Pseudoginsenoside F11 ameliorates the dysfunction of the autophagy-lysosomal pathway by activating calcineurin-mediated TFEB nuclear translocation in neuron during permanent cerebral ischemia

Berberine Alleviates Ischemic Brain Injury by Enhancing Autophagic Flux via Facilitation of TFEB Nuclear Translocation

Berberine has been demonstrated to alleviate cerebral ischemia/reperfusion injury, but its neuroprotective mechanism has yet to be understood. Studies have indicated that ischemic neuronal damage was frequently driven by autophagic/lysosomal dysfunction, which could be restored by boosting transcription factor EB (TFEB) nuclear translocation. Therefore, this study investigated the pharmacological effects of berberine on TFEB-regulated autophagic/lysosomal signaling in neurons after cerebral stroke. A rat model of ischemic stroke and a neuronal ischemia model in HT22 cells were prepared using middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation (OGD), respectively. Berberine was pre-administered at a dose of 100[Formula: see text]mg/kg/d for three days in rats and 90[Formula: see text][Formula: see text]M in HT22 neurons for 12[Formula: see text]h. 24[Formula: see text]h after MCAO and 2[Formula: see text]h after OGD, the penumbral tissues and OGD neurons were obtained to detect nuclear and cytoplasmic TFEB, and the key proteins in the autophagic/lysosomal pathway were examined using western blot and immunofluorescence, respectively. Meanwhile, neuron survival, infarct volume, and neurological deficits were assessed to evaluate the therapeutic efficacy. The results showed that berberine prominently facilitated TFEB nuclear translocation, as indicated by increased nuclear expression in penumbral neurons as well as in OGD HT22 cells. Consequently, both autophagic activity and lysosomal capacity were simultaneously augmented to alleviate the ischemic injury. However, berberine-conferred neuroprotection could be greatly counteracted by lysosomal inhibitor Bafilomycin A1 (Baf-A1). Meanwhile, autophagy inhibitor 3-Methyladenine (3-MA) also slightly neutralized the pharmacological effect of berberine on ameliorating autophagic/lysosomal dysfunction. Our study suggests that berberine-induced neuroprotection against ischemic stroke is elicited by enhancing autophagic flux via facilitation of TFEB nuclear translocation in neurons.

Transcription Factor EB: A Promising Therapeutic Target for Ischemic Stroke

Transcription factor EB (TFEB) is an important endogenous defensive protein that responds to ischemic stimuli. Acute ischemic stroke is a growing concern due to its high morbidity and mortality. Most survivors suffer from disabilities such as numbness or weakness in an arm or leg, facial droop, difficulty speaking or understanding speech, confusion, impaired balance or coordination, or loss of vision. Although TFEB plays a neuroprotective role, its potential effect on ischemic stroke remains unclear. This article describes the basic structure, regulation of transcriptional activity, and biological roles of TFEB relevant to ischemic stroke. Additionally, we explore the effects of TFEB on the various pathological processes underlying ischemic stroke and current therapeutic approaches. The information compiled here may inform clinical and basic studies on TFEB, which may be an effective therapeutic drug target for ischemic stroke.

The Pathological Mechanism of Neuronal Autophagy-Lysosome Dysfunction After Ischemic Stroke

The abnormal initiation of autophagy flux in neurons after ischemic stroke caused dysfunction of autophagy-lysosome, which not only led to autophagy flux blockage, but also resulted in autophagic death of neurons. However, the pathological mechanism of neuronal autophagy-lysosome dysfunction did not form a unified viewpoint until now. In this review, taking the autophagy lysosomal dysfunction of neurons as a starting point, we summarized the molecular mechanisms that led to neuronal autophagy lysosomal dysfunction after ischemic stroke, which would provide theoretical basis for the clinical treatment of ischemic stroke.

Esketamine is neuroprotective against traumatic brain injury through its modulation of autophagy and oxidative stress via AMPK/mTOR-dependent TFEB nuclear translocation

Recent clinical studies highlight the neuroprotective effects of esketamine, but its benefits following traumatic brain injury (TBI) have not been defined. Here, we investigated the effects of esketamine following TBI and its associated neuroprotection mechanisms. In our study, controlled cortical impact injury on mice was utilized to induce the TBI model in vivo. TBI mice were randomized to receive vehicle or esketamine at 2 h post-injury for 7 consecutive days. Neurological deficits and brain water content in mice were detected, respectively. Cortical tissues surrounding focal trauma were obtained for Nissl staining, immunofluorescence, immunohistochemistry, and ELISA assay. In vitro, esketamine were added in culture medium after cortical neuronal cells induced by H2O2 (100μM). After exposed for 12h, neuronal cells were obtained for western blotting, immunofluorescence, ELISA and CO-IP assay. Following administration of 2-8 mg/kg esketamine, we observed that 8 mg/kg esketamine produced no additional recovery of neurological function and ability to alleviate brain edema in TBI mice model, so 4 mg/kg esketamine was selected for subsequent experiments. Additionally, esketamine can effectively reduce TBI-induced oxidative stress, the number of damaged neurons, and the number of TUNEL-positive cells in the cortex of TBI models. Meanwhile, the levels of Beclin 1, LC3 II, and the number of LC3-positive cells in injured cortex were also increased following esketamine exposure. Western blotting and immunofluorescence assays showed that esketamine accelerated the nuclear translocation of TFEB, increased the p-AMPKα level and decreased the p-mTOR level. Similar results including nuclear translocation of TFEB, the increases of autophagy-related markers, and influences of AMPK/mTOR pathway were observed in H2O2-induced cortical neuronal cells; however, BML-275 (AMPK inhibitor) can reverse these effects of esketamine. Furthermore, TFEB silencing not only decreased the Nrf2 level in H2O2-induced cortical neuronal cells, but also alleviated the oxidative stress. Importantly, CO-IP confirmed the interaction between TFEB and Nrf2 in cortical neuronal cells. These findings suggested that esketamine exerts the neuroprotective effects of esketamine in TBI mice model via enhancing autophagy and alleviating oxidative stress; its mechanism involves AMPK/mTOR-dependent TFEB nuclear translocation-induced autophagy and TFEB/Nrf2-induced antioxidant system.

Exercise pretreatment alleviates neuroinflammation and oxidative stress by TFEB-mediated autophagic flux in mice with ischemic stroke

BACKGROUND

Neuroinflammation and oxidative stress are important pathological mechanisms underlying cerebral ischemic stroke. Increasing evidence suggests that regulation autophagy in ischemic stroke may improve neurological functions. In this study, we aimed to explore whether exercise pretreatment attenuates neuroinflammation and oxidative stress in ischemic stroke by improving autophagic flux.

METHODS

2,3,5-Triphenyltetrazolium chloride staining was used to determine the infarction volume, and modified Neurological Severity Scores and rotarod test were used to evaluate neurological functions after ischemic stroke. The levels of oxidative stress, neuroinflammation, neuronal apoptosis and degradation, autophagic flux, and signaling pathway proteins were determined using immunofluorescence, dihydroethidium, TUNEL, and Fluoro-Jade B staining, western blotting, and co-immunoprecipitation.

RESULTS

Our results showed that, in middle cerebral artery occlusion (MCAO) mice, exercise pretreatment improved neurological functions and defective autophagy, and reduced neuroinflammation and oxidative stress. Mechanistically, after using chloroquine, impaired autophagy abolished the neuroprotection of exercise pretreatment. And transcription factor EB (TFEB) activation mediated by exercise pretreatment contributes to improving autophagic flux after MCAO. Furthermore, we showed that TFEB activation mediated by exercise pretreatment in MCAO was regulated by the AMPK-mTOR and AMPK-FOXO3a-SKP2-CARM1 signaling pathways.

CONCLUSIONS

Exercise pretreatment has the potential to improve the prognosis of ischemic stroke patients, and it can exert neuroprotective effects in ischemic stroke by inhibiting neuroinflammation and oxidative stress, which might be due to the TFEB-mediated autophagic flux. And targeting autophagic flux may be promising strategies for the treatment of ischemic stroke.

The Protective Effect of (-)-Tetrahydroalstonine against OGD/R-Induced Neuronal Injury via Autophagy Regulation

Here, (-)-Tetrahydroalstonine (THA) was isolated from Alstonia scholaris and investigated for its neuroprotective effect towards oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced neuronal damage. In this study, primary cortical neurons were pre-treated with THA and then subjected to OGD/R induction. The cell viability was tested by the MTT assay, and the states of the autophagy-lysosomal pathway and Akt/mTOR pathway were monitored by Western blot analysis. The findings suggested that THA administration increased the cell viability of OGD/R-induced cortical neurons. Autophagic activity and lysosomal dysfunction were found at the early stage of OGD/R, which were significantly ameliorated by THA treatment. Meanwhile, the protective effect of THA was significantly reversed by the lysosome inhibitor. Additionally, THA significantly activated the Akt/mTOR pathway, which was suppressed after OGD/R induction. In summary, THA exhibited promising protective effects against OGD/R-induced neuronal injury by autophagy regulation through the Akt/mTOR pathway.

Cellular Prion Protein Attenuates OGD/R-Induced Damage by Skewing Microglia toward an Anti-inflammatory State via Enhanced and Prolonged Activation of Autophagy

Modulation of microglial pro/anti-inflammatory states and autophagy are promising new therapies for ischemic stroke, but the underlying mechanisms remain largely unexplored. The objective of the study is to determine the intrinsic role of PrP^C (cellular prion protein) in the regulation of microglial inflammatory states and autophagy in ischemic stroke. PrP^C was expressed in murine microglia, and an in vitro oxygen-glucose deprivation/reperfusion (OGD/R) model was established in microglia of different PRNP genotypes. During reperfusion following OGD, wild-type (WT) microglia had significantly increased pro/anti-inflammatory microglial percentages and related cytokine [interleukin [IL]-6, IL-10, IL-4, tumor necrosis factor, and interferon-gamma] release at reperfusion after 48 or 72 h. WT microglia also showed greater accumulation of the autophagy markers LC3B-II/I (microtubule-associated protein B-light chain 3), but not of p62 or LAMP1 (lysosome-associated membrane protein) at reperfusion after 24 h and 48 h. Inhibition of autophagy using 3-methyladenine or bafilomycin A1 aggravated the OGD/R-induced pro-inflammatory state, and the effect of 3-methyladenine was significantly stronger than that of bafilomycin A1. Concomitantly, PRNP knockout shortened the accumulation of LC3B-II/I, suppressed microglial anti-inflammatory states, and further aggravated the pro-inflammatory states. Conversely, PRNP overexpression had the opposite effects. Bafilomycin A1 reversed the effect of PrP^C on microglial inflammatory state transformation. Moreover, microglia with PRNP overexpression exhibited higher levels of LAMP1 expression in the control and OGD/R groups and delayed the OGD/R-induced decrease of LAMP1 to reperfusion after 48 h. PrP^C attenuates OGD/R-induced damage by skewing microglia toward an anti-inflammatory state via enhanced and prolonged activation of autophagy.

Neuroprotective effect of pseudoginsenoside-F11 on permanent cerebral ischemia in rats by regulating calpain activity and NR2A submit-mediated AKT-CREB signaling pathways

BACKGROUND

N-methyl-d-aspartate receptors (NMDARs) have been demonstrated to play central roles in stroke pathology and recovery, including dual roles in promoting either neuronal survival or death with their different subtypes and locations.

PURPOSE

We have previously demonstrated that pseudoginsenoside-F11 (PF11) can provide long-term neuroprotective effects on transient and permanent ischemic stroke-induced neuronal damage. However, it is still needed to clarify whether NMDAR-2A (NR2A)-mediated pro-survival signaling pathway is involved in the beneficial effect of PF11 on permanent ischemic stroke.

MATERIAL AND METHODS

PF11 was administrated in permanent middle cerebral artery occlusion (pMCAO)-operated rats. The effect of PF11 on oxygen-glucose deprivation (OGD)-exposed primary cultured neurons were further evaluated. The regulatory effect of PF11 on NR2A expression and the activation of its downstream AKT-CREB pathway were detected by Western blotting and immunofluorescence in the presence or absence of a specific NR2A antagonist NVP-AAM077 (NVP) both in vivo and in vitro.

RESULTS

PF11 dose- and time-dependently decreased calpain1 (CAPN1) activity and its specific breakdown product α-Fodrin expression, while the expression of Ca²⁺/calmodulin-dependent protein kinase II alpha (CaMKII-α) was significantly upregulated in the cortex and striatum of rats at 24 h after the onset of pMCAO operation. Moreover, PF11 prevented the downregulation of NR2A, p-AKT/AKT, and p-CREB/CREB in both in vivo and in vitro stroke models. Finally, the results indicated treatment with NVP can abolish the effects of PF11 on alleviating the ischemic injury and activating NR2A-mediated AKT-CREB signaling pathway.

CONCLUSIONS

Our results demonstrate that PF11 can exert neuroprotective effects on ischemic stroke by inhibiting the activation of CAPN1 and subsequently enhancing the NR2A-medicated activation of AKT-CREB pathway, which provides a mechanistic link between the neuroprotective effect of PF11 against cerebral ischemia and NR2A-associated pro-survival signaling pathway.

Trehalose protects against cisplatin-induced cochlear hair cell damage by activating TFEB-mediated autophagy

Cisplatin is a widely used chemotherapeutic agent for the treatment of various tumors, but its side effects limit its application. Ototoxicity, a major adverse effect of cisplatin, causes irreversible sensorineural hearing loss. Unfortunately, there are no effective approaches to protect against this damage. Autophagy has been shown to exert beneficial effects in various diseases models. However, the role of autophagy in cisplatin-induced ototoxicity has been not well elucidated. In this study, we aimed to investigate whether the novel autophagy activator trehalose could prevent cisplatin-induced damage in the auditory cell line HEI-OC1 and mouse cochlear explants and to further explore its mechanisms. Our data demonstrated that trehalose alleviated cisplatin-induced hair cell (HC) damage by inhibiting apoptosis, attenuating oxidative stress and rescuing mitochondrial dysfunction. Additionally, trehalose significantly enhanced autophagy levels in HCs, and inhibiting autophagy with 3-methyladenine (3-MA) abolished these protective effects. Mechanistically, we showed that the effect of trehalose was attributed to increased nuclear translocation of transcription factor EB (TFEB), and this effect could be mimicked by TFEB overexpression and inhibited by TFEB gene silencing or treatment with cyclosporin A (CsA), a calcineurin inhibitor. Taken together, our findings suggest that trehalose and autophagy play a role in protecting against cisplatin-induced ototoxicity and that pharmacological enhancement of TFEB-mediated autophagy is a potential treatment for cisplatin-induced damage in cochlear HCs and HEI-OC1 cells.

GSK-3β inhibition elicits a neuroprotection by restoring lysosomal dysfunction in neurons via facilitation of TFEB nuclear translocation after ischemic stroke

Lysosomal dysfunction is an essential pathogenesis of autophagic neuronal injury after ischemic stroke. As a result of cerebral ischemia, transcription factor EB (TFEB) is greatly phosphorylated by prominently activated glycogen synthase kinase-3β (GSK-3β). This increased TFEB phosphorylation decreases its nuclear translocation and subsequently leads to reduced lysosomal biosynthesis, which ultimately results in lysosomal dysfunction. The present study is to investigate whether the lysosomal dysfunction in neurons can be restored to alleviate post-stroke damage by GSK-3β inhibition. The GSK-3β activity was inhibited by pre-treatment with CHIR-99021 (CHIR) for 3 days before middle cerebral artery occlusion (MCAO) surgery in rats. Besides, the lysosomal capacity was altered by pre-administration with Bafilomycin A1 (Baf-A1) and EN6, respectively. Twenty-four hours after MCAO/reperfusion, the penumbral tissues were obtained to detect the GSK-3β, cytoplasmic and nuclear TFEB, and proteins in autophagic/lysosomal pathway by western blot and immunofluorescence, respectively. Meanwhile, the infarct volume, neurological deficits and neuron survival were assessed to evaluate the neurological outcomes elicited by GSK-3β inhibition. The results demonstrated that the neurological injury could be significantly mitigated by GSK-3β inhibition in MCAO+CHIR group, compared with that in MCAO group. Moreover, CHIR-facilitated TFEB nuclear translocation in neurons was coupled with reinforced lysosomal activities and attenuated autophagic substrates. However, GSK-3β inhibition-induced neuroprotection was greatly counteracted by Baf-A1-weakened lysosomal capacity. Conversely, EN6-reinforced lysosomal activities further ameliorated the autophagic/lysosomal signaling, and synergistically alleviated the neurological damage upon GSK-3β inhibition after MCAO/reperfusion. Our data suggests that GSK-3β inhibition-augmented neuroprotection against ischemic stroke is elicited by restoring the lysosomal dysfunction in neurons.

Melibiose Confers a Neuroprotection against Cerebral Ischemia/Reperfusion Injury by Ameliorating Autophagy Flux via Facilitation of TFEB Nuclear Translocation in Neurons

Autophagic/lysosomal dysfunction is a critical pathogenesis of neuronal injury after ischemic stroke. Trehalose has been validated to restore the impaired autophagy flux by boosting transcription factor EB (TFEB) nuclear translocation, but orally administrated trehalose can be greatly digested by intestinal trehalase before entering into brain. Melibiose (MEL), an analogue of trehalose, may thoroughly exert its pharmacological effects through oral administration due to absence of intestinal melibiase. The present study was to investigate whether melibiose could also confer a neuroprotection by the similar pharmacological mechanism as trehalose did after ischemic stroke. The rats were pretreated with melibiose for 7 days before middle cerebral artery occlusion (MCAO) surgery. Twenty-four hours following MCAO/reperfusion, the cytoplasmic and nuclear TFEB, and the proteins in autophagic/lysosomal pathway at the penumbra were detected by western blot and immunofluorescence, respectively. Meanwhile, the neurological deficit, neuron survival, and infarct volume were assessed to evaluate the therapeutic outcomes. The results showed that the neurological injury was significantly mitigated in MCAO+MEL group, compared with that in MCAO group. Meanwhile, nuclear TFEB expression in neurons at the penumbra was significantly promoted by melibiose. Moreover, melibiose treatment markedly enhanced autophagy flux, as reflected by the reinforced lysosomal capacity and reduced autophagic substrates. Furthermore, the melibiose-elicited neuroprotection was prominently counteracted by lysosomal inhibitor Bafilomycin A1 (Baf-A1). Contrarily, reinforcement of lysosomal capacity with EN6 further improved the neurological performance upon melibiose treatment. Our data suggests that melibiose-augmented neuroprotection may be achieved by ameliorating autophagy flux via facilitation of TFEB nuclear translocation in neurons after ischemic stroke.

Pseudoginsenoside F11 Enhances the Viability of Random-Pattern Skin Flaps by Promoting TFEB Nuclear Translocation Through AMPK-mTOR Signal Pathway

Random-pattern skin flap is widely used in tissue reconstruction. However, necrosis occurring in the distal part of the flap limits its clinical application to some extent. Activation of autophagy has been considered as an effective approach to enhance the survival of skin flaps. Pseudoginsenoside F11 (PF11), an ocotillol-type saponin, is an important component of Panax quinquefolium which has been shown to confer protection against cerebral ischemia and alleviate oxidative stress. However, it is currently unknown whether PF11 induces autophagy to improve the survival of skin flaps. In this study, we investigated the effects of PF11 on blood flow and tissue edema. The results of histological examination and western blotting showed that PF11 enhanced angiogenesis, alleviated apoptosis and oxidative stress, thereby improving the survival of the flap. Further experiments showed that PF11 promoted nuclear translocation of TFEB and by regulating the phosphorylation of AMPK. In summary, this study demonstrates that PF11 activates autophagy through the AMPK-TFEB signal pathway in skin flaps and it could be a promising strategy for enhancing flap viability.