4-Аminopyridine sequesters intracellular Ca2+ which triggers exocytosis in excitable and non-excitable cells

4-Aminopyridine Promotes BMP2 Expression and Accelerates Tibial Fracture Healing in Mice

BACKGROUND

Delayed bone healing is common in orthopaedic clinical care. Agents that alter cell function to enhance healing would change treatment paradigms. 4-aminopyridine (4-AP) is a U.S. Food and Drug Administration (FDA)-approved drug shown to improve walking in patients with chronic neurological disorders. We recently showed 4-AP's positive effects in the setting of nerve, wound, and even combined multi-tissue limb injury. Here, we directly investigated the effects of 4-AP on bone fracture healing, where differentiation of mesenchymal stem cells into osteoblasts is crucial.

METHODS

All animal experiments conformed to the protocols approved by the Institutional Animal Care and Use Committee at the University of Arizona and Pennsylvania State University. Ten-week-old C57BL/6J male mice (22 to 28 g), following midshaft tibial fracture, were assigned to 4-AP (1.6 mg/kg/day, intraperitoneal [IP]) and saline solution (0.1 mL/mouse/day, IP) treatment groups. Tibiae were harvested on day 21 for micro-computed tomography (CT), 3-point bending tests, and histomorphological analyses. 4-AP's effect on human bone marrow mesenchymal stem cell (hBMSC) and human osteoblast (hOB) cell viability, migration, and proliferation; collagen deposition; matrix mineralization; and bone-forming gene/protein expression analyses was assessed.

RESULTS

4-AP significantly upregulated BMP2 gene and protein expression and gene expression of RUNX2, OSX, BSP, OCN, and OPN in hBMSCs and hOBs. 4-AP significantly enhanced osteoblast migration and proliferation, collagen deposition, and matrix mineralization. Radiographic and micro-CT imaging confirmed 4-AP's benefit versus saline solution treatment in mouse tibial fracture healing (bone mineral density, 687.12 versus 488.29 mg hydroxyapatite/cm 3 [p ≤ 0.0021]; bone volume/tissue volume, 0.87 versus 0.72 [p ≤ 0.05]; trabecular number, 7.50 versus 5.78/mm [p ≤ 0.05]; and trabecular thickness, 0.08 versus 0.06 mm [p ≤ 0.05]). Three-point bending tests demonstrated 4-AP's improvement of tibial fracture biomechanical properties versus saline solution (stiffness, 27.93 versus 14.30 N/mm; p ≤ 0.05). 4-AP also increased endogenous BMP2 expression and matrix components in healing callus.

CONCLUSIONS

4-AP increased the healing rate, biomechanical properties, and endogenous BMP2 expression of tibiae following fracture.

LEVEL OF EVIDENCE

Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Sleep Deprivation-Induced Anxiety Alleviated by Oral Administration of 4-Aminopyridine in Male Mice

PURPOSE

Insufficient sleep and insomnia are common issues associated with modern lifestyles that often contribute to the development of mental health disorders. 4-aminopyridine (4-AP), a voltage-gated potassium (Kv) channel antagonist, is commonly used in the treatment of multiple sclerosis (MS). It has been shown to improve nerve conduction velocity, strengthen myelin, and increase axonal area after injury. In addition, 4-AP has been reported to reduce behavioral disorders, including depression. The aim of this study was to investigate the effects of 4-AP on anxiety-like behavior in mice subjected to rapid eye movement (REM) sleep deprivation.

METHODS

Fifty male mice were randomly divided into five groups: control, normal saline (NS) (receiving normal saline via gavage), AP-0.25, AP-0.5, and AP-1 (receiving daily doses of 0.25, 0.5, and 1 mg/kg of 4-AP, respectively by gavage). All groups except the control group underwent SD for five consecutive days. The animals' locomotion and anxiety-like behavior were assessed using the open field and elevated plus maze tests. After behavioral testing, N-methyl-D-aspartate receptor (NMDA-R), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPA-R), and tumor necrosis factor (TNF-α) were measured by western blotting, and also malondialdehyde (MDA) and total antioxidant capacity (TAC) were analyzed by ELISA in the hippocampus.

FINDING

AP-1 significantly reduced the levels of anxiety-like behavior compared to the NS group in both tests. In AP-1, a significant decrease in the levels of NMDA-R, AMPA-R, TNF-α, and MDA was observed. While these levels were increased in the NS group. In addition, AP-1 showed a higher level of TAC compared to the NS group, indicating an increase in antioxidant levels.

CONCLUSION

4-AP may be effective in reducing anxiety-like behavior in sleep-deprived mice by modifying the levels of NMDA-R, AMPA-R, and TNF-α, while simultaneously reducing oxidative stress induced by sleep deprivation in the hippocampus.

Increasing glutathione levels by a novel posttranslational mechanism inhibits neuronal hyperexcitability

Glutathione (GSH) depletion, and impaired redox homeostasis have been observed in experimental animal models and patients with epilepsy. Pleiotropic strategies that elevate GSH levels via transcriptional regulation have been shown to significantly decrease oxidative stress and seizure frequency, increase seizure threshold, and rescue certain cognitive deficits. Whether elevation of GSH per se alters neuronal hyperexcitability remains unanswered. We previously showed that thiols such as dimercaprol (DMP) elevate GSH via post-translational activation of glutamate cysteine ligase (GCL), the rate limiting GSH biosynthetic enzyme. Here, we asked if elevation of cellular GSH by DMP altered neuronal hyperexcitability in-vitro and in-vivo. Treatment of primary neuronal-glial cerebrocortical cultures with DMP elevated GSH and inhibited a voltage-gated potassium channel blocker (4-aminopyridine, 4AP) induced neuronal hyperexcitability. DMP increased GSH in wildtype (WT) zebrafish larvae and significantly attenuated convulsant pentylenetetrazol (PTZ)-induced acute 'seizure-like' swim behavior. DMP treatment increased GSH and inhibited convulsive, spontaneous 'seizure-like' swim behavior in the Dravet Syndrome (DS) zebrafish larvae (scn1Lab). Furthermore, DMP treatment significantly decreased spontaneous electrographic seizures and associated seizure parameters in scn1Lab zebrafish larvae. We investigated the role of the redox-sensitive mammalian target of rapamycin (mTOR) pathway due to the presence of several cysteine-rich proteins and their involvement in regulating neuronal excitability. Treatment of primary neuronal-glial cerebrocortical cultures with 4AP or l-buthionine-(S,R)-sulfoximine (BSO), an irreversible inhibitor of GSH biosynthesis, significantly increased mTOR complex I (mTORC1) activity which was rescued by pre-treatment with DMP. Furthermore, BSO-mediated GSH depletion oxidatively modified the tuberous sclerosis protein complex (TSC) consisting of hamartin (TSC1), tuberin (TSC2), and TBC1 domain family member 7 (TBC1D7) which are critical negative regulators of mTORC1. In summary, our results suggest that DMP-mediated GSH elevation by a novel post-translational mechanism can inhibit neuronal hyperexcitability both in-vitro and in-vivo and a plausible link is the redox sensitive mTORC1 pathway.

Maternal hyperhomocysteinemia increases seizures susceptibility of neonatal rats

AIMS

Neonatal seizures are severe pathologies which may result in long-term neurological consequences. High plasma concentrations of homocysteine - hyperhomocysteinemia (hHCy) - are associated with epilepsy. In the present study, we evaluated susceptibility to seizure of neonatal rats with prenatal hHCy.

MAIN METHODS

Prenatal hHCy was induced by feeding females with a high-methionine diet. Experiments were performed on pups during the first three postnatal weeks. Flurothyl-induced epileptic behavior was assessed according to Racine's scale. Epileptiform activity in the hippocampus was recorded using electrophysiological methods. The balance of excitation/inhibition, functional GABAergic inhibition and GABA reversal potential in hippocampal neurons were analyzed.

KEY FINDINGS

Rats with hHCy developed more severe stages of behavioral patterns during flurothyl-induced epilepsy with shorter latency. Electrophysiological recordings demonstrated higher background neuronal activity in rats with hHCy. Seizure-like events triggered by flurothyl (in vivo) or 4-aminopyridine (in vitro) showed shorter latency, higher power and amplitude. An increased glutamate/GABA synaptic ratio was shown in the pyramidal neurons of rats with hHCy and more slices demonstrated excitation by isoguvacine, a selective GABA(A) receptor agonist, during the first and second postnatal weeks. The GABA driving force and the reversal potential of GABA(A) currents were more positive during the second postnatal week for hHCy rats.

SIGNIFICANCE

The higher susceptibility to seizures in rats with prenatal hHCy due to a shift in the balance of excitation/inhibition toward excitation may underlie the clinical evidence about the association of hHCy with an increased risk of epilepsy.

N-Stearoylethanolamine Inhibits Integrin-Mediated Activation, Aggregation, and Adhesion of Human Platelets

N-stearoylethanolamine (NSE), a lipid mediator that belongs to the N-acylethanolamine (NAE) family, has anti-inflammatory, antioxidant, and membranoprotective actions. In contrast to other NAEs, NSE does not interact with cannabinoid receptors. The exact mechanism of its action remains unclear. The aim of this study is to evaluate the action of NSE on activation, aggregation, and adhesion of platelets that were chosen as a model of cellular response. Aggregation of platelets was measured to analyze the action of NSE (10-6-10-10 M) on platelet reactivity. Changes in granularity and shape of resting platelets and platelets stimulated with ADP in the presence of NSE were monitored by flow cytometry, and platelet deganulation was monitored by spectrofluorimetry. In vivo studies were performed using obese insulin-resistant rats. Binding of fibrinogen to the GPIIb/IIIa receptor was estimated using indirect ELISA and a scanning electron microscopy (SEM). It was found that NSE inhibits the activation and aggregation of human platelets. Our results suggest that NSE may decrease the activation and subsequent aggregation of platelets induced by ristocetin, epinephrine, and low doses of ADP. NSE also reduced the binding of fibrinogen to GPIIb/IIIa on activated platelets. These effects could be explained by the inhibition of platelet activation mediated by integrin receptors: the GPIb-IX-V complex for ristocetin-induced activation and GPIIb/IIIa when epinephrine and low doses of ADP were applied. The anti-platelet effect of NSE complements its anti-inflammatory effect and allows us to prioritize studies of NSE as a potent anti-thrombotic agent. SIGNIFICANCE STATEMENT: N-stearoylethanolamine (NSE) was shown to possess inhibitory action on platelet activation, adhesion, and aggregation. The mechanism of inhibition possibly involves integrin receptors. This finding complements the known anti-inflammatory effects of NSE.

SYT1-Associated Neurodevelopmental Disorder: A Narrative Review

Synaptic dysregulations often result in damaging effects on the central nervous system, resulting in a wide range of brain and neurodevelopment disorders that are caused by mutations disrupting synaptic proteins. SYT1, an identified synaptotagmin protein, plays an essential role in mediating the release of calcium-triggered neurotransmitters (NT) involved in regular synaptic vesicle exocytosis. Considering the significant role of SYT1 in the physiology of synaptic neurotransmission, dysfunction and degeneration of this protein can result in a severe neurological impairment. Genetic variants lead to a newly discovered rare disorder, known as SYT1-associated neurodevelopment disorder. In this review, we will discuss in depth the function of SYT1 in synapse and the underlying molecular mechanisms. We will highlight the genetic basis of SYT1-associated neurodevelopmental disorder along with known phenotypes, with possible interventions and direction of research.

Anesthetics and Cell-Cell Communication: Potential Ca2+-Calmodulin Role in Gap Junction Channel Gating by Heptanol, Halothane and Isoflurane

Cell–cell communication via gap junction channels is known to be inhibited by the anesthetics heptanol, halothane and isoflurane; however, despite numerous studies, the mechanism of gap junction channel gating by anesthetics is still poorly understood. In the early nineties, we reported that gating by anesthetics is strongly potentiated by caffeine and theophylline and inhibited by 4-Aminopyridine. Neither Ca²⁺ channel blockers nor 3-isobutyl-1-methylxanthine (IBMX), forskolin, CPT-cAMP, 8Br-cGMP, adenosine, phorbol ester or H7 had significant effects on gating by anesthetics. In our publication, we concluded that neither cytosolic Ca²⁺_i nor pH_i were involved, and suggested a direct effect of anesthetics on gap junction channel proteins. However, while a direct effect cannot be excluded, based on the potentiating effect of caffeine and theophylline added to anesthetics and data published over the past three decades, we are now reconsidering our earlier interpretation and propose an alternative hypothesis that uncoupling by heptanol, halothane and isoflurane may actually result from a rise in cytosolic Ca²⁺ concentration ([Ca²⁺]_i) and consequential activation of calmodulin linked to gap junction proteins.

4-Aminopyridine Induces Nerve Growth Factor to Improve Skin Wound Healing and Tissue Regeneration

The discovery of ways to enhance skin wound healing is of great importance due to the frequency of skin lesions. We discovered that 4-aminopyridine (4-AP), a potassium channel blocker approved by the FDA for improving walking ability in multiple sclerosis, greatly enhances skin wound healing. Benefits included faster wound closure, restoration of normal-appearing skin architecture, and reinnervation. Hair follicle neogenesis within the healed wounds was increased, both histologically and by analysis of K15 and K17 expression. 4-AP increased levels of vimentin (fibroblasts) and alpha-smooth muscle actin (α-SMA, collagen-producing myofibroblasts) in the healed dermis. 4-AP also increased neuronal regeneration with increased numbers of axons and S100⁺ Schwann cells (SCs), and increased expression of SRY-Box Transcription Factor 10 (SOX10). Treatment also increased levels of transforming growth factor-β (TGF-β), substance P, and nerve growth factor (NGF), important promoters of wound healing. In vitro studies demonstrated that 4-AP induced nerve growth factor and enhanced proliferation and migration of human keratinocytes. Thus, 4-AP enhanced many of the key attributes of successful wound healing and offers a promising new approach to enhance skin wound healing and tissue regeneration.

Astrocytes Exhibit a Protective Role in Neuronal Firing Patterns under Chemically Induced Seizures in Neuron-Astrocyte Co-Cultures

Astrocytes and neurons respond to each other by releasing transmitters, such as γ-aminobutyric acid (GABA) and glutamate, that modulate the synaptic transmission and electrochemical behavior of both cell types. Astrocytes also maintain neuronal homeostasis by clearing neurotransmitters from the extracellular space. These astrocytic actions are altered in diseases involving malfunction of neurons, e.g., in epilepsy, Alzheimer's disease, and Parkinson's disease. Convulsant drugs such as 4-aminopyridine (4-AP) and gabazine are commonly used to study epilepsy in vitro. In this study, we aim to assess the modulatory roles of astrocytes during epileptic-like conditions and in compensating drug-elicited hyperactivity. We plated rat cortical neurons and astrocytes with different ratios on microelectrode arrays, induced seizures with 4-AP and gabazine, and recorded the evoked neuronal activity. Our results indicated that astrocytes effectively counteracted the effect of 4-AP during stimulation. Gabazine, instead, induced neuronal hyperactivity and synchronicity in all cultures. Furthermore, our results showed that the response time to the drugs increased with an increasing number of astrocytes in the co-cultures. To the best of our knowledge, our study is the first that shows the critical modulatory role of astrocytes in 4-AP and gabazine-induced discharges and highlights the importance of considering different proportions of cells in the cultures.

Seizures are a druggable mechanistic link between TBI and subsequent tauopathy

Traumatic brain injury (TBI) is a prominent risk factor for dementias including tauopathies like chronic traumatic encephalopathy (CTE). The mechanisms that promote prion-like spreading of Tau aggregates after TBI are not fully understood, in part due to lack of tractable animal models. Here, we test the putative role of seizures in promoting the spread of tauopathy. We introduce 'tauopathy reporter' zebrafish expressing a genetically encoded fluorescent Tau biosensor that reliably reports accumulation of human Tau species when seeded via intraventricular brain injections. Subjecting zebrafish larvae to a novel TBI paradigm produced various TBI features including cell death, post-traumatic seizures, and Tau inclusions. Bath application of dynamin inhibitors or anticonvulsant drugs rescued TBI-induced tauopathy and cell death. These data suggest a role for seizure activity in the prion-like seeding and spreading of tauopathy following TBI. Further work is warranted regarding anti-convulsants that dampen post-traumatic seizures as a route to moderating subsequent tauopathy.

Examinations of Bilateral Epileptiform Activities in Hippocampal Slices Obtained From Young Mice

Bilateral interconnections through the hippocampal commissure play important roles in synchronizing or spreading hippocampal seizure activities. Intact hippocampi or bilateral hippocampal slices have been isolated from neonatal or immature rats (6–7 or 12–21 days old, respectively) and the mechanisms underlying the bilateral synchrony of hippocampal epileptiform activities have been investigated. However, the feasibility of examining bilateral epileptiform activities of more developed hippocampal circuitry in vitro remains to be explored. For this, we prepared bilateral hippocampal slices from C57 black mice, a strain commonly used in neuroscience and for genetic/molecular modifications. Young mice (21–24-day-old) were used in most experiments. A 600-μm-thick slice was obtained from each mouse by horizontal vibratome sectioning. Bilateral dorsal hippocampal and connecting dorsal hippocampal commissure (DHC) tissues were preserved in the slice and extrahippocampal tissues were removed. Slices were recorded in a submerged chamber mainly at a room temperature (21–22°C). Bilateral CA3 areas were monitored by extracellular recordings, and unilateral electrical stimulation was used to elicit CA3 synaptic field potentials. The unilateral stimulation could elicit population spikes in the contralateral CA3 area. These contralateral spikes were attenuated by inhibiting synaptic transmission with cobalt-containing medium and were abolished when a cut was made at the DHC. Self-sustained and bilaterally correlated epileptiform potentials were observed following application of 4-aminopyradine and became independent after the DHC cut. Bilateral hippocampal activities were detectable in some slices of adult mice and/or at 35–36°C, but with smaller amplitudes and variable waveforms compared to those observed from slices of young mice and at the room temperature. Together, these observations suggested that examining bilateral epileptiform activities in hippocampal slices of young mice is feasible. The weaknesses and limitations of this preparation and our experimentation are discussed.

Positive Allosteric Modulation of CB1 and CB2 Cannabinoid Receptors Enhances the Neuroprotective Activity of a Dual CB1R/CB2R Orthosteric Agonist

Preclinical studies highlighted that compounds targeting cannabinoid receptors could be useful for developing novel therapies against neurodegenerative disorders. However, the chronic use of orthosteric agonists alone has several disadvantages, limiting their usefulness as clinically relevant drugs. Positive allosteric modulators might represent a promising approach to achieve the potential therapeutic benefits of orthosteric agonists of cannabinoid receptors through increasing their activity and limiting their adverse effects. The aim of the present study was to show the effects of positive allosteric ligands of cannabinoid receptors on the activity of a potent dual orthosteric agonist for neuroinflammation and excitotoxic damage by excessive glutamate release. The results indicate that the combination of an orthosteric agonist with positive allosteric modulators could represent a promising therapeutic approach to the treatment of neurodegenerative disorders.

Chronic Pharmacological Increase of Neuronal Activity Improves Sensory-Motor Dysfunction in Spinal Muscular Atrophy Mice

Dysfunction of neuronal circuits is an important determinant of neurodegenerative diseases. Synaptic dysfunction, death, and intrinsic activity of neurons are thought to contribute to the demise of normal behavior in the disease state. However, the interplay between these major pathogenic events during disease progression is poorly understood. Spinal muscular atrophy (SMA) is a neurodegenerative disease caused by a deficiency in the ubiquitously expressed protein SMN and is characterized by motor neuron death, skeletal muscle atrophy, as well as dysfunction and loss of both central and peripheral excitatory synapses. These disease hallmarks result in an overall reduction of neuronal activity in the spinal sensory-motor circuit. Here, we show that increasing neuronal activity by chronic treatment with the FDA-approved potassium channel blocker 4-aminopyridine (4-AP) improves motor behavior in both sexes of a severe mouse model of SMA. 4-AP restores neurotransmission and number of proprioceptive synapses and neuromuscular junctions (NMJs), while having no effects on motor neuron death. In addition, 4-AP treatment with pharmacological inhibition of p53-dependent motor neuron death results in additive effects, leading to full correction of sensory-motor circuit pathology and enhanced phenotypic benefit in SMA mice. Our in vivo study reveals that 4-AP-induced increase of neuronal activity restores synaptic connectivity and function in the sensory-motor circuit to improve the SMA motor phenotype.SIGNIFICANCE STATEMENT Spinal muscular atrophy (SMA) is a neurodegenerative disease, characterized by synaptic loss, motor neuron death, and reduced neuronal activity in spinal sensory-motor circuits. However, whether these are parallel or dependent events is unclear. We show here that long-term increase of neuronal activity by the FDA-approved drug 4-aminopyridine (4-AP) rescues the number and function of central and peripheral synapses in a SMA mouse model, resulting in an improvement of the sensory-motor circuit and motor behavior. Combinatorial treatment of pharmacological inhibition of p53, which is responsible for motor neuron death and 4-AP, results in additive beneficial effects on the sensory-motor circuit in SMA. Thus, neuronal activity restores synaptic connections and improves significantly the severe SMA phenotype.

β1-Integrin- and KV1.3 channel-dependent signaling stimulates glutamate release from Th17 cells

Although the impact of Th17 cells on autoimmunity is undisputable, their pathogenic effector mechanism is still enigmatic. We discovered soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) complex proteins in Th17 cells that enable a vesicular glutamate release pathway that induces local intracytoplasmic calcium release and subsequent damage in neurons. This pathway is glutamine dependent and triggered by binding of β1-integrin to vascular cell adhesion molecule 1 (VCAM-1) on neurons in the inflammatory context. Glutamate secretion could be blocked by inhibiting either glutaminase or KV1.3 channels, which are known to be linked to integrin expression and highly expressed on stimulated T cells. Although KV1.3 is not expressed in CNS tissue, intrathecal administration of a KV1.3 channel blocker or a glutaminase inhibitor ameliorated disability in experimental neuroinflammation. In humans, T cells from patients with multiple sclerosis secreted higher levels of glutamate, and cerebrospinal fluid glutamine levels were increased. Altogether, our findings demonstrate that β1-integrin- and KV1.3 channel-dependent signaling stimulates glutamate release from Th17 cells upon direct cell-cell contact between Th17 cells and neurons.

Continuous behavioural 'switching' in human spermatozoa and its regulation by Ca2+-mobilising stimuli

Human sperm show a variety of different behaviours (types of motility) that have different functional roles. Previous reports suggest that sperm may reversibly switch between these behaviours. We have recorded and analysed the behaviour of individual human sperm (180 cells in total), each cell monitored continuously for 3–3.5 min either under control conditions or in the presence of Ca²⁺-mobilising stimuli. Switching between different behaviours was assessed visually (1 s bins using four behaviour categories), and was verified by fractal dimension analysis of sperm head tracks. In the absence of stimuli, ~90% of cells showed at least one behavioural transition (mean rate under control conditions = 6.4 ± 0.8 transitions.min⁻¹). Type 1 behaviour (progressive, activated-like motility) was most common, but the majority of cells (>70%) displayed at least three behaviour types. Treatment of sperm with Ca²⁺-mobilising agonists had negligible effects on the rate of switching but increased the time spent in type 2 and type 3 (hyperactivation-like) behaviours (P < 2^*10⁻⁸; chi-square). Treatment with 4-aminopyridine under alkaline conditions (pH_o = 8.5), a highly-potent Ca²⁺-mobilising stimulus, was the most effective in increasing the proportion of type 3 behaviour, biasing switching away from type 1 (P < 0.005) and dramatically extending the duration of type 3 events (P < 10⁻¹⁶). Other stimuli, including 300 nM progesterone and 1% human follicular fluid, had qualitatively similar effects but were less potent. We conclude that human sperm observed in vitro constitutively display a range of behaviours and regulation of motility by [Ca²⁺]_i, at the level of the single cell, is achieved not by causing cells to adopt a ‘new’ behaviour but by changing the relative contributions of those behaviours.

Stearoylethanolamide interferes with retrograde endocannabinoid signalling and supports the blood-brain barrier integrity under acute systemic inflammation

Neuroinflammation plays a prominent role in the onset of demyelinating diseases, major depressive disorder and delayed neurodegeneration. An open question remains whether pharmacological suppression of inflammation can effectively reduce the progression of these states. Bioactive lipid mediators such as N-acylethanolamines (NAEs) have an anti-inflammatory activity and are of pharmacological interest due to their endogenous on-demand production and the existence of distinct biological targets in humans and animals. Here we demonstrate for the first time, that treatment with stearoylethanolamide (SEA), a prevailing endogenously formed NAE, is neuroprotective against LPS-induced neuroinflammation in C57BL/6 male mice. SEA restricted the spreading of peripheral inflammation to the brain, and averted the activation of resident microglia and leukocyte trafficking to the brain parenchyma. Treatment with SEA per se increased the neuronal expression of cannabinoid receptors CB_1/2 and brain levels of the most potent endogenous CB_1/2 agonist 2-arachidonoylglycerol in vivo. SEA enhanced the amplitude of synaptic vesicle release, supported the balanced signal-to-noise ratio in glutamate- and GABAergic neurotransmission and decreased the excitotoxic risk associated with higher extracellular glutamate levels under neuroinflammation. The interference of SEA with the endocannabinoid system and presynaptic neurotransmitter release may represent an intrinsic neuroprotective mechanism that is triggered by inflammation and glutamate excitotoxicity. Thus, our data allows to consider SEA for the preventive therapy of acute and late-onset neuroinflammation-associated synaptic dysfunction and neurodegeneration.

Vitamin D deficiency induces the excitation/inhibition brain imbalance and the proinflammatory shift

Vitamin D₃ is among the major neurosteroids whose role in developing and adult brain is intensively studied now. Its active form 1,25(OH)₂D₃ regulates the expression and functioning of a range of brain-specific proteins, which orchestrate the neurotransmitter turnover, neurogenesis and neuroplasticity. Despite numerous studies of the vitamin D role in normal and pathological brain function, there is little evidence on the mechanisms of alterations in excitatory and inhibitory neurotransmission under vitamin D deficiency (VDD). Using the animal model we characterized the dysfunction of excitatory and inhibitory neurotransmission under alimentary VDD. The shift between unstimulated and evoked GABA release under VDD was largely reversed after treatment of VDD, whereas the impairments in glutamatergic system were only partially recovered after 1-month vitamin D₃ supplementation. The increase of the external glutamate level and unstimulated GABA release in brain nerve terminals was associated with intensified ROS production and higher [Ca²⁺]_i in presynapse. The negative allosteric modulation of presynaptic mGlu7 receptors significantly enhanced exocytotic GABA release, which was decreased under VDD, thereby suggesting the neuroprotective effect of such modulation of inhibitory neurotransmission. Synaptic plasma membranes and cytosolic proteins contribute to the decreased stimulated release of neurotransmitter, by being the crucial components, whose functional state is impaired under VDD. The critical changes with synaptic vesicles occurred at the docking step of the process, whereas malfunctioning of synaptic cytosolic proteins impacted the fusion event foremost. The decreased amplitude of exocytosis was inherent for non-excitable cells as well, as evidenced by lower platelet degranulation. Our data suggest the presynaptic dysfunction and proinflammatory shift as the early events in the pathogenesis of VDD-associated disorders and provide evidences for the neuroprotective role of vitamin D₃.

Study on Dalfampridine in the treatment of Multiple Sclerosis Mobility Disability: A meta-analysis

Objective

Systematic Review was used to evaluate the efficacy and safety of Dalfampridine (DAP) in the treatment of Mobility Disability (MS) in patients with Multiple Sclerosis.

Methods

Clinical randomized controlled studies about DAP and placebo in the treatment of Mobility Disability in patients with Multiple Sclerosis until March 2019 were explored by searching Embase, PubMed, Cochrane, Web of Knowledge, and ClinicalTrials.gov. Literature screening, data extraction, quality assessment, and statistical analysis were performed by using Stata 14.0.

Results

10 papers were included in the meta-analysis, and the number of patients was 2100. In conclusion, the application of DAP in clinical can significantly improve the Mobility Disability of patients [OR = 2.73, 95%CI (1.66, 4.50), P<0.001, I² = 74.1%] and boost the mobility speed of patients in Timing 24 Minute Walk Test (T24FW) [SMD = 3,08, 95%CI(1,58, 4.58), P<0.001, I² = 98.7%]. There are no significant differences of the incidence of adverse events [RR = 1.06, 95%CI (0.99, 1.14), P = 0.928, I² = 0.0%] and urinary tract infection [RR = 1.21, 95%CI(0.91, 1.60), P = 0.145, I² = 37.2%] between the DAP test group (Doses≤10 mg) and the placebo control group, and the incidence of adverse events [RR = 1.14, 95%CI(1.02, 1.28), P = 0.793, I² = 0.0%] and urinary tract infection[RR = 3.05, 95%CI(1.04, 8.99), P = 0.680, I² = 0.0%] for the DAP test group (Doses>10 mg) is a litter higher than the placebo control group.

Conclusion

DAP can effectively improve Mobility Disability in patients with Multiple Sclerosis, which is safe and reliable in specific DAP usage doses.

Effects of 4-aminopyridine on attention and executive functions of patients with multiple sclerosis: Randomized, double-blind, placebo-controlled clinical trial. Preliminary report

BACKGROUND

A high percentage of patients with multiple sclerosis present cognitive alterations. Because 4-aminopyridine improves nerve conduction and efficient synaptic connection could improve cognitive dysfunction.

OBJECTIVE

To evaluate the efficacy on cognitive performance and safety of 4-aminopyridine administered to patients with relapsing-remitting multiple sclerosis.

METHODS

A randomized, double-blind, placebo controlled clinical trial was conducted in patients with relapsing-remitting multiple sclerosis diagnosis according to the McDonald criteria. At the beginning and at the end of the treatment different tests were used to assess cognitive performance. Subsequently, patients were randomized 1:1 to receive treatment or placebo. A bootstrap-t test was proposed to test the effectiveness of cognitive performance, considering a p-value < 0.05 as statistically significant.

RESULTS

Twenty-four patients were recruited of which 21 completed the trial, 11 with 4-aminopyridine and 10 with placebo treatment. No significant differences between groups in the initial assessments were observed. In terms of efficacy, the experimental group achieved significantly higher scores in attention span, verbal fluency, planning and graphics and constructive motion.

CONCLUSIONS

4-aminopyridine proved to be an effective treatment on cognitive aspects in patients with relapsing-remitting multiple sclerosis. Drug doses were shown to be safe with mild to moderate adverse events (ClinicalTrials.gov number, NCT02280096).

Modulation of neurosecretion and approaches for its multistep analysis

BACKGROUND

Neurosecretion is the multistep process occurring in separate spatial and temporal cellular boundaries which complicates its comprehensive analysis. Most of the research are focused on one distinct stage of synaptic vesicle recycling. Here, we describe approaches for complex analysis of synaptic vesicle (SV) endocytosis and separate steps of exocytosis at the level of presynaptic bouton and highly purified SVs.

METHODS

Proposed fluorescence-based strategies and analysis of neurotransmitter transport provided the advantages in studies of exocytosis steps. We evaluated SV docking/tethering, their Ca²⁺-dependent fusion and release of neurotransmitters gamma-aminobutyric acid (GABA) and glutamate in two animal models.

RESULTS

Approaches enabled us to study: 1) endocytosis/Ca²⁺-dependent release of fluorescent carbon nanodots (CNDs) during stimulation of nerve terminals; 2) the action of levetiracetam, modulator of SV glycoprotein SV2, on fusion competence of SVs and stimulated release of GABA and glutamate; 3) impairments of several steps of neurosecretion under vitamin D₃ deficiency.

CONCLUSIONS

Our algorithm enabled us to verify the method validity for multidimensional analysis of SV turnover. By increasing SV docking and the size of readily releasable pool (RRP), levetiracetam is able to selectively enhance the stimulated GABA secretion in hippocampal neurons. Findings suggest that SV2 regulates RRP through impact on the number of docked/primed SVs.

GENERAL SIGNIFICANCE

Methodology can be widely applied to study the stimulated neurosecretion in presynapse, regulation of SV docking, their Ca²⁺-dependent fusion with target membranes, quantitative analysis of expression of neuron-specific proteins, as well as for testing the efficiency of pre-selected designed neuroactive substances.