Overriding defective FPR chemotaxis signaling in diabetic neutrophil stimulates infection control in diabetic wound

Abstract

Infection is a major co-morbidity that contributes to impaired healing in diabetic wounds. Although impairments in diabetic neutrophils have been blamed for this co-morbidity, what causes these impairments and whether they can be overcome, remain largely unclear. Diabetic neutrophils, extracted from diabetic individuals, exhibit chemotaxis impairment but this peculiar functional impairment has been largely ignored because it appears to contradict the clinical findings which blame excessive neutrophil influx (neutrophilia) as a major impediment to healing in chronic diabetic ulcers. Here, we report that exposure to glucose in diabetic range results in impaired chemotaxis signaling through the FPR1 chemokine receptor in neutrophils, culminating in reduced chemotaxis and delayed neutrophil trafficking in wound in diabetic animals, and rendering diabetic wound vulnerable to infection. We further show that at least some auxiliary chemokine receptors remain functional under diabetic conditions and their engagement by the pro-inflammatory cytokine CCL3, overrides the requirement for FPR1 signaling and substantially improves infection control by jumpstarting the neutrophil response toward infection, and stimulates healing in diabetic wound. We posit that CCL3 may have real therapeutic potential for the treatment of diabetic foot ulcers if it is applied topically after the surgical debridement process which is intended to reset chronic ulcers into acute fresh wounds.