UCN enhances TGF-beta-mediated mitoinhibition of VSMCs via counteracting TGF-beta-induced cPLA2 expression and activation.

Urocortins (UCNs) and transforming growth factor-beta (TGF-beta) have been demonstrated to participate in various cardiovascular diseases, many of which involve vascular smooth muscle cells (VSMCs) proliferation. Cytosolic phospholipase A2 (cPLA2)-mediated arachidonic acid (AA) release is an important cause of VSMCs proliferation. The work was to investigate the regulation of VSMCs proliferation by UCN/TGF-beta and whether cPLA2 was a link between their signaling pathways. VSMCs proliferation was measured by colorimetric assay and immunofluorescence microscopy. Using cell flow cytometry, the changes in the cell cycle phases were investigated. Lentiviral Vector Particle was performed to overexpress cPLA2 gene. Both UCN and TGF-beta inhibited VSMCs proliferation and an additive effect was observed when the cells were treated with UCN plus TGF-beta. TGF-beta increased the percentage of cells in G1-phase while UCN increased the cell percentage in G2-phase with a concomitant decrease in S-phase. Furthermore, cPLA2 expression was increased by TGF-beta but decreased by UCN and UCN attenuated TGF-beta-induced cPLA2 expression. In primary VSMCs, TGF-beta induced cPLA2 phosphorylation, and this effect was also attenuated by UCN. Similar to UCN, the cPLA2 inhibitor, pyrrophenone (PYR), also played a role in enhancing TGF-beta-mediated mitoinhibition. Inversely, overexpression of cPLA2 eliminated the effect of UCN on the mitoinhibition. The pretreatment with UCN counteracted TGF-beta-mediated cPLA2 expression and activation, thereby contributing to TGF-beta-mediated mitoinhibition of VSMCs.

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