Augmenter Of Liver Regeneration Research Articles

Loss of nephric augmenter of liver regeneration facilitates acute kidney injury via ACSL4-mediated ferroptosis.

Ferroptosis, characterized by lipid accumulation in intracellular compartments, is related to acute kidney injury (AKI), but the mechanism remains obscure. In our previous study, the protective effect of augmenter of liver regeneration (ALR) on AKI was not fully clarified. In this study, we established an AKI mouse model by knocking out proximal tubule-specific ALR and an AKI cell model by inducing hypoxia, as well as enrolled AKI patients, to investigate the effects of ALR on ferroptosis and the progression of AKI. We found that ALR knockout aggravated ferroptosis and increased ROS accumulation and mitochondrial damage, whereas ALR overexpression attenuated ferroptosis through clearance of ROS and maintenance of mitochondrial morphology. Mechanistically, we demonstrated that ALR could directly bind to long-chain-fatty-acid-CoA ligase 4 (ACSL4) and further inhibit the expression of ACSL4 by interacting with certain regions. By resolution liquid chromatography coupled with triple quadruple mass spectrometry, we found that ALR could reduce the contents of polyunsaturated fatty acids, especially arachidonic acid. In addition, we showed that ALR binds to ACSL4 and attenuates oxylipin accumulation, exerting a protective effect against ferroptosis in AKI. Therefore, targeting renal ALR can attenuate ferroptosis and can offer a promising strategy for the treatment of AKI.

TMPRSS11D/ALR-mediated ER stress regulates the function of myeloid-derived suppressor cells in the cervical cancer microenvironment

Myeloid-derived suppressor cells (MDSCs) contribute to tumor immune evasion, and have been identified as immunosuppressive cells in cervical cancer. The effect of TMPRSS11D (transmembrane serine protease 11D) in some cancers has been reported, but its role in immune escape of cervical cancer is still unclear. This study aims to elucidate the regulatory mechanism of TMPRSS11D on the immunosuppressive function of MDSCs in cervical cancer. Our data showed that the proportion of polymorphonucleoid MDSCs (PMN-MDSCs), the contents of immunosuppressive factors (including INOS, IDO, and ARG-1) secreted by MDSCs, and TMPRSS11D mRNA level in peripheral blood mononuclear cells (PBMCs) of malignant cervical cancer patients was significantly higher than that of benign tumor patients. Next, CD3+ T cells from PBMCs of cervical cancer patients were stimulated with anti-CD3 and anti-CD28, and then co-cultured with PMN-MDSCs from the same donors at a ratio of 1:2 for 3 days. PMN-MDSCs from malignant tumors produced more ROS, while TMPRSS11D knockdown blocked ROS production. PMN-MDSCs inhibited T cell proliferation and IFN-γ production, while silencing TMPRSS11D in PMN-MDSCs hindered the immunosuppressive effect of PMN-MDSCs. Mechanistically, TMPRSS11D bound to ALR (Augmenter of liver regeneration) and negatively regulated ALR expression, inducing ER stress in PMN-MDSCs, thereby enhancing the immunosuppressive effect of PMN-MDSCs on T cells. Additionally, mouse xenograft tumor assay was conducted to assess the role of TMPRSS11D in tumor growth and MDSC accumulation in vivo. Silencing TMPRSS11D impeded the growth of cervical cancer xenografts and reduced the accumulation of MDSCs in tumor tissues. In conclusion, TMPRSS11D induced ER stress in MDSCs through negative regulation of ALR, thus enhancing the immunosuppressive effect of MDSCs on T cells, so as to promote the growth of cervical cancer tumors.

Role of augmenter of liver regeneration on testicular ischemia and ischemia/reperfusion injury: An experimental study.

Testicular torsion causes ischemic injury, and torsion causes reperfusion injury. Evaluating the role of augmenter of liver regeneration (ALR) in testicular ischemia and ischemia/reperfusion injury. Seventy-eight (78) healthy Wistar albino male rats were randomly divided into four groups; control (C) (n = 6), sham (S) (n = 24), torsion (T) (n = 24), and torsion/detorsion (T/D) (n = 24). S, T, and T/D groups were divided into four subgroups (n = 6) as 1st, 2nd, 3rd, and 4th hours. Blood, tissue ALR, and histology analyses were performed between groups and subgroups. The increase in plasma ALR values at the 3rd and 4th hours compared to the 1st hour in the T group were significant (P < 0.01, P < 0.001, respectively). In the T/D group, a significant increase was observed in plasma ALR values at the 3rd and 4th hours compared to the 1st hour (P < 0.05, P < 0.001, respectively). Plasma ALR values at the 1st, 2nd, 3rd, and 4th hours were higher in the T and T/D groups than in the C group (P < 0.001, P < 0.05, respectively). Plasma ALR values were higher in the T group at the 1st, 2nd, 3rd, and 4th hours than in the S group (P < 0.05). A significant increase was observed in tissue ALR at the 3rd and 4th hours than at the 1st hour in the T group (P < 0.05, P < 0.001, respectively). A significant increase was observed in tissue ALR at the 3rd and 4th hours than in the 1st hour in the T/D group (P < 0.05, P < 0.001, respectively). ALR in plasma and testicular tissue has a potential role in the early diagnosis of testicular torsion and in predicting the prognosis of T and T/D.

Augmenter of liver regeneration promotes drug resistance of acute lymphoblastic leukemia through the alteration of mitochondrial functions and the inhibition of the mitochondrial apoptosis pathway.

Acute T lymphoblastic leukemia (T-ALL) occurs in 25% of adults diagnosed with Acute lymphocytic leukemia (ALL), and drug resistance is still a clinical obstacle. Augmenter of liver regeneration (ALR) is important to ALL drug resistance and is involved in the regulation of mitochondrial function; we speculated that the high expression of ALR in T-ALL promotes drug resistance through the alteration of mitochondrial function and the inhibition of the mitochondrial apoptosis pathway. We silenced and overexpressed ALR in the T-ALL cell lines that were untreated or treated with dexamethasone (DXM) or methotrexate (MTX). Apoptosis, proliferation, reactive oxygen species and ATP productions, mitochondrial membrane potential, and mitochondrial respiratory chain complex expression in cells were examined. The data were collated to comprehensively evaluate the effects of ALR expression change on mitochondrial function and drug resistance in T-ALL cells. ALR knockdown led to the inhibition of proliferation, an increase in apoptosis, and the promotion of the cells' sensitivity to drugs. It also showed mitochondrial dysfunction. ALR knockdown actived the mitochondrial apoptosis pathway. The treatment of ALR knockdown T-ALL cells with MTX or DXM further altered the mitochondrial function of T-ALL cells and actived the mitochondrial apoptosis pathway. Overexpression of ALR promoted cell proliferation and drug resistance, reduced apoptosis, protected mitochondrial function, and inhibited the mitochondrial apoptosis pathway. T-ALL resistance caused by ALR through the alteration of mitochondrial function is associated with the inhibition of the mitochondrial apoptosis pathway.

Interleukin-1ß Attenuates Expression of Augmenter of Liver Regeneration (ALR) by Regulating HNF4α Independent of c-Jun.

Inflammasomes and innate immune cells have been shown to contribute to liver injury, thereby activating Kupffer cells, which release several cytokines, including IL-6, IL-1ß, and TNFα. Augmenter of liver regeneration (ALR) is a hepatotropic co-mitogen that was found to have anti-oxidative and anti-apoptotic properties and to attenuate experimental non-alcoholic fatty liver disease (NAFLD) and cholestasis. Additionally, hepatic ALR expression is diminished in patients with NAFLD or cholestasis, but less is known about the mechanisms of its regulation under these conditions. Therefore, we aimed to investigate the role of IL-1ß in ALR expression and to elucidate the molecular mechanism of this regulation in vitro. We found that ALR promoter activity and mRNA and protein expression were reduced upon treatment with IL-1ß. Early growth response protein-1 (Egr-1), an ALR inducer, was induced by IL-1ß but could not activate ALR expression, which may be attributed to reduced Egr-1 binding to the ALR promoter. The expression and nuclear localization of hepatocyte nuclear factor 4 α (HNF4α), another ALR-inducing transcription factor, was reduced by IL-1ß. Interestingly, c-Jun, a potential regulator of ALR and HNF4α, showed increased nuclear phosphorylation levels upon IL-1ß treatment but did not change the expression of ALR or HNF4α. In conclusion, this study offers evidence regarding the regulation of anti-apoptotic and anti-oxidative ALR by IL-1ß through reduced Egr-1 promoter binding and diminished HNF4α expression independent of c-Jun activation. Low ALR tissue levels in NAFLD and cholestatic liver injury may be caused by IL-1ß and contribute to disease progression.

Augmenter of Liver Regeneration Monoclonal Antibody Promotes Apoptosis of Hepatocellular Carcinoma Cells.

Hepatocellular carcinoma (HCC) is one of the most common types of cancer, often resulting in death. Augmenter of liver regeneration (ALR), a widely expressed multifunctional protein, has roles in liver disease. In our previous study, we reported that ALR knockdown inhibited cell proliferation and promoted cell death. However, there is no study on the roles of ALR in HCC. We used in vitro and in vivo models to investigate the effects of ALR in HCC as well as its mechanism of action. We produced and characterized a human ALR-specific monoclonal antibody (mAb) and investigated the effects of the mAb in HCC cells. The purified ALR-specific mAb matched the predicted molecular weight of IgG heavy and light chains. Thereafter, we used the ALR-specific mAb as a therapeutic strategy to suppress tumor growth in nude mice. Additionally, we assessed the proliferation and viability of three HCC cell lines, Hep G2, Huh-7, and MHC97-H, treated with the ALR-specific mAb. Compared with controls, tumor growth was inhibited in mice treated with the ALR-specific mAb at 5 mg/kg, as shown by hematoxylin and eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling. Simultaneous treatment with the ALR-specific mAb and adriamycin promoted apoptosis, whereas treatment with the ALR-specific mAb alone inhibited cell proliferation. The ALR-specific mAb might be a novel therapy for HCC by blocking extracellular ALR.

Multicomponent microspheres with spatiotemporal drug release for post-surgical liver cancer treatment and liver regeneration

Tumor recurrence after hepatic resection is a severe challenge of current liver cancer treatment. Here we present novel multicomponent microspheres (MCMs) with co-encapsulation and spatiotemporal drug release capabilities for post-surgical liver cancer treatment and liver regeneration. The MCMs were fabricated via a stepwise microfluidic platform and were composed of a sodium alginate (ALG) shell and gelatin methacrylate (GelMA) cores. Benefitting from the “particle-in-particle” structure, the MCMs provided the possibility of loading doxorubicin (DOX) and augmenter of liver regeneration (ALR) into the shell and the cores, respectively. Besides, the MCMs enabled rapid release of DOX and more sustained release of ALR. Therefore, the dual-drug-loaded MCMs exhibited prominent effects of postsurgical tumor killing and promoting liver regeneration. We anticipate that the present MCMs have remarkable potentials as versatile drug delivery systems for post-surgical cancer therapy.

Imbalance in ALR ubiquitination accelerates the progression of nonalcoholic steatohepatitis to hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the most common form of primary liver cancer. Accumulating evidence indicates that non-alcoholic steatohepatitis (NASH) is a key predisposing factor for HCC occurrence. However, the precise mechanisms driving NASH transition to HCC remain largely obscure. Augmenter of liver regeneration (ALR) is a sulfhydryl oxidase and cytochrome c reductase that functions as an important regulator of mitochondrial dynamics. In this study, we focused on ALR ubiquitination-mediated degradation and its potential contribution to NASH-driven HCC progression at the mitochondrial level. Hepatic ALR expression in HCC patients was determined using immunohistochemical analysis. Mice with liver-specific deletion of ALR (ALRCKO) and ALRWT mice were fed a western diet (WD) and high-sugar solution for induction of NASH. HCC in animals was induced via peritoneal administration of CCl4. ALR expression was markedly decreased in liver tissues of patients with NASH and HCC compared with non-NASH and non-tumor tissues. Similarly, in ALRWT mice, the ALR level in tumor tissue was reduced relative to that in para-tumor tissue. In the ALRCKO group, mice fed WD plus CCl4 developed HCC starting at week 12 while ALRWT mice fed WD plus CCl4 developed HCC at week 24. Analysis of protein posttranslational modifications revealed ubiquitylation (Ub) and deubiquitination (DUb) of ALR by murine double minute 2 (MDM2) and ubiquitin-specific protease 36 (USP36), respectively. Imbalance between Ub and DUb of ALR resulted in profound ALR degradation, which appeared to be reversibly associated with Edmondson-Steiner tumor grade. Rescue of ALR levels via gene transfection abolished tumor malignant features to a certain extent in vitro. Notably, ALR deletion substantially enhanced mitochondrial fission by activating Drp1 phosphorylation at Ser616, thus disrupting the balance of mitochondrial dynamics between fission and fusion and severely impairing oxidative phosphorylation (OXPHOS) and ATP synthesis, instead enhancing anaerobic metabolism, which might be attributed to steatotic hepatocyte transition into the malignant HCC phenotype. Hepatic ALR depletion via dysregulation of ubiquitination is a critical aggravator of NASH-HCC progression and represents a promising therapeutic target for related liver diseases.

Augmenter of liver regeneration reduces mitochondria-derived ROS and NLRP3 inflammasome activation through PINK1/Parkin-mediated mitophagy in ischemia-reperfusion-induced renal tubular injury.

Ischemia-reperfusion (IR) injury is one of the main causes of acute kidney disease (AKI). Several studies have shown that mitochondrial damage, which leads to increased production of reactive oxygen species (ROS), plays a vital role in the pathogenesis of IR-induced AKI. Increased ROS production can cause oxidative damage and activate the inflammasome in renal tubular cells, ultimately resulting in apoptosis or necrosis. Mitophagy is a type of selective autophagy that plays a protective role in AKI by regulating the quality of mitochondria and reducing the production of ROS. We previously reported that the augmenter of liver regeneration (ALR) exhibits antiapoptotic and antioxidant functions, although the precise mechanisms of action need to be studied further. In the current study, ALR was overexpressed and an in vitro model of IR injury was constructed. The overexpression of ALR reduced the production of mitochondria-derived ROS (mtROS), the activation of the NLRP3 inflammasome, and the rate of apoptosis. Moreover, this suppression of mtROS production and inflammasome activation was mediated through the PTEN-induced kinase 1 (PINK1)/Parkin pathway of mitophagy. These results suggest that ALR can alleviate IR-induced apoptosis via the PINK1/Parkin mitophagy pathway to reduce the production of mtROS and limit the activation of the NLRP3 inflammasome.

Augmenter of liver regeneration: Mitochondrial function and steatohepatitis.

Augmenter of liver regeneration (ALR), a ubiquitous fundamental life protein, is expressed more abundantly in the liver than other organs. Expression of ALR is highest in hepatocytes, which also constitutively secrete it. ALR gene transcription is regulated by NRF2, FOXA2, SP1, HNF4α, EGR-1 and AP1/AP4. ALR's FAD-linked sulfhydryl oxidase activity is essential for protein folding in the mitochondrial intermembrane space. ALR's functions also include cytochrome c reductase and protein Fe/S maturation activities. ALR depletion from hepatocytes leads to increased oxidative stress, impaired ATP synthesis and apoptosis/necrosis. Loss of ALR's functions due to homozygous mutation causes severe mitochondrial defects and congenital progressive multiorgan failure, suggesting that individuals with one functional ALR allele might be susceptible to disorders involving compromised mitochondrial function. Genetic ablation of ALR from hepatocytes induces structural and functional mitochondrial abnormalities, dysregulation of lipid homeostasis and development of steatohepatitis. High-fat diet-fed ALR-deficient mice develop non-alcoholic steatohepatitis (NASH) and fibrosis, while hepatic and serum levels of ALR are lower than normal in human NASH and NASH-cirrhosis. Thus, ALR deficiency may be a critical predisposing factor in the pathogenesis and progression of NASH.

The protective roles of augmenter of liver regeneration in hepatocytes in the non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) occurs in 25% of the global population and manifests as lipid deposition, hepatocyte injury, activation of Kupffer and stellate cells, and steatohepatitis. Predominantly expressed in hepatocytes, the augmenter of liver regeneration (ALR) is a key factor in liver regulation that can alleviate fatty liver disease and protect the liver from abnormal liver lipid metabolism. ALR has three isoforms (15-, 21-, and 23-kDa), amongst which 23-kDa ALR is the most extensively studied. The 23-kDa ALR isoform is a sulfhydryl oxidase that resides primarily in the mitochondrial intermembrane space (IMS), whereby it protects the liver against various types of injury. In this review, we describe the role of ALR in regulating hepatocytes in the context of NAFLD. We also discuss questions about ALR that remain to be explored in the future. In conclusion, ALR appears to be a promising therapeutic target for treating NAFLD.

Augmenter of Liver Regeneration (ALR) Protects Kidney from Ischemia/Reperfusion (I/R) Injury via Regulation of TLR4/MAPK Signaling Pathway.

Toll-like receptor 4 (TLR4) can mediate innate activation and inflammation, and it is typically expressed within the ischemic kidney. Augmenter of liver regeneration (ALR) acts as an immunoregulator with a high expression in the kidney induced by renal ischemia/reperfusion (I/R) injury. Exogenous ALR has indicated a role in protecting the kidney from I/R injury. The protective effect of ALR is due to the immune regulatory function which remains to be elucidated. In this study, rats induced by renal I/R were treated with recombinant human ALR (rhALR) and demonstrated that the animals were protected from kidney I/R injury, implying that the rhALR-treated rats had less tubular damage than those untreated rats. Meanwhile, tubular epithelial cell apoptosis, neutrophil (24 h) and macrophage (72 h) infiltration to tubulointerstitium, and levels of inflammatory cytokines were decreased considerably in the rhALR-treated rats as compared to control. Additionally, rhALR could downregulate mRNA expression of TLR4 endogenous ligands and restrain its activation in renal I/R injury rats. It has also been proved that anti-rhALR antibody blocked the inhibition of rhALR of the immune inflammatory response in hypoxia/reoxygenation (H/R) injury in vitro. In rhALR+anti-rhALR antibody-intervened H/R cells, the expression of inflammatory cytokines was upregulated compared with the rhALR-treated cells. Taken together, rhALR could regulate the TLR4 signaling pathway to relieve inflammatory response, thereby protecting renal I/R injury, indicating that ALR is likely to be introduced to develop novel immune therapies for renal I/R injury.

Farnesoid X receptor (FXR) agonists induce hepatocellular apoptosis and impair hepatic functions via FXR/SHP pathway

Farnesoid X receptor (FXR) plays an indispensable role in liver homeostasis and has been a promising drug target for hepatic diseases. However, the concerns of undesired biological actions limit the clinical applications of FXR agonists. To reveal the intrinsic mechanism of FXR agonist-induce hepatotoxicity, two typical FXR agonists with different structures (obeticholic acid (OCA) and Px-102) were investigated in the present study. By detecting MMP, ROS, and ATP and analyzing the fate of cells, we found that both OCA and Px-102 reduced the mitochondrial function of hepatocytes and promoted cell apoptosis. Gene ablation or inhibition of FXR or SHP ameliorated the cytotoxicities of OCA and Px-102, which indicated the adverse actions of FXR/SHP activation including down-regulation of phosphorylation of PI3K/AKT and functional hepatic genes. The dose-related injurious effects of OCA (10mg/kg and 30mg/kg) and Px-102 (5mg/kg and 15mg/kg) on the liver were confirmed on a high-fat diet mouse model. The decrease of hepatocyte-specific genes and augmenter of liver regeneration in the liver caused by OCA or Px-102 suggested an imbalance of liver regeneration and a disruption of hepatic functions. Exploration of intestinally biased FXR agonists or combination of FXR agonist with apoptosis inhibitor may be more beneficial strategies for liver diseases.

Augmenter of liver regeneration protects the kidney against ischemia-reperfusion injury by inhibiting necroptosis

ABSTRACT Necroptosis plays an important role in the pathogenesis of acute kidney injury (AKI), and necroptosis-related interventions may therefore be an important measure for the treatment of AKI. Our previous study has shown that augmenter of liver regeneration (ALR) inhibits renal tubular epithelial cell apoptosis and regulates autophagy; however, the influence of ALR on necroptosis remains unclear. In this study, we investigated the effect of ALR on necroptosis caused by ischemia-reperfusion and the underlying mechanism. In vivo experiments indicated that kidney-specific knockout of ALR aggravated the renal dysfunction and pathological damage induced by ischemia-reperfusion. Simultaneously, the expression of renal necroptosis-associated protein receptor-interacting protein 1 (RIP1), receptor-interacting protein 3 (RIP3), and mixed-lineage kinase domain-like protein (MLKL) significantly increased. In vitro experiments indicated that overexpression of ALR decreased the expression of hypoxia-reoxygenation-induced kidney injury molecules, the inflammation-associated factor tumor necrosis factor-alpha (TNF-α), and monocyte chemotactic protein. Additionally, the expression of RIP1, RIP3, and MLKL, which are elevated after hypoxia and reoxygenation, was also inhibited by ALR overexpression. Both in vivo and in vitro results indicated that ALR has a protective effect against acute kidney injury caused by ischemia-reperfusion, and the RIP1/RIP3/MLKL pathway should be further verified as a probable necroptosis regulating mechanism.

Augmenter of liver regeneration-mediated mitophagy protects against hepatic ischemia/reperfusion injury

Augmenter of liver regeneration (ALR) is an anti-apoptotic protein found mainly in mitochondria. It protects hepatocytes from ischemia-reperfusion (I/R) injury, but the underlying mechanism is not clear. We found that in rats, delivery of the ALR gene alleviated hepatic I/R injury during orthotopic liver transplantation as evidenced by reduced serum aminotransferase, oxidative stress and apoptosis, and increased expression of autophagy markers. In an in vitro hypoxia/reoxygenation (H/R) model, overexpression of the ALR gene activated autophagy and relieved defective mitophagy via the PINK1/Parkin pathway. Mechanistically, ALR transfection induced the expression of mitofusin 2 (Mfn2) in the H/R model, which led to PINK1 accumulation and mitochondrial translocation of Parkin. Deletion of Mfn2 abolished mitophagy activation induced by ALR transfection, promoted mitochondrial dysfunction, and eventually increased cell apoptosis. Mfn2 administration prevented the inhibition of mitophagy in ALR-knockout (KO) cells, thus attenuated mitochondrial dysfunction and cell apoptosis. In heterozygous ALR-knockout mice treated with a warm I/R injury, marked aggravation of liver injury was associated with mitophagy inhibition and reduction in Mfn2 expression. Taken together, our results confirm that ALR accelerated Parkin translocation and mitophagy via Mfn2, and protected hepatocytes from I/R-induced injury. Our findings provide a novel rationale for the treatment of hepatic I/R injury.

Alleviation of CCCP-induced mitochondrial injury by augmenter of liver regeneration via the PINK1/Parkin pathway-dependent mitophagy

The occurrence of liver diseases is attributed to mitochondrial damage. Mitophagy selectively removes dysfunctional mitochondria, thereby preserving mitochondrial function. Augmenter of liver regeneration (ALR) protects the mitochondria from injury. However, whether ALR protection is associated with mitophagy remains unclear. In this study, mitochondrial damage was induced by carbonyl cyanide 3-chlorophenylhydrazone (CCCP), and long-form ALR (lfRNA)-mediated protection against this damage was investigated. Treatment of HepG2 cells with CCCP elevated the level of intracellular ROS, inhibited ATP production, and increased the mitochondrial membrane potential and cell apoptotic rate. However, in lfALR-transfected cells, CCCP-induced cell injury was clearly alleviated, the apoptosis and ROS levels clearly declined, and the ATP production was significantly enhanced as compared with that in vector-Tx cells. Furthermore, lfALR overexpression promoted autophagy and mitophagy via a PINK1/Parkin-dependent pathway, whereas knockdown of ALR suppressed mitophagy. In lfALR-transfected cells, the phosphorylation of AKT was decreased, thus, downregulating the phosphorylation of the transcription factor FOXO3a at Ser315. In contrast, the phosphorylation of AMPK was enhanced, thereby upregulating the phosphorylation of FOXO3a at Ser413. Consequently, FOXO3a′s nuclear translocation and binding to the promoter region of PINK1 was enhanced, and the accumulation of PINK1/Parkin in mitochondria increased. Meanwhile, short-form ALR (sfALR) also increased PINK1 expression through FOXO3a with the similar pathway to lfALR. In conclusion, our data suggest a novel mechanism through which both lfALR and sfALR protect mitochondria by promoting PINK1/Parkin-dependent mitophagy through FOXO3a activation.

Mitochondrial Impairment by MitoBloCK-6 Inhibits Liver Cancer Cell Proliferation.

Augmenter of liver regeneration (ALR) is a critical multi-isoform protein with its longer isoform, located in the mitochondrial intermembrane space, being part of the mitochondrial disulfide relay system (DRS). Upregulation of ALR was observed in multiple forms of cancer, among them hepatocellular carcinoma (HCC). To shed light into ALR function in HCC, we used MitoBloCK-6 to pharmacologically inhibit ALR, resulting in profound mitochondrial impairment and cancer cell proliferation deficits. These effects were mostly reversed by supplementation with bioavailable hemin b, linking ALR function to mitochondrial iron homeostasis. Since many tumor cells are known for their increased iron demand and since increased iron levels in cancer are associated with poor clinical outcome, these results help to further advance the intricate relation between iron and mitochondrial homeostasis in liver cancer.

Downregulation of augmenter of liver regeneration impairs the therapeutic efficacy of liver epithelial progenitor cells against acute liver injury by enhancing mitochondrial fission.

Cell-based therapeutic approaches have been proven to be effective strategies for the treatment of acute liver injury (ALI). However, widespread application of these procedures is limited by several key issues, including rapid loss of stemness in vitro, aberrant differentiation into undesirable cell types, and low engraftment in vivo. In this study, liver epithelial progenitor cells (LEPCs) were characterized and transfected with augmenter of liver regeneration (ALR). The results revealed that in ALI mice with CCl4 , the transplantation of ALR-bearing LEPCs into the liver markedly protected mice against ALI by decreasing the levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST), thus relieving hepatic tissue injury and attenuating inflammatory infiltration. Mechanistically, the knockdown of ALR in LEPCs activated the phosphorylation of dynamin-related protein 1 (Drp1) at the S616 site and thereby enhanced mitochondrial fission. In contrast, the transfection of ALR into LEPCs significantly inhibited Drp1 phosphorylation, thereby favoring the maintenance of mitochondrial integrity and the preservation of adenosine triphosphate contents in LEPCs. Consequently, the ALR-bearing LEPCs transplanted into ALI mice exhibited substantially greater homing ability to the injured liver via the SDF-1/CXCR4 axis than that of LEPCs-lacking ALR. In conclusion, we demonstrated that the transplantation of ALR-transfected LEPCs protected mice against CCl4 -induced ALI, thus offering immense curative potential in the clinic.

Augmenter of liver regeneration ameliorates ischemia-reperfusion injury in steatotic liver via inhibition of the TLR4/NF-κB pathway.

Hepatocytes from donors with preexisting hepatic steatosis exhibited increased sensitivity to ischemia-reperfusion injury (IRI) during liver transplantation. Augmenter of liver regeneration (ALR) protected the liver against IRI, but the mechanism was not clarified. Therefore, the hypothesis that ALR attenuated IRI in steatotic liver by inhibition of inflammation and downregulation of the Toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) pathway was examined. C57BL/6 mice were subjected to a methionine-choline-deficient (MCD) diet to induce liver steatosis. Mice were transfected with ALR-containing adenovirus 3 days prior to partial warm hepatic IRI. After 30 min of ischemia and 6 h of reperfusion injury, liver function, hepatic injury, the inflammatory response and TLR4/NF-κB signaling pathway activation were assessed. ALR maintained liver function and alleviated hepatic injury as indicated by the decreased levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST), preserved hepatic structure and reduced apoptosis. ALR also reduced the IRI-induced inflammatory response by suppressing Kupffer cell activation, inhibiting neutrophil chemotaxis and reducing inflammatory cytokine production. Further investigation using reverse transcription-quantitative PCR, western blotting and immunohistochemistry revealed that ALR reduced TLR4/NF-κB signaling pathway activation, which led to a decreased synthesis of inflammatory cytokines. ALR functioned as a regulator of the IRI-induced inflammatory response by suppressing the TLR4/NF-κB pathway, which supports the use of ALR in therapeutic applications for fatty liver transplantation.

Augmenter of liver regeneration regulates cellular iron homeostasis by modulating mitochondrial transport of ATP-binding cassette B8.

Chronic loss of Augmenter of Liver Regeneration (ALR) results in mitochondrial myopathy with cataracts; however, the mechanism for this disorder remains unclear. Here, we demonstrate that loss of ALR, a principal component of the MIA40/ALR protein import pathway, results in impaired cytosolic Fe/S cluster biogenesis in mammalian cells. Mechanistically, MIA40/ALR facilitates the mitochondrial import of ATP-binding cassette (ABC)-B8, an inner mitochondrial membrane protein required for cytoplasmic Fe/S cluster maturation, through physical interaction with ABCB8. Downregulation of ALR impairs mitochondrial ABCB8 import, reduces cytoplasmic Fe/S cluster maturation, and increases cellular iron through the iron regulatory protein-iron response element system. Our finding thus provides a mechanistic link between MIA40/ALR import machinery and cytosolic Fe/S cluster maturation through the mitochondrial import of ABCB8, and offers a potential explanation for the pathology seen in patients with ALR mutations.