Tetrahydrobiopterin synthesis. An absolute requirement for cytokine-induced nitric oxide generation by vascular smooth muscle.

摘要: Nitric oxide (NO) synthesis is induced in vascular smooth muscle cells by lipopolysaccharide (LPS) where it appears to mediate a variety of dysfunctions. In some cell types tetrahydrobiopterin (BH4) has also been found be cytokines. Because BH4 cofactor for NO synthase, we investigated whether required LPS-induced production rat aortic (RASMC). The total biopterin content (BH4 and more oxidized states) untreated RASMC was below our limit detection. However, treatment with LPS caused significant rise levels an induction synthesis; both effects were markedly potentiated interferon-gamma. 2,4-Diamino-6-hydroxypyrimidine (DAHP), selective inhibitor GTP cyclohydrolase I, the rate-limiting enzyme de novo synthesis, completely abolished elevated LPS. DAHP concentration-dependent inhibition synthesis. Inhibition reversed sepiapterin, agent which circumvents serving as substrate via pterin salvage pathway. reversal sepiapterin overcome methotrexate, Sepiapterin, lesser extent BH4, dose-dependently enhanced indicating that concentration limits rate LPS-activated RASMC. Sepiapterin appear abbreviated lag period phase, suggesting availability onset contrast stimulation observed when given alone, became potent presence methotrexate. This attributable direct inhibitory action on activity only revealed after blocking metabolism BH4. Further studies N-acetylserotonin (an synthetic enzyme, reductase) indicated synthesized predominantly from GTP; however, amount may derive salvage. We demonstrate absolute requirement muscle. Our findings suggest inhibitors useful therapy endotoxin- cytokine-induced shock.