Transforming growth factor beta regulates cyclooxygenase-2 in glomerular mesangial cells

This study examines the hypothesis that transforming growth factor beta (TGFβ) regulates cyclooxygenase-2 (COX-2) and induces prostaglandin E synthase (mPGES-1) in rat mesangial cells. COX-2 expression was determined by Northern blot analysis after treatment with either TGFβ1 or the selective COX-2 inhibitor, NS398. mPGES-1 expression was determined by real-time polymerase chain reaction. The effect of TGFβ1 on COX-2 gene transcription was assessed using a luciferase reporter assay, and mRNA stability was also determined. To determine whether TGFβ1 activates elements of the COX-2 promoter, we performed gel shift analyses to examine activation of activator protein-1 (AP-1) and nuclear factor κB (NF-κB). Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) production was assayed by enzyme immunoassay. Finally, the pathophysiological relevance of COX-2 inhibition on the downstream effects of TGFβ was assessed by examining collagen type I mRNA and net collagen production. COX-2 mRNA and mPGES-1 were induced after treatment with TGFβ1 for 4 h, and this rise was accompanied by a three-fold increase in PGE2 production that could be antagonized by selective inhibition of COX-2 with NS398. TGFβ1 increased transcription by approximately 50% and activated both AP-1 and NF-κB. These effects were antagonized by co-treatment with NS398. Treatment with TGFβ1 also doubled the half-life of COX-2 mRNA. Neither collagen type I mRNA nor net collagen production were altered by co-treatment with NS398. In conclusion, these results indicate that TGFβ stimulates COX-2 and mPGES-1, with additional effects on transcription and stability of COX-2 mRNA.