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.