Role of Caspase-12 in Hepatocyte Apoptosis Induced by Carbon Tetrachloride in Mice

Toxic liver damage can lead to acute liver failure, hepatic fibrosis, and even carcinogenesis. This study aimed to explore the role of caspase-12 and its downstream targets in hepatocyte apoptosis induced by carbon tetrachloride (CCl4). To determine the role of caspase-12, caspase-12 knockout mice were used. Wild-type and caspase-12 knockout mice received a single intraperitoneal injection of either CCl4 (300
l/kg BW) or vehicle (corn oil). The animals were sacrificed 24 hours after treatment, and blood samples were collected to assess liver function through alanine aminotransferase activity. Liver samples were analyzed for reactive oxygen species (ROS) levels using plasma malondialdehyde as a biomarker, hepatocyte apoptosis via TUNEL assay and morphological analysis, and cytochrome C release and caspase activation through western blotting.

In wild-type mice, low-dose CCl4 administration caused hepatocyte apoptosis and acute liver injury, accompanied by increased ROS production and endoplasmic reticulum (ER) stress in the liver. These events triggered the activation of caspases-12, -9, and -3, along with the release of small amounts of cytochrome C. However, in CCl4-treated caspase-12 knockout mice, the activation of caspases-9 and -3 was significantly reduced, while cytochrome C release remained unaffected. Compared to wild-type mice, CCl4-induced apoptosis and liver damage were substantially attenuated in caspase-12 knockout mice (p < 0.05). Notably, the active form of caspase-8 was not detected in either wild-type or knockout mice. Additionally, there was no significant difference in ROS formation between the two groups following CCl4 treatment.

These findings demonstrate that caspase-12 plays a critical role in CCl4-induced hepatic apoptosis by directly or indirectly activating effector caspase-3 downstream, with partial involvement of caspase-9 activation. In conclusion, prolonged exposure to even low levels of CCl4 could cause liver pathology in humans, warranting further clinical and animal studies to investigate the long-term consequences of minimal exposure.