Vascular Biology |
From the Cardiology Research Center (M.M., O.P., Y.P., P.B., V.T.), Moscow, Russia; Center for Cardiovascular Research and Department of Medicine (M.M., O.P., B.C.B.), University of Rochester Medical Center, NY; and Section of Cardiology (H.C., K.C.), Department of Medicine, the University of Chicago, Illinois.
Correspondence to Bradford C. Berk, MD, PhD, University of Rochester, Department of Medicine, Box MED, Rochester, NY 14642. E-mail bradford_berk{at}urmc.rochester.edu
Objective We showed previously that increased urokinase plasminogen activator (uPA) expression contributes to vascular smooth muscle cell (VSMC) proliferation and neointima formation after injury. Proliferation of cultured rat aortic VSMCs induced by uPA was inhibited by the antioxidant ebselen. Because increases in VSMC reactive oxygen species (ROS) contribute to VSMC proliferation, we hypothesized that uPA increases ROS generation by regulating expression or activity of cellular oxidases.
Methods and Results uPA stimulated ROS production to levels equivalent to angiotensin II as measured by electron spin resonance and fluorescent redox indicators (dichlorofluorescein diacetate, lucigenin, and hydroethidine). The increase in ROS was biphasic, with the first peak at 30 minutes and the second peak at 4 hours. uPA increased expression of the NAD(P)H oxidases Nox1 and Nox4 as measured by RT-PCR and Western blot analysis. Knockdown of Nox1 and Nox4 expression with small interfering RNA showed that both isoforms (Nox1>Nox4) contributed significantly to uPA-stimulated ROS production and VSMC proliferation. Transfection of VSMCs with uPA cDNA to increase endogenous uPA expression enhanced ROS production dramatically, suggesting that autocrine uPA production may be an important mechanism for uPA-mediated VSMC events.
Conclusion These data show that uPA is an autocrine VSMC growth factor that increases ROS generated by both Nox1 and Nox4 oxidases.
uPA stimulates VSMC proliferation after vascular injury. uPA biphasically stimulated ROS production (which was partly inhibited by Nox1 or Nox4 siRNA) and increased expression of the oxidases Nox1 and Nox4. Transfection with uPA cDNA enhanced ROS production, suggesting that uPA-mediated autocrine ROS production contributes to vascular remodeling.
Key Words: urokinase superoxide VSMC proliferation arterial remodeling
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