title: Enhanced angiotensin II production by renal mesangium is responsible for apoptosis/proliferation of endothelial and epithelial cells in a model of malignant hypertension.
abstract: OBJECTIVE
  The systemic renin-angiotensin system (RAS) plays a crucial role in the pathogenesis of malignant hypertension. However, the intrarenal RAS might be at least equally important. We investigated the relationship between intrarenal RAS and mesangial, epithelial and endothelial cell proliferation/apoptosis in a model of malignant hypertension.
  
  
  METHODS
  Cultured murine mesangial cells were subjected to 160 mmHg hydrostatic pressure for 1 h. Angiotensin II was assessed by radio-immunoassay (RIA); pro-metalloproteinase-1 (pro-MMP-1) by enzyme-linked immunosorbent assay (ELISA); hydrogen peroxide (H2O2) by photocolorimetric assay, apoptosis by terminal dUTP (2-deoxyuridine 5'-triphosphate) nick-end labelling (TUNEL), p53 by western blot and proliferation by [H]thymidine incorporation, with or without angiotensin II and/or angiotensin II type 1/angiotensin II type 2 (AT-1/AT-2) receptor blockers. Endothelial and epithelial cells were similarly treated, and the same parameters evaluated. Further, untreated cells of both lines were cultured in conditioned medium of mesangial cells exposed to pressure. Their proliferation, apoptosis and angiotensin II production were also assessed.
  
  
  RESULTS
  High hydrostatic pressure increased angiotensin II production by mesangial cells, coinciding with augmented apoptosis and proliferation. Co-stimulation with exogenous angiotensin II amplified both effects. Pressure per se evoked no response in endothelial/epithelial cells, while exogenous angiotensin II stimulated proliferation and apoptosis. No augmentation of p53 expression was evident. These effects were abolished by anti-angiotensin-II peptide, saralasine and losartan, but not by PD123319. Incubation of untreated cells in medium of mesangium subjected to pressure, augmented proliferation and apoptosis. No significant changes were noticed in pro-MMP or H2O2.
  
  
  CONCLUSIONS
  Mesangium plays a deleterious role in the pathogenesis of malignant hypertension. High hydrostatic pressure stimulates angiotensin II synthesis by mesangial cells. The latter is responsible for hypercellularity and apoptotic death of mesangial, endothelial and epithelial cells. In this model, exaggerated apoptosis and proliferation are mediated via the angiotensin II pathway independently of p53 gene activation.
authors.affiliation: Division of Nephrology, Assaf Harofeh Medical Center, Zerifin, Israel. efratishai@013.net
authors.forename: Shai
authors.initials: S
authors.lastname: Efrati
authors.forename: Sylvia
authors.initials: S
authors.lastname: Berman
authors.forename: Naomi
authors.initials: N
authors.lastname: Goldfinger
authors.forename: Neta
authors.initials: N
authors.lastname: Erez
authors.forename: Zhan
authors.initials: Z
authors.lastname: Averbukh
authors.forename: Ahuva
authors.initials: A
authors.lastname: Golik
authors.forename: Varda
authors.initials: V
authors.lastname: Rotter
authors.forename: Joshua
authors.initials: J
authors.lastname: Weissgarten
mesh_terms: D000804:Angiotensin II / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D004730:Endothelium, Vascular / Q000378:metabolism / Q000502:physiology; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology; D006861:Hydrogen Peroxide / Q000378:metabolism; D006974:Hypertension, Malignant / Q000378:metabolism / Q000503:physiopathology*; D007668:Kidney / Q000378:metabolism / Q000503:physiopathology*; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D050527:Mesangial Cells / Q000378:metabolism / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D019459:Urothelium / Q000378:metabolism / Q000502:physiology
chemical_list: D016159:Tumor Suppressor Protein p53; D000804:Angiotensin II; D006861:Hydrogen Peroxide; D020781:Matrix Metalloproteinase 1