The lipid-associated membrane proteins derived from Mycoplasma pneumoniae strains induced the expression of HO-1 in THP-1 cells

Abstract

Objective To investigate the effects of lipid-associated membrane proteins (LAMPs) derived from Mycoplasma pneumoniae (M. pneumoniae) strains on the expression of heme oxygenase 1 (HO-1) in a human monocyte cell line (THP-1). Methods THP-1 cells were in vitro cultured with different concentrations of LAMPs for different times. The cytotoxicity of LAMPs to THP-1 cells was analyzed by using lactate dehydrogenase (LDH) releasing test. The expression of HO-1 at protein and mRNA levels were detected by Western blot and real-time RT-PCR, respectively. The enzymatic activity of HO-1 protein was examined by colorimetric assay. THP-1 cells stimulated with PBS and LPS were set up as the negative and positive controls, respectively. Results A significantly enhanced LDH releasing rate was observed in THP-1 cells treated with 10 μg/ml of LAMPs. The expression of HO-1 at protein and mRNA levels in THP-1 cells were induced by LAMPs in a dose-dependent and time-dependent manner. The highest level of HO-1 protein was detected in THP-1 cells treated with 5.0 μg/ml of LAMPs. The transcriptional levels of HO-1 induced by LAMPs were significantly elevated at 3 h, peaked at 9 h and were decreased at 12 h. The expression of HO-1 protein in THP-1 cells was enhanced after 8 h of treatment with LAMPs and a significant decrease was observed at 20 h after reaching peaks at 12 h and 16 h. The activity of HO-1 protein was significantly enhanced along with the increased expression of HO-1 protein. Conclusion The LAMPs derived from M. pneumoniae strains induced the expression of HO-1 at mRNA and protein levels. Moreover, the enzyme activity of HO-1 protein was enhanced in LAMPs treated THP-1 cells. Key words: Mycoplasma pneumoniae; Lipid-associated membrane proteins (LAMPs); Heme oxygenase 1 (HO-1)