Botulinum toxin: Clinical use

Oromandibular dystonia and hormonal factors: twelve years follow-up of a case report

Oromandibular dystonia (OMD) is a focal neurological movement disorder characterized by involuntary sustained and often painful muscle contraction, usually producing repetitive movements or abnormal positions of the mouth, jaw and/or tongue. We report on a 30-year-old woman affected with OMD with a 12-year follow-up. Focal dystonia involved an involuntary activity of the lateral pterygoid muscles causing forceful jaw displacement in the maximal protrusive position. These episodes initially occurred during jaw function and increased up to an open-lock with bilateral pre-auricular pain. Dystonic spasms were absent during sleep and were reduced temporarily by sensory tricks. Treatment with botulinum toxin type A (BTX) was performed during three different sessions over a 1-year period. Electromyographic-guided BTX injections into the lateral pterygoid muscles were given with cannula electrodes. Botox reduced the involuntary activity of the muscles. Recurrence and exacerbation of dystonic symptoms occurred during the two pregnancies and completely disappeared immediately after both deliveries with prolonged symptom-free periods. During the last 8 years, the patient had a slight relapse of symptoms during flu attacks, periods of stress and during menses. The temporal pattern of these symptoms indicates a possible relationship between OMD and hormonal factors.

Central origin of the antinociceptive action of botulinum toxin type A

Here we provide behavioural evidence for an axonal transport and the central origin of the antinociceptive effect of botulinum toxin type A (BTX-A). In rats we investigated the effectiveness of BTX-A on "mirror pain" induced by unilateral repeated intramuscular acidic saline injections (pH 4.0). Since experimental evidence suggest that bilateral pain induced by acidic saline is of central origin, peripheral application of BTX-A should have no effect on this type of pain. However, here we demonstrated that the unilateral subcutaneous BTX-A (5U/kg) application diminished pain on the ipsilateral, and on the contralateral side too. When injected into the proximal part of a distally cut sciatic nerve, BTX-A still reduced pain on the contralateral side. Colchicine, an axonal transport blocker, when injected into the ipsilateral sciatic nerve, prevented the effect of the peripheral BTX-A injection on both sides. Additionally, when BTX-A (1U/kg) was applied intrathecally in the lumbar cerebrospinal fluid, the bilateral hyperalgesia was also reduced. The results demonstrate the necessity of retrograde axonal transport and involvement of the central nervous system for the antinociceptive activity of BTX-A.

The Rac GTPase-activating bacterial protein toxin CNF1 induces analgesia up-regulating mu-opioid receptors

Cytotoxic Necrotizing Factor 1 (CNF1) is a protein toxin from Escherichia coli that constitutively activates the Rho, Rac and Cdc42 GTPases. These regulatory proteins oscillate between a cytosolic GDP-bound inactive form and a membrane-linked GTP-bound active form, orchestrating the actin cytoskeleton assembly and dynamics. We herein describe, for the first time, the ability of CNF1 to potently counteract the formalin-induced inflammatory pain in mice. The analgesic response due to CNF1 requires both the sustained activation of the Rac GTPase, with consequent cerebral actin cytoskeleton remodeling, and the up-regulation of the mu-opioid receptors (MORs), the most important receptors controlling pain perception. The crucial role of Rac is proved by the lack of analgesic activity in mice challenged with a recombinant CNF1, in which the enzymatic activity was abolished by substituting serine with cysteine at position 866. The importance of MORs is proved by the inability of CNF1 to induce any analgesic effect in MORs knockout mice and by the ability of naloxone to antagonize the analgesic effects. Furthermore, it is worth noting that the analgesic effect in mice occurs after both peripheral and central administration of CNF1. Hence, taken altogether, our findings provide new insights into the comprehension of intracellular mechanisms involved in pain modulation, and indicate this bacterial protein toxin as a novel tool in the field of pain control. Conceivably, this might pave the way for new therapeutic strategies.

The strange case of the botulinum neurotoxin: using chemistry and biology to modulate the most deadly poison

In the classic novella "The Strange Case of Dr. Jekyll and Mr. Hyde", Robert Louis Stevenson paints a stark picture of the duality of good and evil within a single man. Botulinum neurotoxin (BoNT), the most potent known toxin, possesses an analogous dichotomous nature: It shows a pronounced morbidity and mortality, but it is used with great effect in much lower doses in a wide range of clinical scenarios. Recently, tremendous strides have been made in the basic understanding of the structure and function of BoNT, which have translated into widespread efforts towards the discovery of biomacromolecules and small molecules that specifically modulate BoNT activity. Particular emphasis has been placed on the identification of inhibitors that can counteract BoNT exposure in the event of a bioterrorist attack. This Review summarizes the current advances in the development of therapeutics, including vaccines, peptides, and small-molecule inhibitors, for the prevention and treatment of botulism.

Biological activity of two botulinum toxin type A complexes (Dysport and Botox) in volunteers: a double-blind, randomized, dose-ranging study

Despite extensive clinical experience and published data regarding botulinum toxin, questions remain about the clinical substitution of one botulinum toxin formulation for another. In the case of Dysport and Botox, dose-equivalence ratios ranging from 1:1 to 6:1 (Dysport:Botox) have been advocated. This dose-ranging, electroneurographic study investigated the dose equivalence, diffusion characteristics (spread) and safety of these two type-A toxins in 79 volunteers. Dysport and Botox caused significant and similar reductions in compound muscle action potential (CMAP) amplitude in the target muscle (extensor digitorum brevis, EDB) 2 weeks after injection, with effects persisting to the 12-week timepoint. For both products, the reduction in amplitude was increased with increasing doses and with increasing concentration. The effects of toxin on neighbouring muscles were much smaller and of a shorter duration than those on the target muscle, implying a modest spread of toxin. Unlike the target muscle, the effects were greater with the higher volume, suggesting this volume led to greater diffusion from the EDB. No adverse events were reported. Statistical modelling with CMAP amplitude data from the target muscle gave a bioequivalence of 1.57 units of Dysport:1 unit of Botox (95 % CI: 0.77-3.20 units). The data indicate that a dose-equivalence ratio of 3:1 was within the statistical error limits, but ratios over 3:1 are too high.

Lack of anti-inflammatory effect of botulinum toxin type A in experimental models of inflammation

Botulinum toxin type A (BTX-A) has a long-lasting antinociceptive activity and less clear effect on inflammation. It was proposed that these two effects share the same mechanism--the inhibition of neurotransmitter exocytosis from peripheral nerve endings. However, till now possible anti-inflammatory action of BTX-A did not evoke much attention. In the present paper, we investigate possible anti-inflammatory action of the toxin in carrageenan and capsaicin models of inflammation in rats. BTX-A (5 and 10 U/kg) was injected into the plantar surface of the rat right hind-paw pad 5 days before the injection of the carrageenan (1%) or capsaicin (0.1%) at the same site. Carrageenan-induced paw oedema and capsaicin-induced protein extravasation were measured. Control, inflamed and BTX-A pretreated inflamed paws were photographed and histopathological analysis (haematoxylin & eosin) was performed. Pretreatment with BTX-A had no effect on the size of carrageenan-induced paw oedema, measured as paw volume and weight or capsaicin-induced plasma extravasations, measured by Evans blue as a marker of protein leakage. Neither macroscopic nor microscopic analysis showed a significant difference between BTX-A pretreated and control inflamed tissue. Results show dissociation between the effect of BTX-A on pain and inflammation thus questioning the validity of the suggested assumption about the common peripheral mechanism of action.

The Intercostal NMJ Assay: a new alternative to the conventional LD50 assay for the determination of the therapeutic potency of botulinum toxin preparations

Therapeutic botulinum neurotoxin type A preparations have found an increasing number of clinical uses for a large variety of neuromuscular disorders and dermatological conditions. The accurate determination of potency in the clinical application of botulinum toxins is critical to ensuring clinical efficacy and safety, and is currently achieved by using a lethal dose (LD50) assay in mice. Ethical concerns and operational constraints associated with this assay have prompted the development of alternative assay systems that could potentially lead to its replacement. As one such alternative, we describe the development and evaluation of a novel ex vivo assay (the Intercostal Neuromuscular Junction [NMJ] Assay), which uses substantially fewer animals and addresses ethical concerns associated with the LD50 assay. The assay records the decay of force from electrically-stimulated muscle tissue sections in response to the toxin, and thus combines the important mechanisms of receptor binding, translocation, and the enzymatic action of the toxin molecule. Toxin application leads to a time-related and dose-related reduction in contractile force. A regression model describing the relationship between the applied dose and force decay was determined statistically, and was successfully tested as able to correctly predict the potency of an unknown sample. The tissue sections used were found to be highly reproducible, as determined through the innervation pattern and the localisation of NMJs in situ. Furthermore, the efficacy of the assay protocol to successfully deliver the test sample to the cellular target sites, was critically assessed by using molecular tracer molecules.

Successful treatment of tardive lingual dystonia with botulinum toxin: case report and review of the literature

Tardive dyskinesia (TD) is a dreaded side effect of antipsychotic medication. Recommended treatments for TD may provide reliable improvement but can be, in turn, associated with additional adverse reactions. Recently, several reports have suggested that botulinum toxin A (BTX-A) injection in affected muscles may significantly improve TD. Here, we report a case of severe tongue protrusion dystonia secondary to an antipsychotic medication in a young man. Several approaches including clozapine, amisulpride, aripiprazole, ziprasidone, tiapride and clonazepam failed to improve the symptoms. Injection of 50 U of BTX-A (Dysport, Ipsen, Ettlingen, Germany) into each genioglossal muscle dramatically improved tongue protrusion within few days with a sustained effect. If reasonable precautions are taken, the application seems to be well tolerated with only minor side effects. A review of the literature that is part of this article adverts BTX-A injection as a potential beneficial approach of various kinds of TD.

The use of botulinum toxin in head and face medicine: an interdisciplinary field

Background

In this review article different interdisciplinary relevant applications of botulinum toxin type A (BTA) in the head and face region are demonstrated.

Patients with head and face disorders of different etiology often suffer from disorders concerning their musculature (example: synkinesis in mimic muscles) or gland-secretion.

This leads to many problems and reduces their quality of life. The application of BTA can improve movement disorders like blepharospasm, hemifacial spasm, synkinesis following defective healing of the facial nerve, palatal tremor, severe bruxism, oromandibular dystonias hypertrophy of the masseter muscle and disorders of the autonomous nerve system like hypersalivation, hyperlacrimation, pathological sweating and intrinsic rhinitis.

Conclusion

The application of botulinum toxin type A is a helpful and minimally invasive treatment option to improve the quality of life in patients with head and face disorders of different quality and etiology. Side effects are rare.

Investigating novel therapeutic targets and molecular mechanisms to treat botulinum neurotoxin A intoxication

Botulinum neurotoxin (BoNT) has recently catapulted into the public consciousness in two seemingly disparate roles: potential use as a biological weapon and treatment of neuromuscular disorders. This bacterially produced protein is the most potent toxin known to humans, with a lethal dose estimated at approximately 1 ng/kg of body weight. BoNT intoxication occurs via a multistep process that includes recognition of peripheral neuronal cell membrane receptors, endocytosis and translocation of the light chain metalloprotease into the cytosol, and catalytic cleavage of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins critical for vesicle fusion and neurotransmitter release. Each of these distinct steps has been studied at the molecular level and is a valid target for the development of pharmacological interventions to prevent the considerable mortality associated with botulism. Alternatively, clinical uses of BoNT continue to expand at an ever-increasing rate; however, further optimization of BoNT therapy is critical to maximize efficacy.

Presynaptic neurotoxins with enzymatic activities

Toxins that alter neurotransmitter release from nerve terminals are of considerable scientific and clinical importance. Many advances were recently made in the understanding of their molecular mechanisms of action and use in human therapy. Here, we focus on presynaptic neurotoxins, which are very potent inhibitors of the neurotransmitter release because they are endowed with specific enzymatic activities: (1) clostridial neurotoxins with a metallo-proteolytic activity and (2) snake presynaptic neurotoxins with a phospholipase A2 activity.

Treatment of sialorrhoea in patients with Parkinson's disease: best current evidence

(1) Sialorrhoea is a common condition in patients with Parkinson's disease that has a negative impact on patient quality of life. (2) Traditionally, muscarinic antagonists have been the pharmacological agents of choice for the treatment of sialorrhoea; however, these agents are frequently associated with adverse events in patients with Parkinsonian disorders. (3) Recent studies suggest that botulinum toxin injection is currently the most effective treatment option for Parkinsonian-related sialorrhoea.

Efficacy and safety of botulinum neurotoxin type A free of complexing proteins (NT 201) in cervical dystonia and blepharospasm

Botulinum neurotoxin type A (BTX-A) weakens voluntary muscle power and is an effective therapy for focal dystonia, including cervical dystonia (CD) and benign essential blepharospasm (BEB). Antibody formation against BTX-A may lead to failure of treatment. NT 201 (XEOMIN®) is a formulation of pure BTX-A that is free of complexing proteins and therefore may have a reduced immunogenic potential in comparison with other BTX-A preparations. In clinical trials, NT 201 was found to be effective, well-tolerated and at least noninferior to a BTX-A preparation containing complexing proteins in the treatment of CD and BEB. There were no differences between the two therapies in terms of onset of action, duration and waning of effect. Future research is aimed at evaluating the benefits of NT 201.

[Botulinum toxin treatment in the head and neck region: current aspects, developments, and problems]

Some interesting developments, aspects, and problems concerning botulinum toxin treatment of disorders of the head and neck region have recently been reported. These new approaches are discussed in this review. They include applications into mimic muscles (prevention of scar formation, treatment of depressions), into laryngeal muscles, and into the upper esophagus. In addition, treatment of different forms of headache and tinnitus as well as applications in the autonomic nervous system are addressed. Some of these options will shortly be put into clinical use, while others have to be checked further in clinical studies.

Botulinum toxin in the treatment of blepharospasm and hemifacial spasm

Blepharospasm and hemifacial spasm are the two most common craniofacial movement disorders. Blepharospasm is a syndrome characterized by excessive or continuous eye closure related to overactivity of the orbicularis oculi and adjacent muscles bilaterally. Hemifacial spasm is a peripherally-induced movement disorder typically caused by vascular compression of cranial nerve VII (CN VII) leading to involuntary unilateral contractions of muscles used in facial expression. Treatment options for both conditions include medications, botulinum toxin, and various surgical interventions. This article summarizes the existing medical literature which indicates that botulinum toxin is the treatment of choice for blepharospasm and hemifacial spasm.

Botulinum toxin in the management of dystonia

Dystonia is a neurologic disorder that can occur at any age and often results in significant disability. The therapeutic application of botulinum toxin has revolutionized the treatment of this disorder, particularly for the adult-onset focal forms such as cervical dystonia and blepharospasm. The two available commercial preparations, botulinum toxin types A and B, have been shown to be equally efficacious in cervical dystonia and are both reasonable first-line choices for treating other forms of focal dystonia. Preliminary studies have suggested that differences in tolerability and immunogenicity may exist between the two preparations, but this has not been adequately evaluated. Because of high cost, complicated administration, potentially serious side effects, and the risk of developing immunoresistance, this treatment should be administered only by a physician with sufficient background in the diagnosis and treatment of dystonia, to ensure optimal outcomes.

Primary cultures of embryonic chicken neurons for sensitive cell-based assay of botulinum neurotoxin: implications for therapeutic discovery

Botulinum toxin is an exceedingly potent inhibitor of neurotransmission across the neuromuscular junction, causing flaccid paralysis and death. The potential for misuse of this deadly poison as a bioweapon has added a greater urgency to the search for effective therapeutics. The development of sensitive and efficient cell-based assays for the evaluation of toxin antagonists is crucial to the rapid and successful identification of therapeutic compounds. The authors evaluated the sensitivity of primary cultures from 4 distinct regions of the embryonic chick nervous system to botulinum neurotoxin A (BoNT/A) cleavage of synaptosomal-associated protein of 25 kD (SNAP-25). Although differences in sensitivity were apparent, SNAP-25 cleavage was detectable in neuronal cells from each of the 4 regions within 3 h at BoNT/A concentrations of 1 nM or lower. Co-incubation of chick neurons with BoNT/A and toxin-neutralizing antibodies inhibited SNAP-25 cleavage, demonstrating the utility of these cultures for the assay of BoNT/A antagonists.

An in vitro and in vivo disconnect uncovered through high-throughput identification of botulinum neurotoxin A antagonists

Among the agents classified as "Category A" by the U.S. Centers for Disease Control and Prevention, botulinum neurotoxin (BoNT) is the most toxic protein known, with microgram quantities of the protein causing severe morbidity and mortality by oral or i.v. routes. Given that this toxin easily could be used in a potential bioterrorist attack, countermeasures urgently are needed to counteract the pathophysiology of BoNT. At a molecular level, BoNT exerts its paralytic effects through intracellular cleavage of vesicle docking proteins and subsequent organism-wide autonomic dysfunction. In an effort to identify small molecules that would disrupt the interaction between the light-chain metalloprotease of BoNT serotype A and its cognate substrate, a multifaceted screening effort was undertaken. Through the combination of in vitro screening against an optimized variant of the light chain involving kinetic analysis, cellular protection assays, and in vivo mouse toxicity assays, molecules that prevent BoNT/A-induced intracellular substrate cleavage and extend the time to death of animals challenged with lethal toxin doses were identified. Significantly, the two most efficacious compounds in vivo showed less effective activity in cellular assays intended to mimic BoNT exposure; indeed, one of these compounds was cytotoxic at concentrations three orders of magnitude below its effective dose in animals. These two lead compounds have surprisingly simple molecular structures and are readily amenable to optimization efforts for improvements in their biological activity. The findings validate the use of high-throughput screening protocols to define previously unrecognized chemical scaffolds for the development of therapeutic agents to treat BoNT exposure.