[Role of SIRTs in cerebral ischemia reperfusion injury and targeted intervention of Chinese medicine].

Cerebral ischemia-reperfusion injury(CIRI) is a complex cascade process and seriously hinders the recovery of patients with acute ischemic stroke, which has become an urgent public health issue to be addressed. Silent information regulators(SIRTs) are a family of nicotinamide adenine dinucleotide(NAD~+)-dependent deacetylases, capable of deacylating the histone and non-histone lysine groups. Accumulating evidence has demonstrated that SIRTs are able to regulate the pathological processes such as oxidative stress, inflammatory response, mitochondrial dysfunction, and programmed cell death of CIRI through post-translational deacetylation, and exert the neuroprotection function. In this study, we reviewed the papers about the role and regulatory mechanisms of SIRTs in the pathological process of CIRI published in the past decade. Further, we summarized the research advance in the prevention and treatment of CIRI with Chinese medicine targeting SIRTs and the related signaling pathways. This review will provide new targets and theoretical support for the clinical application of Chinese medicine in treating CIRI during the occurrence of ischemic stroke.

The NEDD8-activating enzyme inhibitor MLN4924 reduces ischemic brain injury in mice.

Blood-brain barrier (BBB) breakdown and inflammation occurring at the BBB have a key, mainly a deleterious role in the pathophysiology of ischemic stroke. Neddylation is a ubiquitylation-like pathway that is critical in various cellular functions by conjugating neuronal precursor cell-expressed developmentally down-regulated protein 8 (NEDD8) to target proteins. However, the roles of neddylation pathway in ischemic stroke remain elusive. Here, we report that NEDD8 conjugation increased during acute phase after ischemic stroke and was present in intravascular and intraparenchymal neutrophils. Inhibition of neddylation by MLN4924, also known as pevonedistat, inactivated cullin-RING E3 ligase (CRL), and reduced brain infarction and improved functional outcomes. MLN4924 treatment induced the accumulation of the CRL substrate neurofibromatosis 1 (NF1). By using virus-mediated NF1 silencing, we show that NF1 knockdown abolished MLN4924-dependent inhibition of neutrophil trafficking. These effects were mediated through activation of endothelial P-selectin and intercellular adhesion molecule-1 (ICAM-1), and blocking antibodies against P-selectin or anti-ICAM-1 antibodies reversed NF1 silencing-induced increase in neutrophil infiltration in MLN4924-treated mice. Furthermore, we found that NF1 silencing blocked MLN4924-afforded BBB protection and neuroprotection through activation of protein kinase C δ (PKCδ), myristoylated alanine-rich C-kinase substrate (MARCKS), and myosin light chain (MLC) in cerebral microvessels after ischemic stroke, and treatment of mice with the PKCδ inhibitor rottlerin reduced this increased BBB permeability. Our study demonstrated that increased neddylation promoted neutrophil trafficking and thus exacerbated injury of the BBB and stroke outcomes. We suggest that the neddylation inhibition may be beneficial in ischemic stroke.

Aconitate decarboxylase 1 suppresses cerebral ischemia-reperfusion injury in mice.

Immunometabolic changes have been shown to be a key factor in determining the immune cell response in disease models. The immunometabolite, itaconate, is produced by aconitate decarboxylase 1 (Acod1) and has been shown to inhibit inflammatory signaling in macrophages. In this study, we explore the role of Acod1 and itaconate in cerebral ischemia/reperfusion injury. We assessed the effect of global Acod1 knockout (Acod1KO, loss of endogenous itaconate) in a transient ischemia/reperfusion occlusion stroke model. Mice received a transient 90-min middle cerebral artery occlusion followed with 24-h of reperfusion. Stroke lesion volume was measured by MRI analysis and brain tissues were collected for mRNA gene expression analysis. Acod1KO mice showed significant increases in lesion volume compared to control mice, however no differences in pro-inflammatory mRNA levels were observed. Cell specific knockout of Acod1 in myeloid cells (LysM-Cre), microglia cells (CX3CR1, Cre-ERT2) and Endothelial cells (Cdh5(PAC), Cre-ERT2) did not reproduce lesion volume changes seen in global Acod1KO, indicating that circulating myeloid cells, resident microglia and endothelial cell populations are not the primary contributors to the observed phenotype. These effects however do not appear to be driven by changes in inflammatory gene regulation. These data suggests that endogenous Acod1 is protective in cerebral ischemia/reperfusion injury.

Legumain knockout improved cognitive impairment via reducing neuroinflammation in right unilateral common carotid artery occlusion mice.

AIMS: Chronic cerebral hypoperfusion (CCH) is a state of chronic cerebral blood flow reduction, and it is the main cause of cognitive impairment and neurodegenerative diseases. The abnormal upregulation of legumain, a lysosomal cysteine protease, trigger synaptic plasticity impairment and neuroinflammation, which are involved in the underlying pathophysiology of CCH. At present, few studies have reported the role of legumain in cognitive impairment caused by CCH. In our study, we aimed to investigate the involvement of legumain knockout in cognitive function and neuroinflammation in a CCH mouse model. MAIN METHODS: In this study, right unilateral common carotid artery occlusion (rUCCAO) was used to simulate the pathological state of cerebral ischemic injury. Various behavioural tests were executed to assess cognitive performance. In vivo electrophysiological recordings were used to measure synaptic functions. Western blotting, Golgi staining, haematoxylin/eosin staining, and immunofluorescence assays were conducted to examine pathological changes and molecular mechanisms. KEY FINDINGS: The data showed that the level of legumain was significantly increased in the hippocampus of mice subjected to rUCCAO. Legumain knockout significantly improved cognitive function and synaptic plasticity induced by rUCCAO, suggesting that legumain knockout-regulation effectively protected against CCH-induced behavioural dysfunctions. Moreover, legumain knockout suppressed rUCCAO-induced microglial activation, reduced the abnormal expression of inflammatory cytokines and the inflammasome complex, and impeded the activation of P65 and pyroptosis. SIGNIFICANCE: These findings suggest that legumain is an effective regulator of CCH, and may be an ideal target for the development of cerebral ischemia treatments in the future.

Carnosine Protects against Cerebral Ischemic Injury by Inhibiting Matrix-Metalloproteinases.

Stroke is one of the leading causes of death and disability worldwide. However, treatment options for ischemic stroke remain limited. Matrix-metalloproteinases (MMPs) contribute to brain damage during ischemic strokes by disrupting the blood-brain barrier (BBB) and causing brain edemas. Carnosine, an endogenous dipeptide, was found by us and others to be protective against ischemic brain injury. In this study, we investigated whether carnosine influences MMP activity. Brain MMP levels and activity were measured by gelatin zymography after permanent occlusion of the middle cerebral artery (pMCAO) in rats and in vitro enzyme assays. Carnosine significantly reduced infarct volume and edema. Gelatin zymography and in vitro enzyme assays showed that carnosine inhibited brain MMPs. We showed that carnosine inhibited both MMP-2 and MMP-9 activity by chelating zinc. Carnosine also reduced the ischemia-mediated degradation of the tight junction proteins that comprise the BBB. In summary, our findings show that carnosine inhibits MMP activity by chelating zinc, an essential MMP co-factor, resulting in the reduction of edema and brain injury. We believe that our findings shed new light on the neuroprotective mechanism of carnosine against ischemic brain damage.

Effect of Global Brain Ischemia on Amyloid Precursor Protein Metabolism and Expression of Amyloid-Degrading Enzymes in Rat Cortex: Role in Pathogenesis of Alzheimer's Disease.

The incidence of Alzheimer's disease (AD) increases significantly following chronic stress and brain ischemia which, over the years, cause accumulation of toxic amyloid species and brain damage. The effects of global 15-min ischemia and 120-min reperfusion on the levels of expression of the amyloid precursor protein (APP) and its processing were investigated in the brain cortex (Cx) of male Wistar rats. Additionally, the levels of expression of the amyloid-degrading enzymes neprilysin (NEP), endothelin-converting enzyme-1 (ECE-1), and insulin-degrading enzyme (IDE), as well as of some markers of oxidative damage were assessed. It was shown that the APP mRNA and protein levels in the rat Cx were significantly increased after the ischemic insult. Protein levels of the soluble APP fragments, especially of sAPPß produced by ß-secretase, (BACE-1) and the levels of BACE-1 mRNA and protein expression itself were also increased after ischemia. The protein levels of APP and BACE-1 in the Cx returned to the control values after 120-min reperfusion. The levels of NEP and ECE-1 mRNA also decreased after ischemia, which correlated with the decreased protein levels of these enzymes. However, we have not observed any changes in the protein levels of insulin-degrading enzyme. Contents of the markers of oxidative damage (di-tyrosine and lysine conjugates with lipid peroxidation products) were also increased after ischemia. The obtained data suggest that ischemia shifts APP processing towards the amyloidogenic ß-secretase pathway and accumulation of the neurotoxic Aß peptide as well as triggers oxidative stress in the cells. These results are discussed in the context of the role of stress and ischemia in initiation and progression of AD.

ß-1, 3-galactosyltransferase 2 ameliorates focal ischemic cerebral injury by maintaining blood-brain barrier integrity.

Blood-brain barrier (BBB) damage at the early stage of ischemic stroke is a vital cause of brain parenchymal injury. The mechanism of BBB disruption has been intensively investigated, but still not fully understood. ß-1, 3-galactosyltransferase 2 (B3galt2) is expressed in the brain, but its role in the pathogenesis of cerebral ischemia remains unknown. In this study, we investigated the role of B3galt2 in cerebral ischemia in mice. Focal cerebral ischemia was induced in mice by middle cerebral artery occlusion (MCAO). B3galt2 protein levels were determined in microvessels which were isolated from ischemic brain at 12, 24 and 72 h after MCAO. Mice were administered lentiviral vectors encoding B3galt2 (LV- B3galt2) or recombinant transforming growth factor-ß1 (r-TGF-ß1) by intracerebroventricular injection. We assessed infarct volume and neurologic deficits on days 1, 3, and 14 after MCAO, blood-brain barrier (BBB) integrity at 12 and 24 h after MCAO, and the levels of TGF-ß1, TGF-ßR(Ⅱ) and p-Smad2/3 at 24 and 72 h after MCAO. Our results indicated that B3galt2 was expressed in brain microvascular endothelial cells and increased in the ischemic microvessels. Overexpression of B3galt2 by LV- B3galt2 administration reduced infarct volume and improved functional outcome after cerebral ischemia. Moreover, the neuroprotective effects were associated with preventing BBB damage. Compared with wild-type (WT) mice, heterozygous B3galt2 knockout (B3galt2-/+) mice not only showed severe BBB damage, neurologic functional deficits, but also showed reduced expression of TGF-ß1, TGF-ßR(Ⅱ) and p-Smad2/3 in microvessels after cerebral ischemia. Pre-administration of r-TGF-ß1 reduced BBB damage, and improved the neurological outcomes in both WT mice and B3galt2-/+ mice after cerebral ischemia. Our results suggested B3galt2 protected against ischemic stroke in mice, and the underlying mechanism might include TGF-ß signaling pathway in brain microvascular endothelial cells.

Role of pERK1/2-NFκB signaling in the neuroprotective effect of thalidomide against cerebral ischemia reperfusion injury in rats.

In the present investigation, we tested the hypothesis that suppression of the phospho-extracellular signal regulated kinase (pERK1/2)-nuclear factor kappa (NFκ)-B signaling, subsequent to tumor necrosis factor-α (TNF-α) inhibition, underlies thalidomide (TLM) mediated neuroprotection. Male Wistar rats (250-280 g) were divided into five groups: (1) sham; (2) negative control receiving TLM (5µg/1µl/site) and 3 groups of ischemia-reperfusion (IR) injury rats pretreated with: (3) vehicle (DMSO 100%); (4) TLM (5µg/1µl/site) or (5) PD98059 (0.16µg/1µl/site). IR rats were subjected to occlusion of both common carotid arteries for 45 min followed by reperfusion for 24 h. Drugs and/or vehicles were administered by unilateral intrahippocampal injection after removal of the carotid occlusion and at the beginning of the reperfusion period. IR rats exhibited significant infarct size, histopathological damage, memory impairment, motor incoordination and hyperactivity. Unilateral intra-hippocampal TLM ameliorated these behavioral deficits along with the following ex vivo hippocampal effects: (i) abrogation of the IR-evoked elevations in hippocampal TNF-α, pERK1/2, NFκB, BDNF, iNOS contents and (ii) partial restoration of the reduced anti-inflammatory cytokine IL-10 and p-nNOS S852. These neurochemical effects, which were replicated by the pERK1/2 inhibitor PD98059, likely underlie the reductions in c-Fos and caspase-3 levels as well as the anti-apoptotic effect of TLM in the IR model. These results suggest a crucial anti-inflammatory role for pERK1/2 inhibition in the salutary neuronal and behavioral effects of TLM in a model of brain IR injury.

CHRFAM7A Overexpression Attenuates Cerebral Ischemia-Reperfusion Injury via Inhibiting Microglia Pyroptosis Mediated by the NLRP3/Caspase-1 pathway.

Cerebral ischemia-reperfusion (I/R) injury is an inflammation-related disease. CHRFAM7A can regulate inflammatory responses. Therefore, the present study investigated the mechanism of CHRFAM7A in cerebral I/R injury. CHRFAM7A expression and inflammatory cytokine levels in patients with cerebral I/R injury and oxygen-glucose deprivation/reperfusion (OGD/R)-treated microglia were detected. The proliferation, inflammatory cytokine expressions, nod-like receptor protein 3 (NLRP3) level, cell pyroptosis, and viability and lactate dehydrogenase (LDH) activity in OGD/R-treated microglia were detected after CHRFAM7A overexpression. The NLRP3/Caspase-1 pathway was activated to assess the effect of CHRFAM7A on microglia. Expressions of microglial M1 phenotype marker iNOS and M2 marker Arg1 were detected. Downregulated CHRFAM7A and elevated inflammatory cytokine levels were observed in patients with cerebral I/R injury and OGD/R-treated microglia. In OGD/R-treated microglia, CHRFAM7A overexpression promoted cell proliferation and viability, reduced inflammation and LDH activity, and inhibited NLRP3 inflammasome activation and cell pyroptosis. Mechanically, CHRFAM7A inhibited microglia pyroptosis via inhibiting the NLRP3/Caspase-1 pathway and reduced cell inflammatory injury via promoting microglia polarization from M1 to M2. Overall, CHRFAM7A overexpression attenuated cerebral I/R injury by inhibiting microglia pyroptosis in a NLRP3/Caspase-1 pathway-dependent manner and promoting microglia polarization to M2 phenotype.

Knockdown of Arginyl-tRNA Synthetase Attenuates Ischemia-Induced Cerebral Cortex Injury in Rats After Middle Cerebral Artery Occlusion.

Some researchers have previously shown that RNAi knockdown of arginyl-tRNA synthetase (ArgRS) before or after a hypoxic injury can rescue animals from death, based on the model organism, C. elegans. However, there has been no study on the application of arginyl-tRNA synthetase knockdown in treating mammalian ischemic stroke, and its potential mechanism and effect on ischemic brain damage are still unknown. Here, we focused on the Rars gene, which encodes an arginyl-tRNA synthetase, and examined the effects of Rars knockdown in a permanent middle cerebral artery occlusion model in rats. To achieve this aim, adult male Sprague-Dawley (SD) rats were given right cerebral cortex injections of short hairpin RNA (shRNA) adenovirus (AV) particles to knock down arginyl-tRNA synthetase, and a non-targeting control (NTC) vector or phosphate-buffered solution served as the controls. After 4 days, the rats were exposed to permanent middle cerebral artery occlusion (pMCAO). Then, the right cerebral cortex level of arginyl-tRNA synthetase was examined, and the effects of the Rars knockdown were evaluated by differences in infarction volume, oxidative stress, blood-brain barrier, mitochondrial function, and glucose metabolism at 1 day and 3 days after MCAO. The injection of shRNA adenovirus particles successfully suppressed the expression of arginyl-tRNA synthetase in the cerebral cortex. We observed an improvement in oxidative stress, mitochondrial function, and glucose utilization and a reduction in brain edema compared with the non-targeting control rats with suppressed expression of arginyl-tRNA synthetase mRNA in the ipsilateral ischemic cortex of the brain. Our findings indicate that knockdown of arginyl-tRNA synthetase in the cerebral cortex exerted neuroprotective effects, which were achieved not only by the improvement of oxidative stress and glucose utilization but also by the maintenance of mitochondrial morphological integrity and the preservation of mitochondrial function. Knockdown of ArgRS administration could be a promising approach to protect ischemic stroke.

Soluble epoxide hydrolase inhibition improves cognitive function and parenchymal artery dilation in a hypertensive model of chronic cerebral hypoperfusion.

OBJECTIVE: Parenchymal arterioles (PAs) regulate perfusion of the cerebral microcirculation, and impaired PA endothelium-dependent dilation occurs in dementia models mimicking chronic cerebral hypoperfusion (CCH). Epoxyeicosatrienoic acids (EETs) are vasodilators; their actions are potentiated by soluble epoxide hydrolase (sEH) inhibition. We hypothesized that chronic sEH inhibition with trifluoromethoxyphenyl-3 (1-propionylpiperidin-4-yl) urea (TPPU) would prevent cognitive dysfunction and improve PA dilation in a hypertensive CCH model. METHODS: Bilateral carotid artery stenosis (BCAS) was used to induce CCH in twenty-week-old male stroke-prone spontaneously hypertensive rats (SHSRP) that were treated with vehicle or TPPU for 8 weeks. Cognitive function was assessed by novel object recognition. PA dilation and structure were assessed by pressure myography, and mRNA expression in brain tissue was assessed by qRT-PCR. RESULTS: TPPU did not enhance resting cerebral perfusion, but prevented CCH-induced memory deficits. TPPU improved PA endothelium-dependent dilation but reduced the sensitivity of PAs to a nitric oxide donor. TPPU treatment had no effect on PA structure or biomechanical properties. TPPU treatment increased brain mRNA expression of brain derived neurotrophic factor, doublecortin, tumor necrosis factor-alpha, sEH, and superoxide dismutase 3, CONCLUSIONS: These data suggest that sEH inhibitors may be viable treatments for cognitive impairments associated with hypertension and CCH.

Inhibition of endogenous blood glutamate oxaloacetate transaminase enhances the ischemic damage.

Glutamate oxaloacetate transaminase 1 (GOT1) enzyme plays a critical role in the cell metabolism by participating in the carbohydrate and amino acid metabolism. In ischemic stroke, we have demonstrated that recombinant GOT1 acts as a novel neuroprotective treatment against the excess of extracellular glutamate that accumulates in the brain following ischemic stroke. In this study, we investigated the inhibitory effect of GOT1 on brain metabolism and on the ischemic damage in a rat model of ischemic stroke by means of a specific antibody developed against this enzyme. Inhibition of GOT1 caused higher brain glutamate and lactate levels and this response was associated with larger ischemic lesion. This study represents the first demonstration that the inhibition of the blood GOT1 activity leads to more severe ischemic damage and poorer outcome and supports the protective role of GOT1 against ischemic insults.

Inhibition of microglial receptor-interacting protein kinase 1 ameliorates neuroinflammation following cerebral ischaemic stroke.

Microglia are rapidly activated following ischaemic stroke and participate in the induction of neuroinflammation, which exacerbates the injury of ischaemic stroke. However, the mechanisms regulating ischaemic microglia remain unclear. In the present study, middle cerebral artery occlusion and oxygen and glucose deprivation models were established for in vivo and vitro monitoring of experimental stroke. We applied recombinant human thioredoxin-1 (rhTrx-1) and Necrostatin-1 (Nec-1, inhibitor of RIPK1) to examine the role of receptor-interacting protein kinase 1 (RIPK1) in the development of inflammation in ischaemic microglia via explored the inflammatory responses and the associated mechanisms. Molecular docking results indicated that rhTrx-1 could directly bind to RIPK1. In vivo and vitro data revealed that rhTrx-1 reduced necroptosis, mitochondrial membrane potential damage, reactive oxygen species accumulation and NLR Family, pyrin domain-containing 3 protein (NLRP3) inflammasome activation and regulated the microglial M1/M2 phenotypic changes by inhibiting RIPK1 expression in ischaemic microglia. Consistent with these findings, further in vivo experiments revealed that rhTrx-1 treatment attenuated cerebral ischaemic injury by inhibiting the inflammatory response. Our data demonstrated the role of RIPK1 in microglia-induced neuroinflammation following cerebral ischaemia. Administration of rhTrx-1 provides neuroprotection in ischaemic stroke-induced microglial neuroinflammation by inhibiting RIPK1 expression.

Predictors of Recurrent Ischemic Stroke in Obese Patients With Type 2 Diabetes Mellitus: A Population-based Study.

BACKGROUND: Diabetes and obesity are established risk factors for stroke. The current study aimed to assess risk factors of ischemic stroke recurrence in diabetic patients based on their body mass index (BMI). METHODS: A total of 4005 diabetic patients who had a history of ischemic stroke were identified in a retrospective cross-sectional dataset from the Malaysian National Neurology Registry. Patients were classified based on BMI, and multivariable regression analysis was used to evaluate the association between risk factors and recurrent ischemic stroke. RESULTS: Among obese patients, those with ischemic heart disease (aOR, 1.873; 95% CI, 1.131-3.103), received formal education (aOR, 2.236; 95% CI, 1.306-3.830), and received anti-diabetic medication (aOR, 1.788; 95% CI, 1.180-2.708) had a higher stroke recurrence risk, while receiving angiotensin receptors blockers (aOR, 0.261; 95% CI, 0.126-0.543) lowered the odds of recurrence. Overweight patients with hypertension (aOR, 1.011; 95% CI, 1.002-1.019) for over 10 years (aOR, 3.385; 95% CI, 1.088-10.532) and diabetes prior to the first stroke (aOR, 1.823; 95% CI, 1.020-3.259) as well as those received formal education (aOR, 2.403; 95% CI, 1.126-5.129) had higher odds of stroke recurrence, while receiving angiotensin-converting enzyme inhibitors (aOR, 0.244; 95% CI, 0.111-0.538) lowered the recurrence risk. Normal weight East Malaysians (aOR, 0.351; 95% CI, 0.164-0.750) receiving beta-blockers (aOR, 0.410; 95% CI, 0.174-0.966) had lower odds of stroke recurrence. CONCLUSIONS: Ischemic heart disease, hypertension, receiving anti-hypertensive agents, and educational level were independent predictors of recurrent stroke in obese patients. Managing the modifiable risk factors can decrease the odds of stroke recurrence.

Lung SOD3 limits neurovascular reperfusion injury and systemic immune activation following transient global cerebral ischemia.

BACKGROUND AND OBJECTIVES: Studies implicate the lung in moderating systemic immune activation via effects on circulating leukocytes. In this study, we investigated whether targeted expression of the antioxidant extracellular superoxide dismutase (SOD3) within the lung would influence post-ischemic peripheral neutrophil activation and CNS reperfusion injury. METHODS: Adult, male mice expressing human SOD3 within type II pneumocytes were subjected to 15 min of transient global cerebral ischemia. Three days post-reperfusion, lung and brain tissue was collected and analyzed by immunohistochemistry for inflammation and injury markers. In vitro motility and neurotoxicity assays were conducted to ascertain the direct effects of hSOD3 on PMN activation. Results were compared against C57BL/6 age and sex-matched controls. RESULTS: Relative to wild-type controls, hSOD3 heterozygous mice exhibited a reduction in lung inflammation, blood-brain barrier damage, and post-ischemic neuronal injury within the hippocampus and cortex. PMNs harvested from hSOD3 mice were also resistant to LPS priming, slower-moving, and less toxic to primary neuronal cultures. CONCLUSIONS: Constitutive, focal expression of hSOD3 is neuroprotective in a model of global cerebral ischemia-reperfusion injury. The underlying mechanism of SOD3-dependent protection is attributable in part to effects on the activation state and toxic potential of circulating neutrophils. These results implicate lung-brain coupling as a determinant of cerebral ischemia-reperfusion injury and highlight post-stroke lung inflammation as a potential therapeutic target in acute ischemic cerebrovascular injuries.

Typhae pollen polysaccharides protect hypoxia-induced PC12 cell injury via regulation of miR-34a/SIRT1.

This current research was performed to investigate the role of typhae pollen polysaccharides (TPP) in hypoxia-treated PC12 cell which was an in vitro cell model of cerebral ischemia. Hypoxia-treated cells were treated with TPP for 12 h. Cell viability and apoptosis were detected by 3-(4,5-dimethylthiazol-2-yl)-2 5-diphenyl-2H-tetrazolium bromide (MTT) assay and flow cytometry, respectively. Cell apoptotic proteins and PI3K/AKT and Ras/Raf/MEK/ERK signal pathway-associated proteins were also examined by western blot. Furthermore, abnormal expression of miR-34a and silent information regulator 1 (SIRT1) was achieved by transfection. Besides, the expression of miR-34a and SIRT1 was examined by quantitative real-time polymerase chain reaction (qRT-PCR). The expression of SIRT1 was detected by qRT-PCR and western blot. The relationship between miR-34a and SIRT1 was verified by luciferase assay. We found that TPP enhanced cell viability and inhibited apoptosis in hypoxia-treated PC12 cells. Moreover, TPP increased the accumulated levels of Bcl-2 while decreased expression of Bax, cleaved Caspase-3, and cleaved PARP. TPP downregulated miR-34a expression while induced by hypoxia. Further results showed that miR-34a overexpression reversed the results led by TPP in cell viability, apoptosis, and its related proteins. In addition, SIRT1 was upregulated by TPP and was verified to be a target of miR-34a. Silence of SIRT1 led to the opposite results led by TPP. In the end, TPP activated PI3K/AKT and Ras/Raf/MEK/ERK signal pathways. In conclusion, TPP plays important roles in regulating cell viability and apoptosis in hypoxia-treated PC12 cells via modulating miR-34a/SIRT1, as well as activating PI3K/AKT and Ras/Raf/MEK/ERK signal pathways.

Glutaminase 1 Regulates Neuroinflammation After Cerebral Ischemia Through Enhancing Microglial Activation and Pro-Inflammatory Exosome Release.

Cerebral ischemia induces a robust neuroinflammatory response that is largely mediated by the activation of CNS resident microglia. Activated microglia produce pro-inflammatory molecules to cause neuronal damage. Identifying regulators of microglial activation bears great potential in discovering promising candidates for neuroprotection post cerebral ischemia. Previous studies demonstrate abnormal elevation of glutaminase 1 (GLS1) in microglia in chronic CNS disorders including Alzheimer's disease and HIV-associated neurocognitive disorders. Ectopic expression of GLS1 induced microglia polarization into pro-inflammatory phenotype and exosome release in vitro. However, whether GLS1 is involved in neuroinflammation in acute brain injury remains unknown. Here, we observed activation of microglia, elevation of GLS1 expression, and accumulation of pro-inflammatory exosomes in rat brains 72 h post focal cerebral ischemia. Treatment with CB839, a glutaminase inhibitor, reversed ischemia-induced microglial activation, inflammatory response, and exosome release. Furthermore, we found that the application of exosome secretion inhibitor, GW4869, displayed similar anti-inflammatory effects to that of CB839, suggesting GLS1-mediated exosome release may play an important role in the formation of neuroinflammatory microenvironment. Therefore, GLS1 may serve as a key mediator and promising target of neuroinflammatory response in cerebral ischemia.

Transforming Growth Factor Beta-Activated Kinase 1-Dependent Microglial and Macrophage Responses Aggravate Long-Term Outcomes After Ischemic Stroke.

Background and Purpose- Microglia/macrophages (Mi/MΦ) can profoundly influence stroke outcomes by acquiring functionally dominant phenotypes (proinflammatory or anti-inflammatory; deleterious or salutary). Identification of the molecular mechanisms that dictate the functional status of Mi/MΦ after brain ischemia/reperfusion may reveal novel therapeutic targets for stroke. We hypothesized that activation of TAK1 (transforming growth factor beta-activated kinase 1), a key MAP3K upstream of multiple inflammation-regulating pathways, drives Mi/MΦ toward a proinflammatory phenotype and potentiates ischemia/reperfusion brain injury. Methods- Young adult mice were subjected to 1 hour of middle cerebral artery occlusion (MCAO) followed by reperfusion. TAK1 was targeted by tamoxifen-induced Mi/MΦ-specific knockout or administration of a selective inhibitor 5Z-7-Oxozeaenol after MCAO. Neurobehavioral deficits and long-term gray matter and white matter injury were assessed up to 35 days after MCAO. Mi/MΦ functional status and brain inflammatory profiles were assessed 3 days after MCAO by RNA-seq, flow cytometry, and immunohistochemistry. Results- TAK1 Mi/MΦ-specific knockout markedly ameliorated neurological deficits in the rotarod and cylinder tests for at least 35 days after MCAO. Mechanistically, RNA-seq of purified brain Mi/MΦ demonstrated that proinflammatory genes and their predicted biological functions were downregulated or inhibited in microglia and macrophages from TAK1 Mi/MΦ-specific knockout mice versus WT mice 3 days after MCAO. Consistent with the anti-inflammatory phenotype of Mi/MΦ-specific knockout, oxozeaenol treatment mitigated neuroinflammation 3 days after MCAO, manifested by less Iba1+/CD16+ proinflammatory Mi/MΦ and suppressed brain invasion of various peripheral immune cells. Oxozeaenol treatment beginning 2 hours after MCAO improved long-term sensorimotor and cognitive functions in the foot fault, rotarod, and water maze tests. Furthermore, Oxozeaenol promoted both gray matter and white matter integrity 35 days after MCAO. Conclusions- TAK1 promotes ischemia/reperfusion-induced inflammation, brain injury, and maladaptive behavior by enhancing proinflammatory and deleterious Mi/MΦ responses. Therefore, TAK1 inhibition is a promising therapy to improve long-term stroke outcomes.

Identification and neuroprotective evaluation of a potential c-Jun N-terminal kinase 3 inhibitor through structure-based virtual screening and in-vitro assay.

The c-Jun N-terminal kinase 3 (JNK3) signaling cascade is activated during cerebral ischemia leading to neuronal damage. The present study was carried out to identify and evaluate novel JNK3 inhibitors using in-silico and in-vitro approach. A total of 380 JNK3 inhibitors belonging to different organic groups was collected from the previously reported literature. These molecules were used to generate a pharmacophore model. This model was used to screen a chemical database (SPECS) to identify newer molecules with similar chemical features. The top 1000 hits molecules were then docked against the JNK3 enzyme coordinate following GLIDE rigid receptor docking (RRD) protocol. Best posed molecules of RRD were used during induced-fit docking (IFD), allowing receptor flexibility. Other computational predictions such as binding free energy, electronic configuration and ADME/tox were also calculated. Inferences from the best pharmacophore model suggested that, in order to have specific JNK3 inhibitory activity, the molecules must possess one H-bond donor, two hydrophobic and two ring features. Docking studies suggested that the main interaction between lead molecules and JNK3 enzyme consisted of hydrogen bond interaction with methionine 149 of the hinge region. It was also observed that the molecule with better MM-GBSA dG binding free energy, had greater correlation with JNK3 inhibition. Lead molecule (AJ-292-42151532) with the highest binding free energy (dG = 106.8 Kcal/mol) showed better efficacy than the SP600125 (reference JNK3 inhibitor) during cell-free JNK3 kinase assay (IC50 = 58.17 nM) and cell-based neuroprotective assay (EC50 = 7.5 µM).