Eicosapentaenoic acid protects cardiomyoblasts from lipotoxicity in an autophagy-dependent manner

Ubiquitin-specific peptidase 10 ameliorates hepatic steatosis in nonalcoholic steatohepatitis model by restoring autophagic activity

BACKGROUND

Nonalcoholic steatohepatitis (NASH) is a critical event in the progression of nonalcoholic fatty liver disease (NAFLD). Steatosis induces lipotoxicity, driving the transition of simple fatty liver (NAFL) to NASH. Autophagy affects NAFLD by improving steatosis.

AIM

To investigate whether ubiquitin-specific peptidase (USP)10 alleviates hepatic steatosis through autophagy.

METHODS

A methionine-choline-deficient diet (MCDD) and choline-deficient diet (CDD) were used to model rodent NASH and NAFL, respectively. HepG2 cells were treated with palmitic acid to model hepatocellular steatosis. A viral carrier was used to regulate the USP10 level. Real-time fluorescence quantitative polymerase chain reaction, western blotting, histology, and electron microscopy were used to detect autophagic activity and steatosis.

RESULTS

In vivo, a time-dependent correlation of USP10 and autophagic activity in the liver was found during NAFLD (including NAFL and NASH) modeling. After 8 weeks of modeling, the autophagic activity of NASH was lower than that of the healthy controls and those with NAFL. USP10 could promote autophagy-related pathways and molecules and increase the synthesis of autophagosomes in NASH, improving steatosis, inflammation, and fibrosis. In vitro, autophagy inhibitors reversed the lipid-lowering effect of USP10 without decreasing the level of fatty acid β-oxidation.

CONCLUSION

USP10 ameliorated histological steatosis, inflammation, and fibrosis. USP10 alleviated hepatic steatosis in NASH in an autophagy-dependent manner.

Oxidative Stress and Lipid Dysregulation in Lipid Droplets: A Connection to Chronic Kidney Disease Revealed in Human Kidney Cells

Chronic kidney disease (CKD), which is defined as a condition causing the gradual loss of kidney function, shows renal lipid droplet (LD) accumulation that is associated with oxidative damage. There is a possibility that an LD abnormality in quality plays a role in CKD development. This study aimed to explore the chemical composition of LDs that are induced in human kidney cells during exposure to free fatty acids as an LD source and oxidized lipoproteins as oxidative stress. The LDs were aspirated directly from cells using nanotips, followed by in-tip microextraction, and the LD lipidomic profiling was conducted using nanoelectrospray mass spectrometry. As a result, the free fatty acids increased the LD lipid content and, at the same time, changed their composition significantly. The oxidized lipoproteins caused distorted proportions of intact lipids, such as triacylglycerols (TG), phosphatidylcholines (PC), phosphatidylethanolamines (PE), and cholesteryl esters (CE). Notably, the oxidized lipids, including the hydroperoxides of TG, PC, and PE, exhibited significant elevations in dose-dependent manners. Furthermore, the dysregulation of intact lipids was paralleled with the accumulation of lipid hydroperoxides. The present study has revealed that the oxidation of lipids and the dysregulation of the lipid metabolism coexisted in LDs in the kidney cells, which has provided a potential new target for diagnosis and new insights into CKD.

Severe Hyperosmotic Stress Issues an ER Stress-Mediated “Death Sentence” in H9c2 Cells, with p38-MAPK and Autophagy “Coming to the Rescue”

With several cardiovascular pathologies associated with osmotic perturbations, researchers are in pursuit of identifying the signaling sensors, mediators and effectors involved, aiming at formulating novel diagnostic and therapeutic strategies. In the present study, H9c2 cells were treated with 0.5 M sorbitol to elicit hyperosmotic stress. Immunoblotting as well as cell viability analyses revealed the simultaneous but independent triggering of multiple signaling pathways. In particular, our findings demonstrated the phosphorylation of eukaryotic translation initiation factor 2 (eIF2α) and upregulation of the immunoglobulin heavy-chain-binding protein (BiP) expression, indicating the onset of the Integrated Stress Response (IRS) and endoplasmic reticulum stress (ERS), respectively. In addition, autophagy was also induced, evidenced by the enhancement of Beclin-1 protein expression and of AMP-dependent kinase (AMPK) and Raptor phosphorylation levels. The involvement of a Na+/H+ exchanger-1 (NHE-1) as well as NADPH oxidase (Nox) in 0.5 M sorbitol-induced eIF2α phosphorylation was also indicated. Of note, while inhibition of ERS partially alleviated the detrimental effect of 0.5 M sorbitol on H9c2 cellular viability, attenuation of p38-MAPK activity and late phase autophagy further mitigated it. Deciphering the mode of these pathways’ potential interactions and of their complications may contribute to the quest for effective clinical interventions against associated cardiovascular diseases.

Mitochondrial Adaptive Responses to Hypertriglyceridemia and Bioactive Lipids

Significance: Altered plasma triglyceride metabolism and changes in dietary fatty acid types and levels are major contributors to the development of metabolic and cardiovascular diseases such as fatty liver disease, obesity, diabetes, and atherosclerosis. Lipid accumulation in visceral adipose tissue and ectopically in other organs, as well as lipid-induced redox imbalance, is connected to mitochondrial dysfunction in a range of oxidative stress-associated metabolic and degenerative disorders. Recent Advances: Successful mitochondrial adaptive responses in the context of hypertriglyceridemia and dietary bioactive polyunsaturated fatty acids contribute to increase body energy expenditure and reduce oxidative stress, thus allowing several cell types to cope with metabolic challenges and stresses. These responses include mitochondrial redox signaling, mild uncoupling, and changes in network dynamic behavior. Critical Issues: Mitochondrial bioenergetics and redox changes in a lipid overload context are relatively well characterized. However, the turning point between adaptive and maladaptive mitochondrial responses remains a critical issue to be elucidated. In addition, the relationship between changes in fusion/fission machinery and mitochondrial function is less well understood. Future Directions: The effective mitochondrial responses described here support the research for new drug design and diet or nutraceutical formulations targeting mitochondrial mild uncoupling and effective quality control as putative strategies for cardiometabolic diseases. Antioxid. Redox Signal. 36, 953-968.

Natural and chemical compounds as protective agents against cardiac lipotoxicity

Cardiac lipotoxicity results from the deleterious effects of excess lipid deposition in cardiomyocytes. Lipotoxic cardiomyopathy involves cardiac lipid overload leading to changes in myocardial structure and function. Cardiac dysfunction has been associated with cardiac lipotoxicity through abnormal lipid metabolism. Lipid accumulation, especially saturated free fatty acids (SFFAs), in cardiac cells can cause cardiomyocyte distress and subsequent myocardial contractile dysfunction. Reducing the excess FAs supply or promoting FA storage is beneficial for cardiac function, especially under a lipotoxic condition. The protective effects of several compounds against lipotoxicity progression in the heart have been investigated. A variety of mechanisms has been suggested to prevent or treat cardiac lipotoxicity, including improvement of calcium homeostasis, lipid metabolism, and mitochondrial dysfunction. Known targets and signaling pathways involving a select group of chemicals that interfere with cardiac lipotoxicity pathogenesis are reviewed.

A Five Autophagy-Related Long Non-Coding RNA Prognostic Model for Patients with Lung Adenocarcinoma

Purpose

Lung adenocarcinoma is the most common pathological type among non-small cell lung cancer. Although huge progress has been made in terms of early diagnosis and precision treatment in recent years, the overall 5-year survival rate of a patient remains low. In our study, we try to construct an autophagy-related lncRNA prognostic signature that may guide clinical practice.

Methods

The mRNA and lncRNA expression matrix of lung adenocarcinoma patients were retrieved from the TCGA database. Next, we constructed a co-expression network of lncRNAs and autophagy-related genes. Lasso regression and multivariate Cox regression were then applied to establish a prognostic risk model. Subsequently, a risk score was generated to differentiate the high and low risk groups and a ROC curve and nomogram to visualize the predictive ability of the current signature. Finally, gene ontology and pathway enrichment analysis were executed via GSEA.

Results

A total of 1,703 autophagy-related lncRNAs were screened and five autophagy-related lncRNAs (LINC01137, AL691432.2, LINC01116, AL606489.1, and HLA-DQB1-AS1) were finally included in our signature. Judging from univariate (HR=1.075, 95% CI=1.046–1.104) and multivariate (HR=1.088, 95% CI=1.057−1.120) Cox regression analysis, the risk score is an independent factor for LUAD patients. Further, the AUC value based on the risk score for 1-year, 3-years, and 5-years, was 0.735, 0.672, and 0.662, respectively, indicating a reliable model. Drug sensitivity analysis revealed low risk patients were more sensitive to Gemcitabine and Gefitinib, while high risk patients had a better response to Paclitaxel and Erlotinib. Moreover, the lncRNAs included in our signature were primarily enriched in the autophagy process, metabolism, p53 pathway, and JAK/STAT pathway. Finally, a multi-omics analysis of correlated genes showed CFLAR overexpressed in the tumor sample, while GAPDH and MLST8 had a slightly higher expression in the normal sample.

Conclusion

Overall, our study indicated that the prognostic model we generated had certain predictability for LUAD patients’ prognosis and the related genes might be potential biomarkers and therapeutic targets.

An Autophagy-Related Long Non-Coding RNA Prognostic Signature for Patients with Lung Squamous Carcinoma Based on Bioinformatics Analysis

Purpose

Lung cancer is the most common and deadly cancer type affecting humans. Although huge progress has been made on early diagnosis and precision treatment, the overall 5 year survival rate remains low. In this study, we constructed an autophagy-related long non-coding RNA (lncRNA) prognostic signature for guiding clinical practice.

Methods

From The Cancer Genome Atlas, we retrieved mRNA and lncRNA expression matrices of patients with lung squamous carcinoma. We then established a prognostic risk model using Lasso regression and multivariate Cox regression. The model generated a risk score to differentiate high- and low-risk groups. An ROC curve and nomogram were used to visualize the predictive ability of the current signatures. Finally, we used Gene Set Enrichment Analysis to determine gene ontology and pathway enrichment.

Results

After screening 1248 autophagy-related lncRNAs, we selected seven lncRNAs (LUCAT1, AC022150.2, AL035425.3, AC138976.2, AC106786.1, GPRC5D-AS1 and AP006545.2) for our signature. Univariate (hazard ratio [HR] = 2.147, 95% confidence interval [CI]: 1.681–2.743, P < 0.001) and multivariate (HR = 2.096, 95% CI: 1.652–2.658, P < 0.001) Cox regression analyses revealed that the risk score is an independent predictive factor for LUSC patients. Further, areas under the receiver operating characteristic curve were 0.622, 0.699, and 0.721, respectively, for the 1 year, 3 year, and 5 year risk scores—indicating a reliable model. Selected lncRNAs were primarily enriched in autophagy, metabolism, MAPK pathway, and JAK/STAT pathway. Further drug sensitivity analysis revealed that low-risk patients were more sensitive to Cisplatin, Docetaxel, Vinblastine, and Vinorelbine. Finally, a multi-omics analysis found that lncRNA-linked proteins IKBKB and SQSTM1 were expressed at low levels and significantly correlated in tumor samples, compared with normal tissue.

Conclusion

Our prognostic model successfully predicted patient prognosis in lung cancer.

Endoplasmic Reticulum Stress and Autophagy Markers in Soleus Muscle Disuse-Induced Atrophy of Rats Treated with Fish Oil

Endoplasmic reticulum stress (ERS) and autophagy pathways are implicated in disuse muscle atrophy. The effects of high eicosapentaenoic (EPA) or high docosahexaenoic (DHA) fish oils on soleus muscle ERS and autophagy markers were investigated in a rat hindlimb suspension (HS) atrophy model. Adult Wistar male rats received daily by gavage supplementation (0.3 mL per 100 g b.w.) of mineral oil or high EPA or high DHA fish oils (FOs) for two weeks. Afterward, the rats were subjected to HS and the respective treatments concomitantly for an additional two-week period. After four weeks, we evaluated ERS and autophagy markers in the soleus muscle. Results were analyzed using two-way analysis of variance (ANOVA) and Bonferroni post hoc test. Gastrocnemius muscle ω-6/ω-3 fatty acids (FAs) ratio was decreased by both FOs indicating the tissue incorporation of omega-3 fatty acids. HS altered (p < 0.05) the protein content (decreasing total p38 and BiP and increasing p-JNK2/total JNK2 ratio, and caspase 3) and gene expressions (decreasing BiP and increasing IRE1 and PERK) of ERS and autophagy (decreasing Beclin and increasing LC3 and ATG14) markers in soleus. Both FOs attenuated (p < 0.05) the increase in PERK and ATG14 expressions induced by HS. Thus, both FOs could potentially attenuate ERS and autophagy in skeletal muscles undergoing atrophy.

Blue-Print Autophagy in 2020: A Critical Review

Autophagy is an elegant and complex biological process that has recently attracted much attention from the scientific community. The compounds which are capable of control and modulation of this process have a promising potential as therapeutics for a number of pathological conditions, including cancer and neurodegenerative disorders. At the same time, due to the relatively young age of the field, there are still some pitfalls in the autophagy monitoring assays and interpretation of the experimental data. This critical review provides an overview of the marine natural compounds, which have been reported to affect autophagy. The time period from the beginning of 2016 to the middle of 2020 is covered. Additionally, the published data and conclusions based on the experimental results are re-analyzed with regard to the guidelines developed by Klionsky and colleagues (Autophagy. 2016; 12(1): 1–222), which are widely accepted by the autophagy research community. Remarkably and surprisingly, more than half of the compounds reported to be autophagy activators or inhibitors could not ultimately be assigned to either category. The experimental data reported for those substances could indicate both autophagy activation and inhibition, requiring further investigation. Thus, the reviewed molecules were divided into two groups: having validated and non-validated autophagy modulatory effects. This review gives an analysis of the recent updates in the field and raises an important problem of standardization in the experimental design and data interpretation.

Palmitic acid induces human osteoblast-like Saos-2 cell apoptosis via endoplasmic reticulum stress and autophagy

Palmitic acid (PA) is the most common saturated long-chain fatty acid in food that causes cell apoptosis. However, little is known about the molecular mechanisms of PA toxicity. In this study, we explore the effects of PA on proliferation and apoptosis in human osteoblast-like Saos-2 cells and uncover the signaling pathways involved in the process. Our study showed that endoplasmic reticulum (ER) stress and autophagy are involved in PA-induced Saos-2 cell apoptosis. We found that PA inhibited the viability of Saos-2 cells in a dose- and time-dependent manner. At the same time, PA induced the expression of ER stress marker genes (glucose-regulated protein 78 (GRP78) and CCAAT/enhancer binding protein homologous protein (CHOP)), altered autophagy-related gene expression (microtubule-associated protein 1 light chain 3 (LC3), ATG5, p62, and Beclin), promoted apoptosis-related gene expression (Caspase 3 and BAX), and affected autophagic flux. Inhibiting ER stress with 4-PBA diminished the PA-induced cell apoptosis, activated autophagy, and increased the expression of Caspase 3 and BAX. Inhibiting autophagy with 3-MA attenuated the PA and ER stress-induced cell apoptosis and the apoptosis-related gene expression (Caspase 3 and BAX), but seemed to have no obvious effects on ER stress, although the CHOP expression was downregulated. Taken together, our results suggest that PA-induced Saos-2 cell apoptosis is activated via ER stress and autophagy, and the activation of autophagy depends on the ER stress during this process.

Roles of Mitochondrial DNA in Energy Metabolism

Mitochondria are independent double-membrane organelles responsible for energy production, specifically by completing oxidative phosphorylation. Mitochondria are essential to regulate energy metabolism, signaling pathways, and cell death. Mitochondrial DNA (mtDNA) can be altered by metabolic disorders, oxidative stress, or inflammation in the progression and development of various diseases. In this chapter, we overview the role of mtDNA in energy metabolism and the diseases that are associated with mtDNA abnormality, with a special focus on the major factors which regulate the mechanism of mtDNA in metabolism.

Significance of Mitochondria DNA Mutations in Diseases

Mitochondria are essential double-membraned cytoplasmic organelles to support aerobic respiration and produce cellular energy by oxidative phosphorylation (OXPHOS). Mitochondrial functions are controlled by mitochondrial (mtDNA) and nuclear genomes (nDNA). Mutations of mtDNA result in mitochondrial dysfunction and multisystem diseases through compromising OXPHOS function directly by a point mutation or a large-scale mtDNA rearrangement. One or more of OXPHOS complexes are impaired and dysfunctional to affect tissues with high energy demands. mtDNA is more susceptible to oxidative damage and has more mutations than nDNA. Unlike diploid nDNA, mtDNA is a multi-copy genome transmitted and maternally inherited through oocyte. The multi-copy nature of mtDNA easily causes the heteroplasmy as a unique aspect of mtDNA, making mitochondrial diseases more complex and heterogeneous. mtDNA-associated mitochondrial dysfunction plays the important role in the development of multisystemic primary mitochondrial disease, neurodegeneration, and cancer. The present article overviews the occurrence of mtDNA mutation, interactions with other factors, and molecular mechanisms of mtDNA-associated diseases.