Activation of the hepatic endothelin-system in rats with biliary liver fibrosis

Gliptins Suppress Inflammatory Macrophage Activation to Mitigate Inflammation, Fibrosis, Oxidative Stress, and Vascular Dysfunction in Models of Nonalcoholic Steatohepatitis and Liver Fibrosis

AIMS

Nonalcoholic steatohepatitis (NASH) is characterized by steatosis, panlobular inflammation, liver fibrosis, and increased cardiovascular mortality. Dipeptidyl peptidase-4 inhibitors (gliptins) are indirect glucagon-like peptide 1 agonists with antidiabetic and anti-inflammatory activity, used for the treatment of type 2 diabetes. Their potential and underlying mechanisms to treat metabolic liver inflammation and fibrosis as well as the associated vascular dysfunction remain to be explored.

RESULTS

In the methionine/choline-deficient (MCD) diet and Mdr2^-/- models of NASH and liver fibrosis, treatment with sitagliptin and linagliptin significantly decreased parameters of steatosis and inflammation, which was accompanied by suppression of hepatic transcript levels reflecting metabolic inflammation and fibrosis, including SREBP-1c, FAS, TNFα, iNOS, α-SMA, Col1α1, and MMP-12. Moreover, gliptins reduced the number of liver infiltrating CD11b⁺Ly6C^hi proinflammatory monocytes/macrophages and liver-resident F4/80⁺ macrophages, with an increase of Ym1⁺ alternative macrophages and (anti-inflammatory) macrophage markers Arg1 and IL-10. This was paralleled by decreased hepatic and aortic reactive oxygen species (ROS) production and NOX-2 mRNA expression, a normalization of endothelial dysfunction, cardiac NADPH oxidase activity, mitochondrial ROS formation, and whole blood oxidative burst in the MCD model. Innovation and Conclusions: Gliptins via suppression of inflammation decrease steatosis, apoptosis, oxidative stress, and vascular dysfunction in murine models of NASH and liver fibrosis, with mild direct antifibrotic properties. They reduce the numbers of liver and vascular inflammatory monocytes/macrophages and induce their alternative polarization, with beneficial effect on NASH-associated hepatic and cardiovascular complications. Therefore, gliptins qualify as drugs for treatment of NASH and associated liver fibrosis and cardiovascular complications. Antioxid. Redox Signal. 28, 87-109.

Acute effects of endothelin receptor antagonists on hepatic hemodynamics of cirrhotic and noncirrhotic rats

Hepatic and circulating endothelin-1 (ET-1) are increased in patients with cirrhosis and in cirrhotic animals. However, the distinct roles of ET receptor subtypes ETA and ETB in cirrhosis and portal hypertension (PHT) have not been clearly elucidated. Thus, we studied the effects of selective ET-1 antagonists (ETA-ant or ETB-ant) and nonselective ET-1 antagonist (ETA/B-ant) on hepatic hemodynamics in cirrhotic rats. Liver fibrosis and PHT were induced by complete bile duct ligation (BDL) in rats. Two weeks after BDL or sham surgery, hemodynamic responses were measured during intraportal infusion of incremental doses of the following ET-ants: (i) BQ-123, (ii) BQ-788, and (iii) bosentan. After equilibration with vehicle, doses of ET-ants were infused for 30 min periods, and steady-state systemic and hepatic hemodynamics, portal venous pressure (PVP), and hepatic blood flow (HBF) were measured. BDL induced significant PHT and elevated concentrations of plasma ET-1 compared with sham. ETA-ant decreased PVP of cirrhotic rats but had no effect on sham, whereas ETB-ant increased PVP in sham but had no effect in BDL. Nonselective ETA/B-ant decreased PVP of BDL similarly to ETA-ant. Both ETA-ant and ETB-ant decreased local HBF, whereas a nonselective antagonist did not change HBF in sham; however no significant changes were observed in HBF of BDL rats with any of the antagonists. These findings suggest ETA activation contributes to PHT in cirrhotic rats, whereas ETB-mediated portal depressor effects are attenuated in cirrhotic rats compared with noncirrhotic rats.

Pathophysiology and clinical practice analysis on endothelin system and portal hypertension

Portal hypertension (PHT) is a common clinical syndrome which leads to various severe, even lethal complications. The concentration of endothelin-1 (ET-1) in plasma is increased both in human body and PHT animal model. The effect of ET-1 depends on the kind of tissue and the expression of ET-1 receptor in this tissue. However, the expression of ET-1 receptor is not identical even in the same tissue at different PHT phases. This review aims to give an update on the endothelin syetem in PHT and elucidate a potential novel strategy.

Effects of Fuzheng Huayu Decoction on elevated portal pressure in rat model of dimethylnitrosamine-induced liver cirrhosis

AIM: To investigate the effect of Fuzheng Huayu Decoction (FHD) on portal hypertension due to liver cirrhosis induced by dimethylnitrosamine (DMN).

METHODS: After the rat model of hepatic cirrhosis was successfully established via intraperitoneal injection of 5 g/L DMN, traditional Chinese medicine formula FHD was administrated intragastrically. Three weeks later, serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin (ALB) and total bilirubin (TBIL), as well as hepatic levels of hydroxyproline (Hyp) and endothelin-1 (ET-1) were measured. For portal pressure measurement, a catheter was inserted into the superior mesenteric vein and gently advanced up to the portal vein. The pathological alterations of liver tissues were observed and compared between control group and treatment group.

RESULTS: Portal pressure of the model group was 2.4 times higher than those in normal group; the ET-1 contents in liver tissue significantly increased in comparison with that of normal group (344.48 ± 71.42 pg/mg vs 247.00 ± 49.51 pg/mg, P < 0.01). The above two markers in model group were positively correlated (r = 0.675, P < 0.01). Portal pressure of the treatment group remarkably declined by 67% (P < 0.01) and ET-1 contents remarkably dropped to 292.13 ± 52.07 pg/mg (P < 0.05). There were significant differences between the treatment group and model group in the serum levels of ALT, AST, and TBIL and tissue contents of Hyp and ET-1. Pathological findings showed restoration of normal liver structure in the treatment group.

CONCLUSION: The elevation of portal pressure is positively correlated with the increase of ET-1 content during the process of liver cirrhosis; FHD can significantly decrease the cirrhosis-induced elevation of portal pressure and ET-1 content in liver tissues through its anti-hepatic fibrosis effect in rats.