Activation of autophagy through calcium-dependent AMPK/mTOR and PKCθ pathway causes activation of rat hepatic stellate cells under hypoxic stress

The dynamic equilibrium between the protective and toxic effects of matrine in the development of liver injury: a systematic review and meta-analysis

Background: Matrine, an alkaloid derived from the dried roots of Sophora flavescens Aiton, has been utilized for the treatment of liver diseases, but its potential hepatotoxicity raises concerns. However, the precise condition and mechanism of action of matrine on the liver remain inconclusive. Therefore, the objective of this systematic review and meta-analysis is to comprehensively evaluate both the hepatoprotective and hepatotoxic effects of matrine and provide therapeutic guidance based on the findings. Methods: The meta-analysis systematically searched relevant preclinical literature up to May 2023 from eight databases, including PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Infrastructure, WanFang Med Online, China Science and Technology Journal Database, and China Biomedical Literature Service System. The CAMARADES system assessed the quality and bias of the evidence. Statistical analysis was conducted using STATA, which included the use of 3D maps and radar charts to display the effects of matrine dosage and frequency on hepatoprotection and hepatotoxicity. Results: After a thorough screening, 24 studies involving 657 rodents were selected for inclusion. The results demonstrate that matrine has bidirectional effects on ALT and AST levels, and it also regulates SOD, MDA, serum TG, serum TC, IL-6, TNF-α, and CAT levels. Based on our comprehensive three-dimensional analysis, the optimal bidirectional effective dosage of matrine ranges from 10 to 69.1 mg/kg. However, at a dose of 20-30 mg/kg/d for 0.02-0.86 weeks, it demonstrated high liver protection and low toxicity. The molecular docking analysis revealed the interaction between MT and SERCA as well as SREBP-SCAP complexes. Matrine could alter Ca2+ homeostasis in liver injury via multiple pathways, including the SREBP1c/SCAP, Notch/RBP-J/HES1, IκK/NF-κB, and Cul3/Rbx1/Keap1/Nrf2. Conclusion: Matrine has bidirectional effects on the liver at doses ranging from 10 to 69.1 mg/kg by influencing Ca2+ homeostasis in the cytoplasm, endoplasmic reticulum, Golgi apparatus, and mitochondria. Systematic review registration: https://inplasy.com/, identifier INPLASY202340114.

Lifestyle effects on aging and CVD: A spotlight on the nutrient-sensing network

Aging is widespread worldwide and a significant risk factor for cardiovascular disease (CVD). Mechanisms underlying aging have attracted considerable attention in recent years. Remarkably, aging and CVD overlap in numerous ways, with deregulated nutrient sensing as a common mechanism and lifestyle as a communal modifier. Interestingly, lifestyle triggers or suppresses multiple nutrient-related signaling pathways. In this review, we first present the composition of the nutrient-sensing network (NSN) and its metabolic impact on aging and CVD. Secondly, we review how risk factors closely associated with CVD, including adverse life states such as sedentary behavior, sleep disorders, high-fat diet, and psychosocial stress, contribute to aging and CVD, with a focus on the bridging role of the NSN. Finally, we focus on the positive effects of beneficial dietary interventions, specifically dietary restriction and the Mediterranean diet, on the regulation of nutrient metabolism and the delayed effects of aging and CVD that depend on the balance of the NSN. In summary, we expound on the interaction between lifestyle, NSN, aging, and CVD.

Fluorofenidone alleviates liver fibrosis by inhibiting hepatic stellate cell autophagy via the TGF-β1/Smad pathway: implications for liver cancer

Objectives

Liver fibrosis is a key stage in the progression of various chronic liver diseases to cirrhosis and liver cancer, but at present, there is no effective treatment. This study investigated the therapeutic effect of the new antifibrotic drug fluorofenidone (AKF-PD) on liver fibrosis and its related mechanism, providing implications for liver cancer.

Materials and Methods

The effects of AKF-PD on hepatic stellate cell (HSC) autophagy and extracellular matrix (ECM) expression were assessed in a carbon tetrachloride (CCl4)-induced rat liver fibrosis model. In vitro, HSC-T6 cells were transfected with Smad2 and Smad3 overexpression plasmids and treated with AKF-PD. The viability and number of autophagosomes in HSC-T6 cells were examined. The protein expression levels of Beclin-1, LC3 and P62 were examined by Western blotting. The Cancer Genome Atlas (TCGA) database was used for comprehensively analyzing the prognostic values of SMAD2 and SMAD3 in liver cancer. The correlation between SMAD2, SMAD3, and autophagy-related scores in liver cancer was explored. The drug prediction of autophagy-related scores in liver cancer was explored.

Results

AKF-PD attenuated liver injury and ECM deposition in the CCl4-induced liver fibrosis model. In vitro, the viability and number of autophagosomes in HSCs were reduced significantly by AKF-PD treatment. Meanwhile, the protein expression of FN, α-SMA, collagen III, Beclin-1 and LC3 was increased, and P62 was reduced by the overexpression of Smad2 and Smad3; however, AKF-PD reversed these effects. SMAD2 and SMAD3 were hazardous factors in liver cancer. SMAD2 and SMAD3 correlated with autophagy-related scores in liver cancer. Autophagy-related scores could predict drug response in liver cancer.

Conclusions

AKF-PD alleviates liver fibrosis by inhibiting HSC autophagy via the transforming growth factor (TGF)-β1/Smadpathway. Our study provided some implications about how liver fibrosis was connected with liver cancer by SMAD2/SMAD3 and autophagy.

Ferroptosis, autophagy, tumor and immunity

Ferroptosis was first proposed in 2012, a new form of cell death. Autophagy plays a crucial role in cell clearance and maintaining homeostasis. Autophagy is involved in the initial step of ferroptosis under the action of histone elements such as NCOA4, RAB7A, and BECN1. Ferroptosis and autophagy are involved in tumor progression, treatment, and drug resistance in the tumor microenvironment. In this review, we described the mechanisms of ferroptosis, autophagy, and tumor and immunotherapy, respectively, and emphasized the relationship between autophagy-related ferroptosis and tumor.

Diagnostic and prognostic value of autophagy-related key genes in sepsis and potential correlation with immune cell signatures

Background: Autophagy is involved in the pathophysiological process of sepsis. This study was designed to identify autophagy-related key genes in sepsis, analyze their correlation with immune cell signatures, and search for new diagnostic and prognostic biomarkers. Methods: Whole blood RNA datasets GSE65682, GSE134347, and GSE134358 were downloaded and processed. Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were used to identify autophagy-related key genes in sepsis. Then, key genes were analyzed by functional enrichment, protein-protein interaction (PPI), transcription factor (TF)-gene and competing endogenous RNA (ceRNA) network analysis. Subsequently, key genes with diagnostic efficiency and prognostic value were identified by receiver operating characteristic (ROC) curves and survival analysis respectively. The signatures of immune cells were estimated using CIBERSORT algorithm. The correlation between significantly different immune cell signatures and key genes was assessed by correlation analysis. Finally, key genes with both diagnostic and prognostic value were verified by RT-qPCR. Results: 14 autophagy-related key genes were identified and their TF-gene and ceRNA regulatory networks were constructed. Among the key genes, 11 genes (ATIC, BCL2, EEF2, EIF2AK3, HSPA8, IKBKB, NLRC4, PARP1, PRKCQ, SH3GLB1, and WIPI1) had diagnostic efficiency (AUC > 0.90) and 5 genes (CAPN2, IKBKB, PRKCQ, SH3GLB1 and WIPI1) were associated with survival prognosis (p-value < 0.05). IKBKB, PRKCQ, SH3GLB1 and WIPI1 had both diagnostic and prognostic value, and their expression were verified by RT-qPCR. Analysis of immune cell signatures showed that the abundance of neutrophil, monocyte, M0 macrophage, gamma delta T cell, activated mast cell and M1 macrophage subtypes increased in the sepsis group, while the abundance of resting NK cell, resting memory CD4+ T cell, CD8+ T cell, naive B cell and resting dendritic cell subtypes decreased. Most of the key genes correlated with the predicted frequencies of CD8+ T cells, resting memory CD4+ T cells, M1 macrophages and naive B cells. Conclusion: We identified autophagy-related key genes with diagnostic and prognostic value in sepsis and discovered associations between key genes and immune cell signatures. This work may provide new directions for the discovery of promising biomarkers for sepsis.

Peroxisome proliferator-activated receptor γ activation ameliorates liver fibrosis-differential action of transcription factor EB and autophagy on hepatocytes and stellate cells

BACKGROUND

Peroxisome proliferator-activated receptor γ (PPARγ) activation suppresses HSC activation and liver fibrosis. Moreover, autophagy is implicated in hepatic lipid metabolism. Here, we determined whether PPARγ activation ameliorates HSC activation by downregulating transcription factor EB (TFEB)-mediated autophagy.

METHODS AND RESULTS

Atg7 or Tfeb knockdown in human HSC line LX-2 cells downregulated the expression of fibrogenic markers including α smooth muscle actin, glial fibrillary acidic protein, and collagen type 1. Conversely, Atg7 or Tfeb overexpression upregulated fibrogenic marker expression. Rosiglitazone (RGZ)-mediated PPARγ activation and/or overexpression in LX-2 cells and primary HSCs decreased autophagy, as indicated by LC3B conversion, total and nuclear-TFEB contents, mRFP-LC3 and BODIPY 493/503 colocalization, and GFP-LC3 and LysoTracker colocalization. RGZ treatment decreased liver fat content, liver enzyme levels, and fibrogenic marker expression in high-fat high-cholesterol diet-fed mice. Electron microscopy showed that RGZ treatment restored the high-fat high-cholesterol diet-mediated lipid droplet decrease and autophagic vesicle induction in primary HSCs and liver tissues. However, TFEB overexpression in LX-2 cells offset the aforementioned effects of RGZ on autophagic flux, lipid droplets, and fibrogenic marker expression.

CONCLUSIONS

Activation of PPARγ with RGZ ameliorated liver fibrosis and downregulation of TFEB and autophagy in HSCs may be important for the antifibrotic effects of PPARγ activation.

Melatonin Alleviates Liver Fibrosis by Inhibiting Autophagy

OBJECTIVE

Melatonin has been reported to suppress inflammation and alleviate liver fibrosis, but its effect on autophagy in liver fibrosis has not been studied. This study investigated the effect of melatonin on autophagy in an animal model of liver fibrosis and the hepatic stellate cell (HSC)-T6 cell line.

METHODS

The model was established in rats through carbon tetrachloride treatment, and melatonin was administered at three doses (2.5, 5.0, and 10.0 mg/kg). Haematoxylin and eosin staining and Van Gieson's staining were performed to examine the pathological changes of liver. The expression of alpha-smooth muscle actin (α-SMA) and Beclin1 in liver tissues was detected by immunohistochemical staining. The protein levels of α-SMA, Beclin1 and LC3 in the animal model were detected by Western blot analysis, and gene levels of Beclin1 and LC3 were detected by quantitative real-time PCR (qRT-PCR) in the animal model. HSC-T6 cells were activated by platelet-derived growth factor-BB (PDGF-BB). The expression of α-SMA, Beclin1 and collagen I was detected by Western blot analysis, and the gene expression of Beclin1 and LC3 was detected by qRT-PCR.

RESULTS

Melatonin reduced the expression of α-SMA, Beclin1 and LC3 in liver tissues. In addition, melatonin inhibited the activation of HSC-T6 cells and the expression of α-SMA, Beclin1 and LC3 in these cells. These results revealed that melatonin could inhibit autophagy and HSC activation.

CONCLUSION

Melatonin might ameliorate liver fibrosis by regulating autophagy, suggesting that melatonin is a potential therapeutic agent for liver fibrosis.

Profiles of messenger RNAs and MicroRNAs in hypoxia-induced hepatic stellate cells

Background

MicroRNA (miRNA) plays an important role in hepatic stellate cell (HSCs) activation and liver fibrosis. The purpose of this study is to explore the effect of hypoxia on the differential expression of mRNAs and miRNAs in rat HSCs.

Methods

HSC-T6 cells were treated with cobalt chloride (CoCl₂), and the activity of HSC-T6 cells was measured by the CCK-8 assay. The mRNA expression levels of hypoxia inducible factor-1α (HIF-1α), collagen type I, transforming growth factor-β1 (TGF-β1), and Smad7 were measured by RT-qPCR. The protein expression levels of HIF-1α, Bax, Bcl-2, and caspase-3 were assayed by western blot. We used basal medium and 400 µmol/L CoCl₂ medium to treat HSC-T6 cells for 48 h. Cells were harvested after 48 h to extract RNA. Transcriptome sequencing was performed to investigate differentially expressed miRNAs and mRNAs (fold change >2; P<0.05). Bioinformatics analysis was performed to predict the functions of differentially expressed miRNAs and mRNAs. Further, we used RT-qPCR to detect the expression of mRNAs and miRNAs to confirm the accuracy of sequencing.

Results

With the increase of CoCl₂ concentration, the activity of HSC-T6 cells decreased (P<0.05). The mRNA expression levels of HIF-1α, collagen I, TGF-β1, and Smad7, and the protein expressions levels of HIF-1α, Bax, caspase-3, and the Bcl-2/Bax ratio were increased compared with the control group (P<0.05), while the expression of Bcl-2 decreased. A total of 54 miRNAs (20 upregulated and 34 downregulated) and 1,423 mRNAs (685 upregulated and 738 downregulated) were differentially expressed in the 400 µmol/L CoCl₂ medium group compared to the control basal medium group. Further bioinformatics analysis demonstrated that the differentially expressed mRNAs and miRNAs were mainly enriched in the synthesis of extracellular matrix. In addition, we used RT-qPCR to detect the expression of mRNAs and miRNAs to confirm the accuracy of sequencing.

Conclusions

Our results presented the profiles of mRNAs and miRNAs in hypoxia-induced HSC-T6 cells in rats, the signaling pathways, and co-expression networks. These findings may suggest novel insights for the early diagnosis and treatment of HSC activation and liver fibrosis.

Understanding the implication of autophagy in the activation of hepatic stellate cells in liver fibrosis: are we there yet?

Liver fibrosis (LF) occurs as a result of persistent liver injury and can be defined as a pathologic, chronic, wound-healing process in which functional parenchyma is progressively replaced by fibrotic tissue. As a phenomenon involved in the majority of chronic liver diseases, and therefore prevalent, it exerts a significant impact on public health. This impact becomes even more patent given the lack of a specific pharmacological therapy, with LF only being ameliorated or prevented through the use of agents that alleviate the underlying causes. Hepatic stellate cells (HSCs) are fundamental mediators of LF, which, activated in response to pro-fibrotic stimuli, transdifferentiate from a quiescent phenotype into myofibroblasts that deposit large amounts of fibrotic tissue and mediate pro-inflammatory effects. In recent years, much effort has been devoted to understanding the mechanisms through which HSCs are activated or inactivated. Using cell culture and/or different animal models, numerous studies have shown that autophagy is enhanced during the fibrogenic process and have provided specific evidence to pinpoint the fundamental role of autophagy in HSC activation. This effect involves - though may not be limited to - the autophagic degradation of lipid droplets. Several hepatoprotective agents have been shown to reverse the autophagic alteration present in LF, but clinical confirmation of these effects is pending. On the other hand, there is evidence that implicates autophagy in several anti-fibrotic mechanisms in HSCs that stimulate HSC cell cycle arrest and cell death or prevent the generation of pro-fibrotic mediators, including excess collagen accumulation. The objective of this review is to offer a comprehensive analysis of published evidence of the role of autophagy in HSC activation and to provide hints for possible therapeutic targets for the treatment and/or prevention of LF related to autophagy. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Interaction of non‑parenchymal hepatocytes in the process of hepatic fibrosis (Review)

Hepatic fibrosis (HF) is the process of fibrous scar formation caused by chronic liver injury of different etiologies. Previous studies have hypothesized that the activation of hepatic stellate cells (HSCs) is the central process in HF. The interaction between HSCs and surrounding cells is also crucial. Additionally, hepatic sinusoids capillarization, inflammation, angiogenesis and fibrosis develop during HF. The process involves multiple cell types that are highly connected and work in unison to maintain the homeostasis of the hepatic microenvironment, which serves a key role in the initiation and progression of HF. The current review provides novel insight into the intercellular interaction among liver sinusoidal endothelial cells, HSCs and Kupffer cells, as well as the hepatic microenvironment in the development of HF.

The roles and mechanisms of hypoxia in liver fibrosis

Liver fibrosis occurs in response to any etiology of chronic liver injury. Lack of appropriate clinical intervention will lead to liver cirrhosis or hepatocellular carcinoma (HCC), seriously affecting the quality of life of patients, but the current clinical treatments of liver fibrosis have not been developed yet. Recent studies have shown that hypoxia is a key factor promoting the progression of liver fibrosis. Hypoxia can cause liver fibrosis. Liver fibrosis can, in turn, profoundly further deepen the degree of hypoxia. Therefore, exploring the role of hypoxia in liver fibrosis will help to further understand the process of liver fibrosis, and provide the theoretical basis for its diagnosis and treatment, which is of great significance to avoid further deterioration of liver diseases and protect the life and health of patients. This review highlights the recent advances in cellular and molecular mechanisms of hypoxia in developments of liver fibrosis.

AMPK-mTOR-ULK1-mediated autophagy protects carbon tetrachloride-induced acute hepatic failure by inhibiting p21 in rats

Autophagy is a lysosomal-dependent degradation pathway in eukaryotic cells. Recent studies have reported that autophagy can facilitate the activation of hepatic stellate cells (HSCs) and fibrogenesis of the liver during long-term carbon tetrachloride (CCl₄) exposure. However, little is known about the role of autophagy in CCl₄-induced acute hepatic failure (AHF). This study aimed to identify whether modulation of autophagy can affect CCl₄-induced AHF and evaluate the upstream signaling pathways mediated by CCl₄-induced autophagy in rats. The accumulation of specific punctate distribution of endogenous LC3-II, increased expression of LC3-II, Atg5, and Atg7 genes/proteins, and decreased expression of p62 gene were observed after acute liver injury was induced by CCl₄ in rats, indicating that CCl₄ resulted in a high level of autophagy. Moreover, loss of autophagic function by using chloroquine (CQ, an autophagic inhibitor) aggravated liver function, leading to increased expression of p21 (a cyclin-dependent kinase inhibitor) in CCl₄-treated rats. Furthermore, the AMPK-mTORC1-ULK1 axis was found to serve a function in CCl₄-induced autophagy. These results reveal that AMPK-mTORC1-ULK1 signaling-induced autophagy has a protective role in CCl₄-induced hepatotoxicity by inhibiting the p21 pathway. This study suggests a useful strategy aimed at ameliorating CCl₄-induced acute hepatotoxicity by autophagy.

The neuroprotective effects of activated α7 nicotinic acetylcholine receptor against mutant copper-zinc superoxide dismutase 1-mediated toxicity

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the selective and progressive loss of motor neurons. Although many drugs have entered clinical trials, few have shown effectiveness in the treatment of ALS. Other studies have shown that the stimulation of α7 nicotinic acetylcholine receptor (nAChR) can have neuroprotective effects in some models of neurodegenerative disease, as well as prevent glutamate-induced motor neuronal death. However, the effect of α7 nAChR agonists on ALS-associated mutant copper-zinc superoxide dismutase 1 (SOD1) aggregates in motor neurons remains unclear. In the present study, we examined whether α7 nAChR activation had a neuroprotective effect against SOD1^G85R-induced toxicity in a cellular model for ALS. We found that α7 nAChR activation by PNU282987, a selective agonist of α7 nAChR, exhibited significant neuroprotective effects against SOD1^G85R-induced toxicity via the reduction of intracellular protein aggregates. This reduction also correlated with the activation of autophagy through the AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR) signaling pathway. Furthermore, the activation of α7 nAChRs was found to increase the biogenesis of lysosomes by inducing translocation of the transcription factor EB (TFEB) into the nucleus. These results support the therapeutic potential of α7 nAChR activation in diseases that are characterized by SOD1^G85R aggregates, such as ALS.

The Remedial Potential of Lycopene in Pancreatitis through Regulation of Autophagy

Autophagy is an evolutionarily conserved process that degrades damaged organelles and recycles macromolecules to support cell survival. However, in certain disease states, dysregulated autophagy can play an important role in cell death. In pancreatitis, the accumulation of autophagic vacuoles and damaged mitochondria and premature activation of trypsinogen are shown in pancreatic acinar cells (PACs), which are the hallmarks of impaired autophagy. Oxidative stress mediates inflammatory signaling and cytokine expression in PACs, and it also causes mitochondrial dysfunction and dysregulated autophagy. Thus, oxidative stress may be a mediator for autophagic impairment in pancreatitis. Lycopene is a natural pigment that contributes to the red color of fruits and vegetables. Due to its antioxidant activity, it inhibited oxidative stress-induced expression of cytokines in experimental models of acute pancreatitis. Lycopene reduces cell death through the activation of 5′-AMP-activated protein kinase-dependent autophagy in certain cells. Therefore, lycopene may ameliorate pancreatitis by preventing oxidative stress-induced impairment of autophagy and/or by directly activating autophagy in PACs.

Diacylglycerol-evoked activation of PKC and PKD isoforms in regulation of glucose and lipid metabolism: a review

Protein kinase C (PKC) and Protein kinase D (PKD) isoforms can sense diacylglycerol (DAG) generated in the different cellular compartments in various physiological processes. DAG accumulates in multiple organs of the obese subjects, which leads to the disruption of metabolic homeostasis and the development of diabetes as well as associated diseases. Multiple studies proved that aberrant activation of PKCs and PKDs contributes to the development of metabolic diseases. DAG-sensing PKC and PKD isoforms play a crucial role in the regulation of metabolic homeostasis and therefore might serve as targets for the treatment of metabolic disorders such as obesity and diabetes.

Enzyme-based autophagy in anti-neoplastic management: From molecular mechanisms to clinical therapeutics

Autophagy is an evolutionarily conserved self-cannibalization process commonly found in all eukaryotic cells. Through autophagy, long-lived or damaged organelles, superfluous proteins, and pathogens are sequestered and encapsulated into the double-membrane autophagosomes prior to fusion with lysosomes for ultimate degradation and recycling. Given that autophagy is deemed both protective and detrimental in malignancies, the clinical therapeutic utilization of autophagy modulators in cancer has attracted immense attentions over the past decades. Dependence of tumor cells on autophagy during amino acid insufficiency or deprivation has prompted us to explore the underlying autophagy regulatory mechanisms to inject amino acid degrading enzymes and enzyme-based strategies into therapeutic maneuvers of autophagy in cancer.

Current understanding of metal ions in the pathogenesis of Alzheimer's disease

Background

The homeostasis of metal ions, such as iron, copper, zinc and calcium, in the brain is crucial for maintaining normal physiological functions. Studies have shown that imbalance of these metal ions in the brain is closely related to the onset and progression of Alzheimer's disease (AD), the most common neurodegenerative disorder in the elderly.

Main body

Erroneous deposition/distribution of the metal ions in different brain regions induces oxidative stress. The metal ions imbalance and oxidative stress together or independently promote amyloid-β (Aβ) overproduction by activating β- or γ-secretases and inhibiting α-secretase, it also causes tau hyperphosphorylation by activating protein kinases, such as glycogen synthase kinase-3β (GSK-3β), cyclin-dependent protein kinase-5 (CDK5), mitogen-activated protein kinases (MAPKs), etc., and inhibiting protein phosphatase 2A (PP2A). The metal ions imbalances can also directly or indirectly disrupt organelles, causing endoplasmic reticulum (ER) stress; mitochondrial and autophagic dysfunctions, which can cause or aggravate Aβ and tau aggregation/accumulation, and impair synaptic functions. Even worse, the metal ions imbalance-induced alterations can reversely exacerbate metal ions misdistribution and deposition. The vicious cycles between metal ions imbalances and Aβ/tau abnormalities will eventually lead to a chronic neurodegeneration and cognitive deficits, such as seen in AD patients.

Conclusion

The metal ions imbalance induces Aβ and tau pathologies by directly or indirectly affecting multiple cellular/subcellular pathways, and the disrupted homeostasis can reversely aggravate the abnormalities of metal ions transportation/deposition. Therefore, adjusting metal balance by supplementing or chelating the metal ions may be potential in ameliorating AD pathologies, which provides new research directions for AD treatment.

Protein Kinase C Isozymes and Autophagy during Neurodegenerative Disease Progression

Protein kinase C (PKC) isozymes are members of the Serine/Threonine kinase family regulating cellular events following activation of membrane bound phospholipids. The breakdown of the downstream signaling pathways of PKC relates to several disease pathogeneses particularly neurodegeneration. PKC isozymes play a critical role in cell death and survival mechanisms, as well as autophagy. Numerous studies have reported that neurodegenerative disease formation is caused by failure of the autophagy mechanism. This review outlines PKC signaling in autophagy and neurodegenerative disease development and introduces some polyphenols as effectors of PKC isozymes for disease therapy.

Autophagy Triggered by Oxidative Stress Appears to Be Mediated by the AKT/mTOR Signaling Pathway in the Liver of Sleep-Deprived Rats

Sleep deprivation adversely affects the digestive system. Multiple studies have suggested sleep deprivation and oxidative stress are closely related. Autophagy can be triggered by oxidative stress as a self-defense strategy to promote survival. In this study, we investigated the effects of sleep deprivation on liver functions, oxidative stress, and concomitant hepatocyte autophagy, as well as the associated pathways. Enzymatic and nonenzymatic biochemical markers in the serum were used to assess hepatic function and damage. To evaluate the occurrence of autophagy, expression of autophagy-related proteins was tested and autophagosomes were labeled. Additionally, methane dicarboxylic aldehyde (MDA), antioxidant enzymes, and the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway were analyzed using chemical methods and a Western blot. Serum alanine transaminase, aspartate aminotransferase, and alkaline phosphatase increased in sleep-deprived rats. Total protein and albumin abundance was also abnormal. Sleep deprivation induced histopathological changes in the liver. The superoxide dismutase level decreased significantly in the liver of sleep-deprived rats. In contrast, the MDA content increased in the sleep deprivation group. Moreover, the microtubule-associated protein 1 light chain 3 beta (LC3B) II/I ratio and Beclin I content increased considerably in the sleep-deprived rats, while p62 levels decreased. Sleep deprivation apparently inhibited the AKT/mTOR signaling pathway. We conclude that sleep deprivation can induce oxidative stress and ultimately cause liver injury. Autophagy triggered by oxidative stress appears to be mediated by the AKT/mTOR pathway and plays a role in relieving oxidative stress caused by sleep deprivation.

Long noncoding RNA XIST enhances ethanol-induced hepatic stellate cells autophagy and activation via miR-29b/HMGB1 axis

Activation of hepatic stellate cells (HSCs) is a prominent driver of liver fibrogenesis, including alcoholic liver fibrosis (ALF). Furthermore, autophagy contributes to HSCs activation. This study aims to investigate the role and the mechanisms of long noncoding RNA XIST in regulating HSCs autophagy and activation. Human HSC cells (LX-2) were treated with 100 mmol/L ethanol to mimic HSCs activation. The HSCs activation was evaluated by determining cell viability and protein levels of fibrosis markers α-smooth muscle actin (α-SMA) and collagen type 1 α1 (CoL1A1). The autophagy was evaluated by measuring autophagy markers Beclin-1 and LC3-II. The interaction among XIST, miR-29b, and high-mobility group box-1 (HMGB1) were analyzed using luciferase reporter assay, qRT-PCR, and western blot. Lentiviruses targeting sh-XIST (LV-sh-XIST) were injected into ALF model mice via tail vein to elucidate the in vivo role of XIST in ALF injury. XIST was upregulated in ethanol-activated LX-2 cells. Furthermore, XIST served as a competitive endogenous RNA of miR-29b to facilitate HMGB1 expression, and thus enhanced ethanol-induced HSCs autophagy and activation. Further in vivo assay showed that downregulation of XIST by LV-sh-XIST alleviated ALF injury in ALF model mice. Collectively, XIST enhances ethanol-induced HSCs autophagy and activation via miR-29b/HMGB1 axis.

Activation of CaMKKβ-AMPK-mTOR pathway is required for autophagy induction by β,β-dimethylacrylshikonin against lung adenocarcinoma cells

β,β-Dimethylacrylshikonin (DMAS), an active ingredient of Lithospermum erythrorhizon and Arnebia euchroma, possess anti-neoplasm properties. Recently, DMAS was reported to stimulate autophagy in lung adenocarcinoma cells. However, the mechanisms by which DMAS modulates autophagy. have not yet been clearly elucidated. In this study, we found that DMAS significantly elevated intracellular free calcium accumulation. This activated the CaMKKβ-AMPK-mTOR pathway, subsequently inhibited mTOR and its substrate p70s6k and 4E-BP1, eventually leading to autophagy. In addition, we demonstrated that inhibition of autophagy by BAPTA-AM or STO-609 or compound C potently enhanced DMAS-induced lung adenocarcinoma cells apoptosis and growth inhibition. Overall, our results suggested that cytoprotective autophagy was triggered by DMAS via CaMKKβ-AMPK-mTOR signaling cascade in human lung adenocarcinoma cells, meaning that combining use of DMAS and autophagy inhibitors as a novel therapeutic option for lung adenocarcinoma will be very promising.

Role of estrogen and its receptors mediated-autophagy in cell fate and human diseases

Studies have shown that morbidity of several diseases varies between males and females. This difference likely arises due to sex-related hormones. Estrogen, a primary female sex steroid hormone, plays a critical role in mediating many of the physiological functions like growth, differentiation, metabolism, and cell death. Recently, it has been demonstrated that estrogen mediates autophagy through its receptors (ERs) namely ERα, ERβ, and G-protein coupled estrogen receptor (GPER). However, the specific role of estrogen and its receptors mediated-autophagy in cell fate and human diseases such as cancers, cardiovascular disease and nervous system disease remains unclear. In this review, we comprehensively summarize the complex role of estrogen and its receptors-mediated autophagy in different cell lines and human diseases. In addition, we further discuss the key signaling molecules governing the role of ERs in autophagy. This review will serve as the basis for a proposed model of autophagy constituting a new frontier in estrogen-related human diseases. Here, we discuss the dual role of ERα in classical and non-classical autophagy through B-cell lymphoma 2 (BCL2)-associated athanogene 3 (BAG3). Next, we review the role of ERβ in pro-survival pathways through the promotion of autophagy under stress conditions. We further discuss activation of GPER via estrogen often mediates autophagy or mitophagy suppression, respectively. In summary, we believe that understanding the relationship between estrogen and its receptors mediated-autophagy on cell fate and human diseases will provide insightful knowledge for future therapeutic implications.

Estrogen Receptor Beta (ERβ) Mediated-CyclinD1 Degradation via Autophagy Plays an Anti-Proliferation Role in Colon Cells

Dysfunction of autophagic degradation machinery causes tumorigenesis, including colorectal cancer (CRC). Overexpression of CyclinD1 in CRC has been reported. Recent evidence also suggests that ERβ deficiency is related to the pathogenesis of CRC. Very little is known, however, about the detailed molecular mechanisms underlying the relationship among ERβ, autophagy, and CyclinD1 in CRC. Here, results showed that ERβ played an anti-proliferation role in HCT116 through impairing cell cycle but not apoptosis. Additionally, CyclinD1 accumulation was increased in response to chloroquine (CQ) or in MEF Atg7 knockout cells. Further, ERβ could inhibit the mammalian target of rapamycin (mTOR) or activate Bcl-2/adenovirus E1B 19-kDa-interacting protein 3 (BNIP3) to promote autophagy in HCT116. In summary, these results indicate that ERβ-mediated CyclinD1 degradation can inhibit colon cancer cell growth via autophagy.

The roles of PKCs in regulating autophagy

PURPOSE

Autophagy, as a highly conserved cellular degradation and recycling process, plays an important part in maintaining cellular homeostasis. PKC signaling is involved in multiple pathways including cell cycle progression, tumorigenesis, migration and autophagy.

METHODS

Literatures about PKC and autophagy from PubMed databases were reviewed in this study.

RESULTS

Studies regarding the association of PKC and autophagy remain debatable. Different duration of the stimulation of autophagy and distinct cell contexts result in different function of PKC in regulating autophagy. The subcellular localization of PKCs and their downstream regulators may influence the autophagy regulation as well. As important intracellular components, the mitochondria play an important role in regulating autophagy, by metabolic modulation and structural derangement.

CONCLUSION

Phase II studies regarding PKC-β inhibitor, enzastaurin, showed promising results in MCL, DLBCL and recurrent high-grade gliomas. However, the detailed mechanism is still in need. The mechanism of PKC-β in mediating autophagy in lymphoma and high-grade gliomas remains elusive as well. Moreover, several studies were in agreement that rottlerin enhanced autophagy in breast cancer cells, which warrants further clinical studies to verify PKC-δ as a therapeutic target. Thus, identifying the function of PKC in modulating autophagy and conducting related clinical studies help find novel target for chemotherapy.

Neuronal-targeted TFEB rescues dysfunction of the autophagy-lysosomal pathway and alleviates ischemic injury in permanent cerebral ischemia

Mounting attention has been focused on defects in macroautophagy/autophagy and the autophagy-lysosomal pathway (ALP) in cerebral ischemia. TFEB (transcription factor EB)-mediated induction of ALP has been recently considered as the common mechanism in ameliorating the pathological lesion of myocardial ischemia and neurodegenerative diseases. Here we explored the vital role of TFEB in permanent middle cerebral artery occlusion (pMCAO)-mediated dysfunction of ALP and ischemic insult in rats. The results showed that ALP function was first enhanced in the early stage of the ischemic process, especially in neurons of the cortex, and this was accompanied by increased TFEB expression and translocation to the nucleus, which was mediated at least in part through activation by PPP3/calcineurin. At the later stages of ischemia, a gradual decrease in the level of nuclear TFEB was coupled with a progressive decline in lysosomal activity, accumulation of autophagosomes and autophagy substrates, and exacerbation of the ischemic injury. Notably, neuron-specific overexpression of TFEB significantly enhanced ALP function and rescued the ischemic damage, starting as early as 6 h and even lasting to 48 h after ischemia. Furthermore, neuron-specific knockdown of TFEB markedly reversed the activation of ALP and further aggravated the neurological deficits and ischemic outcome at the early stage of pMCAO. These results highlight neuronal-targeted TFEB as one of the key players in the pMCAO-mediated dysfunction of ALP and ischemic injury, and identify TFEB as a promising target for therapies aimed at neuroprotection in cerebral ischemia. Abbreviations: AAV, adeno-associated virus; AIF1/IBA1, allograft inflammatory factor 1; ALP, autophagy-lysosomal pathway; CQ, chloroquine; CTSB, cathepsin B; CTSD, cathepsin D; CsA, cyclosporin A; GFAP, glial fibrillary acidic protein; LAMP, lysosomal-associated membrane protein; LC3, microtubule-associated protein 1 light chain 3; MAP2, microtubule-associated protein 2; mNSS, modified Neurological Severity Score; MTOR, mechanistic target of rapamycin kinase; OGD, oxygen and glucose deprivation; pMCAO, permanent middle cerebral artery occlusion; RBFOX3/NeuN, RNA binding fox-1 homolog 3; SQSTM1, sequestosome1; TFEB, transcription factor EB; TTC, 2,3,5-triphenyltetrazolium chloride.

Hypoxia-induced autophagy promotes gemcitabine resistance in human bladder cancer cells through hypoxia-inducible factor 1α activation

Overcoming the chemoresistance of bladder cancer is a pivotal obstacle in clinical treatments. Hypoxia widely exists in solid tumors and has been demonstrated to contribute to chemoresistance through hypoxia-inducible factor 1α (HIF‑1α)-mediated autophagy in several types of cancer. However, it is unclear whether HIF‑1α-mediated autophagy and chemoresistance occur in bladder cancer. The present study demonstrated that HIF‑1α was overexpressed in 20 bladder cancer tissues compared with matched paracarcinoma tissues. Gemcitabine-induced apoptosis during hypoxia was significantly reduced compared with that observed under normoxic conditions. In addition, hypoxia activated autophagy and enhanced gemcitabine-induced autophagy. Combined treatment using gemcitabine and an autophagy inhibitor (3-methyladenine) under hypoxia significantly increased gemcitabine cytotoxicity. Furthermore, it was demonstrated that hypoxia-activated autophagy depended on the HIF‑1α/BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3)/Beclin1 signaling pathway. Suppressing HIF‑1α inhibited autophagy, BNIP3 and Beclin1, as well as enhanced gemcitabine-induced apoptosis in bladder cancer cells under hypoxic conditions. Consequently, the results of the present study demonstrated that hypoxia-induced cytoprotective autophagy counteracted gemcitabine-induced apoptosis through increasing HIF‑1α expression. Therefore, targeting HIF‑1α-associated pathways or autophagy in bladder cancer may be a successful strategy to enhance the sensitivity of bladder cancer chemotherapy.

Saikosaponin-d inhibits proliferation by up-regulating autophagy via the CaMKKβ-AMPK-mTOR pathway in ADPKD cells

Autosomal dominant polycystic kidney disease (ADPKD) is a common heritable human disease. Recently, the role of repressed autophagy in ADPKD has drawn increasing attention. Here, we investigate the mechanism underlying the effect of Saikosaponin-d (SSd), a sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase pump (SERCA) inhibitor. We show that SSd suppresses proliferation in ADPKD cells by up-regulating autophagy. We found that treatment with SSd results in the accumulation of intracellular calcium, which in turn activates the CaMKKβ-AMPK signalling cascade, inhibits mTOR signalling and induces autophagy. Conversely, we also found that treatment with an autophagy inhibitor (3-methyladenine), AMPK inhibitor (Compound C), CaMKKβ inhibitor (STO-609) and intracellular calcium chelator (BAPTA/AM) could reduce autophagy puncta formation mediated by SSd. Our results demonstrated that SSd induces autophagy through the CaMKKβ-AMPK-mTOR signalling pathway in ADPKD cells, indicating that SSd might be a potential therapy for ADPKD and that SERCA might be a new target for ADPKD treatment.

PPARγ Antagonizes Hypoxia-Induced Activation of Hepatic Stellate Cell through Cross Mediating PI3K/AKT and cGMP/PKG Signaling

Background and Aims

Accumulating evidence reveals that PPARγ plays a unique role in the regulation of hepatic fibrosis and hepatic stellate cells (HSCs) activation. This study was aimed at investigating the role of PPARγ in hypoxia-induced hepatic fibrogenesis and its possible mechanism.

Methods

Rats used for CCl4-induced hepatic fibrosis model were exposed to hypoxia for 8 hours each day. Rats exposed to hypoxia were treated with or without the PPARγ agonist rosiglitazone. Liver sections were stained with HE and Sirius red staining 8 weeks later. HSCs were exposed to hypoxic environment in the presence or absence of rosiglitazone, and expression of PPARγ and two fibrosis markers, α-SMA and desmin, were measured using western blot and immunofluorescence staining. Next, levels of PPARγ, α-SMA, and desmin as well as PKG and cGMP activity were detected using PI3K/AKT and a cGMP activator or inhibitor.

Results

Hypoxia promoted the induction and progress of hepatic fibrosis and HSCs activation. Meanwhile, rosiglitazone significantly antagonized the effects induced by hypoxia. Signaling by sGC/cGMP/PKG promoted the inhibitory effect of PPARγ on hypoxia-induced activation of HSCs. Moreover, PI3K/AKT signaling or PDE5 blocked the above response of PPARγ.

Conclusion

sGC/cGMP/PKG and PI3K/AKT signals act on PPARγ synergistically to attenuate hypoxia-induced HSC activation.

Relationship between mTOR signaling pathway and hepatic stellate cells function

The activation of hepatic stellate cells (HSCs) is generally considered to be the central link in the formation of hepatic fibrosis. Various factors can regulate the function of HSCs through multiple signaling pathways, of which the mammalian target of rapamycin (mTOR) signaling pathway is especially important. Elucidating the relationship between the mTOR signaling pathway and the proliferation, apoptosis, autophagy, and senescence of HSCs can provide new therapeutic targets and methods for the clinical treatment of hepatic fibrosis. This paper discusses the relationship between the mTOR signaling pathway and the function of HSCs.

Engineering in vitro models of hepatofibrogenesis

Chronic liver disease is a major cause of morbidity and mortality worldwide marked by chronic inflammation and fibrosis/scarring, resulting in end-stage liver disease and its complications. Hepatic stellate cells (HSCs) are a dominant contributor to liver fibrosis by producing excessive extracellular matrix (ECM), irrespective of the underlying disease aetiologies, and for many decades research has focused on the development of a number of anti-fibrotic strategies targeting this cell. Despite major improvements in two-dimensional systems (2D) by using a variety of cell culture models of different complexity, an efficient anti-fibrogenic therapy has yet to be developed. The development of well-defined three-dimensional (3D) in vitro models, which mimic ECM structures as found in vivo, have demonstrated the importance of cell-matrix bio-mechanics, the complex interactions between HSCs and hepatocytes and other non-parenchymal cells, and this to improve and promote liver cell-specific functions. Henceforth, refinement of these 3D in vitro models, which reproduce the liver microenvironment, will lead to new objectives and to a possible new era in the search for antifibrogenic compounds.

AMPK orchestrates an elaborate cascade protecting tissue from fibrosis and aging

Fibrosis is a common process characterized by excessive extracellular matrix (ECM) accumulation after inflammatory injury, which is also a crucial cause of aging. The process of fibrosis is involved in the pathogenesis of most diseases of the heart, liver, kidney, lung, and other organs/tissues. However, there are no effective therapies for this pathological alteration. Annually, fibrosis represents a huge financial burden for the USA and the world. 5'-AMP-activated protein kinase (AMPK) is a pivotal energy sensor that alleviates or delays the process of fibrogenesis. In this review, we first present basic background information on AMPK and fibrogenesis and describe the protective roles of AMPK in three fibrogenic phases. Second, we analyze the protective action of AMPK during fibrosis in myocardial, hepatic, renal, pulmonary, and other organs/tissues. Third, we present a comprehensive discussion of AMPK during fibrosis and draw a conclusion. This review highlights recent advances, vital for basic research and clinical drug design, in the regulation of AMPK during fibrosis.

AMPK: a novel target for treating hepatic fibrosis

Fibrosis is a common process of excessive extracellular matrix (ECM) accumulation following inflammatory injury. Fibrosis is involved in the pathogenesis of almost all liver diseases for which there is no effective treatment. 5'-AMP-activated protein kinase (AMPK) is a cellular energy sensor that can ameliorate the process of hepatic fibrogenesis. Given the existing evidence, we first introduce the basic background of AMPK and hepatic fibrosis and the actions of AMPK in hepatic fibrosis. Second, we discuss the three phases of hepatic fibrosis and potential drugs that target AMPK. Third, we analyze possible anti-fibrosis mechanisms and other benefits of AMPK on the liver. Finally, we summarize and briefly explain the current objections to targeting AMPK. This review may aid clinical and basic research on AMPK, which may be a novel drug candidate for hepatic fibrosis.

Significance of dynamic changes in gastric smooth muscle cell apoptosis, PI3K-AKT-mTOR and AMPK-mTOR signaling in a rat model of diabetic gastroparesis

The aim of the present study was to investigate the significance of cell apoptosis, the phosphoinositide-3-kinase (PI3K)-protein kinase B (AKT)-mammalian target of rapamycin (mTOR) pathway, and the 5' adenosine monophosphate-activated protein kinase (AMPK)‑mTOR pathways in the process of diabetic gastroparesis. Changes in gastric smooth muscle cells of diabetic rats with induced gastroparesis were examined. The diabetic rat model was established by dividing animals into a normal control group and diabetic model groups examined at 2, 4 and 6 weeks. Diabetic gastroparesis was evaluated by examining the rates of gastric residual pigment, whereas flow cytometry was used to detect the apoptosis of gastric smooth muscle cells. The expression levels of PI3K and phosphorylated (p‑) AKT, AMPK, mTOR, tuberous sclerosis complex 2, p70 ribosomal S6 kinase, and eukaryotic translation initiation factor 4‑binding protein 1 were determined in gastric muscles using western blot analysis. Diabetic gastroparesis was confirmed in models at 6 weeks. The apoptosis of gastric smooth muscle cells gradually increased in all diabetic groups, and significant changes were observed in key proteins involved in PI3K‑AKT‑mTOR and AMPK‑mTOR signaling. The results indicated that apoptosis was important in the occurrence of diabetic gastroparesis, and the PI3K‑AKT‑mTOR and AMPK‑mTOR pathways were activated during the apoptotic processes, but were incapable of regulating apoptosis.

Naringin in Ganshuang Granule suppresses activation of hepatic stellate cells for anti-fibrosis effect by inhibition of mammalian target of rapamycin

A previous study has demonstrated that Ganshuang granule (GSG) plays an anti-fibrotic role partially by deactivation of hepatic stellate cells (HSCs). In HSCs activation, mammalian target of rapamycin (mTOR)-autophagy plays an important role. We attempted to investigate the role of mTOR-autophagy in anti-fibrotic effect of GSG. The cirrhotic mouse model was prepared to demonstrate the anti-fibrosis effect of GSG. High performance liquid chromatography (HPLC) analyses were used to identify the active component of GSG. The primary mouse HSCs were isolated and naringin was added into activated HSCs to observe its anti-fibrotic effect. 3-methyladenine (3-MA) and Insulin-like growth factor-1 (IGF-1) was added, respectively, into fully activated HSCs to explore the role of autophagy and mTOR. GSG played an anti-fibrotic role through deactivation of HSCs in cirrhotic mouse model. The concentration of naringin was highest in GSG by HPLC analyses and naringin markedly suppressed HSCs activation in vitro, which suggested that naringin was the main active component of GSG. The deactivation of HSCs caused by naringin was not because of the autophagic activation but mTOR inhibition, which was supported by the following evidence: first, naringin induced autophagic activation, but when autophagy was blocked by 3-MA, deactivation of HSCs was not attenuated or reversed. Second, naringin inhibited mTOR pathway, meanwhile when mTOR was activated by IGF-1, deactivation of HSCs was reversed. In conclusion, we have demonstrated naringin in GSG suppressed activation of HSCs for anti-fibrosis effect by inhibition of mTOR, indicating a potential therapeutic application for liver cirrhosis.

Extracellular pH regulates autophagy via the AMPK-ULK1 pathway in rat cardiomyocytes

Various pathological conditions contribute to pH fluctuations and affect the functions of vital organs such as the heart. In this study, we show that in rat cardiomyocytes, acidic extracellular pH (pHe) inhibits autophagy, whereas alkaline pHe stimulates it. We also find that adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR) and Unc-51-like kinase 1 (ULK1) are very sensitive to pHe changes. Furthermore, by interfering with AMPK, mTOR or ULK1 activity, we demonstrate that the AMPK-ULK1 pathway, but not the mTOR pathway, plays a crucial role on pHe-regulated autophagy and cardiomyocyte viability. These data provide a potential therapeutic strategy against cardiomyocyte injury triggered by pH fluctuations.

Modulation of Autophagy by Calcium Signalosome in Human Disease

Autophagy is a catabolic process that is largely regulated by extracellular and intracellular signaling pathways that are central to cellular metabolism and growth. Mounting evidence has shown that ion channels and transporters are important for basal autophagy functioning and influence autophagy to handle stressful situations. Besides its role in cell proliferation and apoptosis, intracellular Ca(2+) is widely recognized as a key regulator of autophagy, acting through the modulation of pathways such as the mechanistic target of rapamycin complex 1, calcium/calmodulin-dependent protein kinase kinase 2, and protein kinase C. Proper spatiotemporal Ca(2+) availability, coupled with a controlled ionic flow among the extracellular milieu, storage compartments, and the cytosol, is critical in determining the role played by Ca(2+) on autophagy and on cell fate. The crosstalk between Ca(2+) and autophagy has a central role in cellular homeostasis and survival during several physiologic and pathologic conditions. Here we review the main findings concerning the mechanisms and roles of Ca(2+)-modulated autophagy, focusing on human disorders ranging from cancer to neurologic diseases and immunity. By identifying mechanisms, players, and pathways that either induce or suppress autophagy, new promising approaches for preventing and treating human disorders emerge, including those based on the modulation of Ca(2+)-mediated autophagy.