Autophagy: An Exposing Therapeutic Target in Atherosclerosis

Vericiguat protects against cardiac damage in a pig model of ischemia/reperfusion

BACKGROUND

The purpose of this research was to verify that vericiguat, a soluble guanylate cyclase (sGC) stimulator, reduces myocardial ischemic reperfusion injury (MIRI), and to learn how this reduction happens.

METHODS AND RESULTS

To develop an ischaemia/reperfusion (I/R) model, the left anterior descending artery was blocked in minipigs under anesthesia for 90 minutes, followed by 180 minutes of reperfusion. Vericiguat is administered three hours before surgery. Two weeks after receiving therapy, pigs underwent cardiovascular magnetic resonance imaging (MRI) to evaluate the results. The MRI results suggest improvement in the myocardial infarct after vericiguat treatment. Vericiguat treatment for two weeks enhanced vascularity, inhibited pro-inflammatory cells, and decreased collagen deposition in the infarct zone of pigs. Short-term experiments investigating possible explanations have indicated that vericiguat has antiapoptotic effects on cardiomyocytes and increases levels of autophagy.

CONCLUSIONS

Vericiguat, an SGC activator, reduces MIRI in pigs by boosting autophagy, preventing apoptosis, and promoting angiogenesis.

Autophagy-related proteins: Potential diagnostic and prognostic biomarkers of aging-related diseases

Autophagy plays a key role in cellular, tissue and organismal homeostasis and in the production of the energy load needed at critical times during development and in response to nutrient shortage. Autophagy is generally considered as a pro-survival mechanism, although its deregulation has been linked to non-apoptotic cell death. Autophagy efficiency declines with age, thus contributing to many different pathophysiological conditions, such as cancer, cardiomyopathy, diabetes, liver disease, autoimmune diseases, infections, and neurodegeneration. Accordingly, it has been proposed that the maintenance of a proper autophagic activity contributes to the extension of the lifespan in different organisms. A better understanding of the interplay between autophagy and risk of age-related pathologies is important to propose nutritional and life-style habits favouring disease prevention as well as possible clinical applications aimed at promoting long-term health.

Inhibition of Ca2+-calpain signaling is a new mechanism using Laminaria japonica polysaccharide to prevent macrophage foam cell formation and atherosclerosis

The Ca2+-calpain signaling plays a pivotal role in regulating the upstream signaling pathway of cellular autophagy. The aim of the current work was to investigate the role of Ca2+-calpain signaling in the regulation of macrophage autophagy by a Laminaria japonica polysaccharide (LJP61A) in Ox-LDL induced macrophages and high fat diet fed atherosclerotic mice. Results revealed that the LJP61A markedly decreased the levels of intracellular Ca2+, calpain1, calpain2 and their downstream effectors (Gsα, cAMP and IP3), and simultaneously enhanced autophagy activity and lipid metabolism, thereby reducing lipid accumulation in the Ox-LDL stimulated macrophages and lipid-laden plaques in atherosclerotic mice. Moreover, BAPTA-AM (a Ca2+ chelator) and calpeptin (a calpain inhibitor) synergistically strengthened the beneficial effects of LJP61A on autophagy and lipid metabolism by decreasing the levels of intracellular Ca2+, calpain1, calpain2, and their downstream effectors (Gsα, cAMP and IP3) induced by Ox-LDL. These findings suggested that the LJP61A suppressed macrophage derived foam cell formation and atherosclerosis by modulating the Ca2+-calpain-mediated autophagy.

Laminaria japonica Polysaccharide Suppresses Atherosclerosis via Regulating Autophagy-Mediated Macrophage Polarization

The present work aimed to explore the effect and underlying mechanism of a homogeneous Laminaria japonica polysaccharide (LJP61A) on macrophage polarization in high-fat-diet-fed LDLr-/- mice and Ox-LDL-induced macrophages. Results showed that LJP61A remarkably reduced the lesion burden in atherosclerotic mice, alleviated lipid deposition in Ox-LDL-stimulated macrophages, decreased the expression of M1 macrophage markers, and increased the expression of M2 macrophage markers, thus reducing the M1/M2 macrophage phenotype ratio. Meanwhile, the autophagic flux of macrophages was enhanced by LJP61A treatment in vitro and in vivo. 3-Methyladenine is an autophagic inhibitor. As expected, this inhibitor blocked the effects of LJP61A on macrophage polarization. SIRT1 and FoxO1 are two key upstream genes that control the autophagy behavior. We also found that LJP61A significantly up-regulated the expression of SIRT1 and FoxO1. However, these effects of LJP61A were abolished by the SIRT1 siRNA and FoxO1 inhibitor AS1842856. These results suggested that LJP61A reduced atherosclerosis in HFD-induced LDLr-/- mice via regulating autophagy-mediated macrophage polarization.

Relationship Between Autophagy and Metabolic Syndrome Characteristics in the Pathogenesis of Atherosclerosis

Atherosclerosis is the main cause of mortality in metabolic-related diseases, including cardiovascular disease and type 2 diabetes (T2DM). Atherosclerosis is characterized by lipid accumulation and increased inflammatory cytokines in the vascular wall, endothelial cell and vascular smooth muscle cell dysfunction and foam cell formation initiated by monocytes/macrophages. The characteristics of metabolic syndrome (MetS), including obesity, glucose intolerance, dyslipidemia and hypertension, may activate multiple mechanisms, such as insulin resistance, oxidative stress and inflammatory pathways, thereby contributing to increased risks of developing atherosclerosis and T2DM. Autophagy is a lysosomal degradation process that plays an important role in maintaining cellular metabolic homeostasis. Increasing evidence indicates that impaired autophagy induced by MetS is related to oxidative stress, inflammation, and foam cell formation, further promoting atherosclerosis. Basal and mild adaptive autophagy protect against the progression of atherosclerotic plaques, while excessive autophagy activation leads to cell death, plaque instability or even plaque rupture. Therefore, autophagic homeostasis is essential for the development and outcome of atherosclerosis. Here, we discuss the potential role of autophagy and metabolic syndrome in the pathophysiologic mechanisms of atherosclerosis and potential therapeutic drugs that target these molecular mechanisms.

Oxiapoptophagy: A type of cell death induced by some oxysterols

Oxysterols are oxidized forms of cholesterol generated from cholesterol by auto-oxidation, enzymatic processes, or both. Some of them (7-ketocholesterol, 7β-hydroxycholesterol and 24(S)-hydroxycholesterol), when used at cytotoxic concentrations on different cell types from different species (mesenchymal bone marrow cells, monocytic cells and nerve cells), induce a type of cell death associated with OXIdative stress and several characteristics of APOPTOsis and autoPHAGY, defined as oxiapoptophagy. Oxidative stress is associated with overproduction of ROS, increased antioxidant enzyme activities, lipid peroxidation and protein carbonylation. Apoptosis is associated with activation of the mitochondrial pathway, opening of the mitochondrial permeability pore, loss of mitochondrial membrane potential, caspase-3 activation, PARP degradation, nuclear condensation and/or fragmentation. Autophagy is characterized by autophagic vacuoles revealed by monodansylcadaverine staining and transmission electron microscopy, plus increased ratio of LC-3II/LC-3I. In addition, morphological, topographical and functional changes of the peroxisome are observed. LINKED ARTICLES: This article is part of a themed issue on Oxysterols, Lifelong Health and Therapeutics. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v178.16/issuetoc.

Metformin suppresses inflammation and apoptosis of myocardiocytes by inhibiting autophagy in a model of ischemia-reperfusion injury

Metformin (Met) is a major widely used oral glucose lowering drug for the treatment of type 2 diabetes. It is reported that metformin could regulate autophagy in various diseases of cardiovascular system including in I/R injury, diabetic cardiomyopathy and heart failure. Autophagy plays a controversial role in ischemia/reperfusion (I/R) injury, and this research was performed to explore the cardioprotective effect of Met on I/R injury and discuss the underlying mechanism of autophagy in it. In vivo and in vitro, Met exerted cardioprotection function of decreasing myocardial inflammation and apoptosis with a decrease in the level of autophagy. Moreover, Met significantly inhibited autophagosome formation and restore the impairment of autophagosome processing, which lead to cardioprotection effect of Met. Akt was up-regulated in Met-treated I/R hearts and miransertib, a pan-AKT inhibitor, was able to reverse the alleviating autophagy effect of Met. We demonstrate that Met protects cardiomyocytes from I/R-induced apoptosis and inflammation through down regulation of autophagy mediated by Akt signaling pathway.

The protective effects of angelica organic acid against ox-LDL-induced autophagy dysfunction of HUVECs

BACKGROUND

Angelica root is the dry root of the Umbelliferae plant Angelica sinensis (oliv) Diels. Angelica organic acid (OA) is the main active ingredient in Angelica sinensis, and it exerts potential anti-atherosclerotic effects by preventing Oxidized low-density lipoprotein (Ox-LDL) induced endothelial injury. To study the protective effects of OA on ox-LDL-induced HUVECs autophagic flux dysfunction and inflammatory injury.

METHODS

OA were isolated by water extraction and alcohol precipitation, and then the content of ferulic acid (FA) in the OA was determined by high performance liquid chromatography. The ox-LDL-induced endothelial injury model was established. The effect of ferulic acid on the survival of Human umbilical vein endothelial cells (HVUECs) was detected by CCK-8 assay. HUVECs were pretreated with different concentrations of OA (20 μmol/L, 40 μmol/L, and 80 μmol/L), and Western Blot was used to detect the expressions of LC3II, p62, MCP-1, VCAM-1 and LOX-1. The autophagosomes in HUVECs were observed by transmission electron microscopy (TEM).

RESULTS

20 μmol/L OA could increase the expression of LC3II and decrease the expression of p62, MCP-1, VCAM-1 and LOX-1. The results of TEM showed that angelica organic acids promoted cell organelle degradation in autolysosomes.

CONCLUSION

OA could reduce inflammation, protect endothelial cells and play an anti-atherosclerotic role by enhancing the autophagy flux of damaged endothelial cells, in which FA the major active ingredient of OA played a major role.

Cav-1 (Caveolin-1) Deficiency Increases Autophagy in the Endothelium and Attenuates Vascular Inflammation and Atherosclerosis

Supplemental Digital Content is available in the text.

Endothelial Cav-1 (caveolin-1) expression plays a relevant role during atherogenesis by controlling NO production, vascular inflammation, LDL (low-density lipoprotein) transcytosis, and extracellular matrix remodeling. Additional studies have identified cholesterol-rich membrane domains as important regulators of autophagy by recruiting ATGs (autophagy-related proteins) to the plasma membrane. Here, we investigate how the expression of Cav-1 in the aortic endothelium influences autophagy and whether enhanced autophagy contributes to the atheroprotective phenotype observed in Cav-1–deficient mice.

Araloside C attenuates atherosclerosis by modulating macrophage polarization via Sirt1-mediated autophagy

Atherosclerosis-related cardiovascular disease is still the predominant cause of death worldwide. Araloside C (AsC), a natural saponin, exerts extensive anti-inflammatory properties. In this study, we explored the protective effects and mechanism of AsC on macrophage polarization in atherosclerosis in vivo and in vitro. Using a high-fat diet (HFD)-fed ApoE-/- mouse model and RAW264.7 macrophages exposed to ox-LDL, AsC was evaluated for its effects on polarization and autophagy. AsC significantly reduced the plaque area in atherosclerotic mice and lipid accumulation in ox-LDL-treated macrophages, promoted M2 phenotype macrophage polarization, increased the number of autophagosomes and modulated the expression of autophagy-related proteins. Moreover, the autophagy inhibitor 3-methyladenine and BECN1 siRNA obviously abolished the antiatherosclerotic and M2 macrophage polarization effects of AsC. Mechanistically, AsC targeted Sirt1and increased its expression, and this increase in expression was associated with increased autophagy and M2 phenotype polarization. In contrast, the effects of AsC were markedly blocked by EX527 and Sirt1 siRNA. Altogether, AsC attenuates foam cell formation and lessens atherosclerosis by modulating macrophage polarization via Sirt1-mediated autophagy.

MALAT1 affects hypoxia-induced vascular endothelial cell injury and autophagy by regulating miR-19b-3p/HIF-1α axis

Cardiovascular disease has become the leading cause of death in the world. Metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) plays an important role in cardiovascular disease, such as stroke. However, the role of MALAT1 in hypoxia (HYP)-induced vascular endothelial cells (VECs) remains unclear. In the present study, HYP-treated human umbilical vein endothelial cells (HUVECs) were utilized to simulate HYP-induced VEC injury. It was found that after HYP treatment, the levels of MALAT1 and hypoxia-induced factor-1 (HIF-1α) in HUVECs were upregulated, while the level of miR-19b-3p was downregulated. Knockdown of MALAT1 with siRNA significantly reduced the HIF-1α level induced by HYP. In addition, MALAT1 knockdown inhibited HYP-induced HUVECs apoptosis, autophagy and inflammation. The overexpression of HIF-1α overcame the effect of MALAT1 knockdown. Mechanism analysis showed that MALAT1-targeted miR-19b-3p and then regulated downstream HIF-1α. MALAT1 knockdown increased the level of miR-19b-3p in cells, and increased miR-19b-3p further inhibited the expression of HIF-1α, thereby reducing the HYP-induced HUVECs apoptosis, autophagy and inflammation. Taken together, these results suggest that MALAT1 may be a potential target for mitigating HYP-induced endothelial cell injury.

The active components derived from Penthorum chinensePursh protect against oxidative-stress-induced vascular injury via autophagy induction

Oxidative stress-induced damage has been proposed as a major risk factor for cardiovascular disease and is a pathogenic feature of atherosclerosis. Although autophagy was reported to have a protective effect against atherosclerosis, its mechanism for reducing oxidative stress remains un-elucidated. In this study, we have identified 4 novel autophagic compounds from traditional Chinese medicines (TCMs), which activated the AMPK mediated autophagy pathway for the recovery of mitochondrial membrane potential (MMP) to reduce the production of reactive oxygen species (ROS) in Human umbilical vein endothelial cells (HUVECs). In this study, 4 compounds (TA, PG, TB and PG1) identified from Penthorum chinense Pursh (PCP) were demonstrated for the first time to possess binding affinity to HUVECs cell membranes via cell membrane chromatography (CMC) accompanied by UHPLC-TOF-MS analysis, and the 4 identified compounds induce autophagy in HUVECs. Among the 4 autophagic activators identified from PCP, TA (Thonningianin A, Pinocembrin dihydrochalcone-7-O-[3″-O-galloyl-4″,6″-hexahydroxydiphenoyl]-glucoside) is the major chemcial component in PCP, which possesses the most potent autophagy effect via a Ca²⁺/AMPK-dependent and mTOR-independent pathways. Moreover, TA efficiently reduced the level of ROS in HUVECs induced by H₂O₂. Additionally, the expression of pro- and cleaved-IL-1β in the aortic artery of ApoE-KO mice were also alleviated at the transcription and post-transcription levels after the administration of TA, which might be correlated to the reduction of oxidative-stress induced inflammasome-related Nod-like receptor protein3 (NLRP3) in the aortic arteries of ApoE-KO mice. This study has pinpointed the novel autophagic role of TA in alleviating the oxidative stress of HUVECs and aortic artery of ApoE-KO mice, and provided insight into the therapeutic application of TA in treatment of atherosclerosis or other cardiovascular diseases.

CAV1-CAVIN1-LC3B-mediated autophagy regulates high glucose-stimulated LDL transcytosis

Diabetes is a recognized high-risk factor for the development of atherosclerosis, in which macroautophagy/autophagy is emerging to play essential roles. The retention of low-density lipoprotein (LDL) particles in subendothelial space following transcytosis across the endothelium is the initial step of atherosclerosis. Here, we identified that high glucose could promote atherosclerosis by stimulating transcytosis of LDL. By inhibiting AMPK-MTOR-PIK3C3 pathway, high glucose suppresses the CAV-CAVIN-LC3B-mediated autophagic degradation of CAV1; therefore, more CAV1 is accumulated in the cytosol and utilized to form more caveolae in the cell membrane and facilitates the LDL transcytosis across endothelial cells. For a proof of concept, higher levels of lipids were accumulated in the subendothelial space of umbilical venous walls from pregnant women with gestational diabetes mellitus (GDM), compared to those of pregnant women without GDM. Our results reveal that high glucose stimulates LDL transcytosis by a novel CAV1-CAVIN1-LC3B signaling-mediated autophagic degradation pathway.

ABBREVIATIONS

3-MA: 3-methyladenine; ACTB: actin beta; AMPK: AMP-activated protein kinase; Bafi: bafilomycin A₁; CAV1: caveolin-1; CAVIN1: caveolae associated protein 1; CSD: the CAV1 scaffolding domain; GDM: gestational diabetes mellitus; IMD: intramembrane domain; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule- associated protein 1 light chain 3; MFI: mean fluorescence intensity; MTOR: mechanistic target of rapamycin kinase; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; SQSTM1/p62: sequestosome 1.

Autophagy: A Lysosome-Dependent Process with Implications in Cellular Redox Homeostasis and Human Disease

SIGNIFICANCE

Autophagy, a lysosome-dependent homeostatic process inherent to cells and tissues, has emerging significance in the pathogenesis of human disease. This process enables the degradation and turnover of cytoplasmic substrates via membrane-dependent sequestration in autophagic vesicles (autophagosomes) and subsequent lysosomal delivery of cargo. Recent Advances: Selective forms of autophagy can target specific substrates (e.g., organelles, protein aggregates, and lipids) for processing. Autophagy is highly regulated by oxidative stress, including exposure to altered oxygen tension, by direct and indirect mechanisms, and contributes to inducible defenses against oxidative stress. Mitochondrial autophagy (mitophagy) plays a critical role in the oxidative stress response, through maintenance of mitochondrial integrity.

CRITICAL ISSUES

Autophagy can impact a number of vital cellular processes including inflammation and adaptive immunity, host defense, lipid metabolism and storage, mitochondrial homeostasis, and clearance of aggregated proteins, all which may be of significance in human disease. Autophagy can exert both maladaptive and adaptive roles in disease pathogenesis, which may also be influenced by autophagy impairment. This review highlights the essential roles of autophagy in human diseases, with a focus on diseases in which oxidative stress or inflammation play key roles, including human lung, liver, kidney and heart diseases, metabolic diseases, and diseases of the cardiovascular and neural systems.

FUTURE DIRECTIONS

Investigations that further elucidate the complex role of autophagy in the pathogenesis of disease will facilitate targeting this pathway for therapies in specific diseases.

A novel antioxidant Mito-Tempol inhibits ox-LDL-induced foam cell formation through restoration of autophagy flux

A bulk of cholesteryl esters accumulation in macrophage foam cells drives the occurrence and development of atherosclerosis. Evidence now shows that autophagy plays key roles in the degradation of intracellular lipid droplets via autolysosome, and also in the release of intracellular lipids via cholesterol efflux. In this study, we identified that a mitochondria-targeted antioxidant, Mito-Tempol, has protective effects against cholesteryl esters accumulation by activating autophagy. Mito-Tempol was shown to ameliorate the lipid burden for atherosclerosis, both in vitro and in vivo. In the established in vitro foam cell formation system using oxidized low-density lipoprotein (ox-LDL)-loaded THP-1 macrophages, Mito-Tempol prevented intracellular oxidative stress and attenuated lipid accumulation. Mito-Tempol rescued ox-LDL-impaired autophagic flux, thereby facilitating autophagy-mediated lipid degradation in THP-1 macrophages. Meanwhile, Mito-Tempol also increased the efflux of cholesterol via autophagy-dependent ABCA1 and ABCG1 up-regulation. The classical autophagy pathway of mTOR may be one of the effector for the autophagy restoration of Mito-Tempol. Our findings give the first insight that cardiovascular system disease may benefits more from the treatment of Mito-Tempol for its impact of reversing atherosclerosis via autophagy.

Platelet membrane-coated nanoparticle-mediated targeting delivery of Rapamycin blocks atherosclerotic plaque development and stabilizes plaque in apolipoprotein E-deficient (ApoE-/-) mice

Although certain success has been achieved in atherosclerosis treatment, tremendous challenges remain in developing more efficient strategies to treat atherosclerosis. Platelets have inherent affinity to plaques and naturally home to atherosclerotic sites. Rapamycin features potent anti-atherosclerosis effect, but its clinical utility is limited by its low concentration at the atherosclerotic site and severe systemic toxicity. In the present study, we used platelet membrane-coated nanoparticles (PNP) as a targeted drug delivery platform to treat atherosclerosis through mimicking platelets' inherent targeting to plaques. PNP displayed 4.98-fold greater radiant efficiency than control nanoparticles in atherosclerotic arterial trees, indicating its effective homing to atherosclerotic plaques in vivo. In an atherosclerosis model established in apolipoprotein E-deficient mice, PNP encapsulating rapamycin significantly attenuated the progression of atherosclerosis and stabilized atherosclerotic plaques. These results demonstrated the perfect efficacy and pro-resolving potential of PNP as a targeted drug delivery platform for atherosclerosis treatment.

Paeonol Inhibits Oxidized Low-Density Lipoprotein-Induced Vascular Endothelial Cells Autophagy by Upregulating the Expression of miRNA-30a

Paeonol from Cortex Moutan root is a potential therapeutic agent for atherosclerosis (AS). However, its mechanisms of action are still not fully understood. Vascular endothelial cells (VECs) autophagy plays a vital role in the initiation and progression of AS. In this study, we aim to investigate whether the protective effect of paeonol on ox-LDL-induced VECs injury by regulating autophagy. To address this question, we used ox-LDL-induced rat VECs as a model system to elucidate the protective effect of paeonol on VECs injury. This study displayed that ox-LDL (100 mg/L) treatment inhibited VEC growth in dose- and time-dependent manners, paeonol (60 μM) shown potential in inhibiting ox-LDL-induced death. Furthermore, paeonol significantly reduced ox-LDL-induced the formation of autophagy vacuoles and the expression of LC3II in VECs. Further double-luciferase reporter assay shown that miR-30a specifically binds to the 3′-UTR of Beclin-1 mRNA in VECs. Moreover, we found that ox-LDL decreased miR-30a and increased Beclin-1 expression, pretreatment with paeonol could reverse the process of regulation in dose-dependent manners. In ox-LDL treated VECs, transfection with a miR-30a mimic significantly increased miR-30a expression and inhibited Beclin-1 and LC3II expression, thus enhanced the protective effects of paeonol. Whereas transfection with a miR-30a inhibitor significantly decreased miR-30a expression and increased Beclin-1 and LC3II expression, thus attenuated the protective effects of paeonol. In conclusion, this study has, for the ?rst time, highlighted that miR-30a might be a critical target of paeonol against ox-LDL-induced VECs injury by inhibiting excessive autophagy. Paeonol may be one of promising candidate drug for treatment of AS.

MicroRNA-21 suppresses ox-LDL-induced human aortic endothelial cells injuries in atherosclerosis through enhancement of autophagic flux: Involvement in promotion of lysosomal function

Atherosclerosis is a common pathological basis of cardiovascular disease and remains the leading cause of mortality. Endothelial cell (EC) injury and autophagy dysfunction have been proved to contribute to the development of atherosclerosis. Recently, accumulating evidence confirms that microRNAs (miRNAs) have emerged as vital regulators and fine-tuners of various pathophysiological cellular impacts and molecular signaling pathways involved in atherosclerosis. Herein, the objective of the present study was to explore the biological function of miR-21 in oxidized low-density lipoprotein (ox-LDL)-induced human aortic endothelial cells (HAECs) injury and the underlying molecular mechanism. The results showed that ox-LDL treatment significantly decreased HAECs viability, increased caspase-3 activity, apoptosis ratio and Bax protein expression, and reduced Bcl-2 protein expression resulting in EC injuries. Simultaneously, ox-LDL treatment obviously reduced miR-21 level in a time-and dose-dependent manner. Notably, ox-LDL-induced EC injuries were abolished by miR-21 mimics transfection. In addition, miR-21 mimics alleviated ox-LDL-induced impaired autophagic flux as illustrated by the increases in LC3-II/LC3-I ratio and Beclin-1 protein expression, and the decrease in p62 protein expression in HAECs. Moreover, ox-LDL suppressed the expressions of lysosomal membrane protein (LAMP1) and cathepsin D proteins, and attenuated cathepsin D activity in HAECs, leading to lysosomal dysfunction, while these effects were also blocked by miR-21 mimics. These findings indicated that miR-21 restored impaired autophagic flux and lysosomal dysfunction, thereby attenuating ox-LDL-induced HAECs injuries.

Green tea polyphenol treatment attenuates atherosclerosis in high-fat diet-fed apolipoprotein E-knockout mice via alleviating dyslipidemia and up-regulating autophagy

Background: Green tea polyphenol (GTP) is a polyphenol source from green tea that has drawn wide attention owing to epidemiological evidence of its beneficial effects in the prevention of cardiovascular disease; the underlying molecular mechanisms of these effects are not well understood. This study aimed to investigate the effects of GTP treatment on autophagy regulation in the vessel wall and lipid metabolism of HFD-fed male ApoE-knockout mice. Methods: Adult male ApoE-knockout mice (n = 30) fed with a high-fat diet (HFD) were treated with either vehicle or GTP (3.2 or 6.4 g/L) administered via drinking water for 15 weeks, and C57BL/6J mice fed with standard chow diet (STD) were used as the control group. Metabolic parameters, expression of key mRNAs and proteins of hepatic lipid metabolism and autophagy in the vessel wall of mice were determined after the 15-week treatment. Results: A HFD induced atherosclerosis formation and lipid metabolism disorders as well as reduced autophagy expression in the vessel wall of ApoE-knockout mice, but GTP treatment alleviated the lipid metabolism disorders, decreased the oxLDL levels in serum, and increased the mRNA and protein expressions of hepatic PPARα and autophagy markers (LC3, Beclin1 and p62) in the vessel wall of ApoE-knockout mice. Conclusions: Our findings suggest that GTP supplementation showed marked suppression of atherogenesis through improved lipid metabolism as well as through a direct impact on oxLDL and autophagy flux in the vessel wall.

Protoporphyrin IX-mediated sonodynamic therapy promotes autophagy in vascular smooth muscle cells

Sonodynamic therapy (SDT) is effective in treating intimal hyperplasia and promoting plaque stability in animal models. The present study aimed to evaluate the effects of SDT with the sonosensitizer protoporphyrin IX (PpIX) on vascular smooth muscle cell (VSMC) viability and autophagy. Cultured VSMCs cells were divided into the following groups: i) Control, ii) ultrasound, iii) PpIX and iv) SDT. Flow cytometry and laser confocal detection were used to measure Annexin V stained VSMCs following different treatments. Alterations in mitochondrial membrane potential (MMP) were evaluated via JC-1 staining. Autophagosome formation was observed using electron and fluorescence microscopy. Western blotting was used to analyze the expression levels of the autophagy markers light chain 3 (LC3-I) and LC3-II. The results demonstrated that SDT did not trigger apoptosis nor induce a significant decline in MMP of VSMCs. However, SDT significantly increased autophagasome formation and increased the LC3-II/LC3-I ratio. The findings demonstrated that PpIX-SDT increased autophagy without inducing mitochondrial-dependent apoptosis in VSMCs.

Cyclophilin A mediates the ox-LDL-induced activation and apoptosis of macrophages via autophagy

BACKGROUND

Oxidized low-density lipoprotein (ox-LDL) is the most common inflammatory factor that mediates the activation and apoptosis of macrophages. Cyclophilin A (CyPA) is expressed following oxidative stress, hypoxia, and infection. However, the role of CyPA in the activation and apoptosis of macrophages is unclear. The aims of the study were to determine whether CyPA mediates the ox-LDL-induced activation and apoptosis in RAW264.7 cells and to analyze potential mechanisms.

METHODS AND RESULTS

Through Western blot and ELISA test, the expression of CyPA induced by ox-LDL is time-dependent in RAW264.7 cells. Gene silencing of CyPA reduced the generation of lipid droplets in the cytoplasm and downregulated the expression of the surface markers of macrophage activation, namely, CD80, CD86, and major histocompatibility complex class 2 antigen. Cell apoptosis is significantly decreased and the level of anti-apoptosis protein bcl-2 is increased in CyPA silent cells compared with the control group. Finally, autophagy-related protein LC3-II/LC3-I ratio level significantly decreased in CyPA silent cells with less autophagosome formation while the blocked autophagy flux was recovered. The differences in the activation and apoptosis between CyPA silent cells and the control cells were inhibited by pre-treatment with class III PI 3-kinase inhibitor 3-MA.

CONCLUSIONS

These results indicate that CyPA mediates the ox-LDL-induced activation and apoptosis in RAW264.7 cells by regulating autophagy.

Danshensu alleviates cardiac ischaemia/reperfusion injury by inhibiting autophagy and apoptosis via activation of mTOR signalling

The traditional Chinese medicine Danshensu (DSS) has a protective effect on cardiac ischaemia/reperfusion (I/R) injury. However, the molecular mechanisms underlying the DSS action remain undefined. We investigated the potential role of DSS in autophagy and apoptosis using cardiac I/R injury models of cardiomyocytes and isolated rat hearts. Cultured neonatal rat cardiomyocytes were subjected to 6 hrs of hypoxia followed by 18 hrs of reoxygenation to induce cell damage. The isolated rat hearts were used to perform global ischaemia for 30 min., followed by 60 min. reperfusion. Ischaemia/reperfusion injury decreased the haemodynamic parameters on cardiac function, damaged cardiomyocytes or even caused cell death. Pre-treatment of DSS significantly improved cell survival and protected against I/R-induced deterioration of cardiac function. The improved cell survival upon DSS treatment was associated with activation of mammalian target of rapamycin (mTOR) (as manifested by increased phosphorylation of S6K and S6), which was accompanied with attenuated autophagy flux and decreased expression of autophagy- and apoptosis-related proteins (including p62, LC3-II, Beclin-1, Bax, and Caspase-3) at both protein and mRNA levels. These results suggest that alleviation of cardiac I/R injury by pre-treatment with DSS may be attributable to inhibiting excessive autophagy and apoptosis through mTOR activation.