[Study of regulatory effect of insulin on expression of epithelial sodium channel alpha subunit in A549 cells].
OBJECTIVE
To observe the effects of insulin on the expression of epithelial sodium channel alpha subunit (ENaC-alpha) in human pulmonary adenocarcinoma cell line (A549 cells) and its impact on apoptosis of the cells.


METHODS
A549 cells were cultured with insulin in a concentration of 30 U/L for 30 minutes or 60 minutes. Then ENaC-alpha, serum and glucocorticoid-inducible kinase-1 (SGK-1) protein and mRNA were determined with Western blotting and reverse transcription-polymerase chain reaction (RT-PCR). Then chelidonii, a blocking agent of protein kinase C (PKC), which could inhibit the effect of SGK-1, was added to the cells culture for 60 minutes, and ENaC-alpha protein was then determined. Cells were cultured in a hypoxia circumstance for 30 minutes, to induce apoptosis, the rate of which was detected with terminal-deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL), in cells cultured with or without insulin.


RESULTS
Insulin could up-regulate the protein and mRNA expression of ENaC-alpha and SGK-1 in A549 cells, and there was a significant difference at 30 minutes, and it gradually increased with prolongation of time. When A549 cells were cultured without insulin, the protein expression of A549 cells was 100%. The protein expression of ENaC-alpha and SGK-1 was 124% and 135% at 30 minutes after being cultured with insulin, and 186% and 176% at 60 minutes, respectively (all P<0.05). Insulin also could inhibit apoptosis which was induced by hypoxia (10.3% vs. 21.6%, P<0.05).


CONCLUSIONS
Insulin can up-regulate expression of the ENaC-alpha in A549 cells via PKC and SGK-1 pathways, also insulin can inhibit hypoxia induced apoptosis. So insulin can be beneficial in the prognosis of acute lung injury/acute respiratory distress syndrome (ALI/ARDS).
Zhang
Wei
W
The Respiratory Department of Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, China.
Wang
Dao-xin
DX
D017209:Apoptosis / Q000187:drug effects; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D053503:Epithelial Sodium Channels / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000166:cytology*
D053503:Epithelial Sodium Channels; D007328:Insulin; C507045:SCNN1A protein, human