Activation of microglia depends on Na+/H+ exchange-mediated H+ homeostasis

Lavandula angustifolia Mill. inhibits high glucose and nicotine-induced Ca2+ influx in microglia and neuron-like cells via two distinct mechanisms

Smoking remains a significant health problem in patients with type 2 diabetes mellitus. This study compared intracellular Ca2+ ([Ca2+]i) in microglia, neurons, and astrocytes in the presence of high glucose (HG) and nicotine and evaluated the effects of Lavandula angustifolia Mill. essential oil (LEO) on this process. [Ca2+]i concentrations were measured by monitoring the fluorescence of Fura-2 acetoxymethyl ester. Treatment with HG and nicotine significantly increased [Ca2+]i in both microglia and neurons through Ca2+ influx from extracellular sources. This increased Ca2+ influx in microglia, however, was significantly reduced by LEO, an effect partially inhibited by the Na+/Ca2+ exchanger (NCX) inhibitor Ni2+. Ca2+ influx in neuron-like cells pretreated with HG plus nicotine was also significantly decreased by LEO, an effect partially inhibited by the L-type Ca2+ channel blocker nifedipine and the T-type Ca2+ channel blocker mibefradil. LEO or a two-fold increase in the applied number of astrocytes attenuated Ca2+ influx caused by high glucose and nicotine in the mixed cells of the microglia, neuron-like cells and astrocytes. These findings suggest that LEO can regulate HG and nicotine-induced Ca2+ influx into microglia and neurons through two distinct mechanisms.

NHE1 Protein in Repetitive Mild TBI-Mediated Neuroinflammation and Neurological Function Impairment

Mild traumatic brain injuries (mTBIs) are highly prevalent and can lead to chronic behavioral and cognitive deficits often associated with the development of neurodegenerative diseases. Oxidative stress and formation of reactive oxygen species (ROS) have been implicated in mTBI-mediated axonal injury and pathogenesis. However, the underlying mechanisms and contributing factors are not completely understood. In this study, we explore these pathogenic mechanisms utilizing a murine model of repetitive mTBI (r-mTBI) involving five closed-skull concussions in young adult C57BL/6J mice. We observed a significant elevation of Na+/H+ exchanger protein (NHE1) expression in GFAP+ reactive astrocytes, IBA1+ microglia, and OLIG2+ oligodendrocytes across various brain regions (including the cerebral cortex, corpus callosum, and hippocampus) after r-mTBI. This elevation was accompanied by astrogliosis, microgliosis, and the accumulation of amyloid precursor protein (APP). Mice subjected to r-mTBI displayed impaired motor learning and spatial memory. However, post-r-mTBI administration of a potent NHE1 inhibitor, HOE642, attenuated locomotor and cognitive functional deficits as well as pathological signatures of gliosis, oxidative stress, axonal damage, and white matter damage. These findings indicate NHE1 upregulation plays a role in r-mTBI-induced oxidative stress, axonal damage, and gliosis, suggesting NHE1 may be a promising therapeutic target to alleviate mTBI-induced injuries and restore neurological function.

The Early Pathogenesis of Diabetic Retinopathy and Its Attenuation by Sodium-Glucose Transporter 2 Inhibitors

The early pathogenetic mechanism of diabetic retinopathy (DR) and its treatment remain unclear. Therefore, we used streptozotocin-induced diabetic mice to investigate the early pathogenic alterations in DR and the protective effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors against these alterations. Retinal vascular leakage was assessed by dextran fluorescence angiography. Retinal thickness and vascular leakage were increased 2 and 4 weeks after onset of diabetes, respectively. Immunostaining showed that morphological change of microglia (amoeboid form) was observed at 2 weeks. Subsequently, increased angiopoietin-2 expression, simultaneous loss of pericytes and endothelial cells, decreased vessel density, retinal hypoxia, and increased vascular endothelial growth factor (VEGF)-A/VEGF receptor system occurred at 4 weeks. SGLT2 inhibitors (luseogliflozin and ipragliflozin) had a significant protective effect on retinal vascular leakage and retinal thickness at a low dose that did not show glucose-lowering effects. Furthermore, both inhibitors at this dose attenuated microglia morphological changes and these early pathogenic alterations in DR. In vitro study showed both inhibitors attenuated the lipopolysaccharide-induced activation of primary microglia, along with morphological changes toward an inactive form, suggesting the direct inhibitory effect of SGLT2 inhibitors on microglia. In summary, SGLT2 inhibitors may directly prevent early pathogenic mechanisms, thereby potentially playing a role in preventing DR.

ARTICLE HIGHLIGHTS

Resveratrol alleviates endoplasmic reticulum stress-induced cell death and improves functional prognosis after traumatic brain injury in mice

Resveratrol (RSV) is a polyphenol antioxidant that has been shown to have neuroprotective effects. We sought molecular mechanisms that emphasize the anti-inflammatory activity of RSV in traumatic brain injury (TBI) in mice associated with endoplasmic reticulum stress (ERS). After establishing three experimental groups (sham, TBI, and TBI+RSV), we explored the results of RSV after TBI on ERS and caspase-12 apoptotic pathways. The expression levels of C/EBP homologous protein (CHOP), glucose regulated protein 78kD (GRP78), caspase-3, and caspase-12 in cortical brain tissues were assessed by western blotting. The qPCR analysis was also performed on mRNA expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β in cortical brain tissue. In addition, the expression of GRP78 in microglia (ionized calcium binding adaptor molecule 1; Iba-1) and neurons (neuronal nuclei; NeuN) was identified by immunofluorescence staining. The neurological function of mice was assessed by modified neurological severity scores (mNSS). After drug treatment, the expression of CHOP, GRP78, caspase-3 and caspase-12 decreased, and qPCR results showed that TNF-α and IL-1β were down-regulated. Immunofluorescence staining showed down-regulation of Iba-1+/GRP78+ and NeuN+/GRP78+ cells after RSV treatment. The mNSS analysis confirmed improvement after RSV treatment. RSV improved apoptosis by downregulating the ERS signaling pathway and improved neurological prognosis in mice with TBI.

Deletion of Slc9a1 in Cx3cr1+ cells stimulated microglial subcluster CREB1 signaling and microglia-oligodendrocyte crosstalk

Microglial Na/H exchanger-1 (NHE1) protein, encoded by Slc9a1, plays a role in white matter demyelination of ischemic stroke brains. To explore underlying mechanisms, we conducted single cell RNA-seq transcriptome analysis in conditional Slc9a1 knockout (cKO) and wild-type (WT) mouse white matter tissues at 3 days post-stroke. Compared to WT, Nhe1 cKO brains expanded a microglial subgroup with elevated transcription of white matter myelination genes including Spp1, Lgals3, Gpnmb, and Fabp5. This subgroup also exhibited more acidic pHi and significantly upregulated CREB signaling detected by ingenuity pathway analysis and flow cytometry. Moreover, the Nhe1 cKO white matter tissues showed enrichment of a corresponding oligodendrocyte subgroup, with pro-phagocytosis and lactate shuffling gene expression, where activated CREB signaling is a likely upstream regulator. These findings demonstrate that attenuation of NHE1-mediated H+ extrusion acidifies microglia/macrophage and may underlie the stimulation of CREB1 signaling, giving rise to restorative microglia-oligodendrocyte interactions for remyelination.

Microglial reactivity in brainstem chemosensory nuclei in response to hypercapnia

Microglia, the resident immune cells of the CNS, surveil, detect, and respond to various extracellular signals. Depending on the nature of these signals, an integrative microglial response can be triggered, resulting in a phenotypic transformation. Here, we evaluate whether hypercapnia modifies microglia phenotype in brainstem respiratory-related nuclei. Adult C57BL/6 inbred mice were exposed to 10% CO2 enriched air (hypercapnia), or pure air (control), for 10 or 30 min and immediately processed for immunohistochemistry to detect the ubiquitous microglia marker, ionized calcium binding adaptor molecule 1 (Iba1). Hypercapnia for thirty, but not 10 min reduced the Iba1 labeling percent coverage in the ventral respiratory column (VRC), raphe nucleus (RN), and nucleus tractus solitarius (NTS) and the number of primary branches in VRC. The morphological changes persisted, at least, for 60 min breathing air after the hypercapnic challenge. No significant changes were observed in Iba1+ cells in the spinal trigeminal nucleus (Sp5) and the hippocampus. In CF-1 outbred mice, 10% CO2 followed by 60 min of breathing air, resulted in the reduction of Iba1 labeling percent coverage and the number and length of primary branches in VRC, RN, and NTS. No morphological change was observed in Iba1+ cells in Sp5 and hippocampus. Double immunofluorescence revealed that prolonged hypercapnia increased the expression of CD86, an inflammatory marker for reactive state microglia, in Iba1+ cells in VRC, RN, and NTS, but not in Sp5 and hippocampus in CF-1 mice. By contrast, the expression of CD206, a marker of regulatory state microglia, persisted unmodified. In brainstem, but not in hippocampal microglia cultures, hypercapnia increased the level of IL1β, but not that of TGFβ measured by ELISA. Our results show that microglia from respiratory-related chemosensory nuclei, are reactive to prolonged hypercapnia acquiring an inflammatory-like phenotype.

An overview of mild traumatic brain injuries and emerging therapeutic targets

The majority of traumatic brain injuries (TBIs), approximately 90%, are classified as mild (mTBIs). Globally, an estimated 4 million injuries occur each year from concussions or mTBIs, highlighting their significance as a public health crisis. TBIs can lead to substantial long-term health consequences, including an increased risk of developing Alzheimer's Disease, Parkinson's Disease (PD), chronic traumatic encephalopathy (CTE), and nearly doubling one's risk of suicide. However, the current management of mTBIs in clinical practice and the available treatment options are limited. There exists an unmet need for effective therapy. This review addresses various aspects of mTBIs based on the most up-to-date literature review, with the goal of stimulating translational research to identify new therapeutic targets and improve our understanding of pathogenic mechanisms. First, we provide a summary of mTBI symptomatology and current diagnostic parameters such as the Glasgow Coma Scale (GCS) for classifying mTBIs or concussions, as well as the utility of alternative diagnostic parameters, including imaging techniques like MRI with diffusion tensor imaging (DTI) and serum biomarkers such as S100B, NSE, GFAP, UCH-L1, NFL, and t-tau. Our review highlights several pre-clinical concussion models employed in the study of mTBIs and the underlying cellular mechanisms involved in mTBI-related pathogenesis, including axonal damage, demyelination, inflammation, and oxidative stress. Finally, we examine a selection of new therapeutic targets currently under investigation in pre-clinical models. These targets may hold promise for clinical translation and address the pressing need for more effective treatments for mTBIs.

SGLT2 Inhibitor Canagliflozin Alleviates High Glucose-Induced Inflammatory Toxicity in BV-2 Microglia

Patients with diabetes mellitus can experience hyperglycemia, which affects brain function and produces cognitive impairment or neurodegeneration. Neuroinflammation is an important cause of cognitive dysfunction. Sodium-glucose cotransporter 2 (SGLT2) inhibitors are antihyperglycemic agents that reportedly possess anti-inflammatory properties and may produce beneficial cognitive effects. We hypothesized that SGLT2 inhibitors alleviate hyperglycemia-related inflammation in brain immune cells. Cultured BV-2 microglia were exposed to high glucose (HG) in the absence or presence of SGLT2 inhibitors including canagliflozin (Cana), dapagliflozin (Dapa), empagliflozin (Empa), and ertugliflozin (Ertu). Afterward, we evaluated the cytotoxic and inflammatory responses by specific biochemical assays. Treatments with non-toxic Cana or Dapa, but not Empa or Ertu, inhibited proliferation without cell death. Only Cana rescued BV-2 microglia from HG-induced cytotoxicity, including apoptosis or autophagic degradation. None of SGLT2 inhibitors affected the HG-stimulated induction of stress proteins HO-1 and HSP70. Also, compared to the other three SGLT2 inhibitors, Cana was better at inhibiting HG-induced oxidative/inflammatory stress, as evidenced by its ability to repress proinflammatory factors (e.g., oxygen free radicals, iNOS, NLRP3, IL-1β, and TNF-α) other than COX-2. Cana's action to alleviate HG insults was mediated not by altering SGLT2 protein expression, but by reducing HG-stimulated signaling activities of NFκB, JNK, p38, and PI3K/Akt pathways. Particularly, Cana imitated the effects of NFκB inhibitor on HG-induced iNOS and COX-2. Of the four SGLT2 inhibitors, Cana provided BV-2 microglia with the best protection against HG-induced inflammatory toxicity. Thus, Cana may help to reduce innate neuroimmune damage caused by hyperglycemia.

Pharmacological Inhibition of NHE1 Protein Increases White Matter Resilience and Neurofunctional Recovery after Ischemic Stroke

To date, recanalization interventions are the only available treatments for ischemic stroke patients; however, there are no effective therapies for reducing stroke-induced neuroinflammation. We recently reported that H+ extrusion protein Na+/H+ exchanger-1 (NHE1) plays an important role in stroke-induced inflammation and white matter injury. In this study, we tested the efficacy of two potent NHE1 inhibitors, HOE642 and Rimeporide, with a delayed administration regimen starting at 24 h post-stroke in adult C57BL/6J mice. Post-stroke HOE642 and Rimeporide treatments accelerated motor and cognitive function recovery without affecting the initial ischemic infarct, neuronal damage, or reactive astrogliosis. However, the delayed administration of NHE1 blockers after ischemic stroke significantly reduced microglial inflammatory activation while enhanced oligodendrogenesis and white matter myelination, with an increased proliferation and decreased apoptosis of the oligodendrocytes. Our findings suggest that NHE1 protein plays an important role in microglia-mediated inflammation and white matter damage. The pharmacological blockade of NHE1 protein activity reduced microglia inflammatory responses and enhanced oligodendrogenesis and white matter repair, leading to motor and cognitive function recovery after stroke. Our study reveals the potential of targeting NHE1 protein as a therapeutic strategy for ischemic stroke therapy.

Guanidine Derivatives of Quinazoline-2,4(1H,3H)-Dione as NHE-1 Inhibitors and Anti-Inflammatory Agents

Quinazolines are a rich source of bioactive compounds. Previously, we showed NHE-1 inhibitory, anti-inflammatory, antiplatelet, intraocular pressure lowering, and antiglycating activity for a series of quinazoline-2,4(1H,3H)-diones and quinazoline-4(3H)-one guanidine derivatives. In the present work, novel N1,N3-bis-substituted quinazoline-2,4(1H,3H)-dione derivatives bearing two guanidine moieties were synthesized and pharmacologically profiled. The most potent NHE-1 inhibitor 3a also possesses antiplatelet and intraocular-pressure-reducing activity. Compound 4a inhibits NO synthesis and IL-6 secretion in murine macrophages without immunotoxicity and alleviates neutrophil infiltration, edema, and tissue lesions in a model of LPS-induced acute lung injury. Hence, we considered quinazoline derivative 4a as a potential agent for suppression of cytokine-mediated inflammatory response and acute lung injury.

Microglial-oligodendrocyte interactions in myelination and neurological function recovery after traumatic brain injury

Differential microglial inflammatory responses play a role in regulation of differentiation and maturation of oligodendrocytes (OLs) in brain white matter. How microglia-OL crosstalk is altered by traumatic brain injury (TBI) and its impact on axonal myelination and neurological function impairment remain poorly understood. In this study, we investigated roles of a Na⁺/H⁺ exchanger (NHE1), an essential microglial pH regulatory protein, in microglial proinflammatory activation and OL survival and differentiation in a murine TBI model induced by controlled cortical impact. Similar TBI-induced contusion volumes were detected in the Cx3cr1-Cre^ERT2 control (Ctrl) mice and selective microglial Nhe1 knockout (Cx3cr1-Cre^ERT2;Nhe1^flox/flox, Nhe1 cKO) mice. Compared to the Ctrl mice, the Nhe1 cKO mice displayed increased resistance to initial TBI-induced white matter damage and accelerated chronic phase of OL regeneration at 30 days post-TBI. The cKO brains presented increased anti-inflammatory phenotypes of microglia and infiltrated myeloid cells, with reduced proinflammatory transcriptome profiles. Moreover, the cKO mice exhibited accelerated post-TBI sensorimotor and cognitive functional recovery than the Ctrl mice. These phenotypic outcomes in cKO mice were recapitulated in C57BL6J wild-type TBI mice receiving treatment of a potent NHE1 inhibitor HOE642 for 1-7 days post-TBI. Taken together, these findings collectively demonstrated that blocking NHE1 protein stimulates restorative microglial activation in oligodendrogenesis and neuroprotection, which contributes to accelerated brain repair and neurological function recovery after TBI.

Anti-Inflammatory Properties of the SGLT2 Inhibitor Empagliflozin in Activated Primary Microglia

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, including empagliflozin, are routinely used as antidiabetic drugs. Recent studies indicate that beside its beneficial effects on blood glucose level, empagliflozin may also exert vascular anti-inflammatory and neuroprotective properties. In the brain, microglia are crucial mediators of inflammation, and neuroinflammation plays a key role in neurodegenerative disorders. Dampening microglia-mediated inflammation may slow down disease progression. In this context, we investigated the immunomodulatory effect of empagliflozin on activated primary microglia. As a validated experimental model, rat primary microglial cells were activated into a pro-inflammatory state by stimulation with LPS. The influence of empagliflozin on the expression of pro-inflammatory mediators (NO, Nos2, IL6, TNF, IL1B) and on the anti-inflammatory mediator IL10 was assessed using quantitative PCR and ELISA. Further, we investigated changes in the activation of the ERK1/2 cascade by Western blot and NFkB translocation by immunostaining. We observed that empagliflozin reduces the expression of pro- and anti-inflammatory mediators in LPS-activated primary microglia. These effects might be mediated by NHE-1, rather than by SGLT2, and by the further inhibition of the ERK1/2 and NFkB pathways. Our results support putative anti-inflammatory effects of empagliflozin on microglia and suggest that SGLT2 inhibitors may exert beneficial effects in neurodegenerative disorders.

NOX activation in reactive astrocytes regulates astrocytic LCN2 expression and neurodegeneration

Reactive astrocytes (RA) secrete lipocalin-2 (LCN2) glycoprotein that regulates diverse cellular processes including cell death/survival, inflammation, iron delivery and cell differentiation. Elevated levels of LCN2 are considered as a biomarker of brain injury, however, the underlying regulatory mechanisms of its expression and release are not well understood. In this study, we investigated the role of astrocytic Na+/H+ exchanger 1 (NHE1) in regulating reactive astrocyte LCN2 secretion and neurodegeneration after stroke. Astrocyte specific deletion of Nhe1 in Gfap-CreER+/-;Nhe1f/f mice reduced astrogliosis and astrocytic LCN2 and GFAP expression, which was associated with reduced loss of NeuN+ and GRP78+ neurons in stroke brains. In vitro ischemia in astrocyte cultures triggered a significant increase of secreted LCN2 in astrocytic exosomes, which caused neuronal cell death and neurodegeneration. Inhibition of NHE1 activity during in vitro ischemia with its potent inhibitor HOE642 significantly reduced astrocytic LCN2+ exosome secretion. In elucidating the cellular mechanisms, we found that stroke triggered activation of NADPH oxidase (NOX)-NF-κB signaling and ROS-mediated LCN2 expression. Inhibition of astrocytic NHE1 activity attenuated NOX signaling and LCN2-mediated neuronal apoptosis and neurite degeneration. Our findings demonstrate for the first time that RA use NOX signaling to stimulate LCN2 expression and secretion. Blocking astrocytic NHE1 activity is beneficial to reduce LCN2-mediated neurotoxicity after stroke.

Poly d,l-(lactic-co-glycolic) Acid PEGylated Isoliquiritigenin Alleviates Traumatic Brain Injury by Reversing Cyclooxygenase 2 Level

As a severe neurological disease of trauma, traumatic brain injury (TBI) leads to other disorders, such as depression, dementia and epilepsy. This study investigated whether poly d,l-(lactic-co-glycolic) acid (PLGA) PEGylated isoliquiritigenin could alleviate TBI. One hundred and eighty-three patients with clinical brain trauma were divided into two groups with or without intracranial injury in magnetic resonance imaging. The clinical results showed that serum cyclooxygenase 2 (COX-2) levels were obviously increased in the TBI patients compared to the patients with head trauma only or healthy individuals. Intracranial injection of isoliquiritigenin in TBI rats reversed TBI induced increase of COX-2 level, significantly reduced water content and contusion volume. Our findings suggest that PLGA PEG nanoparticles loaded with isoliquiritigenin can achieve the same effects as intracranial administration of isoliquiritigenin in reducing serum COX-2 level.

Elevated microglial oxidative phosphorylation and phagocytosis stimulate post-stroke brain remodeling and cognitive function recovery in mice

New research shows that disease-associated microglia in neurodegenerative brains present features of elevated phagocytosis, lysosomal functions, and lipid metabolism, which benefit brain repair. The underlying mechanisms remain poorly understood. Intracellular pH (pH_i) is important for regulating aerobic glycolysis in microglia, where Na/H exchanger (NHE1) is a key pH regulator by extruding H⁺ in exchange of Na⁺ influx. We report here that post-stroke Cx3cr1-Cre^ER+/-;Nhe1^flox/flox (Nhe1 cKO) brains displayed stimulation of microglial transcriptomes of rate-limiting enzyme genes for glycolysis, tricarboxylic acid cycle, and oxidative phosphorylation. The other upregulated genes included genes for phagocytosis and LXR/RXR pathway activation as well as the disease-associated microglia hallmark genes (Apoe, Trem2, Spp1). The cKO microglia exhibited increased oxidative phosphorylation capacity, and higher phagocytic activity, which likely played a role in enhanced synaptic stripping and remodeling, oligodendrogenesis, and remyelination. This study reveals that genetic blockade of microglial NHE1 stimulated oxidative phosphorylation immunometabolism, and boosted phagocytosis function which is associated with tissue remodeling and post-stroke cognitive function recovery.

Synthesis and multifaceted pharmacological activity of novel quinazoline NHE-1 inhibitors

The Na⁺/H⁺ exchanger isoform 1 (NHE-1) attracts ongoing attention as a validated drug target for the management of cardiovascular and ocular diseases owing to cytoprotective, anti-ischemic and anti-inflammatory properties of NHE-1 inhibitors. Herein we report novel NHE-1 inhibitors realized via functionalization of N¹-alkyl quinazoline-2,4(1H,3H)-dione and quinazoline-4(3H)-one with N-acylguanidine or 3-acyl(5-amino-1,2,4-triazole) side chain. Lead compounds show activity in a nanomolar range. Their pharmacophoric features were elucidated with neural network modeling. Several compounds combine NHE-1 inhibition with antiplatelet activity. Compound 6b reduces intraocular pressure in rats and effectively inhibits the formation of glycated proteins. Compounds 3e and 3i inhibit pro-inflammatory activation of murine macrophages, LPS-induced interleukin-6 secretion and also exhibit antidepressant activity similar to amiloride. Hence, novel compounds represent an interesting starting point for the development of agents against cardiovascular diseases, thrombotic events, excessive inflammation, long-term diabetic complications and glaucoma.

Cerebral Edema Formation After Stroke: Emphasis on Blood-Brain Barrier and the Lymphatic Drainage System of the Brain

Brain edema is a severe stroke complication that is associated with prolonged hospitalization and poor outcomes. Swollen tissues in the brain compromise cerebral perfusion and may also result in transtentorial herniation. As a physical and biochemical barrier between the peripheral circulation and the central nervous system (CNS), the blood–brain barrier (BBB) plays a vital role in maintaining the stable microenvironment of the CNS. Under pathological conditions, such as ischemic stroke, the dysfunction of the BBB results in increased paracellular permeability, directly contributing to the extravasation of blood components into the brain and causing cerebral vasogenic edema. Recent studies have led to the discovery of the glymphatic system and meningeal lymphatic vessels, which provide a channel for cerebrospinal fluid (CSF) to enter the brain and drain to nearby lymph nodes and communicate with the peripheral immune system, modulating immune surveillance and brain responses. A deeper understanding of the function of the cerebral lymphatic system calls into question the known mechanisms of cerebral edema after stroke. In this review, we first discuss how BBB disruption after stroke can cause or contribute to cerebral edema from the perspective of molecular and cellular pathophysiology. Finally, we discuss how the cerebral lymphatic system participates in the formation of cerebral edema after stroke and summarize the pathophysiological process of cerebral edema formation after stroke from the two directions of the BBB and cerebral lymphatic system.

Attenuating vascular stenosis-induced astrogliosis preserves white matter integrity and cognitive function

BACKGROUND

Chronic cerebral hypoperfusion (CCH) causes white matter damage and cognitive impairment, in which astrogliosis is the major pathology. However, underlying cellular mechanisms are not well defined. Activation of Na+/H+ exchanger-1 (NHE1) in reactive astrocytes causes astrocytic hypertrophy and swelling. In this study, we examined the role of NHE1 protein in astrogliosis, white matter demyelination, and cognitive function in a murine CCH model with bilateral carotid artery stenosis (BCAS).

METHODS

Sham, BCAS, or BCAS mice receiving vehicle or a selective NHE1 inhibitor HOE642 were monitored for changes of the regional cerebral blood flow and behavioral performance for 28 days. Ex vivo MRI-DTI was subsequently conducted to detect brain injury and demyelination. Astrogliosis and demyelination were further examined by immunofluorescence staining. Astrocytic transcriptional profiles were analyzed with bulk RNA-sequencing and RT-qPCR.

RESULTS

Chronic cerebral blood flow reduction and spatial working memory deficits were detected in the BCAS mice, along with significantly reduced mean fractional anisotropy (FA) values in the corpus callosum, external capsule, and hippocampus in MRI DTI analysis. Compared with the sham control mice, the BCAS mice displayed demyelination and axonal damage and increased GFAP+ astrocytes and Iba1+ microglia. Pharmacological inhibition of NHE1 protein with its inhibitor HOE642 prevented the BCAS-induced gliosis, damage of white matter tracts and hippocampus, and significantly improved cognitive performance. Transcriptome and immunostaining analysis further revealed that NHE1 inhibition specifically attenuated pro-inflammatory pathways and NADPH oxidase activation.

CONCLUSION

Our study demonstrates that NHE1 protein is involved in astrogliosis with pro-inflammatory transformation induced by CCH, and its blockade has potentials for reducing astrogliosis, demyelination, and cognitive impairment.

Salvianolic Acids for Injection alleviates cerebral ischemia/reperfusion injury by switching M1/M2 phenotypes and inhibiting NLRP3 inflammasome/pyroptosis axis in microglia in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

After cerebral ischemia/reperfusion injury, pro-inflammatory M1 and anti-inflammatory M2 phenotypes of microglia are involved in neuroinflammation, in which activation of NLRP3 inflammasome and subsequent pyroptosis play essential roles. Salvianolic Acids for Injection (SAFI) is Chinese medicine injection which composed of multiple phenolic acids extracted from Radix Salviae Miltiorrhizae, and has been reported to generate neuroprotective effects after cerebral ischemic insult in clinical and animal studies.

AIM OF THE STUDY

The present study was designed to investigate whether SAFI exerts neuroprotective effects by switching microglial phenotype and inhibiting NLRP3 inflammasome/pyroptosis axis in microglia.

MATERIALS AND METHODS

The middle cerebral artery occlusion/reperfusion (MCAO/R) model in rats and oxygen-glucose deprivation/reoxygenation (OGD/R) model in co-cultured primary neurons and primary microglia were utilized. The neuroprotective effect of SAFI was evaluated through measuring neurological deficit scores, neuropathological changes, inflammatory factors, cell phenotype markers, and related proteins of NLRP3 inflammasome/pyroptosis axis.

RESULTS

The results showed that SAFI treatment was able to: (1) produce a significant increase in neurological deficit scores and decrease in infarct volumes, and alleviate histological injury and neuronal apoptosis in cerebral cortex in MCAO/R model; (2) increase neuronal viability and reduce neuronal apoptosis in the OGD model; (3) reshape microglial polarization patterns from M1-like phenotype to M2-like phenotype; (4) inhibit the activation of the NLRP3 inflammasome and the expression of proteins related to NLRP3 inflammasome/pyroptosis axis in vivo and in vitro.

CONCLUSION

These findings indicate that SAFI exert neuroprotective effect, probably via reducing neuronal apoptosis, switching microglial phenotype from M1 towards M2, and inhibiting NLRP3 inflammasome/pyroptosis axis in microglia.

Inhibition of Na+/H+exchanger modulates microglial activation and scar formation following microelectrode implantation

Objective.Intracortical microelectrodes are an important tool for neuroscience research and have great potential for clinical use. However, the use of microelectrode arrays to treat neurological disorders and control prosthetics is limited by biological challenges such as glial scarring, which can impair chronic recording performance. Microglia activation is an early and prominent contributor to glial scarring. After insertion of an intracortical microelectrode, nearby microglia transition into a state of activation, migrate, and encapsulate the device. Na⁺/H⁺exchanger isoform-1 (NHE-1) is involved in various microglial functions, including their polarity and motility, and has been implicated in pro-inflammatory responses to tissue injury. HOE-642 (cariporide) is an inhibitor of NHE-1 and has been shown to depress microglial activation and inflammatory response in brain injury models.Approach.In this study, the effects of HOE-642 treatment on microglial interactions to intracortical microelectrodes was evaluated using two-photon microscopyin vivo.Main results.The rate at which microglia processes and soma migrate in response to electrode implantation was unaffected by HOE-642 administration. However, HOE-642 administration effectively reduced the radius of microglia activation at 72 h post-implantation from 222.2µm to 177.9µm. Furthermore, treatment with HOE-642 significantly reduced microglial encapsulation of implanted devices at 5 h post-insertion from 50.7 ± 6.0% to 8.9 ± 6.1%, which suggests an NHE-1-specific mechanism mediating microglia reactivity and gliosis during implantation injury.Significance.This study implicates NHE-1 as a potential target of interest in microglial reactivity and HOE-642 as a potential treatment to attenuate the glial response and scar formation around implanted intracortical microelectrodes.

Snapshot of microglial physiological functions

Microglia as a defensive arm of the nervous system emerged early in evolution. The surveilling microglia with motile and ramified processes are the main phenotype in the healthy CNS; the surveilling microglial patrol neuronal somata, dendrites, dendritic spines and axons. Increasing evidence suggests that microglia play fundamental roles in development, maturation and ageing of the brain, as well as contribute to a variety of physiological brain processes including sleep and circadian rhythm. Physiological state of microglia is tightly regulated by brain microenvironment and controlled by a sophisticated system of receptors and signalling cascades including ionotropic and metabotropic purinoceptors, pattern-recognition receptors, and receptors for chemokines and cytokines. Microglia also utilise ion channels and transporters in regulating ionic homeostasis and various aspects of microglial function. The major ion transporters expressed by microglia include Na⁺/H⁺ exchanger 1 and Na⁺/Ca²⁺ exchangers, which are involved in regulation of pH_i and Ca²⁺ homeostasis during microglial physiological responses. Microglial cells control development, maturation and plasticity of neuronal ensembles through controlled physiological phagocytosis of synapses or synaptic fragments - processes known as synaptic pruning and trogocytosis. This special issue on "Physiological roles of microglia" is an assembly of papers written by the leading experts in this research field. We start this special issue with this snapshot of microglial physiological functions as a prelude to the indepth discussion of microglia in physiological processes in the nervous system.

Phagocytic activity of splenic macrophages is enhanced and accompanied by cytosolic alkalinization in TRPM7 kinase-dead mice

Transient receptor potential melastatin 7 (TRPM7) is a unique protein functioning as a cation channel as well as a serine/threonine kinase and is highly expressed in immune cells such as lymphocytes and macrophages. TRPM7 kinase-dead (KD) mouse model has been used to investigate the role of this protein in immune cells; these animals display moderate splenomegaly and ectopic hemopoiesis. The basal TRPM7 current magnitudes in peritoneal macrophages isolated from KD mice were higher; however, the maximum currents, achieved after cytoplasmic Mg²⁺ washout, were not different. In the present study, we investigated the consequences of TRPM7 kinase inactivation in splenic and peritoneal macrophages. We measured the basal phagocytic activity of splenic macrophages using fluorescent latex beads, pHrodo zymosan bioparticles, and opsonized red blood cells. KD macrophages phagocytized more efficiently and had slightly higher baseline calcium levels compared to WT cells. We found no obvious differences in store-operated Ca²⁺ entry between WT and KD macrophages. By contrast, the resting cytosolic pH in KD macrophages was significantly more alkaline than in WT. Pharmacological blockade of sodium hydrogen exchanger 1 (NHE1) reversed the cytosolic alkalinization and reduced phagocytosis in KD macrophages. Basal TRPM7 channel activity in KD macrophages was also reduced after NHE1 blockade. Cytosolic Mg²⁺ sensitivity of TRPM7 channels measured in peritoneal macrophages was similar in WT and KD mice. The higher basal TRPM7 channel activity in KD macrophages is likely due to alkalinization. Our results identify a novel role for TRPM7 kinase as a suppressor of basal phagocytosis and a regulator of cellular pH.

Ion channels and transporters in microglial function in physiology and brain diseases

Microglial cells interact with all components of the central nervous system (CNS) and are increasingly recognized to play essential roles during brain development, homeostasis and disease pathologies. Functions of microglia include maintaining tissue integrity, clearing cellular debris and dead neurons through the process of phagocytosis, and providing tissue repair by releasing anti-inflammatory cytokines and neurotrophic factors. Changes of microglial ionic homeostasis (Na⁺, Ca²⁺, K⁺, H⁺, Cl^-) are important for microglial activation, including proliferation, migration, cytokine release and reactive oxygen species production, etc. These are mediated by ion channels and ion transporters in microglial cells. Here, we review the current knowledge about the role of major microglial ion channels and transporters, including several types of Ca²⁺ channels (store-operated Ca²⁺ entry (SOCE) channels, transient receptor potential (TRP) channels and voltage-gated Ca²⁺ channels (VGCCs)) and Na⁺ channels (voltage-gated Na⁺ channels (Nav) and acid-sensing ion channels (ASICs)), K⁺ channels (inward rectifier K⁺ channels (K_ir), voltage-gated K⁺ channels (K_V) and calcium-activated K⁺ channels (K_Ca)), proton channels (voltage-gated proton channel (Hv1)), and Cl^- channels (volume (or swelling)-regulated Cl^- channels (VRCCs) and chloride intracellular channels (CLICs)). In addition, ion transporter proteins such as Na⁺/Ca²⁺ exchanger (NCX), Na⁺-K⁺-Cl^- cotransporter (NKCC1), and Na⁺/H⁺ exchanger (NHE1) are also involved in microglial function in physiology and brain diseases. We discussed microglial activation and neuroinflammation in relation to the ion channel/transporter stimulation under brain disease conditions and therapeutic aspects of targeting microglial ion channels/transporters for neurodegenerative disease, ischemic stroke, traumatic brain injury and neuropathic pain.

Neosaxitoxin Inhibits the Expression of Inflammation Markers of the M1 Phenotype in Macrophages

(1) Background: Neosaxitoxin (NeoSTX) has been used as a local anesthetic, but its anti-inflammatory effects have not been well defined. In the present study, we investigate the effects of NeoSTX on lipopolysaccharide (LPS)-activated macrophages. (2) Methods: Raw 264.7 and equine PBMC cells were incubated with or without 100 ng/mL LPS in the presence or absence of NeoSTX (1µM). The expression of inflammatory mediators was assessed: nitric oxide (NO) content using the Griess assay, TNF-α content using the ELISA assay, and mRNA of inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) using a real-time polymerase chain reaction. (3) Results: NeoSTX (1 μM) significantly inhibited the release of NO, TNF-α, and expression of iNOS, IL-1β, and TNF-α in LPS-activated macrophages of both species studied. Furthermore, our study shows that the LPS-induced release of inflammatory mediators was suppressed by NeoSTX. Additionally, NeoSTX deactivated polarized macrophages to M1 by LPS without compromising its polarization towards M2. (4) Conclusions: NeoSTX inhibits LPS-induced release of inflammatory mediators from macrophages, and these effects may be mediated by the blockade of voltage-gated sodium channels (VGSC).

The SLC9A-C Mammalian Na+/H+ Exchanger Family: Molecules, Mechanisms, and Physiology

Na⁺/H⁺ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na⁺ and H⁺ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na⁺/H⁺ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.

Roles of glial ion transporters in brain diseases

Glial ion transporters are important in regulation of ionic homeostasis, cell volume, and cellular signal transduction under physiological conditions of the central nervous system (CNS). In response to acute or chronic brain injuries, these ion transporters can be activated and differentially regulate glial functions, which has subsequent impact on brain injury or tissue repair and functional recovery. In this review, we summarized the current knowledge about major glial ion transporters, including Na⁺ /H⁺ exchangers (NHE), Na⁺ /Ca²⁺ exchangers (NCX), Na⁺ -K⁺ -Cl^- cotransporters (NKCC), and Na⁺ -HCO₃ ^- cotransporters (NBC). In acute neurological diseases, such as ischemic stroke and traumatic brain injury (TBI), these ion transporters are rapidly activated and play significant roles in regulation of the intra- and extracellular pH, Na⁺ , K⁺ , and Ca²⁺ homeostasis, synaptic plasticity, and myelin formation. However, overstimulation of these ion transporters can contribute to glial apoptosis, demyelination, inflammation, and excitotoxicity. In chronic brain diseases, such as glioma, Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS), glial ion transporters are involved in the glioma Warburg effect, glial activation, neuroinflammation, and neuronal damages. These findings suggest that glial ion transporters are involved in tissue structural and functional restoration, or brain injury and neurological disease development and progression. A better understanding of these ion transporters in acute and chronic neurological diseases will provide insights for their potential as therapeutic targets.

Mild Acidosis Protects Neurons during Oxygen-Glucose Deprivation by Reducing Loss of Mitochondrial Respiration

Brain ischemia is often accompanied by brain acidosis and this acidosis can affect ischemic neuronal injury. Ischemic neuronal injury is initiated by a decrease in ATP production which mainly relies on mitochondrial oxidative phosphorylation. Ischemia often causes mitochondrial dysfunction, and acidosis has been found to affect mitochondrial function, suggesting that acidosis accompanying ischemia may influence neurons by targeting mitochondrial metabolism. However, the effects of acidosis on mitochondrial energy metabolism during ischemia lacks thorough investigation. Here, we found that mild acidosis significantly reduced neuronal death possibly by slowing the process of ATP deprivation during oxygen-glucose deprivation (OGD), an in vitro ischemic model. The maintaining of neuronal ATP depended on protecting mitochondrial ATP production. Further investigation of mitochondrial function revealed that mild acidosis alleviated OGD-induced collapse of mitochondrial membrane potentials as well as damage to respiratory function, at least in part by reducing impacts on complex I and II activities. Inhibition of complex I activity aggravated neuronal death, which suggests that the contribution of mild acidosis to maintaining complex I activity promoted neuronal survival during OGD. Our findings reveal maintaining mitochondrial respiration as a new possible protective mechanism of mild acidosis during ischemia, on neurons.

The TRAPs From Microglial Vesicles Protect Against Listeria Infection in the CNS

Previous studies have demonstrated that T cells and microglia could fight against cerebral Listeria monocytogenes (Listeria); however, their synergistic anti-Listeria mechanisms remain unknown. Following Listeria infection in a culture system, we found that microglia, but not nerve cells, could release extracellular traps (ETs) which originated from microglial vesicles. Specific inhibitor analysis showed that extracellular DNA (eDNA), matrix metallopeptidases (MMP9 and MMP12), citrullinated histone H3, and peptidyl arginine deiminase 2 were the major components of microglial ETs (MiETs) and were also the components of vesicles. Systematic analysis indicated that Listeria-induced MiETs were cytosolic reactive oxygen species (ROS)- and NADPH oxidase (NOX)-dependent and involved ERK. MiETs were exhibited in Listeria-infected mouse brain and might protected against Listeria infection via bacterial killing in a mouse meningitis model, and MiETs existed in cerebrospinal fluid (CSF) from Listeria meningitis patients in vivo and in vitro. Additionally, interferon-γ could induce MiET formation in Listeria-infected microglia in vitro that was mediated by NOX, and there was a positive relationship between the elevated level of IFN-γ and eDNA and nucleosomes in the brain homogenates and CSF of Listeria meningitis model mice and in the CSF before treatment in clinical Listeria meningitis patients. Together, this is the first report of MiET formation, these findings pave the way for deeper exploration of the innate immune response to pathogens in CNS.

Isoliquiritigenin protects against blood‑brain barrier damage and inhibits the secretion of pro-inflammatory cytokines in mice after traumatic brain injury

Traumatic brain injury (TBI) caused by an external mechanical force acting on the brain is a serious neurological condition. Inflammation plays an important role in prolonging secondary tissue injury after TBI, leading to neuronal cell death and dysfunction. Isoliquiritigenin (ILG) is a flavonoid monomer with anti-inflammatory characteristic. Thus, we had investigated the potential protective effects of ILG on TBI-induced injuries and identified the mechanisms underlying it. Here, we have demonstrated that ILG preserves blood brain barrier (BBB) integrity in vivo, suppresses the activation of microglia and inflammatory responses in mice after TBI, consequently leading to neurofunctional deficits, brain oedema, structural damage, and macrophage infiltration. In vitro, ILG exerts anti-inflammatory effect, and upregulates tight junction proteins 120‑β‑catenin and occludin in SH‑SY5Y cells under oxygen glucose deprivation/reoxygenation (OGD/D) condition. Additionally, we found that PI3K/AKT/GSK‑3β signalling pathway is involved in ILG treatment for TBI. To further confirm it, we had used SC79 (ethyl 2‑amino‑6‑chloro‑4‑(1‑cyano‑2‑ethoxy‑2‑oxoethyl)‑4H‑chromene‑3‑carboxylate), an Akt specific activator, to activate Akt, we found that SC79 partially reduces the protective effect of ILG for TBI. Overall, our current study reveals the neuroprotective role of ILG on TBI-induced BBB damage, downregulated tight junction proteins via PI3K/AKT/GSK‑3β signalling pathway. Furthermore, ILG suppresses the secretion of pro-inflammatory cytokines after TBI through inhibiting the PI3K/AKT/GSK‑3β/NF‑κB signalling pathway. Our findings suggest that GSK‑3β is a key regulatory factor during TBI-induced secretion of inflammatory cytokines, neuronal apoptosis and destruction of BBB.

Selective role of Na+ /H+ exchanger in Cx3cr1+ microglial activation, white matter demyelination, and post-stroke function recovery

Na⁺ /H⁺ exchanger (NHE1) activation is required for multiple microglial functions. We investigated effects of selective deletion of microglial Nhe1 in Cx3cr1-Cre^ER ;Nhe1^f/f mice on neuroinflammation and tissue repair after ischemic stroke. Infarct volume was similar in corn oil or tamoxifen (Tam)-treated mice at 48 hr and 14 days post-stroke. However, the Tam-treated mice showed significantly higher survival rate and faster neurological function recovery during day 1-14 post-stroke. Deletion of microglial Nhe1 prevented the elevation of CD11b⁺ /CD45^low-med microglia in the ischemic hemisphere at day 3 post-stroke, but stimulated expression of Ym1, CD68, TGF-β, IL-10, decreased expression of CD86 and IL-1β, and reduced GFAP⁺ reactive astrocytes. Moreover, at day 14 post-stroke, enhanced white matter myelination was detected in the microglial Nhe1 deleted mice. In comparison, neuronal Nhe1-null mice (the CamKII-Cre^+/- ;Nhe1^f/f mice) showed a significant reduction in both acute and subacute infarct volume, along with increased survival rate and moderate neurological function recovery. However, these neuronal Nhe1-null mice did not exhibit reduced activation of CD11b⁺ /CD45^low-med microglia or CD11b⁺ /CD45^hi macrophages in the ischemic brains, and they exhibited no reductions in white matter lesions. Taken together, this study demonstrated that deletion of microglial and neuronal Nhe1 had differential effects on ischemic brain damage. Microglial NHE1 is involved in pro-inflammatory responses during post-stroke brain tissue repair. In contrast, neuronal NHE1 activation is directly associated with the acute ischemic neuronal injury but not inflammation. Our study reveals that NHE1 protein is a potential therapeutic target critical for differential regulation of ischemic neuronal injury, demyelination and tissue repair.

The anti-parkinsonian drug zonisamide reduces neuroinflammation: Role of microglial Nav 1.6

Parkinson's disease (PD), the second most common age-related progressive neurodegenerative disorder, is characterized by dopamine depletion and the loss of dopaminergic (DA) neurons with accompanying neuroinflammation. Zonisamide is an-anti-convulsant drug that has recently been shown to improve clinical symptoms of PD through its inhibition of monoamine oxidase B (MAO-B). However, zonisamide has additional targets, including voltage-gated sodium channels (Na_v), which may contribute to its reported neuroprotective role in preclinical models of PD. Here, we report that Na_v1.6 is highly expressed in microglia of post-mortem PD brain and of mice treated with the parkinsonism-inducing neurotoxin MPTP. Administration of zonisamide (20 mg/kg, i.p. every 4 h × 3) following a single injection of MPTP (12.5 mg/kg, s.c.) reduced microglial Na_v 1.6 and microglial activation in the striatum, as indicated by Iba-1 staining and mRNA expression of F4/80. MPTP increased the levels of the pro-inflammatory cytokine TNF-α and gp91^phox, and this was significantly reduced by zonisamide. Together, these findings suggest that zonisamide may reduce neuroinflammation through the down-regulation of microglial Na_v 1.6. Thus, in addition to its effects on parkinsonian symptoms through inhibition of MAO-B, zonisamide may have disease modifying potential through the inhibition of Na_v 1.6 and neuroinflammation.

Pretreatment with magnesium sulfate attenuates white matter damage by preventing cell death of developing oligodendrocytes

AIM

Antenatal maternal administration of magnesium sulfate (MgSO₄ ) reduces cerebral palsy in preterm infants. However, it remains controversial as to whether it also reduces occurrence of white matter damage, or periventricular leukomalacia. We assessed the effect of MgSO₄ against white matter damage induced by hypoxic-ischemic insult using a neonatal rat model and culture of premyelinating oligodendrocytes (pre-OL).

METHODS

Rat pups at postnatal day (P) 6 were administered either MgSO₄ or vehicle intraperitoneally before hypoxic-ischemic insult (unilateral ligation of the carotid artery followed by 6% oxygen for 1 h). The population of oligodendrocyte (OL) markers and CD-68-positive microglia at P11, and TdT-mediated biotin-16-dUTP nick-end labeling (TUNEL)-positive cells at P8 were evaluated in pericallosal white matter. Primary cultures of mouse pre-OL were subjected to oxygen glucose deprivation condition, and the lactate dehydrogenase release from culture cells was evaluated to assess cell viability.

RESULTS

Pretreatment with MgSO₄ attenuated the loss of OL markers, such as myelin basic protein and Olig2, in ipsilateral pericallosal white matter and decreased the number of CD-68-positive microglia and TUNEL-positive cells in vivo. Pretreatment with MgSO₄ also inhibited lactate dehydrogenase release from pre-OL induced by oxygen glucose deprivation in vitro.

CONCLUSION

Pretreatment with MgSO₄ attenuates white matter damage by preventing cell death of pre-OL.

Immunoglobulins G from Sera of Amyotrophic Lateral Sclerosis Patients Induce Oxidative Stress and Upregulation of Antioxidative System in BV-2 Microglial Cell Line

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with a very fast progression, no diagnostic tool for the presymptomatic phase, and still no effective treatment of the disease. Although ALS affects motor neurons, the overall pathophysiological condition points out to the non-cell autonomous mechanisms, where astrocytes and microglia play crucial roles in the disease progression. We have already shown that IgG from sera of ALS patients (ALS IgG) induce calcium transients and an increase in the mobility of acidic vesicles in cultured rat astrocytes. Having in mind the role of microglia in neurodegeneration, and a well-documented fact that oxidative stress is one of the many components contributing to the disease, we decided to examine the effect of ALS IgG on activation, oxidative stress and antioxidative system of BV-2 microglia, and to evaluate their acute effect on cytosolic peroxide, pH, and on reactive oxygen species (ROS) generation. All tested ALS IgGs (compared to control IgG) induced oxidative stress (rise in nitric oxide and the index of lipid peroxidation) followed by release of TNF-α and higher antioxidative defense (elevation of Mn- and CuZn-superoxide dismutase, catalase, and glutathione reductase with a decrease of glutathione peroxidase and glutathione) after 24 h treatment. Both ALS IgG and control IgG showed same localization on the membrane of BV-2 cells following 24 h treatment. Cytosolic peroxide and pH alteration were evaluated with fluorescent probes HyPer and SypHer, respectively, having in mind that HyPer also reacts to pH changes. Out of 11 tested IgGs from ALS patients, 4 induced slow exponential rise of HyPer signal, with maximal normalized fluorescence in the range 0.2–0.5, also inducing similar increase of SypHer intensity, but of a lower amplitude. None of the control IgGs induced changes with neither of the indicators. Acute ROS generation was detected in one out of three tested ALS samples with carboxy-H2DCFDA. The observed phenomena demonstrate the potential role of inflammatory humoral factors, IgGs, as potential triggers of the activation in microglia, known to occur in later stages of ALS. Therefore, revealing the ALS IgG signaling cascade in microglial cells could offer a valuable molecular biomarker and/or a potential therapeutic target.

The volume-regulated anion channel (LRRC8) in nodose neurons is sensitive to acidic pH

The leucine rich repeat containing protein 8A (LRRC8A), or SWELL1, is an essential component of the volume-regulated anion channel (VRAC) that is activated by cell swelling and ionic strength. We report here for the first time to our knowledge its expression in a primary cell culture of nodose ganglia neurons and its localization in the soma, neurites, and neuronal membrane. We show that this neuronal VRAC/SWELL1 senses low external pH (pH_o) in addition to hypoosmolarity. A robust sustained chloride current is seen in 77% of isolated nodose neurons following brief exposures to extracellular acid pH. Its activation involves proton efflux, intracellular alkalinity, and an increase in NOX-derived H₂O_2. The molecular identity of both the hypoosmolarity-induced and acid pH_o-conditioned VRAC as LRRC8A (SWELL1) was confirmed by Cre-flox-mediated KO, shRNA-mediated knockdown, and CRISPR/Cas9-mediated LRRC8A deletion in HEK cells and in primary nodose neuronal cultures. Activation of VRAC by low pH_o reduces neuronal injury during simulated ischemia and N-methyl-D-aspartate-induced (NMDA-induced) apoptosis. These results identify the VRAC (LRRC8A) as a dual sensor of hypoosmolarity and low pH_o in vagal afferent neurons and define the mechanisms of its activation and its neuroprotective potential.

Acute neuroinflammation provokes intracellular acidification in mouse hippocampus

Background

Maintaining pH levels within the physiological norm is an important component of brain homeostasis. However, in some pathological or physiological conditions, the capacity of the pH regulatory system could be overpowered by various factors resulting in a transient or permanent alteration in pH levels. Such changes are often observed in pathological conditions associated with neuroinflammation. We hypothesized that neuroinflammation itself is a factor affecting pH levels in neural tissue. To assess this hypothesis, we examined the effects of acute LPS-induced neuroinflammation on intra- and extracellular pH (pHi and pHo) levels in the CA1 region of mouse hippocampus.

Methods

Acute neuroinflammation was induced using two approaches: (1) in vivo by i.p. injections of LPS (5 mg/kg) and (2) in vitro by incubating hippocampal slices of naïve animals in the LPS-containing media (1 μg/mL, 1 h at 35 °C). Standard techniques were used to prepare hippocampal slices. pHi was measured using ratiometric pH-sensitive fluorescent dye BCECF-AM. pHo was assessed using calibrated pH-sensitive micropipettes. The presence of neuroinflammation was verified with immunohistochemistry (IL-1β and Iba1) and ELISA (IL-1β and TNF-α).

Results

A significant reduction of pHi was observed in the slices of the LPS-injected 3-month-old (LPS 7.13 ± 0.03; Sal 7.22 ± 0.03; p = 0.043, r = 0.43) and 19-month-old (LPS 6.78 ± 0.08; Sal 7.13 ± 0.03; p = 0.0001, r = 0.32) mice. In contrast, the levels of pHo within the slice, measured in 19-month-old animals, were not affected (LPS 7.27 ± 0.02; Sal 7.26 ± 0.02; p = 0.6, r = 0.13). A reduction of pHi was also observed in the LPS-treated slices during the interval 3.5–7 h after the LPS exposure (LPS 6.92 ± 0.07; Veh 7.28 ± 0.05; p = 0.0001, r = 0.46).

Conclusions

Acute LPS-induced neuroinflammation results in a significant intracellular acidification of the CA1 neurons in mouse hippocampus, while the pHo remains largely unchanged. Such changes may represent a specific protective reaction of neural tissue in unfavorable external conditions or be a part of the pathological process.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0747-8) contains supplementary material, which is available to authorized users.

Annexin-1 Mediates Microglial Activation and Migration via the CK2 Pathway during Oxygen-Glucose Deprivation/Reperfusion

Annexin-1 (ANXA1) has shown neuroprotective effects and microglia play significant roles during central nervous system injury, yet the underlying mechanisms remain unclear. This study sought to determine whether ANXA1 regulates microglial response to oxygen–glucose deprivation/reperfusion (OGD/R) treatment and to clarify the downstream molecular mechanism. In rat hippocampal slices, OGD/R treatment enhanced the ANXA1 expression in neuron, the formyl peptide receptor (FPRs) expression in microglia, and the microglial activation in the CA1 region (cornu ammonis 1). These effects were reversed by the FPRs antagonist Boc1. The cell membrane currents amplitude of BV-2 microglia (the microglial like cell-line) was increased when treated with Ac2-26, the N-terminal peptide of ANXA1. Ac2-26 treatment enhanced BV-2 microglial migration whereas Boc1 treatment inhibited the migration. In BV-2 microglia, both the expression of the CK2 target phosphorylated α-E-catenin and the binding of casein kinase II (CK2) with α-E-catenin were elevated by Ac2-26, these effects were counteracted by the CK2 inhibitor TBB and small interfering (si) RNA directed against transcripts of CK2 and FPRs. Moreover, both TBB and siRNA-mediated inhibition of CK2 blocked Ac2-26-mediated BV-2 microglia migration. Our findings indicate that ANXA1 promotes microglial activation and migration during OGD/R via FPRs, and CK2 target α-E-catenin phosphorylation is involved in this process.

Exercise Attenuates Intermittent Hypoxia-Induced Cardiac Fibrosis Associated with Sodium-Hydrogen Exchanger-1 in Rats

Purpose: To investigate the role of sodium–hydrogen exchanger-1 (NHE-1) and exercise training on intermittent hypoxia-induced cardiac fibrosis in obstructive sleep apnea (OSA), using an animal model mimicking the intermittent hypoxia of OSA.

Methods: Eight-week-old male Sprague–Dawley rats were randomly assigned to control (CON), intermittent hypoxia (IH), exercise (EXE), or IH combined with exercise (IHEXE) groups. These groups were randomly assigned to subgroups receiving either a vehicle or the NHE-1 inhibitor cariporide. The EXE and IHEXE rats underwent exercise training on an animal treadmill for 10 weeks (5 days/week, 60 min/day, 24–30 m/min, 2–10% grade). The IH and IHEXE rats were exposed to 14 days of IH (30 s of hypoxia—nadir of 2–6% O₂—followed by 45 s of normoxia) for 8 h/day. At the end of 10 weeks, rats were sacrificed and then hearts were removed to determine the myocardial levels of fibrosis index, oxidative stress, antioxidant capacity, and NHE-1 activation.

Results: Compared to the CON rats, IH induced higher cardiac fibrosis, lower myocardial catalase, and superoxidative dismutase activities, higher myocardial lipid and protein peroxidation and higher NHE-1 activation (p < 0.05 for each), which were all abolished by cariporide. Compared to the IH rats, lower cardiac fibrosis, higher myocardial antioxidant capacity, lower myocardial lipid, and protein peroxidation and lower NHE-1 activation were found in the IHEXE rats (p < 0.05 for each).

Conclusion: IH-induced cardiac fibrosis was associated with NHE-1 hyperactivity. However, exercise training and cariporide exerted an inhibitory effect to prevent myocardial NHE-1 hyperactivity, which contributed to reduced IH-induced cardiac fibrosis. Therefore, NHE-1 plays a critical role in the effect of exercise on IH-induced increased cardiac fibrosis.

Pyrethroid Insecticides Directly Activate Microglia Through Interaction With Voltage-Gated Sodium Channels

Microglia are considered to be the resident immune cells of the central nervous system and contribute significantly to ongoing neuroinflammation in a variety of neurodegenerative diseases. Recently, we and others identified that voltage-gated sodium channels (VGSC) are present on microglia cells and contribute to excessive accumulation of intracellular Na⁺and release of major pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α). Based on this finding and the fact that pyrethroid pesticides act on VGSC, we hypothesized that exposure of microglia to the pyrethroid pesticides, permethrin and deltamethrin, would activate microglia and increase the release of TNF-α. BV2 cells or primary microglia were treated with 0-5 µM deltamethrin or permethrin in the presence or absence of tetrodotoxin (TTX), a VGSC blocker for 24-48 h. Both pyrethroids caused a rapid Na⁺influx and increased accumulation of intracellular sodium [(Na⁺)i] in the microglia in a dose- and time-dependent manner, which was significantly reduced by TTX. Furthermore, deltamethrin and permethrin increased the release of TNF-α in a dose- and time-dependent manner, which was significantly reduced by pre-treatment of cells with TTX. These results demonstrate that pyrethroid pesticides may directly activate microglial cells through their interaction with microglial VGSC. Because neuroinflammation plays a key role in many neurodegenerative diseases, these data provide an additional mechanism by which exposure to pyrethroid insecticides may contribute to neurodegeneration.

Glioma-mediated microglial activation promotes glioma proliferation and migration: roles of Na+/H+ exchanger isoform 1

Microglia play important roles in extracellular matrix remodeling, tumor invasion, angiogenesis, and suppression of adaptive immunity in glioma. Na(+)/H(+) exchanger isoform 1 (NHE1) regulates microglial activation and migration. However, little is known about the roles of NHE1 in intratumoral microglial activation and microglia-glioma interactions. Our study revealed up-regulation of NHE1 protein expression in both glioma cells and tumor-associated Iba1(+) microglia in glioma xenografts and glioblastoma multiforme microarrays. Moreover, we observed positive correlation of NHE1 expression with Iba1 intensity in microglia/macrophages. Glioma cells, via conditioned medium or non-contact glioma-microglia co-cultures, concurrently upregulated microglial expression of NHE1 protein and other microglial activation markers (iNOS, arginase-1, TGF-β, IL-6, IL-10 and the matrix metalloproteinases MT1-MMP and MMP9). Interestingly, glioma-stimulated microglia reciprocally enhanced glioma proliferation and migration. Most importantly, inhibition of microglial NHE1 activity via small interfering RNA (siRNA) knockdown or the potent NHE1-specific inhibitor HOE642 significantly attenuated microglial activation and abolished microglia-stimulated glioma migration and proliferation. Taken together, our findings provide the first evidence that NHE1 function plays an important role in glioma-microglia interactions, enhancing glioma proliferation and invasion by stimulating microglial release of soluble factors. NHE1 upregulation is a novel marker of the glioma-associated microglial activation phenotype. Inhibition of NHE1 represents a novel glioma therapeutic strategy by targeting tumor-induced microglial activation.

Glial Na(+) -dependent ion transporters in pathophysiological conditions

Sodium dynamics are essential for regulating functional processes in glial cells. Indeed, glial Na(+) signaling influences and regulates important glial activities, and plays a role in neuron-glia interaction under physiological conditions or in response to injury of the central nervous system (CNS). Emerging studies indicate that Na(+) pumps and Na(+) -dependent ion transporters in astrocytes, microglia, and oligodendrocytes regulate Na(+) homeostasis and play a fundamental role in modulating glial activities in neurological diseases. In this review, we first briefly introduced the emerging roles of each glial cell type in the pathophysiology of cerebral ischemia, Alzheimer's disease, epilepsy, Parkinson's disease, Amyotrophic Lateral Sclerosis, and myelin diseases. Then, we discussed the current knowledge on the main roles played by the different glial Na(+) -dependent ion transporters, including Na(+) /K(+) ATPase, Na(+) /Ca(2+) exchangers, Na(+) /H(+) exchangers, Na(+) -K(+) -Cl(-) cotransporters, and Na(+) - HCO3- cotransporter in the pathophysiology of the diverse CNS diseases. We highlighted their contributions in cell survival, synaptic pathology, gliotransmission, pH homeostasis, and their role in glial activation, migration, gliosis, inflammation, and tissue repair processes. Therefore, this review summarizes the foundation work for targeting Na(+) -dependent ion transporters in glia as a novel strategy to control important glial activities associated with Na(+) dynamics in different neurological disorders. GLIA 2016;64:1677-1697.

Treadmill exercise ameliorates ischemia-induced brain edema while suppressing Na⁺/H⁺ exchanger 1 expression

Exercise may be one of the most effective and sound therapies for stroke; however, the mechanisms underlying the curative effects remain unclear. In this study, the effects of forced treadmill exercise with electric shock on ischemic brain edema were investigated. Wistar rats were subjected to transient (90 min) middle cerebral artery occlusion (tMCAO). Eighty nine rats with substantially large ischemic lesions were evaluated using magnetic resonance imaging (MRI) and were randomly assigned to exercise and non-exercise groups. The rats were forced to run at 4-6m/s for 10 min/day on days 2, 3 and 4. Brain edema was measured on day 5 by MRI, histochemical staining of brain sections and tissue water content determination (n=7, each experiment). Motor function in some rats was examined on day 30 (n=6). Exercise reduced brain edema (P<0.05-0.001, varied by the methods) and ameliorated motor function (P<0.05). The anti-glucocorticoid mifepristone or the anti-mineralocorticoid spironolactone abolished these effects, but orally administered corticosterone mimicked the ameliorating effects of exercise. Exercise prevented the ischemia-induced expression of mRNA encoding aquaporin 4 (AQP4) and Na(+)/H(+) exchangers (NHEs) (n=5 or 7, P<0.01). Microglia and NG2 glia expressed NHE1 in the peri-ischemic region of rat brains and also in mixed glial cultures. Corticosterone at ~10nM reduced NHE1 and AQP4 expression in mixed glial and pure microglial cultures. Dexamethasone and aldosterone at 10nM did not significantly alter NHE1 and AQP4 expression. Exposure to a NHE inhibitor caused shrinkage of microglial cells. These results suggest that the stressful short-period and slow-paced treadmill exercise suppressed NHE1 and AQP4 expression resulting in the amelioration of brain edema at least partly via the moderate increase in plasma corticosterone levels.

Administration of DHA Reduces Endoplasmic Reticulum Stress-Associated Inflammation and Alters Microglial or Macrophage Activation in Traumatic Brain Injury

We investigated the effects of the administration of docosahexaenoic acid (DHA) post-traumatic brain injury (TBI) on reducing neuroinflammation. TBI was induced by cortical contusion injury in Sprague Dawley rats. Either DHA (16 mg/kg in dimethyl sulfoxide) or vehicle dimethyl sulfoxide (1 ml/kg) was administered intraperitonially at 5 min after TBI, followed by a daily dose for 3 to 21 days. TBI triggered activation of microglia or macrophages, detected by an increase of Iba1 positively stained microglia or macrophages in peri-lesion cortical tissues at 3, 7, and 21 days post-TBI. The inflammatory response was further characterized by expression of the proinflammatory marker CD16/32 and the anti-inflammatory marker CD206 in Iba1⁺ microglia or macrophages. DHA-treated brains showed significantly fewer CD16/32⁺ microglia or macrophages, but an increased CD206⁺ phagocytic microglial or macrophage population. Additionally, DHA treatment revealed a shift in microglial or macrophage morphology from the activated, amoeboid-like state into the more permissive, surveillant state. Furthermore, activated Iba1⁺ microglial or macrophages were associated with neurons expressing the endoplasmic reticulum (ER) stress marker CHOP at 3 days post-TBI, and the administration of DHA post-TBI concurrently reduced ER stress and the associated activation of Iba1⁺ microglial or macrophages. There was a decrease in nuclear translocation of activated nuclear factor kappa-light-chain-enhancer of activated B cells protein at 3 days in DHA-treated tissue and reduced neuronal degeneration in DHA-treated brains at 3, 7, and 21 days after TBI. In summary, our study demonstrated that TBI mediated inflammatory responses are associated with increased neuronal ER stress and subsequent activation of microglia or macrophages. DHA administration reduced neuronal ER stress and subsequent association with microglial or macrophage polarization after TBI, demonstrating its therapeutic potential to ameliorate TBI-induced cellular pathology.

Implications of sodium hydrogen exchangers in various brain diseases

Na+/H+ exchangers (NHEs) are the transporter proteins that play an important role in intracellular pH (pHi) regulation, cell differentiation and cell volume and that mediate transepithelial Na+ and HCO3- absorption on the basis of chemical gradients across the plasma membrane. Its activation causes an increase in intracellular Na+, which further leads to Ca+ overload and cell death. The pharmacological inhibition of these transporter proteins prevents myocardial infarction and other heart diseases like congestive heart failure in experimental animal models as well as in clinical situations. The more recent studies have implicated the role of these exchangers in the pathophysiology of brain diseases. Out of nine NHE isoforms, NHE-1 is the major isoform present in the brain and regulates the trans-cellular ion transport through blood-brain barrier membrane, and alteration in their function leads to severe brain abnormalities. NHEs were shown to be involved in pathophysiologies of many brain diseases like epilepsy, Alzheimer's disease, neuropathic pain and ischemia/reperfusion-induced cerebral injury. Na+/H+-exchanger inhibitors (e.g., amiloride and cariporide) produce protective effects on ischemia/reperfusion-induced brain injury (e.g., stroke), exhibit good antiepileptic potential and attenuate neuropathic pain in various animal models. The present review focuses on the pathophysiological role of these ion exchangers in different brain diseases with possible mechanisms.

Inhibition of endogenous heat shock protein 70 attenuates inducible nitric oxide synthase induction via disruption of heat shock protein 70/Na(+) /H(+) exchanger 1-Ca(2+) -calcium-calmodulin-dependent protein kinase II/transforming growth factor β-activated kinase 1-nuclear factor-κB signals in BV-2 microglia

Inducible nitric oxide synthase (iNOS) critically contributes to inflammation and host defense. The inhibition of heat shock protein 70 (Hsp70) prevents iNOS induction in lipopolysaccharide (LPS)-stimulated macrophages. However, the role and mechanism of endogenous Hsp70 in iNOS induction in microglia remains unclear. This study addresses this issue in BV-2 microglia, showing that Hsp70 inhibition or knockdown prevents LPS-induced iNOS protein expression and nitric oxide production. Real-time PCR experiments showed that LPS-induced iNOS mRNA transcription was blocked by Hsp70 inhibition. Further studies revealed that the inhibition of Hsp70 attenuated LPS-stimulated nuclear translocation and phosphorylation of nuclear factor (NF)-κB as well as the degradation of inhibitor of κB (IκB)-α and phosphorylation of IκB kinase β (IKKβ). This prevention effect of Hsp70 inhibition on IKKβ-NF-κB activation was found to be dependent on the Ca(2+) /calcium-calmodulin-dependent protein kinase II (CaMKII)/transforming growth factor β-activated kinase 1 (TAK1) signals based on the following observations: 1) chelation of intracellular Ca(2+) or inhibition of CaMKII reduced LPS-induced increases in TAK1 phosphorylation and 2) Hsp70 inhibition reduced LPS-induced increases in CaMKII/TAK1 phosphorylation, intracellular pH value, [Ca(2+) ]i , and CaMKII/TAK1 association. Mechanistic studies showed that Hsp70 inhibition disrupted the association between Hsp70 and Na(+) /H(+) exchanger 1 (NHE1), which is an important exchanger responsible for Ca(2+) influx in LPS-stimulated cells. These studies demonstrate that the inhibition of endogenous Hsp70 attenuates the induction of iNOS, which likely occurs through the disruption of NHE1/Hsp70-Ca(2+) -CaMKII/TAK1-NF-κB signals in BV-2 microglia, providing further insight into the functions of Hsp70 in the CNS.

NADPH oxidase-2: linking glucose, acidosis, and excitotoxicity in stroke

SIGNIFICANCE

Neuronal superoxide production contributes to cell death in both glutamate excitotoxicity and brain ischemia (stroke). NADPH oxidase-2 (NOX2) is the major source of neuronal superoxide production in these settings, and regulation of NOX2 activity can thereby influence outcome in stroke.

RECENT ADVANCES

Reduced NOX2 activity can rescue cells from oxidative stress and cell death that otherwise occur in excitotoxicity and ischemia. NOX2 activity is regulated by several factors previously shown to affect outcome in stroke, including glucose availability, intracellular pH, protein kinase ζ/δ, casein kinase 2, phosphoinositide-3-kinase, Rac1/2, and phospholipase A2. The newly identified functions of these factors as regulators of NOX2 activity suggest alternative mechanisms for their effects on ischemic brain injury.

CRITICAL ISSUES

Key aspects of these regulatory influences remain unresolved, including the mechanisms by which rac1 and phospholipase activities are coupled to N-methyl-D-aspartate (NMDA) receptors, and whether superoxide production by NOX2 triggers subsequent superoxide production by mitochondria.

FUTURE DIRECTIONS

It will be important to establish whether interventions targeting the signaling pathways linking NMDA receptors to NOX2 in brain ischemia can provide a greater neuroprotective efficacy or a longer time window to treatment than provided by NMDA receptor blockade alone. It will likewise be important to determine whether dissociating superoxide production from the other signaling events initiated by NMDA receptors can mitigate the deleterious effects of NMDA receptor blockade.

Na⁺/H⁺ exchangers and intracellular pH in perinatal brain injury

Encephalopathy consequent on perinatal hypoxia–ischemia occurs in 1–3 per 1,000 term births in the UK and frequently leads to serious and tragic consequences that devastate lives and families, with huge financial burdens for society. Although the recent introduction of cooling represents a significant advance, only 40 % survive with normal neurodevelopmental function. There is thus a significant unmet need for novel, safe, and effective therapies to optimize brain protection following brain injury around birth. The Na⁺/H⁺ exchanger (NHE) is a membrane protein present in many mammalian cell types. It is involved in regulating intracellular pH and cell volume. NHE1 is the most abundant isoform in the central nervous system and plays a role in cerebral damage after hypoxia–ischemia. Excessive NHE activation during hypoxia–ischemia leads to intracellular Na⁺ overload, which subsequently promotes Ca²⁺ entry via reversal of the Na⁺/Ca²⁺ exchanger. Increased cytosolic Ca²⁺ then triggers the neurotoxic cascade. Activation of NHE also leads to rapid normalization of pH_i and an alkaline shift in pH_i. This rapid recovery of brain intracellular pH has been termed pH paradox as, rather than causing cells to recover, this rapid return to normal and overshoot to alkaline values is deleterious to cell survival. Brain pH_i changes are closely involved in the control of cell death after injury: an alkalosis enhances excitability while a mild acidosis has the opposite effect. We have observed a brain alkalosis in 78 babies with neonatal encephalopathy serially studied using phosphorus-31 magnetic resonance spectroscopy during the first year after birth (151 studies throughout the year including 56 studies of 50 infants during the first 2 weeks after birth). An alkaline brain pH_i was associated with severely impaired outcome; the degree of brain alkalosis was related to the severity of brain injury on MRI and brain lactate concentration; and a persistence of an alkaline brain pH_i was associated with cerebral atrophy on MRI. Experimental animal models of hypoxia–ischemia show that NHE inhibitors are neuroprotective. Here, we review the published data on brain pH_i in neonatal encephalopathy and the experimental studies of NHE inhibition and neuroprotection following hypoxia–ischemia.

Proton-sensitive cation channels and ion exchangers in ischemic brain injury: new therapeutic targets for stroke?

Ischemic brain injury results from complicated cellular mechanisms. The present therapy for acute ischemic stroke is limited to thrombolysis with the recombinant tissue plasminogen activator (rtPA) and mechanical recanalization. Therefore, a better understanding of ischemic brain injury is needed for the development of more effective therapies. Disruption of ionic homeostasis plays an important role in cell death following cerebral ischemia. Glutamate receptor-mediated ionic imbalance and neurotoxicity have been well established in cerebral ischemia after stroke. However, non-NMDA receptor-dependent mechanisms, involving acid-sensing ion channel 1a (ASIC1a), transient receptor potential melastatin 7 (TRPM7), and Na(+)/H(+) exchanger isoform 1 (NHE1), have recently emerged as important players in the dysregulation of ionic homeostasis in the CNS under ischemic conditions. These H(+)-sensitive channels and/or exchangers are expressed in the majority of cell types of the neurovascular unit. Sustained activation of these proteins causes excessive influx of cations, such as Ca(2+), Na(+), and Zn(2+), and leads to ischemic reperfusion brain injury. In this review, we summarize recent pre-clinical experimental research findings on how these channels/exchangers are regulated in both in vitro and in vivo models of cerebral ischemia. The blockade or transgenic knockdown of these proteins was shown to be neuroprotective in these ischemia models. Taken together, these non-NMDA receptor-dependent mechanisms may serve as novel therapeutic targets for stroke intervention.