L-arginine administration reduces neointima formation after stent injury in rats by a nitric oxide-mediated mechanism

The clinical outcome of vascular stenting is limited by in-stent stenosis. Increased nitric oxide (NO)/cGMP signaling by L-arginine (L-Arg) supplement ation, the substrate for NO synthase (NOS), or NOS gene transfer may reduce in-stent neointima formation. After stenting, vascular cell proliferation in rat carotid arteries, as measured by 5'-bromodeoxyuridine (5'-BrdU) inco rporation, indicated 15 +/-8%, 28 +/-5%, and 33 +/-7% 5'-BrdU-positive vasc ular cells at 4, 7, and 14 days, respectively. Reporter beta -galactosidase gene transfer efficacy was evidenced by 30% beta -galactosidase-expressing medial smooth muscle cells at 14 days. The intima-to-media ratio (I/M) pro gressively increased to 2.32 +/-0.24 at 14 days. To target in-stent neointi ma formation, animals were infected with adenoviral vectors (4x10(10) plaqu e-forming units per mL) expressing NOS2 (AdNOS2) or no transgene (AdRR5), o r they received daily doses of L-Arg (500 mg.kg(-1).(d-1) IP). The neointim a at 14 days was smaller in L-Arg-treated than in untreated rats (I/M 1.25 +/-0.35 vs 2.32 +/-0.24, P<0.05, n=7 each) or in AdRR5- and AdNOS2-infected rats (I/M 2.57<plus/minus>0.43, n=7 and 1.82 +/-0.75, n= 8, respectively; P<0.05 for both). The effect of L-Arg was abolished by simultaneous adminis tration of N-G-nitro L-arginine methyl ester, an NOS inhibitor (2.03<plus/m inus>0.39, P<0.05, VS L-Arg). Inflammation was markedly less in L-Arg- and AdNOS2-treated than in AdRR5-infected rats. Supplemental L-Arg reduces neoi ntima formation after stenting by way of an NOS-dependent mechanism and may be a valuable strategy to target in-stent stenosis.