Slow release of isotopically labelled hydrogen sulfide to track its location in animals and tissues

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Hydrogen sulfide is a key gasotransmitter in human cells, and the addition of exogenous hydrogen sulfide at single micromolar or lower concentrations is actively being explored for clinical applications. Three drugs based on the release of hydrogen sulfide are in phase I or II clinical trials. Although the location of where exogenous hydrogen sulfide partitions inside of cells can be tracked using several two-step tagging methods, tracking the location of exogenous hydrogen sulfide in tissue or animal models cannot be done. This limits the development of therapies based on the slow release of hydrogen sulfide because it cannot be tracked once it is administered to an animal or tissue. The long-term goal is to investigate the mechanisms of how exogenous hydrogen sulfide is transported and accumulates in the body. The overall objective of this application is to synthesize chemicals widely used to add exogenous hydrogen sulfide, so these chemicals release radioactive 35S labelled hydrogen sulfide which will allow it to be tracked on a tissue and animal level for the first time. The central hypothesis is that 35S labeled sulfate can be converted into several key chemicals that release hydrogen sulfide in response to different stimuli, and that the concentration and amount of 35S labelled hydrogen sulfide can be rationally controlled. This proposal builds on prior work by others that used 35S labelled methionine, cysteine, and other chemicals to investigate where they partitioned in animal and tissue models using scintillation and light microscopy autoradiography. Despite the success of the use of these 35S labelled chemicals, no one has described the synthesis of chemicals that slowly release 35S labelled hydrogen sulfide despite its importance in medicine. The rationale for completing this work is that it will allow scientists to track where exogenous hydrogen sulfide partitions in tissue and animal models for the first time to thoroughly investigate the origins of the effect of exogenous hydrogen sulfide in treating diseases in animal models. The central hypothesis will be tested by pursuing two specific aims: 1) Identify the reactions to synthesize GYY- 4137, dialkyldithiophosphates, caged perthiols, and DTT to release 35S labelled hydrogen sulfide at controlled rates and doses; and 2) Identify the reactions to synthesize diallyl trisulfide and trisulfides of cysteine and glutathione that will release 35S labelled hydrogen sulfide in the presence of thiols. The research proposed in this application is innovative, in the applicant's opinion, because it challenges the status quo of tracking the location of exogenous hydrogen sulfide by the synthesis of chemicals that will allow it to be tracked on the tissue and animal levels for the first time. This proposal combines scintillation and light microscopy autoradiography that were used to image 35S labelled amino acids with the first synthesis of chemicals to slowly release 35S labelled hydrogen sulfide to solve a key problem in biology. The proposed research is significant because it will advance research already underway to understand the effects of exogenous H2S and to more rapidly develop clinical applications of these chemicals.