P75: H2S induced S-nitrosoglutathione decomposition – Effect of thiols, ph and oxygen

Abstract

Hydrogen sulfide (H 2 S) and nitric oxide (NO) have some similar biological properties. Interaction of NO with sulfhydryl group of thiols leads to the formation of Snitrosothiols, the biological reservoirs of NO. Snitrosoglutathione (GSNO) is the most abundant and relatively stable S-nitrosothiol. We studied the effect of low molecular thiols, pH and oxygen on the reaction of H 2 S donor Na 2 S (0.2 mM) with GSNO (0.2 mM) by time resolved UV–vis absorption spectroscopy. We found that this decomposition is pH dependent, the maximum rate is at physiological pH 7.4, higher or lower pH decelerated the reaction (7.4 > 8.0 ≫ 6.0). Next we studied the effect of low molecular thiols - L-cysteine (Cys), N-acetyl-L-cysteine (NAC) and reduced glutathione (GSH) on this reaction. At physiological and alkaline pH (7.4 and 8.0), they had a deceleration effect (NAC > GSH > Cys). At acidic pH (6.0), they had the reverse effect – acceleration of GSNO decomposition (Cys > GSH > NAC). Oxidized thiols (oxidized glutathione or cystine) had no effect at any studied pH values. Measurements in nitrogen deaerated solutions revealed that oxygen is not necessary for H 2 S induced GSNO decomposition, although it slightly accelerates the reaction. Presented results can contribute to understanding of the involvement of H 2 S and low molecular thiols in NO signaling pathways. This work was supported by VEGA 2/0050/13 and APVV-0074-11.