IL-1 beta regulates rat mesangial cyclooxygenase II gene expression by tyrosine phosphorylation

The pro-inflammatory cytokine, interleukin-1 beta, induces the mRNA for prostaglandin endoperoxide synthase II gene in renal mesangial cells. This inductive effect is selective for prostaglandin endoperoxide synthase II and not prostaglandin endoperoxide synthase I. In the present experiments IL-1 beta increased COX II mRNA, and this was inhibited by genistein and herbimycin A, both inhibitors of protein tyrosine kinases. The dose dependent effect of genistein on inhibition of mRNA for COX II correlated with the inhibition of the release of PGE2 into the media. Induction of COX II by interleukin-1 beta was mimicked by incubating the cells in the presence of a protein tyrosine phosphatase inhibitor, vanadate. These experiments also illustrate selective induction of COX II mRNA without induction of COX I mRNA. Western analysis utilizing antiphosphotyrosine antibodies demonstrated in whole lysates of mesangial cells treated with interleukin-1 beta that the transient phosphorylation of several proteins occurred. Interleukin-1 beta induced the transient phosphorylation of a protein of about 39/40 kD. Similarly, vanadate also produced a rapid and transient phosphorylation of a protein of about 39/40 kD in addition to other proteins. Immunoprecipitation of mesangial cell lysates with agarose conjugated antiphosphotyrosine antibody and Western analysis of precipitated proteins with anti-ERK2 antibody demonstrate that the 39/40 kD protein phosphorylated on tyrosine is ERK2 and suggests participation of one of the MAP kinase family of extracellular receptor kinases in IL-1 beta stimulated induction of the COX II gene.