Modulation of pathogenicity with norepinephrine related to the type III secretion system of Vibrio parahaemolyticus

Background. Norepinephrine (NE) controls the functions of the gastrointestinal tract, but its role in the pathogenicity of enteropathogens is not clear. We examined the effect of NE on the pathogenicity of Vibrio parahaemolyticus with regard to its type III secretion systems (TTSSs). Methods. To evaluate the effect of NE on pathogenicity of V. parahaemolyticus, we examined the cytotoxic activity to Caco-2 cells and enterotoxicity by use of the rat ileal loop model. It has been reported that TTSS1 causes cytotoxicity and that TTSS2 causes enterotoxicity in the animal ileal loop model. Results. Our results showed that, although NE alone did not affect the viability of Caco-2 cells, NE stimulated the cytotoxic activity of V. parahaemolyticus. Furthermore, NE increased the transcription of the TTSS1-related genes vscQ and vscU. These results indicate that NE regulates V. parahaemolyticus cytotoxic activity. The enterotoxicity of V. parahaemolyticus was increased by NE through interaction with a 1-adrenergic receptors. These results indicate that a 1-adrenergic receptors on the intestinal epithelium appear to interact with V. parahaemolyticus enterotoxicity. Conclusions. The present findings suggest that enteric NE may modulate V. parahaemolyticus pathogenicity.