Role of protein kinase Cα/heme oxygenase-1 signaling pathway in LPS-caused damage to typeII alveolar epithelial cells of rats: the relationship with mitochondrial fusion

Objective To evaluate the role of protein kinase Cα(PKCα)/heme oxygenase-1(HO-1) signaling pathway in lipopolysaccharide(LPS)-caused damage to typeⅡ alveolar epithelial cells of rats and the relationship with mitochondrial fusion. Methods TypeⅡ alveolar epithelial cells were seeded in 96-well plates at a density of 2×105cells/ml and divided into 5 groups(n=40 each) using a random number table method: control group(group C), Go6976 group(group G), LPS group(group L), LPS plus PKCα inhibitor Go6976 group(group LG) and LPS plus dimethyl sulfoxide(DMSO) group(group LD). Group LG and group LD were pretreated with 5 μmol/L Go6976 and the equal volume of 0.1% DMSO, respectively, for 30 min, lipopolysaccharide(LPS) 10 μg/ml was then given to establish the model of type Ⅱ alveolar epithelial cell damage in L, LG and LD groups, Go6976 5 μmol/L was added in group G, and the equal volume of phosphate buffer solution was added in group C. The cells were collected after 24 h of incubation for measurement of malondialdehyde(MDA) and reactive oxygen species(ROS) contents, superoxide dismutase(SOD) activity and expression of PKCα, HO-1, mitochondrial fusion-related proteins 1 and 2(Mfn1, Mfn2), optic atrophy 1(OPA1) protein and mRNA(by fluorescent quantitative polymerase chain reaction or Western blot). Results Compared with group C, MDA and ROS contents were significantly increased, the SOD activity was decreased, the expression of PKCα and HO-1 protein and mRNA was up-regulated, and the expression of Mfn1, Mfn2 and OPA1 protein and mRNA was down-regulated in L, LG and LD groups(P 0.05). Compared with group L, MDA and ROS contents were significantly increased, the SOD activity was decreased, and the expression of PKCα, HO-1, Mfn1, Mfn2 and OPA1 protein and mRNA was down-regulated in group LG(P 0.05). Conclusion Activation of PKCα/HO-1 signaling pathway is the endogenous protective mechanism of LPS-caused damage to typeⅡ alveolar epithelial cells, which may be related to promoting mitochondrial fusion in rats. Key words: Protein kinase c-alpha; Heme oxygenase-1; Lipopolysaccharides; Epithelial cells; Pulmonary alveoli; Mitochondrial fusion