Non-lethal endotoxin (LPS) treatment decreases contraction rate and induces nitric oxide synthase activity in cultured rat cardiac myocytes.
Snawder-JE; Mathias-P; Tirmenstein-MA
Toxicologist 1996 Mar; 30(1)(Part 2):270
Sepsis and endotoxic shock often result in myocardial depression. Recently, nitric oxide (NO) production by inflammatory cells and other tissues has been proposed to contribute to this phenomenon. In studies to determine the effect of cytokine stimulated NO production on cardiac myocytes, the inflammatory, cytokines TNF, IFN and IL-1 were found to increase nitrite in cell media over 48 h treatment. TNF, IL1, and IL6 increased contraction rates as did the NO synthase inhibitor NMA. Other researchers have shown that LPS-stimulated macrophages co-cultured with myocytes also increased nitrite production and decreased contraction rates. We investigated the effects of non-lethal concentrations of Escherichia coli endotoxin (LPS) without added cytokines on cultured cardiac myocytes. Parameters measured included- cytotoxicity, myocyte contraction rate, and NO synthesis as measured by nitrate and nitrite present in the culture media. The concentrations of LPS used were not overtly toxic to cells up to 24 h exposure (as measured by LDH release and cell attachment). Nitrite/nitrate in the media remained low at all concentrations from 0 - 4h and then rapidly increased in a concentration dependent manner out to 24 h. Myocyte contraction rate followed a similar response pattern in that from 0 - 4h cells contracted at similar rates regardless of LPS concentration. After 6 h, contraction rates were observed to decrease in a time and concentration-dependent manner with contraction rate inversely correlated to media nitrate/nitrite concentrations. In summary, this research demonstrates that LPS-exposed cardiac myocytes generate NO independent of additional cytokine or other inflammatory/immunological stimulus.
Endotoxins; Laboratory-animals; Animals; Animal-studies; Cardiac-function; Cytotoxins; Cytotoxicity; Cytotoxic-effects; Exposure-levels; Exposure-assessment; Nitrates
The Toxicologist. Society of Toxicology 35th Annual Meeting, March 10-14,1996, Anaheim, California