[Outer membrane protein 31 of B. melitensis induces the formation of autophagosomes in BV-2 microglia cells].

Objective To determine the influence of outer membrane protein 31 (Omp31) of B. melitensis on the formation of autophagosomes in BV-2 microglia cells. Methods BV-2 cells were treated for 6 hours with Omp31 at 0.17, 0.50, 1.50, 4.50, 13.50 μg/mL. Real-time quantitative PCR was used to detect the expression of microtubule associated protein 1 light chain 3B (LC3B) mRNA; Western blotting was applied to detect the expressions of LC3B II and LC3B proteins; transmission electron microscopy was performed to observe cell autophagy in each group. The levels of tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and IL-10 in the culture cell supernatant were determined with ELISA. Results Omp31 treatment resulted in an increase in the level of LC3B II protein, especially the most obvious increase in the ones treated by 0.5 μg/mL Omp31. The concentration of Omp31, being no more than 0.5 μg/mL, could promote the expression of LC3B mRNA, while more than 0.5 μg/mL Omp31, it could inhibit the expression of LC3B mRNA; 0.5 μg/mL Omp31 could induce the formation of more autophagosomes in BV-2 cells. Omp31 promoted the expressions of TNF-α and IL-6, and inhibited the expression of IL-10 in BV-2 cells. Conclusion Omp31 at the concentration of 0.5 μg/mL can significantly induce autophagy in BV-2 cells.