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

Saturated phosphatidic acids induce mTORC1-driven integrated stress response contributing to glucolipotoxicity in hepatocytes

Hepatic glucolipotoxicity, characterized by the synergistic detrimental effects of elevated glucose levels combined with excessive lipid accumulation in hepatocytes, plays a central role in the pathogenesis of various metabolic liver diseases. Despite recent advancements, the precise mechanisms underlying this process remain unclear. Using cultured AML12 and HepG2 cells exposed to excess palmitate, with and without high glucose, as an in vitro model, we aimed to elucidate the cellular and molecular mechanisms underlying hepatic glucolipotoxicity. Our data showed that palmitate exposure induced the integrated stress response (ISR) in hepatocytes, evidenced by increased eukaryotic translation initiation factor 2 alpha (eIF2α) phosphorylation (serine 51) and upregulated activating transcription factor 4 (ATF4) expression. Moreover, we identified mammalian target of rapamycin complex 1 (mTORC1) as a novel upstream kinase responsible for palmitate-triggered ISR induction. Furthermore, we showed that either mTORC1 inhibitors, ISRIB (an ISR inhibitor), or ATF4 knockdown abolished palmitate-induced cell death, indicating that the mTORC1-eIF2α-ATF4 pathway activation plays a mechanistic role in mediating palmitate-induced hepatocyte cell death. Our continuous investigations revealed that glycerol-3-phosphate acyltransferase (GPAT4)-mediated metabolic flux of palmitate into the glycerolipid synthesis pathway is required for palmitate-induced mTORC1 activation and subsequent ISR induction. Specifically, we uncovered that saturated phosphatidic acid production contributes to palmitate-triggered mTORC1 activation. Our study provides the first evidence that high glucose enhances palmitate-induced activation of the mTORC1-eIF2α-ATF4 pathway, thereby exacerbating palmitate-induced hepatotoxicity. This effect is mediated by the increased availability of glycerol-3-phosphate, a substrate essential for phosphatidic acid synthesis. In conclusion, our study highlights that the activation of the mTORC1-eIF2α-ATF4 pathway, driven by saturated phosphatidic acid overproduction, plays a mechanistic role in hepatic glucolipotoxicity.NEW & NOTEWORTHY Integrated stress response (ISR) activation contributes to palmitate-induced lipotoxicity in hepatocytes. mTORC1 acts as an upstream kinase essential for palmitate-mediated ISR activation and hepatocyte death. The formation of saturated phosphatidic acid mechanistically regulates hepatic mTORC1 activation induced by palmitate. Glucose-enhanced generation of saturated phosphatidic acid amplifies palmitate-induced hepatotoxicity, contributing to glucolipotoxicity.

Autophagy and endoplasmic reticulum stress-related protein homeostasis links palmitic acid to hepatic lipotoxicity in zebrafish (Danio rerio), counteracted by linoleic acid

Saturated fatty acids (SFAs) are the primary contributors to hepatic lipotoxic injuries accompanied by the accumulation of hepatic insoluble protein inclusions that are composed of ubiquitinated proteins and p62, but the role of these inclusions in the SFA-induced hepatic lipotoxic injuries and their regulatory mechanisms are incompletely understood. In this study, we demonstrated that palmitic acid (PA), a dietary SFA, induced aberrant accumulation of hepatic insoluble protein inclusions, leading to hepatic lipotoxic injuries in zebrafish. Mechanistically, the accumulation of hepatic insoluble protein inclusions and the subsequent lipotoxic injuries induced by PA were attributed to reduced autophagy activity and increased endoplasmic reticulum (ER) stress. In addition, the upregulation of p62 by the ER stress response factor XBP1s and ATF4 further exacerbated PA-induced accumulation of hepatic insoluble protein inclusions and subsequent lipotoxic injuries. Importantly, the ω-6 PUFA linoleic acid (LA) attenuated PA-induced accumulation of hepatic insoluble protein inclusions and subsequent lipotoxic injuries by improving defective autophagy and reducing ER stress induced by PA. Overall, the present study provides new mechanisms by which SFAs and ω-6 PUFA influence hepatic lipotoxic injuries. These findings not only advance the understanding of hepatic lipotoxic injuries induced by SFAs, but also provide new insights for optimizing the rational substitution of fish oil by vegetable oils in aquaculture and the balance of fatty acid intake in human diets.

Synthesis of Autotaxin-Inhibiting Lipid Nanoparticles to Regulate Autophagy and Inflammatory Responses in Activated Macrophages

BACKGROUND

Autotaxin (ATX), an ENPP2 enzyme, regulates lipid signaling by converting lysophosphatidylcholine to lysophosphatidic acid (LPA). Dysregulation of the ATX/LPA axis promotes inflammation and disease progression. BMP-22, a lipid ATX inhibitor, effectively reduces LPA production. However, its clinical utility is hampered by limitations in solubility and pharmacokinetics. To overcome these limitations, we developed BMP-22-incorporated lipid nanoparticles (LNP-BMP) to improve utility while maintaining ATX inhibition efficacy.

METHODS

LNP-BMP was synthesized by incorporating DOTAP, DOPE, cholesterol, 18:0 PEG2000-PE, and together with BMP-22. The formulation of LNP-BMP was optimized and characterized by testing different molar ratios of BMP-22. The autophagy recovery and anti-inflammatory effects of LNP-BMP via ATX inhibition were evaluated in both macrophage cell line and mouse-derived primary macrophages.

RESULTS

LNP-BMP was shown to retain its functionality as an ATX inhibitor and maintain the physical characteristics upon BMP-22 integration. Synthesized LNP-BMP exerted superior ability to inhibit ATX activity. When applied to M1-induced macrophages, LNP-BMP exhibited substantial anti-inflammatory effects and successfully restored autophagy activity.

CONCLUSION

The results demonstrate that LNP-BMP effectively inhibits ATX, achieving both anti-inflammatory effects and autophagy restoration, highlighting its potential as a standalone immunotherapeutic agent. Furthermore, the capacity to load therapeutic drugs into this formulation offers promising opportunities for further therapeutic strategies.

Rapamycin induced autophagy enhances lipid breakdown and ameliorates lipotoxicity in Atlantic salmon cells

Autophagy is a highly conserved cellular recycling process essential for homeostasis in all eukaryotic cells. Lipid accumulation and its regulation by autophagy are key areas of research for understanding metabolic disorders in human and model mammals. However, the role of autophagy in lipid regulation remains poorly characterized in non-model fish species of importance to food production, which could be important for managing health and welfare in aquaculture. Addressing this knowledge gap, we investigate the role of autophagy in lipid regulation using a macrophage-like cell line (SHK-1) from Atlantic salmon (Salmo salar L.), the world's most commercially valuable farmed finfish. Multiple lines of experimental evidence reveal that the autophagic pathway responsible for lipid droplet breakdown is conserved in Atlantic salmon cells. We employed global lipidomics and proteomics analyses on SHK-1 cells subjected to lipid overload, followed by treatment with rapamycin to induce autophagy. This revealed that activating autophagy via rapamycin enhances storage of unsaturated triacylglycerols and suppresses key lipogenic proteins, including fatty acid elongase 6, fatty acid binding protein 2 and acid sphingomyelinase. Moreover, fatty acid elongase 6 and fatty acid binding protein 2 were identified as possible cargo for autophagosomes, suggesting a critical role for autophagy in lipid metabolism in fish. Together, this study establishes a novel model of lipotoxicity and advances understanding of lipid autophagy in fish cells, with significant implications for addressing fish health issues in aquaculture.

Tetrahydropalmatine promotes macrophage autophagy by inhibiting the AMPK/mTOR pathway to attenuate atherosclerosis

BACKGROUND

Atherosclerosis (AS) is a chronic progressive arterial disease that is associated with macrophage autophagy and AMP-activated protein kinase (AMPK)/mechanistic target of the rapamycin (mTOR) pathway. Tetrahydropalmatine (THP) can activate AMPK-dependent autophagy. We aim to study the mechanism of macrophage autophagy mediated by THP in the treatment of AS via the AMPK/mTOR pathway.

METHODS

High-fat diet apolipoprotein E-deficient mice and ox-LDL-induced RAW264.7 cells were used to mimic the AS model, then THP was administered. Cell viability was detected by MTT. Pathological aorta lesions were detected using Hematoxylin and Eosin, Masson, and oil red staining. Lipid metabolism indices and inflammatory factors were measured using ELISA. A transmission electron microscope was used to observe autophagosomes. Autophagy and AMPK/mTOR pathway protein expression was detected by immunofluorescence and Western blot. The AMPK inhibitor 9-β-d-Arabinofuranosyl Adenine (Ara-A) was used to validate the effect of THP. The mRNA expression of Beclin-1 and MCP-1 was detected by q-PCR.

RESULTS

THP administration regulated lipid metabolism by lowering total cholesterol, triacylglycerol, low-density lipoprotein, and high-density lipoprotein levels, and suppressed aortic damage. THP suppressed aortic damage and regulated lipid metabolism by altering serum lipid levels. THP reduced inflammation and macrophage CD68 expression. Twenty μg/mL THP reduced cell viability. THP decreased cholesterol uptake and increased efflux, promoting autophagy. THP increased autophagosome number, LC3B expression, and autophagy markers p-AMPK/AMPK and LC3-II/LC3-I. THP also decreased p-mTOR/mTOR and P62. THP increased Beclin-1 mRNA expression and decreased MCP-1 mRNA expression. Ara-A reversed THP's effects.

CONCLUSION

THP promotes macrophage autophagy by inhibiting the AMPK/mTOR pathway to attenuate AS.

Autophagy dysfunction links palmitic acid with macrophage inflammatory responses in large yellow croaker (Larimichthys crocea)

Autophagy is a cellular degradation process reliant on lysosome, crucial for preserving intracellular homeostasis. The key saturated fatty acid palmitic acid (PA) has been demonstrated to exert regulatory effects on autophagic activity in mammals. However, the precise impact of PA on autophagy and its role in fish remains incompletely understood. Thus, this study aimed to investigate the regulation of PA on autophagy and explore the role of autophagy in inflammatory responses triggered by PA in the head kidney macrophages of large yellow croaker. This study indicates that PA exposure can inhibit macrophage autophagy by reducing the expression of genes related to autophagy (e.g., beclin1, ulk1, and lc3), activating the negative regulator mTORC1 signaling pathway (p70S6K and S6), and hindering autophagic flux. This effect was observed to be amplified with increasing exposure time and concentration of PA. Similarly to the in vitro results, the palm oil (PO) diet significantly reduced autophagic activity in the head kidney of the croaker in vivo. Subsequent studies demonstrated that restoring autophagy led to a notable reduction in the expression of PA and PO-induced pro-inflammatory genes (il-1β, il-6, tnf-α, and cox-2), the activation of the MAPK signaling pathway (p38 and JNK), and the NLRP3 inflammasome levels, both in vitro and in vivo. In contrast, further inhibition of autophagy produced the opposite effect in vitro. In conclusion, this study demonstrates that PA exerts a dynamic inhibitory effect on autophagy in the head kidney macrophage, which in turn promotes PA-induced inflammatory responses. These findings provide valuable insights into how PA influences autophagy and inflammatory responses in fish immune cells, contributing to the theoretical framework for improving the use of vegetable oils in aquaculture.

Identification and validation of mitochondrial endoplasmic reticulum membrane-related genes in atherosclerosis

The mitochondria-associated endoplasmic reticulum membrane is implicated in atherosclerosis (AS). However, its precise molecular mechanisms remain undefined. This study identified KLRC1 and SOCS2 as key protective genes against AS through transcriptomic analysis integrated with Mendelian randomization. Both genes exhibited significantly reduced expression in the AS group. Immune infiltration analysis revealed a strong positive correlation between activated CD8+ T cells and these genes, while eosinophils displayed the most pronounced negative correlation with KLRC1, and regulatory T cells exhibited the strongest negative association with SOCS2. Notably, SOCS2 emerged as a pivotal protective factor, offering novel insights into AS pathogenesis and providing a robust theoretical foundation for early diagnosis and potential therapeutic strategies.

Dialogue between mitochondria and endoplasmic reticulum-potential therapeutic targets for age-related cardiovascular diseases

Mitochondria-associated endoplasmic reticulum membranes (MAMs) act as physical membrane contact sites facilitating material exchange and signal transmission between mitochondria and endoplasmic reticulum (ER), thereby regulating processes such as Ca2+/lipid transport, mitochondrial dynamics, autophagy, ER stress, inflammation, and apoptosis, among other pathological mechanisms. Emerging evidence underscores the pivotal role of MAMs in cardiovascular diseases (CVDs), particularly in aging-related pathologies. Aging significantly influences the structure and function of the heart and the arterial system, possibly due to the accumulation of reactive oxygen species (ROS) resulting from reduced antioxidant capacity and the age-related decline in organelle function, including mitochondria. Therefore, this paper begins by describing the composition, structure, and function of MAMs, followed by an exploration of the degenerative changes in MAMs and the cardiovascular system during aging. Subsequently, it discusses the regulatory pathways and approaches targeting MAMs in aging-related CVDs, to provide novel treatment strategies for managing CVDs in aging populations.

Activation of the IKK2/NF-κB pathway in VSMCs inhibits calcified vascular stiffness in CKD

IKK2/NF-κB pathway-mediated inflammation in vascular smooth muscle cells (VSMCs) has been proposed to be an etiologic factor in medial calcification and stiffness. However, the role of the IKK2/NF-κB pathway in medial calcification remains to be elucidated. In this study, we found that chronic kidney disease (CKD) induces inflammatory pathways through the local activation of the IKK2/NF-κB pathway in VMSCs associated with calcified vascular stiffness. Despite reducing the expression of inflammatory mediators, complete inhibition of the IKK2/NF-κB pathway in vitro and in vivo unexpectedly exacerbated vascular mineralization and stiffness. In contrast, activation of NF-κB by SMC-specific IκBα deficiency attenuated calcified vascular stiffness in CKD. Inhibition of the IKK2/NF-κB pathway induced cell death of VSMCs by reducing anti-cell death gene expression, whereas activation of NF-κB reduced CKD-dependent vascular cell death. In addition, increased calcification of extracellular vesicles through the inhibition of the IKK2/NF-κB pathway induced mineralization of VSMCs, which was significantly reduced by blocking cell death in vitro and in vivo. This study reveals that activation of the IKK2/NF-κB pathway in VSMCs plays a protective role in CKD-dependent calcified vascular stiffness by reducing the release of apoptotic calcifying extracellular vesicles.

Mitochondria-associated endoplasmic reticulum membrane (MAM): a dark horse for diabetic cardiomyopathy treatment

Diabetic cardiomyopathy (DCM), an important complication of diabetes mellitus (DM), is one of the most serious chronic heart diseases and has become a major cause of heart failure worldwide. At present, the pathogenesis of DCM is unclear, and there is still a lack of effective therapeutics. Previous studies have shown that the homeostasis of mitochondria and the endoplasmic reticulum (ER) play a core role in maintaining cardiovascular function, and structural and functional abnormalities in these organelles seriously impact the occurrence and development of various cardiovascular diseases, including DCM. The interplay between mitochondria and the ER is mediated by the mitochondria-associated ER membrane (MAM), which participates in regulating energy metabolism, calcium homeostasis, mitochondrial dynamics, autophagy, ER stress, inflammation, and other cellular processes. Recent studies have proven that MAM is closely related to the initiation and progression of DCM. In this study, we aim to summarize the recent research progress on MAM, elaborate on the key role of MAM in DCM, and discuss the potential of MAM as an important therapeutic target for DCM, thereby providing a theoretical reference for basic and clinical studies of DCM treatment.

Activation of the IKK2-NFκB pathway in VSMCs inhibits calcified vascular stiffness in CKD by reducing the secretion of calcifying extracellular vesicles

IKK2-NFκB pathway mediated-inflammation in vascular smooth muscle cells (VSMCs) has been proposed to be an etiologic factor in medial calcification and stiffness. However, the role of the IKK2-NFκB pathway in medial calcification remains to be elucidated. In this study, we found that CKD induces inflammatory pathways through the local activation of the IKK2-NFκB pathway in VMSCs associated with calcified vascular stiffness. Despite reducing the expression of inflammatory mediators, complete inhibition of the IKK2-NFκB pathway in vitro and in vivo unexpectedly exacerbated vascular mineralization and stiffness. In contrast, activation of NFκB by SMC-specific IκB deficiency attenuated calcified vascular stiffness in CKD. Inhibition of the IKK2-NFκB pathway induced apoptosis of VSMCs by reducing anti-apoptotic gene expression, whereas activation of NFκB reduced CKD-dependent vascular cell death. In addition, increased calcifying extracellular vesicles through the inhibition of the IKK2-NFκB pathway induced mineralization of VSMCs, which was significantly reduced by blocking cell death. This study reveals that activation of the IKK2-NFκB pathway in VSMCs plays a protective role in CKD-dependent calcified vascular stiffness by reducing the release of apoptotic calcifying extracellular vesicles.

Mitochondria-Associated Endoplasmic Reticulum Membranes: Inextricably Linked with Autophagy Process

Mitochondria-associated membranes (MAMs), physical connection sites between the endoplasmic reticulum (ER) and the outer mitochondrial membrane (OMM), are involved in numerous cellular processes, such as calcium ion transport, lipid metabolism, autophagy, ER stress, mitochondria morphology, and apoptosis. Autophagy is a highly conserved intracellular process in which cellular contents are delivered by double-membrane vesicles, called autophagosomes, to the lysosomes for destruction and recycling. Autophagy, typically triggered by stress, eliminates damaged or redundant protein molecules and organelles to maintain regular cellular activity. Dysfunction of MAMs or autophagy is intimately associated with various diseases, including aging, cardiovascular, infections, cancer, multiple toxic agents, and some genetic disorders. Increasing evidence has shown that MAMs play a significant role in autophagy development and maturation. In our study, we concentrated on two opposing functions of MAMs in autophagy: facilitating the formation of autophagosomes and inhibiting autophagy. We recognized the link between MAMs and autophagy in the occurrence and progression of the diseases and therefore collated and summarized the existing intrinsic molecular mechanisms. Furthermore, we draw attention to several crucial data and open issues in the area that may be helpful for further study.

Sulforaphane induces lipophagy through the activation of AMPK-mTOR-ULK1 pathway signaling in adipocytes

Lipophagy, a form of selective autophagy, degrades lipid droplet (LD) in adipose tissue and the liver. The chemotherapeutic isothiocyanate sulforaphane (SFN) contributes to lipolysis through the activation of hormone-sensitive lipase and the browning of white adipocytes. However, the details concerning the regulation of lipolysis in adipocytes by SFN-mediated autophagy remain unclear. In this study, we investigated the effects of SFN on autophagy in the epididymal fat of mice fed a high-fat diet (HFD) or control-fat diet and on the molecular mechanisms of autophagy in differentiated 3T3-L1 cells. Western blotting revealed that the protein expression of lipidated LC3 (LC3-II), an autophagic substrate, was induced after 3T3-L1 adipocytes treatment with SFN. In addition, SFN increased the LC3-II protein expression in the epididymal fat of mice fed an HFD. Immunofluorescence showed that the SFN-induced LC3 expression was co-localized with LDs in 3T3-L1 adipocytes and with perilipin, the most abundant adipocyte-specific protein, in adipocytes of mice fed an HFD. Next, we confirmed that SFN activates autophagy flux in differentiated 3T3-L1 cells using the mCherry-EGFP-LC3 and GFP-LC3-RFP-LC3ΔG probe. Furthermore, we examined the induction mechanisms of autophagy by SFN in 3T3-L1 adipocytes using western blotting. ATG5 knockdown partially blocked the SFN-induced release of fatty acids from LDs in mature 3T3-L1 adipocytes. SFN time-dependently elicited the phosphorylation of AMPK, the dephosphorylation of mTOR, and the phosphorylation of ULK1 in differentiated 3T3-L1 cells. Taken together, these results suggest that SFN may provoke lipophagy through AMPK-mTOR-ULK1 pathway signaling, resulting in partial lipolysis of adipocytes.

MEF2D-NR4A1-FAM134B2-mediated reticulophagy contributes to amino acid homeostasis

We recently identified FAM134B2, which is an N-terminal truncated reticulophagy receptor highly induced by starvation such as fasting of mice and treatment of mammalian cells with a starvation medium that does not contain amino acids, glucose and growth factors. However, which starvation signal mediates the induction of FAM134B2 is still obscure. In this study, we found that amino acid deficiency (AAD) could mimic the starvation condition to induce FAM134B2 expression. Unexpectedly, EIF2AK4/GCN2-mediated integrated signal response (ISR) and MTOR (mechanistic target of rapamycin kinase) signals, which constitute two major signaling pathways that respond to AAD, did not contribute to AAD-induced FAM134B2 induction. mRNA-seq and siRNA screenings identified two ISR-independent transcription factors, MEF2D (myocyte enhancer factor 2D) and NR4A1 (nuclear receptor subfamily 4 group A member 1), involved in AAD-induced FAM134B2 expression. AAD induces MEF2D, resulting in the induction of NR4A1, which in turn induces FAM134B2-mediated reticulophagy to maintain intracellular amino acid levels. In conclusion, the MEF2D-NR4A1-FAM134B2 cascade is a critical signal in amino acid homeostasis.

Molecular Dysfunctions of Mitochondria-Associated Endoplasmic Reticulum Contacts in Atherosclerosis

Atherosclerosis is a chronic lipid-driven inflammatory disease that results in the formation of lipid-rich and immune cell-rich plaques in the arterial wall, which has high morbidity and mortality in the world. The mechanism of atherosclerosis is still unclear now. Potential hypotheses involved in atherosclerosis are chronic inflammation theory, lipid percolation theory, mononuclear-macrophage theory, endothelial cell (EC) injury theory, and smooth muscle cell (SMC) mutation theory. Changes of phospholipids, glucose, critical proteins, etc. on mitochondria-associated endoplasmic reticulum membrane (MAM) can cause the progress of atherosclerosis. This review describes the structural and functional interaction between mitochondria and endoplasmic reticulum (ER) and explains the role of critical molecules in the structure of MAM during atherosclerosis.

Free Deoxycholic Acid Exacerbates Vascular Calcification in CKD through ER Stress-Mediated ATF4 Activation

BACKGROUND

Our metabolome approach found that levels of circulating, free deoxycholic acid (DCA) is associated with the severity of vascular calcification in patients with CKD. However, it is not known whether DCA directly causes vascular calcification in CKD.

METHODS

Using various chemicals and animal and cell culture models, we investigated whether the modulation of DCA levels influences vascular calcification in CKD.

RESULTS

CKD increased levels of DCA in mice and humans by decreasing urinary DCA excretion. Treatment of cultured VSMCs with DCA but no other bile acids (BAs) induced vascular calcification and osteogenic differentiation through endoplasmic reticulum (ER) stress-mediated activating transcription factor-4 (ATF4) activation. Treatment of mice with Farnesoid X receptor (FXR)-specific agonists selectively reduced levels of circulating cholic acid-derived BAs, such as DCA, protecting from CKD-dependent medial calcification and atherosclerotic calcification. Reciprocal FXR deficiency and DCA treatment induced vascular calcification by increasing levels of circulating DCA and activating the ER stress response.

CONCLUSIONS

This study demonstrates that DCA plays a causative role in regulating CKD-dependent vascular diseases through ER stress-mediated ATF4 activation.

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.

The Protective Effects of the Autophagic and Lysosomal Machinery in Vascular and Valvular Calcification: A Systematic Review

BACKGROUND

Autophagy is a highly conserved catabolic homeostatic process, crucial for cell survival. It has been shown that autophagy can modulate different cardiovascular pathologies, including vascular calcification (VCN).

OBJECTIVE

To assess how modulation of autophagy, either through induction or inhibition, affects vascular and valvular calcification and to determine the therapeutic applicability of inducing autophagy.

DATA SOURCES

A systematic review of English language articles using MEDLINE/PubMed, Web of Science (WoS) and the Cochrane library. The search terms included autophagy, autolysosome, mitophagy, endoplasmic reticulum (ER)-phagy, lysosomal, calcification and calcinosis. Study characteristics: Thirty-seven articles were selected based on pre-defined eligibility criteria. Thirty-three studies (89%) studied vascular smooth muscle cell (VSMC) calcification of which 27 (82%) studies investigated autophagy and six (18%) studies lysosomal function in VCN. Four studies (11%) studied aortic valve calcification (AVCN). Thirty-four studies were published in the time period 2015-2020 (92%).

CONCLUSION

There is compelling evidence that both autophagy and lysosomal function are critical regulators of VCN, which opens new perspectives for treatment strategies. However, there are still challenges to overcome, such as the development of more selective pharmacological agents and standardization of methods to measure autophagic flux.