Reduction in Autophagy by (-)-Epigallocatechin-3-Gallate (EGCG): a Potential Mechanism of Prevention of Mitochondrial Dysfunction After Subarachnoid Hemorrhage

Paeonol Alleviates Subarachnoid Hemorrhage Injury in Rats Through Upregulation of SIRT1 and Inhibition of HMGB1/TLR4/MyD88/NF-κB Pathway

Paeonol is a principle bioactive compound separated from the root bark of Cortex Moutan and has been shown to confer various biological functions, including antineuroinflammation and neuroprotection. Inflammation, blood-brain barrier (BBB), permeability, and apoptosis are three major underlying mechanisms involved in early brain injury (EBI) postsubarachnoid hemorrhage (SAH). This study aimed to detect the roles and mechanisms of paeonol in EBI following SAH. A SAH model was established by an endovascular perforation method in Sprague-Dawley rats. The localizations of HMGB1 and p65 were identified by immunofluorescence staining. Protein levels were measured by western blot analysis. The serum levels of HMGB1 and the levels of inflammatory cytokines in the brain cortex were evaluated by ELISA. Hematoxylin and eosin staining was conducted to detect neuronal degeneration. Brain water content and Evans blue extravasation were assessed to determine EBI. Neuronal apoptosis was examined by TUNEL. Paeonol deacetylated HMGB1 by upregulating SIRT1 level. SIRT1 inhibition attenuated the protective effects of paeonol against neurological dysfunctions, brain edema, and BBB disruption. SIRT1 inhibition rescued the paeonol-induced inhibition in inflammatory response. The paeonol-induced decrease in neuronal apoptosis was restored by SIRT1 inhibitor. The paeonol-mediated deactivated TLR4/MyD88/NF-κB pathway was activated by SIRT1 inhibitor. Paeonol alleviates the SAH injury in rats by upregulating SIRT1 to inactivate the HMGB1/TLR4/MyD88/NF-κB pathway.

Epigallocatechin gallate improves oleic acid-induced hepatic steatosis in laying hen hepatocytes via the MAPK pathway

Fatty liver disease in laying hens, characterized by excessive lipid accumulation in hepatocytes, poses significant challenges to poultry health and production efficiency. In this study, we investigated the therapeutic potential of epigallocatechin gallate (EGCG), a bioactive compound found in green tea, in mitigating oleic acid (OA)-induced hepatic steatosis in primary chicken hepatocytes. Treatment with EGCG effectively attenuated lipid deposition by downregulating lipid synthesis-related genes. Moreover, EGCG mitigated oxidative stress, inflammation, DNA damage, and apoptosis induced by OA, thereby preserving hepatocyte viability. Mechanistically, EGCG exerted its protective effects by modulating the p38 MAPK signaling pathway. Our findings suggest that EGCG holds promise as a therapeutic agent for managing fatty liver disease in poultry, offering insights into novel strategies for improving poultry health and production outcomes.

EGCG-NPs inhibition HO-1-mediated reprogram iron metabolism against ferroptosis after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH), a devastating disease with a high mortality rate and poor outcomes, tightly associated with the dysregulation of iron metabolism and ferroptosis. (-)-Epigallocatechin-3-gallate (EGCG) is one of major bioactive compounds of tea catechin because of its well-known iron-chelating and antioxidative activities. However, the findings of iron-induced cell injuries after SAH remain controversial and the underlying therapeutic mechanisms of EGCG in ferroptosis is limited. Here, the ability of EGCG to inhibit iron-induced cell death following the alleviation of neurological function deficits was investigated by using in vivo SAH models. As expected, EGCG inhibited oxyhemoglobin (OxyHb)-induced the over-expression of HO-1, which mainly distributed in astrocytes and microglial cells. Subsequently, EGCG blocked ferrous iron accumulation through HO-1-mediated iron metabolic reprogramming. Therefore, oxidative stress and mitochondrial dysfunction was rescued by EGCG, which resulted in the downregulation of ferroptosis and ferritinophagy rather than apoptosis after SAH. As a result, EGCG exerted the superior therapeutic effects in the maintenance of iron homeostasis in glial cells, such as astrocytes and microglial cells, as well as in the improvement of functional outcomes after SAH. These findings highlighted that glial cells were not only the iron-rich cells in the brain but also susceptible to ferroptosis and ferritinophagy after SAH. The detrimental role of HO-1-mediated ferroptosis in glial cells can be regarded as an effective therapeutic target of EGCG in the prevention and treatment of SAH.

Targeting autophagy drug discovery: Targets, indications and development trends

Autophagy plays a vital role in sustaining cellular homeostasis and its alterations have been implicated in the etiology of many diseases. Drugs development targeting autophagy began decades ago and hundreds of agents were developed, some of which are licensed for the clinical usage. However, no existing intervention specifically aimed at modulating autophagy is available. The obstacles that prevent drug developments come from the complexity of the actual impact of autophagy regulators in disease scenarios. With the development and application of new technologies, several promising categories of compounds for autophagy-based therapy have emerged in recent years. In this paper, the autophagy-targeted drugs based on their targets at various hierarchical sites of the autophagic signaling network, e.g., the upstream and downstream of the autophagosome and the autophagic components with enzyme activities are reviewed and analyzed respectively, with special attention paid to those at preclinical or clinical trials. The drugs tailored to specific autophagy alone and combination with drugs/adjuvant therapies widely used in clinical for various diseases treatments are also emphasized. The emerging drug design and development targeting selective autophagy receptors (SARs) and their related proteins, which would be expected to arrest or reverse the progression of disease in various cancers, inflammation, neurodegeneration, and metabolic disorders, are critically reviewed. And the challenges and perspective in clinically developing autophagy-targeted drugs and possible combinations with other medicine are considered in the review.

Microneedles: A Versatile Drug Delivery Carrier for Phytobioactive Compounds as a Therapeutic Modulator for Targeting Mitochondrial Dysfunction in the Management of Neurodegenerative Diseases

Neurodegenerative disease (ND) is the fourth leading cause of death worldwide, with limited symptomatic therapies. Mitochondrial dysfunction is a major risk factor in the progression of ND, and it-increases the generation of reactive oxygen species (ROS). Overexposure to these ROS induces apoptotic changes leading to neuronal cell death. Many studies have shown the prominent effect of phytobioactive compounds in managing mitochondrial dysfunctions associated with ND, mainly due to their antioxidant properties. The drug delivery to the brain is limited due to the presence of the blood-brain barrier (BBB), but effective drug concentration needs to reach the brain for the therapeutic action. Therefore, developing safe and effective strategies to enhance drug entry in the brain is required to establish ND's treatment. The microneedle-based drug delivery system is one of the effective non-invasive techniques for drug delivery through the transdermal route. Microneedles are micronsized drug delivery needles that are self-administrable. It can penetrate through the stratum corneum skin layer without hitting pain receptors, allowing the phytobioactive compounds to be released directly into systemic circulation in a controlled manner. With all of the principles mentioned above, this review discusses microneedles as a versatile drug delivery carrier for the phytoactive compounds as a therapeutic potentiating agent for targeting mitochondrial dysfunction for the management of ND.

Urolithin A alleviates early brain injury after subarachnoid hemorrhage by regulating the AMPK/mTOR pathway-mediated autophagy

OBJECTIVE

Unfavorable outcomes in patients with subarachnoid hemorrhage (SAH) are mainly attributed to early brain injury (EBI). Reduction of neuronal death can improve the prognosis in SAH patients. Autophagy and apoptosis are critical players in neuronal death. Urolithin A (UA) is a natural compound produced by gut bacteria from ingested ellagitannins and ellagic acid. Here, we detected the role of UA in EBI post-SAH.

METHODS

We established an animal model of SAH in rats by endovascular perforation, with administration of UA, 3-methyladenine (3-MA) and Compound C. SAH grading, neurological function, brain water content, western blotting analysis of levels of proteins related to apoptosis, autophagy and pathways, blood-brain barrier (BBB) integrity, TUNEL staining, and immunofluorescence staining of LC3 were evaluated at 24h after SAH.

RESULTS

SAH induction led to neurological dysfunctions, BBB disruption, and cerebral edema at 24h post-SAH in rats, which were relieved by UA. Additionally, cortical neuronal apoptosis in SAH rats was also attenuated by UA. Moreover, UA restored autophagy level in SAH rats. Mechanistically, UA activated the AMPK/mTOR pathway. Furthermore, inhibition of autophagy and AMPK limited UA-mediated protection against EBI post-SAH CONCLUSION: UA alleviates neurological deficits, BBB permeability, and cerebral edema by inhibiting cortical neuronal apoptosis through regulating the AMPK/mTOR pathway-dependent autophagy in rats following SAH.

Analysis of cerebral glucose metabolism following experimental subarachnoid hemorrhage over 7 days

Little is known about changes in brain metabolism following SAH, possibly leading towards secondary brain damage. Despite sustained progress in the last decade, analysis of in vivo acquired data still remains challenging. The present interdisciplinary study uses a semi-automated data analysis tool analyzing imaging data independently from the administrated radiotracer. The uptake of 2-[¹⁸F]Fluoro-2-deoxy-glucose ([¹⁸F]FDG) was evaluated in different brain regions in 14 male Sprague-Dawley rats, randomized into two groups: (1) SAH induced by the endovascular filament model and (2) sham operated controls. Serial [¹⁸F]FDG-PET measurements were carried out. Quantitative image analysis was performed by uptake ratio using a self-developed MRI-template based data analysis tool. SAH animals showed significantly higher [¹⁸F]FDG accumulation in gray matter, neocortex and olfactory system as compared to animals of the sham group, while white matter and basal forebrain region showed significant reduced tracer accumulation in SAH animals. All significant metabolic changes were visualized from 3 h, over 24 h (day 1), day 4 and day 7 following SAH/sham operation. This [¹⁸F]FDG-PET study provides important insights into glucose metabolism alterations following SAH-for the first time in different brain regions and up to day 7 during course of disease.

Evaluation of the synergistic effects of epigallocatechin-3-gallate-loaded PEGylated-PLGA nanoparticles with nimodipine against neuronal injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating subtype of stroke with high mortality and morbidity. Although serious side effects might occur, nimodipine, a second-generation 1,4-dihydropyridine calcium channel blocker, is clinically used to improve neurological outcomes after SAH. Recently, (-)-epigallocatechin-3-gallate (EGCG) has been reported to inhibit Ca²⁺ overloading-induced mitochondrial dysfunction, oxidative stress, and neuronal cell death after SAH; however, low bioavailability, instability, and cytotoxicity at a high dose limited the clinical application of EGCG. To overcome these limitations, PEGylated-PLGA EGCG nanoparticles (EGCG-NPs) were constructed to enhance the bioavailability by using the double-emulsion method. Antioxidative activity, cytotoxicity, behavioral, and immunohistochemistry studies were carried out to determine the neuroprotective effectiveness after cotreatment with EGCG-NPs (75 mg/kg/d preconditioning for 7 days before SAH) and nimodipine (10 mg/kg/d after 30 min of SAH) by using in vivo SAH models. The optimized EGCG-NPs with a Box-Behnken design showed a small particle size of 167 nm, a zeta potential value of -22.6 mV, an encapsulation efficiency of 86%, and a sustained-release profile up to 8 days in vitro. Furthermore, EGCG-NPs (75 mg/kg/d) had superior antioxidative activity to free EGCG (100 mg/kg/d). EGCG-NPs combined with nimodipine exhibited significant synergistic effects against neuronal cell death by suppressing oxidative stress, Ca²⁺ overloading, mitochondrial dysfunction, and autophagy after SAH. These results suggest that cotreatment with EGCG-NPs and nimodipine may serve as a promising novel strategy for the treatment of SAH.

New Mechanisms and Targets of Subarachnoid Hemorrhage: A Focus on Mitochondria

Spontaneous subarachnoid hemorrhage (SAH) accounts for 5-10% of all strokes and is a subtype of hemorrhagic stroke that places a heavy burden on health care. Despite great progress in surgical clipping and endovascular treatment for ruptured aneurysms, cerebral vasospasm (CVS) and delayed cerebral ischemia (DCI) threaten the long-term outcomes of patients with SAH. Moreover, there are limited drugs available to reduce the risk of DCI and adverse outcomes in SAH patients. New insight suggests that early brain injury (EBI), which occurs within 72 h after the onset of SAH, may lay the foundation for further DCI development and poor outcomes. The mechanisms of EBI mainly include excitotoxicity, oxidative stress, neuroinflammation, blood-brain barrier (BBB) destruction, and cellular death. Mitochondria are a double-membrane organelle, and they play an important role in energy production, cell growth, differentiation, apoptosis, and survival. Mitochondrial dysfunction, which can lead to mitochondrial membrane potential (Δψm) collapse, overproduction of reactive oxygen species (ROS), release of apoptogenic proteins, disorders of mitochondrial dynamics, and activation of mitochondria-related inflammation, is considered a novel mechanism of EBI related to DCI as well as post-SAH outcomes. In addition, mitophagy is activated after SAH. In this review, we discuss the latest perspectives on the role of mitochondria in EBI and DCI after SAH. We emphasize the potential of mitochondria as therapeutic targets and summarize the promising therapeutic strategies targeting mitochondria for SAH.

The blood-brain barrier and the neurovascular unit in subarachnoid hemorrhage: molecular events and potential treatments

The response of the blood-brain barrier (BBB) following a stroke, including subarachnoid hemorrhage (SAH), has been studied extensively. The main components of this reaction are endothelial cells, pericytes, and astrocytes that affect microglia, neurons, and vascular smooth muscle cells. SAH induces alterations in individual BBB cells, leading to brain homeostasis disruption. Recent experiments have uncovered many pathophysiological cascades affecting the BBB following SAH. Targeting some of these pathways is important for restoring brain function following SAH. BBB injury occurs immediately after SAH and has long-lasting consequences, but most changes in the pathophysiological cascades occur in the first few days following SAH. These changes determine the development of early brain injury as well as delayed cerebral ischemia. SAH-induced neuroprotection also plays an important role and weakens the negative impact of SAH. Supporting some of these beneficial cascades while attenuating the major pathophysiological pathways might be decisive in inhibiting the negative impact of bleeding in the subarachnoid space. In this review, we attempt a comprehensive overview of the current knowledge on the molecular and cellular changes in the BBB following SAH and their possible modulation by various drugs and substances.

ACE2 Rescues Impaired Autophagic Flux Through the PI3K/AKT Pathway After Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is one of the life-threatening neurosurgical diseases in central nervous system. Autophagy has been previously demonstrated to exert vital roles in SAH development. Angiotensin I converting enzyme 2 (ACE2) has been revealed as a regulator of autophagy in neurosurgical diseases. However, effect of ACE2 on autophagy in SAH progression has not been clarified. First, we explored the relationship between autophagy and SAH progression by establishing a mouse model of SAH under the administration of 3-MA (the autophagy inhibitor). Next, we examined ACE2 expression in the cerebral cortex of SAH mice ex vivo with RT-qPCR. Subsequently, we assessed the biological function of ACE2 on brain injury, the autophagic flux pathway and the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling ex vivo via neurological scoring, TUNEL assay, western blot analysis and immunofluorescence staining assay. Finally, we carried out rescue assays under chloroquine (CQ, the autophagic flux inhibitor) and LY294002 (the PI3K/AKT signaling inhibitor) administration. 3-MA mitigated brain injury after SAH, and ACE2 was downregulated in cerebral cortex of SAH mice. Moreover, ACE2 elevation alleviated cell apoptosis, cerebral edema, and neurological deficits, ameliorated the autophagic flux pathway and activated the PI3K/AKT signaling in SAH mice. Furthermore, CQ and LY294002 neutralized the effects of overexpressed ACE2 on neuronal apoptosis, cerebral edema, and neurological deficits in SAH mice. Overall, ACE2 lessened neuronal injury via the autophagic flux and PI3K/AKT pathways. This research might provide a potential novel direction for clinical treatment of SAH.

Mitochondrial dysfunction associated with autophagy and mitophagy in cerebrospinal fluid cells of patients with delayed cerebral ischemia following subarachnoid hemorrhage

Decreased mitochondrial membrane potential in cerebrospinal fluid (CSF) was observed in patients with subarachnoid hemorrhage (SAH) accompanied by delayed cerebral ischemia (DCI). However, whether abnormal mechanisms of mitochondria are associated with the development of DCI has not been reported yet. Under cerebral ischemia, mitochondria can transfer into the extracellular space. Mitochondrial dysfunction can aggravate neurologic complications. The objective of this study was to evaluate whether mitochondrial dysfunction might be associated with autophagy and mitophagy in CSF cells to provide possible insight into DCI pathogenesis. CSF samples were collected from 56 SAH patients (DCI, n = 21; and non-DCI, n = 35). We analyzed CSF cells using autophagy and mitophagy markers (DAPK1, BNIP3L, BAX, PINK1, ULK1, and NDP52) via qRT-PCR and western blotting of proteins (BECN1, LC3, and p62). Confocal microscopy and immunogold staining were performed to demonstrate the differentially expression of markers within dysfunctional mitochondria. Significant induction of autophagic flux with accumulation of autophagic vacuoles, increased expression of BECN1, LC3-II, and p62 degradation were observed during DCI. Compared to non-DCI patients, DCI patients showed significantly increased mRNA expression levels (2^-ΔCt) of DAPK1, BNIP3L, and PINK1, but not BAX, ULK1, or NDP52. Multivariable logistic regression analysis revealed that Hunt and Hess grade ≥ IV (p = 0.023), DAPK1 (p = 0.003), and BNIP3L (p = 0.039) were related to DCI. Increased mitochondrial dysfunction associated with autophagy and mitophagy could play an important role in DCI pathogenesis.

Neuroprotective Strategies in Aneurysmal Subarachnoid Hemorrhage (aSAH)

Aneurysmal subarachnoid hemorrhage (aSAH) remains a disease with high mortality and morbidity. Since treating vasospasm has not inevitably led to an improvement in outcome, the actual emphasis is on finding neuroprotective therapies in the early phase following aSAH to prevent secondary brain injury in the later phase of disease. Within the early phase, neuroinflammation, thromboinflammation, disturbances in brain metabolism and early neuroprotective therapies directed against delayed cerebral ischemia (DCI) came into focus. Herein, the role of neuroinflammation, thromboinflammation and metabolism in aSAH is depicted. Potential neuroprotective strategies regarding neuroinflammation target microglia activation, metalloproteases, autophagy and the pathway via Toll-like receptor 4 (TLR4), high mobility group box 1 (HMGB1), NF-κB and finally the release of cytokines like TNFα or IL-1. Following the link to thromboinflammation, potential neuroprotective therapies try to target microthrombus formation, platelets and platelet receptors as well as clot clearance and immune cell infiltration. Potential neuroprotective strategies regarding metabolism try to re-balance the mismatch of energy need and supply following aSAH, for example, in restoring fuel to the TCA cycle or bypassing distinct energy pathways. Overall, this review addresses current neuroprotective strategies in aSAH, hopefully leading to future translational therapy options to prevent secondary brain injury.

FGF-2 suppresses neuronal autophagy by regulating the PI3K/Akt pathway in subarachnoid hemorrhage

The degree of early brain injury (EBI) is a significant factor that affects the prognosis of patients with subarachnoid hemorrhage (SAH). Evidence has shown that fibroblast growth factor-2 (FGF-2) may alleviate the serious consequences of EBI after SAH. The objective of the current study was to investigate the underlying mechanism that mediates the neuroprotective effects of FGF-2 in the SAH rat model. Sprague-Dawley (SD) rats that underwent different treatments were divided into various groups. FGF-2 was administered intranasally to rats in the treatment group within 30 min after modeling. Rapamycin (an autophagy activator) or LY294002 (a PI3K/Akt pathway inhibitor) was administered intracerebroventricularly (i.c.v.) 30 min before modeling. Neurological scale and brain water content were measured in the brain tissue of the rats. TUNEL staining, Western blot, and immunofluorescence staining were performed to examine and compare the diverse effects of FGF-2 treatment, activated autophagy, and inhibited the PI3K/Akt pathway. We found that FGF-2 treatment effectively reduced the number of TUNEL-positive cells, decreased the brain water content, and improved the neurological function of rats after SAH. Additionally, the expression levels of autophagy-related proteins (LC3 and Beclin-1) were obviously decreased in the FGF-2 treatment group compared with the SAH + vehicle group. The therapeutic effects of FGF-2 in the SAH + FGF-2+rapamycin group were weakened compared with that in the SAH + FGF-2+DMSO group. In the event of the PI3K/Akt pathway inhibition, the expression levels of LC3 and Beclin-1 were enhanced, and the therapeutic effects of FGF-2 were compromised. In summary, our data collectively demonstrated that FGF-2 may suppress autophagy levels to play a neuroprotective role, at least partially by activating the PI3K/Akt pathway. These results highlight FGF-2 as a promising solution to the clinical intervention of SAH.

Dihydrolipoic acid enhances autophagy and alleviates neurological deficits after subarachnoid hemorrhage in rats

Autophagy is a crucial pathological process in early brain injury (EBI) after subarachnoid hemorrhage (SAH). In this study, we investigated the role of dihydrolipoic acid (DHLA) on enhancing autophagy and alleviating neurological deficits after SAH. SAH was induced by endovascular perforation in male Sprague-Dawley rats. DHLA (30 mg/kg) was administered intraperitoneally 1 h (h) after SAH. Small interfering ribonucleic acid (siRNA) for lysosome-associated membrane protein-1 (LAMP1) was administered through intracerebroventricular (i.c.v) route 48 h before SAH induction. SAH grading score, neurological score, immunofluorescence staining, Fluoro-Jade C (FJC) staining, and Western blot were examined. DHLA treatment increased autophagy-related protein expression and downregulated the apoptosis-related protein expression 24 h after SAH. In addition, the DHLA treatment reduced neuronal cell death and alleviated neurological deficits after SAH. Furthermore, knockdown of LAMP1 abolished the neuroprotective effects of DHLA. These results indicate that LAMP1 may participate in autophagy after SAH. DHLA treatment can enhance autophagy, attenuate apoptosis, and alleviate neurofunctional deficits in EBI after SAH. It may provide an effective alternative method for the treatment of EBI after SAH.

Natural products targeting mitochondria: emerging therapeutics for age-associated neurological disorders

Mitochondria are the primary source of energy production in the brain thereby supporting most of its activity. However, mitochondria become inefficient and dysfunctional with age and to a greater extent in neurological disorders. Thus, mitochondria represent an emerging drug target for many age-associated neurological disorders. This review summarizes recent advances (covering from 2010 to May 2020) in the use of natural products from plant, animal, and microbial sources as potential neuroprotective agents to restore mitochondrial function. Natural products from diverse classes of chemical structures are discussed and organized according to their mechanism of action on mitochondria in terms of modulation of biogenesis, dynamics, bioenergetics, calcium homeostasis, and membrane potential, as well as inhibition of the oxytosis/ferroptosis pathway. This analysis emphasizes the significant value of natural products for mitochondrial pharmacology as well as the opportunities and challenges for the discovery and development of future neurotherapeutics.

EGCG Promotes Neurite Outgrowth through the Integrin β1/FAK/p38 Signaling Pathway after Subarachnoid Hemorrhage

The abnormal neurites have long been regarded as the main player contributing to the poor outcome of patients with subarachnoid hemorrhage (SAH). (-)-Eigallocatechin-3-gallate (EGCG), the major biological component of tea catechin, exhibited strong neuroprotective effects against central nervous system diseases; however, the role of EGCG-mediated neurite outgrowth after SAH has not been delineated. Here, the effect of reactive oxygen species (ROS)/integrin β1/FAK/p38 pathway on neurite outgrowth was investigated. As expected, oxyhemoglobin- (OxyHb-) induced excessive ROS level was significantly reduced by EGCG as well as antioxidant N-acetyl-l-cysteine (NAC). Consequently, the expression of integrin β1 was significantly inhibited by EGCG and NAC. Meanwhile, EGCG significantly inhibited the overexpression of phosphorylated FAK and p38 to basal level after SAH. As a result, the abnormal neurites and cell injury were rescued by EGCG, which eventually increased energy generation and neurological score after SAH. These results suggested that EGCG promoted neurite outgrowth after SAH by inhibition of ROS/integrin β1/FAK/p38 signaling pathway. Therefore, EGCG might be a new pharmacological agent that targets neurite outgrowth in SAH therapy.

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.

The Role of Epigallocatechin-3-Gallate in Autophagy and Endoplasmic Reticulum Stress (ERS)-Induced Apoptosis of Human Diseases

Tea containing abundant catechins is a popular non-alcoholic beverage worldwide. Epigallocatechin-3-gallate (EGCG) is the predominately active substance in catechins, exhibiting a wide range of functional properties including cancer suppression, neuroprotective, metabolic regulation, cardiovascular protection, stress adjustment, and antioxidant in various diseases. Autophagy, a basic cell function, participates in various physiological processes which include clearing away abnormally folded proteins and damaged organelles, and regulating growth. EGCG not only regulates autophagy via increasing Beclin-1 expression and reactive oxygen species generation, but also causing LC3 transition and decreasing p62 expression. EGCG-induced autophagy is involved in the occurrence and development of many human diseases, including cancer, neurological diseases, diabetes, cardiovascular diseases, and injury. Apoptosis is a common cell function in biology and is induced by endoplasmic reticulum stress (ERS) as a cellular stress response which is caused by various internal and external factors. ERS-induced apoptosis of EGCG influences cell survival and death in various diseases via regulating IRE1, ATF6, and PERK signaling pathways, and activating GRP78 and caspase proteins. The present manuscript reviews that the effect of EGCG in autophagy and ERS-induced apoptosis of human diseases.

Neuroprotective Properties of Green Tea (Camellia sinensis) in Parkinson's Disease: A Review

Neurodegenerative disease is a collective term given for the clinical condition, which results in progressive degeneration of neurons and the loss of functions associated with the affected brain region. Apart from the increase in age, neurodegenerative diseases are also partly affected by diet and lifestyle practices. Parkinson's disease (PD) is a slow onset neurodegenerative disorder and the second most common neurodegenerative disease, which affects the motor system. Although there is no prescribed treatment method to prevent and cure PD, clinical procedures help manage the disease symptoms. Green tea polyphenols are known for several health benefits, including antioxidant, anti-inflammatory, and neuroprotective activity. The current manuscript summarizes the possible mechanisms of neuroprotective potential of green tea with a special focus on PD. Studies have suggested that the consumption of green tea protects against free-radicals, inflammation, and neuro-damages. Several in vivo studies aid in understanding the overall mechanism of green tea. However, the same dose may not be sufficient in humans to elicit similar effects due to complex physiological, social, and cultural development. Future research focused on more clinical trials could identify an optimum dose that could impart maximum health benefits to impart neuroprotection in PD.

Protein Kinase C Isozymes and Autophagy during Neurodegenerative Disease Progression

Protein kinase C (PKC) isozymes are members of the Serine/Threonine kinase family regulating cellular events following activation of membrane bound phospholipids. The breakdown of the downstream signaling pathways of PKC relates to several disease pathogeneses particularly neurodegeneration. PKC isozymes play a critical role in cell death and survival mechanisms, as well as autophagy. Numerous studies have reported that neurodegenerative disease formation is caused by failure of the autophagy mechanism. This review outlines PKC signaling in autophagy and neurodegenerative disease development and introduces some polyphenols as effectors of PKC isozymes for disease therapy.

Receptor-Mediated Delivery of Astaxanthin-Loaded Nanoparticles to Neurons: An Enhanced Potential for Subarachnoid Hemorrhage Treatment

Astaxanthin (ATX) is a carotenoid that exerts strong anti-oxidant and anti-inflammatory property deriving from its highly unsaturated molecular structures. However, the low stability and solubility of ATX results in poor bioavailability, which markedly hampers its application as therapeutic agent in clinic advancement. This study investigated a promising way of transferrin conjugated to poly (ethylene glycol) (PEG)-encapsulated ATX nanoparticles (ATX-NPs) on targeted delivery and evaluated the possible mechanism underlying neuroprotection capability. As a result, the ATX integrated into nanocarrier presented both well water-dispersible and biocompatible, primely conquering its limitations. More than that, the transferrin-containing ATX-NPs exhibited enhanced cellular uptake efficiency than that of ATX-NPs without transferrin conjugated in primary cortical neurons. Additionally, compared to free ATX, transferrin-containing ATX-NPs with lower ATX concentration showed powerful neuroprotective effects on OxyHb-induced neuronal damage. Taken together, the improved bioavailability and enhanced neuroprotective effects enabled ATX-NPs as favorable candidates for targeted delivery and absorption of ATX. We believe that these in vitro findings will provide insights for advancement of subarachnoid hemorrhage therapy.

Evaluation of the neuroprotective effect of EGCG: a potential mechanism of mitochondrial dysfunction and mitochondrial dynamics after subarachnoid hemorrhage

(-)-Epigallocatechin-3-gallate (EGCG), the main bioactive component of tea catechins, exhibits broad-spectrum health efficacy against mitochondrial damage after subarachnoid hemorrhage (SAH). The mechanisms, however, are largely unknown. Here, the ability of EGCG to rescue mitochondrial dysfunction and mitochondrial dynamics following the inhibition of cell death was investigated by using in vitro and in vivo SAH models. EGCG blocked the cytosolic channel ([Ca2+])i influx via voltage-gated calcium channels (VGCCs), which induced mitochondrial dysfunction, including mitochondrial membrane potential depolarization and reactive oxygen species (ROS) release. As expected, EGCG ameliorated oxyhemoglobin (OxyHb)-induced impairment of mitochondrial dynamics by regulating the expression of Drp1, Fis1, OPA1, Mfn1, and Mfn2. As a result, EGCG restored the increases in fragmented mitochondria and the mtDNA copy number in the OxyHb group to almost the normal level after SAH. In addition, the normal autophagic flux induced by EGCG at both the initiation and formation stages regulated Atg5 and Beclin-1 after SAH for the timely elimination of damaged mitochondria. In the end, EGCG increased the neurological score by decreasing cell death through the cyt c-mediated intrinsic apoptotic pathway. The results revealed the mechanisms behind the neuroprotective effects of EGCG via inhibition of the overloaded [Ca2+]i-induced mitochondrial dysfunction and the imbalanced mitochondrial fusion and fission cycle. Therefore, the simultaneous inhibition and timely elimination of damaged mitochondria could determine the therapeutic effect of EGCG.

The Role of Autophagy in Subarachnoid Hemorrhage: An Update

BACKGROUND

Autophagy is an extensive self-degradation process for the disposition of cytosolic aggregated or misfolded proteins and defective organelles which executes the functions of pro-survival and pro-death to maintain cellular homeostasis. The pathway plays essential roles in several neurological disorders. Subarachnoid Hemorrhage (SAH) is a devastating subtype of hemorrhagic stroke with high risk of neurological deficit and high mortality. Early brain injury (EBI) plays a role in the poor clinical course and outcome after SAH. Recent studies have paid attention on the role of the autophagy pathway in the development of EBI after SAH. We aim to update the multifaceted roles of autophagy pathway in the pathogenesis of SAH, especially in the phase of EBI.

METHODS

We reviewed early researches related to autophagy and SAH. The following three aspects of contents will be mainly discussed: the process of the autophagy pathway, the role of the autophagy in SAH and the interaction between organelle dysfunction and autophagy pathway after SAH.

RESULTS

Accumulating evidence shows an increased autophagy reaction in response to early stages of SAH. However, others suggest inadequate or excessive autophagy activation can result in cell injury and death. In addition to autophagy, apoptosis and necrosis can occur in neurons simultaneously after SAH, leading to mixed features of cell death morphologies. And it is also known that there is extensive crosstalk between autophagy and apoptosis pathway. Subcellular organelles of neural cells generally participate in the formation and functional parts of autophagy process.

CONCLUSION

Autophagy plays an important role in the SAH-induced brain injury. A better understanding of the interrelationship among autophagy, apoptosis, and necrosis might provide us better therapeutic targets for the treatment of SAH.

Autophagy after Subarachnoid Hemorrhage: Can Cell Death be Good?

BACKGROUND

Autophagy is a prosurvival, reparative process that maintainsww cellular homeostasis through lysosomal degradation of selected cytoplasmic components and programmed death of old, dysfunctional, or unnecessary cytoplasmic entities. According to growing evidence, autophagy shows beneficial effects following subarachnoid hemorrhage (SAH). SAH is considered one of the most devastating forms of stroke.

METHODS

In this review lies in revealing the pathophysiological pathways and the effects of autophagy. Current results from animal studies will be discussed focusing on the effects of inhibitors and inducers of autophagy. In addition, this review discusses the clinical translation of potential neuropharmacological targets that can help prevent early brain injury (EBI) following SAH by incorporating programmed cell death into clinical management.

RESULTS

Published data showed that autophagy mechanisms have a prosurvival effect to reduce apoptotic cell death after SAH. However, if SAH exceeds a certain stress threshold, autophagy mechanisms lead to increased apoptotic cell death, more brain injury, and worse outcome.

CONCLUSION

Future investigation on the differences and molecular switches between protective mechanisms of autophagy and excessive "self-eating" autophagy leading to cell death is needed to achieve more insight into the complex pathophysiology of brain injury after SAH. If autophagy after SAH can be controlled to lead to beneficial effects only, as the physiological self-control mechanism, this could be an important target for treatment.

Neuroprotective Role of Phytochemicals

Neurodegenerative diseases are normally distinguished as disorders with loss of neurons. Various compounds are being tested to treat neurodegenerative diseases (NDs) but they possess solitary symptomatic advantages with numerous side effects. Accumulative studies have been conducted to validate the benefit of phytochemicals to treat neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD). In this present review we explored the potential efficacy of phytochemicals such as epigallocatechin-3-galate, berberin, curcumin, resveratrol, quercetin and limonoids against the most common NDs, including Alzheimer's disease (AD) and Parkinson's disease (PD). The beneficial potentials of these phytochemicals have been demonstrated by evidence-based but more extensive investigation needs to be conducted for reducing the progression of AD and PD.

NF-κB-Mediated Inflammation in the Pathogenesis of Intracranial Aneurysm and Subarachnoid Hemorrhage. Does Autophagy Play a Role?

The rupture of saccular intracranial aneurysms (IA) is the commonest cause of non-traumatic subarachnoid hemorrhage (SAH)—the most serious form of stroke with a high mortality rate. Aneurysm walls are usually characterized by an active inflammatory response, and NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) has been identified as the main transcription factor regulating the induction of inflammation-related genes in IA lesions. This transcription factor has also been related to IA rupture and resulting SAH. We and others have shown that autophagy interacts with inflammation in many diseases, but there is no information of such interplay in IA. Moreover, NF-κB, which is a pivotal factor controlling inflammation, is regulated by autophagy-related proteins, and autophagy is regulated by NF-κB signaling. It was also shown that autophagy mediates the normal functioning of vessels, so its disturbance can be associated with vessel-related disorders. Early brain injury, delayed brain injury, and associated cerebral vasospasm are among the most serious consequences of IA rupture and are associated with impaired function of the autophagy⁻lysosomal system. Further studies on the role of the interplay between autophagy and NF-κB-mediated inflammation in IA can help to better understand IA pathogenesis and to identify IA patients with an increased SAH risk.

The critical role of epigallocatechin gallate in regulating mitochondrial metabolism

Epigallocatechin gallate (EGCG), one of polyphenols isolated from green tea, exhibits biology-benefiting effects with minimum severe adverse. EGCG is known to be a mitochondrion-targeting medicinal agent, regulating mitochondrial metabolism, including mitochondrial biogenesis, mitochondrial bioenergetics, and mitochondria-mediated cell cycle and apoptosis. EGCG might exhibit either antioxidative activity to prevent against oxidative stress or pro-oxidative activity to counteract cancer cells, which depends on the cellular stress situations, cell types and the concentration of EGCG. Recent research has gained positive and promising data. This review will discuss the interaction between EGCG and mitochondrion.

The critical role of epigallocatechin gallate in regulating mitochondrial metabolism

Epigallocatechin gallate (EGCG), one of polyphenols isolated from green tea, exhibits biology-benefiting effects with minimum severe adverse. EGCG is known to be a mitochondrion-targeting medicinal agent, regulating mitochondrial metabolism, including mitochondrial biogenesis, mitochondrial bioenergetics, and mitochondria-mediated cell cycle and apoptosis. EGCG might exhibit either antioxidative activity to prevent against oxidative stress or pro-oxidative activity to counteract cancer cells, which depends on the cellular stress situations, cell types and the concentration of EGCG. Recent research has gained positive and promising data. This review will discuss the interaction between EGCG and mitochondrion.

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.

Phytochemicals as potent modulators of autophagy for cancer therapy

The dysregulation of autophagy is involved in the pathogenesis of a broad range of diseases, and accordingly universal research efforts have focused on exploring novel compounds with autophagy-modulating properties. While a number of synthetic autophagy modulators have been identified as promising cancer therapy candidates, autophagy-modulating phytochemicals have also attracted attention as potential treatments with minimal side effects. In this review, we firstly highlight the importance of autophagy and its relevance in the pathogenesis and treatment of cancer. Subsequently, we present the data on common phytochemicals and their mechanism of action as autophagy modulators. Finally, we discuss the challenges associated with harnessing the autophagic potential of phytochemicals for cancer therapy.

A new molecular mechanism underlying the EGCG-mediated autophagic modulation of AFP in HepG2 cells

Epigallocatechingallate (EGCG) is a major bioactive component of green tea and is associated with health benefits against multiple diseases including cancer. As an indicator of hepatocellular carcinoma (HCC), high levels of α-fetal protein (AFP) are related to malignant differentiation and poor prognosis of cancer cells. In this study, EGCG can effectively reduce AFP secretion and simultaneously induce AFP aggregation in human HCC HepG₂ cells. EGCG-stimulated autophagy induces the degradation of AFP aggregates in HepG₂ cells. Furthermore, we thoroughly studied the underlying molecular mechanisms behind EGCG-stimulated autophagy by using large-scale all-atom molecular dynamics simulations, which revealed a novel molecular mechanism. EGCG directly interacts with LC3-I protein, readily exposing the pivotal Gly-120 site of the latter to other important binding partners such as 1,2-distearoyl-sn-glycero-3-phosphoethanolamine and promoting the synthesis of LC3-II, a characteristic autophagosomal marker. Our results suggest that EGCG is critical in regulating AFP secretion and in modulating autophagic activities of HepG₂ cells, providing a molecular basis for potentially preventing and treating HCC.

Differential expression of microRNAs contributed to the health efficacy of EGCG inin vitrosubarachnoid hemorrhage model

(1) EGCG prevented miRNA dysregulation after SAH; (2) multi-target mechanisms of EGCG might rely on its regulatory roles on miRNAs expression, such as those miRNAs targeting p38, Ca²⁺, and autophagic activation; (3) the differential expression of miRNAs might determine the therapeutic efficacy of different concentration of EGCG.