Glycine confers neuroprotection through PTEN/AKT signal pathway in experimental intracerebral hemorrhage

Metabolic Reprogramming in Gliocyte Post-cerebral Ischemia/ Reperfusion: From Pathophysiology to Therapeutic Potential

Ischemic stroke is a leading cause of disability and death worldwide. However, the clinical efficacy of recanalization therapy as a preferred option is significantly hindered by reperfusion injury. The transformation between different phenotypes of gliocytes is closely associated with cerebral ischemia/ reperfusion injury (CI/RI). Moreover, gliocyte polarization induces metabolic reprogramming, which refers to the shift in gliocyte phenotype and the overall transformation of the metabolic network to compensate for energy demand and building block requirements during CI/RI caused by hypoxia, energy deficiency, and oxidative stress. Within microglia, the pro-inflammatory phenotype exhibits upregulated glycolysis, pentose phosphate pathway, fatty acid synthesis, and glutamine synthesis, whereas the anti-inflammatory phenotype demonstrates enhanced mitochondrial oxidative phosphorylation and fatty acid oxidation. Reactive astrocytes display increased glycolysis but impaired glycogenolysis and reduced glutamate uptake after CI/RI. There is mounting evidence suggesting that manipulation of energy metabolism homeostasis can induce microglial cells and astrocytes to switch from neurotoxic to neuroprotective phenotypes. A comprehensive understanding of underlying mechanisms and manipulation strategies targeting metabolic pathways could potentially enable gliocytes to be reprogrammed toward beneficial functions while opening new therapeutic avenues for CI/RI treatment. This review provides an overview of current insights into metabolic reprogramming mechanisms in microglia and astrocytes within the pathophysiological context of CI/RI, along with potential pharmacological targets. Herein, we emphasize the potential of metabolic reprogramming of gliocytes as a therapeutic target for CI/RI and aim to offer a novel perspective in the treatment of CI/RI.

Aqueous Fraction from Cucumis sativus Aerial Parts Attenuates Angiotensin II-Induced Endothelial Dysfunction In Vivo by Activating Akt

BACKGROUND

Endothelial dysfunction (ED) is a marker of vascular damage and a precursor of cardiovascular diseases such as hypertension, which involve inflammation and organ damage. Nitric oxide (NO), produced by eNOS, which is induced by pAKT, plays a crucial role in the function of a healthy endothelium.

METHODS

A combination of subfractions SF1 and SF3 (C4) of the aqueous fraction from Cucumis sativus (Cs-Aq) was evaluated to control endothelial dysfunction in vivo and on HMEC-1 cells to assess the involvement of pAkt in vitro. C57BL/6J mice were injected daily with angiotensin II (Ang-II) for 10 weeks. Once hypertension was established, either Cs-AqC4 or losartan was orally administered along with Ang-II for a further 10 weeks. Blood pressure (BP) was measured at weeks 0, 5, 10, 15, and 20. In addition, serum creatinine, inflammatory status (in the kidney), tissue damage, and vascular remodeling (in the liver and aorta) were evaluated. Cs-AqC4 was also tested in vitro on HMEC-1 cells stimulated by Ang-II to assess the involvement of Akt phosphorylation.

RESULTS

Cs-AqC4 decreased systolic and diastolic BP, reversed vascular remodeling, decreased IL-1β and TGF-β, increased IL-10, and decreased kidney and liver damage. In HMEC-1 cells, AKT phosphorylation and NO production were increased.

CONCLUSIONS

Cs-AqC4 controlled inflammation and vascular remodeling, alleviating hypertension; it also improved tissue damage associated with ED, probably via Akt activation.

The Regulated Cell Death and Potential Interventions in Preterm Infants after Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) in preterm infants is one of the major co-morbidities of preterm birth and is associated with long-term neurodevelopmental deficits. There are currently no widely accepted treatments to prevent ICH or therapies for the neurological sequelae. With studies broadening the scope of cell death, the newly defined concept of regulated cell death has enriched our understanding of the underlying mechanisms of secondary brain injury after ICH and has suggested potential interventions in preterm infants. In this review, we will summarize the current evidence for regulated cell death pathways in preterm infants after ICH, including apoptosis, necroptosis, pyroptosis, ferroptosis, autophagy, and PANoptosis as well as several potential intervention strategies that may protect the immature brain from secondary injury after ICH through regulating regulated cell death.

Glycine-induced NMDA receptor internalization provides neuroprotection and preserves vasculature following ischemic stroke

Ischemic stroke is the second leading cause of death worldwide. Following an ischemic event, neuronal death is triggered by uncontrolled glutamate release leading to overactivation of glutamate sensitive N-methyl-d-aspartate receptor (NMDAR). For gating, NMDARs require not only the binding of glutamate, but also of glycine or a glycine-like compound as a co-agonist. Low glycine doses enhance NMDAR function, whereas high doses trigger glycine-induced NMDAR internalization (GINI) in vitro. Here, we report that following an ischemic event, in vivo, GINI also occurs and provides neuroprotection in the presence of a GlyT1 antagonist (GlyT1-A). Mice pretreated with a GlyT1-A, which increases synaptic glycine levels, exhibited smaller stroke volume, reduced cell death, and minimized behavioral deficits following stroke induction by either photothrombosis or endothelin-1. Moreover, we show evidence that in ischemic conditions, GlyT1-As preserve the vasculature in the peri-infarct area. Therefore, GlyT1 could be a new target for the treatment of ischemic stroke.

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GINI is a dynamic phenomenon which dampens NMDAR-mediated excitotoxicity during stroke

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GlyT1-antagonists (GlyT1-As) trigger GINI during stroke in vivo

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GlyT1-As mitigate post-stroke behavioral deficits and preserve peri-infarct vasculature

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GlyT1 could be a novel and viable therapeutic target for ischemic stroke

Glycinergic Signaling in Macrophages and Its Application in Macrophage-Associated Diseases

Accumulating evidences support that amino acids direct the fate decision of immune cells. Glycine is a simple structural amino acid acting as an inhibitory neurotransmitter. Besides, glycine receptors as well as glycine transporters are found in macrophages, indicating that glycine alters the functions of macrophages besides as an inhibitory neurotransmitter. Mechanistically, glycine shapes macrophage polarization via cellular signaling pathways (e.g., NF-κB, NRF2, and Akt) and microRNAs. Moreover, glycine has beneficial effects in preventing and/or treating macrophage-associated diseases such as colitis, NAFLD and ischemia-reperfusion injury. Collectively, this review highlights the conceivable role of glycinergic signaling for macrophage polarization and indicates the potential application of glycine supplementation as an adjuvant therapy in macrophage-associated diseases.

Revisiting promising preclinical intracerebral hemorrhage studies to highlight repurposable drugs for translation

Intracerebral hemorrhage is a devastating global health burden with limited treatment options and is responsible for 49% of 6.5 million annual stroke-related deaths comparable to ischemic stroke. Despite the impact of intracerebral hemorrhage, there are currently no effective treatments and so weaknesses in the translational pipeline must be addressed. There have been many preclinical studies in intracerebral hemorrhage models with positive outcomes for potential therapies in vivo, but beyond advancing the understanding of intracerebral hemorrhage pathology, there has been no translation toward successful clinical application. Multidisciplinary preclinical research, use of multiple models, and validation in human tissue are essential for effective translation. Repurposing of therapeutics for intracerebral hemorrhage may be the most promising strategy to help relieve the global health burden of intracerebral hemorrhage. Here, we have reviewed the existing literature to highlight repurposable drugs with successful outcomes in preclinical models of intracerebral hemorrhage that have realistic potential for development into the clinic for intracerebral hemorrhage.

Inhibition of PTEN Ameliorates Secondary Hippocampal Injury and Cognitive Deficits after Intracerebral Hemorrhage: Involvement of AKT/FoxO3a/ATG-Mediated Autophagy

Spontaneous intracerebral hemorrhage (ICH) commonly causes secondary hippocampal damage and delayed cognitive impairments, but the mechanisms remain elusive. Here, we sought to identify the molecular mechanisms underlying these hemorrhagic outcomes in a rat autologous blood model of ICH. First, a significant increase in phosphatase and tensin homolog (PTEN) expression was observed in nonhemorrhagic ipsilateral hippocampus. However, systemic administration of PTEN inhibitor BPV or hippocampal injection of PTEN siRNA could prevent hippocampal neuronal injury and cognitive dysfunctions after ICH. Furthermore, we also found that ICH robustly triggered autophagic neuronal death in the ipsilateral hippocampus, but which were strongly reduced by PTEN knockdown. Notably, suppression of autophagy effectively attenuated poststroke hippocampal inflammation, neuronal damage, and cognitive decline, suggesting the beneficial effects of PTEN deletion was associated with autophagy inactivation. Specifically, PTEN antagonized the PI3K/AKT signaling and downstream effector FoxO3a phosphorylation and subsequently enhanced nuclear translocation of FoxO3a to drive proautophagy gene program, but these changes were diminished upon PTEN inhibition. More importantly, lentivirus-mediated FoxO3a overexpression apparently abrogated the antiauotphagy effect of PTEN deletion via enhancing autophagy-related gene (ATG) transcription. Collectively, these results suggest that knockdown of PTEN alleviated progressive hippocampal injury and cognitive deficits by suppression of autophagy induction involving the AKT/FoxO3a/ATG axis after ICH. Thus, this study provides a novel and promising therapeutic target for the treatment of hemorrhagic stroke.

miR‑183‑5p attenuates cerebral ischemia injury by negatively regulating PTEN

Cerebral ischemia is a common cerebrovascular disease caused by the occlusion of a cerebral blood vessel. MicroRNAs (miRNAs/miRs) are emerging regulators of various human diseases, including cerebral ischemia. Upregulation of miR‑183‑5p has been reported to alleviate liver injury induced by ischemia‑reperfusion (I/R). However, the effect of miR‑183‑5p on cerebral ischemia injury remains unknown. The present study evaluated the effects of miR‑183‑5p on ischemia injury using ischemic models of mouse brains exposed to transient middle cerebral artery occlusion and Neuro‑2A (N2A) neuroblastoma cells exposed to oxygen‑glucose‑deprivation (OGD) and subsequently reoxygenated. Ischemia was evaluated in mice using neurological function scores, cerebral edema, 2,3,5‑triphenyltetrazoliumchloride, Nissl and Fluoro‑Jade B staining assays. In addition, miR‑183‑5p expression, N2A cell viability and the expression levels of apoptosis‑associated proteins were detected by quantitative PCR, Cell Counting Kit‑8 assay, flow cytometry and western blotting. The association between miR‑183‑5p and phosphatase and tensin homolog (PTEN) was also confirmed by a luciferase reporter assay. The results revealed that miR‑183‑5p expression was decreased and brain damage was increased in ischemic mice compared with the sham group. Additionally, miR‑183‑5p levels were reduced, and apoptosis was increased in N2A cells exposed to ischemia compared with the control group. Following transfection with agomiR‑183‑5p, cerebral ischemic injury and apoptosis levels were reduced in the in vivo I/R stroke model and OGD‑induced N2A cells. In addition, PTEN was determined to be a target of miR‑183‑5p following elucidation of a direct binding site. Overexpression of PTEN reversed the miR‑183‑5p‑induced N2A cell apoptosis inhibition and survival after OGD. The results of the present study suggested that miR‑183‑5p reduced ischemic injury by negatively regulating PTEN, which may aid the development of a novel therapeutic strategy for cerebral ischemia.

Using Serum Amino Acids to Predict Traumatic Brain Injury: A Systematic Approach to Utilize Multiple Biomarkers

Traumatic brain injury (TBI) can cause biochemical and metabolomic alterations in the brain tissue and serum. These alterations can be used for diagnosis and prognosis of TBI. Here, the serum concentrations of seventeen amino acids (AA) were studied for their potential utility as biomarkers of TBI. Twenty-five female, 4-week-old piglets received diffuse (n = 13) or focal (n = 12) TBI. Blood samples were obtained both pre-injury and at either 24-h or 4-days post-TBI. To find a robust panel of biomarkers, the results of focal and diffuse TBIs were combined and multivariate logistic regression analysis, coupled with the best subset selection technique and repeated k-fold cross-validation method, was used to perform a thorough search of all possible subsets of AAs. The combination of serum glycine, taurine, and ornithine was optimal for TBI diagnosis, with 80% sensitivity and 86% overall prediction rate, and showed excellent TBI diagnostic performance, with 100% sensitivity and 78% overall prediction rate, on a separate validation dataset including four uninjured and five injured animals. We found that combinations of biomarkers outperformed any single biomarker. We propose this 3-AA serum biomarker panel to diagnose mild-to-moderate focal/diffuse TBI. The systematic approaches implemented herein can be used for combining parameters from various TBI assessments to develop/evaluate optimal multi-factorial diagnostic/prognostic TBI metrics.

MicroRNA-181c provides neuroprotection in an intracerebral hemorrhage model

Apoptosis is an important factor during the early stage of intracerebral hemorrhage. MiR-181c plays a key regulatory role in apoptosis. However, whether miR-181c is involved in apoptosis of prophase cells after intracerebral hemorrhage remains unclear. Therefore, in vitro and in vivo experiments were conducted to test this hypothesis. In vivo experiments: collagenase type VII was injected into the basal ganglia of adult Sprague-Dawley rats to establish an intracerebral hemorrhage model. MiR-181c mimic or inhibitor was injected in situ 4 hours after intracerebral hemorrhage. Neurological functional defects (neurological severity scores) were assessed 1, 7, and 14 days after model establishment. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling and western blot assay were conducted 14 days after model establishment. In vitro experiments: PC12 cells were cultured under oxygen-glucose deprivation, and hemins were added to simulate intracerebral hemorrhage in vitro. MiR-181c mimic or inhibitor was added to regulate miR-181c expression. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, luciferase reporter system, and western blot assay were performed. Experimental results revealed differences in miR-181c expression in brain tissues of both patients and rats with cerebral hemorrhage. In addition, in vitro experiments found that miR-181c overexpression could upregulate the Bcl-2/Bax ratio to inhibit apoptosis, while inhibition of miR-181c expression could reduce the Bcl-2/Bax ratio and aggravate apoptosis of cells. Regulation of apoptosis occurred through the phosphoinositide 3 kinase (PI3K)/Akt pathway by targeting of phosphatase and tensin homolog deleted on chromosome ten (PTEN). Higher miR-181c overexpression correlated with lower neurological severity scores, indicating better recovery of neurological function. In conclusion, miR-181c affects the prognosis of intracerebral hemorrhage by regulating apoptosis, and these effects might be directly mediated and regulated by targeting of the PTEN\PI3K/Akt pathway and Bcl-2/Bax ratio. Furthermore, these results indicated that miR-181c played a neuroprotective role in intracerebral hemorrhage by regulating apoptosis of nerve cells, thus providing a potential target for the prevention and treatment of intracerebral hemorrhage. Testing of human serum was authorized by the Ethics Committee of China Medical University (No. 2012-38-1) on February 20, 2012. The protocol was registered with the Chinese Clinical Trial Registry (Registration No. ChiCTR-COC-17013559). The animal study was approved by the Institutional Animal Care and Use Committee of China Medical University (approval No. 2017008) on March 8, 2017.

Glycine Protects against Hypoxic-Ischemic Brain Injury by Regulating Mitochondria-Mediated Autophagy via the AMPK Pathway

Hypoxic-ischemic encephalopathy (HIE) is detrimental to newborns and is associated with high mortality and poor prognosis. Thus, the primary aim of the present study was to determine whether glycine could (1) attenuate HIE injury in rats and hypoxic stress in PC12 cells and (2) downregulate mitochondria-mediated autophagy dependent on the adenosine monophosphate- (AMP-) activated protein kinase (AMPK) pathway. Experiments conducted using an in vivo HIE animal model and in vitro hypoxic stress to PC12 cells revealed that intense autophagy associated with mitochondrial function occurred during in vivo HIE injury and in vitro hypoxic stress. However, glycine treatment effectively attenuated mitochondria-mediated autophagy. Additionally, after identifying alterations in proteins within the AMPK pathway in rats and PC12 cells following glycine treatment, cyclosporin A (CsA) and 5-aminoimidazole-4-carboxamide-1-b-4-ribofuranoside (AICAR) were administered in these models and indicated that glycine protected against HIE and CoCl₂ injury by downregulating mitochondria-mediated autophagy that was dependent on the AMPK pathway. Overall, glycine attenuated hypoxic-ischemic injury in neurons via reductions in mitochondria-mediated autophagy through the AMPK pathway both in vitro and in vivo.