High-throughput determination of glutathione and reactive oxygen species in single cells based on fluorescence images in a microchannel

Insight into the Vacuolar Compartmentalization Process and the Effect Glutathione Regulation to This Process in the Hyperaccumulator Plant Solanum nigrum L

Vacuole compartmentalization plays an important role in the storage of heavy metals in hyperaccumulators. Is the vacuolar compartmentation a simple shielding process or a dynamic process that continuously consumes cell sap resources? How does glutathione affect the process of vacuolar compartmentalization? These unknown questions are very important to understand the mechanism of vacuole compartmentalization and can provide a guide for the design of hyperaccumulator plants by genetic engineering. Therefore, this study explored the enzyme activities, total cadmium, Cd²⁺, glutathione, oxidized glutathione, and reactive oxygen species contents in protoplasts and vacuoles of leaf cells in Solanum nigrum L. through subcellular separation. The results showed that vacuolar compartmentalization was a dynamic process that actively induced the related substances produced by cell sap to enter the vacuole for detoxification. When regulating the decreased glutathione content with buthionine sulfoximine, the total cadmium and combined cadmium in protoplasm decreased significantly, but the vacuole still maintained a high proportion of cadmium content and stable ROS content, which indicated that various external resources were preferentially used to maintain cadmium storage and homeostasis in vacuole rather than outside vacuole. These findings could guide the use of genetic engineering to design hyperaccumulator plants.

Visualization and quantification of cadmium accumulation, chelation and antioxidation during the process of vacuolar compartmentalization in the hyperaccumulator plant Solanum nigrum L

Hyperaccumulators store metals in the vacuoles of leaf cells. To investigate the role of vacuolar compartmentalization in Cd accumulation, chelation and induced antioxidation, we quantified the amounts of total cadmium (Cd), Cd²⁺, glutathione (GSH) and reactive oxygen species (ROS) in leaf cells of Solanum nigrum L. The results confirmed that vacuoles were, indeed, the main storage compartments for Cd. We then found that with increased Cd treatment concentration, the proportion of vacuolar Cd in protoplasts showed its ultimate storage capacity (82.24 %-83.40 %), and the Cd concentration stored in the protoplast maintained at a certain level (73.81-77.46 mg L^-1). Besides, studies on different forms of Cd showed that the chelation state was dominant in the protoplast. The large level appearance of Cd²⁺ outside the vacuole revealed the limitations of vacuolar Cd²⁺ sequestration. The relationships between the combined forms of Cd and GSH outside the vacuole (R² = 0.9906) showed GSH was mainly distributed to important compartments for chelation, not to vacuoles. We also demonstrated the presence of ROS-induced oxidative stress and detoxification mediated by the antioxidant GSH in vacuoles, suggesting that sequestration into vacuoles is an active process accompanied by chelation and antioxidant-mediated detoxification.

Mitochondrial superoxide anions induced by exogenous oxidative stress determine tumor cell fate: an individual cell-based study

OBJECTIVE

Reactive oxygen species (ROS) are involved in a variety of biological phenomena and serve both deleterious and beneficial roles. ROS quantification and assessment of reaction networks are desirable but difficult because of their short half-life and high reactivity. Here, we describe a pro-oxidative model in a single human lung carcinoma SPC-A-1 cell that was created by application of extracellular H₂O₂ stimuli.

METHODS

Modified microfluidics and imaging techniques were used to determine O₂ ^•- levels and construct an O₂ ^•- reaction network. To elucidate the consequences of increased O₂ ^•- input, the mitochondria were given a central role in the oxidative stress mode, by manipulating mitochondria-interrelated cytosolic Ca²⁺ levels, mitochondrial Ca²⁺ uptake, auto-amplification of intracellular ROS and the intrinsic apoptotic pathway.

RESULTS AND CONCLUSIONS

Results from a modified microchip demonstrated that 1 mmol/L H₂O₂ induced a rapid increase in cellular O₂ ^•- levels (>27 vs. >406 amol in 20 min), leading to increased cellular oxidizing power (evaluated by ROS levels) and decreased reducing power (evaluated by glutathione (GSH) levels). In addition, we examined the dynamics of cytosolic Ca²⁺ and mitochondrial Ca²⁺ by confocal laser scanning microscopy and confirmed that Ca²⁺ stores in the endoplasmic reticulum were the primary source of H₂O₂-induced cytosolic Ca²⁺ bursts. It is clear that mitochondria have pivotal roles in determining how exogenous oxidative stress affects cell fate. The stress response involves the transfer of Ca²⁺ signals between organelles, ROS auto-amplification, mitochondrial dysfunction, and a caspase-dependent apoptotic pathway.

Microfluidic single-cell analysis of oxidative stress in Dictyostelium discoideum

Microfluidic chemical cytometry is a powerful technique for examining chemical contents of individual cells, but applications have focused on cells from multicellular organisms, especially mammals. We demonstrate the first use of microfluidic chemical cytometry to examine a unicellular organism, the social amoeba Dictyostelium discoideum. We used the reactive oxygen species indicator dichlorodihydrofluorescein diacetate to report on oxidative stress and controlled for variations in indicator loading and retention using carboxyfluorescein diacetate as an internal standard. After optimizing indicator concentration, we investigated the effect of peroxide treatment through single-cell measurements of 353 individual cells. The peak area ratio of dichlorofluorescein to carboxyfluorescein increased from 1.69 ± 0.89 for untreated cells to 5.19 ± 2.72 for cells treated with 40 mM hydrogen peroxide. Interestingly, the variance of the data also increased with oxidative stress. While preliminary, these results are consistent with the hypothesis that heterogeneous stress responses in unicellular organisms may be adaptive.

Fluorescent analysis of bioactive molecules in single cells based on microfluidic chips

Single-cell analysis of bioactive molecules is an essential strategy for a better understanding of cell biology, exploring cell heterogeneity, and improvement of the ability to detect early diseases. In single-cell analysis, highly efficient single-cell manipulation techniques and high-sensitive detection schemes are in urgent need. The rapid development of fluorescent analysis techniques combined with microfluidic chips have offered a widely applicable solution. Thus, in this review, we mainly focus on the application of fluorescence methods in components analysis on microchips at a single-cell level. By targeting different types of biological molecules in cells such as nucleic acids, proteins, and active small molecules, we specially introduce and comment on their corresponding fluorescent probes, fluorescence labelling and sensing strategies, and different fluorescence detection instruments used in single-cell analysis on a microfluidic chip. We hope that through this review, readers will have a better understanding of single-cell fluorescence analysis, especially for single-cell component fluorescence analysis based on microfluidic chips.

Novel synthesis of a mixed Cu/CuO–reduced graphene oxide nanocomposite with enhanced peroxidase-like catalytic activity for easy detection of glutathione in solution and using a paper strip

Mixed copper nanocomposite, Cu/CuO–rGO is prepared through a novel one-step oxidation-reduction reaction between aqueous graphene oxide (GO) and copper(ii) chloride (CuCl₂) solutions at ambient temperature and pressure.

Detection of glutathione within single erythrocyte of different ages and pathological state using microfluidic chips coupled with laser induced fluorescence

As a major factor participating in the organism antioxidation and detoxification process, GSH is of vital importance to human beings. Detecting GSH content in single cells is significant to diagnosis and prevention of many diseases. In this work, the amount of GSH within single erythrocytes was detected and analyzed via statistical analysis. All erythrocytes tested were collected from people in different ages and people of different pathological states. The correlation between GSH level, age and pathological state were investigated. Results showed that the GSH level in erythrocytes decreased with the ages of patients increased. There was little difference between the GSH level in erythrocytes from people who had chronic diseases (hyperglycemia, hyperlipidemia and hypertension) and from healthy people. However, the GSH level in erythrocytes from people who had inflammation (myocarditis, nephritis and gastritis) was generally higher than that from the healthy people. This study provides basic data for researches of cell senescence and cytopathic effect and is helpful to diagnosis and prevention of diseases. In addition, it also provides a simple and effective method for rapid GSH detection within single cell.

Probing the in vitro cytotoxicity of the veterinary drug oxytetracycline

The study investigated the effect of oxytetracycline (OTC) on the anti-oxidative defense system, the structure (hemolysis rate and morphology) and function (ATP enzyme activity) of human red blood cells (hRBCs) to investigate the possible toxic mechanism of OTC to hRBCs. The experimental results indicate that OTC can cause a decline in the function of the antioxidant defense system of hRBCs, resulting in oxidative stress. OTC can bring about morphological changes to hRBCs, and further leads to hemolysis, when the concentration of OTC is over 8×10(-5) M (about 164 µg/ml). At a low OTC concentration, below 4×10(-5) M (82 µg/ml), OTC can enhance the activity of ATP enzyme of hRBCs, known as hormesis. However, at a high concentration, above 4×10(-5) M (about 82 µg/ml), the ATP enzymatic activity was inhibited, affecting the function of hRBCs. The estalished mechanism of toxicity of OTC to hRBCs can facilitate a deeper understanding of the toxicity of OTC in vivo.

Oxidative stress response of two fluoroquinolones with catalase and erythrocytes: a combined molecular and cellular study

Ciprofloxacin (CPFX) and enrofloxacin (ENFX), two representatives of fluoroquinolones (FQs), pose potential threats to health for their wide exposures in environment. The aim of the study is to characterize the harmful effects of oxidative stress induced by CPFX and ENFX from the structure and function of catalase (CAT), a vital enzyme involved in protection against oxidative damage. The cellular tests firstly confirmed an enhanced oxidative stress in FQs treated erythrocytes from the depletion of GSH contents and decrease of CAT activity. Besides, CPFX posed more of an oxidative threat than ENFX. During the spectroscopic and computational investigations, both FQs could bind into its central cavity with only one binding site and interact with Arg 65, Arg 362 and His 363 mainly through electrostatic forces. Furthermore, the binding of two FQs not only caused the conformational and micro-environmental changes of CAT, but also inhibited its molecular activity, consistent with the cellular activity measurements. All these results suggested that the structural and functional changes of CAT were closely associated with increased risk of oxidative stress induced by both FQs. The established methods in this work can help to comprehensively understanding the oxidative stress-induced cellular damage of other pollutants via antioxidant effects.

Subcytotoxic mercury chloride inhibits gap junction intercellular communication by a redox- and phosphorylation-mediated mechanism

Gap junctions play a central role in coordinating intercellular signal-transduction pathways to control tissue homeostasis. Deregulation of gap junctional intercellular communication is a common phenotype of cancer cells and supports its involvement in the carcinogenesis process. Many carcinogens, like environmental heavy-metal chemical pollutants, are known to activate various signal transduction mechanisms and modulate GJIC. They act as tumor promoters on preexisting "initiated" cells, rather than as genotoxic initiators, albeit their mode of action is often unknown. In this study we investigated the effect of Hg(II) (HgCl(2)) on GJIC in cultured human keratinocytes. It is shown that subcytotoxic concentrations of HgCl(2) as low as 10 nM cause inhibition of the GJIC, assessed by dye transfer assay, despite enhanced expression of connexins. In addition, HgCl(2)-treated keratinocytes exhibited a decrease of free thiols and accumulation of mitochondria-derived reactive oxygen species, albeit no effect on the respiratory chain activity was observed. Treatment of HgCl(2)-exposed keratinocytes with the PKC inhibitor calphostin C and with all-trans retinoic acid resulted in rescue of the mitochondrial ROS overproduction and full recovery of the GJIC. Similar results were obtained with the PKA activator db-cAMP. Overall, the presented results support a cross-talk between the altered intracellular redox tone and PKA- and PKC-mediated signaling in HgCl(2)-challenged keratinocytes. These events, although not cytotoxic, lead to inhibition of GJIC and possibly to carcinogenic priming.

Effect of 4-aminoantipyrine on oxidative stress induced by glutathione depletion in single human erythrocytes using a microfluidic device together with fluorescence imaging

The effects of 4-aminoantipyrine (AAP) on oxidative stress induced by glutathione (GSH) depletion in single human erythrocytes were investigated using microfluidic technique and fluorescence imaging. Most cell-based toxicity evaluations on GSH are performed with bulk experiments based on analysis of cell populations. This work established a single-cell toxicity evaluation method to statistically analyze the GSH amount in single erythrocytes incubated with AAP in different concentrations. The experimental conditions of cell flow rate and cell concentration were optimized. The GSH contents in erythrocytes decreased with increasing dose of AAP. At low concentration, AAP had a little effect on GSH; while at high concentration, AAP led to GSH depletion reaching a maximum of 14.53%. The depletion of GSH leads to a significant shift to a more oxidizing intracellular environment. This study provides basic data for presenting the effect of AAP on GSH in erythrocytes and is helpful for understanding its toxicity during the blood transportation process. In addition, it will also complement studies on the environmental risk assessment of AAP pollution.

Simultaneous determination of superoxide and hydrogen peroxide in macrophage RAW 264.7 cell extracts by microchip electrophoresis with laser-induced fluorescence detection

A method for the first time to simultaneously determine superoxide and hydrogen peroxide in macrophage RAW 264.7 cell extracts by microchip electrophoresis with laser-induced fluorescence detection (MCE-LIF) was developed. 2-Chloro-1,3-dibenzothiazolinecyclohexene (DBZTC) and bis(p-methylbenzenesulfonyl) dichlorofluorescein (FS), two probes that can be specifically derivatized by superoxide and hydrogen peroxide, respectively, were synthesized and used. Parameters influencing the derivatization and on-chip separation were optimized. With the use of a HEPES (20 mM, pH 7.4) running buffer, a 50 mm long separation channel, and a separation voltage of 1800 V, baseline separation was achieved within 48 s for the two derivatization products, DBZTC-oxide (DBO) and 2,7-dichlorofluorescein (DCF). The linearity ranges of the method were 0.08-5.0 and 0.02-5.0 microM with detection limits (signal-to-noise ratio = 3) of 10 nM (1.36 amol) and 5.6 nM (0.76 amol) for superoxide and hydrogen peroxide, respectively. The relative standard deviations (RSDs) of migration time and peak area were less than 2.0% and 5.0%, respectively. The recoveries of the cell extract samples spiked with 1.0 microM standard solutions were 96.1% and 93.0% for superoxide and hydrogen peroxide, respectively. With the use of this method, superoxide and hydrogen peroxide in phorbol myristate acetate (PMA)-stimulated macrophage RAW 264.7 cell extracts were found to be 0.78 and 1.14 microM, respectively. The method has paved a way for simultaneously determining two or more reactive oxygen species (ROS) in a biological system with high resolution.

Determination of intracellular glutathione and cysteine using HPLC with a monolithic column after derivatization with monobromobimane

An optimized high-performance liquid chromatography (HPLC) method is used to show that, as myoblasts differentiate into multinucleated muscle fibers, there is a shift to a more oxidized cell redox state. The HPLC method incorporated derivatization with monobromobimane for the determination of the reduced (GSH) and oxidized (GSSG) forms of glutathione and the reduced (Cys) and oxidized (CysSS) forms of cysteine. The derivatization was optimized to improve the sensitivity of the approach; the limits of detection for glutathione and cysteine were 3 x 10(-8) and 5 x 10(-8) M, respectively.