Am J Physiol Renal Physiol. 2012 Dec 15;303(12):F1601-7. doi: 10.1152/ajprenal.00449.2012. Epub 2012 Sep 19.
Vascular access dysfunction causes morbidity in hemodialysis patients. This study examined the generation and pathobiological significance of superoxide anion in a rat femoral arteriovenous fistula (AVF). One week after AVF creation, there was increased production of superoxide anion accompanied by decreased total superoxide dismutase (SOD) and Cu/Zn SOD activities and induction of the redox-sensitive gene heme oxygenase-1. Immunohistochemical studies of nitrotyrosine formation demonstrated that peroxynitrite, a product of superoxide anion and nitric oxide, was present in increased amounts in endothelial and smooth muscle cells in the AVF. Because uncoupled NOS isoforms generate superoxide anion, and NOS coupling requires tetrahydrobiopterin (BH(4)) as a cofactor, we assessed NOS uncoupling by determining the ratio of BH(4) to dihydrobiopterin (BH(2)); the BH(4)-to-BH(2) ratio was markedly attenuated in the AVF. Because Src is a vasculopathic signaling species upstream and downstream of superoxide anion, such expression was evaluated; expression of Src and phosphorylated Src was both markedly increased in the AVF. Expression of NADPH oxidase (NOX) 1, NOX2, NOX4, cyclooxygenase (COX) 1, COX2, p47(phox), and p67(phox) was all unchanged, as assessed by Western analyses, thereby suggesting that these proteins may not be involved in increased production of superoxide anion. Finally, administration of tempol, a superoxide anion scavenger, decreased neointima formation in the juxta-anastomotic venous segment and improved AVF blood flow. We conclude that the AVF exhibits increased superoxide anion generation that may reflect the combined effects of decreased scavenging by SOD and increased generation by uncoupled NOS, and that enhanced superoxide anion production promotes juxta-anastomotic stenosis and impairs AVF function.
血管通路功能障碍会导致血液透析患者发病。本研究检测了超氧阴离子在大鼠动静脉瘘（AVF）中的产生和病理生物学意义。在 AVF 形成后 1 周，超氧阴离子的产生增加，同时总超氧化物歧化酶（SOD）和 Cu/Zn SOD 活性降低，并且氧化还原敏感基因血红素加氧酶-1 被诱导。硝基酪氨酸形成的免疫组织化学研究表明，超氧阴离子和一氧化氮的产物过氧亚硝酸盐在 AVF 中的内皮细胞和平滑肌细胞中含量增加。因为脱偶联的 NOS 同工型产生超氧阴离子，而 NOS 偶联需要四氢生物蝶呤（BH(4)）作为辅助因子，我们通过测定 BH(4)与二氢生物蝶呤（BH(2)）的比值来评估 NOS 脱偶联；AVF 中的 BH(4)与 BH(2)比值明显降低。由于 Src 是超氧阴离子上游和下游的血管病变信号物质，因此评估了 Src 的表达；AVF 中 Src 和磷酸化 Src 的表达均明显增加。通过 Western 分析，评估 NADPH 氧化酶（NOX）1、NOX2、NOX4、环加氧酶（COX）1、COX2、p47(phox)和 p67(phox)的表达均无变化，这表明这些蛋白质可能不参与超氧阴离子的产生增加。最后，给予超氧阴离子清除剂替米沙坦可减少吻合口静脉段的新生内膜形成，并改善 AVF 血流。我们得出结论，AVF 表现出超氧阴离子产生增加，这可能反映了 SOD 清除减少和脱偶联 NOS 产生增加的综合作用，并且增强的超氧阴离子产生促进吻合口狭窄并损害 AVF 功能。
