Botulinum Neurotoxin Type Research Articles

Advanced Non-Operative Interventions for Anterior Knee Pain.

This review presents evidence for advanced non-operative interventions, including extracorporeal shockwave therapy (ESWT), prolotherapy, platelet-rich plasma (PRP), adipose tissue-derived cells, bone marrow aspirate concentrate, various additional non-corticosteroid injectates, and needle-based interventions for common causes of anterior knee pain in the adult population. These etiologies include osteoarthritis of the knee, patellofemoral pain syndrome, chondromalacia patella, Hoffa fat pad impingement syndrome, patellar/quadriceps tendinopathy, and prepatellar bursitis. This review discusses patient care options using a case-based understanding of interventions by condition while recognizing strength of evidence. ESWT and PRP are the most robustly studied and have greatest evidence for treating tibiofemoral osteoarthritis and for long-term benefit in treating patellar tendinopathy. PRP may have evidence for treatment of chondromalacia and prolotherapy for management of tibiofemoral arthritis; both have limited evidence. Botulinum neurotoxin type A has strong evidence to support use in treating patellofemoral pain syndrome. There is limited evidence to support the use of viscosupplementation, percutaneous needle tenotomy, and medicinal signaling cell-based therapies beyond platelet-rich plasma for anterior knee pain. There is limited research on the management of quadriceps tendinopathy, prepatellar bursitis, patellofemoral osteoarthritis, and Hoffa's fat pad impingement syndrome. Further research and standardization of protocols are necessary to fully assess these treatments' efficacy. ESWT, cell-based, and needle-based interventions, may serve as effective treatment options for patients with anterior knee pain. Selection of each intervention requires understanding the evidence, level of risk, and appropriate application based on a patient's level of activity to enable clinicians to enhance patient outcomes and quality of life.

Application of botulinum toxin A in tissue repair and regeneration

Tissue repair and regeneration present significant clinical challenges. Despite the array of treatments currently available in this domain, the urgent demand for innovative therapies persists, with the goal of enhancing patient quality of life. Recently, the application of botulinum neurotoxin type A (BoNT/A) has expanded within the realm of tissue repair and regeneration. This review critically examines the utilization of BoNT/A, specifically focusing on its vascular effects, potential in nerve regeneration, and contributions to bone healing. This analysis not only offers fresh insights into the diverse mechanisms of action of BoNT/A but also explores additional therapeutic possibilities for patients.

Excitation-contraction coupling inhibitors potentiate the actions of botulinum neurotoxin type A at the neuromuscular junction.

Botulinum neurotoxin type A1 (BoNT/A) is one of the most potent neurotoxins known. At the same time, it is also one of the safest therapeutic agents used for the treatment of several human disorders and in aesthetic medicine. Notwithstanding great effectiveness, strategies to accelerate the onset and prolong BoNT/A action would significantly ameliorate its pharmacological effects with beneficial outcomes for clinical use. Here, we combined BoNT/A with two fast-acting inhibitors of excitation-contraction coupling inhibitors (ECCI), either the μ-conotoxin CnIIIC or dantrolene, and tested the effect of their co-injection on a model of hind-limb paralysis in rodents using behavioural, biochemical, imaging and electrophysiological assays. The BoNT/A-ECCI combinations accelerated the onset of muscle relaxation. Surprisingly, they also potentiated the peak effect and extended the duration of the three BoNT/A commercial preparations OnabotulinumtoxinA, AbobotulinumtoxinA and IncobotulinumtoxinA. ECCI co-injection increased the number of BoNT/A molecules entering motoneuron terminals, which induced a faster and greater cleavage of SNAP-25 during the onset and peak phases, and prolonged the attenuation of nerve-muscle neurotransmission during the recovery phase. We estimate that ECCI co-injection yields a threefold potentiation in BoNT/A pharmacological activity. Overall, our results show that the pharmacological activity of BoNT/A can be combined and synergized with other bioactive molecules and uncover a novel strategy to enhance the neuromuscular effects of BoNT/A without altering the neurotoxin moiety or intrinsic activity, thus maintaining its exceptional safety profile.

Pelvic floor muscle electrical coupling in chronic pelvic pain: Insights into pathophysiology and botulinum toxin treatment effects

This study aimed to assess the electrical coupling between both pelvic floor muscle (PFM) sides (two-sided coupling) and within individual PFM sides (one-sided coupling) in chronic pelvic pain (CPP) before and after botulinum neurotoxin type A (BoNT/A) treatment. Surface electromyographic (sEMG) signals were recorded from the left and right PFM of 24 patients (P) with CPP before and after being treated with BoNT/A (Weeks 0,8,12,24). Recordings were also made in 24 healthy women (H). PFM two-sided and one-sided coupling was evaluated during contractions by the cross-correlation (CC) and the imaginary part of coherency (iCOH) of their sEMG signals. Significant differences between their values were assessed comparing P(0) vs. P(8,12,24) and H vs. P(0,8,12,24). This study showed that PFM two-sided coupling is similar across groups before treatment, while PFM one-sided coupling on the patients’ most painful side is deranged before and also after BoNT/A treatment: amplitude coupling is lower (<CC) and phase difference is greater (>iCOH) than healthy women’s. This could be justified by altered neuromotor control strategies developed as an adaptation to muscle pain, structural and electrical changes in PFM, and alterations in their innervation pattern, which may influence the onset, perpetuation, or recurrence of CPP after treatment.

Impact of botulinum toxin type A on tooth movement and bone remodeling in male Wistar rats

ObjectiveWe evaluated whether the use of botulinum neurotoxin type A (BTX-A) in masticatory muscles influences tooth movement and bone remodeling. DesignSeventy-seven male Wistar rats were allocated to the groups: S - Saline (n=20); SM - Saline with movement (n=20); BT - Botulinum toxin (n=18); BTM - Botulinum toxin with movement (n=19). On day 1, 0.02mL of sterile 0.9% saline was administered to groups S and SM and BTX-A (1U in 0.02mL of saline) to groups BT and BTM, in the masseter and temporal muscles laterally. On day 30, a nickel titanium spring was installed to move the first maxillary molar and euthanasia was performed on days 32 and 51. Tooth displacement, maxillary and mandibular bone volumes, collagen neoformation, bone and root resorptions, and masseter morphometry were assessed. Statistical analysis was conducted (p < 0.05). ResultsA higher percentage of type I collagen was observed in the BT than in the S group on day 51 and lower mass, length, and diameter of the masseter fibers in BT and BTM (p < 0.05). Tooth displacement, bone volume, bone and root resorptions, hyaline area, and masseter height showed no difference among groups with and without BTX-A, regardless of tooth movement (p > 0.05). ConclusionsBTX-A did not interfere with tooth displacement, bone volume, and dental and periodontal tissues related to tooth movement in rats; it increased mature collagen in animals without tooth movement; and it caused a decrease in the mass, length, and diameter of the masseter fibers.

Botulinum Neurotoxin Type A in paediatric non-neurogenic therapy resistant overactive bladder: a cohort study.

Intradetrusor Botulinum Neurotoxin Type A (BoNT-A) is an increasingly applied treatment modality for overactive bladder (OAB) in children with refractory urinary incontinence. Despite that, evidence is sparse, and the potential not fully understood. The aim of this study was to evaluate the effectiveness and safety of intradetrusor injection in children with refractory functional OAB and urinary incontinence. Furthermore, we aimed to identify predictors of efficacy and side effects to BoNT-A treatment. We conducted a cohort study of children with OAB and urinary incontinence who received intradetrusor injection of BoNT-A in the period 01.01.2016 to 31.12.2020 at our centre. All patients were refractory to standard urotherapy, anticholinergics, mirabegron and the combination of these treatments. Patients with neurogenic bladder were excluded. Primary endpoint was the reduction on the frequency of urinary incontinence episodes from baseline. Secondary endpoints included urodynamic parameters and uroflowmetry characteristics as well as side effects. Forty-three children (mean age at first treatment 10.7 ± 1.8, 30 males) were included. After first treatment, a reduction of ≥ 50% in incontinence episodes was seen in 58% of patients with daytime urinary incontinence (DUI) and 47% of patients with nocturnal enuresis (NE). Adverse events, mainly urinary tract infections (UTI), were reported by 16% of patients after first treatment. Our analysis identified normal cystometric compliance as a significant predictor of treatment effect We estimated the mean duration of effect to be approximately 7months. Intradetrusor BoNT-A injection appears to be a safe and effective option in treating refractory urinary incontinent children with overactive bladder. We identified cystometric compliance as a predictor of response. Most children necessitate repeated treatments. Further prospective and controlled studies are necessary in order to fully identify predictors and potential of treatment.

Association analysis of ADRB3:rs4994 with urodynamic outcome, six months after a single intra-detrusor injection of botulinum toxin, in women with overactive bladder.

Intra-detrusor injection of botulinum neurotoxin type A (BoNT/A) is recommended as a possible treatment for patients with overactive bladder (OAB) in whom first-line therapies have failed. The c.190T > C (rs4994) polymorphism in the gene encoding the beta-3 adrenergic receptor (ADRB3) has been suggested to be associated with predisposition to OAB or with response to OAB treatment via a cholinergic muscarinic receptor antagonist. This prospective study aimed to use a urodynamic parameter-based assessment of response, six months after a single intra-detrusor injection of BoNT/A in female OAB patients, to elucidate possible association with the ADRB3 polymorphism. The study group consisted of 138 consecutive, Polish, adult, female OAB patients. Urodynamic parameters were recorded before injection of BoNT/A and at six months after administration. ADRB3:rs4994 variants were identified by the sequencing of genomic DNA extracted from buccal swabs. Apart from baseline, and relative, increase in Maximum Cystometric Capacity (MCC) six months after BoNT/A injection, no significant differences were found in urodynamic parameters between reference TT homozygotes and women with at least one C allele. Our results do not exclude that ADRB3:rs4994 variants are associated with a positive urodynamic test-based response to intra-detrusor injection of BoNT/A in females with OAB.

Do Diagnostic Nerve Blocks Affect the Starting Dose of Botulinum Neurotoxin Type A for Spasticity? A Case-Control Study.

One of the aims of diagnostic nerve blocks is to identify the overactive muscles that lead to a specific spasticity pattern. However, to date, there is no evidence on how nerve blocks may affect botulinum neurotoxin-A (BoNT-A) dose in patients with spasticity. This case-control study aims to assess the role of diagnostic nerve block in defining BoNT-A starting dose at first treatment. Patients with upper and lower limb spasticity treated for the first time with BoNT-A were retrospectively divided into two groups: Group 1 (n = 43) was evaluated with clinical assessment and diagnostic nerve block; Group 2 (n = 56) underwent clinical assessment only. Group 1 was injected with higher BoNT-A doses in some muscles (i.e., flexor digitorum profundus, soleus), and received a higher BoNT-A cumulative dose with a larger number of injected muscles for some spasticity patterns (i.e., "clenched fist", "flexed fingers", "adducted thigh"). Diagnostic nerve block may help the clinician to optimize and personalize the BoNT-A dose since the first BoNT-A treatment.

Delphi Analysis: Optimizing Anatomy Teaching and Ultrasound Training for Botulinum Neurotoxin Type A Injection in Spasticity and Dystonia.

Our objective was to provide expert consensus on best practices for anatomy teaching and training on ultrasound-guided botulinum neurotoxin type A (BoNT-A) injection for specialists involved in treating spasticity and dystonia. Nine experts (three neurologists; six physical medicine and rehabilitation physicians) participated in a three-round modified Delphi process. Over three rounds, experts reached consensus on 15 of 16 statements describing best practices for anatomy and BoNT-A injection training. They unanimously agreed that knowledge of the target audience, including their needs and current competency, is crucial when designing training programs. Experts also agreed that alignment between instructors is essential to ensure consistency of approach over time and between regions, and that training programs should be simple, adaptable, and "hands-on" to enhance engagement and learning. Consensus was also reached for several other key areas of training program development. The best-practice principles identified by expert consensus could aid in the development of effective, standardized programs for anatomy teaching and BoNT-A injection training for the purposes of treating spasticity and dystonia. This will enhance the exchange of knowledge, skills, and educational approaches between global experts, allowing more specialists to treat important movement disorders and ultimately improving patient outcomes.

New and Future Developments in Neurotoxins.

There are 7 known serotypes of botulinum neurotoxins (A through G). Currently, commercially available toxins are those in serotypes A and B. This paper will discuss new toxins on the horizon, developments in prolonging and shortening the duration of outcomes, and novel therapeutic indications on the horizon. To provide insight into new toxins and new therapeutic modalities surrounding toxins on the horizon. The authors have reviewed the relevant literature and shared their insights and opinions as to future developments in toxin research and potential clinical applications. Botulinum neurotoxin type E's faster onset and shorter duration of effect represent true clinical differentiators. Future development of botulinum neurotoxin type E for aesthetic and therapeutic uses will be in areas where fast onset and short duration of effect are desirable. Current challenges with neuromodulators include the need for frequent treatments and lack of reversal agents. Agents to address both challenges and novel indications, including inhibition of melanogenesis, are being developed.

Functional prediction and assignment of Clostridium botulinum type A1 operome: A quest for prioritizing drug targets

Clostridium botulinum strain Hall produces potent botulinum neurotoxin type A1, which causes food-borne, infant, and wound botulism in humans. Antibiotics and botulinum antitoxins can control growth and prevent botulinum toxicity. However, limited information on a protein with an unknown function hinders the discovery of new drug targets for this disease. In this study, a combined bioinformatics approach with literature support was applied to predict, assign, and validate operome functions. Our functional annotation scheme was based on sequence motifs, conserved domains, structures, protein folds, and evolutionary relationships. Approximately 14.62 % of the operome exhibited sequence similarity to known proteins, with 6.65 % predicted functions for 293 proteins, including 121 proteins exclusive to C. botulinum. Structural analysis revealed a significant presence of the Rossmann fold (26 %) and miscellaneous folds (43 %) among the operome. Transporters (>85) and transcriptional regulators (>45) were prevalent, underscoring their importance in C. botulinum adaptive strategies. The newly identified operome contributed to the diverse cellular and metabolic processes of this organism. The function of its operome was involved in amino acid metabolism and botulinum neurotoxin biosynthesis. In this study, we identified and characterized 13 new virulence proteins from the operome to determine their structure–function relationships. These new metabolic and virulence proteins allow the organism to colonize and interact with the human gastrointestinal tract. This study provides a quest for new drugs and targets for treating the underlying diseases of C. botulinum in humans.

Tanycytic transcytosis inhibition disrupts energy balance, glucose homeostasis and cognitive function in male mice

ObjectivesIn Western society, high-caloric diets rich in fats and sugars have fueled the obesity epidemic and its related disorders. Disruption of the body-brain communication, crucial for maintaining glucose and energy homeostasis, arises from both obesogenic and genetic factors, leading to metabolic disorders. Here, we investigate the role of hypothalamic tanycyte shuttles between the pituitary portal blood and the third ventricle cerebrospinal fluid in regulating energy balance. MethodsWe inhibited vesicle-associated membrane proteins (VAMP1-3)-mediated release in tanycytes by expressing the botulinum neurotoxin type B light chain (BoNT/B) in a Cre-dependent manner in tanycytes. This was achieved by injecting either TAT-Cre in the third ventricle or an AAV1/2 expressing Cre under the control of the tanycyte-specific promoter iodothyronine deiodinase 2 into the lateral ventricle of adult male mice. ResultsIn male mice fed a standard diet, targeted expression of BoNT/B in adult tanycytes blocks leptin transport into the mediobasal hypothalamus and results in normal-weight central obesity, including increased food intake, abdominal fat deposition, and elevated leptin levels but no marked change in body weight. Furthermore, BoNT/B expression in adult tanycytes promotes fatty acid storage, leading to glucose intolerance and insulin resistance. Notably, these metabolic disturbances occur despite a compensatory increase in insulin secretion, observed both in response to exogenous glucose boluses in vivo and in isolated pancreatic islets. Intriguingly, these metabolic alterations are associated with impaired spatial memory in BoNT/B-expressing mice. ConclusionsThese findings underscore the central role of tanycytes in brain-periphery communication and highlight their potential implication in the age-related development of type 2 diabetes and cognitive decline. Our tanycytic BoNT/B mouse model provides a robust platform for studying how these conditions progress over time, from prediabetic states to full-blown metabolic and cognitive disorders, and the mechanistic contribution of tanycytes to their development. The recognition of the impact of tanycytic transcytosis on hormone transport opens new avenues for developing targeted therapies that could address both metabolic disorders and their associated cognitive comorbidities, which often emerge or worsen with advancing age.

Model-based interspecies interpretation of botulinum neurotoxin type A on muscle-contraction inhibition.

Botulinum neurotoxins (BoNTs) are commonly used in therapeutic and cosmetic applications. One such neurotoxin, BoNT type A (BoNT/A), has been studied widely for its effects on muscle function and contraction. Despite the importance of BoNT/A products, determining the blood concentrations of these toxins can be challenging. To address this, researchers have focused on pharmacodynamic (PD) markers, including compound muscle action potential (CMAP) and digit abduction scoring (DAS). In this study, we aimed to develop a probabilistic kinetic-pharmacodynamic (K-PD) model to interpret CMAP and DAS data obtained from mice and rats during the development of BoNT/A products. The researchers also wanted to gain a better understanding of how the estimated parameters from the model relate to the bridging of animal models to human responses. We used female Institute of Cancer Research mice and Sprague-Dawley (SD) rats to measure CMAP and DAS levels over 32weeks after administering BoNT/A. We developed a muscle-contraction inhibition model using a virtual pharmacokinetic (PK) compartment combined with an indirect response model and performed model diagnostics using goodness-of-fit analysis, visual predictive checks (VPC), and bootstrap analysis. The CMAP and DAS profiles were dose-dependent, with recovery times varying depending on the administered dose. The final K-PD model effectively characterized the data and provided insights into species-specific differences in the PK and PD parameters. Overall, this study demonstrated the utility of PK-PD modeling in understanding the effects of BoNT/A and provides a foundation for future research on other BoNT/A products.

Rare and novel complications of botulinum neurotoxin type A and dermal filler injections

Botulinum neurotoxin type A (BoNTA) and filler injection procedures usually provide predicted outcomes with a low incidence of complications. Most of the complications after these procedures have been extensively discussed. In this study, we report on these injectables’ less well-known, recently reported, and novel complications and attempt to clarify the underlying mechanisms. Counterfeit or mishandled BoNTA has been associated with botulism. BoNTA has been linked to uncommon complications, including morphea-like lesions, nontuberculous mycobacterial infections, vascular occlusion, and pseudoaneurysm of the superficial temporal artery. Unusual complications from filler injection include nonscarring alopecia, intraoral necrosis, nontuberculous mycobacterial infections, xanthelasma-like reactions, intracranial perforation, and pneumosinus dilatans. Post-BoNTA injection nodules and filler infection from bone destruction due to cocaine use are new complications. These complications pose a challenge for diagnosis and treatment. This publication aims to assist in promptly identifying and managing these rare and novel complications when necessary.

Comprehensive Observational and Longitudinal study on the Outbreak of Stroke-related Spasticity focusing on the Early Onset management with Botulinum NeuroToxin (COLOSSEO-BoNT): protocol for a real-world prospective observational study on upper limb spasticity

IntroductionPoststroke spasticity (PSS) affects up to 40% of patients who had a stroke. Botulinum neurotoxin type A (BoNT-A) has been shown to improve spasticity, but the optimal timing of its...

Assessing muscle architecture with ultrasound: implications for spasticity.

Botulinum Neurotoxin Type A (BoNT-A) injections using Ultrasound (US) guidance have led to research evaluating changes in muscle architecture. Controversy remains as to what constitutes increased Echo-Intensity (EI) in spastic muscles and whether this may affect outcomes. We aim to provide a narrative review of US muscle architecture changes following Central Nervous System (CNS) lesions and explore their relationship to spasticity. Medline, CINAHL, and Embase databases were searched with keywords: ultrasonography, hypertonia, spasticity, fibrosis, and Heckmatt. Three physicians reviewed the results of the search to select relevant papers. Reviews identified in the search were used as a resource to identify additional studies. A total of 68 papers were included. Four themes were identified, including histopathological changes in spastic muscle, effects of BoNT-A on the muscle structure, available US modalities to assess the muscle, and utility of US assessment in clinical spasticity. Histopathological studies revealed atrophic and fibro-fatty changes after CNS lesions. Several papers described BoNT-A injections contributing to those modifications. These changes translated to increased EI. The exact significance of increased muscle EI remains unclear. The Modified Heckmatt Scale (MHS) is a validated tool for grading muscle EI in spasticity. The use of the US may be an important tool to assess muscle architecture changes in spasticity and improve spasticity management. Treatment algorithms may be developed based on the degree of EI. Further research is needed to determine the incidence and impact of these EI changes in spastic muscles.

Ready-to-use abobotulinumtoxinA solution versus powder botulinumtoxinA for treatment of glabellar lines: Investigators' and subjects' experience in a Phase IV study.

Botulinum neurotoxin type A (BoNT-A) is well-established for treatment of glabellar lines (GLs), and mostly formulated as powders requiring reconstitution for injection. The approved liquid formulation, ready-to-use (RTU) abobotulinumtoxinA was developed to ease injection procedures and prevent reconstitution errors. This multicenter, open-label, Phase IV study evaluated GL treatment experience using RTU abobotulinumtoxinA versus powder BoNT-A (onabotulinumtoxinA). Females with experience of BoNT-A facial treatment were randomized 2:1 to GL treatment with 50 U RTU abobotulinumtoxinA (N = 99) or 20 U powder BoNT-A (N = 51) and followed-up for 6 months or 1 month, respectively. Assessments included: time to prepare each product for injection (primary endpoint); investigators' experience with product preparation/reconstitution; investigators' and subjects' treatment experience; safety; and for the RTU product: aesthetic improvement of GLs; subject satisfaction. Compared with powder BoNT-A, RTU abobotulinumtoxinA required statistically significantly less preparation time (mean 0:33 vs. 1:34 min: s; p < 0.0001). Investigators preferred RTU abobotulinumtoxinA over powder BoNT-A (81% of treatment sessions) and found it allowed more time to communicate with subjects (97%). All investigators (100%) also found it easy-to-use, easy-to-learn, and that it fulfilled their expectations. Subjects found the RTU abobotulinumtoxinA treatment comfortable (91%), and through 6 months posttreatment, most reported satisfaction with their appearance (≥88%), looking natural (≥95%) and refreshed (≥80%). At Month 1, 99% of RTU-treated subjects had investigator-assessed improved aesthetic appearance in GLs, maintained in 76% at Month 6. No serious adverse events occurred. RTU abobotulinumtoxinA for GL treatment is well-tolerated, efficacious, shows high levels of subject satisfaction throughout 6 months, saves time, and is preferred by clinicians over powder BoNT-A. NCT05277337.

Isolation and characterization of Hc-targeting chimeric heavy chain antibodies neutralizing botulinum neurotoxin type B.

Botulinum neurotoxin (BoNT) produced by Clostridium botulinum is one of the most potent known toxins. Moreover, BoNT is classified as one of the most important biological warfare agents that threatens the biosafety of the world. Currently, the approved treatment for botulism in humans is the use of polyvalent horse serum antitoxins. However, they are greatly limited because of insufficient supply and adverse reactions. Thus, treatment of human botulism requires the development of effective toxin-neutralizing antibodies. Considering their advantages, neutralizing nanobodies will play an increasing role as BoNTs therapeutics. Herein, neutralizing nanobodies binding to the heavy chain (Hc) domain of BoNT/B (BHc) were screened from a phage display library. Then, BoNT/B-specific clones were identified and fused with the human Fc fragment (hFc) to form chimeric heavy chain antibodies. Finally, the affinity, specificity, and neutralizing activity of antibodies against BoNT/B in vivo were evaluated. The B5-hFc, B9-hFc and B12-hFc antibodies demonstrated high affinity for BHc in the nanomolar range. The three antibodies were proven to have potent neutralizing activity against BoNT/B in vivo. The results demonstrate that inhibiting toxin binding to the host receptor is an efficient strategy and the three antibodies could be used as candidates for the further development of drugs to prevent and treat botulism.

Rab8a/SNARE complex activation promotes vesicle anchoring and transport in spinal astrocytes to drive neuropathic pain.

Neuropathic pain (NPP) remains a clinically challenging condition, driven by the activation of spinal astrocytes and the complex release of inflammatory mediators. This study aimed to examine the roles of Rab8a and SNARE complex proteins in activated astrocytes to uncover the underlying mechanisms of NPP. The research was conducted using a rat model with chronic constriction injury (CCI) of the sciatic nerve and primary astrocytes treated with lipopolysaccharide. Enhanced expression of Rab8a was noted specifically in spinal dorsal horn astrocytes through immunofluorescence. Electron microscopy observations showed increased vesicular transport and exocytic activity in activated astrocytes, which was corroborated by elevated levels of inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α detected through quantitative PCR. Western blot analyses confirmed significant upregulation of Rab8a, VAMP2, and Syntaxin16 in these cells. Furthermore, the application of botulinum neurotoxin type A (BONT/A) reduced the levels of vesicle transport-associated proteins, inhibiting vesicular transport in activated astrocytes. These findings suggest that the Rab8a/SNARE pathway in astrocytes enhances vesicle transport and anchoring, increasing the secretion of bioactive molecules that may play a crucial role in the pathophysiology of NPP. Inhibiting this pathway with BONT/A offers a novel therapeutic target for managing NPP, highlighting its potential utility in clinical interventions.

Analgesic effect of Botulinum toxin in neuropathic pain is sodium channel independent

Botulinum neurotoxin type A BoNT/A is used off-label as a third line therapy for neuropathic pain. However, the mechanism of action remains unclear. In recent years, the role of voltage-gated sodium channels (Nav) in neuropathic pain became evident and it was suggested that block of sodium channels by BoNT/A would contribute to its analgesic effect.We assessed sodium channel function in the presence of BoNT/A in heterologously expressed Nav1.7, Nav1.3, and the neuronal cell line ND7/23 by high throughput automated and manual patch-clamp. We used both the full protein and the isolated catalytic light chain LC/A for acute or long-term extracellular or intracellular exposure. To assess the toxin's effect in a human cellular system, we differentiated induced pluripotent stem cells (iPSC) into sensory neurons from a healthy control and a patient suffering from a hereditary neuropathic pain syndrome (inherited erythromelalgia) carrying the Nav1.7/p.Q875E-mutation and carried out multielectrode-array measurements.Both BoNT/A and the isolated catalytic light chain LC/A showed limited effects in heterologous expression systems and the neuronal cell line ND7/23. Spontaneous activity in iPSC derived sensory neurons remained unaltered upon BoNT/A exposure both in neurons from the healthy control and the mutation carrying patient.BoNT/A may not specifically be beneficial in pain syndromes linked to sodium channel variants. The favorable effects of BoNT/A in neuropathic pain are likely based on mechanisms other than sodium channel blockage and new approaches to understand BoNT/A's therapeutic effects are necessary.