Novel mechanism of hydrogen sulfide-induced guinea pig urinary bladder smooth muscle contraction: role of BK channels and cholinergic neurotransmission

Abstract

Fernandes VS, Xin W, Petkov GV. Novel mechanism of hydrogen sulfide-induced guinea pig urinary bladder smooth muscle contraction: role of BK channels and cholinergic neurotransmission. Am J Physiol Cell Physiol 309: C107-C116, 2015. First published May 6, 2015; doi:10.1152/ajpcell.00021.2015.-Hydrogen sulfide (H2S) is a key signaling molecule regulating important physiological processes, including smooth muscle function. However, the mechanisms underlying H2S-induced detrusor smooth muscle (DSM) contractions are not well understood. This study investigates the cellular and tissue mechanisms by which H2S regulates DSM contractility, excitatory neurotransmission, and large-conductance voltage-and Ca 2ϩ -activated K ϩ (BK) channels in freshly isolated guinea pig DSM. We used a multidisciplinary experimental approach including isometric DSM tension recordings, colorimetric ACh measurement, Ca 2ϩ imaging, and patch-clamp electrophysiology. In isolated DSM strips, the novel slow release H2S donor, P-(4-methoxyphenyl)-p-4-morpholinylphosphinodithioic acid morpholine salt (GYY4137), significantly increased the spontaneous phasic and nerve-evoked DSM contractions. The blockade of neuronal voltage-gated Na ϩ channels or muscarinic ACh receptors with tetrodotoxin or atropine, respectively, reduced the stimulatory effect of GYY4137 on DSM contractility. GYY4137 increased ACh release from bladder nerves, which was inhibited upon blockade of L-type voltage-gated Ca 2ϩ channels with nifedipine. Furthermore, GYY4137 increased the amplitude of the Ca 2ϩ transients and basal Ca 2ϩ levels in isolated DSM strips. GYY4137 reduced the DSM relaxation induced by the BK channel opener, NS11021. In freshly isolated DSM cells, GYY4137 decreased the amplitude and frequency of transient BK currents recorded in a perforated whole cell configuration and reduced the single BK channel open probability measured in excised inside-out patches. GYY4137 inhibited spontaneous transient hyperpolarizations and depolarized the DSM cell membrane potential. Our results reveal the novel findings that H2S increases spontaneous phasic and nerveevoked DSM contractions by activating ACh release from bladder nerves in combination with a direct inhibition of DSM BK channels. detrusor smooth muscle; GYY4137; acetylcholine; Ca 2ϩ transients DETRUSOR SMOOTH MUSCLE (DSM) is the major component of the urinary bladder wall. Coordinated complex mechanisms involving the contraction and relaxation of DSM facilitate bladder voiding and filling phases (1). DSM contractions in rodents are induced by two main neurotransmitters, ACh and ATP, which are released from parasympathetic nerve endings (1). However, in humans, evidence points to ACh as the major neurotransmitter triggering DSM voiding contractions (7, 34).In experimental animals and humans, activation of muscarinic ACh receptors (mAChRs) depolarizes the DSM cell membrane potential, enhances action potential generation, promotes influx of Ca 2ϩ via L-type voltage-gated Ca 2ϩ (Ca V ) channels, and leads to increased D...

Possible role of hydrogen sulfide as an endogenous relaxation factor in the rat bladder and prostate

“…Therefore, NaHS‐induced contraction in vitro and in vivo might indicate a toxic effect of H 2 S on the bladder. In guinea pigs, the urothelium and lamina propria‐removed detrusor strips were contracted by GYY4137 . In contrast, in this study, rat BL‐D and BL‐T strips contained these components and enzymes related to H 2 S biosynthesis were expressed not only in the smooth muscle layer but also in the urothelium of both bladder tissues.…”

“…To our knowledge, this is the first report to show H 2 S‐induced relaxation of the prostate. Regarding the bladder, both pre‐contracted BL‐D and BL‐T strips were relaxed by NaHS in this study, although site‐specific effects of H 2 S donors are expected, based on previous reports . NaHS has been shown to induce the contraction of Wistar rat detrusor strips at a millimolar orders, which is much higher than the level inducing the relaxation of bladder strips in this study.…”

“…Regarding the bladder, both pre-contracted BL-D and BL-T strips were relaxed by NaHS in this study, although sitespecific effects of H 2 S donors are expected, based on previous reports. [6][7][8] NaHS has been shown to induce the contraction of Wistar rat detrusor strips at a millimolar orders, 6 which is much higher than the level inducing the relaxation of bladder strips in this study. In addition, intravesically instilled NaHS at 1 mM increased the frequency of micturition and reduced voiding volume in Sprague-Dawley rats, 25 while GYY4137, a slowreleasing H 2 S donor, at a submicromolar order prolonged ICI and tended to reduce MVP in Wistar rats in this study.…”

“…Hydrogen sulfide (H 2 S), an endogenous gasotransmitter, has a wide range of biological functions including neuromodulation, vasorelaxation, and cytoprotection . Some groups reported that H 2 S donors induced contraction of the rat and guinea pig detrusor as well as relaxation of the pig bladder neck and human bladder tissues . These findings suggest a possibility that H 2 S has site‐specific effects on the bladder smooth muscle, or that there is a species‐specific difference in H 2 S‐induced effects on bladder contractility.…”

The Role of Nitric Oxide and Hydrogen Sulfide in Urinary Tract Function

“…In guinea pig detrusor, the H 2 S donor GYY4137 enhances the nerve‐mediated and spontaneous phasic detrusor smooth muscle contractions, thus involving direct and indirect regulatory mechanisms. In fact, H 2 S promotes neuronal ACh release, in a Ca 2+ ‐dependent manner, and at the same time, H 2 S regulates the large conductance Ca 2+ ‐activated K + (BK) channels . H 2 S directly diminishes the single BK channel activity in isolated detrusor smooth muscle cells and thus depolarizes the cell membrane, therefore increasing the cytosolic basal Ca 2+ levels and the amplitude of the Ca 2+ transients.…”