Hydrogen Sulfide Inhibits L-Type Calcium Currents Depending upon the Protein Sulfhydryl State in Rat Cardiomyocytes

Abstract

Hydrogen sulfide (H2S) is a novel gasotransmitter that inhibits L-type calcium currents (I Ca, L). However, the underlying molecular mechanisms are unclear. In particular, the targeting site in the L-type calcium channel where H2S functions remains unknown. The study was designed to investigate if the sulfhydryl group could be the possible targeting site in the L-type calcium channel in rat cardiomyocytes. Cardiac function was measured in isolated perfused rat hearts. The L-type calcium currents were recorded by using a whole cell voltage clamp technique on the isolated cardiomyocytes. The L-type calcium channel containing free sulfhydryl groups in H9C2 cells were measured by using Western blot. The results showed that sodium hydrosulfide (NaHS, an H2S donor) produced a negative inotropic effect on cardiac function, which could be partly inhibited by the oxidant sulfhydryl modifier diamide (DM). H2S donor inhibited the peak amplitude of I Ca, L in a concentration-dependent manner. However, dithiothreitol (DTT), a reducing sulfhydryl modifier markedly reversed the H2S donor-induced inhibition of I Ca, L in cardiomyocytes. In contrast, in the presence of DM, H2S donor could not alter cardiac function and L type calcium currents. After the isolated rat heart or the cardiomyocytes were treated with DTT, NaHS could markedly alter cardiac function and L-type calcium currents in cardiomyocytes. Furthermore, NaHS could decrease the functional free sulfhydryl group in the L-type Ca2+ channel, which could be reversed by thiol reductant, either DTT or reduced glutathione. Therefore, our results suggest that H2S might inhibit L-type calcium currents depending on the sulfhydryl group in rat cardiomyocytes.

Role of Calcium Channels in the Protective Effect of Hydrogen Sulfide in Rat Cardiomyoblasts

“…On the other hand, no significant differences were detected between NaHS-insensitive cells treated or untreated with Nifedipine (Fig. 2A) in agreement with an earlier report [23]. In particular, our data suggest that H 2 S-sensitive L-type VOCCs are active in resting conditions in a subpopulation of H9c2 cells.…”

Targeting Calcium Channels to Block Tumor Vascularization

“…More specifically, NaHS (up to 1 mM) causes a dose-dependent reduction in the Ca 2+ current peak. This effect is only partial: the current density diminishes by 50% at 1 mM NaHS [34]. The mechanism could involve a direct modification of Cav free sulfhydryl groups [34].…”

“…Indeed, whole patch clamp experiments in rat cardiomyocytes revealed that NaHS negatively modulates L-type Ca 2+ channels composed by the CaV1.2 subunits [12,30,34]. More specifically, NaHS (up to 1 mM) causes a dose-dependent reduction in the Ca 2+ current peak.…”

Hydrogen Sulfide, a Potential Cardioprotective Gas Activating a Life Span Regulator

“…2,3) Some mechanisms have been proposed by which H2S exerts cardioprotective effects, including reduction of apoptosis, preservation of mitochondrial function, anti-inflammatory responses, and angiogenic actions. [4][5][6][7] However, the specific mechanism of cardioprotection mediated by H 2 S in I/R injury is still largely unknown.…”