A near-infrared fluorescent probe for observing thionitrous acid-mediated hydrogen polysulfides formation and fluctuation in cells and in vivo under hypoxia stress

Hydrogen polysulfides (H2Sn, n>1) as important intracellular reactive sulfur species (RSS) are believe to be responsible for cellular redox regulation. Lots of researches about H2Sn focusing on their formation, detection and bio-function in signalling regulation are spring up but with poor understanding, especially for biosynthesis and bio-function remain complicated and confusing. Recent studies reveal that thionitrous acid (HSNO) as potential intermediate linked signalling molecules of nitrogenous and sulphureous during biotic redox regulation. However, there are limited evidences for supporting the interrelation and bioeffect between HSNO and H2Sn. Herein, we have successfully designed a near-infrared (NIR) fluorescent probe ((2-fluoro-5-nitrobenzoyl)oxy)-Benzo[e]cyanine (BCy-FN) for detection H2Sn and for the first time observing HSNO-mediated H2Sn generation in cells and in vivo. The probe is harvested from fluorophore BCy-Keto and 2-fluoro-5-nitrobenzoic acid in one step, featuring mitochondria localization. The unique Enol-Keto tautomerization of fluorophore enables the probe becomes more sensitive and has powerful application. Hypoxia model has been constructed and powerfully interpreted the pretreatment of HSNO for zebrafish hypoxia process effectively improves H2Sn levels and defends the hypoxia induced brain damage. We believe the present studies will help environmentalist and biologist for better understanding of biosynthesis and bio-function in HSNO-mediated H2Sn formation process under hypoxia stress.