Pharmacology of botulinum neurotoxin type A

The efficacies and potencies of Dysport and Botox, botulinum neurotoxin type A complexes approved for therapy, were investigated under various conditions. Conditions for maximal expression of biological activities of both commercial products were explored in vitro in the phrenic nerve-hemidiaphragm preparation whilst conditions for optimal distribution of Dysport were tested in vivo in a double blind trial involving volunteers, using the foot Muscles extensor digitorum brevis. Whilst Dysport and Botox expressed the same potency in vitro when albumin was added, their potencies markedly departed from each other when the products were reconstituted as recommended by the manufacturer. The biological availability of Dysport could be enhanced in vivo by (1) lowering its concentration, (2) supplementing with albumin and (3) increasing the injection volume. Thus, Dysport can be recovered more efficiently by deviating from the manufacturer's recommendations allowing a more economical use of Dysport.     

Sialorrhea, hyperhidrosis and botulinum toxin]

OBJECTIVE: The first clinical studies indicate that Botox provides effective treatment for hyperhidrosis and sialorrhea. The aim of this work is to sum up current evaluation of this use. METHOD: A systematic literature search was conducted on the Pub Med database, along with on chapters in other publications. The most interesting articles in relation to our own personal experience were chosen. RESULTS: Despite recent use of BT to treat focal hyperhidrosis, there have been numerous publications since 1997. However, the injected areas have not been listed so frequently. Axillary hyperhidrosis has been studied most; it is also in this case and in the case of gustatory sweating that the best results have been obtained. Publications about palmar and especially plantar hyperhidrosis are much rarer, almost anecdotic. It has been demonstrated to a lesser extent that BT injections are effective in these cases. Literature about sialorrhea is just beginning. However, the reduction of the production of saliva following intra parenchymatic injection of toxin into the parotid and submandibular glands, thus rarifying drooling, has been demonstrated.For each of the pathological indications, both the injection techniques and the optimal doses remain to be determined. DISCUSSION: Because BT blocks all cholinergic transmission, including the autonomous nervous system, it was plausible to expect a reduction in sweating and salivation on local injection of the product. In fact, the first publications indicated such efficiency without serious side effects.For hyperhidrosis, there has developed a consensus for making intracutaneous injections only. Of the injections in axillary areas, the palms of the hands, the plantar regions, the face or other cutaneous areas, palmoplantar hyperhidrosis is the least accessible, in any case causes the most technical problems, because of difficulty in pain management. For sialorrhea and the drooling that accompanies certain chronical neurological diseases, BT seems to have very promising effects. However, it has not been precisely determined whether to inject the parotid gland, the submandibular gland, or both. Necessary and sufficient means of targeting are still imprecise. It also remains to be determined the number of sites per gland and the doses to be injected.     

Skin, wrinkles and botulinum toxin]

OBJECTIVE: To present an up-to-date analysis about the use of botulinum toxin for treating facial lines and wrinkles.Method. - A systematic search of the literature was conducted to select the most recent or relevant publications on this topic, through Medline. RESULTS: Out of the 583 articles retrieved, 90 were finally selected for the study. DISCUSSION: Validity of using botulinum toxin for cosmetic use is demonstrated, together with contra-indications and different methods to objectivate the results. The different available types of toxin are presented and compared. Modalities of preparation, conservation, and waste disposal are detailed. Anatomical bases of muscular facial balance are reviewed, with techniques of injection presented for each site, and also with adjunctive procedures. Complications and side effects are described and analysed. Most complications can be prevented through: perfect knowledge of local anatomy;use of small volumes;orientation of the needle bevel towards the muscle body, injection within the muscle body if thick, more superficial if thin;application of ice on the skin pre- and post-injecting. Adding epinephrin or diluting with xyloca?ne and epinephrin is not commonly used. CONCLUSION: Botulinum toxin has found its way as a major component of the therapeutic armamentarium. Its efficacy for facial rejuvenation has made it extremely popular, but its use does follow strict rules, and should be restricted to soundly trained practitioners.     

Effectiveness of different doses of botulinum neurotoxin in lateral epicondylalgia: A network meta-analysis

BackgroundPrevious studies have investigated the role of botulinum neurotoxin (BoNT) in lateral epicondylalgia, with controversial results. We hypothesized that BoNT would be effective and safe for the treatment of lateral epicondylalgia.ObjectiveTo investigate the effectiveness and safety of different doses of BoNT in participants with lateral epicondylalgia.MethodsPubMed, Embase, and Cochrane Library were searched up to August 27, 2022, for randomized controlled trials (RCTs) of BoNT treatment for epicondylalgia. The Cochrane risk of bias tool was used for quality assessment. A network meta-analysis and a trial sequential analysis (TSA) were conducted on pain, grip strength and adverse events. Meta-regression was applied for high heterogeneity comparisons.ResultsWe included 8 RCTs consisting of 448 participants. Four studies scored low risk of bias in all categories, whereas the other 4 studies had unclear risk only in the selection bias category. The network meta-analysis and TSA revealed that corticosteroid (standardized mean difference [SMD]: ?1.32, 95% CI: ?2.13; ?0.50), high-dose BoNT (SMD ?1.32, ?2.04; ?0.61), and low-dose BoNT (SMD –0.52, ?0.93; ?0.10), relieved pain significantly better than placebo for up to 7 to 10 weeks. High-dose BoNT demonstrated a significantly greater reduction in pain than low-dose BoNT for up to 7 to 10 weeks (SMD ?0.81, –1.39; ?0.22). Finally, after low-dose BoNT, younger participants (p = 0.023) and women (p = 0.012) showed more pain decrease than older individuals and men at 2 to 6 weeks. As for grip strength and adverse events, only grip strength after low-dose BoNT versus placebo (SMD ?0.49, ?0.88; ?0.10) and corticosteroid (SMD ?1.36, ?2.15; ?0.57) at 2 to 6 weeks reached significance after threshold adjustment in TSA.ConclusionsOur meta-analysis confirmed the effectiveness of low-dose BoNT in the reduction of pain for lateral epicondylalgia. Further conclusions cannot be drawn due to insufficient available data.     

Comparison of botulinum neurotoxin preparations for the treatment of cervical dystonia

BACKGROUND: Comparative studies of botulinum neurotoxin preparations to date have generally examined 2 preparations at prespecified dose ratios in relatively homogeneous groups of patients under controlled study conditions. It is unclear whether the differences in adverse-event rates that have been noted under these controlled conditions can be generalized to the broader population of cervical dystonia patients, who are treated with a wider range of doses in a variety of settings. OBJECTIVE: We conducted a systematic review and analysis of the published literature to compare rates of dysphagia and dry mouth in studies of botulinum neurotoxin products. METHODS: We searched the MEDLINE, EMBASE, Biosis, SciSearch, JICST (Japan Science and Technology Center), and Pascal databases from 1985 through 2006 using the terms cervical dystonia, spasmodic torticollis, and botulinum toxin for original English-language studies of Botox, Dysport, or Myobloc in the treatment of cervical dystonia (or spasmodic torticollis) that documented adverse events by treatment or patient. Studies that involved patients with various types of dystonias or movement disorders were included as long as adverse events were reported separately for those with cervical dystonia. Rates of dysphagia with the original preparation of Botox were considered separately from those with the current preparation of Botox. RESULTS: Seventy published articles were included in the analysis (30 Botox, 24 Dysport, 3 Botox + Dysport, 11 Myobloc, 2 Botox + Myobloc). Mean total doses per treatment ranged from 60 to 374 U for Botox, 125 to 1200 U for Dysport, and 579 to 19,853 U for Myobloc. Botox was associated with a significantly lower rate of dysphagia than Dysport, with mean dysphagia rates of 10.5% for original Botox, 8.9% for current Botox, and 26.8% for Dysport (both, P < 0.05). Myobloc was associated with dry mouth (3.2%-90.0%) in 9 of 13 studies, but this adverse event was not reported in a sufficient number of studies of botulinum toxin type A preparations (Botox, n = 2; Dysport, n = 6) to permit statistical comparison. In the weighted analysis, the duration of effect differed between botulinum neurotoxin products (current Botox > Myobloc > original Botox > Dysport; all, P < 0.001), but only 43 (61.4%) of the 70 studies reported duration, and the definitions varied. CONCLUSION: The results of this analysis indicate differences in adverse-event rates between botulinum neurotoxin preparations, suggesting that use of these products should be based on their individual dosing, efficacy, and safety profiles.     

Bruxism, temporo-mandibular dysfunction and botulinum toxin]

Tooth grinding and tooth clenching are unvoluntary mainly nocturnal habits that result in an hypertrophy of masseter and temporalis muscles with an unbalance between opening and closing muscles of the jaw and lead to an alteration of mandibular condyles movements and to hyper pressure in the temporo-mandibular joints (TMJ) which can generate severe pain. Intra muscular injections of botulinum toxin permit to restablish the balance between closing and opening muscles, to relieve pain, to treat masseteric hypertrophy with improvement of face outline and to recover a normal cinetic of temporo-mandibular joints. Moreover, botulinum toxin injections permit to quit habits of tooth grinding and clenching and one single session of injections is curative for 2/3 of the patients. There are no side effects apart from slight diffusion to superficial muscles of the face resulting in a "fixed" smile for about 6 to 8 weeks. So injections of botulinum toxin in masseter and temporalis muscles are an efficient treatment of bruxism and TMJ dysfunction, cheap with no lasting side effect.     

Mode of action and molecular target of ECH, a specific inhibitor of death receptor-dependent apoptosis

ECH (epoxycyclohexenone) specifically blocks death receptor-mediated apoptosis induced by anti-Fas antibody, Fas ligand, or TNF-alpha, whereas it has no effect on death receptor independent apoptosis induced by staurosporine, MG-132, C2-ceramide, or UV irradiation. ECH blocks the activation of pro-caspase-8 in the death-inducing signaling complex (DISC), even though recruitment of FADD and pro-caspase-8 is not affected. In Fas ligand treated cells, ECH is only able to inhibit the activation of pro-caspase-8 and it has no effect on the already-activated caspase-8. ECH has a relatively higher affinity to pro-caspase-8, although it directly binds both pro- and active-form of caspase-8. In conclusion, ECH targets pro-caspase-8 and blocks the self-activation of pro-caspase-8 in the DISC, and thus selectively inhibits death receptor-mediated apoptosis. Moreover novel non-peptide inhibitors, RKTS-33 & RKTS-34 that are chemically synthesized derivatives of ECH have been developed.     

Immunomagnetic beads assay for the detection of botulinum neurotoxin types C and D

An immunomagnetic beads assay for the simultaneous quantification of botulinum neurotoxin types C and D was developed. Specific monoclonal antibodies against the heavy chain of the toxin and affinity-purified biotinylated polyclonal antibodies (pAbs) were used. The antibodies were preincubated with the sample. The complex being formed was then captured by magnetic beads coated with antimouse IgG. Streptavidin-poly-horseradish peroxidase, a signal amplifier, bound to the biotinylated pAb. A maximum sensitivity of approximately 0.3 minimal lethal doses for mice per milliliter was achieved with culture supernatants of both toxin types.     

Brugada syndrome: clinical, genetic, molecular, cellular and ionic aspects

Brugada syndrome, first described as a new clinical entity by Pedro and Josep Brugada in 1992, has attracted great interest because of its high prevalence in many regions of the world and its association with high risk for sudden death. The syndrome has captured the attention of the cardiac electrophysiology community because it serves as a paradigm for our understanding of the role of spatial dispersion of repolarization in the development of cardiac arrhythmias. The past decade has witnessed an exponential rise in the number of reported cases and a striking proliferation of papers serving to define the clinical, genetic, cellular, ionic and molecular aspects of this disease. This brief review summarizes the key clinical and experimental milestones that have brought us to our current understanding and approach to therapy of the Brugada syndrome.     

Brugada syndrome: clinical,genetic, molecular,cellular and ionic aspects

Brugada syndrome, first described as a new clinical entity by Pedro and Josep Brugada in 1992, has attracted great interest because of its high prevalence in many regions of the world and its association with high risk for sudden death. The syndrome has captured the attention of the cardiac electrophysiology community because it serves as a paradigm for our understanding of the role of spatial dispersion of repolarization in the development of cardiac arrhythmias. The past decade has witnessed an exponential rise in the number of reported cases and a striking proliferation of papers serving to define the clinical, genetic, cellular, ionic and molecular aspects of this disease. This brief review summarizes the key clinical and experimental milestones that have brought us to our current understanding and approach to therapy of the Brugada syndrome.     

Botulinum neurotoxin type E: studies on mechanism of action and on structure-activity relationships

Single chain type E botulinum neurotoxin was isolated from culture fluids of Clostridium botulinum (strain Alaska E-43). The neurotoxin, which migrated as a single band in polyacrylamide gel electrophoresis with sodium dodecylsulfate, had a molecular weight of approximately 147,000. Single chain type E neurotoxin that was exposed to trypsin was converted to a dichain molecule. Pretreatment of the single chain molecule with 1,2-cyclohexanedione, a reagent that selectively modifies arginine residues, inhibited trypsin-induced generation of the dichain molecule. In dose-response experiments (10(-13) to 10(-9) M) on the isolated neuromuscular junction (phrenic nerve-hemidiaphragm preparation), the dichain neurotoxin was approximately two orders of magnitude more potent than the single chain neurotoxin. Neither specie of neurotoxin (1 pmol/mouse, in vivo; 1 X 10(-11) M, in vitro) was very effective in blocking autonomic transmission (vagus nerve-atrium preparation). The neuromuscular blocking action of the dichain molecule was divided into a sequence of three steps. There was an initial binding step that was relatively rapid, little influenced by temperature and which left the neurotoxin partially accessible to the neutralizing effects of antitoxin. There was a translocation step that was temperature dependent, antagonized by ammonium chloride and methylamine hydrochloride and which caused the neurotoxin to become inaccessible to the neutralizing effects of antitoxin. Finally, there was an intracellular lytic step, during which the toxin blocked excitation-secretion coupling.     

Mode of action of sulfasalazine in chronic inflammatory enterocolonic diseases]

We have investigated the mode of action of the sulphasalazine in ulcerative colitis and Crohn's ileitis. We point out: a) the activity of sulphasalazine and its derivative, 5-aminosalicylic acid in prostaglandin's metabolites pathway, by inhibition of lipoxygenase; b) a moderate activity on the cell-mediated immunity by weak inhibition of natural killer activity; c) the 5-amino salicylic acid is effective strongly like a radical scavenger.     

Use of monoclonal antibodies as probes for the structure and biological activity of botulinum neurotoxin

Experiments were done to help clarify the structure-function relationships that govern the interaction between botulinum neurotoxin and the cholinergic neuromuscular junction. Work was done with type E toxin in three different states: 1) unactivated (post-translational product before proteolytic processing), 2) activated (proteolytically modified product) and 3) denatured. Four different monoclonal antibodies were studied (E3, E14, E17 and E32), three of which were capable of diminishing the potency of the toxin. All four antibodies had approximately equivalent affinity for the unactivated and the activated forms of the toxin. Monoclonals E17 and E32 had little ability to interact with denatured toxin, suggesting they recognized conformational epitopes; monoclonals E3 and E14 retained partial ability to bind to denatured toxin, suggesting they recognized both conformational and linear determinants. When phrenic nerve-hemidiaphragm preparations were exposed to toxin under conditions that allowed binding but retarded internalization, the toxin remained accessible to antibodies. However, when tissues were stimulated in an effort to promote endocytosis, the toxin disappeared from accessibility to antibodies. The data indicate that various antigenic domains remain exposed after binding and suggest that certain parts of the toxin molecule undergo little or no conformational change during binding. The data further indicate that the molecular domains recognized by E14, E17 and E32 are internalized simultaneously.     

Detrusor-sphincter dyssynergia and botulinum toxin]

OBJECTIVE: Botulinum toxin (BT) injection into the external urethral sphincter is a promising therapy for neurogenic voiding disorders due to detrusor-sphincter dyssynergia (DSD). However the optimal treatment protocol remains unclear. METHOD: A PubMed reference search and manual bibliography review were performed, along with a search in the Annales de réadaptation et de médecine physique and in the reports of the International French-language Society of Urodynamics and the International Continence Society, which allowed us to select twelve pertinent articles with PubMed, two articles from the Annales and two conference reports. Our analysis gave special emphasis to assessment criteria, application, dosage and BT injection technique. RESULTS: Used for the first time in 1988 in spinal cord injury patients to reduce outflow obstruction due to DSD, BT injections have been shown to be a valuable alternative management of bladder dysfunction with DSD. They have been proposed in neurological patients unable to perform self-catheterisation, after drug failure and before surgery. Parameters for results assessment are mostly clinical (increased free interval between voiding, decreased post-void residual urine volumes), urodynamic (improvement in bladder emptying, increase in functional bladder capacity and decrease in urethral pressure) and electromyographic (denervation of striated urethral sphincter). The literature data regarding type of BT, dosage and protocol vary widely. Duration of action is from 2 to 12 months. Both transurethral and transperineal injections monitored by EMG are equally effective in improving detrusor-sphincter dyssynergia. CONCLUSION: With few side effects and satisfactory medium-term results, BT should be recommended as a component of DSD therapies. We propose a practical method for BT use.     

Digestive tract and botulinum toxin]

INTRODUCTION: the aim of this work was to check literature to assess botulinum toxin injection efficacy in gastrointestinal motor disorders with special emphasis on controlled clinical trials. METHODS: literature was carried out with the Medline data bank. RESULTS: seventy three articles in French and in English including a recent general review were retained. Comparative clinical trials only concerned achalasia and anal fissure. The other gastrointestinal motor disorders only gave rise to open non-controlled trials assessed on clinical end points. DISCUSSION: this review of literature helps to determine usefulness and safety of Botulinum toxin injection in the treatment of esophageal achalasia and anal fissure. The main limitation is its brief duration of action. Studies concerning the others spastic motor disorders are based on unknown physiopathology and controlled trials are required to assess its efficacy. CONCLUSION: botulinum toxin is increasingly used for gastrointestinal motor disorders with worthwhile results. Its efficacy has been yet established for only two disorders : it has a valuable palliative role in achalasia and may be curative for anal fissure.     

Multiple sclerosis and botulinum toxin]

INTRODUCTION: The aim of this work was to collect litterature datas to have an indication of botulinum toxin in multiple sclerosis disease. METHOD: The international literature relating the years 1982-2002 was carried out with the Medline data bank. The article presenting of the controlled studies were mainly retained. RESULTS: Thirty-seven articles were indexed, 6 were retained according to our criteria. The selected articles show mainly a use of botulinum toxin in the spasticity. The principal criteria of evaluation were the muscular tone, the spasms, the pain, the or passive amplitude of joint.Two articles report the effectiveness of toxin injection in acquired nystagmus and the paralysis of a vocal fold. DISCUSSION: This review shows that the principal indication of toxin in multiple sclerosis is spasticity with a good effectiveness of the treatment. However controlled-placebo studies among these patients are still very few. The side effects are rare but sometimes appearance of muscular weakness always making discuss the existence of a push. It is necessary to take account of these effects and their consequences before proposing the treatment. CONCLUSION: Botulinum toxin has an indication in the treatment of spasticity of patients with multiple sclerosis. However more studies are necessary with more sits of injection to fix the good indications.     

Anti-nociceptive effect of a conjugate of substance P and light chain of botulinum neurotoxin type A

Neuropathic pain is a debilitating condition resulting from damage to sensory transmission pathways in the peripheral and central nervous system. A potential new way of treating chronic neuropathic pain is to target specific pain-processing neurons based on their expression of particular receptor molecules. We hypothesized that a toxin–neuropeptide conjugate would alter pain by first being taken up by specific receptors for the neuropeptide expressed on the neuronal cells. Then, once inside the cell the toxin would inhibit the neurons’ activity without killing the neurons, thereby providing pain relief without lesioning the nervous system. In an effort to inactivate the nociceptive neurons in the trigeminal nucleus caudalis in mice, we targeted the NK1 receptor (NK1R) using substance P (SP). The catalytically active light chain of botulinum neurotoxin type A (LC/A) was conjugated with SP. Our results indicate that the conjugate BoNT/A-LC:SP is internalized in cultured NK1R-expressing neurons and also cleaves the target of botulinum toxin, a component-docking motif necessary for release of neurotransmitters called SNAP-25. The conjugate was next tested in a murine model of Taxol-induced neuropathic pain. An intracisternal injection of BoNT/A-LC:SP decreased thermal hyperalgesia as measured by the operant orofacial nociception assay. These findings indicate that conjugates of the light chain of botulinum toxin are extremely promising agents for use in suppressing neuronal activity for extended time periods, and that BoNT/A-LC:SP may be a useful agent for treating chronic pain.