Botulinum toxin a inhibits acetylcholine release from cultured neurons in vitro

Pore Size-Dependent Stereoscopic Hydrogels Enhance the Therapeutic Efficiency of Botulinum Toxin for the Treatment of Nerve-Related Diseases

Botulinum toxin (BoNT) is a major neurotherapeutic protein that has been used at low doses for diverse pharmacological applications. However, the pleiotropic effect of BoNT depends on multiple periodic injections owing to its rapid elimination profile, short-term therapeutic effect, and high mortality rate when administered at high doses. In addition to low patient compliance, these drawbacks represent the significant challenges that limit the further clinical use of BoNT. This study developed a new hydrogel-based single dosage form of BoNT by employing a one-step cross-linking chemistry. Its controlled porous structures and composition facilitated uniform drug distribution inside the hydrogel and controllable release of BoNT mediated by slow diffusion. A single dose remained stable for at least 2.5 months and showed sustained effect for at least 20 weeks, meeting the requirements for a single-dose form of BoNT. Additionally, this dosage form was evaluated as safe from all aspects of toxicology. This delivery system resulted in a 100% survival rate after administering a BoNT dose of 30 units, while a dose of more than 5 units of naked BoNT caused a 100% mortality rate within a few days. Overall, this strategy could provide patients with the first single-dose treatment option of BoNT and improve their quality of life.

Emerging Opportunities in Human Pluripotent Stem-Cells Based Assays to Explore the Diversity of Botulinum Neurotoxins as Future Therapeutics

Botulinum neurotoxins (BoNTs) are produced by Clostridium botulinum and are responsible for botulism, a fatal disorder of the nervous system mostly induced by food poisoning. Despite being one of the most potent families of poisonous substances, BoNTs are used for both aesthetic and therapeutic indications from cosmetic reduction of wrinkles to treatment of movement disorders. The increasing understanding of the biology of BoNTs and the availability of distinct toxin serotypes and subtypes offer the prospect of expanding the range of indications for these toxins. Engineering of BoNTs is considered to provide a new avenue for improving safety and clinical benefit from these neurotoxins. Robust, high-throughput, and cost-effective assays for BoNTs activity, yet highly relevant to the human physiology, have become indispensable for a successful translation of engineered BoNTs to the clinic. This review presents an emerging family of cell-based assays that take advantage of newly developed human pluripotent stem cells and neuronal function analyses technologies.

Changes in Cerebellar Activation After Onabotulinumtoxin A Injections for Spasticity After Chronic Stroke: A Pilot Functional Magnetic Resonance Imaging Study

OBJECTIVE

To investigate the effect of reducing spasticity via onabotulinumtoxin A (Obtx-A) injection on cerebellar activation after chronic stroke during unilateral gripping.

DESIGN

Pre-post, case series.

SETTING

Outpatient spasticity clinic.

PARTICIPANTS

Individuals with chronic spasticity (N=4).

INTERVENTIONS

Upper-limb Obtx-A injection.

MAIN OUTCOME MEASURES

Functional magnetic resonance imaging (fMRI) was used to measure changes in cerebellar activation before and after upper-limb Obtx-A injection. During fMRI testing, participants performed the same motor task before and after injection, which was 15% and 30% of maximum voluntary isometric gripping measured before Obtx-A injection.

RESULTS

After Obtx-A injection, cerebellar activation increased bilaterally during gripping with the paretic hand and during rest. During both pre- and postinjection scans, the paretic hand showed larger cerebellar activation during gripping compared with the nonparetic hand. Cerebellar activation during gripping with the nonparetic hand did not change significantly after Obtx-A injection.

CONCLUSIONS

Reducing spasticity via Obtx-A injection may increase cerebellar activation both during gripping tasks with the paretic hand and during rest. To our knowledge, this is the first study that examines changes in cerebellar activation after spasticity treatment with Obtx-A.

Model for studying Clostridium botulinum neurotoxin using differentiated motor neuron-like NG108-15 cells

Cancerous cell lines have traditionally shown low sensitivity to laboratory or pharmaceutical preparations of botulinum neurotoxin. The work presented here demonstrates that the mouse neuroblastoma/rat glioma hybrid cell line NG108-15 is capable of more sensitively detecting BoNT/A1 than any cell line previously described. This cell line has previously been described to have motor neuron like characteristics, therefore making it a good model to study BoNTs. Differentiation of NG108-15 cells in serum-free medium containing retinoic acid and purmorphamine dramatically increased sensitivity of the neurons to BoNT/A (EC(50) = ~16 LD(50) U). Additional pre-treatment with triasialoganglioside GT1B prior to toxin exposure reduced the EC(50) further to ~11 LD(50) U. Co-culture of the neurons with C2C12 myotubes also significantly increased BoNT/A sensitivity of NG108-15 cells (EC(50) = 26 U) in the absence of differentiation factors.

Achalasia: a comprehensive review

Achalasia is a rare neurologic deficit of the esophagus, producing a syndrome of impaired relaxation of the lower esophageal sphincter and decreased motility of the esophageal body for which the cause is unknown. The resultant chronic esophageal stasis produces discomforting symptoms that can be managed with medication, chemical paralysis of the lower esophageal sphincter, mechanical dilation, or surgical esophagomyotomy. Chemical paralysis by injection of the esophagus with botulinum toxin and dilation with an inflatable balloon offers good short-term relief of symptoms; however, the best long-term results are produced by surgery, and advancing minimally invasive techniques continually reduce the morbidity of these operations. The type of surgical procedure, the necessity for fundoplication, and the order of treatment continue to be unresolved issues, but prospective evaluation with objective followup should allow us to provide the optimal treatment regimen to our patients.

Effect of botulinum toxin A on the autonomic nervous system of the rat lower urinary tract

PURPOSE

The magnitude and duration of the effects of botulinum toxin A on acetylcholine (ACh) and norepinephrine release from the bladder and urethra of rats were measured using a radiochemical method.

MATERIALS AND METHODS

Saline (sham treatment) or botulinum toxin A was injected into the bladder (50 microl.) or urethra (30 microl.) in separate groups of animals. The release of 3H-norepinephrine or 14C-choline was measured at 2 time points after injection (5 or 30 days).

RESULTS

The fractional release of ACh in botulinum toxin A treated animals was significantly inhibited at higher frequencies of electrical field stimulation (20 Hz.) but not at lower frequencies (2 Hz.) 5 days after injection. However, ACh release recovered to sham injected values 30 days after toxin injection. No significant differences in the fractional release of norepinephrine from sham injected or botulinum toxin A bladders were observed. In contrast, norepinephrine release from the urethra was inhibited by botulinum toxin A for at least 30 days after injection. Similar to its effect on transmitter release in the bladder, botulinum toxin A inhibited norepinephrine release in the urethra at high (20 Hz.) but not at low (4 Hz.) electrical stimulation frequencies.

CONCLUSIONS

These data indicate that the clinical effects of botulinum toxin A on the lower urinary tract may vary depending on the site of injection and level of nerve activity.

Effects of botulinum toxin type A on the superior cervical ganglia in rabbits

Sympathetic neurolysis is very important in treating chronic pain, especially sympathetically maintained pain. However, conventional neurolytic agents destroy nerve fibers nonselectively and may leave serious complications. Botulinum toxin type A (BTA) selectively acts on cholinergic nerves and inhibits the secretion of acetylcholines (Ach) at the involved nerve endings. Because cholinergic nerves also exist in autonomic ganglia, it is believed that BTA has pharmacological effects on sympathetic ganglia. In this study, after the administration of BTA into the superior cervical ganglion (SCG) in rabbits, the possible clinical use of BTA as a neurolytic agent was evaluated. In the normal saline-treated control group, miosis was not observed in all 12 rabbits. However, in the BTA-treated group, 15 cases of miosis were observed among 40 rabbits (37.5%). Furthermore, BTA induced miosis in a dose-dependent manner, though onset time and duration of miosis varied. Mean time of onset and duration were 1.8 days and 5.3 weeks, respectively. By eosin-hematoxylin (H&E) staining finding, no significant chronological and histological changes between the control and the experimental groups were observed. In conclusion, BTA was found to have a sympathetic ganglion blocking effect over a period of more than 1 month without causing considerable pathologic changes in the SCG, that is, this toxin may be used in the case of sympathetically maintained pain control as a sympatholytic.

Nociceptin/orphanin FQ-induced nociceptive responses through substance P release from peripheral nerve endings in mice

We have studied the in vivo signaling mechanisms involved in nociceptin/orphanin FQ (Noci)-induced pain responses by using a flexor-reflex paradigm. Noci was 10,000 times more potent than substance P (SP) in eliciting flexor responses after intraplantar injection into the hind limb of mice, but the action of Noci seems to be mediated by SP. Mice pretreated with an NK1 tachykinin receptor antagonist or capsaicin, or mice with a targeted disruption of the tachykinin 1 gene no longer respond to Noci. The action of Noci appears to be mediated by the Noci receptor, a pertussis toxin-sensitive G protein-coupled receptor that stimulates inositol trisphosphate receptor and Ca2+ influx. These findings suggest that Noci indirectly stimulates nerve endings of nociceptive primary afferent neurons through a local SP release.

Gating and permeability of ion channels produced by botulinum toxin types A and E in PC12 cell membranes

Botulinum neurotoxin (BoNT) is known to produce cationic channels in artificial bilayers. This study examined ion channels formed by BoNT in native membranes from cultured PC12 cells under conditions approximating those thought to occur during toxin internalization. Membrane patches were excised from PC12 cells using patch electrodes and exposed to symmetrical solutions containing either 200 mM CsCl, RbCl or KCl. The patch pipettes also contained 1-5 microg/ml BoNT buffered to pH 5.3 while the bath solutions were buffered to pH 7.0. In the presence of toxin, bursts of ion channel openings were observed. These toxin-induced channels were most active with a negative voltage applied to the same side as the toxin (cis). The increased activity at negative voltages was due to an increase in mean open time of e-fold per 120 mV and a decrease in mean closed time between bursts of e-fold per 110 mV. The shorter mean closed time within a burst was independent of membrane voltage. While BoNT-induced ion channels started as a single conductance level of 27 pS (KCl), 34 pS (RbCl) or 46 pS (CsCl) they typically increased in roughly equal steps to five or more times the original channel conductance. These higher conductance BoNT 'channels' opened and closed synchronously and could be distinguished from superposition of multiple independent channels. Despite differences in putative transmembrane sequences between BoNT/A and BoNT/E, both serotypes evidenced the same channel conductance and mean open time.

Negative chronotropic effect of botulinum toxin on neonatal rat cardiac myocytes

We demonstrated that botulinum neurotoxin attenuated the spontaneous beating rate of cultured cardiac myocytes. Primary cultured cardiac myocytes were prepared from the ventricles of neonatal Wistar rats (1-3 days old). On 7 days after cell seeding, botulinum toxin type A incorporated into liposomes was added to the culture medium. At a final concentration of 5.0 micrograms/ml, botulinum toxin markedly attenuated the beating rate of cardiac myocytes within 2-4 hours. These results demonstrated the effect of SNARE-complex proteins on the spontaneous beating of cardiac myocytes.

Pharmacologic characterization of botulinum toxin for basic science and medicine

The use of Botulinum neurotoxin (BoNT) is increasing in both clinical and basic science. Clinically, intramuscular injection of nanogram quantities of BoNT is fast becoming the treatment of choice for a spectrum of disorders including movement disorders such as torticollis, blepharospasm, Meige Disease, and hemifacial spasm (Borodic et al., 1991, 1994a; Jankovic and Brin, 1991; Clarke, 1992). Neuroscientists are using BoNTs as tools to develop a better understanding of the mechanisms underlying the neurotransmitter release process. Consequently, our ability to accurately and reliably quantify the biologic activity of botulinum toxin has become more important than ever. The accurate measurement of the pharmacologic activity of BoNTs has become somewhat problematic with the most significant problems occurring with the clinical use of the toxins. The biologic activity of BoNTs has been measured using a variety of techniques including assessment of whole animal responses to in vitro effects on neurotransmitter release. The purpose of this review is to examine the approaches employed to characterize, quantify and investigate the actions of the BoNTs and to provide a guide to aid investigators in determining which of these methods is most appropriate for their particular application or use.

Synaptic transmission blockade increases plasminogen activator activity in mouse skeletal muscle poisoned with botulinum toxin type A

Experimental denervation, either by nerve crush or axotomy, leads to a dramatic increase in muscle plasminogen activator (PA) activity, suggesting a regulation of muscle PA levels by some neural influence (Festoff et al., 1986, J. Cell Biol., 103:1415-1421; Hantaï et al., 1990, Proc. Natl. Acad. Sci. U.S.A., 87:2926-2930). The Botulinum toxin (BoTx) type A is known to selectively interrupt the release of acetylcholine without structurally altering synaptic morphology. In the present study we have used acute BoTx poisoning of hind limb muscles to further explore the neural regulation of muscle PA activities directly after poisoning and during the process of collateral reinnervation. Electromyographic recording and study of ultraterminal sprouting after zinc iodideosmium and silver-cholinesterase staining were used to monitor "denervation" and reinnervation. Muscle choline acetyltransferase activity did not decrease, as is observed after experimental denervation, but in contrast increased and, therefore, reflected the functional integrity of intramuscular nerve endings. Within 2 days of BoTx poisoning, muscle urokinase-PA, and to a lesser extent, tissue-PA activities, rose in muscle extracts as shown by an amidolytic assay and fibrin zymography. When reinnervation occurred, muscle urokinase-PA activity decreased but did not return to baseline levels within the 80 days of our study. These results suggest that cholinergic transmission-regulated events determine activity of muscle PAs and that PAs likely have a role in neuromuscular formation and plasticity.