Endotoxin-induced endogenous protective mechanism of alveolar type II epithelial cells of rats: the relationship with p38MAPK-HO-1-mitochondrial fusion signaling pathway

Objective To evaluate the endotoxin-induced endogenous protective mechanism of alveolar type Ⅱ epithelial cells of rats and the relationship with p38 mitogen-activated protein kinase(p38MAPK)-HO-1-mitochondrial fusion signaling pathway. Methods Rat alveolar type Ⅱepithelial cells were seeded in 6-well plates at a density of 2×105 cells/ml and divided into 5 groups(n=15 each)using a random number table method: control group(group C), lipopolysaccharide(LPS)group(group L), LPS plus p38MAPK inhibitor SB203580 group(group LS), LPS plus dimethyl sulfoxide group(group LD), and SB203580 group(group S). Cells were conventionally cultured in group C. The model of endotoxin-challenged alveolar type Ⅱ epithelial cells was established by giving LPS 10 μg/ml in L, LS and LD groups. SB203580 10 μmol and 0.1% dimethyl sulfoxide 100 μmol were added at 1 h before giving LPS in group LS and group LD, respectively. SB203580 10 μmol was added to the culture medium in group S. All the cells were incubated for 24 h. The malonaldehyde(MDA)content and superoxide dismutase(SOD)activity in the culture medium were determined by thiobarbituric acid assay and xanthine oxidase method, respectively. The expression of p38MAPK, phosphorylated p38MAPK(p-p38MAPK), hemeoxygenase-1(HO-1), mitofusin 1(Mfn1), Mfn2, and optical atrophy-1(OPA1)was measured by Western blot. Results Compared with group C, the MDA content was significantly increased, the SOD activity was decreased, and the expression of p-p38MAPK and HO-1 was up-regulated, and the expression of Mfn1, Mfn2 and OPA1 was down-regulated in L, LS and LD groups(P 0.05). Conclusion The endotoxin-induced endogenous protective mechanism of alveolar type Ⅱ epithelial cells is related to p38MAPK-HO-1-mitochondrial fusion signaling pathway in rats. Key words: p38 Mitogen-activated protein kinases; Epithelial cells; Mitochondria; Ester polysaccharides; Pulmonary alveoli