Similarly, leptin incubation alone also resulted in a significant decrease in gel surface area compared with a gel treated with buffer alone. Furthermore, the concomitant administration of leptin with ETAR antagonist (BQ123) reversed the leptin-induced decrease in gel surface area. In contrast, simultaneous administration of ETBR antagonist (BQ788) with leptin did not modify the
leptin-induced RG7204 solubility dmso contraction of gel. It should be noted that leptin incubation resulted in an up-regulated in the expression of ETAR and OBRb protein as well as higher levels of activator protein-1 mRNA in the HSC-T6 and primary HSC supernatant (Fig. 6C-E; Supporting Fig. 2C-E). In the current study, we successfully created a NASH cirrhotic model that was characterized by insulin and leptin resistance, hyperleptinemia, increased IHR, and portal hypertension in obese Zucker rats by feeding the rats an HF/MCD diet and in lean rats by feeding them the HF/MCD diet in addition to chronic exogenous leptin administration.5, 6, 22 Microcirculatory dysfunction in the NASH liver is characterized by increased adherence of leukocytes to the sinusoidal lining (sticky leukocytes) and impaired sinusoidal perfusion.7 Consistent AZD1208 chemical structure with previous reports, in the present study we observed the typical microcirculatory dysfunction associated with cirrhosis and portal hypertension in HF/MCD-Zucker
and HF/MCD+leptin-lean rats.7, 8 Both leptin and osteopontin are profibrogenic extracellular matrix proteins that can be activated in the NASH liver.1, 2, 5 In our HF/MCD-Zucker rats with hyperleptinemia, up-regulated hepatic TGF-β1, leptin and osteopontin expression were associated with severe hepatic steatosis, inflammation, fibrogenesis and cirrhosis compared with normal-Zucker rats. In our HF/MCD+leptin-lean rats, concomitant exogenous leptin administration and an HF/MCD diet creates liver cirrhosis that is similar to that which occurs in HF/MCD-Zucker rats. Increased hepatic endocannabinoids also participate in the mechanisms that result in hepatic fibrogenesis and increased IHR in cirrhosis.15
Endocannabinoids are mainly released by aminophylline activated leukocytes through the TNF-α/MAPK pathway.17 Our current study showed that the increased IHR and liver cirrhosis in the HF/MCD-Zucker rats was associated with an increase in hepatic endocannabinoid level and an up-regulation of the TNF-α/p38MAPK and CB1 receptors. In parallel, we found a positive correlation between hepatic endocannabinoid levels and increased sticky leukocyte numbers in the HF/MCD-Zucker and HF/MCD+leptin-lean rats with NASH cirrhotic livers. It has been reported that hyperleptinemia may cause leukocyte activation in obese rats.23 We observed a positive correlation among plasma leptin levels and the numbers of sticky leukocytes in our Zucker rats. It has also been reported that leptin enhances TNF-α production by way of the p38MAPK pathway in Kupffer cells.