Abstract 1704: Nitro-Fatty Acid Inhibition of Neointima Formation after Endoluminal Vessel Injury
Nitro-fatty acid derivatives, a class of lipid signaling mediators generated by nitric oxide and nitrite dependent oxidative inflammatory reactions, induce cell signaling events that promote the resolution of inflammation. We hypothesized that nitro-oleic acid (OA-NO2) will inhibit neointimal hyperplasia in response to arterial injury and that this effect might be mediated by heme oxygenase-1 (HO-1). Either vehicle (V), oleic acid (OA, 2 mg/kg/d), or OA-NO2 (2 mg/kg/d) was administered subcutaneously via osmotic minipumps in 8–10 wks old wildtype C57BL/6 male mice, immediately prior to guide wire-induced injury of the left femoral artery. OA-NO2 levels were monitored using HPLC-mass spectrometry. Intima/media ratio was assessed after 21 days. Immunofluorescent analysis was used to reveal HO-1 distribution in vessels, and in cultured rat aortic smooth muscle cells (RASMC), RNA and protein expression of HO-1 induced by OA-NO2 was assessed by rt-PCR and western blotting. The influence of OA-NO2 on RASMC proliferation and platelet-derived growth factor-induced migration was also determined. Following femoral artery injury in vivo, OA-NO2 administration significantly reduced intima/media ratio compared to OA or V (OA-NO2: 0.74 ± 0.26; OA: 2.02 ± 0.20; V: 2.16 ± 0.27; p = 0.003). In RASMC, OA-NO2 increased RNA as well as protein expression of HO-1 in a dose-dependent manner (P < 0.01). HO-1 was also expressed more abundantly in the vessel wall of OA-NO2-treated mice as revealed by immunofluorescent analysis. In addition, OA-NO2 significantly inhibited RASMC migration (P < 0.01) and proliferation (P < 0.001). Sn(IV)-protoporphyrin inhibition of HO-1 reversed OA-NO2-induced inhibition of RASMC migration, and upon in vivo administration also attenuated OA-NO2-induced inhibition of neointimal hyperplasia following femoral artery injury (intima/media ratio of SnPP-treated mice: 1.75 ± 0.27; p = 0.023). The fatty acid nitration product OA-NO2 acts as a potent inhibitor of neointimal hyperplasia induced by femoral artery injury in a murine model, in part by serving as a potent inducer of HO-1. In conclusion, nitro-fatty acids induce anti-inflammatory and anti-proliferative genes and cell functional responses.