Inhibition of autophagy rescues palmitic acid-induced necroptosis of endothelial cells

Bridging lipid metabolism and mitochondrial genome maintenance

Mitochondria are the nexus of cellular energy metabolism and major signaling hubs that integrate information from within and without the cell to implement cell function. Mitochondria harbor a distinct polyploid genome, mitochondrial DNA (mtDNA), that encodes respiratory chain components required for energy production. MtDNA mutation and depletion have been linked to obesity and metabolic syndrome in humans. At the cellular and subcellular levels, mtDNA synthesis is coordinated by membrane contact sites implicated in lipid transfer from the endoplasmic reticulum, tying genome maintenance to lipid storage and homeostasis. Here, we examine the relationship between mtDNA and lipid trafficking, the influence of lipotoxicity on mtDNA integrity, and how lipid metabolism may be disrupted in primary mtDNA disease.

Effects of taurine on metabolomics of bovine mammary epithelial cells under high temperature conditions

High temperature induces heat stress, adversely affecting the growth and lactation performance of cows. Research has shown the protective effect of taurine against hepatotoxicity both in vivo and in vitro. This study aimed to investigate the effect of taurine on the metabolomics of mammary epithelial cells of dairy cows under high-temperature conditions. Mammary epithelial cells were exposed to 0 mmol/L (HS, control), 8 mmol/L (HT-8), and 32 mmol/L (HT-32) of taurine, then incubated at 42°C for 6 h. Metabolomics analysis was conducted using Liquid Chromatograph Mass Spectrometer (LC-MS). Compared with the HS group, 2,873 and 3,243 metabolites were detected in the HT-8 group in positive and negative ion modes. Among these, 108 and 97 metabolites were significantly upregulated in positive and negative ion modes, while 60 and 166 metabolites were downregulated. Notably, 15 different metabolites such as palmitic acid, adenine and hypoxanthine were screened out in the HT-8 group. Compared with the HS group, 2,873 and 3,243 metabolites were, respectively, detected in the HT-32 group in the positive and negative ion modes. Among those metabolites, 206 metabolites were significantly up-regulated, while 206 metabolites were significantly downregulated in the positive mode. On the other hand, 497 metabolites were significantly upregulated in the negative mode, while 517 metabolites were reported to be downregulated. Noteworthy, 30 distinct metabolites, such as palmitic acid, phytosphingosine, hypoxanthine, nonanoic acid, and octanoic acid, were screened out in the HT-32 group. KEGG enrichment analysis showed that these metabolites were mainly involved in lipid metabolism, purine metabolism and other biological processes. Overall, our study indicates that taurine supplementation alters the metabolites primarily associated with purine metabolism, lipid metabolism and other pathways to alleviate heat stress in bovine mammary epithelial cells.

DACH1 attenuated PA-induced renal tubular injury through TLR4/MyD88/NF-κB and TGF-β/Smad signalling pathway

BACKGROUND

Palmitic acid (PA), the major saturated fatty acid in the blood, often induces the initiation and progression of diabetic kidney disease (DKD). However, the underlying mechanism remains unclear. DACH1 is an important regulator of kidney functions. Herein, we investigated the roles of DACH1 in PA-induced kidney injury.

METHODS

Clinical data from the NHANES database were subjected to analyse the association between serum PA (sPA), blood glucose and kidney function. Molecular docking of PA was performed with DACH1. Immunohistochemistry, cell viability, annexin V/7-AAD double staining, TUNEL assay, immunofluorescent staining, autophagic flux analysis, qRT-PCR and western blot were performed.

RESULTS

Clinical data confirmed that sPA was increased significantly in the pathoglycemia individuals compared with controls and correlated negatively with renal function. Our findings suggested that PA could dock with DACH1. DACH1 enhances cell viability by inhibiting apoptosis and attenuating autophagy blockage induced by PA. Furthermore, the results demonstrated that DACH1 ameliorated inflammation and fibrosis through TLR4/MyD88/NF-κB and TGF-β/Smad signalling pathway in PA-treated renal tubular epithelial cell line (HK-2).

CONCLUSIONS

This study proved that sPA presents a risk factor for kidney injuries and DACH1 might serve as a protective target against renal function deterioration in diabetic patients.

The role of fatty acids in patients with Behçet's disease and their association with thrombosis

Behçet's disease (BD) is a systemic disease with unknown etiopathogenesis and varying disease presentations. Fatty acids (FA) are essential biological compounds that are involved in complex metabolic pathways. They may contribute to inflammation and endothelial dysfunction by participating in many signaling pathways. Increased FAs levels are associated with an increased risk for various diseases. This study aimed to determine the relationship between FA, BD, and thrombotic complications. A total of 97 patients were recruited from the rheumatology department of a single center as a case-control study. The participants were divided into three groups: 36 patients with BD with thrombosis (Group 1), 24 patients with BD without thrombosis (Group 2), and 37 age- and sex-matched controls (Group 3). The analysis of 37 different FA with carbon numbers in the range of (4:0) and (24:1) in the samples were analyzed and compared between groups. Myristic acid (MA), methyl eicosatrienoate, and stearic acid (STA) levels were found to be significantly higher in BD with thrombosis than in BD without thrombosis, and palmitic acid (PA) levels were significantly higher in BD with thrombosis than in healthy individuals. MA was found to be a significant marker for differentiating between thrombotic BD. PA and STA are important markers for detecting thrombotic BD. In BD, lipotoxicity created by FA, such as PA, STA, and MA, plays a role as an inducer of inflammation and thrombosis through various mechanisms.

Liver sinusoidal endothelial cells rely on oxidative phosphorylation but avoid processing long-chain fatty acids in their mitochondria

BACKGROUND

It is generally accepted that endothelial cells (ECs), primarily rely on glycolysis for ATP production, despite having functional mitochondria. However, it is also known that ECs are heterogeneous, and their phenotypic features depend on the vascular bed. Emerging evidence suggests that liver sinusoidal ECs (LSECs), located in the metabolically rich environment of the liver, show high metabolic plasticity. However, the substrate preference for energy metabolism in LSECs remains unclear.

METHODS

Investigations were conducted in primary murine LSECs in vitro using the Seahorse XF technique for functional bioenergetic assays, untargeted mass spectrometry-based proteomics to analyse the LSEC proteome involved in energy metabolism pathways, liquid chromatography-tandem mass spectrometry-based analysis of acyl-carnitine species and Raman spectroscopy imaging to track intracellular palmitic acid.

RESULTS

This study comprehensively characterized the energy metabolism of LSECs, which were found to depend on oxidative phosphorylation, efficiently fuelled by glucose-derived pyruvate, short- and medium-chain fatty acids and glutamine. Furthermore, despite its high availability, palmitic acid was not directly oxidized in LSEC mitochondria, as evidenced by the acylcarnitine profile and etomoxir's lack of effect on oxygen consumption. However, together with L-carnitine, palmitic acid supported mitochondrial respiration, which is compatible with the chain-shortening role of peroxisomal β-oxidation of long-chain fatty acids before further degradation and energy generation in mitochondria.

CONCLUSIONS

LSECs show a unique bioenergetic profile of highly metabolically plastic ECs adapted to the liver environment. The functional reliance of LSECs on oxidative phosphorylation, which is not a typical feature of ECs, remains to be determined.

Protein phosphatase 4 mediates palmitic acid-induced endothelial dysfunction by decreasing eNOS phosphorylation at serine 633 in HUVECs

Plasma saturated free fatty acid (FFA)-induced endothelial dysfunction (ED) contributes to the pathogenesis of atherosclerosis and cardiovascular diseases. However, the mechanism underlying saturated FFA-induced ED remains unclear. This study demonstrated that palmitic acid (PA) induced ED by activating the NADPH oxidase (NOX)/ROS signaling pathway to activate protein phosphatase 4 (PP4) and protein phosphatase 2A (PP2A), thereby reducing endothelial nitric oxide synthase (eNOS) phosphorylation at Ser633 and Ser1177, respectively. Okadaic acid (OA) and fostriecin (FST), which are inhibitors of PP2A, inhibited the PA-induced decreases in eNOS phosphorylation at Ser633 and Ser1177. The antioxidants N-acetylcysteine (NAC) and apocynin (APO) or knockdown of gp91phox or p67phox (NOX subunits) restored PA-mediated downregulation of PP4R2 protein expression and eNOS Ser633 phosphorylation. Knockdown of the PP4 catalytic subunit (PP4c) specifically increased eNOS Ser633 phosphorylation, while silencing the PP2A catalytic subunit (PP2Ac) restored only eNOS Ser1177 phosphorylation. Furthermore, PA dramatically decreased the protein expression of the PP4 regulatory subunit R2 (PP4R2) but not the other regulatory subunits. PP4R2 overexpression increased eNOS Ser633 phosphorylation, nitric oxide (NO) production, cell migration and tube formation but did not change eNOS Ser1177 phosphorylation levels. Coimmunoprecipitation (Co-IP) suggested that PP4R2 and PP4c interacted with the PP4R3α and eNOS proteins. In summary, PA decreases PP4R2 protein expression through the Nox/ROS pathway to activate PP4, which contributes to ED by dephosphorylating eNOS at Ser633. The results of this study suggest that PP4 is a novel therapeutic target for ED and ED-associated vascular diseases.

The role of LncRNA-regulated autophagy in AKI

Acute kidney injury (AKI) is a complex clinical syndrome involving a series of pathophysiological processes regulated by multiple pathways at the molecular and cellular level. Long noncoding RNAs (lncRNAs) play an important role in the regulation of epigenetics, and their regulation of autophagy-related genes in AKI has attracted increasing attention. However, the role of lncRNA-regulated autophagy in AKI has not been fully elucidated. Evidence indicated that lncRNAs play regulatory roles in most factors that induce AKI. LncRNAs can regulate autophagy in AKI via a complex network of regulatory pathways to affect the development and prognosis of AKI. This article reviewed and analyzed the pathways of lncRNA regulation of autophagy in AKI in recent years. The results provide new ideas for further study of the pathophysiological process and targeted therapy for AKI.

Inhibition of autophagy and RIP1/RIP3/MLKL-mediated necroptosis by edaravone attenuates blood spinal cord barrier disruption following spinal cord injury

The disruption of the blood spinal cord barrier (BSCB) after spinal cord injury (SCI) can trigger secondary tissue damage. Edaravone is likely to protect the BSCB as a free radical scavenger, whereas it has been rarely reported thus far. In this study, the protective effect of edaravone was investigated with the use of compression spinal cord injured rats and human brain microvascular endothelial cells (HBMECs) injury. As indicated by the result of this study, edaravone treatment facilitated functional recovery after rats were subjected to SCI, ameliorated the vascular damage, and up-regulated the expression of BSCB-associated proteins. In vitro results, edaravone improved HBMECs viability, restored intercellular junctions, and promoted cellular angiogenic activities. It is noteworthy that autophagy was activated and RIP1/RIP3/MLKL phosphorylation was notably up-regulated. However, edaravone treatment exhibited the capability of mitigating above-mentioned tendency in vivo and in vitro. Moreover, rapamycin (Rapa) treatment deteriorated the protective effect of edaravone while aggravating the phosphorylation of RIP1/RIP3/MLKL expression. In the model of necrotic activator-induced HBMECs, autophagic expression was increased, whereas edaravone prevented autophagy and phosphorylation of RIP1/RIP3/MLKL. In general, our results suggested that edaravone is capable of reducing the destruction of BSCB and promoting functional recovery after SCI. The possible underlying mechanism is that edaravone is capable of protecting angiogenic activity and improving autophagy and the phosphorylation of RIP1/RIP3/MLKL, as well as their mutual deterioration. Accordingly, edaravone can be a favorable option for the treatment of SCI.

The Associations of Individual and Subclasses of Nonesterified Fatty Acids With Disability, and Mobility Limitation in Older Adults: The Cardiovascular Health Study

BACKGROUND

We sought to determine the associations between individual nonesterified fatty acids (NEFAs) and disability and mobility limitation.

METHODS

We studied 1 734 participants in the Cardiovascular Health Study (CHS), an ongoing population-based cohort study of community-living older American adults. We measured 35 individual NEFA species in fasting serum samples obtained at the 1996-1997 clinic visit. Using yearly assessments of activities of daily living and self-reported mobility, we identified participants with incident disability or mobility limitation during 15 years of follow-up. Cox proportional hazards regression models were used to determine the associations between per SD increment in the individual NEFAs and incident disability and mobility limitations with adjustment for potential confounding factors.

RESULTS

Higher concentrations of total and a broad range of individual NEFA species were associated with risk of disability and mobility limitation (disability: HR per SD of total NEFA [SD = 174.70] = 1.11, 95% CI = 1.04-1.18, p = .001; mobility limitation: HR per SD of total NEFA = 1.09, 95% CI = 1.02-1.16, p = .01). Among individual saturated NEFAs (SFAs), myristic (14:0) and palmitic (16:0) acids were significantly associated with higher risk of both disability and mobility limitations, but longer-chain FAs were not. Most individual monounsaturated (MUFA), n-6 polyunsaturated fatty acids (PUFAs), and trans FAs were positively significantly associated with higher risks of both disability and mobility limitation. In contrast, most n-3 PUFA species were not associated with disability or mobility limitation.

CONCLUSIONS

Higher risks of disability and mobility limitation were observed for proinflammatory intermediate-chain SFAs, MUFAs, n-6 PUFAs, and trans FAs. Our findings indicated no significant association for anti-inflammatory n-3 PUFAs.

Upregulation of necroptosis markers RIPK3/MLKL and their crosstalk with autophagy-related protein Beclin-1 in primary immune thrombocytopenia

Necroptosis is a novel form of programmed necrotic cell death involved in various autoimmune diseases. The potential role of necroptosis in primary immune thrombocytopenia (ITP) and the possible interlink with autophagy have not been fully investigated. The gene expression of mixed lineage kinase-like domain (MLKL), receptor-interacting protein kinase 3 (RIPK3) and Beclin-1 were quantified in peripheral blood of 45 ITP patients and 20 healthy controls. Their associations with clinical, laboratory parameters and response to steroid therapy in ITP patients were evaluated. RIPK3, MLKL, and Beclin-1 were significantly upregulated in ITP patients than in healthy controls (P < 0.001). Beclin-1 mRNA levels were positively correlated with both RIPK3 and MLKL mRNA levels in ITP patients (P < 0.0001). In addition, MLKL, RIPK3, and Beclin-1 mRNA levels were inversely correlated with platelet count (r = -0.330, -0.527 and -0.608, respectively). On the hand, positive correlations between MLKL (P = 0.01), RIPK3 (P = 0.005), Beclin-1 (P = 0.002) mRNA levels and severity of bleeding in ITP patients were reported. Steroid responders (n = 18, 40%) had significantly lower MLKL, RIPK3, Beclin-1 mRNA expression levels than their levels in the non-responders (n = 27, 60%). Necroptosis may play a critical role in the pathogenesis of ITP and provide both novel therapeutic targets and promising biomarkers for the prediction of bleeding severity and treatment response in ITP patients. Additionally, this study highlighted the crosstalk between autophagy and necroptosis in ITP patients.

Lysosomal Ca2+ as a mediator of palmitate-induced lipotoxicity

While the mechanism of lipotoxicity by palmitic acid (PA), an effector of metabolic stress in vitro and in vivo, has been extensively investigated, molecular details of lipotoxicity are still not fully characterized. Since recent studies reported that PA can exert lysosomal stress in addition to well-known ER and mitochondrial stress, we studied the role of lysosomal events in lipotoxicity by PA, focusing on lysosomal Ca²⁺. We found that PA induced accumulation of mitochondrial ROS and that mitochondrial ROS induced release of lysosomal Ca²⁺ due to lysosomal Ca²⁺ exit channel activation. Lysosomal Ca²⁺ release led to increased cytosolic Ca²⁺ which induced mitochondrial permeability transition (mPT). Chelation of cytoplasmic Ca²⁺ or blockade of mPT with olesoxime or decylubiquinone (DUB) suppressed lipotoxicity. Lysosomal Ca²⁺ release led to reduced lysosomal Ca²⁺ content which was replenished by ER Ca²⁺, the largest intracellular Ca²⁺ reservoir (ER → lysosome Ca²⁺ refilling), which in turn activated store-operated Ca²⁺ entry (SOCE). Inhibition of ER → lysosome Ca²⁺ refilling by blockade of ER Ca²⁺ exit channel using dantrolene or inhibition of SOCE using BTP2 inhibited lipotoxicity in vitro. Dantrolene or DUB also inhibited lipotoxic death of hepatocytes in vivo induced by administration of ethyl palmitate together with LPS. These results suggest a novel pathway of lipotoxicity characterized by mPT due to lysosomal Ca²⁺ release which was supplemented by ER → lysosome Ca²⁺ refilling and subsequent SOCE, and also suggest the potential role of modulation of ER → lysosome Ca²⁺ refilling by dantrolene or other blockers of ER Ca²⁺ exit channels in disease conditions characterized by lipotoxicity such as metabolic syndrome, diabetes, cardiomyopathy or nonalcoholic steatohepatitis.

Oleoylethanolamide alleviates hyperlipidaemia-mediated vascular calcification via attenuating mitochondrial DNA stress triggered autophagy-dependent ferroptosis by activating PPARα

Vascular calcification, a prevalent pathological alteration in metabolic syndromes, is tightly related with cardiometabolic risk events. Ferroptosis, a newly iron-dependent programmed cell death, induced by palmitic acid (PA), the major saturated free fatty acid in hyperlipidemia, is a vital mechanism of vascular calcification. Recent studies reported that ferroptosis is a distinctive type of cell death dependent on autophagy, with the lipotoxicity of PA on cell viability being closely linked with autophagy. Oleoylethanolamide (OEA), an endogenous bioactive mediator of lipid homeostasis, exerts vascular protection against intimal calcification, atherosclerosis; however, its beneficial effect on vascular smooth muscle cell (VSMC)-associated medial calcification has not been investigated. Our aim was to characterize the effect of OEA on vascular calcification and ferroptosis of VSMCs under hyperlipidaemia/PA exposure. In vivo, vascular calcification model was induced in rats by high-fat diet and vitamin D3 plus nicotine; in vitro, VSMCs ferroptosis was induced by PA or plus β-glycerophosphate mimicking vascular calcification. The calcium deposition in hyperlipidaemia-mediated rat thoracic aortas, the PA-induced ferroptosis and subsequent calcium deposition in VSMCs, were suppressed by OEA treatment. Additionally, CGAS-STING1-induced ferritinophagy, the main molecular mechanism of PA-triggered ferroptosis of VSMCs, was activated by mitochondrial DNA damage; however, early administration of OEA alleviated these phenomena. Intriguingly, overexpression of peroxisome proliferator activated receptor alpha (PPARα) contributed to a decrease in PA-induced ferroptosis, whereas PPARɑ knockdown inhibited the OEA-mediated anti-ferroptotic effects. Collectively, our study demonstrated that OEA serves as a prospective candidate for the prevention and treatment of vascular calcification in metabolic abnormality syndromes.

Transcriptome analysis highlights the role of ferroptosis in palmitic acid–induced endothelial dysfunction

Background

Palmitic acid (PA) has a lipotoxic effect on blood vessels, leading to endothelial dysfunction and cell death. The underlying mechanisms are not yet fully understood.

Aim

We sought to investigate the effects of PA on endothelial cells, with an emphasis on ferroptosis.

Methods

Rat corpus cavernosum endothelial cells (RCCECs) and human umbilical vein endothelial cells (HUVECs) were treated with PA to induce a pattern of cell death, as evidenced by the evaluation of cell viability. The differentially expressed genes were measured via RNA sequencing to reveal potential mechanisms. The intracellular levels of glutathione (GSH), malondialdehyde (MDA), ferrous ion (Fe2+), and reactive oxygen species (ROS) were evaluated using commercial kits. Western blot was performed to determine the expressions of relative proteins.

Outcomes

At the end of the study period, the evaluated outcomes were cell viability, transcriptome profiles, the expressions of glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11), as well as levels of GSH, MDA, Fe2+, and ROS.

Results

PA-induced cell death of RCCECs and HUVECs was demonstrated in a dose- and time-dependent manner. Based on the findings of RNA-sequencing (RNA-seq), enrichment of many biological processes associated with cell cycle and response to stimulus occurred. More importantly, ferroptosis was highlighted in the bioinformatic analysis of both endothelial cells. The levels of intracellular Fe2+, MDA, and ROS were significantly increased following PA exposure while GSH was decreased, suggesting excessive iron accumulation, development of lipid peroxidation, and imbalanced redox homeostasis. Mechanistically, PA decreased the protein expression levels of GPX4 and SLC7A11 in endothelial cells, both of which played crucial roles in ferroptotic cell death.

Clinical Translation

This study suggests that ferroptosis may be a useful target for novel therapeutic interventions for endothelial dysfunction and cell death in vascular diseases such as erectile dysfunction.

Strengths and Limitations

In this study, we found that ferroptosis could participate in PA-induced endothelial dysfunction and cell death. A limitation of the study is that it did not shed light on the overall mechanisms of this process. Therefore, further research on the intricate networks of regulating ferroptosis is needed.

Conclusion

Overall, the occurrence of ferroptosis was demonstrated in the PA-treated HUVECs and RCCECs in this study.

In Vitro Modeling of Diabetes Impact on Vascular Endothelium: Are Essentials Engaged to Tune Metabolism?

Angiopathy is a common complication of diabetes mellitus. Vascular endothelium is among the first targets to experience blood-borne metabolic alterations, such as hyperglycemia and hyperlipidemia, the hallmarks of type 2 diabetes. To explore mechanisms of vascular dysfunction and eventual damage brought by these pathologic conditions and to find ways to protect vasculature in diabetic patients, various research approaches are used including in vitro endothelial cell-based models. We present an analysis of the data available from these models that identifies early endothelial cell apoptosis associated with oxidative stress as the major outcome of mimicking hyperglycemia and hyperlipidemia in vitro. However, the fate of endothelial cells observed in these studies does not closely follow it in vivo where massive endothelial damage occurs mainly in the terminal stages of diabetes and in conjunction with comorbidities. We propose that the discrepancy is likely in missing essentials that should be available to cultured endothelial cells to adjust the metabolic state and withstand the immediate apoptosis. We discuss the role of carnitine, creatine, and AMP-activated protein kinase (AMPK) in suiting the endothelial metabolism for long-term function in diabetic type milieu in vitro. Engagement of these essentials is anticipated to expand diabetes research options when using endothelial cell-based models.

Free Fatty Acid Overload Targets Mitochondria: Gene Expression Analysis of Palmitic Acid-Treated Endothelial Cells

Lipotoxicity is known to cause cellular dysfunction and death in non-adipose tissue. A major cause of lipotoxicity is the accumulation of saturated free fatty acids (FFA). Palmitic acid (PA) is the most common saturated fatty acid found in the human body. Endothelial cells form the blood vessels and are the first non-adipose cells to encounter FFA in the bloodstream. FFA overload has a direct impact on metabolism, which is evident through the changes occurring in mitochondria. To study these changes, the PA-treated human coronary artery endothelial cell (HCAEC) dataset was obtained from the Gene Expression Omnibus (GEO), and it was analyzed to obtain differentially expressed genes (DEGs) from the nucleus and mitochondria. Functional and pathway enrichment analyses were performed on DEGs. Results showed that nuclear and mitochondrial DEGs were implicated in several processes, e.g., reactive oxygen species (ROS) production, mitochondrial fusion and fission, Ca2+ sequestering, membrane transport, the electron transport chain and the process of apoptosis. To better understand the role of FFA in endothelial cell damage, these DEGs can lead to future experiments based on these findings.

[Effects of 4'-O-methylochnaflavone on endothelial dysfunction induced by palmitic acid in rat cavernous endothelial cells]

OBJECTIVE

To investigate the effect of biflavonoid 4'-O-methylochnaflavone (MF) on palmitic acid-induced endothelial dysfunction in rat cavernous endothelial cells (RCECs).

METHODS

The isolated RCECs were commercially available and randomly divided into four groups: normal+BSA group (NC group), palmitic acid (PA) group, MF group, and icariside Ⅱ (ICA Ⅱ) group. The protein expression levels of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in each group were evaluated via Western blotting. The differences in the intracellular nitric oxide of RCECs treated by MF or ICA Ⅱ were detected by DAF-FM DA that served as a nitric oxide fluorescent probe. Effects of MF and ICA Ⅱ on cell proliferation of PA-stimulated RCECs were determined via CCK-8 assay.

RESULTS

The content of nitric oxide in RCECs was significantly increased after the treatment of MF and ICA Ⅱ in comparison with the NC group (P < 0.05). Moreover, compared with ICA Ⅱ group, MF demonstrated a more obvious effect in promoting nitric oxide production (P < 0.05). Compared with the NC group, the expression levels of eNOS and AKT in the PA group were significantly decreased, indicating that a model for simulating the high-fat environment in vitro was successfully constructed (P < 0.05). Meanwhile, the intervention of MF and ICA Ⅱ could effectively increase the expression of eNOS and AKT, suggesting that MF and ICA Ⅱ could promote the recovery of endothelial dysfunction caused by high levels of free fatty acids (P < 0.05). The results of CCK-8 assays showed that PA could significantly reduce the proli-feration ability of RCECs (P < 0.05). Furthermore, the decreased cell viability induced by PA was significantly elevated by treatment with ICA Ⅱ and MF (P < 0.05).

CONCLUSION

In RCECs, MF and ICA Ⅱ could effectively increase the content of nitric oxide. The down-regulation of the expression of proteins associated with the AKT/eNOS pathway after PA treatment revealed that this pathway was involved in the development of endothelial dysfunction, which could be effectively reversed by MF and ICA Ⅱ. In addition, the cell proliferation ability was significantly decreased following PA treatment, but MF and ICA Ⅱ could restore the above changes. Overall, biflavonoid MF has an obvious repairing effect on PA-stimulated endothelial dysfunction.

[Effects of 4'-O-methylochnaflavone on endothelial dysfunction induced by palmitic acid in rat cavernous endothelial cells]

OBJECTIVE

To investigate the effect of biflavonoid 4'-O-methylochnaflavone (MF) on palmitic acid-induced endothelial dysfunction in rat cavernous endothelial cells (RCECs).

METHODS

The isolated RCECs were commercially available and randomly divided into four groups: normal+BSA group (NC group), palmitic acid (PA) group, MF group, and icariside Ⅱ (ICA Ⅱ) group. The protein expression levels of protein kinase B (PKB/AKT) and endothelial nitric oxide synthase (eNOS) in each group were evaluated via Western blotting. The differences in the intracellular nitric oxide of RCECs treated by MF or ICA Ⅱ were detected by DAF-FM DA that served as a nitric oxide fluorescent probe. Effects of MF and ICA Ⅱ on cell proliferation of PA-stimulated RCECs were determined via CCK-8 assay.

RESULTS

The content of nitric oxide in RCECs was significantly increased after the treatment of MF and ICA Ⅱ in comparison with the NC group (P < 0.05). Moreover, compared with ICA Ⅱ group, MF demonstrated a more obvious effect in promoting nitric oxide production (P < 0.05). Compared with the NC group, the expression levels of eNOS and AKT in the PA group were significantly decreased, indicating that a model for simulating the high-fat environment in vitro was successfully constructed (P < 0.05). Meanwhile, the intervention of MF and ICA Ⅱ could effectively increase the expression of eNOS and AKT, suggesting that MF and ICA Ⅱ could promote the recovery of endothelial dysfunction caused by high levels of free fatty acids (P < 0.05). The results of CCK-8 assays showed that PA could significantly reduce the proli-feration ability of RCECs (P < 0.05). Furthermore, the decreased cell viability induced by PA was significantly elevated by treatment with ICA Ⅱ and MF (P < 0.05).

CONCLUSION

In RCECs, MF and ICA Ⅱ could effectively increase the content of nitric oxide. The down-regulation of the expression of proteins associated with the AKT/eNOS pathway after PA treatment revealed that this pathway was involved in the development of endothelial dysfunction, which could be effectively reversed by MF and ICA Ⅱ. In addition, the cell proliferation ability was significantly decreased following PA treatment, but MF and ICA Ⅱ could restore the above changes. Overall, biflavonoid MF has an obvious repairing effect on PA-stimulated endothelial dysfunction.

C1q/tumour necrosis factor-related protein-3 alleviates high-glucose-induced lipid accumulation and necroinflammation in renal tubular cells by activating the adenosine monophosphate-activated protein kinase pathway

Lipid accumulation and progressive necroinflammation play pivotal roles in the development of diabetic nephropathy. C1q tumour necrosis factor-related protein-3 (CTRP3) is an adipokine with pleiotropic functions in cell proliferation, glucose and lipid metabolism, and inflammation. However, the mechanism and involvement of CTRP3 in lipid metabolism and the necroinflammation of renal tubular cells remain unclear. Here, we report that CTRP3 expression decreased in a time- and concentration-dependent manner in high glucose-stimulated HK-2 cells. We noted that the overexpression of CTRP3 or recombinant CTRP3 (rCTRP3) treatment prevented high glucose-induced lipid accumulation by inhibiting the expression of sterol regulatory element-binding protein-1 and increasing the expression of peroxisome proliferator-activated receptor-α and ATP-binding cassette A1. Moreover, the nucleotide-binding oligomerisation domain-like receptor protein 3-mediated inflammatory response and mixed lineage kinase domain-like protein-dependent necroinflammation were inhibited by CTRP3 overexpression or rCTRP3 treatment in HK-2 cells cultured in high glucose. Furthermore, lipotoxicity-induced by palmitic acid was found to be involved in necroinflammation in HK-2 cells, and CTRP3 displayed the same protective effect. CTRP3 also activated the adenosine monophosphate-activated protein kinase (AMPK) pathway, whereas adenine 9-β-D-arabinofuranoside, an AMPK inhibitor, replicated the protective effects of CTRP3. Besides, using kidney biopsies from patients with diabetes, we found that decreased CTRP3 expression was accompanied by increased lipid deposition, as well as the structural and functional injury of renal tubular cells. Our findings demonstrate that CTRP3 affects lipid metabolism and necroinflammation in renal tubular cells via the AMPK signalling pathway. Thus, CTRP3 may be a potential therapeutic target in diabetic renal injury.

Glucolipotoxicity induces endothelial cell dysfunction by activating autophagy and inhibiting autophagic flow

OBJECTIVES

This study aims to determine the role and mechanism of autophagy in endothelial cell dysfunction by glucolipotoxicity.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with high glucose and high palmitic acid. The number of autophagosomes was evaluated by monodansylcadaverine (MDC) staining and transmission electron microscopy (TEM). The expression of autophagy-related proteins (LC3 and P62) was assessed by Western blotting. Capillary tube-like formation was evaluated on Matrigel. Reactive oxygen species (ROS) production was detected by DCFH-DA. Cell apoptosis was measured by Hoechst 33258 staining and flow cytometry. Phosphorylation of AMPK, mTOR, and ULK1 was also analyzed by Western blotting.

RESULTS

We found that glucolipotoxicity induced autophagy initiation and hindered autophagosomes degradation. Moreover, glucolipotoxicity increased the production of intracellular ROS, decreased the ability of tubular formation, and increased cell apoptosis. However, endothelial cell dysfunction was alleviated by 3-methyladenine, an early-stage autophagy inhibitor. Additionally, glucolipotoxicity promoted the phosphorylation of AMPK and ULK1 and inhibited the phosphorylation of mTOR.

CONCLUSIONS

Glucolipotoxicity initiates autophagy through the AMPK/mTOR/ULK1 signaling pathway and inhibits autophagic flow, leading to the accumulation of autophagosomes, thereby inducing apoptosis and impairing endothelial cell function.

Pan-Caspase Inhibitor zVAD Induces Necroptotic and Autophagic Cell Death in TLR3/4-Stimulated Macrophages

In addition to inducing apoptosis, caspase inhibition contributes to necroptosis and/or autophagy depending on the cell type and cellular context. In macrophages, necroptosis can be induced by co-treatment with Toll-like receptor (TLR) ligands (lipopolysaccharide [LPS] for TLR4 and polyinosinic-polycytidylic acid [poly I:C] for TLR3) and a cell-permeable pan-caspase inhibitor zVAD. Here, we elucidated the signaling pathways and molecular mechanisms of cell death. We showed that LPS/zVAD- and poly I:C/zVAD-induced cell death in bone marrow-derived macrophages (BMDMs) was inhibited by receptor-interacting protein kinase 1 (RIP1) inhibitor necrostatin-1 and autophagy inhibitor 3-methyladenine. Electron microscopic images displayed autophagosome/autolysosomes, and immunoblotting data revealed increased LC3II expression. Although zVAD did not affect LPS- or poly I:C-induced activation of IKK, JNK, and p38, it enhanced IRF3 and STAT1 activation as well as type I interferon (IFN) expression. In addition, zVAD inhibited ERK and Akt phosphorylation induced by LPS and poly I:C. Of note, zVAD-induced enhancement of the IRF3/IFN/STAT1 axis was abolished by necrostatin-1, while zVAD-induced inhibition of ERK and Akt was not. Our data further support the involvement of autocrine IFNs action in reactive oxygen species (ROS)-dependent necroptosis, LPS/zVAD-elicited ROS production was inhibited by necrostatin-1, neutralizing antibody of IFN receptor (IFNR) and JAK inhibitor AZD1480. Accordingly, both cell death and ROS production induced by TLR ligands plus zVAD were abrogated in STAT1 knockout macrophages. We conclude that enhanced TRIF-RIP1-dependent autocrine action of IFNβ, rather than inhibition of ERK or Akt, is involved in TLRs/zVAD-induced autophagic and necroptotic cell death via the JAK/STAT1/ROS pathway.

Oxidative Stress-Induced Growth Inhibitor (OSGIN1), a Target of X-Box-Binding Protein 1, Protects Palmitic Acid-Induced Vascular Lipotoxicity through Maintaining Autophagy

Saturated free fatty acids (FFAs) strongly correlate with metabolic syndromes and are well-known risk factors for cardiovascular diseases (CVDs). The mechanism of palmitic acid (PA)-induced vascular lipotoxicity under endoplasmic reticulum (ER) stress is unknown. In the present paper, we investigate the roles of spliced form of X-box-binding protein 1 (XBP1s) target gene oxidative stress-induced growth inhibitor 1 (OSGIN1) in PA-induced vascular dysfunction. PA inhibited the tube formation assay of primary human umbilical vein endothelial cells (HUVECs). Simultaneously, PA treatment induced the XBP1s expression in HUVECs. Attenuate the induction of XBP1s by silencing the XBP1s retarded cell migration and diminished endothelial nitric oxide synthase (eNOS) expression. OSGIN1 is a target gene of XBP1s under PA treatment. The silencing of OSGIN1 inhibits cell migration by decreasing phospho-eNOS expression. PA activated autophagy in endothelial cells, inhibiting autophagy by 3-methyladenine (3-MA) decreased endothelial cell migration. Silencing XBP1s and OSGIN1 would reduce the induction of LC3 II; therefore, OSGIN1 could maintain autophagy to preserve endothelial cell migration. In conclusion, PA treatment induced ER stress and activated the inositol-requiring enzyme 1 alpha–spliced XBP1 (IRE1α–XBP1s) pathway. OSGIN1, a target gene of XBP1s, could protect endothelial cells from vascular lipotoxicity by regulating autophagy.

Protection of Quiescence and Longevity of IgG Memory B Cells by Mitochondrial Autophagy

The development of long-lived immune memory cells against pathogens is critical for the success of vaccines to establish protection against future infections. However, the mechanisms governing the long-term survival of immune memory cells remain to be elucidated. In this article, we show that the maintenance mitochondrial homeostasis by autophagy is critical for restricting metabolic functions to protect IgG memory B cell survival. Knockout of mitochondrial autophagy genes, Nix and Bnip3, leads to mitochondrial accumulation and increases in oxidative phosphorylation and fatty acid synthesis, resulting in the loss of IgG⁺ memory B cells in mice. Inhibiting fatty acid synthesis or silencing necroptosis gene Ripk3 rescued Nix^-/-Bnip3^-/- IgG memory B cells, indicating that mitochondrial autophagy is important for limiting metabolic functions to prevent cell death. Our results suggest a critical role for mitochondrial autophagy in the maintenance of immunological memory by protecting the metabolic quiescence and longevity of memory B cells.

Palmitate impairs the autophagic flux to induce p62-dependent apoptosis through the upregulation of CYLD in NRCMs

The most abundant saturated free fatty acid such as palmitate (PA), can accumulate in cardiomyocytes and induce lipotoxicity. CYLD is a known regulator in the development of cardiovascular disease and an important mediator of apoptosis. The role of CYLD in PA-induced cardiomyocyte apoptosis is not completely known. Here, we showed that PA treatment resulted in a concentration- and time-dependent effect on neonatal rat cardiomyocytes (NRCMs) apoptosis. PA impaired autophagy by significantly increasing the expression levels of LC3-II, Beclin 1, and also p62 in NRCMs. The autophagy flux was measured by detecting the fluorescence in the cells with Ad-mCherry-GFP-LC3B, a decrease in red puncta and a significant increase in yellow puncta in response to PA stimulation indicated that PA impairs the autophagic flux at the late stage of autophagosome-lysosome fusion. We further found knocked down of p62 by siRNA significantly decreased the expression level of cleaved caspase-3, decreased the apoptosis rate, also alleviated the loss of mitochondrial membrane potential, and decreased AIF and Cyt C releasing from mitochondria into the cytoplasm in the PA-treated NRCMs. From this, we considered that p62 accumulation was responsible for mitochondria-mediated apoptosis in PA-treated NRCMs. In addition, PA-induced a strong elevation of CYLD, siRNA-mediated knockdown of CYLD significantly antagonized PA-induced apoptosis and restored the autophagic flux in NRCMs. Knockdown of CYLD activation of the Wnt/β-catenin pathway to restore the autophagic flux and reduce the accumulation of p62 in PA- stimulated NRCMs, while an inhibitor of the Wnt/β-catenin pathway reversed this effect. Thus, our findings provide new insight into the molecular mechanism of PA toxicity in myocardial cells and suggest that CYLD may be a new therapeutic target for lipotoxic cardiomyopathy.

Tetracationic porphyrin derivatives against human breast cancer

Photodynamic therapy (PDT) is an approved therapeutic approach and an alternative to conventional chemotherapy for the treatment of several types of cancer with the advantages of reducing the side effects and developing resistance mechanisms. Here, was evaluated the photosensitization capabilities of 5,10,15,20-tetrakis[4-(pyridinium-1-yl-methyl)phenyl]porphyrin (3), its N-confused isomer (4) and of the neutral precursors (1) and (2) and the results were compared with the ones obtained with the cationic 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP). Both regular porphyrin derivatives 1 and 3 showed higher efficiency to generate singlet oxygen than TMPyP. The PDT assays towards MCF-7 cells under red light irradiation (λ > 640 nm, 23.7 mW cm^-2) demonstrated that the cationic porphyrin 3 is an efficient photosensitizer to kill MCF-7 breast cancer cells. The study of the cell death mechanisms induced by the photodynamic process showed that the studied porphyrin 3 and TMPyP caused cell death by autophagic flux and necrosis.

Upregulation of hepatic autophagy under nutritional ketosis

Many of the metabolic effects evoked by the ketogenic diet mimic the actions of fasting and the benefits of the ketogenic diet are often attributed to these similarities. Since fasting is a potent autophagy inductor in vivo and in vitro it has been hypothesized that the ketogenic diet may upregulate autophagy. The aim of the present study was to provide a comprehensive evaluation of the influence of the ketogenic diet on the hepatic autophagy. C57BL/6N male mice were fed with two different ketogenic chows composed of fat of either animal or plant origin for 4 weeks. To gain some insight into the time frame for the induction of autophagy on the ketogenic diet, we performed a short-term experiment in which animals were fed with ketogenic diets for only 24 or 48 h. The results showed that autophagy is upregulated in the livers of animals fed with the ketogenic diet. Moreover, the size of the observed effect was likely dependent on the diet composition. Subsequently, the markers of regulatory pathways that may link ketogenic diet action to autophagy were measured, i.e., the activity of mTORC1, activation of AMPK, and the levels of SIRT1, p53, and FOXO3. Overall, observed treatment-specific effects including the upregulation of SIRT1 and downregulation of FOXO3 and p53. Finally, a GC/MS analysis of the fatty acid composition of animals' livers and the chows was performed in order to obtain an idea about the presence of specific compounds that may shape the effects of ketogenic diets on autophagy.

5-ALA Attenuates the Palmitic Acid-Induced ER Stress and Apoptosis in Bovine Mammary Epithelial Cells

The conservation of mammary gland physiology by maintaining the maximum number of mammary epithelial cells (MECs) is of the utmost importance for the optimum amount of milk production. In a state of negative energy balance, palmitic acid (PA) reduces the number of bovine MECs. However, there is no effective strategy against PA-induced apoptosis of MECs. In the present study, 5-aminolevulinic acid (5-ALA) was established as a remedial agent against PA-induced apoptosis of MAC-T cells (an established line of bovine MECs). In PA-treated cells, the apoptosis-related genes BCL2 and BAX were down- and upregulated, respectively. The elevated expression of major genes of the unfolded protein response (UPR), such as CHOP, a proapoptotic marker (C/EBP homologous protein), reduced the viability of PA-treated MAC-T cells. In contrast, 5-ALA pretreatment increased and decreased BCL2 and BAX expression, respectively. Moreover, cleaved caspase-3 protein expression was significantly reduced in the 5-ALA-pretreated group in comparison with the PA group. The downregulation of major UPR-related genes, including CHOP, extended the viability of MAC-T cells pretreated with 5-ALA and also reduced the enhanced intensity of the PA-induced expression of phospho-protein kinase R-like ER kinase. Moreover, the enhanced expression of HO-1 (antioxidant gene heme oxygenase) by 5-ALA reduced PA-induced oxidative stress (OxS). HO-1 is not only protective against OxS but also effective against ER stress. Collectively, these findings offer new insights into the protective effects of 5-ALA against PA-induced apoptosis of bovine MECs.

HSF1 functions as a key defender against palmitic acid-induced ferroptosis in cardiomyocytes

Palmitic acid (PA)-induced myocardial injury is considered a critical contributor to the development of obesity and type 2 diabetes mellitus (T2DM)-related cardiomyopathy. However, the underlying mechanism has not been fully understood. Here, we demonstrated that PA induced the cell death of H9c2 cardiomyoblasts in a dose- and time-dependent manner, while different ferroptosis inhibitors significantly abrogated the cell death of H9c2 cardiomyoblasts and primary neonatal rat cardiomyocytes exposed to PA. Mechanistically, PA decreased the protein expression levels of both heat shock factor 1 (HSF1) and glutathione peroxidase 4 (GPX4) in a dose- and time-dependent manner, which were restored by different ferroptosis inhibitors. Overexpression of HSF1 not only alleviated PA-induced cell death and lipid peroxidation but also improved disturbed iron homeostasis by regulating the transcription of iron metabolism-related genes (e.g., Fth1, Tfrc, Slc40a1). Additionally, PA-blocked GPX4 protein expression was evidently restored by HSF1 overexpression. Inhibition of endoplasmic reticulum (ER) stress rather than autophagy contributed to HSF1-mediated GPX4 expression. Moreover, GPX4 overexpression protected against PA-induced ferroptosis, whereas knockdown of GPX4 reversed the anti-ferroptotic effect of HSF1. Consistent with the in vitro findings, PA-challenged Hsf1-/- mice exhibited more serious ferroptosis, increased Slc40a1 and Fth1 mRNA expression, decreased GPX4 and TFRC expression and enhanced ER stress in the heart compared with Hsf1+/+ mice. Altogether, HSF1 may function as a key defender against PA-induced ferroptosis in cardiomyocytes by maintaining cellular iron homeostasis and GPX4 expression.

miR-155-5p alleviates ethanol-induced myocardial insulin resistance in H9C2 cells via regulating the mTOR signalling pathway

Alcohol exposure impairs myocardium insulin sensitivity, which links to heart dysfunction. miR-155 regulates mTOR signaling pathway and is involved in multiple functions. However, the underlying mechanism of miR-155 in ethanol-induced myocardial insulin resistance remains unclear. Here, in this study we aimed to identify the role of miR-155 in myocardial insulin sensitivity and the involvement of mTOR pathway. H9C2 cells were cultured with or without 100 mM ethanol for 24 h. miR-155-5p inhibitor, miR-155-5p mimics or their respective negative control (inhibitor NC and mimic NC) were transfected to regulate miR-155-5p expression. mTOR signaling, including Ras homolog enriched in brain (Rheb), rapamycin insensitive companion of mTOR (Rictor) and ribosomal protein S6 kinase B2 (S6K2), was investigated by western blotting and qPCR, and insulin responsiveness was evaluated by glucose uptake and phosphorylation of insulin receptor substrate-1 (p-IRS1). The miR-155-5p level increased under ethanol exposure, accompanied by a decrease in glucose uptake, an increase in p-IRS1(ser 307) and activation of the mTOR signaling pathway in H9C2 cells. In addition, miR-155-5p downregulation decreased the glucose uptake, increased the p-IRS1(ser 307) level and activated the mTOR signaling pathway. miR-155-5p upregulation increased the glucose uptake, decreased the p-IRS1(ser 307) level and suppressed the mTOR signaling pathway. Collectively, these findings suggest miR-155-5p upregulation ameliorates myocardial insulin resistance via mTOR signaling in vitro, and miR-155-5p downregulation attenuates myocardial insulin resistance, which might become a potential therapeutic target for alcohol-induced cardiomyopathy.

Upregulation of CFTR Protects against Palmitate-Induced Endothelial Dysfunction by Enhancing Autophagic Flux

Saturated free fatty acids (FFAs) elevate in metabolic symptom leading to endothelial dysfunction. Cystic fibrosis transmembrane regulator (CFTR) functionally expresses in endothelial cells. The role of CFTR in FFA-induced endothelial dysfunction remains unclear. This study is aimed at exploring the effects of CFTR on palmitate- (PA-) induced endothelial dysfunction and its underlying mechanisms. We found that PA-induced endothelial dysfunction is characterized by a decrease of cell viability, reduction of NO generation and mitochondrial membrane potential, impairment of the tube formation, but an increase of ROS generation and cell apoptosis. Simultaneously, PA decreased CFTR protein expression. CFTR agonist Forskolin upregulated CFTR protein expression and protected against PA-induced endothelial dysfunction, while CFTR knockdown exacerbated endothelial dysfunction induced by PA and blunted the protective effects of Forskolin. In addition, PA impaired autophagic flux, and autophagic flux inhibitors aggravated PA-induced endothelial apoptosis. CFTR upregulation significantly restored autophagic flux in PA-insulted endothelial cells, which was involved in increasing the protein expression of Atg16L, Atg12-Atg5 complex, cathepsin B, and cathepsin D. In contrast, CFTR knockdown significantly inhibited the effects of Forskolin on autophagic flux and the expression of the autophagy-regulated proteins. Our findings illustrate that CFTR upregulation protects against PA-induced endothelial dysfunction by improving autophagic flux and underlying mechanisms are involved in enhancing autophagic signaling mediated by the Atg16L-Atg12-Atg5 complex, cathepsin B, and cathepsin D. CFTR might serve as a novel drug target for endothelial protection in cardiovascular diseases with a characteristic of elevation of FFAs.

Interaction of TPPP3 with VDAC1 Promotes Endothelial Injury through Activation of Reactive Oxygen Species

Endothelial injury plays a critical role in the pathogenesis of cardiovascular disorders and metabolic-associated vascular complications which are the leading cause of death worldwide. However, the mechanism underlying endothelial dysfunction is not completely understood. The study is aimed at investigating the role of tubulin polymerization-promoting protein family member 3 (TPPP3) in palmitic acid- (PA-) induced endothelial injury. The effect of TPPP3 on human umbilical vein endothelial cells (HUVECs) was determined by evaluating apoptosis, tube formation, and reactive oxygen species (ROS) production. TPPP3 silencing inhibited PA overload-induced apoptosis and production of ROS, along with the alteration of apoptosis-related key proteins such as BCL-2 and Bax. Mechanically, voltage-dependent anion channel 1 (VDAC1) was identified as a novel functional binding partner of TPPP3, and TPPP3 promoted VDAC1 protein stability and its activity. Further studies indicated that TPPP3 could promote apoptosis, ROS production, tube formation, and proapoptotic protein expression and reduce antiapoptotic protein expression through increasing VDAC1 expression under mildly elevated levels of PA. Collectively, these results demonstrated that TPPP3 could promote PA-induced oxidative damage in HUVECs via a VDAC1-dependent pathway, suggesting that TPPP3 might be considered as a potential therapeutic target in vascular disease.

The Underlying Role of Mitophagy in Different Regulatory Mechanisms of Chronic Obstructive Pulmonary Disease

COPD is a common disease of the respiratory system. Inflammation, cellular senescence and necroptosis are all pathological alterations of this disease, which may lead to emphysema and infection that aggravate disease progression. Mitochondria acting as respiration-related organelles is usually observed with abnormal changes in morphology and function in CS-stimulated models and COPD patients. Damaged mitochondria can activate mitophagy, a vital mechanism for mitochondrial quality control, whereas under the persistent stimulus of CS or other forms of oxidative stress, mitophagy is impaired, resulting in insufficient clearance of damaged mitochondria. However, the excessive activation of mitophagy also seems to disturb the pathology of COPD. In this review, we demonstrate the variations in mitochondria and mitophagy in CS-induced models and COPD patients and discuss the underlying regulatory mechanism of mitophagy and COPD, including the roles of inflammation, senescence, emphysema and infection.

CYLD exaggerates pressure overload-induced cardiomyopathy via suppressing autolysosome efflux in cardiomyocytes

Deubiquitinating enzymes (DUBs) appear to be a new class of regulators of cardiac homeostasis and disease. However, DUB-mediated signaling in the heart is not well understood. Herein we report a novel mechanism by which cylindromatosis (CYLD), a DUB mediates cardiac pathological remodeling and dysfunction. Cardiomyocyte-restricted (CR) overexpression of CYLD (CR-CYLD) did not cause gross health issues and hardly affected cardiac function up to age of one year in both female and male mice at physiological conditions. However, CR-CYLD overexpression exacerbated pressure overload (PO)-induced cardiac dysfunction associated with suppressed cardiac hypertrophy and increased myocardial apoptosis in mice independent of the gender. At the molecular level, CR-CYLD overexpression enhanced PO-induced increases in poly-ubiquitinated proteins marked by lysine (K)48-linked ubiquitin chains and autophagic vacuoles containing undegraded contents while suppressing autophagic flux. Augmentation of cardiac autophagy via CR-ATG7 overexpression protected against PO-induced cardiac pathological remodeling and dysfunction in both female and male mice. Intriguingly, CR-CYLD overexpression switched the CR-ATG7 overexpression-dependent cardiac protection into myocardial damage and dysfunction associated with increased accumulation of autophagic vacuoles containing undegraded contents in the heart. Genetic manipulation of Cyld in combination with pharmacological modulation of autophagic functional status revealed that CYLD suppressed autolysosomal degradation and promoted cell death in cardiomyocytes. In addition, Cyld gene gain- and/or loss-of-function approaches in vitro and in vivo demonstrated that CYLD mediated cardiomyocyte death associated with impaired reactivation of mechanistic target of rapamycin complex 1 (mTORC1) and upregulated Ras genes from rat brain 7 (Rab7), two key components for autolysosomal degradation. These results demonstrate that CYLD serves as a novel mediator of cardiac pathological remodeling and dysfunction by suppressing autolysosome efflux in cardiomyocytes. Mechanistically, it is most likely that CYLD suppresses autolysosome efflux via impairing mTORC1 reactivation and interrupting Rab7 release from autolysosomes in cardiomyocytes.

Emerging roles of ATG proteins and membrane lipids in autophagosome formation

Autophagosome biogenesis is a dynamic membrane event, which is executed by the sequential function of autophagy-related (ATG) proteins. Upon autophagy induction, a cup-shaped membrane structure appears in the cytoplasm, then elongates sequestering cytoplasmic materials, and finally forms a closed double membrane autophagosome. However, how this complex vesicle formation event is strictly controlled and achieved is still enigmatic. Recently, there is accumulating evidence showing that some ATG proteins have the ability to directly interact with membranes, transfer lipids between membranes and regulate lipid metabolism. A novel role for various membrane lipids in autophagosome formation is also emerging. Here, we highlight past and recent key findings on the function of ATG proteins related to autophagosome biogenesis and consider how ATG proteins control this dynamic membrane formation event to organize the autophagosome by collaborating with membrane lipids.

GPAT4-Generated Saturated LPAs Induce Lipotoxicity through Inhibition of Autophagy by Abnormal Formation of Omegasomes

Excessive levels of saturated fatty acids are toxic to vascular smooth muscle cells (VSMCs). We previously reported that mice lacking VSMC-stearoyl-CoA desaturase (SCD), a major enzyme catalyzing the detoxification of saturated fatty acids, develop severe vascular calcification from the massive accumulation of lipid metabolites containing saturated fatty acids. However, the mechanism by which SCD deficiency causes vascular calcification is not completely understood. Here, we demonstrate that saturated fatty acids significantly inhibit autophagic flux in VSMCs, contributing to vascular calcification and apoptosis. Mechanistically, saturated fatty acids are accumulated as saturated lysophosphatidic acids (LPAs) (i.e. 1-stearoyl-LPA) possibly synthesized through the reaction of GPAT4 at the contact site between omegasomes and the MAM. The accumulation of saturated LPAs at the contact site causes abnormal formation of omegasomes, resulting in accumulation of autophagosomal precursor isolation membranes, leading to inhibition of autophagic flux. Thus, saturated LPAs are major metabolites mediating autophagy inhibition and vascular calcification.

Protective effects of phenolic acid extract from ginseng on vascular endothelial cell injury induced by palmitate via activation of PI3K/Akt/eNOS pathway

Elevated free fatty acids may impair insulin-mediated signaling to eNOS that contributes to the pathophysiology of endothelial dysfunction. Previous studies have indicated the protective effect of ginseng and the regulatory potential of phenolic acid components from other plants on endothelial function. Therefore, this study investigated the protective effects of phenolic acid extract from ginseng (PG2) on endothelial cells against palmitate-induced damage. We found that PG2 increases cell viability, inhibits the palmitate-induced intracellular accumulation of lipids, and the overexpression of endothelin-1 (ET-1) through enhancing the phosphorylation of the phosphatidylinositol 3-kinase/Akt/endothelial nitric oxide synthase (PI3K/Akt/eNOS) signaling pathway. The results of this study may be valuable for the development of PG2 to combat the endothelial cell damage caused by hyperlipidemia. PRACTICAL APPLICATION: We proved that phenolic acid extract from ginseng has a protective effect on free fatty acid-induced endothelial dysfunction in vitro. This study provides experimental data for the application of ginseng-derived phenolic acids in treating cardiovascular disease.

The novel proautophagy anticancer drug ABTL0812 potentiates chemotherapy in adenocarcinoma and squamous nonsmall cell lung cancer

Around 40% of newly diagnosed lung cancer patients are Stage IV, where the improvement of survival and reduction of disease-related adverse events is the main goal for oncologists. In this scenario, we present preclinical evidence supporting the use of ABTL0812 in combination with chemotherapy for treating advanced and metastatic Nonsmall cell lung adenocarcinomas (NSCLC) and squamous carcinomas. ABTL0812 is a new chemical entity, currently in Phase 1b/2a clinical trial for advanced squamous NSCLC in combination with paclitaxel and carboplatin (P/C), after successfully completing the first-in-human trial where it showed an excellent safety profile and signs of efficacy. We show here that ABTL0812 inhibits Akt/mTOR axis by inducing the overexpression of TRIB3 and activating autophagy in lung squamous carcinoma cell lines. Furthermore, treatment with ABTL0812 also induces AMPK activation and ROS accumulation. Moreover, combination of ABTL0812 with chemotherapy markedly increases the therapeutic effect of chemotherapy without increasing toxicity. We further show that combination of ABTL0812 and chemotherapy induces nonapoptotic cell death mediated by TRIB3 activation and autophagy induction. We also present preliminary clinical data indicating that TRIB3 could serve as a potential novel pharmacodynamic biomarker to monitor ABTL0812 activity administered alone or in combination with chemotherapy in squamous NSCLC patients. The safety profile of ABTL0812 and its good synergy with chemotherapy potentiate the therapeutic potential of current lines of treatment based on chemotherapy regimens, arising as a promising option for improving these patients therapeutic expectancy.

Ischemia and Reperfusion Injury in Kidney Transplantation: Relevant Mechanisms in Injury and Repair

Ischemia and reperfusion injury (IRI) is a complex pathophysiological phenomenon, inevitable in kidney transplantation and one of the most important mechanisms for non- or delayed function immediately after transplantation. Long term, it is associated with acute rejection and chronic graft dysfunction due to interstitial fibrosis and tubular atrophy. Recently, more insight has been gained in the underlying molecular pathways and signalling cascades involved, which opens the door to new therapeutic opportunities aiming to reduce IRI and improve graft survival. This review systemically discusses the specific molecular pathways involved in the pathophysiology of IRI and highlights new therapeutic strategies targeting these pathways.

Autophagy Function and Regulation in Kidney Disease

Autophagy is a dynamic process by which intracellular damaged macromolecules and organelles are degraded and recycled for the synthesis of new cellular components. Basal autophagy in the kidney acts as a quality control system and is vital for cellular metabolic and organelle homeostasis. Under pathological conditions, autophagy facilitates cellular adaptation; however, activation of autophagy in response to renal injury may be insufficient to provide protection, especially under dysregulated conditions. Kidney-specific deletion of Atg genes in mice has consistently demonstrated worsened acute kidney injury (AKI) outcomes supporting the notion of a pro-survival role of autophagy. Recent studies have also begun to unfold the role of autophagy in progressive renal disease and subsequent fibrosis. Autophagy also influences tubular cell death in renal injury. In this review, we reported the current understanding of autophagy regulation and its role in the pathogenesis of renal injury. In particular, the classic mammalian target of rapamycin (mTOR)-dependent signaling pathway and other mTOR-independent alternative signaling pathways of autophagy regulation were described. Finally, we summarized the impact of autophagy activation on different forms of cell death, including apoptosis and regulated necrosis, associated with the pathophysiology of renal injury. Understanding the regulatory mechanisms of autophagy would identify important targets for therapeutic approaches.

Integrated metabolomics and network toxicology to reveal molecular mechanism of celastrol induced cardiotoxicity

Celastrol (CS), an active triterpene derived from traditional Chinese medicine Tripterygium wilfordii Hook. f, has been used to treat chronic inflammation, arthritis and other diseases. However, it has been reported that CS can trigger cardiotoxicity and the molecular mechanism of heart injury induced by CS is not clear. Considering the wide application of Tripterygium wilfordii Hook. f in clinics, it is necessary to develop an accurate and reliable method to assess the safety of CS, and to elucidate as much as possible the mechanism of cardiotoxicity induced by CS. In this study, Ultra-performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC-Q-TOF/MS)-based metabolomics revealed clues to the mechanism of CS-induced heart injury. Palmitic acid significantly increased in plasma from CS-treated rats, and this increase resulted in oxidative stress response in vivo. Excessive ROS further activate TNF signaling pathway and caspase family, which were obtained from the KEGG enrichment analysis of network toxicology strategy. Protein expression level of caspase-3, caspase-8, bax were significantly increased by western blot. Q-PCR also showed the similar results as western blot. It means that apoptosis plays a key role in the process of celastrol induced cardiotoxicity. Blocking this signal axis may be a potential way to protect myocardial tissue.

Cell Death Mechanisms in Esophageal Squamous Cell Carcinoma Induced by Vesicular Stomatitis Virus Matrix Protein

Objectives

Vesicular stomatitis virus (VSV) is under development as an oncolytic virus due to its preferential replication in cancer cells and oncolytic activity, however the viral components responsible have not yet been determined. In this study the effects of VSV wild-type (wt) and M51R-mutant matrix proteins (M51R-mMP) on apoptosis, pyroptosis, necroptosis, and autophagy pathways, in an esophagus cancer cell line (KYSE-30) were investigated.

Methods

The KYSE-30 cells were transfected with pcDNA3.1 plasmids encoding wt or M51R-mMP, and apoptosis, pyroptosis, necroptosis, and autophagy were evaluated 48 and 72 hours after transfection.

Results

KYSE-30 cells transfected with VSV wt and M51R-mMPs significantly reduced cell viability to < 50% at 72 hours post-transfection. M51R-MP significantly increased the concentration of caspase-8 and caspase-9 at 48 and 72 hours post-transfection, respectively ( p < 0.05). In contrast, no significant changes were detected following transfection with the VSV wt plasmid. Moreover, VSV wt and M51R-mMP transfected cells did not change the expression of caspase-3. VSV wt and M51R-mMPs did not mMP change caspase-1 expression (a marker of pyroptosis) at 48 and 72 hours post-transfection. However, M51R-mMP and VSV wt transfected cells significantly increased RIP-1 (a marker of necroptosis) expression at 72 hours post-infection ( p < 0.05). Beclin-1, a biomarker of autophagy, was also induced by transfection with VSV wt or M51R-mMPs at 48 hours post-transfection.

Conclusion

The results in this study indicated that VSV exerts oncolytic activity in KYSE-30 tumor cells through different cell death pathways, suggesting that M51R-mMP may potentially be used to enhance oncolysis.

Oxidative stress induced by palmitic acid modulates KCa2.3 channels in vascular endothelium

Elevated plasma free fatty acids level has been implicated in the development of insulin resistance, inflammation, and endothelial dysfunction in diabetic and nondiabetic individuals. However, the underlying mechanisms still remain to be defined. Herein, we investigated the effect of palmitic acid (PA), the most abundant saturated fatty acid in the human body, on small-conductance Ca²⁺-activated potassium channels (K_Ca2.3)-mediated relaxation in rodent resistance arteries and the underlying molecular mechanism. The effect of PA on K_Ca2.3 in endothelium was evaluated using real-time PCR, Western blotting, whole-cell patch voltage-clamp, wire and pressure myograph system, and reactive oxygen species (ROS) were measured by using dihydroethidium and 2', 7'-dichlorofluorescein diacetate. K_Ca2.3-mediated vasodilatation responses to acetylcholine and NS309 (agonist of K_Ca2.3 and K_Ca3.1) were impaired by incubation of normal mesenteric arteries with 100 μM PA for 24 h. In cultured human umbilical vein endothelial cells (HUVECs), PA decreased K_Ca2.3 current and expression at mRNA and protein levels. Incubation with the NADPH oxidase (Nox) inhibitor dibenziodolium (DPI) partly inhibited the PA-induced ROS production and restored K_Ca2.3 expression. Inhibition of either p38-MAPK or NF-κB using specific inhibitors (SB203580, SB202190 or Bay11-7082, pyrrolidinedithiocarbamate) attenuated PA-induced downregulation of K_Ca2.3 and inhibition of p38-MAPK also attenuated PA-induced phosphorylation of NF-κB p65. Furthermore, DPI reversed the increment of phospho-p38-MAPK by PA. These results demonstrated that PA downregulated K_Ca2.3 expressions via Nox/ROS/p38-MAPK/NF-κB signaling leading to endothelial vasodilatory dysfunction.

Hydrogen Sulfide Gas Exposure Induces Necroptosis and Promotes Inflammation through the MAPK/NF-κB Pathway in Broiler Spleen

Hydrogen sulfide (H2S) is one of the main pollutants in the atmosphere, which is a serious threat to human health. The decomposition of sulfur-containing organics in chicken houses could produce a large amount of H2S, thereby damaging poultry health. In this study, one-day-old broilers were selected and exposed to 4 or 20 ppm of H2S gas (0-3 weeks: 4 ± 0.5 ppm, 4-6 weeks: 20 ± 0.5 ppm). The spleen samples were collected immediately after the chickens were euthanized at 2, 4, and 6 weeks. The histopathological and ultrastructural observations showed obvious necrosis characteristics of H2S-exposed spleens. H2S exposure suppressed GSH, CAT, T-AOC, and SOD activities; increased NO, H2O2, and MDA content and iNOS activity; and induced oxidative stress. ATPase activities and the expressions of energy metabolism-related genes were significantly decreased. Also, the expressions of related necroptosis (RIPK1, RIPK3, MLKL, TAK1, TAB2, and TAB3) were significantly increased, and the MAPK pathway was activated. Besides, H2S exposure activated the NF-κB classical pathway and induced TNF-α and IL-1β release. Taken together, we conclude that H2S exposure induces oxidative stress and energy metabolism dysfunction; evokes necroptosis; activates the MAPK pathway, eventually triggering the NF-κB pathway; and promotes inflammatory response in chicken spleens.

Lipotoxicty in yeast: a focus on plasma membrane signalling and membrane contact sites

Lipotoxicity is a pathophysiological process triggered by lipid overload. In metazoans, lipotoxicity is characterised by the ectopic deposition of lipids on organs other than adipose tissue. This leads to organ dysfunction, cell death, and is intimately linked to lipid-associated diseases such as cardiac dysfunction, atherosclerosis, stroke, hepatosteatosis, cancer and the metabolic syndrome. The molecules involved in eliciting lipotoxicity include FAs and their acyl-CoA derivatives, triacylglycerol (TG), diacylglycerol (DG), ceramides, acyl-carnitines and phospholipids. However, the cellular transport of toxic lipids through membrane contact sites (MCS) and vesicular mechanisms as well as lipid metabolism that progress lipotoxicity to the onset of disease are not entirely understood. Yeast has proven a useful model organism to study the molecular mechanisms of lipotoxicity. Recently, the Rim101 pathway, which senses alkaline pH and the lipid status at the plasmamembrane, has been connected to lipotoxicity. In this review article, we summarise recent research advances on the Rim101 pathway and MCS in the context of lipotoxicity in yeast and present a perspective for future research directions.

Palmitic acid-induced autophagy increases reactive oxygen species via the Ca2+/PKCα/NOX4 pathway and impairs endothelial function in human umbilical vein endothelial cells

It is well known that the lipotoxic mechanism of palmitic acid (PA), a main constituent of triglyceride, is dependent on reactive oxygen species (ROS). Recently, it has also been reported that PA is an autophagy inducer. However, the causal association and underlying mechanism of induced autophagy and ROS in PA toxicity remain unclear. The present study demonstrates for the first time that PA-induced autophagy enhances ROS generation via activating the calcium ion/protein kinase Cα/nicotinamide adenine dinucleotide phosphate oxidase 4 (Ca²⁺/PKCα/NOX4) pathway in human umbilical vein endothelial cells (HUVECs). It was revealed that PA treatment resulted in a significant increase in ROS generation and autophagic activity, leading to endothelial dysfunction as indicated by downregulated nitric oxide synthesis, decreased capillary-like structure formation and damaged cell repair capability. Furthermore, PA effectively activated the Ca²⁺/PKCα/NOX4 pathway, which is indicative of upregulated cytosolic Ca²⁺ levels, activated PKCα and increased NOX4 protein expression. 3-Methyladenine was then used to inhibit autophagy, which significantly reduced PA-induced ROS generation and blocked the Ca²⁺/PKCα/NOX4 pathway. The endothelial dysfunction caused by PA was ameliorated by downregulating ROS generation using a NOX4 inhibitor. In conclusion, PA-induced autophagy contributes to endothelial dysfunction by increasing oxidative stress via the Ca²⁺/PKCα/NOX4 pathway in HUVECs.

Inhibition of acid‑sensing ion channel 1a attenuates acid‑induced activation of autophagy via a calcium signaling pathway in articular chondrocytes

Acid-sensing ion channel 1a (ASIC1a), member of the degenerin/epithelial sodium channel protein superfamily, serves a critical role in various physiological and pathological processes. The aim of the present study was to examine the role of ASIC1a in the autophagy of rat articular chondrocytes. Autophagy was induced by acidic stimulation in rat articular chondrocytes and the extent of autophagy was evaluated via the expression levels of microtubule-associated protein 1 light chain 3II, Beclin1 and uncoordinated-51 like kinase1. Suppression of ASIC1a was achieved using small interfering RNA technology and/or inhibitor psalmotoxin-1. The expression levels of autophagy markers were measured by western blot analysis and reverse transcription-quantitative polymerase chain reaction methods. Intracellular calcium ([Ca²⁺]_i) was analyzed using a Ca²⁺-imaging method. Additionally, protein expression levels of the Ca²⁺/calmodulin-dependent protein kinase kinase β (CaMKKβ)/5′-monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathway were measured by western blot analysis. The results showed that autophagy was increased in a pH-and time-dependent manner with exposure to an acidic environment. In addition, silencing ASIC1a significantly decreased the expression levels of autophagy makers, accompanied by abrogation of the acid-induced [Ca²⁺]_i increase. Furthermore, silencing of ASIC1a downregulated the levels of CaMKKβ/β-actin and phosphorylated (p-) AMPK/AMPK, and upregulated the levels of p-mTOR/mTOR. These results indicated that ASIC1a is a potent regulator of autophagy in chondrocytes, which may be associated with decreased Ca²⁺ influx and the CaMKKβ/AMPK/mTOR pathway.

Autophagy in endothelial cells and tumor angiogenesis

In mammalian cells, autophagy is the major pathway for the degradation and recycling of obsolete and potentially noxious cytoplasmic materials, including proteins, lipids, and whole organelles, through the lysosomes. Autophagy maintains cellular and tissue homeostasis and provides a mechanism to adapt to extracellular cues and metabolic stressors. Emerging evidence unravels a critical function of autophagy in endothelial cells (ECs), the major components of the blood vasculature, which delivers nutrients and oxygen to the parenchymal tissue. EC-intrinsic autophagy modulates the response of ECs to various metabolic stressors and has a fundamental role in redox homeostasis and EC plasticity. In recent years moreover, genetic evidence suggests that autophagy regulates pathological angiogenesis, a hallmark of solid tumors. In the hypoxic, nutrient-deprived, and pro-angiogenic tumor microenvironment, heightened autophagy in the blood vessels is emerging as a critical mechanism enabling ECs to dynamically accommodate their higher bioenergetics demands to the extracellular environment and connect with other components of the tumor stroma through paracrine signaling. In this review, we provide an overview of the major cellular mechanisms regulated by autophagy in ECs and discuss their potential role in tumor angiogenesis, tumor growth, and response to anticancer therapy.

Vascular homeostasis relies on the proper behavior of endothelial cells (ECs). Emerging evidence indicate a critical role of autophagy, a vesicular process for lysosomal degradation of cytoplasmic content, in EC biology. While EC-intrinsic autophagy promotes EC function and quiescent state through redox homeostasis and possibly metabolic control, a role for EC-associated autophagy in cancer seems more complex.