Activation of proMMP-2 by U46619 occurs via involvement of p38MAPK-NFκB-MT1MMP signaling pathway in pulmonary artery smooth muscle cells

We investigated the mechanism by which TxA(2) mimetic, U46619, activates proMMP-2 in bovine pulmonary artery smooth muscle cells. Our study showed that treatment of the cells with U46619 caused an increase in the expression and subsequently activation of proMMP-2 in the cells. Pretreatment with p(38)MAPK inhibitor, SB203580; and NF-kappa B inhibitor, Bay11-7082 inhibited the expression and activation of proMMP-2 induced by U46619. U46619 also induced increase in MT1-MMP expression, which was inhibited upon pretreatment with SB203580 and Bay11-7082. U46619 treatment to the cells stimulated p(38)MAPK activity as well as NF-kappa B activation by I kappa B-alpha phosphorylation, translocation of NF-kappa Bp65 subunit from cytosol to nucleus and subsequently, by increasing its DNA-binding activity. Induction of NF-kappa B activation seems to be mediated through IKK, as transfection of cells with either IKK alpha or IKK beta siRNA prevented U46619-induced phosphorylation of I kappa B-alpha and NF-kappa Bp65 DNA-binding activity. U46619 treatment to the cells also downregulated the TIMP-2 level. Pretreatment of the cells with SB203580 and Bay11-7082 did not show any discernible change in TIMP-2 level by U46619. Overall, U46619-induced activation of proMMP-2 is mediated via involvement of p(38)MAPK-NF kappa B-MT1MMP signaling pathway with concomitant downregulation of TIMP-2 expression in bovine pulmonary artery smooth muscle cells.