Development of acute respiratory distress syndrome (ARDS) in influenza A virus (IAV)-infected mice is associated with inhibition of ATII (alveolar type II) epithelial cell de novo phosphatidylcholine synthesis, and administration of the phosphatidylcholine precursor cytidine 5'-diphosphocholine (CDP-choline) attenuates IAV-induced acute respiratory distress syndrome in mice. We hypothesized inhibition of phosphatidylcholine synthesis would also impact the function of ATII cell mitochondria. To test this hypothesis, adult C57BL/6 mice of both sexes were inoculated intranasally with 10,000 pfu/mouse influenza A/WSN/33 (H1N1). Control mice were mock-infected with virus diluent. Mice were treated with saline vehicle or CDP-choline (100 μg/mouse i.p.) once daily from 1 to 5 days postinoculation (dpi). ATII cells were isolated by a standard lung digestion protocol at 6 dpi for analysis of mitochondrial function. IAV infection increased uptake of the glucose analog fludeoxyglucose F 18 by the lungs and caused a switch from oxidative phosphorylation to aerobic glycolysis as a primary means of ATII cell ATP synthesis by 6 dpi. Infection also induced ATII cell mitochondrial depolarization and shrinkage, upregulation of PGC-1α, decreased cardiolipin content, and reduced expression of mitofusin 1, OPA1, DRP1, complexes I and IV of the electron transport chain, and enzymes involved in cardiolipin synthesis. Daily CDP-choline treatment prevented the declines in oxidative phosphorylation, mitochondrial membrane potential, and cardiolipin synthesis resulting from IAV infection but did not fully reverse the glycolytic shift. CDP-choline also did not prevent the alterations in mitochondrial protein expression resulting from infection. Taken together, our data show ATII cell mitochondrial dysfunction after IAV infection results from impaired de novo phospholipid synthesis, but the glycolytic shift does not.
Keywords: cardiolipin; glycolysis; oxidative phosphorylation; phospholipids.