Rhein alleviates renal interstitial fibrosis by inhibiting tubular cell apoptosis in rats

Abstract

Background: Ureteral obstruction causes injury of the renal tissues and can irreversibly progress to renal fibrosis, with atrophy and apoptosis of tubular cells. The goal of the current study was to examine the effects of rhein on the apoptosis o renal tubular cells as well as renal fibrosis using a rodent model of unilateral ureteral obstruction (UUO).

Methods: UUO was induced through ureteral ligation, then animals received treatments with rhein or vehicle. The control rats only received sham operation. The renal tissue was harvested 1 week after surgery for assessment of kidney fibrosis.

Results: The expressions of collagen I and α-smooth muscle actin (α-SMA), as well as the severity of renal tubular apoptosis and fibrosis were time-dependently increased following UUO. Treatments with rhein partially inhibited such responses. Renal interstitial fibrosis was associated with STAT3 (signal transducer and activator of transcription 3) phosphorylation as well as altered expressions of Bax and Bcl2, both apoptosis-related proteins. Treatment with rhein also partly blocked these responses.

Conclusion: These findings demonstrated that rhein mitigated apoptosis of renal tubular cell as well as renal fibrosis in a UUO rodent model. This curative effect is likely mediated via suppression of STAT3 phosphorylation.

Keywords: Apoptosis; Collagen; Renal interstitial fibrosis; Rhein; Unilateral ureteral obstruction.

Fig. 1

Effect of UUO on the expression levels of renal type I collagen and α-SMA in the rat kidneys. mRNA (a) and protein (b) expression levels of renal type I collagen and α-SMA in the kidneys of sham and UUO model rats. Data were shown as mean ± SD. *p < 0.05, **p < 0.01, compared to sham

Fig. 2

Effect of UUO on the levels of renal tubular apoptosis (TUNEL assay). a Representative images of TUNEL staining in the kidneys of sham and UUO model rats, scale bar 50 μm. b Quantitation of the TUNEL staining results in a. Data were shown as mean ± SD. **p < 0.01, compared to sham

Fig. 3

Effect of rhein on the phosphorylation levels of STAT3 in the kidney of UUO model rats. a Western blot analysis of the kidney tissue lysates of sham and UUO rats with vehicle (veh) or rhein treatment, using antibodies against STAT3, p-STAT3 and GAPDH (as loading control). b Quantification of the Western blot results in a by densitometry, expressed as fold-increase over the controls. Data were shown as mean ± SD. **p < 0.01, compared to UUO + veh/STAT3. ^#p < 0.05, compared to UUO + veh/p-STAT3

Fig. 4

Effect of rhein on renal fibrosis in UUO model rats. a Representative images of Masson trichrome staining of sham and UUO rats with vehicle (veh) or rhein treatment, scale bar 50 μm. b Quantification of Masson trichrome staining results. Data were shown as mean ± SD. **p < 0.01, compared to sham + veh and sham + rhein. ^##p < 0.01, compared to UUO + veh

Fig. 5

Effect of rhein on the expression levels of renal type I collagen and α-SMA in the UUO model rats. mRNA (a) and protein (b) expression levels of renal type I collagen and α-SMA in the kidneys of sham and UUO rats with vehicle (veh) or rhein treatment. Data were shown as mean ± SD. **p < 0.01, compared to sham + veh and sham + rhein. ^#p < 0.05, ^##p < 0.01, compared to UUO + veh

Fig. 6

Effect of rhein on the levels of renal tubular cell apoptosis following UUO injury. a Western blot analysis of the kidney tissue lysates of sham and UUO rats with vehicle (veh) or rhein treatment, using antibodies against Bax, Bcl-2 and GAPDH (as loading control). b Quantification of the Western blot results in (A) by densitometry, expressed as Bax/Bcl-2 ratio. *p < 0.05, compared to sham + veh and sham + rhein. ^#p < 0.05, compared to UUO + veh