Acute neuroprotection by the synaptic blocker botulinum neurotoxin E in a rat model of focal cerebral ischaemia

An emerging role of SNAREs in ischemic stroke: From pre-to post-diseases

Ischemic stroke is a debilitating condition characterized by high morbidity, disability, recurrence, and mortality rates on a global scale, posing a significant threat to public health and economic stability. Extensive research has thoroughly explored the molecular mechanisms underlying ischemic stroke, elucidating a strong association between soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein receptor proteins (SNAREs) and the pathogenesis of this condition. SNAREs, a class of highly conserved proteins involved in membrane fusion, play a crucial role in modulating neuronal information transmission and promoting myelin formation in the central nervous system (CNS). Preventing the SNARE complex formation, malfunctions in SNARE-dependent exocytosis, and altered regulation of SNARE-mediated vesicle fusion are linked to excitotoxicity, endoplasmic reticulum (ER) stress, and programmed cell death (PCD) in ischemic stroke. However, its underlying mechanisms remain unclear. This study conducts a comprehensive review of the existing literature on SNARE proteins, encompassing the structure, classification, and expression of the SNARE protein family, as well as the assembly - disassembly cycle of SNARE complexes and their physiological roles in the CNS. We thoroughly examine the mechanisms by which SNAREs contribute to the pathological progression and associated risk factors of ischemic stroke (hypertension, hyperglycemia, dyslipidemia, and atherosclerosis). Furthermore, our findings highlight the promise of SNAREs as a viable target for pharmacological interventions in the treatment of ischemic stroke.

Can Botulinum Toxin Type E Serve as a Novel Therapeutic Target for Managing Chronic Orofacial Pain?

The existing literature offers limited experimental evidence on the role of botulinum neurotoxin type E (BoNT-E) in pain transmission. The present study investigated the antinociceptive effects of subcutaneously administered BoNT-E in chronic orofacial pain conditions. This study used orofacial formalin-induced pronociceptive behavior and complete Freund's adjuvant (CFA)-induced thermal hyperalgesia as inflammatory pain models in male Sprague Dawley rats. A neuropathic pain model was also developed by causing an injury to the inferior alveolar nerve. Subcutaneously administered BoNT-E (6, 10 units/kg) significantly reduced nociceptive behavior during the second phase of the formalin test compared to that of the vehicle treatment. These doses similarly alleviated thermal hypersensitivity in the CFA-treated rats. Moreover, BoNT-E (6, 10 units/kg) markedly attenuated mechanical allodynia in rats with an inferior alveolar nerve injury. At a dose of 10 units/kg, BoNT-E produced antinociceptive effects that became evident 8 h post-injection and persisted for 48 h. Notably, BoNT-E (10 units/kg) significantly reduced the number of c-fos-immunostained neurons in the trigeminal subnucleus caudalis of rats with an inferior alveolar nerve injury. In comparison, intraperitoneally administered gabapentin (30, 100 mg/kg) demonstrated significant mechanical anti-allodynic effects but exhibited lower analgesic efficacy than that of BoNT-E. These findings highlight the potential of BoNT-E as a therapeutic agent for chronic pain management.

Botulinum Neurotoxins in Central Nervous System: An Overview from Animal Models to Human Therapy

Botulinum neurotoxins (BoNTs) are potent inhibitors of synaptic vesicle fusion and transmitter release. The natural target of BoNTs is the peripheral neuromuscular junction (NMJ) where, by blocking the release of acetylcholine (ACh), they functionally denervate muscles and alter muscle tone. This leads them to be an excellent drug for the therapy of muscle hyperactivity disorders, such as dystonia, spasticity, and many other movement disorders. BoNTs are also effective in inhibiting both the release of ACh at sites other than NMJ and the release of neurotransmitters other than ACh. Furthermore, much evidence shows that BoNTs can act not only on the peripheral nervous system (PNS), but also on the central nervous system (CNS). Under this view, central changes may result either from sensory input from the PNS, from retrograde transport of BoNTs, or from direct injection of BoNTs into the CNS. The aim of this review is to give an update on available data, both from animal models or human studies, which suggest or confirm central alterations induced by peripheral or central BoNTs treatment. The data will be discussed with particular attention to the possible therapeutic applications to pathological conditions and degenerative diseases of the CNS.

Engineering Botulinum Neurotoxins for Enhanced Therapeutic Applications and Vaccine Development

Botulinum neurotoxins (BoNTs) show increasing therapeutic applications ranging from treatment of locally paralyzed muscles to cosmetic benefits. At first, in the 1970s, BoNT was used for the treatment of strabismus, however, nowadays, BoNT has multiple medical applications including the treatment of muscle hyperactivity such as strabismus, dystonia, movement disorders, hemifacial spasm, essential tremor, tics, cervical dystonia, cerebral palsy, as well as secretory disorders (hyperhidrosis, sialorrhea) and pain syndromes such as chronic migraine. This review summarizes current knowledge related to engineering of botulinum toxins, with particular emphasis on their potential therapeutic applications for pain management and for retargeting to non-neuronal tissues. Advances in molecular biology have resulted in generating modified BoNTs with the potential to act in a variety of disorders, however, in addition to the modifications of well characterized toxinotypes, the diversity of the wild type BoNT toxinotypes or subtypes, provides the basis for innovative BoNT-based therapeutics and research tools. This expanding BoNT superfamily forms the foundation for new toxins candidates in a wider range of therapeutic options.

Perspectives for the use of therapeutic Botulinum toxin as a multifaceted candidate drug to attenuate COVID-19

The recent outbreak of coronavirus disease (COVID-19) resulting from a distinctive severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) continues to evolve in many countries and pose life-threatening clinical issues to global public health. While the lungs are the primary target for the SARS-CoV-2-mediated pathological consequence, the virus appears to invade the brain and cause unpredicted neurological deficits. In the later stage, COVID-19 can progress to pneumonia, acute respiratory failure, neurodegeneration and multi-organ dysfunctions leading to death. Though a significant portion of individuals with COVID-19 has been recovering from clinical symptoms, the pathological impact of the SARS-CoV-2 infection on the structural and functional properties of the lungs, heart, brain and other organs at the post-recovery state remains unknown. Presently, there is an urgent need for a remedial measure to combat this devastating COVID-19. Botulinum toxins (BoNTs) are potent neurotoxins that can induce paralysis of muscle and acute respiratory arrest in humans. However, a mild dose of the purified form of BoNT has been known to attenuate chronic cough, dyspnoea, pneumonia, acute respiratory failure, abnormal circulation, cardiac defects and various neurological deficits that have been recognised as the prominent clinical symptoms of COVID-19. Considering the fact, this review article provides 1) an overview of the SARS-CoV-2 mediated pathological impact on the lungs, heart and brain, 2) signifies the therapeutic uses of BoNTs against pulmonary failure, cardiac arrest and neurological deficits, and 3) emphasize the rationality for the possible use of BoNT to prevent SARS-CoV-2 infection and manage COVID-19.

Experimental Intrastriatal Applications of Botulinum Neurotoxin-A: A Review

Parkinson’s disease (PD) is one of the most frequent neurodegenerative disorders. Its main pathophysiological characteristic is the loss of dopaminergic neurons in the substantia nigra pars compacta followed by a lack of striatal dopaminergic input and a consequent disinhibition of tonically active cholinergic interneurons. The resulting striatal hypercholinism causes major motor symptoms in PD. Anticholinergic pharmacotherapies have antiparkinsonian effects on motor symptoms, but, due to systemic actions, also numerous severe side effects occur on a regular basis. To circumvent these side effects, a local anticholinergic therapy acting exclusively in the striatum would be reasonable. Botulinum neurotoxin-A (BoNT-A) is synthesized by Clostridium botulinum and blocks the release of acetylcholine from the presynaptic bouton. For several decades, BoNT-A has been used successfully for medical and cosmetic purposes to induce controlled paralyses of single muscles. Our group and others investigated the experimental treatment of striatal hypercholinism by the direct injection of BoNT-A into the striatum of rats and mice as well as of hemiparkinsonian animal models. This review gives an overview of the most important results of the experimental intrastriatal BoNT-A application, with a focus on hemiparkinsonian rats.

Exploiting Botulinum Neurotoxins for the Study of Brain Physiology and Pathology

Botulinum neurotoxins are metalloproteases that specifically cleave N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins in synaptic terminals, resulting in a potent inhibition of vesicle fusion and transmitter release. The family comprises different serotypes (BoNT/A to BoNT/G). The natural target of these toxins is represented by the neuromuscular junction, where BoNTs block acetylcholine release. In this review, we describe the actions of botulinum toxins after direct delivery to the central nervous system (CNS), where BoNTs block exocytosis of several transmitters, with near-complete silencing of neural networks. The use of clostridial neurotoxins in the CNS has allowed us to investigate specifically the role of synaptic activity in different physiological and pathological processes. The silencing properties of BoNTs can be exploited for therapeutic purposes, for example to counteract pathological hyperactivity and seizures in epileptogenic brain foci, or to investigate the role of activity in degenerative diseases like prion disease. Altogether, clostridial neurotoxins and their derivatives hold promise as powerful tools for both the basic understanding of brain function and the dissection and treatment of activity-dependent pathogenic pathways.

Combining robotic training and inactivation of the healthy hemisphere restores pre-stroke motor patterns in mice

Focal cortical stroke often leads to persistent motor deficits, prompting the need for more effective interventions. The efficacy of rehabilitation can be increased by ‘plasticity-stimulating’ treatments that enhance experience-dependent modifications in spared areas. Transcallosal pathways represent a promising therapeutic target, but their role in post-stroke recovery remains controversial. Here, we demonstrate that the contralesional cortex exerts an enhanced interhemispheric inhibition over the perilesional tissue after focal cortical stroke in mouse forelimb motor cortex. Accordingly, we designed a rehabilitation protocol combining intensive, repeatable exercises on a robotic platform with reversible inactivation of the contralesional cortex. This treatment promoted recovery in general motor tests and in manual dexterity with remarkable restoration of pre-lesion movement patterns, evaluated by kinematic analysis. Recovery was accompanied by a reduction of transcallosal inhibition and ‘plasticity brakes’ over the perilesional tissue. Our data support the use of combinatorial clinical therapies exploiting robotic devices and modulation of interhemispheric connectivity.

Vitamin D3 protects against Aβ peptide cytotoxicity in differentiated human neuroblastoma SH- SY5Y cells: A role for S1P1/p38MAPK/ATF4 axis

Besides its classical function of bone metabolism regulation, 1alpha, 25-dihydroxyvitamin D3 (1,25(OH)₂D₃), acts on a variety of tissues including the nervous system, where the hormone plays an important role as neuroprotective, antiproliferating and differentiating agent. Sphingolipids are bioactive lipids that play critical and complex roles in regulating cell fate. In the present paper we have investigated whether sphingolipids are involved in the protective action of 1,25(OH)₂D_3. We have found that 1,25(OH)₂D₃ prevents amyloid-β peptide (Aβ(1-42)) cytotoxicity both in differentiated SH-SY5Y human neuroblastoma cells and in vivo. In differentiated SH-SY5Y cells, Aβ(1-42) strongly reduces the sphingosine-1-phosphate (S1P)/ceramide (Cer) ratio while 1,25(OH)₂D₃ partially reverts this effect. 1,25(OH)₂D₃ reverts also the Aβ(1-42)-induced reduction of sphingosine kinase activity. We have also studied the crosstalk between 1,25(OH)₂D₃ and S1P signaling pathways downstream to the activation of S1P receptor subtype S1P1. Notably, we found that 1,25(OH)₂D₃ prevents the reduction of S1P1 expression promoted by Aβ(1-42) and thereby it modulates the downstream signaling leading to ER stress damage (p38MAPK/ATF4). Similar effects were observed by using ZK191784. In addition, chronic treatment with 1,25(OH)₂D₃ protects from aggregated Aβ(1-42)-induced damage in the CA1 region of the rat hippocampus and promotes cell proliferation in the hippocampal dentate gyrus of adult mice. In conclusion, these results represent the first evidence of the role of 1,25(OH)₂D₃ and its structural analogue ZK191784 in counteracting the Aβ(1-42) peptide-induced toxicity through the modulation of S1P/S1P1/p38MAPK/ATF4 pathway in differentiated SH-SY5Y cells.

Intrastriatal injection of botulinum neurotoxin-A is not cytotoxic in rat brain - A histological and stereological analysis

Parkinson's disease (PD) is caused by progressive degeneration of dopaminergic neurons in the substantia nigra pars compacta, resulting in a deficiency of dopamine in the striatum and an increased release of acetylcholine by tonically active interneurons. Botulinum neurotoxin-A (BoNT-A) is well known for blocking transmitter release by cholinergic presynaptic terminals. Treating striatal hypercholinism by local application of BoNT-A could be a possible new local therapy option of PD. In previous studies of our group, we analyzed the effect of BoNT-A injection into the CPu of 6-OHDA lesioned hemiparkinsonian rats. Our studies showed that BoNT-A application in hemiparkinson rat model is capable of abolishing apomorphine induced rotations for approximately 3 months. Regularly occurring axonal swellings in the BoNT-A infiltrated striata were also discovered, which we named BoNT-A induced varicosities (BiVs). Résumé: Here we investigated the long-term effect of the injection of 1ng BoNT-A into the right CPu of naive Wistar rats on the number of ChAT-ir interneurons as well as on the numeric density and the volumetric size of the BiVs in the CPu. Significant differences in the number of ChAT-ir neurons between the right BoNT-A treated CPu and the left untreated CPu were not detected up to 12 month post BoNT-A injection. The numeric density of BiVs in the treated CPu reached a maximum 3 months after BoNT-A treatment and decreased afterwards, whereas the volume of single BiVs increased steadily throughout the whole time course of the experiment.

PRRT2 Mutant Leads to Dysfunction of Glutamate Signaling

Paroxysmal kinesigenic choreoathetosis (PKC) is an inherited disease of the nervous system. We previously identified PRRT2 as the causative gene of PKC. However, as little is known about the function of PRRT2, elucidating its function will benefit not only PKC studies, but also many other related disorders. Here, we reveal higher levels of glutamate in the plasma of PKC patients and the culture medium of neurons following knock-out Prrt2 expression. Using double immunostaining assays we confirm Prrt2 is located at the glutamatergic neurons in accordance with its function. Our co-immunoprecipitation assays reveal mutant PRRT2 interferes with SNAP25 and GRIA1 interactions, respectively. Furthermore, using live-labeling techniques, we confirmed co-transfection with mutant PRRT2 caused an increase in GRIA1 distribution on the cell surface. Therefore, our results suggest that mutant PRRT2, probably through its weakened interaction with SNAP25, affects glutamate signaling and glutamate receptor activity, resulting in the increase of glutamate release and subsequent neuronal hyperexcitability.

Neuroprotective effects of Gualou Guizhi decoction in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

Gualou Guizhi decoction (GLGZD) prescribed in traditional Chinese medicine has been reported to have protective effects on ischemic stroke. The present study is to investigate the therapeutic effect of GLGZD on ischemic stroke and explore its mode of action.

MATERIALS AND METHODS

GLGZD was studied on transient middle cerebral artery occlusion (MCAO) followed by reperfusion in vivo, as well as on hippocampal primary neuron cultures in vitro.

RESULTS

In vivo, it was shown that GLGZD treatment for 7 days could ameliorate transient middle cerebral artery occlusion (MCAO)-induced neurological deficit, histopathology changes and decrease infarct area. Further study demonstrated that GLGZD inhibited over-activation of astrocytes and apoptosis of neurons and GLGZD promoted up-regulation of neuronal specific marker neuron-specific nuclear (NeuN) and microtubule-associated protein 2 (MAP-2) in brain. Moreover, the in vitro study revealed that GLGZD treatment protected against NMDA-induced cell apoptosis and neuronal loss, and promoted up-regulation of neuronal specific marker NeuN.

CONCLUSIONS

Taken together, the present study demonstrates that GLGZD produces a protection in the MCAO model rats via inhibiting over-activation of astrocytes, apoptosis of neurons and up-regulation of neuronal specific marker NeuN and MAP-2. Our study reveals that GLGZD might be a potential neuroprotective agent for stroke and can provide basic data for clinical use.

More than at the neuromuscular synapse: actions of botulinum neurotoxin A in the central nervous system

Botulinum neurotoxin type A (BoNT/A) is a metalloprotease that produces a sustained yet transitory blockade of transmitter release from peripheral nerve terminals. Local delivery of this neurotoxin is successfully employed in clinical practice to reduce muscle hyperactivity such as in spasticity and dystonia, and to relieve pain with long-lasting therapeutic effects. However, not all BoNT/A effects can be explained by an action at peripheral nerve terminals. Indeed, it appears that BoNT/A is endowed with trafficking properties similar to the parental tetanus neurotoxin and thus be able to directly affect the CNS. In this review, we present and discuss novel compelling evidence for a direct central effect of BoNT/A in both dorsal and ventral horns of the animal and human spinal cord after peripheral injection of the neurotoxin, with important consequences on pain and motor control. This new knowledge is expected to radically change the approach to the use of BoNT/A in the future. As BoNT/A central action appears to also contribute to functional improvement, for instance in human spastic gait, the challenge will be to develop new subtypes or BoNT derivatives with deliberate, cell-specific central effects in order to fully exploit the spectrum of BoNT/A therapeutic activity.

A robotic system for quantitative assessment and poststroke training of forelimb retraction in mice

BACKGROUND

Neurorehabilitation protocols based on the use of robotic devices have recently shown to provide promising clinical results. However, their efficacy is still limited because of the poor comprehension of the mechanisms at the basis of functional enhancements.

OBJECTIVE

To increase basic understanding of robot-mediated neurorehabilitation by performing experiments on a rodent model of stroke.

METHODS

Mice were trained to pull back a handle on a robotic platform and their performances in the task were evaluated before and after a focal cortical ischemic stroke. The platform was designed for the quantitative assessment of forelimb function via a series of parameters (time needed to complete the task, t-target; average force; number of sub-movements).

RESULTS

The animals rapidly learned the retraction task and reached asymptotic performance by the fifth session of training. Within 2 to 6 days after a small, endothelin-1-induced lesion in the caudal forelimb area, mice showed an increase in t-target and number of sub-movements and a corresponding decrease in the average force exerted. These parameters returned to baseline, pre-lesion values with continued platform training (10-14 days after stroke).

CONCLUSIONS

These results highlight the utility of the devised platform for characterizing post-infarct deficits and improvements of forelimb performance. Further research is warranted to widen the understanding of device-dependent rehabilitation effects.

Endothelial cell-by-cell profiling reveals the temporal dynamics of VEGFR1 and VEGFR2 membrane localization after murine hindlimb ischemia

VEGF receptor (VEGFR) cell surface localization plays a critical role in transducing VEGF signaling toward angiogenic outcomes, and quantitative characterization of these parameters is critical to advancing computational models for predictive medicine. However, studies to this point have largely examined intact muscle; thus, essential data on the cellular localization of the receptors within the tissue are currently unknown. Therefore, our aims were to quantitatively analyze VEGFR localization on endothelial cells (ECs) from mouse hindlimb skeletal muscles after the induction of hindlimb ischemia, an established model for human peripheral artery disease. Flow cytometry was used to measure and compare the ex vivo surface localization of VEGFR1 and VEGFR2 on CD31(+)/CD34(+) ECs 3 and 10 days after unilateral ligation of the femoral artery. We determined that 3 days after hindlimb ischemia, VEGFR2 surface levels were decreased by 80% compared with ECs from the nonischemic limb; 10 days after ischemia, we observed a twofold increase in surface levels of the modulatory receptor, VEGFR1, along with increased proliferating cell nuclear antigen, urokinase plasminogen activator, and urokinase plasminogen activator receptor mRNA expression compared with the nonischemic limb. The significant upregulation of VEGFR1 surface levels indicates that VEGFR1 indeed plays a critical role in the ischemia-induced perfusion recovery process, a process that includes both angiogenesis and arteriogenesis. The quantification of these dissimilarities, for the first time ex vivo, provides insights into the balance of modulatory (VEGFR1) and proangiogenic (VEGFR2) receptors in ischemia and lays the foundation for systems biology approaches toward therapeutic angiogenesis.

Behavioral and structural effects of unilateral intrastriatal injections of botulinum neurotoxin a in the rat model of Parkinson's disease

Botulinum neurotoxin (BoNT) inhibits the release of acetylcholine from presynaptic vesicles through its proteinase activity cleaving the SNARE complex. Parkinson's disease (PD) is associated with locally increased cholinergic activity in the striatum. Therefore, the present study investigates the effect of unilateral intrastriatal BoNT-A injection in naïve rats on striatal morphology; i.e., the total number of Nissl-stained neurons and the volume of caudate-putamen (CPu) were estimated. Furthermore, stainings for markers of gliosis (glial fibrillary acidic protein) and microglia (Iba1) were performed. In addition, the potential beneficial effects of a unilateral intrastriatal injection of BoNT-A on motor activity in the rat model of hemi-PD were evaluated. Hemi-PD was induced by unilateral injection of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle. Six weeks later, rats received an ipsilateral intrastriatal injection of BoNT-A. Behaviorally, motor performance was tested. The total number of CPu neurons and the striatal volume were not significantly different between the BoNT-A-injected right and the intact left hemispheres of naïve rats. In hemi-PD rats, intrastriatal BoNT-A abolished apomorphine-induced rotations, increased amphetamine-induced rotations, and tended to improve left forelimb usage. Forced motor function in the accelerod test was not significantly changed by BoNT-A, and open field activity was also unaltered compared with sham treatment. Thus, intrastriatal BoNT-A affects spontaneous motor activity of hemi-PD rats to a minor degree compared with drug-induced motor function. In the future, tests assessing the cognitive and emotional performance should be performed to ascertain finally the potential therapeutic usefulness of intrastriatal BoNT-A for PD.