P2287Hydrogen sulfide (H2S) regulates mitochondrial function, Ca2+ accumulation and mitochondrial permeability transition pore opening in old rat heart

Abstract

Background: Hydrogen sulfide is a novel gasotransmitter and regulator of functions in all system of the body. In cardiovascular system H2S acts as vasodilator, antiapoptotic, antiinflammatory, and proangiogenic agent. To provide its effects, hydrogen sulfide interacts with transcription factors, cellular kinases, membrane proteins and ion channels. It is known that H2S may regulate some processes under aging; in particular it activates SIRT1, interacts with age-related gene Klotho and acts as antioxidant. In mitochondria, which have also age-related alterations, H2S acts as an electrons donor for the electron transport chain (ETC) and protects organelles from ischemic-reperfusion injury. Also, it is known that H2S is produced enzymatically by three different enzymes and two of them are located in mitochondria. The oxidation of H2S also takes place in these organelles. But little is known about its influence on calcium homeostasis of mitochondria, while Ca2+ is important for excitation-contraction coupling, ATP synthesis and opening of mitochondrial permeability transition pore, which leads to the development of apoptosis. Material and methods: In our research we used adult (5-7 months) and old (22-24 months) rats. Mitochondria were isolated by differential centrifugation method. Calcium accumulation in isolated organelles was studied by flow cytometry analysis. MPTP opening we registered spectrophotometrically as mitochondrial swelling. The functions of electron transport chain (ETC) were estimated using oxygraph high-resolution respirometry. Results: It was shown that mitochondria, isolated from old hearts had increased ability to accumulate calcium from the outside environment, on first three minutes by 27% max compared to mitochondria, isolated from adult cardiac tissue. Furthermore, exogenous H2S in concentration 10-6-10-7 mol/l elevates mitochondria calcium capacity in cardiac tissue both in adult and in old rats. However, exogenous H2S also prevents MPTP opening in concentration-dependent manner, which indicates that gasotransmitter regulates both input and output of mitochondrial calcium. Also inhibition of mitochondrial H2S-synthesis enzyme 3-MST in vivo increases the sensitivity of MPTP to Ca2+, decreases the rate of oxygen consumption in states 2-4 by Chance and respiratory control ratio. The use of 3-MST inhibitor in vitro causes significantly dose-dependent increase of Ca2+- induced mitochondrial swelling in adult and old rat heart. Conclusions: H2S regulates mitochondrial function in old cardiac tissue trough the effect on ETC, increase of Ca2+ accumulation and inhibition of MPTP opening.