p62/SQSTM1-Dr. Jekyll and Mr. Hyde that prevents oxidative stress but promotes liver cancer

Trim21 deficiency in mice increases HCC carcinogenesis in a NASH context and is associated with immune checkpoint upregulation

The global pandemic of metabolic diseases has increased the incidence of hepatocellular carcinoma (HCC) in the context of non-alcoholic steatohepatitis (NASH). The downregulation of the E3 ubiquitin ligase TRIM21 has been linked to poor prognosis in different cancers including HCC. In order to investigate the role of TRIM21 in liver cancer progression on NASH, Trim21+/+ and Trim21-/- male mice were injected with streptozotocin at the neonatal stage. The hypoinsulinemic mice were then fed with a high-fat high-cholesterol diet (HFHCD) for 4, 8 or 12 weeks. All mice developed NASH which systematically resulted in HCC progression. Interestingly, compared to the Trim21+/+ control mice, liver damage was worsened in Trim21-/- mice, with more HCC nodules found after 12 weeks on HFHCD. Immune population analysis in the spleen and liver revealed a higher proportion of CD4+PD-1+ and CD8+PD-1+ T cells in Trim21-/- mice. The liver and HCC tumors of Trim21-/- mice also exhibited an increase in the number of PD-L1+ and CD68+ PD-L1+ cells. Thus, TRIM21 limits the emergence of HCC nodules in mice with NASH by potentially restricting the expression of PD-1 in lymphocytes and PD-L1 in tumors.

Autophagy impairment in human bile duct carcinoma cells

Bile duct epithelial cells, named cholangiocytes, may undergo a neoplastic transformation leading to cholangiocarcinoma. The role autophagy plays in cancer is still debated and few information are available in cholangiocarcinoma. We report in vitro data, at least in part validated in vivo,i ndicating that autophagy is impaired in intrahepatic cholangiocarcinoma cells, as compared to healthy cholangiocytes, evaluated through LC3II and p62 Western blot analyses. Autophagy impairment was found to be associated with low expression of TFEB protein and high expression of three proteins i.e., c-FLIP, caspase-10 and cleaved BCLAF-1, as compared to healthy cholangiocytes. We highlight biological effects of autophagy impairment in cholangiocarcinoma showing that autophagy induction, via rapamycin, as well as caspase inhibition, via Q-VD-OPh, are able to reduce proliferation marker PCNA level, colony size and protein content of cultured cholangiocarcinoma cells. The increased protein expression of p62, c-FLIP, caspase-10 observed in vitro in cholangiocarcinoma cells was paralleled by significant increase at gene expression levels in vivo; in fact, significant increase of transcript levels of p62, c-FLIP and caspase-10 was observed in 34 biopsies from human cholangiocarcinoma patients compared to 9 biopsies from 9 healthy controls, as reported in the GEPIA2 public database. The significant increase of p62 level in cholangiocarcinoma was found as a relatively uncommon finding in solid cancers, since it was also found in only 7 cancer types out of 31 cancer types investigated, including melanoma and hepatocarcinoma. In conclusion, we present data suggesting a molecular machinery controlling autophagy in cholangiocytes and autophagy impairment in cholangiocarcinoma.

Complementary gene regulation by NRF1 and NRF2 protects against hepatic cholesterol overload

Hepatic cholesterol overload promotes steatohepatitis. Insufficient understanding of liver stress defense impedes therapy development. Here, we elucidate the role of stress defense transcription factors, nuclear factor erythroid 2 related factor-1 (NRF1) and -2 (NRF2), in counteracting cholesterol-linked liver stress. Using a diet that increases liver cholesterol storage, expression profiles and phenotypes of liver from mice with hepatocyte deficiency of NRF1, NRF2, or both are compared with controls, and chromatin immunoprecipitation sequencing is undertaken to identify target genes. Results show NRF1 and NRF2 co-regulate genes that eliminate cholesterol and mitigate inflammation and oxidative damage. Combined deficiency, but not deficiency of either alone, results in severe steatohepatitis, hepatic cholesterol overload and crystallization, altered bile acid metabolism, and decreased biliary cholesterol. Moreover, therapeutic effects of NRF2-activating drug bardoxolone require NRF1 and are supplemented by NRF1 overexpression. Thus, we discover complementary gene programming by NRF1 and NRF2 that counteract cholesterol-associated fatty liver disease progression.

The TRAF2-p62 axis promotes proliferation and survival of liver cancer by activating mTORC1 pathway

TRAF2 (Tumor necrosis factor receptor-associated factor 2) is a dual function protein, acting as an adaptor protein and a ubiquitin E3 ligase, which plays an essential role in mediating the TNFα-NFκB signal pathway. Dysregulated expression of TRAF2 has been reported in a variety of human cancers. Whether and how TRAF2 regulates the growth of liver cancer cells remains elusive. The goal of this study is to investigate potential dysregulation of TRAF2 and its biological function in liver cancer, and to elucidate the underlying mechanism, leading to validation of TRAF2 as an attractive liver cancer target. Here, we reported TRAF2 is up-regulated in human liver cancer cell lines and tissues, and high TRAF2 expression is associated with a poor prognosis of HCC patients. Proteomics profiling along with Co-immunoprecipitation analysis revealed that p62 is a new substrate of TRAF2, which is subjected to TRAF2-induced polyubiquitination via the K63 linkage at the K420 residue. A strong negative correlation was found between the protein levels of p62 and TRAF2 in human HCC samples. TRAF2 depletion inhibited growth and survival of liver cancer cells both in vitro and in vivo by causing p62 accumulation, which is partially rescued by simultaneous p62 knockdown. Mechanistically, TRAF2-mediated p62 polyubiquitylation activates the mTORC1 by forming the p62-mTORC1-Rag complex, which facilitates the lysosome localization of mTORC1. TRAF2 depletion inhibited mTORC1 activity through the disruption of interaction between p62 and the mTORC1 complex. In conclusion, our study provides the proof-of-concept evidence that TRAF2 is a valid target for liver cancer.

A novel approach to repositioning memantine for metabolic syndrome-induced steatohepatitis: Modulation of hepatic autophagy, inflammation, and fibrosis

AIMS

This study investigated the possible hepatoprotective effects of memantine, compared to pioglitazone, in rat steatohepatitis, emphasizing its role in modulating hepatic autophagy.

MAIN METHODS

Metabolic syndrome (MetS) was provoked in adult male Wistar rats by a high fructose/fat/salt regimen for eight weeks. Then, rats were administered either memantine or pioglitazone daily for 10 weeks (both at 20 mg/kg, orally). An oral glucose tolerance test (OGTT) was done at the end of the study, and serum liver enzymes, lipids, and fasting blood glucose were measured. Also, hepatic contents of inflammatory, oxidative, and autophagy markers were quantified. Additionally, histopathological examinations of general hepatic structure and glycogen content were performed.

KEY FINDINGS

Compared to the MetS rats, memantine normalized fasting serum insulin, Homeostatic Model Assessment (HOMA-IR), serum lipids, and liver enzymes (ALT and AST). Memantine also markedly reduced hepatic inflammatory markers; NF-κB and TNF-α. In addition, hepatic NRF2 and GSH were augmented, while hepatic MDA was reduced by memantine. Interestingly, livers of the memantine group showed elevated Beclin1 and LC3 and reduced p62 contents compared to the MetS group indicating that memantine preserved hepatic autophagy. Histopathological examination revealed that memantine ameliorated hepatic steatosis and inflammation. Pioglitazone also mitigated most of the steatohepatitis-related changes, however, memantine was more effective in most of the studied parameters.

SIGNIFICANCE

The hepatoprotective effect of memantine against steatohepatitis is mediated, at least partly, through conserving hepatic autophagy along with anti-inflammatory, antioxidant, and anti-fibrotic effects.

Reactive Oxygen Species and NRF2 Signaling, Friends or Foes in Cancer?

The imbalance between reactive oxygen species (ROS) production and clearance causes oxidative stress and ROS, which play a central role in regulating cell and tissue physiology and pathology. Contingent upon concentration, ROS influence cancer development in contradictory ways, either stimulating cancer survival and growth or causing cell death. Cells developed evolutionarily conserved programs to sense and adapt redox the fluctuations to regulate ROS as either signaling molecules or toxic insults. The transcription factor nuclear factor erythroid 2-related factor 2 (NRF2)-KEAP1 system is the master regulator of cellular redox and metabolic homeostasis. NRF2 has Janus-like roles in carcinogenesis and cancer development. Short-term NRF2 activation suppresses tissue injury, inflammation, and cancer initiation. However, cancer cells often exhibit constitutive NRF2 activation due to genetic mutations or oncogenic signaling, conferring advantages for cancer cells' survival and growth. Emerging evidence suggests that NRF2 hyperactivation, as an adaptive cancer phenotype under stressful tumor environments, regulates all hallmarks of cancer. In this review, we summarized the source of ROS, regulation of ROS signaling, and cellular sensors for ROS and oxygen (O₂), we reviewed recent progress on the regulation of ROS generation and NRF2 signaling with a focus on the new functions of NRF2 in cancer development that reach beyond what we originally envisioned, including regulation of cancer metabolism, autophagy, macropinocytosis, unfolded protein response, proteostasis, and circadian rhythm, which, together with anti-oxidant and drug detoxification enzymes, contributes to cancer development, metastasis, and anticancer therapy resistance.

p62/SQSTM1 in liver diseases: the usual suspect with multifarious identities

p62/Sequestosome-1 (SQSTM1) is a selective autophagy receptor that recruits and delivers intracellular substrates for bulk clearance through the autophagy lysosomal pathway. Interestingly, p62 also serves as a signaling scaffold to participate in the regulation of multiple physiological processes, including oxidative stress response, metabolism, inflammation, and programmed cell death. Perturbation of p62 activity has been frequently found to be associated with the pathogenesis of many liver diseases. p62 has been identified as a critical component of protein aggregates in the forms of Mallory-Denk bodies (MDBs) or intracellular hyaline bodies (IHBs), which are known to be frequently detected in biopsy samples from alcoholic steatohepatitis (ASH), non-alcoholic steatohepatitis (NASH), and hepatocellular carcinoma (HCC) patients. Importantly, abundance of these p62 inclusion bodies is increasingly recognized as a biomarker for NASH and HCC. Although the level of p62 bodies seems to predict the progression and prognosis of these liver diseases, understanding of the underlying mechanisms by which p62 regulates and contributes to the development and progression of these diseases remains incomplete. In this review, we will focus on the function and regulation of p62, and its pathophysiological roles in the liver, by critically reviewing the findings from preclinical models that recapitulate the pathogenesis and manifestation of these liver diseases in humans. In addition, we will also explore the suitability of p62 as a predictive biomarker and a potential therapeutic target for the treatment of liver diseases, including NASH and HCC, as well as recent development of small-molecule compounds for targeting the p62 signaling axis.

In-Cell Chemical Crosslinking Identifies Hotspots for SQSTM-1/p62-IκBα Interaction That Underscore a Critical Role of p62 in Limiting NF-κB Activation Through IκBα Stabilization

We have previously documented that in liver cells, the multifunctional protein scaffold p62/SQSTM1 is closely associated with IκBα, an inhibitor of the transcriptional activator NF-κB. Such an intimate p62-IκBα association we now document leads to a marked 18-fold proteolytic IκBα-stabilization, enabling its nuclear entry and termination of the NF-κB-activation cycle. In p62^-/--cells, such termination is abrogated resulting in the nuclear persistence and prolonged activation of NF-κB following inflammatory stimuli. Utilizing various approaches both classic (structural deletion, site-directed mutagenesis) as well as novel (in-cell chemical crosslinking), coupled with proteomic analyses, we have defined the precise structural hotspots of p62-IκBα association. Accordingly, we have identified such IκBα hotspots to reside around N-terminal (K38, K47, and K67) and C-terminal (K238/C239) residues in its fifth ankyrin repeat domain. These sites interact with two hotspots in p62: One in its PB-1 subdomain around K13, and the other comprised of a positively charged patch (R₁₈₃/R₁₈₆/K₁₈₇/K₁₈₉) between its ZZ- and TB-subdomains. APEX proximity analyses upon IκBα-cotransfection of cells with and without p62 have enabled the characterization of the p62 influence on IκBα-protein-protein interactions. Interestingly, consistent with p62's capacity to proteolytically stabilize IκBα, its presence greatly impaired IκBα's interactions with various 20S/26S proteasomal subunits. Furthermore, consistent with p62 interaction with IκBα on an interface opposite to that of its NF-κB-interacting interface, p62 failed to significantly affect IκBα-NF-κB interactions. These collective findings together with the known dynamic p62 nucleocytoplasmic shuttling leads us to speculate that it may be involved in "piggy-back" nuclear transport of IκBα following its NF-κB-elicited transcriptional activation and de novo synthesis, required for termination of the NF-κB-activation cycle. Consequently, mice carrying a liver-specific deletion of p62-residues 68 to 252 reveal age-dependent-enhanced liver inflammation. Our findings reveal yet another mode of p62-mediated pathophysiologically relevant regulation of NF-κB.

Immunometabolic factors contributing to obesity-linked hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major public health concern that is promoted by obesity and associated liver complications. Onset and progression of HCC in obesity is a multifactorial process involving complex interactions between the metabolic and immune system, in which chronic liver damage resulting from metabolic and inflammatory insults trigger carcinogenesis-promoting gene mutations and tumor metabolism. Moreover, cell growth and proliferation of the cancerous cell, after initiation, requires interactions between various immunological and metabolic pathways that provide stress defense of the cancer cell as well as strategic cell death escape mechanisms. The heterogenic nature of HCC in addition to the various metabolic risk factors underlying HCC development have led researchers to focus on examining metabolic pathways that may contribute to HCC development. In obesity-linked HCC, oncogene-induced modifications and metabolic pathways have been identified to support anabolic demands of the growing HCC cells and combat the concomitant cell stress, coinciding with altered utilization of signaling pathways and metabolic fuels involved in glucose metabolism, macromolecule synthesis, stress defense, and redox homeostasis. In this review, we discuss metabolic insults that can underlie the transition from steatosis to steatohepatitis and from steatohepatitis to HCC as well as aberrantly regulated immunometabolic pathways that enable cancer cells to survive and proliferate in the tumor microenvironment. We also discuss therapeutic modalities targeted at HCC prevention and regression. A full understanding of HCC-associated immunometabolic changes in obesity may contribute to clinical treatments that effectively target cancer metabolism.

Analysis of fluoro based pyrazole analogues as a potential therapeutics candidate against Japanese encephalitis virus infection

Japanese encephalitis virus (JEV) is the leading causative agent of encephalitis and its associated mortality among children. JEV modulates host cell machinery for its advantage, such as oxidative damage which subsequently leads to stress responsive pathways. The present study analyzes new series of dinitroaryl substituted derivatives (1a-1f), containing pyrazole moiety and explores its potential ensuing anti-JEV activity. Out of all synthesized derivatives, compounds 1b and 1f were selected based on minimal cytotoxicity. In vitro inhibition of more than 70% and 90% were observed with compounds 1b and 1f, respectively, in neuronal cells. Dose-response analyses highlighted 1f exhibiting better antiviral activity than 1b. The mice treated with compound 1b or 1f did not show any noticeable toxicity at a dose of 100mg/kg/day when administered intraperitoneally till 96th h. Inhibition of up to 41% and 70% JEV mRNA in spleen and 33% to 43% in brain tissue was observed with compounds 1b and 1f, respectively. Both the compounds suppressed JEV induced ROS generation by up-regulating the NQO1 and HO-1 proteins. Our result suggests the interlocked positive feedback loops of NRF2-SQSTM1 signaling pathway to be regulated by the synthesized compounds. The potential of these compounds can be further tested for broad-spectrum antiviral effects with other flaviviruses in the path towards the development of therapeutics.

Role of Nrf2 Pathway Activation in Neurological Disorder: A Brief Review

Oxidative stress plays a crucial role in the emergence of numerous neurodegenerative diseases, with protein accumulation and mitochondrial damage, which result in neurological disorders. To minimize oxidative stress, several defensive mechanisms protect nerve cells by releasing antioxidants such as nuclear erythroid factor2 (Nrf2)-Kelch-like ECH-associated protein1 (Keap1) signaling pathway activation has been proved to be a prospective treatment to reduce oxidative stress and neuroinflammation for protection of neurons in a variety of neurological disorders. In this review, we focus beneficial role of Nrf2 in Alzheimer’s and Parkinson’s diseases. Nrf2 is proved to be a master regulator of antioxidants by releasing over 250 cytoprotective genes aimed at oxidative stress and neuroinflammation. In animal studies Nrf2 activation is proved to improve autophagy, mitochondrial biogenesis, and Suppression of inflammatory cytokinin which protects neuronal cells and inhibit progressive neurodegeneration.

Nanotherapeutics in autophagy: a paradigm shift in cancer treatment

Autophagy is a catabolic process in which an organism responds to its nutrient or metabolic emergencies. It involves the degradation of cytoplasmic proteins and organelles by forming double-membrane vesicles called "autophagosomes." They sequester cargoes, leading them to degradation in the lysosomes. Although autophagy acts as a protective mechanism for maintaining homeostasis through cellular recycling, it is ostensibly a cause of certain cancers, but a cure for others. In other words, insufficient autophagy, due to genetic or cellular dysfunctions, can lead to tumorigenesis. However, many autophagy modulators are developed for cancer therapy. Diverse nanoparticles have been documented to induce autophagy. Also, the highly stable nanoparticles show blockage to autophagic flux. In this review, we revealed a general mechanism by which autophagy can be induced or blocked via nanoparticles as well as several studies recently performed to prove the stated fact. In addition, we have also elucidated the paradoxical roles of autophagy in cancer and how their differential role at different stages of various cancers can affect its treatment outcomes. And finally, we summarize the breakthroughs in cancer disease treatments by using metallic, polymeric, and liposomal nanoparticles as potent autophagy modulators.

Upregulation of Nox4 induces a pro-survival Nrf2 response in cancer-associated fibroblasts that promotes tumorigenesis and metastasis, in part via Birc5 induction

BACKGROUND

A pro-oxidant enzyme, NADPH oxidase 4 (Nox4) has been reported to be a critical downstream effector of TGFβ-induced myofibroblast transformation during fibrosis. While there are a small number of studies suggesting an oncogenic role of Nox4 derived from activated fibroblasts, direct evidence linking this pro-oxidant to the tumor-supporting CAF phenotype and the mechanisms involved are lacking, particularly in breast cancer.

METHODS

We targeted Nox4 in breast patient-derived CAFs via siRNA-mediated knockdown or administration of a pharmaceutical inhibitor (GKT137831). We also determine primary tumor growth and metastasis of implanted tumor cells using a stable Nox4-/- syngeneic mouse model. Autophagic flux of CAFs was assessed using a tandem fluorescent-tagged ptfl-LC3 plasmid via confocal microscopy analysis and determination of the expression level of autophagy markers (beclin-1 and LC3B). Nox4 overexpressing CAFs depend on the Nrf2 (nuclear factor-erythroid factor 2-related factor 2) pathway for survival. We then determined the dependency of Nox4-overexpressing CAFs on the Nrf2-mediated adaptive stress response pathway for survival. Furthermore, we investigated the involvement of Birc5 on CAF phenotype (viability and collagen contraction activity) as well as the expression level of CAF markers, FAP and αSMA.

CONCLUSIONS

We found that deletion of stroma Nox4 and pharmaceutically targeting its activity with GKT137831 significantly inhibited orthotopic tumor growth and metastasis of implanted E0771 and 4T1 murine mammary carcinoma cell lines in mice. More importantly, we found a significant upregulation of Nox4 expression in CAFs isolated from human breast tumors versus normal mammary fibroblasts (RMFs). Our in situ RNA hybridization analysis for Nox4 transcription on a human breast tumor microarray further support a role of this pro-oxidant in the stroma of breast carcinomas. In addition, we found that Nox4 promotes autophagy in CAFs. Moreover, we found that Nox4 promoted survival of CAFs via activation of Nrf2, a master regulator of oxidative stress response. We have further shown Birc5 is involved as a downstream modulator of Nrf2-mediated pro-survival phenotype. Together these studies indicate a role of redox signaling via the Nox4-Nrf2 pathway in tumorigenesis and metastasis of breast cancer cells by promoting autophagy and survival of CAFs.

Therapeutic targeting of TANK-binding kinase signaling towards anticancer drug development: Challenges and opportunities

TANK-binding kinase 1 (TBK1) plays a fundamental role in regulating the cellular responses and controlling several signaling cascades. It regulates inflammatory, interferon, NF-κB, autophagy, and Akt pathways. Post-translational modifications (PTM) of TBK1 control its action and subsequent cellular signaling. The dysregulation of the TBK1 pathway is correlated to many pathophysiological conditions, including cancer, that implicates the promising therapeutic advantage for targeting TBK1. The present study summarizes current updates on the molecular mechanisms and cancer-inducing roles of TBK1. Designed inhibitors of TBK1 are considered a potential therapeutic agent for several diseases, including cancer. Data from pre-clinical tumor models recommend that the targeting of TBK1 could be an attractive strategy for anti-tumor therapy. This review further highlighted the therapeutic potential of potent and selective TBK1 inhibitors, including Amlexanox, Compound II, BX795, MRT67307, SR8185 AZ13102909, CYT387, GSK8612, BAY985, and Domainex. These inhibitors may be implicated to facilitate therapeutic management of cancer and TBK1-associated diseases in the future.

Inhibiting SCAP/SREBP exacerbates liver injury and carcinogenesis in murine nonalcoholic steatohepatitis

Enhanced de novo lipogenesis mediated by sterol regulatory element-binding proteins (SREBPs) is thought to be involved in nonalcoholic steatohepatitis (NASH) pathogenesis. In this study, we assessed the impact of SREBP inhibition on NASH and liver cancer development in murine models. Unexpectedly, SREBP inhibition via deletion of the SREBP cleavage-activating protein (SCAP) in the liver exacerbated liver injury, fibrosis, and carcinogenesis, despite markedly reduced hepatic steatosis. These phenotypes were ameliorated by restoring SREBP function. Transcriptome and lipidome analyses revealed that SCAP-SREBP pathway inhibition altered the fatty acid (FA) composition of phosphatidylcholines due to both impaired FA synthesis and disorganized FA incorporation into phosphatidylcholine via lysophosphatidylcholine acyltransferase 3 (LPCAT3) downregulation, which led to endoplasmic reticulum (ER) stress and hepatocyte injury. Supplementation of phosphatidylcholines significantly improved liver injury and ER stress induced by SCAP deletion. The activity of SCAP-SREBP-LPCAT3 axis was found inversely associated with liver fibrosis severity in human NASH. SREBP inhibition also cooperated with impaired autophagy to trigger liver injury. Thus, excessively strong and broad lipogenesis inhibition was counterproductive for NASH therapy, which will have important clinical implications in NASH treatment.

RNF4 silencing induces cell growth arrest and DNA damage by promoting nuclear targeting of p62 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the largest causes of cancer-related deaths worldwide owing to the limitation of effective treatment options. The ubiquitin-proteasome system has been rapidly recognized as a frequent target of deregulation leading to cancers. Enhanced DNA damage response (DDR) promotes HCC growth and prevents chemosensitivity, and ubiquitin E3 ligases are key modulators in DDR. Therefore, a better understanding of how E3 ligases regulate cell growth and DNA damage may provide novel insights in understanding the oncogenic mechanism and improving the efficacy of DNA damage therapeutic agents. Here, we performed a high-content RNAi screening targeting 52 DDR-related E3 ligases in HCC and found that ring finger protein 4 (RNF4) was essential for HCC growth. RNF4 was highly expressed in HCC tissues, and the expression levels of RNF4 were associated with poor outcomes. RNF4 silencing significantly suppressed the cell growth, and subsequently induced G2/M arrest and apoptosis of HCC cells in vitro; RNF4 silencing also demonstrated the tumor-suppressive efficacy on HCC in vivo. Moreover, RNF4 silencing increased DNA damage, and rendered HCC cells more sensitive to DNA damage drugs and radiation. We found RNF4 functionally interacts with p62, and mechanistic analyses indicated that RNF4 silencing triggered the nuclear enrichment of p62. Moreover, the p62 nuclear targeting was required for increased DNA damage and growth suppression mediated by RNF4 silencing. Thus, our findings suggest RNF4 is essential for HCC proliferation via preventing nuclear translocation of p62. RNF4 silencing promotes DNA damage and may serve as a novel strategy to suppress cell growth and increase the sensitivity of DNA damage therapeutic agents in HCC.

PERK prevents hepatic lipotoxicity by activating the p62-ULK1 axis-mediated noncanonical KEAP1-Nrf2 pathway

Hepatic lipotoxicity is a crucial factor in nonalcoholic steatohepatitis resulting from excessive saturated fatty acid-induced reactive oxygen species (ROS)-mediated cell death, which is associated with the accumulation of endoplasmic reticulum (ER) stress in the liver. The unfolded protein response (UPR) alleviates ER stress by restoring ER protein folding homeostasis. However, whether UPR contributes ROS elimination under lipotoxicity remains unclear. The Kelch like ECH-associated protein 1 (KEAP1)-nuclear factor, erythroid 2 like 2 (Nrf2) pathway provides antioxidant defense against lipotoxic stress by eliminating ROS and can be activated by the p62-Unc-51 like autophagy activating kinase 1 (ULK1) axis. However, the upstream molecular regulator of the p62-ULK1 axis-induced KEAP1-Nrf2 pathway in the same context remains unidentified. Here, we demonstrated that PKR-like ER kinase (PERK), a UPR sensor, directly phosphorylates p62 and ULK1, thereby activating the noncanonical KEAP1-Nrf2 pathway. We also elucidated the molecular mechanism underlying the PERK-mediated p62-ULK1 axis-dependent noncanonical KEAP1-Nrf2 pathway, which could represent a promising therapeutic strategy against hepatic lipotoxicity.

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Hepatic lipotoxicity is a crucial factor in the progression of NASH, associated with the increased ER stress.

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PERK, one of UPR sensors, activates noncanonical KEAP1-Nrf2 pathway by phosphorylating p62 at S351.

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PERK also phosphorylates ULK1 at S317, which mediates autophagic KEAP1 degradation and Nrf2 activation.

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PERK protects mouse liver against lipotoxicity via Nrf2 activation.

Dual roles of p62/SQSTM1 in the injury and recovery phases of acetaminophen-induced liver injury in mice

Acetaminophen (APAP) overdose can induce liver injury and is the most frequent cause of acute liver failure in the United States. We investigated the role of p62/SQSTM1 (referred to as p62) in APAP-induced liver injury (AILI) in mice. We found that the hepatic protein levels of p62 dramatically increased at 24 h after APAP treatment, which was inversely correlated with the hepatic levels of APAP-adducts. APAP also activated mTOR at 24 h, which is associated with increased cell proliferation. In contrast, p62 knockout (KO) mice showed increased hepatic levels of APAP-adducts detected by a specific antibody using Western blot analysis but decreased mTOR activation and cell proliferation with aggravated liver injury at 24 h after APAP treatment. Surprisingly, p62 KO mice recovered from AILI whereas the wild-type mice still sustained liver injury at 48 h. We found increased number of infiltrated macrophages in p62 KO mice that were accompanied with decreased hepatic von Willebrand factor (VWF) and platelet aggregation, which are associated with increased cell proliferation and improved liver injury at 48 h after APAP treatment. Our data indicate that p62 inhibits the late injury phase of AILI by increasing autophagic selective removal of APAP-adducts and mitochondria but impairs the recovery phase of AILI likely by enhancing hepatic blood coagulation.

Serum Anti-14-3-3 Zeta Autoantibody as a Biomarker for Predicting Hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is a common malignancy worldwide. Alpha-fetoprotein (AFP) is still the only serum biomarker widely used in clinical settings. However, approximately 40% of HCC patients exhibit normal AFP levels, including very early HCC and AFP-negative HCC; for these patients, serum AFP is not applicable as a biomarker of early detection. Thus, there is an urgent need to identify novel biomarkers for patients for whom disease cannot be diagnosed early. In this study, we screened and identified novel proteins in AFP-negative HCC and evaluated the feasibility of using autoantibodies to those protein to predict hepatocarcinogenesis. First, we screened and identified differentially expressed proteins between AFP-negative HCC tissue and adjacent non-tumor liver tissue using SWATH-MS proteome technology. In total, 2,506 proteins were identified with a global false discovery rate of 1%, of which 592 proteins were expressed differentially with 175 upregulated and 417 downregulated (adjusted p-value <0.05, fold-change FC ≥1.5 or ≤0.67) between the tumor and matched benign samples, including 14-3-3 zeta protein. For further serological verification, autoantibodies against 14-3-3 zeta in serum were evaluated using enzyme-linked immunosorbent, Western blotting, and indirect immunofluorescence assays. Five serial serum samples from one patient with AFP-negative HCC showed anti-14-3-3 zeta autoantibody in sera 9 months before the diagnosis of HCC, which gradually increased with an increase in the size of the nodule. Based on these findings, we detected the prevalence of serum anti-14-3-3 zeta autoantibody in liver cirrhosis (LC) patients, which is commonly considered a premalignant liver disease of HCC. We found that the prevalence of autoantibodies against 14-3-3 zeta protein was 16.1% (15/93) in LC patient sera, which was significantly higher than that in patients with chronic hepatitis (0/75, p = 0.000) and normal human sera (1/60, 1.7%, p = 0.01). Therefore, we suggest that anti-14-3-3 zeta autoantibody might be a biomarker for predicting hepatocarcinogenesis. Further follow-up and research of patients with positive autoantibodies will be continued to confirm the relationship between anti-14-3-3 zeta autoantibody and hepatocarcinogenesis.

CDK1-Mediated Phosphorylation of BAG3 Promotes Mitotic Cell Shape Remodeling and the Molecular Assembly of Mitotic p62 Bodies

The cochaperone BCL2-associated athanogene 3 (BAG3), in complex with the heat shock protein HSPB8, facilitates mitotic rounding, spindle orientation, and proper abscission of daughter cells. BAG3 and HSPB8 mitotic functions implicate the sequestosome p62/SQSTM1, suggesting a role for protein quality control. However, the interplay between this chaperone-assisted pathway and the mitotic machinery is not known. Here, we show that BAG3 phosphorylation at the conserved T285 is regulated by CDK1 and activates its function in mitotic cell shape remodeling. BAG3 phosphorylation exhibited a high dynamic at mitotic entry and both a non-phosphorylatable BAG3^T285A and a phosphomimetic BAG3^T285D protein were unable to correct the mitotic defects in BAG3-depleted HeLa cells. We also demonstrate that BAG3 phosphorylation, HSPB8, and CDK1 activity modulate the molecular assembly of p62/SQSTM1 into mitotic bodies containing K63 polyubiquitinated chains. These findings suggest the existence of a mitotically regulated spatial quality control mechanism for the fidelity of cell shape remodeling in highly dividing cells.

Parkin-mediated mitochondrial quality control protects against aluminum-induced liver damage in mice

Aluminum (Al) is known to be hepatotoxic. Oxidative stress is the main mechanism of liver injury caused by Al, and can also lead to mitochondrial damage. Mitochondrial damage is a prerequisite for mitochondrial quality control (MQC) dysregulation. Parkin can activate MQC and maintain mitochondrial homeostasis. However, the role of Parkin-mediated MQC in Al-induced liver damage has not been elucidated. In this study, forty male wild type (WT) C57BL/6N mice were treated with 0, 44.825, 89.65 or 179.3 mg/kg body weight AlCl₃ in drinking water for 90 days, respectively. We found that Al induced mitophagy and disrupted mitochondrial dynamics and mitochondrial biogenesis. Then, twenty male WT C57BL/6N mice and twenty male Parkin knockout (Parkin^-/-) C57BL/6N mice were divided into four groups and treated with 0, 89.65, 0, 89.65 mg/kg body weight AlCl₃ in drinking water for 90 days, respectively. We found that Parkin^-/- inhibited mitophagy and further disrupted mitochondrial dynamics and mitochondrial biogenesis. These results indicated that Parkin-mediated MQC could be disrupted by Al and protected against Al-induced liver damage.

The role of P62 in the development of human thyroid cancer and its possible mechanism

BACKGROUND

Thyroid cancer is the most common malignancy in human endocrine system. Increasing evidence has indicated that p62 plays a key role in tumorigenesis. The roles and underlying molecular mechanisms of P62 in thyroid cancer, however, remain to be elucidated.

METHODS

The expression levels of P62 in thyroid tumor tissues and thyroid cancer cells were detected by western blotting and qRT-PCR. Then, the effects of up-regulation or down-regulation of P62 on thyroid cancer cell proliferation, migration, invasion, cell cycle and apoptosis were measured by CCK-8 assay, transwell assay, flow cytometry and transwell assay, respectively. In terms of the mechanism, P62 could stimulate thyroid cancer progression by the activation of nuclear factor-kappa B (NF-κB) signaling pathway.

RESULTS

P62 was highly expressed in thyroid tumor tissues. Furthermore, high expression of p62 was observed in PTC cell lines, and especially in the K1 and TPC-1 cells. In vitro, the up-regulation of p62 promoted cell proliferation, migration, and invasion of thyroid cancer cells, whereas the knockdown of p62 resulted in the opposite effect. Knock-down of P62 increased the number of cells in the G0/G1 phase but reduced it in the S and G2/M phase. Moreover, we confirmed that overexpression of p62 inactivated NF-κB pathway with sequencing analysis and bioinformatics analysis.

CONCLUSION

This research work suggested that p62 could promote PTC cell proliferation, migration, and invasion via NF-κB signaling pathway. Furthermore, p62 is a potential biomarker which might be closely related to the tumorigenesis in PTC. Its potential role as a therapeutic target for PTC is worthy of further study.

The Pathways Underlying the Multiple Roles of p62 in Inflammation and Cancer

p62 is a highly conserved, multi-domain, and multi-functional adaptor protein critically involved in several important cellular processes. Via its pronounced domain architecture, p62 binds to numerous interaction partners, thereby influencing key pathways that regulate tissue homeostasis, inflammation, and several common diseases including cancer. Via binding of ubiquitin chains, p62 acts in an anti-inflammatory manner as an adaptor for the auto-, xeno-, and mitophagy-dependent degradation of proteins, pathogens, and mitochondria. Furthermore, p62 is a negative regulator of inflammasome complexes. The transcription factor Nrf2 regulates expression of a bundle of ROS detoxifying genes. p62 activates Nrf2 by interaction with and autophagosomal degradation of the Nrf2 inhibitor Keap1. Moreover, p62 activates mTOR, the central kinase of the mTORC1 sensor complex that controls cell proliferation and differentiation. Through different mechanisms, p62 acts as a positive regulator of the transcription factor NF-κB, a central player in inflammation and cancer development. Therefore, p62 represents not only a cargo receptor for autophagy, but also a central signaling hub, linking several important pro- and anti-inflammatory pathways. This review aims to summarize knowledge about the molecular mechanisms underlying the roles of p62 in health and disease. In particular, different types of tumors are characterized by deregulated levels of p62. The elucidation of how p62 contributes to inflammation and cancer progression at the molecular level might promote the development of novel therapeutic strategies.

A review on the role of TANK-binding kinase 1 signaling in cancer

TANK-binding kinase 1 (TBK1) regulates various biological processes including, NF-κB signaling, immune response, autophagy, cell division, Ras-mediated oncogenesis, and AKT pro-survival signaling. Enhanced TBK1 activity is associated with autoimmune diseases and cancer, suggesting its role in therapeutic targeting of interferonopathies. In addition, dysregulation of TBK1 activity promotes several inflammatory disorders and oncogenesis. Structural and biochemical study reports provide the molecular process of TBK1 activation and recap the substrate selection about TBK1. This review summarizes recent findings on the molecular mechanisms by which TBK1 is involved in cancer signaling. The IKK-ε and TBK1 are together associated with inflammatory diseases by inducing type I IFNs. Furthermore, TBK1 signaling regulates radiation-induced epithelial-mesenchymal transition by controlling phosphorylation of GSK-3β and expression of Zinc finger E-box-binding homeobox 1, suggesting, TBK1 could be targeted for radiotherapy-induced metastasis therapy. Despite a considerable increase in the list of TBK1 inhibitors, only a few has potential to control cancer. Among them, a compound BX795 is considered a potent and selective inhibitor of TBK1. We discussed the therapeutic potential of small-molecule inhibitors of TBK1, particularly those with high selectivity, which will enable further exploration in the therapeutic management of cancer and inflammatory diseases.

Correlation analysis of tumor mutation burden of hepatocellular carcinoma based on data mining

Background

The aim of this study was to determine the relationship between tumor mutation burden (TMB) and prognosis of patients with hepatocellular carcinoma (HCC), and to explore the differential expression of genes in HCC by TMB and the relationship between immune cells, TMB, and HCC.

Methods

Somatic variation data, gene transcriptional expression data and clinical information of patients with HCC were obtained from cancer genome map (TCGA) database. Analyze the characteristics of the gene mutation data of the sample, divide the high and low TMB groups and draw the survival curve at the same time, carry on the difference analysis to the gene of TMB, further carry on the univariate Cox regression analysis and Lasso regression analysis and construct the clinical model. Download the dataset GSE14520, from the Gene Expression Omnibus (GEO) database to verify the genes of the prognostic model. The differential genes were analyzed by gene ontology (GO) enrichment analysis and Kyoto encyclopedia of genes and genomes by (KEGG) enrichment analysis. Then the relative abundance of 22 immune cell types in HCC and normal control samples was calculated. Finally, the correlation between the scores of immune cells and Risk model was analyzed.

Results

Tumor protein p53 (TP53), catenin1 (CTNNB1), titin (TTN), mucin 16 (MUC16), and albumin (ALB) are the most common top 5 mutations in HCC. The prognosis of high level TMB group is worse than that of low TMB group. A total of 122 differentially expressed genes were screened by differential analysis of TMB genes. SQSTM1, ME1, BAMBI and PTTG1 are independent risk factors for poor prognosis of HCC. GO and KEGG analysis showed that the differential genes were mainly in extracellular matrix and immune response. There were significant differences in the distribution of Macrophages M0 and T cells CD4 native cells between HCC and normal tissues, which were correlated with the differential genes of TMB and correlated with prognosis.

Conclusions

There is a negative correlation between TMB and the prognosis of patients with HCC. TMB has an effect on the differential expression of genes in HCC cells and the distribution of immune cells in tumor tissues.

Remodeling of Mitochondrial Plasticity: The Key Switch from NAFLD/NASH to HCC

Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver and the third-leading cause of cancer-related mortality. Currently, the global burden of nonalcoholic fatty liver disease (NAFLD) has dramatically overcome both viral and alcohol hepatitis, thus becoming the main cause of HCC incidence. NAFLD pathogenesis is severely influenced by lifestyle and genetic predisposition. Mitochondria are highly dynamic organelles that may adapt in response to environment, genetics and epigenetics in the liver ("mitochondrial plasticity"). Mounting evidence highlights that mitochondrial dysfunction due to loss of mitochondrial flexibility may arise before overt NAFLD, and from the early stages of liver injury. Mitochondrial failure promotes not only hepatocellular damage, but also release signals (mito-DAMPs), which trigger inflammation and fibrosis, generating an adverse microenvironment in which several hepatocytes select anti-apoptotic programs and mutations that may allow survival and proliferation. Furthermore, one of the key events in malignant hepatocytes is represented by the remodeling of glucidic-lipidic metabolism combined with the reprogramming of mitochondrial functions, optimized to deal with energy demand. In sum, this review will discuss how mitochondrial defects may be translated into causative explanations of NAFLD-driven HCC, emphasizing future directions for research and for the development of potential preventive or curative strategies.

Autophagy in Hepatic Steatosis: A Structured Review

Steatosis is the accumulation of neutral lipids in the cytoplasm. In the liver, it is associated with overeating and a sedentary lifestyle, but may also be a result of xenobiotic toxicity and genetics. Non-alcoholic fatty liver disease (NAFLD) defines an array of liver conditions varying from simple steatosis to inflammation and fibrosis. Over the last years, autophagic processes have been shown to be directly associated with the development and progression of these conditions. However, the precise role of autophagy in steatosis development is still unclear. Specifically, autophagy is necessary for the regulation of basic metabolism in hepatocytes, such as glycogenolysis and gluconeogenesis, response to insulin and glucagon signaling, and cellular responses to free amino acid contents. Also, genetic knockout models for autophagy-related proteins suggest a critical relationship between autophagy and hepatic lipid metabolism, but some results are still ambiguous. While autophagy may seem necessary to support lipid oxidation in some contexts, other evidence suggests that autophagic activity can lead to lipid accumulation instead. This structured literature review aims to critically discuss, compare, and organize results over the last 10 years regarding rodent steatosis models that measured several autophagy markers, with genetic and pharmacological interventions that may help elucidate the molecular mechanisms involved.

Predicting postoperative liver cancer death outcomes with machine learning

OBJECTIVE

To investigate the effect of 5 machine learning algorithms in predicting total hepatocellular carcinoma (HCC) postoperative death outcomes.

METHODS

This study was a secondary analysis. A prognosis model was established using machine learning with python.

RESULTS

The results from the machine learning gbm algorithm showed that the most important factors, ranked from first to fifth, were: preoperative aspartate aminotransferase (GOT), preoperative AFP, preoperative cereal third transaminase (GPT), preoperative total bilirubin, and LC3. Postoperative death model results for liver cancer patients in the test group: of the 5 algorithm models, the highest accuracy rate was that of forest (0.739), followed by the gbm algorithm (0.714); of the 5 algorithms, the AUC values, from high to low, were forest (0.803), GradientBoosting (0.746), gbm (0.724), Logistic (0.660) and DecisionTree (0.578).

CONCLUSION

Machine learning can predict total hepatocellular carcinoma postoperative death outcomes.

Sestrin2 Regulates Osteoclastogenesis via the p62-TRAF6 Interaction

The receptor activator of nuclear factor-kappa B ligand (RANKL) mediates osteoclast differentiation and functions by inducing Ca²⁺ oscillations, activating mitogen-activated protein kinases (MAPKs), and activating nuclear factor of activated T-cells type c1 (NFATc1) via the RANK and tumor necrosis factor (TNF) receptor-associated factor 6 (TRAF6) interaction. Reactive oxygen species (ROS) also plays an important role during osteoclastogenesis and Sestrin2, an antioxidant, maintains cellular homeostasis upon stress injury via regulation of ROS, autophagy, and inflammation. However, the role of Sestrin2 in osteoclastogenesis remains unknown. In this study, we investigated the role of Sestrin2 in the RANKL-RANK-TRAF6 signaling pathway during osteoclast differentiation. Deletion of Sestrin2 (Sesn2) increased bone mass and reduced the number of multinucleated osteoclasts on bone surfaces. RANKL-induced osteoclast differentiation and function decreased in Sesn2 knockout (KO) bone marrow-derived monocytes/macrophages (BMMs) due to inhibition of NFATc1 expression, but osteoblastogenesis was not affected. mRNA expression of RANKL-induced specific osteoclastogenic genes and MAPK protein expression were lower in Sesn2 KO BMMs than wild-type (WT) BMMs after RANKL treatment. However, the Sesn2 deletion did not affect ROS generation or intracellular Ca²⁺ oscillations during osteoclastogenesis. In contrast, the interaction between TRAF6 and p62 was reduced during osteoclasts differentiation in Sesn2 KO BMMs. The reduction in the TRAF6/p62 interaction and TRAP activity in osteoclastogenesis in Sesn2 KO BMMs was recovered to the WT level upon expression of Flag-Sesn2 in Sesn2 KO BMMs. These results suggest that Sestrin2 has a novel role in bone homeostasis and osteoclasts differentiation through regulation of NFATc1 and the TRAF6/p62 interaction.

Sequestosome 1/p62 enhances chronic skin inflammation

BACKGROUND

The molecular control of inflammation and epidermal thickening in skin lesions of patients with atopic dermatitis (AD) is not known. Sequestosome 1/p62 is a multifunctional adapter protein implicated in the control of key regulators of cellular homeostasis, such as proinflammatory and mechanistic target of rapamycin signaling.

OBJECTIVE

We sought to determine whether p62 plays a role in the cutaneous and systemic manifestations of an AD-like mouse model.

METHODS

AD-like skin lesions were induced by deletion of JunB/AP-1, specifically in epidermal keratinocytes (JunB^Δep). The contribution of p62 to pathological changes was determined by inactivation of p62 in JunB^Δepp62^-/- double knockout mice.

RESULTS

Expression of p62 was elevated in skin lesions of JunB^Δep mice, resembling upregulation of p62 in AD and psoriasis. When p62 was inactivated, JunB^Δep-associated defects in the differentiation of keratinocytes, epidermal thickening, skin infiltration by mast cells and neutrophils, and the development of macroscopic skin lesions were significantly reduced. p62 inactivation had little effect on circulating cytokines, but decreased serum IgE. Signaling through mechanistic target of rapamycin and natural factor kappa B was increased in JunB^Δep but not in JunB^Δepp62^-/- double knockout skin, indicating an important role of p62 in enhancing these signaling pathways in the skin during AD-like inflammation.

CONCLUSIONS

Our results provide the first in vivo evidence for a proinflammatory role of p62 in skin and suggest that p62-dependent signaling pathways may be promising therapeutic targets to ameliorate the skin manifestations of AD and possibly psoriasis.

ARMCX3 Mediates Susceptibility to Hepatic Tumorigenesis Promoted by Dietary Lipotoxicity

Simple Summary

An excess fat in the liver enhances the susceptibility to hepatic cancer. We found that Armcx3, a protein only known to date to play a role in neural development, is strongly increased in mouse liver in response to lipid availability and proliferation-inducing insults. In patients, the levels of hepatic Armcx3 are also increased in conditions of high exposure of the liver to fat. We wanted to determine the role of Armcx3 in the hepatocarcinogenesis favored by a high-fat diet. We generated mice with genetically driven suppression of Armcx3, and we found that they were protected against experimentally induced hepatic cancer, especially in conditions of a high-fat diet. Armcx3 was also found to promote hepatic cell proliferation through the interaction with Sox9, a known proliferation factor in hepatocellular carcinoma. Armcx3 is identified as a novel factor in meditating propensity to liver cancer in conditions of high hepatic lipid insults.

Abstract

ARMCX3 is encoded by a member of the Armcx gene family and is known to be involved in nervous system development and function. We found that ARMCX3 is markedly upregulated in mouse liver in response to high lipid availability, and that hepatic ARMCX3 is upregulated in patients with NAFLD and hepatocellular carcinoma (HCC). Mice were subjected to ARMCX3 invalidation (inducible ARMCX3 knockout) and then exposed to a high-fat diet and diethylnitrosamine-induced hepatocarcinogenesis. The effects of experimental ARMCX3 knockdown or overexpression in HCC cell lines were also analyzed. ARMCX3 invalidation protected mice against high-fat-diet-induced NAFLD and chemically induced hepatocarcinogenesis. ARMCX3 invalidation promoted apoptotic cell death and macrophage infiltration in livers of diethylnitrosamine-treated mice maintained on a high-fat diet. ARMCX3 downregulation reduced the viability, clonality and migration of HCC cell lines, whereas ARMCX3 overexpression caused the reciprocal effects. SOX9 was found to mediate the effects of ARMCX3 in hepatic cells, with the SOX9 interaction required for the effects of ARMCX3 on hepatic cell proliferation. In conclusion, ARMCX3 is identified as a novel molecular actor in liver physiopathology and carcinogenesis. ARMCX3 downregulation appears to protect against hepatocarcinogenesis, especially under conditions of high dietary lipid-mediated hepatic insult.

Mitochondrial integration and ovarian cancer chemotherapy resistance

Ovarian cancer has been nicknamed the "silent killer". Most patients with ovarian cancer are diagnosed at an advanced stage of the disease for the first time because of its insignificant early clinical symptoms. In addition to the difficulty of early screening and delay in diagnosis, the high recurrence rate and relapsed refractory status of patients with ovarian cancer are also important factors for their high mortality. Patients with recurrent ovarian cancer often use neoadjuvant chemotherapy followed by surgery as the first choice. However, this is often accompanied by chemotherapy resistance, leading to treatment failure and a mortality rate of more than 90%. In the past, it was believed that the anti-tumor effect of chemotherapeutics represented by cisplatin was entirely attributable to its irreversible damage to DNA, but current research has found that it can inhibit cell growth and cytotoxicity via nuclear and cytoplasmic coordinated integration. As an important hub and integration platform for intracellular signal communication, mitochondria are responsible for multiple key factors during tumor occurrence and development, such as metabolic reprogramming, acquisition of metastatic ability, and chemotherapy drug response. The role of mitochondria in ovarian cancer chemotherapy resistance is becoming increasingly recognized. In this review, we discuss the cellular interactive regulatory network surrounding mitochondria, elucidate the mechanisms of tumor cell survival under chemotherapy, and discuss potential means of interfering with mitochondrial function as a novel anti-cancer therapy.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

The Ubiquitin E3 Ligase TRIM21 Promotes Hepatocarcinogenesis by Suppressing the p62-Keap1-Nrf2 Antioxidant Pathway

BACKGROUND AND AIMS

TRIM21 is a ubiquitin E3 ligase that is implicated in numerous biological processes including immune response, cell metabolism, redox homeostasis, and cancer development. We recently reported that TRIM21 can negatively regulate the p62-Keap1-Nrf2 antioxidant pathway by ubiquitylating p62 and prevents its oligomerization and protein sequestration function. As redox homeostasis plays a pivotal role in many cancers including liver cancer, we sought to determine the role of TRIM21 in hepatocarcinogenesis.

METHODS

We examined the correlation between TRIM21 expression and the disease using publicly available data sets and 49 cases of HCC clinical samples. We used TRIM21 genetic knockout mice to determine how TRIM21 ablation impact HCC induced by the carcinogen DEN plus phenobarbital (PB). We explored the mechanism that loss of TRIM21 protects cells from DEN-induced oxidative damage and cell death.

RESULTS

There is a positive correlation between TRIM21 expression and HCC. Consistently, TRIM21-knockout mice are resistant to DEN-induced hepatocarcinogenesis. This is accompanied by decreased cell death and tissue damage upon DEN treatment, hence reduced hepatic tissue repair response and compensatory proliferation. Cells deficient in TRIM21 display enhanced p62 sequestration of Keap1 and are protected from DEN-induced ROS induction and cell death. Reconstitution of wild-type but not the E3 ligase-dead and the p62 binding-deficient mutant TRIM21 impedes the protection from DEN-induced oxidative damage and cell death in TRIM21-deficient cells.

CONCLUSIONS

Increased TRIM21 expression is associated with human HCC. Genetic ablation of TRIM21 leads to protection against oxidative hepatic damage and decreased hepatocarcinogenesis, suggesting TRIM21 as a preventive and therapeutic target.

The involvement of autophagy in the maintenance of endothelial homeostasis: The role of mitochondria

Endothelial mitochondria play important signaling roles critical for the regulation of various cellular processes, including calcium signaling, ROS generation, NO synthesis or inflammatory response. Mitochondrial stress or disturbances in mitochondrial function may participate in the development and/or progression of endothelial dysfunction and could precede vascular diseases. Vascular functions are also strictly regulated by properly functioning degradation machinery, including autophagy and mitophagy, and tightly coordinated by mitochondrial and endoplasmic reticulum responses to stress. Within this review, current knowledge related to the development of cardiovascular disorders and the importance of mitochondria, endoplasmic reticulum and degradation mechanisms in vascular endothelial functions are summarized.

The Role of Autophagy in Liver Cancer: Crosstalk in Signaling Pathways and Potential Therapeutic Targets

Autophagy is an evolutionarily conserved lysosomal-dependent pathway for degrading cytoplasmic proteins, macromolecules, and organelles. Autophagy-related genes (Atgs) are the core molecular machinery in the control of autophagy, and several major functional groups of Atgs coordinate the entire autophagic process. Autophagy plays a dual role in liver cancer development via several critical signaling pathways, including the PI3K-AKT-mTOR, AMPK-mTOR, EGF, MAPK, Wnt/β-catenin, p53, and NF-κB pathways. Here, we review the signaling pathways involved in the cross-talk between autophagy and hepatocellular carcinoma (HCC) and analyze the status of the development of novel HCC therapy by targeting the core molecular machinery of autophagy as well as the key signaling pathways. The induction or the inhibition of autophagy by the modulation of signaling pathways can confer therapeutic benefits to patients. Understanding the molecular mechanisms underlying the cross-link of autophagy and HCC may extend to translational studies that may ultimately lead to novel therapy and regimen formation in HCC treatment.

NRF2 as a regulator of cell metabolism and inflammation in cancer

Nuclear factor erythroid 2-related factor 2 (NRF2) is a master transcriptional regulator of genes whose products defend our cells for toxic and oxidative insults. Although NRF2 activation may reduce cancer risk by suppressing oxidative stress and tumor-promoting inflammation, many cancers exhibit elevated NRF2 activity either due to mutations that disrupt the negative control of NRF2 activity or other factors. Importantly, NRF2 activation is associated with poor prognosis and NRF2 has turned out to be a key activator of cancer-supportive anabolic metabolism. In this review, we summarize the diverse roles played by NRF2 in cancer focusing on metabolic reprogramming and tumor-promoting inflammation.

Autophagy and liver cancer

Autophagy is a highly conserved catabolic process that degrades cytosolic proteins and organelles via formation of autophagosomes that fuse with lysosomes to form autolysosomes, whereby autophagic cargos are degraded. Numerous studies have demonstrated that autophagy plays a critical role in the regulation of liver physiology and homeostasis, and impaired autophagy leads to the pathogenesis of various liver diseases such as viral hepatitis, alcohol associated liver diseases (AALD), non-alcoholic fatty liver diseases (NAFLD), and liver cancer. Recent evidence indicates that autophagy may play a dual role in liver cancer: inhibiting early tumor initiation while promoting progression and malignancy of already formed liver tumors. In this review, we summarized the progress of current understanding of how hepatic viral infection, alcohol consumption and diet-induced fatty liver diseases impair hepatic autophagy. We also discussed how impaired autophagy promotes liver tumorigenesis, and paradoxically how autophagy is required to promote the malignancy and progression of liver cancer. Understanding the molecular mechanisms underlying how autophagy differentially affects liver cancer development and progression may help to design better therapeutic strategies for prevention and treatment of liver cancer.

Hydroxyurea Scavenges Free Radicals and Induces the Expression of Antioxidant Genes in Human Cell Cultures Treated With Hemin

The excessive release of heme during hemolysis contributes to the severity of sickle cell anemia (SCA) by exacerbating hemoglobin S (HbS) autoxidation, inflammation and systemic tissue damage. The present study investigated the effect of hydroxyurea (HU) on free radical neutralization and its stimulation of antioxidant genes in human peripheral blood mononuclear cells (PBMC) and human umbilical vein endothelial cells (HUVEC) in the presence or absence of hemin. HU (100 and 200 μM) significantly reduced the production of intracellular reactive oxygen species (ROS) induced by hemin at 70 μM in HUVEC. HUVECs treated with HU+hemin presented significant increases in nitric oxide (NO) production in culture supernatants. HU alone or in combination with hemin promoted the induction of superoxide dismutase-1 (SOD1) and glutathione disulfide-reductase (GSR) in HUVECs and PBMCs, and glutathione peroxidase (GPX1) in PBMCs. Microarray analysis performed in HUVECs indicated that HU induces increased expression of genes involved in the antioxidant response system: SOD2, GSR, microsomal glutathione S-transferase (MGST1), glutathione S-transferase mu 2 (GSTM2), carbonyl reductase 1 (CBR1) and klotho B (KLB). Significant increases in expression were observed in genes with kinase activity: protein kinase C beta (PRKCB), zeta (PRKCZ) and phosphatidylinositol-4-phosphate 3-kinase catalytic subunit type 2 beta (PIK3C2B). HU also induced a significant increase in expression of the gene p62/sequestosome (p62/SQSTM1) and a significant decrease in the expression of the transcriptional factor BACH1 in HUVECs. Upstream analysis predicted the activation of Jun, miR-155-5p and mir-141-3p. These results suggest that HU directly scavenges free radicals and induces the expression of antioxidant genes via induction of the Nrf2 signaling pathway.

NRF2, a Transcription Factor for Stress Response and Beyond

Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor that regulates the cellular defense against toxic and oxidative insults through the expression of genes involved in oxidative stress response and drug detoxification. NRF2 activation renders cells resistant to chemical carcinogens and inflammatory challenges. In addition to antioxidant responses, NRF2 is involved in many other cellular processes, including metabolism and inflammation, and its functions are beyond the originally envisioned. NRF2 activity is tightly regulated through a complex transcriptional and post-translational network that enables it to orchestrate the cell’s response and adaptation to various pathological stressors for the homeostasis maintenance. Elevated or decreased NRF2 activity by pharmacological and genetic manipulations of NRF2 activation is associated with many metabolism- or inflammation-related diseases. Emerging evidence shows that NRF2 lies at the center of a complex regulatory network and establishes NRF2 as a truly pleiotropic transcription factor. Here we summarize the complex regulatory network of NRF2 activity and its roles in metabolic reprogramming, unfolded protein response, proteostasis, autophagy, mitochondrial biogenesis, inflammation, and immunity.

The Autophagy Machinery Contributes to E-cadherin Turnover in Breast Cancer

Autophagy is an intracellular catabolic process that is increasingly being recognized as a crucial factor in several human diseases including cancers. Mounting evidence suggests that autophagy allows tumor cells to overcome otherwise fatal stresses and to increase dissemination. Nevertheless, how autophagy controls these processes and in particular how it impinges on cell-cell adhesion is still poorly understood. Here, we investigate the role of autophagy in the turnover of the epithelial adhesion molecule E-cadherin in the context of breast cancer. We demonstrated in breast cancer cell lines that autophagy impinges on E-cadherin expression and in the configuration of adherens junctions. Besides, we showed that E-cadherin colocalizes with LC3B and SQSTM1/p62, two components of the autophagosome machinery. Pull down and immunoprecipitation analyses provided evidence that E-cadherin and SQSTM1/p62 physically interact. Moreover, the physical closeness of E-cadherin and SQSTM1/p62 was demonstrated by proximity ligation assays in breast cancer cell lines and primary tumors. Finally, we proved that the silencing of SQSTM1/p62 diminished the E-cadherin/LC3B colocalization, further supporting the role of SQSTM1/p62 in E-cadherin delivery to autophagosomes. These findings suggest that the activation of autophagy, reported in breast cancers with poor prognosis and in dormant breast cancer cells, may contribute to the control of tumor progression via downmodulation of E-cadherin protein levels.

Ginsenoside Rg3 promotes regression from hepatic fibrosis through reducing inflammation-mediated autophagy signaling pathway

Inflammation and autophagy occur during hepatic fibrosis development caused by various pathogens, and effectively curbing of autophage may delay the occurrence of hepatic fibrosis. The current study aimed to unravel the inhibitory effects of Ginsenoside Rg3 (G-Rg3) on inflammation-mediated hepatic autophagy to curb hepatic fibrosis caused by thioacetamide (TAA)-induced subacute and chronic hepatic injury. TAA is mainly metabolized in the liver to cause liver dysfunction. After intraperitoneal injection of TAA for 4 or 10 weeks (TAA-chronic mouse models), severe inflammatory infiltration and fibrosis occurred in the liver. Treatment with G-Rg3 alleviated hepatic pathological changes and reversed hepatic fibrosis in the TAA-chronic models with decreased deposition of collagen fibers, reduced expression of HSCs activation marker (α-SMA), and reduced secretion of profibrogenic factors (TGF-β1). G-Rg3 decreased expressions of autophagy-related proteins in mice of TAA-chronic models. Notably, G-Rg3 inhibited the survival of activated rat hepatic stellate cells (HSC-T6), but had no cytotoxicity on human hepatocytes (L02 cell lines). G-Rg3 dose-dependently inhibited autophagy in vitro with less expression of p62 and fewer LC3a transformation into LC3b in inflammatory inducer lipopolysaccharide (LPS)-induced rat HSC-T6 cells. Furthermore, G-Rg3 enhanced the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) in vivo and in vitro. Besides, mTOR inhibitor Rapamycin and PI3K inhibitors LY294002 were employed in LPS-treated HSC-T6 cell cultures to verify that Rg3 partially reversed the increase in autophagy in hepatic fibrosis in vitro. Taken together, G-Rg3 exerted anti-fibrosis effect through the inhibition of autophagy in TAA-treated mice and LPS-stimulated HSC-T6 cells. These data collectively unravel that G-Rg3 may serve a promising anti-hepatic fibrosis drug.

NRF2 activates growth factor genes and downstream AKT signaling to induce mouse and human hepatomegaly

BACKGROUND & AIMS

Hepatomegaly can be triggered by insulin and insulin-unrelated etiologies. Insulin acts via AKT, but how other challenges cause hepatomegaly is unknown.

METHODS

Since many hepatomegaly-inducing toxicants and stressors activate NRF2, we examined the effect of NRF2 activation on liver size and metabolism using a conditional allele encoding a constitutively active NRF2 variant to generate Nrf2Act-hep mice in which NRF2 is selectively activated in hepatocytes. We also used adenoviruses encoding variants of the autophagy adaptor p62/SQSTM1, which activates liver NRF2, as well as liver-specific ATG7-deficient mice (Atg7Δhep) and liver specimens from patients with hepatic sinusoidal obstruction syndrome (HSOS) and autoimmune hepatitis (AIH). RNA sequencing and cell signaling analyses were used to determine cellular consequences of NRF2 activation and diverse histological analyses were used to study effects of the different manipulations on liver and systemic pathophysiology.

RESULTS

Hepatocyte-specific NRF2 activation, due to p62 accumulation or inhibition of KEAP1 binding, led to hepatomegaly associated with enhanced glycogenosis, steatosis and G2/M cell cycle arrest, fostering hyperplasia without cell division. Surprisingly, all manipulations that led to NRF2 activation also activated AKT, whose inhibition blocked NRF2-induced hepatomegaly and glycogenosis, but not NRF2-dependent antioxidant gene induction. AKT activation was linked to NRF2-mediated transcriptional induction of PDGF and EGF receptor ligands that signaled through their cognate receptors in an autocrine manner. Insulin and insulin-like growth factors were not involved. The NRF2-AKT signaling axis was also activated in human HSOS- and AIH-related hepatomegaly.

CONCLUSIONS

NRF2, a transcription factor readily activated by xenobiotics, oxidative stress and autophagy disruptors, may be a common mediator of hepatomegaly; its effects on hepatic metabolism can be reversed by AKT/tyrosine kinase inhibitors.

LAY SUMMARY

Hepatomegaly can be triggered by numerous etiological factors, including infections, liver cancer, metabolic disturbances, toxicant exposure, as well as alcohol abuse or drug-induced hepatitis. This study identified the oxidative stress response transcription factor NRF2 as a common mediator of hepatomegaly. NRF2 activation results in elevated expression of several growth factors. These growth factors are made by hepatocytes and activate their receptors in an autocrine fashion to stimulate the accumulation of glycogen and lipids that lead to hepatocyte and liver enlargement. The protein kinase AKT plays a key role in this process and its inhibition leads to reversal of hepatomegaly.

Inhibitors of the protein-protein interaction between phosphorylated p62 and Keap1 attenuate chemoresistance in a human hepatocellular carcinoma cell line

Resistance to anticancer agents has been an obstacle to developing therapeutics and reducing medical costs. Whereas sorafenib is used for the treatment of human hepatocellular carcinoma (HCC), resistance limits its efficacy. p62, a multifunctional protein, is overexpressed in several HCC cell lines, such as Huh-1 cells. Phosphorylated p62 (p-p62) inhibits the protein-protein interaction (PPI) between Keap1 and Nrf2, resulting in the Nrf2 overactivation that causes drug resistance. We have found a unique Nrf2 inactivator, named K67, that inhibited the PPI between Keap1 and p-p62 and attenuated sorafenib resistance in Huh-1 cells. Herein, we designed and synthesised novel K67 derivatives by modification of the substituent at the 4-position of the two benzenesulfonyl groups of K67. Although these new derivatives inhibited the Keap1-p-p62 PPI to a level comparable to or weaker than that of K67, the isopropoxy derivative enhanced the sensitivity of Huh-1 cells to sorafenib to a greater extent than K67 without any influence on the viability of Huh-7 cells, which is a non-resistant HCC cell line. The isopropoxy derivative also increased the sensitivity of Huh-1 cells to regorafenib, which suggests that this derivative has the potential to be used as an agent to overcome chemoresistance based on Nrf2 inactivation.

Inflammation in Primary and Metastatic Liver Tumorigenesis-Under the Influence of Alcohol and High-Fat Diets

The liver plays an outsized role in oncology. Liver tumors are one of the most frequently found tumors in cancer patients and these arise from either primary or metastatic disease. Hepatocellular carcinoma (HCC), the most prevalent form of primary liver cancer and the 6th most common cancer type overall, is expected to become the 3rd leading cause of cancer mortality in the US by the year 2030. The liver is also the most common site of distant metastasis from solid tumors. For instance, colorectal cancer (CRC) metastasizes to the liver in two-thirds of cases, and CRC liver metastasis is the leading cause of mortality in these patients. The interplay between inflammation and cancer is unmistakably evident in the liver. In nearly every case, HCC is diagnosed in chronic liver disease (CLD) and cirrhosis background. The consumption of a Western-style high-fat diet is a major risk factor for the development of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), both of which are becoming more prevalent in parallel with the obesity epidemic. Excessive alcohol intake also contributes significantly to the CLD burden in the form of alcoholic liver disease (ALD). Inflammation is a key component in the development of all CLDs. Additionally, during the development of liver metastasis, pro-inflammatory signaling is crucial in eliminating invading cancer cells but ironically also helps foster a pro-metastatic environment that supports metastatic seeding and colonization. Here we review how Westernized high-fat diets and excessive alcohol intake can influence inflammation within the liver microenvironment, stimulating both primary and metastatic liver tumorigenesis.

Recent advances in neurogenic and neuroprotective effects of curcumin through the induction of neural stem cells

Curcumin is extensively used in the prevention and treatment of various diseases. Recently, growing attention has been paid to the use of curcumin as a neurogenic and neuroprotective agent. This review study is aimed to collect and categorize the recent findings regarding the effects of curcumin on various neurological diseases through the induction of neural stem cell proliferation and differentiation. In addition, we have discussed the molecular mechanisms modulated by curcumin that contribute to this efficacy and have summarized the recent advancements in the novel delivery strategies used to improve the induction of neural stem cells by curcumin.

SQSTM1/p62 activates NFE2L2/NRF2 via ULK1-mediated autophagic KEAP1 degradation and protects mouse liver from lipotoxicity

Lipotoxicity, induced by saturated fatty acid (SFA)-mediated cell death, plays an important role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The KEAP1 (kelch like ECH associated protein 1)-NFE2L2/NRF2 (nuclear factor, erythroid 2 like 2) pathway is a pivotal defense mechanism against lipotoxicity. We previously reported that SQSTM1/p62 has a cytoprotective role against lipotoxicity through activation of the noncanonical KEAP1- NFE2L2 pathway in hepatocytes. However, the underlying mechanisms and physiological relevance of this pathway have not been clearly defined. Here, we demonstrate that NFE2L2-mediated induction of SQSTM1 activates the noncanonical KEAP1-NFE2L2 pathway under lipotoxic conditions. Furthermore, we identified that SQSTM1 induces ULK1 (unc-51 like autophagy activating kinase 1) phosphorylation by facilitating the interaction between AMPK (AMP-activated protein kinase) and ULK1, leading to macroautophagy/autophagy induction, followed by KEAP1 degradation and NFE2L2 activation. Accordingly, the activity of this SQSTM1-mediated noncanonical KEAP1-NFE2L2 pathway conferred hepatoprotection against lipotoxicity in the livers of conventional sqstm1- and liver-specific sqstm1-knockout mice. Moreover, this pathway activity was evident in the livers of patients with nonalcoholic fatty liver. This axis could thus represent a novel target for NAFLD treatment. Abbreviations: ACACA: acetyl-CoA carboxylase alpha; ACTB: actin beta; BafA1: bafilomycin A₁; CM-H2DCFDA:5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate; CQ: chloroquine; CUL3: cullin 3; DMSO: dimethyl sulfoxide; FASN: fatty acid synthase; GSTA1: glutathione S-transferase A1; HA: hemagglutinin; Hepa1c1c7: mouse hepatoma cells; HMOX1/HO-1: heme oxygenase 1; KEAP1: kelch like ECH associated protein 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3; MEF: mouse embryonic fibroblast; MTORC1: mechanistic target of rapamycin kinase complex 1; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NAC: N-acetyl-L-cysteine; NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis; NFE2L2/NRF2: nuclear factor, erythroid 2 like 2; NQO1: NAD(P)H quinone dehydrogenase 1; PA: palmitic acid; PARP: poly (ADP-ribose) polymerase 1; PRKAA1/2: protein kinase AMP-activated catalytic subunits alpha1/2; RBX1: ring-box 1; ROS: reactive oxygen species; SESN2: sestrin 2; SFA: saturated fatty acid; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; SREBF1: sterol regulatory element binding transcription factor 1; TBK1: TANK binding kinase 1; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; ULK1: unc-51 like autophagy activating kinase.

Hepatitis C Virus Downregulates Core Subunits of Oxidative Phosphorylation, Reminiscent of the Warburg Effect in Cancer Cells

Hepatitis C Virus (HCV) mainly infects liver hepatocytes and replicates its single-stranded plus strand RNA genome exclusively in the cytoplasm. Viral proteins and RNA interfere with the host cell immune response, allowing the virus to continue replication. Therefore, in about 70% of cases, the viral infection cannot be cleared by the immune system, but a chronic infection is established, often resulting in liver fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Induction of cancer in the host cells can be regarded to provide further advantages for ongoing virus replication. One adaptation in cancer cells is the enhancement of cellular carbohydrate flux in glycolysis with a reduction of the activity of the citric acid cycle and aerobic oxidative phosphorylation. To this end, HCV downregulates the expression of mitochondrial oxidative phosphorylation complex core subunits quite early after infection. This so-called aerobic glycolysis is known as the “Warburg Effect” and serves to provide more anabolic metabolites upstream of the citric acid cycle, such as amino acids, pentoses and NADPH for cancer cell growth. In addition, HCV deregulates signaling pathways like those of TNF-β and MAPK by direct and indirect mechanisms, which can lead to fibrosis and HCC.