Astrocytes, but not microglia, rapidly sense H₂O₂via STAT6 phosphorylation, resulting in cyclooxygenase-2 expression and prostaglandin release

Targeting monoamine oxidase A: a strategy for inhibiting tumor growth with both immune checkpoint inhibitors and immune modulators

Monoamine oxidase A (MAOA) is a membrane-bound mitochondrial enzyme present in almost all vertebrate tissues that catalyzes the degradation of biogenic and dietary-derived monoamines. MAOA is known for regulating neurotransmitter metabolism and has been implicated in antitumor immune responses. In this review, we retrospect that MAOA inhibits the activities of various types of tumor-associated immune cells (such as CD8+ T cells and tumor-associated macrophages) by regulating their intracellular monoamines and metabolites. Developing novel MAOA inhibitor drugs and exploring multidrug combination strategies may enhance the efficacy of immune governance. Thus, MAOA may act as a novel immune checkpoint or immunomodulator by influencing the efficacy and effectiveness of immunotherapy. In conclusion, MAOA is a promising immune target that merits further in-depth exploration in preclinical and clinical settings.

Mitochondrial complex I ROS production and redox signaling in hypoxia

Mitochondria are a main source of cellular energy. Oxidative phosphorylation (OXPHOS) is the major process of aerobic respiration. Enzyme complexes of the electron transport chain (ETC) pump protons to generate a protonmotive force (Δp) that drives OXPHOS. Complex I is an electron entry point into the ETC. Complex I oxidizes nicotinamide adenine dinucleotide (NADH) and transfers electrons to ubiquinone in a reaction coupled with proton pumping. Complex I also produces reactive oxygen species (ROS) under various conditions. The enzymatic activities of complex I can be regulated by metabolic conditions and serves as a regulatory node of the ETC. Complex I ROS plays diverse roles in cell metabolism ranging from physiologic to pathologic conditions. Progress in our understanding indicates that ROS release from complex I serves important signaling functions. Increasing evidence suggests that complex I ROS is important in signaling a mismatch in energy production and demand. In this article, we review the role of ROS from complex I in sensing acute hypoxia.

Divergent transcriptional regulation of astrocyte reactivity across disorders

Astrocytes respond to injury and disease in the central nervous system with reactive changes that influence the outcome of the disorder1-4. These changes include differentially expressed genes (DEGs) whose contextual diversity and regulation are poorly understood. Here we combined biological and informatic analyses, including RNA sequencing, protein detection, assay for transposase-accessible chromatin with high-throughput sequencing (ATAC-seq) and conditional gene deletion, to predict transcriptional regulators that differentially control more than 12,000 DEGs that are potentially associated with astrocyte reactivity across diverse central nervous system disorders in mice and humans. DEGs associated with astrocyte reactivity exhibited pronounced heterogeneity across disorders. Transcriptional regulators also exhibited disorder-specific differences, but a core group of 61 transcriptional regulators was identified as common across multiple disorders in both species. We show experimentally that DEG diversity is determined by combinatorial, context-specific interactions between transcriptional regulators. Notably, the same reactivity transcriptional regulators can regulate markedly different DEG cohorts in different disorders; changes in the access of transcriptional regulators to DNA-binding motifs differ markedly across disorders; and DEG changes can crucially require multiple reactivity transcriptional regulators. We show that, by modulating reactivity, transcriptional regulators can substantially alter disorder outcome, implicating them as therapeutic targets. We provide searchable resources of disorder-related reactive astrocyte DEGs and their predicted transcriptional regulators. Our findings show that transcriptional changes associated with astrocyte reactivity are highly heterogeneous and are customized from vast numbers of potential DEGs through context-specific combinatorial transcriptional-regulator interactions.

Crosstalk Between the Oxidative Stress and Glia Cells After Stroke: From Mechanism to Therapies

Stroke is the second leading cause of global death and is characterized by high rates of mortality and disability. Oxidative stress is accompanied by other pathological processes that together lead to secondary brain damage in stroke. As the major component of the brain, glial cells play an important role in normal brain development and pathological injury processes. Multiple connections exist in the pathophysiological changes of reactive oxygen species (ROS) metabolism and glia cell activation. Astrocytes and microglia are rapidly activated after stroke, generating large amounts of ROS via mitochondrial and NADPH oxidase pathways, causing oxidative damage to the glial cells themselves and neurons. Meanwhile, ROS cause alterations in glial cell morphology and function, and mediate their role in pathological processes, such as neuroinflammation, excitotoxicity, and blood-brain barrier damage. In contrast, glial cells protect the Central Nervous System (CNS) from oxidative damage by synthesizing antioxidants and regulating the Nuclear factor E2-related factor 2 (Nrf2) pathway, among others. Although numerous previous studies have focused on the immune function of glial cells, little attention has been paid to the role of glial cells in oxidative stress. In this paper, we discuss the adverse consequences of ROS production and oxidative-antioxidant imbalance after stroke. In addition, we further describe the biological role of glial cells in oxidative stress after stroke, and we describe potential therapeutic tools based on glia cells.

Modulation of the Primary Astrocyte-Enriched Cultures' Oxylipin Profiles Reduces Neurotoxicity

Recently, manipulations with reactive astrocytes have been viewed as a new therapeutic approach that will enable the development of treatments for acute brain injuries and neurodegenerative diseases. Astrocytes can release several substances, which may exert neurotoxic or neuroprotective effects, but the nature of these substances is still largely unknown. In the present work, we tested the hypothesis that these effects may be attributed to oxylipins, which are synthesized from n-3 or n-6 polyunsaturated fatty acids (PUFAs). We used astrocyte-enriched cultures and found that: (1) lipid fractions secreted by lipopolysaccharide (LPS)-stimulated rat primary astrocyte-enriched cultures-possessed neurotoxic activity in rat primary neuronal cultures; (2) both of the tested oxylipin synthesis inhibitors, ML355 and Zileuton, reduce the LPS-stimulated release of interleukin 6 (IL-6) by astrocyte cultures, but only ML355 can change lipid fractions from neurotoxic to non-toxic; and (3) oxylipin profiles, measured by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) from neurotoxic and non-toxic lipid fractions, reveal a group of n-3 docosahexaenoic acid derivatives, hydroxydocosahexaenoic acids (HdoHEs)-4-HdoHE, 8-HdoHE, and 17-HdoHE, which may reflect the neuroprotective features of lipid fractions. Regulating the composition of astrocyte oxylipin profiles may be suggested as an approach for regulation of neurotoxicity in inflammatory processes.

Targeting monoamine oxidase A-regulated tumor-associated macrophage polarization for cancer immunotherapy

Targeting tumor-associated macrophages (TAMs) is a promising strategy to modify the immunosuppressive tumor microenvironment and improve cancer immunotherapy. Monoamine oxidase A (MAO-A) is an enzyme best known for its function in the brain; small molecule MAO inhibitors (MAOIs) are clinically used for treating neurological disorders. Here we observe MAO-A induction in mouse and human TAMs. MAO-A-deficient mice exhibit decreased TAM immunosuppressive functions corresponding with enhanced antitumor immunity. MAOI treatment induces TAM reprogramming and suppresses tumor growth in preclinical mouse syngeneic and human xenograft tumor models. Combining MAOI and anti-PD-1 treatments results in synergistic tumor suppression. Clinical data correlation studies associate high intratumoral MAOA expression with poor patient survival in a broad range of cancers. We further demonstrate that MAO-A promotes TAM immunosuppressive polarization via upregulating oxidative stress. Together, these data identify MAO-A as a critical regulator of TAMs and support repurposing MAOIs for TAM reprogramming to improve cancer immunotherapy.

CRISPR/Cas9 Editing of Glia Maturation Factor Regulates Mitochondrial Dynamics by Attenuation of the NRF2/HO-1 Dependent Ferritin Activation in Glial Cells

Microglial cells are brain specific professional phagocytic immune cells that play a crucial role in the inflammation- mediated neurodegeneration especially in Parkinson's disease (PD) and Alzheimer's disease. Glia maturation factor (GMF) is a neuroinflammatory protein abundantly expressed in the brain. We have previously shown that GMF expression is significantly upregulated in the substantia nigra (SN) of PD brains. However, its possible role in PD progression is still not fully understood. The Clustered-Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR Associated (Cas) protein9 (CRISPR/Cas9) system is a simple, rapid and often extremely efficient gene editing tool at desired loci, enabling complete gene knockout or homology directed repair. In this study, we examined the effect of GMF editing by using the CRISPR/Cas9 technique in BV2 microglial cells (hereafter referred to as BV2-G) on oxidative stress and nuclear factor erythroid 2-related factor 2 (NRF2)/Hemeoxygenase1 (HO-1)-dependent ferritin activation after treatment with (1-methyl-4-phenylpyridinium) MPP⁺. Knockout of GMF in BV2-G cells significantly attenuated oxidative stress via reduced ROS production and calcium flux. Furthermore, deficiency of GMF significantly reduced nuclear translocation of NRF2, which modulates HO-1 and ferritin activation, cyclooxygenase 2 (COX2) and nitric oxide synthase 2 (NOS2) expression in BV2 microglial cells. Lack of GMF significantly improved CD11b and CD68 positive microglial cells as compared with untreated cells. Our results also suggest that pharmacological and genetic intervention targeting GMF may represent a promising and a novel therapeutic strategy in controlling Parkinsonism by regulating microglial functions. Targeted regulation of GMF possibly mediates protein aggregation in microglial homeostasis associated with PD progression through regulation of iron metabolism by modulating NRF2-HO1 and ferritin expression.

Astrocytes, Microglia, and Parkinson's Disease

Astrocytes and microglia support well-being and well-function of the brain through diverse functions in both intact and injured brain. For example, astrocytes maintain homeostasis of microenvironment of the brain through up-taking ions and neurotransmitters, and provide growth factors and metabolites for neurons, etc. Microglia keep surveying surroundings, and remove abnormal synapses or respond to injury by isolating injury sites and expressing inflammatory cytokines. Therefore, their loss and/or functional alteration may be directly linked to brain diseases. Since Parkinson's disease (PD)-related genes are expressed in astrocytes and microglia, mutations of these genes may alter the functions of these cells, thereby contributing to disease onset and progression. Here, we review the roles of astrocytes and microglia in intact and injured brain, and discuss how PD genes regulate their functions.

Redox Mechanisms in Migraine: Novel Therapeutics and Dietary Interventions

SIGNIFICANCE

Migraine represents the third most prevalent and the seventh most disabling human disorder. Approximately 30% of migraine patients experience transient, fully reversible, focal neurological symptoms (aura) preceding the attack. Recent Advances: Awareness of the hypothesis that migraine actually embodies a spectrum of illnesses-ranging from episodic to chronic forms-is progressively increasing and poses novel challenges for clarifying the underlying pathophysiological mechanisms of migraine as well as for the development of novel therapeutic interventions. Several theories have evolved to the current concept that a combination of genetic, epigenetic, and environmental factors may play a role in migraine pathogenesis, although their relative importance is still being debated.

CRITICAL ISSUES

One critical issue that deserves a particular attention is the role of oxidative stress in migraine. Indeed, potentially harmful oxidative events occur during the migraine attack and long-lasting or frequent migraine episodes may increase brain exposure to oxidative events that can lead to chronic transformation. Moreover, a wide variety of dietary, environmental, physiological, behavioral, and pharmacological migraine triggers may act through oxidative stress, with clear implications for migraine treatment and prophylaxis. Interestingly, almost all current prophylactic migraine agents exert antioxidant effects.

FUTURE DIRECTIONS

Increasing awareness of the role of oxidative stress and/or decreased antioxidant defenses in migraine pathogenesis and progression to a chronic condition lays the foundations for the design of novel prophylactic approaches, which, by reducing brain oxidative phenomena, could favorably modify the clinical course of migraine. Antioxid. Redox Signal. 28, 1144-1183.

Astrocytes as targets for drug discovery

Recent studies have illuminated the crucial role of astrocytes in maintaining proper neuronal health and function. Abnormalities in astrocytic functions have now been implicated in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), and amyotrophic lateral sclerosis (ALS). Historically, drug development programs for neurodegenerative diseases generally target only neurons, overlooking the contributions of astrocytes. Therefore, targeting both disease neurons and astrocytes offers a new approach for drug development for the treatment of neurological diseases. Looking forward, the co-culturing of human neurons with astrocytes could be the next evolutionary step in drug discovery for neurodegenerative diseases.

Sulfur dioxide exposure enhances Th2 inflammatory responses via activating STAT6 pathway in asthmatic mice

Sulfur dioxide (SO₂) is one of potential risk factors for induction and/or exacerbation of asthma, but the underlying mechanisms are not well understood. In this study, we investigate the role of SO₂ in asthma using a classical asthmatic model with allergic airway inflammation by treating C57BL/6 mice with ovalbumin (OVA) and/or 10 mg/m³ SO₂. Our results showed that SO₂ exposure alone induced slight pathological changes but did not significantly increase inflammatory cell counts, pro-inflammatory cytokine expression, and mucus production in the airway of mice, whereas SO₂ exposure in OVA-induced asthmatic mice caused marked pulmonary pathological changes and significantly increased the counts of eosinophil-rich leukocytes compared with OVA alone asthmatic mice. The expression of MUC5AC, TNF-α, Th2 cytokines (IL-4, IL-5, and IL-13) and STAT6 was further up-regulated in OVA plus SO₂ treated mice compared with OVA alone treated mice. In addition, exposure to SO₂ alone markedly elevated STAT6 mRNA levels and hydrogen peroxide (H₂O₂) content in the lung. These findings suggest that SO₂ amplifies Th2 inflammatory responses in OVA-induced asthmatic mice by activating STAT6, which can further induce Th2 cytokine expression. Induction of STAT6 expression might be an important mechanism underlying the increased risk for asthma after environmental exposure.

The STAT-ROS cycle extends IFN‑induced cancer cell apoptosis

In mammals, the signal transducer and activator of transcription (STAT) protein processes mitochondria importation targets and mitochondria respiratory complexes, and triggers reactive oxygen species (ROS) generation, which conversely rapidly initiates the activation of STAT. Interferon (IFN) administration increases cancer cell apoptosis via STAT activation and ROS accumulation. However, the existence of a STAT-ROS cycle and how it affects IFN‑induced cancer cellular apoptosis are unclear. In the present study, we used MCF7 breast cancer cells and confirmed that a combination of IFN‑α/β/γ incubation induced STAT1/3 phosphorylation and mitochondria importation, which increased mitochondria respiratory complexes, the cellular oxygen consumption rate (OCR), and ROS production, followed by cellular apoptosis. We also found that STAT1/3 overexpression induced mitochondria respiratory complexes and ROS production. Additionally, ROS induced by H2O2 induced phosphorylation of STAT1/3 and promoted mitochondria importation. STAT1/3 deletion suppressed H2O2-induced acute cellular OCR, increasing the ROS level and indicating that STAT1/3 is necessary for ROS-induced mitochondria OCR and further ROS production, suggesting the existence of a STAT-ROS cycle. We next found that IFN induced mitochondria respiratory complexes followed by induction of OCR, ROS, and apoptosis, which were partially blocked by STAT1/3 deletion. Additionally, the suppression of ROS inhibited IFN‑induced STAT1/3 activation. Finally, we discovered that this cycle exists also in A431 and HeLa cancer cells. These results indicate that a STAT-ROS cycle extends IFN‑induced cellular apoptosis.

Curcumin alleviates oxidative stress and mitochondrial dysfunction in astrocytes

Oxidative stress plays a critical role in various neurodegenerative diseases, thus alleviating oxidative stress is a potential strategy for therapeutic intervention and/or prevention of neurodegenerative diseases. In the present study, alleviation of oxidative stress through curcumin is investigated in A172 (human glioblastoma cell line) and HA-sp (human astrocytes cell line derived from the spinal cord) astrocytes. H2O2 was used to induce oxidative stress in astrocytes (A172 and HA-sp). Data show that H2O2 induces activation of astrocytes in dose- and time-dependent manner as evident by increased expression of GFAP in A172 and HA-sp cells after 24 and 12h respectively. An upregulation of Prdx6 was also observed in A172 and HA-sp cells after 24h of H2O2 treatment as compared to untreated control. Our data also showed that curcumin inhibits oxidative stress-induced cytoskeleton disarrangement, and impedes the activation of astrocytes by inhibiting upregulation of GFAP, vimentin and Prdx6. In addition, we observed an inhibition of oxidative stress-induced inflammation, apoptosis and mitochondria fragmentation after curcumin treatment. Therefore, our results suggest that curcumin not only protects astrocytes from H2O2-induced oxidative stress but also reverses the mitochondrial damage and dysfunction induced by oxidative stress. This study also provides evidence for protective role of curcumin on astrocytes by showing its effects on attenuating reactive astrogliosis and inhibiting apoptosis.

Naproxen, a Nonsteroidal Anti-Inflammatory Drug, Can Affect Daily Hypobaric Hypoxia-Induced Alterations of Monoamine Levels in Different Areas of the Brain in Male Rats

Goswami, Ananda Raj, Goutam Dutta, and Tusharkanti Ghosh. Naproxen, a nonsteroidal anti-inflammatory drug can affect daily hypobaric hypoxia-induced alterations of monoamine levels in different areas of the brain in male rats. High Alt Med Biol. 17:133-140, 2016.-The oxidative stress (OS)-induced prostaglandin (PG) release, in hypobaric hypoxic (HHc) condition, may be linked with the changes of brain monoamines. The present study intends to explore the changes of monoamines in hypothalamus (H), cerebral cortex (CC), and cerebellum (CB) along with the motor activity in rats after exposing them to simulated hypobaric condition and the role of PGs on the daily hypobaric hypoxia (DHH)-induced alteration of brain monoamines by administering, an inhibitor of PG synthesis, naproxen. The rats were exposed to a decompression chamber at 18,000 ft for 8 hours per day for 6 days after administration of vehicle or naproxen (18 mg/kg body wt.). The monoamine levels (epinephrine, E; norepinephrine, NE; dopamine, DA; and 5-hydroxytryptamine, 5-HT) in CC, CB, and H were assayed by high-performance liquid chromatography (HPLC) with electrochemical detection, and the locomotor behavior was measured by open field test. The NE and DA levels were decreased in CC, CB, and H of the rat brain in HHc condition. The E and 5-HT levels were decreased in CC, but in H and CB, they remained unaltered in HHc condition. These DHH-induced changes of monoamines in brain areas were prevented after administration of naproxen in HHc condition. The locomotor behavior remained unaltered in HHc condition and after administration of naproxen in HHc condition. The DHH-induced changes of monoamines in the brain in HHc condition are probably linked with PGs that may be induced by OS.

Protein-protein interaction between caveolin-1 and SHP-2 is dependent on the N-SH2 domain of SHP-2

Src homology 2-containing protein tyrosine phosphatase 2 (SHP-2) is known to protect neurons from neurodegeneration during ischemia/reperfusion injury. We recently reported that ROS-mediated oxidative stress promotes phosphorylation of endogenous SHP-2 in astrocytes and complex formation between caveolin-1 and SHP-2 in response to oxidative stress. To examine the region of SHP-2 participating in complex formation with caveolin-1, we generated three deletion mutant constructs and six point mutation constructs of SHP-2. Compared with wild-type SHP-2, binding of the N-SH2 domain deletion mutant of SHP-2 to p-caveolin-1 was reduced greatly, using flow cytometric competitive binding assays and surface plasmon resonance (SPR). Moreover, deletion of the N-SH2 domain of SHP-2 affected H2O2-mediated ERK phosphorylation and Src phosphorylation at Tyr 419 in primary astrocytes, suggesting that N-SH2 domain of SHP-2 is responsible for the binding of caveolin-1 and contributes to the regulation of Src phosphorylation and activation following ROS-induced oxidative stress in brain astrocytes.

The control of reactive oxygen species production by SHP-1 in oligodendrocytes

We have previously described reduced myelination and corresponding myelin basic protein (MBP) expression in the central nervous system of Src homology 2 domain-containing protein tyrosine phosphatase 1 (SHP-1) deficient motheaten (me/me) mice compared with normal littermate controls. Deficiency in myelin and MBP expression in both brains and spinal cords of motheaten mice correlated with reduced MBP mRNA expression levels in vivo and in purified oligodendrocytes in vitro. Therefore, SHP-1 activity seems to be a critical regulator of oligodendrocyte gene expression and function. Consistent with this role, this study demonstrates that oligodendrocytes of motheaten mice and SHP-1-depleted N20.1 cells produce higher levels of reactive oxygen species (ROS) and exhibit corresponding markers of increased oxidative stress. In agreement with these findings, we demonstrate that increased production of ROS coincides with ROS-induced signaling pathways known to affect myelin gene expression in oligodendrocytes. Antioxidant treatment of SHP-1-deficient oligodendrocytes reversed the pathological changes in these cells, with increased myelin protein gene expression and decreased expression of nuclear factor (erythroid-2)-related factor 2 (Nrf2) responsive gene, heme oxygenase-1 (HO-1). Furthermore, we demonstrate that SHP-1 is expressed in human white matter oligodendrocytes, and there is a subset of multiple sclerosis subjects that demonstrate a deficiency of SHP-1 in normal-appearing white matter. These studies reveal critical pathways controlled by SHP-1 in oligodendrocytes that relate to susceptibility of SHP-1-deficient mice to both developmental defects in myelination and to inflammatory demyelinating diseases.

N-acetyl cysteine mitigates the acute effects of cocaine-induced toxicity in astroglia-like cells

Cocaine has a short half-life of only about an hour but its effects, predominantly on the central nervous system (CNS), are fairly long-lasting. Of all cells within the CNS, astrocytes may be the first to display cocaine toxicity owing to their relative abundance in the brain. Cocaine entry could trigger several early response changes that adversely affect their survival, and inhibiting these changes could conversely increase their rate of survival. In order to identify these changes and the minimal concentrations of cocaine that can elicit them in vitro, rat C6 astroglia-like cells were treated with cocaine (2–4 mM for 1h) and assayed for alterations in gross cell morphology, cytoplasmic vacuolation, viability, reactive oxygen species (ROS) generation, glutathione (GSH) levels, cell membrane integrity, F-actin cytoskeleton, and histone methylation. We report here that all of the above identified features are significantly altered by cocaine, and may collectively represent the key pathology underlying acute toxicity-mediated death of astroglia-like cells. Pretreatment of the cells with the clinically available antioxidant N-acetyl cysteine (NAC, 5 mM for 30 min) inhibited these changes during subsequent application of cocaine and mitigated cocaine-induced toxicity. Despite repeated cocaine exposure, NAC pretreated cells remained highly viable and post NAC treatment also increased viability of cocaine treated cells to a smaller yet significant level. We show further that this alleviation by NAC is mediated through an increase in GSH levels in the cells. These findings, coupled with the fact that astrocytes maintain neuronal integrity, suggest that compounds which target and mitigate these early toxic changes in astrocytes could have a potentially broad therapeutic role in cocaine-induced CNS damage.

SHP-2 binds to caveolin-1 and regulates Src activity via competitive inhibition of CSK in response to H2O2 in astrocytes

Reactive oxygen species (ROS) regulate diverse cellular functions by triggering signal transduction events, such as Src and mitogen-activated protein (MAP) kinases. Here, we report the role of caveolin-1 and Src homology 2 domain-containing protein tyrosine phosphatase 2 (SHP-2) in H₂O₂-induced signaling pathway in brain astrocytes. H₂O₂-mediated oxidative stress induced phosphorylation of caveolin-1 and association between p-caveolin-1 and SHP-2. SHP-2 specifically bound to wild-type caveolin-1 similarly to c-Src tyrosine kinase (CSK), but not to phosphorylation-deficient mutant of caveolin-1 (Y14A), and interfered with complex formation between caveolin-1 and CSK. In the presence of CSK siRNA, binding between caveolin-1 and SHP-2 was enhanced by H₂O₂ treatment, which led to reduced Src phosphorylation at tyrosine (Tyr) 530 and enhanced Src phosphorylation at Tyr 419. In contrast, siRNA targeting of SHP-2 facilitated H₂O₂-mediated interaction between caveolin-1 and CSK and enhanced Src phosphorylation at Tyr 530, leading to subsequent decrease in Src downstream signaling, such as focal adhesion kinase (FAK) and extracellular signal-related kinase (ERK). Our results collectively indicate that SHP-2 alters Src kinase activity by interfering with the complex formation between CSK and phosphotyrosine caveolin-1 in the presence of H₂O₂, thus functions as a positive regulator in Src signaling under oxidative stress in brain astrocytes.

Absence of Delayed Neuronal Death in ATP-Injected Brain: Possible Roles of Astrogliosis

Although secondary delayed neuronal death has been considered as a therapeutic target to minimize brain damage induced by several injuries, delayed neuronal death does not occur always. In this study, we investigated possible mechanisms that prevent delayed neuronal death in the ATP-injected substantia nigra (SN) and cortex, where delayed neuronal death does not occur. In both the SN and cortex, ATP rapidly induced death of the neurons and astrocytes in the injection core area within 3 h, and the astrocytes in the penumbra region became hypertropic and rapidly surrounded the damaged areas. It was observed that the neurons survived for up to 1-3 months in the area where the astrocytes became hypertropic. The damaged areas of astrocytes gradually reduced at 3 days, 7 days, and 1-3 months. Astrocyte proliferation was detectable at 3-7 days, and vimentin was expressed in astrocytes that surrounded and/or protruded into the damaged sites. The NeuN-positive cells also reappeared in the injury sites where astrocytes reappeared. Taken together, these results suggest that astroycte survival and/or gliosis in the injured brain may be critical for neuronal survival and may prevent delayed neuronal death in the injured brain.

Stat3 inhibition attenuates mechanical allodynia through transcriptional regulation of chemokine expression in spinal astrocytes

BACKGROUND

Signal transducer and activator of transcription 3 (Stat3) is known to induce cell proliferation and inflammation by regulating gene transcription. Recent studies showed that Stat3 modulates nociceptive transmission by reducing spinal astrocyte proliferation. However, it is unclear whether Stat3 also contributes to the modulation of nociceptive transmission by regulating inflammatory response in spinal astrocytes. This study aimed at investigating the role of Stat3 on neuroinflammation during development of pain in rats after intrathecal injection of lipopolysaccharide (LPS).

METHODS

Stat3 specific siRNA oligo and synthetic selective inhibitor (Stattic) were applied to block the activity of Stat3 in primary astrocytes or rat spinal cord, respectively. LPS was used to induce the expression of proinflammatory genes in all studies. Immunofluorescence staining of cells and slices of spinal cord was performed to monitor Stat3 activation. The impact of Stat3 inhibition on proinflammatory genes expression was determined by cytokine antibody array, enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Mechanical allodynia, as determined by the threshold pressure that could induce hind paw withdrawal after application of standardized von Frey filaments, was used to detect the effects of Stat3 inhibition after pain development with intrathecal LPS injection.

RESULTS

Intrathecal injection of LPS activated Stat3 in reactive spinal astrocytes. Blockade of Stat3 activity attenuated mechanical allodynia significantly and was correlated with a lower number of reactive astrocytes in the spinal dorsal horn. In vitro study demonstrated that Stat3 modulated inflammatory response in primary astrocytes by transcriptional regulation of chemokine expression including Cx3cl1, Cxcl5, Cxcl10 and Ccl20. Similarly, inhibition of Stat3 reversed the expression of these chemokines in the spinal dorsal horn.

CONCLUSIONS

Stat3 acted as a transcriptional regulator of reactive astrocytes by modulating chemokine expression. Stat3 regulated inflammatory response in astrocytes and contributed to pain modulation. Blockade of Stat3 represents a new target for pain control.

Genome-wide meta-analysis identifies new susceptibility loci for migraine

Migraine is the most common brain disorder, affecting approximately 14% of the adult population, but its molecular mechanisms are poorly understood. We report the results of a meta-analysis across 29 genome-wide association studies, including a total of 23,285 individuals with migraine (cases) and 95,425 population-matched controls. We identified 12 loci associated with migraine susceptibility (P<5×10(-8)). Five loci are new: near AJAP1 at 1p36, near TSPAN2 at 1p13, within FHL5 at 6q16, within C7orf10 at 7p14 and near MMP16 at 8q21. Three of these loci were identified in disease subgroup analyses. Brain tissue expression quantitative trait locus analysis suggests potential functional candidate genes at four loci: APOA1BP, TBC1D7, FUT9, STAT6 and ATP5B.

Brain inflammation and microglia: facts and misconceptions

THE INFLAMMATION THAT ACCOMPANIES ACUTE INJURY HAS DUAL FUNCTIONS: bactericidal action and repair. Bactericidal functions protect damaged tissue from infection, and repair functions are initiated to aid in the recovery of damaged tissue. Brain injury is somewhat different from injuries in other tissues in two respects. First, many cases of brain injury are not accompanied by infection: there is no chance of pathogens to enter in ischemia or even in traumatic injury if the skull is intact. Second, neurons are rarely regenerated once damaged. This raises the question of whether bactericidal inflammation really occurs in the injured brain; if so, how is this type of inflammation controlled? Many brain inflammation studies have been conducted using cultured microglia (brain macrophages). Even where animal models have been used, the behavior of microglia and neurons has typically been analyzed at or after the time of neuronal death, a time window that excludes the inflammatory response, which begins immediately after the injury. Therefore, to understand the patterns and roles of brain inflammation in the injured brain, it is necessary to analyze the behavior of all cell types in the injured brain immediately after the onset of injury. Based on our experience with both in vitro and in vivo experimental models of brain inflammation, we concluded that not only microglia, but also astrocytes, blood inflammatory cells, and even neurons participate and/or regulate brain inflammation in the injured brain. Furthermore, brain inflammation played by these cells protects neurons and repairs damaged microenvironment but not induces neuronal damage.

Cooling treatment transiently increases the permeability of brain capillary endothelial cells through translocation of claudin-5

The blood-brain-barrier (BBB) is formed by different cell types, of which brain microvascular endothelial cells are major structural constituents. The goal of this study was to examine the effects of cooling on the permeability of the BBB with reference to tight junction formation of brain microendothelial cells. The sensorimotor cortex above the dura mater in adult male Wistar rats was focally cooled to a temperature of 5 °C for 1 h, then immunostaining for immunoglobulin G (IgG) was performed to evaluate the permeability of the BBB. Permeability produced by cooling was also evaluated in cultured murine brain endothelial cells (bEnd3) based on measurement of trans-epithelial electric resistance (TEER). Immunocytochemistry and Western blotting of proteins associated with tight junctions in bEnd3 were performed to determine protein distribution before and after cooling. After focal cooling of the rat brain cortex, diffuse immunostaining for IgG was observed primarily around the small vasculature and in the extracellular spaces of parenchyma of the cortex. In cultured bEnd3, TEER significantly decreased during cooling (15 °C) and recovered to normal levels after rewarming to 37 °C. Immunocytochemistry and Western blotting showed that claudin-5, a critical regulatory protein for tight junctions, was translocated from the membrane to the cytoplasm after cooling in cultured bEnd3 cells. These results suggest that focal brain cooling may open the BBB transiently through an effect on tight junctions of brain microendothelial cells, and that therapeutically this approach may allow control of BBB function and drug delivery through the BBB.

Recombinant PTD-Cu/Zn SOD attenuates hypoxia-reoxygenation injury in cardiomyocytes

BACKGROUND

Oxidative stress plays a pivotal role in myocardial ischemia-reperfusion injury. Increasing the protein expression of intracellular Cu/Zn SOD, which is the major endogenous antioxidant enzyme, may attenuate or prevent hypoxia-reoxygenation injury (HRI) in cultured cardiomyocytes. However, ectogenic Cu/Zn-SOD can hardly be transferred into cells to exert biological effects. In this study, we constructed PTD-Cu/Zn SOD plasmid with a kind of translocation structure-Protein transduction domain (PTD) and detected its transmembrane ability and antioxidant effects in H9c2 rat cardiomyocytes subjected to hypoxia/reoxygenation injury (HRI).

METHODS

We constructed the pET-PTD-Cu/Zn SOD (CDs) prokaryotic expression vectors in plasmid that were inserted into E. coli BL21 to induce the protein expression of PTD-Cu/Zn SOD. H9c2 cardiomyocyte HRI was achieved by exposing cardiomyocytes to 12 h hypoxia followed by 2 h reoxygenation. Protein expression of PTD-Cu/Zn SOD in cardiomyocytes was assayed by Western blot and their enzyme activities were investigated by immunohistochemistry and flow cytometry.

RESULTS

In cultured cardiomyocytes hypoxia-reoxygenation injury model, exogenous PTD-Cu/Zn SOD could penetrate cell membrane to clear superoxide anion and decrease hydrogen peroxide level in H9c2 cardiomyocytes subjected to HRI. The level of mitochondrial membrane potential was restored to normal, and the cell apoptosis was reduced in cardiomyocytes with PTD-Cu/Zn SOD treatment during HRI.

CONCLUSION

Recombinant PTD-Cu/Zn SOD could scavenge intracellular-free superoxide anion, protect mitochondria from damages, and attenuate the hypoxia-reoxygenation injury in cultured cardiomyocytes.

The role of free radicals in the aging brain and Parkinson's Disease: convergence and parallelism

Free radical production and their targeted action on biomolecules have roles in aging and age-related disorders such as Parkinson's disease (PD). There is an age-associated increase in oxidative damage to the brain, and aging is considered a risk factor for PD. Dopaminergic neurons show linear fallout of 5-10% per decade with aging; however, the rate and intensity of neuronal loss in patients with PD is more marked than that of aging. Here, we enumerate the common link between aging and PD at the cellular level with special reference to oxidative damage caused by free radicals. Oxidative damage includes mitochondrial dysfunction, dopamine auto-oxidation, α-synuclein aggregation, glial cell activation, alterations in calcium signaling, and excess free iron. Moreover, neurons encounter more oxidative stress as a counteracting mechanism with advancing age does not function properly. Alterations in transcriptional activity of various pathways, including nuclear factor erythroid 2-related factor 2, glycogen synthase kinase 3β, mitogen activated protein kinase, nuclear factor kappa B, and reduced activity of superoxide dismutase, catalase and glutathione with aging might be correlated with the increased incidence of PD.