Abstract
The inflammatory cytokine interleukin-1beta (IL-1beta) induces cyclooxygenase-2 (Cox-2) expression with a concomitant release of prostaglandins from glomerular mesangial cells. We reported previously that IL-1beta rapidly activates the c-Jun NH2-terminal/stress-activated protein kinases (JNK/SAPK) and p38 mitogen-activated protein kinase (MAPK) and also induces Cox-2 expression and prostaglandin E2 (PGE2) production. The current study demonstrates that overexpression of the dominant negative form of JNK1 or p54 JNK2/SAPKbeta reduces Cox-2 expression and PGE2 production stimulated by IL-1beta. Similarly, overexpression of the kinase-dead form of p38 MAPK also inhibits IL-1beta-induced Cox-2 expression and PGE2 production. These results suggest that activation of both JNK/SAPK and p38 MAPK is required for Cox-2 expression after IL-1beta activation. Furthermore, our experiments confirm that IL-1beta activates MAP kinase kinase-4 (MKK4)/SEK1, MKK3, and MKK6 in renal mesangial cells. Overexpression of the dominant negative form of MKK4/SEK1 decreases IL-1beta- induced Cox-2 expression with inhibition of both JNK/SAPK and p38 MAPK phosphorylation. Overexpression of the kinase-dead form of MKK3 or MKK6 demonstrated that either of these two mutant kinases inhibited IL-1beta-induced p38 MAPK phosphorylation and Cox-2 expression but not JNK/SAPK phosphorylation and activation. This study suggests that the activation of both JNK/SAPK and p38 MAPK signaling cascades is required for IL-1beta-induced Cox-2 expression and PGE2 synthesis.
Highlights
We evaluated whether the kinase-negative mutant of JNK2/p54 stress-activated protein kinases (SAPKs) could inhibit Cox-2 expression and prostaglandin E2 (PGE2) production after IL-1 stimulation
Overexpression of JNK2/p54 SAPK was verified by the Western blot analysis followed by immunocomplex jun-NH2-terminal kinases (JNKs) activity assays that revealed that the kinase-negative form of p54 SAPK inhibited total JNK activity induced by IL-1
Similar to JNK1, the dominant negative JNK2/p54 SAPK expressed in pLXSN blocked IL-1-induced Cox-2 expression and PGE2 production in renal mesangial cells (Fig. 2)
Summary
JNK/SAPK Mediates IL-1-induced Cox-2 Expression—To determine whether the activation of JNK/SAPK in response to IL-1 is required for induction of Cox-2 protein expression and PGE2 biosynthesis, stably transfected cells overexpressing JNK/SAPK in rat glomerular mesangial cells as well as NIH 3T3 cells were used. The kinase-dead mutant JNK1 inhibited Cox-2 protein expression and PGE2 production in response to IL-1 stimulation. This finding was demonstrated in NIH 3T3 cells in which Cox-2 expression and PGE2 production were inhibited by the kinase-dead form of JNK2/p54 SAPK (data not shown).
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