Due to the redox properties closely related to numerous physiological and pathological processes, biothiols, including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), have received considerable attention in biological science. On account of the important physiological roles of these biothiols, it is of profound significance to develop sensitive and selective detection of biothiols to understand their biological profiles. In this work, we reported an efficient fluorescent probe, PHPQ-SH, for detecting biothiols in vitro and vivo, based on the phenothiazine-HPQ skeleton, with DNBS (2,4-dinitrobenzenesulfonate) as the response unit. Probe PHPQ-SH exhibited brilliant sensing performances toward thiols, including a large Stokes shift (138 nm), excellent sensitivity (for GSH, LOD = 18.3 nM), remarkable fluorescence enhancement (163-fold), low cytotoxicity, rapid response (8 min), and extraordinary selectivity. Finally, the probe PHPQ-SH illustrated herein was capable of responding and visualizing biothiols in MCF-7 cells and zebrafish.

Brain aging is a major factor in cognitive decline and Alzheimer’s disease (AD) progression. Aging-induced microglial senescence critically drives inflammaging and brain aging processes. Nevertheless, the underlying reasons and mechanisms that promote microglial aging remain unclear. This study explores how 27-hydroxycholesterol (27-OHC), a key oxysterol, accelerates brain aging by promoting microglial senescence, iron overload, and neuroinflammation. Clinically, we observed a significant inverse correlation between plasma 27-OHC levels and Mini-Mental State Examination (MMSE) scores in AD patients, accompanied by reduced 24S-OHC concentrations. Experimental studies revealed that 27-OHC administration in mice induced hippocampal-dependent cognitive impairment and anxiety-like behaviors, concurrent with elevated expression of cellular senescence markers (P21, P16, SA-β-Gal) and M1 microglial polarization. In BV-2 cells, 27-OHC disrupted iron homeostasis (DMT1/ferritin/GPX4 dysregulation), elevating ROS and impairing mitochondrial function. Deferoxamine (DFX) mitigated microglial senescence and ferroptosis. These findings establish the 27-OHC-iron axis as a novel therapeutic target for combating cholesterol-driven neurodegeneration.