Effect of surfactant protein A on lipopolysaccharide-induced tumor necrosis factor-α expression in human proximal tubular epithelial cells.
BACKGROUND
Surfactant protein A (SP-A) contributes to the regulation of sepsis-induced acute lung injury. In a previous study, we demonstrated the expression and localization of SP-A in the kidneys. The present study evaluated the effect of SP-A on lipopolysaccharide (LPS)-induced tumor necrosis factor-a (TNF-α) expression and its underlying mechanisms in the human renal tubular epithelial (HK-2) cells.


METHODS
Indirect immunofluorescence assay was used to detect SP-A distribution and expression in HK-2 cells. HK-2 cells were treated with various concentrations of LPS (0, 0.1, 1, 2, 5, and 10 mg/L) for 8 hours and with 5 mg/L LPS for different times (0, 2, 4, 8, 16, and 24 hours) to determine the effects of LPS on SP-A and TNF-α expression. Then, HK-2 cells were transfected with SP-A siRNA to analyze nuclear factor κB (NF-κB) P65 and TNF-α expression of HK-2 cells after LPS-treatment.


RESULTS
Indirect immunofluorescence assay revealed that SP-A is localized to the membrane and cytoplasm of HK-2 cells. Interestingly, SP-A1/SP-A2 and TNF-a expression were found to be significantly increased in HK-2 cells upon LPS treatment. Transfection of LPS-treated HK-2 cells with SP-A siRNA resulted in significant increases in the levels of NF-κB P65 protein and TNF-α mRNA and protein compared to those in non-transfected LPS-treated HK-2 cells.


CONCLUSIONS
SP-A plays an important role in protecting cells against sepsis-induced acute kidney injury by inhibiting NF-κB activity to modulate LPS-induced increase in TNF-α expression.
Department of Critical Care Medicine, Wuhan University Renmin Hospital, Wuhan, Hubei 430060, China.
Jiao
J
Liu
Department of General Surgery, Wuhan University Renmin Hospital, Wuhan, Hubei 430060, China.
Zhiyong
Z
Liu
Department of Critical Care Medicine, Wuhan University Renmin Hospital, Wuhan, Hubei 430060, China.
Lizhi
L
Feng
Department of Nephropathy, Wuhan University Renmin Hospital, Wuhan, Hubei 430060, China.
Guohua
G
Ding
Critical Care and Emergency Department, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China.
Dechang
D
Chen
Department of Critical Care Medicine, Wuhan University Renmin Hospital, Wuhan, Hubei 430060, China.
Qingshan
Q
Zhou
D002460:Cell Line; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D037662:Pulmonary Surfactant-Associated Protein A / Q000378:metabolism / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D008070:Lipopolysaccharides; D037662:Pulmonary Surfactant-Associated Protein A; C445842:SFTPA1 protein, human; D014409:Tumor Necrosis Factor-alpha