Introduction

1. 1.5 NS 1.0 Pyocyanin (relative amount) 0.5 0 PAO1 PAO1 PAO1 Vfr- Vfr- Vfr- + + + + BNP CNP BNP CNP C-type natriuretic peptide (CNP) enhances quorum sensing factors production through activation of intracellular cyclic nucleotides synthesis in Pseudomonas aeruginosa PAO1 VERON W.1, BLIER A.S., TAUPIN L.2, REHEL K.2, ORANGE N.1, FEUILLOLEY M.G.J.1, LESOUHAITIER O.1 1. Laboratoire de Microbiologie Du Froid-Signaux et Micro-Environnement UPRES 4312, Université de Rouen, 27000 Évreux, France 2. Laboratoire de Biotechnologie et Chimie Marine, Université de Bretagne Sud B.P. 92116, 56321 Lorient, France Introduction There is now ample evidence that eukaryotic signal molecules synthesized and released by the host may activate the virulence of opportunistic pathogens through specific bacterial sensors. Natriuretic peptides represent a family of diuretic and osmoregulatory peptideswhich are increased in human blood during septic shock. It was shown that Pseudomonas aeruginosa PAO1 is sensitive to two members of this peptide family, the Brain Natriuretic Peptide (BNP) and the C-type natriuretic peptide (CNP) which are able to increase the global cytotoxic activity of the bacteria through the Vfr protein. In order to understand the precise mechanism of action of natriuretic peptides on PAO1, we studied the impact of BNP and CNP on bacterial physiological parameters (second messengers rates, toxins and homoserine lactone and PQS production). 1. Involvement of bacterial cyclase in the effect of natriuretic peptides on Pseudomonas aeruginosa PAO1 2. Natriuretic peptides enhance the production of both C4-HSL and oxo-C12-HSLby P. aeruginosa 2.5 2.5 NS 150 200 2.0 2.0 150 100 1.5 1.5 C4-HSL (relative amount) 3oxoC12HSL (relative amount) LDH (% of control) cAMP (pmol/ml) 100 1.0 1.0 50 50 0.5 0.5 0 0 0 0 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 + + + + + + + + 8bGMP dbAMP BNP BNP CNP BNP CNP CNP Conclusion 3.CNP reduces the P. aeruginosa production of PQS and its precursor HHQ BNP / CNP 1.5 1.5 Pseudomonas Inner Membrane SENSOR CyaA/B ? 1.0 1.0 HHQ (relative amount) PQS (relative amount) AMPc/GMPc 0.5 0.5 HHQ/PQS Vfr 0 0 C4-HSL / 3oxoC12-HSL PAO1 PAO1 PAO1 PAO1 PAO1 PAO1 Pyocyanin + + + + BNP BNP CNP CNP Taken together our present study suggests that natriuretic peptides modulate Pseudomonas aeruginosa virulence through activation of a putative sensor coupled to a cyclase (CyaA/B ?). The resulting increase of cAMP level provokes an activation of the Vfr protein. Finally, the Vfr protein modifies physiological parameters involved in the virulence of the bacterium, such as quorum sensing molecules production, PQS synthesis or pyocyanin production. These data suggest that the communication mechanisms expressed by Pseudomonas are probably more complex than usually considered and deserve further investigation to determine the precise mechanisms of natriuretic peptides action on Pseudomonas. 4. CNP reduces the production of pyocyanin by P. aeruginosa through the Vfr protein Supported by grants from CG27 and CA Evreux