title: Angiotensin II-induced hypertensive renal inflammation is mediated through HMGB1-TLR4 signaling in rat tubulo-epithelial cells.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  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
  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.
authors.affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States.
authors.forename: Anand R
authors.initials: AR
authors.lastname: Nair
authors.affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Ebenezer
authors.affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States.
authors.forename: Yogesh
authors.initials: Y
authors.lastname: Saini
authors.affiliation: Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, United States. Electronic address: jfrancis@vetmed.lsu.edu.
authors.forename: Joseph
authors.initials: J
authors.lastname: Francis
mesh_terms: D000804:Angiotensin II; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D002460:Cell Line; D004847:Epithelial Cells / Q000276:immunology / Q000378:metabolism*; D024243:HMGB1 Protein / Q000378:metabolism*; D006973:Hypertension / Q000139:chemically induced / Q000150:complications / Q000378:metabolism*; D007676:Kidney Failure, Chronic / Q000209:etiology / Q000276:immunology / Q000378:metabolism*; D007684:Kidney Tubules / Q000473:pathology; D019808:Losartan / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D000959:Antihypertensive Agents; D024243:HMGB1 Protein; C104200:Hbp1 protein, rat; D016328:NF-kappa B; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4; D000804:Angiotensin II; D019808:Losartan
keywords: Angiotensin II; HMGB1; Hypertensive renal injury; Inflammation; Reactive oxygen species; TLR4