Date of Award

Spring 5-21-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Science

First Advisor

Dennis W. McGee

Abstract

Inflammatory Bowel Disease (IBD) affects over 1 million Americans and can cause severe tissue damage and even death. TNF-α is a pro-inflammatory cytokine that is elevated in IBD and plays a central role in inflammation. Previous results in our laboratory showed that another cytokine, IL-1β, induces chemokine expression in intestinal epithelial cells (IEC), which is mediated by Rho-associated kinase (ROCK). Because ROCK may be an important mediator of inflammation, we extended our investigations to examine the role of ROCK in TNF-α-stimulated chemokine responses in IEC. Inhibiting ROCK with the Y-27632 compound resulted in a significant, but incomplete, suppression of TNF-α-induced CXCL8 expression in Caco-2 cells, indicating that ROCK is required for optimal CXCL8 production in IEC. ROCK inhibition also blocked TNF-α-stimulated JNK phosphorylation in Caco-2 cells but did not affect NF-κB activation, suggesting an explanation for the partial suppression of CXCL8, as CXCL8 is under the control of both NF-κB and the JNK-activated AP-1 transcription factor. Unlike CXCL8, the production of TNF-α-induced CCL2 and CCL20 expression was enhanced by ROCK inhibition in Caco-2 cells, indicating that ROCK activity had a suppressive effect on these responses. Further experiments showed that the ROCK-dependent suppression was likely mediated by ERK since the MEK/ERK inhibitor, PD98059, had the same enhancement effect as the ROCK inhibitor on TNF-α-induced CCL2 secretion. These results suggest that ROCK plays a complex role in chemokine production in IEC. Furthermore, since ROCK appears to control the expression of several pro-inflammatory mediators, ROCK may be a promising therapeutic target for IBD.

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