Augmenter of liver regeneration: An important intracellular survival factor for hepatocytes

Abstract

Background/Aims-Augmenter of liver regeneration (ALR), a protein synthesized and stored in hepatocytes, is associated with mitochondria, and possesses sulfhydryl oxidase and cytochrome c reductase activities. We sought to determine the effects of ALR depletion in hepatocytes by antisense oligonucleotide transfection.Methods-Rat hepatocytes in primary culture were transfected with antisense oligonucleotide for ALR mRNA (ALR-AS) or scrambled oligonucleotide. Various analyses were performed at times up to 24 h after transfection.Results-Treatment with ALR-AS caused a decrease in ALR mRNA, cellular depletion of ALR protein primarily from mitochondria, and decreased viability. Flow cytometric analysis of ALR-AStransfected hepatocytes stained with annexin-V cy3 and 7-aminoactinomycin D revealed apoptosis as the predominant cause of death up to 6 h; incubation beyond this time resulted in necrosis in addition to apoptosis. ALR-AS-transfection caused release of mitochondrial cytochrome c, activation of caspase-3, profound reduction in the ATP content, and cellular release of LDH. Inhibition of caspase-3 inhibited the early phase of ALR-AS-induced death but not the late phase that included ALR and LDH release.Conclusions-These results suggest that ALR is critically important for the survival of hepatocytes by its association with mitochondria and regulation of ATP synthesis. KeywordsAugmenter of liver regeneration; Antisense; Hepatocytes; Apoptosis; Necrosis ☆ The authors who have taken part in the research of this paper declared that they do not have a relationship with the manufacturers of the materials involved either in the past or present and they did not receive funding from the manufacturers to carry out their research.

Augmenter of Liver Regeneration Attenuates Tubular Cell Apoptosis in Acute Kidney Injury in Rats: The Possible Mechanisms

“…33 The PI3K/ AKT and ERK pathways are also known to be important pathways for apoptosis. Although recent studies have reported anti-apoptotic effects of ALR in human hepatocytes, neuroblastoma cells, and hepatoma cells, [23][24][25][26] and rrALR has been shown to inhibit gentamicin-induced renal tubular cell apoptosis in vitro, 29 the mechanisms of ALR-inhibiting apoptosis remain unclear. Caspase-3 is the most important executioner in most apoptotic signaling cascades.…”

“…[20][21][22] Recent studies have shown that depletion of ALR in hepatocytes by anti-sense oligonucleotide transfection induced hepatocyte apoptosis, while recombinant human ALR (rhALR) significantly decreased hepatocyte apoptosis in vitro. 23,24 The expression of exogenous ALR increased the survival of hepatoma cells, accompanied by a decrease in apoptosis. 25 A protective effect of ALR on hydrogen peroxide-induced apoptosis in SH-SY5Y human neuroblastoma cells has also been found.…”

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

“…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 (Thirunavukkarasu et al, 2008). In practice, administration of an HSS-bearing plasmid by hydrodynamic tail vein injection protects mice from hepatic failure, implying its potential role in clinical application.…”

“…HSS seems to have additional clinical implications because exogenous HSS administration to rats with thioacetamide-induced liver fibrosis/cirrhosis is able to significantly decrease fibrosis and suppress the onset of cirrhosis (Gribilas et al, 2009). ALR is critically important for the survival of hepatocytes because of its association with the maintenance of mitochondrial stability (Thirunavukkarasu et al, 2008). The results of our previous studies (Wu et al, 2007(Wu et al, , 2010Li et al, 2010) also demonstrated that the function of the HSS gene in liver cells may be related to its antiapoptotic effects, and the protective effect of HSS may be associated with the mitochondria via blockade of the mitochondrial permeability transition.…”

Nrf2 Activates Augmenter of Liver Regeneration (ALR) via Antioxidant Response Element and Links Oxidative Stress to Liver Regeneration

“…This was mainly due to the reduction of mitochondrial-mediated apoptosis characterized by ameliorated mitochondria membrane integrity, reduced cytochrome c release and enhanced ATP levels (23)(24)(25). In addition, downregulation of ALR expression using antisense oligonucleotide has demonstrated similar results in rat hepatocytes (26) and hepatoma cells (24) as well as a prosurvival role of ALR in the maintenance of murine embryonic stem cell pluripotency (27). Less is known about the regulation of ALR expression under conditions of oxidative stress.…”