Genetic and Pharmacological Modulation of P75 Neurotrophin Receptor Attenuate Brain Damage After Ischemic Stroke in Mice.

The precursor nerve growth factor (ProNGF) and its receptor p75 neurotrophin receptor (p75NTR) are upregulated in several brain diseases, including ischemic stroke. The activation of p75NTR is associated with neuronal apoptosis and inflammation. Thus, we hypothesized that p75NTR modulation attenuates brain damage and improves functional outcomes after ischemic stroke. Two sets of experiments were performed. (1) Adult wild-type (WT) C57BL/6 J mice were subjected to intraluminal suture-middle cerebral artery occlusion (MCAO) to induce cerebral ischemia. Pharmacological inhibitor of p75NTR, LM11A-31 (50 mg/kg), or normal saline was administered intraperitoneally (IP) 1 h post-MCAO, and animals survived for 24 h. (2) Adult p75NTR heterozygous knockout (p75NTR+/-) and WT were subjected to photothrombotic (pMCAO) to induce ischemic stroke, and the animals survived for 72 h. The sensory-motor function of animals was measured using Catwalk XT. The brain samples were collected to assess infarction volume, edema, hemorrhagic transformation, neuroinflammation, and signaling pathway at 24 and 72 h after the stroke. The findings described that pharmacological inhibition and genetic knocking down of p75NTR reduce infarction size, edema, and hemorrhagic transformation following ischemic stroke. Additionally, p75NTR modulation significantly decreased several anti-apoptosis markers and improved sensory motor function compared to the WT mice following ischemic stroke. Our observations exhibit that the involvement of p75NTR in ischemic stroke and modulation of p75NTR could improve the outcome of ischemic stroke by increasing cell survival and enhancing motor performance. LM11A-31 has the potential to be a promising therapeutic agent for ischemic stroke. However, more evidence is needed to illuminate the efficacy of LM11A-31 in ischemic stroke.

Intranasal Delivery of Mitochondria Attenuates Brain Injury by AMPK and SIRT1/PGC-1α Pathways in a Murine Model of Photothrombotic Stroke.

Ischemic stroke is one of the major causes of morbidity and mortality worldwide. Mitochondria play a vital role in the pathological processes of cerebral ischemic injury, but its transplantation and underlying mechanisms remain unclear. In the present study, we examined the effects of mitochondrial therapy on the modulation of AMPK and SIRT1/PGC-1α signaling pathway, oxidative stress, and NLRP3 inflammasome activation after photothrombotic ischemic stroke (pt-MCAO). The adult male mice were subjected to the pt-MCAO in which the proximal-middle cerebral artery was exposed with a 532-nm laser beam for 4 min by retro-orbital injection of a photosensitive dye (Rose Bengal: 15 mg/kg) before the laser light exposure and isolated mitochondria (100 µg protein) were administered intranasally at 30 min, 24 h, and 48 h following post-stroke. After 72 h, mice were tested for neurobehavioral outcomes and euthanized for infarct volume, brain edema, and molecular analysis. First, we found that mitochondria therapy significantly decreased brain infarct volume and brain edema, improved neurological dysfunction, attenuated ischemic stroke-induced oxidative stress, and neuroinflammation. Second, mitochondria treatment inhibited NLRP3 inflammasome activation. Finally, mitochondria therapy accelerated p-AMPKα(Thr172) and PGC-1α expression and resorted SIRT1 protein expression levels in pt-MCAO mice. In conclusion, our results demonstrate that mitochondria therapy exerts neuroprotective effects by inhibiting oxidative damage and inflammation, mainly dependent on the heightening activation of the AMPK and SIRT1/PGC-1α signaling pathway. Thus, intranasal delivery of mitochondria might be considered a new therapeutic strategy for ischemic stroke treatment.

Pro-survival Phenotype of HIF-1α: Neuroprotection Through Inflammatory Mechanisms.

Hypoxia-inducible factor 1 (HIF-1) is a major player in the oxygen sensor system as well as a transcription factor. HIF-1 is also associated in the pathogenesis of many brain diseases including Alzheimer's disease (AD), epilepsy and stroke. HIF-1 regulates the expression of many genes such as those involved in glycolysis, erythropoiesis, angiogenesis and proliferation in hypoxic condition. Despite several studies, the mechanism through which HIF-1 confers neuroprotection remains unclear, one of them is modulating metabolic profiles and inflammatory pathways. Characterization of the neuroprotective role of HIF-1 may be through its stabilization and the regulation of target genes that aid in the early adaptation to the oxidative stressors. It is interesting to note that mounting data from recent years point to an additional crucial regulatory role for hypoxia-inducible factors (HIFs) in inflammation. HIFs in immune cells regulate the production of glycolytic energy as well as innate immunity, pro-inflammatory gene expression, and mediates activation of pro-survival pathways. The present review highlights the contribution of HIF-1 to neuroprotection where inflammation is the crucial factor in the pathogenesis contributing to neural death. The potential mechanisms that contribute to neuroprotection as a result of the downstream targets of HIF-1α are discussed. Such mechanisms include those mediated through IL-10, an anti-inflammatory molecule involved in activating pro-survival signaling mechanisms via AKT/ERK and JAK/STAT pathways.

A modified murine photothrombotic stroke model: a minimally invasive and reproducible cortical and sub-cortical infarct volume and long-term deficits.

Ischemic stroke is one of the major causes of devastating neurological disabilities and mortality worldwide. Despite extensive research for treatment approaches, there remains limited therapy in the stroke field. Therefore, more research is required for reproducibility to understand stroke pathology in pre-clinical studies. In the current modified method, mice were subjected to photothrombotic stroke (pt-MCA; proximal-middle cerebral artery was exposed with a 532 nm laser beam for 4 min) by retro-orbital injection of photosensitive dye, Rose Bengal (15 mg/kg) before the laser light exposure. Sensorimotor deficits were assessed by rotarod and catwalk test at 72 h following post-pt-MCAO, and brain samples were collected for infarct volume and hemorrhagic transformation (HT) assessments. Cognitive impairments were assessed by a novel objective recognition and Morris's water maze tests at the end of the follow-up. pt-MCAO animals significantly reduced body weight and impaired motor and cognitive functions. Furthermore, pt-MCAO animals showed apparent infarction, brain edema, and increased HT compared to the sham animals. Additionally, this method enables concurrent measurement of short-term and long-term neurological dysfunction with relatively larger cortical and sub-cortical infarct volume following pt-MCAO. With respect to the other models, this modified model offers enhanced reproducibility regarding infarct volume and cognitive/functional outcomes and avoids complications associated with critical surgeries and craniotomy. In conclusion, this modified model helps to understand stroke pathogenesis and minimize the animals' numbers which help to increase the scientific and statistical potential in pre-clinical studies.

Intra-arterial verapamil improves functional outcomes of thrombectomy in a preclinical model of extended hyperglycemic stroke.

The abrupt hyperglycemic reperfusion following thrombectomy has been shown to harm the efficacy of the intervention in stroke patients with large vessel occlusion. Studies of ours and others have shown thioredoxin-interacting protein (TXNIP) is critically involved in hyperglycemic stroke injury. We recently found verapamil ameliorates cerebrovascular toxicity of tissue plasminogen activators in hyperglycemic stroke. The present study aims to answer if verapamil exerts direct neuroprotective effects and alleviates glucose toxicity following thrombectomy in a preclinical model of hyperglycemic stroke. Primary cortical neural (PCN) cultures were exposed to hyperglycemic reperfusion following oxygen-glucose deprivation (OGD), with or without verapamil treatment. In a mouse model of intraluminal stroke, animals were subjected to 4 h middle cerebral artery occlusion (MCAO) and intravenous glucose infusion. Glucose infusion lasted one more hour at reperfusion, along with intra-arterial (i.a.) verapamil infusion. Animals were subjected to sensorimotor function tests and histological analysis of microglial phenotype at 72 h post-stroke. According to our findings, glucose concentrations (2.5-20 mM) directly correlated with TXNIP expression in OGD-exposed PCN cultures. Verapamil (100 nM) effectively improved PCN cell neurite growth and reduced TXNIP expression as well as interaction with NOD-like receptor pyrin domain-containing-3 (NLRP3) inflammasome, as determined by immunoblotting and immunoprecipitation. In our mouse model of extended hyperglycemic MCAO, i.a. verapamil (0.5 mg/kg) could attenuate neurological deficits induced by hyperglycemic stroke. This was associated with reduced microglial pro-inflammatory transition. This finding encourages pertinent studies in hyperglycemic patients undergoing thrombectomy where the robust reperfusion may exacerbate glucose toxicity.

Protective Role of Short-Chain Fatty Acids against Ang- II-Induced Mitochondrial Dysfunction in Brain Endothelial Cells: A Potential Role of Heme Oxygenase 2.

OBJECTIVES: Short-chain fatty acids (SCFAs), the main metabolites released from the gut microbiota, are altered during hypertension and obesity. SCFAs play a beneficial role in the cardiovascular system. However, the effect of SCFAs on cerebrovascular endothelial cells is yet to be uncovered. In this study, we use brain endothelial cells to investigate the in vitro effect of SCFAs on heme oxygenase 2 (HO-2) and mitochondrial function after angiotensin II (Ang-II) treatment. METHODS: Brain human microvascular endothelial cells were treated with Ang-II (500 nM for 24 h) in the presence and absence of an SCFAs cocktail (1 µM; acetate, propionate, and butyrate) and/or HO-2 inhibitor (SnPP 5 µM). At the end of the treatment, HO-2, endothelial markers (p-eNOS and NO production), inflammatory markers (TNFα, NFκB-p50, and -p65), calcium homeostasis, mitochondrial membrane potential, mitochondrial ROS and H2O2, and mitochondrial respiration were determined in all groups of treated cells. KEY RESULTS: Our data showed that SCFAs rescued HO-2 after Ang-II treatment. Additionally, SCFAs rescued Ang-II-induced eNOS reduction and mitochondrial membrane potential impairment and mitochondrial respiration damage. On the other hand, SCFAs reduced Ang-II-induced inflammation, calcium dysregulation, mitochondrial ROS, and H2O2. All of the beneficial effects of SCFAs on endothelial cells and mitochondrial function occurred through HO-2. CONCLUSIONS: SCFAs treatment restored endothelial cells and mitochondrial function following Ang-II-induced oxidative stress. SCFAs exert these beneficial effects by acting on HO-2. Our results are opening the door for more studies to investigate the effect the of SCFAs/HO-2 axis on hypertension and obesity-induced cerebrovascular diseases.

The p75 neurotrophin receptor inhibitor, LM11A-31, ameliorates acute stroke injury and modulates astrocytic proNGF.

The precursor form of nerve growth factor (proNGF) is essential to maintain NGF survival signaling. ProNGF is also among endogenous ligands for p75 neurotrophin receptor (p75ntr). Mounting evidence implies that p75ntr signaling contributes to neural damage in ischemic stroke. The present study examines the therapeutic effect of the p75ntr modulator LM11A-31. Adult mice underwent transient distal middle cerebral artery occlusion (t-dMCAO) followed by LM11A-31 treatment (25 mg/kg, i.p., twice daily) either for 72 h post-injury (acute phase) or afterward till two weeks post-stroke (subacute phase). LM11A-31 reduced blood-brain barrier permeability, cerebral tissue injury, and sensorimotor function in the acute phase of stroke. Ischemic brain samples showed repressed proNGF/P75ntr signaling and Caspase 3 activation in LM11A-31 treated mice, where we observed less reactive microglia and IL-1ß production. LM11A-31 (20-80 nM) also mitigated neural injury induced by oxygen-glucose deprivation (OGD) in sandwich co-cultures of primary cortical neurons (PCN) and astrocytes. This concurred with JNK/PARP downregulation and reduced caspase-3 cleavage in the PCNs and was associated with repressed proNGF generation in astrocytes. Further in vitro experiments indicated human proNGF suppresses the pro-inflammatory phenotype in microglial cultures, as determined by a sharp decline in HMGB-1 production and moderate arginase-1 upregulation. Despite significant protection in acute stroke, LM11A-31 treatment did not improve cortical atrophy and sensorimotor function in the subacute phase. Our findings provide preclinical evidence supporting LM11A-31 as a promising therapy for acute stroke injury. Further investigations may elucidate if reduced astrocytic proNGF, an endogenous reservoir of pro-neurotrophins, may restrict the therapeutic window.

Transplantation of Exercise-Induced Extracellular Vesicles as a Promising Therapeutic Approach in Ischemic Stroke.

Clinical evidence affirms physical exercise is effective in preventive and rehabilitation approaches for ischemic stroke. This sustainable efficacy is independent of cardiovascular risk factors and associates substantial reprogramming in circulating extracellular vesicles (EVs). The intricate journey of pluripotent exercise-induced EVs from parental cells to the whole-body and infiltration to cerebrovascular entity offers several mechanisms to reduce stroke incidence and injury or accelerate the subsequent recovery. This review delineates the potential roles of EVs as prospective effectors of exercise. The candidate miRNA and peptide cargo of exercise-induced EVs with both atheroprotective and neuroprotective characteristics are discussed, along with their presumed targets and pathway interactions. The existing literature provides solid ground to hypothesize that the rich vesicles link exercise to stroke prevention and rehabilitation. However, there are several open questions about the exercise stressors which may optimally regulate EVs kinetic and boost brain mitochondrial adaptations. This review represents a novel perspective on achieving brain fitness against stroke through transplantation of multi-potential EVs generated by multi-parental cells, which is exceptionally reachable in an exercising body.

Lost in Translation: Neurotrophins Biology and Function in the Neurovascular Unit.

The neurovascular unit (NVU) refers to the functional building unit of the brain and the retina, where neurons, glia, and microvasculature orchestrate to meet the demand of the retina's and brain's function. Neurotrophins (NTs) are structural families of secreted proteins and are known for exerting neurotrophic effects on neuronal differentiation, survival, neurite outgrowth, synaptic formation, and plasticity. NTs include several molecules, such as nerve growth factor, brain-derived neurotrophic factor, NT-3, NT-4, and their precursors. Furthermore, NTs are involved in signaling pathways such as inflammation, apoptosis, and angiogenesis in a nonneuronal cell type. Interestingly, NTs and the precursors can bind and activate the p75 neurotrophin receptor (p75NTR) at low and high affinity. Mature NTs bind their cognate tropomyosin/tyrosine-regulated kinase receptors, crucial for maintenance and neuronal development in the brain and retina axis. Activation of p75NTR results in neuronal apoptosis and cell death, while tropomysin receptor kinase upregulation contributes to differentiation and cell growth. Recent findings indicate that modulation of NTs and their receptors contribute to neurovascular dysfunction in the NVU. Several chronic metabolic and acute ischemic diseases affect the NVU, including diabetic and ischemic retinopathy for the retina, as well as stroke, acute encephalitis, and traumatic brain injury for the brain. This work aims to review the current evidence through published literature studying the impact of NTs and their receptors, including the p75NTR receptor, on the injured and healthy brain-retina axis.

Verapamil inhibits TXNIP-NLRP3 inflammasome activation and preserves functional recovery after intracerebral hemorrhage in mice.

Intracerebral hemorrhage (ICH) is the second most common type of stroke with no satisfactory treatment. Recent studies from our group and others indicated a potential positive effect of verapamil, a commonly prescribed calcium channel blocker, with thioredoxin-interacting protein (TXNIP) inhibitor properties, in ischemic stroke and cognitive disorders. It is unclear whether there would be a beneficial effect of verapamil administration in ICH. Therefore, this study was designed to determine the neuroprotective effects of verapamil in a murine ICH model. ICH was induced by stereotactic injection of collagenase type VII (0.075 U) into the right striatum of adult male C57BL/6 mice. Verapamil (0.15 mg/kg) or saline was administered intravenously at 1 h post-ICH followed by oral (1 mg/kg/d) administration in drinking water for 28 days. Motor and cognitive function were assessed using established tests for motor coordination, spatial learning, short- and long-term memory. A subset of animals was sacrificed at 72 h after ICH for molecular analysis. Verapamil treatment reduced expression of TXNIP and NOD-like receptor pyrin domain-containing-3 inflammasome activation in the perihematomal area. These protective effects of verapamil were associated with decreased proinflammatory mediators, microglial activation, and blood-brain barrier permeability markers and paralleled less phosphorylated nuclear factor kappa B level. Our findings also demonstrate that long-term low-dose verapamil effectively attenuated motor and cognitive impairments. Taken together, these data indicate that verapamil has therapeutic potential in improving acute motor function after ICH. Further investigations are needed to confirm whether verapamil treatment could be a promising candidate for clinical trials.

White matter damage as a consequence of vascular dysfunction in a spontaneous mouse model of chronic mild chronic hypoperfusion with eNOS deficiency.

Vascular cognitive impairment and dementia (VCID) is the second most common form of dementia after Alzheimer's disease (AD). Currently, the mechanistic insights into the evolution and progression of VCID remain elusive. White matter change represents an invariant feature. Compelling clinical neuroimaging and pathological evidence suggest a link between white matter changes and neurodegeneration. Our prior study detected hypoperfused lesions in mice with partial deficiency of endothelial nitric oxide (eNOS) at very young age, precisely matching to those hypoperfused areas identified in preclinical AD patients. White matter tracts are particularly susceptible to the vascular damage induced by chronic hypoperfusion. Using immunohistochemistry, we detected severe demyelination in the middle-aged eNOS-deficient mice. The demyelinated areas were confined to cortical and subcortical areas including the corpus callosum and hippocampus. The intensity of demyelination correlated with behavioral deficits of gait and associative recognition memory performances. By Evans blue angiography, we detected blood-brain barrier (BBB) leakage as another early pathological change affecting frontal and parietal cortex in eNOS-deficient mice. Sodium nitrate fortified drinking water provided to young and middle-aged eNOS-deficient mice completely prevented non-perfusion, BBB leakage, and white matter pathology, indicating that impaired endothelium-derived NO signaling may have caused these pathological events. Furthermore, genome-wide transcriptomic analysis revealed altered gene clusters most related to mitochondrial respiratory pathways selectively in the white matter of young eNOS-deficient mice. Using eNOS-deficient mice, we identified BBB breakdown and hypoperfusion as the two earliest pathological events, resulting from insufficient vascular NO signaling. We speculate that the compromised BBB and mild chronic hypoperfusion trigger vascular damage, along with oxidative stress and astrogliosis, accounting for the white matter pathological changes in the eNOS-deficient mouse model. We conclude that eNOS-deficient mice represent an ideal spontaneous evolving model for studying the earliest events leading to white matter changes, which will be instrumental to future therapeutic testing of drug candidates and for targeting novel/specific vascular mechanisms contributing to VCID and AD.

Candesartan Effectively Preserves Cognition in Senescence Accelerated Mouse Prone 8 (SAMP8) mice.

Background: Alzheimer's disease (AD) has become a worldwide crisis with no effective therapeutic options. The medications currently available for AD are only palliative; their effect is temporary, and they are associated with unfavorable side effects. Even the newest medication aducanumab, granted accelerated FDA approval in 2021, failed to show cognitive benefits in clinical trials and continued approval requires verification in subsequent clinical trials. There is an urgent need for safe and effective therapies to preserve cognition and effectively manage AD. Generally, a new drug product takes several years for FDA approval and exceeds 2.5 billion dollars in research and development, with most new drug products never even reaching the market. This has led to a recent shift for repurposing/repositioning existing FDA-approved medications, to new therapeutic indications. Objective: To investigate the effects of long-term treatment with candesartan, an FDA-approved angiotensin-II type-1 receptor blocker (ARB), on the development of cognitive impairment associated with premature aging. Methods: Candesartan was given at a dose of 1 mg/kg/d in an AD model of senescence-accelerated mouse prone-8 (SAMP8) and senescence-accelerated mouse resistant (SAMR1) mice. Oral treatment with candesartan or vehicle was started, in 2-month-old mice and administered continuously for 4-months. Results: Low-dose candesartan prevented the development of cognitive impairment, otherwise associated with accelerated aging, in SAMP8 mice, by reducing inflammation and nitro-oxidative stress. Candesartan did not affect the cognitive function of control SAMR1 mice. Conclusion: Early ARB treatment might be beneficial in preventing age-related cognitive deficits in AD-prone individuals.

Effects of pramipexole on beta-amyloid1-42 memory deficits and evaluation of oxidative stress and mitochondrial function markers in the hippocampus of Wistar rat.

Oxidative damage and mitochondrial dysfunction are two prominent pathological features and gradually understood as important pathogenic events for neurodegenerative diseases, including aging and Alzheimer's disease (AD). The present study was aimed to explore the prolonged treatment of pramipexole (PPX) following amyloid beta (Aß1-42)-induced cognitive impairments , oxidative stress, and mitochondrial dysfunction in a Wistar rat model. We have found that PPX (1.0 mg/kg, b.wt.) improves cognitive impairments of Aß1-42-infused rats in Morris water maze. At the same time, PPX attenuated Aß1-42-induced oxidative damage and increased reduced-glutathione content level, decreased lipid peroxidation rate and suppressed the activity of acetylcholinesterase and shows antioxidant effects. Additionally, PPX treatment has shown inhibition of mitochondrial reactive oxygen species production and restored mitochondrial membrane potential, oxidative phosphorylation, and enhanced ATP levels in Aß1-42 rats. Furthermore, PPX treatment reduced bioenergetics loss and dynamics alterations by upregulating PGC-1α protein level and mitigating translocation of Bax and Drp-1 to mitochondria and cytochrome-c release into the cytoplasm. PPX also increased mitofusin-2 protein expression, a basic element of mitochondrial fusion process. We conclude that remedial role of PPX in mitigating oxidative damage and mitochondrial perturbation that are modulated in Aß1-42 rats may have the propensity in AD pathogenesis.

Contralesional angiotensin type 2 receptor activation contributes to recovery in experimental stroke.

We and others have previously shown that angiotensin II receptor type 2 receptor (AT2R) is upregulated in the contralesional hemisphere after stroke in normoglycemic Wistar rats. In this study, we examined the expression of AT2R in type 2 diabetic Goto-Kakizaki (GK) rats and control Wistars after stroke. We also tested the contribution of the contralesional AT2R in recovery after stroke through a specific knockdown of the AT2R in this hemisphere only. Two experiments were conducted. In the first experiment, GK rats were subjected to middle cerebral artery occlusion (MCAO) and treated with the angiotensin II receptor type 1 receptor (AT1R) blocker candesartan or saline at reperfusion. Stroke outcomes, as well as AT2R expression, were examined and compared to control Wistars at 24 h. In the second experiment, localized AT2R knockdown was achieved through intrastriatal injection of short hairpin RNA (shRNA) lentiviral particles or non-targeting control into the left-brain hemisphere of Wistar rats. After 14 days, rats were subjected to right MCAO and treated with the AT2R agonist, Compound 21 (C21), or saline for 7 days. Behavioral outcomes were assessed for up to 10 days. In the first experiment, stroke reduced the expression of AT2R in GK rats. Candesartan treatment failed to improve the neurobehavioral outcomes, preserve vascular integrity or reduce oxidative/nitrative stress or apoptotic markers at 24 h post stroke in these animals. In the second experiment, contralesional AT2R knockdown reduced the C21-mediated functional recovery after stroke. In conclusion, contralesional AT2R upregulation after stroke is blunted in diabetic rats which show reduced sensitivity to post-stroke candesartan treatment. Contralesional AT2R could be involved in C21-mediated functional recovery after stroke.

Direct AT2R Stimulation Slows Post-stroke Cognitive Decline in the 5XFAD Alzheimer's Disease Mice.

Alzheimer's disease (AD), currently the single leading cause of death still on the rise, almost always coexists alongside vascular cognitive impairment (VCI). In fact, the ischemic disease affects up to 90% of AD patients, with strokes and major infarctions representing over a third of vascular lesions. Studies also confirmed that amyloid plaques, typical of AD, are much more likely to cause dementia if strokes or cerebrovascular damage also exist, leading to the term "mixed pathology" cognitive impairment. Although its incidence is expected to grow, there are no satisfactory treatments. There is hence an urgent need for safe and effective therapies that preserve cognition, maintain function, and prevent the clinical deterioration that results from the progression of this irreversible, neurodegenerative disease. To our knowledge, this is the first study to investigate the effects of long-term treatment with C21, a novel angiotensin II type 2 receptor (AT2R) agonist, on the development of "mixed pathology" cognitive impairment. This was accomplished using a unique model that employs the fundamental elements of both AD and VCI. Treatment with C21/vehicle was started 1 h post-stroke and continued for 5 weeks in mice with concurrent AD pathology. Efficacy was established through a series of functional tests assessing various aspects of cognition, including spatial learning, short-term/working memory, long-term/reference memory, and cognitive flexibility, in addition to the molecular markers characteristic of AD. Our findings demonstrate that C21 treatment preserves cognitive function, maintains cerebral blood flow, and reduces Aß accumulation and toxic tau phosphorylation in AD animals post-stroke.

A Systematic Review of Inflammatory Cytokine Changes Following Aneurysmal Subarachnoid Hemorrhage in Animal Models and Humans.

Aneurysmal subarachnoid hemorrhage (aSAH) is a severe form of stroke that occurs following rupture of a cerebral aneurysm. Acute inflammation and secondary delayed inflammatory responses, both largely controlled by cytokines, work together to create high mortality and morbidity for this group. The trajectory and time course of cytokine change must be better understood in order to effectively manage unregulated inflammation and improve patient outcomes following aSAH. A systematic review was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Three different search phrases ("cytokines and subarachnoid hemorrhage," "cytokine levels and subarachnoid hemorrhage," and "cytokine measurement and subarachnoid hemorrhage") were applied across three databases (PubMed, SCOPUS, and the Cochrane Library). Our procedures returned 856 papers. After application of inclusion/exclusion criteria, 95 preclinical animal studies and 41 clinical studies remained. Across studies, 22 different cytokines had been investigated, 5 different tissue types were analyzed, and 3 animal models were utilized. Three main pro-inflammatory cytokines (IL-1ß, IL-6, and TNF-α) demonstrated reliable increases following aSAH across the included studies. While this is a promising area of research for potential therapeutics, there are gaps in the knowledge base that bar progress for clinical translation of this information. In particular, there is a need for investigations that explore the systemic inflammatory response following injury in a more diverse number of cytokines, the balance of specific pro-/anti- inflammatory cytokines, and how these biomarkers relate to patient outcomes and recovery over time.

Acute Hyperglycemia Exacerbates Hemorrhagic Transformation after Embolic Stroke and Reperfusion with tPA: A Possible Role of TXNIP-NLRP3 Inflammasome.

OBJECTIVES: Acute hyperglycemia (HG) exacerbates reperfusion injury after stroke. Our recent studies showed that acute HG upregulates thioredoxin-interacting protein (TXNIP) expression, which in turn induces inflammation and neurovascular damage in a suture model of ischemic stroke. The aim of the present study was to investigate the effect of acute HG on TXNIP-associated neurovascular damage, in a more clinically relevant murine model of embolic stroke and intravenous tissue plasminogen activator (IV-tPA) reperfusion. MATERIALS AND METHODS: HG was induced in adult male mice, by intraperitoneal injection of 20% glucose. This was followed by embolic middle cerebral artery occlusion (eMCAO), with or without IV-tPA (10 mg/kg) given 3 h post embolization. Brain infarction, edema, hemoglobin content, expression of matrix metalloproteinase (MMP-9), vascular endothelial growth factor A (VEGFA), tight junction proteins (claudin-5, occluding, and zonula occludens-1), TXNIP, and NOD-like receptor protein3 (NLRP3)-inflammasome activation were evaluated at 24 h after eMCAO. RESULTS: HG alone significantly increased TXNIP in the brain after eMCAO, and this was associated with exacerbated hemorrhagic transformation (HT; as measured by hemoglobin content). IV-tPA in HG conditions showed a trend to decrease infarct volume, but worsened HT after eMCAO, suggesting that HG reduces the therapeutic efficacy of IV-tPA. Further, HG and tPA-reperfusion did not show significant differences in expression of MMP-9, VEGFA, junction proteins, and NLRP3 inflammasome activation between the groups. CONCLUSION: The current findings suggest a potential role for TXNIP in the occurrence of HT in hyperglycemic conditions following eMCAO. Further studies are needed to understand the precise role of vascular TXNIP on HG/tPA-induced neurovascular damage after stroke.

Compound 21, a Direct AT2R Agonist, Induces IL-10 and Inhibits Inflammation in Mice Following Traumatic Brain Injury.

Recent studies demonstrated that the angiotensin type 2 receptor (AT2R) agonist, compound 21 (C21), provides neuroprotection and enhances recovery in experimental stroke. However, C21 has never been tested in traumatic brain injury (TBI). Here, we aim to examine whether C21 confers protection after TBI. Unilateral cortical impact injury was induced in young adult C57BL/6 mice. C21 (0.03 mg/kg, i.p.) was administered at 1 h and 3 h post-TBI. After neurological severity score (NSS) assessments, all animals were sacrificed for immunoblotting analysis at 24 h post-TBI. C21 treatment significantly ameliorated NSS and reduced TBI's biomarkers [high mobility group box 1 (HMGB1), aquaporin-4 (AQ4)] and inflammatory markers [interlukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α)] in the pericontusional areas compared to saline TBI. Further, C21 treatment induced interleukin-10 (IL-10) and phosphorylation of endothelial nitric oxide synthase (eNOS) after TBI. C21 also attenuated pro-apoptotic activation of poly (ADP-ribose) polymerase (PARP) and caspase-3. These findings support the therapeutic potential of C21 against TBI.