This study was designed to assess the effect of hypoxia on AhR transcriptional KU-55933 DNA Damage/DNA Repair inhibitor responses after exposure to 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126). Exposure to 1% 02 prior to PCB 126 treatment significantly inhibited CYP1A1 mRNA and protein expression in human HepG2 and HaCaT

cells. CYP1A1 transcriptional activation was significantly decreased upon PCB 126 stimulation under conditions of hypoxia. Additionally, hypoxia pretreatment reduced PCB 126 induced AhR binding to CYP1 target gene promoters. Importantly, ARNT overexpression rescued cells from the inhibitory effect of hypoxia on XRE-luciferase reporter activity. Therefore, the mechanism of interference of the signaling crosstalk between the AhR and hypoxia pathways appears to be at least in part dependent on ARNT availability. Our results show that AhR activation and CYP1A1 expression induced by PCB 126 were significantly inhibited by hypoxia and hypoxia might therefore play an important role in PCB metabolism and toxicity. (C) 2013

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“Mechanical ventilation may cause harm by straining lungs at a time they are particularly prone to injury from deforming stress. The objective of this study was to define the relative contributions of alveolar overdistension and cyclic recruitment and “collapse” of Fer-1 manufacturer unstable lung units to membrane wounding of alveolar epithelial cells. We measured the A-1210477 interactive effects of tidal volume (V-T), transpulmonary pressure (P-TP), and of airspace liquid on the number of alveolar epithelial cells with plasma membrane wounds

in ex vivo mechanically ventilated rat lungs. Plasma membrane integrity was assessed by propidium iodide (PI) exclusion in confocal images of subpleural alveoli. Cyclic inflations of normal lungs from zero end-expiratory pressure to 40 cmH(2)O produced V-T values of 56.9 +/- 3.1 ml/kg and were associated with 0.12 +/- 0.12 PI-positive cells/alveolus. A preceding tracheal instillation of normal saline (3 ml) reduced V-T to 49.1 +/- 6 ml/kg but was associated with a significantly greater number of wounded alveolar epithelial cells (0.52 +/- 0.16 cells/alveolus; P < 0.01). Mechanical ventilation of completely saline-filled lungs with saline (V-T = 52 ml/kg) to pressures between 10 and 15 cmH2O was associated with the least number of wounded epithelial cells (0.02 +/- 0.02 cells/alveolus; P < 0.01). In mechanically ventilated, partially saline-filled lungs, the number of wounded cells increased substantially with V-T, but, once V-T was accounted for, wounding was independent of maximal P-TP. We found that interfacial stress associated with the generation and destruction of liquid bridges in airspaces is the primary biophysical cell injury mechanism in mechanically ventilated lungs.