Pyocyanin-induced neutrophil apoptosis modulated by the presence of a bacterial sonicate and LPS in vitro

Abstract

The paradigm of pathogen-driven neutrophil apoptosis is exemplified by the Pseudomonas aeruginosa toxic metabolite, pyocyanin that induce a dramatic acceleration of neutrophil apoptosis in Cystic fibrosis lung disease. Whether the course of pyocyanin-induced neutrophil apoptosis can be modulated or not by bacterial cell wall product present significantly in inflammatory foci is unknown.Materials and methods : Purification of neutrophils and preparation of exotoxin pyocyanin, bacterial sonicate and LPS-HE were performed according to many standard methods. Apoptotic neutrophils were identified microscopically based on morphological changes characteristic of apoptosis.Results: Pyocyanin-induced neutrophil apoptosis was significantly delayed at earlier time points of 6 hr. in the presence of bacterial sonicate recording of a neutrophil apoptosis rate of 24.8% when compared to 42.3% of apoptosis in the absence of bacterial product. Combinatorial preincubation of LPS-HE with sonicate cell wall product more decreased synergistically the apoptotic rate to reach 17.1% at the same time point of treatment.Conclusions: Our findings suggest that bacterial sonicate most probably cell wall components are an antiapoptotic stimulus for delaying pyocyanin-induced neutrophil apoptosis in vitro, thereby may contribute to attenuate the neutrophilic inflammation in lungs of Cystic fibrosis patients.