Human platelets and megakaryocytes express the BPIFB4 protein and their stimulation with the recombinant Longevity-associated variant LAV-BPIFB4 displays anti-aggregating activity

Abstract

Abstract Platelets are not only the main players in primary haemostasis and cardiovascular disease, but recent advances attribute them a key role in immune defence mechanisms via the release of plasma mediators of potential clinical relevance. The bactericidal/permeability-increasing fold-containing family B, member 4 (BPIFB4) belongs to a family protein participating in the innate mechanism of host defence. It is a secreted protein and its plasma levels inversely correlated with COVID-19 and coronary artery disease (CAD) severity and the degree of carotid stenosis and intima media thickness in human patient cohorts. Interestingly, Long Living Individuals (LLIs) displayed high BPIFB4 circulating levels and an enrichment of the 4 SNPs missense haplotype at BPIFB4 locus, the Longevity-Associated Variant (LAV). LAV-BPIFB4 genotype correlate with higher BPIFB4 plasma levels and the transfer of LAV-BPIFB4 gene delayed major age-related diseases, mainly rescuing the immunesenescence and the endothelial and cardiac dysfunctions, yet the critical assessment of the BPIFB4 protein as a platelet release product is lacking. Herein we observed BPIFB4 release by calcium activated human platelets, a process that is amplified in LAV allele carriers donors. Furthermore, LAV gene transfer resulted in an enhanced protein enrichment in bone marrow megakaryocyte precursor cells and in a more efficient process of platelets formation in vitro. At functional level, LAV genotype was mimicked by the rhLAV-BPIFB4 platelet stimulation that induced endogenous BPIFB4 release similarly to calcium stimuli. In a small cohort of treatment-naive patients with type 2 diabetes, while ADP and Collagene agonist stimulation induced high aggregation, the co-treatment with the rhLAV-BPIFB4 significantly reduced the activation capacity of patients’ platelets. Accordingly, an administration of rhLAV-BPIFB4 24 hours before tromboembolism induction partly protected from mortality in a murine model of lethal pulmonary thromboembolism in vivo. As a result of reduced platelets’ activation, lower level of circulating leukocyte-platelets aggregates (LPA) was found in rhLAV-BPIFB4-treated mice compared to control. In summary, our data report for the first time that both, human platelets and megakaryocytes, can express BPIFB4 and unravel a novel rhLAV-BPIFB4 therapeutic action in platelet iperaggregation and thrombocytopenia.