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PERSPECTIVES IN PHARMACOLOGY

The Role of Protein Kinase C Isoforms in Modulating Injury and Repair of the Intestinal Barrier

Section of Gastroenterology and Nutrition, Rush University Medical Center, Chicago, Illinois

Received February 25, 2005; accepted June 30, 2005.

	Abstract

Top Abstract Barrier Function Protein Kinases Future Therapeutic Direction and... References

 
Gastrointestinal cells express a diverse group of protein kinase C (PKC) isoforms that play critical roles in a number of cell functions, including intracellular signaling and barrier integrity. PKC isoforms expressed by gastrointestinal epithelial cells consist of three major PKC subfamilies: conventional isoforms (, 1, 2, and ), novel isoforms (, , , , and µ), and atypical isoforms (, , and ). This review highlights recent discoveries, including our own, that some PKC isoforms in gastrointestinal epithelia monolayer cell culture are involved in injury to, whereas others are involved in protection of, intestinal barrier integrity. For example, certain PKC isoforms aggravate oxidative damage, whereas others protect against it. These findings suggest that the development of agents that selectively activate or inhibit specific PKC isoforms may lead to new therapeutic modalities for important gastrointestinal disorders such as cancer and inflammatory bowel disease.

	Barrier Function

Top Abstract Barrier Function Protein Kinases Future Therapeutic Direction and... References

 
The intestinal barrier is the largest interface between humans and their external environment (Farhadi et al., 2003). As a filter with selective permeability, this interface allows absorption of required nutrients and excludes the penetration of harmful proinflammatory factors, including luminal antigens, microorganisms, and their products. The integrity of the intestinal barrier requires both healthy epithelial cells and a functionally normal paracellular pathway (tight junction). Disruption of the gastrointestinal barrier, on the other hand, permits penetration into the mucosa of normally excluded luminal substances and leads to the initiation or perpetuation of inflammatory processes (Keshavarzian et al., 2000).

An important structure essential for the integrity of both epithelial cells and paracellular transport is the cytoskeleton. This intracellular organelle has an intricate structure that extends throughout the cytosol and is involved in cell-cell contact through adherens junctions on the outer part of cells (Alvia, 1987). The cytoskeleton is also an essential structural component of paracellular pathways, which are controlled by tight junctions between epithelial cells. As might be expected, this pathway is a key regulator of intestinal permeability to macromolecules, such as bacterial byproducts, through dynamic changes in size that occur under various physiological and pathological conditions (Madara, 1990). The cytoskeleton also serves as a pivotal element in maintaining normal structural and functional integrity of all eukaryotic cells, including gastrointestinal epithelium. Predictably, disruption of the cytoskeleton can severely limit cell function and disrupt the structural integrity of the intestinal barrier (Alvia, 1987).

Regulation of intestinal permeability involves a diverse array of intracellular mediators. For example, nitric oxide seems to be an important mediator for regulating intracellular functions and the microcirculation that nourishes cells (Alican and Kubes, 1996). A low level of nitric oxide, which is normally synthesized by constitutional nitric-oxide synthase, is important for maintenance of normal mucosal barrier function. However, overproduction of nitric oxide, which is carried out by inducible nitric-oxide synthase (iNOS), has been identified as a culprit in abnormal intestinal barrier function (Salzman et al., 1995). The mechanism by which nitric oxide overproduction induces intestinal barrier dysfunction is complex and multifactorial. It includes protein oxidation, nitration, S-nitrosylation, cGMP activation, and cellular energy depletion (Alican and Kubes, 1996).

In addition to nitric oxide, other reactive oxygen species (ROS) affect the intestinal barrier. Indeed, ROS has been implicated in the pathophysiology of aging and in numerous chronic disorders, including gastrointestinal disorders (Cross et al., 1987). Thus, although ROS functions as intracellular messengers (e.g., nitric oxide) in normal physiologic signaling cascades triggered by growth factors or cytokines in all cells, including gastrointestinal epithelial cells, (Victor et al., 2000) under pathophysiological conditions, when intracellular levels of ROS increase and overwhelm the cell's antioxidant capacity, damage occurs to cellular macromolecules such as lipids, proteins, and DNA. It is thus not surprising that oxidative stress can lead to intestinal barrier disruption. These dynamics also suggest that damaging and protective agents might modify intestinal permeability by, respectively, increasing or decreasing oxidative tissue damage.

Several other mediators of defense in epithelial cells protect them from noxious stimuli. One is epidermal growth factor (EGF). We and others have shown that EGF can prevent damage to gastrointestinal epithelium (Banan et al., 2002b) by oxidants or ethanol (Banan et al., 1999a). The exact mechanism underlying intracellular EGF signaling is not fully established, but it seems that this factor increases barrier and cytoskeletal integrity through changes in the activity of several protein kinases (Banan et al., 2001b). To understand the consequences of these changes in activity, it is helpful to discuss the intracellular roles of protein kinases.

	Protein Kinases

Top Abstract Barrier Function Protein Kinases Future Therapeutic Direction and... References

 
Protein kinases are key intracellular mediators of signal transduction pathways and are involved various cell functions throughout the body, including membrane dynamics and permeability. This function provides them a pivotal role in barrier function in gastrointestinal epithelium and vascular endothelium. Protein kinases accomplish this regulation by their ability to phosphorylate proteins. Phosphorylation occurs at specific amino acids of proteins (e.g., serine, threonine, and tyrosine) and results in rapid changes in the activity of those proteins or enzymes. For instance, protein kinase A activation increases the ionic conductance of tight junctions without changing gastrointestinal barrier permeability for large molecules. Considering the whole family of the protein kinases, PKC is the one that has been studied more intensely in gastrointestinal epithelium and has been shown to be involved in several vital intracellular pathways, including barrier permeability (Karczewski and Groot, 2000).

PKC is not a single entity but includes a subfamily of kinases that are serine- and threonine-specific, including at least 12 known isoenzymes. These can be classified into three subgroups based on differences in sequence homology and cofactor requirements (Davidson et al., 1994; Banan et al., 2001a). The first subgroup includes conventional or "classic" PKC isoforms and includes PKC-, -1, -2, and -. Classic PKC isoforms require calcium, diacylglycerol, and phospholipids for their activation. The "novel" PKC isoenzymes include PKC-, -, -, -, and -µ, which are similar to the conventional subgroup in that they still require diacylglycerol and phospholipid for activation but are calcium-independent. "Atypical" PKC isoforms are independent of both calcium and diacylglycerol and include PKC-, -, and -. Intestinal epithelial cells express at least 10 isoforms of PKC, including PKC-, PKC-1, PKC-2, PKC-, PKC-, PKC-, PKC-, PKC-, PKC-, and PKC-.

The distribution of PKC in the gastrointestinal tract is not limited to epithelial cells; PKC can be detected in gastrointestinal smooth muscle cells (Di Mari et al., 2003), cells of cajal (Poole et al., 2004) and basal granulated cells (Kawakita et al., 1995). In this review, we only discuss the effects of PKC isoforms of intestinal epithelial cells. The differences in mode of activation, intracellular distribution, tissue expression, and substrate specificity of these isoforms suggest that there may be unique and nonredundant roles in gastrointestinal signal transduction for each isoenzyme. To begin to define these unique roles, we used monolayers of colon cancer intestinal cells as a model with which to study the integrity of intestinal cells and the intestinal barrier.

PKC isoforms in the gastrointestinal tract are involved in several vital intracellular pathways, including cell proliferation/cytostasis (Batlle et al., 1998; Verstovsek et al., 1998; Assert et al., 1999; Umar et al., 2000), cell differentiation (Abraham et al., 1998; Verstovsek et al., 1998; Frey et al., 2001), apoptosis (Chang and Tepperman, 2001; Frey et al., 2001), cell adhesion (Batlle et al., 1998; Hollande et al., 2003), membrane remodeling (Song et al., 1999, 2002), epithelial migration (Andre et al., 1999), transepithelial permeability (Marano et al., 2001), ion secretion (Van den Berghe et al., 1992; Yoo et al., 2001), receptor and brush border enzyme expression (Murray et al., 2002), cytoskeletal modulation (Fasano et al., 1995; Banan et al., 2002a,c,d, 2003a,b, 2004a,b), tight junction modification (Clarke et al., 2000), and epithelial responses to inflammatory (Chang and Tepperman, 2001, 2003), cytotoxic (Tepperman et al., 1999; Chang and Tepperman, 2001), and carcinogenic (Pongracz et al., 1995; Murray et al., 1999, 2002; Perletti et al., 1999; Mullin et al., 2000) mediators. These multiple roles suggest that this group of enzymes is involved in the regulation of the health and damage of epithelial cells and the intestinal barrier. Thus, it is not surprising that these enzymes are modified by a wide variety of physical and physiological stimuli such as age (Balogh et al., 2000), diet (Murray et al., 2002), and hormones (Balogh et al., 2000). Nevertheless, the detailed mechanisms by which PKC isoforms are involved in these vital pathways remains to be elucidated. Moreover, some results are inconsistent and even contradictory. Herein we review known functions of individual PKC isoforms and suggest a model that may be helpful for understanding the cellular functions of this group of enzymes.

Conventional PKCs
PKC-. PKC- has been associated with several cell functions. Mullin et al. (2000) and Marano et al. (2000) showed that phorbol ester tumor promoters, which are general PKC activators, cause immediate translocation of PKC- from cytosolic- to membrane-associated compartments. This translocation is associated with paracellular leakiness and multilayered cell growth. This effect is attenuated by transfection of cells with dominant-negative-transfected cells for PKC- (Mullin et al., 2000). Song et al. (2002) showed that the effect of PKC- on membrane remodeling is mainly mediated through stabilizing F-actin (the polymerized form; G-actin is the soluble form), and this effect opposes the effect of PKC-, which is the key isoform responsible for early actin disruption and basolateral membrane endocytosis induced by phorbol ester. Although Van den Berghe et al. (1992) noticed over a decade ago that activation of PKC- is associated with ion secretion, the recent study by Song et al. (2002) showed that phorbol ester myristate acetate activated PKC- and PKC-. Phorbol ester myristate acetate activation resulted in the redistribution of PKC- in basolateral membranes, which was associated with Cl^– secretion; the redistribution of PKC- predominantly in apical membranes, which was associated with the modulation of transepithelial resistance (Song et al., 2002); increased epithelial permeability in an ex vivo model (Berin and Buell, 1995); and eventually intestinal inflammation in in vivo models (Brown et al., 1999). Although Fasano et al. (1995) showed that zonula occludens toxin increases tight junction permeability and actin rearrangement through activation of PKC-, recent studies did not confirm any significant changes in the composition and or localization of tight junction proteins, including occludin and zonula occludens-1 (Marano et al., 2001). This was also demonstrated by Hollande et al. (2003), who showed that adherens junctions but not tight junctions are modulated by PKC-. In addition, activation of PKC- is associated with inactivation of E-cadherin, a key factor in the regulation of cell-cell contact, and might be the reason for multilayered cell growth (Batlle et al., 1998; Mullin et al., 2000).

The role of PKC- in epithelial cell proliferation and differentiation is even more complex. Studies show that increases in the total amount of PKC enzyme is associated with the cessation of cell proliferation and increasing cell maturation (Assert et al., 1999). Several investigators noted that there is a trend toward an increase in PKC- as epithelial cells move from the mitotic phase in the crypt to the differentiating phase in the villous (Verstovsek et al., 1998). Other studies found that phorbol esters result in parallel activation of PKC- and retardation of epithelial cell growth in a cell culture model (Batlle et al., 1998). However, measurements of PKC- in colonic cancer tissue and the comparison of that with healthy mucosa has yielded conflicting results. Some studies show that the amount of PKC- is decreased in polyp and cancer tissue (Perletti et al., 1999), whereas other studies did not find any differences (Pongracz et al., 1995; Banan et al., 2001a) or even found increases in the level of cytosolic PKC- (Assert et al., 1999). Using a Caco-2 cell monolayer model, Abraham et al. (1998) showed PKC- but not other PKCs are involved in proliferation/differentiation through a pathway involving p21waf1, a cyclin-dependent kinase inhibitor. Overall, it was concluded that PKC- is involved in the process of cell maturation and proliferation and that its activation might result in multilayer cell proliferation and modulation of lateral cell-to-cell connections and transepithelial resistance.

PKC-. A role for the PKC-1 isoform of PKC has mainly been explored in the field of barrier function (Karczewski and Groot, 2000). Using monolayers of human Caco-2 cells exposed to oxidants as a model of barrier disruption, we found that protection of barrier integrity is mediated by PKC-1, including stabilization of the microtubule and actin cytoskeletons through EGF or TGF- signaling (Banan et al., 1999a, 2001b). (Fig. 1).

View larger version (21K): [in this window] [in a new window]   Fig. 1. Proposed schema for PKC-1- and PKC--dependent intestinal barrier protection.

PKC-. This is one of the least explored isoforms of the PKC family. It is considered a conventional PKC, but knowledge about it is limited. Andre et al. (1999) showed that PKC- is involved in insulin-like growth factor-induced colonic epithelial cell migration and thus could be important in tissue repair (Andre et al., 1999). This isoform could not be detected in most colonic neoplasms and could not be detected in exfoliated colonocytes (Banan et al., 2001a).

Novel PKCs
PKC-. This isoenzyme is one of the calcium-independent PKC isoforms. However, like classic PKC isoforms, it requires both diacylglycerol and phospholipid for activation. Several recent studies have addressed the role of PKC- in various cellular processes from cytotoxicity and cell barrier protection to proliferation and differentiation. It has been postulated that the cytotoxicity and apoptosis induced by tumor necrosis factor (TNF) during inflammatory processes is mediated through PKC- signaling. Chang and Tepperman (2001) reported that TNF- induced translocation of PKC-, PKC-, and PKC- from cytosol to membrane, and the cytotoxicity and apoptosis induced by TNF- were reduced using inhibitors of PKC- and PKC-. We showed, using a monolayer model, that exposure to oxidants causes PKC- activation and translocation to particulate fractions, which coincided with disruption of barrier integrity (Banan et al., 2002a). Using transfection, we showed that overexpression of PKC- results in increased PKC- in the particulate fraction (active form) and in cellular damage even without exposure of cells to oxidants. In addition, dominant-negative-transfected cells showed 98% inhibition of native PKC- enzyme activity and protected the cell against oxidant-induced injury (Banan et al., 2002a). We pointed out that the mechanism through which PKC- damages cells is tightly associated with iNOS up-regulation, which is a common pathway through which stimuli damage cells (Banan et al., 2003a). Chang and Tepperman (2003) recently reported that the mechanism of injury from PKC- and PKC- activation involves degradation of IB and activation of NFB. These observations suggest a pathway through which PKC- and PKC- exert their cytopathic effects (Fig. 2).

View larger version (21K): [in this window] [in a new window]   Fig. 2. Proposed schema of PKC-- and PKC--dependent intestinal barrier disruption.

PKC-. Nitric oxide-induced cell injury is associated with an increased level of PKC-, and this increase is accompanied by redistribution of PKC- from the cytosolic compartment to the membrane (active) fraction (Tepperman et al., 1999). Through a series of pharmacological experiments using a monolayer model, Yoo et al. (2001) showed that PKC- may inhibit hypoxia-induced secretory responses in epithelial cells. This finding was later reproduced by Saksena et al. (2002), who showed that EGF inhibited basolateral Cl^– secretion through activation of PKC-. Later studies suggested that PKC- has an inhibitory role in TNF-induced barrier dysfunction (Yoo et al., 2001). However, this view was seriously challenged by another study that showed that PKC- mediates cytotoxicity and apoptosis in cells exposed to TNF- (Chang and Tepperman, 2001). On the other hand, Song et al. (1999, 2002) showed that PKC- may have a role in the stimulation of basolateral membrane endocytosis and remodeling, and this effect opposes the PKC- effect on membrane stabilization. Yoo et al. (2003) showed that bryostatin-1-induced changes in barrier function were attenuated by the conventional and novel PKC inhibitor Gö-6850 (but not by the conventional PKC inhibitor Gö-6976 or the PKC inhibitor rottlerin), implicating a novel isoenzyme, likely PKC-.

A role for PKC- in the proliferation and differentiation of epithelial cells has not yet been found. This isoform modulates mucin gene expression in epithelial cells (Hong et al., 1999). In addition, Pongracz et al. (1995) showed that the level of PKC- in tumor tissue is extremely low. However, Perletti et al. (1999) failed to show a significant role for PKC- in a neoplastic phenotype rat model.

PKC-. In a recent study, we showed that the PKC- isoform is a required part of cytoskeletal assembly and barrier function in monolayers (Banan et al., 2004b). The molecular events underlying this novel biological effect of PKC- involves changes in phosphorylation and/or assembly of the cytoskeleton. The ability to alter cytoskeletal and barrier dynamics is a unique function not previously attributed to PKC-.

Atypical PKCs
PKC-. This atypical PKC isoform is independent of both calcium and diacylglycerol, and its functional properties have recently attracted the attention of many scientists in the field of epithelial biology. We reported the initial study of the involvement of PKC- in modulating intestinal barrier function. In our early study, we reported that EGF activated PKC-, PKC-1, and PKC-, and this activation resulted in the redistribution of these enzymes from cytosolic to membrane compartments, which resulted in protection of the intestinal barrier against oxidant-induced damage (Banan et al., 2001b). Later, we used a transfected Caco-2 cell monolayer model and were able to stably over- and underexpress PKC- in these cells. We showed that PKC- is an essential part of EGF-induced protection of the intestinal barrier and that cells with overexpressed PKC- are protected against oxidants even in the absence of EGF. Inhibition of expression of PKC- resulted in attenuation of EGF protection against oxidants and loss of barrier integrity (Banan et al., 2002c). The protective mechanism involved enhanced the stability of the microtubule and cytoskeleton against oxidative stress and was mediated by down-regulation of iNOS (Banan et al., 2002d) and inhibition of the activation of NFB through the suppression of phosphorylation and enhancement of stabilization of IB (Banan et al., 2003b) (Fig. 1).

A role for PKC- in cell proliferation and differentiation is still not fully understood. Pongracz et al. (1995) did not find any difference in the amount of PKC- in tumor tissue compared with normal colon. However, Davidson et al. (1998) used the level of mRNA of this PKC isoform as a marker for neoplastic activity. In their study, Davidson et al. noticed a lower level of PKC- mRNA in fecal samples in a colon carcinogenesis model. In particular, they found that the ratio of PKC-2/PKC- mRNA was useful as a noninvasive marker for the surveillance of colon cancer (Davidson et al., 1998). Verstovsek et al. (1998) also showed a relatively low level of PKC-, particularly in the cytosolic compartment in proliferating cells of the crypt base. As these cells cease proliferation and start differentiation, they move toward the villi, a process that coincides with increases in the level of PKC-, particularly in the membrane- and cytoskeletal-associated form. Umar et al. (2000) successfully fractionated PKC- into three cellular fractions, PKC- holoenzyme, catalytic subunit, and membrane-bound fragment, and noticed that all three types are associated with enhanced mitosis in colonocytes in a transmissible murine colon hyperplasia.

PKC-. This atypical PKC isoform has the ability to induce oxidant-like injury, including cytoskeletal depolymerization and instability. In fact, in our recent study, we showed that oxidant induces disruption of epithelial barrier integrity, in large part through activation of the PKC- isoform (Banan et al., 2004a). The cells that did not express endogenous PKC- because of having been transfected with a dominant-negative gene were protected against all measures of oxidant-induced disruption. The ability to cause oxidative tissue damage is a novel mechanism not previously attributed to the atypical subfamily of PKC isoforms.

	Future Therapeutic Direction and Conclusions

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Although PKC isoforms modulate almost all vital functions of cells, our knowledge of their mechanisms is limited. This is due to several experimental impediments in this field. The most important is the lack of specific activators and inhibitors of PKC isoforms, which would be important pharmacologic tools in the investigation of these PKC isoforms. In addition, the very fact that PKC isoenzymes are involved in so many biological functions of cells makes it hard to experimentally isolate individual intracellular pathways in cells without interfering with parallel pathways. Moreover, compartment-specific PKC isoforms (e.g., membrane-associated, nuclear, or cytosolic) or subisoforms (e.g., PKC-1 and PKC-2) might have different or even opposite functions, and this makes interpreting experimental outcomes difficult. In addition, most PKC studies use an intestinal monolayer model made of colon cancer cells, which might be a potential source of conflicting results. These malignant cells may behave differently compared with normal intestinal epithelial cells in culture, in vivo gastrointestinal epithelia, or even to other cells in the body. Another issue is deciding what protection and/or damage mean. For example, in an in vitro model, a protective PKC isoform may protect the cell against damage by noxious stimuli (e.g., oxidants), but in an in vivo model, this same PKC isoform may protect cancer cells against immune system attack and thus promote cancer cell survival. Should we consider this PKC as protective?

Despite these difficulties in investigating the roles of different PKC isoforms in biological models, progress has been made in investigating PKC status in various gastrointestinal diseases. For example, PKC activators and inhibitors have been used with some success in animal models of colitis. As mentioned earlier, generalized PKC activation induces colitis in animal models, whereas generalized PKC inhibition protects against the development of colitis. It seems that the barrier integrity of gastrointestinal epithelium coincides with a homeostatic balance among various PKC isoforms, and imbalances in this homeostasis can result in either barrier dysfunction or barrier overprotection. PKC-, PKC-, PKC-, and PKC- seem to be involved in epithelial barrier dysfunction, whereas PKC-1, PKC-, and PKC- protect barrier integrity. PKC-, PKC-2, PKC-, and PKC- are involved in cell proliferation and possibly, therefore, carcinogenesis. Increasing our knowledge of the basic functions of the various isoforms of PKC will make it possible to develop specific activators and inhibitors of individual PKC isoenzymes, and this should lead to our ability to dissect individual PKC functions. It should also lead to new and improved strategies for the management of gastrointestinal disorders. As we enter this largely untapped area, several basic questions will have to be answered. Why is there so much diversity in the cellular functions that PKC isoenzymes mediate? Why do many PKC isoforms protect cells and barrier function, whereas other PKC isoforms cause damage? Why should cells harbor damaging factors? Could this mechanism be useful for controlling cell differentiation and proliferation? Or could this mechanism be part of programmed cell death (apoptosis)? Our ability to answer these questions is at present limited. Fortunately, however, new techniques and agents are continually being developed in pharmacology and molecular biology studies and hold promise for helping to answer the above questions. This should lead to new insights into PKC-mediated intracellular mechanisms and may open new windows for the treatment of a variety of disorders.

	Footnotes

 
doi:10.1124/jpet.105.085449.

ABBREVIATIONS: PKC, protein kinase C; iNOS, inducible nitric-oxide synthase; ROS, reactive oxygen species; EGF, epidermal growth factor; TGF, transforming growth factor; NF, nuclear factor; TNF, tumor necrosis factor; Gö6850, 3-[1-[-3-(dimethylaminopropyl]-1H-indol-3-yl]-4-(1H-indol-3-yl)-1H-pyrrole-2,5-dione monohydrochloride; Gö-6976, 1-[6-[(3-acetyl-2,4,6-trihydroxy-5-methylphenyl)methyl]-5,7-dihydroxy-2,2-dimethyl-2H-1-benzopyran-8-yl]-3-phenyl-2-propen-1-one mallotoxin.

Address correspondence to: Dr. Ashkan Farhadi, Rush University Medical Center, Division of Digestive Diseases, 1725 W. Harrison, Suite 206, Chicago, IL 60612. E-mail: ashkan_farhadi{at}rush.edu

	References

Top Abstract Barrier Function Protein Kinases Future Therapeutic Direction and... References

 

Abraham C, Scaglione-Sewell B, Skarosi SF, Qin W, Bissonnette M, and Brasitus TA (1998) Protein kinase C alpha modulates growth and differentiation in Caco-2 cells. Gastroenterology 114: 503–509.[CrossRef][Medline]

Alican I and Kubes P (1996) A critical role for nitric oxide in intestinal barrier function and dysfunction. Am J Physiol 270: G225–G237.[Medline]

Alvia J (1987) Microtubule function. Life Sci 50: 327–333.[CrossRef]

Andre F, Rigot V, Remacle-Bonnet M, Luis J, Pommier G, and Marvaldi J (1999) Protein kinases C-gamma and -delta are involved in insulin-like growth factor I-induced migration of colonic epithelial cells. Gastroenterology 116: 64–77.[CrossRef][Medline]

Assert R, Kotter R, Bisping G, Scheppach W, Stahlnecker E, Muller KM, Dusel G, Schatz H, and Pfeiffer A (1999) Anti-proliferative activity of protein kinase C in apical compartments of human colonic crypts: evidence for a less activated protein kinase C in small adenomas. Int J Cancer 80: 47–53.[CrossRef][Medline]

Balogh G, Boland R, and de Boland AR (2000) 1,25(OH)(2)-vitamin D(3) affects the subcellular distribution of protein kinase C isoenzymes in rat duodenum: influence of aging. J Cell Biochem 79: 686–694.[CrossRef][Medline]

Banan A, Choudhary S, Zhang Y, Fields JZ, and Keshavarzian A (1999a) Ethanol-induced barrier dysfunction and its prevention by growth factors in human intestinal monolayers: evidence for oxidative and cytoskeletal mechanisms. J Pharmacol Exp Ther 291: 1075–1085.[Abstract/Free Full Text]

Banan A, Farhadi A, Fields JZ, Zhang LJ, Shaikh M, and Keshavarzian A (2003a) The -isoform of protein kinase C causes inducible nitric-oxide synthase and nitric oxide up-regulation: key mechanism for oxidant-induced carbonylation, nitration and disassembly of the microtubule cytoskeleton and hyperpermeability of barrier of intestinal epithelia. J Pharmacol Exp Ther 305: 482–494.[Abstract/Free Full Text]

Banan A, Fields JZ, Farhadi A, Talmage DA, Zhang L, and Keshavarzian A (2002a) Activation of -isoform of protein kinase C is required for oxidant-induced disruption of both the microtubule cytoskeleton and permeability barrier of intestinal epithelia. J Pharmacol Exp Ther 303: 17–28.[Abstract/Free Full Text]

Banan A, Fields JZ, Farhadi A, Talmage DA, Zhang L, and Keshavarzian A (2002b) The beta 1 isoform of protein kinase C mediates the protective effects of epidermal growth factor on the dynamic assembly of F-actin cytoskeleton and normalization of calcium homeostasis in human colonic cells. J Pharmacol Exp Ther 301: 852–866.[Abstract/Free Full Text]

Banan A, Fields JZ, Talmage DA, Zhang L, and Keshavarzian A (2002c) PKC-zeta is required in EGF protection of microtubules and intestinal barrier integrity against oxidant injury. Am J Physiol Gastrointest Liver Physiol 282: G794–G808.[Abstract/Free Full Text]

Banan A, Fields JZ, Talmage DA, Zhang Y, and Keshavarzian A (2001a) PKC-beta1 mediates EGF protection of microtubules and barrier of intestinal monolayers against oxidants. Am J Physiol Gastrointest Liver Physiol 281: G833–G847.[Abstract/Free Full Text]

Banan A, Fields JZ, Zhang LJ, Shaikh M, Farhadi A, and Keshavarzian A (2003b) Isoform of protein kinase C prevents oxidant-induced nuclear factor-B activation and I-B degradation: a fundamental mechanism for epidermal growth factor protection of the microtubule cytoskeleton and intestinal barrier integrity. J Pharmacol Exp Ther 307: 53–66.[Abstract/Free Full Text]

Banan A, Fields JZ, Zhang Y, and Keshavarzian A (2001b) Key role of PKC and Ca2+ in EGF protection of microtubules and intestinal barrier against oxidants. Am J Physiol Gastrointest Liver Physiol 280: G828–G843.[Abstract/Free Full Text]

Banan A, Zhang L, Farhadi A, Fields JZ, Shaikh M, Forsyth CB, Choudhary S, and Keshavarzian A (2004a) Critical role of the atypical isoform of PKC (PKC-) in oxidant-induced disruption of the microtubule cytoskeleton and barrier function of intestinal epithelium. J Pharmacol Exp Ther 312: 458–471.[CrossRef][Medline]

Banan A, Zhang L, Fields JZ, Farhadi A, Talmage DA, and Keshavarzian A (2002d) PKC-zeta prevents oxidant-induced iNOS upregulation and protects the microtubules and gut barrier integrity. Am J Physiol Gastrointest Liver Physiol 283: G909–G922.[Abstract/Free Full Text]

Banan A, Zhang LJ, Shaikh M, Fields JZ, Farhadi A, and Keshavarzian A (2004b) Theta-isoform of PKC is required for alterations in cytoskeletal dynamics and barrier permeability in intestinal epithelium: a novel function for PKC-theta. Am J Physiol Cell Physiol 287: C218–C234.[Abstract/Free Full Text]

Batlle E, Verdu J, Dominguez D, del Mont Llosas M, Diaz V, Loukili N, Paciucci R, Alameda F, and de Herreros AG (1998) Protein kinase C-alpha activity inversely modulates invasion and growth of intestinal cells. J Biol Chem 273: 15091–15098.[Abstract/Free Full Text]

Berin MC and Buell MG (1995) Phorbol myristate acetate ex vivo model of enhanced colonic epithelial permeability. Reactive oxygen metabolitic and protease independence. Dig Dis Sci 40: 2268–2279.[CrossRef][Medline]

Brown JF, Chang Q, Soper BD, and Tepperman BL (1999) Protein kinase C mediates experimental colitis in the rat. Am J Physiol Gastrointest Liver Physiol 276: G583–G590.[Abstract/Free Full Text]

Chang Q and Tepperman BL (2003) Effect of selective PKC isoform activation and inhibition on TNF-alpha-induced injury and apoptosis in human intestinal epithelial cells. Br J Pharmacol 140: 41–52.[CrossRef][Medline]

Chang Q and Tepperman BL (2001) The role of protein kinase C isozymes in TNF-alpha-induced cytotoxicity to a rat intestinal epithelial cell line. Am J Physiol Gastrointest Liver Physiol 280: G572–G583.[Abstract/Free Full Text]

Clarke H, Marano CW, Peralta Soler A, and Mullin JM (2000) Modification of tight junction function by protein kinase C isoforms. Adv Drug Deliv Rev 41: 283–301.[CrossRef][Medline]

Cross CE, Halliwell B, Borish ET, Pryor WA, Ames BN, Saul RL, McCord JM, and Harman D (1987) Oxygen radicals and human disease. Ann Intern Med 107: 526–545.[Abstract/Free Full Text]

Davidson LA, Aymond CM, Jiang YH, Turner ND, Lupton JR, and Chapkin RS (1998) Non-invasive detection of fecal protein kinase C betaII and zeta messenger RNA: putative biomarkers for colon cancer. Carcinogenesis 19: 253–257.[Abstract/Free Full Text]

Davidson LA, Jiang YH, Derr JN, Aukema HM, Lupton JR, and Chapkin RS (1994) Protein kinase C isoforms in human and rat colonic mucosa. Arch Biochem Biophys 312: 547–553.[CrossRef][Medline]

Di Mari JF, Mifflin RC, Adegboyega PA, Saada JI, and Powell DW (2003) IL-1alpha-induced COX-2 expression in human intestinal myofibroblasts is dependent on a PKCzeta-ROS pathway. Gastroenterology 124: 1855–1865.[CrossRef][Medline]

Farhadi A, Banan A, Fields J, and Keshavarzian A (2003) Intestinal barrier: an interface between health and disease. J Gastroenterol Hepatol 18: 479–497.[CrossRef][Medline]

Fasano A, Fiorentini C, Donelli G, Uzzau S, Kaper JB, Margaretten K, Ding X, Guandalini S, Comstock L, and Goldblum SE (1995) Zonula occludens toxin modulates tight junctions through protein kinase C-dependent actin reorganization, in vitro. J Clin Investig 96: 710–720.[Medline]

Frey MR, Leontieva O, Watters DJ, and Black JD (2001) Stimulation of protein kinase C-dependent and -independent signaling pathways by bistratene A in intestinal epithelial cells. Biochem Pharmacol 61: 1093–1100.[CrossRef][Medline]

Hollande F, Lee DJ, Choquet A, Roche S, and Baldwin GS (2003) Adherens junctions and tight junctions are regulated via different pathways by progastrin in epithelial cells. J Cell Sci 116: 1187–1197.[Abstract/Free Full Text]

Hong DH, Petrovics G, Anderson WB, Forstner J, and Forstner G (1999) Induction of mucin gene expression in human colonic cell lines by PMA is dependent on PKC-epsilon. Am J Physiol 277: G1041–G1047.[Medline]

Karczewski J and Groot J (2000) Molecular physiology and pathophysiology of tight junction III. Tight junction regulation by intracellular messengers: differences in response within and between epithelia. Am J Physiol Gastrointest Liver Physiol 279: G660–G665.[Abstract/Free Full Text]

Kawakita N, Nagahata Y, Saitoh Y, and Ide C (1995) Protein kinase C alpha-, beta- and gamma-subspecies in basal granulated cells of rat duodenal mucosa. Anat Embryol 191: 329–336.[CrossRef][Medline]

Keshavarzian A, Sedghi S, Kanofsky J, List T, Robinson C, Ibrahim C, and Winship D (2000) Excessive production of reactive oxygen metabolites by inflamed colon: analysis by chemiluminescence probe. Gastroenterology 103: 177–185.

Madara JL (1990) Pathobiology of the intestinal epithelial barrier. Am J Pathol 137: 1273–1281.[Abstract]

Marano CW, Garulacan LA, Ginanni N, and Mullin JM (2001) Phorbol ester treatment increases paracellular permeability across IEC-18 gastrointestinal epithelium in vitro. Dig Dis Sci 46: 1490–1499.[CrossRef][Medline]

Massoumi R, Larsson C, and Sjolander A (2002) Leukotriene D(4) induces stress-fibre formation in intestinal epithelial cells via activation of RhoA and PKCdelta. J Cell Sci 115: 3509–3515.[Abstract/Free Full Text]

Mullin JM, Laughlin KV, Ginanni N, Marano CW, Clarke HM, and Peralta Soler A (2000) Increased tight junction permeability can result from protein kinase C activation/translocation and act as a tumor promotional event in epithelial cancers. Ann NY Acad Sci 915: 231–236.[Medline]

Murray NR, Davidson LA, Chapkin RS, Clay Gustafson W, Schattenberg DG, and Fields AP (1999) Overexpression of protein kinase C betaII induces colonic hyperproliferation and increased sensitivity to colon carcinogenesis. J Cell Biol 145: 699–711.[Abstract/Free Full Text]

Murray NR, Weems C, Chen L, Leon J, Yu W, Davidson LA, Jamieson L, Chapkin RS, Thompson EA, and Fields AP (2002) Protein kinase C betaII and TGFbetaRII in omega-3 fatty acid-mediated inhibition of colon carcinogenesis. J Cell Biol 157: 915–920.[Abstract/Free Full Text]

Perletti GP, Marras E, Concari P, Piccinini F, and Tashjian AH Jr (1999) PKCdelta acts as a growth and tumor suppressor in rat colonic epithelial cells. Oncogene 18: 1251–1256.[CrossRef][Medline]

Pongracz J, Clark P, Neoptolemos JP, and Lord JM (1995) Expression of protein kinase C isoenzymes in colorectal cancer tissue and their differential activation by different bile acids. Int J Cancer 61: 35–39.[Medline]

Poole DP, Van Nguyen T, Kawai M, and Furness JB (2004) Protein kinases expressed by interstitial cells of Cajal. Histochem Cell Biol 121: 21–30.[CrossRef][Medline]

Saksena S, Gill RK, Syed IA, Tyagi S, Alrefai WA, Ramaswamy K, and Dudeja PK (2002) Inhibition of apical Cl–/OH– exchange activity in Caco-2 cells by phorbol esters is mediated by PKC epsilon. Am J Physiol Cell Physiol 283: C1492–C1500.[Abstract/Free Full Text]

Salzman AL, Menconi MJ, Unno N, Ezzell RM, Casey DM, Gonzalez PK, and Fink MP (1995) Nitric oxide dilates tight junction and depletes ATP in cultured Caco-2BBe intestinal epithelial monolayers. Am J Physiol 31: G361–G373.

Song JC, Hrnjez BJ, Farokhzad OC, and Matthews JB (1999) PKC-epsilon regulates basolateral endocytosis in human T84 intestinal epithelia: role of F-actin and MARCKS. Am J Physiol 277: C1239–C1249.[Medline]

Song JC, Rangachari PK, and Matthews JB (2002) Opposing effects of PKCalpha and PKCepsilon on basolateral membrane dynamics in intestinal epithelia. Am J Physiol Cell Physiol 283: C1548–C1556.[Abstract/Free Full Text]

Tepperman BL, Chang Q, and Soper BD (1999) The involvement of protein kinase C in nitric oxide-induced damage to rat isolated colonic mucosal cells. Br J Pharmacol 128: 1268–1274.[CrossRef][Medline]

Umar S, Sellin JH, and Morris AP (2000) Increased nuclear translocation of catalytically active PKC-zeta during mouse colonocyte hyperproliferation. Am J Physiol Gastrointest Liver Physiol 279: G223–G237.[Abstract/Free Full Text]

Van den Berghe N, Vaandrager AB, Bot AG, Parker PJ, and de Jonge HR (1992) Dual role for protein kinase C alpha as a regulator of ion secretion in the HT29cl. 19A human colonic cell line. Biochem J 285: 673–679.[Medline]

Verstovsek G, Byrd A, Frey MR, Petrelli NJ, and Black JD (1998) Colonocyte differentiation is associated with increased expression and altered distribution of protein kinase C isozymes. Gastroenterology 115: 75–85.[CrossRef][Medline]

Victor J, Fanburg TL, and Fanburg BL (2000) Reactive oxygen species in cell signaling. Am J Physiol 279: L1005–L1028.

Yoo J, Nichols A, Mammen J, Calvo I, Song JC, Worrell RT, Matlin K, and Matthews JB (2003) Bryostatin-1 enhances barrier function in T84 epithelia through PKC-dependent regulation of tight junction proteins. Am J Physiol Cell Physiol 285: C300–C309.[Abstract/Free Full Text]

Yoo J, Nichols A, Song JC, Mun EC, and Matthews JB (2001) Protein kinase epsilon dampens the secretory response of model intestinal epithelia during ischemia. Surgery 130: 310–318.[CrossRef][Medline]

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