Academic Renal Unit, University of Bristol, Southmead Hospital, Bristol, United Kingdom.
Am J Physiol Renal Physiol. 2011 Oct;301(4):F733-42. doi: 10.1152/ajprenal.00458.2010. Epub 2011 Jul 20.
Laminar shear stress is a key determinant of systemic vascular behavior, including through activation of endothelial nitric oxide synthase (eNOS), but little is known of its role in the glomerulus. We confirmed eNOS expression by glomerular endothelial cells (GEnC) in tissue sections and examined effects of acute exposure (up to 24 h) to physiologically relevant levels of laminar shear stress (10-20 dyn/cm(2)) in conditionally immortalized human GEnC. Laminar shear stress caused an orientation of GEnC and stress fibers parallel to the direction of flow and induced Akt and eNOS phosphorylation along with NO production. Inhibition of the phophatidylinositol (PI)3-kinase/Akt pathway attenuated laminar shear stress-induced eNOS phosphorylation and NO production. Laminar shear stress of 10 dyn/cm(2) had a dramatic effect on GEnC permeability, reversibly decreasing the electrical resistance across GEnC monolayers. Finally, the laminar shear stress-induced reduction in electrical resistance was attenuated by the NOS inhibitors l-N(G)-monomethyl arginine (l-NMMA) and l-N(G)-nitroarginine methyl ester (l-NAME) and also by inhibition of the PI3-kinase/Akt pathway. Hence we have shown for GEnC in vitro that acute permeability responses to laminar shear stress are dependent on NO, produced via activation of the PI3-kinase/Akt pathway and increased eNOS phosphorylation. These results suggest the importance of laminar shear stress and NO in regulating the contribution of GEnC to the permeability properties of the glomerular capillary wall.
层流切应力是系统性血管行为的关键决定因素，包括通过激活内皮型一氧化氮合酶（eNOS），但其在肾小球中的作用知之甚少。我们通过组织切片确认了肾小球内皮细胞（GEnC）中的 eNOS 表达，并在条件性永生化的人 GEnC 中检查了生理相关水平的层流切应力（10-20 dyn/cm²）急性暴露（长达 24 小时）的影响。层流切应力使 GEnC 及其应力纤维平行于流向排列，并诱导 Akt 和 eNOS 磷酸化以及 NO 产生。磷脂酰肌醇（PI）3-激酶/Akt 途径的抑制减弱了层流切应力诱导的 eNOS 磷酸化和 NO 产生。10 dyn/cm²的层流切应力对 GEnC 的通透性有显著影响，可逆地降低 GEnC 单层的电阻。最后，NOS 抑制剂 l-N(G)-单甲基精氨酸（l-NMMA）和 l-N(G)-硝基精氨酸甲酯（l-NAME）以及 PI3-激酶/Akt 途径的抑制减弱了层流切应力诱导的电阻降低。因此，我们已经在体外的 GEnC 中表明，对层流切应力的急性通透性反应依赖于 NO，通过激活 PI3-激酶/Akt 途径和增加 eNOS 磷酸化产生。这些结果表明，层流切应力和 NO 在调节 GEnC 对肾小球毛细血管壁通透性的贡献方面具有重要意义。
