Shining Light on the Invisible: Fluorescent Detection of Reactive Oxygen Species

Background Reactive oxygen species (ROS) play an important role in cell signaling and homeostasis. However, overproduction of ROS leads to oxidative stress, as well as other related diseases, including cancer, neurodegenerative diseases, and cardiovascular disorders. Conventional ROS detection methods are limited by their low sensitivity and low specificity in real-time measurements. Fluorescent probes can offer valuable tools to detect ROS in biological systems. This study is focused on the detection of ROS formation during hypoxia and reoxygenation. Methods We used fluorescence detection techniques to study ROS in isolated rodent skeletal muscle models, which were exposed to alternating hyperoxia and hypoxia. To assess hydrogen peroxide (H2O2) and superoxide formation, dihydrofluorescein (Hfluor) and hydroethidine (DHE) probes were used, respectively. Results Oxygenation Effects: During hypoxia, tissues loaded with Hfluor or DHE probes showed a significant increase in fluorescence, indicating elevated production of H2O2 and superoxide. Upon reoxygenation, the fluorescence signals declined, suggesting that oxygen availability is related to ROS levels. Oxidized Probe Fluorescence: To validate the specificity of the probes, experiments using the oxidized forms of Hfluor and DHE were conducted. Those control experiments exhibited fluorescence patterns similar to those during hypoxia, but the signals cannot be blocked by the antioxidant. Antioxidant Trials: Exogenously introduced ROS-specific antioxidants were effective in reducing hypoxia-fluorescence in hypoxic tissues. This supports that the increased fluorescence during hypoxia is due to ROS production, as antioxidants neutralized the ROS and decreased fluorescence. Conclusion In this study, decreased oxygen levels induce hydrogen peroxide formation in skeletal muscles, suggesting the key role of ROS during hypoxia and reoxygenation. Findings suggest that methodological approaches should be focused on the real-time ROS signals, and such information can help in the understanding of muscle responses to different oxygen environments.