The Akt/mTOR/p70S6K Pathway Is Involved in the Neuroprotective Effect of Erythropoietin on Hypoxic/Ischemic Brain Injury in a Neonatal Rat Model

The promotive effect of activation of the Akt/mTOR/p70S6K signaling pathway in oligodendrocytes on nerve myelin regeneration in rats with spinal cord injury

PURPOSE

Akt/mTOR/p70S6K signaling pathway promotes motor function recovery after spinal cord injury (SCI) in both neurons and astrocytes. But the role and mechanism of this pathway in oligodendrocytes during nerve repair following SCI has not been researched. This study aimed to investigate the effect and mechanism of this signaling pathway in oligodendrocytes on nerve myelin regeneration and motor function recovery in rats with SCI.

METHODS

After inhibiting or activating this signaling pathway, Western blotting and double immunofluorescence labeling were used to determine the levels of the signaling molecules in this pathway and myelin formation-related proteins in the plane of the thoracic segment of the injured spinal cord. The level of motor function recovery was evaluated and the oligodendrocytes involved in nerve myelin regeneration were studied. Primary oligodendrocytes were isolated and cultured in vitro, then MBP, PLP, and MOG were measured with reverse transcription-quantitative polymerase chain reaction (RT-qPCR).

RESULTS

Akt/mTOR/p70S6K signaling pathway was activated after SCI compared with the sham-operated rats, prominently elevated levels of the pathway components were observed in the SC79-treated group. The activation of the signaling pathway significantly increased the expression levels of myelin formation-related proteins, including MBP, PLP, and MOG, and improved the Basso, Beattie, and Bresnahan (BBB) scores in the injured spinal cord. Conversely, rapamycin suppressed the expression of these signaling molecules and reduced the levels of myelin formation-related proteins.

CONCLUSION

Akt/mTOR/p70S6K signaling pathway activation can contribute to nerve myelin regeneration and has the potential to improve the regenerative environment and motor function, as well as the potential to promote repair of SCI.

Cornerstone Cellular Pathways for Metabolic Disorders and Diabetes Mellitus: Non-Coding RNAs, Wnt Signaling, and AMPK

Metabolic disorders and diabetes (DM) impact more than five hundred million individuals throughout the world and are insidious in onset, chronic in nature, and yield significant disability and death. Current therapies that address nutritional status, weight management, and pharmacological options may delay disability but cannot alter disease course or functional organ loss, such as dementia and degeneration of systemic bodily functions. Underlying these challenges are the onset of aging disorders associated with increased lifespan, telomere dysfunction, and oxidative stress generation that lead to multi-system dysfunction. These significant hurdles point to the urgent need to address underlying disease mechanisms with innovative applications. New treatment strategies involve non-coding RNA pathways with microRNAs (miRNAs) and circular ribonucleic acids (circRNAs), Wnt signaling, and Wnt1 inducible signaling pathway protein 1 (WISP1) that are dependent upon programmed cell death pathways, cellular metabolic pathways with AMP-activated protein kinase (AMPK) and nicotinamide, and growth factor applications. Non-coding RNAs, Wnt signaling, and AMPK are cornerstone mechanisms for overseeing complex metabolic pathways that offer innovative treatment avenues for metabolic disease and DM but will necessitate continued appreciation of the ability of each of these cellular mechanisms to independently and in unison influence clinical outcome.

Cognitive Impairment in Multiple Sclerosis

Almost three million individuals suffer from multiple sclerosis (MS) throughout the world, a demyelinating disease in the nervous system with increased prevalence over the last five decades, and is now being recognized as one significant etiology of cognitive loss and dementia. Presently, disease modifying therapies can limit the rate of relapse and potentially reduce brain volume loss in patients with MS, but unfortunately cannot prevent disease progression or the onset of cognitive disability. Innovative strategies are therefore required to address areas of inflammation, immune cell activation, and cell survival that involve novel pathways of programmed cell death, mammalian forkhead transcription factors (FoxOs), the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), and associated pathways with the apolipoprotein E (APOE-ε4) gene and severe acute respiratory syndrome coronavirus (SARS-CoV-2). These pathways are intertwined at multiple levels and can involve metabolic oversight with cellular metabolism dependent upon nicotinamide adenine dinucleotide (NAD+). Insight into the mechanisms of these pathways can provide new avenues of discovery for the therapeutic treatment of dementia and loss in cognition that occurs during MS.

Cellular Metabolism: A Fundamental Component of Degeneration in the Nervous System

It is estimated that, at minimum, 500 million individuals suffer from cellular metabolic dysfunction, such as diabetes mellitus (DM), throughout the world. Even more concerning is the knowledge that metabolic disease is intimately tied to neurodegenerative disorders, affecting both the central and peripheral nervous systems as well as leading to dementia, the seventh leading cause of death. New and innovative therapeutic strategies that address cellular metabolism, apoptosis, autophagy, and pyroptosis, the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), growth factor signaling with erythropoietin (EPO), and risk factors such as the apolipoprotein E (APOE-ε4) gene and coronavirus disease 2019 (COVID-19) can offer valuable insights for the clinical care and treatment of neurodegenerative disorders impacted by cellular metabolic disease. Critical insight into and modulation of these complex pathways are required since mTOR signaling pathways, such as AMPK activation, can improve memory retention in Alzheimer's disease (AD) and DM, promote healthy aging, facilitate clearance of β-amyloid (Aß) and tau in the brain, and control inflammation, but also may lead to cognitive loss and long-COVID syndrome through mechanisms that can include oxidative stress, mitochondrial dysfunction, cytokine release, and APOE-ε4 if pathways such as autophagy and other mechanisms of programmed cell death are left unchecked.

Bilirubin oxidation end product B prevents CoCl2-induced primary cortical neuron apoptosis by promoting cell survival Akt/mTOR/p70S6K signaling pathway

Bilirubin oxidation end products (BOXes) are associated with the late-developing neurological deficits after subarachnoid hemorrhage (SAH) possibly by direct constricting the cerebral arteries, but their specific impacts on neurons especially in the state of hypoxia, a prominent feature during the late stage of SAH, remain unclear. Here, we explored the effects of BOXes on the primary cortical neurons subjected to CoCl₂-induced hypoxia by evaluating the morphological and apoptotic changes of neurons. The present study showed that Z-BOX B but not Z-BOX A greatly alleviated CoCl₂-induced neuronal cell deterioration and apoptosis. Immunocytochemical staining assay showed Z-BOX B significantly increased neurite length, the numbers of both secondary and tertiary branches, and the protein level of Synaptophysin. Caspase 3/7 apoptosis assay and DAPI staining showed that Z-BOX B markedly reduced primary cortical neurons apoptosis. The expression of cleaved Caspase-3 was suppressed by Z-BOX B treatment, while the expression of Bcl-xL was upregulated. To further discover the mechanism of the neuroprotective effect observed in Z-BOX B, we found Z-BOX B increased the expression of p-mTOR, p-Akt, and p-p70S6K. In general, our results implicated Z-BOX B may prevent CoCl₂-induced primary cortical neurons apoptosis by activating sAkt/mTOR/p70S6K signaling pathway. Hence, the present data may provide new insights into the pathophysiological mechanism of delayed neurological dysfunction after SAH and novel targets for treating SAH.

The Role of PI3K/AKT and MAPK Signaling Pathways in Erythropoietin Signalization

Erythropoietin (EPO) is a glycoprotein cytokine known for its pleiotropic effects on various types of cells and tissues. EPO and its receptor EPOR trigger signaling cascades JAK2/STAT5, MAPK, and PI3K/AKT that are interconnected and irreplaceable for cell survival. In this article, we describe the role of the MAPK and PI3K/AKT signaling pathways during red blood cell formation as well as in non-hematopoietic tissues and tumor cells. Although the central framework of these pathways is similar for most of cell types, there are some stage-specific, tissue, and cell-lineage differences. We summarize the current state of research in this field, highlight the novel members of EPO-induced PI3K and MAPK signaling, and in this respect also the differences between erythroid and non-erythroid cells.

Dysregulation of metabolic flexibility: The impact of mTOR on autophagy in neurodegenerative disease

Non-communicable diseases (NCDs) that involve neurodegenerative disorders and metabolic disease impact over 400 million individuals globally. Interestingly, metabolic disorders, such as diabetes mellitus, are significant risk factors for the development of neurodegenerative diseases. Given that current therapies for these NCDs address symptomatic care, new avenues of discovery are required to offer treatments that affect disease progression. Innovative strategies that fill this void involve the mechanistic target of rapamycin (mTOR) and its associated pathways of mTOR complex 1 (mTORC1), mTOR complex 2 (mTORC2), AMP activated protein kinase (AMPK), trophic factors that include erythropoietin (EPO), and the programmed cell death pathways of autophagy and apoptosis. These pathways are intriguing in their potential to provide effective care for metabolic and neurodegenerative disorders. Yet, future work is necessary to fully comprehend the entire breadth of the mTOR pathways that can effectively and safely translate treatments to clinical medicine without the development of unexpected clinical disabilities.

Pyrazolo[4,3-c]pyridine-4-one (PP-4-one) Exhibits Anti-Epileptogenic Effect in Rat Model of Traumatic Epilepsy by Mammalian Target of Rapamycin (mTOR) Signaling Pathway Downregulation

Background

Post-traumatic epilepsy (PTE) is a common type of acquired epilepsies secondary to traumatic brain injury (TBI), accounting for approximately 10–25% of patients. The present study evaluated activity of PP-4-one against mTOR signaling activation in a rat model of FeCl₂-induced post-traumatic epilepsy.

Material/Methods

Epilepsy in rats was induced by injecting 10 μl FeCl₂ (concentration 100 mM) at a uniform rate of 1 μl/minute. The iNOS expression was detected using a Leica microscope connected to a digital camera system. Reverse transcription polymerase chain reaction (RT-PCR) was used for determination of NR1 mRNA expression.

Results

The post-traumatic epilepsy induced neuronal degeneration in the hippocampus and frontal cortex of the rats. Treatment with PP-4-one prevented neuronal degeneration in the hippocampus and frontal cortex in rats with post-traumatic epilepsy. The data revealed markedly higher levels of p-mTOR and p-P70S6K in rat hippocampal tissues after induction of traumatic epilepsy. Treatment of post-traumatic epilepsy rats with PP-4-one significantly suppressed p-mTOR and p-P70S6K expression, and PP-4-one treatment reduced epileptic brain injury in the rats with post-traumatic epilepsy.

Conclusions

PP-4-one exhibits an anti-epileptogenic effect in the rat model of PTE by inhibiting behavioral seizures through suppression of iNOS and astrocytic proliferation. Moreover, PP-4-one treatment suppressed NR1 expression and targeted the mTOR pathway in PTE-induced rats. Thus, PP-4-one shows promise as a novel and effective therapeutic agent for treatment of epilepsy induced by PTE.

New Insights for nicotinamide: Metabolic disease, autophagy, and mTOR

Metabolic disorders, such as diabetes mellitus (DM), are increasingly becoming significant risk factors for the health of the global population and consume substantial portions of the gross domestic product of all nations. Although conventional therapies that include early diagnosis, nutritional modification of diet, and pharmacological treatments may limit disease progression, tight serum glucose control cannot prevent the onset of future disease complications. With these concerns, novel strategies for the treatment of metabolic disorders that involve the vitamin nicotinamide, the mechanistic target of rapamycin (mTOR), mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP activated protein kinase (AMPK), and the cellular pathways of autophagy and apoptosis offer exceptional promise to provide new avenues of treatment. Oversight of these pathways can promote cellular energy homeostasis, maintain mitochondrial function, improve glucose utilization, and preserve pancreatic beta-cell function. Yet, the interplay among mTOR, AMPK, and autophagy pathways can be complex and affect desired clinical outcomes, necessitating further investigations to provide efficacious treatment strategies for metabolic dysfunction and DM.

The role of mTOR signalling pathway in hypoxia-induced cognitive impairment

Hypoxia has been associated with cognitive impairment. Many studies have investigated the role of mTOR signalling pathway in cognitive functions but its role in hypoxia-induced cognitive impairment remains controversial. This review aimed to elucidate the role of mTOR in the mechanisms of cognitive impairment that may pave the way towards the mechanistic understanding and therapeutic intervention of hypoxia-induced cognitive impairment. mTORC1 is normally regulated during mild or acute hypoxic exposure giving rise to neuroprotection, whereas it is overactivated during severe or chronic hypoxia giving rise to neuronal cells death. Thus, it is worth exploring the possibility of maintaining normal mTORC1 activity and thereby preventing cognitive impairment during severe or chronic hypoxia.

Nicotinamide: Oversight of Metabolic Dysfunction Through SIRT1, mTOR, and Clock Genes

Metabolic disorders that include diabetes mellitus present significant challenges for maintaining the welfare of the global population. Metabolic diseases impact all systems of the body and despite current therapies that offer some protection through tight serum glucose control, ultimately such treatments cannot block the progression of disability and death realized with metabolic disorders. As a result, novel therapeutic avenues are critical for further development to address these concerns. An innovative strategy involves the vitamin nicotinamide and the pathways associated with the silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), the mechanistic target of rapamycin (mTOR), mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), AMP activated protein kinase (AMPK), and clock genes. Nicotinamide maintains an intimate relationship with these pathways to oversee metabolic disease and improve glucose utilization, limit mitochondrial dysfunction, block oxidative stress, potentially function as antiviral therapy, and foster cellular survival through mechanisms involving autophagy. However, the pathways of nicotinamide, SIRT1, mTOR, AMPK, and clock genes are complex and involve feedback pathways as well as trophic factors such as erythropoietin that require a careful balance to ensure metabolic homeostasis. Future work is warranted to gain additional insight into these vital pathways that can oversee both normal metabolic physiology and metabolic disease.

Cognitive impairment with diabetes mellitus and metabolic disease: innovative insights with the mechanistic target of rapamycin and circadian clock gene pathways

Introduction: Dementia is the 7th leading cause of death that imposes a significant financial and service burden on the global population. Presently, only symptomatic care exists for cognitive loss, such as Alzheimer's disease.Areas covered: Given the advancing age of the global population, it becomes imperative to develop innovative therapeutic strategies for cognitive loss. New studies provide insight to the association of cognitive loss with metabolic disorders, such as diabetes mellitus.Expert opinion: Diabetes mellitus is increasing in incidence throughout the world and affects 350 million individuals. Treatment strategies identifying novel pathways that oversee metabolic and neurodegenerative disorders offer exciting prospects to treat dementia. The mechanistic target of rapamycin (mTOR) and circadian clock gene pathways that include AMP activated protein kinase (AMPK), Wnt1 inducible signaling pathway protein 1 (WISP1), erythropoietin (EPO), and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1) provide novel strategies to treat cognitive loss that has its basis in metabolic cellular dysfunction. However, these pathways are complex and require precise regulation to maximize treatment efficacy and minimize any potential clinical disability. Further investigations hold great promise to treat both the onset and progression of cognitive loss that is associated with metabolic disease.

Carbamazepine Alleviates Retinal and Optic Nerve Neural Degeneration in Diabetic Mice via Nerve Growth Factor-Induced PI3K/Akt/mTOR Activation

Aim: Diabetic retinopathy causes loss of vision in adults at working-age. Few therapeutic options are available for treatment of diabetic retinopathy. Carbamazepine (CARB), a widely used antiepileptic drug, was recently accounted for its neuroprotective effect. Nerve growth factor (NGF) activates various cascades among which, PI3K/Akt/mTOR pathway has a vital action in NGF-mediated neuronal differentiation and survival. This study evaluated the effect of CARB in the treatment of diabetic retina and unveiled some of the underlying molecular mechanisms. Main Methods: Alloxan diabetes model was induced in 36 albino well-acclimatized mice. After establishment of the diabetic model in 9 weeks, mice were assigned to treatment groups: (1) saline, (2) alloxan-diabetic, (3 and 4) alloxan+CARB (25 or 50 mg per kg p.o) for 4 weeks. After completion of the therapeutic period, mice were sacrificed and eyeballs were enucleated. Retinal levels of NGF and PI3K/Akt were assessed using real-time polymerase chain reaction. Further, total and phosphorylated TrKA, PI3K, Akt, mTOR as well as Caspase-3 were measured by Western blot analysis. Key Findings: Histopathological examination demonstrated that CARB attenuated vacuolization and restored normal thickness and organization of retinal cell layers. In addition, CARB increased pTrKA/TrKA ratio and ameliorated diabetes-induced reduction of NGF mRNA and immunostaining in retina. Additionally, it augmented the mRNA expression of PI3K and Akt, as well as the protein level of the phosphorylated PI3/Akt/mTOR. Significance: Results highlighted, for the first time, the neuronal protective effect for CARB in diabetic retina, which is mediated, at least in part, by activation of the NGF/PI3K/Akt/mTOR pathway.

Downregulation of long noncoding RNA Sox2ot protects PC-12 cells from hydrogen peroxide-induced injury in spinal cord injury via regulating the miR-211-myeloid cell leukemia-1 isoform2 axis

This study aimed to investigate the effects and possible mechanisms of long noncoding RNA (lncRNA) Sox2 overlapping transcript (Sox2ot) on hydrogen peroxide (H₂ O₂ )-induced injury in pheochromocytoma (PC-12) cells. PC-12 cells were treated with H₂ O₂ to cell injury. The cells were transfected with short-hairpin RNA directed against Sox2ot (sh-Sox2ot), small interfering RNA directed against myeloid cell leukemia-1 (MCL-1) isoform2 (si-MCL-1), a miR-211 mimic, a miR-211 inhibitor, and their negative controls. Under different transfected treatments, cell viability, migration, invasion, and apoptosis as well as the expressions of apoptosis- and autophagy-related proteins were investigated. Besides, the regulatory relationships between Sox2ot and miR-211, miR-211 and MCL-1, as well as between MCL-1 and the protein kinase B (Akt)/mammalian target of the rapamycin (mTOR)/p70 ribosomal S6 protein kinase (p70S6K) signaling pathway were explored. Suppression of Sox2ot inhibited H₂ O₂ -induced PC-12 cell injury by increasing cell viability, migration, invasion, and decreasing apoptosis and autophagy. Moreover, suppression of Sox2ot increased miR-211 expression and alleviated H₂ O₂ -induced injury in PC-12 cells possibly via upregulation of miR-211. Furthermore, MCL-1 isoform2 was identified as a direct target of miR-211 and could be negatively regulated by miR-211. Suppression of miR-211 aggravated H₂ O₂ -induced cell injury by regulation of MCL-1 isoform2. Besides, inhibition of miR-211 suppressed the activation of the Akt/mTOR/p70S6K signaling pathway in H₂ O₂ -treated PC-12 cells, which was reversed after knockdown of MCL-1 isoform2 at the same time. Our findings indicate that downregulation of Sox2ot may protect PC-12 cells from H₂ O₂ -induced injury in SCI via targeting the miR-211/MCL-1 isoform2 axis. MCL-1 isoform2 may further regulate the activation of the Akt/mTOR/p70S6K pathway to mediate H₂ O₂ -induced injury. The Sox2ot-miR-211-MCL-1 isoform2 axis may be a promising therapeutic strategy for SCI.

Rapamycin provides anti-epileptogenic effect in a rat model of post-traumatic epilepsy via deactivation of mTOR signaling pathway

The mammalian target of rapamycin (mTOR) signaling pathway has attracted much attention in recent years. However, the contribution of mTOR activation to the development of post-traumatic epilepsy (PTE) remains largely unknown. The purpose of the present study was to investigate the activation of mTOR signaling in a rat model of FeCl₂-induced PTE, and to explore the potential effect of its specific inhibitor rapamycin. The results indicated that the expression levels of p-mTOR and p-P70S6K, the overactivation biomarkers of mTOR signaling, increased significantly in hippocampal and perilesional cortex following PTE induction. Notably, they were significantly decreased in the aformementioned brain regions following rapamycin treatment. Furthermore, the frequency and number of behavioral seizures and epileptic brain injury were also greatly reduced. These results suggest that hyperactivation of the mTOR signaling pathway is a crucial mechanism of PTE development, and it may be considered a novel therapeutic target for PTE treatment.

Warming Up to New Possibilities with the Capsaicin Receptor TRPV1: mTOR, AMPK, and Erythropoietin

BACKGROUND

Transient receptor potential (TRP) channels are a superfamily of ion channels termed after the trp gene in Drosophila that are diverse in structure and control a wide range of biological functions including cell development and growth, thermal regulation, and vascular physiology. Of significant interest is the transient receptor potential cation channel subfamily V member 1 (TRPV1) receptor, also known as the capsaicin receptor and the vanilloid receptor 1, that is a non-selective cation channel sensitive to a host of external stimuli including capsaicin and camphor, venoms, acid/basic pH changes, and temperature.

METHODS

Given the multiple modalities that TRPV1 receptors impact in the body, we examined and discussed the role of these receptors in vasomotor control, metabolic disorders, cellular injury, oxidative stress, apoptosis, autophagy, and neurodegenerative disorders and their overlap with other signal transduction pathways that impact trophic factors.

RESULTS

Surprisingly, TRPV1 receptors do not rely entirely upon calcium signaling to affect cellular biology, but also have a close relationship with the mechanistic target of rapamycin (mTOR), AMP activated protein kinase (AMPK), and protein kinase B (Akt) that have roles in pain sensitivity, stem cell development, cellular survival, and cellular metabolism. These pathways with TRPV1 converge in the signaling of growth factors with recent work highlighting a relationship with erythropoietin (EPO). Angiogenesis and endothelial tube formation controlled by EPO requires, in part, the activation of TRPV1 receptors in conjunction with Akt and AMPK pathways.

CONCLUSION

TRPV1 receptors could prove to become vital to target disorders of vascular origin and neurodegeneration. Broader and currently unrealized implementations for both EPO and TRPV1 receptors can be envisioned for for the development of novel therapeutic strategies in multiple systems of the body.

Erythropoietin and mTOR: A "One-Two Punch" for Aging-Related Disorders Accompanied by Enhanced Life Expectancy

Life expectancy continues to increase throughout the world, but is accompanied by a rise in the incidence of non-communicable diseases. As a result, the benefits of an increased lifespan can be limited by aging-related disorders that necessitate new directives for the development of effective and safe treatment modalities. With this objective, the mechanistic target of rapamycin (mTOR), a 289-kDa serine/threonine protein, and its related pathways of mTOR Complex 1 (mTORC1), mTOR Complex 2 (mTORC2), proline rich Akt substrate 40 kDa (PRAS40), AMP activated protein kinase (AMPK), Wnt signaling, and silent mating type information regulation 2 homolog 1 (Saccharomyces cerevisiae) (SIRT1), have generated significant excitement for furthering novel therapies applicable to multiple systems of the body. Yet, the biological and clinical outcome of these pathways can be complex especially with oversight of cell death mechanisms that involve apoptosis and autophagy. Growth factors, and in particular erythropoietin (EPO), are one avenue under consideration to implement control over cell death pathways since EPO can offer potential treatment for multiple disease entities and is intimately dependent upon mTOR signaling. In experimental and clinical studies, EPO appears to have significant efficacy in treating several disorders including those involving the developing brain. However, in mature populations that are affected by aging-related disorders, the direction for the use of EPO to treat clinical disease is less clear that may be dependent upon a number of factors including the understanding of mTOR signaling. Continued focus upon the regulatory elements that control EPO and mTOR signaling could generate critical insights for targeting a broad range of clinical maladies.