Adenoviral Gene Transfer of Hepatic Stimulator Substance Confers Resistance Against Hepatic Ischemia–Reperfusion Injury by Improving Mitochondrial Function

Abstract

Hepatic stimulator substance (HSS) has been suggested to protect liver cells from various toxins. However, the precise role of HSS in hepatic ischemia-reperfusion (I/R) injury remains unknown. This study aims to elucidate whether overexpression of HSS could attenuate hepatic ischemia-reperfusion injury and its possible mechanisms. Both in vivo hepatic I/R injury in mice and in vitro hypoxia-reoxygenation (H/R) in a cell model were used to evaluate the effect of HSS protection after adenoviral gene transfer. Moreover, a possible mitochondrial mechanism of HSS protection was investigated. Efficient transfer of the HSS gene into liver inhibited hepatic I/R injury in mice, as evidenced by improvement in liver function tests, the preservation of hepatic morphology, and a reduction in hepatocyte apoptosis. HSS overexpression also inhibited H/R-induced cell death, as detected by cell viability and cell apoptosis assays. The underlying mechanism of this hepatic protection might involve the attenuation of mitochondrial dysfunction and mitochondrial-dependent cell apoptosis, as shown by the good preservation of mitochondrial ultrastructure, mitochondrial membrane potential, and the inhibition of cytochrome c leakage and caspase activity. Moreover, the suppression of H/R-induced mitochondrial ROS production and the maintenance of mitochondrial respiratory chain complex activities may participate in this mechanism. This new function of HSS expands the possibility of its application for the prevention of I/R injury, such as hepatic resection and liver transplantation in clinical practice.

Enhanced endoplasmic reticulum SERCA activity by overexpression of hepatic stimulator substance gene prevents hepatic cells from ER stress-induced apoptosis

“…More recently, the data confirmed that HSS plays the crucial function as an antioxidative agent sustaining the levels of reducing agents such as clusterin (38). A recent work in our laboratory demonstrated that HSS transfection decreases hypoxia and reoxygenation-induced mitochondrial ROS production and preserves mitochondrial respiratory chain complex activities (20). Hence, we propose that HSS might function as a free radical scavenger, thereby alleviating hepatic injury and promoting the survival of hepatocytes after HSS transfection.…”

Hepatic stimulator substance resists hepatic ischemia/reperfusion injury by regulating Drp1 translocation and activation

“…Current research on mitochondrial involvement in I/R damage has focused mainly on the metabolic function rather than on mitochondrial dynamics and its mediated apoptosis, such as the reduction of adenosine triphosphate production, loss of mitochondrial membrane potential, reactive oxygen species generation, and cytochrome c release . However, the reason for these changes has not been explored.…”

“…Nonlethal segmental (70%) hepatic warm ischemia was performed under 4% chloral hydrate anesthesia . An atraumatic clip was used to interrupt the arterial/portal venous blood supply to the cephalad liver lobes.…”

“…(20) Many studies have revealed that HSS protects the liver from injuries caused by various types of toxins, such as carbon tetrachloride, d-galactosamine, ethanol, and H 2 O 2 . (21) Consistently, inhibition of intracellular HSS expression by an antisense approach reduces cell survival against free radical insults, suggesting that HSS might be a cell survival factor, (21) while administration of exogenous HSS could protect mice from hepatic failure, significantly decrease thioacetamide-induced liver fibrosis, and suppress the onset of cirrhosis, implying its potential role in clinical application. (22) HSS is even regarded as a fundamental life protein or an important intracellular survival factor for hepatocytes (23,24) because of its association with the maintenance of mitochondrial stability.…”

“…Hepatic stimulator substance (HSS), a liver growth‐promoting factor, was initially identified in regenerating rat livers and reported to stimulate liver regeneration after partial hepatectomy . Many studies have revealed that HSS protects the liver from injuries caused by various types of toxins, such as carbon tetrachloride, d‐galactosamine, ethanol, and H 2 O 2 . Consistently, inhibition of intracellular HSS expression by an antisense approach reduces cell survival against free radical insults, suggesting that HSS might be a cell survival factor, while administration of exogenous HSS could protect mice from hepatic failure, significantly decrease thioacetamide‐induced liver fibrosis, and suppress the onset of cirrhosis, implying its potential role in clinical application .…”