Determination of high mitochondrial membrane potential in spermatozoa loaded with the mitochondrial probe 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide (JC-1) by using fluorescence-activated flow cytometry

Toll-like receptor 2 mediates the immune response of the bovine oviductal ampulla to sperm binding

We previously reported that sperm binding to cultured bovine oviduct epithelial cells induces an anti-inflammatory immune response. Now we have developed a differentiated explant model to focus on the oviductal ampulla, where fertilization occurs, and to study the effect of sperm capacitation on the immune response. We used heparin to stimulate bovine sperm capacitation. Fluorescence imaging showed that 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide-labeled sperm pretreated with (Hep⁽⁺⁾ ) or without (Hep^{( -)} ) heparin rapidly attached to the explant ciliated epithelium in similar numbers. However, only Hep⁽⁺⁾ sperm upregulated explant messenger RNA (mRNA) transcription of TLR2, IL8, TGFB1, and PGES, without changes in TNFA and IL-10 expression, while Hep^{( -)} sperm only upregulated PGES. The responses were primarily anti-inflammatory, with a greater response produced by Hep⁽⁺⁾ sperm, which also produced a substantial increase in TLR2 protein expression in the epithelium. The addition of TLR1/2 (toll-like receptor 1/2) antagonist to the Hep⁽⁺⁾ and (Hep^{( -)} ) sperm-explant coincubations reduced sperm attachment to the epithelium and inhibited TLR2 protein expression and some of the Hep⁽⁺⁾ sperm-induced mRNA transcription. Our observations suggest that the ampullar epithelium immunologically reacts more strongly to sperm that have undergone heparin stimulation of capacitation. This anti-inflammatory response could serve to protect capacitated sperm as they approach the oocyte in the ampulla.

HVCN1 Channels Are Relevant for the Maintenance of Sperm Motility During In Vitro Capacitation of Pig Spermatozoa

The objective of the present study was to determine the physiological role of voltage-gated hydrogen channels 1 (HVCN1 channels) during in vitro capacitation of pig spermatozoa. Sperm samples from 20 boars were incubated in capacitating medium for 300 minutes (min) in the presence of 2-guanidino benzimidazole (2-GBI), a specific HVCN1-channel blocker, added either at 0 min or after 240 min of incubation. Control samples were incubated in capacitating medium without the inhibitor. In all samples, acrosomal exocytosis was triggered with progesterone after 240 min of incubation. Sperm viability, sperm motility and kinematics, acrosomal exocytosis, membrane lipid disorder, intracellular calcium levels and mitochondrial membrane potential were evaluated after 0, 60, 120, 180, 240, 250, 270 and 300 min of incubation. While HVCN1-blockage resulted in altered sperm viability, sperm motility and kinematics and reduced mitochondrial membrane potential as compared to control samples, at any blocker concentration and incubation time, it had a non-significant effect on intracellular Ca²⁺ levels determined through Fluo3-staining. The effects on acrosomal exocytosis were only significant in blocked samples at 0 min, and were associated with increased membrane lipid disorder and Ca²⁺ levels of the sperm head determined through Rhod5-staining. In conclusion, HVCN1 channels play a crucial role in the modulation of sperm motility and kinematics, and in Ca²⁺ entrance to the sperm head.

Synergistic in-vitro effects of combining an antiglycolytic, 3-bromopyruvate, and a bromodomain-4 inhibitor on U937 myeloid leukemia cells

This project investigated the in-vitro effects of a glycolytic inhibitor, 3-bromopyruvate (3-BrP), in combination with and a new in silico-designed inhibitor of the bromodomain-4 (BRD-4) protein, ITH-47, on the U937 acute myeloid leukemia cell line. 3-BrP is an agent that targets the altered metabolism of cancer cells by interfering with glucose metabolism in the glycolytic pathway. ITH-47 is an acetyl-lysine inhibitor that displaces bromdomain 4 proteins from chromatin by competitively binding to the acetyl-lysine recognition pocket of this bromodomain and extraterminal (BET) BRD protein, thereby preventing transcription of cancer-associated genes and further cell growth. Cell growth studies determined the IC50 after 48 h exposure for 3-BrP and ITH-47 to be 6 and 2 μmol/l, respectively. When combined, 2.4 and 1 μmol/l of 3-BrP and ITH-47, respectively, inhibited 50% of the cell population, yielding a synergistic combination index of 0.9. Subsequent mechanistic studies showed that the IC50 concentrations of ITH-47 and 3-BrP and the combination increased observable apoptotic bodies and cell shrinkage in U937 cells treated for 48 h. Cell cycle analysis showed an increase in the sub-G1 fraction in all treated cells, suggesting that cell death was increased in the treated samples. Annexin-V-FITC apoptosis analysis showed a statistically significant increase in the number of cells in early and late apoptosis, indicating that cell death occurred through apoptosis and not necrosis. Only U937 cells exposed to ITH-47 showed a decrease in mitochondrial membrane potential compared with the vehicle control. Reactive oxygen species production was decreased in all treated samples. ITH-47-exposed cells showed a decrease in c-Myc, Bcl-2, and p53 gene expressions. 3-BrP-treated cells showed an increase in c-myc and p53 gene expressions. The combination of ITH-47 and 3-BrP lead to downregulation of c-myc and Bcl-2 genes. ITH-47 exposure conditions yielded a marked decrease in c-myc protein levels as well as a decrease in Ser70 phosphorylated Bcl-2. Analysis of 3-BrP and the combination of ITH-47 and 3-BrP test conditions indicated an increase in p53 protein levels. This novel study is the first to investigate the in-vitro synergistic therapeutic effect of ITH-47 and 3-BrP. The current study contributes toward unraveling the in-vitro molecular mechanisms and signal transduction associated with a novel combination of BRD inhibitors and antiglycolytic agents, providing a basis for further research on these combinations.

Rasagiline for amyotrophic lateral sclerosis: A randomized, controlled trial

INTRODUCTION

Rasagiline is a monoamine oxidase B (MAO-B) inhibitor with possible neuroprotective effects in patients with amyotrophic lateral sclerosis (ALS).

METHODS

We performed a randomized, double-blind, placebo-controlled trial of 80 ALS participants with enrichment of the placebo group with historical controls (n = 177) at 10 centers in the United States. Participants were randomized in a 3:1 ratio to 2 mg/day rasagiline or placebo. The primary outcome was average slope of decline on the ALS Functional Rating Scale-Revised (ALSFRS-R). Secondary measures included slow vital capacity, survival, mitochondrial and molecular biomarkers, and adverse-event reporting.

RESULTS

There was no difference in the average 12-month ALSFRS-R slope between rasagiline and the mixed placebo and historical control cohorts. Rasagiline did not show signs of drug-target engagement in urine and blood biomarkers. Rasagiline was well tolerated with no serious adverse events.

DISCUSSION

Rasagiline did not alter disease progression compared with controls over 12 months of treatment. Muscle Nerve 59:201-207, 2019.

LTBP2 knockdown and oxidative stress affect glaucoma features including TGFβ pathways, ECM genes expression and apoptosis in trabecular meshwork cells

Glaucoma is the leading cause of irreversible blindness worldwide. Although the etiology of glaucoma is incompletely understood, it is known that the extracellular matrix (ECM) of the trabecular meshwork, oxidative stress, TGFβ signaling pathways, and apoptosis are important components of glaucoma pathogenesis. These components appear to be interrelated, but knowledge on their interactions remains incomplete. Relevant to this gap in knowledge, LTBP2, glaucoma causing gene, may also be related to the mentioned components of glaucoma pathogenesis because of its putative roles in TGFβ signaling and ECM functions. This background prompted us to further query interactions among some molecules and pathways thought to be important in glaucoma etiology, with emphasis on oxidative stress and LTBP2. To this end, effects of LTBP2 siRNA knockdown, oxidative stress induction, TGFβ2 and gremlin exposures on canonical TGFβ and BMP signaling pathways, expression of ECM related genes, and apoptosis were assayed in primary human trabecular meshwork cell cultures. We found that oxidative stress induction and LTBP2 knockdown both affected all the processes queried, and that their affects paralleled one another. We suggest that effects of both oxidative stress and LTBP2 knockdown on the ECM and apoptosis may be mediated by TGFβ and BMP signaling pathway activation.

Silencing calreticulin gene might protect cardiomyocytes from angiotensin II-induced apoptosis

AIMS

Calreticulin (CRT), as a chaperone, contributes to protein folding and quality control cycle. CRT is an important factor regulating Ca²⁺ that participates in cell apoptosis. However, the function of CRT in the heart is still controversial. Therefore, we aimed to investigate the potential role of CRT in angiotensin II-induced cardiomyocytes apoptosis.

MAIN METHODS

Primary cultured neonatal cardiomyocytes were stimulated with angiotensin II to induce the apoptosis. Expression of CRT and endoplasmic reticulum (ER) stress associated protein was detected by western blotting after angiotensin II stimulation for 24 h. The reactive oxygen species (ROS) production and mitochondrial membrane potential (MMP) were also detected. Additionally, the function of CRT on cardiomyocytes apoptosis and ER stress/unfolded protein response signaling pathway was investigated by transfecting specific CRT-targeting siRNA.

KEY FINDINGS

Cardiomyocytes apoptosis was induced by angiotensin II. The protein level of CRT was elevated after angiotensin -II stimulation for 24 h. Additionally, the protein levels of GRP78, ATF4, C-ATF6, CHOP and the ROS production were elevated, but the Bcl-2 expression and the level of MMP were down-regulated. After silencing CRT gene in the process of angiotensin II-induced cardiomyocytes apoptosis, cardiomyocytes apoptosis rate decreased, meanwhile the protein expression of CRT, GRP78, ATF4, C-ATF6 and CHOP were down-regulated. However, the Bcl-2 expression was up-regulated, and the increase of ROS and the loss of MMP were alleviated.

SIGNIFICANCE

Our study demonstrated that CRT might protect cardiomyocytes from apoptosis induced by angiotensin II, in which ER stress and mitochondria function were identified as possible underlying molecular bases.

Arsenite-induced endoplasmic reticulum-dependent apoptosis through disturbance of calcium homeostasis in HBE cell line

Calcium (Ca²⁺ ) is a ubiquitous cell signal responsible for multiple fundamental cellular functions, including apoptosis. Whether the homeostasis of Ca²⁺ is involved in arsenite-induced apoptosis remains unclear. In this study, we observed that arsenite significantly elevated the intracellular Ca²⁺ concentration in a dose- and time-dependent manner. By using the Ca²⁺ -ATPase inhibitor, thapsigargin, and the inositol 1,4,5- trisphosphate receptors (IP3Rs) inhibitor, heparin, we further confirmed that the disturbance of endoplasmic reticulum (ER) Ca²⁺ homeostasis caused Ca²⁺ overload in the cells. Moreover, loss of ER Ca²⁺ homeostasis also led to ER stress, mitochondrial dysfunction, and NF-κB activation. Importantly, pretreatment of cells with heparin remarkably attenuated the elevated cell apoptosis induced by arsenite, but inhibition of ER Ca²⁺ uptake with thapsigargin exacerbated arsenite-induced cell damage significantly. Together, we demonstrated for the first time that arsenite disturbed the Ca²⁺ homeostasis in ER, which subsequently led to ER stress, mitochondrial dysfunction, and NF-κB nuclear translocation, and thus consequently triggering cell apoptosis. Our findings indicate regulation of disrupted Ca²⁺ homeostasis in ER may be a potential strategy for prevention of arsenite toxicity. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 197-216, 2017.

SKF-96365 activates cytoprotective autophagy to delay apoptosis in colorectal cancer cells through inhibition of the calcium/CaMKIIγ/AKT-mediated pathway

Store-operated Ca(2+) entry (SOCE) inhibitors are emerging as an attractive new generation of anti-cancer drugs. Here, we report that SKF-96365, an SOCE inhibitor, exhibits potent anti-neoplastic activity by inducing cell-cycle arrest and apoptosis in colorectal cancer cells. In the meantime, SKF-96365 also induces cytoprotective autophagy to delay apoptosis by preventing the release of cytochrome c (cyt c) from the mitochondria into the cytoplasm. Mechanistically, SKF-96365 treatment inhibited the calcium/calmodulin-dependent protein kinase IIγ (CaMKIIγ)/AKT signaling cascade in vitro and in vivo. Overexpression of CaMKIIγ or AKT abolished the effects of SKF-96365 on cancer cells, suggesting a critical role of the CaMKIIγ/AKT signaling pathway in SFK-96365-induced biological effects. Moreover, Hydroxychloroquine (HCQ), an FDA-approved drug used to inhibit autophagy, could significantly augment the anti-cancer effect of SFK-96365 in a mouse xenograft model. To our best knowledge, this is the first report to demonstrate that calcium/CaMKIIγ/AKT signaling can regulate apoptosis and autophagy simultaneously in cancer cells, and the combination of the SOCE inhibitor SKF-96365 with autophagy inhibitors represents a promising strategy for treating patients with colorectal cancer.

A multi-center screening trial of rasagiline in patients with amyotrophic lateral sclerosis: Possible mitochondrial biomarker target engagement

Rasagiline, a monoamine oxidase B inhibitor, slowed disease progression in the SOD1 mouse, and in a case series of patients with amyotrophic lateral sclerosis (ALS). Here we determine whether rasagiline is safe and effective in ALS compared to historical placebo controls, and whether it alters mitochondrial biomarkers. We performed a prospective open-label, multicenter screening trial of 36 ALS patients treated with 2 mg oral rasagiline daily for 12 months. Outcomes included the slope of deterioration of the revised ALS Functional Rating Scale (ALSFRS-R), adverse event monitoring, time to treatment failure, and exploratory biomarkers. Participants experienced no serious drug-related adverse events, and the most common adverse event was nausea (11.1%). Rasagiline did not improve the rate of decline in the ALSFRS-R; however, differences in symptom duration compared to historical placebo controls differentially affected ALSFRS-R slope estimates. Rasagiline changed biomarkers over 12 months, such that the mitochondrial membrane potential increased (JC-1 red/green fluorescent ratio 1.92, p = 0.0001) and apoptosis markers decreased (Bcl-2/Bax ratio 0.24, p < 0.0001). In conclusion, engagement of exploratory biomarkers and questions about comparability of baseline characteristics lead us to recommend a further placebo-controlled trial.

The apoptotic effect of apigenin on human gastric carcinoma cells through mitochondrial signal pathway

This study aims to explore the apoptotic function of apigenin on the gastric cancer cells and the related mechanism. The gastric cancer cell lines HGC-27 and SGC-7901, and normal gastric epithelial cell line GES1 were treated with different concentrations of apigenin. Cell proliferation was tested. Morphological changes of the apoptotic cells were observed after Hoechst33342 staining. The apoptosis rate of the gastric cancer cells were measured with flow cytometry. Changes of the cell cycle were explored. The mitochondrial membrane potential changes were analyzed after JC-1 staining. Bcl-2 family proteins and caspases-3 expression with apigenin treatment was analyzed by real-time PCR. Cell proliferation of HGC-27 and SGC-7901 was inhibited by apigenin, and the inhibition was dose-time-dependent. Gastric carcinoma cells treated by apigenin had no obvious cell cycle arrest, but were observed with the higher apoptosis rate and the typical apoptotic morphological changes of the cell nucleus. JC-1 staining showed that apigenin could reduce mitochondrial membrane potential of gastric carcinoma cells. Real-time PCR results showed that apigenin significantly increased caspase-3 and Bax expression level, and down-regulated Bcl-2 expression in a dose-dependent manner in gastric carcinoma cells. However, the GES1 was almost not affected by apigenin treatment. Apigenin can inhibit cell lines HGC-27 and SGC-7901 proliferation in a time and dose-dependent manner, reduce anti-apoptotic protein Bcl-2 levels, enhance apoptosis-promoting protein Bax level, result in mitochondrial membrane potential decreasing and caspase-3 enzyme activating, then lead to cell apoptosis.

Mitochondrial dysfunction in early life resulted from perinatal bisphenol A exposure contributes to hepatic steatosis in rat offspring

An emerging literature suggests that bisphenol A (BPA), a widespread endocrine disrupting chemical, when exposure occurs in early life, may increase the risk of metabolic syndrome. In this study, we investigated the hypothesis that perinatal exposure to BPA predisposed offspring to fatty liver disease: the hepatic manifestation of metabolic syndrome, and its possible mechanism. Pregnant Wistar rats were administered with BPA (40μg/kg/day) or vehicle during gestation and lactation. Liver histology, biochemical analysis, transcriptome, and mitochondrial function were examined in male offspring at postnatal 3, 15 and 26 weeks. At 3 weeks of age, abnormal liver morphology and function were not observed in the BPA-exposed offspring, but a decrease in mitochondrial respiratory complex (MRC) activity (I and III) and significant changes in gene expression involved in mitochondrial fatty acid metabolism were observed compared with controls. At 15 weeks, micro-vesicular steatosis in liver, up-regulated genes involved in lipogenesis pathways, increased ROS generation and Cytc release were observed in the BPA-exposed offspring. Then, extensive fatty accumulation in liver and elevated serum ALT were observed in BPA-exposed offspring at 26 weeks. In the longitudinal observation, hepatic mitochondrial function including MRC activity, ATP production, ROS generation and mitochondrial membrane potential were progressively worsened in the BPA-exposed offspring. Perinatal BPA exposure contributes to the development of hepatic steatosis in the offspring of rats, which may be mediated through impaired hepatic mitochondrial function and up-regulated hepatic lipid metabolism.

Interaction of delta-like 1 homolog (Drosophila) with prohibitins and its impact on tumor cell clonogenicity

Cancer stem cell characteristics, especially their self-renewal and clonogenic potentials, play an essential role in malignant progression and response to anticancer therapies. Currently, it remains largely unknown what pathways are involved in the regulation of cancer cell stemness and differentiation. Previously, we found that delta-like 1 homolog (Drosophila) or DLK1, a developmentally regulated gene, plays a critical role in the regulation of differentiation, self-renewal, and tumorigenic growth of neuroblastoma cells. Here, we show that DLK1 specifically interacts with the prohibitin 1 (PHB1) and PHB2, two closely related genes with pleiotropic functions, including regulation of mitochondrial function and gene transcription. DLK1 interacts with the PHB1-PHB2 complex via its cytoplasmic domain and regulates mitochondrial functions, including mitochondrial membrane potential and production of reactive oxygen species. We have further found that PHB1 and especially PHB2 regulate cancer cell self-renewal as well as their clonogenic potential. Hence, the DLK1-PHB interaction constitutes a new signaling pathway that maintains clonogenicity and self-renewal potential of cancer cells.

IMPLICATIONS

This study provides a new mechanistic insight into the regulation of the stem cell characteristics of cancer cells.

Signaling pathways of ESE-16, an antimitotic and anticarbonic anhydrase estradiol analog, in breast cancer cells

The aim of this study was to characterize the in vitro action of 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10)16-tetraene (ESE-16) on non-tumorigenic MCF-12A, tumorigenic MCF-7 and metastatic MDA-MB-231 breast cancer cells. ESE-16 is able to inhibit the activity of a carbonic anhydrase II and a mimic of carbonic anhydrase IX in the nanomolar range. Gene and protein expression studies using various techniques including gene and antibody microarrays and various flow cytometry assays yielded valuable information about the mechanism of action of ESE-16. The JNK pathway was identified as an important pathway mediating the effects of ESE-16 while the p38 stress-induced pathway is more important in MDA-MB-231 cells exposed to ESE-16. Lysosomal rupture and iron metabolism was identified as important mediators of mitochondrial membrane depolarization. Abrogation of Bcl-2 phosphorylation status as a result of ESE-16 also plays a role in inducing mitochondrial membrane depolarization. The study provides a basis for future research projects to develop the newly synthesized compound into a clinically usable anticancer agent either alone or in combination with other agents.

Keywords: Antimitotic, anticarbonic anhydrase IX, apoptosis, autophagy, cell cycle arrest, Bcl-2, JNK, p38, mitochondrial membrane depolarization, flow cytometry, gene expression and protein microarray, anticancer.

Flow cytometric methods for sperm assessment

Flow cytometry allows the assessment of multiple sperm parameters following a diverse number of protocols. Here, we describe three methods for evaluating critical aspects of sperm quality: the double stain SYBR-14 and propidium iodide (PI) for assessing sperm viability; the double stain PNA-FITC (peanut agglutinin-fluorescein isothiocyanate) and PI for assessing acrosomal integrity combined with sperm viability; and JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolylcarbocyanine iodide) for assessing mitochondrial membrane potential. These three stains are widely used and can be analyzed with basic flow cytometers.

In vitro evaluation of ESE-15-ol, an estradiol analogue with nanomolar antimitotic and carbonic anhydrase inhibitory activity

Antimitotic compounds are still one of the most widely used chemotherapeutic anticancer drugs in the clinic today. Given their effectiveness against cancer it is beneficial to continue enhancing these drugs. One way is to improve the bioavailability and efficacy by synthesizing derivatives that reversibly bind to carbonic anhydrase II (CAII) in red blood cells followed by a slow release into the blood circulation system. In the present study we describe the in vitro biological activity of a reduced derivative of 2-ethyl-3-O-sulphamoyl-estradiol (2EE), 2-ethyl-3-O-sulphamoyl-estra-1,3,5(10),15-tetraen-17-ol (ESE-15-ol). ESE-15-ol is capable of inhibiting carbonic anhydrase activity in the nanomolar range and is selective towards a mimic of carbonic anhydrase IX when compared to the CAII isoform. Docking studies using Autodock Vina suggest that the dehydration of the D-ring plays a role towards the selectivity of ESE-15-ol to CAIX and that the binding mode of ESE-15-ol is substantially different when compared to 2EE. ESE-15-ol is able to reduce cell growth to 50% after 48 h at 50–75 nM in MCF-7, MDA-MB-231, and MCF-12A cells. The compound is the least potent against the non-tumorigenic MCF-12A cells. In vitro mechanistic studies demonstrate that the newly synthesized compound induces mitochondrial membrane depolarization, abrogates the phosphorylation status of Bcl-2 and affects gene expression of genes associated with cell death and mitosis.

Platelet senescence and phosphatidylserine exposure

BACKGROUND

The exposure of phosphatidylserine occurs during platelet (PLT) activation and during in vitro storage. Phosphatidylserine exposure also occurs during apoptosis after the release of mitochondrial cytochrome c. We have examined the role of cytochrome c release, mitochondrial membrane potential (ΔΨm), and cyclophilin D (CypD) in phosphatidylserine exposure due to activation and storage.

STUDY DESIGN AND METHODS

The exposure of phosphatidylserine and the loss of ΔΨm were determined in a flow cytometer using fluorescein isothiocyanate-lactadherin and JC-1, a lipophilic cationic reporter dye. The role of CypD was determined with cyclosporin A and CypD-deficient murine PLTs. Cytochrome c-induced caspase-3 and Rho-associated kinase I (ROCK1) activation were determined by immunoblotting and using their inhibitors.

RESULTS

Collagen- and thrombin-induced exposure of phosphatidylserine was accompanied by a decrease in ΔΨm. Cyclosporin A inhibited the phosphatidylserine exposure and the loss of ΔΨm. CypD(-/-) mice had decreased loss of ΔΨm and impaired phosphatidylserine exposure. Collagen and thrombin did not induce the release of cytochrome c nor the activation of caspase-3 and ROCK1. In contrast, in PLTs stored for more than 5 days, the phosphatidylserine exposure was associated with cytochrome c-induced caspase-3 and ROCK1 activation. ABT737, a BH3 mimetic that induces mitochondrial pathway of apoptosis, induced cytochrome c release and activation of caspase-3 and ROCK1 and phosphatidylserine exposure independent of CypD.

CONCLUSION

These results show that in stored PLTs cytochrome c release and the subsequent activation of caspase-3 and ROCK1 mediate phosphatidylserine exposure and it is distinct from activation-induced phosphatidylserine exposure.

An integrated imaging approach to the study of oxidative stress generation by mitochondrial dysfunction in living cells

BACKGROUND

The mechanisms of action of many environmental agents commonly involve oxidative stress resulting from mitochondrial dysfunction. Zinc is a common environmental metallic contaminant that has been implicated in a variety of oxidant-dependent toxicological responses. Unlike ions of other transition metals such as iron, copper, and vanadium, Zn(2+) does not generate reactive oxygen species (ROS) through redox cycling.

OBJECTIVE

To characterize the role of oxidative stress in zinc-induced toxicity.

METHODS

We used an integrated imaging approach that employs the hydrogen peroxide (H2O2)-specific fluorophore Peroxy Green 1 (PG1), the mitochondrial potential sensor 5,5 ,6,6 -tetrachloro-1,1 ,3,3 -tetraethylbenzimidazolylcarbocyanine iodide (JC-1), and the mitochondria-targeted form of the redox-sensitive genetically encoded fluorophore MTroGFP1 in living cells.

RESULTS

Zinc treatment in the presence of the Zn(2+) ionophore pyrithione of A431 skin carcinoma cells preloaded with the H(2)O(2)-specific indicator PG1 resulted in a significant increase in H(2)O(2) production that could be significantly inhibited with the mitochondrial inhibitor carbonyl cyanide 3-chlorophenylhydrazone. Mitochondria were further implicated as the source of zinc-induced H(2)O(2) formation by the observation that exposure to zinc caused a loss of mitochondrial membrane potential. Using MTroGFP1, we showed that zinc exposure of A431 cells induces a rapid loss of reducing redox potential in mitochondria. We also demonstrated that zinc exposure results in rapid swelling of mitochondria isolated from mouse hearts.

CONCLUSION

Taken together, these findings show a disruption of mitochondrial integrity, H(2)O(2) formation, and a shift toward positive redox potential in cells exposed to zinc. These data demonstrate the utility of real-time, live-cell imaging to study the role of oxidative stress in toxicological responses.