Effect of irbesartan on angiotensin II-induced hypertrophy of human proximal tubular cells.
BACKGROUND
Intrarenal activation of the renin angiotensin system (RAS) plays an important role in mediating renal fibrosis. Both angiotensin converting enzyme inhibitors (ACEIs) and angiotensin II (AngII) receptor antagonists have been shown to exert a protective role against diabetic and non-diabetic nephropathy. However, the exact mechanism of how blocking local RAS prevents renal fibrosis is unclear. The present study was to investigate the influence of a new AngII receptor antagonist, irbesartan (Irb), on AngII-induced hypertrophy in human proximal tubular cell line (HK-2).


METHODS
The cell line, HK-2, was grown in Dulbeccos's Modified Eagle's Medium containing 10% heat-inactivated fetal calf serum. After rested in serum-free medium for 24 hours, the effects of Irb on AngII (10(-7) mol/L)-induced [(3)H]-leucine incorporation, total protein content (measured by the Coomassie brilliant blue G250 method), and change in cell size (determined by scanning electron microscopy) were observed. The influence of Irb on the cell cycle was analyzed by fluorescence activated cell sorter (FACS) flow cytometry.


RESULTS
AngII induced cell hypertrophy in a time and dose dependent manner. Stimulation of cells with AngII for 48 hours resulted in a increase in [(3)H]-leucine incorporation [0 hour: (5584 +/- 1016) cpm/10(5) cells vs 48 hours: (10741 +/- 802) cpm/10(5) cells, P < 0.05], which was significantly attenuated by treatment with Irb. AngII significantly increased the total protein content in HK-2 cells [control: (0.169 +/- 0.011) mg/10(5) cells vs AngII group: (0.202 +/- 0.010) mg/10(5) cells, P < 0.05], which was also markedly inhibited by cotreatment with Irb (P < 0.01). Scanning electron microscopy showed that AngII induced an increase in average physical cell size, which was significantly inhibited by Irb [control: (11.92 +/- 1.62) microm; AngII group: (20.63 +/- 3.83) micro m; AngII + Irb group: (13.59 +/- 3.15) micro m; P < 0.01 vs control, respectively]. Furthermore, flow cytometry revealed that AngII arrested cells in the G(0)-G(1) phase, which was significantly reversed by treatment with Irb [G(0)-G(1) cells in AngII group: (76.09 +/- 1.82)%, in AngII + Irb group: (67.00 +/- 2.52)%, P < 0.05].


CONCLUSIONS
Irb can inhibit AngII-induced hypertrophy in HK-2 cells.
Liu
Bi-Cheng
BC
Institute of Nephrology, Zhongda Hospital, Southeast University School of Medicine, Nanjing 210009, China. kidney@jlonline.com
Sun
Jing
J
Chen
Qi
Q
Luo
Dong-Dong
DD
Ma
Kun-Ling
KL
Ruan
Xiong-Zhong
XZ
D000804:Angiotensin II / Q000494:pharmacology*; D047228:Angiotensin II Type 1 Receptor Blockers; D001713:Biphenyl Compounds / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D006984:Hypertrophy; D000077405:Irbesartan; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000473:pathology / Q000648:ultrastructure; D014176:Protein Biosynthesis; D013777:Tetrazoles / Q000494:pharmacology*
D047228:Angiotensin II Type 1 Receptor Blockers; D001713:Biphenyl Compounds; D013777:Tetrazoles; D000804:Angiotensin II; D000077405:Irbesartan