Effect of Outer Membrane Vesicles on Host Oxidative Stress Response.

Outer membrane vesicles (OMVs) are spherical bodies containing proteins and nucleic acids that are released by Gram-negative bacteria, including , the causative agent of Lyme disease. The functional relationship between OMVs and host neuron homeostasis is not well understood. The objective of this study was to examine how OMVs impact the host cell environment. First, an in vitro model was established by co-culturing human BE2C neuroblastoma cells with B31. was able to invade BE2C cells within 24 h. Despite internalization, BE2C cell viability and levels of apoptosis remained unchanged, but resulted in dramatically increased production of MCP-1 and MCP-2 cytokines. Elevated secretion of MCP-1 has previously been associated with changes in oxidative stress. BE2C cell mitochondrial superoxides were reduced as early as 30 min after exposure to and OMVs. To rule out whether BE2C cell antioxidant response is the cause of decline in superoxides, superoxide dismutase 2 (SOD2) gene expression was assessed. SOD2 expression was reduced upon exposure to , suggesting that might be responsible for superoxide reduction. These results suggest that modulates cell antioxidant defense and immune system reaction in response to the bacterial infection. In summary, these results show that OMVs serve to directly counter superoxide production in BE2C neurons, thereby 'priming' the host environment to support colonization.