Antiproliferative effect of L-NAME on rat vascular smooth muscle cells

The nitric oxide synthase (NOS) inhibitor L-NAME may have growth inhibitory effects in vivo. We investigated in vitro the potential growth inhibitory effects of three different NOS inhibitors: L-NAME (1 mM), LNMMA (1 mM) and aminoguanidine (0.5 mM), on fetal bovine serum (FBS) and platelet derived g rowth factor (PDGF-BB)-stimulated growth in cultured vascular smooth muscle cells (VSMCs), [H-3]-thymidine incorporation into rat mesenteric VSMCs was measured as an index of VSMCs proliferation (DNA synthesis) and activation of extracellular signal regulated kinase (ERK1/2), a major signaling event in cell growth, was measured by western blot assay. PDGF-BB (0-5 ngl/mL) a nd FBS (0-5%) increased [H-3]-thymidine incorporation in a dose-dependent m anner up to 6-10 fold. L-NAME significantly reduced PDGF-BB (5 ng/ml) and F BS (5%) stimulated DNA synthesis by 46% and 38% respectively. The increase of [H-3]-thymidine incorporation induced by PDGF-BB and FBS was unaltered b y L-NMMA. In contrast, aminoguanidine induced an increase in FBS and PDGF-B B-stimulated [H-3]-thymidine incorporation of 64% and 34% respectively abov e cells not exposed to aminoguanidine. ERK1/2 phosphorylation induced by PD GF-BB and FBS was not affected by pretreatment with L-NAME or aminoguanidin e. In conclusion, NOS inhibitors differentially influence DNA synthesis in VSMCs: L-NAME inhibits FBS and PDGF-BB-stimulated cellular proliferation wh ereas aminoguanidine accentuates FBS and PDGF-BB-stimulated VSMCs prolifera tion. These phenomena are independent of the ERK1/2 pathway. The growth inh ibitory effects of L-NAME may be related to differences in properties from other NOS inhibitors, and independent of its ability to inhibit NOS. (C) 20 00 Elsevier Science Inc. All rights reserved.