Lipid droplets (LDs) are involved in various physiological processes and associated with cancer development, and are regarded as a potential tumor marker for cancer diagnosis. Monitoring LDs is of prior importance to understand their involvement in biological mechanisms and the early detection of cancers. Highly sensitive and specific noninvasive fluorescent probes are particularly desirable for imaging LDs and cancer diagnosis. Herein, according to the high-viscosity and low-polarity microenvironment in LDs, we developed four easily prepared LDsspecific probes based on noncharged merocyanines. Among them, LD-1 absorbs and emits in the near-infrared (NIR) region with a large Stokes shift. Importantly, LD-1 displayed high sensitivity to high viscosity and low polarity, which allowed it to show high LDstargeting ability. In cell imaging, LD-1 successfully probed the changes in LDs in the presence of oleic acid or during ferroptosis and was used to distinguish cancer cells from normal cells.
Limonium bicolor is a typical recretohalophyte with salt glands in the epidermis, which shows maximal growth at moderate salt concentrations (100mM NaCl) but reduced growth in the presence of excess salt (more than 200mM). Jasmonic acid (JA) alleviates the reduced growth of L. bicolor under salt stress; however, the underlying mechanism is unknown. In this study we investigated the effects of exogenous methyl jasmonate (MeJA) application on L. bicolor growth at high NaCl concentrations. We found that treatment with 300mM NaCl led to dramatic inhibition of seedling growth that was significantly alleviated by the application of 0.03mM MeJA, resulting in a biomass close to that of plants not subjected to salt stress. To determine the parameters that correlate with MeJA-induced salt tolerance (assessed as the biomass production in saline and control conditions), we measured 14 physiological parameters relating to ion contents, plasma membrane permeability, photosynthetic parameters, salt gland density, and salt secretion. We identified a correlation between individual indicators and salt tolerance: the most positively correlated indicator was net photosynthetic rate, and the most negatively correlated one was relative electrical conductivity. These findings provide insights into a possible mechanism underlying MeJA-mediated salt stress alleviation.
Mitochondrial viscosity affects metabolite diffusion and mitochondrial metabolism and is associated with many diseases. However, the accuracy of mitochondria-targeting fluorescent probes in measuring viscosity is unsatisfactory because these probes can diffuse from mitochondria during mitophagy with a decreased mitochondrial membrane potential (MMP). To avoid this problem, by incorporating different alkyl side chains into dihydroxanthene fluorophores (denoted as DHX), we developed six near-infrared (NIR) probes for the accurate detection of mitochondrial viscosity, and the sensitivity to viscosity and the mitochondrial targeting and anchoring capability of these probes increased by increasing the alkyl chain length. Among them, DHX-V-C 12 had a highly selective response to viscosity variations with minimum interference from polarity, pH, and other biologically relevant species. Furthermore, DHX-V-C 12 was used to monitor the mitochondrial viscosity changes of HeLa cells treated by ionophores (nystatin, monensin) or under starvation conditions. We hope that this mitochondrial targeting and anchoring strategy based on increasing the alkyl chain length will be a general strategy for the accurate detection of mitochondrial analytes, enabling the accurate study of mitochondrial functions.
Aberrant
mitochondrial viscosity is closely associated with many
diseases and cellular malfunctions. Thus, the development of reliable
methods for monitoring mitochondrial viscosity variations has attracted
considerable attention. Herein, through stepwise structural modulation
of the dihydroxanthene fluorophore (DHX), we developed
three NIR fluorescent probes, named DHX-V-1–3,
for detecting mitochondrial viscosity. Among them, DHX-V-3 displayed the highest signal-to-noise ratio (67-fold) for viscosity
with outstanding selectivity and showed excellent mitochondria targeting
and immobilization ability. At the cellular level, the DHX-V-3 probe was successfully applied to image the mitochondrial viscosity
in live cells upon treatment with lipopolysaccharide (LPS) or nystatin.
Moreover, benefiting from its NIR emission and the increased depth
of tissue imaging, DHX-V-3 demonstrated the ability to
visualize the increased viscosity in LPS-treated mice.
Herein, seven viscosity-sensitive probes were developed via simple structural modification of dicyanoisophorone (DCO)-derived dyes. Among the new dyes, DCO-5 significantly enhances (180-fold) the response signal in highly viscous aqueous media...
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