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Abstract
Oxidative stress is important for the etiology and pathogenesis of Alzheimer's disease (AD). Research tools that can conveniently evaluate oxidative stress in AD models are expected to catalyze and accelerate research on AD. This study explored the use of genetically encoded fluorescent indicators (GEFIs) to detect mitochondrial oxidative stress in organotypic brain slices and AD mouse models. To enable ratiometric normalization and avoid tissue autofluorescence, we genetically fused a green fluorescent hydrogen peroxide (H2O2) indicator, HyPer7, with each of two selected, bright red fluorescent proteins (RFPs), mScarlet-I and tdTomato. The resultant indicators, namely, HyPerGRS and HyPerGRT, were tagged with mitochondrial targeting sequences and examined for localization and function in cultured HeLa cells and primary mouse neurons. We further utilized HyPerGRT, which is a genetic fusion of HyPer7 with tdTomato, to monitor mitochondrial H2O2 in response to the human β-amyloid 1-42 isoform (Aβ42) in cultured brain slices and an AD mouse model. Owing to the high sensitivity and low autofluorescence interference resulting from HyPerGRT, we successfully detected Aβ42-mediated mitochondrial H2O2 in these AD models. The results suggest that HyPerGRT is a valuable tool for studying mitochondrial oxidative stress in tissues and animals.
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Affiliation(s)
- Xinyu Li
- Department of Molecular Physiology and Biological Physics, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
- Center for Membrane and Cell Physiology, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
| | - Yiyu Zhang
- Department of Molecular Physiology and Biological Physics, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
- Center for Membrane and Cell Physiology, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
| | - Hui-wang Ai
- Department of Molecular Physiology and Biological Physics, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
- Center for Membrane and Cell Physiology, School of Medicine, University of Virginia, Charlottesville, VA, 22908, USA
- The UVA Cancer Center, University of Virginia, Charlottesville, VA, 22908, USA
- Corresponding Author.
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Byrne MB, Leslie MT, Patel HS, Gaskins HR, Kenis PJA. Design considerations for open-well microfluidic platforms for hypoxic cell studies. BIOMICROFLUIDICS 2017; 11:054116. [PMID: 29152027 PMCID: PMC5659862 DOI: 10.1063/1.4998579] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 10/03/2017] [Indexed: 05/24/2023]
Abstract
Regions of hypoxia are common in solid tumors and are associated with enhanced malignancy, metastasis, and chemo/radio resistance. Real-time hypoxic cellular experimentation is challenging due to the constant need for oxygen control. Most microfluidic platforms developed thus far for hypoxic cell studies are burdened by complex design parameters and are difficult to use for uninitiated investigators. However, open-well microfluidic platforms enable short and long term hypoxic cell studies with an ease of use workflow. Specifically, open-well platforms enable manipulation and addition of cells, media, and reagents using a micropipette for hypoxic cell studies in tunable dissolved oxygen concentrations as low 0.3 mg/l. We analyzed design considerations for open-well microfluidic platforms such as media height, membrane thickness, and impermeable barriers to determine their effects on the amount of dissolved oxygen within the platform. The oxygen concentration was determined by experimental measurements and computational simulations. To examine cell behavior under controlled oxygen conditions, hypoxia-induced changes to hypoxia inducible factor activity and the mitochondrial redox environment were studied. A fluorescent reporter construct was used to monitor the stabilization of hypoxia inducible factors 1α and 2α throughout chronic hypoxia. Reporter construct fluorescence intensity inversely correlated with dissolved oxygen in the medium, as expected. Additionally, the glutathione redox poise of the mitochondrial matrix in living cancer cells was monitored throughout acute hypoxia with a genetically encoded redox probe and was observed to undergo a reductive response to hypoxia. Overall, these studies validate an easy to use open-well platform suitable for studying complex cell behaviors in hypoxia.
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Affiliation(s)
| | | | - Heeral S Patel
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Schwarzländer M, Dick TP, Meyer AJ, Morgan B. Dissecting Redox Biology Using Fluorescent Protein Sensors. Antioxid Redox Signal 2016; 24:680-712. [PMID: 25867539 DOI: 10.1089/ars.2015.6266] [Citation(s) in RCA: 191] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
SIGNIFICANCE Fluorescent protein sensors have revitalized the field of redox biology by revolutionizing the study of redox processes in living cells and organisms. RECENT ADVANCES Within one decade, a set of fundamental new insights has been gained, driven by the rapid technical development of in vivo redox sensing. Redox-sensitive yellow and green fluorescent protein variants (rxYFP and roGFPs) have been the central players. CRITICAL ISSUES Although widely used as an established standard tool, important questions remain surrounding their meaningful use in vivo. We review the growing range of thiol redox sensor variants and their application in different cells, tissues, and organisms. We highlight five key findings where in vivo sensing has been instrumental in changing our understanding of redox biology, critically assess the interpretation of in vivo redox data, and discuss technical and biological limitations of current redox sensors and sensing approaches. FUTURE DIRECTIONS We explore how novel sensor variants may further add to the current momentum toward a novel mechanistic and integrated understanding of redox biology in vivo. Antioxid. Redox Signal. 24, 680-712.
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Affiliation(s)
- Markus Schwarzländer
- 1 Plant Energy Biology Lab, Department Chemical Signalling, Institute of Crop Science and Resource Conservation (INRES), University of Bonn , Bonn, Germany
| | - Tobias P Dick
- 2 Division of Redox Regulation, German Cancer Research Center (DKFZ) , DKFZ-ZMBH Alliance, Heidelberg, Germany
| | - Andreas J Meyer
- 3 Department Chemical Signalling, Institute of Crop Science and Resource Conservation (INRES), University of Bonn , Bonn, Germany
| | - Bruce Morgan
- 2 Division of Redox Regulation, German Cancer Research Center (DKFZ) , DKFZ-ZMBH Alliance, Heidelberg, Germany .,4 Cellular Biochemistry, Department of Biology, University of Kaiserslautern , Kaiserslautern, Germany
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Fan Y, Ai HW. Development of redox-sensitive red fluorescent proteins for imaging redox dynamics in cellular compartments. Anal Bioanal Chem 2016; 408:2901-11. [PMID: 26758595 DOI: 10.1007/s00216-015-9280-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 12/13/2015] [Accepted: 12/17/2015] [Indexed: 01/01/2023]
Abstract
We recently reported a redox-sensitive red fluorescent protein, rxRFP1, which is one of the first genetically encoded red-fluorescent probes for general redox states in living cells. As individual cellular compartments have different basal redox potentials, we hereby describe a group of rxRFP1 mutants, showing different midpoint redox potentials for detection of redox dynamics in various subcellular domains, such as mitochondria, the cell nucleus, and endoplasmic reticulum (ER). When these redox probes were expressed and subcellularly localized in human embryonic kidney (HEK) 293 T cells, they responded to membrane-permeable oxidants and reductants. In addition, a mitochondrially localized rxRFP1 mutant, Mito-rxRFP1.1, was used to detect mitochondrial oxidative stress induced by doxorubicin-a widely used cancer chemotherapy drug. Our work has expanded the fluorescent protein toolkit with new research tools for studying compartmentalized redox dynamics and oxidative stress under various pathophysiological conditions.
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Affiliation(s)
- Yichong Fan
- Environmental Toxicology Graduate Program, University of California Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA
| | - Hui-wang Ai
- Environmental Toxicology Graduate Program, University of California Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA.
- Department of Chemistry, University of California Riverside, 501 Big Springs Road, Riverside, CA, 92521, USA.
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Kolossov VL, Beaudoin JN, Ponnuraj N, DiLiberto SJ, Hanafin WP, Kenis PJA, Gaskins HR. Thiol-based antioxidants elicit mitochondrial oxidation via respiratory complex III. Am J Physiol Cell Physiol 2015; 309:C81-91. [PMID: 25994788 DOI: 10.1152/ajpcell.00006.2015] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Excessive oxidation is widely accepted as a precursor to deleterious cellular function. On the other hand, an awareness of the role of reductive stress as a similar pathological insult is emerging. Here we report early dynamic changes in compartmentalized glutathione (GSH) redox potentials in living cells in response to exogenously supplied thiol-based antioxidants. Noninvasive monitoring of intracellular thiol-disulfide exchange via a genetically encoded biosensor targeted to cytosol and mitochondria revealed unexpectedly rapid oxidation of the mitochondrial matrix in response to GSH ethyl ester or N-acetyl-l-cysteine. Oxidation of the probe occurred within seconds in a concentration-dependent manner and was attenuated with the membrane-permeable ROS scavenger tiron. In contrast, the cytosolic sensor did not respond to similar treatments. Surprisingly, the immediate mitochondrial oxidation was not abrogated by depolarization of mitochondrial membrane potential or inhibition of mitochondrial GSH uptake. After detection of elevated levels of mitochondrial ROS, we systematically inhibited multisubunit protein complexes of the mitochondrial respiratory chain and determined that respiratory complex III is a downstream target of thiol-based compounds. Disabling complex III with myxothiazol completely blocked matrix oxidation induced with GSH ethyl ester or N-acetyl-l-cysteine. Our findings provide new evidence of a functional link between exogenous thiol-containing antioxidants and mitochondrial respiration.
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Ezeriņa D, Morgan B, Dick TP. Imaging dynamic redox processes with genetically encoded probes. J Mol Cell Cardiol 2014; 73:43-9. [DOI: 10.1016/j.yjmcc.2013.12.023] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 12/23/2013] [Accepted: 12/27/2013] [Indexed: 12/13/2022]
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Kolossov VL, Hanafin WP, Beaudoin JN, Bica DE, DiLiberto SJ, Kenis PJA, Gaskins HR. Inhibition of glutathione synthesis distinctly alters mitochondrial and cytosolic redox poise. Exp Biol Med (Maywood) 2014; 239:394-403. [PMID: 24586100 DOI: 10.1177/1535370214522179] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The glutathione couple GSH/GSSG is the most abundant cellular redox buffer and is not at equilibrium among intracellular compartments. Perturbation of glutathione poise has been associated with tumorigenesis; however, due to analytical limitations, the underlying mechanisms behind this relationship are poorly understood. In this regard, we have implemented a ratiometric, genetically encoded redox-sensitive green fluorescent protein fused to human glutaredoxin (Grx1-roGFP2) to monitor real-time glutathione redox potentials in the cytosol and mitochondrial matrix of tumorigenic and non-tumorigenic cells. First, we demonstrated that recovery time in both compartments depended upon the length of exposure to oxidative challenge with diamide, a thiol-oxidizing agent. We then monitored changes in glutathione poise in cytosolic and mitochondrial matrices following inhibition of glutathione (GSH) synthesis with L-buthionine sulphoximine (BSO). The mitochondrial matrix showed higher oxidation in the BSO-treated cells indicating distinct compartmental alterations in redox poise. Finally, the contributory role of the p53 protein in supporting cytosolic redox poise was demonstrated. Inactivation of the p53 pathway by expression of a dominant-negative p53 protein sensitized the cytosol to oxidation in BSO-treated tumor cells. As a result, both compartments of PF161-T+p53(DD) cells were equally oxidized ≈20 mV by inhibition of GSH synthesis. Conversely, mitochondrial oxidation was independent of p53 status in GSH-deficient tumor cells. Taken together, these findings indicate different redox requirements for the glutathione thiol/disulfide redox couple within the cytosol and mitochondria of resting cells and reveal distinct regulation of their redox poise in response to inhibition of glutathione biosynthesis.
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Affiliation(s)
- Vladimir L Kolossov
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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