SB 239063, a novel p38 inhibitor, attenuates early neuronal injury following ischemia

Neuroprotective Effects of Tryptanthrin-6-Oxime in a Rat Model of Transient Focal Cerebral Ischemia

The activation of c-Jun N-terminal kinase (JNK) plays an important role in stroke outcomes. Tryptanthrin-6-oxime (TRYP-Ox) is reported to have high affinity for JNK and anti-inflammatory activity and may be of interest as a promising neuroprotective agent. The aim of this study was to investigate the neuroprotective effects of TRYP-Ox in a rat model of transient focal cerebral ischemia (FCI), which involved intraluminal occlusion of the left middle cerebral artery (MCA) for 1 h. Animals in the experimental group were administered intraperitoneal injections of TRYP-Ox 30 min before reperfusion and 23 and 47 h after FCI. Neurological status was assessed 4, 24, and 48 h following FCI onset. Treatment with 5 and 10 mg/kg of TRYP-Ox decreased mean scores of neurological deficits by 35-49 and 46-67% at 24 and 48 h, respectively. At these doses, TRYP-Ox decreased the infarction size by 28-31% at 48 h after FCI. TRYP-Ox (10 mg/kg) reduced the content of interleukin (IL) 1β and tumor necrosis factor (TNF) in the ischemic core area of the MCA region by 33% and 38%, respectively, and attenuated cerebral edema by 11% in the left hemisphere, which was affected by infarction, and by 6% in the right, contralateral hemisphere 24 h after FCI. TRYP-Ox reduced c-Jun phosphorylation in the MCA pool at 1 h after reperfusion. TRYP-Ox was predicted to have high blood-brain barrier permeability using various calculated descriptors and binary classification trees. Indeed, reactive oxidant production was significantly lower in the brain homogenates from rats treated with TRYP-Ox versus that in control animals. Our data suggest that the neuroprotective activity of TRYP-Ox may be due to the ability of this compound to inhibit JNK and exhibit anti-inflammatory and antioxidant activity. Thus, TRYP-Ox may be considered a promising neuroprotective agent that potentially could be used for the development of new treatment strategies in cerebral ischemia.

Continuous administration of a p38α inhibitor during the subacute phase after transient ischemia-induced stroke in the rat promotes dose-dependent functional recovery accompanied by increase in brain BDNF protein level

There is unmet need for effective stroke therapies. Numerous neuroprotection attempts for acute cerebral ischemia have failed and as a result there is growing interest in developing therapies to promote functional recovery through increasing synaptic plasticity. For this research study, we hypothesized that in addition to its previously reported role in mediating cell death during the acute phase, the alpha isoform of p38 mitogen-activated protein kinase, p38α, may also contribute to interleukin-1β-mediated impairment of functional recovery during the subacute phase after acute ischemic stroke. Accordingly, an oral, brain-penetrant, small molecule p38α inhibitor, neflamapimod, was evaluated as a subacute phase stroke treatment to promote functional recovery. Neflamapimod administration to rats after transient middle cerebral artery occlusion at two dose levels was initiated outside of the previously characterized therapeutic window for neuroprotection of less than 24 hours for p38α inhibitors. Six-week administration of neflamapimod, starting at 48 hours after reperfusion, significantly improved behavioral outcomes assessed by the modified neurological severity score at Week 4 and at Week 6 post stroke in a dose-dependent manner. Neflamapimod demonstrated beneficial effects on additional measures of sensory and motor function. It also resulted in a dose-related increase in brain-derived neurotrophic factor (BDNF) protein levels, a previously reported potential marker of synaptic plasticity that was measured in brain homogenates at sacrifice. Taken together with literature evidence on the role of p38α-dependent suppression by interleukin-1β of BDNF-mediated synaptic plasticity and BDNF production, our findings support a mechanistic model in which inhibition of p38α promotes functional recovery after ischemic stroke by blocking the deleterious effects of interleukin-1β on synaptic plasticity. The dose-related in vivo efficacy of neflamapimod offers the possibility of having a therapy for stroke that could be initiated outside the short time window for neuroprotection and for improving recovery after a completed stroke.

δ-Opioid receptor activation ameliorates lipopolysaccharide-induced inflammation and apoptosis by inhibiting the MAPK/caspase-3 pathway in BV2 microglial cells

Delta-opioid receptor (DOR) is widely distributed in the central nervous system, and its activation protects against ischaemic/hypoxic brain injury. However, the role of DOR in microglia in ischaemic stroke has not yet been fully investigated. We found that DOR was expressed in both human and mouse cerebral microglia, besides, it was upregulated in activated BV2 microglial cells by immunofluorescence staining and Western blot. DOR activation by the specific agonist TAN-67 significantly enhanced BV2 microglial cell viability and reduced apoptosis, as evidenced by decreased cleaved caspase-3 levels and TdT-mediated aUTP-X nick end labelling (TUNEL) staining after LPS stimulation. Furthermore, activation of DOR significantly inhibited inducible nitric oxide synthase (iNOS) production and dose-dependently inhibited the mRNA and protein expression levels of other pro-inflammatory cytokines, including IL-1β and IL-6, whereas it increased the expression of the anti-inflammatory cytokine IL-10 in LPS-stimulated BV2 microglial cells; these effects were correlated with diminished phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38. Moreover, these effects could be reversed by the DOR antagonist naltrindole. DOR activation can activate microglia to switch to the beneficial phenotype and inhibit LPS-induced inflammation and apoptosis via the mitogen-activated protein kinase (MAPK)/caspase-3 pathway in BV2 microglial cells. This study provides new insight into neuroprotection against and treatment of ischaemic stroke.

Functions of p38 MAP Kinases in the Central Nervous System

Mitogen-activated protein (MAP) kinases are a central component in signaling networks in a multitude of mammalian cell types. This review covers recent advances on specific functions of p38 MAP kinases in cells of the central nervous system. Unique and specific functions of the four mammalian p38 kinases are found in all major cell types in the brain. Mechanisms of p38 activation and downstream phosphorylation substrates in these different contexts are outlined and how they contribute to functions of p38 in physiological and under disease conditions. Results in different model organisms demonstrated that p38 kinases are involved in cognitive functions, including functions related to anxiety, addiction behavior, neurotoxicity, neurodegeneration, and decision making. Finally, the role of p38 kinases in psychiatric and neurological conditions and the current progress on therapeutic inhibitors targeting p38 kinases are covered and implicate p38 kinases in a multitude of CNS-related physiological and disease states.

Pre-clinical to Clinical Translational Failures and Current Status of Clinical Trials in Stroke Therapy: A Brief Review

In stroke (cerebral ischemia), despite continuous efforts both at the experimental and clinical level, the only approved pharmacological treatment has been restricted to tissue plasminogen activator (tPA). Stroke is the leading cause of functional disability and mortality throughout worldwide. Its pathophysiology starts with energy pump failure, followed by complex signaling cascade that ultimately ends in neuronal cell death. Ischemic cascade involves excessive glutamate release followed by raised intracellular sodium and calcium influx along with free radicals' generation, activation of inflammatory cytokines, NO synthases, lipases, endonucleases and other apoptotic pathways leading to cell edema and death. At the pre-clinical stage, several agents have been tried and proven as an effective neuroprotectant in animal models of ischemia. However, these agents failed to show convincing results in terms of efficacy and safety when the trials were conducted in humans following stroke. This article highlights the various agents which have been tried in the past but failed to translate into stroke therapy along with key points that are responsible for the lagging of experimental success to translational failure in stroke treatment.

Delta Opioids: Neuroprotective Roles in Preclinical Studies

Since ancient times, opioids have been used clinically and abused recreationally. In the early stages (about 1,000 AD) of opium history, an Arab physician, Avicenna, administered opioids to control diarrhea and eye diseases. ¹ Opioids have very strong pain relieving properties and they also regulate numerous cellular responses. Opioid receptors are expressed throughout the body, including the nervous system, heart, lungs, liver, gastrointestinal tract, and retina. ^2-6 Delta opioid receptors (DORs) are a very attractive target from the perspective of both receptor function and their therapeutic potential. Due to a rapid progress in mouse mutagenesis and development of small molecules as DOR agonist, novel functions and roles of DORs have emerged in recent years. This review article focuses on the recent advances in the neuroprotective roles of DOR agonists in general and retina neuroprotection in particular. Rather than being exhaustive, this review highlights the selected studies of DOR function in neuroprotection. We also highlight our preclinical studies using rodent models to demonstrate the potentials of DOR agonists for retinal neuroprotection. Based on existing literature and our recently published data on the eye, DOR agonists possess therapeutic abilities that protect the retina and optic nerve injury against glaucoma and perhaps other retinopathies as well. This review also highlights the signaling events associated with DOR for neuroprotection in the eye. There is a need for translational research on DORs to recognize their potential for clinical application such as in glaucoma.

Minocycline reduces intracerebral hemorrhage-induced white matter injury in piglets

Aims

White matter (WM) injury after intracerebral hemorrhage (ICH) results in poor or even fatal outcomes. As an anti‐inflammatory drug, minocycline has been considered a promising choice to treat brain injury after ICH. However, whether minocycline can reduce WM injury after ICH is still controversial. In the present study, we investigate the effect and underlying mechanism of minocycline on WM injury after ICH.

Methods

An ICH model was induced by an injection of autologous blood into the right frontal lobe of piglets. First, transcriptional analysis was performed at day 1 or 3 to investigate the dynamic changes in neuroinflammatory gene expression in WM after ICH. Second, ICH piglets were treated either with minocycline or with vehicle alone. All piglets then underwent magnetic resonance imaging to measure brain swelling. Brain tissue was used for real‐time polymerase chain reaction (RT‐PCR), immunohistochemistry, Western blot, and electron microscopy.

Results

Transcriptional analysis demonstrated that transforming growth factor‐β (TGF‐β)/mitogen‐activated protein kinase (MAPK) signaling is associated with microglia/macrophage‐mediated inflammation activation after ICH and is then involved in WM injury after ICH in piglets. Minocycline treatment results in less ICH‐induced brain swelling, fewer neurological deficits, and less WM injury in comparison with the vehicle alone. In addition, minocycline reduces microglial activation and alleviates demyelination in white matter after ICH. Finally, we found that minocycline attenuates WM injury by increasing the expression of TGF‐β and suppressing MAPK activation after ICH.

Conclusion

These results indicate that TGF‐β–mediated MAPK signaling contributes to WM injury after ICH, which can be altered by minocycline treatment.

Analysis of long non-coding RNA expression profiles in neonatal rats with hypoxic-ischemic brain damage

Hypoxic-ischemic brain damage (HIBD) which is a common cause of acute mortality and neurological dysfunction in neonates still lacks effective therapeutic methods. Long non-coding RNAs (lncRNAs) were demonstrated to play a crucial role in many diseases. To give a foundation for subsequent functional studies of lncRNAs in HIBD, we investigated the profiling of lncRNAs and messenger RNAs (mRNAs) using neonatal HIBD rat model. Six neonatal rats were divided into sham-operated group (n = 3) and HIBD group (n = 3) randomly. Deep RNA sequencing was implemented to find out the meaningful lncRNAs and mRNAs. Quantitative real-time PCR was used to validate expressions of lncRNAs and mRNAs. The Gene Ontology (GO) and kyoto encyclopedia of genes a genomes (KEGG) database were used to predict functions of lncRNAs. A total of 328 differentially expressed lncRNAs (177 down-regulated vs 151 up-regulated) and 7157 differentially expressed mRNAs (2552 down-regulated vs 4605 up-regulated) were identified. The Quantitative real-time PCR results showed significant differential expressions of five lncRNAs and five mRNAs which were consistent with the RNA-Seq data. Gene ontology and KEGG analysis showed these lncRNAs and their expression-correlated mRNAs were closely related to the Janus tyrosine kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway, NF-kappa B signaling pathway, Toll-like receptor signaling pathway, calcium signaling pathway, Notch signaling pathway, mitogen activated protein kinase signaling pathway, neuroactive ligand-receptor interaction pathway and more. The results of our study identified the characterization and expression profiles of lncRNAs in neonatal HIBD and may be a basis for further therapeutic research. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* and *Open Data* because it provided all relevant information to reproduce the study in the manuscript and because it made the data publicly available. The data can be accessed at https://osf.io/yf3da/. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.

Humanin Attenuates NMDA-Induced Excitotoxicity by Inhibiting ROS-dependent JNK/p38 MAPK Pathway

Humanin (HN) is a novel 24-amino acid peptide that protects neurons against N-methyl-d-aspartate (NMDA)-induced toxicity. However, the contribution of the different mitogen-activated protein kinases (MAPKs) signals to HN neuroprotection against NMDA neurotoxicity remains unclear. The present study was therefore aimed to investigate neuroprotective mechanisms of HN. We analyzed intracellular Ca²⁺ levels, reactive oxygen species (ROS) production, and the MAPKs signal transduction cascade using an in vitro NMDA-mediated excitotoxicity of cortical neurons model. Results showed that: (1) HN attenuated NMDA-induced neuronal insults by increasing cell viability, decreasing lactate dehydrogenase (LDH) release, and increasing cell survival; (2) HN reversed NMDA-induced increase in intracellular calcium; (3) pretreatment by HN or 1,2-bis(2-aminophenoxy)ethane-N,N,N’,N’-tetraacetic acid (BAPTA-AM), an intracellular calcium chelator, decreased ROS generation after NMDA exposure; (4) administration of HN or N-Acetyl-l-cysteine (NAC), a ROS scavenger, inhibited NMDA-induced JNK and p38 MAPK activation. These results indicated that HN reduced intracellular elevation of Ca²⁺ levels, which, in turn, inhibited ROS generation and subsequent JNK and p38 MAPK activation that are involved in promoting cell survival in NMDA-induced excitotoxicity. Therefore, the present study suggests that inhibition of ROS-dependent JNK/p38 MAPK signaling pathway serves an effective strategy for HN neuroprotection against certain neurological diseases.

Targeting NMDA receptors in stroke: new hope in neuroprotection

NMDA (N-methyl-d-aspartate) receptors (NMDARs) play a central role in excitotoxic neuronal death caused by ischemic stroke, but NMDAR channel blockers have failed to be translated into clinical stroke treatments. However, recent research on NMDAR-associated signaling complexes has identified important death-signaling pathways linked to NMDARs. This led to the generation of inhibitors that inhibit these pathways downstream from the receptor without necessarily blocking NMDARs. This therapeutic approach may have fewer side effects and/or provide a wider therapeutic window for stroke as compared to the receptor antagonists. In this review, we highlight the key findings in the signaling cascades downstream of NMDARs and the novel promising therapeutics for ischemic stroke.

Sulfosuccinimidyl oleate sodium is neuroprotective and alleviates stroke-induced neuroinflammation

BACKGROUND

Ischemic stroke is one of the main causes of death and disability worldwide. It is caused by the cessation of cerebral blood flow resulting in the insufficient delivery of glucose and oxygen to the neural tissue. The inflammatory response initiated by ischemic stroke in order to restore tissue homeostasis in the acute phase of stroke contributes to delayed brain damage.

METHODS

By using in vitro models of neuroinflammation and in vivo model of permanent middle cerebral artery occlusion, we demonstrate the neuroprotective and anti-inflammatory effects of sulfosuccinimidyl oleate sodium (SSO).

RESULTS

SSO significantly reduced the lipopolysaccharide/interferon-γ-induced production of nitric oxide, interleukin-6 and tumor necrosis factor-α, and the protein levels of inflammatory enzymes including nitric oxide synthase 2, cyclooxygenase-2 (COX-2), and p38 mitogen-activated protein kinase (MAPK) in microglia, without causing cell toxicity. Although SSO failed to directly alleviate glutamate-induced excitotoxicity in murine cortical neurons, it prevented inflammation-induced neuronal death in microglia-neuron co-cultures. Importantly, oral administration of SSO in Balb/c mice subjected to permanent occlusion of the middle cerebral artery reduced microglial activation in the peri-ischemic area and attenuated brain damage. This in vivo neuroprotective effect of SSO was associated with a reduction in the COX-2 and heme oxygenase-1 immunoreactivities.

CONCLUSIONS

Our results suggest that SSO is an anti-inflammatory and a possible therapeutic candidate in diseases such as stroke where inflammation is a central hallmark.

Transglutaminase 2 modulation of NF-κB signaling in astrocytes is independent of its ability to mediate astrocytic viability in ischemic injury

Transglutaminase 2 (TG2) is a multifunctional protein that can contribute to cell death and cell survival processes in a variety of disease contexts. Within the brain, TG2 has been shown to promote cell death in ischemic injury when expressed in astrocytes (Colak and Johnson, 2012). However, the specific functions and characteristics of astrocytic TG2 that mediate this effect are largely unknown. Therefore, the goal of this study was to investigate the role of astrocytic TG2 in mediating cellular viability processes in the context of ischemic injury, with a specific focus on its contributions to intracellular signaling cascades. We show that, in response to oxygen/glucose deprivation (OGD), acute lentiviral-mediated knockdown of TG2, as well as inhibition with an irreversible TG2 inhibitor, enhances cell survival. We also show that TG2 depletion increases nuclear factor-κB (NF-κB) signaling, whereas inhibition reduces NF-κB activity. Despite its clear contribution to NF-κB signaling, however, TG2 modulation of NF-κB signaling is not likely to be a major contributor to its ability to mediate astrocytic viability in this context. Overall, the results of this study provide insight into the role of TG2 in astrocytes and suggest possible avenues for future study of the relationship between astrocytic TG2 and ischemic injury.

Phytochemicals in Ischemic Stroke

Stroke is the second foremost cause of mortality worldwide and a major cause of long-term disability. Due to changes in lifestyle and an aging population, the incidence of stroke continues to increase and stroke mortality predicted to exceed 12 % by the year 2030. However, the development of pharmacological treatments for stroke has failed to progress much in over 20 years since the introduction of the thrombolytic drug, recombinant tissue plasminogen activator. These alarming circumstances caused many research groups to search for alternative treatments in the form of neuroprotectants. Here, we consider the potential use of phytochemicals in the treatment of stroke. Their historical use in traditional medicine and their excellent safety profile make phytochemicals attractive for the development of therapeutics in human diseases. Emerging findings suggest that some phytochemicals have the ability to target multiple pathophysiological processes involved in stroke including oxidative stress, inflammation and apoptotic cell death. Furthermore, epidemiological studies suggest that the consumption of plant sources rich in phytochemicals may reduce stroke risk, and so reinforce the possibility of developing preventative or neuroprotectant therapies for stroke. In this review, we describe results of preclinical studies that demonstrate beneficial effects of phytochemicals in experimental models relevant to stroke pathogenesis, and we consider their possible mechanisms of action.

Identification of NADPH oxidase as a key mediator in the post-ischemia-induced sequestration and degradation of the GluA2 AMPA receptor subunit

A hallmark of ischemic/reperfusion injury is a change in subunit composition of synaptic 2-amino-3-(3-hydroxy-5-methylisoazol-4-yl)propionic acid receptors (AMPARs). This change in AMPAR subunit composition leads to an increase in surface expression of GluA2-lacking Ca(2+) /Zn(2+) permeable AMPARs. These GluA2-lacking AMPARs play a key role in promoting delayed neuronal death following ischemic injury. At present, the mechanism(s) responsible for the ischemia/reperfusion-induced subunit composition switch and degradation of the GluA2 subunit remain unclear. In this study, we investigated the role of NADPH oxidase, and its importance in mediating endocytosis and subsequent degradation of the GluA2 AMPAR subunit in adult rat hippocampal slices subjected to oxygen-glucose deprivation/reperfusion (OGD/R) injury. In hippocampal slices pre-treated with the NADPH oxidase inhibitor apocynin attenuated OGD/R-mediated sequestration of GluA2 and GluA1 as well as prevent the degradation of GluA2. We provide compelling evidence that NADPH oxidase mediated sequestration of GluA1- and GluA2- involved activation of p38 MAPK. Furthermore, we demonstrate that inhibition of NADPH oxidase blunts the OGD/R-induced association of GluA2 with protein interacting with C kinase-1. In summary, this study identifies a novel mechanism that may underlie the ischemia/reperfusion-induced AMPAR subunit composition switch and a potential therapeutic target.

p38α (MAPK14) critically regulates the immunological response and the production of specific cytokines and chemokines in astrocytes

In CNS lesions, “reactive astrocytes” form a prominent cellular response. However, the nature of this astrocyte immune activity is not well understood. In order to study astrocytic immune responses to inflammation and injury, we generated mice with conditional deletion of p38α (MAPK14) in GFAP+ astrocytes. We studied the role of p38α signaling in astrocyte immune activation both in vitro and in vivo, and simultaneously examined the effects of astrocyte activation in CNS inflammation. Our results showed that specific subsets of cytokines (TNFα, IL-6) and chemokines (CCL2, CCL4, CXCL1, CXCL2, CXCL10) are critically regulated by p38α signaling in astrocytes. In an in vivo CNS inflammation model of intracerebral injection of LPS, we observed markedly attenuated astrogliosis in conditional GFAPcre p38α^−/− mice. However, GFAPcre p38α^−/− mice showed marked upregulation of CCL2, CCL3, CCL4, CXCL2, CXCL10, TNFα, and IL-1β compared to p38αfl/fl cohorts, suggesting that in vivo responses to LPS after GFAPcre p38α deletion are complex and involve interactions between multiple cell types. This finding was supported by a prominent increase in macrophage/microglia and neutrophil recruitment in GFAPcre p38α^−/− mice compared to p38αfl/fl controls. Together, these studies provide important insights into the critical role of p38α signaling in astrocyte immune activation.

The p38alpha mitogen-activated protein kinase limits the CNS proinflammatory cytokine response to systemic lipopolysaccharide, potentially through an IL-10 dependent mechanism

BACKGROUND

The p38α mitogen-activated protein kinase (MAPK) is a well-characterized intracellular kinase involved in the overproduction of proinflammatory cytokines from glia. As such, p38α appears to be a promising therapeutic target for neurodegenerative diseases associated with neuroinflammation. However, the in vivo role of p38α in cytokine production in the CNS is poorly defined, and prior work suggests that p38α may be affecting a yet to be identified negative feedback mechanism that limits the acute, injury-induced proinflammatory cytokine surge in the CNS.

METHODS

To attempt to define this negative feedback mechanism, we used two in vitro and two in vivo models of neuroinflammation in a mouse where p38α is deficient in cells of the myeloid lineage.

RESULTS

We found that p38α in myeloid cells has an important role in limiting amplitude of the acute proinflammatory cytokine response to a systemic inflammatory challenge. Moreover, we identified IL-10 as a potential negative feedback mechanism regulated by p38α.

CONCLUSIONS

Our data suggest that p38α regulates a proper balance between the pro- and anti-inflammatory cytokine responses to systemic inflammation, and that if circulating IL-10 levels are not elevated to counter-balance the increased systemic proinflammatory responses, the spread of the inflammatory response from the periphery to the CNS is exaggerated.

Neuroprotective effects of bilobalide on cerebral ischemia and reperfusion injury are associated with inhibition of pro-inflammatory mediator production and down-regulation of JNK1/2 and p38 MAPK activation

BACKGROUND

Mitogen-activated protein kinase (MAPK) signaling pathways are implicated in inflammatory and apoptotic processes of cerebral ischemia and reperfusion (I/R) injury. Hence, MAPK pathways represent a promising therapeutic target. Exploring the full potential of inhibitors of MAPK pathways is a useful therapeutic strategy for ischemic stroke. Bilobalide, a predominant sesquiterpene trilactone constituent of Ginkgo biloba leaves, has been shown to exert powerful neuroprotective properties, which are closely related to both anti-inflammatory and anti-apoptotic pathways. We investigated the neuroprotective roles of bilobalide in the models of middle cerebral artery occlusion and reperfusion (MCAO/R) and oxygen-glucose deprivation and reoxygenation (OGD/R) of cerebral I/R injury. Moreover, we attempted to confirm the hypothesis that its protection effect is via modulation of pro-inflammatory mediators and MAPK pathways.

METHODS

Male Sprague-Dawley rats were subjected to MCAO for 2 h followed by reperfusion for 24 h. Bilobalide was administered intraperitoneally 60 min before induction of middle cerebral artery occlusion (MCAO). After reperfusion, neurological deficit scores, infarct volume, infarct weight, and brain edema were assessed. Ischemic penumbrae of the cerebral cortex were harvested to determine superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide, TNF-α, interleukin 1β (IL-1β), p-ERK1/2, p-JNK1/2, and p-p38 MAPK concentration. Similarly, the influence of bilobalide on the expression of nitric oxide, TNF-α, IL-1β, p-ERK1/2, p-JNK1/2, and p-p38 MAPK was also observed in an OGD/R in vitro model of I/R injury.

RESULTS

Pretreatment with bilobalide (5, 10 mg/kg) significantly decreased neurological deficit scores, infarct volume, infarct weight, brain edema, and concentrations of MDA, nitric oxide, TNF-α, IL-1β, and increased SOD activity. Furthermore, bilobalide (5, 10 mg/kg) pretreatment significantly down-regulated both p-JNK1/2 and p-p38 MAPK expression, whereas they had no effect on p-ERK1/2 expression in the ischemic penumbra. Supporting these observations in vivo, pretreatment with bilobalide (50, 100 μM) significantly down-regulated nitric oxide, TNF-α, IL-1β, p-JNK1/2, and p-p38 MAPK expression, but did not change p-ERK1/2 expression in rat cortical neurons after OGD/R injury.

CONCLUSIONS

These data indicate that the neuroprotective effects of bilobalide on cerebral I/R injury are associated with its inhibition of pro-inflammatory mediator production and down-regulation of JNK1/2 and p38 MAPK activation.

Anti-inflammatory activity of iridoid and catechol derivatives from Eucommia ulmoides Oliver

Neuroinflammation and pro-inflammatory mediators play key roles in the pathogenesis of neurodegenerative diseases including stroke, which account for a significant burden of morbidity and mortality worldwide. Recently, the unsatisfactory pharmacotherapy and side effects of the drugs led to the development of alternative medicine for treating these diseases. Du Zhong (DZ), Eucommia ulmoides Oliver leaves, is a commonly used herb in the therapy of stroke in China. We hypothesize that the components from DZ inhibit neuroinflammation. In this study, DZ was extracted and the bioactive fractions with inhibitory effect on lipopolysaccharide (LPS)-stimulated nitric oxide (NO) production in BV-2 microglial cells were further separated using chromatography. Two purified bioactive compounds, genipin (compound C) and 4-(1,2-dimethoxyethyl)benzene-1,2-diol (compound F), were isolated and identified after spectroscopic analysis. The results showed that they inhibited LPS-stimulated NO and tumor necrosis factor-alpha (TNF-α) production. Genipin exerted its anti-inflammatory effects through PI3K/Akt signaling pathway, whereas compound F inhibited phosphorylation of p38 mitogen-activated protein kinase (MAPK). In conclusion, genipin and compound F have potential for developing into new drugs for treating neurodegenerative diseases.

Intermittent fasting attenuates inflammasome activity in ischemic stroke

Recent findings have revealed a novel inflammatory mechanism that contributes to tissue injury in cerebral ischemia mediated by multi-protein complexes termed inflammasomes. Intermittent fasting (IF) can decrease the levels of pro-inflammatory cytokines in the periphery and brain. Here we investigated the impact of IF (16h of food deprivation daily) for 4months on NLRP1 and NLRP3 inflammasome activities following cerebral ischemia. Ischemic stroke was induced in C57BL/6J mice by middle cerebral artery occlusion, followed by reperfusion (I/R). IF decreased the activation of NF-κB and MAPK signaling pathways, the expression of NLRP1 and NLRP3 inflammasome proteins, and both IL-1β and IL-18 in the ischemic brain tissue. These findings demonstrate that IF can attenuate the inflammatory response and tissue damage following ischemic stroke by a mechanism involving suppression of NLRP1 and NLRP3 inflammasome activity.

Involvement of p38 MAPK in reactive astrogliosis induced by ischemic stroke

Reactive astrogliosis is an essential feature of astrocytic response to all forms of central nervous system (CNS) injury and disease, which may benefit or harm surrounding neural and non-neural cells. Despite extensive study, its molecular triggers remain largely unknown in term of ischemic stroke. In the current study we investigated the role p38 mitogen-activated protein kinase (MAPK) in astrogliosis both in vitro and in vivo. In a mouse model of middle cerebral artery occlusion (MCAO), p38 MAPK activation was observed in the glia scar area, along with increased glial fibrillary acidic protein (GFAP) expression. In primary astrocyte cultures, hypoxia and scratch injury-induced astrogliosis was attenuated by both p38 inhibition and knockout of p38 MAPK. In addition, both knockout and inhibition of p38 MAPK also reduced astrocyte migration, but did not affect astrocyte proliferation. In a mouse model of permanent MCAO, no significant difference in motor function recovery and lesion volume was observed between conditional GFAP/p38 MAPK knockout mice and littermates. While a significant reduction of astrogliosis was observed in the GFAP/p38 knockout mice compared with the littermates. Our findings suggest that p38 MAPK signaling pathway plays an important role in the ischemic stroke-induced astrogliosis and thus may serve as a novel target to control glial scar formation.

VPAC2 receptor agonist BAY 55-9837 increases SMN protein levels and moderates disease phenotype in severe spinal muscular atrophy mouse models

Background

Spinal Muscular Atrophy (SMA) is one of the most common inherited causes of infant death and is caused by the loss of functional survival motor neuron (SMN) protein due to mutations or deletion in the SMN1 gene. One of the treatment strategies for SMA is to induce the expression of the protein from the homologous SMN2 gene, a rescuing paralog for SMA.

Methods and results

Here we demonstrate the promise of pharmacological modulation of SMN2 gene by BAY 55-9837, an agonist of the vasoactive intestinal peptide receptor 2 (VPAC2), a member of G protein coupled receptor family. Treatment with BAY 55-9837 lead to induction of SMN protein levels via activation of MAPK14 or p38 pathway in vitro. Importantly, BAY 55-9837 also ameliorated disease phenotype in severe SMA mouse models.

Conclusion

Our findings suggest the VPAC2 pathway is a potential SMA therapeutic target.

Protective effects of p38 MAPK inhibitor SB202190 against hippocampal apoptosis and spatial learning and memory deficits in a rat model of vascular dementia

Vascular dementia (VaD) is a common age-related neurodegenerative disease resulting from chronic hypoxia. In the present study, we examined the protective effects of p38 MAPK inhibitor SB202190 against hippocampal apoptosis and spatial learning and memory deficits in a chronic hypoperfusion rat model of VaD established by permanent bilateral carotid occlusion (2-VO). Sixty rats were randomly divided into sham-operated, VaD model, and VaD plus SB202190 groups (n = 20/group). After sham/2-VO surgery, rats were administered 0.1% DMSO (sham-operated and VaD groups) or SB202190 by intracerebroventricular injection. One week after inhibitor/vehicle treatment, hippocampal p38 MAPK phosphorylation was higher in the model group than in the SB202190 group (P < 0.01). Compared to the model group, the SB202190 group exhibited significantly shorter escape latencies in the Morris water maze hidden platform trials (P < 0.01) and longer times in the original platform quadrant during probe trials (P < 0.01). The SB202190 group also showed significantly reduced neuronal apoptosis in the hippocampus compared to VaD model rats (P < 0.01) as well as higher (antiapoptotic) Bcl-2 expression and lower (proapoptotic) caspase-3 expression (P < 0.01 for both). In conclusion, blockade of the p38 MAPK signaling pathway by SB202190 following permanent 2-OV reduced apoptosis of hippocampal neurons and rescued spatial learning and memory deficits.

Pathogenesis of acute stroke and the role of inflammasomes

Inflammation is an innate immune response to infection or tissue damage that is designed to limit harm to the host, but contributes significantly to ischemic brain injury following stroke. The inflammatory response is initiated by the detection of acute damage via extracellular and intracellular pattern recognition receptors, which respond to conserved microbial structures, termed pathogen-associated molecular patterns or host-derived danger signals termed damage-associated molecular patterns. Multi-protein complexes known as inflammasomes (e.g. containing NLRP1, NLRP2, NLRP3, NLRP6, NLRP7, NLRP12, NLRC4, AIM2 and/or Pyrin), then process these signals to trigger an effector response. Briefly, signaling through NLRP1 and NLRP3 inflammasomes produces cleaved caspase-1, which cleaves both pro-IL-1β and pro-IL-18 into their biologically active mature pro-inflammatory cytokines that are released into the extracellular environment. This review will describe the molecular structure, cellular signaling pathways and current evidence for inflammasome activation following cerebral ischemia, and the potential for future treatments for stroke that may involve targeting inflammasome formation or its products in the ischemic brain.

Proximal inhibition of p38 MAPK stress signaling prevents distal axonopathy

The p38 mitogen-activated protein kinase (MAPK) isoforms are phosphorylated by a variety of stress stimuli in neurodegenerative disease and act as upstream activators of myriad pathogenic processes. Thus, p38 MAPK inhibitors are of growing interest as possible therapeutic interventions. Axonal dysfunction is an early component of most neurodegenerative disorders, including the most prevalent optic neuropathy, glaucoma. Sensitivity to intraocular pressure at an early stage disrupts anterograde transport along retinal ganglion cell (RGC) axons to projection targets in the brain with subsequent degeneration of the axons themselves; RGC body loss is much later. Here we show that elevated ocular pressure in rats increases p38 MAPK activation in retina, especially in RGC bodies. Topical eye-drop application of a potent and selective inhibitor of the p38 MAPK catalytic domain (Ro3206145) prevented both the degradation of anterograde transport to the brain and degeneration of axons in the optic nerve. Ro3206145 reduced in the retina phosphorylation of tau and heat-shock protein 27, both down-stream targets of p38 MAPK activation implicated in glaucoma, as well as expression of two inflammatory responses. We also observed increased p38 MAPK activation in mouse models. Thus, inhibition of p38 MAPK signaling in the retina may represent a therapeutic target for preventing early pathogenesis in optic neuropathies.

The p38α MAPK regulates microglial responsiveness to diffuse traumatic brain injury

Neuropathology after traumatic brain injury (TBI) is the result of both the immediate impact injury and secondary injury mechanisms. Unresolved post-traumatic glial activation is a secondary injury mechanism that contributes to a chronic state of neuroinflammation in both animal models of TBI and human head injury patients. We recently demonstrated, using in vitro models, that p38α MAPK signaling in microglia is a key event in promoting cytokine production in response to diverse disease-relevant stressors and subsequent inflammatory neuronal dysfunction. From these findings, we hypothesized that the p38α signaling pathway in microglia could be contributing to the secondary neuropathologic sequelae after a diffuse TBI. Mice where microglia were p38α-deficient (p38α KO) were protected against TBI-induced motor deficits and synaptic protein loss. In wild-type (WT) mice, diffuse TBI produced microglia morphological activation that lasted for at least 7 d; however, p38α KO mice failed to activate this response. Unexpectedly, we found that the peak of the early, acute phase cytokine and chemokine levels was increased in injured p38α KO mice compared with injured WT mice. The increased cytokine levels in the p38α KO mice could not be accounted for by more infiltration of macrophages or neutrophils, or increased astrogliosis. By 7 d after injury, the cytokine and chemokine levels remained elevated in injured WT mice but not in p38α KO mice. Together, these data suggest that p38α balances the inflammatory response by acutely attenuating the early proinflammatory cytokine surge while perpetuating the chronic microglia activation after TBI.

Delta-opioid agonist SNC-121 protects retinal ganglion cell function in a chronic ocular hypertensive rat model

PURPOSE

This study examined if the delta-opioid (δ-opioid) receptor agonist, SNC-121, can improve retinal function and retinal ganglion cell (RGC) survival during glaucomatous injury in a chronic ocular hypertensive rat model.

METHODS

IOP was raised in brown Norway rats by injecting hypertonic saline into the limbal venous system. Rats were treated with 1 mg/kg SNC-121 (intraperitoneally [IP]) once daily for 7 days. Pattern-electroretinograms (PERGs) were obtained in response to contrast reversal of patterned visual stimuli. RGCs were visualized by fluorogold retrograde labeling. Expression of TNF-α and p38 mitogen-activated protein (MAP) kinase was measured by immunohistochemistry and Western blotting.

RESULTS

PERG amplitudes in ocular hypertensive eyes were significantly reduced (14.3 ± 0.60 μvolts) when compared with healthy eyes (18.0 ± 0.62 μvolts). PERG loss in hypertensive eyes was inhibited by SNC-121 treatment (17.20 ± 0.1.3 μvolts; P < 0.05). There was a 29% loss of RGCs in the ocular hypertensive eye, which was inhibited in the presence of SNC-121. TNF-α production and activation of p38 MAP kinase in retinal sections and optic nerve samples were upregulated in ocular hypertensive eyes and inhibited in the presence of SNC-121. Furthermore, TNF-α induced increase in p38 MAP kinase activation in astrocytes was inhibited in the presence of SNC-121.

CONCLUSIONS

These data provide evidence that activation of δ-opioid receptors inhibited the loss of PERG amplitudes and rate of RGC loss during glaucomatous injury. Mechanistic data provided clues that TNF-α is mainly produced from glial cells and activates p38 MAP kinase, which was significantly inhibited by SNC-121 treatment. Overall, data indicate that enhancement of δ-opioidergic activity in the eye may provide retina neuroprotection against glaucoma.

Pharmacological inhibition of p38 mitogen-activated protein kinases affects KC/CXCL1-induced intraluminal crawling, transendothelial migration, and chemotaxis of neutrophils in vivo

p38 mitogen-activated protein kinase (MAPK) signalling is critical in the pathophysiology of a variety of inflammatory processes. Leukocyte recruitment to the site of inflammation is a multistep process governed by specific signalling cascades. After adhesion in the lumen, many leukocytes crawl to optimal sites at endothelial junctions and transmigrate to extravascular tissue in a Mac-1-dependent manner. The signalling mechanisms that regulate postadhesion steps of intraluminal crawling, transmigration, and chemotaxis in tissue remain incompletely understood. The present study explored the effect of p38 MAPK inhibitor SB203580 on various parameters of neutrophil recruitment triggered by chemokine KC (CXCL1) gradient. Neutrophil-endothelial interactions in microvasculature of murine cremaster muscle were determined using intravital microscopy and time-lapsed video analysis. SB203580 (100 nM) did not change leukocyte rolling but significantly attenuated neutrophil adhesion, emigration, and transmigration and impaired the initiation of neutrophil crawling and transmigration. In response to KC chemotactic gradient, SB203580 significantly reduced the velocity of migration and chemotaxis index of neutrophils in tissue. The upregulation of Mac-1 expression in neutrophils stimulated by KC was significantly blunted by SB203580 in vitro. Collectively, our findings demonstrate that pharmacological suppression of p38 MAPK significantly impairs multiple steps of neutrophil recruitment in vivo.

Dipyridamole decreases inflammatory metalloproteinase-9 expression and release by human monocytes

Matrix metalloproteinase (MMP)-9 plays an important role in stroke by accelerating matrix degradation, disrupting the blood-brain barrier and increasing infarct size. Dipyridamole is an antiplatelet agent with recognised benefits in ischaemic stroke prevention. In addition to its antiplatelet properties, recent studies have reported that dipyridamole also features anti-inflammatory and anti-oxidant properties. We therefore investigated whether dipyridamole can ameliorate the proinflammatory profile of human monocytes, a source of MMP-9 in stroke, in terms of regulation of MMP-9 activity and expression, and explored underlying mechanisms. Human peripheral blood mononuclear cells (PBMC) and U937 cells were treated with increasing concentrations of dipyridamole (up to 10 µg/ml) for 60 minutes before stimulation with tumour necrosis factor (TNF)-α or phorbol myristate acetate (PMA). Exposure of PBMC and U937 to dipyridamole reduced TNF-α- and PMA-induced MMP-9 activity and protein release as well as MMP-9 mRNA, without significantly affecting the release of TIMP-1. This inhibitory effect was independent of dipyridamole-induced cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) increase. Correspondingly, dipyridamole also significantly inhibited TNF-α-induced nuclear factor (NF)-κB activation and nuclear translocation of the p65 NF-κB subunit through a mechanism involving the inhibition of IkBα degradation and p38 MAPK activation. In conclusion, dipyridamole, at therapeutically achievable concentrations, reduces the expression and release of MMP-9 through a mechanism involving p38 MAPK and NF-κB inhibition. These results indicate that dipyridamole exerts anti-inflammatory properties in human monocytes that may favourably contribute to its actions in the secondary prevention of stroke, independent of its antiplatelet properties.

Modulation of inflammatory cytokines and mitogen-activated protein kinases by acetate in primary astrocytes

Acetate supplementation attenuates neuroglia activation in a rat model of neuroinflammation by a mechanism associated with an increase in brain acetyl-CoA, an alteration in histone acetylation, and reduction of interleukin (IL)-1β expression. We propose that reduced astroglial activation occurs by disrupting astrocyte-derived inflammatory signaling and cytokine release. Using primary astroglial cultures, we found that LPS (0-25 ng/ml, 4 h) increased tumor necrosis factor (TNF-α) and IL-1β in a concentration-dependent manner, which was reduced by treatment with sodium acetate (12 mM). LPS did not alter H3K9 acetylation or IL-6 levels, whereas acetate treatment increased H3K9 acetylation by 2-fold and decreased basal levels of IL-6 by 2-fold. Acetate treatment attenuated the LPS-induced increase in TNF-α mRNA, but did not reverse the mRNA levels of other pro-inflammatory cytokines. By contrast, LPS decreased TGF-β1 and IL-4 protein and TGF-β1 mRNA, all of which was reversed with acetate treatment. Further, we found that acetate treatment completely reversed LPS-induced phosphorylation of MAPK p38 and decreased basal levels of phosphorylated extracellular signal-regulated kinases1/2 (ERK1/2) by 2-fold. Acetate treatment also reversed LPS-elevated NF-κB p65, CCAAT/enhancer-binding protein beta protein levels, and reduced basal levels of phosphorylated NF-κB p65 at serine 536. These results suggest that acetate treatment has a net anti-inflammatory effect in LPS-stimulated astrocytes that is largely associated with a disruption in MAPK and NF-κB signaling.

Increased NADPH oxidase-derived superoxide is involved in the neuronal cell death induced by hypoxia-ischemia in neonatal hippocampal slice cultures

Neonatal brain hypoxia-ischemia (HI) results in neuronal cell death. Previous studies indicate that reactive oxygen species, such as superoxide, play a key role in this process. However, the cellular sources have not been established. In this study we examine the role of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex in neonatal HI brain injury and elucidate its mechanism of activation. Rat hippocampal slices were exposed to oxygen glucose deprivation (OGD) to mimic the conditions seen in HI. Initial studies confirmed an important role for NADPH oxidase-derived superoxide in the oxidative stress associated with OGD. Further, the OGD-mediated increase in apoptotic cell death was inhibited by the NADPH oxidase inhibitor apocynin. The activation of NADPH oxidase was found to be dependent on the p38 mitogen-activated protein kinase-mediated phosphorylation and activation of the p47(phox) subunit. Using an adeno-associated virus antisense construct to selectively decrease p47(phox) expression in neurons showed that this led to inhibition of both the increase in superoxide and the neuronal cell death associated with OGD. We also found that NADPH oxidase inhibition in a neonatal rat model of HI or scavenging hydrogen peroxide reduced brain injury. Thus, we conclude that activation of the NADPH oxidase complex contributes to the oxidative stress during HI and that therapies targeted against this complex could provide neuroprotection against the brain injury associated with neonatal HI.

Intravenous immunoglobulin protects neurons against amyloid beta-peptide toxicity and ischemic stroke by attenuating multiple cell death pathways

Intravenous immunoglobulin (IVIg) preparations obtained by fractionating blood plasma, are increasingly being used increasingly as an effective therapeutic agent in treatment of several inflammatory diseases. Its use as a potential therapeutic agent for treatment of stroke and Alzheimer's disease has been proposed, but little is known about the neuroprotective mechanisms of IVIg. In this study, we investigated the effect of IVIg on downstream signaling pathways that are involved in neuronal cell death in experimental models of stroke and Alzheimer's disease. Treatment of cultured neurons with IVIg reduced simulated ischemia- and amyloid βpeptide (Aβ)-induced caspase 3 cleavage, and phosphorylation of the cell death-associated kinases p38MAPK, c-Jun NH2 -terminal kinase and p65, in vitro. Additionally, Aβ-induced accumulation of the lipid peroxidation product 4-hydroxynonenal was attenuated in neurons treated with IVIg. IVIg treatment also up-regulated the anti-apoptotic protein, Bcl2 in cortical neurons under ischemia-like conditions and exposure to Aβ. Treatment of mice with IVIg reduced neuronal cell loss, apoptosis and infarct size, and improved functional outcome in a model of focal ischemic stroke. Together, these results indicate that IVIg acts directly on neurons to protect them against ischemic stroke and Aβ-induced neuronal apoptosis by inhibiting cell death pathways and by elevating levels of the anti-apoptotic protein Bcl2.

Ras family small GTPase-mediated neuroprotective signaling in stroke

Selective neuronal cell death is one of the major causes of neuronal damage following stroke, and cerebral cells naturally mobilize diverse survival signaling pathways to protect against ischemia. Importantly, therapeutic strategies designed to improve endogenous anti-apoptotic signaling appear to hold great promise in stroke treatment. While a variety of complex mechanisms have been implicated in the pathogenesis of stroke, the overall mechanisms governing the balance between cell survival and death are not well-defined. Ras family small GTPases are activated following ischemic insults, and in turn, serve as intrinsic switches to regulate neuronal survival and regeneration. Their ability to integrate diverse intracellular signal transduction pathways makes them critical regulators and potential therapeutic targets for neuronal recovery after stroke. This article highlights the contribution of Ras family GTPases to neuroprotective signaling cascades, including mitogen-activated protein kinase (MAPK) family protein kinase- and AKT/PKB-dependent signaling pathways as well as the regulation of cAMP response element binding (CREB), Forkhead box O (FoxO) and hypoxiainducible factor 1(HIF1) transcription factors, in stroke.

Microglial p38α MAPK is critical for LPS-induced neuron degeneration, through a mechanism involving TNFα

Background

The p38α MAPK isoform is a well-established therapeutic target in peripheral inflammatory diseases, but the importance of this kinase in pathological microglial activation and detrimental inflammation in CNS disorders is less well understood. To test the role of the p38α MAPK isoform in microglia-dependent neuron damage, we used primary microglia from wild-type (WT) or p38α MAPK conditional knockout (KO) mice in co-culture with WT cortical neurons, and measured neuron damage after LPS insult.

Results

We found that neurons in co-culture with p38α-deficient microglia were protected against LPS-induced synaptic loss, neurite degeneration, and neuronal death. The involvement of the proinflammatory cytokine TNFα was demonstrated by the findings that p38α KO microglia produced much less TNFα in response to LPS compared to WT microglia, that adding back TNFα to KO microglia/neuron co-cultures increased the LPS-induced neuron damage, and that neutralization of TNFα in WT microglia/neuron co-cultures prevented the neuron damage. These results using cell-selective, isoform-specific KO mice demonstrate that the p38α MAPK isoform in microglia is a key mediator of LPS-induced neuronal and synaptic dysfunction. The findings also provide evidence that a major mechanism by which LPS activation of microglia p38α MAPK signaling leads to neuron damage is through up-regulation of the proinflammatory cytokine TNFα.

Conclusions

The data suggest that selective targeting of p38α MAPK signaling should be explored as a potential therapeutic strategy for CNS disorders where overproduction of proinflammatory cytokines is implicated in disease progression.

Increased p38 mitogen-activated protein kinase signaling is involved in the oxidative stress associated with oxygen and glucose deprivation in neonatal hippocampal slice cultures

The pathological basis of neonatal hypoxia-ischemia (HI) brain damage is characterized by neuronal cell loss. Oxidative stress is thought to be one of the main causes of HI-induced neuronal cell death. The p38 mitogen-activated protein kinase (MAPK) is activated under conditions of cell stress. However, its pathogenic role in regulating the oxidative stress associated with HI injury in the brain is not well understood. Thus, this study was conducted to examine the role of p38 MAPK signaling in neonatal HI brain injury using neonatal rat hippocampal slice cultures exposed to oxygen/glucose deprivation (OGD). Our results indicate that OGD led to a transient increase in p38 MAPK activation that preceded increases in superoxide generation and neuronal death. This increase in neuronal cell death correlated with an increase in the activation of caspase-3 and the appearance of apoptotic neuronal cells. Pre-treatment of slice cultures with the p38 MAPK inhibitor, SB203580, or the expression of an antisense p38 MAPK construct only in neuronal cells, through a Synapsin I-1-driven adeno-associated virus vector, inhibited p38 MAPK activity and exerted a neuroprotective effect as demonstrated by decreases in OGD-mediated oxidative stress, caspase activation and neuronal cell death. Thus, we conclude that the activation of p38 MAPK in neuronal cells plays a key role in the oxidative stress and neuronal cell death associated with OGD.

Microglial activation in stroke: therapeutic targets

Microglial activation is an early response to brain ischemia and many other stressors. Microglia continuously monitor and respond to changes in brain homeostasis and to specific signaling molecules expressed or released by neighboring cells. These signaling molecules, including ATP, glutamate, cytokines, prostaglandins, zinc, reactive oxygen species, and HSP60, may induce microglial proliferation and migration to the sites of injury. They also induce a nonspecific innate immune response that may exacerbate acute ischemic injury. This innate immune response includes release of reactive oxygen species, cytokines, and proteases. Microglial activation requires hours to days to fully develop, and thus presents a target for therapeutic intervention with a much longer window of opportunity than acute neuroprotection. Effective agents are now available for blocking both microglial receptor activation and the microglia effector responses that drive the inflammatory response after stroke. Effective agents are also available for targeting the signal transduction mechanisms linking these events. However, the innate immune response can have beneficial as well deleterious effects on outcome after stoke, and a challenge will be to find ways to selectively suppress the deleterious effects of microglial activation after stroke without compromising neurovascular repair and remodeling.

Hepatic response to oxidative injury in long-lived Ames dwarf mice

Multiple stress resistance pathways were evaluated in the liver of Ames dwarf mice before and after exposure to the oxidative toxin diquat, seeking clues to the exceptional longevity conferred by this mutation. Before diquat treatment, Ames dwarf mice, compared with nonmutant littermate controls, had 2- to 6-fold higher levels of expression of mRNAs for immediate early genes and 2- to 5-fold higher levels of mRNAs for genes dependent on the transcription factor Nrf2. Diquat led to a 2-fold increase in phosphorylation of the stress kinase ERK in control (but not Ames dwarf) mice and to a 50% increase in phosphorylation of the kinase JNK2 in Ames dwarf (but not control) mice. Diquat induction of Nrf2 protein was higher in dwarf mice than in controls. Of 6 Nrf2-responsive genes evaluated, 4 (HMOX, NQO-1, MT-1, and MT-2) remained 2- to 10-fold lower in control than in dwarf liver after diquat, and the other 2 (GCLM and TXNRD) reached levels already seen in dwarf liver at baseline. Thus, livers of Ames dwarf mice differ systematically from controls in multiple stress resistance pathways before and after exposure to diquat, suggesting mechanisms for stress resistance and extended longevity in Ames dwarf mice.

MAPK signal transduction underlying brain inflammation and gliosis as therapeutic target

A majority, if not all, acute and progressive neurodegenerative diseases are accompanied by local microglia-mediated inflammation, astrogliosis, infiltration of immune cells, and activation of the adaptive immunity. These processes progress by the expression of cytokines, adhesion molecules, proteases, and other inflammation mediators. In response to brain injury or infection, intracellular signaling pathways are activated in microglia, which turn on inflammatory and antigen-presenting cell functions. Different extrinsic signals shape microglial activation toward neuroprotective or neurotoxic phenotype under pathological conditions. This review discusses recent advances regarding molecular mechanisms of inflammatory signal transduction in neurological disorders and in in vitro models of inflammation/gliosis. Mitogen-activated protein kinases (MAPKs) are a family of serine/threonine protein kinases responsible for most cellular responses to cytokines and external stress signals and crucial for regulation of the production of inflammation mediators. Increased activity of MAPKs in activated microglia and astrocytes, and their regulatory role in the synthesis of inflammatory cytokines mediators, make them potential targets for novel therapeutics. MAPK inhibitors emerge as attractive anti-inflammatory drugs, because they are capable of reducing both the synthesis of inflammation mediators at multiple levels and are effective in blocking inflammatory cytokine signaling. Small molecule inhibitors targeting of p38 MAPK and JNK pathways have been developed and offer a great potential as potent modulators of brain inflammation and gliosis in neurological disorders, where cytokine overproduction contributes to disease progression. Many of the pharmacological MAPK inhibitors can be administered orally and initial results show therapeutic benefits in preclinical animal models.

Targeting p38 MAPK pathway for the treatment of Alzheimer's disease

Accumulating evidence indicates that p38 mitogen-activated protein kinase (MAPK) could play more than one role in Alzheimer's disease (AD) pathophysiology and that patients suffering from AD dementia could benefit from p38 MAPK inhibitors. The p38 MAPK signalling has been widely accepted as a cascade contributing to neuroinflammation. However, deepening insight into the underlying biology of Alzheimer's disease reveals that p38 MAPK operates in other events related to AD, such as excitotoxicity, synaptic plasticity and tau phosphorylation. Although quantification of behavioural improvements upon p38 MAPK inhibition and in vivo evaluation of p38 MAPK significance to various aspects of AD pathology is still missing, the p38 MAPK is emerging as a new Alzheimer's disease treatment strategy. Thus, we present here an update on the role of p38 MAPK in neurodegeneration, with a focus on Alzheimer's disease, by summarizing recent literature and several key papers from earlier years.

Targeting protein kinases in central nervous system disorders

Protein kinases are a growing drug target class in disorders in peripheral tissues, but the development of kinase-targeted therapies for central nervous system (CNS) diseases remains a challenge, largely owing to issues associated specifically with CNS drug discovery. However, several candidate therapeutics that target CNS protein kinases are now in various stages of preclinical and clinical development. We review candidate compounds and discuss selected CNS protein kinases that are emerging as important therapeutic targets. In addition, we analyse trends in small-molecule properties that correlate with key challenges in CNS drug discovery, such as blood-brain barrier penetrance and cytochrome P450-mediated metabolism, and discuss the potential of future approaches that will integrate molecular-fragment expansion with pharmacoinformatics to address these challenges.

Repeated preconditioning with hyperbaric oxygen induces neuroprotection against forebrain ischemia via suppression of p38 mitogen activated protein kinase

We previously reported in rats that preconditioning with hyperbaric oxygen (HBO; 100% O(2) 3.5-atomsphere absolute (ATA), 1 h/day for 5 days) provided neuroprotection against transient (8 min) forebrain ischemia possibly through protein synthesis relevant to neurotrophin receptor and inflammatory-immune system. A recent report suggested that HBO-induced neuroprotection is relevant to brain derived neurotrophic factor and its downstream event involving suppression of p38 mitogen activated protein kinase (p38) activation. In the present study, we first performed a dose comparison (1, 2, and 3.5 ATA) of HBO-induced neuroprotection and then investigated pharmacological modification by 10 mg/kg anisomycin (a protein synthesis inhibitor and potent activator for p38) and 200 microg/kg SB203580 (a p38 inhibitor), which were given intraperitoneally 60 and 30 min before every 3.5 ATA-HBO treatment, respectively. Most prominent protective effect on hippocampal CA1 neurons was observed with 3.5 ATA-HBO (survived neurons: 69% [62-73%] vs. untreated: 3.9% [2-8%], 1 ATA: 8.8% [0-26%], 2 ATA-HBO: 46% [22-62%] (median [range]) (7 days after ischemia). Anisomycin abolished a neuroprotective effect (survived neuron: 1.2% [0-7%]). SB203580, when given between administration of anisomycin and HBO treatment, resumed a neuroprotective effect (survived neuron: 52% [37-62%]). The level of phosphorylated p38 at 10-min reperfusion was significantly decreased in 3.5 ATA-HBO group (32% [12-53%] of sham). Single pretreatment with 100 and 200 microg/kg of SB203580 exerted a similar neuroprotective effect (39% [25-51%] and 59% [50-72%]) to 2 and 3.5 ATA-HBO preconditioning, respectively. It is concluded that suppression of p38 phosphorylation plays a key role in HBO-induced neuroprotection and that pretreatment with a p38 inhibitor (SB203580) can provide similar neuroprotection.

The p38alpha mitogen-activated protein kinase as a central nervous system drug discovery target

Protein kinases are critical modulators of a variety of cellular signal transduction pathways, and abnormal phosphorylation events can be a cause or contributor to disease progression in a variety of disorders. This has led to the emergence of protein kinases as an important new class of drug targets for small molecule therapeutics. A serine/threonine protein kinase, p38α mitogen-activated protein kinase (MAPK), is an established therapeutic target for peripheral inflammatory disorders because of its critical role in regulation of proinflammatory cytokine production. There is increasing evidence that p38α MAPK is also an important regulator of proinflammatory cytokine levels in the central nervous system, raising the possibility that the kinase may be a drug discovery target for central nervous system disorders where cytokine overproduction contributes to disease progression. Development of bioavailable, central nervous system-penetrant p38α MAPK inhibitors provides the required foundation for drug discovery campaigns targeting p38α MAPK in neurodegenerative disorders.