Both p38 alpha(MAPK) and JNK/SAPK pathways are important for induction of nitric-oxide synthase by interleukin-1 beta in rat glomerular mesangial cells

Interleukin 1 beta (IL-1 beta) induces expression of the inducible nitric-o xide synthase (iNOS) with concomitant release of nitric oxide (NO) from glo merular mesangial cells. These events are preceded by activation of the c-J un NH2-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38(M APK). Our current study demonstrates that overexpression of the dominant ne gative form of JNK1 or p54 SAPK beta/JNK2 significantly reduces the iNOS pr otein expression and NO production induced by IL-1 beta. Similarly, overexp ression of the kinase-dead mutant form of p38 alpha(MAPK) also inhibits IL- 1 beta-induced iNOS expression and NO production. In previous studies we de monstrated that IL-1 beta can activate MKK4/SEK1, MKK3, and MKK6 in renal m esangial cells; therefore, we examined the role of these MAPK kinases in th e modulation of iNOS induced by IL-1 beta. Overexpression of the dominant n egative form of MKK4/SEK1 decreases IL-1 beta-induced iNOS expression and N O production with inhibition of both SAPK/JNK and p38(MAPK) phosphorylation . Overexpression of the kinase-dead mutant form of MKK3 or MKK6 demonstrate d that either of these two mutant kinase inhibited IL-1 beta-induced p38(MA PK) (but not JNK/SAPK) phosphorylation and iNOS expression. Interestingly o verexpression of wild type MKK3/6 was associated with phosphorylation of p3 8(MAPK); however, in the absence of IL-1 beta, iNOS expression was not enha nced. This study suggests that the activation of both SAPK/JNK and p38 alph a(MAPK) Signaling cascades are necessary for the IL-1 beta-induced expressi on of iNOS and production of NO in renal mesangial cells.