Howitt Lauren, Matthaei Klaus I, Drummond Grant R, Hill Caryl E
Eccles Institute of Neuroscience, John Curtin School of Medical Research, Australian National University, Building 131, Garran Road, Acton, Canberra, ACT, 2601, Australia.
Pflugers Arch. 2015 Apr;467(4):727-35. doi: 10.1007/s00424-014-1548-5. Epub 2014 Jun 14.
Cardiovascular disease is characterised by reduced nitric oxide bioavailability resulting from oxidative stress. Our previous studies have shown that nitric oxide deficit per se increases the contribution of T-type calcium channels to vascular tone through increased superoxide from NADPH oxidase (Nox). The aim of the present study was therefore to identify the Nox isoform responsible for modulating T-type channel function, as T-type channels are implicated in several pathophysiological conditions involving oxidative stress. We evaluated T-channel function in skeletal muscle arterioles in vivo, using a novel T-channel blocker, TTA-A2 (3 μmol/L), which demonstrated no cross reactivity with L-type channels. Wild-type and Nox2 knockout (Nox2ko) mice were treated with the nitric oxide synthase inhibitor L-NAME (40 mg/kg/day) for 2 weeks. L-NAME treatment significantly increased systolic blood pressure and the contribution of T-type calcium channels to arteriolar tone in wild-type mice, and this was not prevented by Nox2 deletion. In Nox2ko mice, pharmacological inhibition of Nox1 (10 μmol/L ML171), Nox4 (10 μmol/L VAS2870) and Nox4-derived hydrogen peroxide (500 U/mL catalase) significantly reduced the effect of chronic nitric oxide inhibition on T-type channel function. In contrast, in wild-type mice, ML171 and VAS2870, but not catalase, reduced the contribution of T-type channels to vascular tone, suggesting a role for Nox1 and non-selective actions of VAS2870. We conclude that Nox1, but not Nox2 or Nox4, is responsible for the upregulation of T-type calcium channels elicited by chronic nitric oxide deficit. These data point to an important role for this isoform in increasing T-type channel function during oxidative stress.
心血管疾病的特征是氧化应激导致一氧化氮生物利用度降低。我们之前的研究表明，一氧化氮缺乏本身会通过增加烟酰胺腺嘌呤二核苷酸磷酸氧化酶（Nox）产生的超氧化物，增强T型钙通道对血管张力的作用。因此，本研究的目的是确定负责调节T型通道功能的Nox亚型，因为T型通道与几种涉及氧化应激的病理生理状况有关。我们在体内评估了骨骼肌小动脉中的T通道功能，使用了一种新型T通道阻滞剂TTA-A2（3 μmol/L），该阻滞剂对L型通道无交叉反应。野生型和Nox2基因敲除（Nox2ko）小鼠用一氧化氮合酶抑制剂L-NAME（40 mg/kg/天）处理2周。L-NAME处理显著提高了野生型小鼠的收缩压以及T型钙通道对小动脉张力的作用，而Nox2缺失并不能阻止这种情况。在Nox2ko小鼠中，对Nox1（10 μmol/L ML171）、Nox4（10 μmol/L VAS2870）和Nox4衍生的过氧化氢（500 U/mL过氧化氢酶）的药理学抑制显著降低了慢性一氧化氮抑制对T型通道功能的影响。相反，在野生型小鼠中，ML171和VAS2870，但不是过氧化氢酶，降低了T型通道对血管张力的作用，这表明Nox1的作用以及VAS2870的非选择性作用。我们得出结论，Nox1而非Nox2或Nox4负责慢性一氧化氮缺乏引起的T型钙通道上调。这些数据表明该亚型在氧化应激期间增加T型通道功能方面具有重要作用。
