Spinal cord injury-induced lower urinary tract dysfunction in mice can be improved by imidazoline 2 receptor activation

Hashimoto M1, Matsuoka K2, Cho K3, Kamijo T2, Daugherty S4, Sugimoto K1, Shimizu N5, Hirayama A6, Uemura H1, Fujita K1, Karnup S4, Yoshimura N2

Research Type

Pure and Applied Science / Translational

Abstract Category

Research Methods / Techniques

Abstract 92
Neurobiology
Scientific Podium Short Oral Session 9
Wednesday 23rd October 2024
17:07 - 17:15
Hall N105
Spinal Cord Injury Neuropathies: Central Detrusor Overactivity Voiding Dysfunction Pharmacology
1. Department of Urology, Kindai University Faculty of Medicine, Osaka-Sayama, Osaka, Japan, 2. Department of Urology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA, 3. Department of Urology, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea, 4. Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA, 5. Pelvic Floor Center, Kochi Medical School, Kochi University, Nankoku, Japan, 6. Department of Urology, Kindai University Nara Hospital, Ikoma, Japan
Presenter
Links

Abstract

Hypothesis / aims of study
We conducted this study to evaluate the effects of an imidazoline 2 receptor (I2R) agonist, 2BFI, on lower urinary tract dysfunction (LUTD) in mice with spinal cord injury (SCI). It is reported that clonidine, activator of α2-adrenoceptors and imidazoline receptors, improved detrusor sphincter dyssynergia (DSD) caused by SCI through the action in the spinal cord [1]. Thus, we hypothesized that I2Rs could be involved in neurogenic LUTD after SCI.
Study design, materials and methods
C57BL/6N female mice at 9-10-weeks old were used. SCI mice underwent complete transection of the Th8-9 spinal cord. Mice were divided into three groups (1) spinal intact (SI), (2) SCI with vehicle, and (3) SCI with 2BFI treatment (20mg/kg, twice daily, i.p.), which was initiated 2 weeks after SCI. Four weeks after SCI, cystometrograms (CMG) and external urethral sphincter (EUS)-electromyography (EMG) were recorded. Thereafter, L6-S1 dorsal root ganglia (DRG) were harvested to evaluate the transcripts of TRPV1, TNF-alpha and iNOS using qPCR. Furthermore, using another set of mice, we tested intrathecal (i.t.) application of 2BFI (20µg per administration) at the L6 spinal cord level during CMG and EMG. In organ bath study, we cut the bladder into two longitudinal strips. Bladder body muscle strips were mounted longitudinally in a vertical double-jacketed organ bath with 37℃oxygenated 15 mL Krebs solution. Precontraction of muscle strips was induced by adding KCL (80μM) or Carbachol (10μM) to each bath. We waited for 30-40 minutes for precontraction stabilization and then, 2BFI application (1, 10, 100µM) (I2R agonist) was applied to each bath without or with BU224 (100µM) (I2R antagonist), which was applied 15 minutes prior to 2BFI.
Results
SCI mice showed the significantly higher number of non-voiding contractions (NVCs) and lower voiding efficiency than SI mice. However, 2BFI-treated SCI mice exhibited a lower number of NVCs and improved voiding efficiency along with increased EUS relaxation time during voiding than vehicle-treated SCI mice. mRNA levels of TRPV1, TNF-alpha and iNOS in L6-S1 DRG were significantly higher in vehicle-treated SCI mice than in SI mice; however, decreased after 2BFI treatment. In the treatment with intrathecal application of 2BFI, significant reductions in residual urine and NVCs, and an increase of EUS relaxation time were seen after a transient stimulation period in SCI mice following i.t. application of 2BFI (Figure 1 and Table 1). In the organ bath study, 2BFI induced relaxation in muscle strips precontracted with KCL or Carbachol. BU224 reduced the relaxation effects of 2BFI.
Interpretation of results
We demonstrated that 2BFI (i.p. injection daily or intrathecal application) can improve DO, evident as NVC reduction, and DSD, evident as increase EUS relaxation time, in SCI mice. As shown in a previous report with clonidine [1], DSD was improved by i.t. application of 2BFI, indicating that I2R activation at spinal sites contributes to the improvement of vesicourethral coordination during voiding after SCI. The improvement of DO by 2BFI were accompanied by the decrease of the expression of a C-fiber afferent marker (TRPV1) and inflammatory mediators (TNF-alpha and iNOS) in L6-S1 DRG, as similarly shown in a previous study [2]. Furthermore, in the organ bath study, 2BFI significantly reduced detrusor contractility through peripheral effects of 2BFI, as evidenced by its relaxation effects on bladder muscle strips of SCI mice.
Concluding message
I2R activation, at the lumbosacral spinal cord and the bladder, could be effective for the treatment of both storage and voiding LUTD induced by SCI.
Figure 1 The effects of i.t. injection of 2BFI on detrusor overactivity in a SCI mouse. 2BFI transiently increased nonvoiding contractions (NVCs), but later (15-30 min) improved detrusor overactivity evident as a reduction in the number of NVCs.
Figure 2 Table1
References
  1. J Urol. 1998 Dec;160(6 Pt 1):2137-8.
  2. Neurourol Urodyn. 2020 Jan;39(1):108-115.
Disclosures
Funding NIH R01DK129194 Clinical Trial No Subjects Animal Species Mouse Ethics Committee University of Pittsburgh Institutional Animal Care and Use Committee (Protocol Approval No. 22061313)
Citation

Continence 12S (2024) 101434
DOI: 10.1016/j.cont.2024.101434

14/11/2024 01:10:35