Lin Chian-Shiung, Lee Shang-Hsing, Huang Ho-Shiang, Chen Yih-Sharng, Ma Ming-Chieh
Department of Surgery, Liou-Ying Hospital, Chi-Mei Medical Center, Tainan Hsien, Taiwan;
Department of Urology, Cardinal Tien Hospital, New Taipei, Taiwan;
Am J Physiol Renal Physiol. 2015 Aug 15;309(4):F369-76. doi: 10.1152/ajprenal.00462.2014. Epub 2015 Jul 1.
The presence of NADPH oxidase (Nox) in the kidney, especially Nox4, results in H2O2 production, which regulates Na(+) excretion and urine formation. Redox-sensitive transient receptor potential vanilloid 1 channels (TRPV1s) are distributed in mechanosensory fibers of the renal pelvis and monitor changes in intrapelvic pressure (IPP) during urine formation. The present study tested whether H2O2 derived from Nox4 affects TRPV1 function in renal sensory responses. Perfusion of H2O2 into the renal pelvis dose dependently increased afferent renal nerve activity and substance P (SP) release. These responses were attenuated by cotreatment with catalase or TRPV1 blockers. In single unit recordings, H2O2 activated afferent renal nerve activity in response to rising IPP but not high salt. Western blots revealed that Nox2 (gp91(phox)) and Nox4 are both present in the rat kidney, but Nox4 is abundant in the renal pelvis and originates from dorsal root ganglia. This distribution was associated with expression of the Nox4 regulators p22(phox) and polymerase δ-interacting protein 2. Coimmunoprecipitation experiments showed that IPP increases polymerase δ-interacting protein 2 association with Nox4 or p22(phox) in the renal pelvis. Interestingly, immunofluorescence labeling demonstrated that Nox4 colocalizes with TRPV1 in sensory fibers of the renal pelvis, indicating that H2O2 generated from Nox4 may affect TRPV1 activity. Stepwise increases in IPP and saline loading resulted in H2O2 and SP release, sensory activation, diuresis, and natriuresis. These effects, however, were remarkably attenuated by Nox inhibition. Overall, these results suggest that Nox4-positive fibers liberate H2O2 after mechanostimulation, thereby contributing to a renal sensory nerve-mediated diuretic/natriuretic response.
肾脏中存在NADPH氧化酶（Nox），尤其是Nox4，可导致过氧化氢生成，从而调节钠（+）排泄和尿液形成。氧化还原敏感的瞬时受体电位香草酸受体1通道（TRPV1）分布于肾盂的机械感觉纤维中，并在尿液形成过程中监测肾盂内压（IPP）的变化。本研究检测了源自Nox4的过氧化氢是否会影响肾感觉反应中的TRPV1功能。向肾盂灌注过氧化氢剂量依赖性地增加了肾传入神经活动和P物质（SP）释放。过氧化氢酶或TRPV1阻滞剂共同处理可减弱这些反应。在单单位记录中，过氧化氢在IPP升高时激活肾传入神经活动，但对高盐无反应。蛋白质免疫印迹显示，Nox2（gp91（phox））和Nox4均存在于大鼠肾脏中，但Nox4在肾盂中含量丰富且起源于背根神经节。这种分布与Nox4调节因子p22（phox）和聚合酶δ相互作用蛋白2的表达有关。免疫共沉淀实验表明，IPP增加了聚合酶δ相互作用蛋白2与肾盂中Nox4或p22（phox）的结合。有趣的是，免疫荧光标记显示Nox4与肾盂感觉纤维中的TRPV1共定位，表明Nox4产生的过氧化氢可能影响TRPV1活性。IPP和盐水负荷的逐步增加导致过氧化氢和SP释放、感觉激活、利尿和利钠。然而，Nox抑制可显著减弱这些效应。总体而言，这些结果表明，Nox4阳性纤维在机械刺激后释放过氧化氢，从而促进肾感觉神经介导的利尿/利钠反应。
