The role of p38 MAPK in neutrophil functions: single cell chemotaxis and surface marker expression.

Neutrophils act as the first line of defence in the human immune system by migrating to the site of abnormal events and performing their designated roles. One major signalling pathway that drives neutrophil action in vivo is the p38 mitogen-activated protein kinase (MAPK)-dependent pathway. Herein, a microfluidic platform is employed to explore the mechanistic role of p38 MAPK in neutrophil chemotaxis. Neutrophils, with and without p38 MAPK inhibition, were exposed to pairwise competing gradients of chemotaxis-inducing molecules. Overall, p38 MAPK inhibitor-treated neutrophils were still capable of moving toward a chemoattractant signal; however, the hierarchy of neutrophil response to various chemoattractants changed and there was more deviation from direct movement toward a chemoattractant signal in p38 MAPK-blocked cells. In a parallel fluorescence imaging study, neutrophil expression of surface receptors (CXCR1, FPR2, BLTR, CD11b and CD66b) changed when comparing untreated and p38 MAPK-blocked cells. All results demonstrate that the p38 MAPK-dependent pathway plays a critical role in neutrophil chemotaxis and this role is, in part, through the regulation of surface receptor expression. These data regarding how receptor expression and chemotaxis are influenced by the p38 MAPK pathways lend insight into neutrophil behaviour in physiological environments and the potential manipulation of p38 MAPK for therapeutic purposes.