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Chakrabarty B, Lee S, Exintaris B. Generation and Regulation of Spontaneous Contractions in the Prostate. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:195-215. [PMID: 31183828 DOI: 10.1007/978-981-13-5895-1_8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Spontaneous myogenic contractions have been shown to be significantly upregulated in prostate tissue collected from men with Benign Prostatic Hyperplasia (BPH), an extremely common disorder of the ageing male. Although originally thought likely to be involved in 'housekeeping' functions, mixing prostatic secretions to prevent stagnation, these spontaneous myogenic contractions provide a novel opportunity to understand and treat BPH. This treatment potential differs from previous models, which focused exclusively on attenuating nerve-mediated neurogenic contractions. Previous studies in the rodent prostate have provided an insight into the mechanisms underlying the regulation of myogenic contractions. 'Prostatic Interstitial Cells' (PICs) within the prostate appear to generate pacemaker potentials, which arise from the summation of number of spontaneous transient depolarisations triggered by the spontaneous release of Ca2+ from internal stores and the opening of Ca2+-activated Cl- channels. Pacemaker potentials then conduct into neighbouring smooth muscle cells to generate spontaneous slow waves. These slow waves trigger the firing of 'spike-like' action potentials, Ca2+ entry and contraction, which are not attenuated by blockers of neurotransmission. However, these spontaneous prostatic contractions can be modulated by the autonomic nervous system. Here, we discuss the mechanisms underlying rodent and human prostate myogenic contractions and the actions of existing and novel pharmacotherapies for the treatment of BPH. Understanding the generation of human prostatic smooth muscle tone will confirm the mechanism of action of existing drugs, inform the identification and effectiveness of new pharmacotherapies, as well as predict patient outcomes.
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Affiliation(s)
- Basu Chakrabarty
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Melbourne, VIC, Australia
| | - Sophie Lee
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Melbourne, VIC, Australia
| | - Betty Exintaris
- Drug Discovery Biology, Monash Institute of Pharmaceutical Science, Melbourne, VIC, Australia.
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Abstract
The prostate is a gland whose secretions contribute to the seminal fluids ejaculated upon
activation of autonomic sympathetic nerves. In elder males, the prostate undergoes an
increase in stroma mass and myogenic tone, leading to benign prostatic hyperplasia that
occludes the proximal urethra and the presentation of various lower urinary tract symptoms
that decrease their quality of life. This review summarises the role of prostatic
interstitial cells (PICs) in the generation of the spontaneous tone in the prostate. It
presents current knowledge of the role of Ca2+ plays in PIC pacemaking, as well as the
mechanisms by which this spontaneous activity triggers slow wave generation and stromal
contraction. PICs display a small T-type Ca2+ current (ICaT) and a large L-type Ca2+
current (ICaL). In contrast to other interstitial cells in the urinary and
gastrointestinal tracts, spontaneous Ca2+ signalling in PICs is uniquely dependent on Ca2+
influx through ICaL channels. A model of prostatic pacemaking is presented describing how
ICaL can be triggered by an initial membrane depolarization evoked upon the selective
opening of Ca2+-activated Cl– channels by Ca2+ flowing only through ICaT channels. The
resulting current flow through ICaL results in release of Ca2+ from internal stores and
the summation of Cl–-selective spontaneous transient depolarizations (STDs) to form
pacemaker potentials that propagate passively into the prostatic stroma to evoke
regenerative action potentials and excitation-contraction coupling.
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Affiliation(s)
- Richard J Lang
- Department of Physiology, School of Biomedical Sciences, Monash University, Clayton Victoria 3800, Australia
| | - Hikaru Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya 467-8601, Japan
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Lam M, Mitsui R, Hashitani H. Electrical properties of purinergic transmission in smooth muscle of the guinea-pig prostate. Auton Neurosci 2016; 194:8-16. [DOI: 10.1016/j.autneu.2015.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 11/18/2015] [Accepted: 11/23/2015] [Indexed: 11/24/2022]
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Calcium signalling in Cajal-like interstitial cells of the lower urinary tract. Nat Rev Urol 2014; 11:555-64. [PMID: 25224445 DOI: 10.1038/nrurol.2014.241] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Interstitial cells of Cajal (ICC) serve several critical physiological roles in visceral smooth muscle organs, including acting as electrical pacemakers to modulate phasic contractile activity and as intermediaries in motor neurotransmission. The major roles of ICC have been described in the gastrointestinal tract, however, ICC-like cells (ICC-LC) can also be found in other visceral organs, including those of the lower urinary tract (LUT), where they provide similar functions, acting as electrical pacemakers and as intermediary cells involved in the modulation of neurotransmission to adjacent smooth muscle cells. The physiological functions of ICC-LC, in particular their role as pacemakers, relies on their ability to generate transient and propagating intracellular Ca(2+) events. The role of ICC-LC as pacemakers and neuromodulators in the LUT is increasingly apparent and the study of their intracellular Ca(2+) dynamics will provide a better understanding of their role in LUT excitability.
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Chakrabarty B, Dey A, Lam M, Ventura S, Exintaris B. Tamsulosin modulates, but does not abolish the spontaneous activity in the guinea pig prostate gland. Neurourol Urodyn 2014; 34:482-8. [PMID: 24436088 DOI: 10.1002/nau.22557] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 12/13/2013] [Indexed: 11/12/2022]
Abstract
AIMS To examine the effects of the α1A -adrenoceptor antagonist, tamsulosin, on spontaneous contractile and electrical activity in the guinea-pig prostate gland. METHODS The effects of tamsulosin (0.1 and 0.3 nM) were investigated in adult and ageing male guinea pig prostate glands using conventional tension recording and electrophysiological intracellular microelectrode recording techniques. RESULTS Tamsulosin reduced spontaneous activity, and had different age-dependent effects on adult and ageing guinea pigs at different concentrations. 0.1 nM tamsulosin caused a significantly greater reduction of spontaneous contractile and electrical activity in ageing guinea pigs in comparison to adult guinea pigs. In contrast, 0.3 nM tamsulosin had a significantly greater reduction of spontaneous contractile and electrical activity in adult guinea pigs in comparison to ageing guinea pigs. CONCLUSIONS This study demonstrates that tamsulosin can modulate spontaneous myogenic stromal contractility and the underlying spontaneous electrical activity; tamsulosin does not block spontaneous activity. This reduction in spontaneous activity suggests that downstream cellular mechanisms underlying smooth muscle tone are being targeted, and these may represent novel therapeutic targets to better treat benign prostatic hyperplasia.
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Affiliation(s)
- Basu Chakrabarty
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia
| | - Anupa Dey
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia
| | - Michelle Lam
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia
| | - Sabatino Ventura
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia
| | - Betty Exintaris
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Melbourne, Victoria 3052, Australia
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Lam M, Shigemasa Y, Exintaris B, Lang RJ, Hashitani H. Spontaneous Ca2+ signaling of interstitial cells in the guinea pig prostate. J Urol 2011; 186:2478-86. [PMID: 22019167 DOI: 10.1016/j.juro.2011.07.082] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Indexed: 10/24/2022]
Abstract
PURPOSE We investigated whether prostate interstitial cells generate spontaneous Ca(2+) oscillation, a proposed mechanism underlying pacemaker potentials to drive spontaneous activity in stromal smooth muscle cells. MATERIALS AND METHODS Intracellular free Ca(2+) in portions of guinea pig prostate and freshly isolated, single prostate interstitial cells were visualized using fluo-4 Ca(2+) fluorescence. Spontaneous electrical activity was recorded in situ with intracellular microelectrodes. RESULTS In whole tissue preparations spontaneous Ca(2+) flashes firing synchronously across all smooth muscle cells within the field of view resulted in muscle wall contractions. Nonpropagating Ca(2+) waves were also recorded in individual smooth muscle cells. Nifedipine (Sigma®) (1 μM) largely decreased or abolished these Ca(2+) flashes and suppressed slow wave discharge upon blockade of their superimposed action potentials. Isolated prostate interstitial cells were readily distinguished from smooth muscle cells by their spiky processes and lack of contraction during intracellular Ca(2+) increases. Prostate interstitial cells generated spontaneous Ca(2+) transients in the form of whole cell flashes, intracellular Ca(2+) waves or localized Ca(2+) sparks. All 3 Ca(2+) signals were abolished by nicardipine (1 μM), cyclopiazonic acid (10 μM), caffeine (Sigma) (10 mM) or extracellular Ca(2+) removal. CONCLUSIONS Prostate interstitial cells generate spontaneous Ca(2+) transients that occur at a frequency comparable to Ca(2+) flashes in situ or slow waves relying on functional internal Ca(2+) stores. However, unlike other interstitial cells in the urinary tract, Ca(2+) influx through L-type Ca(2+) channels is fundamental to Ca(2+) transient firings in prostate interstitial cells. Thus, it is not possible to conclude that prostate interstitial cells are responsible for pacemaker potential generation.
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Affiliation(s)
- Michelle Lam
- Medicinal Chemistry and Drug Action, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia
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Dey A, Kusljic S, Lang RJ, Exintaris B. Role of connexin 43 in the maintenance of spontaneous activity in the guinea pig prostate gland. Br J Pharmacol 2011; 161:1692-707. [PMID: 20735413 DOI: 10.1111/j.1476-5381.2010.01001.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE To investigate the role of connexin 43 in the maintenance of spontaneous activity in prostate tissue from young and old guinea pigs. EXPERIMENTAL APPROACH Conventional intracellular microelectrode and tension recording techniques, coupled with Western blot analysis and immunohistochemistry for connexin 43 (CX43) were used. The effects of three gap junction uncouplers, 18β glycyrrhetinic acid (10 µM, 40 µM), carbenoxolone (10 µM, 50 µM) and octanol (0.5 mM, 1 mM), were studied in cells displaying slow wave activity and on spontaneously contracting tissue from prostate glands of young (2-5 months) and old (9-16 months) guinea pigs. KEY RESULTS 18β Glycyrrhetinic acid (40 µM), carbenoxolone (50 µM) or octanol (0.5 mM) abolished slow wave activity in prostate tissue from young and old guinea pigs and depolarized membrane potential by approximately 5 mV. These treatments also abolished all contractions in both sets of prostate tissue. These effects were reversed upon washout. Western blot analysis and CX43 immunohistochemistry showed that there was no age-related difference in the expression and distribution of CX43 in prostate tissues. CONCLUSION AND IMPLICATIONS When gap junctional communication via CX43 was disrupted, spontaneous activity was abolished at a cellular and whole tissue level; CX43 is therefore essential for the maintenance of spontaneous slow wave activity and subsequent contractile activity in the guinea pig prostate gland.
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Affiliation(s)
- Anupa Dey
- Medicinal Chemistry & Drug Action, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia
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Nguyen DTT, Dey A, Lang RJ, Ventura S, Exintaris B. Contractility and pacemaker cells in the prostate gland. J Urol 2011; 185:347-51. [PMID: 21075393 DOI: 10.1016/j.juro.2010.09.036] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2010] [Indexed: 11/27/2022]
Abstract
PURPOSE We focused on the current opinion on mechanisms generating stromal tone in the prostate gland. MATERIALS AND METHODS We selected the guinea pig as the main species for investigation since its prostate has a high proportion of smooth muscle that undergoes age related changes similar in many respects to that in humans. The main techniques that we used were tension recording and electrophysiology. RESULTS We previously reported distinct electrical activity and cell types in the prostate, and speculated on their functional roles. We believe that a specialized group of c-kit immunoreactive prostatic interstitial cells that lie between glandular epithelium and smooth muscle stroma have a role similar to that of gastrointestinal interstitial cells of Cajal, generating the pacemaker signal that manifests as slow wave activity and triggers contraction in smooth muscle cells in guinea pig prostates. CONCLUSIONS Since changes in muscle tone are involved in the etiology of age dependent prostate specific conditions such as benign prostatic hyperplasia, knowledge of the electrical properties of the various prostatic cell types and their interactions with each other, with nerves and with the hormonal environment, and how these factors change with age is of considerable medical importance.
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Affiliation(s)
- Dan-Thanh T Nguyen
- Monash Institute of Pharmaceutical Sciences, Parkville and Department of Physiology, Monash University, Clayton, Victoria, Australia
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Abstract
Although the etiology of benign prostatic hyperplasia (BPH) is unknown, various animal models have been used for several decades to identify potential therapeutic approaches. These models can be divided into those measuring smooth muscle tone and those measuring cellular proliferation. Animal models have played an important role in the development of the two drug classes currently approved for the treatment of BPH: the α-adrenoceptor antagonists and the steroid 5-α-reductase inhibitors. However, models measuring prostatic tone have not been particularly useful in the identification of new α-adrenoceptor antagonists having advantages over currently available drugs, and it is not certain that reduction of prostatic smooth muscle tone is responsible for the relief of BPH symptoms. A further limitation with BPH models is that prostatic hyperplasia similar to the human condition does not occur spontaneously or cannot be induced in any suitable animal species. The identification of a more useful BPH model is focused on cellular mechanisms of prostatic growth, looking similarities between humans and experimental animals.
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Affiliation(s)
- J Paul Hieble
- Department of Urology Research, GlaxoSmithKline Pharmaceuticals, King of Prussia, PA, 19406, USA
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Abstract
Interstitial cells of Cajal (ICC)-like cells (ICC-LCs) have been identified in many regions of the urinary tract and male genital organs by immunohistochemical studies and electron microscopy. ICC-LCs are characterized by their spontaneous electrical and Ca2+ signalling and the cellular mechanisms of their generation have been extensively investigated. Spontaneous activity in ICC-LCs rises from the release of internally stored Ca2+ and the opening of Ca2+-activated Cl− channels to generate spontaneous transient depolarizations (STDs) in a manner not fundamentally dependent on Ca2+ influx through L-type voltage-dependent Ca2+ channels. Since urogenital ICC-LCs have been identified by their immunoreactivity to Kit (CD117) antibodies, the often-used specific marker for ICC in the gastrointestinal tract, their functions have been thought likely to be similar. Thus ICC-LCs in the urogenital tract might be expected to act as either electrical pacemaker cells to drive the smooth muscle wall or as intermediaries in neuromuscular transmission. However, present knowledge of the functions of ICC-LCs suggests that their functions are not so predetermined, that their functions may be very region specific, particularly under pathological conditions. In this review, we summarize recent advances in our understanding of the location and function of ICC-LCs in various organs of the urogenital system. We also discuss several unsolved issues regarding the identification, properties and functions of ICC-LCs in various urogenital regions in health and disease.
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Affiliation(s)
- Hikaru Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
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