DOWN-REGULATION OF ENDOTHELIAL CONSTITUTIVE NITRIC-OXIDE SYNTHASE EXPRESSION BY LIPOPOLYSACCHARIDE

Lipopolysaccharide (LPS), a causal agent of sepsis, has been shown to induce systemic nitric oxide (NO) synthesis through complex mechanisms . However, the effect of LPS on endothelial cells is incompleted under stood. To investigate the mechanism by which LPS influences the releas e of NO from endothelial cells, the effect of this compound on endothe lial constitutive nitric oxide synthase (ecNOS) was studied in culture d bovine coronary venular endothelial cells. Western and Northern anal yses showed that LPS decreased ecNOS expression at the protein and mRN A levels in a time-dependent and dose-responsive manner. Concurrent tr eatment of the endothelial cells with LPS and a transcription inhibito r, actinomycin D. resulted in decreased ecNOS mRNA within 8 hours. In contrast, treatment with actinomycin D had only a relatively insienifi cant effect on the ecNOS transcript level. This result suggests that t he reduction of ecNOS by LPS resulted from an increased degradation ra te of its transcript. (C) 1996 Academic Press, Inc.