Keratinocyte Arginase1 Deficiency Impairs Healing and Antimicrobial Defence against Pseudomonas aeruginosa Infection

Wound infection is a major disruptor of wound healing. Keratinocytes, critical in repair and microbial responses, require the L-arginine hydrolysing enzyme arginase1, for effective healing. Wound pathogens such as Pseudomonas aeruginosa may also need L-arginine. We therefore investigated host-microbial interactions in the context of wound healing and L-arginine metabolism. Arginase-inhibited murine wounds challenged with P. aeruginosa, exhibited significantly delayed re-epithelialisation. This finding was recapitulated in vitro using P. aeruginosa- challenged, arginase1 deficient ( shARG1) keratinocytes, associated with reduced epithelial proliferation and viability, and heightened inflammation. Whilst P. aeruginosa challenge promoted host metabolism of L-arginine, this was perturbed in wounded shARG1 keratinocytes. There was, however, heightened downstream polyamine metabolism in shARG1 cells when under P. aeruginosa challenge. Host keratinocyte arginase1 deficiency promoted bacterial growth in vitro , in line with a failure to upregulate the anti-microbial peptides, β-defensins, in shARG1 scratches. This work demonstrates a pivotal role for keratinocyte arginase1 in wound infection.