AJP - Gastrointestinal and Liver Physiology, Vol 272, Issue 5 1230-G1235, Copyright © 1997 by American Physiological Society
Regulation of superoxide dismutase in primary cultures of rat colonic smooth muscle cells
C. L. Tannahill, S. A. Stevenot, E. Y. Eaker, J. E. Sallustio, H. S. Nick and J. F. Valentine
Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville, USA.
We have observed a rapid induction of manganese superoxide dismutase
(MnSOD) in epithelial, neuronal, and smooth muscle cells (SMC) after acetic
acid-induced colitis. To examine the regulation of MnSOD in the SMC more
specifically, primary cultures of colonic SMC were developed by enzymatic
digestion of the circular muscle layer from an adult rat. SMC were treated
for 2-72 h with 0.5 microgram/ml Escherichia coli endotoxin
[lipopolysaccharide (LPS)], 10 ng/ml tumor necrosis factor (TNF)-alpha, or
2 ng/ml interleukin-1 beta (IL-1 beta). Cotreatments were performed with
IL-1 beta and 4 microM actinomycin or 50 microM cycloheximide. Northern
analysis demonstrated 23-fold, 8-fold, and 6-fold inductions of MnSOD mRNA
by IL-1 beta, LPS, and TNF-alpha, respectively. Induction of MnSOD by IL-1
beta was eliminated by actinomycin but not by cycloheximide, implicating a
requirement for de novo transcription. Western analysis resulted in a
23.7-fold induction of MnSOD protein after 48-h treatment with IL-1 beta.
Induction of MnSOD by IL-1 beta and other inflammatory mediators may serve
as a protective mechanism to reduce oxygen free radical- and nitric
oxide-mediated cell damage during inflammation.
