Increased phosphorylation of mTOR is involved in remote ischemic preconditioning of hippocampus in mice

Selenium alleviates modafinil-induced neurobehavioral toxicity in rat via PI3K/Akt/mTOR/GSK3B signaling pathway and suppression of oxidative stress and apoptosis: in vivo and in silico study

Nonmedical use of modafinil (MOD) led to increased rates of overdose toxicity, road accidents, addiction, withdrawal, suicide, and mental illnesses. The current study aims to determine the probable MOD brain toxicity and elucidate the possible role of selenium (Se) in ameliorating the neurotoxicity in rat models. Fifty-four male Albino rats were randomly assigned into nine groups. The groups were G1 (control negative), G2 (Se0.1), G3 (Se0.2), G4 (MOD300), G5 (MOD600), G6 (Se0.1 + MOD300), G7 (Se0.2 + MOD300), G8 (Se0.1 + MOD600), and G9 (Se0.2 + MOD600). After finishing the experiment, blood and brain tissue were harvested for biochemical and histological investigation. Neurobehavior parameters were assessed. Tissue neurotransmitter levels and oxidative stress markers were assessed. Gene expression of PI3K/Akt/mTOR-GSK3B, orexin, and orexin receptor2 was measured by qRT-PCR. Histological and immunohistochemistry assessments, as well as molecular docking, were carried out. MOD-induced neurobehavioral toxicity exhibited by behavioral and cognitive function impairments, which are associated with decreased antioxidant activities, increased MDA levels, and decreases in neurotransmitter levels. Brain levels of mRNA expression of PI3K, Akt, and mTOR were decreased, while GS3K, orexin, and orexin receptors were significantly elevated. These disturbances were confirmed by histopathological brain changes with increased silver and Bax immunostaining and decreased crystal violet levels. MOD induced neurotoxic effects in a dose-dependent manner. Compared with the MOD groups, SE coadministration significantly attenuates MOD-induced toxic changes. Docking study shows the protective role of Se as an apoptosis inhibitor and inflammation inhibitor. In conclusion, Se could be used as a biologically effective antioxidant compound to protect from MOD neurobehavioral toxicity in Wistar rats by reversing behavioral alterations, inflammation, apoptosis, and oxidative injury.

Neuroprotection of everolimus against focal cerebral ischemia-reperfusion injury in rats

BACKGROUND

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates cell growth and metabolism and integrates various signals under physiological and pathological conditions. Altered signaling of mTOR has been shown to play pathogenic roles in ischemic stroke. In the present study, the protective effect of everolimus, the selective mTOR inhibitor, in the middle cerebral artery occlusion (MCAO) model of ischemic stroke was evaluated.

METHODS

Wistar rats were exposed to MCAO (30 min) followed by reperfusion for 24 h. Everolimus (100, and 500 µg/kg) was administered at the time of reperfusion, intraperitoneally. 24 h post operation, the neurological function, infarct volume, histopathological alterations and the markers of oxidative stress including superoxide dismutase (SOD) activity, malondialdehyde (MDA), and total thiol levels were analyzed in the peri-infarct region.

RESULTS

In the rats subjected to MCAO, everolimus ameliorated neurological deficits, neuronal cell loss, and infarct volume, as compared to the stroke group. Also, everolimus significantly increased SOD activity and total thiol content, while markedly decreased the MDA level, as compared to MCAO group.

CONCLUSION

Single-dose administration of everolimus significantly improved neurological deficits and inhibited cortical cell loss by enhancing redox status, subsequently protected cerebral ischemia-reperfusion injury in rats.

Electroacupuncture Pretreatment Alleviates Cerebral Ischemia-Reperfusion Injury by Regulating Mitophagy via mTOR-ULK1/FUNDC1 Axis in Rats

OBJECTIVE

Electroacupuncture (EA) pretreatment has been shown to alleviate cerebral ischemia-reperfusion (I/R) injury; however, the underlying mechanism remains unclear. To investigate the involvement of mTOR signaling in the protective role of EA in I/R-induced brain damage and mitochondrial injury.

METHODS

Sprague-Dawley male rats were pretreated with vehicle, EA (at Baihui and Shuigou acupoints), or rapamycin + EA for 30 min daily for 5 consecutive days, followed by the middle cerebral artery occlusion to induce I/R injury. The neurological functions of the rats were assessed using the Longa neurological deficit scores. The rats were sacrificed immediately after neurological function assessment. The brains were obtained for the measurements of cerebral infarct area. The mitochondrial structural alterations were observed under transmission electron microscopy. The mitochondrial membrane potential changes were detected by JC-1 staining. The alterations in autophagy-related protein expression were examined using Western blot analysis.

RESULTS

Compared with untreated I/R rats, EA-pretreated rats exhibited significantly decreased neurological deficit scores and cerebral infarct volumes. EA pretreatment also reversed I/R-induced mitochondrial structural abnormalities and loss of mitochondrial membrane potential. Furthermore, EA pretreatment downregulated the protein expression of LC3-II, p-ULK1, and FUNDC1 while upregulating the protein expression of p-mTORC1 and LC3-I. Rapamycin effectively blocked the above-mentioned effects of EA.

CONCLUSION

EA pretreatment at Baihui and Shuigou alleviates cerebral I/R injury and mitochondrial impairment in rats through activating the mTORC1 signaling. The suppression of autophagy-related p-ULK1/FUNDC1 pathway is involved in the neuroprotective effects of EA.

Therapeutic Potential of Remote Ischemic Conditioning in Vascular Cognitive Impairment

Vascular cognitive impairment (VCI) is a heterogeneous disease caused by a variety of cerebrovascular diseases. Patients with VCI often present with slower cognitive processing speed and poor executive function, which affects their independence in daily life, thus increasing social burden. Remote ischemic conditioning (RIC) is a non-invasive and efficient intervention that triggers endogenous protective mechanisms to generate neuroprotection. Over the past decades, evidence from basic and clinical research has shown that RIC is promising for the treatment of VCI. To further our understanding of RIC and improve the management of VCI, we summarize the evidence on the therapeutic potential of RIC in relation to the risk factors and pathobiologies of VCI, including reducing the risk of recurrent stroke, decreasing high blood pressure, improving cerebral blood flow, restoring white matter integrity, protecting the neurovascular unit, attenuating oxidative stress, and inhibiting the inflammatory response.

Neuroprotective effects and mechanisms of ischemic/hypoxic preconditioning on neurological diseases

As the organ with the highest demand for oxygen, the brain has a poor tolerance to ischemia and hypoxia. Despite severe ischemia/hypoxia induces the occurrence and development of various central nervous system (CNS) diseases, sublethal insult may induce strong protection against subsequent fatal injuries by improving tolerance. Searching for potential measures to improve brain ischemic/hypoxic is of great significance for treatment of ischemia/hypoxia related CNS diseases. Ischemic/hypoxic preconditioning (I/HPC) refers to the approach to give the body a short period of mild ischemic/hypoxic stimulus which can significantly improve the body's tolerance to subsequent more severe ischemia/hypoxia event. It has been extensively studied and been considered as an effective therapeutic strategy in CNS diseases. Its protective mechanisms involved multiple processes, such as activation of hypoxia signaling pathways, anti-inflammation, antioxidant stress, and autophagy induction, etc. As a strategy to induce endogenous neuroprotection, I/HPC has attracted extensive attention and become one of the research frontiers and hotspots in the field of neurotherapy. In this review, we discuss the basic and clinical research progress of I/HPC on CNS diseases, and summarize its mechanisms. Furthermore, we highlight the limitations and challenges of their translation from basic research to clinical application.

Mammalian/mechanistic target of rapamycin (mTOR) complexes in neurodegeneration

Novel targets to arrest neurodegeneration in several dementing conditions involving misfolded protein accumulations may be found in the diverse signaling pathways of the Mammalian/mechanistic target of rapamycin (mTOR). As a nutrient sensor, mTOR has important homeostatic functions to regulate energy metabolism and support neuronal growth and plasticity. However, in Alzheimer's disease (AD), mTOR alternately plays important pathogenic roles by inhibiting both insulin signaling and autophagic removal of β-amyloid (Aβ) and phospho-tau (ptau) aggregates. It also plays a role in the cerebrovascular dysfunction of AD. mTOR is a serine/threonine kinase residing at the core in either of two multiprotein complexes termed mTORC1 and mTORC2. Recent data suggest that their balanced actions also have implications for Parkinson's disease (PD) and Huntington's disease (HD), Frontotemporal dementia (FTD) and Amyotrophic Lateral Sclerosis (ALS). Beyond rapamycin; an mTOR inhibitor, there are rapalogs having greater tolerability and micro delivery modes, that hold promise in arresting these age dependent conditions.

Role of Polyphenols on Gut Microbiota and the Ubiquitin-Proteasome System in Neurodegenerative Diseases

Today, neurodegenerative diseases have become a remarkable public health challenge due to their direct relation with aging. Accordingly, understanding the molecular and cellular mechanisms occurring in the pathogenesis of them is essential. Both protein aggregations as a result of the ubiquitin-proteasome system (UPS) inefficiency and gut microbiota alternation are the main pathogenic hallmarks. Polyphenols upregulating this system may decrease the developing rate of neurodegenerative diseases. Most of the dietary intake of polyphenols is converted into other microbial metabolites, which have completely different biological properties from the original polyphenols and should be thoroughly investigated. Herein, several prevalent neurodegenerative diseases are pinpointed to explain the role of gut microbiota alternations and the role of molecular changes, especially UPS down-regulation in their pathogenesis. Some of the most important polyphenols found in our diet are explained along with their microbial metabolites in the body.

Eriodictyol Attenuates MCAO-Induced Brain Injury and Neurological Deficits via Reversing the Autophagy Dysfunction

The present study was designed to investigate the protective effect of eriodictyol on MCAO-induced brain injury and its regulation of neural function and to explore the mechanism of its regulation of autophagy in rats. Brain injury was induced by middle cerebral artery occlusion (MCAO) in adult rats and pretreated with eriodictyol (low dose: 20 mg/kg; medium dose: 40 mg/kg; high dose: 80 mg/kg) or saline. Rats in the treatment group had a smaller volume of infarction and improved neurological outcome and reduced the latency to the platform, increased the time spent in the correct quadrant compared to MCAO rats pretreated with saline. ELISA kits results confirmed that eriodictyol reduced the inflammatory response induced by MCAO. The results of apoptosis and proliferation by Nissl staining and immunofluorescence detection indicated that eriodictyol could inhibit apoptosis and promote the proliferation in MCAO rats. The expressions of LC3, ATG5, p62, and Beclin1 were used to evaluate the autophagy, as well as the reversal of the autophagy activator (rapamycin) on the neuroprotective effect of eriodictyol, which suggested that the protective effect of eriodictyol on brain injury may be related to the inhibition of autophagy. In summary, we, therefore, suggested that eriodictyol could reduce the inflammation response of brain injury and inhibit neuroapoptosis, directly affecting autophagy to alleviate brain injury. It will provide theoretical support for eriodictyol in the treatment of ischemic stroke.

Hamartin: An Endogenous Neuroprotective Molecule Induced by Hypoxic Preconditioning

Hypoxic/ischemic preconditioning (HPC/IPC) is an innate neuroprotective mechanism in which a number of endogenous molecules are known to be involved. Tuberous sclerosis complex 1 (TSC1), also known as hamartin, is thought to be one such molecule. It is also known that hamartin is involved as a target in the rapamycin (mTOR) signaling pathway, which functions to integrate a variety of environmental triggers in order to exert control over cellular metabolism and homeostasis. Understanding the role of hamartin in ischemic/hypoxic neuroprotection will provide a novel target for the treatment of hypoxic-ischemic disease. Therefore, the proposed molecular mechanisms of this neuroprotective role and its preconditions are reviewed in this paper, with emphases on the mTOR pathway and the relationship between the expression of hamartin and DNA methylation.

Two episodes of remote ischemia preconditioning improve motor and sensory function of hind limbs after spinal cord ischemic injury

Objectives: To investigate the effect of one and two remote ischemia preconditioning episodes (1-RIPC or 2-RIPC, respectively) on neuro-protection after spinal cord ischemic injury (SCI) in rats. Design: Experimental animal study. Setting: College of Medicine, King Khalid University, Abha, KSA. Interventions: Male rats (n = 10/group) were divided into control, sham, SCIRI, 1-RIPC + SCIRI, and 2-RIPC + SCIRI. SCI was induced by aortic ligation for 45 min and each RIPC episode was induced by 3 cycles of 10 min ischemia/10 min perfusion. The two preconditioning procedures were separated by 24 h. Outcome measures: after 48 h of RIPC procedure, Tarlov's test, withdrawal from the painful stimulus and placing/stepping reflex (SPR) were used to evaluate the hind limbs neurological function. SC homogenates were used to measure various biochemical parameters. Results: Motor and sensory function of hind limbs were significantly improved and levels of MDA, AOPPs, PGE2, TNF-α, and IL-6, as well as the activity of SOD, was significantly decreased in SC tissue in either 1 or 2 episodes of RIPC intervention. Concomitantly, levels of total nitrate/nitrite and eNOS activity were significantly increased in both groups. Interestingly, except for activity of SOD, eNOS and levels of nitrate/nitrite, the improvements in all neurological biochemical endpoint were more profound in 2-RIPC + SCIRI compared with 1-RIPC + SCIRI. Conclusion: applying two preconditioning episodes of 3 cycles of 10 min ischemia/10 min perfusion, separated by 24 h, boost the neuro-protection effect of RIPC maneuver in rats after ischemic induced SCI in rats.

Translation Regulation by eIF2α Phosphorylation and mTORC1 Signaling Pathways in Non-Communicable Diseases (NCDs)

Non-communicable diseases (NCDs) are medical conditions that, by definition, are non-infectious and non-transmissible among people. Much of current NCDs are generally due to genetic, behavioral, and metabolic risk factors that often include excessive alcohol consumption, smoking, obesity, and untreated elevated blood pressure, and share many common signal transduction pathways. Alterations in cell and physiological signaling and transcriptional control pathways have been well studied in several human NCDs, but these same pathways also regulate expression and function of the protein synthetic machinery and mRNA translation which have been less well investigated. Alterations in expression of specific translation factors, and disruption of canonical mRNA translational regulation, both contribute to the pathology of many NCDs. The two most common pathological alterations that contribute to NCDs discussed in this review will be the regulation of eukaryotic initiation factor 2 (eIF2) by the integrated stress response (ISR) and the mammalian target of rapamycin complex 1 (mTORC1) pathways. Both pathways integrally connect mRNA translation activity to external and internal physiological stimuli. Here, we review the role of ISR control of eIF2 activity and mTORC1 control of cap-mediated mRNA translation in some common NCDs, including Alzheimer’s disease, Parkinson’s disease, stroke, diabetes mellitus, liver cirrhosis, chronic obstructive pulmonary disease (COPD), and cardiac diseases. Our goal is to provide insights that further the understanding as to the important role of translational regulation in the pathogenesis of these diseases.

Carvacrol reduces hippocampal cell death and improves learning and memory deficits following lead-induced neurotoxicity via antioxidant activity

Carvacrol is a monoterpene with neuroprotective effects in several animal models of neurodegeneration, including epilepsy, ischemia, and traumatic neuronal events. In this study, we aimed to examine the effects of carvacrol on neurodegeneration induced by lead acetate in rats. A total of 50 male Wistar rats were divided into five equal groups. The control group received drinking water, while the neurotoxic group was exposed to 500 ppm of lead acetate in drinking water for 40 days. The three remaining groups, which were also exposed to 500 ppm of lead acetate, received carvacrol at doses of 25, 50, and 100 mg/kg orally for 40 days. The Morris water maze test was employed to examine spatial learning and memory. Pathological damage to the hippocampus was determined by Nissl staining. The level of malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were detected using biochemical analysis and the free radical scavenging activity as evaluated by the DPPH test. Administration of carvacrol significantly restored learning and memory impairment induced by lead acetate. Moreover, carvacrol ameliorated neurodegeneration, antioxidative capacity, and lipid peroxidation in the hippocampus of rats exposed to lead. The present results provide a rationale for the inhibitory role of carvacrol in the attenuation of lead-induced neurotoxicity.

Aluminum-Induced Cognitive Impairment and PI3K/Akt/mTOR Signaling Pathway Involvement in Occupational Aluminum Workers

Epidemiological studies indicate that long-term occupational exposure to aluminum (Al) causes neurotoxicity and cognitive impairment. While the molecular underpinnings associated with workers' cognitive impairment is unclear, one mechanism may involve Al-induced PI3K/Akt/mTOR activation and neuronal cell death, which impairs learning and memory in rats. Here, we sought to determine whether PI3K/Akt/mTOR is also associated with cognitive impairment in Al-exposed occupational workers. Cognitive function was screened by Mini-Mental State Examination (MMSE) and Clock-Drawing Test (CDT), and serum Al and PI3K/Akt/mTOR-associated gene expression was quantified. A negative correlation between serum Al and scores of MMSE and CDT was found, which might relate with downregulation of PI3K/Akt/mTOR. To determine the role of the PI3K/Akt/mTOR pathway cognitive function, we treated zebrafish with Al and observed a profound impairment in learning and memory. Increased brain Al levels was associated with decreased expression of PI3K/Akt/mTOR in Al-exposed zebrafish. Finally, rapamycin, an mTOR inhibitor, was added to isolate the role of mTOR specifically in the Al exposed zebrafish. The results suggested that Al induces learning and memory deficits by downregulating PI3K, Akt, and mTOR1 expression and inducing neuronal cell death like rapamycin group. This study indicates that aluminum exposure can cause cognitive impairment through PI3K/Akt/mTOR pathway, with mTOR activity being a critical player involved in this mechanism. Future studies are necessary to further characterize the role of PI3K/Akt/mTOR1 signaling in Al-induced neurocognitive decline among Al occupational workers. These findings draw attention to Al risk exposure among occupational workers and the need to implement novel safety and protective measures to mitigate neurocognitive health risks in the Al industrial workspace.

Remote ischemic conditioning: a promising therapeutic intervention for multi-organ protection

Despite decades of formidable exploration, multi-organ ischemia-reperfusion injury (IRI) encountered, particularly amongst elderly patients with clinical scenarios, such as age-related arteriosclerotic vascular disease, heart surgery and organ transplantation, is still an unsettled conundrum that besets clinicians. Remote ischemic conditioning (RIC), delivered via transient, repetitive noninvasive IR interventions to distant organs or tissues, is regarded as an innovative approach against IRI. Based on the available evidence, RIC holds the potential of affording protection to multiple organs or tissues, which include not only the heart and brain, but also others that are likely susceptible to IRI, such as the kidney, lung, liver and skin. Neuronal and humoral signaling pathways appear to play requisite roles in the mechanisms of RIC-related beneficial effects, and these pathways also display inseparable interactions with each other. So far, several hurdles lying ahead of clinical translation that remain to be settled, such as establishment of biomarkers, modification of RIC regimen, and deep understanding of underlying minutiae through which RIC exerts its powerful function. As this approach has garnered an increasing interest, herein, we aim to encapsulate an overview of the basic concept and postulated protective mechanisms of RIC, highlight the main findings from proof-of-concept clinical studies in various clinical scenarios, and also to discuss potential obstacles that remain to be conquered. More well designed and comprehensive experimental work or clinical trials are warranted in future research to confirm whether RIC could be utilized as a non-invasive, inexpensive and efficient adjunct therapeutic intervention method for multi-organ protection.

Activation of mitochondrial KATP channels mediates neuroprotection induced by chronic morphine preconditioning in hippocampal CA-1 neurons following cerebral ischemia

PURPOSE

Pharmacologic preconditioning, through activating several mechanisms and mediators, can increase the tolerance of different tissues against ischemia/reperfusion (I/R) injury. Recent studies have shown that morphine preconditioning has protective effects in different organs, especially in the heart. Nevertheless, its mechanisms are not well elucidated in the brain. The present study aimed to clarify whether the activation of mitochondrial KATP (mKATP) channels in chronic morphine (CM) preconditioning could decrease hippocampus damage following I/R injury.

MATERIALS AND METHODS

CM preconditioning was performed by the administration of additive doses of morphine for 5days before I/R injury induction. I/R injury was induced by the occlusion of bilateral common carotid arteries. The possible role of mKATP channels was evaluated by the injection of 5-hydroxydecanoate (5-HD) before I/R injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was performed to detect apoptosis in hippocampal neurons. The expressions of B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (BAX) and levels of malondialdehyde (MDA) and catalase (CAT) enzymes were assessed.

RESULTS

CM attenuated apoptosis in the hippocampal CA1 neurons (P<0.001 vs I/R), and mKATP channel blocking with 5-HD significantly increased apoptosis (P<0.001 vs CM+I/R). CM increased CAT activity (P<0.05 vs I/R) and Bcl-2 protein expression (P<0.01 vs I/R), while it decreased MDA level (P<0.05 vs I/R) and BAX protein expression (P<0.05 vs I/R). Pretreatment with 5-HD abolished all the above-mentioned effects of CM.

CONCLUSIONS

These findings describe novel evidence whereby CM preconditioning in hippocampal CA1 neurons can improve oxidative stress and apoptosis through the activation of mKATP channels and eventually protect the hippocampal tissue against I/R injury.

The mechanistic target of rapamycin (mTOR) and the silent mating-type information regulation 2 homolog 1 (SIRT1): oversight for neurodegenerative disorders

As a result of the advancing age of the global population and the progressive increase in lifespan, neurodegenerative disorders continue to increase in incidence throughout the world. New strategies for neurodegenerative disorders involve the novel pathways of the mechanistic target of rapamycin (mTOR) and the silent mating-type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) that can modulate pathways of apoptosis and autophagy. The pathways of mTOR and SIRT1 are closely integrated. mTOR forms the complexes mTOR Complex 1 and mTOR Complex 2 and can impact multiple neurodegenerative disorders that include Alzheimer's disease, Huntington's disease, and Parkinson's disease. SIRT1 can control stem cell proliferation, block neuronal injury through limiting programmed cell death, drive vascular cell survival, and control clinical disorders that include dementia and retinopathy. It is important to recognize that oversight of programmed cell death by mTOR and SIRT1 requires a fine degree of precision to prevent the progression of neurodegenerative disorders. Additional investigations and insights into these pathways should offer effective and safe treatments for neurodegenerative disorders.

Rapamycin prevents cerebral stroke by modulating apoptosis and autophagy in penumbra in rats

Objective

Whether activation or inhibition of the mTOR pathway is beneficial to ischemic injury remains controversial. It may result from the different reaction of ischemic penumbra and core to modulation of mTOR pathway after cerebral ischemia-reperfusion injury in rats.

Methods

Longa's middle cerebral artery occlusion (MCAO) method was conducted to induce the focal cerebral ischemia-reperfusion. Western blot analysis was used to examine the protein expression involving mTOR pathway, apoptosis, and autophagy-related proteins. TTC staining and Fluoro-Jade B staining was conducted to detect the infarct volume and cell apoptosis, respectively. Neurological function was measured by modified neurological severity score and left-biased swing.

Results

mTOR signaling pathway was activated in ischemic penumbra and decreased in ischemic core after ischemia and ischemia-reperfusion. Ischemia-reperfusion injury induced the increase in cleaved caspase 9 and caspase 3 both in ischemic penumbra and in ischemic core, whereas the expression of phosphorylated ULK1, Beclin 1 and LC3-II was decreased. Rapamycin pre or postadministration inhibited the overactivation of mTOR pathway in ischemic penumbra. Ameliorated neurological function and reduced infarct volume were observed after pre or postrapamycin treatment. Rapamycin markedly decreased the number of FJB-positive cells and the expression of cleaved caspase-3 and cleaved caspase-9 proteins as well as increased the activation of autophagy reflected by ULK1, Beclin-1 and LC3.

Interpretation

mTOR signaling pathway was activated in ischemic penumbra after cerebral ischemia-reperfusion injury in rats. mTOR inhibitor rapamycin significantly decreased the mTOR activation and infarct volume and subsequently improved neurological function. These results may relate to inhibition of neuron apoptosis and activation of autophagy.

Preconditioning with morphine protects hippocampal CA1 neurons from ischemia-reperfusion injury via activation of the mTOR pathway

The signaling pathway of chronic morphine treatment to prevent neuronal damage following transient cerebral ischemia is not clear. In this study, we examined the role of mammalian target of rapamycin (mTOR) to identify the neuroprotective effects of chronic morphine preconditioning on the hippocampus following ischemia-reperfusion (I/R) injury. Morphine was administered for 5 days, twice a day, before inducing I/R injury. The possible role of mTOR was evaluated by the injection of rapamycin (5 mg/kg body weight, by intraperitoneal injection) before I/R was induced. The passive avoidance test was used to evaluate memory performance. Neuronal density and apoptosis were measured in the CA1 region, 72 h after I/R injury. The expressions of mTOR and phosphorylated mTOR (p-mTOR), as well as superoxide dismutase (SOD) activity were determined 24 h after I/R injury. Chronic morphine treatment attenuated apoptosis and neuronal loss in the hippocampus after I/R injury, which led to improvement in memory (P < 0.05 vs. untreated I/R) and increase in the expression of p-mTOR (P < 0.05 vs. untreated I/R) and SOD activity (P < 0.05 vs. untreated I/R) in the hippocampus. Pretreatment with rapamycin abolished all the above-mentioned protective effects. These results describe novel findings whereby chronic morphine preconditioning in hippocampal CA1 neurons is mediated by the mTOR pathway, and through increased phosphorylation of mTOR can alleviate oxidative stress and apoptosis, and eventually protect the hippocampus from I/R injury.

Temporal changes in mammalian target of rapamycin (mTOR) and phosphorylated-mTOR expressions in the hippocampal CA1 region of rat with vascular dementia

Mammalian target of rapamycin (mTOR) has an important role in various biological processes in cells. In the present study, we investigated temporal changes in mTOR and phosphorylated-mTOR (p-mTOR) expressions in the rat hippocampal CA1 region following chronic cerebral hypoperfusion (CCH) induced by permanent bilateral common carotid arteries occlusion (2VO). The mTOR immunoreactivity in the pyramidal neurons and mTOR protein level in the hippocampal CA1 region were markedly decreased at 21 and 28 days after 2VO surgery. However, p-mTOR protein expression was significantly increased at 7 days following CCH but then decreased with time. The results indicate that mTOR and p-mTOR expressions change in the hippocampal CA1 region after 2VO surgery and that reduced expressions of mTOR and p-mTOR may be closely related to the CCH-induced neuronal damage in the hippocampal CA1 region.

The Molecular Mechanism of Glucagon-Like Peptide-1 Therapy in Alzheimer's Disease, Based on a Mechanistic Target of Rapamycin Pathway

The mechanistic target of rapamycin (mTOR) is an important molecule that connects aging, lifespan, energy balance, glucose and lipid metabolism, and neurodegeneration. Rapamycin exerts effects in numerous biological activities via its target protein, playing a key role in energy balance, regulation of autophagy, extension of lifespan, immunosuppression, and protection against neurodegeneration. There are many similar pathophysiological processes and molecular pathways between Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM), and pharmacologic agents used to treat T2DM, including glucagon-like peptide-1 (GLP-1) analogs, seem to be beneficial for AD. mTOR mediates the effects of GLP-1 analogs in the treatment of T2DM; hence, I hypothesize that mTOR is a key molecule for mediating the protective effects of GLP-1 for AD.

Berberine confers neuroprotection in coping with focal cerebral ischemia by targeting inflammatory cytokines

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Berberine reduces brain edema and infarct volume through regulation of inflammatory responses in focal cerebral ischemia.

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Berberine increases the expression of anti-inflammatory cytokines after ischemic stroke.

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Berberine contributes to recovery of motor function after focal cerebral ischemia.

Scope

Existing research indicates that anti-inflammatory and antioxidant properties of berberine play major roles in coping with oxidative stress in neurodegenerative diseases, but it is not known if this isoquinoline alkaloid affects inflammatory cytokines such as interleukin 10 in focal cerebral ischemia.

Methods and results

Male Wistar rats (10 weeks old) were treated with 40 mg/kg concentration of berberine 1 h after focal cerebral ischemia and the anti-inflammatory properties of berberine were evaluated by immunohistochemical analysis, water content measure and behavioral tests. Evaluation of infarct volume was performed by TTC staining. Immunohistochemistry and behavioral assessment indicated recovery in treatment group compared to only ischemia group. The infarct volume decreased in treatment group compared to ischemia group. Berberine administration significantly decreased brain edema and contributed to the restoration of motor function. Moreover, berberine potently contributed to neuroprotection in motor area through downregulation of pro-inflammatory cytokines and upregulation of anti-inflammatory cytokines.

Conclusions

These findings confirm the validity of berberine as a potent anti-inflammatory agent in treatment of ischemic stroke.

The role of erythropoietin in remote renal preconditioning on hippocampus ischemia/reperfusion injury

Remote ischemic preconditioning (RIPC) is an intriguing approach which exposes a remote organ/tissue to a non-lethal transient ischemia/reperfusion (I/R) in order to potentiate the resistance of the desired organ/tissue against the next unwanted I/R. It has been suggested that RIPC exerts its effect through neuronal and hormonal pathways. The underlying mechanisms of RIPC are obscure and should be elucidated. In this study, we induced RIPC in mice using 3 cycles of 5 min ischemia alternating with 5 min reperfusion of the left renal artery. Renal failure was induced in mice by intra-peritoneal (i.p.) injection of 200 mg/kg body weight of gentamicin twice per day for 4 consecutive days. Global hippocampal ischemia reperfusion (I/R) was performed by bilateral carotid artery occlusion for 20 min followed by reperfusion for 72 h. Moreover, the retention trial of passive avoidance test was determined 72 h after global ischemia. Histopathological changes of hippocampus neurons were observed using Nissl staining to detect neuronal loss. Finally, terminal deoxynucleotidyl transferase mediated dUTP nick end-labeling (TUNEL) was performed to assess the status of apoptotic cells in the hippocampus. The results of this study suggest that renal ischemic preconditioning is a good candidate for prevention of I/R-induced hippocampal injury. However, RRPC (remote renal preconditioning) failed to exert a neuroprotective effect in mice with renal failure (RF), indicating the probable role of a humoral factor which is released from kidneys in response to ischemia. In agreement with this hypothesis, treatment of mice with rhEPO (5000 IU/kg intraperitoneal) before induction of RRPC restored the neuroprotective effects of RRPC in RF mice. Accordingly, it is plausible to expect that erythropoietin is released from kidneys to act as a mediator for RRPC-induced neuroprotective effects. Renal ischemic preconditioning prevents I/R-induced hippocampal injury. In contrast, renal failure hampers protective effects of RRPC, while exogenous administration of erythropoietin (EPO) significantly prevents the inhibiting effects of renal failure.

Therapeutic role of sirtuins in neurodegenerative disease and their modulation by polyphenols

Searching for effective therapeutic agents‏‎ to ‎‏prevent‏ ‏neurodegeneration ‎is a challenging task due ‎to ‎the growing list of neurodegenerative disorders associated with a multitude of inter-related pathways.‎ The induction and inhibition of several different signaling pathways has been shown to slow down and/or attenuate ‎neurodegeneration and decline in cognition and locomotor function. Among these signaling pathways, a new class of enzymes known as sirtuins or silent information regulators of gene transcription has been shown to play important regulatory roles in the ageing process. SIRT1, a nuclear sirtuin, has received ‎particular interest due to its role as a deacetylase for several metabolic and signaling proteins involved in stress response, apoptosis, mitochondrial function, self-renewal, and ‎neuroprotection. ‎A new strategy to treat ‎neurodegenerative diseases is targeted therapy. In ‎this ‎paper, we‎ ‎ reviewed up-to-date findings regarding the targeting of ‎SIRT1 by polyphenolic ‎compounds,‎ ‎as a ‎new ‎‏approach in the search for novel, safe and effective treatments for ‎ ‎neurodegenerative ‎diseases. ‎.

Targeting mTOR signaling by polyphenols: A new therapeutic target for ageing

Current ageing research is aimed not only at the promotion of longevity, but also at improving ‎health span‎ through the‎ discovery and development‎ of new therapeutic strategies‎‏‎ by investigating ‎molecular and ‎cellular ‎pathways involved in cellular senescence.‎ Understanding the mechanism of action ‎of ‎polyphenolic compounds targeting mTOR (mechanistic target of rapamycin) and related pathways opens up new directions ‎‎to revolutionize ways to slow down the ‎onset and development of age-dependent degeneration. Herein, we will ‎discuss the mechanisms by which polyphenols can delay the‎ molecular ‎pathogenesis of ageing via manipulation or more specifically inhibition of mTOR-signaling pathways. We will also discuss the implications of polyphenols in targeting mTOR and its related ‎pathways‎‎ on ‎health life span extension and longevity.‎.

Rodent Gymnastics: Neurobehavioral Assays in Ischemic Stroke

Despite years of research, most preclinical trials on ischemic stroke have remained unsuccessful owing to poor methodological and statistical standards leading to "translational roadblocks." Various behavioral tests have been established to evaluate traits such as sensorimotor function, cognitive and social interactions, and anxiety-like and depression-like behavior. A test's validity is of cardinal importance as it influences the chance of a successful translation of preclinical results to clinical settings. The mission of choosing a behavioral test for a particular project is, therefore, imperative and the present review aims to provide a structured way to evaluate rodent behavioral tests with implications in ischemic stroke.

Metformin pretreatment enhanced learning and memory in cerebral forebrain ischaemia: the role of the AMPK/BDNF/P70SK signalling pathway

Context Metformin induced AMP-activated protein kinase (AMPK) and protected neurons in cerebral ischaemia. Objective This study examined pretreatment with metformin and activation of AMPK in molecular and behavioral levels associated with memory. Materials and methods Rats were pretreated with metformin (200 mg/kg) for 2 weeks and 4-vessels occlusion global cerebral ischaemia was induced. Three days after ischaemia, memory improvement was done by passive avoidance task and neurological scores were evaluated. The amount of Brain-Derived Neurotropic Factor (BDNF) and phosphorylated and total P70S6 kinase (P70S6K) were measured. Results Pretreatment with metformin (met) in the met + ischaemia/reperfusion (I/R) group reduced latency time for enter to dark chamber compared with the sham group (p < 0.001) and increased latency time compared with the I/R group (p < 0.001). Injection of Compound C (CC) (as an AMPK inhibitor) concomitant with metformin reduced latency time in I/R rats compared with the I/R + met group (p < 0.05). Neurological scores were reduced in met treated rats compared with the sham group. Pretreatment with metformin in I/R animals reduced levels of pro-BDNF compared with the I/R group (p < 0.001) but increased that compared with the sham group (p < 0.001). The level of pro-BDNF decreased in the met + CC + I/R group compared with the met + I/R group (p < 0.01). Pretreatment with metformin in I/R animals significantly increased P70S6K compared with the I/R group (p < 0.001). Conclusion Short-term memory in ischaemic rats treated with metformin increased step-through latency; sensory-motor evaluation was applied and a group of ischaemia rats that were pretreated with metformin showed high levels of BDNF, P70S6K that seemed to be due to increasing AMPK.

Conjugated linoleic acid rat pretreatment reduces renal damage in ischemia/reperfusion injury: Unraveling antiapoptotic mechanisms and regulation of phosphorylated mammalian target of rapamycin

SCOPE

Conjugated linoleic acids (CLAs) are dietary components with beneficial effects on human health. The aim of this study was to evaluate the potential benefits of CLA pretreatment in a rat model of renal ischemia/reperfusion injury (IRI).

METHODS AND RESULTS

Animals were treated with CLAs (200 mg/kg/day) or water for two weeks prior to sham surgery or to surgery to induce IRI. Renal function, oxidative stress, apoptosis, and cell proliferation markers, were evaluated. Moreover, kidney sections were submitted to histological evaluation. IRI induced increased serum creatinine, blood urea nitrogen, fractional sodium excretion, malondialdehyde, Bax, and phosphorylated mammalian target of rapamycin (P-mTOR), and decreased clearance of creatine, superoxide dismutase and catalase activities, and Bax in comparison with control groups. CLA prefeeding restored, at least in part, the above reported markers to normal levels, increased the anti-apoptotic protein, B-cell lymphoma 2 (Bcl-2), and reduce the histological damage.

CONCLUSION

The results suggest that the decreased renal tissue damage and improved renal function and oxidative stress, in rats pretreated with CLAs before renal IRI induction, could be associated with downregulation of Bax and P-mTOR, and upregulation of Bcl-2. CLAs pretreatment resulted to protect against IRI through the regulation of signaling pathways involved in apoptosis.

Inhibition of AMP-activated protein kinase alleviates focal cerebral ischemia injury in mice: Interference with mTOR and autophagy

Ischemic stroke is one of the most frequent acute cerebrovascular events worldwide. This study evaluated the variability of AMPK and mTOR and their relevance on LC3 and Beclin-1 expression, and further expounded the possible protective mechanism of inhibiting AMPK activity in the cerebral cortex after permanent focal cerebral ischemia injury in mice. Western blot and immunohistochemistry showed that p-AMPK expression was low in the cerebral cortex of the sham group; whereas it was significantly increased at 3h and 6h and peaked at 3h after pMCAO in the cerebral ischemic cortex, and was decreased at 12h and 24h. The expression patterns of LC3 and Beclin-1 were the same as that of p-AMPK after occlusion, and the variability pattern between p-AMPK and p-mTOR levels was completely inverted. After treatment with the AMPK inhibitor Compound C, p-AMPK/LC3/Beclin-1 expression was decreased significantly, whereas p-mTOR level was increased significantly. Deficiency of Nissl bodies was reduced compared with that in the vehicle group at all times points after occlusion. Neurological deficits, infarct areas, and brain water content were also significantly reduced 24h after occlusion with compound C treatment. The results suggested that the AMPK-autophagy pathway was activated, concomitant with mTOR inhibition in cerebral cortex after ischemic injury in mice. Moreover, inhibition of AMPK activity by Compound C inhibited autophagy and conferred protection against brain damage by restoring mTOR activity.

Targeting Adenosine Monophosphate-Activated Protein Kinase by Metformin Adjusts Post-Ischemic Hyperemia and Extracellular Neuronal Discharge in Transient Global Cerebral Ischemia

OBJECTIVE

I/R and its subsequent reactive hyperemia results in different adverse effects such as brain edema and BBB disruption. AMPK activation has been perceived as one of the target factors for I/R treatment. We investigated the effect of Met (an AMPK activator) on some physiological parameters including vascular responses, hyperemia, BBB disruption, and electrophysiological activity following tGCI.

METHODS

Rats were pretreated with Met for two weeks and CC was administered half an hour before tGCI. Brain vascular responses, hyperemia, BBB disruption, and electrophysiological activity were evaluated following the ischemia.

RESULTS

Met attenuated BBB disruption and reactive hyperemia in tGCI rats compared with the untreated I/R rats (p < 0.001). Met administration along with CC in the ischemic rats reversed the beneficial effects of Met on BBB disruption and reactive hyperemia (p < 0.001). Electrophysiological records indicated that Met increased spike rates in the ischemic rats comparing with I/R rats (p < 0.001), whereas, CC administration blocked the beneficial effects of Met on the neuronal discharges (p < 0.05).

CONCLUSION

We established a regulatory role for AMPK in vascular and electrophysiological responses to tGCI. Studies are ongoing to determine if activation of AMPK in the reperfusion period would offer similar protection.

Effects of rapamycin pretreatment on blood-brain barrier disruption in cerebral ischemia-reperfusion

The mammalian target of rapamycin (mTOR) pathway is essential in neuronal survival and repair in cerebral ischemia. Decreases in blood-brain barrier (BBB) disruption are associated with a decrease in neuronal damage in cerebral ischemia. This study was performed to investigate how pre-inhibition of the mTOR pathway with rapamycin would affect BBB disruption and the size of the infarcted cortical area in the early stage of focal cerebral ischemia-reperfusion using quantitative analysis of BBB disruption. Rats were treated with 20mg/kg of rapamycin i.p. once a day for 2days (Rapamycin Group) or vehicle (Control Group) before transient middle cerebral artery (MCA) occlusion. After one hour of MCA occlusion and two hours of reperfusion, the transfer coefficient (Ki) of (14)C-α-aminoisobutyric acid ((14)C-AIB) to measure the degree of BBB disruption and the size of the cortical infarct were determined. Ischemia-reperfusion increased the Ki in the Rapamycin treated (+15%) as well as in the untreated control group (+13%). However, rapamycin pretreatment moderately decreased Ki in the contralateral (-30%) as well as in the ischemic-reperfused (-29%) cortex when compared with the untreated control group. Rapamycin pretreatment substantially increased the percentage of cortical infarct compared with the control group (+56%). Our data suggest that activation of mTOR pathway is necessary for neuronal survival in the early stage of cerebral ischemia-perfusion and that the reason for the enlarged cortical infarct by rapamycin pretreatment may be related to its non-BBB effects on the mTOR pathway.

Targeting molecules to medicine with mTOR, autophagy and neurodegenerative disorders

Neurodegenerative disorders are significantly increasing in incidence as the age of the global population continues to climb with improved life expectancy. At present, more than 30 million individuals throughout the world are impacted by acute and chronic neurodegenerative disorders with limited treatment strategies. The mechanistic target of rapamycin (mTOR), also known as the mammalian target of rapamycin, is a 289 kDa serine/threonine protein kinase that offers exciting possibilities for novel treatment strategies for a host of neurodegenerative diseases that include Alzheimer's disease, Parkinson's disease, Huntington's disease, epilepsy, stroke and trauma. mTOR governs the programmed cell death pathways of apoptosis and autophagy that can determine neuronal stem cell development, precursor cell differentiation, cell senescence, cell survival and ultimate cell fate. Coupled to the cellular biology of mTOR are a number of considerations for the development of novel treatments involving the fine control of mTOR signalling, tumourigenesis, complexity of the apoptosis and autophagy relationship, functional outcome in the nervous system, and the intimately linked pathways of growth factors, phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), AMP activated protein kinase (AMPK), silent mating type information regulation two homologue one (Saccharomyces cerevisiae) (SIRT1) and others. Effective clinical translation of the cellular signalling mechanisms of mTOR offers provocative avenues for new drug development in the nervous system tempered only by the need to elucidate further the intricacies of the mTOR pathway.

Inhibition of mTOR Pathway by Rapamycin Reduces Brain Damage in Rats Subjected to Transient Forebrain Ischemia

The aims of this study are to clarify the role of mTOR in mediating cerebral ischemic brain damage and the effects of rapamycin on ischemic outcomes. Ten minutes of forebrain ischemia was induced in rats, and their brains were sampled after 3 h, 16 h, and 7 days reperfusion for histology, immunohistochemistry and biochemical analysis. Our data demonstrated that cerebral ischemia resulted in both apoptotic and necrotic neuronal death; cerebral ischemia and reperfusion led to significant increases of mRNA and protein levels of p-mTOR and its downstream p-P70S6K and p-S6; elevation of LC3-II, and release of cytochrome c into the cytoplasm in both the cortex and hippocampus. Inhibition of mTOR by rapamycin markedly reduced ischemia-induced damage; suppressed p-Akt, p-mTOR, p-P70S6K and p-S6 protein levels; decreased LC3-II and Beclin-1; and prevented cytochrome c release in the two structures. All together, these data provide evidence that cerebral ischemia activates mTOR and autophagy pathways. Inhibition of mTOR deactivates the mTOR pathway, suppresses autophagy, prevents cytochrome c release and reduces ischemic brain damage.

Ischemic Conditioning Is Safe and Effective for Octo- and Nonagenarians in Stroke Prevention and Treatment

Symptomatic intracranial arterial stenosis (SIAS) is very common in octo- and nonagenarians, especially in the Chinese population, and is likely the most common cause of stroke recurrence worldwide. Clinical trials demonstrate that endovascular treatment, such as stenting, may not be suitable for octogenarians with systemic diseases. Hence, less invasive methods for the octogenarian patients are urgently needed. Our previous study (unique identifier: NCT01321749) showed that repetitive bilateral arm ischemic preconditioning (BAIPC) reduced the incidence of stroke recurrence by improving cerebral perfusion (confirmed by single photon emission computed tomography and transcranial Doppler sonography) in patients younger than 80 years of age; however, the safety and effectiveness of BAIPC on stroke prevention in octo- and nonagenarians with SIAS are still unclear. The objective of this study was to evaluate the safety and effectiveness of BAIPC in reducing stroke recurrence in octo- and nonagenarian patients with SIAS. Fifty-eight patients with SIAS were enrolled in this randomized controlled prospective study for 180 consecutive days. All patients enrolled in the study received standard medical management. Patients in the BAIPC group (n = 30) underwent 5 cycles consisting of bilateral arm ischemia followed by reperfusion for 5 min each twice daily. Those in the control group (n = 28) underwent sham-BAIPC twice daily. Blood pressure, heart rate, local skin status, plasma myoglobin, and plasma levels of thrombotic and inflammatory markers were documented in both groups before beginning the study and for the first 30 days. Finally, the incidences of stroke recurrence and magnetic resonance imaging during the 180 days of treatment were compared. Compared with the control, BAIPC had no adverse effects on blood pressure, heart rate, local skin integrity, or plasma myoglobin, and did not induce cerebral hemorrhage in the studied cohort. BAIPC reduced plasma high sensitive C-reactive protein, interleukin-6, plasminogen activator inhibitor-1, leukocyte count, and platelet aggregation rate and elevated plasma tissue plasminogen activator (all p < 0.01). In 180 days, 2 infarctions and 7 transient ischemic attacks were observed in the BAIPC group compared with 8 infarctions and 11 transient ischemic attacks in the sham BAIPC group (p < 0.05). BAIPC may safely inhibit stroke recurrence, protect against brain ischemia, and ameliorate plasma biomarkers of inflammation and coagulation in octo- and nonagenarians with SIAS. A multicenter trial is ongoing.

CLINICAL TRIAL REGISTRATION

www.clinicaltrials.gov, unique identifier: NCT01570231.

A critical review of mechanisms regulating remote preconditioning-induced brain protection

Remote preconditioning (rPC) is the phenomenon whereby brief organ ischemia evokes an endogenous response such that a different (remote) organ is protected against subsequent, normally injurious ischemia. Experiments show rPC to be effective at evoking cardioprotection against ischemic heart injury and, more recently, neuroprotection against brain ischemia. Such is the enthusiasm for rPC that human studies have been initiated. Clinical trials suggest rPC to be safe (phase II trial) and effective in reducing stroke incidence in a population with high stroke risk. However, despite the therapeutic potential of rPC, there is a large gap in knowledge regarding the effector mechanisms of rPC and how it might be orchestrated to improve outcome after stroke. Here we provide a critical review of mechanisms that are directly attributable to rPC-induced neuroprotection in preclinical trials of rPC.

Cutting through the complexities of mTOR for the treatment of stroke

On a global basis, at least 15 million individuals suffer some form of a stroke every year. Of these individuals, approximately 800,000 of these cerebrovascular events occur in the United States (US) alone. The incidence of stroke in the US has declined from the third leading cause of death to the fourth, a result that can be attributed to multiple factors that include improved vascular disease management, reduced tobacco use, and more rapid time to treatment in patients that are clinically appropriate to receive recombinant tissue plasminogen activator. However, treatment strategies for the majority of stroke patients are extremely limited and represent a critical void for care. A number of new therapeutic considerations for stroke are under consideration, but it is the mammalian target of rapamycin (mTOR) that is receiving intense focus as a potential new target for cerebrovascular disease. As part of the phosphoinositide 3-kinase (PI 3-K) and protein kinase B (Akt) cascade, mTOR is an essential component of mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) to govern cell death involving apoptosis, autophagy, and necroptosis, cellular metabolism, and gene transcription. Vital for the consideration of new therapeutic strategies for stroke is the ability to understand how the intricate and complex pathways of mTOR signaling sometimes lead to disparate clinical outcomes.

Taking aim at Alzheimer's disease through the mammalian target of rapamycin

A significant portion of the world's population suffers from sporadic Alzheimer's disease (AD) with available present therapies limited to symptomatic care that does not alter disease progression. Over the next decade, advancing age of the global population will dramatically increase the incidence of AD and severely impact health care resources, necessitating novel, safe, and efficacious strategies for AD. The mammalian target of rapamycin (mTOR) and its protein complexes mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) offer exciting and unique avenues of intervention for AD through the oversight of programmed cell death pathways of apoptosis, autophagy, and necroptosis. mTOR modulates multi-faceted signal transduction pathways that involve phosphoinositide 3-kinase (PI 3-K), protein kinase B (Akt), hamartin (tuberous sclerosis 1)/ tuberin (tuberous sclerosis 2) (TSC1/TSC2) complex, proline-rich Akt substrate 40 kDa (PRAS40), and p70 ribosomal S6 kinase (p70S6K) and can interface with the neuroprotective pathways of growth factors, sirtuins, wingless, forkhead transcription factors, and glycogen synthase kinase-3β. With the ability of mTOR to broadly impact cellular function, clinical strategies for AD that implement mTOR must achieve parallel objectives of protecting neuronal, vascular, and immune cell survival in conjunction with preserving networks that determine memory and cognitive function.

Acute, delayed and chronic remote ischemic conditioning is associated with downregulation of mTOR and enhanced autophagy signaling

Background

Remote ischemic conditioning (RIC), induced by brief periods of limb ischemia has been shown to decrease acute myocardial injury and chronic responses after acute coronary syndromes. While several signaling pathways have been implicated, our understanding of the cardioprotection and its underlying mediators and mechanisms remains incomplete. In this study we examine the effect of RIC on pro-autophagy signaling as a possible mechanism of benefit.

Methods and Results

We examined the role of autophagy in the acute/first window (15 minutes after RIC), delayed/second window (24 hours after RIC) and chronic (24 hours after 9 days of repeated RIC) phases of cardioprotection. C57BL/6 mice (N = 69) were allocated to each treatment phase and further stratified to receive RIC, induced by four cycles of 5 minutes of limb ischemia followed by 5 minutes of reperfusion, or control treatment consisting solely of handling without transient ischemia. The groups included, group 1 (1W control), group 2 (1W RIC), group 3 (2W control), group 4 (2W RIC), group 5 (3W control) and group 6 (3W RIC). Hearts were isolated for assessment of cardiac function and infarct size after global ischemia using a Langendorff preparation. Infarct size was reduced in all three phases of cardioprotection, in association with improvements in post-ischemic left ventricular end diastolic pressure (LVEDP) and developed pressure (LVDP) (P<0.05). The pattern of autophagy signaling varied; 1W RIC increased AMPK levels and decreased the activation of mammalian target of rapamycin (mTOR), whereas chronic RIC was associated with persistent mTOR suppression and increased levels of autophagosome proteins, LC3II/I and Atg5.

Conclusions

Cardioprotection following transient ischemia exists in both the acute and delayed/chronic phases of conditioning. RIC induces pro-autophagy signaling but the pattern of responses varies depending on the phase, with the most complete portfolio of responses observed when RIC is administered chronically.

Driving neural regeneration through the mammalian target of rapamycin

Neurodegenerative disorders affect more than 30 million individuals throughout the world and lead to significant disability as well as death. These statistics will increase almost exponentially as the lifespan and age of individuals increase globally and individuals become more susceptible to acute disorders such as stroke as well as chronic diseases that involve cognitive loss, Alzheimer's disease, and Parkinson's disease. Current therapies for such disorders are effective only for a small subset of individuals or provide symptomatic relief but do not alter disease progression. One exciting therapeutic approach that may turn the tide for addressing neurodegenerative disorders involves the mammalian target of rapamycin (mTOR). mTOR is a component of the protein complexes mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) that are ubiquitous throughout the body and control multiple functions such as gene transcription, metabolism, cell survival, and cell senescence. mTOR through its relationship with phosphoinositide 3-kinase (PI 3-K) and protein kinase B (Akt) and multiple downstream signaling pathways such as p70 ribosomal S6 kinase (p70S6K) and proline rich Akt substrate 40 kDa (PRAS40) promotes neuronal cell regeneration through stem cell renewal and oversees critical pathways such as apoptosis, autophagy, and necroptosis to foster protection against neurodegenerative disorders. Targeting by mTOR of specific pathways that drive long-term potentiation, synaptic plasticity, and β-amyloid toxicity may offer new strategies for disorders such as stroke and Alzheimer's disease. Overall, mTOR is an essential neuroprotective pathway but must be carefully targeted to maximize clinical efficacy and eliminate any clinical toxic side effects.