Receptor activator of NF-κB ligand (RANKL) increases the release ofneutrophil products associated with coronary vulnerability

Summary The "blood vulnerability", resulting from the complex balance betweenserum molecules and inflammatory cell atherosclerotic activities, is amajor determinant in the evaluation of the "global patient cardiovascularvulnerability". In the present study, we focused on the role of the solublereceptor activator of nuclear factor kappa-B (NF-κB) ligand(RANKL, a potential marker of coronary calcification and vulnerability)in the release of neutrophilic proteases. Then, the association betweenthese mediators and the degree of coronary calcification (assessed bycoronary calcium score [CCS]) was investigated in 20 subjects (aged≥65 years) asymptomatic for cardiovascular disease. Results showedthat RANKL dose-dependently induced matrix metalloprotease(MMP)-8 and MMP-9 release from human primary neutrophils culturedin Teflon dishes (suspension condition, mimicking cells circulating in theblood stream). Conversely, when adherent to polystyrene, neutrophilsbecame unresponsive to RANKL. RANKL did not influence the release ofother neutrophilic products in suspension and adherence cultures aswell as neutrophil migration. RANKL-induced release of MMPs was dependenton the activation of defined intracellular signalling pathways(PI3K/Akt and ERK1/2). In asymptomatic subjects, serum levels ofRANKL, MMP-8 and MMP-9 positively correlated with CCS, reflecting apotential relationship between circulating RANKL and coronary calcification.In conclusion, RANKL increased the release of neutrophilic productspotentially related to the "blood" vulnerability via defined intracellularpathways. Serum levels of RANKL might represent a potentialbiomarker of coronary calcification and related cardiovascular risk.