Molecular Optimization of a Near-Infrared Fluorogenic Probe for Hydrogen Polysulfide Imaging in Acute Liver Injury

Hydrogen polysulfides (H₂S<i>_n</i>), a key reactive sulfur species, play pivotal roles in cellular signaling, antioxidative stress, and cell death regulation. Revealing the dynamic changes of H₂S<i>_n</i> levels <i>in vivo</i> is crucial for elucidating its physiological functions. However, real-time detection of H₂S<i>_n</i> <i>in vivo</i> faces significant challenges due to its inherent instability. In this study, we screened a near-infrared fluorogenic (NIRF) probe DCICl-H₂S_n for the detection of H₂S<i>_n</i> in cells and mice models. This probe employed a dicyanoisophorone scaffold functionalized with ortho-NO₂ substituted phenyl sulfonate groups, which endowed it with exceptional photophysical properties and high specificity toward H₂S<i>_n</i>. Upon reaction with H₂S<i>_n</i>, DCICl-H₂S<i>_n</i> emitted a fluorescent "turn-on" signal at 675 nm. Benefiting from its excellent optical properties, DCICl-H₂S<i>_n</i> enabled monitoring of both exogenous and endogenous H₂S<i>_n</i> level changes in live cells. Leveraging DCICl-H₂S<i>_n</i>, we explored the role of H₂S<i>_n</i> in APAP or CCl₄-induced acute liver injury (ALI) mice models. The results revealed a negative correlation between H₂S<i>_n</i> levels and the severity of liver injury, suggesting that H₂S<i>_n</i> could be used as a potential biomarker for assessing the severity of ALI. Moreover, oral administration of silybin (SLB) significantly reduced liver injury and up-regulated H₂S<i>_n</i> levels. The present probe DCICl-H₂S<i>_n</i> proved to be an effective tool for investigating the dynamic changes of H₂S<i>_n</i>, which could help to uncover the molecular mechanisms of liver injury.