366 Role of calcium ions released by a calcium alginate dressing on NK cell activation

Abstract

Wound healing is a physiological process involving 4 major stages, among which an inflammatory phase to eradicate causal aggression. The wound bed is infiltrated by inflammatory cells from the innate response, including natural killer (NK) cells detected within the first 24 hours. Calcium alginate dressings including Algosteril® (Algo) are widely used in wound management. They release calcium ions in the exudates and enrich its level locally. Calcium ion is a key factor in this process and a well-known activator of NK cells. Our aim was to study the effects of Algo on the activation of the innate response through the analysis of the cytotoxic capacities and the activation of NK cells. NK cells from healthy donors’ blood were incubated with conditioned media of the Algo dressing (ISO 10-993 standard) in vitro for 18h. A control 3 mM CaCl2 solution was used as a supply of exogenous calcium. The cytotoxicity and activation of NK cells were assessed by flow cytometry using respectively the death rate of target K562 cells, the expression levels of the degranulation marker CD107a and of intracytoplasmic cytokines (ex: IFN-γ). The mode of action of Algo-released calcium on NK cells and the calcium channels involved were evaluated using a calcium probe in the presence of calcium channel blockers. Algo dressing significantly stimulated the cytotoxicity of NK cells against K562 cells (x1.3 at 10 NK/1 K562 ratio). It also induced a significant increase in the percentage of cytotoxic CD56dim/CD107a+ NK cells and in the expression of IFN-γ in CD56bright NKs. Incubation with EDTA (calcium chelator) inhibited the stimulatory effect of Algo on NK cytotoxicity by 69% at the 10/1 ratio. SOCE calcium channels are the major one involved in NK stimulation by the dressing-released calcium ions. Altogether, these results demonstrate the major role of calcium in innate response during wound healing and the interest in using the calcium alginate dressing Algo to control infection.