RESUMO
An increasing number of reports in the literature indicate that endogenously produced inhibitors of nitric oxide synthase (NOS), particularly asymmetric dimethylarginine (ADMA) regulate nitric oxide generation in numerous disease states. Two dimethylarginine dimethylaminohydrolase (DDAH) enzymes metabolise ADMA. We and others have postulated that activity of DDAH is a key determinant of ADMA levels in vivo. This review summarises recent advances in the regulation and function of DDAH enzymes and its role in the regulation of nitric oxide generation.
Assuntos
Amidoidrolases/metabolismo , Arginina/análogos & derivados , Arginina/metabolismo , Inibidores Enzimáticos/metabolismo , Óxido Nítrico Sintase/metabolismo , Amidoidrolases/efeitos dos fármacos , Animais , Arginina/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Pressão Sanguínea/fisiologia , Células Endoteliais/metabolismo , Endotélio Vascular/citologia , Endotélio Vascular/metabolismo , Endotélio Vascular/fisiopatologia , Inibidores Enzimáticos/farmacologia , Humanos , Óxido Nítrico Sintase/efeitos dos fármacos , Vasodilatação/efeitos dos fármacos , Vasodilatação/fisiologiaRESUMO
all-trans-Retinoic acid (atRA) has important effects on the developing and mature cardiovascular system. Nitric oxide (NO) production has been associated with the atRA-induced differentiation of neuronal cells, and we hypothesized that NO may also mediate certain actions of atRA in the cardiovascular system. We studied the effects of atRA on NO production by endothelial cells and determined whether regulation of enzymes responsible for metabolism of asymmetric dimethylarginine (ADMA) contributed to the effects seen. Murine endothelioma (sEnd.1) cells were incubated with or without atRA. Nitrite production was determined using the Griess reaction. The expression of NO synthase (NOS) and dimethylarginine dimethylaminohydrolase (DDAH) genes was determined by Northern blotting. A reporter gene assay was also used to study the effect of atRA on the DDAH II promoter. atRA significantly increased nitrite production by sEnd.1 cells despite no increase in eNOS expression. atRA also increased DDAH II gene expression and promoter activity and reduced the ratio of ADMA to symmetric dimethylarginine (SDMA) in culture medium. The DDAH inhibitor 4124W significantly reduced the induction of NO synthesis by atRA. The present study demonstrates that atRA increases NO synthesis in endothelial cells without increasing eNOS expression. atRA also increases the expression of DDAH II, the predominant DDAH isoform in endothelial cells. Our data suggests that the induction of NO synthesis by atRA may be facilitated by DDAH II. This pathway may help to explain some of the effects of atRA on the cardiovascular system.
