Declined vasorelaxation function in aging resistance arteries is responsible for aging-related multiple organ dysfunctions. The aim of the present study is to explore the role of peroxynitrite (ONOO-) in aging resistance arterial vasorelaxation dysfunction and the possible mechanism. In the present study, young (3–4 months olds) and aging (20 months olds) male SD rats were randomized to receive vehicle (Saline) or FeTMPyP (ONOO- scavenger) for 2 weeks. The vasorelaxation of resistance arteries was determined in vitro; NOx level was tested by a colorimetric assay; the expression of nitrotyrosine (NT), soluble Guanylate Cyclase (sGC), vasodilator-stimulated phosphoprotein (VASP), phosphorylated VASP (P-VASP) and cGMP in resistance arteries were detected by immunohistochemical staining. In the present study, endothelium-dependent dilation in aging resistance arteries was lower than in those from young rats (young vs. aging: 68.0%±4.5% vs. 50.4%±2.9%, P<0.01). And the endothelium-independent dilation remained constant. Compared with young rats, aging increased nitrative stress in resistance arteries, evidenced by elevated NOx production in serum (5.3±1.0 nmol/ml vs. 3.3±1.4 nmol/ml, P<0.05) and increased NT expression (P<0.05). ONOO- was responsible for the vasorelaxation dysfunction, evidenced by normalized vasorelaxation after inhibit ONOO- or its sources (P<0.05) and suppressed NT expression after FeTMPyP treatment (P<0.05). The expression of sGC was not significantly different between young and aging resistance arteries, but the cGMP level and P-VASP/VASP ratio (biochemical marker of NO-sGC-cGKs signaling) decreased, which was reversed by FeTMPyP treatment in vivo (P<0.05). The present study suggested that ONOO- mediated the decline of endothelium-dependent vasorelaxation of aging resistance arteries by induction of the NO-sGC-cGKs pathway dysfunction.

Hyperhomocysteinemia (HHcy) is a well-known independent risk factor for vascular diseases in the general population. This study was to explore the effect of genistein (GST), a natural bioactive compound derived from legumes, on HHcy-induced vascular endothelial impairment in ovariectomized rats in vivo. Thirty-two adult female Wistar rats were assigned randomly into four groups (n = 8): (a) Con: control; (b) Met: 2.5% methionine diet; (c) OVX + Met: ovariectomy + 2.5% methionine diet; (d) OVX + Met + GST: ovariectomy + 2.5% methionine diet + supplementation with genistein. After 12 wk of different treatment, the rats' blood, toracic aortas and liver samples were collected for analysis. Results showed that high-methionine diet induced both elevation of plasma Hcy and endothelial dysfunction, and ovariectomy deteriorated these injuries. Significant improvement of both functional and morphological changes of vascular endothelium was observed in OVX + Met + GST group; meanwhile the plasma Hcy levels decreased remarkably. There were significant elevations of plasma ET-1 and liver MDA levels in ovariectomized HHcy rats, and supplementation with genistein could attenuate these changes. These results implied that genistein could lower the elevated Hcy levels, and prevent the development of endothelial impairment in ovariectomized HHcy rats. This finding may shed a novel light on the anti-atherogenic activities of genistein in HHcy patients.

Hyperhomocysteinemia is an independent risk factor for cardiovascular diseases. The enhanced nitrative stress plays an important role in homocysteine-induced endothelial dysfunction. Previous studies have showed that phytoestrogen α-zearalanol alleviated endothelial injury in ovariectomized hyperhomocysteinemic rats; however, the underlying mechanism remains to be clarified. This study was to investigate the effects of α-zearalanol on homocysteine-induced endothelial apoptosis in vitro and explore the possible role of nitrative stress in these effects. Results showed that homocysteine (500 μmol/L, 24 h) induced the apoptosis of human umbilical vein endothelial cells (HUVECs) obviously, and this effect was significantly attenuated by pretreatment with α-zearalanol (10−8~10−6 mol/L). Moreover, α-zearalanol downregulated proapoptotic protein Bax, upregulated antiapoptotic proteins Bcl-2 and Bcl-XL, and decreased the expression and activity of caspase-9. These findings demonstrated that α-zearalanol could effectively alleviate homocysteine-induced endothelial apoptosis, and this antiapoptosis effect might be related to the inhibition of the intrinsic pathway. Western blot indicated an enhanced 3-nitrotyrosine expression in HUVECs when challenged with homocysteine, which was attenuated by pretreatment with α-zearalanol. This result implied that inhibition of nitrative stress might play a role in the protective effect of α-zearalanol on endothelial cells. Such discovery may shed a novel light on the antiatherogenic activities of α-zearalanol in hyperhomocysteinemia.

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