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Ge Y, AlObaidi AS, Kuchel GA, Bartley JM, Smith PP, He W, Hu X. Dysfunctional Bladder Morphology and Functional Impairments Are Identified in the Alzheimer's Disease APPNL-G-F/NL-G-F Murine Model. J Alzheimers Dis 2024; 97:395-408. [PMID: 38160353 DOI: 10.3233/jad-230547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
BACKGROUND While symptoms related to lower urinary tract dysfunction (LUTD) are common in individuals with Alzheimer's disease (AD), pathophysiological links between AD and LUTD remain unclear. OBJECTIVE This study aimed to investigate whether AD neuropathology would cause autonomic dysfunction along the spinal cord-bladder axis, which could result in alterations in bladder muscle kinetics. METHODS We utilized APPNL-G-F/NL-G-F knock-in (APP KI) and APPwt/wt (wild-type) mice at two different ages, 4- and 10-month-old, to investigate how AD impacts bladder tissue function by immunohistochemistry, western blotting, and pharmacomyography. RESULTS We showed that the mucosal layer partially separated from the detrusor in 10-month-old APP KI mouse bladders. Although there was no detectable amyloid deposition in the APP KI bladder, we found amyloid plaques in APP KI lumbar spinal cord. Further immunoblot analysis revealed that tyrosine hydroxylase protein levels were significantly reduced in both 4- and 10-month-old bladder tissues, suggesting reduction of norepinephrine synthesis in APP KI mouse bladders. In contrast, the level of β2 adrenergic receptor was increased in 4-month-old but not 10-month-old APP KI bladders. In bladder strips, the adrenergic agonist isoproterenol induced increased relaxation in 4- but not 10-month-old APP KI bladders. With 10 Hz electrical field stimulation, 10-month-old APP KI bladder strips were more responsive than wild-type controls, with no differences observed in 4-month-old APP KI bladders. CONCLUSIONS APP KI mice exhibit LUTD, which is likely arising from amyloid pathology in the spinal cord, and results in maturational declines in presynaptic activity combined with compensatory postsynaptic upregulation.
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Affiliation(s)
- Yingying Ge
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Alya S AlObaidi
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
- Center on Aging, UConn Health, Farmington, CT, USA
| | | | - Jenna M Bartley
- Center on Aging, UConn Health, Farmington, CT, USA
- Department of Immunology, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Phillip P Smith
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
- Center on Aging, UConn Health, Farmington, CT, USA
| | - Wanxia He
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Xiangyou Hu
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
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2
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Hardy CC, Korstanje R. Aging and urinary control: Alterations in the brain-bladder axis. Aging Cell 2023; 22:e13990. [PMID: 37740454 PMCID: PMC10726905 DOI: 10.1111/acel.13990] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 08/29/2023] [Accepted: 09/05/2023] [Indexed: 09/24/2023] Open
Abstract
Age-associated alterations in bladder control affect millions of older adults, with a heavy burden added to families both economically and in quality of life. Therapeutic options are limited with poor efficacy in older adults, lending to a growing need to address the gaps in our current understanding of urinary tract aging. This review summarizes the current knowledge of age-associated alterations in the structure and function of the brain-bladder axis and identifies important gaps in the field that have yet to be addressed. Urinary aging is associated with decreased tissue responsiveness, decreased control over the voiding reflex, signaling dysfunction along the brain-bladder axis, and structural changes within the bladder wall. Studies are needed to improve our understanding of how age affects the brain-bladder axis and identify genetic targets that correlate with functional outcomes.
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3
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Ramasamy R, Baker DS, Lemtiri-Chlieh F, Rosenberg DA, Woon E, Al-Naggar IM, Hardy CC, Levine ES, Kuchel GA, Bartley JM, Smith PP. Loss of resilience contributes to detrusor underactivity in advanced age. Biogerontology 2023; 24:163-181. [PMID: 36626035 PMCID: PMC10006334 DOI: 10.1007/s10522-022-10005-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 12/13/2022] [Indexed: 01/11/2023]
Abstract
Volume hyposensitivity resulting from impaired sympathetic detrusor relaxation during bladder filling contributes to detrusor underactivity (DU) associated with aging. Detrusor tension regulation provides an adaptive sensory input of bladder volume to the brainstem and is challenged by physiological stressors superimposed upon biological aging. We recently showed that HCN channels have a stabilizing role in detrusor sympathetic relaxation. While mature mice maintain homeostasis in the face of stressors, old mice are not always capable. In old mice, there is a dichotomous phenotype, in which resilient mice adapt and maintain homeostasis, while non-resilient mice fail to maintain physiologic homeostasis. In this DU model, we used cystometry as a stressor to categorize mice as old-responders (old-R, develop a filling/voiding cycle) or old-non-responders (old-NR, fail to develop a filling/voiding cycle; fluctuating high pressures and continuous leaking), while also assessing functional and molecular differences. Lamotrigine (HCN activator)-induced bladder relaxation is diminished in old-NR mice following HCN-blockade. Relaxation responses to NS 1619 were reduced in old-NR mice, with the effect lost following HCN-blockade. However, RNA-sequencing revealed no differences in HCN gene expression and electrophysiology studies showed similar percentage of detrusor myocytes expressing HCN (Ih) current between old-R and old-NR mice. Our murine model of DU further defines a role for HCN, with failure of adaptive recalibration of HCN participation and intensity of HCN-mediated stabilization, while genomic studies show upregulated myofibroblast and fibrosis pathways and downregulated neurotransmitter-degradation pathways in old-NR mice. Thus, the DU phenotype is multifactorial and represents the accumulation of age-associated loss in homeostatic mechanisms.
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Affiliation(s)
- Ramalakshmi Ramasamy
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, CT, USA
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Dylan S Baker
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Department of Genetics and Genome Sciences, Institute for Systems Genomics, University of Connecticut School of Medicine, Farmington, CT, USA
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
| | - Fouad Lemtiri-Chlieh
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Dawn A Rosenberg
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Department of Cell Biology, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Eric Woon
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Department of Biomedical Engineering, University of Connecticut, Storrs, CT, USA
| | - Iman M Al-Naggar
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Department of Cell Biology, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Cara C Hardy
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, CT, USA
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - Eric S Levine
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
| | - George A Kuchel
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
| | - Jenna M Bartley
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA.
- Department of Immunology, University of Connecticut School of Medicine, Farmington, CT, USA.
| | - Phillip P Smith
- UConn Center on Aging, UConn Health, 263 Farmington Avenue, Farmington, CT, 06030-8073, USA
- Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, CT, USA
- Department of Surgery, University of Connecticut School of Medicine, Farmington, CT, USA
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, CT, USA
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4
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Lemtiri-Chlieh F, Baker DS, Al-Naggar IM, Ramasamy R, Kuchel GA, Levine ES, Robson P, Smith PP. The hyperpolarization-activated, cyclic nucleotide-gated channel resides on myocytes in mouse bladders and contributes to adrenergic-induced detrusor relaxation. Am J Physiol Regul Integr Comp Physiol 2022; 323:R110-R122. [PMID: 35503519 PMCID: PMC9236879 DOI: 10.1152/ajpregu.00277.2021] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Control of urinary continence is predicated on sensory signaling about bladder volume. Bladder sensory nerve activity is dependent on tension, implicating autonomic control over detrusor myocyte activity during bladder filling. Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels are known contributors to bladder control, but their mechanism of action is not well understood. The lack of a definitive identification of cell type(s) expressing HCN in the bladder presents a significant knowledge gap. We recently reported a complete transcriptomic atlas of the C57BL/6 mouse bladder showing the dominant HCN paralog in mouse bladder, Hcn1, is limited to a subpopulation of detrusor smooth myocytes (DSMs). Here, we report details of these findings, along with results of patch-clamp experiments, immunohistochemistry, and functional myobath/tension experiments in bladder strips. With the use of a transgenic mouse expressing fluorescence-tagged α-smooth muscle actin, our data confirmed location and function of DSM HCN channels. Despite previous associations of HCN with postulated bladder interstitial cells, neither evidence of specific interstitial cell types nor an association of nonmyocytes with HCN was discovered. We confirm that HCN activation participates in reducing sustained (tonic) detrusor tension via cAMP, with no effect on intermittent (phasic) detrusor activity. In contrast, blockade of HCN increases phasic activity induced by a protein kinase A (PKA) blocker or a large-conductance Ca2+-activated K+ (BK) channel opener. Our findings, therefore, suggest a central role for detrusor myocyte HCN in regulating and constraining detrusor myocyte activity during bladder filling.
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Affiliation(s)
- Fouad Lemtiri-Chlieh
- 1University of Connecticut Center on Aging, University of Connecticut Health, Farmington, Connecticut,5Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Dylan S. Baker
- 1University of Connecticut Center on Aging, University of Connecticut Health, Farmington, Connecticut,4Department of Genetics and Genome Sciences, Institute for Systems Genomics, University of Connecticut School of Medicine, Farmington, Connecticut,7The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Iman M. Al-Naggar
- 1University of Connecticut Center on Aging, University of Connecticut Health, Farmington, Connecticut,6Department of Cell Biology, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Ramalakshmi Ramasamy
- 1University of Connecticut Center on Aging, University of Connecticut Health, Farmington, Connecticut,5Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut
| | - George A. Kuchel
- 1University of Connecticut Center on Aging, University of Connecticut Health, Farmington, Connecticut
| | - Eric S. Levine
- 2Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, Connecticut,5Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut
| | - Paul Robson
- 4Department of Genetics and Genome Sciences, Institute for Systems Genomics, University of Connecticut School of Medicine, Farmington, Connecticut,7The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
| | - Phillip P. Smith
- 1University of Connecticut Center on Aging, University of Connecticut Health, Farmington, Connecticut,2Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, Connecticut,3Department of Surgery, University of Connecticut School of Medicine, Farmington, Connecticut
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5
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Ramasamy R, Hardy CC, Crocker SJ, Smith PP. Cuprizone-mediated demyelination reversibly degrades voiding behavior in mice while sparing brainstem reflex. J Neurosci Res 2022; 100:1707-1720. [PMID: 35596557 DOI: 10.1002/jnr.25065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 03/30/2022] [Accepted: 04/22/2022] [Indexed: 11/12/2022]
Abstract
Multiple sclerosis (MS) is a chronic, progressively debilitating demyelinating disease of the central nervous system (CNS). Nearly 80% of MS patients experience lower urinary tract dysfunction early in their diagnosis. This significantly affects the quality of life, and in latter stages of disease is a leading cause of hospitalization. Previously, animal models have shown that inflammatory demyelination in the CNS causes profound bladder dysfunction, but the confounding influence of systemic inflammation limits the potential interpretation of the contribution of CNS demyelination to bladder dysfunction. Since the micturition circuit has myelinated neuronal connections in the cortex, brainstem, and spinal cord, we examined alterations in bladder function in the cuprizone model characterized by demyelinating lesions in the cortex and corpus callosum that are independent of T-cell-mediated autoimmunity. Herein, we report that a 4-week dietary cuprizone treatment in C57Bl/6J mice induced alterations in voiding behavior with increased micturition frequency and reduced volume voided, similar to human MS bladder dysfunction. Subsequently, recovery from cuprizone treatment restored normal bladder function. Demyelination and remyelination were confirmed by Luxol Fast Blue staining of the corpus callosum. Additionally, we also determined that an 8-week cuprizone treatment, resulting in chronic demyelination lacking spontaneous remyelination potential, is associated with an exacerbated voiding phenotype. Interestingly, while cuprizone-induced CNS demyelination severely affected conscious (cortical) urinary behavior, the brainstem and spinal cord reflex remained unchanged, as confirmed by urethane-anesthetized cystometry. This is the first study to show that cortical demyelination independent of inflammation can negatively impact urinary function.
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Affiliation(s)
- Ramalakshmi Ramasamy
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut, USA.,UConn Center on Aging, University of Connecticut School of Medicine, Farmington, Connecticut, USA
| | - Cara C Hardy
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut, USA.,UConn Center on Aging, University of Connecticut School of Medicine, Farmington, Connecticut, USA
| | - Stephen J Crocker
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut, USA.,UConn Center on Aging, University of Connecticut School of Medicine, Farmington, Connecticut, USA
| | - Phillip P Smith
- Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut, USA.,UConn Center on Aging, University of Connecticut School of Medicine, Farmington, Connecticut, USA.,Department of Surgery, University of Connecticut School of Medicine, Farmington, Connecticut, USA
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6
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Singh N, Zabbarova I, Ikeda Y, Kanai A, Chermansky C, Yoshimura N, Tyagi P. Role of hyperpolarization-activated cyclic nucleotide-gated channels in aging bladder phenotype. Life Sci 2022; 289:120203. [PMID: 34875252 PMCID: PMC8724453 DOI: 10.1016/j.lfs.2021.120203] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 11/22/2021] [Accepted: 11/29/2021] [Indexed: 01/17/2023]
Abstract
OBJECTIVE To assess the functional role of Hyperpolarization-activated cyclic nucleotide-gated gated channel (HCN) subtypes in the aging bladder phenotype characterized by diminished bladder volume sensation (BVS) with or without the detrusor instability (DI). METHODS Expression of HCN subtypes was examined by quantitative RT-PCR and Western blot in aged male Fisher 344 rats (n = 15) and young rats (n = 15). Nocturnal urination and awake cystometry (CMG) were assessed in presence and absence of a steady state HCN channel blockade achieved with daily oral gavage of vehicle or Ivabradine (HCN blocker) 6 mg/kg for 7 days. RESULTS The association of BVS with the age-related downregulation (~30%) of cAMP sensitive HCN1, HCN2 subtypes, and (~50%) upregulation of cAMP insensitive HCN3 subtype is evinced by the doubling in the mean urine volume of nocturnal voids (0.82 ± 0.22 mL vs 0.41 ± 0.12 mL; n = 10; p < 0.05) predicting an age-related rise in the micturition volume threshold (p < 0.0001) in CMG, which is raised further by Ivabradine treatment (p < 0.0005). Ivabradine also doubled non-voiding contractions (NVC) and maximum voiding pressure (MVP) in young and aged rats, respectively (p < 0.0001) to abolish the age-related, innate two -fold elevation in NVC not accompanied with MVP rise in untreated aged rats (p < 0.005). CONCLUSION The age-related HCN downregulation is mechanistically linked to the exhibition of aging bladder phenotype with the manifestation of DI following steady state blockade of HCN channels in Ivabradine treated young rats. The amplification of MVP in aged rats mediated by FDA approved Ivabradine hints at potential repurposing opportunity in detrusor underactivity.
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Affiliation(s)
- Nishant Singh
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Irina Zabbarova
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Youko Ikeda
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Anthony Kanai
- Department of Medicine, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Christopher Chermansky
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Naoki Yoshimura
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, United States of America
| | - Pradeep Tyagi
- Department of Urology, University of Pittsburgh, Pittsburgh, PA, United States of America
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7
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Benzoni P, Bertoli G, Giannetti F, Piantoni C, Milanesi R, Pecchiari M, Barbuti A, Baruscotti M, Bucchi A. The funny current: Even funnier than 40 years ago. Uncanonical expression and roles of HCN/f channels all over the body. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 166:189-204. [PMID: 34400215 DOI: 10.1016/j.pbiomolbio.2021.08.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 06/25/2021] [Accepted: 08/09/2021] [Indexed: 12/25/2022]
Abstract
Discovered some 40 years ago, the If current has since been known as the "pacemaker" current due to its role in the initiation and modulation of the heartbeat and of neuronal excitability. But this is not all, the funny current keeps entertaining the researchers; indeed, several data discovering novel and uncanonical roles of f/HCN channel are quickly accumulating. In the present review, we provide an overview of the expression and cellular functions of HCN/f channels in a variety of systems/organs, and particularly in sour taste transduction, hormones secretion, activation of astrocytes and microglia, inhibition of osteoclastogenesis, renal ammonium excretion, and peristalsis in the gastrointestinal and urine systems. We also analyzed the role of HCN channels in sustaining cellular respiration in mitochondria and their participation to mitophagy under specific conditions. The relevance of HCN currents in undifferentiated cells, and specifically in the control of stem cell cycle and in bioelectrical signals driving left/right asymmetry during zygote development, is also considered. Finally, we present novel data concerning the expression of HCN mRNA in human leukocytes. We can thus conclude that the emerging evidence presented in this review clearly points to an increasing interest and importance of the "funny" current that goes beyond its role in cardiac sinoatrial and neuronal excitability regulation.
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Affiliation(s)
- Patrizia Benzoni
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy
| | - Giorgia Bertoli
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy
| | - Federica Giannetti
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy
| | - Chiara Piantoni
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy; Present Address: Institute of Neurophysiology, Hannover Medical School, Carl-Neuberg-Str.1, 30625, Hannover, Germany
| | - Raffaella Milanesi
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy; Present Address: Dipartimento di Medicina Veterinaria, Università degli Studi di Milano, Via Dell'Università 6, 26900, Lodi, Italy
| | - Matteo Pecchiari
- Department of Pathophysiology and Transplantation, Università degli Studi di Milano, Via L. Mangiagalli 32, 20133, Milan, Italy
| | - Andrea Barbuti
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy
| | - Mirko Baruscotti
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy
| | - Annalisa Bucchi
- The Cell Physiology MiLab, Department of Biosciences, Università degli Studi di Milano, Via G. Celoria 26, 20133, Milan, Italy.
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8
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Hardy CC, Al-Naggar IM, Kuo CL, Kuchel GA, Smith PP. Aging Changes in Bladder Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels Are Associated With Increasing Heterogeneity of Adrenergic/Mucosal Influence on Detrusor Control in the Mouse. J Gerontol A Biol Sci Med Sci 2021; 76:1153-1160. [PMID: 33693872 DOI: 10.1093/gerona/glab070] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Indexed: 11/14/2022] Open
Abstract
A geroscience-informed approach to the increasing prevalence of bladder control problems in older adults requires understanding the impact of aging on dynamic mechanisms that ensure resilience in response to stressors challenging asymptomatic voluntary control over urine storage and voiding. Bladder control is predicated on sensory neural information about bladder volume. Modulation of volume-induced bladder wall tensions by autonomic and mucosal factors controls neural sensitivity to bladder volume. We hypothesized that hyperpolarization-activated cyclic nucleotide-gated (HCN) channels integrate these factors and thereby mediate adrenergic detrusor tension control. Furthermore, loss of HCN expression compromises that integration and could result in loss of precision of detrusor control. Using a life-span mouse model, reverse transcription quantitative real-time PCR and pharmacologic studies in pretensioned intact and mucosa-denuded bladder strips were made. The dominant hcn1 expression declines with maturation and aging; however, aging is also associated with increased variance around mean values. In strips from Mature animals, isoproterenol had less effect in denuded muscle strips than in intact strips, and HCN blockade diminished isoproterenol responsiveness. With aging, variances about mean response values significantly increased, paralleling hcn1 expression. Our findings support a role for HCN in providing neuroendocrine/paracrine integration and suggest an association of increased heterogeneity of HCN expression in aging with reductions in response precision to neuroendocrine control. The functional implication is an increased risk of dysfunction of brainstem/bladder regulation of neuronal sensitivity to bladder volume. This supports the clinical model of the aging bladder phenotype as an expression of loss of resilience, and not as emerging bladder pathology with aging.
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Affiliation(s)
- Cara C Hardy
- Center on Aging, University of Connecticut School of Medicine, Farmington, USA.,Department of Neuroscience, University of Connecticut School of Medicine, Farmington, USA.,Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, USA
| | - Iman M Al-Naggar
- Center on Aging, University of Connecticut School of Medicine, Farmington, USA
| | - Chia-Ling Kuo
- Center on Aging, University of Connecticut School of Medicine, Farmington, USA.,Connecticut Convergence Institute for Translation in Regenerative Engineering, UConn Health, Farmington, USA
| | - George A Kuchel
- Center on Aging, University of Connecticut School of Medicine, Farmington, USA.,Department of Neuroscience, University of Connecticut School of Medicine, Farmington, USA.,Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, USA
| | - Phillip P Smith
- Center on Aging, University of Connecticut School of Medicine, Farmington, USA.,Department of Neuroscience, University of Connecticut School of Medicine, Farmington, USA.,Connecticut Institute for the Brain and Cognitive Sciences, University of Connecticut, Storrs, USA.,Department of Surgery, University of Connecticut School of Medicine, Farmington, USA
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