[Role of protein phosphatase 2A in renal interstitial fibrosis]

To explore the role of protein phosphatase 2A (PP2A) in renal interstitial fibrosis by using rat model of unilateral ureteral obstructive (UUO) or cell model of human kidney proximal tubular epithelial (HK)-2 cells treated with transforming growth factor-β1 (TGF-β1).

1) A total of 15 Sprague-Dawley rats were randomly divided into a sham group, a UUO group and an okadaic acid (OA) treated group (OA group) (n=5 in each group). The OA 
[30 μg/(kg·d)], diluted with 1.8% alcohol, was given to the rats in the OA group through gastric tube after at 72 h after the surgery, while the equal volume of 1.8% alcohol was given to the rats in the sham group and the UUO group. After sacrificing rats, the blood and kidney were collected to detect the renal function and the expression of PP2Ac, fibronectin (FN), collagen-I (Col-I), E-cadherin (E-cad) and α-smooth muscle actin (α-SMA) by immunohistochemistry, Western blot and RT-PCR, respectively; 2) The likely concentration of OA was determined by Trypan blue dye exclusive assay and methylthiazolyldiphenyl-tetrazolium bromide (MTT) assay. The HK-2 cells were incubated with serum-free Dulbecco's modified eagle medium (DMEM) for 24 h; then they were divided into a control group, a TGF-β1 group (treated with 5 ng/mL TGF-β1 for 24 h) and a TGF-β1+OA group (treated with 5 ng/mL TGF-β1 and 40 nmol/L OA for 24 h). The HK-2 cells were collected and the expression of PP2Ac, FN, Col-I, E-cad and α-SMA were detected by Western blot.

1) Compared with the sham group, the BUN and Scr in the UUO group increased (both P<0.05); compared with the UUO group, the BUN and Scr in the OA group decreased (both P<0.05); the expression of PP2Ac, FN, Col-I and α-SMA was up-regulated while the expression of E-cad was down-regulated in the UUO group compared with those in the sham group (all P<0.05). The expression of PP2Ac, FN, Col-I and α-SMA was down-regulated while the expressions of E-cad was up-regulated in the OA group compared with those in the UUO group (all P<0.05); 2) The likely concentration of OA was 40 nmol/L. Western blot showed that the expression of PP2Ac, FN, Col-I and α-SMA was up-regulated while the expressions of E-cad was down-regulated in the TGF-β1 group compared with those in the control group (all P<0.05); the expression of PP2Ac, FN, Col-I and α-SMA were down-regulated while the expression of E-cad was up-regulated in the TGF-β1+OA group compared with those in the TGF-β1 group (all P<0.05).

PP2A might be able to promote the renal interstitial fibrosis.
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