Hyperoxia Decreases Glycolytic Capacity, Glycolytic Reserve and Oxidative Phosphorylation in MLE-12 Cells and Inhibits Complex I and II Function, but Not Complex IV in Isolated Mouse Lung Mitochondria

Abstract

High levels of oxygen (hyperoxia) are frequently used in critical care units and in conditions of respiratory insufficiencies in adults, as well as in infants. However, hyperoxia has been implicated in a number of pulmonary disorders including bronchopulmonary dysplasia (BPD) and adult respiratory distress syndrome (ARDS). Hyperoxia increases the generation of reactive oxygen species (ROS) in the mitochondria that could impair the function of the mitochondrial electron transport chain. We analyzed lung mitochondrial function in hyperoxia using the XF24 analyzer (extracellular flux) and optimized the assay for lung epithelial cells and mitochondria isolated from lungs of mice. Our data show that hyperoxia decreases basal oxygen consumption rate (OCR), spare respiratory capacity, maximal respiration and ATP turnover in MLE-12 cells. There was significant decrease in glycolytic capacity and glycolytic reserve in MLE-12 cells exposed to hyperoxia. Using mitochondria isolated from lungs of mice exposed to hyperoxia or normoxia we have shown that hyperoxia decreased the basal, state 3 and state3 μ (respiration in an uncoupled state) respirations. Further, using substrate or inhibitor of a specific complex we show that the OCR via complex I and II, but not complex IV was decreased, demonstrating that complexes I and II are specific targets of hyperoxia. Further, the activities of complex I (NADH dehydrogenase, NADH-DH) and complex II (succinate dehydrogenase, SDH) were decreased in hyperoxia, but the activity of complex IV (cytochrome oxidase, COX) remains unchanged. Taken together, our study show that hyperoxia impairs glycolytic and mitochondrial energy metabolism in in tact cells, as well as in lungs of mice by selectively inactivating components of electron transport system.

Proteomic analysis of mitochondrial proteins in the guinea pig heart following long-term normobaric hyperoxia

“…However, evidence exist that hyperoxia causes significant shift of substrate preference from fatty acids to glycolysis [38,39]. On the other hand, studies on mouse lung suggest that hyperoxia decreases glycolytic capacity and reserve and impairs mitochondrial energy metabolism [40]. Our proteomics findings support the viewpoint that glucose metabolism is stimulated by hyperoxia.…”

Cigarette smoke extract affects mitochondrial function in alveolar epithelial cells

“…Oxygen consumption was measured at basal conditions (basal respiration), after addition of 2.5 M oligomycin (blocking proton backflow through complex V to measure residual proton leak), after addition of 1 M CCCP (uncoupling the respiratory chain to enable unlimited proton flow through the mitochondrial membrane to induce maximum respiration), and after addition of 2.5 M antimycin A/rotenone (blocking complex I and III to inhibit mitochondrial respiration). These concentrations were also previously shown to be suitable for measuring oxygen consumption rates in MLE12 cells (11).…”

Postnatal Hyperoxia Exposure Durably Impairs Right Ventricular Function and Mitochondrial Biogenesis

“…Thus, a direct effect of hyperoxia on the immature RV cardiomyocyte should be considered. Although postnatal Hx is known to acutely worsen mitochondrial dysfunction and oxidative stress in the lung, relative hyperoxia, as is encountered at birth into a normoxic environment, is critical to initiate neonatal cardiac mitochondrial biogenesis and oxidative metabolism within the LV (35)(36)(37)(38). However, (normalized to vinculin) after Hx, all key elements of mitochondrial structure.…”