Search

Your search keyword '"Gribar, Steven C."' showing total 22 results
Start Over Author "Gribar, Steven C."
22 results on '"Gribar, Steven C."'

3. Interferon-[gamma] inhibits enterocyte migration by reversibly displacing connexin43 from lipid rafts

Author

Leaphart, Cynthia L., Dai, Shipan, Gribar, Steven C., Richardson, Ward, Ozolek, John, Shi, Xia-hua, Bruns, Jennifer R., Branca, Maria, Li, Jun, Weisz, Ora A., Sodhi, Chhinder, and Hackam, David J.

Subjects
Interferon gamma -- Properties, Cell migration -- Evaluation, Cell junctions -- Properties, Enterocolitis, Neonatal necrotizing -- Development and progression, Enterocolitis, Pseudomembranous -- Development and progression, Cytokines -- Properties, Biological sciences
Abstract

Necrotizing enterocolitis (NEC) is associated with the release of interferon-[gamma] (IFN) by enterocytes and delayed intestinal restitution. Our laboratory has recently demonstrated that IFN inhibits enterocyte migration by impairing enterocyte gap junctions, intercellular channels that are composed of connexin43 (Cx43) monomers and that are required for enterocyte migration to occur. The mechanisms by which IFN inhibits gap junctions are incompletely understood. Lipid rafts are cholesterol-sphingolipid-rich microdomains of the plasma membrane that play a central role in the trafficking and signaling of various proteins. We now hypothesize that Cx43 is present on enterocyte lipid rafts and that IFN inhibits enterocyte migration by displacing Cx43 from lipid rafts in enterocytes. We now confirm our previous observations that intestinal restitution is impaired in NEC and demonstrate that Cx43 is present on lipid rafts in IEC-6 enterocytes. We show that lipid rafts are required for enterocyte migration, that IFN displaces Cx43 from lipid rafts, and that the phorbol ester phorbol 12-myristate 13-acetate (PMA) restores Cx43 to lipid rafts after treatment with IFN in a protein kinase C-dependent manner. IFN also reversibly decreased the phosphorylation of Cx43 on lipid rafts, which was restored by PMA. Strikingly, restoration of Cx43 to lipid rafts by PMA or by transfection of enterocytes with adenoviruses expressing wild-type Cx43 but not mutant Cx43 is associated with the restoration of enterocyte migration after IFN treatment. Taken together, these findings suggest an important role for lipid raft-Cx43 interactions in the regulation of enterocyte migration during exposure to IFN, such as NEC. gap junctions; connexin; necrotizing enterocolitis; cytokine; phorbol ester

Published
2008

4. Activated macrophages inhibit enterocyte gap junctions via the release of nitric oxide

Author

Anand, Rahul J., Dai, Shipan, Rippel, Christopher, Leaphart, Cynthia, Qureshi, Faisal, Gribar, Steven C., Kohler, Jeff W., Li, Jun, Stolz, Donna Beer, Sodhi, Chhinder, and Hackam, David J.

Subjects
Macrophages -- Influence, Macrophages -- Physiological aspects, Epithelial cells -- Properties, Junctional complexes (Epithelium) -- Properties, Nitric oxide -- Influence, Nitric oxide -- Physiological aspects, Enterocolitis, Neonatal necrotizing -- Physiological aspects, Enterocolitis, Pseudomembranous -- Physiological aspects, Cell migration -- Research, Biological sciences
Abstract

Enterocytes exist in close association with tissue macrophages, whose activation during inflammatory processes leads to the release of nitric oxide (NO). Repair from mucosal injury requires the migration of enterocytes into the mucosal defect, a process that requires connexin43 (Cx43)-mediated gap junction communication between adjacent enterocytes. Enterocyte migration is inhibited during inflammatory conditions including necrotizing enterocolitis, in part, through impaired gap junction communication. We now hypothesize that activated macrophages inhibit gap junctions of adjacent enterocytes and seek to determine whether NO release from macrophages was involved. Using a coculture system of enterocytes and macrophages, we now demonstrate that 'activation' of macrophages with lipopolysaccharide and interferon reduces the phosphorylation of Cx43 in adjacent enterocytes, an event known to inhibit gap junction communication. The effects of macrophages on enterocyte gap junctions could be reversed by treatment of macrophages with the inducible nitric oxide synthase (iNOS) inhibitor L-Lysine [omega]-acetamidine hydrochloride (L-NIL) and by incubation with macrophages from [iNOS.sup.-/-] mice, implicating NO in the process. Activated macrophages also caused a NO-dependent redistribution of connexin43 in adjacent enterocytes from the cell surface to an intracellular location, further suggesting NO release may inhibit gap junction function. Treatment of enterocytes with the NO donor S-nitroso-N-acetylpenicillamine (SNAP) markedly inhibited gap junction communication as determined using single cell microinjection of the gap junction tracer Lucifer yellow. Strikingly, activated macrophages inhibited enterocyte migration into a scraped wound, which was reversed by L-NIL pretreatment. These results implicate enterocyte gap junctions as a target of the NO-mediated effects of macrophages during intestinal inflammation, particularly where enterocyte migration is impaired. inflammation; intestinal restitution; enterocyte migration; necrotizing enterocolitis

Published
2008

5. A Role for Connexin43 in Macrophage Phagocytosis and Host Survival after Bacterial Peritoneal Infection1

Author

Anand, Rahul J., Dai, Shipan, Gribar, Steven C., Richardson, Ward, Kohler, Jeff W., Hoffman, Rosemary A., Branca, Maria F., Li, Jun, Shi, Xiao-Hua, Sodhi, Chhinder P., and Hackam, David J.

Subjects
Male, Mice, Knockout, Macrophages, Peritonitis, Survival Analysis, Article, Cell Line, Mice, Inbred C57BL, Mice, Liver, Connexin 43, Phagosomes, cardiovascular system, Macrophages, Peritoneal, Animals, Humans, Female, sense organs, biological phenomena, cell phenomena, and immunity, Escherichia coli Infections, HeLa Cells
Abstract

The pathways that lead to the internalization of pathogens via phagocytosis remain incompletely understood. We now demonstrate a previously unrecognized role for the gap junction protein connexin43 (Cx43) in the regulation of phagocytosis by macrophages and in the host response to bacterial infection of the peritoneal cavity. Primary and cultured macrophages were found to express Cx43, which localized to the phagosome upon the internalization of IgG-opsonized particles. The inhibition of Cx43 using small interfering RNA or by obtaining macrophages from Cx43 heterozygous or knockout mice resulted in significantly impaired phagocytosis, while transfection of Cx43 into Fc-receptor expressing HeLa cells, which do not express endogenous Cx43, conferred the ability of these cells to undergo phagocytosis. Infection of macrophages with adenoviruses expressing wild-type Cx43 restored phagocytic ability in macrophages from Cx43 heterozygous or deficient mice, while infection with viruses that expressed mutant Cx43 had no effect. In understanding the mechanisms involved, Cx43 was required for RhoA-dependent actin cup formation under adherent particles, and transfection with constitutively active RhoA restored a phagocytic phenotype after Cx43 inactivation. Remarkably, mortality was significantly increased in a mouse model of bacterial peritonitis after Cx43 inhibition and in Cx43 heterozygous mice compared with untreated and wild-type counterparts. These findings reveal a novel role for Cx43 in the regulation of phagocytosis and rearrangement of the F-actin cytoskeleton, and they implicate Cx43 in the regulation of the host response to microbial infection.

Published
2008

11. The NOD2 agonist muramyl-di-peptide (MDP) reverses the inhibitory effects of TLR4 activation on enterocyte proliferation through effects on beta-catenin signaling, and attenuates the severity of experimental necrotizing enterocolitis

Author

Richardson, Ward M., primary, Shi, Xiao-Hua, additional, Gribar, Steven C., additional, Branca, Maria, additional, Dubowski, Theresa, additional, Li, Jun, additional, Sodhi, Chhindler, additional, and Hackam, David J., additional

Published
2008
Full Text
View/download PDF

14. Increased expression and internalization of the endotoxin coreceptor CD14 in enterocytes occur as an early event in the development of experimental necrotizing enterocolitis

Author

Mollen, Kevin P., primary, Gribar, Steven C., additional, Anand, Rahul J., additional, Kaczorowski, David J., additional, Kohler, Jeffrey W., additional, Branca, Maria F., additional, Dubowski, Theresa D., additional, Sodhi, Chhinder P., additional, and Hackam, David J., additional

Published
2008
Full Text
View/download PDF

16. 204. The TLR9 Agonist CpG-DNA Protects Against LPS-Induced Enterocyte Apoptosis Through the Up-Regulation of Heat Shock Protein 70 and Reduces the Severity of Necrotizing Enterocolitis in Mice

Author

Gribar, Steven C., primary, Evans, Anna C., additional, Richardson, Ward M., additional, Anand, Rahul J., additional, Kohler, Jeffrey W., additional, Branca, Maria F., additional, Dubowski, Theresa D., additional, Li, Jun, additional, Sodhi, Chhinder P., additional, and Hackam, David J., additional

Published
2008
Full Text
View/download PDF

22. The role of epithelial Toll‐like receptor signaling in the pathogenesis of intestinal inflammation

Author

Gribar, Steven C., Anand, Rahul J., Sodhi, Chhinder P., and Hackam, David J.

Abstract

Emerging evidence suggests that the innate immune system, comprised of Toll‐like receptors (TLRs) and their associated molecules, plays a pivotal role in the regulation of intestinal inflammation and in the response to invading pathogens. Although TLRs are thought to have predominantly beneficial effects in pathogen recognition and bacterial clearance by leukocytes, their dysregulation and unique signaling effects within intestinal epithelia in the setting of inflammation may have devastating consequences. For instance, activation of TLR4 in enterocytes leads to an inhibition of enterocyte migration and proliferation as well as the induction of enterocyte apoptosis—factors that would be expected to promote intestinal injury while inhibiting intestinal repair. TLR signaling has been shown to be abnormal in several intestinal inflammatory diseases, including Crohn’s disease, ulcerative colitis, and necrotizing enterocolitis. This review serves to examine the evidence regarding the patterns of expression and signaling of TLRs in the intestinal mucosa at basal levels and during physiologic stressors to gain insights into the pathogenesis of intestinal inflammation. We conclude that the data reviewed suggest that epithelial TLR signaling—acting in concert with TLR signaling by leukocytes—participates in the development of intestinal inflammation. We further conclude that the evidence reviewed provides a rationale for the development of novel, epithelial‐specific, TLR‐based agents in the management of diseases of intestinal inflammation.

Published
2008
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results