title: Oxidative damages in tubular epithelial cells in IgA nephropathy: role of crosstalk between angiotensin II and aldosterone.
abstract: BACKGROUND
  Inhibition of the renin-angiotensin-aldosterone system (RAAS) slows down the progression of chronic renal diseases (CKD) including IgA nephropathy (IgAN). Herein, we studied the pathogenetic roles of aldosterone (Aldo) in IgAN.
  
  
  METHODS
  Human mesangial cells (HMC) was activated with polymeric IgA (pIgA) from IgAN patients and the effects on the expression of RAAS components and TGF-β synthesis examined. To study the roles of RAAS in the glomerulotubular communication, proximal tubular epithelial cells (PTEC) was cultured with conditioned medium from pIgA-activated HMC with eplerenone or PD123319, the associated apoptotic event was measured by the generation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and reactive oxygen species (ROS).
  
  
  RESULTS
  Polymeric IgA up-regulated the Aldo synthesis and aldosterone synthase expression by HMC. The release of TGF-β by HMC was up-regulated synergistically by AngII and Aldo and this was inhibited by incubation of HMC with losartan plus eplerenone. Cultured PTEC express the mineralocorticoid receptor, but not synthesizing aldosterone. Apoptosis, demonstrated by cleaved PARP expression and caspase 3 activity, was induced in PTEC activated by conditioned medium prepared from HMC cultured with pIgA from IgAN patients. This apoptotic event was associated with increased generation of NADPH oxidase and ROS. Pre-incubation of PTEC with PD123319 and eplerenone achieved complete inhibition of PTEC apoptosis.
  
  
  CONCLUSIONS
  Our data suggest that AngII and Aldo, released by pIgA activated HMC, served as mediators for inducing apoptosis of PTEC in glomerulo-tubular communications. Crosstalk between AngII and Aldo could participate in determining the tubular pathology of IgAN.
authors.affiliation: Department of Medicine, Queen Mary Hospital, University of Hong Kong, Pokfulam, Hong Kong. jckleung@hku.hk
authors.forename: Joseph C K
authors.initials: JC
authors.lastname: Leung
authors.forename: Loretta Y Y
authors.initials: LY
authors.lastname: Chan
authors.forename: Sydney C W
authors.initials: SC
authors.lastname: Tang
authors.forename: Man-Fai
authors.initials: MF
authors.lastname: Lam
authors.forename: Chui-Wa
authors.initials: CW
authors.lastname: Chow
authors.forename: Ai-Ing
authors.initials: AI
authors.lastname: Lim
authors.forename: Kar-Neng
authors.initials: KN
authors.lastname: Lai
mesh_terms: D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2 / Q000235:genetics / Q000378:metabolism; D000450:Aldosterone / Q000494:pharmacology*; D000804:Angiotensin II / Q000378:metabolism / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D019405:Cytochrome P-450 CYP11B2 / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000473:pathology*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D005922:Glomerulonephritis, IGA / Q000201:enzymology / Q000473:pathology*; D006801:Humans; D007070:Immunoglobulin A / Q000494:pharmacology; D007687:Kidney Tubules, Proximal / Q000473:pathology*; D008297:Male; D050527:Mesangial Cells / Q000187:drug effects / Q000201:enzymology; D018384:Oxidative Stress / Q000187:drug effects*; D044139:Receptor, Angiotensin, Type 2 / Q000378:metabolism; D018161:Receptors, Mineralocorticoid / Q000235:genetics / Q000378:metabolism; D012084:Renin-Angiotensin System / Q000187:drug effects; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D007070:Immunoglobulin A; D044139:Receptor, Angiotensin, Type 2; D018161:Receptors, Mineralocorticoid; D016212:Transforming Growth Factor beta; C034639:polymeric IgA; D000804:Angiotensin II; D000450:Aldosterone; D043209:11-beta-Hydroxysteroid Dehydrogenase Type 2; D019405:Cytochrome P-450 CYP11B2