Curcumin induces autophagy to protect vascular endothelial cell survival from oxidative stress damage

ROS-induced autophagy regulates porcine trophectoderm cell apoptosis, proliferation, and differentiation

Significant embryo loss remains a serious problem in pig production. Reactive oxygen species (ROS) play a critical role in embryonic implantation and placentation. However, the potential mechanism of ROS on porcine trophectoderm (pTr) cell fate during the peri-implantation period has not been investigated. This study aimed to elucidate the effects of ROS on pTr cell phenotypes and the regulatory role in cell attachment and differentiation. Herein, results showed that exogenous H₂O₂ inhibited pTr cell viability, arrested the cell cycle at S and G2/M phases, and increased cell apoptosis and autophagy protein light chain 3B and Beclin-1, whereas these effects were reversed by different concentrations of N-acetyl-l-cysteine (NAC) posttreatment. In addition, NAC abolished H₂O₂-induced autophagic flux, inhibited intracellular and mitochondrial ROS, and restored expression of genes important for mitochondrial DNA and biogenesis, cell attachment, and differentiation. NAC reversed H₂O₂-activated MAPK and Akt/mammalian target of rapamycin pathways in dose-dependent manners. Furthermore, analyses with pharmacological and RNA interference approaches suggested that autophagy regulated cell apoptosis and gene expression of caudal-related homeobox 2 and IL-1β. Collectively, these results provide new insights into the role of the ROS-induced autophagy in pTr cell apoptosis, attachment, and differentiation, indicating a promising target for decreasing porcine conceptus loss during the peri-implantation period.

Distinct role of autophagy on angiogenesis: highlights on the effect of autophagy in endothelial lineage and progenitor cells

Autophagy plays a critical role in the dynamic growth of each cell through different conditions. It seems that this intracellular mechanism acts as a two-edged sword against the numerous cell insults. Previously, autophagy was described in the context of cell activity and behavior, but little knowledge exists related to the role of autophagy in endothelial cells, progenitors, and stem cells biology from different tissues. Angiogenic behavior of endothelial lineage and various stem cells are touted as an inevitable feature in the restoration of different damaged tissues and organs. This capacity was found to be dictated by autophagy signaling pathway. This review article highlights the fundamental role of cell autophagic response in endothelial cells function, stem cells dynamic, and differentiation rate. It seems that elucidation of the mechanisms related to pro- and/or anti-angiogenic potential of autophagy inside endothelial cells and stem cells could help us to modulate stem cell therapeutic feature post-transplantation.

Functional variants of the ATG7 gene promoter in acute myocardial infarction

BACKGROUND

Coronary artery disease including acute myocardial infarction (AMI) is mainly caused by atherosclerosis, an inflammatory and metabolic disease. Autophagy has been demonstrated to play critical roles in lipid metabolism and inflammation. Altered autophagic activity has been reported in AMI patients. However, molecular basis for dysfunctional autophagy in AMI remains unexplained.

METHODS

In this study, the promoter of the ATG7 gene, encoding a core protein for autophagy, was genetically and functionally analyzed in large cohorts of AMI patients (n = 355) and ethnic-matched healthy controls (n = 363). Related molecular mechanisms were also explored.

RESULTS

A total of 19 DNA sequence variants (DSVs) including single-nucleotide polymorphisms (SNPs) were found in the ATG7 gene promoter. Two novel DSVs and five SNPs were only identified in AMI patients group. These DSVs and SNPs, except one SNP, significantly altered the transcriptional activity of the ATG7 gene promoter in both HEK-293 and H9c2 cells (p < 0.05). Further electrophoretic mobility shift assay revealed that the DSVs and SNPs evidently affected the binding of transcription factors.

CONCLUSIONS

ATG7 gene DSVs and SNPs identified in AMI patients may alter the transcriptional activity of the ATG7 gene promoter and change ATG7 level, contributing to the AMI development as a rare risk factor.

A phase 1 dose-escalation study on the safety, tolerability and activity of liposomal curcumin (Lipocurc™) in patients with locally advanced or metastatic cancer

PURPOSE

This study was conducted to investigate the safety and tolerability of increasing doses of liposomal curcumin in patients with metastatic cancer. Investigations of anti-tumor activity and of the pharmacokinetics of curcumin were secondary objectives.

METHODS

In this phase I, single-center, open-label study in patients with metastatic tumors, liposomal curcumin was administered as a weekly intravenous infusion for 8 weeks. Dose escalation was started at 100 mg/m2 over 8 h and the dose increased to 300 mg/m2 over 6 h.

RESULTS

32 patients were treated. No dose-limiting toxicity was observed in 26 patients at doses between 100 and 300 mg/m2 over 8 h. Of six patients receiving 300 mg/m2 over 6 h, one patient developed hemolysis, and three other patients experienced hemoglobin decreases > 2 g/dL without signs of hemolysis. Pharmacokinetic analyses revealed stable curcumin plasma concentrations during infusion followed by rapid declines to undetectable levels after the infusion. Anti-tumor activity by RECIST V1.1 was not detected. Significant tumor marker responses and transient clinical benefit were observed in two patients.

CONCLUSION

300 mg/m2 liposomal curcumin over 6 h was the maximum tolerated dose in these heavily pretreated patients, and is the recommended starting dose for anti-cancer trials.

The Reactive Oxygen Species-Mitophagy Signaling Pathway Regulates Liver Endothelial Cell Survival During Ischemia/Reperfusion Injury

Ischemia/reperfusion injury (IRI) is the main cause of complications following liver transplantation. Reactive oxygen species (ROS) were thought to be the main regulators of IRI. However, recent studies demonstrate that ROS activate the cytoprotective mechanism of autophagy promoting cell survival. Liver IRI initially damages the liver endothelial cells (LEC), but whether ROS-autophagy promotes cell survival in LEC during IRI is not known. Primary human LEC were isolated from human liver tissue and exposed to an in vitro model of IRI to assess the role of autophagy in LEC. The role of autophagy during liver IRI in vivo was assessed using a murine model of partial liver IRI. During IRI, ROS specifically activate autophagy-related protein (ATG) 7 promoting autophagic flux and the formation of LC3B-positive puncta around mitochondria in primary human LEC. Inhibition of ROS reduces autophagic flux in LEC during IRI inducing necrosis. In addition, small interfering RNA knockdown of ATG7 sensitized LEC to necrosis during IRI. In vivo murine livers in uninjured liver lobes demonstrate autophagy within LEC that is reduced following IRI with concomitant reduction in autophagic flux and increased cell death. In conclusion, these findings demonstrate that during liver IRI ROS-dependent autophagy promotes the survival of LEC, and therapeutic targeting of this signaling pathway may reduce liver IRI following transplantation.

Curcumin, Cardiometabolic Health and Dementia

Current research indicates curcumin [diferuloylmethane; a polyphenolic compound isolated from the rhizomes of the dietary spice turmeric (Curcuma longa)] exerts a beneficial effect on health which may be partly attributable to its anti-oxidative and anti-inflammatory properties. The aim of this review is to examine potential mechanisms of the actions of curcumin in both animal and human studies. Curcumin modulates relevant molecular target pathways to improve glucose and lipid metabolism, suppress inflammation, stimulate antioxidant enzymes, facilitate insulin signalling and reduce gut permeability. Curcumin also inhibits Aβ and tau accumulation in animal models and enhances mitochondria and synaptic function. In conclusion, in high-dose animal studies and in vitro, curcumin exerts a potential beneficial effect on cardiometabolic disease. However, human studies are relatively unconvincing. More intervention studies should be conducted with the new curcumin formulation with improved oral bioavailability.

Curcumin: A naturally occurring autophagy modulator

Autophagy is a self-degradative process that plays a pivotal role in several medical conditions associated with infection, cancer, neurodegeneration, aging, and metabolic disorders. Its interplay with cancer development and treatment resistance is complicated and paramount for drug design since an autophagic response can lead to tumor suppression by enhancing cellular integrity and tumorigenesis by improving tumor cell survival. In addition, autophagy denotes the cellular ability of adapting to stress though it may end up in apoptosis activation when cells are exposed to a very powerful stress. Induction of autophagy is a therapeutic option in cancer and many anticancer drugs have been developed to this aim. Curcumin as a hydrophobic polyphenol compound extracted from the known spice turmeric has different pharmacological effects in both in vitro and in vivo models. Many reports exist reporting that curcumin is capable of triggering autophagy in several cancer cells. In this review, we will focus on how curcumin can target autophagy in different cellular settings that may extend our understanding of new pharmacological agents to overcome relevant diseases.

Identification of compound CA-5f as a novel late-stage autophagy inhibitor with potent anti-tumor effect against non-small cell lung cancer

Currently, particular focus is placed on the implication of autophagy in a variety of human diseases, including cancer. Discovery of small-molecule modulators of autophagy as well as their potential use as anti-cancer therapeutic agents would be of great significance. To this end, a series of curcumin analogs previously synthesized in our laboratory were screened. Among these compounds, (3E,5E)-3-(3,4-dimethoxybenzylidene)-5-[(1H-indol-3-yl)methylene]-1-methylpiperidin-4-one (CA-5f) was identified as a potent late-stage macroautophagy/autophagy inhibitor via inhibiting autophagosome-lysosome fusion. We found that CA-5f neither impaired the hydrolytic function nor the quantity of lysosomes. Use of an isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomic screen in combination with bioinformatics analysis suggested that treatment of human umbilical vein endothelial cells (HUVECs) with CA-5f for 1 h suppressed the levels of cytoskeletal proteins and membrane traffic proteins. Subsequent studies showed that CA-5f exhibited strong cytotoxicity against A549 non-small cell lung cancer (NSCLC) cells, but low cytotoxicity to normal human umbilical vein endothelial cells (HUVECs), by increasing mitochondrial-derived reactive oxygen species (ROS) production. Moreover, CA-5f effectively suppressed the growth of A549 lung cancer xenograft as a single agent with an excellent tolerance in vivo. Results from western blot, immunofluorescence, and TdT-mediated dUTP nick end labeling (TUNEL) assays showed that CA-5f inhibited autophagic flux, induced apoptosis, and did not affect the level of CTSB (cathepsin B) and CTSD (cathepsin D) in vivo, which were consistent with the in vitro data. Collectively, these results demonstrated that CA-5f is a novel late-stage autophagy inhibitor with potential clinical application for NSCLC therapy. Abbreviations: 3-MA, 3-methyladenine; ANXA5, annexin A5; ATG, autophagy related; CA-5f, (3E,5E)-3-(3,4-dimethoxybenzylidene)-5-[(1H-indol-3-yl)methylene]-1-methylpiperidin-4-one; CQ, chloroquine; CTSB, cathepsin B; CTSD, cathepsin D; DMSO, dimethyl sulfoxide; DNM2, dynamin 2; EBSS, Earle's balanced salt solution; GFP, green fluorescent protein; HCQ, hydroxyl CQ; HEK293, human embryonic kidney 293; HUVEC, human umbilical vein endothelial cells; LAMP1, lysosomal associated membrane protein 1; LC-MS/MS, liquid chromatography coupled to tandem mass spectrometry; LDH, lactic acid dehydrogenase; LMO7, LIM domain 7; MAP1LC3B/LC3B, microtubule associated protein 1 light chain 3 beta; NAC, N-acetyl cysteine; MYO1E, myosin IE; NSCLC, non-small cell lung cancer; PARP1, poly(ADP-ribose) polymerase 1; PI, propidium iodide; RFP, red fluorescent protein; ROS, reactive oxygen species; SQSTM1, sequestosome 1; TUNEL, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling.

Aggregation is impaired in starved platelets due to enhanced autophagy and cellular energy depletion

Platelet hyperactivity is the hallmark of thrombosis and hemostasis disorders including atherosclerosis, diabetes, stroke, arthritis, and cancer causing significant mortality and morbidity. Therefore, regulating platelet hyperactivity is an ever growing interest. Very recently, basal autophagic process has been demonstrated to be essential for normal functioning of platelets. However, autophagy can be elevated above basal level under conditions like starvation, and how platelets respond in these settings remains to be elucidative. Therefore, in this study we demonstrate a substantial autophagy induction (above basal level) by starvation, which decreases platelet aggregation responses to various agonists. The decreased aggregation in starved platelets was restored in combination with autophagy inhibitors (3-methyladenine and NH₄Cl) and acetate supplementation. Starved platelets also showed decreased calcium mobilization, granule release, and adhesive properties. Furthermore, ex vivo platelets obtained from starved rats showed increased autophagy markers and decreased aggregation responses to various agonists. Our results distinctly explain that enhanced autophagy and cellular energy depletion are the cause for decreased platelet activation and aggregation. The study emphasizes the cardinal role of starvation and autophagy in the management of diseases and disorders associated with platelet hyperactivity.

Curcumin and dietary polyphenol research: beyond drug discovery

Numerous natural products available over the counter are commonly consumed by healthy, sub-healthy or ill people for the treatment and prevention of various chronic diseases. Among them, a few dietary polyphenols, including the curry compound curcumin, have been attracting the most attention from biomedical researchers and drug developers. Unlike many so-called "good drug candidates", curcumin and several other dietary polyphenols do not have a single known therapeutic target or defined receptor. In addition, the bioavailability of these polyphenols is usually very low due to their poor absorption in the gut. These recently debated features have created enormous difficulties for drug developers. In this review, I do not discuss how to develop curcumin, other dietary polyphenols or their derivatives into pharmaceutical agents. Instead, I comment on how curcumin and dietary polyphenol research has enriched our knowledge of insulin signaling, including the presentation of my perspectives on how these studies will add to our understanding of the famous hepatic insulin function paradox.

Role of AMPK in atherosclerosis via autophagy regulation

Atherosclerosis is characterized by the accumulation of lipids and deposition of fibrous elements in the vascular wall, which is the primary cause of cardiovascular diseases. Adenosine monophosphate-activated protein kinase (AMPK) is a metabolic sensor of energy metabolism that regulates multiple physiological processes, including lipid and glucose metabolism and the normalization of energy imbalances. Overwhelming evidence indicates that AMPK activation markedly attenuates atherosclerosis development. Autophagy inhibits cell apoptosis and inflammation and promotes cholesterol efflux and efferocytosis. Physiological autophagy is essential for maintaining normal cardiovascular function. Increasing evidence demonstrates that autophagy occurs in developing atherosclerotic plaques. Emerging evidence indicates that AMPK regulates autophagy via a downstream signaling pathway. The complex relationship between AMPK and autophagy has attracted the attention of many researchers because of this close relationship to atherosclerosis development. This review demonstrates the role of AMPK and autophagy in atherosclerosis. An improved understanding of this interrelationship will create novel preventive and therapeutic strategies for atherosclerosis.

Celosins inhibit atherosclerosis in ApoE-/- mice and promote autophagy flow

ETHNOPHARMACOLOGICAL RELEVANCE

Semen celosiae is a traditional Chinese medicine for purging hepatic pathogenic fire and removing nebula to improve eyesight, treating hepatopyretic vertigo and hypertension. It possesses a serial of potential bioactivities such as hepatoprotection, anti-tumor and anti-inflammatory, anti-diabetes. The triterpenoid saponins celosins from it were proved to have hepatoprotection, lipid lowing and anti-inflammatory. However, the anti-atherosclerosis activities were not reported to date.

AIM OF THE STUDY

This study was designed to examine the therapeutic effects of celosins (CES), the active constituents extracted from Semen celosiae.

MATERIALS AND METHODS

Atherosclerosis model by feeding high fat diet for 12 weeks in ApoE^-/- mice and foam cell model by ox-LDL-treated peritoneal macrophages were performed. The lipid plaque was measured by histopathological analysis. The LC3 dots in the aortic root lesion examined through tissue immunofluorescence. The peritoneal macrophage phagocytosis, formation of foam cells, genes associated protein expression and autophagy flux were measured on foam cell model by oxidized low-density lipoprotein (Ox-LDL) stimulating peritoneal macrophages. The mRNA expression of CD36, SR-A1, ABCA1 and ABCG1 were determined by Real-Time PCR method. The expressions of LC3 and beclin 1 were measured using Western blot.

RESULTS

CES (10, 30, 90mg/kg; p.o.) administrated for 4 weeks significantly reduced the prevalence of the relative area of plaque in mouse aorta, and showed the therapeutic effect on atherosclerosis. In the tissue section of immunofluorescence for aortic root, compared with high fat diet model group, the number of autophagy bodies in CES group increased significantly, suggesting that inhibiting atherosclerosis effect of CES may be related to its promoting autophagy. In vitro, CES significantly reduced phagocytosis of macrophages on lipid and formation rate of foam cells. CES down-regulated the mRNA expression of CD36 and SR-A1 while up-regulated mRNA expression of ABCA1 and ABCG1. Further, CES increased the autophagy specific protein LC3 and beclin 1, and it also increased the level of autophagy in the cells, and promoted the process of autophagy.

CONCLUSIONS

The therapeutic effect of CES on atherosclerosis may be related to the promotion of autophagy.

Inhibition of mTOR protects the blood-brain barrier in models of Alzheimer's disease and vascular cognitive impairment

An intact blood-brain barrier (BBB) limits entry of proinflammatory and neurotoxic blood-derived factors into the brain parenchyma. The BBB is damaged in Alzheimer's disease (AD), which contributes significantly to the progression of AD pathologies and cognitive decline. However, the mechanisms underlying BBB breakdown in AD remain elusive, and no interventions are available for treatment or prevention. We and others recently established that inhibition of the mammalian/mechanistic target of rapamycin (mTOR) pathway with rapamycin yields significant neuroprotective effects, improving cerebrovascular and cognitive function in mouse models of AD. To test whether mTOR inhibition protects the BBB in neurological diseases of aging, we treated hAPP(J20) mice modeling AD and low-density lipoprotein receptor-null (LDLR-/-) mice modeling vascular cognitive impairment with rapamycin. We found that inhibition of mTOR abrogates BBB breakdown in hAPP(J20) and LDLR-/- mice. Experiments using an in vitro BBB model indicated that mTOR attenuation preserves BBB integrity through upregulation of specific tight junction proteins and downregulation of matrix metalloproteinase-9 activity. Together, our data establish mTOR activity as a critical mediator of BBB breakdown in AD and, potentially, vascular cognitive impairment and suggest that rapamycin and/or rapalogs could be used for the restoration of BBB integrity. NEW & NOTEWORTHY This report establishes mammalian/mechanistic target of rapamycin as a critical mediator of blood-brain barrier breakdown in models of Alzheimer's disease and vascular cognitive impairment and suggests that drugs targeting the target of rapamycin pathway could be used for the restoration of blood-brain barrier integrity in disease states.

Curcumin Suppresses IL-1β Secretion and Prevents Inflammation through Inhibition of the NLRP3 Inflammasome

Turmeric is traditionally used as a spice and coloring in foods. Curcumin is the primary active ingredient in the turmeric, and compelling evidence has shown that it has the ability to inhibit inflammation. However, the mechanism mediating its anti-inflammatory effects are not fully understood. We report that curcumin inhibited caspase-1 activation and IL-1β secretion through suppressing LPS priming and the inflammasome activation pathway in mouse bone marrow-derived macrophages. The inhibitory effect of curcumin on inflammasome activation was specific to the NLRP3, not to the NLRC4 or the AIM2 inflammasomes. Curcumin inhibited the NLRP3 inflammasome by preventing K⁺ efflux and disturbing the downstream events, including the efficient spatial arrangement of mitochondria, ASC oligomerization, and speckle formation. Reactive oxygen species, autophagy, sirtuin-2, or acetylated α-tubulin was ruled out as the mechanism by which curcumin inhibits the inflammasome. Importantly, in vivo data show that curcumin attenuated IL-1β secretion and prevented high-fat diet-induced insulin resistance in wide-type C57BL/6 mice but not in Nlrp3-deficient mice. Curcumin also repressed monosodium urate crystal-induced peritoneal inflammation in vivo. Taken together, we identified curcumin as a common NLRP3 inflammasome activation inhibitor. Our findings reveal a mechanism through which curcumin represses inflammation and suggest the potential clinical use of curcumin in NLRP3-driven diseases.

Natural products as modulator of autophagy with potential clinical prospects

Natural compounds derived from living organisms are well defined for their remarkable biological and pharmacological properties likely to be translated into clinical use. Therefore, delving into the mechanisms by which natural compounds protect against diverse diseases may be of great therapeutic benefits for medical practice. Autophagy, an intricate lysosome-dependent digestion process, with implications in a wide variety of pathophysiological settings, has attracted extensive attention over the past few decades. Hitherto, accumulating evidence has revealed that a large number of natural products are involved in autophagy modulation, either inducing or inhibiting autophagy, through multiple signaling pathways and transcriptional regulators. In this review, we summarize natural compounds regulating autophagy in multifarious diseases including cancer, neurodegenerative diseases, cardiovascular diseases, metabolic diseases, and immune diseases, hoping to inspire further investigation of the underlying mechanisms of natural compounds and to facilitate their clinical use for multiple human diseases.

α-Asarone blocks 7β-hydroxycholesterol-exposed macrophage injury through blocking elF2α phosphorylation and prompting beclin-1-dependent autophagy

Macrophage apoptosis is salient in advanced atherosclerotic lesions and is induced by several stimuli including endoplasmic reticulum (ER) stress. This study examined that a-asarone present in purple perilla abrogated macrophage injury caused by oxysterols via ER stress- and autophagy-mediated mechanisms. Nontoxic a-asarone at 1-20 M attenuated 7β-hydroxycholesterol-induced activation of eukaryotic initiation factor 2a in macrophages leading to C/EBP homologous protein (CHOP) expression and apoptosis due to sustained ER stress. The a-asarone treatment increased the formation of autophagolysosomes localizing in perinuclear regions of 7β-hydroxycholesterol-exposed macrophages. Consistently, this compound promoted the induction of the key autophagic proteins of beclin-1, vacuolar protein sorting 34 and p150 responsible for vesicle nucleation, and prompted the conversion of microtubule-associated protein 1A/1B-light chain 3 and the induction of p62, neighbor of BRCA1 and autophagy-related (Atg) 12-Atg5-Atg16L conjugate involved in phagophore expansion and autophagosome formation. Additionally, a-asarone increased ER phosphorylation of bcl-2 facilitating beclin-1 entry to autophagic process. Furthermore, the deletion of Atg5 or beclin-1 gene enhanced apoptotic CHOP induction. Collectively, a-asarone-stimulated autophagy may be potential multi-targeted therapeutic avenues in treating ER stress-associated macrophage apoptosis.

Curcumin prevents strokes in stroke-prone spontaneously hypertensive rats by improving vascular endothelial function

BACKGROUND

Antioxidants have shown great promise in stroke prevention. Diarylheptanoids (also known as diphenylheptanoids) are a small class of plant secondary metabolites that possess antioxidant activity greater than that of α-tocopherol. Curcumin is the best known member and is mainly extracted from turmeric. This study aimed to explore whether curcumin has a preventive effect on stroke.

METHODS

Stroke-prone spontaneously hypertensive rats (SHRsp) were randomly divided into control group (n = 10) and curcumin group (n = 10), and saline or curcumin (100 mg/kg/day) was administrated daily. Vascular endothelial function was examined by the relaxation of the artery in response to acetylcholine (ACH). The levels of reactive oxygen species (ROS) and nitric oxide (NO) were measured by using dihydroethidium (DHE) and 4, 5-diaminofluorescein (DAF-2 DA), respectively. The expression of uncoupling protein 2 (UCP2) was examined by RT-PCR and immunoblotting.

RESULTS

Administration of curcumin significantly delayed the onset of stroke and increased the survival of SHRsp, which was ascribed to decreased ROS and improved endothelial dependent relaxation of carotid arteries. In the presence of UCP2 inhibitor genipin, both curcumin-mediated decrease of ROS and increase of NO production were blocked.

CONCLUSION

Our study suggests that curcumin exerts a stroke preventive effect by attenuating oxidative stress to improve vascular endothelial function, which might be associated with UCP2 signaling.

Curcumin targets the TFEB-lysosome pathway for induction of autophagy

Curcumin is a hydrophobic polyphenol derived from the herb Curcumalonga and its wide spectrum of pharmacological activities has been widely studied. It has been reported that Curcumin can induce autophagy through inhibition of the Akt-mTOR pathway. However, the effect of Curcumin on lysosome remains largely elusive. In this study, we first found that Curcumin treatment enhances autophagic flux in both human colon cancer HCT116 cells and mouse embryonic fibroblasts (MEFs). Moreover, Curcumin treatment promotes lysosomal function, evidenced by the increased lysosomal acidification and enzyme activity. Second, Curcumin is capable of suppressing the mammalian target of rapamycin (mTOR). Interestingly, Curcumin fails to inhibit mTOR and to activate lysosomal function in Tsc2^−/−MEFs with constitutive activation of mTOR, indicating that Curcumin-mediated lysosomal activation is achieved via suppression of mTOR. Third, Curcumin treatment activates transcription factor EB (TFEB), a key nuclear transcription factor in control of autophagy and lysosome biogenesis and function, based on the following observations: (i) Curcumin directly binds to TFEB, (ii) Curcumin promotes TFEB nuclear translocation; and (iii) Curcumin increases transcriptional activity of TFEB. Finally, inhibition of autophagy and lysosome leads to more cell death in Curcumin-treated HCT116 cells, suggesting that autophagy and lysosomal activation serves as a cell survival mechanism to protect against Curcumin-mediated cell death. Taken together, data from our study provide a novel insight into the regulatory mechanisms of Curcumin on autophagy and lysosome, which may facilitate the development of Curcumin as a potential cancer therapeutic agent.

Mouse Sirt3 promotes autophagy in AngII-induced myocardial hypertrophy through the deacetylation of FoxO1

Sirt3, a mitochondrial NAD+-dependent histone deacetylase, is the only member proven to promote longevity in mammalian Sirtuin family. The processed short form of Sirt3 has been demonstrated to target many mediators of energy metabolism and mitochondrial stress adaptive program. Autophagy serves as a dynamic recycling mechanism and provides energy or metabolic substrates. Among the mechanisms triggered by cardiac stress, opinions vary as to whether autophagy is a protective or detrimental response. Here, by inducing the Sirt3-knockout mice to myocardial hypertrophy with chronic angiotensin II infusion for four weeks, we determined the role of Sirt3 in myocardial hypertrophy and autophagy. In this study, the Sirt3-knockout mice developed deteriorated cardiac function and impaired autophagy compared to wild-type mice. What's more, the overexpression of Sirt3 by lentivirus transfection attenuated cardiomyocytes hypertrophy by promoting autophagy. We further demonstrated that Sirt3 could bind to FoxO1 and activate its deacetylation. Sequentially, deacetylated FoxO1 translocates to the nucleus where it facilitates downstream E3 ubiquitin ligases such as Muscle RING Finger 1 (MuRF1) and muscle atrophy F-box (MAFbx, Atrogin1). Altogether, these results revealed that Sirt3 activation is essential to improve autophagy flux by reducing the acetylation modification on FoxO1, which in turn alleviates myocardial hypertrophy.

Low shear stress induces vascular eNOS uncoupling via autophagy-mediated eNOS phosphorylation

Uncoupled endothelial nitric oxide synthase (eNOS) produces O₂^- instead of nitric oxide (NO). Earlier, we reported rapamycin, an autophagy inducer and inhibitor of cellular proliferation, attenuated low shear stress (SS) induced O₂^- production. Nevertheless, it is unclear whether autophagy plays a critical role in the regulation of eNOS uncoupling. Therefore, this study aimed to investigate the modulation of autophagy on eNOS uncoupling induced by low SS exposure. We found that low SS induced endothelial O₂^- burst, which was accompanied by reduced NO release. Furthermore, inhibition of eNOS by L-NAME conspicuously attenuated low SS-induced O₂^- releasing, indicating eNOS uncoupling. Autophagy markers such as LC3 II/I ratio, amount of Beclin1, as well as ULK1/Atg1 were increased during low SS exposure, whereas autophagic degradation of p62/SQSTM1 was markedly reduced, implying impaired autophagic flux. Interestingly, low SS-induced NO reduction could be reversed by rapamycin, WYE-354 or ATG5 overexpression vector via restoration of autophagic flux, but not by N-acetylcysteine or apocynin. eNOS uncoupling might be ascribed to autophagic flux blockade because phosphorylation of eNOS Thr495 by low SS or PMA stimulation was also regulated by autophagy. In contrast, eNOS acetylation was not found to be regulated by low SS and autophagy. Notably, although low SS had no influence on eNOS Ser1177 phosphorylation, whereas boosted eNOS Ser1177 phosphorylation by rapamycin were in favor of the eNOS recoupling through restoration of autophagic flux. Taken together, we reported a novel mechanism for regulation of eNOS uncoupling by low SS via autophagy-mediated eNOS phosphorylation, which is implicated in geometrical nature of atherogenesis.

Role of FOXO1 in aldosterone-induced autophagy: a compensatory protective mechanism related to podocyte injury

This study was undertaken to elucidate whether and how autophagy was regulated in aldosterone (Aldo)-induced podocyte injury and to examine its role in this model both in vitro and in vivo. In cultured podocytes, Aldo increased autophagy flux as indicated by the enhanced expression of LC3-II/LC3-I and the reduction of p62. Autophagy induction with rapamycin (RP) provided a cytoprotective effect, and inhibition of autophagy with Atg7-specific siRNA, chloroquine (CQ) or 3-methyladenine (3-MA) worsened Aldo-induced podocyte injury by attenuating endoplasmic reticulum (ER) stress. Aldo inhibited Akt phosphorylation but increased the mammalian target of rapamycin (mTOR) signaling pathway; however, Aldo up-regulated the expression of FOXO1 and its downstream effector Rab7. Either knockdown of FOXO1 or Rab7 inhibited Aldo-induced autophagy. Additionally, an elevated level of P300-regulated acetylation of FOXO1 and the interaction of acetylated FOXO1 and Atg7 were also confirmed to be involved in regulating autophagy in Aldo-induced podocytes. Similar results were further confirmed in vivo. We propose that autophagy enhancement through enhancing of the FOXO1/Rab7 axis and post-translational modification of FOXO1 may represent a potential therapeutic strategy against podocyte injury by promoting autophagy.

Sialic acid-modified solid lipid nanoparticles as vascular endothelium-targeting carriers for ischemia-reperfusion-induced acute renal injury

In an attempt to improve therapeutic efficacy of dexamethasone (DXM)-loaded solid lipid nanoparticles (NPs) for renal ischemia-reperfusion injury (IRI)-induced acute renal injury (AKI), sialic acid (SA) is used as a ligand to target the inflamed vascular endothelium. DXM-loaded SA-conjugated polyethylene glycol (PEG)ylated NPs (SA-NPs) are prepared via solvent diffusion method and show the good colloidal stability. SA-NPs reduce apoptotic human umbilical vein endothelial cells (HUVECs) via downregulating oxidative stress-induced Bax, upregulating Bcl-xL, and inhibiting Caspase-3 and Caspase-9 activation. Cellular uptake results suggest SA-NPs can be specifically internalized by the inflamed vascular endothelial cells (H₂O₂-pretreated HUVECs), and the mechanism is associated with the specific binding between SA and E-selectin receptor expressed on the inflamed vascular endothelial cells. Bio-distribution results further demonstrated the enhanced renal accumulation of DXM is achieved in AKI mice treated with SA-NPs, and its content is 2.70- and 5.88-fold higher than those treated with DXM and NPs at 6 h after intravenous administration, respectively. Pharmacodynamic studies demonstrate SA-NPs effectively ameliorate renal functions in AKI mice, as reflected by improved blood biochemical indexes, histopathological changes, oxidative stress levels and pro-inflammatory cytokines. Moreover, SA-NPs cause little negative effects on lymphocyte count and bone mineral density while DXM leads to severe osteoporosis. It is concluded that SA-NPs provide an efficient and targeted delivery of DXM for ischemia-reperfusion-induced injury-induced AKI, with improved therapeutic outcomes and reduced adverse effects.

Melatonin ameliorates hypoglycemic stress-induced brain endothelial tight junction injury by inhibiting protein nitration of TP53-induced glycolysis and apoptosis regulator

Severe hypoglycemia has a detrimental impact on the cerebrovasculature, but the molecular events that lead to the disruption of the integrity of the tight junctions remain unclear. Here, we report that the microvessel integrity was dramatically compromised (59.41% of wild-type mice) in TP53-induced glycolysis and apoptosis regulator (TIGAR) transgenic mice stressed by hypoglycemia. Melatonin, a potent antioxidant, protects against hypoglycemic stress-induced brain endothelial tight junction injury in the dosage of 400 nmol/L in vitro. FRET (fluorescence resonance energy transfer) imaging data of endothelial cells stressed by low glucose revealed that TIGAR couples with calmodulin to promote TIGAR tyrosine nitration. A tyrosine 92 mutation interferes with the TIGAR-dependent NADPH generation (55.60% decreased) and abolishes its protective effect on tight junctions in human brain microvascular endothelial cells. We further demonstrate that the low-glucose-induced disruption of occludin and Caludin5 as well as activation of autophagy was abrogated by melatonin-mediated blockade of nitrosative stress in vitro. Collectively, we provide information on the detailed molecular mechanisms for the protective actions of melatonin on brain endothelial tight junctions and suggest that this indole has translational potential for severe hypoglycemia-induced neurovascular damage.

Curcumin suppresses AGEs induced apoptosis in tubular epithelial cells via protective autophagy

Renal tubular cell apoptosis and tubular dysfunction is an important process underlying diabetic nephropathy (DN). Understanding the mechanisms underlying renal tubular epithelial cell survival is important for the prevention of kidney damage associated with glucotoxicity. Curcumin has been demonstrated to possess potent anti-apoptotic properties. However, the roles of curcumin in renal epithelial cells are yet to be defined. The present study investigated advanced glycation or glycoxidation end-product (AGE)-induced toxicity in renal tubular epithelial cells via several complementary assays, including cell viability, cell apoptosis and cell autophagy in the NRK-52E rat kidney tubular epithelial cell line. The extent of apoptosis was significantly increased in the NRK-52E cells following treatment with AGEs. The results also indicated that curcumin reversed this effect by promoting autophagy through the phosphoinositide 3-kinase/AKT serine/threonine kinase signaling pathway. These conclusions suggested that curcumin exerts a renoprotective effect in the presence of AGEs, at least in part by activating autophagy in NRK-52E cells. Collectively, these findings indicate that curcumin not only exerts renoprotective effects, however may also act as a novel therapeutic strategy for the treatment of diabetic nephropathy.

Autophagy in vascular endothelial cells

The importance of autophagy in cardiovascular physiology and cardiovascular disease is increasingly recognized; however, the precise biological effects and underlying mechanisms of autophagy in the cardiovascular system are still poorly understood. In the last few years, the effects of autophagy in endothelial cells have attracted great interests. This article provides a summary of our current knowledge on the regulatory factors, signalling mechanisms, and functional outcomes of autophagy in endothelial cells. It is suggested that in most situations, induction of an autophagic response has cytoprotective effects. The beneficial effects of autophagy in endothelial cells are likely to be context-dependent, since autophagy may also contribute to cell death under certain circumstances. In addition to regulating endothelial cell survival or death, autophagy is also involved in modulating other important functions, such as nitric oxide production, angiogenesis and haemostasis/thrombosis. The mounting data will help us draw a clear picture of the roles of autophagy in endothelial cell biology and dysfunction. Given the pivotal role of endothelial dysfunction in the pathogenesis of vascular disease, disruptions of autophagy in endothelial cells are likely to have significant contributions. This is supported by some preliminary ex vivo data indicating that compromised autophagic functions may be important in the development of endothelial dysfunctions associated with diabetes and ageing.

Endothelial deletion of mTORC1 protects against hindlimb ischemia in diabetic mice via activation of autophagy, attenuation of oxidative stress and alleviation of inflammation

Peripheral arterial disease (PAD) complicated with diabetes mellitus (DM) still remains a thorny issue due to lack of effective strategies. Our previous study has demonstrated that inhibition of mTORC1 protected adipose-derived stromal cells from hindlimb ischemic injury in PAD mice. However, whether inhibition of mTORC1 could protect against PAD in diabetes mellitus and the underlying mechanisms remained elusive. In this study, we employed endothelial-specific raptor (an essential component of the mTORC1 signaling complex) knockout (KO) mice (Tie2-mTORC1^ko) to investigate whether and how mTORC1 downregulation could alleviate hindlimb ischemic injury in diabetic mice. Tie2-mTORC1^ko mice and their wild-type littermates were intraperitoneally injected with streptozocin to induce type 1 diabetic model, after which the hyperglycemic mice were randomly allocated to sham operation or PAD operation (femoral artery ligation). The restoration of hindlimb blood perfusion and recovery of limb functions were improved in diabetic Tie2-mTORC1^ko PAD mice with significant improvements of autophagy, angiogenesis and vascular integrity as well as attenuation of apoptosis, inflammation and oxidative stress. In vitro, high glucose combining with hypoxia/serum deprivation treatment (HG+H/SD) significantly triggered apoptosis, reactive oxygen species generation and inflammation while inhibited autophagy and tube formation in HUVECs. The effect could be accentuated and attenuated by mTORC1 over-expression (TSC2 siRNA) and mTORC1 silencing (raptor siRNA), respectively. Moreover, autophagy inhibitor 3-MA could simulate the effects of TSC2 siRNA while autophagy inducer rapamycin could mimic the effects of raptor siRNA, suggesting that the beneficial effects of mTORC1 deletion were associated with autophagy induction. In conclusion, our present study demonstrates that endothelial mTORC1 deletion protects against hindlimb ischemic injury in diabetic mice possibly via activation of autophagy, attenuation of oxidative stress and alleviation of inflammation. Therapeutics targeting mTORC1 may therefore represents a promising strategy to rescue limb ischemia in diabetes mellitus.

Arginine vasopressin ameliorates spatial learning impairments in chronic cerebral hypoperfusion via V1a receptor and autophagy signaling partially

Chronic cerebral hypoperfusion (CCH) is a major factor contributing to neurological disorders and cognitive decline. Autophagy activation is believed to provide both beneficial and detrimental roles during hypoxic/ischemic cellular injury. Although arginine vasopressin (AVP) has been strongly involved in many behaviors, especially in learning and memory, the effects of AVP on CCH and their molecular mechanisms remain unclear. Here, to investigate whether there was neuroprotective effects of AVP on CCH through V1a receptor (an AVP receptor) signaling, permanent bilateral carotid arteries occlusion (two vessel occlusion, 2VO) was used to establish a rat model of CCH, and hypertonic saline (5.3%) was injected intraperitoneally to induce the secretion of AVP. Results showed that hypertonic saline effectively alleviated spatial learning and memory deficit, enhanced synaptic plasticity of CA3-CA1 hippocampal synapses, upregulated N-methyl-d-aspartate receptor subunit 2B (NR2B) and postsynaptic density protein 95 (PSD-95) surface expressions, reduced oxidative stress and increased Nissl bodies in 2VO model rats. These phenomena were significantly decreased by V1a receptor antagonist SR49059. Interestingly, hypertonic saline also upregulated autophagy in the hippocampus of 2VO rats partly through V1a receptor. These findings imply that AVP has a beneficial role for the treatment of cognitive impairments partly through V1a receptor signaling in CCH, which is possibly related to improving synaptic plasticity by promoting NR2B and PSD-95 externalization and by enhancing autophagy.

Curcumin accelerates the repair of sciatic nerve injury in rats through reducing Schwann cells apoptosis and promoting myelinization

BACKGROUND

Schwann cells (SCs) play an indispensable role in the repair and regeneration of injured peripheral nerve. Curcumin can reduce SCs apoptosis, and promote the regeneration and functional recovery of injured peripheral nerves. However, the corresponding mechanisms are not clear.

OBJECTIVE

The article was aimed to explore the effect and corresponding mechanisms of curcumin on the repair of sciatic nerve injury in rats.

METHODS

After surgery induced sciatic nerve injury, the model rats were divided into three groups and treated with curcumin, curcumin+PD98059 and curcumin+IGF-1 respectively for 4days. The phosphorylation of Erk1/2 and Akt, and the expression of LC3-II, Beclin 1 and p62 were measured using western blotting. After treatment for 60days, myelination of the injured sciatic nerve was evaluated by MBP immunohistochemical staining and the expression of PMP22, Fibrin and S100 were determined using qRT-PCR and western blotting. In vitro, RSC96 cells were starved for 12h to induce autophagy, and received DMSO, curcumin, PD98059+curcumin, IGF-1+curcumin and BFA1 respectively. The phosphorylation of Erk1/2、Akt and the expression of LC3-II, Beclin 1, p62, PMP22, Fibrin and S100 were measured using western blotting, and the cell apoptosis was detected by flow cytometry.

RESULTS

Curcumin could promote injury-induced cell autophagy, remyelination and axon regeneration in sciatic nerve of rats. In vitro, curcumin could accelerate cell autophagy through regulating autophagy related Erk1/2 and Akt pathway, prevent cell apoptosis and promote expression of PMP22 and S100, and reduced deposition of Fibrin in cultured RSC96 SCs.

CONCLUSIONS

Curcumin could accelerate injured sciatic nerve repair in rats through reducing SCs apoptosis and promoting myelinization.

Protective mechanism of FSH against oxidative damage in mouse ovarian granulosa cells by repressing autophagy

Oxidative stress-induced granulosa cell (GCs) death represents a common reason for follicular atresia. Follicle-stimulating hormone (FSH) has been shown to prevent GCs from oxidative injury, although the underlying mechanism remains to be elucidated. Here we first report that the suppression of autophagic cell death via some novel signaling effectors is engaged in FSH-mediated GCs protection against oxidative damage. The decline in GCs viability caused by oxidant injury was remarkably reduced following FSH treatment, along with impaired macroautophagic/autophagic flux under conditions of oxidative stress both in vivo and in vitro. Blocking of autophagy displayed similar levels of suppression in oxidant-induced cell death compared with FSH treatment, but FSH did not further improve survival of GCs pretreated with autophagy inhibitors. Further investigations revealed that activation of the phosphoinositide 3-kinase (PI3K)-AKT-MTOR (mechanistic target of rapamycin [serine/threonine kinase]) signaling pathway was required for FSH-mediated GCs survival from oxidative stress-induced autophagy. Additionally, the FSH-PI3K-AKT axis also downregulated the autophagic response by targeting FOXO1, whereas constitutive activation of FOXO1 in GCs not only abolished the protection from FSH, but also emancipated the autophagic process, from the protein level of MAP1LC3B-II to autophagic gene expression. Furthermore, FSH inhibited the production of acetylated FOXO1 and its interaction with Atg proteins, followed by a decreased level of autophagic cell death upon oxidative stress. Taken together, our findings suggest a new mechanism involving FSH-FOXO1 signaling in defense against oxidative damage to GCs by restraining autophagy, which may be a potential avenue for the clinical treatment of anovulatory disorders.

Nutritional approaches for managing obesity-associated metabolic diseases

Obesity is an ongoing pandemic and serves as a causal factor of a wide spectrum of metabolic diseases including diabetes, fatty liver disease, and cardiovascular disease. Much evidence has demonstrated that nutrient overload/overnutrition initiates or exacerbates inflammatory responses in tissues/organs involved in the regulation of systemic metabolic homeostasis. This obesity-associated inflammation is usually at a low-grade and viewed as metabolic inflammation. When it exists continuously, inflammation inappropriately alters metabolic pathways and impairs insulin signaling cascades in peripheral tissues/organs such as adipose tissue, the liver and skeletal muscles, resulting in local fat deposition and insulin resistance and systemic metabolic dysregulation. In addition, inflammatory mediators, e.g., proinflammatory cytokines, and excessive nutrients, e.g., glucose and fatty acids, act together to aggravate local insulin resistance and form a vicious cycle to further disturb the local metabolic pathways and exacerbate systemic metabolic dysregulation. Owing to the critical role of nutrient metabolism in controlling the initiation and progression of inflammation and insulin resistance, nutritional approaches have been implicated as effective tools for managing obesity and obesity-associated metabolic diseases. Based on the mounting evidence generated from both basic and clinical research, nutritional approaches are commonly used for suppressing inflammation, improving insulin sensitivity, and/or decreasing fat deposition. Consequently, the combined effects are responsible for improvement of systemic insulin sensitivity and metabolic homeostasis.

Curcumin Improves Palmitate-Induced Insulin Resistance in Human Umbilical Vein Endothelial Cells by Maintaining Proteostasis in Endoplasmic Reticulum

Dysfunction of proteasome and autophagy will result in disturbance of endoplasmic reticulum (ER) proteostasis, and thus lead to long-term and chronic ER stress and subsequent unfolded protein response (UPR), which is implicated in the occurrence and development of insulin resistance. Curcumin exerts beneficial metabolic effects in in vitro cells and in vivo animal models of diabetes and diabetic complications including cardiovascular diseases, due to its powerful anti-oxidative and anti-inflammatory properties. However, its impacts on insulin resistance of endothelial cells and its underlying mechanism(s) remain ill-defined. Herein, we tested the hypothesis that curcumin action in ER protein quality control was related to improvement of insulin resistance in human umbilical vein endothelial cells (HUVECs) cultured with saturated fatty acid palmitate. We found that palmitate treatment induced insulin resistance of HUVECs and activated both the ubiquitin-proteasome system (UPS) and autophagy. Palmitate-stimulated activation of the UPS and autophagy was attenuated by pharmacological inhibition of ER stress. In addition, curcumin supplementation mitigated palmitate-induced insulin resistance, inhibited the UPS, and activated autophagy. Furthermore, curcumin administration suppressed palmitate-induced protein aggregation and ER stress. Genetic inhibition of autophagy by silencing autophagy protein 5 (Atg5) completely restored total protein ubiquitination and protein aggregation in HUVECs treated with combined curcumin and palmitate. Atg5-knockdown also abolished the beneficial effects of curcumin on palmitate-induced ER stress, JNK/IRS-1 pathway as well as insulin signaling. Our results reveal that curcumin-activated autophagy could maintain proteostasis in ER leading to attenuation of ER stress and subsequent inhibition of JNK/IRS-1 pathway and improvement of insulin resistance.

Catalpol protects glucose-deprived rat embryonic cardiac cells by inducing mitophagy and modulating estrogen receptor

Catalpol, a bioactive component from Rehmannia glutinosa (Di Huang), has been widely used to protect cardiomyocytes against myocardial ischemia. The aim of the present study was to investigate the anti-apoptotic and anti-oxidative effects of Catalpol on glucose-starved H9c2 cells for cardio-protection and to elucidate the underlying mechanisms. Here, we showed that Catalpol protected the glucose-starved H9c2 cells through reducing apoptosis and attenuating oxidative damage. Moreover, the increases of autophagic lysosomes, LC3, autophagic flux and autophagic vacuole were observed in Catalpol-treated cells using flow cytometer and fluorescence microscope. Western blotting analyses showed that the autophagy-related proteins (LC3, Beclin1 and ULK) were markedly increased in Catalpol-treated cells, suggesting that Catalpol up-regulated autophagy in glucose starved H9c2 cells. Mechanistic investigations revealed that the autophagy inhibitor 3-MA markedly abrogated Catalpol's anti-apoptotic and anti-oxidative effects and prevented Catalpol-induced mitophagy. Furthermore, the estrogen receptor inhibitor tamoxifen significantly abolished Catalpol up-regulation of mitophagic related proteins (LC3, Beclin 1, p62, ATG5). Collectively, these data revealed that Catalpol inhibited apoptosis and oxidative stress in glucose-deprived H9c2 cell through promoting cell mitophagy and modulating estrogen receptor, supporting the notion that Catalpol could be a novel drug candidate against myocardial ischemia for the treatment of cardiovascular diseases.

Regulation of autophagy by some natural products as a potential therapeutic strategy for cardiovascular disorders

Autophagy is a lysosomal degradation process through which long-lived and misfolded proteins and organelles are sequestered, degraded by lysosomes, and recycled. Autophagy is an essential part of cardiomyocyte homeostasis and increases the survival of cells following cellular stress and starvation. Recent studies made clear that dysregulation of autophagy in the cardiovascular system leads to heart hypertrophy and failure. In this manner, autophagy seems to be an attractive target in the new treatment of cardiovascular diseases. Although limited activation of autophagy is generally considered to be cardioprotective, excessive autophagy leads to cell death and cardiac atrophy. Natural products such as resveratrol, berberine, and curcumin that are present in our diet, can trigger autophagy via canonical (Beclin-1-dependent) and non-canonical (Beclin-1-independent) pathways. The autophagy-modifying capacity of these compounds should be taken into consideration for designing novel therapeutic agents. This review focuses on the role of autophagy in the cardioprotective effects of these compounds.

Quercetin induces autophagy via FOXO1-dependent pathways and autophagy suppression enhances quercetin-induced apoptosis in PASMCs in hypoxia

Quercetin, an important dietary flavonoid has been demonstrated to potentially reverse or even prevent pulmonary arterial hypertension (PAH) progression. However, the effects of quercetin on apoptosis and autophagy in pulmonary arterial smooth muscle cells (PASMCs) have not yet been clearly elucidated. The current study found that quercetin significantly induce the apoptotic and autophagic capacities of PASMCs in vitro and in vivo in hypoxia. In addition, we found that quercetin increases FOXO1 (a major mediator in autophagy regulation) expression and transcriptional activity. Moreover, FOXO1 knockdown by siRNAs inhibited the phosphorylation of mTOR and 4E-BPI, which is downstream of P70-S6K, and markedly blocked quercetin-induced autophagy. We also observed that FOXO1-mediated autophagy was achieved via SESN3 not Rictor upregulation and after mTOR suppression. Furthermore, Treatment with autophagy-specific inhibitors could markedly enhance quercetin-induced apoptosis in PASMCs under hypoxia. Finally, quercetin in combination with autophagy inhibition treatment could enhance the therapeutic effects of quercetin in hypoxia-associated PAH in vivo. Taken together, quercetin could enhance hypoxia-induced autophagy through the FOXO1-SENS3-mTOR pathway in PASMCs. Combining quercetin and autophagy inhibitors may be a novel therapeutic strategy for treating hypoxia-associated PAH.

Plant Phenols and Autophagy

Many plant phenols (stilbenes, curcumins, catechins, flavonoids, etc.) are effective antioxidants and protect cells during oxidative stress. Extensive clinical studies on the potential of phenolic compounds for treatment of cardiovascular, neurodegenerative, oncological, and inflammatory diseases are now being conducted. In addition to direct antioxidant effect, plant phenols may provide a protective effect via activation of the Keap1/Nrf2/ARE redox-sensitive signaling system and regulation of autophagy. In this review, mechanisms of effects of the most common plant phenols on autophagy are presented.

Protective Effect of Psoralea corylifolia L. Seed Extract against Palmitate-Induced Neuronal Apoptosis in PC12 Cells

The extract of Psoralea corylifolia seeds (PCE) has been widely used as a herbal medicine because of its beneficial effect on human health. In this study, we investigated the protective effects and molecular mechanisms of PCE on palmitate- (PA-) induced toxicity in PC12 cells, a neuron-like cell line. PCE significantly increased cell viability in PA-treated PC12 cells and showed antiapoptotic effects, as evidenced by decreased expression of cleaved caspase-3, cleaved poly(ADP-ribose) polymerase, and bax protein as well as increased expression of bcl-2 protein. In addition, PCE treatment reduced PA-induced reactive oxygen species production and upregulated mRNA levels of antioxidant genes such as nuclear factor (erythroid-derived 2)-like 2 and heme oxygenase 1. Moreover, PCE treatment recovered the expression of autophagy marker genes such as beclin-1 and p62, which was decreased by PA treatment. Treatment with isopsoralen, one of the major components of PCE extract, also recovered the expression of autophagy marker genes and reduced PA-induced apoptosis. In conclusion, PCE exerts protective effects against lipotoxicity via its antioxidant function, and this effect is mediated by activation of autophagy. PCE might be a potential pharmacological agent to protect against neuronal cell injury caused by oxidative stress or lipotoxicity.

The Anti-Cancer Effect of Polyphenols against Breast Cancer and Cancer Stem Cells: Molecular Mechanisms

The high incidence of breast cancer in developed and developing countries, and its correlation to cancer-related deaths, has prompted concerned scientists to discover novel alternatives to deal with this challenge. In this review, we will provide a brief overview of polyphenol structures and classifications, as well as on the carcinogenic process. The biology of breast cancer cells will also be discussed. The molecular mechanisms involved in the anti-cancer activities of numerous polyphenols, against a wide range of breast cancer cells, in vitro and in vivo, will be explained in detail. The interplay between autophagy and apoptosis in the anti-cancer activity of polyphenols will also be highlighted. In addition, the potential of polyphenols to target cancer stem cells (CSCs) via various mechanisms will be explained. Recently, the use of natural products as chemotherapeutics and chemopreventive drugs to overcome the side effects and resistance that arise from using chemical-based agents has garnered the attention of the scientific community. Polyphenol research is considered a promising field in the treatment and prevention of breast cancer.

6-Gingerol induces autophagy to protect HUVECs survival from apoptosis

6-Gingerol, the major pharmacologically-active component of ginger, has the potential to prevent heart disease. However, the mechanisms are not well understood. In this study, the protective effect of 6-gingerol against hydrogen peroxide-induced apoptosis in human umbilical vein endothelial cells (HUVECs) was investigated. Apoptosis was detected by Hoechst 33342 and Flow cytometry analysis. To further elucidate the crosstalk between apoptosis and autophagy, we tested the expression of autophagy related proteins, LC3B, Bcl-2, Beclin1, AKT, p-AKT, mechanistic target of rapamycin (mTOR), and p-mTOR. Furthermore, mitochondrial membrane potential and the intracellular generation of reactive oxygen species (ROS) were also investigated. Our data revealed that 6-gingerol significantly reduced apoptosis by inducing autophagy. It has been demonstrated that 6-gingerol suppressed the phosphatidylinositol 3-kinase (PI3K)/AKT/mTOR signaling pathway, increased the expression of Beclin1 to promote autophagy, and increased Bcl-2 expression to inhibit apoptosis. In addition, the damage of mitochondrial was protected, and ROS level was decreased by 6-gingerol. These firmly indicate 6-gingerol has a strong protective ability against the apoptosis caused by oxidative stress in HUVECs, and the mechanism may relate to the induction of autophagy. Our data suggest 6-gingerol may be beneficial in the prevention of atherosclerosis.

Ginsenoside Rg1 protects starving H9c2 cells by dissociation of Bcl-2-Beclin1 complex

Background

Autophagy can result in cellular adaptation, as well as cell survival or cell death. We investigated how ginsenoside Rg1(G-Rg1) regulates the relationship between autophagy and apoptosis induced by continuous starvation.

Methods

H9c2 cells under continuous starvation were treated with or without ginsenoside Rg1, and autophagy and apoptosis related proteins were assessed over a continuous time course by Western blot. Dynamic fluorescence intensity of green fluorescent protein (GFP)-LC3 was used to assess autophagosome formation by live cell imaging. Cyan fluorescent protein (CFP) -Beclin1(BECN1) and yellow fluorescent protein (YFP) -Bcl-2 were co-transfected into cells to observe ginsenoside Rg1 regulation of BECN1/Bcl-2 interaction using Fluorescence Resonance Energy Transfer (FRET). Immunoprecipitation was also used to assess BECN1/Bcl-2 interaction over a continuous time course.

Results

In H9c2 cells, starvation induced both apoptosis and autophagy. Cell apoptosis was significantly attenuated in ginsenoside Rg1-treated conditions, while autophagy was promoted. Ginsenoside Rg1 weakened the interaction between Beclin1 and Bcl-2, inhibiting apoptosis while promoting autophagy. Our results suggest that autophagy is beneficial to starved cardiac cells over a period of time. Furthermore, we describe the effect of ginsenoside Rg1 on the relationship between autophagy and apoptosis during starvation.

Conclusions

Our findings provide valuable evidence for employing ginsenoside Rg1 as a specific promoter of autophagy and inhibitor of apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12906-016-1112-2) contains supplementary material, which is available to authorized users.

A novel curcumin analog binds to and activates TFEB in vitro and in vivo independent of MTOR inhibition

Autophagy dysfunction is a common feature in neurodegenerative disorders characterized by accumulation of toxic protein aggregates. Increasing evidence has demonstrated that activation of TFEB (transcription factor EB), a master regulator of autophagy and lysosomal biogenesis, can ameliorate neurotoxicity and rescue neurodegeneration in animal models. Currently known TFEB activators are mainly inhibitors of MTOR (mechanistic target of rapamycin [serine/threonine kinase]), which, as a master regulator of cell growth and metabolism, is involved in a wide range of biological functions. Thus, the identification of TFEB modulators acting without inhibiting the MTOR pathway would be preferred and probably less deleterious to cells. In this study, a synthesized curcumin derivative termed C1 is identified as a novel MTOR-independent activator of TFEB. Compound C1 specifically binds to TFEB at the N terminus and promotes TFEB nuclear translocation without inhibiting MTOR activity. By activating TFEB, C1 enhances autophagy and lysosome biogenesis in vitro and in vivo. Collectively, compound C1 is an orally effective activator of TFEB and is a potential therapeutic agent for the treatment of neurodegenerative diseases.

miR-1273g-3p participates in acute glucose fluctuation-induced autophagy, dysfunction, and proliferation attenuation in human umbilical vein endothelial cells

Acute glucose fluctuations (AGF) often cause high mortality among critically ill patients, but the mechanisms induced by AGF are not clear. Recent studies suggest that endothelial dysfunction is a key factor that leads to high mortality among critically ill patients. Our goal is to evaluate the phenomenon and mechanisms of endothelial dysfunction induced by AGF. In this study, the functions of human umbilical vein endothelial cells (HUVECs) were compared after treatment with sustained high glucose (SHG), AGF in two groups (AGF1 fluctuations between 5 and 16 mM and AGF2 fluctuations between 5 and 25 mM), and normal glucose levels as a control group (CTR). The medium of the groups was changed every 4 h. The influence of AGF on wound healing was also tested on C57BL/6 mice. The results show that cell proliferation, angiogenesis, and migration functions were injured in the SHG and both AGF groups. AGF2 group shows the worse condition in vitro. In vivo, the wound healing was delayed after the AGF treatment. Furthermore, the markers of apoptosis and autophagy were analyzed. We observed that the autophagy changed in all treatment groups, but apoptosis showed no change. To get to know the mechanism of dysfunction and autophagy, we performed the microRNA chip assay and real-time PCR and found miR-1273g-3p remarkably changed in AGF2 group. After the mimic and inhibitor of miR-1273g-3p were transfected during the AGF2 treatment, we found that the dysfunction and autophagy were partially enhanced by miR-1273g-3p mimic and reversed by miR-1273g-3p inhibitor in AGF2 group. Thus, we conclude that AGF can induce more dysfunction and autophagy, and miR-1273g-3p is also an important factor that leads to the injury.

Nicotinate-Curcumin Impedes Foam Cell Formation from THP-1 Cells through Restoring Autophagy Flux

Our previous studies have indicated that a novel curcumin derivate nicotinate-curcumin (NC) has beneficial effects on the prevention of atherosclerosis, but the precise mechanisms are not fully understood. Given that autophagy regulates lipid metabolism, the present study was designed to investigate whether NC decreases foam cell formation through restoring autophagy flux in oxidized low-density lipoprotein (ox-LDL)-treated THP-1 cells. Our results showed that ox-LDL (100 μg/ml) was accumulated in THP-1 cells and impaired autophagy flux. Ox-LDL-induced impairment of autophagy was enhanced by treatment with the autophagy inhibitor chloroquine (CQ) and rescued by the autophagy inducer rapamycin. The aggregation of ox-LDL was increased by CQ, but decreased by rapamycin. In addition, colocalization of lipid droplets with LC3-II was remarkably reduced in ox-LDL group. In contrast, NC (10 μM) rescued the impaired autophagy flux by significantly increasing level of LC3-II, the number of autophagolysosomes, and the degradation of p62 in ox-LDL-treated THP-1 cells. Inhibition of the PI3K-Akt-mTOR signaling was required for NC-rescued autophagy flux. Notably, our results showed that NC remarkably promoted the colocalization of lipid droplets with autophagolysosomes, increased efflux of cholesterol, and reduced ox-LDL accumulation in THP-1 cells. However, treatment with 3-methyladenine (3-MA) or CQ reduced the protective effects of NC on lipid accumulation. Collectively, the findings suggest that NC decreases lipid accumulation in THP-1 cells through restoring autophagy flux, and further implicate that NC may be a potential therapeutic reagent to reverse atherosclerosis.