Role of platelet derived sphingosine-1-phosphate in thrombosis and vascular ageing

Background Ageing is linked to chronic inflammation ("inflammaging") and increased thrombus formation, contributing to cardiovascular events like stroke and heart attack. Platelets and megakaryocytes are central to these processes. Our single-cell RNA-seq analysis of aging bone marrow megakaryocytes (Mk) showed upregulation of the sphingosine-1-phosphate (S1P) transporter major facilitator superfamily transporter 2b (Mfsd2b). S1P is a lipid mediator involved in vascular integrity, inflammation, and thrombosis, and is increased in plasma upon platelet activation. Here, we investigate the role of S1P in thrombus formation in the ageing, focusing on its molecular mechanisms and potential contributions to age-related cardiovascular risk (Figure 1). Purpose To validate S1P’s role in cardiovascular aging by investigating its effects in both healthy ageing individuals and patients with cardiovascular disease (CVD). Methods Bone marrow Mks were isolated from young (3 months) and old (24 months) mice for RNAseq. Tissue Factor (TF) expression was analyzed in Tumor necrosis factor alpha (TNF-α) stimulated human aortic endothelial cells (hAECs) treated with different S1P concentrations. Platelet aggregation and thrombus formation were studied ex vivo in platelet-rich plasma (PRP) and whole blood from young donors treated with S1P. Results RNAseq revealed increased Mfsd2b expression and S1P plasma levels in aged mice (Figure 2A). We found that high S1P levels (1μM) in TNF-α-stimulated hAECs elevated TF expression suggesting a pro-thrombotic activity (Figure 2B). In sharp contrast, high concentration of S1P reduced platelet aggregation in PRP and thrombus formation in whole blood from young donors (Figure 2C). Conclusions Our preliminary data suggest that in young healthy individuals, platelets store high levels of S1P while maintaining low circulating concentrations. Upon strong pro-thrombotic stimulation, activated platelets efficiently release S1P, which acts in an autocrine manner to prevent excessive aggregation and promote thrombus resolution. In contrast, aged platelets, due to increased levels of the transporter Mfsd2b, have a reduced capacity to store S1P, leading to lower S1P release upon activation and impaired thrombus resolution.