Abstracts
1998 Digestive Disease Week

#986

ABDOMINAL SURGERY RESULTS IN EARLY STAT PROTEIN ACTIVATION WITHIN THE RAT INTESTINAL MUSCULARIS. J.C. Kalff, C. Hierholzer, W.H. Schraut, T.R. Billiar, D.J. Tweardy and A.J. Bauer. Departments of Surgery and Medicine, University of Pittsburgh, Pittsburgh, PA.

Previously we demonstrated that surgical manipulation of the small intestine causes a massive leukocyte infiltration into the intestinal muscularis that results in an impairment of smooth muscle function. This phenomenon appears to play a key role in the development of postoperative ileus. Since the ICAM-1 gene contains a response element for Stat3 and a Stat3 isoform profile is prototypic for IL-6, we sought to test the hypothesis that surgical manipulation initiates an inflammatory cascade within the muscularis externa consisting of cytokine production (IL-6), Stat3 activation and ICAM-1 upregulation. ACI rats underwent a laparotomy with minor manipulation of the small intestine, unoperated rats served as controls (N=5, each). IL-6 and ICAM-1 mRNA levels measured by quantitative RT-PCR in intestinal muscularis externa RNA extracts demonstrated a significant increase compared to controls postoperatively with a peak at 3 hours (6.0 and 18.8 fold respectively) and a second peak at 24 hours. Electrophoretic mobility shift assay (EMSA) of muscularis protein extracts also demonstrated a marked increase in Stat3 activation measured as protein-hSIE (high-affinity serum-inducible element) complex compared to controls (p<0.05). The time course showed an early peak at 30 minutes and a later peak at 12 hours postoperatively (32.7 and 37.1 fold). Supershift analysis using specific antibodies against Stat3_ and Stat3_ proved that this complex was composed of Stat3_ and Stat3_ as well as a nonsupershifted portion, Stat3_. These data demonstrate that the inflammatory response after surgical manipulation very rapidly includes Stat3 activation in the intestinal muscularis and that this could induce ICAM-1 resulting in leukocyte recruitment. Although contrary to the current IL-6/STAT literature, the later temporal induction of IL-6 within the muscularis compared to the very rapid STAT activation would suggest that a preformed or very rapidly generated mediator initiates the observed Stat3 phosphorylation.

Copyright 1996 - 1998, SSAT, Inc. Revised 29 June 1998.