In vivo detection of hydrogen sulfide in the brain of live mouse: application in neuroinflammation models

Hydrogen sulfide (Hsub2/subS) plays important roles in brain pathophysiology. However, nuclear imaging probes for the in vivo detection of brain Hsub2/subS in living animals have not been developed. Here, we report the first nuclear imaging probe that enables in vivo imaging of endogenous Hsub2/subS in the brain of live mice.Utilizing a bis(thiosemicarbazone) backbone, a fluorescent ATSM-FITC conjugate was synthesized. Its copper complex, Cu(ATSM-FITC) was thoroughly tested as a biosensor for Hsub2/subS. The same ATSM-FITC ligand was quantitatively labeled with [sup64/supCu]CuClsub2/subto obtain a radioactive [sup64/supCu][Cu(ATSM-FITC)] imaging probe. Biodistribution and positron emission tomography (PET) imaging studies were performed in healthy mice and neuroinflammation models.The Cu(ATSM-FITC) complex reacts instantly with Hsub2/subS to release CuS and becomes fluorescent. It showed excellent reactivity, sensitivity, and selectivity to Hsub2/subS. Endogenous Hsub2/subS levels in living cells were successfully detected by fluorescence microscopy. Exceptionally high brain uptake of [sup64/supCu][Cu(ATSM-FITC)] (gt; 9% ID/g) was observed in biodistribution and PET imaging studies. Subtle changes in brain Hsub2/subS concentrations in live mice were accurately detected by quantitative PET imaging. Due to its dual modality feature, increased Hsub2/subS levels in neuroinflammation models were characterized at the subcellular level by fluorescence imaging and at the whole-body scale by PET imaging.Our biosensor can be readily utilized to study brain Hsub2/subS function in live animal models and shows great potential as a novel imaging agent for diagnosing brain diseases.