Role of PKC-α in NF-κB-MT1-MMP-mediated activation of proMMP-2 by TNF-α in pulmonary artery smooth muscle cells

We sought to evaluate the mechanism(s) associated with pro matrix metalloprotease 2 (proMMP-2) activation in bovine pulmonary artery smooth muscle cells. Preincubation of cells with anti-TNFR1 antibody prevented tumour necrosis factor-alpha (TNF-alpha)-induced proMMP-2 activation and increase in membrane type 1 matrix metalloprotease (MT1-MMP) expression as well as inhibition of tissue inhibitor of metalloproteinase 2 (TIMP-2) expression, indicating the role of TNFR1 receptor during TNF-alpha stimulation. Anti-MT1-MMP antibody abrogated proMMP-2 activation by TNF-alpha-stimulated cell membrane, suggesting the involvement of MT1-MMP in proMMP-2 activation. Induction of MT1-MMP expression in response to TNF-alpha occurs via activation of nuclear factor (NF)-kappa B on inhibitory kappa B kinase (IKK) activation and subsequently phosphorylation/degradation of I kappa B-alpha. Inhibition of protein kinase C (PKC)-alpha activity by Go6976 and PKC-alpha siRNA prevented TNF-alpha-induced IKK activity, I kappa B-alpha phosphorylation/degradation and NF-kappa B activation. Inhibition of PKC-alpha activity also prevented TNF-alpha-induced MT1-MMP expression and proMMP-2 activation as well as down regulation of TIMP-2 expression. Inhibition of I kappa B-alpha phosphorylation by PS-1145, an IKK selective inhibitor, prevented TNF-alpha-induced increase in MT1-MMP expression and proMMP-2 activation, which although did not alter inhibition of TIMP-2 expression. Overall, we unravelled a hitherto unknown mechanism of the involvement of PKC-alpha in proMMP-2 activation and inhibition of TIMP-2 expression by NF-kappa B-MT1-MMP-dependent and -independent pathway, respectively, during TNF-alpha stimulation in pulmonary artery smooth muscle cells.