Role of PI3K/Akt signaling pathway in mitochondrial fission in endotoxin-challenged alveolar type II epithelial cells of rats

Objective To evaluate the role of phosphatidylinositol 3-kinase/serine-threonine kinase (PI3K/Akt) signaling pathway in mitochondrial fission in endotoxin-challenged alveolar type Ⅱ epithelial cells of rats. Methods Rat alveolar type Ⅱ epithelial cells CCL-149 were seeded in 6-well plates at a density of 2×105 cells/ml.CCL-149 cells were divided into 6 groups (n =10 each) using a random number table: control group (group C), lipopolysaccharide (LPS) group (group L), LPS plus CO-releasing molecule-2 (CORM-2) group (group L+ CO), LPS plus PI3K inhibitor LY294002 group (group L+ LY), LPS plus iCORM-2 group (group L+ iCO) and LPS plus dimethyl sulfoxide (DMSO) group (group L+ D). CCL-149 cells were stimulated with 10 μg/ml LPS for 24 h in L, L+ CO, L+ LY, L+ iCO and L+ D groups.CORM-2 100 μmol, LY294002 25 μg and iCORM-2 100 μmol were added at 1 h before stimulation with LPS in L+ CO, L+ LY and LPS+ iCO groups, respectively.In group L+ D, 0.1% DMSO 100 μmol was added at 1 h before stimulation with LPS.After the end of incubation, the concentrations of tumor necrosis factor-α (TNF-α) and interleukin-6(IL-6) in the culture medium were determined by enzyme-linked immunosorbent assay, and the expression of phosphorylated-Akt (p-Akt), heme oxygenase-1 (HO-1), dynamin-related protein 1 (Drp1) and fission1 (Fis1) was detected by Western blot. Results Compared with group C, IL-6 and TNF-α concentrations in the culture medium were significantly increased, and the expression of p-Akt, HO-1, Drp1and FIS1 was up-regulated in L, L+ CO, L+ LY, L+ iCO and L+ D groups (P<0.05). Compared with group L, IL-6 and TNF-α concentrations in the culture medium were significantly decreased, the expression of p-Akt and HO-1 was up-regulated, and the expression of Drp1 and Fis1 was down-regulated in group L+ CO, and IL-6 and TNF-α concentrations in the culture medium were significantly increased, the expression of p-Akt and HO-1 was down-regulated, and the expression of Drp1 and Fis1 was up-regulated in group L+ LY (P<0.05). Conclusion Activation of PI3K/Akt signaling pathway can inhibit mitochondrial fission in endotoxin-challenged alveolar type Ⅱ epithelial cells of rats. Key words: 1-Phosphatidylinositol 3-kinase; Protein-serine-threonine kinases; Endotoxins; Mitochondria; Epithelial cells; Pulmonary alveoli