Effect Of APJ Antagonist Apelin13(F13A) On The Fibrosis And The Possible Mechanism In Rats With Hepatic Fibrosis

OBJECTIVE To investigate the effect of putative receptor protein related to the angiotensinreceptor AT1(APJ) antagonist Apelin13(F13A) and to explore the possible mechanism in rats with hepatic fibrosis.METHODS The sprague-dawley(S-D) male rats were randomly divided into the control group, hepatic fibrosis model group and Apelin13(F13A) group. The rat model of hepatic fibrosis was induced by intraperitoneal injection with 3 m L/kg 40% carbon tetrachloride(CCl4). Apelin13(F13A)(100 μg/kg) was administered by intraperitoneal injection for 8 weeks. After 8 weeks, the indexs reflected the liver metabolism and synthesis of protein function including the total protein(TPROT), albumin(ALB) and globin(GLB) and the indexs reflected the hepatocellular damage including the alanine transaminase(ALT) and aspartate transaminase(AST) and were measured by automatic biochemistry analyzer. The levels of serum hyaluronic acid(HA), 1aminin(LN), procollagen Ⅲ(PcⅢ) and collagen IV(IV-C) were tested by ELISA assay. The levels of serum Apelin-36, transforming growth factor-β1(TGF-β1) and α-Smooth muscle actin(α-SMA) by ELISA assay. The pathological structure of liver was observated by Hematoxylin-Eosin(H-E) staining. The m RNA and protein expressions of Apelin-36, APJ, TGF-β1, α-SMA and endoplasmic reticulum stress protein markers including glucose-regulated protein 78(GRP78), CCAAT/enhaneer-binding protein homologous protein(CHOP) and tribbles homolog 3(TRB3) in liver were measured by Real-time PCR and Western blot respectively.RESULTS(1) At the end of the experiment after 8 weeks, all the rats were survival in control group, the five rats were dead in hepatic fibrosis model group and one rat was dead in the Apelin13(F13A) group. The hair was brown and dull, spirits was drooping, the activity was significantly decreased, the response to external stimuli was slow and the weight was significantly decreased in the rats of hepatic fibrosis model group. The rats moved freely, above-mentioned phenomenons did not appear in the control group. The above-mentioned phenomenons were significantly reduced, the activity was improved in the Apelin13(F13A) group.(2) Compared to the control group, the level of serum Apelin-36, m RNA and protein expressions of Apelin-36 and APJ in the liver were significantly increased in the hepatic fibrosis model group(all P﹤0.05). Apelin13(F13A) did not affect the serum Apelin-36, m RNA and protein expressions of Apelin-36 and APJ in the liver compared to the hepatic fibrosis model group(all P﹥0.05).(3) Compared to the control group, the levels of serum TPROT and ALB were significantly decreased(all P﹤0.05), the levels of serum GLB, ALT, and AST were significantly increased in the hepatic fibrosis model group(all P﹤0.05). Compared to the model group, the levels of serum TPROT and ALB were significantly increased(all P﹤0.05), the levels of serum GLB, ALT and AST were significantly decreased in the Apelin13(F13A) group(all P﹤0.05).(4) Compared to the control group, the levels of serum HA、LN、PCⅢ and IV-C were significantly increased in the hepatic fibrosis model group(all P﹤0.05). Compared to the model group, the levels of serum HA、LN、PC Ⅲand IV-C were significantly decreased in the Apelin13(F13A) group(all P﹤0.05).(5) The lobules of liver of rats was integrate, hepatic cord arranged regularity, the structure of hepatic cord was integrate, the hepatic cords and sinusoids with central vein were arranged radially, therr was no obvious hyperplasia of collagen fiber and the degree of liver fibrosis was 0 in the control group. The lobules of liver was destroyed severely, hepatic cord arranged turbidly, there were many inflammatory cells and necrotic cells and fibrous connective tissue hyperplasia in the hepatic portal area, the false lobule was formatted and the degree of liver fibrosis was 3-4 in the hepatic fibrosis model group. Compared to the model group, the amount of degenerating cells and necrotic cells was significantly decreased, the degree of liver fibrosis was significantly reduced and the degree of liver fibrosis was 1-2 in the Apelin13(F13A) group.(6) Compared to the control group, the levels of serum TGF-β1 and α-SMA and m RNA and protein expressions of TGF-β1 and α-SMA in the liver were significantly increased in the hepatic fibrosis model group(all P﹤0.05). Compared to the model group, the levels of serum TGF-β1 and α-SMA and m RNA and protein expressions of TGF-β1 and α-SMA in the liver were significantly decreased in the Apelin13(F13A) group(all P﹤0.05).(7) Compared to the control group, the m RNA and protein expressions of GRP78, CHOP and TRB3 were significantly increased in the hepatic fibrosis model group(all P﹤0.05). Compared to the model group, the m RNA and protein expressions of GRP78, CHOP and TRB3 were significantly decreased in the Apelin13(F13A) group(all P﹤0.05).CONCLUSIONS APJ antagonist Apelin13(F13A) inhibits the hepatic fibrosis in rats with hepatic fibrosis, which the mechanism may be related with down-regulation of TGF-β1 expressions and inhibition of endoplasmic reticulum stress.