Abstract
Ferroptosis is closely associated with cancer, neurodegenerative diseases and ischemia-reperfusion injury and the detection of its pathological process is very important for early disease diagnosis. Fluorescence based sensing technologies have become excellent tools due to the real-time detection of cellular physiological or pathological processes. However, to date the detection of ferroptosis using reducing substances as markers has not been achieved since the reducing substances are not only present at extremely low concentrations during ferroptosis but also play a key role in the further development of ferroptosis. Significantly, sensors for reducing substances usually consume reducing substances, instigating a redox imbalance, which further aggravates the progression of ferroptosis. In this work, a H2S triggered and H2S releasing near-infrared fluorescent probe (HL-H2S) was developed for the high-fidelity in situ imaging of ferroptosis. In the imaging process, HL-H2S consumes H2S and releases carbonyl sulfide, which is then catalyzed by carbonic anhydrase to produce H2S. Importantly, this strategy does not intensify ferroptosis since it avoids disruption of the redox homeostasis. Furthermore, using erastin as an inducer for ferroptosis, the observed trends for Fe2+, MDA, and GSH, indicate that the introduction of the HL-H2S probe does not exacerbate ferroptosis. In contrast, ferroptosis progression was significantly promoted when the release of H2S from HL-H2S was inhibited using AZ. These results indicate that the H2S triggered and H2S releasing fluorescent probe did not interfere with the progression of ferroptosis, thus enabling high-fidelity in situ imaging of ferroptosis.
Highlights
When HL-H2S responds to H2S, Carbonyl sul de (COS) is released through 1,6-elimination, which is catalyzed by carbonic anhydrase (CA) to release H2S
HL-H2S could be used to detect the ferroptosis of cells of high viscosity, but there was no signi cant change in normal cells.[6,35]
The results indicated that the changes of H2S monitored using methylene blue (MB) were consistent with the uorescence results obtained for the probe, indicating that under these conditions HL-H2S can be catalyzed by CA to produce H2S (Fig. S8c†), which con rms that HL-H2S can release H2S in the presence of CA
Summary
With strong tissue penetration ability, minor cell and tissue damage, and low interference from auto uorescence, nearinfrared (NIR) uorescence imaging is gradually replacing traditional uorescence imaging as one of the most popular tools for real-time, in situ, visual tracking of biomolecules.[1,2,3,4,5] The recent success of in situ tracking of ferroptosis (an irondependent oxidative stress) based on NIR uorescence sensing has provided a basis for the treatment and drug design for neurodegenerative diseases, acute kidney injuries, and malignant tumors.[6,7] the current NIR uorescent probes used to monitor ferroptosis progression detect oxidizing substances such as lipid ROS and free ferrous ions, but the detection of reducing substances is rarely reported.[6,8,9] Compared with oxidizing substances, reducing substances such as GSH and GPX4 are considered to be the key biomarkers to directly monitor ferroptosis, because ferroptosis can be regulated by the XcÀ/GSH/GPX4 system by controlling the generation of phospholipid hydroperoxides.[10]. Intracellular H2S content and viscosity levels were regulated using NaHS (10 mM) to release H2S, viscosity inducer monensin[41] (10 mM), and different cell incubation temperatures (25 C and 4 C) since lowering the temperature increases the intracellular viscosity.[42,43] As shown in Fig. S10a and b,† the red channel uorescence intensity of the groups with NaHS or monensin were slightly higher than those of the control group.
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