The Vibrio cholerae Cytotoxin (VCC) Simultaneously Activates Responses of Death, Inflammation (NF-κB) and Survival (AP-1) through the MAPK Signaling in Human Macrophages THP-1

The human innate immune response to the pore-forming toxin of Vibrio cholerae VCC, is currently under study. Here, in vitro studies on a human macrophage cell line (THP-1), helped explore the activated pathways involved on the onset the innate immune response towards the cytotoxin. The secreted monomeric 65 KDa form interacts with mature macrophages in pg/ml concentrations, determined by dose response experiments after treatments under 1 h. Non vacuolating concentrations (pg/ml) were applied to the cells; immunoblots revealed activation of MAPKs: early overexpression of p38 and ERK. Cell lysis by release of lactate dehydrogenase (LDH) was not apparent in the first hour, nonetheless it was positive after 24 h. Finally, to discern whether the VCC stimulates transcriptional activators via MAPKs pathway, NF-κB and AP-1 were studied by real time quantitation. Increased expression of p50 (NF-κB), cJun and cFos (AP-1) was observed. Given that NF-κB is the transcription factor initiating inflammation of innate immune response and in turn, AP-1 is responsible for cell surviving response, results from this study lead us to conclude that VCC in vitro treatments, induce a pro-inflammatory and a surviving response, in less than one hour on activated macrophages.