Hydrogen sulfide is a partially redox-independent activator of the human jejunum Na⁺ channel, Na_v1.5

Abstract

gen sulfide (H 2S) is produced endogenously by L-cysteine metabolism. H 2S modulates several ion channels with an unclear mechanism of action. A possible mechanism is through reduction-oxidation reactions attributable to the redox potential of the sulfur moiety. The aims of this study were to determine the effects of the H 2S donor NaHS on Na V1.5, a voltage-dependent sodium channel expressed in the gastrointestinal tract in human jejunum smooth muscle cells and interstitial cells of Cajal, and to elucidate whether H 2S acts on NaV1.5 by redox reactions. Whole cell Na ϩ currents were recorded in freshly dissociated human jejunum circular myocytes and Na V1.5-transfected human embryonic kidney-293 cells. RT-PCR amplified mRNA for H 2S enzymes cystathionine ␤-synthase and cystathionine ␥-lyase from the human jejunum. NaHS increased native Na ϩ peak currents and shifted the half-point (V 1/2) of steady-state activation and inactivation by ϩ21 Ϯ 2 mV and ϩ15 Ϯ 3 mV, respectively. Similar effects were seen on the heterologously expressed Na V1.5 ␣ subunit with EC50s in the 10 Ϫ4 to 10 Ϫ3 M range. The reducing agent dithiothreitol (DTT) mimicked in part the effects of NaHS by increasing peak current and positively shifting steady-state activation. DTT together with NaHS had an additive effect on steady-state activation but not on peak current, suggesting that the latter may be altered via reduction. Pretreatment with the Hg 2ϩ -conjugated oxidizer thimerosal or the alkylating agent N-ethylmaleimide inhibited or decreased NaHS induction of NaV1.5 peak current. These studies show that H2S activates the gastrointestinal Na ϩ channel, and the mechanism of action of H2S is partially redox independent. patch clamp; intestine; smooth muscle; dithiothreitol; thimerosal HYDROGEN SULFIDE (H 2 S) IS A GAS produced endogenously through L-cysteine metabolism predominantly by two enzymes, cystathione ␥-lyase (CSE) and cystathione ␤-synthase (CBS) (reviewed in Refs. 4,14,19). H 2 S is detected in mammalian tissues and in circulation. Moreover, H 2 S and/or HS Ϫ have been shown to be an active molecule, with clear pharmacological effects on smooth muscle tissues, including relaxation of vascular, corpus cavernosum, uterine, and gastrointestinal smooth muscle.Ion channels regulate contractility of gastrointestinal smooth muscle. H 2 S is known to target various ion channels. Evidence for this involvement of channel activity is strongest for the K ATP channel with some evidence for modulation of BK, Cl Ϫ , and L-type and T-type Ca 2ϩ channels (15,19,42). In human intestinal smooth muscle cells, channels that allow entry of ions into the cell include Na V 1.5 [Na ϩ current: (10, 27, 38, 48), Ca V 1.2 L-type Ca 2ϩ current: (6, 7, 22, 47), Ca V 3.2 T-type Ca 2ϩ current: (8, 47)], and nonselective cation channels (16). The mechanism by which H 2 S modulates ion-channel activity is still largely unknown, and, although the chemistry of H 2 S favors redox modification of proteins, there has been little study of this effect. H 2 S and alterna...

The cardiac sodium current Nav1.5 is functionally expressed in rabbit bronchial smooth muscle cells

“…In cells exposed to DTT alone, there was no tendency for the current to decline with time; indeed, an increase in current was observed over the period of the experiment ( Fig. 6; n ϭ 6), similar to an effect of DTT previously reported (33). In contrast, in cells treated with papain ϩ DTT, the current declined over the period of the experiment ( Fig.…”

“…We also found a similar effect on the Na V 1.5-mediated current in HEK cells (M. A. Hollywood, unpublished observations). In contrast, when DTT was used alone, we observed a small increase in current, consistent with similar findings for Na V 1.5 in jejunal smooth muscle (33). Although the experiments of Janssen (16) did not use papain ϩ DTT, they were done using the perforated-patch configuration of the patch clamp.…”

Hydrogen Sulfide as an Allosteric Modulator of ATP-Sensitive Potassium Channels in Colonic Inflammation

“…L-type Ca 21 channels are inhibited, whereas T-type channels are sensitized (Sun et al, 2008;Matsunami et al, 2012). In the human jejenum smooth muscle cells, H 2 S enhanced Na 1 influx through Na v 1.5 via a redoxindependent mechanism (Strege et al, 2011). S-sulfhydration of cysteine residues by H 2 S has been established as a posttranslational modification altering protein function.…”

BK Channels – Focus on Polyamines, Ethanol/Acetaldehyde and Hydrogen Sulfide (H2S)

“…However, the universal applicability of a K ATP dependent action has been questioned (Kubo et al, 2007;Szabó 2007). In the gastrointestinal tract (human jejunum smooth muscle) H 2 S activates sodium channels in a partially redox dependent manner (Strege et al, 2011). In contrast to other gasotransmittes H 2 S appears not to act on the intracellular signaling pathway guanylyl cyclase (Garthwaite 2010).…”