Botulinum toxin A in the treatment of bladder dysfunction after spinal cord injury: beyond SNAP 25 cleavage
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1
Faculty of Medicine, University of Porto, Portugal
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2
i3S, Instituto de Investigação e Inovação em Saúde, Portugal
Introduction & Aims Bladder wall injections of botulinum toxin A (BoNT/A) is the gold-standard treatment for neurogenic detrusor overactivity (NDO) (2), leading to long-lasting improvements on bladder function. BoNT/A acts on motor, autonomic and sensory bladder fibres, cleaving the synaptic protein SNAP-25 and impairing vesicle-mediated neurotransmission (2). The mechanisms underlying the enduring effects of the toxin are still mostly unknown (3) but may reflect neuronal injury and stress . Here we evaluated effects of NDO treatment with BoNT/A in neuronal growth patterns and expression of cell stress markers of bladder afferent neurons.
Material & Methods Female rats were submitted to T8/T9 largely incomplete spinal cord transection (SCT) or sham surgery. Awake cystometries were performed at baseline, 1 week and 4 weeks after SCT to evaluate the development of urinary dysfunction. At 4 weeks post-SCT, when NDO is typically present, rats received 10 bladder-wall injections of BoNT/A 10U diluted in 50uL of saline. Control rats received only saline. Three days after bladder injections, awake cystometries were performed and rats were euthanized, followed by bladder and DRG L5-S1 collection. Bladders were processed for immunohistochemistry to evaluate the catalytic activity of BoNT/A and DRG were processed for western blotting (n=4/group) to measure levels of cell stress markers and primary cell culture (n=3/group) to evaluate neuronal growth and dendritic branching.
Results Four weeks after SCT, rats presented increased bladder pressure and frequent bladder contractions associated with high voided volumes. BoNT/A treatment reduced maximal bladder pressure and frequency of bladder contractions and induced SNAP-25 cleavage in the bladder wall. This was accompanied by upregulation of cellular stress markers, such as ATF3 and PERK. In vitro assays, used to evaluate intrinsic ability of terminal growth, suggested a tendency for reduced dendritic length in BoNT/A-treated SCT rats, but not in control animals.
Conclusions Preliminary results suggest that urodynamic improvements following bladder treatment with BoNT/A, known to reflect SNAP-25 cleavage, may indicate the occurrence of metabolic injury in affected bladder afferent neurons. Severity of this neuronal stress could underlie the prolonged duration of the beneficial effects of BoNT/A in SCI-induced bladder dysfunction.
Acknowledgements
Programa Doutoral em Neurociências – Faculdade de Medicina da Universidade do Porto
Prémio Melo e Castro Neurociências 2016, Santa Casa da Misericórdia de Lisboa – INSPIReD
Raquel Oliveira PhD fellowship: NORTE-08-5369-FSE-000026 - Programas Doutorais, FSE – Fundo Social Europeu – NORTE2020 – Programa Operacional Regional do Norte
Sílvia Chambel PhD fellowship: SFRH/BD/135868/2018, FCT- Fundação para a Ciência e Tecnologia
References
(1) L.F. Cooley, S. Kielb, A Review of Botulinum Toxin A for the Treatment of Neurogenic Bladder, PM R, DOI 10.1016/j.pmrj.2018.07.016(2018)
(2) A. Coelho, F. Cruz, C.D. Cruz, A. Avelino, Spread of OnabotulinumtoxinA After Bladder Injection. Experimental Study Using the Distribution of Cleaved SNAP-25 as the Marker of the Toxin Action, European urology, 61 (2012) 1178-1184
(3) O. Rossetto, The binding of botulinum neurotoxins to different peripheral neurons, Toxicon : official journal of the International Society on Toxinology, 147 (2018) 27-31.
Keywords:
Botulinum Toxin,
neurogenic bladder,
spinal cord injury,
Neuronal sprouting,
cellular stress
Conference:
XVI Meeting of the Portuguese Society for Neuroscience (SPN2019), Lisboa, Portugal, 30 May - 1 Jun, 2019.
Presentation Type:
Poster presentation
Topic:
Cellular and Molecular Neurosciences
Citation:
Oliveira
R,
Chambel
SS,
Cavaleiro
H and
Cruz
CD
(2019). Botulinum toxin A in the treatment of bladder dysfunction after spinal cord injury: beyond SNAP 25 cleavage.
Front. Cell. Neurosci.
Conference Abstract:
XVI Meeting of the Portuguese Society for Neuroscience (SPN2019).
doi: 10.3389/conf.fncel.2019.01.00011
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Received:
16 Apr 2019;
Published Online:
27 Sep 2019.
*
Correspondence:
Dr. Raquel Oliveira, Faculty of Medicine, University of Porto, Porto, Portugal, raquellmmoliveira@gmail.com