Nishikawa T, F Sato E, Choudhury T, Nagata K, Kasahara E, Matsui H, Watanabe K, Inoue M. Effect of Nitric Oxide on the Oxygen Metabolism and Growth of E. faecalis.
J Clin Biochem Nutr 2009;
44:178-84. [PMID:
19308272 PMCID:
PMC2654474 DOI:
10.3164/jcbn.08-235]
[Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2008] [Accepted: 11/04/2008] [Indexed: 12/27/2022] Open
Abstract
Gastro-intestinal mucosal cells have a potent mechanism to eliminate a variety of pathogens using enzymes that generate reactive oxygen species and/or nitric oxide (NO). However, a large number of bacteria survive in the intestine of human subjects. Enterococcus faecalis (E. faecalis) is a Gram-positive bacterium that survives not only in the intestinal lumen but also within macrophages generating NO. It has been reported that E. faecalis generated the superoxide radical (O2−). To elucidate the role of O2− and NO in the mechanism for the pathogen surviving in the intestine and macrophages, we studied the role and metabolism of O2− and NO in and around E. faecalis. Kinetic analysis revealed that E. faecalis generated 0.5 µmol O2−/min/108 cells in a glucose-dependent manner as determined using the cytochrome c reduction method. The presence of NOC12, an NO donor, strongly inhibited the growth of E. faecalis without affecting in the oxygen consumption. However, the growth rate of NOC12-pretreated E. faecalis in NO-free medium was similar to that of untreated cells. Western blotting analysis revealed that the NOC12-treated E. faecalis revealed a large amount of nitrotyrosine-posititive proteins; the amounts of the modified proteins were higher in cytosol than in membranes. These observations suggested that O2− generated by E. faecalis reacted with NO to form peroxinitrite (ONOO−) that preferentially nitrated tyrosyl residues in cytosolic proteins, thereby reversibly inhibited cellular growth. Since E. faecalis survives even within macrophages expressing NO synthase, similar metabolism of O2− and NO may occur in and around phagocytized macrophages.
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