Chloride channels mediate sodium sulphide‐induced relaxation in rat uteri

Abstract

BACKGROUND AND PURPOSEHydrogen sulphide reduces uterine contractility and is of potential interest as a treatment for uterine disorders. The aim of this study was to explore the mechanism of sodium sulphide (Na2S)-induced relaxation of rat uterus, investigate the importance of redox effects and ion channel-mediated mechanisms, and any interactions between these two mechanisms. EXPERIMENTAL APPROACHOrgan bath studies were employed to assess the pharmacological effects of Na2S in uterine strips by exposing them to Na2S with or without Cl − channel blockers (DIDS, NFA, IAA-94, T16Ainh-A01, TA), raised KCl (15 and 75 mM), K + channel inhibitors (glibenclamide, TEA, 4-AP), L-type Ca 2+ channel activator (S-Bay K 8644), propranolol and methylene blue. The activities of antioxidant enzymes were measured in homogenates of treated uteri. The expression of bestrophin channel 1 (BEST-1) was determined by Western blotting and RT-PCR. KEY RESULTSNa2S caused concentration-dependent reversible relaxation of spontaneously active and calcium-treated uteri, affecting both amplitude and frequency of contractions. Uteri exposed to 75 mM KCl were less sensitive to Na2S compared with uteri in 15 mM KCl. Na2S-induced relaxations were abolished by DIDS, but unaffected by other modulators or by the absence of extracellular HCO3 − , suggesting the involvement of chloride ion channels. Na2S in combination with different modulators provoked specific changes in the anti-oxidant profiles of uteri. The expression of BEST-1, both mRNA and protein, was demonstrated in rat uteri. CONCLUSIONS AND IMPLICATIONSThe relaxant effects of Na2S in rat uteri are mediated mainly via a DIDS-sensitive Cl − -pathway. Components of the relaxation are redox-and Ca 2+ -dependent.Abbreviations ANO (TMEM16), anoctamin chloride channels; BEST, bestrophin chloride channels; CaCCs, calcium-activated chloride channels; CAT, catalase; GR, glutathione reductase; GSH-Px, glutathione peroxidase; KATP, ATP-sensitive K + channel; NFA, niflumic acid; ROS, reactive oxygen species IntroductionThe smooth muscle layer of the uterus, the myometrium, undergoes profound remodelling that allows rapid changes to occur in different physiological (and pathophysiological) conditions. In a non-pregnant state, myometrial activity is at its highest level during oestrus (Crane and Martin, 1991). Abnormal contractility can underlie disorders such as dysmenorrhea and endometriosis. Several potential inhibitors of myometrial activity have been identified: CGRP (Anouar et al., 1998), NO (Buxton et al., 2001) and carbon monoxide (CO; Acevedo and Ahmed, 1998). Endogenously produced hydrogen sulphide (H2S), which, together with NO and CO, is a recognized gasotransmitter, also appears to be a signalling molecule in rat uterus. Both enzymes responsible for its endogenous production (cystathionine β-synthase and cystathionine γ-lyase) were identified in all rat intrauterine tissues (Patel et al., 2009). Hydrogen sulphide is a potent inhibitor of spontaneous contractions of the pregnant myometrium ...

Trophic sympathetic influence weakens pro-contractile role of Cl− channels in rat arteries during postnatal maturation

“…We used two different blockers, DIDS and MONNA. DIDS is a conventional blocker widely used to inhibit Cl − conductance 31,32 . Structurally different from DIDS, MONNA was suggested to be a putative TMEM16A channel blocker 27 .…”

Gasotransmitters in pregnancy: from conception to uterine involution†

“…K ATP is active when the ATP:ADP ratio decreases, and increased K + permeability maintains uterine myocyte hyperpolarization and quiescence [259,260]. Cysteine and sulfide donors activate myometrial K ATP via persulfidation, but tocolysis is sensitive to the K ATP inhibitor glibenclamide [9,239,261]. The mechanism may be more complex, as antagonists of myometrial Cl Ca channels (which conduct outward Cl − current and are therefore depolarizing/procontractile) [262,263] paradoxically inhibit sulfide relaxation of rat myometrium [9].…”

“…Gasotransmitters participate in myriad aspects of pregnancy, and signaling can vary by gestational age. Genetic or pharmacologic impairment of gasotransmitter biosynthesis adversely impacts placentation [4,5], maternal-and feto-placental hemodynamic adaptations of pregnancy [6,7], the timing of parturition [8][9][10], and long-term neonatal outcomes [11].…”

Calcium-Activated Chloride Channels in Myometrial and Vascular Smooth Muscle

“…Both cGMP-dependent and classical I ClCa currents are expressed in spontaneously active portal vein (Matchkov et al, 2005). This differs from myometrium, where only classical CaCC are expressed and BEST-3 has not been reported, but BEST-1 has (Mijuskovic et al, 2015). Thus, I ClCaGMP is a feature of VSM -irrespective of it being phasic or tonic.…”