Endonuclease G promotes hepatic mitochondrial respiration by selectively increasing mitochondrial tRNA production.

Mitochondrial endonuclease G (EndoG) contributes to chromosomal degradation when it is released from mitochondria during apoptosis. It is presumed to also have a mitochondrial function because EndoG deficiency causes mitochondrial dysfunction. However, the mechanism by which EndoG regulates mitochondrial function is not known.

High resolution spatial investigation of intracellular oxygen in muscle cells.

Unlabelled: Molecular oxygen (O ) is one of the most functionally relevant metabolites. O is essential for mito-chondrial aerobic respiration. Changes in O affect muscle metabolism and play a critical role in the maintenance of skeletal muscle mass, with lack of sufficient O resulting in detrimental loss of muscle mass and function.

Mitochondrial respiration reduces exposure of the nucleus to oxygen.

The endosymbiotic theory posits that ancient eukaryotic cells engulfed O-consuming prokaryotes, which protected them against O toxicity. Previous studies have shown that cells lacking cytochrome c oxidase (COX), required for respiration, have increased DNA damage and reduced proliferation, which could be improved by reducing O exposure. With recently developed fluorescence lifetime microscopy-based probes demonstrating that the mitochondrion has lower [O] than the cytosol, we hypothesized that the perinuclear distribution of mitochondria in cells may create a barrier for O to access the nuclear core, potentially affecting cellular physiology and maintaining genomic integrity.

Computational Modeling and Imaging of the Intracellular Oxygen Gradient.

Computational modeling can provide a mechanistic and quantitative framework for describing intracellular spatial heterogeneity of solutes such as oxygen partial pressure (pO). This study develops and evaluates a finite-element model of oxygen-consuming mitochondrial bioenergetics using the COMSOL Multiphysics program. The model derives steady-state oxygen (O) distributions from Fickian diffusion and Michaelis-Menten consumption kinetics in the mitochondria and cytoplasm.

Fluorescence lifetime imaging of Myoglobin formation due to nitric oxide stress.

Myoglobin is a protein that is expressed quite unevenly among different cell types. Nevertheless, it has been widely acknowledged that the Fe state of myoglobin, myoglobin (Mb) has a broad functional role in metabolism, oxidative/nitrative regulation and gene networks. Accordingly, real-time monitoring of oxygenated, deoxygenated and Mb proportions- or, more broadly, of the mechanisms by which Mb is formed, presents a promising line of research.

Intracellular imaging of metmyoglobin and oxygen using new dual purpose probe EYFP-Myoglobin-mCherry.

The biological relevance of nitric oxide (NO) and reactive oxygen species (ROS) in signaling, metabolic regulation, and disease treatment has become abundantly clear. The dramatic change in NO/ROS processing that accompanies a changing oxygen landscape calls for new imaging tools that can provide cellular details about both [O ] and the production of reactive species. Myoglobin oxidation to the met state by NO/ROS is a known sensor with absorbance changes in the visible range.

Mitochondria and oxygen homeostasis.

Molecular oxygen possesses a dual nature due to its highly reactive free radical property: it is capable of oxidizing metabolic substrates to generate cellular energy, but can also serve as a substrate for genotoxic reactive oxygen species generation. As a labile substance upon which aerobic life depends, the mechanisms for handling cellular oxygen have been fine-tuned and orchestrated in evolution. Protection from atmospheric oxygen toxicity as originally posited by the Endosymbiotic Theory of the Mitochondrion is likely to be one basic principle underlying oxygen homeostasis.

Developing Analysis Protocols for Monitoring Intracellular Oxygenation Using Fluorescence Lifetime Imaging of Myoglobin-mCherry.

Oxygen (O) is a critical metabolite for cellular function as it fuels aerobic cellular metabolism; further, it is a known regulator of gene expression. Monitoring oxygenation within cells and organelles can provide valuable insights into how O, or lack thereof, both influences and responds to cell processes. In recent years, fluorescence lifetime imaging microscopy (FLIM) has been used to track several probe concentration independent intracellular phenomena, such as pH, viscosity, and, in conjunction with Förster resonance energy transfer (FRET), protein-protein interactions.

Single cell-based fluorescence lifetime imaging of intracellular oxygenation and metabolism.

Oxidation-reduction chemistry is fundamental to the metabolism of all living organisms, and hence quantifying the principal redox players is important for a comprehensive understanding of cell metabolism in normal and pathological states. In mammalian cells, this is accomplished by measuring oxygen partial pressure (pO) in parallel with free and enzyme-bound reduced nicotinamide adenine dinucleotide (phosphate) [H] (NAD(P)H) and flavin adenine dinucleotide (FAD, a proxy for NAD). Previous optical methods for these measurements had accompanying problems of cytotoxicity, slow speed, population averaging, and inability to measure all redox parameters simultaneously.

O determined from the measured PDT dose and O predicts long-term response to Photofrin-mediated PDT.

Photodynamic therapy (PDT) that employs the photochemical interaction of light, photosensitizer and oxygen is an established modality for the treatment of cancer. However, dosimetry for PDT is becoming increasingly complex due to the heterogeneous photosensitizer uptake by the tumor, and complicated relationship between the tissue oxygenation ([O]), interstitial light distribution, photosensitizer photobleaching and PDT effect. As a result, experts argue that the failure to realize PDT's true potential is, at least partly due to the complexity of the dosimetry problem.

Global analysis and Decay Associated Images (DAI) derived from Fluorescence Lifetime Imaging Microscopy (FLIM).

The extraction of fluorophore lifetimes in a biological sample provides useful information about the probe environment that is not readily available from fluorescence intensity alone. Cell membrane potential, pH, concentration of oxygen ([O]), calcium ([Ca]), NADH and other ions and metabolites are all regularly measured by lifetime-based techniques. These measurements provide invaluable knowledge about cell homeostasis, metabolism and communication with the cell environment.

Genetically encoded FRET probes for direct mapping and quantification of intracellular oxygenation level via fluorescence lifetime imaging.

Molecular oxygen is an important reporter of metabolic and physiological status at the cellular and tissue level and its concentration is used for the evaluation of many diseases (e.g.: cancer, coronary artery disease).

Intracellular oxygen mapping using a myoglobin-mCherry probe with fluorescence lifetime imaging.

Oxygen (O2) is one of the most important biometabolites. In abundance, it serves as the limiting terminus of aerobic respiratory chains in the mitochondria of higher organisms; in deficit, it is a potent determinant of development and regulation of other physiological and therapeutic processes. Most knowledge on intracellular and interstitial concentration ([O2]) is derived from mitochondria isolated from cells or tissue biopsies, providing detailed but nonnative insight into respiratory chain function.

Investigating the effect of poly-l-lactic acid nanoparticles carrying hypericin on the flow-biased diffusive motion of HeLa cell organelles.

Objectives: In this study, we investigate in human cervical epithelial HeLa cells the intracellular dynamics and the mutual interaction with the organelles of the poly-l-lactic acid nanoparticles (PLLA NPs) carrying the naturally occurring hydrophobic photosensitizer hypericin.

Methods: Temporal and spatiotemporal image correlation spectroscopy was used for the assessment of the intracellular diffusion and directed motion of the nanocarriers by tracking the hypericin fluorescence. Using image cross-correlation spectroscopy and specific fluorescent labelling of endosomes, lysosomes and mitochondria, the NPs dynamics in association with the cell organelles was studied.

A summary of light dose distribution using an IR navigation system for Photofrin-mediated Pleural PDT.

Uniform delivery of light fluence is an important goal for photodynamic therapy. We present summary results for an infrared (IR) navigation system to deliver light dose uniformly during intracavitory PDT by tracking the movement of the light source and providing real-time feedback on the light fluence rate on the entire cavity surface area. In the current intrapleural PDT protocol, 8 detectors placed in selected locations in the pleural cavity monitor the light doses.

Three-dimensional finite-element based deformable image registration for evaluation of pleural cavity irradiation during photodynamic therapy.

Purpose: Photodynamic therapy (PDT) is used after surgical resection to treat the microscopic disease for malignant pleural mesothelioma and to increase survival rates. As accurate light delivery is imperative to PDT efficacy, the deformation of the pleural volume during the surgery is studied on its impact on the delivered light fluence. In this study, a three-dimensional finite element-based (3D FEM) deformable image registration is proposed to directly match the volume of lung to the volume of pleural cavity obtained during PDT to have accurate representation of the light fluence accumulated in the lung, heart and liver (organs-at-risk) during treatment.

Evaluation of the 2-(1-Hexyloxyethyl)-2-devinyl pyropheophorbide (HPPH) mediated photodynamic therapy by macroscopic singlet oxygen modeling [J. Biophotonics 9, No. 11-12, 1344-1354 (2016)].

In the article by R. Penjweini, M. M.

Evaluation of singlet oxygen explicit dosimetry for predicting treatment outcomes of benzoporphyrin derivative monoacid ring A-mediated photodynamic therapy.

Existing dosimetric quantities do not fully account for the dynamic interactions between the key components of photodynamic therapy (PDT) or the varying PDT oxygen consumption rates for different fluence rates. Using a macroscopic model, reacted singlet oxygen ( [ O 2 1 ] rx ) was calculated and evaluated for its effectiveness as a dosimetric metric for PDT outcome. Mice bearing radiation-induced fibrosarcoma tumors were treated with benzoporphyrin derivative monoacid ring A (BPD) at a drug-light interval of 3 h with various in-air fluences (30 to 350 ?? J / cm 2 ) and in-air fluence rates (50 to 150 ?? mW / cm 2 ).

A Comparison of Dose Metrics to Predict Local Tumor Control for Photofrin-mediated Photodynamic Therapy.

This preclinical study examines light fluence, photodynamic therapy (PDT) dose and "apparent reacted singlet oxygen," [ O ] , to predict local control rate (LCR) for Photofrin-mediated PDT of radiation-induced fibrosarcoma (RIF) tumors. Mice bearing RIF tumors were treated with in-air fluences (50-250 J cm ) and in-air fluence rates (50-150 mW cm ) at Photofrin dosages of 5 and 15 mg kg and a drug-light interval of 24 h using a 630-nm, 1-cm-diameter collimated laser. A macroscopic model was used to calculate [ O ] and PDT dose based on in vivo explicit dosimetry of the drug concentration, light fluence and tissue optical properties.

A Comparison of Singlet Oxygen Explicit Dosimetry (SOED) and Singlet Oxygen Luminescence Dosimetry (SOLD) for Photofrin-Mediated Photodynamic Therapy.

Accurate photodynamic therapy (PDT) dosimetry is critical for the use of PDT in the treatment of malignant and nonmalignant localized diseases. A singlet oxygen explicit dosimetry (SOED) model has been developed for in vivo purposes. It involves the measurement of the key components in PDT-light fluence (rate), photosensitizer concentration, and ground-state oxygen concentration ([³₂])-to calculate the amount of reacted singlet oxygen ([¹₂]), the main cytotoxic component in type II PDT.

Explicit macroscopic singlet oxygen modeling for benzoporphyrin derivative monoacid ring A (BPD)-mediated photodynamic therapy.

Photodynamic therapy (PDT) is an effective non-ionizing treatment modality that is currently being used for various malignant and non-malignant diseases. In type II PDT with photosensitizers such as benzoporphyrin monoacid ring A (BPD), cell death is based on the creation of singlet oxygen (O). With a previously proposed empirical five-parameter macroscopic model, the threshold dose of singlet oxygen ([O]]) to cause tissue necrosis in tumors treated with PDT was determined along with a range of the magnitude of the relevant photochemical parameters: the photochemical oxygen consumption rate per light fluence rate and photosensitizer concentration (ξ), the probability ratio of O to react with ground state photosensitizer compared to a cellular target (σ), the ratio of the monomolecular decay rate of the triplet state photosensitizer (β), the low photosensitizer concentration correction factor (δ), and the macroscopic maximum oxygen supply rate (g).

Evaluation of the 2-(1-Hexyloxyethyl)-2-devinyl pyropheophorbide (HPPH) mediated photodynamic therapy by macroscopic singlet oxygen modeling.

Photodynamic therapy (PDT) is known as a non-invasive treatment modality that is based on photochemical reactions between oxygen, photosensitizer, and a special wavelength of light. However, a dosimetric predictor for PDT outcome is still elusive because current dosimetric quantities do not account for the differences in the PDT oxygen consumption rate for different fluence rates. In this study, we evaluate several dose metrics, total fluence, photobleaching ratio, PDT dose, and mean reacted singlet oxygen (mean [ O ] ) for predicting the PDT outcome and a clinically relevant tumor re-growth endpoint.

Macroscopic singlet oxygen modeling for dosimetry of Photofrin-mediated photodynamic therapy: an in-vivo study.

Although photodynamic therapy (PDT) is an established modality for cancer treatment, current dosimetric quantities, such as light fluence and PDT dose, do not account for the differences in PDT oxygen consumption for different fluence rates ( ? ). A macroscopic model was adopted to evaluate using calculated reacted singlet oxygen concentration ( [ O 2 1 ] rx ) to predict Photofrin-PDT outcome in mice bearing radiation-induced fibrosarcoma tumors, as singlet oxygen is the primary cytotoxic species responsible for cell death in type II PDT. Using a combination of fluences (50, 135, 200, and 250 ?? J / cm 2 ) and ? (50, 75, and 150 ?? mW / cm 2 ), tumor regrowth rate, k , was determined for each condition.

Investigating the impact of oxygen concentration and blood flow variation on photodynamic therapy.

Type II photodynamic therapy (PDT) is used for cancer treatment based on the combined action of a photosensitizer, a special wavelength of light, oxygen (O) and generation of singlet oxygen (O). Intra-patient and inter-patient variability of oxygen concentration ([O]) before and after the treatment as well as photosensitizer concentration and hemodynamic parameters such as blood flow during PDT has been reported. Simulation of these variations is valuable, as it would be a means for the rapid assessment of treatment effect.