Watts Bruns A, George Thampi, Badalamenti Andrew, Good David W
Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and.
Department of Internal Medicine, The University of Texas Medical Branch, Galveston, Texas; and Department of Neuroscience and Cell Biology, The University of Texas Medical Branch, Galveston, Texas
Am J Physiol Renal Physiol. 2016 Sep 1;311(3):F600-13. doi: 10.1152/ajprenal.00185.2016. Epub 2016 Jun 29.
High-mobility group box 1 (HMGB1) is a nuclear protein released extracellularly in response to infection or injury, where it activates immune responses and contributes to the pathogenesis of kidney dysfunction in sepsis and sterile inflammatory disorders. Recently, we demonstrated that HMGB1 inhibits HCO3 (-) absorption in perfused rat medullary thick ascending limbs (MTAL) through a basolateral receptor for advanced glycation end products (RAGE)-dependent pathway that is additive to Toll-like receptor 4 (TLR4)-ERK-mediated inhibition by LPS (Good DW, George T, Watts BA III. Am J Physiol Renal Physiol 309: F720-F730, 2015). Here, we examined signaling and transport mechanisms that mediate inhibition by HMGB1. Inhibition of HCO3 (-) absorption by HMGB1 was eliminated by the Rho-associated kinase (ROCK) inhibitor Y27632 and by a specific inhibitor of Rho, the major upstream activator of ROCK. HMGB1 increased RhoA and ROCK1 activity. HMGB1-induced ROCK1 activation was eliminated by the RAGE antagonist FPS-ZM1 and by inhibition of Rho. The Rho and ROCK inhibitors had no effect on inhibition of HCO3 (-) absorption by bath LPS. Inhibition of HCO3 (-) absorption by HMGB1 was eliminated by bath amiloride, 0 Na(+) bath, and the F-actin stabilizer jasplakinolide, three conditions that selectively prevent inhibition of MTAL HCO3 (-) absorption mediated through NHE1. HMGB1 decreased basolateral Na(+)/H(+) exchange activity through activation of ROCK. We conclude that HMGB1 inhibits HCO3 (-) absorption in the MTAL through a RAGE-RhoA-ROCK1 signaling pathway coupled to inhibition of NHE1. The HMGB1-RAGE-RhoA-ROCK1 pathway thus represents a potential target to attenuate MTAL dysfunction during sepsis and other inflammatory disorders. HMGB1 and LPS inhibit HCO3 (-) absorption through different receptor signaling and transport mechanisms, which enables these pathogenic mediators to act directly and independently to impair MTAL function.
高迁移率族蛋白盒1（HMGB1）是一种在感染或损伤时释放到细胞外的核蛋白，它能激活免疫反应，并在脓毒症和无菌性炎症性疾病中导致肾功能障碍的发病机制。最近，我们证明HMGB1通过晚期糖基化终产物（RAGE）依赖的基底外侧受体途径抑制灌注大鼠髓袢升支粗段（MTAL）对HCO3（-）的重吸收，该途径与Toll样受体4（TLR4）-ERK介导的LPS抑制作用相加（Good DW，George T，Watts BA III. Am J Physiol Renal Physiol 309: F720-F730, 2015）。在此，我们研究了介导HMGB1抑制作用的信号传导和转运机制。Rho相关激酶（ROCK）抑制剂Y27632和Rho的特异性抑制剂（ROCK的主要上游激活剂）消除了HMGB1对HCO3（-）重吸收的抑制作用。HMGB1增加了RhoA和ROCK1的活性。RAGE拮抗剂FPS-ZM1和Rho的抑制消除了HMGB1诱导的ROCK1激活。Rho和ROCK抑制剂对浴液中LPS抑制HCO3（-）重吸收没有影响。浴液中的阿米洛利、无钠浴液和F-肌动蛋白稳定剂jasplakinolide消除了HMGB1对HCO3（-）重吸收的抑制作用，这三种情况选择性地阻止了通过NHE1介导的MTAL对HCO3（-）重吸收的抑制。HMGB1通过激活ROCK降低基底外侧Na（+）/H（+）交换活性。我们得出结论，HMGB1通过RAGE-RhoA-ROCK1信号通路抑制MTAL对HCO3（-）的重吸收，该通路与NHE1的抑制相关。因此，HMGB1-RAGE-RhoA-ROCK1途径代表了在脓毒症和其他炎症性疾病期间减轻MTAL功能障碍的潜在靶点。HMGB1和LPS通过不同的受体信号传导和转运机制抑制HCO3（-）重吸收。这使得这些致病介质能够直接且独立地作用，损害MTAL功能。
