The contribution of protein kinase C and CPI-17 signaling pathways to hypercontractility in murine experimental colitis E. IHARA, M. CHAPPELLAZ, S. R. TURNER & J. A. MACDONALD Smooth Muscle and Gastrointestinal Research Groups, Department of Biochemistry & Molecular Biology, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada Abstract Background Colonic smooth muscle contractility is altered in colitis, and several protein kinase pathways can mediate colonic smooth muscle contraction. In the present study, we investigated whether protein kinase C (PKC) pathways also play a role in colonic hypercontractility observed during T H 2 colitis in BALB/c mice. Methods Colitis was induced in BALB/c mice by provision of 5% dextran sodium sulfate (DSS) for 7 days. Changes in smooth muscle contractility were examined using dissected circular smooth mus- cle preparations from the distal colon. The contribu- tion of conventional and novel PKC isozymes to the hypercontractile response was examined with phar- macological PKC inhibitors. Western blot analyses were used to examine protein expression and phos- phorylation changes. Key Results Colonic smooth muscle was associated with inflammation-induced hypercontractility and altered PKC expression. Car- bachol-induced peak (phasic) and sustained (tonic) contractions were increased. Chelerythrine was the most effective PKC inhibitor of both phasic and tonic contractions. There was no general difference in the percent contribution of conventional and novel PKC isozymes toward the DSS-induced hypercontractility, but inhibition of sustained force with GF109203x was higher for inflamed muscle. The CPI-17 phosphoryla- tion was equally suppressed in both normal and DSS conditions by Go ¨ 6976 and chelerythrine, but only for the phasic component of contraction. Conclusions & Inferences The outcomes suggest that both conven- tional and novel PKC isozymes contribute to the phasic and tonic contractile components of BALB/c colonic circular smooth muscle under normal condi- tions, with novel PKC isozymes having a greater con- tribution to the tonic contraction. However, no effect of inflammation was observed on the relative contri- bution of PKC and CPI-17 toward the observed hypercontractility. Keywords calcium sensitization, colon, inflam- mation, myosin phosphatase, MYPT1, smooth muscle. INTRODUCTION The coordinated regulation of contraction is a key property of gastrointestinal (GI) smooth muscle, which when functioning normally, contributes to general health and wellness, but when dysfunctional is asso- ciated with morbidity and mortality. 1,2 In overt inflammatory conditions of the bowel, such as Crohn’s disease and ulcerative colitis (i.e., IBD), there have been longstanding observations of altered motility and impaired function of the GI smooth muscle. 3,4 Alter- ations in GI motility with resultant changes in transit can contribute to the abdominal pain, intestinal cramping, and diarrhea characteristically associated with intestinal inflammation. Impairments in GI motility are a common feature of a variety of important disease manifestations of varying etiologies. 5,6 How- ever, a central mechanistic feature of GI dysmotility is an alteration in the contractile processes that occur at the level of the GI smooth muscle. Smooth muscle contraction is a highly regulated process but is ultimately governed by the phosphory- lation of the regulatory light chain (LC 20 ) of myosin II Address for Correspondence Justin A. MacDonald, Department of Biochemistry & Molecular Biology, Faculty of Medicine, University of Calgary, 3280 Hospital Drive N.W., Calgary, Alberta, T2N 4Z6, Canada. Tel: +403 210 8433; fax: +403 270 2211; e-mail: jmacdo@ucalgary.ca Received: 22 April 2011 Accepted for publication: 26 September 2011 Neurogastroenterol Motil (2012) 24, e15–e26 doi: 10.1111/j.1365-2982.2011.01821.x Ó 2011 Blackwell Publishing Ltd e15 Neurogastroenterology & Motility