Mitochondrial Dysfunction in Acute Lung Injury is Characterized By Loss of Mitochondrial Calcium Uniporter (MCU)

Acute lung injury (ALI) associates with loss of lung mitochondrial function. Oxidant damage by mitochondrial H2O2 may cause mitochondrial dysfunction. Since the mitochondrial calcium uniporter (MCU) determines mitochondrial Ca 2+ levels, hence function, we considered the possibility that oxidant‐induced MCU impairment might underlie mitochondrial dysfunction in ALI. To induce ALI, we intra‐nasally instilled lipopolysaccharide (LPS, 1mg/kg) or PBS (control). To determine H2O2, we expressed a mitochondrial matrix‐targeted probe, matrix‐roGFP, in alveolar type 2 (AT2) cells in situ . By alveolar micropuncture we loaded mitochondrial Ca 2+ dye, rhod 2, or the lamellar body (LB)‐staining dye LysoTracker Red (LTR). In control lungs, H2O2 fluorescence was 145±7 grey levels in AT2 cells, indicating successful probe expression. In LPS lungs, AT2 mitochondrial H2O2 fluorescence was 75±8 (P<0.05), indicating increased H2O2 generation. Immunoblots in AT2 cell mitochondria show that LPS downregulated MCU. However, LPS‐induced MCU downregulation could be reversed in mice over‐expressing human catalase (hmCAT) in mitochondria of AT2 cells. In addition, hmCAT over‐expressing mice reversed LPS‐induced inhibition of mitochondrial Ca 2+ entry and surfactant secretion in response to a 15s lung hyperinflation. These data are the first direct evidence that lung exposure to LPS causes mitochondrial dysfunction marked by oxidant‐induced loss of MCU. Taken together, our findings indicate that alveolar MCU is a major determinant of ALI. Strategies aimed at restoring alveolar MCU expression might lead to novel therapy for ALI. Support or Funding Information PBF fellowship for MNI and HL122730 for JB