Post-injury Nose-to-Brain Delivery of Activin A and SerpinB2 Reduces Brain Damage in a Mouse Stroke Model

TwinF interface inhibitor FP802 prevents retinal ganglion cell loss in a mouse model of amyotrophic lateral sclerosis

Motor neuron loss is well recognized in amyotrophic lateral sclerosis (ALS), but research on retinal ganglion cells (RGCs) is limited. Ocular symptoms are generally not considered classic ALS symptoms, although RGCs and spinal motor neurons share certain cell pathologies, including hallmark signs of glutamate neurotoxicity, which may be triggered by activation of extrasynaptic NMDA receptors (NMDARs). To explore potential novel strategies to prevent ALS-associated death of RGCs, we utilized inhibition of the TwinF interface, a new pharmacological principle that detoxifies extrasynaptic NMDARs by disrupting the NMDAR/TRPM4 death signaling complex. Using the ALS mouse model SOD1G93A, we found that the small molecule TwinF interface inhibitor FP802 prevents the loss of RGCs, improves pattern electroretinogram (pERG) performance, increases the retinal expression of Bdnf, and restores the retinal expression of the immediate early genes, Inhibin beta A and Npas4. Thus, FP802 not only prevents, as recently described, death of spinal motor neurons in SOD1G93A mice, but it also mitigates ALS-associated retinal damage. TwinF interface inhibitors have great potential for alleviating neuro-ophthalmologic symptoms in ALS patients and offer a promising new avenue for therapeutic intervention.

Brain-Targeting Emodin Mitigates Ischemic Stroke via Inhibiting AQP4-Mediated Swelling and Neuroinflammation

Failure to achieve target-specific delivery to ischemic brain sites has hampered the clinical efficacy of newly developed therapies for ischemic stroke. Emodin, an active ingredient isolated from traditional Chinese medicine, has been indicated to alleviate ischemic stroke; however, the underlying mechanism remains unclear. In this study, we aimed to achieve brain-targeted delivery of emodin to maximize its therapeutic efficacy and elucidate the mechanisms by which emodin alleviates ischemic stroke. A polyethylene glycol (PEG)/cyclic Arg-Gly-Asp (cRGD)-modified liposome was used to encapsulate emodin. TTC, HE, Nissl staining, and immunofluorescence staining were employed to evaluate the therapeutic efficacy of brain-targeting emodin in MCAO and OGD/R models. Inflammatory cytokine levels were determined using ELISA. Immunoprecipitation, immunoblotting, and RT-qPCR were utilized for clarifying the changes in key downstream signaling. Lentivirus-mediated gene restoration was employed to verify the core effector of emodin for relieving ischemic stroke. Encapsulating emodin in a PEG/cRGD-modified liposome enhanced its accumulation in the infarct region and substantially raised its therapeutic efficacy. Furthermore, we demonstrated that AQP4, the most abundant water transporter subunit expressed in astrocytes, plays a crucial role in mediating the mechanisms by which emodin inhibits astrocyte swelling, neuroinflammatory blood-brain barrier (BBB) breakdown in vivo and in vitro, and brain edema in general. Our study unveiled the critical target of emodin responsible for alleviating ischemic stroke and a localizable drug delivery vehicle in the therapeutic strategy for ischemic stroke and other brain injuries.

Activin A targets extrasynaptic NMDA receptors to ameliorate neuronal and behavioral deficits in a mouse model of Huntington disease

Cortical-striatal synaptic dysfunction, including enhanced toxic signaling by extrasynaptic N-methyl-d-aspartate receptors (eNMDARs), precedes neurodegeneration in Huntington disease (HD). A previous study showed Activin A, whose transcription is upregulated by calcium influx via synaptic NMDARs, suppresses eNMDAR signaling. Therefore, we examined the role of Activin A in the YAC128 HD mouse model, comparing it to wild-type controls. We found decreased Activin A secretion in YAC128 cortical-striatal co-cultures, while Activin A overexpression in this model rescued altered eNMDAR expression. Striatal overexpression of Activin A in vivo improved motor learning on the rotarod task, and normalized striatal neuronal eNMDAR-mediated currents, membrane capacitance and spontaneous excitatory postsynaptic current frequency in the YAC128 mice. These results support the therapeutic potential of Activin A signaling and targeting eNMDARs to restore striatal neuronal health and ameliorate behavioral deficits in HD.

FUS-mediated HypEVs: Neuroprotective effects against ischemic stroke

Few studies have investigated the properties and protein composition of small extracellular vesicles (sEVs) derived from neurons under hypoxic conditions. Presently, the extent of the involvement of these plentiful sEVs in the onset and progression of ischemic stroke remains an unresolved question. Our study systematically identified the characteristics of sEVs derived from neurons under hypoxic conditions (HypEVs) by physical characterization, sEV absorption, proteomics and transcriptomics analysis. The effects of HypEVs on neurites, cell survival, and neuron structure were assessed in vitro and in vivo by neural complexity tests, magnetic resonance imaging (MRI), Golgi staining, and Western blotting of synaptic plasticity-related proteins and apoptotic proteins. Knockdown of Fused in Sarcoma (FUS) small interfering RNA (siRNA) was used to validate FUS-mediated HypEV neuroprotection and mitochondrial mRNA release. Hypoxia promoted the secretion of sEVs, and HypEVs were more easily taken up and utilized by recipient cells. The MRI results illustrated that the cerebral infarction volume was reduced by 45% with the application of HypEVs, in comparison to the non- HypEV treatment group. Mechanistically, the FUS protein is necessary for the uptake and neuroprotection of HypEVs against ischemic stroke as well as carrying a large amount of mitochondrial mRNA in HypEVs. However, FUS knockdown attenuated the neuroprotective rescue capabilities of HypEVs. Our comprehensive dataset clearly illustrates that FUS-mediated HypEVs deliver exceptional neuroprotective effects against ischemic stroke, primarily through the maintenance of neurite integrity and the reduction of mitochondria-associated apoptosis.

Tonic activin signaling shapes cellular and synaptic properties of CA1 neurons mainly in dorsal hippocampus

Dorsal and ventral hippocampus serve different functions in cognition and affective behavior, but the underpinnings of this diversity at the cellular and synaptic level are not well understood. We found that the basal level of activin A, a member of the TGF-β family, which regulates hippocampal circuits in a behaviorally relevant fashion, is much higher in dorsal than in ventral hippocampus. Using transgenic mice with a forebrain-specific disruption of activin receptor signaling, we identified the pronounced dorsal-ventral gradient of activin A as a major factor determining the distinct neurophysiologic signatures of dorsal and ventral hippocampus, ranging from pyramidal cell firing, tuning of frequency-dependent synaptic facilitation, to long-term potentiation (LTP), long-term depression (LTD), and de-potentiation. Thus, the strong activin A tone in dorsal hippocampus appears crucial to establish cellular and synaptic phenotypes that are tailored specifically to the respective network operations in dorsal and ventral hippocampus.

Dorsal-Ventral Gradient of Activin Regulates Strength of GABAergic Inhibition along Longitudinal Axis of Mouse Hippocampus in an Activity-Dependent Fashion

The functional and neurophysiological distinction between the dorsal and ventral hippocampus affects also GABAergic inhibition. In line with this notion, ventral CA1 pyramidal cells displayed a more dynamic and effective response to inhibitory input compared to their dorsal counterparts. We posit that this difference is effected by the dorsal-ventral gradient of activin A, a member of the transforming growth factor-β family, which is increasingly recognized for its modulatory role in brain regions involved in cognitive functions and affective behavior. Lending credence to this hypothesis, we found that in slices from transgenic mice expressing a dominant-negative mutant of activin receptor IB (dnActRIB), inhibitory transmission was enhanced only in CA1 neurons of the dorsal hippocampus, where the basal activin A level is much higher than in the ventral hippocampus. We next asked how a rise in endogenous activin A would affect GABAergic inhibition along the longitudinal axis of the hippocampus. We performed ex vivo recordings in wild-type and dnActRIB mice after overnight exposure to an enriched environment (EE), which engenders a robust increase in activin A levels in both dorsal and ventral hippocampi. Compared to control mice from standard cages, the behaviorally induced surge in activin A produced a decline in ventral inhibition, an effect that was absent in slices from dnActRIB mice. Underscoring the essential role of activin in the EE-associated modulation of ventral inhibition, this effect was mimicked by acute application of recombinant activin A in control slices. In summary, both genetic and behavioral manipulations of activin receptor signaling affected the dorsal-ventral difference in synaptic inhibition, suggesting that activin A regulates the strength of GABAergic inhibition in a region-specific fashion.

Molecular mechanisms underlying activity-dependent ischemic tolerance in the brain

Ischemic stroke is one of the leading causes of death and disability worldwide. The inhibition of cerebral blood flow triggers intertwined pathological events, resulting in cell death and loss of brain function. Interestingly, animals pre-exposed to short-term ischemia can tolerate subsequent severe ischemia. This phenomenon is called ischemic tolerance and is also triggered by other noxious stimuli. However, whether short-term exposure to non-noxious stimuli can induce ischemic tolerance remains unknown. Recently, we found that pre-exposing mice to an enriched environment for 40 min is sufficient to facilitate cell survival after a subsequent stroke. The neuroprotective process depends on the neuronal activity soon before stroke, of which the activity-dependent transcription factor Npas4 is essential. Excessive Ca²⁺ influx triggers Npas4 expression in ischemic neurons, leading to the activation of neuroprotective programs. Pre-induction of Npas4 in the normal brain effectively supports cell survival after stroke. Furthermore, our study revealed that Npas4 regulates L-type voltage-gated Ca²⁺ channels through expression of the small Ras-like GTPase Gem in ischemic neurons. Ischemic tolerance is a good model for understanding how to promote neuroprotective mechanisms in the normal and injured brain. Here, we highlight activity-dependent ischemic tolerance and discuss its role in promoting neuroprotection against stroke.

The role of plasminogen activator inhibitor-2 in pneumococcal meningitis

Pneumococcal meningitis is associated with dysregulation of the coagulation cascade. Previously, we detected upregulation of cerebral plasminogen activator inhibitor-2 (PAI-2) mRNA expression during pneumococcal meningitis. Diverse functions have been ascribed to PAI-2, but its role remains unclear. We analyzed the function of SERPINB2 (coding for PAI-2) in patients with bacterial meningitis, in a well-established pneumococcal meningitis mouse model, using Serpinb2 knockout mice, and in vitro in wt and PAI-2-deficient bone marrow-derived macrophages (BMDMs). We measured PAI-2 in cerebrospinal fluid of patients, and performed functional, histopathological, protein and mRNA expression analyses in vivo and in vitro. We found a substantial increase of PAI-2 concentration in CSF of patients with pneumococcal meningitis, and up-regulation and increased release of PAI-2 in mice. PAI-2 deficiency was associated with increased mortality in murine pneumococcal meningitis and cerebral hemorrhages. Serpinb2−/− mice exhibited increased C5a levels, but decreased IL-10 levels in the brain during pneumococcal infection. Our in vitro experiments confirmed increased expression and release of PAI-2 by wt BMDM and decreased IL-10 liberation by PAI-2-deficient BMDM upon pneumococcal challenge. Our data show that PAI-2 is elevated during in pneumococcal meningitis in humans and mice. PAI-2 deficiency causes an inflammatory imbalance, resulting in increased brain pathology and mortality.

Activin A Reduces GIRK Current to Excite Dentate Gyrus Granule Cells

Activin A, a member of the TGF-β family, is recognized as a multifunctional protein in the adult brain with a particular impact on neuronal circuits associated with cognitive and affective functions. Activin receptor signaling in mouse hippocampus is strongly enhanced by the exploration of an enriched environment (EE), a behavioral paradigm known to improve performance in learning and memory tasks and to ameliorate depression-like behaviors. To interrogate the relationship between EE, activin signaling, and cellular excitability in the hippocampus, we performed ex vivo whole-cell recordings from dentate gyrus (DG) granule cells (GCs) of wild type mice and transgenic mice expressing a dominant-negative mutant of activin receptor IB (dnActRIB), which disrupts activin signaling in a forebrain-specific fashion. We found that, after overnight EE housing, GC excitability was strongly enhanced in an activin-dependent fashion. Moreover, the effect of EE on GC firing was mimicked by pre-treatment of hippocampal slices from control mice with recombinant activin A for several hours. The excitatory effect of activin A was preserved when canonical SMAD-dependent signaling was pharmacologically suppressed but was blocked by inhibitors of ERK-MAPK and PKA signaling. The involvement of a non-genomic signaling cascade was supported by the fact that the excitatory effect of activin A was already achieved within minutes of application. With respect to the ionic mechanism underlying the increase in intrinsic excitability, voltage-clamp recordings revealed that activin A induced an apparent inward current, which resulted from the suppression of a standing G protein-gated inwardly rectifying K+ (GIRK) current. The link between EE, enhanced activin signaling, and inhibition of GIRK current was strengthened by the following findings: (i) The specific GIRK channel blocker tertiapin Q (TQ) occluded the characteristic electrophysiological effects of activin A in both current- and voltage-clamp recordings. (ii) The outward current evoked by the GIRK channel activator adenosine was significantly reduced by preceding EE exploration as well as by recombinant activin A in control slices. In conclusion, our study identifies GIRK current suppression via non-canonical activin signaling as a mechanism that might at least in part contribute to the beneficial effects of EE on cognitive performance and affective behavior.

Direct moxibustion exerts an analgesic effect on cervical spondylotic radiculopathy by increasing autophagy via the Act A/Smads signaling pathway

BACKGROUND

Direct moxibustion (DM) is reported to be useful for cervical spondylotic radiculopathy (CSR), but the analgesic mechanism remains unknown. Autophagy plays a protective role in neuronal apoptosis, Act A/Smads signaling pathway has been confirmed to be associated with the activation of autophagy. The study aimed to explore the effect of DM on autophagy in rats with CSR and the involvement of Act A/Smads signaling pathway.

METHODS

Rats were randomly divided into Sham, CSR, CSR + DM, CSR + DM + 3-MA (PI3K inhibitor), and CSR + DM + SB (Act A inhibitor) group. Three days after establishment of CSR model with a fish line inserted under the axilla of the nerve roots, DM at Dazhui (GV14) was performed six times once for seven consecutive days. Western blot and immunofluorescence staining were used to observe the expression of the neuronal autophagy molecule LC3II/I, Atg7, and Act A/Smads signaling molecule Act A, p-Smad2, and p-Smad3. Bcl-2/Bax mRNA expression was measured by real time PCR.

RESULTS

DM improved the pain threshold and motor function of CSR rats and promoted the expression of Act A, p-Smad2, p-Smad3, LC3II/I, and Atg7 in the entrapped-nerve root spinal dorsal horn. DM reduced the expression of Bax mRNA and decreased the number of apoptotic neurons. 3-MA and Act A inhibitor SB suppressed the expression of above-mentioned proteins and reduced the protective effect of DM on apoptotic neurons.

CONCLUSION

DM exerts analgesic effects by regulating the autophagy to reduce cell apoptosis and repair nerve injury, and this feature may be related to the Act A/Smads signaling pathway.

CircOGDH Is a Penumbra Biomarker and Therapeutic Target in Acute Ischemic Stroke

BACKGROUND

Acute ischemic stroke (AIS) is a leading cause of disability and mortality worldwide. Prediction of penumbra existence after AIS is crucial for making decision on reperfusion therapy. Yet a fast, inexpensive, simple, and noninvasive predictive biomarker for the poststroke penumbra with clinical translational potential is still lacking. We aim to investigate whether the CircOGDH (circular RNA derived from oxoglutarate dehydrogenase) is a potential biomarker for penumbra in patients with AIS and its role in ischemic neuronal damage.

METHODS

CircOGDH was screened from penumbra of middle cerebral artery occlusion mice and was assessed in plasma of patients with AIS by quantitative polymerase chain reaction. Magnetic resonance imaging was used to examine the penumbra volumes. CircOGDH interacted with miR-5112 in primary cortical neurons was detected by fluorescence in situ hybridization, RNA immunoprecipitation, and luciferase reporter assay. ADV-mediated CircOGDH knockdown ameliorated neuronal apoptosis induced by COL4A4 (Gallus collagen, type VI, alpha VI) overexpression. Transmission electron microscope, nanoparticle tracking analysis, and Western blot were performed to confirm exosomes.

RESULTS

CircOGDH expression was dramatically and selectively upregulated in the penumbra tissue of middle cerebral artery occlusion mice and in the plasma of 45 patients with AIS showing a 54-fold enhancement versus noncerebrovascular disease controls. Partial regression analysis revealed that CircOGDH expression was positively correlated with the size of penumbra in patients with AIS. Sequestering of miR-5112 by CircOGDH enhanced COL4A4 expression to elevate neuron damage. Additionally, knockdown of CircOGDH significantly enhanced neuronal cell viability under ischemic conditions. Furthermore, the expression of CircOGDH in brain tissue was closely related to that in the serum of middle cerebral artery occlusion mice. Finally, we found that CircOGDH was highly expressed in plasma exosomes of patients with AIS compared with those in noncerebrovascular disease individuals.

CONCLUSIONS

These results demonstrate that CircOGDH is a potential therapeutic target for regulating ischemia neuronal viability, and is enriched in neuron-derived exosomes in the peripheral blood, exhibiting a predictive biomarker of penumbra in patients with AIS.

LncRNA SERPINB9P1 expression and polymorphisms are associated with ischemic stroke in a Chinese Han population

Long noncoding RNAs (lncRNAs) were reported to play important roles in the pathogenesis of ischemic stroke (IS). Our study aimed to investigate the role of lncRNA SERPINB9P1 expression in ischemic stroke and the association between SERPINB9P1 polymorphisms and IS risk, as well as examine the correlation of SERPINB9P1 expression and variants with clinical parameters of IS. The SERPINB9P1 levels in human participants and oxygen-glucose deprivation (OGD)-treated human A172 cells were measured by qRT-PCR. The SERPINB9P1 polymorphisms (rs375556 and rs318429) were genotyped by the MassARRAY platform. We found that the SERPINB9P1 expression was significantly downregulated in patients with IS compared with that in healthy controls. On the 14th day in the hospital, the SERPINB9P1 level in patients with moderate and severe stroke was significantly downregulated compared with the normal group. After stratification by gender, the rs375556 polymorphism was significantly associated with susceptibility to female IS in the recessive model, and the significant association remained after adjusting for age. After adjusting for gender and age, rs318429 was significantly associated with FPG and D-D levels, and rs375556 was significantly associated with INR and PTA levels in IS cases. Besides, the lncRNA SERPINB9P1 expressed downregulated in OGD/reoxygenation-treated human A172 cells. In conclusion, the lncRNA SERPINB9P1 may protect against cerebral ischemia-reperfusion injury and neurological impairment after IS. The SERPINB9P1 rs375556 polymorphism was associated with susceptibility to female IS, and SERPINB9P1 polymorphisms may influence the metabolism of blood glucose and regulation of coagulation function in patients with IS.

Convolutions in the rendition of nose to brain therapeutics from bench to bedside: Feats & fallacies

Brain, a subtle organ of multifarious nature presents plethora of physiological, metabolic and bio-chemical convolutions that impede the delivery of biomolecules and thereby resulting in truncated therapeutic outcome in pathological conditions of central nervous system (CNS). The absolute bottleneck in the therapeutic management of such devastating CNS ailments is the BBB. Another pitfall is the lack of efficient technological platforms (due to high cost and low approval rates) as well as limited clinical trials (due to failures of neuro‑leads in late-stage pipelines) for CNS disorders which has become a literal brain drain with poorest success rates compared to other therapeutic areas, owing to time consuming processes, tremendous convolutions and conceivable adverse effects. With the advent of intranasal delivery (via direct N2B or indirect nose to blood to brain), several novel drug delivery carriers viz. unmodified or surface modified nanoparticle based carriers, lipid based colloidal nanocarriers and drysolid/liquid/semisolid nanoformulations or delivery platforms have been designed as a means to deliver therapeutic agents (small and large molecules, peptides and proteins, genes) to brain, bypassing BBB for disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, schizophrenia and CNS malignancies primarily glioblastomas. Intranasal application offers drug delivery through both direct and indirect pathways for the peripherally administered psychopharmacological agents to CNS. This route could also be exploited for the repurposing of conventional drugs for new therapeutic uses. The limited clinical translation of intranasal formulations has been primarily due to existence of barriers of mucociliary clearance in the nasal cavity, enzyme degradation and low permeability of the nasal epithelium. The present review literature aims to decipher the new paradigms of nano therapeutic systems employed for specific N2B drug delivery of CNS drugs through in silico complexation studies using rationally chosen mucoadhesive polymers (exhibiting unique physicochemical properties of nanocarrier's i.e. surface modification, prolonging retention time in the nasal cavity, improving penetration ability, and promoting brain specific delivery with biorecognitive ligands) via molecular docking simulations. Further, the review intends to delineate the feats and fallacies associated with N2B delivery approaches by understanding the physiological/anatomical considerations via decoding the intranasal drug delivery pathways or critical factors such as rationale and mechanism of excipients, affecting the permeability of CNS drugs through nasal mucosa as well as better efficacy in terms of brain targeting, brain bioavailability and time to reach the brain. Additionally, extensive emphasis has also been laid on the innovative formulations under preclinical investigation along with their assessment by means of in vitro /ex vivo/in vivo N2B models and current characterization techniques predisposing an efficient intranasal delivery of therapeutics. A critical appraisal of novel technologies, intranasal products or medical devices available commercially has also been presented. Finally, it could be warranted that more reminiscent pharmacokinetic/pharmacodynamic relationships or validated computational models are mandated to obtain effective screening of molecular architecture of drug-polymer-mucin complexes for clinical translation of N2B therapeutic systems from bench to bedside.

Pathophysiological Ionotropic Glutamate Signalling in Neuroinflammatory Disease as a Therapeutic Target

Glutamate signalling is an essential aspect of neuronal communication involving many different glutamate receptors, and underlies the processes of memory, learning and synaptic plasticity. Despite neuroinflammatory diseases covering a range of maladies with very different biological causes and pathophysiologies, a central role for dysfunctional glutamate signalling is becoming apparent. This is not just restricted to the well-described role of glutamate in mediating neurodegeneration, but also includes a myriad of other influences that glutamate can exert on the vasculature, as well as immune cell and glial regulation, reflecting the ability of neurons to communicate with these compartments in order to couple their activity with neuronal requirements. Here, we discuss the role of pathophysiological glutamate signalling in neuroinflammatory disease, using both multiple sclerosis and Alzheimer's disease as examples, and how current steps are being made to harness our growing understanding of these processes in the development of neuroprotective strategies. This review focuses in particular on N-methyl-D-aspartate (NMDA) and 2-amino-3-(3-hydroxy-5-methylisooxazol-4-yl) propionate (AMPA) type ionotropic glutamate receptors, although metabotropic, G-protein-coupled glutamate receptors may also contribute to neuroinflammatory processes. Given the indispensable roles of glutamate-gated ion channels in synaptic communication, means of pharmacologically distinguishing between physiological and pathophysiological actions of glutamate will be discussed that allow deleterious signalling to be inhibited whilst minimising the disturbance of essential neuronal function.

Enriched environment remedies cognitive dysfunctions and synaptic plasticity through NMDAR-Ca2+-Activin A circuit in chronic cerebral hypoperfusion rats

Chronic cerebral ischemia (CCI) is one of the critical factors in the occurrence and development of vascular cognitive impairment (VCI). Apoptosis of nerve cells and changes in synaptic activity after CCI are the key factors to induce VCI. Synaptic stimulation up-regulates intraneuronal Ca2+ level through N-methyl-D-aspartic acid receptor (NMDAR) via induction of the activity-regulated inhibitor of death (AID) expression to produce active-dependent neuroprotection. Moreover, the regulation of synaptic plasticity could improve cognition and learning ability. Activin A (ActA), an exocrine protein of AID, can promote NMDAR phosphorylation and participate in the regulation of synaptic plasticity. We previously found that exogenous ActA can improve the cognitive function of rats with chronic cerebral ischemia and enhance the oxygenated glucose deprivation of intracellular Ca2+ level. In addition to NMDAR, the Wnt pathway is critical in the positive regulation of LTP through activation or inhibition. It plays an essential role in synaptic transmission and activity-dependent synaptic plasticity. The enriched environment can increase ActA expression during CCI injury. We speculated that the NMDAR-Ca2+-ActA signal pathway has a loop-acting mode, and the environmental enrichment could improve chronic cerebral ischemia cognitive impairment via NMDAR-Ca2+-ActA, Wnt/β-catenin pathway is involved in this process. For the hypothesis verification, this study intends to establish chronic cerebral hypoperfusion (CCH) rat model, explore the improvement effect of enriched environment on VCI, detect the changes in plasticity of synaptic morphology and investigate the regulatory mechanism NMDAR-Ca2+-ActA-Wnt/β-catenin signaling loop, providing a therapeutic method for the treatment of CCH.

Ras-like Gem GTPase induced by Npas4 promotes activity-dependent neuronal tolerance for ischemic stroke

Ischemic stroke, which results in loss of neurological function, initiates a complex cascade of pathological events in the brain, largely driven by excitotoxic Ca2+ influx in neurons. This leads to cortical spreading depolarization, which induces expression of genes involved in both neuronal death and survival; yet, the functions of these genes remain poorly understood. Here, we profiled gene expression changes that are common to ischemia (modeled by middle cerebral artery occlusion [MCAO]) and to experience-dependent activation (modeled by exposure to an enriched environment [EE]), which also induces Ca2+ transients that trigger transcriptional programs. We found that the activity-dependent transcription factor Npas4 was up-regulated under MCAO and EE conditions and that transient activation of cortical neurons in the healthy brain by the EE decreased cell death after stroke. Furthermore, both MCAO in vivo and oxygen-glucose deprivation in vitro revealed that Npas4 is necessary and sufficient for neuroprotection. We also found that this protection involves the inhibition of L-type voltage-gated Ca2+ channels (VGCCs). Next, our systematic search for Npas4-downstream genes identified Gem, which encodes a Ras-related small GTPase that mediates neuroprotective effects of Npas4. Gem suppresses the membrane localization of L-type VGCCs to inhibit excess Ca2+ influx, thereby protecting neurons from excitotoxic death after in vitro and in vivo ischemia. Collectively, our findings indicate that Gem expression via Npas4 is necessary and sufficient to promote neuroprotection in the injured brain. Importantly, Gem is also induced in human cerebral organoids cultured under an ischemic condition, revealing Gem as a new target for drug discovery.

Role of Purinergic Signalling in Endothelial Dysfunction and Thrombo-Inflammation in Ischaemic Stroke and Cerebral Small Vessel Disease

The cerebral endothelium is an active interface between blood and the central nervous system. In addition to being a physical barrier between the blood and the brain, the endothelium also actively regulates metabolic homeostasis, vascular tone and permeability, coagulation, and movement of immune cells. Being part of the blood–brain barrier, endothelial cells of the brain have specialized morphology, physiology, and phenotypes due to their unique microenvironment. Known cardiovascular risk factors facilitate cerebral endothelial dysfunction, leading to impaired vasodilation, an aggravated inflammatory response, as well as increased oxidative stress and vascular proliferation. This culminates in the thrombo-inflammatory response, an underlying cause of ischemic stroke and cerebral small vessel disease (CSVD). These events are further exacerbated when blood flow is returned to the brain after a period of ischemia, a phenomenon termed ischemia-reperfusion injury. Purinergic signaling is an endogenous molecular pathway in which the enzymes CD39 and CD73 catabolize extracellular adenosine triphosphate (eATP) to adenosine. After ischemia and CSVD, eATP is released from dying neurons as a damage molecule, triggering thrombosis and inflammation. In contrast, adenosine is anti-thrombotic, protects against oxidative stress, and suppresses the immune response. Evidently, therapies that promote adenosine generation or boost CD39 activity at the site of endothelial injury have promising benefits in the context of atherothrombotic stroke and can be extended to current CSVD known pathomechanisms. Here, we have reviewed the rationale and benefits of CD39 and CD39 therapies to treat endothelial dysfunction in the brain.

Intranasal temperature-sensitive hydrogels of cannabidiol inclusion complex for the treatment of post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a psychiatric disease that seriously affects brain function. Currently, selective serotonin reuptake inhibitors (SSRIs) are used to treat PTSD clinically but have decreased efficiency and increased side effects. In this study, nasal cannabidiol inclusion complex temperature-sensitive hydrogels (CBD TSGs) were prepared and evaluated to treat PTSD. Mice model of PTSD was established with conditional fear box. CBD TSGs could significantly improve the spontaneous behavior, exploratory spirit and alleviate tension in open field box, relieve anxiety and tension in elevated plus maze, and reduce the freezing time. Hematoxylin and eosin and c-FOS immunohistochemistry slides showed that the main injured brain areas in PTSD were the prefrontal cortex, amygdala, and hippocampus CA1. CBD TSGs could reduce the level of tumor necrosis factor-α caused by PTSD. Western blot analysis showed that CBD TSGs increased the expression of the 5-HT1A receptor. Intranasal administration of CBD TSGs was more efficient and had more obvious brain targeting effects than oral administration, as evidenced by the pharmacokinetics and brain tissue distribution of CBD TSGs. Overall, nasal CBD TSGs are safe and effective and have controlled release. There are a novel promising option for the clinical treatment of PTSD.

Attenuation of Inflammation by DJ-1 May Be a Drug Target for Cerebral Ischemia-Reperfusion Injury

The pathophysiological process of cerebral apoplexy is complex, and there are currently no specific drugs for this condition. The study of effective drug targets has become a hot topic in neuroscience. Currently, adeno-associated viruses (AAVs) and polypeptides are commonly used in drug research. DJ-1 has been widely considered a neuroprotective target in recent times, but the mechanism of its neuroprotective effects is unclear. In this study, we simulated ischemic injury by establishing a middle cerebral artery occlusion reperfusion (MCAO/R) model to compare the protective effect of DJ-1 overexpression induced by DJ-1 AAV and ND-13 on cerebral ischemia-reperfusion (I/R) injury. We found that DJ-1 overexpression and ND-13 significantly reduced the neurological function scores and infarct volume and alleviated pathological damage to brain tissue. In addition, Western blotting, ELISA and immunofluorescence labeling revealed that DJ-1 overexpression and ND-13 increased the expression of the anti-inflammatory cytokines IL-10 and IL-4, and decreased the levels of the pro-inflammatory cytokines IL-1β and TNF-α. In summary, our study shows that DJ-1 overexpression and ND-13 can regulate the expression of inflammatory factors and alleviate cerebral I/R injury. Thus, DJ-1 is a possible drug target for cerebral I/R injury.

Neuroprotective Effects Against Cerebral Ischemic Injury Exerted by Dexmedetomidine via the HDAC5/NPAS4/MDM2/PSD-95 Axis

Numerous evidences have highlighted the efficient role of dexmedetomidine (DEX) in multi-organ protection. In the present study, the neuroprotective role of DEX on cerebral ischemic injury and the underlining signaling mechanisms were explored. In order to simulate cerebral ischemic injury, we performed middle cerebral artery occlusion in mice and oxygen-glucose deprivation in neurons. Immunohistochemistry, Western blot analysis, and RT-qPCR were used to examine expression of HDAC5, NPAS4, MDM2, and PSD-95 in hippocampus tissues of MCAO mice and OGD-treated neurons. MCAO mice received treatment with DEX and sh-PSD-95, followed by neurological function evaluation, behavioral test, infarct volume detection by TTC staining, and apoptosis by TUNEL staining. Additionally, gain- and loss-of-function approaches were conducted in OGD-treated neuron after DEX treatment. Cell viability and apoptosis were assessed with the application of CCK-8 and flow cytometry. The interaction between MDM2 and PSD-95 was evaluated using Co-IP assay, followed by ubiquitination of PSD-95 detection. As per the results, HDAC5 and MDM2 were abundantly expressed, while NPAS4 and PSD-95 were poorly expressed in hippocampus tissues of MCAO mice and OGD-treated neurons. DEX elevated viability, and reduced LDH leakage rate and apoptosis rate of OGD-treated neurons, which was reversed following the overexpression of HDAC5. Moreover, HDAC5 augmented MDM2 expression via NPAS4 inhibition. MDM2 induced PSD-95 ubiquitination and degradation. In MCAO mice, DEX improved neurological function and behaviors and decreased infarct volume and apoptosis, which was negated as a result of PSD-95 silencing. DEX plays a neuroprotective role against cerebral ischemic injury by disrupting MDM2-induced PSD-95 ubiquitination and degradation via HDAC5 and NPAS4.

Activin A improves the neurological outcome after ischemic stroke in mice by promoting oligodendroglial ACVR1B-mediated white matter remyelination

Activin A plays important roles in ischemic injury and white matter remyelination, but its mechanisms are unclear. In this study, the adult male C57BL/6 J mice were used to establish the model of 1 h middle cerebral artery occlusion/reperfusion (MCAO/R) 1 d to 28 d-induced ischemic stroke in vivo. We found that the neurological outcome was positively correlated with the levels of myelin associated proteins (include MAG, CNPase, MOG and MBP, n = 6 per group) both in corpus callosum and internal capsule of mice with ischemic stroke. The dynamic changes of Luxol fast blue (LFB) staining intensity, oligodendrocyte (CC1⁺) and proliferated oligodendrocyte precursor (Ki67⁺/PDGFRα⁺) cell numbers indicated demyelination and spontaneous remyelination occurred in the corpus callosum of mice after 1 h MCAO/R 1 d-28 d (n = 6 per group). Activin receptor type I (ACVR1) inhibitor SB431542 aggregated neurological deficits, and reduced MAG, MOG and MBP protein levels of mice with ischemic stroke (n = 6 per group). Meanwhile, recombinant mouse (rm) Activin A enhanced the neurological function recovery, MAG, MOG and MBP protein levels of mice with 1 h MCAO/R 28 d. In addition, the injection of AAV-based ACVR1B shRNA with Olig2 promoter could reverse rmActivin A-induced the increases of CC1⁺ cell number, LFB intensity, MAG, MOG and MBP protein levels in the corpus callosum (n = 6 per group), and neurological function recovery (n = 10 per group) of mice with 1 h MCAO/R 28 d. These results suggested that Activin A improves the neurological outcome through promoting oligodendroglial ACVR1B-mediated white matter remyelination of mice with ischemic stroke, which may provide a potential therapeutic strategy for ischemic stroke.

Essential Functions of the Transcription Factor Npas4 in Neural Circuit Development, Plasticity, and Diseases

Signaling from the synapse to nucleus is mediated by the integration and propagation of both membrane potential changes (postsynaptic potentials) and intracellular second messenger cascades. The electrical propagation of postsynaptic potentials allows for rapid neural information processing, while propagating second messenger pathways link synaptic activity to the transcription of genes required for neuronal survival and adaptive changes (plasticity) underlying circuit formation and learning. The propagation of activity-induced calcium signals to the cell nucleus is a major synapse-to-nucleus communication pathway. Neuronal PAS domain protein 4 (Npas4) is a recently discovered calcium-dependent transcription factor that regulates the activation of genes involved in the homeostatic regulation of excitatory–inhibitory balance, which is critical for neural circuit formation, function, and ongoing plasticity, as well as for defense against diseases such as epilepsy. Here, we summarize recent findings on the neuroprotective functions of Npas4 and the potential of Npas4 as a therapeutic target for the treatment of acute and chronic diseases of the central nervous system.

Coupling of NMDA receptors and TRPM4 guides discovery of unconventional neuroprotectants

Excitotoxicity induced by NMDA receptors (NMDARs) is thought to be intimately linked to high intracellular calcium load. Unexpectedly, NMDAR-mediated toxicity can be eliminated without affecting NMDAR-induced calcium signals. Instead, excitotoxicity requires physical coupling of NMDARs to TRPM4. This interaction is mediated by intracellular domains located in the near-membrane portions of the receptors. Structure-based computational drug screening using the interaction interface of TRPM4 in complex with NMDARs identified small molecules that spare NMDAR-induced calcium signaling but disrupt the NMDAR/TRPM4 complex. These interaction interface inhibitors strongly reduce NMDA-triggered toxicity and mitochondrial dysfunction, abolish cyclic adenosine monophosphate-responsive element-binding protein (CREB) shutoff, boost gene induction, and reduce neuronal loss in mouse models of stroke and retinal degeneration. Recombinant or small-molecule NMDAR/TRPM4 interface inhibitors may mitigate currently untreatable human neurodegenerative diseases.

Activin-A limits Th17 pathogenicity and autoimmune neuroinflammation via CD39 and CD73 ectonucleotidases and Hif1-α-dependent pathways

In multiple sclerosis (MS), Th17 cells are critical drivers of autoimmune central nervous system (CNS) inflammation and demyelination. Th17 cells exhibit functional heterogeneity fostering both pathogenic and nonpathogenic, tissue-protective functions. Still, the factors that control Th17 pathogenicity remain incompletely defined. Here, using experimental autoimmune encephalomyelitis, an established mouse MS model, we report that therapeutic administration of activin-A ameliorates disease severity and alleviates CNS immunopathology and demyelination, associated with decreased activation of Th17 cells. In fact, activin-A signaling through activin-like kinase-4 receptor represses pathogenic transcriptional programs in Th17-polarized cells, while it enhances antiinflammatory gene modules. Whole-genome profiling and in vivo functional studies revealed that activation of the ATP-depleting CD39 and CD73 ectonucleotidases is essential for activin-A-induced suppression of the pathogenic signature and the encephalitogenic functions of Th17 cells. Mechanistically, the aryl hydrocarbon receptor, along with STAT3 and c-Maf, are recruited to promoter elements on Entpd1 and Nt5e (encoding CD39 and CD73, respectively) and other antiinflammatory genes, and control their expression in Th17 cells in response to activin-A. Notably, we show that activin-A negatively regulates the metabolic sensor, hypoxia-inducible factor-1α, and key inflammatory proteins linked to pathogenic Th17 cell states. Of translational relevance, we demonstrate that activin-A is induced in the CNS of individuals with MS and restrains human Th17 cell responses. These findings uncover activin-A as a critical controller of Th17 cell pathogenicity that can be targeted for the suppression of autoimmune CNS inflammation.

Intranasal Delivery of Nanoformulations: A Potential Way of Treatment for Neurological Disorders

Although the global prevalence of neurological disorders such as Parkinson’s disease, Alzheimer’s disease, glioblastoma, epilepsy, and multiple sclerosis is steadily increasing, effective delivery of drug molecules in therapeutic quantities to the central nervous system (CNS) is still lacking. The blood brain barrier (BBB) is the major obstacle for the entry of drugs into the brain, as it comprises a tight layer of endothelial cells surrounded by astrocyte foot processes that limit drugs’ entry. In recent times, intranasal drug delivery has emerged as a reliable method to bypass the BBB and treat neurological diseases. The intranasal route for drug delivery to the brain with both solution and particulate formulations has been demonstrated repeatedly in preclinical models, including in human trials. The key features determining the efficacy of drug delivery via the intranasal route include delivery to the olfactory area of the nares, a longer retention time at the nasal mucosal surface, enhanced penetration of the drugs through the nasal epithelia, and reduced drug metabolism in the nasal cavity. This review describes important neurological disorders, challenges in drug delivery to the disordered CNS, and new nasal delivery techniques designed to overcome these challenges and facilitate more efficient and targeted drug delivery. The potential for treatment possibilities with intranasal transfer of drugs will increase with the development of more effective formulations and delivery devices.

Nasally delivered VEGFD mimetics mitigate stroke-induced dendrite loss and brain damage

In the adult brain, vascular endothelial growth factor D (VEGFD) is required for structural integrity of dendrites and cognitive abilities. Alterations of dendritic architectures are hallmarks of many neurologic disorders, including stroke-induced damage caused by toxic extrasynaptic NMDA receptor (eNMDAR) signaling. Here we show that stimulation of eNMDARs causes a rapid shutoff of VEGFD expression, leading to a dramatic loss of dendritic structures. Using the mouse middle cerebral artery occlusion (MCAO) stroke model, we have established the therapeutic potential of recombinant mouse VEGFD delivered intraventricularly to preserve dendritic architecture, reduce stroke-induced brain damage, and facilitate functional recovery. An easy-to-use therapeutic intervention for stroke was developed that uses a new class of VEGFD-derived peptide mimetics and postinjury nose-to-brain delivery.

Functional Consequences of Calcium-Dependent Synapse-to-Nucleus Communication: Focus on Transcription-Dependent Metabolic Plasticity

In the nervous system, calcium signals play a major role in the conversion of synaptic stimuli into transcriptional responses. Signal-regulated gene transcription is fundamental for a range of long-lasting adaptive brain functions that include learning and memory, structural plasticity of neurites and synapses, acquired neuroprotection, chronic pain, and addiction. In this review, we summarize the diverse mechanisms governing calcium-dependent transcriptional regulation associated with central nervous system plasticity. We focus on recent advances in the field of synapse-to-nucleus communication that include studies of the signal-regulated transcriptome in human neurons, identification of novel regulatory mechanisms such as activity-induced DNA double-strand breaks, and the identification of novel forms of activity- and transcription-dependent adaptations, in particular, metabolic plasticity. We summarize the reciprocal interactions between different kinds of neuroadaptations and highlight the emerging role of activity-regulated epigenetic modifiers in gating the inducibility of signal-regulated genes.

IM-12 activates the Wnt-β-catenin signaling pathway and attenuates rtPA-induced hemorrhagic transformation in rats after acute ischemic stroke

Hemorrhagic transformation (HT) is a devastating complication for patients with acute ischemic stroke (AIS) who are treated with tissue plasminogen activator (tPA). HT is associated with high morbidity and mortality, but no effective treatments are currently available to reduce the risk of HT. Therefore, methods to prevent HT are urgently needed. In this study, we used IM-12, an inhibitor of glycogen synthase kinase 3β (GSK-3β), to evaluate the role of the Wnt-β-catenin signaling pathway in recombinant tPA (rtPA)-induced HT. Sprague-Dawley rats were subjected to a middle cerebral artery occlusion (MCAO) model of ischemic stroke, and then were either administered rtPA, rtPA combined with IM-12, or the vehicle at 4 h after stroke was induced. Our results indicate that rats subjected to HT had more severe neurological deficits, brain edema, and blood-brain barrier (BBB) breakdown, and had a greater infarction volume than the control group. Rats treated with IM-12 had improved outcomes compared with those of rats treated with rtPA alone. Moreover, IM-12 increased the protein expression of β-catenin and downstream proteins while suppressing the expression of GSK-3β. These results suggest that IM-12 reduces rtPA-induced HT and attenuates BBB disruption, possibly through activation of the Wnt-β-catenin signaling pathway, and provides a potential therapeutic strategy for preventing tPA-induced HT after AIS.

Nose-to-Brain Delivery

The global prevalence of neurologic disorders is rising, and yet we are still unable to deliver most drug molecules, in therapeutic quantities, to the brain. The blood brain barrier consists of a tight layer of endothelial cells surrounded by astrocyte foot processes, and these anatomic features constitute a significant barrier to drug transport from the blood to the brain. One way to bypass the blood brain barrier and thus treat diseases of the brain is to use the nasal route of administration and deposit drugs at the olfactory region of the nares, from where they travel to the brain via mechanisms that are still not clearly understood, with travel across nerve fibers and travel via a perivascular pathway both being hypothesized. The nose-to-brain route has been demonstrated repeatedly in preclinical models, with both solution and particulate formulations. The nose-to-brain route has also been demonstrated in human studies with solution and particle formulations. The entry of device manufacturers into the arena will enable the benefits of this delivery route to become translated into approved products. The key factors that determine the efficacy of delivery via this route include the following: delivery to the olfactory area of the nares as opposed to the respiratory region, a longer retention time at the nasal mucosal surface, penetration enhancement of the active through the nasal epithelia, and a reduction in drug metabolism in the nasal cavity. Indications where nose-to-brain products are likely to emerge first include the following: neurodegeneration, post-traumatic stress disorder, pain, and glioblastoma.