title: Endoplasmic reticulum stress implicated in the development of renal fibrosis.
abstract: Endoplasmic reticulum (ER) stress-associated apoptosis plays a role in organ remodeling after insult. The effect of ER stress on renal tubular damage and fibrosis remains controversial. This study aims to investigate whether ER stress is involved in tubular destruction and interstitial fibrosis in vivo. Renal cell apoptosis was proven by terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) stain and poly-ADP ribose polymerase expression in the unilateral ureteral obstruction (UUO) kidney. ER stress was evoked and confirmed by the upregulation of glucose-regulated protein 78 (GRP78) and the common Lys-Asp-Glu-Leu (KDEL) motif of ER retention proteins after UUO. ER stress-associated proapoptotic signals, including B-cell chronic lymphocytic leukemia (CLL)/lymphoma 2-associated × protein (BAX) expression, caspase-12 and c-Jun N-terminal kinase (JNK) phosphorylation, were activated in the UUO kidney. Prolonged ER stress attenuated both unsplicing and splicing X-box binding protein 1 (XBP-1) protein expression, but continued to activate inositol-requiring 1α (IRE1α)-JNK phosphorylation, protein kinase RNA-like endoplasmic reticulum kinase (PERK), eukaryotic translation initiation factor 2α subunit (eIF2α), activating transcription factor (ATF)-4, CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) and cleavage activating transcription factor 6 (cATF6)-CHOP signals, which induce ER stress-related apoptosis but attenuate adaptive unfolded protein responses in UUO kidneys. However, renal apoptosis and fibrosis were attenuated in candesartan-treated UUO kidney. Candesartan was associated with maintenance of XBP-1 expression and attenuated ATF4, cATF6 and CHOP protein expression. Taken together, results show that overwhelming ER stress leads to renal cell apoptosis and subsequent fibrosis; and candesartan, at least in part, restores renal integrity by blocking ER stress-related apoptosis. Reducing ER stress may present a way to attenuate renal fibrosis.
authors.affiliation: Department of Integrated Diagnostics and Therapeutics, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Chih-Kang
authors.initials: CK
authors.lastname: Chiang
authors.forename: Shih-Ping
authors.initials: SP
authors.lastname: Hsu
authors.forename: Cheng-Tien
authors.initials: CT
authors.lastname: Wu
authors.forename: Jenq-Wen
authors.initials: JW
authors.lastname: Huang
authors.forename: Hui-Teng
authors.initials: HT
authors.lastname: Cheng
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Chang
authors.forename: Kuan-Yu
authors.initials: KY
authors.lastname: Hung
authors.forename: Kuan-Dun
authors.initials: KD
authors.lastname: Wu
authors.forename: Shing-Hwa
authors.initials: SH
authors.lastname: Liu
mesh_terms: D057912:Angiotensin II Type 2 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001562:Benzimidazoles / Q000494:pharmacology; D001713:Biphenyl Compounds; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D003094:Collagen / Q000378:metabolism; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D005355:Fibrosis; D005455:Fluorescent Antibody Technique; D007668:Kidney / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D007677:Kidney Function Tests; D007684:Kidney Tubules / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D018832:Molecular Chaperones / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D013777:Tetrazoles / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects; D014517:Ureteral Obstruction / Q000150:complications / Q000473:pathology / Q000503:physiopathology
chemical_list: D057912:Angiotensin II Type 2 Receptor Blockers; D001562:Benzimidazoles; D001713:Biphenyl Compounds; D018832:Molecular Chaperones; D013777:Tetrazoles; D003094:Collagen; D011065:Poly(ADP-ribose) Polymerases; C081643:candesartan