Nitric oxide reduces vascular smooth muscle cell elastase activity throughcGMP-mediated suppression of ERK phosphorylation and AML1B nuclear partitioning

Nitric oxide (NO) reduces the severity of pulmonary vascular disease in rat s as do elastase inhibitors. We therefore hypothesized that NO inhibits ela stase by suppressing mitogen-activated protein kinases that trans-activate AML1B, a transcription factor for elastase. We used cultured pulmonary arte ry smooth muscle cells in which serum-treated elastin (STE) induces a > thr eefold increase in elastase activity as evaluated by solubilization of [H-3 ]-elastin. NO donors (SNAP and DETA NONO-ate) inhibited elastase in a dose- dependent manner as did a cGMP mimetic (8-pCPT-cGMP). SNAP inhibition of el astase was reversed by coadministration of a cGMP-PKG inhibitor (Rp-8-pCPT- cGMP). The STE-induced increase in phospho-ERK was suppressed by NO donors and the cGMP mimetic, and reversed by cGMP-PKG inhibitor, as was expression of AML1B and DNA binding in nuclear extracts. A concomitant increase in p3 8 phosphorylation was also inhibited by SNAP, but whereas MEK inhibitor (PD 98059) suppressed elastase and AML1B-DNA binding, a p38 inhibitor (SB202190 ) did not. Our study uniquely links NO with inhibition of elastase-dependen t matrix remodeling in vascular disease by suggesting a cGMP-PKG-related me chanism suppressing ERK-mediated partitioning of AML1B in nuclear extracts.