Telmisartan attenuates hepatic fibrosis in bile duct-ligated rats

Abstract

Aim: To evaluate the antifibrotic effect of telmisartan, an angiotensin II receptor blocker, in bile duct-ligated rats.

Methods: Adult Sprague-Dawley rats were allocated to 3 groups: sham-operated rats, model rats underwent common bile duct ligation (BDL), and BDL rats treated with telmisartan (8 mg/kg, po, for 4 weeks). The animals were sacrificed on d 29, and liver histology was examined, the Knodell and Ishak scores were assigned, and the expression of angiotensin-converting enzyme (ACE) and ACE2 was evaluated with immunohistochemical staining. The mRNAs and proteins associated with liver fibrosis were evaluated using RTQ-PCR and Western blot, respectively.

Results: The mean fibrosis score of BDL rats treated with telmisartan was significantly lower than that of the model rats (1.66±0.87 vs 2.13±0.35, P=0.015). However, there was no significant difference in inflammation between the two groups, both of which showed moderate inflammation. Histologically, treatment with telmisartan significantly ameliorated BDL-caused the hepatic fibrosis. Treatment with telmisartan significantly upregulated the mRNA levels of ACE2 and MAS, and decreased the mRNA levels of ACE, angiotensin II type 1 receptor (AT1-R), collagen type III, and transforming growth factor β1 (TGF-β1). Moreover, treatment with telmisartan significantly increased the expression levels of ACE2 and MAS proteins, and inhibited the expression levels of ACE and AT1-R protein.

Conclusion: Telmisartan attenuates liver fibrosis in bile duct-ligated rats via increasing ACE2 expression level.

Figure 1

(A) Identification of the common bile duct. (B) Ligation success was confirmed by assessing bile duct dilation 4 weeks after BDL.

Figure 2

H&E and Masson's trichrome. (A) (G1) Normal liver. (B and D) (G2) Liver sections stained with H&E and Masson's trichrome, respectively. Inflammatory infiltration, bile ductular proliferation, and fibrosis are shown. (C and E) (G3) Liver sections stained with H&E and Masson's trichrome, respectively. These samples showed obvious attenuation of inflammatory infiltration, bile ductular proliferation, and fibrosis (original magnification ×100).

Figure 3

Immunohistochemical staining of ACE2 and ACE in rat liver. (A) Sham-operated rat liver tissue section incubated without ACE2 primary antibody. (B) ACE2 staining of rat liver tissue 4 weeks after BDL without ARB. (C) ACE2 staining of rat liver tissue after 4 weeks of BDL+8 mg/kg telmisartan daily. (D) Sham-operated rat liver tissue section incubated without ACE primary antibody. (E) ACE staining of rat liver tissue 4 weeks after BDL without ARB. (F) ACE staining of rat liver tissue after 4 weeks of BDL+8 mg/kg telmisartan daily (original magnification ×200).

Figure 4

(A) Relative expression of hepatic ACE2, MAS, ACE, AT1-R, col III, and TGF-β1 by real-time PCR. Expression levels were normalized to GAPDH. (B) Representative DNA gel electrophoresis for quantitation of mRNA expression. Lane 1, 4, 7, 10, 13, 16, 19, sham-operated rats (G1); Lane 2, 5, 8, 11, 14, 17, 20, the BDL without ARB (G2); Lane 3, 6, 9, 12, 15, 18, 21, the BDL+8 mg/kg telmisartan group (G3); Lane 1 to 3, GADPH primer pair; Lane 4 to 6, ACE2 primer pair; Lane 7 to 9, Mas primer pair; Lane 10 to 12, ACE primer pair; Lane 13 to 15, AT1 primer pair; Lane 16 to 18, col III primer pair; and Lane 19 to 21, TGF-β1 primer pair.

Figure 5

Expression of ACE2, MAS, ACE, and AT1 detected by Western blotting. Lane 1, sham-operated rats (G1); Lane 2, the BDL without ARB (G2); Lane 3, the BDL+8 mg/kg telmisartan daily (G3).