AIMS Under hypoxic conditions, nitrite (NO2-) can be reduced to nitric oxide (NO) eliciting vasorelaxation. However, nitrite also exerts vasorelaxant effects of potential therapeutic relevance under normal physiological conditions via undetermined mechanisms. We, therefore, sought to investigate the mechanism(s) by which nitrite regulates the vascular system in normoxia and, specifically, whether the biological effects are a result of NO generation (as in hypoxia) or mediated via alternative mechanisms involving classical downstream targets of NO [e.g. effects on protein kinase G1α (PKG1α)]. METHODS AND RESULTS Ex vivo myography revealed that, unlike in thoracic aorta (conduit vessels), the vasorelaxant effects of nitrite in mesenteric resistance vessels from wild-type (WT) mice were NO-independent. Oxidants such as H2O2 promote disulfide formation of PKG1α, resulting in NO- cyclic guanosine monophosphate (cGMP) independent kinase activation. To explore whether the microvascular effects of nitrite were associated with PKG1α oxidation, we used a Cys42Ser PKG1α knock-in (C42S PKG1α KI; 'redox-dead') mouse that cannot transduce oxidant signals. Resistance vessels from these C42S PKG1α KI mice were markedly less responsive to nitrite-induced vasodilation. Intraperitoneal (i.p.) bolus application of nitrite in conscious WT mice induced a rapid yet transient increase in plasma nitrite and cGMP concentrations followed by prolonged hypotensive effects, as assessed using in vivo telemetry. In the C42S PKG1α KI mice, the blood pressure lowering effects of nitrite were lower compared to WT. Increased H2O2 concentrations were detected in WT resistance vessel tissue challenged with nitrite. Consistent with this, increased cysteine and glutathione persulfide levels were detected in these vessels by mass spectrometry, matching the temporal profile of nitrite's effects on H2O2 and blood pressure. CONCLUSION Under physiological conditions, nitrite induces a delayed and long-lasting blood pressure lowering effect, which is NO-independent and occurs via a new redox mechanism involving H2O2, persulfides, and PKG1α oxidation/activation. Targeting this novel pathway may provide new prospects for anti-hypertensive therapy.

中文翻译：

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亚硝酸盐的持久降压作用与 NO 无关，并由过氧化氢、过硫化物和蛋白激酶 G1α 氧化还原信号传导介导。

目的 在缺氧条件下，亚硝酸盐 (NO2-) 可还原为一氧化氮 (NO)，从而引起血管舒张。然而，亚硝酸盐还通过未确定的机制在正常生理条件下发挥潜在治疗相关性的血管舒张作用。因此，我们试图研究亚硝酸盐在常氧环境中调节血管系统的机制，特别是，生物效应是 NO 生成的结果（如缺氧）还是通过涉及经典下游目标的替代机制介导的NO [例如对蛋白激酶 G1α (PKG1α) 的影响]。方法和结果 离体肌动描记术显示，与胸主动脉（导管血管）不同，亚硝酸盐对野生型 (WT) 小鼠肠系膜阻力血管的血管舒张作用与 NO 无关。H2O2 等氧化剂促进 PKG1α 的二硫化物形成，导致 NO-环磷酸鸟苷 (cGMP) 非依赖性激酶激活。为了探索亚硝酸盐的微血管效应是否与 PKG1α 氧化相关，我们使用了不能转导氧化信号的 Cys42Ser PKG1α 敲入（C42S PKG1α KI；“氧化还原死亡”）小鼠。来自这些 C42S PKG1α KI 小鼠的阻力血管对亚硝酸盐诱导的血管舒张反应明显较差。在有意识的 WT 小鼠中腹膜内 (ip) 推注亚硝酸盐诱导血浆亚硝酸盐和 cGMP 浓度快速而短暂的增加，随后是长期的降压作用，如使用体内遥测法评估的那样。在 C42S PKG1α KI 小鼠中，亚硝酸盐的降压作用低于 WT。在用亚硝酸盐攻击的 WT 抗性血管组织中检测到 H2O2 浓度增加。与此一致，通过质谱法在这些血管中检测到增加的半胱氨酸和谷胱甘肽过硫化物水平，这与亚硝酸盐对 H2O2 和血压的影响的时间分布相匹配。结论 在生理条件下，亚硝酸盐具有延迟和持久的降压作用，该作用不依赖于 NO，并通过涉及 H2O2、过硫化物和 PKG1α 氧化/激活的新氧化还原机制发生。针对这一新途径可能为抗高血压治疗提供新的前景。对 H2O2 和血压的影响。结论 在生理条件下，亚硝酸盐具有延迟和持久的降压作用，该作用不依赖于 NO，并通过涉及 H2O2、过硫化物和 PKG1α 氧化/激活的新氧化还原机制发生。针对这一新途径可能为抗高血压治疗提供新的前景。对 H2O2 和血压的影响。结论 在生理条件下，亚硝酸盐具有延迟和持久的降压作用，该作用不依赖于 NO，并通过涉及 H2O2、过硫化物和 PKG1α 氧化/激活的新氧化还原机制发生。针对这一新途径可能为抗高血压治疗提供新的前景。