Basic and clinical aspects of BOTOX

OnabotulinumtoxinA effects on trigeminal nociceptors

BACKGROUND

OnabotulinumtoxinA (onabotA) is approved globally for prevention of chronic migraine; however, the classical mechanism of action of onabotA in motor and autonomic neurons cannot fully explain the effectiveness of onabotulinumtoxinA in this sensory neurological disease. We sought to explore the direct effects of onabotulinumtoxinA on mouse trigeminal ganglion sensory neurons using an inflammatory soup-based model of sensitization.

METHODS

Primary cultured trigeminal ganglion neurons were pre-treated with inflammatory soup, then treated with onabotulinumtoxinA (2.75 pM). Treated neurons were used to examine transient receptor potential vanilloid subtype 1 and transient receptor potential ankyrin 1 cell-surface expression, calcium influx, and neuropeptide release.

RESULTS

We found that onabotulinumtoxinA cleaved synaptosomal-associated protein-25 kDa in cultured trigeminal ganglion neurons; synaptosomal-associated protein-25 kDa cleavage was enhanced by inflammatory soup pre-treatment, suggesting greater uptake of toxin under sensitized conditions. OnabotulinumtoxinA also prevented inflammatory soup-mediated increases in TRPV1 and TRPA1 cell-surface expression, without significantly altering TRPV1 or TRPA1 protein expression in unsensitized conditions. We observed similar inhibitory effects of onabotulinumtoxinA on TRP-mediated calcium influx and TRPV1- and TRPA1-mediated release of calcitonin gene-related peptide and prostaglandin 2 under sensitized, but not unsensitized control, conditions.

CONCLUSIONS

Our data deepen the understanding of the sensory mechanism of action of onabotulinumtoxinA and support the notion that, once endocytosed, the cytosolic light chain of onabotulinumtoxinA cleaves synaptosomal-associated protein-25 kDa to prevent soluble N-ethylmaleimide-sensitive factor attachment protein receptor-mediated processes more generally in motor, autonomic, and sensory neurons.

Botulinum Neurotoxin Type A Directly Affects Sebocytes and Modulates Oleic Acid-Induced Lipogenesis

Excess sebum (seborrhea) results in oily skin and is associated with large pore size and acne. Studies in healthy, seborrheic volunteers have reported that intradermal injection of commercial preparations of botulinum neurotoxin type A (BoNT/A) (onabotulinumtoxinA, abobotulinumtoxinA, and incobotulinumtoxinA) reduced sebum production, and thus, skin oiliness and pore size. The mechanism for these effects has not been fully elucidated; however, several theories involving direct or indirect effects of BoNT/A on neuronal and/or dermal cells (e.g., sebocytes) have been proposed. In the present study, we evaluated the direct effect of native research grade BoNT/A complex, a commercial preparation of BoNT/A (onabotA), and BoNT/A variants on sebocyte lipogenesis using an in vitro sebocyte cell model. We show that picomolar concentrations of BoNT/A (BoNT/A complex: half maximal effective concentration [EC₅₀] = 24 pM; BoNT/A 150 kDa: EC₅₀ = 34 pM) modulate sebocyte lipogenesis and reduce oleic acid-induced sebocyte differentiation, lipogenesis, and holocrine-like secretion. Comparative studies with the binding domain of BoNT/A, which lacks enzymatic activity, show that this effect is independent of the enzymatic activity of BoNT/A and likely occurs via sebocyte cell surface receptors (e.g., fibroblast growth factor receptors). Overall, these results shed light on the potential mechanism of action and rationale for use of BoNT/A for treatment of sebum-related conditions.

Characterization of clostridium botulinum neurotoxin serotype A (BoNT/A) and fibroblast growth factor receptor interactions using novel receptor dimerization assay

Clostridium botulinum neurotoxin serotype A (BoNT/A) is a potent neurotoxin that serves as an effective therapeutic for several neuromuscular disorders via induction of temporary muscular paralysis. Specific binding and internalization of BoNT/A into neuronal cells is mediated by its binding domain (H_C/A), which binds to gangliosides, including GT1b, and protein cell surface receptors, including SV2. Previously, recombinant H_C/A was also shown to bind to FGFR3. As FGFR dimerization is an indirect measure of ligand-receptor binding, an FCS & TIRF receptor dimerization assay was developed to measure rH_C/A-induced dimerization of fluorescently tagged FGFR subtypes (FGFR1-3) in cells. rH_C/A dimerized FGFR subtypes in the rank order FGFR3c (EC₅₀ ≈ 27 nM) > FGFR2b (EC₅₀ ≈ 70 nM) > FGFR1c (EC₅₀ ≈ 163 nM); rH_C/A dimerized FGFR3c with similar potency as the native FGFR3c ligand, FGF9 (EC₅₀ ≈ 18 nM). Mutating the ganglioside binding site in H_C/A, or removal of GT1b from the media, resulted in decreased dimerization. Interestingly, reduced dimerization was also observed with an SV2 mutant variant of H_C/A. Overall, the results suggest that the FCS & TIRF receptor dimerization assay can assess FGFR dimerization with known and novel ligands and support a model wherein H_C/A, either directly or indirectly, interacts with FGFRs and induces receptor dimerization.

Systemic Botulism Toxicity Caused by Pyloric Botox Injection to Treat Gastroparesis

Systemic botulism resulting from therapeutic Botox (OnabotulinumtoxinA) injection has been rarely reported, and never in the context of pylorus injection to treat gastroparesis. We report the case of a 27-year-old female with Emery-Dreifuss muscular dystrophy who developed severe systemic botulism toxicity following the intrapyloric injection of 100 units of Botox to treat gastroparesis. The patient eventually made a full recovery.

Antiviral lectins: Selective inhibitors of viral entry

Many natural lectins have been reported to have antiviral activity. As some of these have been put forward as potential development candidates for preventing or treating viral infections, we have set out in this review to survey the literature on antiviral lectins. The review groups lectins by structural class and class of source organism we also detail their carbohydrate specificity and their reported antiviral activities. The review concludes with a brief discussion of several of the pertinent hurdles that heterologous proteins must clear to be useful clinical candidates and cites examples where such studies have been reported for antiviral lectins. Though the clearest path currently being followed is the use of antiviral lectins as anti-HIV microbicides via topical mucosal administration, some investigators have also found systemic efficacy against acute infections following subcutaneous administration.

Efficacy of botulinum toxin type a for treating chronic low back pain

BACKGROUND

Low back pain is a major cause of disability and can result in substantial morbidity and high healthcare costs. Botulinum toxin has been used successfully to alleviate pain for a number of conditions caused by muscle contractions or spasms.

OBJECTIVES

The aim of this study was to investigate the efficacy of botulinum toxin type A (BoNT-A; Dysport®, Ipsen, UK) for treating chronic low back pain (CLBP).

PATIENTS AND METHODS

This was a single-blind, randomized clinical trial study. Fifty patients with CLBP received either BoNT-A (40 Ipsen units per injection) or saline in 5 sites in the paraspinal muscles (n = 25 per group). A visual analogue system (VAS) was used to measure pain levels at baseline and at 4 and 8 weeks post-injection. Disability was assessed using the Oswestry low back pain disability questionnaire at baseline and at 8 weeks post-injection.

RESULTS

After 4 weeks, 76% of patients in the BoNT-A group reported pain relief compared to 20% in the saline group (P < 0. 005). Additionally, greater pain relief was experienced by patients in the BoNT-A group at 8 weeks (64% vs. 12%; P < 0. 001). By week 8, significant functional improvement (a minimum two-grade improvement between baseline and post-treatment assessments) was demonstrated in a higher number of patients receiving BoNT-A than in the saline group (68% vs. 12% , respectively; P < 0. 005). Patients experienced only minor side effects.

CONCLUSIONS

BoNT-A improves CLBP with a low incidence of side effects and can be used as a therapeutic tool in the management of these patients.

Studies on the dissociation of botulinum neurotoxin type A complexes

The neurotoxins produced by the various strains of the anaerobic bacterium Clostridium botulinum naturally occur associated with complexing proteins which serve to protect the neurotoxins from the harsh environment of the mammalian gastrointestinal tract during bacterial invasion of the host. Three different complex species with the discrete sizes 19S (900 kDa, LL complex), 16S (500 kDa, L complex) and 12S (300 kDa, M complex) may be isolated from C. botulinum type A cultures. However, to affect their target cells these complexes must dissociate releasing the free 150 kDa neurotoxin. This study assesses the stability of these Clostridium botulinum neurotoxin serotype A (BoNT/A) complexes and identifies factors which influence their dissociation. The knowledge gained with purified toxin complexes was subsequently employed to analyze the presence of such complexes in the freeze or spray-dried commercial BoNT/A products Botox and Dysport in comparison to the complexing protein free product Xeomin. Purified 900 kDa and 500 kDa toxin complex preparations show a pH and time dependent release of the 150 kDa neurotoxin with a half-life of less than a minute at pH values >7.0. At pH values of 6.25 or less, the complexes are stable. Furthermore, dilution of concentrated 900 kDa complexes leads to dissociation into 500 kDa, neurotoxin containing complexes. Addition of sodium chloride as contained in isotonic saline leads to further disruption of these complexes resulting in the release of the free 150 kDa neurotoxin. Examination of the commercial botulinum neurotoxin products Botox and Dysport using the same analytical procedures leads to the same conclusion: the dilution, drying and reconstitution processes of these products lead to a complete dissociation of 900 kDa complexes and 85% or more of neurotoxin are present in free form.

CONCLUSION

BoNT A toxin complexes have evolved to quickly respond to specific environmental changes by efficient release of the neurotoxin. During pharmaceutical production and reconstitution of BoNT A products, the same principles effect the quantitative dissociation of 900 kDa complexes and release of free neurotoxin prior to injection into target tissues.

Release of proteolytic activity following reduction in therapeutic human serum albumin containing products: detection with a new neoepitope endopeptidase immunoassay

Botulinum type A toxin (BoNT/A) is defined by its specific endopeptidase cleavage of SNAP25 between Gln(197) and Arg(198) under reducing conditions. The neurotoxin is widely used for therapeutic or cosmetic purposes, but should not contain other toxin serotypes or unwanted protease activities. Using a neoepitope endopeptidase immunoassay, additional cleavage between Arg(198) and Ala(199) was detected with a range of therapeutic BoNT/A products confirming an earlier report of an unidentified proteolytic component. By developing the assay and making it insensitive to BoNT/C1, any activity due to the type C1 toxin was excluded. Therapeutic preparations consist of ng quantities of toxin protein which are typically stabilised by 0.125-30 mg of HSA. An excellent correlation (R(2)=0.993) between HSA content per vial and measured activity was obtained within the therapeutic BoNT/A products tested. No activity was detected in any of the non-albumin formulated preparations, thereby identifying HSA as the source of the unknown protease for the first time. To investigate the cause of this activity, either as an intrinsic molecular activity of albumin or due to an albumin-associated purification contaminant, further studies on a variety of commercial plasma-derived HSA products or recombinant HSA materials free from potential plasma contaminants were carried out. The measured proteolytic levels were highly consistent amongst preparations, and could all be partially inhibited by the presence of zinc and blocked by PKSI-527 and aprotinin. By contrast, the data did not support the role of plasmin, kallikrein, trypsin, α(2)-antiplasmin-plasmin complexes or HSA purification contaminants, PKA (prekallikrein activator) or kallikrein-like activity. Taken together, these findings indicate a new intrinsic proteolytic activity of the albumin molecule revealed under reducing conditions as the source of the unexpected Arg-Ala cleaving activity.

Temporal characteristics of botulinum neurotoxin therapy

Botulinum neurotoxin is a pharmaceutical treatment used for an increasing number of neurological and non-neurological indications, symptoms and diseases. Despite the wealth of clinical reports that involve the timing of the therapeutic effects of this toxin, few studies have attempted to integrate these data into unified models. Secondary reactions have also been examined including the development of adverse events, resistance to repeated applications, and nerve terminal sprouting. Our primary intent for conducting this review was to gather relevant pharmacodynamic data from suitable biomedical literature regarding botulinum neurotoxins via the use of automated data-mining techniques. We envision that mathematical models will ultimately be of value to those who are healthcare decision makers and providers, as well as clinical and basic researchers. Furthermore, we hypothesize that the combination of this computer-intensive approach with mathematical modeling will predict the percentage of patients who will favorably or adversely respond to this treatment and thus will eventually assist in developing the increasingly important area of personalized medicine.