Stimulated innate resistance event (StIR) in Bordetella pertussis infection is dependent on reactive oxygen species production.

ZURITA, MARIA EUGENIA; MORENO, GRISELDA; ERREA, AGUSTINA; ORMAZABAL, MAXIMILIANO; CURCIARELLO, RENATA; RUMBO, MARTIN; D. HOZBOR

Dublin

Simposio; 10th International Symposium on Bordetella; 2013

The exacerbated induction of innate immune response in airways can abrogate diverse lung infections by a phenomenon known as stimulated innate resistance (StIR). We have demonstrated that the enhancement of innate response activation can efficiently impair Bordetella pertussis colonization in a TLR4-dependent manner. The aim of the present work was to further characterize this phenomenon. Our results showed that bacterial infection was completely abrogated in treated mice when the B. pertussis LPS (1µg) was added before (48h or 24h), after (24h) or simultaneously with the B. pertussis challenge (107CFU). Moreover, we detected that LPS completely cleared bacterial infection as soon as 2 h post-treatment. This timing suggests that StIR should be mediated by fast-acting antimicrobial mechanisms. To evaluate the possible role of free radicals in the StIR, we performed animal assays using the antioxidant N-acetyl cysteine (NAC). NAC administration blocked the B. pertussis clearance induced by LPS. Nitrite concentrations were also increased in the LPS-treated mice; however, the inhibition of nitric oxide synthetases did not suppress the LPS-induced bacterial clearance. In order to evaluate the role of epithelial cells in ROS production induced by LPS, we performed in vitro experiments using human alveolar epithelial A549. We observed that the exposure of A549 cells to LPS increased the production of inflammatory cytokines and ROS levels. This induction is LPS concentration- and time-dependent. Taken together, our results showed that ROS induced at least in part by the host epithelial cells play an essential role in the TLR4-dependent innate clearance of B. pertussis.