Nitrite enhances ischemia‐induced angiogenesis by Nitric Oxide dependent pathway

Purpose: We tested the hypothesis that in permanent ischemia, nitrite would enhance angiogenesis as compared to nitrate or PBS Methods: Hind limb ischemia was induced by femoral artery ligation. Nitrite and nitrate were given intraperitoneally in 2 doses 3.3mg/kg and 165μg/kg twice a day for 7 days. PBS injections served as control. Blood flow was measured with Laser Doppler on days 0, 3, 5 and 7. Angiogenic index (AI), cGMP, tissue and blood nitrite (TBN) were done on days 3 and 7. Next, NO scavenger PTIO was used with nitrite 165μg/kg Results: Blood Flow and AI were significantly increased in nitrite treated ischemic limbs vs. control (AI 165: 1.2 vs. 0.4; AI 3.3: 0.6 vs. 0.3 p<0.0001) Both doses of nitrite were better than nitrate. AI was better with the lower dose of 165μg/kg of nitrite as compared to 3.3mg/kg. At day 3, TBN increased in nitrite treated ischemic limbs but this resolved by day 7. Tissue cGMP was elevated in nitrite treated limbs compared to nitrate ischemic limbs at 3.3mg/kg dose but was lower than nitrate at 165μg/kg dose. Blood flow response with 165μg/kg nitrite was completely abolished in presence of PTIO demonstrating NO dependence. Conclusion: Nitrite enhances angiogenesis in response to permanent ischemia via nitric oxide pathway and is a novel therapy in peripheral artery disease and transplant medicine.