endoperoxide synthase 1 (PTGS1) was not altered by either drug administration compared with the control group at any time point (Table 4).
Moreover, using the gene classification from the IPA Knowledge Base, 47 genes were selected as gastric damage-related genes, having functions in apoptosis (in epithelial cells), vasoconstriction, ulcer formation, gastrointestinal disease (inflammatory, immune), loss of gastric acid secretion, imbalance of extracellular matrix, disorder of cell proliferation (in gastric), bleeding, disorder of cell adhesion (in epithelial cells), formation of vascular lesion, disorder of cell migration (in epithelial cells), and imbalance of bicarbonate ion secretion. Comparison of this gastric damage profile with the expression patterns of 47 genes revealed 21 genes with good correspondence. Of these genes, matrix metalloproteinase 10 (MMP-10), matrix metalloproteinase 13 (MMP-13), and caspase 12 (CASP12) may participate directly in the induction of gastric damage because they encode enzymes involved in tissue destruction. In particular, MMP-13 was up-regulated by IBP and down-regulated by IBP and APAP cotreatment.
Furthermore, the IPA Knowledge Base revealed that the change in the expression of MMP-13 may be associated with the genes interleukin-1β (IL-1β), chemokine (C-C motif) ligand 2 (CCL2), MMP-10, and FBJ osteosarcoma oncogene (FOS) (Fig. 2). IL-1β, CCL2, and MMP-10 were significantly up-regulated by IBP treatment and down-regulated by IBP and APAP cotreatment. FOS was not up-regulated by IBP but was down-regulated by IBP and APAP cotreatment (Table 4).
To confirm the expression patterns identified by cDNA microarray at 2 hours and 4 hours after drug administration, expression of the genes IL-1β, CCL2, MMP-10, MMP-13, and FOS was confirmed using real-time PCR (Fig. 3). Although the microarray results overestimated the fold changes observed during real-time PCR for some genes, the methods agreed on the direction of regulation in all cases. Of these five genes, the expression of MMP-13 was most up-regulated by IBP and down-regulated by IBP and APAP cotreatment at 4 hours after drug administration.
Effects of a MMP-13 Inhibitor on IBP-Induced Gastric Damage.
Gene expression analysis indicated that MMP-13 may be a direct pathogenic factor during the induction of gastric damage. To investigate the contribution of MMP-13 down-regulation during gastroprotection by APAP, we evaluated the effects of the MMP-13 inhibitor CL-82198 on IBP-induced gastric damage. CL-82198 decreased gastric lesions in a dose-dependent manner in the presence of IBP (Fig. 4). CL-82198 administered at 0.2 and 1.0 mg/kg led to 40.3% and 72.1% decrease in gastric lesion, respectively, compared with IBP administration alone.
With the exception of selective COX-2 inhibitors, traditional NSAIDs are classified into three types: those carrying an acetic acid moiety, those with a propionic acid moiety, and those carrying other acidic moieties such as salicylate. In the present study, we examined the gastroprotective effects of APAP on gastric damage induced by IBP, which carries a propionic acid moiety. Oral doses of APAP at 200 mg/kg blocked 97.0% of gastric damage caused by same amounts of IBP. In a previous report, APAP suppressed gastric lesions induced by the other NSAIDs aspirin and indomethacin (Seegers et al., 1980; Konturek et al., 1982; Stern et al., 1984), suggesting that gastric damage caused by various types of NSAIDs may be suppressed by combined administration with APAP.
Our present study investigated the protective mechanisms of APAP using gene expression profiling in the gastric mucosa. Using IPA, we found that two major pathways, the cellular assembly pathway and inflammation pathway, were highly activated by IBP and suppressed by APAP. This result agreed with the previous observation of Naito et al. (2007) which showed that administration of indomethacin induced the inflammation-signaling pathway in the gastric mucosa of rats.
In addition, our results demonstrated that IBP up-regulated genes related to gastric damage, which encode IL-1β, CCL2, MMP-10, and MMP-13. In contrast, treatment with APAP down-regulated the expression of these genes and that encoding FOS. IL-1β and CCL2 are cytokines that are involved in immunoregulatory and inflammatory processes (Deshmane et al., 2009; Ren and Torres, 2009). MMP-10 and MMP-13 are proteins of the matrix metalloproteinase (MMP) family that are involved in the breakdown of the extracellular matrix (ECM) (Hofmann et al., 2000). FOS is a transcriptional regulator related to inflammation and pain perception (Shiozawa and Tsumiyama, 2009). Among these five genes, we focused on MMP-13 because it could be a direct pathogenic factor during induction of gastric damage by IBP, and it was suppressed during gastroprotection by APAP.
MMPs are a class of Zn-dependent endopeptidases that regulate cell-matrix composition. Under normal conditions, MMPs are present in tissues at low levels in the latent form and are responsible for normal physiologic tissue turnover (Sengupta and MacDonald, 2007). However, MMPs play a critical role in ECM degradation and remodeling during inflammation and wound-healing processes (Egeblad and Werb, 2002). Several studies describe the involvement of MMPs in degradation and remodeling of ECM during pathogenesis and healing of gastric ulcers (Lempinen et al., 2000; Shahin et al., 2001; Swarnakar et al., 2005; Sengupta and MacDonald, 2007). In particular, MMP-1, -8, -13, and -14 are responsible for cleavage of both collagen I and III, the major types of collagen in the stomach wall (Chakraborti et al., 2003; Yan and Boyd, 2007; Fanjul-Fernandez et al., 2010). In our study, MMP-13 was up-regulated in the gastric mucosa damaged by IBP, whereas it was suppressed to near normal levels by APAP during prevention of gastric damage. The MMP-13 inhibitor CL-82198 decreased IBP-induced gastric damage, indicating that MMP-13 may be a pathogenic and not a healing factor in gastric lesions. In addition, it was considered that the protective action of APAP was possibly mediated by suppression of MMP-13.
The catalytic activities of MMPs are highly regulated at multiple levels, including gene expression, spatial localization, zymogen activation, and inhibition by tissue inhibitors of metalloproteinases (TIMPs). Most MMPs are secreted as inactive proproteins that are activated when cleaved by extracellular proteinases (Chakraborti et al., 2003; Yan and Boyd, 2007; Fanjul-Fernandez et al., 2010). Furthermore, it is suggested that MMP-10 is responsible for activation of proMMP-13 (Barksby et al., 2006). In our study, the expression of MMP-10 and MMP-13 in the gastric mucosa was down-regulated by APAP during gastroprotection. Thus, it is possible that the suppression of MMP-10 may contribute to the decrease activity of MMP-13 in the gastric mucosa during gastroprotection by APAP.
Furthermore, the promoter of MMP-13 has several cis-elements such as TATA boxes and activator protein-1 (AP-1) binding sites that regulate its expression. External stimuli activate the nuclear AP-1 transcription factor complex and AP-1 dimers consisting of members of jun and fos gene families. AP-1 dimers bind to cognate cis-elements, resulting in the activation of gene transcription (Chakraborti et al., 2003; Yan and Boyd, 2007; Fanjul-Fernandez et al., 2010). Chakraborti et al. (2003) reported that overexpression of c-fos in transgenic mice induced the expression of mouse MMP-13 predominantly in bone and also in the thymus and spleen. In our study, down-regulation of FOS and MMP-13 mRNA expression was observed after administration of APAP. These findings suggest that MMP-10 and FOS may regulate the transcription or activity of MMP-13 during prevention of gastric damage by APAP.
In addition, it is possible that other elements, such as PGs, may decrease gastric damage independent of MMP-13 inhibition by APAP because the gastric lesion was not fully suppressed by the MMP-13 inhibitor. In our study, the expression of PTGS1 was not changed at any time point whereas the expression of PTGS2 was up-regulated at 2 hours after drug administration. In contrast, Naito et al. (2007) reported that the expression of PTGS1 in the gastric mucosa was up-regulated at 2 hours after indomethacin administration. Although the relationship between COX and gastric damage has not been fully elucidated, other elements such as MMPs may be involved in the pathogenic mechanism.
In summary, this study demonstrated that APAP suppresses IBP-induced gastric damage in a dose-dependent manner. Administration of APAP down-regulated the expression of genes related to inflammation and ECM degradation that were up-regulated by IBP during gastric damage. Down-regulation of IL-1β, CCL2, MMP-10, MMP-13, and FOS genes was also related to gastroprotection by APAP. In particular, there was a significant reduction in the expression of MMP-13 by APAP, which decreased IBP-induced gastric damage. Collectively, these findings suggest that suppression of MMPs forms an essential part of the gastroprotective effects of APAP. Further studies of the key molecules that regulate catabolic–anabolic balance in the gastric mucosa are essential for understanding the gastrotoxic mechanisms of NSAIDs and gastroprotection by APAP.
The authors thank Kenji Saito of the Organization for Interdisciplinary Research Projects, the University of Tokyo, for helpful comments.
Participated in research design: Fukushima, Monoi, Serizawa, Adachi, Koide, Ohdera, Murakoshi, Kato.
Conducted experiments: Fukushima, Monoi, Mikoshiba, Hirayama.
Performed data analysis: Fukushima, Monoi, Kato.
Wrote or contributed to the writing of the manuscript: Fukushima, Serizawa, Murakoshi, Kato.
- Received September 26, 2013.
- Accepted February 3, 2014.
- activator protein-1
- acetaminophen, N-(4-hydroxyphenyl) acetamide
- chemokine (C-C motif) ligand 2
- N-[4-(4-morpholinyl) butyl]-2-benzofurancarboxamide
- extracellular matrix
- FBJ osteosarcoma oncogene
- glyceraldehyde-3-phosphate dehydrogenase
- ibuprofen, 2-[4-(2-methylpropyl) phenyl] propanoic acid
- Ingenuity pathway analysis
- liver X receptor
- matrix metalloproteinase
- nonsteroidal anti-inflammatory drug
- polymerase chain reaction
- prostaglandin endoperoxide synthase
- retinoid X receptor
- Copyright © 2014 by The American Society for Pharmacology and Experimental Therapeutics