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EPAC null mutation impairs learning and social interactions via aberrant regulation of miR-124 and Zif268 translation.

EPAC proteins are the guanine nucleotide exchange factors that act as the intracellular receptors for cyclic AMP. Two variants of EPAC genes including EPAC1 and EPAC2 are cloned and are widely expressed throughout the brain. But, their functions in the brain remain unknown. Here, we genetically delete EPAC1 (EPAC1(-/-)), EPAC2 (EPAC2(-/-)), or both EPAC1 and EPAC2 genes (EPAC(-/-)) in the forebrain of mice. We show that EPAC null mutation impairs long-term potentiation (LTP) and that this impairment is paralleled with the severe deficits in spatial learning and social interactions and is mediated in a direct manner by miR-124 transcription and Zif268 translation. Knockdown of miR-124 restores Zif268 and hence reverses all aspects of the EPAC(-/-) phenotypes, whereas expression of miR-124 or knockdown of Zif268 reproduces the effects of EPAC null mutation. Thus, EPAC proteins control miR-124 transcription in the brain for processing spatial learning and social interactions.

DAPK1–p53 Interaction Converges Necrotic and Apoptotic Pathways of Ischemic Neuronal Death

Necrosis and apoptosis are two distinct types of mechanisms that mediate ischemic injury. But a signaling point of convergence between them has yet to be identified. Here, we show that activated death-associated protein kinase 1 (DAPK1), phosphorylates p53 at serine-23 (pS23) via a direct binding of DAPK1 death domain (DAPK1DD) to the DNA binding motif of p53 (p53DM). We uncover that the pS23 acts as a functional version of p53 and mediates necrotic and apoptotic neuronal death; in the nucleus, pS23 induces the expression of proapoptotic genes, such as Bax, whereas in the mitochondrial matrix, pS23 triggers necrosis via interaction with cyclophilin D (CypD) in cultured cortical neurons from mice. Deletion of DAPK1DD (DAPK1DDΔ) or application of Tat-p53DM that interrupts DAPK1–p53 interaction blocks these dual pathways of pS23 actions in mouse cortical neurons. Thus, the DAPK1–p53 interaction is a signaling point of convergence of necrotic and apoptotic pathways and is a desirable target for the treatment of ischemic insults.

NLRP3 Inflammasome in Neurological Diseases, from Functions to Therapies

Neuroinflammation has been identified as a causative factor of multiple neurological diseases. The nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3 (NLRP3) inflammasome, a subcellular multiprotein complex that is abundantly expressed in the central nervous system (CNS), can sense and be activated by a wide range of exogenous and endogenous stimuli such as microbes, aggregated and misfolded proteins, and adenosine triphosphate, which results in activation of caspase-1. Activated caspase-1 subsequently leads to the processing of interleukin-1β (IL-1β) and interleukin-18 (IL-18) pro-inflammatory cytokines and mediates rapid cell death. IL-1β and IL-18 drive inflammatory responses through diverse downstream signaling pathways, leading to neuronal damage. Thus, the NLRP3 inflammasome is considered a key contributor to the development of neuroinflammation. In this review article, we briefly discuss the structure and activation the NLRP3 inflammasome and address the involvement of the NLRP3 inflammasome in several neurological disorders, such as brain infection, acute brain injury and neurodegenerative diseases. In addition, we review a series of promising therapeutic approaches that target the NLRP3 inflammasome signaling including anti-IL-1 therapy, small molecule NLRP3 inhibitors and other compounds, however, these approaches are still experimental in neurological diseases. At present, it is plausible to generate cell-specific conditional NLRP3 knockout (KO) mice via the Cre system to investigate the role of the NLRP3 inflammasome, which may be instrumental in the development of novel pharmacologic investigations for neuroinflammation-associated diseases.

Maresin 1 mitigates LPS-induced acute lung injury in mice

Acute lung injury (ALI) is a severe illness with a high rate of mortality. Maresin 1 (MaR1) was recently reported to regulate inflammatory responses. We used a LPS‐induced ALI model to determine whether MaR1 can mitigate lung injury.

Resolvin D1 promotes the interleukin-4-induced alternative activation in BV-2 microglial cells

BackgroundMicroglia play key roles in innate immunity, homeostasis, and neurotropic support in the central nervous system. Similar to macrophages, microglia adopt two different activation phenotypes, the classical and alternative activation. Resolvin D1 (RvD1) is considered to display potent anti-inflammatory and pro-resolving actions in inflammatory models. In this present study, we investigate the effect of RvD1 on IL-4-induced alternative activation in murine BV-2 microglial cells.MethodsBV-2 cells were incubated with RvD1 alone, IL-4 alone, or the combination of RvD1 and IL-4. Western blot and immunofluorescence were performed to detect protein levels of alternative activation markers arginase 1 (Arg1), chitinase 3-like 3 (Ym1). Moreover, we investigated the effects of RvD1 on IL-4-induced activation of signal transducer and activators of transcription 6 (STAT6) and peroxisome proliferator-activated receptor gamma (PPARγ).ResultsRvD1 promoted IL-4-induced microglia alternative activation by increasing the expression of Arg1 and Ym1. RvD1 also enhanced phosphorylation of STAT6, nuclear translocation of PPARγ and the DNA binding activity of STAT6 and PPARγ. These effects were reversed by butyloxycarbonyl-Phe-Leu-Phe-Leu-Phe (a formyl peptide receptor 2 antagonist). Further, the effects of RvD1 and IL-4 on Arg1 and Ym1 were blocked by the application of leflunomide (a STAT6 inhibitor) or GW9662 (a PPARγ antagonist).ConclusionsOur studies demonstrate that RvD1 promotes IL-4-induced alternative activation via STAT6 and PPARγ signaling pathways in microglia. These findings suggest that RvD1 may have therapeutic potential for neuroinflammatory diseases.

A Novel Mechanism of Spine Damages in Stroke via DAPK1 and Tau

Synaptic spine loss is one of the major preceding consequences of stroke damages, but its underlying molecular mechanisms remain unknown. Here, we report that a direct interaction of DAPK1 with Tau causes spine loss and subsequently neuronal death in a mouse model with stroke. We found that DAPK1 phosphorylates Tau protein at Ser262 (pS262) in cortical neurons of stroke mice. Either genetic deletion of DAPK1 kinase domain (KD) in mice (DAPK1-KD−/−) or blocking DAPK1-Tau interaction by systematic application of a membrane permeable peptide protects spine damages and improves neurological functions against stroke insults. Thus, disruption of DAPK1-Tau interaction is a promising strategy in clinical management of stroke.

The pro-resolving lipid mediator Maresin 1 protects against cerebral ischemia/reperfusion injury by attenuating the pro-inflammatory response.

Inflammation plays a crucial role in acute ischemic stroke pathogenesis. Macrophage-derived Maresin 1 (MaR1) is a newly uncovered mediator with potent anti-inflammatory abilities. Here, we investigated the effect of MaR1 on acute inflammation and neuroprotection in a mouse brain ischemia reperfusion (I/R) model. Male C57 mice were subjected to 1-h middle cerebral artery occlusion (MCAO) and reperfusion. By the methods of 2,3,5-triphenyltetrazolium chloride, haematoxylin and eosin or Fluoro-Jade B staining, neurological deficits scoring, ELISA detection, immunofluorescence assay and western blot analysis, we found that intracerebroventricular injection of MaR1 significantly reduced the infarct volume and neurological defects, essentially protected the brain tissue and neurons from injury, alleviated pro-inflammatory reactions and NF-κB p65 activation and nuclear translocation. Taken together, our results suggest that MaR1 significantly protects against I/R injury probably by inhibiting pro-inflammatory reactions.

MARESIN 1 PREVENTS LIPOPOLYSACCHARIDE-INDUCED NEUTROPHIL SURVIVAL AND ACCELERATES RESOLUTION OF ACUTE LUNG INJURY.

ABSTRACT Acute lung injury (ALI) is characterized by lung inflammation and diffuse infiltration of neutrophils. Neutrophil apoptosis is recognized as an important control point in the resolution of inflammation. Maresin 1 (MaR1) is a new docosahexaenoic acid–derived proresolving agent that promotes the resolution of inflammation. However, its function in neutrophil apoptosis is unknown. In this study, isolated human neutrophils were incubated with MaR1, the pan-caspase inhibitor z-VAD-fmk, and lipopolysaccharide (LPS) to determine the mechanism of neutrophil apoptosis. Acute lung injury was induced by intratracheal instillation of LPS. In addition, mice were treated with MaR1 intravenously at the peak of inflammation and administered z-VAD-fmk intraperitoneally. We found that culture of isolated human neutrophils with LPS dramatically delayed neutrophil apoptosis through the phosphorylation of AKT, ERK, and p38 to upregulate the expression of the antiapoptotic proteins Mcl-1 and Bcl-2, which was blocked by pretreatment with MaR1 in vitro. In mice, MaR1 accelerated the resolution of inflammation in LPS-induced ALI through attenuation of neutrophil accumulation, pathohistological changes, and pulmonary edema. Maresin 1 promoted resolution of inflammation by accelerating caspase-dependent neutrophil apoptosis. Moreover, MaR1 also reduced the LPS-induced production of proinflammatory cytokines and upregulated the production of the anti-inflammatory cytokine interleukin-10. In contrast, treatment with z-VAD-fmk inhibited the proapoptotic action of MaR1 and attenuated the protective effects of MaR1 in LPS-induced ALI. Taken together, MaR1 promotes the resolution of LPS-induced ALI by overcoming LPS-mediated suppression of neutrophil apoptosis.

Chloral Hydrate Preconditioning Protects Against Ischemic Stroke via Upregulating Annexin A1

Preconditioning is promising for treating cerebral ischemic stroke. Annexin A1 (ANXA1) is a homeostatic antiinflammatory mediator that participates in countering against ischemic injuries. We investigated whether chloral hydrate preconditioning (CH) exerts neuroprotection via regulation of ANXA1 in stroke.

BML-111, a lipoxin receptor agonist, attenuates ventilator-induced lung injury in rats.

ABSTRACT Mechanical ventilation can cause structural and functional disturbances in the lung termed ventilator-induced lung injury (VILI). The aim of this study was to evaluate whether BML-111, a lipoxin receptor agonist, could attenuate VILI. Following induction of anesthesia and tracheostomy, Sprague-Dawley rats were ventilated with low tidal volume (6 mL/kg) or high tidal volume (20 mL/kg, HVT) for 4 h. Some rats subjected to HVT ventilation received BML-111 or vehicle (saline) by intraperitoneal injection. Some rats subjected to HVT and BML-111(1 mg/kg) received BOC-2 (a FPR2/ALX antagonist) intraperitoneally 30 min before BML-111. Sham rats were tracheotomized without ventilation. Treatment with BML-111 attenuated VILI, as evidenced by improved oxygenation and reduced histological injury compared with HVT-induced lung injury. BML-111 decreased indices of inflammation such as interleukin 1&bgr;, interleukin 6, tumor necrosis factor &agr;, and bronchoalveolar lavage neutrophil infiltration. Administration with BML-111 suppressed the decrement of the nuclear factor &kgr;B (NF-&kgr;B) inhibitor I&kgr;B-&agr;, diminished NF-&kgr;B activation, and reduced activation of mitogen-activated protein kinase in VILI. This study indicates that BML-111 attenuated VILI via a NF-&kgr;B and mitogen-activated protein kinase dependent mechanism. BML-111 may be a promising strategy for alleviation of VILI in patients subjected to mechanical ventilation.