Hyperoxic exposure alters intracellular bioenergetics distribution in human pulmonary cells.

AIMS: Pulmonary oxygen toxicity is caused by exposure to a high fraction of inspired oxygen, which damages multiple cell types within the lung. The cellular basis for pulmonary oxygen toxicity includes mitochondrial dysfunction. The aim of this study was to identify the effects of hyperoxic exposure on mitochondrial bioenergetic and dynamic functions in pulmonary cells. MAIN METHODS: Mitochondrial respiration, inner membrane potential, dynamics (including motility), and distribution of mitochondrial bioenergetic capacity in two intracellular regions were quantified using cultured human lung microvascular endothelial cells, human pulmonary artery endothelial cells and A549 cells. Hyperoxic (95 % O2) exposures lasted 24, 48 and 72 h, durations relevant to mechanical ventilation in intensive care settings. KEY FINDINGS: Mitochondrial motility was altered following all hyperoxic exposures utilized in experiments. Inhomogeneities in inner membrane potential and respiration parameters were present in each cell type following hyperoxia. The partitioning of ATP-linked respiration was also hyperoxia-duration and cell type dependent. Hyperoxic exposure lasting 48 h or longer provoked the largest alterations in mitochondrial motility and the greatest decreases in ATP-linked respiration, with a suggestion of decreases in respiration complex protein levels. SIGNIFICANCE: Hyperoxic exposures of different durations produce intracellular inhomogeneities in mitochondrial dynamics and bioenergetics in pulmonary cells. Oxygen therapy is utilized commonly in clinical care and can induce undesirable decrements in bioenergy function needed to maintain pulmonary cell function and viability. There may be adjunctive or prophylactic measures that can be employed during hyperoxic exposures to prevent the mitochondrial dysfunction that signals the presence of oxygen toxcity.

Hyperbaric oxygen alters intracellular bioenergetics distribution in human dermal fibroblasts.

AIMS: Hyperbaric oxygen therapy (HBOT), used to promote wound healing, has limited efficacy in many clinical conditions. Wound healing exerts bioenergetic demands on cells that can exceed their intrinsic bioenergetic capacity to proliferate and migrate. The aim of this investigation was to quantify the effects of HBOT on mitochondrial dynamics and bioenergetics functions in cells relevant to wound healing. MAIN METHODS: High-resolution respirometry and fluorescence microscopy were used to quantify mitochondrial respiration, intermembrane potential, dynamics, including motility, and the intracellular distribution of mitochondrial bioenergetic capacity partitioned into perinuclear and cell peripheral regions in cultured human dermal fibroblasts. Cells were subjected to a range of gas mixtures and hyperbaric pressures, including conditions utilized in clinical care. KEY FINDINGS: Motility was reduced immediately following all HBOT exposures utilized in experiments. Inhomogeneities in intermembrane potential and respiration parameters were produced by different HBOT conditions. The partitioning of ATP-linked respiration was also HBOT-condition dependent. Application of HBOT at common clinical pressure and oxygen conditions resulted in the largest immediate decrement in mitochondrial motility and reductions in ATP-linked respiration in both the cell periphery and perinuclear zones. Aberrations in motility and respiration were also present 6 h after exposure. SIGNIFICANCE: HBOT produces intracellular distinctions and inhomogeneities in mitochondrial dynamics and bioenergetics. HBOT as is commonly applied in clinical medicine induced undesirable and persistent alterations in bioenergy function needed to support cell migration and/or proliferation. There may be alternative HBOT parameters that more effectively engender maintenance and adequacy of intracellular bioenergy supply to promote wound healing.

Prophylaxis of mitochondrial dysfunction caused by cellular decompression from hyperbaric exposure.

Mitochondrial dysfunction occurring in response to cellular perturbations can include altered mitochondrial motility and bioenergetic function having intracellular heterogeneity. Exogenous mitochondrial directed therapy may correct these dysfunctions. Using in vitro approaches, we find that cell perturbations induced by rapid decompression from hyperbaric conditions with specific gas exposures has differential effects on mitochondrial motility, inner membrane potential, cellular respiration, reactive oxygen species production, impaired maintenance of cell shape and altered intracellular distribution of bioenergetic capacity in perinuclear and cell peripheral domains. Addition of a first-generation cell-permeable succinate prodrug to support mitochondrial function has positive overall effects in blunting the resultant bioenergy responses. Our results with this model of perturbed cell function induced by rapid decompression indicate that alterations in bioenergetic state are partitioned within the cell, as directly assessed by a combination of mitochondrial respiration and dynamics measurements. Reductions in the observed level of dysfunction produced can be achieved with application of the cell-permeable succinate prodrug.

Photo-activated porphyrin in combination with antibiotics: therapies against Staphylococci.

Staphylococcal infections have become difficult to treat due to antibiotic insensitivity and resistance. Antimicrobial combination therapies may minimize acquisition of resistance and photodynamic therapy is an attractive candidate for these combinations. In this manuscript, we explore combined use of antibiotics and meso-tetra (4-aminophenyl) porphine (TAPP), a cationic porphyrin, for treatment of Staphylococcus aureus contamination. We characterize the antimicrobial activity of photoactivated TAPP and show that activity is largely lost in the presence of a radical scavenger. Importantly, TAPP can be reactivated with continued, albeit attenuated, antibacterial activity. We then show that the antimicrobial activity of illuminated TAPP is additive with chloramphenicol and tobramycin for S. aureus and Escherichia coli, and synergistic for MRSA and Staphylococcus epidermidis. Chloramphenicol+methylene blue, another photosensitizer, also show additivity against S. aureus. In contrast, ceftriaxone and vancomycin do not strongly augment the low level effects of TAPP against S. aureus. Eukaryotic cells exhibit a dose-dependent toxicity with illuminated TAPP. Our results suggest that even sub-minimum inhibitory concentrations of photo-activated TAPP could be used to boost the activity of waning antibiotics. This may play an important role in treatments reliant on antibiotic controlled release systems where augmentation with photo-active agents could extend their efficacy.

Gas embolism and surfactant-based intervention: implications for long-duration space-based activity.

Intravascular gas embolism can occur with decompression in space flight, and it commonly occurs during cardiac and vascular surgery. Intravascular bubbles may be deposited into any end organ such as the heart or the brain. Surface interactions between the bubble and the endothelial cells lining the vasculature result in serious impairment of blood flow and can lead to heart attack, stroke, or even death. Surfactant-based intervention is a novel treatment for gas embolism. Intravascular surfactant can adsorb onto the gas-liquid interface and compete with blood-borne macromolecules for interfacial occupancy. Surfactants can retard the progress of pathophysiological molecular and cellular events stimulated by the bubble surface, including endothelial cell injury and initiation of blood clotting. Bulk and surface transport of a surfactant to provide competition for interfacial occupancy is a therapeutic strategy because surfactant adsorption can dominate protein (or other macromolecule) adsorption. The presence of surfactant along the gas-liquid interface also induces variation in the interfacial tension, which in turn affects the blood flow and the bubble motion. We describe the interplay between biological transport processes and physiological events occurring and the cellular and molecular level in vascular gas embolization. Special consideration is given to modeling the transport and hydrodynamic interactions associated with surfactant-based intervention.