ABSTRACT
Objective To construct a mutant strain of Nocardia farcinica ( N. farcinica ) IFM10152 with mammalian cell entry 4A gene (mce4A) deletion and to analyze the function of that gene dur-ing infection. -ethods The mutant strain of N. farcinica was constructed through in-frame deletion without antibiotic labeling and verified by PCR and sequencing analysis. To analyze the function of mce4A gene in the interaction between N. farcinica and host cells, in vitro growth experiment, macrophage killing experi-ment using THP-1 ( a human leukemia mononuclear cell line) as the model and adhesion and invasion exper-iments using HeLa cells ( cervical cancer epithelial cells) were carried out. Results The mutant strain with mce4A gene deletion was successfully constructed and named △mce4A. No significant difference in growth rate was observed between the mutant and the wild-type strains. After knocking out the mce4A gene, the ability of N. farcinica to resist macrophage killing was obviously weakened as well as its ability to adhere and invade. Conclusions The mutant strain of N. farcinica with mce4A gene deletion was successfully construc-ted. The mce4A gene might play an important role in the adhesion and invasion of N. farcinica to host cells and its survival in macrophages.
ABSTRACT
Objective To investigate the effects of high glucose and lysophosphatidylcholine (LPC) on the immune function of in vitro cultured macrophages during Nocardia farcinica infection. Meth-ods RAW264.7 macrophages were cultured in vitro under different conditions as follows: routine culture (control group),50 mmol/L glucose (high glucose group),10 mg/L LPC(LPC groupⅠ),25 mg/L LPC (LPC groupⅡ) and 50 mmol/L glucose+25 mg/L LPC(high glucose and LPC group). The activity of mac-rophages in each group was tested after 6,12,24 and 36 h of culture. After 24 h of culture, macrophages were collected from every group and co-cultured with Nocardia farcinica. Dynamic phagocytosis rates were detected at 1,2,3,4,5 and 6 h after co-culture. Toxic effects of Nocardia farcinica on macrophages and concentrations of IL-10 and TNF-α were measured at 1,3 and 6 h after co-culture. Results Macrophages in all four experimental groups showed decreased activity as compared with those in the control group (P<0.01). Phagocytosis of Nocardia farcinica by macrophages was also reduced by high glucose and LPC. Phagocytosis rates of high glucose group and LPC groupⅡ at 1 and 2 h,LPC groupⅠat 1,2 and 3 h,and high glucose and LPC group at 1,2,3 and 4 h after co-culture were significantly lower than that of the con-trol group (P<0.05 or P<0.01). Compared with the control group, significantly reduced toxic effects on macrophages caused by Nocardia farcinica was observed in the experimental groups (P<0.05 or P<0.01). Compared with the control group,LPC groupsⅠand Ⅱ and high glucose and LPC group had decreased se-cretion of IL-10 at 3 h,and high glucose group and LPC groupⅠhad decreased secretion of TNF-α at 1 h(P<0.05). Conclusion Culture macrophages under the conditions of high glucose and LPC would reduce their activity and impair their ability to phagocytose Nocardia farcinica. Moreover, high glucose and LPC might have impacts on the toxic effects of Nocardia farcinica on macrophages and the secretion of IL-10 and TNF-α.