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pH-Dominated Selective Imaging of Lipid Droplets and Mitochondria via a Polarity-Reversible Ratiometric Fluorescent
Qingqing Bai1, Chaojie Yang2, Majun Yang2
1Innovative Institute of Chinese Medicine and Pharmacy, Chengdu University of Traditional Chinese Medicine, Chengdu 611137, P. R. China.
Abstract:
Elucidating the intrinsic relationship between mitochondrial pH (pHm) fluctuation and lipid droplets (LDs) formation is vital in cell physiology. The development of small-molecular fluorescent probes for discrimination and simultaneous visualization of pHm fluctuation toward LDs has not yet been reported. In this work, utilizing pH-driven polarity-reversible hemicyanine and rhodamine derivatives, a multifunctional fluorescent probe is developed for selectively identifying mitochondria and LDs under specific pH values via dual-emission channels. This rapid-response probe, Hcy-Rh, has two distinct chemical structures under acidic and alkaline circumstances. In acidic conditions, Hcy-Rh exhibits good hydrophilicity that can target mitochondria and display an intense red fluorescence. Conversely, the probe becomes lipophilic under weakly alkaline conditions and targets LDs, showing a strong blue emission. In this manner, Hcy-Rh can selectively label mitochondria and LDs, exhibiting red and blue fluorescence, respectively. Moreover, this ratiometric probe is applied to map pHm changes in living cells under the stimulus with FCCP, NAC, and H2O2. The interplay of LD-mitochondria under oleic acid treatment and starvation-induced autophagy has been studied using this probe at different pH values. In a word, Hcy-Rh is a potential candidate for further exploring mitochondria-LD interaction mechanisms under pHm fluctuation. Moreover, the polarity-dependent strategy is valuable for designing other functional biological probes in imaging multiple organelles.
Insights
Researchers developed a novel fluorescent probe, Hcy-Rh, to simultaneously visualize mitochondria and lipid droplets by changing color with pH. This tool aids in understanding cellular processes and organelle interactions under varying pH conditions.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Imaging
Background:
- Mitochondrial pH (pHm) fluctuation and lipid droplet (LD) formation are crucial in cell physiology.
- Simultaneous visualization of pHm and LDs using fluorescent probes is currently lacking.
Purpose of the Study:
- To develop a multifunctional fluorescent probe for selective and simultaneous visualization of mitochondria and LDs.
- To investigate the relationship between pHm changes and LD formation in living cells.
Main Methods:
- Utilized pH-driven polarity-reversible hemicyanine and rhodamine derivatives to create the Hcy-Rh probe.
- Employed dual-emission channels for distinct fluorescence signals from mitochondria (red) and LDs (blue).
- Applied the probe to map pHm changes in cells stimulated with FCCP, NAC, and H2O2, and studied LD-mitochondria interplay under oleic acid treatment and starvation.
Main Results:
- The Hcy-Rh probe selectively targets mitochondria in acidic conditions (red fluorescence) and LDs in weakly alkaline conditions (blue fluorescence).
- The probe exhibits rapid response and ratiometric imaging capabilities for pHm mapping.
- Demonstrated the probe's utility in studying mitochondria-LD interactions during oleic acid treatment and starvation-induced autophagy.
Conclusions:
- Hcy-Rh is a valuable tool for exploring mitochondria-LD interaction mechanisms under pHm fluctuation.
- The polarity-dependent design strategy is applicable for creating novel functional probes for multi-organelle imaging.
