C-type lectin-like receptor-2 in platelets mediates ferric chloride–induced platelet activation and attenuates ferroptosis of endothelial cells

BackgroundAn iron overload status induces ferroptosis, an iron-dependent nonapoptotic cell death, in various pathological conditions. We previously reported that hemin (heme), protoporphyrin-IX with ferric iron, activates platelets via C-type lectin-like receptor-2 (CLEC-2) and glycoprotein VI/FcRγ, but protoporphyrin-IX alone blocks CLEC-2-dependent platelet activation. Therefore, we hypothesized that free iron has the ability to activate platelets.ObjectivesThis study aimed to elucidate platelet activation mechanisms of iron (ferric chloride), including the identification of signaling pathways and receptors, and to examine whether platelets regulate ferroptosis.MethodsPlatelet aggregometry, platelet activation marker expression, and protein phosphorylation were examined in ferric chloride–stimulated human and murine platelets. Inhibitors of platelet activation signaling pathways and receptor-deleted platelets were utilized to identify the responsible signaling pathway and receptor. The effect of platelets on ferroptosis of endothelial cells was investigated in vitro.ResultsFerric chloride induced platelet activation dependent on Src family kinase pathways in humans and mice. Ferric chloride–induced platelet aggregation was almost lost in CLEC-2–depleted murine platelets and wild-type platelets preincubated with recombinant CLEC-2 proteins. Furthermore, coculture of wild-type platelets, but not CLEC-2–deficient platelets, attenuated ferroptosis of endothelial cells in vitro.ConclusionFerric chloride activates platelets via CLEC-2 and Src family kinase pathways, and platelets have a protective role in the ferroptosis of endothelial cells dependent on CLEC-2.