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

Authors

Anand R. Nair, Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States.
Philip J. Ebenezer, Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States.
Yogesh Saini, Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States.
Joseph Francis, Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States. Electronic address: jfrancis@vetmed.lsu.edu.

Document Type

Article

Publication Date

7-15-2015

Abstract

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 cytometry, and ELISA. KEY RESULTS: AngII-induced inflammation in NRK52E cells increased gene and protein expression of TLR4, HMGB1 and key proinflammatory cytokines (TNFα and IL1β). Pretreatment with Losartan (an AT1 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 Ang II treated cells were pretreated with anti-HMGB1. Downstream activation of NFκB 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.

Publication Source (Journal or Book title)

Experimental cell research

First Page

238

Last Page

47

Recommended Citation

Nair, A. R., Ebenezer, P. J., Saini, Y., & Francis, J. (2015). Angiotensin II-induced hypertensive renal inflammation is mediated through HMGB1-TLR4 signaling in rat tubulo-epithelial cells. Experimental cell research, 335 (2), 238-47. https://doi.org/10.1016/j.yexcr.2015.05.011