Hyperhomocysteinemia impairs angiogenesis in response to hindlimb ischemia

Hyperhomocysteinemia (HH) is an independent risk factor for atherosclerosis , including peripheral arterial occlusive disease (PAOD). Because angiogene sis and collateral vessel formation are important self-salvage mechanisms f or ischemic PAOD, we examined whether HH modulates angiogenesis in vivo in a rat model of hindlimb ischemia. Rats were divided into 3 groups: the cont rol group was given tap water, the HH group was given water containing L-me thionine (1 g.kg(-1).d(-1)), and the HH+L-arg group was given water contain ing methionine (1 g.kg(-1).d(-1)) and L-arginine (2.25 vol%). At day 14 of the dietary modifications, the left femoral artery and vein were excised, a nd the extent of angiogenesis and collateral vessels in the ischemic limb w ere examined for 4 weeks. Plasma homocysteine levels significantly increase d (P<0.001), and plasma and tissue contents of nitrite+nitrate as well as t issue cGMP levels significantly decreased in the HH group compared with the control group (P<0.01). Laser Doppler blood flowmetry (LDBF) revealed a si gnificant decrease in the ischemic/normal limb LDBF ratio in the HH group a t days 7, 14, 21, and 28 (P<0.01 versus control). Angiography revealed a si gnificant decrease in the angiographic score in the HH group at day 14 (P<0 .001 versus control). Immunohistochemistry of ischemic tissue sections show ed a significant reduction in the capillary density in the HH group (P<0.00 1 versus control). Oral L-arginine supplementation in rats with HH (HH+L-ar g) restored the decreased plasma and tissue nitrite+nitrate and cGMP conten ts (P<0.05) as well as angiogenesis, as assessed by LDBF (P<0.05 versus HH) , angiographic score (P<0.01 versus HH), and capillary density (P<0.001 ver sus HH). In summary, HH impaired ischemia-induced angiogenesis and collater al vessel formation in a rat model of hindlimb ischemia in vivo. The mechan ism of the HH-induced impairment of angiogenesis might be mediated in part by a reduced bioactivity of endogenous NO in the I-III state.