Lipopolysaccharide-induced expression of surfactant proteins A1 and A2 in human renal tubular epithelial cells
Surfactant protein A (SP-A), encoded by two functional genes, SP-A1 and SP-A2, is essential for the inflammatory process and host defence in the lungs. Recent studies have demonstrated the extrapulmonary expression of SP-A.
Similar to the lungs, the kidneys are organs exposed to external pathogens. The present study evaluated the expression and location of SP-A in the kidneys.
The effect of lipopolysaccharide (LPS) on the expression of SP-A subtypes was also studied in renal tubular epithelial (HK-2) cells.
Immunohistochemical staining was performed using polyclonal antibody against SP-A. RT-PCR was also performed using mRNA from normal human renal tissues and HK-2 cells.
The expressions of the SP-A1 and SP-A2 genes were determined by PCR-based RFLP analysis, gene-specific amplification, and direct sequencing of RT-PCR products. Western blot was conducted to analyse the SP-A protein.
HK-2 cells were treated with LPS at various concentrations (0, 0.1, 1, 2, 5, and 10 mug/mL) for 8 h and at 5 mug/mL at various time points (0, 2, 4, 8, 16, and 24 h). The LPS-induced expressions of SP-A1 and SP-A2 mRNA and protein were analysed by RT-PCR and Western blot.
SP-A was localised in the renal tubular epithelial cells in the proximal and distal convoluted tubules.
SP-A1 and SP-A2 mRNA and protein were expressed in HK-2 cells and human renal tissues, which were significantly increased in time- and dose-dependent manners after LPS treatment (P <0.05).
Human renal tubular epithelial cells can express both SP-A1 and SP-A2 genes, which may play important roles in the inflammatory modulation of the kidney.
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