The overall objective of the proposed research is to explain the molecular mechanism of adenylate cyclase-activating enterotoxins (e.g., cholera toxin). If time permits, additional experiments will also be performed with purified Salmonella enterotoxin, Escherichia coli LT, and Aeromonas hydrophila enterotoxin. Preliminary studies indicate that synthesis of prostaglandins and protein is markedly enhanced in enterotoxin-stimulated cells and that levels of prostaglandins and H3-leucine incorporation are closely regulated by cyclic AMP concentration. The involvement of prostaglandins in the mode of action of enterotoxins provides a mechanism whereby the effect of enterotoxins on the adenylate cyclase system is substantially amplified. Available data has led to the formulation of a working hypothesis to explain these metabolic interactions in enterotoxin-affected cells involving the adenylate cyclase system and the synthesis of proteins and prostaglandins. In order to test the hypothesis that prostaglandins and protein synthesis are important in the mode of action of adenylate cyclase-activating enterotoxins, antimetabolites will be used in conjunction with tissue culture cells exposed to cholera toxin. Specifically, enterotoxin-treated and control cells will be subjected to protein synthesis blockade using actinomycin D and cycloheximide, while levels of cyclic AMP, H3-leucine incorporation, and prostaglandins will be measured. Similarly, prostaglandin synthesis will be blocked by such drugs as aspirin and indomethacin, and levels of cyclic AMP, H3-leucine incorporation, and prostaglandins will be determined. The sequential effect on cellular levels of cyclic AMP, H3-leucine incorporation, and prostaglandins in enterotoxin-treated cells will be measured in both Chinese hamster ovary (CHO) cells and epithelial cells from rabbit intestinal loops challenged with enterotoxin-producing bacteria. Cholera toxin B subunit will be used to block the binding of cholera toxin to control against membrane perturbation as a cause of prostaglandin synthesis. Finally, selected combinations of drugs, exhibiting antagonistic effects in enterotoxin-treated cells, will be tested for their capacity to protect rabbits against challenge with cholera toxin and enterotoxin-producing bacteria. In summary, this proposal strives to clarify and extend information relating to adenylate cyclase-activating enterotoxins as well as search for possible points for metabolic intervention.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Bacteriology and Mycology Subcommittee 1 (BM)
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University of Texas Medical Br Galveston
Schools of Medicine
United States
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Heming, T A; Tuazon, D M; Dave, S K et al. (2001) Post-transcriptional effects of extracellular pH on tumour necrosis factor-alpha production in RAW 246.7 and J774 A.1 cells. Clin Sci (Lond) 100:259-66
Peterson, J W; King, D; Ezell, E L et al. (2001) Cholera toxin-induced PGE(2) activity is reduced by chemical reaction with L-histidine. Biochim Biophys Acta 1537:27-41
Peterson, J W; Finkelstein, R A; Cantu, J et al. (1999) Cholera toxin B subunit activates arachidonic acid metabolism. Infect Immun 67:794-9
Peterson, J W; Boldogh, I; Popov, V L et al. (1998) Anti-inflammatory and antisecretory potential of histidine in Salmonella-challenged mouse small intestine. Lab Invest 78:523-34
Das, M; Chopra, A K; Cantu, J M et al. (1998) Antisera to selected outer membrane proteins of Vibrio cholerae protect against challenge with homologous and heterologous strains of V. cholerae. FEMS Immunol Med Microbiol 22:303-8
Peterson, J W; Saini, S S; Dickey, W D et al. (1996) Cholera toxin induces synthesis of phospholipase A2-activating protein. Infect Immun 64:2137-43
Peterson, J W; Dickey, W D; Saini, S S et al. (1996) Phospholipase A2 activating protein and idiopathic inflammatory bowel disease. Gut 39:698-704
Peterson, J W; Whipp, S C (1995) Comparison of the mechanisms of action of cholera toxin and the heat-stable enterotoxins of Escherichia coli. Infect Immun 63:1452-61
Peterson, J W; Cantu, J; Duncan, S et al. (1993) Molecular mediators formed in the small intestine in response to cholera toxin. J Diarrhoeal Dis Res 11:227-34
Chopra, A K; Houston, C W; Peterson, J W et al. (1987) Cloning and expression of the Salmonella enterotoxin gene. J Bacteriol 169:5095-100