Endothelin receptor antagonist TAK-044 arrests and reverses the development of carbon tetrachloride-induced cirrhosis in rats. GPx, which are integral part of the cellular antioxidant defense mechanism (Yu, 1994), were lower in aHSCs than in qHSCs. While their activities increased in superoxide-challenged qHSCs, no such effect was observed in aHSCs (Table 2). TABLE 2 Effect of superoxide on superoxide dismutase, catalase and glutathione peroxidase 0.01) and 257 19 to 375 59 ( 0.05) IU/L (n = 4 each) respectively and in cirrhotic rats from 2,067 28 to 2,445 245 IU/L ( 0.025) and 2,085 287 to 2,864 663 IU/L ( 0.05) (n = 5 each) respectively. Hepatic architecture was maintained in GSK2879552 TBHP-treated control rats but there was mild centrilobular hepatocyte swelling GSK2879552 with focal mild mixed lobular inflammation and occasional hepatocyte dropout. Hepatocytes also showed mild reactive changes with mild lobular disarray, but there was no evidence of confluent parenchymal necrosis and significant cholestasis (Fig. 10A). In TBHP-treated GSK2879552 cirrhotic rats, hepatic morphological features (Fig. 10B) were similar to that of vehicle-treated rats (not shown) with architectural destruction by nodules of regenerative hepatocytes surrounded by fibrous bands. There was mild mixed inflammation, mild bile ductular proliferation and minimal interface activity. Hepatocytes showed diffuse swelling with moderate mixed macro- and microvesicular steatosis. Scattered hepatocyte apoptosis was noted, with foci of confluent parenchymal acidophilic necrosis. We used TUNEL staining in conjunction with immunohistochemical localization of desmin as both HSC phenotypes express desmin while -sma is expressed only by aHSCs. By this method, no apoptotic HSCs were found in the livers of vehicle- or TBHP-treated control rats (Fig. 10C,D). Consistent with our previous report (Thirunavukkarasu et al., 2004a), scattered apoptotic HSCs was observed in vehicle-treated cirrhotic liver (Fig. GSK2879552 10E). This increased significantly in the livers of TBHP-treated cirrhotic rats (Fig. 10F) (7 2% in untreated versus 35 5% in TBHP-treated; 0.001). Open in a separate window Fig. 10 Effect of TBHP-induced oxidative stress on HSCs in control and fibrotic rats. CCl4-induced cirrhotic rats or the paired control rats were injected vehicle or TBHP, and at 6 h, the livers were harvested for histopathology and immunohistochemical examination. A,B: Hematoxilyn and Eosin stained sections of livers from TBHP-treated control (A) and cirrhotic (B) rats. CCF: Apoptotic HSCs as determined by desmin (green) and TUNEL (red) co-staining in normal (C,D) and cirrhotic (E,F) livers of vehicle- (C,E) and TBHP- (D,F) treated rats. Photomicrographs are representative of 4 control (vehicle or TBHP-treated) CD80 and 5 cirrhotic (vehicle or BHP-treated) rat livers. Inset shows apoptotic aHSCs at higher magnification (400 ). Discussion ROS, generated as by-products of cellular metabolism and by specific plasma membrane oxidases, elicit several physiological and pathological effects (Yu, 1994; Pietrangelo, 1996; Li et al., 1997, 1999). Moderately improved ROS activate signaling pathways responsible for physiological processes. However, ROS and their lipid peroxidation products can also cause cell death by damaging macromolecules including genomic DNA (Yu, 1994). The qHSCs exhibited significant level of spontaneous apoptosis, which might occur as a result of harsh enzymatic digestion process of cell isolation causing membrane damage and also by intro of serum-free condition. It is also likely that within the heterogeneous human population of HSCs (Geerts, 2001), a subpopulation of the cells might be susceptible to the damage very easily upon removal using their in vivo environment. Considering this, we expected that spontaneously apoptotic qHSCs would be vulnerable to the damaging actions of superoxide during early tradition. However, no GSK2879552 additional DNA damage, nuclear condensation and death were apparent in superoxide-treated qHSCs. These results are compatible with the absence of apoptotic qHSCs in the normal liver subjected to oxidative stress in vivo. In contrast, no spontaneous DNA damage or apoptosis was observed in fully activated HSC, but oxidative stress caused their apoptosis both in vitro and in vivo. Superoxide-induced death of aHSCs was mainly apoptotic as shown by decreased Bcl-xL manifestation, caspase-3 activation, nuclear condensation, and lack of LDH release. Improved oxidative stress and decreased GSH, which settings cells redox state by scavenging ROS and keeping GPx activity, are associated with apoptotic cell death.
Endothelin receptor antagonist TAK-044 arrests and reverses the development of carbon tetrachloride-induced cirrhosis in rats