Assessment of H2S in vivo using the newly developed mitochondria-targeted mass spectrometry probe MitoA

Hydrogen sulfide (H2S) is produced endogenously in vivo and has multiple effects on signaling pathways and cell function. Mitochondria can be both an H2S source and sink, and many of the biological effects of H2S relate to its interactions with mitochondria. However, the significance of mitochondrial H2S is uncertain, in part due to the difficulty of assessing changes in its concentration in vivo. Although a number of fluorescent H2S probes have been developed these are best suited to cells in culture and cannot be used in vivo. To address this unmet need we have developed a mitochondria-targeted H2S probe, MitoA, which can be used to assess relative changes in mitochondrial H2S levels in vivo. MitoA comprises a lipophilic triphenylphosphonium (TPP) cation coupled to an aryl azide. The TPP cation leads to the accumulation of MitoA inside mitochondria within tissues in vivo. There, the aryl azido group reacts with H2S to form an aryl amine (MitoN). The extent of conversion of MitoA to MitoN thus gives an indication of the levels of mitochondrial H2S in vivo. Both compounds can be detected sensitively by liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis of the tissues, and quantified relative to deuterated internal standards. Here we describe the synthesis and characterization of MitoA and show that it can be used to assess changes in mitochondrial H2S levels in vivo. As a proof of principle we used MitoA to show that H2S levels increase in vivo during myocardial ischemia.