Activation of autophagy in rat brain cells following focal cerebral ischemia reperfusion through enhanced expression of Atg1/pULK and LC3

Intracerebroventricular BDNF infusion may reduce cerebral ischemia/reperfusion injury by promoting autophagy and suppressing apoptosis

Here, it was aimed to investigate the effects of intracerebroventricular (ICV) Brain Derived Neurotrophic Factor (BDNF) infusion for 7 days following cerebral ischemia (CI) on autophagy in neurons in the penumbra. Focal CI was created by the occlusion of the right middle cerebral artery. A total of 60 rats were used and divided into 4 groups as Control, Sham CI, CI and CI + BDNF. During the 7-day reperfusion period, aCSF (vehicle) was infused to Sham CI and CI groups, and BDNF infusion was administered to the CI + BDNF group via an osmotic minipump. By the end of the 7th day of reperfusion, Beclin-1, LC3, p62 and cleaved caspase-3 protein levels in the penumbra area were evaluated using Western blot and immunofluorescence. BDNF treatment for 7 days reduced the infarct area after CI, induced the autophagic proteins Beclin-1, LC3 and p62 and suppressed the apoptotic protein cleaved caspase-3. Furthermore, rotarod and adhesive removal test times of BDNF treatment started to improve from the 4th day, and the neurological deficit score from the 5th day. ICV BDNF treatment following CI reduced the infarct area by inducing autophagic proteins Beclin-1, LC3 and p62 and inhibiting the apoptotic caspase-3 protein while its beneficial effects were apparent in neurological tests from the 4th day.

Autophagy-Dependent Secretion: Crosstalk between Autophagy and Exosome Biogenesis

The cellular secretome is pivotal in mediating intercellular communication and coordinating responses to stressors. Exosomes, initially recognized for their role in waste disposal, have now emerged as key intercellular messengers with significant therapeutic and diagnostic potential. Similarly, autophagy has transcended its traditional role as a waste removal mechanism, emerging as a regulator of intracellular communication pathways and a contributor to a unique autophagy-dependent secretome. Secretory authophagy, initiated by various stress stimuli, prompts the selective release of proteins implicated in inflammation, including leaderless proteins that bypass the conventional endoplasmic reticulum-Golgi secretory pathway. This reflects the significant impact of stress-induced autophagy on cellular secretion profiles, including the modulation of exosome release. The convergence of exosome biogenesis and autophagy is exemplified by the formation of amphisomes, vesicles that integrate autophagic and endosomal pathways, indicating their synergistic interplay. Regulatory proteins common to both pathways, particularly mTORC1, emerge as potential therapeutic targets to alter cellular secretion profiles involved in various diseases. This review explores the dynamic interplay between autophagy and exosome formation, highlighting the potential to influence the secretome composition. While the modulation of exosome secretion and cytokine preconditioning is well-established in regenerative medicine, the strategic manipulation of autophagy is still underexplored, presenting a promising but uncharted therapeutic landscape.

Melatonin Attenuates Cerebral Ischemia/Reperfusion Injury through Inducing Autophagy

INTRODUCTION

The aim of this study was to investigate how melatonin administration for 3 days or 7 days following cerebral ischemia (CI) injury would affect autophagy and, therefore, survival in neurons of the penumbra region. Moreover, it was also aimed at determining how this melatonin treatment would affect the neurological deficit score and rotarod and adhesive removal test durations.

METHODS

Focal CI (90 min) was achieved in a total of 105 rats utilizing a middle cerebral artery occlusion model. After the start of reperfusion, the groups were treated with melatonin (10 mg/kg/day) for 3 days or 7 days. In all groups, neurological deficit scoring, rotarod, and adhesive removal tests were executed during reperfusion. Infarct areas were determined by TTC (2,3,5-triphenyltetrazolium chloride) staining at the end of the 3rd and 7th days of reperfusion. Beclin-1, LC3, p62, and caspase-3 protein levels were assessed using Western blot and immunofluorescence methods in the brain tissues. Moreover, penumbra areas were evaluated by transmission electron microscopy (TEM).

RESULTS

Following CI, it was observed that melatonin treatment improved the rotarod and adhesive removal test durations from day 5 and reduced the infarct area after CI. It also induced autophagic proteins Beclin-1, LC3, and p62 and suppressed the apoptotic protein cleaved caspase-3. According to TEM findings, melatonin treatment partially reduced the damage in neurons after CI.

CONCLUSION

Melatonin treatment following CI reduced the infarct area and induced the autophagic proteins Beclin-1, LC3, and p62 by inhibiting the apoptotic caspase-3 protein. The functional reflection of melatonin treatment on neurological test scores was became significant from the 5th day onward.

Local uncoordinated gene 5H2 contributes to nerve injury-induced mechanical allodynia associated to its role in autophagy

Lesions of the peripheral nerves can lead to lifelong neuropathic pain (NP). Autophagic deficiency in the Schwann cells (SCs) is an early event in the origin of NP chronification. Uncoordinated gene 5H2 (UNC5H2), one of the repulsive netrin receptors, mediated the effect of netrin-1 on autophagic activation and cell survival in endothelial cells. However, its role on autophagy regulation in peripheral nerves during NP process remains unidentified. Chronic constriction injury (CCI) of the left sciatic nerve was induced in Sprague-Dawley rats, and UNC5H2 small interfering RNA was transfected to the ipsilateral sciatic nerve immediately after injury. Mechanical allodynia was assessed. Sciatic UNC5H2 and netrin-1 protein levels were investigated. Autophagy in the ipsilateral sciatic nerves was evaluated by detecting punctate light chain 3(LC3) and autophagosomes, as well as the levels of LC3 II, p62 and phosphorylated UNC51-like kinase (ULK1). After CCI, UNC5H2 of the sciatic nerves was upregulated, exclusively expressed in SCs. Small interfering RNA transfection resulted in significant decrease of UNC5H2 and netrin-1 protein, leading to exaggeration of mechanical allodynia through 14 days after CCI. Autophagy was activated but autophagic influx was interfered within a week after CCI, shown by the elevated levels of both LC3II and p62, which was further deteriorated with UNC5H2 knockdown. In addition, the injury-induced augmentation of phosphorylated ULK1 was significantly diminished by UNC5H2 knockdown. Altogether, the results suggest that local UNC5H2 of the peripheral nerve plays a significant role in the process of injury-induced mechanical allodynia, probably associated to its contribution to autophagic regulation.

Crosstalk between exosomes and autophagy: A review of molecular mechanisms and therapies

Exosomes are extracellular vesicles that primarily exist in bodily fluids such as blood. Autophagy is an intracellular degradation process, which, along with exosomes, can significantly influence human health and has therefore attracted considerable attention in recent years. Exosomes have been shown to regulate the intracellular autophagic process, which, in turn, affects the circulating exosomes. However, crosstalk between exosomal and autophagic pathways is highly complex, depends primarily on the environment, and varies greatly in different diseases. In addition, studies have demonstrated that exosomes, from specific cell, can mitigate several diseases by regulating autophagy, which can also affect the excessive release of some harmful exosomes. This phenomenon lays a theoretical foundation for the improvement of many diseases. Herein, we review the mechanisms and clinical significance of the association and regulation of exosomes and autophagy, in order to provide a new perspective for the prevention and treatment of associated diseases.

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.

FoxO3 transcription factor promotes autophagy after transient cerebral ischemia/reperfusion

Aim: Autophagy was activated after cerebral ischemia reperfusion (I/R) injury. However, the molecular mechanisms underlying regulation of autophagy in cerebral I/R injury were not completely understood. Studies reported that Forked-box class O (FoxO) transcription factors involved in autophagy and might be the regulator of autophagy in multiple cells. In this study, we investigated the effects of FoxO3 on regulating autophagy after cerebral I/R injury. Materials and methods: Rats were subjected to MCAO for 2 h and reperfusion for different times, western blot was used to examine the expression of p-FoxO3, FoxO3 and the autophagic marker LC3 and Beclin-1 in penumbral region. Then rats were injected with WT-FoxO3 or TM-FoxO3 adenovirus by lateral cerebral ventricle to increase the function of FoxO3, western blot was used to examine the expression of LC3 and Beclin-1 in penumbral region. TTC and HE staining were used to evaluate the effects of increased FoxO3 activation on I/R induced brain damage. Results: Our studies showed that I/R injury resulted in induction of autophagy in penumbral brain tissue with concomitant dephosphorylation of FoxO3, consistent with increased activity of nuclear FoxO3 transcription factor. Increased FoxO3 activation led to autophagy significantly increased and had a protective effects on I/R injury. Conclusion: These data revealed an important role of FoxO3 in regulating autophagy in brain, and provided a new approach for further prevention and treatment of cerebral ischemia.

Ambiguous Effects of Autophagy Activation Following Hypoperfusion/Ischemia

Autophagy primarily works to counteract nutrient deprivation that is strongly engaged during starvation and hypoxia, which happens in hypoperfusion. Nonetheless, autophagy is slightly active even in baseline conditions, when it is useful to remove aged proteins and organelles. This is critical when the mitochondria and/or proteins are damaged by toxic stimuli. In the present review, we discuss to that extent the recruitment of autophagy is beneficial in counteracting brain hypoperfusion or, vice-versa, its overactivity may per se be detrimental for cell survival. While analyzing these opposite effects, it turns out that the autophagy activity is likely not to be simply good or bad for cell survival, but its role varies depending on the timing and amount of autophagy activation. This calls for the need for an appropriate autophagy tuning to guarantee a beneficial effect on cell survival. Therefore, the present article draws a theoretical pattern of autophagy activation, which is hypothesized to define the appropriate timing and intensity, which should mirrors the duration and severity of brain hypoperfusion. The need for a fine tuning of the autophagy activation may explain why confounding outcomes occur when autophagy is studied using a rather simplistic approach.

Ulk1/FUNDC1 Prevents Nerve Cells from Hypoxia-Induced Apoptosis by Promoting Cell Autophagy

Cell autophagy and cell apoptosis are both observed in the process of hypoxia-induced ischemic cerebral infarction (ICI). Unc-51 like autophagy activating kinase 1 (Ulk1) and FUN14 Domain-containing Protein 1 (FUNDC1) are both involved in the regulation of cell autophagy. This study aimed to investigate the regulatory effects of Ulk1 and FUNDC1 on hypoxia-induced nerve cell autophagy and apoptosis. Cell viability was measured using cell counting kit-8 (CCK-8) assay. Cell apoptosis was detected using Annexin V-PE/7-ADD staining assay. qRT-PCR was used to quantify the mRNA levels of Ulk1 and FUNDC1 in PC-12 cells. Cell transfection was performed to up-regulate the expression of Ulk1. 3-Methyladenine (3-MA) was used as autophagy inhibitor and rapamycin was used as autophagy activator in our experiments. SP600125 was used as c-Jun N-terminal kinase (JNK) inhibitor. Western blotting was performed to analyze the expression levels of key factors that are related to cell autophagy, apoptosis and JNK pathway. We found that hypoxia simultaneously induced apoptosis and autophagy of PC-12 cells. The activation of Ulk1 and FUNDC1 were also found in PC-12 cells after hypoxia induction. Overexpression of Ulk1 promoted the activation of FUNDC1 and prevented PC-12 cells from hypoxia-induced apoptosis. Suppression of Ulk1 had opposite effects. Furthermore, we also found that JNK pathway participated in the effects of Ulk1 overexpression on PC-12 cell apoptosis reduction. To conclude, Ulk1/FUNDC1 played critical regulatory roles in hypoxia-induced nerve cell autophagy and apoptosis. Overexpression of Ulk1 prevented nerve cells from hypoxia-induced apoptosis by promoting cell autophagy.

Ginsenoside Rb1 inhibits autophagy through regulation of Rho/ROCK and PI3K/mTOR pathways in a pressure-overload heart failure rat model

Objective

This study was designed to explore the relationship between ginsenoside Rb1 (Grb1) and high-load heart failure (HF) in rats.

Methods

The parameters of cardiac systolic function (left ventricular posterior wall thickness (LVPWT), left ventricular internal diastolic diameter (LVID), fraction shortening (FS) and mitral valves (MVs)) of rat hearts in each group were inspected by echocardiogram. The expressions of rat myocardial contractile proteins, autophagy-related proteins and the activation of Rho/ROCK and PI3K/mTOR pathways were detected by Western blot.

Key findings

LVPWT, FS, MVs and the expression of myocardial contractile proteins α-MHC, apoptosis-related proteins Bcl-2 and signalling pathway involved proteins pAkt and mTOR were significantly reduced in the HF, HF+5 mg/kg Grb1 (HF+Grb1-5) and HF+Grb1+arachidonic acid (AA) groups with LVID, β-MHC, cell apoptosis, cell autophagy and Rho/ROCK significantly increased compared with the control group, of which the tendency was contrary to the HF+20 mg/kg Grb1 (HF+Grb1-20) group compared with the HF group (P < 0.05). In the HF+Grb1+AA group, there was no significant change in the above indexes compared with the HF group.

Conclusions

The results indicated that Grb1 can exert anti-HF function by inhibiting cardiomyocyte autophagy of rats through regulation of Rho/ROCK and PI3K/mTOR pathways.

Role of HIF-1a in regulating autophagic cell survival during cerebral ischemia reperfusion in rats

Hypoxia-inducible factor-1a (HIF-1a) plays a beneficial role during cerebral ischemia reperfusion (IR), but the underlying molecular mechanisms are not completely understood. Here, we aimed to investigate the effects and molecular regulation of HIF-1a on brain cell apoptosis and autophagy during IR. We found that augmentation of HIF-1a in re-perfused hematopoietic cells significantly reduced brain damage, alleviated brain edema and improved neural function during IR, seemingly through two HIF-1a target genes BNIP3 and NIX, which were critical regulators for cell apoptosis and autophagic cell survival. in vitro, HIF-1a induced up-regulation of BNIP3 and NIX in human cortical neuron cells, HCN-1A. Inhibition of BNIP3 and NIX significantly attenuated HIF-1a-suppressed cell apoptosis and HIF-1a-induced cell autophagy. Together, these data suggest that HIF-1a may ameliorate brain damages during IR through BNIP3 and NIX -dependent augmentation of autophagic cell survival and reduction in cell apoptosis.

Functional and Molecular Insights of Hydrogen Sulfide Signaling and Protein Sulfhydration

Hydrogen sulfide (H2S), a novel gasotransmitter, is endogenously synthesized by multiple enzymes that are differentially expressed in the peripheral tissues and central nervous systems. H2S regulates a wide range of physiological processes, namely cardiovascular, neuronal, immune, respiratory, gastrointestinal, liver, and endocrine systems, by influencing cellular signaling pathways and sulfhydration of target proteins. This review focuses on the recent progress made in H2S signaling that affects mechanistic and functional aspects of several biological processes such as autophagy, inflammation, proliferation and differentiation of stem cell, cell survival/death, and cellular metabolism under both physiological and pathological conditions. Moreover, we highlighted the cross-talk between nitric oxide and H2S in several bilogical contexts.

Sex-dependent mitophagy and neuronal death following rat neonatal hypoxia-ischemia

Males are more susceptible than females to long-term cognitive deficits following neonatal hypoxic-ischemic encephalopathy (HIE). Mitochondrial dysfunction is implicated in the pathophysiology of cerebral hypoxia-ischemia (HI), but the influence of sex on mitochondrial quality control (MQC) after HI is unknown. Therefore, we tested the hypothesis that mitophagy is sexually dimorphic and neuroprotective 20-24h following the Rice-Vannucci model of rat neonatal HI at postnatal day 7 (PN7). Mitochondrial and lysosomal morphology and degree of co-localization were determined by immunofluorescence in the cerebral cortex. No difference in mitochondrial abundance was detected in the cortex after HI. However, net mitochondrial fission increased in both hemispheres of female brain, but was most extensive in the ipsilateral hemisphere of male brain following HI. Basal autophagy, assessed by immunoblot for the autophagosome marker LC3BI/II, was greater in males suggesting less intrinsic reserve capacity for autophagy following HI. Autophagosome formation, lysosome size, and TOM20/LAMP2 co-localization were increased in the contralateral hemisphere following HI in female, but not male brain. An accumulation of ubiquitinated mitochondrial protein was observed in male, but not female brain following HI. Moreover, neuronal cell death with NeuN/TUNEL co-staining occurred in both hemispheres of male brain, but only in the ipsilateral hemisphere of female brain after HI. In summary, mitophagy induction and neuronal cell death are sex dependent following HI. The deficit in elimination of damaged/dysfunctional mitochondria in the male brain following HI may contribute to male vulnerability to neuronal death and long-term neurobehavioral deficits following HIE.

Dynamic changes in neuronal autophagy and apoptosis in the ischemic penumbra following permanent ischemic stroke

The temporal dynamics of neuronal autophagy and apoptosis in the ischemic penumbra following stroke remains unclear. Therefore, in this study, we investigated the dynamic changes in autophagy and apoptosis in the penumbra to provide insight into potential therapeutic targets for stroke. An adult Sprague-Dawley rat model of permanent ischemic stroke was prepared by middle cerebral artery occlusion. Neuronal autophagy and apoptosis in the penumbra post-ischemia were evaluated by western blot assay and immunofluorescence staining with antibodies against LC3-II and cleaved caspase-3, respectively. Levels of both LC3-II and cleaved caspase-3 in the penumbra gradually increased within 5 hours post-ischemia. Thereafter, levels of both proteins declined, especially LC3-II. The cerebral infarct volume increased slowly 1-4 hours after ischemia, but subsequently increased rapidly until 5 hours after ischemia. The severity of the neurological deficit was positively correlated with infarct volume. LC3-II and cleaved caspase-3 levels were high in the penumbra within 5 hours after ischemia, and after that, levels of these proteins decreased at different rates. LC3-II levels were reduced to a very low level, but cleaved caspase-3 levels remained high 72 hours after ischemia. These results indicate that there are temporal differences in the activation status of the autophagic and apoptotic pathways. This suggests that therapeutic targeting of these pathways should take into consideration their unique temporal dynamics.