Angiotensin II-induced hypertensive renal inflammation is mediated through HMGB1-TLR4 signaling in rat tubulo-epithelial cells

作者：Nair Anand R; Ebenezer Philip J; Saini Yogesh; Francis Joseph^*

来源：Experimental Cell Research, 2015, 335(2): 238-247.

DOI：10.1016/j.yexcr.2015.05.011

• Hypertensive renal injury
• Angiotensin II
• TLR4
• HMGB1
• Reactive oxygen species
• Inflammation

Background and purpose: Angiotensin II is a vaso-constrictive peptide that regulates blood pressure homeostasis. Even though the inflammatory effects of AngII in renal pathophysiology have been studied, there still exists a paucity of data with regard to the mechanism of action of AngII-mediated kidney injury. The objective of this study was to elucidate the mechanistic role of HMGB1-TLR4 signaling in AngII-induced inflammation in the kidney.
Experimental approach: Rat tubular epithelial cells (NRK52E) were treated with AngII over a preset time-course. In another set of experiments, HMGB1 was neutralized and TLR4 was knocked down using small interfering RNA targeting TLR4. Cell extracts were subjected to RT-PCR, immunoblotting, flow cytometty, and ELISA.
Key results: AngII-induced inflammation in NRK52E cells increased gene and protein expression of TLR4, HMGB1 and key proinflammatory cytokines (TNF alpha and IL1 beta). Pretreatment with Losartan (an ATI receptor blocker) attenuated the AngII-induced expression of TLR4 and inflammatory cytokines. TLR4 silencing was used to elucidate the specific role played by TLR4 in AngII-induced inflammation. TLR4siRNA treatment in these cells significantly decreased the AngII-induced inflammatory effect Consistent observations were made when the AngII treated cells were pretreated with anti-HMGB1. Downstream activation of NF kappa B and rate of generation of ROS was also decreased on gene silencing of TLR4 and exposure to anti-HMGB1.
Conclusions and implications: These results indicate a key role for HMGB1-TLR4 signaling in AngII-mediated inflammation in the renal epithelial cells. Our data also reveal that AngII-induced effects could be alleviated by HMGB1-TLR4 inhibition, suggesting this pathway as a potential therapeutic target for hypertensive renal dysfunctions.

• 出版日期2015-7-15