Dual-Response Functionalized Mitochondrial Fluorescent Probe for a Double Whammy Monitoring of Hypochlorite and Sulfur Dioxide in Heat Shock via Time Scales
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Heat shock seriously affects the normal functioning of an organism and can lead to damage and even death in severe cases. To prevent or treat heat shock-related diseases, we require a better understanding of the mechanism of thermocytotoxicity. Here, we designed a functionalized dual-response fluorescent probe (HCy-SO2-HClO) that could individually or simultaneously detect hypochlorous acid (HClO) and sulfur dioxide (SO2) without interfering with each other and achieved the simultaneous tracing of both during the heat shock process for the first time. The introduction of the sulfonate group greatly increased the water solubility of the probe. Furthermore, the probe could effectively accumulate in the mitochondrial region. HCy-SO2-HClO could respond to HClO and SO2 within 10 s and 20 min, respectively, realizing a double whammy detection of both on the time scale. HCy-SO2-HClO exhibited high specificity and sensitivity for HClO and SO2. The highly biocompatible probe HCy-SO2-HClO successfully achieved the detection of endogenous and exogenous SO2 and HClO in living cells and in zebrafish. Moreover, the simultaneous detection of HClO and SO2 in heat shock cells and mouse intestines was realized for the first time. This probe has achieved the detection of dual markers, which enhanced the accuracy and precision of disease detection and could serve as an effective research tool to prevent heat stroke-related diseases.
Heat shock is an imbalance in thermoregulation caused by exposure to high temperatures, which in turn causes dysfunction of the central nervous and circulatory systems.
(1,2) Moreover, if heat shock is not treated in a timely manner, it may cause convulsions, kidney damage, or even death.
(3−5) Although there are heat shock proteins in the body, individuals with low immunity or certain genetic diseases are prone to heat stroke, which can have a mortality rate of approximately 40%.
(6) Therefore, understanding the pathogenesis of heat shock is critical. Currently, some reports demonstrate that mitochondrial dysfunction is induced when a person is exposed to high temperatures, leading to the disruption of intracellular redox homeostasis.
(7,8) Despite the severe impact of heat shock on health, research on its specific pathogenesis is relatively scarce, especially in terms of mitochondrial dysfunction and the disruption of intracellular redox homeostasis.
Hypochlorous acid (HClO), as a key intracellular active substance, participates in intracellular signal transduction and affects the growth, differentiation, and reproduction of cells.
(9−11) In addition, it is also an important component of the body’s immune system, providing an effective defense against bacteria and viruses.
(12−14) However, an imbalance of intracellular HClO may trigger a series of diseases, such as inflammatory, neurological, cardiovascular, and cancer.
(15−17) Several recent reports exhibit that HClO is strongly associated with heat stroke (an inflammation-associated disease),
(18,19) so investigating the important role that HClO plays in the balance of cellular redox homeostasis may help to understand heat shock diseases in greater depth. In contrast, sulfur dioxide (SO
2), an indispensable intracellular antioxidant, assumes a crucial function in maintaining cellular homeostasis, preserving vasodilation, regulating cardiovascular disease, and combating blood pressure.
(20−22) However, abnormal SO
2 not only may cause respiratory illnesses, for instance, bronchitis and chronic obstructive pulmonary disease, but also may lead to organ damage.
(23,24) Therefore, the real-time measurement of SO
2 in organisms is helpful in understanding its physiological role. Although some research has correlated SO
2 or HClO with heat shock diseases,
(19,25,26) simultaneous studies of both in heat shock diseases have not been reported. Therefore, we hope to further explore the link between intracellular redox homeostasis and heat shock through the fluctuation of intracellular HClO and SO
2 levels in order to better prevent or treat heat shock diseases.
Currently, numerous methods for detecting HClO and SO
2 have been developed, such as chromatography, colorimetry, and electrochemistry, among others.
(27−30) Although these methods are able to accurately determine changes in HClO and SO
2 levels, they are not well-suited for real-time detection in biological systems due to their lengthy preprocessing or analysis requirements and the potential for damaging biological tissues. Fluorescence imaging technology, with its high sensitivity, high resolution, and capability for noninvasive real-time detection of specific substances within biological systems, has gained widespread popularity.
(31−34) Nowadays, fluorescence imaging technology is widely applied in biomedicine, disease diagnosis, surgical navigation, and environmental science.
(35,36) Compared with single-response fluorescent probes, multiresponse fluorescent probes can obtain more effective information and avoid false-positive signals, thus improving the accuracy of detection and revealing the role of relevant substances in diseases, which is significant in promoting the use of fluorescent probes in biomedical fields.
(37−39) Recently, several reviews have summarized the trends in dual-response probes.
(40−42) Also, fluorescent probes for the dual response of HClO and SO
2 have been developed.
(43−45) However, most of the probes are not capable of detection both individually and simultaneously without interference.
Here, we proposed a mitochondria-targeted dual-responsive fluorescent probe (HCy-SO2-HClO) aimed at visualizing intracellular HClO and SO2. The probe was capable of efficiently and simultaneously monitoring HClO and SO2 through two different fluorescence channels across various time scales, effectively avoiding the problem of inaccurate detection of one substance due to the consumption of the probe by another substance. HCy-SO2-HClO exhibited high sensitivity and specificity for these two substances while also possessing excellent biocompatibility. Furthermore, we further delved into the interrelationship between intracellular redox homeostasis and the heat shock response via monitoring the dynamic changes of HClO and SO2. Notably, we successfully achieved the dual monitoring of HClO and SO2 for the first time in heat shock-treated cells and mouse models, suggesting that these two substances could serve as key biomarkers for heat shock. This finding not only provided important clues for insights into the biological mechanisms of heat shock but also offered a scientific basis and potential therapeutic strategies to prevent or treat heat shock-related diseases.
