RESUMO
The effect of docosahexaenoic acid (DHA) on nitric oxide (NO) production and inducible NO synthase (iNOS) expression induced by interleukin (IL)-1beta, and whether the effect of DHA is related to its effect on mitogen-activated protein kinase (MAPK) activation were investigated in cultured rat vascular smooth muscle cells (VSMCs). DHA and eicosapentaenoic acid (EPA), although less potent, increased the NO production induced by IL-1beta (3 ng ml(-1)) in a concentration-dependent manner (3 - 30 microM) Arachidonic acid had no significant effect. The stimulatory effect of DHA (30 microM) on the NO production was more obvious at lower concentrations of IL-1beta. IL-1beta induced iNOS protein and mRNA expressions, which were significantly potentiated by DHA. EPA (30 microM) had a tendency to increase the iNOS protein and mRNA expressions, but arachidonic acid had no effect. IL-1beta-induced iNOS protein expression was significantly inhibited by PD 98059 (10 microM), a selective inhibitor of p44/42 MAPK kinase, both in the absence and the presence of DHA. SB 203580 (10 microM), a selective inhibitor of p38 MAPK activity, had no significant effect, although had a tendency to inhibit slightly. IL-1beta increased the phosphorylation of p44/42 MAPK, while it did not apparently increase the phosphorylation of p38 MAPK. DHA significantly potentiated the IL-1beta-induced phosphorylation of p44/42 MAPK, while it had no significant effect on the phosphorylation of p38 MAPK. These results suggest that DHA increases NO production by potentiating iNOS expression induced by IL-1beta through mechanism involving p44/42 MAPK signalling cascade in rat VSMCs. The present study may contribute to the understanding of basic mechanisms underlying the beneficial effects of DHA on various cardiovascular disorders.
Assuntos
Ácidos Docosa-Hexaenoicos/farmacologia , Interleucina-1/metabolismo , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Músculo Liso Vascular/efeitos dos fármacos , Óxido Nítrico Sintase/biossíntese , Animais , Ácido Araquidônico/farmacologia , Western Blotting , Células Cultivadas , Ácido Eicosapentaenoico/farmacologia , Ativação Enzimática , Interleucina-1/farmacologia , Proteína Quinase 1 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 3 Ativada por Mitógeno , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Músculo Liso Vascular/citologia , Músculo Liso Vascular/enzimologia , Óxido Nítrico/biossíntese , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase Tipo II , RNA Mensageiro/biossíntese , Ratos , Ratos Endogâmicos WKY , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 are expressed in vascular smooth muscle cells stimulated with interleukin-1beta (IL-1beta), resulting in the production of nitric oxide (NO) and prostaglandins (PGs) such as PGI2. The iNOS and COX-2 proteins and their mRNA expressions in cultured vascular smooth muscle cells isolated from 6-7 week-old stroke-prone spontaneously hypertensive rats (SHRSP) were compared with those in the cells isolated from age-matched normotensive Wistar Kyoto rats (WKY). The IL-1beta-induced NO production and iNOS expression in vascular smooth muscle cells of SHRSP were significantly lower than those in cells of WKY. Similarly, PGI2 production and COX-2 expression were significantly lower in vascular smooth muscle cells of SHRSP than WKY, whereas there was no difference in the COX-1 expression. There were no significant differences in iNOS and COX-2 mRNA expressions between the two strains, suggesting that these protein expression may be reduced at the post-transcriptional level in cells of SHRSP. These results further suggest that the reduction of iNOS and COX-2 expressions in vascular smooth muscle cells may have relevance to the pathophysiology in SHRSP.