Puerarin protects rat brain against ischemia/reperfusion injury by suppressing autophagy via the AMPK-mTOR-ULK1 signaling pathway

Bisphenol A promotes autophagy in ovarian granulosa cells by inducing AMPK/mTOR/ULK1 signalling pathway

BACKGROUND

Bisphenol A (BPA) is a widespread endocrine-disrupting chemical with estrogen like effects, which could interfere with the human reproductive system by disrupting the normal function of granulosa cells (GCs) leading to abnormal ovarian function. However, the mechanism of its toxicity on human GCs has not been clearly described thus far.

METHODS

106 normogonadotropic infertile women undergoing their first in-vitro fertilization-embryo transfer (IVF-ET) cycle were recruited. Urinary BPA level and the early outcomes of IVF-ET were analysed. Patients were divided to low and high BPA exposure groups using the median urinary BPA concentration as the cut-off value. In-vivo and in-vitro studies were conducted using mice and human granulosa cell line (KGN cells). Female Kunming mice approximately 6-8 weeks of age were poisoned with BPA at different dosages (1, 10 or 100 μg/kg) by oral gavage once daily for 2 weeks, while KGN cells were exposed to BPA at the concentration of 1, 10 or 100 nM for 24 h, 48 h or 72 h. BPA-induced ovarian morphologic changes were analysed by histopathology investigation. Cell viability and apoptosis were evaluated using CCK-8, TUNEL and flowcytometric, respectively. Hormone levels were determined using ELISA and the molecular mechanism studies were conducted using immunofluorescence, RT-PCR and western blots.

RESULTS

The oocyte retrieval rate, maturation rate and embryo implantation rate significantly decreased with the higher level of urinary BPA concentration. Peak E2 level was lower in high BPA group, but no statistical significance could be observed. In BPA treated mice, cystic dilation of the follicles with a decreased number of GCs could be observed histopathologically. Decreased E2, P4 and AMH level and GCs autophagy could be detected both in-vivo and in-vitro with the activation of AMPK/mTOR/ULK1 signalling pathway. As being confirmed in KGN cells, phosphorylated AMPK and ULK1 increased while phosphorylated mTOR decreased, and by inhibition autophagy using knockdown of AMPK or 3-MA, adverse effects of BPA exposure in-vitro could be reversed.

CONCLUSION

BPA exposure might abnormally influence human ovarian functions leading to abnormal folliculogenesis by activation of autophagy in GCs through AMPK/mTOR/ULK1 pathway.

Radix Puerarin Extract (Puerarin) Could Improve Meat Quality of Heat-Stressed Beef Cattle Through Changing Muscle Antioxidant Ability and Fiber Characteristics

The experiment was conducted to investigate the effects of dietary supplementation with Puerarin on meat quality, muscle antioxidant ability, and muscle fiber characteristics of beef cattle under a hot environment in summer. Thirty-two 15 ± 1.5-month-old Jinjiang bulls (291.65 ± 8.84 kg) were randomly divided into four groups with dietary Puerarin at 0 (control), 200 (Pue200), 400 (Pue400), and 800 (Pue800) mg/kg in the feed concentrate (n = 8). The feeding trial lasted for 60 days after a 10-day adaptation period (July 1-September 8); the average values of temperature, relative humidity and temperature, and humidity index were 30.68°C, 68.05%, and 81.81, respectively. The growth performance on day 40 of the experiment period was calculated. After 60 days' experimental period, four Jinjiang cattle per treatment from the control group, Pue400 group, and Pue800 group were slaughtered. Compared with the control group, the Pue400 and Pue800 groups improved the growth performance of beef cattle; the Pue800 group elevated the activities of superoxide dismutase, total antioxidant capacity, and glutathione peroxidase in the M. longissimus thoracis (LT) muscle. In the control group, the cell membrane was incomplete, and most of the mitochondria were elongated and in a fission state, while in the Pue400 and Pue800 groups, the cell membrane was clear and complete, and the mitochondria presented with round and oval shapes. Compared with the control group, the Pue400 and Pue800 groups reduced the shear force of the LT muscle, and the Pue400 group decreased the muscle fiber diameter and the myosin heavy-chain (MyHC)-IIb gene expression. Furthermore, the Pue400 and Pue800 groups decreased the ratio of AMP/ATP, the Pue800 group reduced the AMP-activated protein kinase α2 mRNA expression, and the Pue400 group improved the nuclear respiratory factor 1 mRNA expression. These results indicated that dietary supplementation with Puerarin might be beneficial to the meat quality of heat-stressed beef cattle by improving muscle antioxidant ability and reducing the MyHC-IIb muscle fiber composition. Based on the results of this study, we recommended 400 mg/kg Puerarin in the feed concentrate of beef cattle (~300 kg) for mitigation of heat stress.

MTORC1-Regulated Metabolism Controlled by TSC2 Limits Cardiac Reperfusion Injury

RATIONALE

The mTORC1 (mechanistic target of rapamycin complex-1) controls metabolism and protein homeostasis and is activated following ischemia reperfusion (IR) injury and by ischemic preconditioning (IPC). However, studies vary as to whether this activation is beneficial or detrimental, and its influence on metabolism after IR is little reported. A limitation of prior investigations is their use of broad gain/loss of mTORC1 function, mostly applied before ischemic stress. This can be circumvented by regulating one serine (S1365) on TSC2 (tuberous sclerosis complex) to achieve bidirectional mTORC1 modulation but only with TCS2-regulated costimulation.

OBJECTIVE

We tested the hypothesis that reduced TSC2 S1365 phosphorylation protects the myocardium against IR and is required for IPC by amplifying mTORC1 activity to favor glycolytic metabolism.

METHODS AND RESULTS

Mice with either S1365A (TSC2^SA; phospho-null) or S1365E (TSC2^SE; phosphomimetic) knockin mutations were studied ex vivo and in vivo. In response to IR, hearts from TSC2^SA mice had amplified mTORC1 activation and improved heart function compared with wild-type and TSC2^SE hearts. The magnitude of protection matched IPC. IPC requited less S1365 phosphorylation, as TSC2^SE hearts gained no benefit and failed to activate mTORC1 with IPC. IR metabolism was altered in TSC2^SA, with increased mitochondrial oxygen consumption rate and glycolytic capacity (stressed/maximal extracellular acidification) after myocyte hypoxia-reperfusion. In whole heart, lactate increased and long-chain acylcarnitine levels declined during ischemia. The relative IR protection in TSC2^SA was lost by lowering glucose in the perfusate by 36%. Adding fatty acid (palmitate) compensated for reduced glucose in wild type and TSC2^SE but not TSC2^SA which had the worst post-IR function under these conditions.

CONCLUSIONS

TSC2-S1365 phosphorylation status regulates myocardial substrate utilization, and its decline activates mTORC1 biasing metabolism away from fatty acid oxidation to glycolysis to confer protection against IR. This pathway is also engaged and reduced TSC2 S1365 phosphorylation required for effective IPC. Graphic Abstract: A graphic abstract is available for this article.

From Preclinical Stroke Models to Humans: Polyphenols in the Prevention and Treatment of Stroke

Polyphenols are an important family of molecules of vegetal origin present in many medicinal and edible plants, which represent important alimentary sources in the human diet. Polyphenols are known for their beneficial health effects and have been investigated for their potential protective role against various pathologies, including cancer, brain dysfunctions, cardiovascular diseases and stroke. The prevention of stroke promoted by polyphenols relies mainly on their effect on cardio- and cerebrovascular systems. However, a growing body of evidence from preclinical models of stroke points out a neuroprotective role of these molecules. Notably, in many preclinical studies, the polyphenolic compounds were effective also when administered after the stroke onset, suggesting their possible use in promoting recovery of patients suffering from stroke. Here, we review the effects of the major polyphenols in cellular and in vivo models of both ischemic and hemorrhagic stroke in immature and adult brains. The results from human studies are also reported.

P27 Protects Neurons from Ischemic Damage by Suppressing Oxidative Stress and Increasing Autophagy in the Hippocampus

p27^Kip1 (p27), a well-known cell regulator, is involved in the regulation of cell death and survival. In the present study, we observed the effects of p27 against oxidative stress induced by H₂O₂ in HT22 cells and transient ischemia in gerbils. Tat (trans-acting activator of transcription) peptide and p27 fusion proteins were prepared to facilitate delivery into cells and across the blood-brain barrier. The tat-p27 fusion protein, rather than its control protein Control-p27, was delivered intracellularly in a concentration and incubation time-dependent manner and showed its activity in HT22 cells. The localization of the delivered Tat-p27 protein was also confirmted in the HT22 cells and hippocampus in gerbils. In addition, the optimal concentration (5 μM) of Tat-p27 was determined to protect neurons from cell death induced by 1 mM H₂O₂. Treatment with 5 μM Tat-p27 significantly ameliorated H₂O₂-induced DNA fragmentation and the formation of reactive oxygen species (ROS) in HT22 cells. Tat-p27 significantly mitigated the increase in locomotor activity a day after ischemia and neuronal damage in the hippocampal CA1 region. It also reduced the ischemia-induced membrane phospholipids and ROS formation. In addition, Tat-p27 significantly increased microtubule-associated protein 1A/1B light chain 3A/3B expression and ameliorated the H₂O₂ or ischemia-induced increases of p62 and decreases of beclin-1 in the HT22 cells and hippocampus. These results suggest that Tat-p27 protects neurons from oxidative or ischemic damage by reducing ROS-induced damage and by facilitating the formation of autophagosomes in hippocampal cells.

Acupuncture protects against cerebral ischemia-reperfusion injury via suppressing endoplasmic reticulum stress-mediated autophagy and apoptosis

Background

Acupuncture treatment possesses the neuroprotection potential to attenuate cerebral ischemia–reperfusion (I/R) injury. Endoplasmic reticulum (ER) stress has been suggested to be involved in the pathogenic mechanism of cerebral I/R injury. Whether acupuncture protects against cerebral I/R injury via regulating ER stress remains unclear. This study aimed to evaluate the role of ER stress in the neuroprotection of acupuncture against cerebral I/R injury and its underlying mechanisms.

Methods

Cerebral I/R injury was induced by middle cerebral artery occlusion (MCAO) in rats. Acupuncture was carried out at Baihui (GV 20), and Qubin (GB7) acupoints in rats immediately after reperfusion. The infarct volumes, neurological score, ER stress, autophagy and apoptosis were determined.

Results

Acupuncture treatment decreased infarct volume, neurological score and suppressed ER stress via inactivation of ATF-6, PERK, and IRE1 pathways in MCAO rats. Attributing to ER stress suppression, 4-PBA (ER stress inhibitor) promoted the beneficial effect of acupuncture against cerebral I/R injury. Whereas, ER stress activator tunicamycin significantly counteracted the neuroprotective effects of acupuncture. In addition, acupuncture restrained autophagy via regulating ER stress in MCAO rats. Finally, ER stress took part in the neuroprotective effect of acupuncture against apoptosis in cerebral I/R injury.

Conclusions

Our findings suggest that acupuncture offers neuroprotection against cerebral I/R injury, which is attributed to repressing ER stress-mediated autophagy and apoptosis.

Lasting metabolic effect of a high-fructose diet on global cerebral ischemia

Introduction: Obesity is a public health problem that is associated with cerebrovascular diseases, such as ischemic stroke. The coexistence of obesity with cerebral ischemia has been suggested to be considerably detrimental to the neurological system. Objective: Hence, in this study, we evaluated the long-term effects of a 20% high fructose diet (HFD) and global cerebral ischemia on neurological, cognitive and emotional performance in three-month-old male Wistar rats. Results: Our results demonstrated that fructose intake led to increases in body weight and blood glucose, as well as reduced insulin sensitivity. The co-morbidity of fructose intake and cerebral ischemia resulted to hyperlipidemia, as well as increases in liver and adipocyte damage, which worsened neurological performance and resulted in alterations in learning and emotional skills at two weeks post-ischemia. No significant biochemical changes in autophagy and plasticity markers at the late stage of ischemia were observed. Conclusion: These results suggested that obesity causes a lasting effect on metabolic disorders that can contribute to increased neurological impairment after cerebral ischemia.

The Therapeutic Effect of Electroacupuncture Therapy for Ischemic Stroke

Electroacupuncture (EA) stimulation is a supplementary therapy and commonly applied in treatment of ischemic stroke in clinic. Stroke is an important cause of long-term disability in individuals in both developing and developed countries. In our review, we show the application of EA stimulation for apoplectic pain, limbs spasticity, blood flow interruption, depression, swallowing dysfunction, aphasia, urinary incontinence, cognition and memory impairment, and constipation following stroke in patients and the related mechanisms in animals. The effectiveness of EA involves with acupoints, intensity, intervals, and duration of intervention for treatment of stroke. The combination of EA and common rehabilitation treatment may exert better effect compared with EA alone. In summary, EA might provide a potential treatment strategy for treating apoplectic patients in clinic.

Effect of β-Hydroxybutyrate on Autophagy Dynamics During Severe Hypoglycemia and the Hypoglycemic Coma

Glucose supply from blood is mandatory for brain functioning and its interruption during acute hypoglycemia or cerebral ischemia leads to brain injury. Alternative substrates to glucose such as the ketone bodies (KB), acetoacetate (AcAc), and β-hydroxybutyrate (BHB), can be used as energy fuels in the brain during hypoglycemia and prevent neuronal death, but the mechanisms involved are still not well understood. During glucose deprivation adaptive cell responses can be activated such as autophagy, a lysosomal-dependent degradation process, to support cell survival. However, impaired or excessive autophagy can lead to cell dysfunction. We have previously shown that impaired autophagy contributes to neuronal death induced by glucose deprivation in cortical neurons and that D isomer of BHB (D-BHB) reestablishes the autophagic flux increasing viability. Here, we aimed to investigate autophagy dynamics in the brain of rats subjected to severe hypoglycemia (SH) without glucose infusion (GI), severe hypoglycemia followed by GI (SH + GI), and a brief period of hypoglycemic coma followed by GI (Coma). The effect of D-BHB administration after the coma was also tested (Coma + BHB). The transformation of LC3-I to LC3-II and the abundance of autophagy proteins, Beclin 1 (BECN1), ATG7, and ATG12–ATG5 conjugate, were analyzed as an index of autophagosome formation, and the levels of sequestrosome1/p62 (SQSTM1/p62) were determined as a hallmark of autophagic degradation. Data suggest that autophagosomes accumulate in the cortex and the hippocampus of rats after SH, likely due to impaired autophagic degradation. In the cortex, autophagosome accumulation persisted at 6 h after GI in animals exposed to SH but recovered basal levels at 24 h, while in the hippocampus no significant effect was observed. In animals subjected to coma, autophagosome accumulation was observed at 24 h after GI in both regions. D-BHB treatment reduced LC3-II and SQSTM1/p62 content and reduced ULK1 phosphorylation by AMPK, suggesting it stimulates the autophagic flux and decreases AMPK activity reducing autophagy initiation. D-BHB also reduced the number of degenerating cells. Together, data suggest different autophagy dynamics after GI in rats subjected to SH or the hypoglycemic coma and support that D-BHB treatment can modulate autophagy dynamics favoring the autophagic flux.

Detrimental and Beneficial Effect of Autophagy and a Potential Therapeutic Target after Ischemic Stroke

Autophagy, a physiologic mechanism that promotes energy recycling and orderly degradation through self-regulated disassembly of cellular components, helps maintain homeostasis. A series of evidences suggest that autophagy is activated as a response to ischemia and has been well-characterized as a therapeutic target. However, the role of autophagy after ischemia remains controversial. Activated-autophagy can remove necrotic substances against ischemic injury to promote cell survival. On the contrary, activation of autophagy may further aggravate ischemic injury, causing cell death. Therefore, the present review will examine the current understanding of the precise mechanism and role of autophagy in ischemia and recent neuroprotective therapies on autophagy, drug therapies, and nondrug therapies, including electroacupuncture (EA).

Autophagy-Associated lncRNAs: Promising Targets for Neurological Disease Diagnosis and Therapy

Neurological diseases are a major threat to global public health and prosperity. The number of patients with neurological diseases is increasing due to the population aging and increasing life expectancy. Autophagy is one of the crucial mechanisms to maintain nerve cellular homeostasis. Numerous studies have demonstrated that autophagy plays a dual role in neurological diseases. Long noncoding RNAs (lncRNAs) are a vital class of noncoding RNAs with a length of more than 200 nucleotides and cannot encode proteins themselves but are expressed in most neurological diseases. An early phase, emerging knowledge has revealed that long noncoding RNAs (lncRNAs) are crucial in autophagy regulation. Furthermore, autophagy-associated lncRNAs can promote the development of neurological diseases or slow their progression. In this review, we introduce a general overview of lncRNA functional mechanisms and summarizes the recent progress of lncRNAs on autophagy regulation in neurological diseases to reveal possible novel therapeutic targets or useful biomarkers.

Electroacupuncture ameliorates cerebral ischemia/reperfusion injury by suppressing autophagy via the SIRT1-FOXO1 signaling pathway

Cerebral ischemia/reperfusion (CIR) injury occurs when blood flow is restored in the brain, causing secondary damage to the ischemic tissues. Previous studies have shown that electroacupuncture (EA) treatment contributes to brain protection against CIR injury through modulating autophagy. Studies indicated that SIRT1-FOXO1 plays a crucial role in regulating autophagy. Here we investigated the mechanisms underlying the neuroprotective effect of EA and its role in modulating autophagy via the SIRT1-FOXO1 signaling pathway in rats with CIR injury. EA pretreatment at "Baihui", "Quchi" and "Zusanli" acupoints (2/15Hz, 1mA, 30 min/day) was performed for 5 days before the rats were subjected to middle cerebral artery occlusion, and the results indicated that EA pretreatment substantially reduced the Longa score and infarct volume, increased the dendritic spine density and lessened autophagosomes in the peri-ischemic cortex of rats. Additionally, EA pretreatment also reduced the ratio of LC3-II/LC3-I, the levels of Ac-FOXO1 and Atg7, and the interaction of Ac-FOXO1 and Atg7, but increased the levels of p62, SIRT1, and FOXO1. The above effects were abrogated by the SIRT1 inhibitor EX527. Thus, we presume that EA pretreatment elicits a neuroprotective effect against CIR injury, potentially by suppressing autophagy via activating the SIRT1-FOXO1 signaling pathway.

Mu-Xiang-You-Fang protects PC12 cells against OGD/R-induced autophagy via the AMPK/mTOR signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Mu-Xiang-You-Fang (MXYF) is a classic prescription of Hui medicine. It is composed of five herbs and has been used to treat ischemic stroke for many years. However, the potential pharmacological mechanisms of MXYF remain unclear. The present research is aimed to investigate the protective effect and possible mechanisms of MXYF treatment in an in vitro model of cerebral ischemia-reperfusion injury.

MATERIALS AND METHODS

An oxygen-glucose deprivation and reperfusion (OGD/R) model of PC12 cells was established. The effect of MXYF on the cell viability after OGD/R injury was determined using a cell counting kit (CCK-8) assay. The colorimetric method was used to determine the lactate dehydrogenase (LDH) leakage rate. The calcium concentration was determined by the chemical fluorescence method, and mitochondrial membrane potential was determined using flow cytometry. Monodansylcadaverine (MDC) staining and electron microscopic analysis were then conducted to detect autophagy after oxygen-glucose deprivation and reperfusion in PC12 cells. Immunofluorescence and western blot analyses were used to detect the expression of proteins associated with autophagy.

RESULTS

It was found that MXYF (1, 2, 4 μg/mL) could significantly increase cell viability and mitochondrial membrane potential and decrease the calcium concentration and LDH release rate in PC12 cells. After OGD/R injury in PC12 cells, the number of autophagosomes and autophagolysosome significantly increased. MXYF (4 μg/mL) inhibited the autophagy induced by OGD/R and inhibited the expression of LC3, beclin1, p-AMPK, and ULK1. In contrast, the expression of p-mTOR, p-p70s6k, and p62 was significantly enhanced.

CONCLUSIONS

These findings suggest that MXYF inhibits autophagy after OGD/R-induced PC12 cell injury through the AMPK-mTOR pathway. Thus, MXYF might have therapeutic potential in treating ischemic stroke.

Puerarin Attenuates Diabetic Nephropathy by Promoting Autophagy in Podocytes

Puerarin, an active compound of radix puerariae, is a major compound used in Chinese herbal medicines to treat patients with diabetic nephropathy (DN). In the previous studies, we showed that puerarin exerts renoprotective effects in Streptozocin (STZ)-induced diabetic mice through activation of Sirt1 and anti-oxidative effects. Here, we further investigated the underlying mechanism mediating the renal protective effects of puerarin in DN. We studied the effects and mechanism of puerarin in STZ-induced diabetic mice and in cultured immortalized mouse podocytes treated with high glucose. We confirmed that puerarin ameliorated urinary albumin creatinine ratio and kidney injury in STZ-induced DN mice. We found that expression of heme oxygenase 1 (HMOX-1) and Sirt1 was suppressed in diabetic glomeruli but restored by puerarin treatment at both mRNA and protein levels. Additionally, we found that puerarin induced autophagy in the kidney of DN mice. In conditionally immortalized mouse podocytes, puerarin inhibited HG-induced apoptosis and restored the mRNA and protein levels of HMOX-1 and Sirt1. Interestingly, we showed that puerarin decreased liver kinase B1 (LKB1) acetylation, thereby promoting adenosine 5′-monophosphate-activated protein kinase-dependent autophagy. Knockdown of HMOX-1 and Sirt1 expression or treatment with the autophagy inhibitor 3-methyladenine abolished the protective effects of puerarin in HG-treated podocytes. Taken together, these results suggest that puerarin protects podocytes from diabetes-induced injury through HMOX1 and Sirt1-mediated upregulation of autophagy, a novel mechanism explaining its renal protective effects in DN.

MicroRNA-20b-5p regulates propofol-preconditioning-induced inhibition of autophagy in hypoxia-and-reoxygenation-stimulated endothelial cells

Ischemia-reperfusion (IR) injury is a major cause of clinical emergencies during and after surgical procedures. Propofol protects the heart from cardiovascular IR injury by inhibiting autophagy. MicroRNAs (miRNAs) participate in anesthetic-regulated cardiovascular injury. MiR-20b-5p targets unc-51-like autophagy activating kinase 1 (ULK1). Its role in propofol-modulated cardiovascular IR injury remains unclear, however. In this study, we used an in vitro model of hypoxia-reoxygenation (HR)-induced injury to human umbilical vein endothelial cells (HUVECs) to determine the protective effect of miR-20b-5p in cells preconditioned with propofol. We found that miR-20b-5p was significantly higher and ULK1 was lower in propofol-preconditioned HUVECs with HR injury than in HUVECs with HR injury only. Additionally, miR-20b-5p overexpression increased cell viability and repressed autophagy and apoptosis more in propofol-preconditioned HUVECs with HR injury than in HUVECs with HR injury only. A luciferase reporter assay confirmed the target reaction between miR-20b-5p and ULK1. Overexpression of ULK1 restrained the protective effect of miR-20b-5p in propofol-preconditioned HUVECs with HR injury. In conclusion, our results indicate that propofol inhibits autophagic cell death via the miR-20b-5p-ULKI axis and that ULK1 may be a therapeutic target for cardiovascular IR injury.

Autophagy and inflammation in ischemic stroke

Appropriate autophagy has protective effects on ischemic nerve tissue, while excessive autophagy may cause cell death. The inflammatory response plays an important role in the survival of nerve cells and the recovery of neural tissue after ischemia. Many studies have found an interaction between autophagy and inflammation in the pathogenesis of ischemic stroke. This study outlines recent advances regarding the role of autophagy in the post-stroke inflammatory response as follows. (1) Autophagy inhibits inflammatory responses caused by ischemic stimulation through mTOR, the AMPK pathway, and inhibition of inflammasome activation. (2) Activation of inflammation triggers the formation of autophagosomes, and the upregulation of autophagy levels is marked by a significant increase in the autophagy-forming markers LC3-II and Beclin-1. Lipopolysaccharide stimulates microglia and inhibits ULK1 activity by direct phosphorylation of p38 MAPK, reducing the flux and autophagy level, thereby inducing inflammatory activity. (3) By blocking the activation of autophagy, the activation of inflammasomes can alleviate cerebral ischemic injury. Autophagy can also regulate the phenotypic alternation of microglia through the nuclear factor-κB pathway, which is beneficial to the recovery of neural tissue after ischemia. Studies have shown that some drugs such as resveratrol can exert neuroprotective effects by regulating the autophagy-inflammatory pathway. These studies suggest that the autophagy-inflammatory pathway may provide a new direction for the treatment of ischemic stroke.

Resatorvid protects against hypoxic-ischemic brain damage in neonatal rats

Secondary brain damage caused by hyperactivation of autophagy and inflammatory responses in neurons plays an important role in hypoxic-ischemic brain damage (HIBD). Although previous studies have implicated Toll-like receptor 4 (TLR4) and nuclear factor kappa-B (NF-κB) in the neuroinflammatory response elicited by brain injury, the role and mechanisms of the TLR4-mediated autophagy signaling pathway in neonatal HIBD are still unclear. We hypothesized that this pathway can regulate brain damage by modulating neuron autophagy and neuroinflammation in neonatal rats with HIBD. Hence, we established a neonatal HIBD rat model using the Rice-Vannucci method, and injected 0.75, 1.5, or 3 mg/kg of the TLR4 inhibitor resatorvid (TAK-242) 30 minutes after hypoxic ischemia. Our results indicate that administering TAK-242 to neonatal rats after HIBD could significantly reduce the infarct volume and the extent of cerebral edema, alleviate neuronal damage and neurobehavioral impairment, and decrease the expression levels of TLR4, phospho-NF-κB p65, Beclin-1, microtubule-associated protein l light chain 3, tumor necrosis factor-α, and interleukin-1β in the hippocampus. Thus, TAK-242 appears to exert a neuroprotective effect after HIBD by inhibiting activation of autophagy and the release of inflammatory cytokines via inhibition of the TLR4/NF-κB signaling pathway. This study was approved by the Laboratory Animal Ethics Committee of Affiliated Hospital of Yangzhou University, China (approval No. 20180114-15) on January 14, 2018.

Late Exercise Preconditioning Promotes Autophagy against Exhaustive Exercise-Induced Myocardial Injury through the Activation of the AMPK-mTOR-ULK1 Pathway

Accumulating evidence shows that the AMPK-mTOR pathway modulates autophagy via coordinated phosphorylation of ULK1. The aim of the present study was to investigate the relationship between AMPK, mTOR, and ULK1 during late exercise preconditioning (LEP), and to explore whether LEP-induced myocardial protection is related to the autophagy. The exercise preconditioning (EP) protocol was as follows: rats were instructed to for run four repeated in duration of 10 minutes (including 10 minutes rest between each period) on a treadmill. Exhaustive exercise (EE) after LEP pretreatment and administration of wortmannin (an autophagy inhibitor that suppresses Class III PI3K-kinase (PI3KC3) activity) were added to test the protective effect. Cardiac troponin I (cTnI), and transmission electron microscopy (TEM), along with hematoxylin-basic fuchsin-picric acid (HBFP) staining, were used to evaluate the myocardial ischemic-hypoxic injury and protection. Western blot was used to analyze the relationship of autophagy-associated proteins. Exhaustive exercise caused severe myocardial ischemic-hypoxic injury, which led to an increase in cTnI levels, changes of ischemia–hypoxia, and cells ultrastructure. Compared with the EE group, LEP significantly suppressed exhaustive exercise-induced myocardial injury. However, wortmannin attenuated LEP-induced myocardial protection by inhibiting autophagy. Compared with the C group, AMPK was increased in the LEP, EE, and LEP+EE groups, but phosphorylation of AMPK at Thr172 was not significantly changed. Exercise did not have any effect on mTOR expression. Compared with the C group, ULK1 was increased and the ULK1^ser757/ULK1 ratio was decreased in the LEP and LEP+EE groups. ULK1 was not significantly affected in the EE group, however, phosphorylation of ULK1 at Ser757 was remarkably decreased. To sum up, our results suggested that LEP promoted autophagy through the activation of AMPK-mTOR-ULK1 pathway, and that activated autophagy was partially involved in myocardial protection against EE-induced myocardial ischemic-hypoxic injury.

Puerarin inhibits the osteoclastogenesis by inhibiting RANKL-dependent and -independent autophagic responses

Background

Puerarin exerts therapeutic effect on osteoporosis due to its inhibitory effect on the formation of osteoclasts. Puerarin is also widely established as an autophagy inhibitor. The study aimed to investigate the significance of autophagy in Puerarin-treated osteoclast formation.

Methods

Osteoclast precursors (OCPs) derived from bone marrow-derived macrophages (BMMs) were treated with Puerarin along with RANKL or without RANKL, and then the autophagic parameters of OCPs (including autophagic proteins, LC3 transformation, autophagosome or LC3-puncta) were observed through Western Blotting, Transmission Electron Microscopy and Immunofluorescence assays. Next, after using overexpression vectors of autophagic genes (Atg7, Atg5 and BECN1) to alter autophagy activity, OCP proliferation was measured by Ethynyl deoxyuridine (EdU) assays and Cell Counting Kit-8 (CCK-8) kit, and osteoclast differentiation was assessed by Tartrate-resistant acid phosphatase (TRAP) staining.

Results

The results showed that Puerarin could directly inhibit the autophagy and proliferation of OCPs. Importantly, overexpression of autophagic genes Atg5, Atg7 and BECN1 reversed Puerarin-inhibited OCP autophagy and proliferation. What’s more, RANKL could promote the autography of OCPs, which was recovered by Puerarin treatment. Interestingly, different from single-Puerarin treatment, we found that in the presence of RANKL, only BECN1 overexpression significantly reversed Puerarin-inhibited osteoclast differentiation and OCP autophagy.

Conclusion

In conclusion, Puerarin could inhibit the OCP autophagy in the presence or absence of RANKL, which blocked the OCP proliferation and osteoclast differentiation respectively. Moreover, BECN1 plays an essential role in Puerarin-inhibited osteoclastogenesis. Our study provides potential clue to further complete the intrinsic mechanism of Puerarin in treating osteoporosis.

Schizandrin Protects against OGD/R-Induced Neuronal Injury by Suppressing Autophagy: Involvement of the AMPK/mTOR Pathway

The neuroprotective role of schizandrin (SA) in cerebral ischemia-reperfusion (I/R) was recently highlighted. However, whether SA plays a regulatory role on autophagy in cerebral I/R injury is still unclear. This study aimed to explore whether the neuroprotective mechanisms of SA were linked to its regulation of AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/autophagy pathway in vivo and in vitro. The present study confirmed that SA significantly improved oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced PC12 cells injury. The results of immunoblotting and confocal microscope showed that SA decreased autophagy in OGD/R-injured PC12 cells, which was reflected by the decreased Beclin-1 and LC3-II expression, autophagy flux level, and LC3 puncta formation. In addition, the autophagy inducer rapamycin partially prevented the effects of SA on cell viability and autophagy after OGD/R, whereas the autophagy inhibitor 3-methyladenine (3-MA) exerted the opposite effect. The results of Western blotting showed that SA markedly decreased the phosphorylation of AMPK (p-AMPK), whereas the phosphor-mTOR (p-mTOR) levels increased in the presence of OGD/R insult. Furthermore, pretreatment with the AMPK inducer AICAR partially reversed the protective effects and autophagy inhibition of SA. However, AMPK inhibitor Compound C pretreatment further promoted the inhibition of SA on autophagy induction and cell damage induced by OGD/R. Taken together, these findings demonstrate that SA protects against OGD/R insult by inhibiting autophagy through the regulation of the AMPK-mTOR pathway and that SA may have therapeutic value for protecting neurons from cerebral ischemia.

Puerarin prevents progression of experimental hypoxia-induced pulmonary hypertension via inhibition of autophagy

Pulmonary arterial hypertension (PAH) is defined as elevation of mean pulmonary arterial pressure to ≥25 mmHg within the low pressure pulmonary circulatory system. PAH is characterized by obstructive vascular remodeling, partially due to excessive pulmonary arterial smooth muscle cell (PASMC) proliferation. Puerarin is a natural flavonoid isolated from the herb Radix puerariae, which has been widely used for the treatment of cardiovascular and cerebrovascular disorders and diabetes. However, how puerarin mediates autophagy in the progression of pulmonary vascular remodeling is unclear. In this study, we explored the effects of puerarin in a hypoxic pulmonary hypertension (PH) rat model using immunohistochemistry, and morphometric analyses of right ventricle. In addition, cell counting kit 8 assay, western blotting and flow cytometry were employed to test cell proliferation in PASMCs, and then autophagy was tested with mRFP-GFP-LC3 fluorescence microscopy and Western blot. We found that puerarin could alleviate hypoxia-induced PH in rats and improved pulmonary histopathology, and also reduced the expression of autophagy markers in vivo and in vitro. Moreover, puerarin also ameliorated hypoxia-induced PASMC proliferation in an autophagy-dependent manner. Overall, these findings demonstrated that puerarin could prevent hypoxia-induced PH in rats, possibly via reducing autophagy and suppressing cell proliferation.

Pioglitazone protects tubular cells against hypoxia/reoxygenation injury through enhancing autophagy via AMPK-mTOR signaling pathway

Pioglitazone (Pio), a peroxisome proliferators-activated receptor-γ (PPAR-γ) agonist, may protect against renal ischemia/reperfusion injury (IRI). Recent studies have shown that autophagy plays a protective role in IRI. We aimed to evaluate whether autophagy was involved in pioglitazone-induced protection during tubular cell hypoxia/reoxygenation (H/R). Normal rat kidney proximal tubular cells NRK-52E were subjected to H/R injury, and they were divided into 6 groups: control, control + Pio, H/R, H/R + Pio, H/R + MA, H/R + MA + Pio. Autophagy-related proteins were primarily assessed by Western blot and TUNEL was performed to assess cell apoptosis. Our results showed pioglitazone pretreatment had a cytoprotective effect against H/R injury. The H/R + Pio group had an increased ratio of LC3-II to LC3-I and increased Beclin-1, decreased p62. Pioglitazone also reduced apoptosis and enhanced cell survival while inducing autophagy. Correspondingly, autophagy inhibition with 3-MA alleviated this protective effect. Furthermore, pioglitazone-induced enhancement of autophagy could be related to increased AMP-activated protein kinase (AMPK) phosphorylation and decreased Mammalian target of rapamycin (mTOR) phosphorylation. Thus, pioglitazone pretreatment protects against H/R injury by enhancting autophagy through the AMPK-mTOR signaling pathway.

Paeoniflorin protects against intestinal ischemia/reperfusion by activating LKB1/AMPK and promoting autophagy

Intestinal ischemia-reperfusion (I/R) injury is a common pathological process with high clinical morbidity and mortality. Paeoniflorin, a monoterpene glucoside, is found to have diverse health beneficial effects including autophagy modulation, anti-inflammatory, anti-apoptotic, and anti-oxidative effects. Based on our pre-experiments, we proposed that paeoniflorin could ameliorate intestinal I/R injury and restore autophagy through activating LKB1/AMPK signal pathway. Our proposal was verified using rat intestinal I/R model in vivo and intestinal epithelial cell line (IEC-6 cells) hypoxia/reoxygenation (H/R) model in vitro. Our results showed that paeoniflorin pretreatment exerted protective effects in rat intestinal I/R injury by reducing intestinal morphological damage, inflammation, oxidative stress, and apoptosis. Paeoniflorin restored H/R-impaired autophagy flux by up-regulating autophagy-related protein p62/SQSTM1 degradation, LC3II and beclin-1 expression, and autophagosomes synthesis without significantly affecting control IEC-6 cells. Paeoniflorin pretreatment significantly activated LKB1/AMPK signaling pathway by reversing the decreased LKB1 and AMPK phosphorylation without affecting total LKB1 both in vivo and in vitro. LKB1 knockdown reduced AMPK phosphorylation, suppressed LC3II and Beclin-1 level, and decreased the degradation of SQSTM/p62, and the knockdown weakened the effects of paeoniflorin in restoring the impaired autophagy flux in H/R injured IEC-6 cells, suggesting that paeoniflorin mitigated the intestinal I/R-impaired autophagy flux by activating LKB1/AMPK signaling pathway. Our study may provide valuable information for further studies.

The Relationship Between Autophagy and Brain Plasticity in Neurological Diseases

Autophagy, a catabolic degradation system, is utilized for destroying and recycling the damaged or unnecessary cellular components. Brain plasticity refers to the remarkable characteristics of brain neurons that change their structure and function according to previous experience. This review was performed by searching the relevant articles in databases of SCIENCEDIRECT, PUBMED, and Web of Science, from respective inception to January 2019. Here, we review the neuroprotective effect of autophagy in neurological diseases and the mechanism of autophagy in brain plasticity. Moreover, the mechanism of autophagy in the process of brain plasticity can provide the possibility for the development of new treatment methods in the future, thus benefiting patients with neurological diseases. In summary, autophagy and brain plasticity play important roles in neurological diseases.

Suppression of REDD1 attenuates oxygen glucose deprivation/reoxygenation-evoked ischemic injury in neuron by suppressing mTOR-mediated excessive autophagy

Cerebral ischemia/reperfusion (I/R) typically occurs after mechanical thrombectomy to treat ischemic stroke, generation of reactive oxygen species (ROS) after reperfusion may result in neuronal insult, ultimately leading to disability and death. Regulated in development and DNA damage responses 1 (REDD1) is a conserved stress response protein under various pathogenic conditions. Recent research confirms the controversial role of REDD1 in injury processes. Nevertheless, the role of REDD1 in cerebral I/R remains poorly defined. In the current study, increased expression of REDD1 was observed in neurons exposed to simulated I/R via oxygen glucose deprivation/reoxygenation (OGD/R) treatment. Knockdown of REDD1 enhanced OGD/R-inhibited cell viability, but suppressed lactate dehydrogenase (LDH) release in neurons upon OGD/R. Simultaneously, suppression of REDD1 also antagonized OGD/R-evoked cell apoptosis, Bax expression, and caspase-3 activity. Intriguingly, REDD1 depression abrogated neuronal oxidative stress under OGD/R condition by suppressing ROS, MDA generation, and increasing antioxidant SOD levels. Further mechanism analysis corroborated the excessive activation of autophagy in neurons upon OGD/R with increased expression of autophagy-related LC3 and Beclin-1, but decreased autophagy substrate p62 expression. Notably, REDD1 inhibition reversed OGD/R-triggered excessive neuronal autophagy. More importantly, depression of REDD1 also elevated the expression of p-mTOR. Preconditioning with mTOR inhibitor rapamycin engendered not only a reduction in mTOR activation, but also a reactivation of autophagy in REDD1 knockdown-neurons upon OGD/R. In addition, blocking the mTOR pathway muted the protective roles of REDD1 inhibition against OGD/R-induced neuron injury and oxidative stress. Together these data suggested that REDD1 may regulate I/R-induced oxidative stress injury in neurons by mediating mTOR-autophagy signaling, supporting a promising therapeutic strategy against brain ischemic diseases.

Apelin-36 exerts the cytoprotective effect against MPP+-induced cytotoxicity in SH-SY5Y cells through PI3K/Akt/mTOR autophagy pathway

AIMS

Parkinson's disease (PD) is a common neurodegenerative disease typically associated with the accumulation of α-synuclein. Autophagy impairment is thought to be involved in the dopaminergic neurodegeneration in PD. We investigate the effect of Apelin-36 on the activated phosphatidylinositol 3-kinase (PI3K)/protein kinase B(Akt)/the mammalian target of rapamycin (mTOR) autophagy pathway in 1-methyl-4-phenylpyridinium (MPP⁺)-treated SH-SY5Y cells, which is involved in the cytoprotective effect of Apelin-36.

MAIN METHODS

SH-SY5Y cells were treated with 1-Methyl-4-phenylpyridine (MPP⁺) with or without Apelin-36. The cell viability, apoptotic ratio, the form of autophagic vacuoles, the expression of tyrosine hydroxylase (TH), α-synuclein, phosphorylation of PI3K, AKT, mTOR, microtubule-associated protein 1 Light Chain 3 II/I (LC3II/I) and p62 were detected to investigate the neuroprotective effect of Apelin-36.

KEY FINDINGS

The results indicate that Apelin-36 significantly improved the cell viability and decreased the apoptosis in MPP⁺-treated SH-SY5Y cells. The decreased expression of tyrosine hydroxylase (TH) induced by MPP⁺ was significantly increased by Apelin36 pretreatment. Moreover, Apelin36 significantly increased the autophagic vacuoles. The ratio of LC3II/I was significantly increased by Apelin36, as well as the decreased p62 expression. In addition, the activated PI3K/AKT/mTOR pathway induced by MPP⁺ was significantly inhibited by Apelin36. Additionally, Apelin36 significantly decreased the α-synuclein expression. Furthermore, the cytoprotective effect of Apelin-36 was weakened by pretreatment with Insulin-like Growth Factor-1 (IGF-1), an activator of PI3K/Akt, and MHY1485, an mTOR activator.

SIGNIFICANCE

Our results demonstrated that Apelin-36 protects against MPP⁺-induced cytotoxicity through PI3K/Akt/mTOR autophagy pathway in PD model in vitro, which provides a new theoretical basis for the treatment of PD.

The progress of neuronal autophagy in cerebral ischemia stroke: Mechanisms, roles and research methods

There is increasing evidence indicating that autophagy may be a new target in the treatment of ischemic stroke. Moderate autophagy can clear damaged organelles, thereby protecting cells against various injuries. However, long-term excessive autophagy brings redundant degradation of cell contents, leading to cell death and eventually serious damage to tissues and organs. A number of different animal models of ischemic brain injury shows that autophagy is activated and involved in the regulation of neuronal death during ischemic brain injury. This article summarizes the role of autophagy, its underlying regulators and mechanisms in ischemic neuronal injury. We briefly introduce the relationship between apoptosis and autophagy and give a summary of research methods and modulators of autophagy.

Crosstalk Between Autophagy and Cerebral Ischemia

With the use of advanced electron microscopy and molecular biology tools, several studies have shown that autophagy is involved in the development of ischemic stroke. A series of molecular mechanisms are involved in the regulation of autophagy. In this work, the possible molecular mechanisms involved in autophagy during ischemic stroke were reviewed and new potential targets for the study and treatment of ischemic stroke were provided.

Autophagy: novel insights into therapeutic target of electroacupuncture against cerebral ischemia/ reperfusion injury

Electroacupuncture is known as an effective adjuvant therapy in ischemic cerebrovascular disease. However, its underlying mechanisms remain unclear. Studies suggest that autophagy, which is essential for cell survival and cell death, is involved in cerebral ischemia reperfusion injury and might be modulate by electroacupuncture therapy in key ways. This paper aims to provide novel insights into a therapeutic target of electroacupuncture against cerebral ischemia/reperfusion injury from the perspective of autophagy. Here we review recent studies on electroacupuncture regulation of autophagy-related markers such as UNC-51-like kinase-1 complex, Beclin1, microtubule-associated protein-1 light chain 3, p62, and autophagosomes for treating cerebral ischemia/reperfusion injury. The results of these studies show that electroacupuncture may affect the initiation of autophagy, vesicle nucleation, expansion and maturation of autophagosomes, as well as fusion and degradation of autophagolysosomes. Moreover, studies indicate that electroacupuncture probably modulates autophagy by activating the mammalian target of the rapamycin signaling pathway. This review thus indicates that autophagy is a therapeutic target of electroacupuncture treatment against ischemic cerebrovascular diseases.

Neuronal autophagy aggravates microglial inflammatory injury by downregulating CX3CL1/fractalkine after ischemic stroke

Ischemic stroke often induces excessive neuronal autophagy, resulting in brain damage; meanwhile, inflammatory responses stimulated by ischemia exacerbate neural injury. However, interactions between neuronal autophagy and microglial inflammation following ischemic stroke are poorly understood. CX3CL1/fractalkine, a membrane-bound chemokine expressed on neurons, can suppress microglial inflammation by binding to its receptor CX3CR1 on microglia. In the present study, to investigate whether autophagy could alter CX3CL1 expression on neurons and consequently change microglial inflammatory activity, middle cerebral artery occlusion (MCAO) was established in Sprague-Dawley rats to model ischemic stroke, and tissues from the ischemic penumbra were obtained to evaluate autophagy level and microglial inflammatory activity. MCAO rats were administered 3-methyladenine (autophagy inhibitor) or Tat-Beclin 1 (autophagy inducer). Western blot assays were conducted to quantify expression of Beclin-1, nuclear factor kappa B p65 (NF-κB), light chain 3B (LC3B), and CX3CL1 in ischemic penumbra. Moreover, immunofluorescence staining was performed to quantify numbers of LC3B-, CX3CL1-, and Iba-1-positive cells in ischemic penumbra. In addition, enzyme linked immunosorbent assays were utilized to analyze concentrations of tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), interleukin 1 beta (IL-1β), and prostaglandin E2 (PGE2). A dry/wet weight method was used to detect brain water content, while 2,3,5,-triphenyltetrazolium chloride staining was utilized to measure infarct volume. The results demonstrated that autophagy signaling (Beclin-1 and LC3B expression) in penumbra was prominently activated by MCAO, while CX3CL1 expression on autophagic neurons was significantly reduced and microglial inflammation was markedly activated. However, after inhibition of autophagy signaling with 3-methyladenine, CX3CL1 expression on neurons was obviously increased, whereas Iba-1 and NF-κB expression was downregulated; TNF-α, IL-6, IL-1β, and PGE2 levels were decreased; and cerebral edema was obviously mitigated. In contrast, after treatment with the autophagy inducer Tat-Beclin 1, CX3CL1 expression on neurons was further reduced; Iba-1 and NF-κB expression was increased; TNF-α, IL-6, IL-1β, and PGE2 levels were enhanced; and cerebral edema was aggravated. Our study suggests that ischemia-induced neuronal autophagy facilitates microglial inflammatory injury after ischemic stroke, and the efficacy of this process may be associated with downregulated CX3CL1 expression on autophagic neurons.

MiRNA-27b Regulates Angiogenesis by Targeting AMPK in Mouse Ischemic Stroke Model

Stroke is a leading cause of mortality and serious disability worldwide with limited treatment options. Angiogenesis has been reported to be involved in post-stroke recovery. Although the molecular mechanisms that regulate angiogenesis remain ambiguous, microRNAs have emerged as effective regulators of angiogenesis, involved in neurological function outcome. The present study aims to investigate the regulatory effects of miRNA-27b on post-stroke angiogenesis. In primary cultured brain microvascular endothelial cells (BMECs), the inhibition of miRNA-27b induced the activation of adenosine monophosphate-activated protein kinase (AMPK), which increased tube formation and migration. This action was attenuated when AMPKα2 was knocked down. Mice were subjected to middle cerebral artery occlusion (MCAo) surgery and administrated with Lentivirus miR-27b inhibitor. Enhanced angiogenesis in ischemic boundary zone (IBZ) was observed, and the neurological outcome during the entire study period was improved. The number of phosphate-AMPKα2⁺ cells that co-expressed endothelial cell marker CD31 was significantly increased. Taken together, the present study demonstrated that downregulated miRNA-27b promoted recovery after ischemic stroke via AMPK stimulus.

Development of an Oral Compound Pickering Emulsion Composed of Nanocrystals of Poorly Soluble Ingredient and Volatile Oils from Traditional Chinese Medicine

In this study, an oral drug nanocrystals self-stabilized Pickering emulsion (NSSPE), which used nanocrystals of a poorly soluble ingredient from Puerariae Radix called puerarin as solid particle stabilizers and Ligusticumchuanxiong essential oil since the main oil phase had been developed to improve the oral bioavailability of puerarin. The appearance of emulsions, size and zeta potential of droplets, and content of puerarin in emulsified layer during a storage of six months at 4, 25, and 40 °C were investigated. The centrifugation stability at 4000× g was also studied. The micro-structure of emulsion droplets was characterized by a scanning electron micrograph (SEM), confocal laser scanning microscopy (CLSM), a fluorescence microscope (FM), and differential scanning calorimetry (DSC). The in vivo oral bioavailability of puerarin NSSPE was investigated in rats. Results showed that appearances of puerarin NSSPE kept stable after centrifugation at 4000× g for 15 min or storage for six months at 4, 25, and 40 °C. SEM, CLSM, FM, and DSC showed that the puerarin NSSPE had a stable core-shell structure of emulsion droplets formed by the adsorption of puerarin nanocrystals on the surface of oil droplets of mixed oil of Ligusticumchuanxiong essential oil and Labrafil M 1944 CS (9:1, v/v). The relative bioavailability of puerarin NSSPE to puerarin coarse powder suspension, nanocrystal suspension, and surfactant emulsion were 262.43%, 155.92%, and 223.65%, respectively. All these results indicated that puerarin nanocrystals could stabilize Pickering emulsion of Ligusticumchuanxiong essential oil without any other stabilizers and Pickering emulsion could improve the oral bioavailability of puerarin, which suggests that the drug nanocrystal self-stabilized Pickering emulsion as a promising oral drug delivery system for Traditional Chinese Medicine containing poorly soluble ingredients and volatile oils.