Analysis of gene expression in induced pluripotent stem cell-derived human neurons exposed to botulinum neurotoxin A subtype 1 and a type A atoxic derivative

Antinociceptive properties of intravesical/needle-free administration of abobotulinumtoxinA in a rodent model of chronic visceral pain: in vivo and histological evidence

While interstitial cystitis along with bladder pain syndrome (IC/BPS) is still poorly treated, published clinical evidence suggests that onabotulinumtoxinA (natural botulinum neurotoxin type A (BoNT/A)) intradetrusor injections is efficient in IC/BPS. However, as bladder instillation could be a safer and more convenient administration route, we aimed to investigate the effect of BoNT/A needle-free administration in an IC/BPS rodent model. Cyclophosphamide (CYP) was used to induce IC/BPS in rats. The resulting symptoms mimicked the main key features of human non-ulcerative IC/BPS. AbobotulinumtoxinA (aboBoNT-A) or reference compounds used in the clinic were delivered as a single intravesical administration into the bladder via the urethra. Visceral allodynia and hyperalgesia were assessed at the abdominal level with von Frey filaments before and after bladder pain induction. The levels of BoNT/A-cleaved SNAP25 (c-SNAP25), total SNAP25 (SNAP25N-ter), beta-3 tubulin and CGRP in bladders were also quantified using immunohistochemistry (IHC), as well as the histopathological lesions. AboBoNT-A was well tolerated up to 30 U/rat. Allodynia and hyperalgesia were significantly decreased after aboBoNT-A dosing, with higher efficacy compared to references. c-SNAP25 IHC levels were low and similar in the detrusor for the 3 aboBoNT-A groups. Neither CYP or aboBoNT-A induced any change in the amount of SNAP25, beta-3 tubulin or CGRP. Some CYP-induced histopathological lesions showed a trend in improvement under aboBoNT-A. AboBoNT-A displayed analgesic properties that could translate into better therapies for visceral pain. Interestingly, intravesical (needle-free) administration seems like a promising and reproducible route for botulinum toxin therapy in patients with IC/BPS.

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.

Dramatic neurological and biological effects by botulinum neurotoxin type A on SH-SY5Y neuroblastoma cells, beyond the blockade of neurotransmitter release

BACKGROUND

Gene expression profile analysis on mammalian cell lines and animal models after exposure to botulinum neurotoxin (BoNT) has been investigated in several studies in recent years. Microarray analysis provides a powerful tool for identifying critical signaling pathways involved in the biological and inflammatory responses to BoNT and helps determine the mechanism of the function of botulinum toxins. One of the pivotal clinical characteristics of BoNT is its prolonged on-site effects. The role of BoNT on the blockage of neurotransmitter acetylcholine release in the neuromuscular junction has been well established. However, the effects of the treatment time of BoNT on the human cellular model and its potential mechanism remain to be defined.

METHODS

This study aimed to use gene microarray technology to compare the two physiological critical time points of BoNT type A (BoNT/A) treatment of human neuroblastoma cells and to advance our understanding of the profound biological influences that toxin molecules play in the neuronal cellular system. SH-SY5Y neuroblastoma cells were treated with BoNT/A for 4 and 48 h, which represent the time needed for the entrance of toxin into the cells and the time necessary for the initial appearance of the on-site effects after BoNT application, respectively.

RESULTS

A comparison of the two time points identified 122 functional groups that are significantly changed. The top five groups are alternative splicing, phosphoprotein, nucleus, cytoplasm, and acetylation. Furthermore, after 48 h, there were 744 genes significantly up-regulated, and 624 genes significantly down-regulated (p‹ 0.01). These genes fell into the following neurological and biological annotation groups: Nervous system development, proteinaceous extracellular matrix, signaling pathways regulating pluripotency of stem cells, cellular function and signal transduction, and apoptosis. We have also noticed that the up-regulated groups contained neuronal cell development, nervous system development, and metabolic processes. In contrast, the down-regulated groups contained many chromosomes and cell cycle categories.

CONCLUSIONS

The effects of BoNT/A on neuronal cells extend beyond blocking the neurotransmitter release, and that BoNT/A is a multifunctional molecule that can evoke profound cellular responses which warrant a more in-depth understanding of the mechanism of the toxin's effects after administration.

Botulinum toxin type A in motor nervous system: unexplained observations and new challenges

In the motor system, botulinum toxin type A (BoNT/A) actions were classically attributed to its well-known peripheral anticholinergic actions in neuromuscular junctions. However, the enzymatic activity of BoNT/A, assessed by the detection of cleaved synaptosomal-associated protein 25 (SNAP-25), was recently detected in motor and sensory regions of the brainstem and spinal cord after toxin peripheral injection in rodents. In sensory regions, the function of BoNT/A activity is associated with its antinociceptive effects, while in motor regions we only know that BoNT/A activity is present. Is it possible that BoNT/A presence in central motor nuclei is without any function? In this brief review, we analyze this question. Limited data available in the literature warrant further investigations of BoNT/A actions in motor nervous system.

Botulinum neurotoxin type A: Actions beyond SNAP-25?

Botulinum neurotoxin type A (BoNT/A), the most potent toxin known in nature which causes botulism, is a commonly used therapeutic protein. It prevents synaptic vesicle neuroexocytosis by proteolytic cleavage of synaptosomal-associated protein of 25 kDa (SNAP-25). It is widely believed that BoNT/A therapeutic or toxic actions are exclusively mediated by SNAP-25 cleavage. On the other hand, in vitro and in vivo findings suggest that several BoNT/A actions related to neuroexocytosis, cell cycle and apoptosis, neuritogenesis and gene expression are not necessarily mediated by this widely accepted mechanism of action. In present review we summarize the literature evidence which point to the existence of unknown BoNT/A molecular target(s) and modulation of unknown signaling pathways. The effects of BoNT/A apparently independent of SNAP-25 occur at similar doses/concentrations known to induce SNAP-25 cleavage and prevention of neurotransmitter release. Accordingly, these effects might be pharmacologically significant. Potentially the most interesting are observations of antimitotic and antitumor activity of BoNT/A. However, the exact mechanisms require further studies.