Platelet desialylation is mediated by upregulated plasmatic neuraminidase activity and linked to platelet dysfunction in sepsis

Introduction: Sepsis is a life-threatening disease characterised by thrombocytopenia and platelet dysfunction. Immunophenotyping revealed that beyond the platelet count also the subpopulation pattern comprising hyporeactive, reticulated or aged platelets might change during sepsis. Platelet desialylation and clearance by the hepatic Ashwell-Morrell receptor is central for the clearance of aged platelets, however the mechanisms mediating desialylation and its relevance for the change of platelet phenotype and function in sepsis are unknown

Method: We recruited 25 sepsis patients and analyzed the surface lectin-pattern on distinct subpopulations (procoagulant, hyporeactive, reticulated, apoptotic platelets) compared to healthy controls. We analyzed platelet desialylation by using donor-derived platelets and sepsis plasma as well as allogenous controls. Maturation-deficiency was assessed using CD34+derived megakaryocytes (MK). Neuraminidase1 (Neu1) expression localization and function were assessed using confocal microscopy, flow cytometry and ELISA

Results: Sepsis platelets showed reduced SNA binding to the terminal sialic acid (p<0.0163) with corresponding higher levels of RCA binding to the underlying galactose, revealing desialylation. Increased RCA expression was highly associated with thrombocytopenia (r=-0.58; p<0.01). We performed adaptive transfer experiments with donor-derived platelets in sepsis plasma or allogenous healthy controls to identify the mediating factors. Surprisingly, incubation of healthy platelets in sepsis plasma induced desialylation, which was inhibited when adding the neuraminidase inhibitor 2,3-didehydro-2-deoxy-N-acetylneuraminic acid. To assess how sepsis plasma affects glycosylation during thrombopoiesis, we differentiated CD34+hematopoietic stem cells with thrombopoietin, in the presence of allogenous control or sepsis plasma and found desialylation of MK-derived platelet like particles only in sepsis plasma. Flow cytometry and confocal microsocpy analyses revealed increased surface levels of Neu1, suggesting reallocation from a-granules to the cell surface as mechanism causing thrombocytopenia. Finally, we questioned how desialylation is linked to distinct platelet subpopulations and whether sepsis patients have a unique subpopulation signature. We found that the hyporeactive platelet cluster showed lower levels of sialic acid (p<0.0108), we could also see a shift to a bigger desialylated, hyporeactive group of platelets. Unexpectedly, procoagulative platelets were not desialylated, indicating that this subpopulation is not cleared and can thus persist and accumulate in circulation

Conclusion: During sepsis platelets are rapidly desialylated mostly by both cellular and plasmatic Neu1 activity, which is highly linked to thrombocytopenia. Platelet desialylation is strongly associated with hyporeactive and procoagulant platelet subpopulations indicating that targeting of Neu1 activity might be a promising approach to prevent platelet clearance and dysfunction

 

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Conflict of Interest:

Nothing to declare

Publication History

Article published online:
13 February 2025