Biology subjects

Carminita, E.

Publications and source records attributed to Carminita, E..

4 recordsLinked to original sources

bioRxiv2025

Major histocompatibility complex class II-expressing bone marrow megakaryocytes activate CD4+ T cells and induce regulatory T cell fate

While professional antigen-presenting cells drive adaptive immunity, atypical cell types can fulfill this role in the bone marrow. Megakaryocytes (MKs) are canonically recognized for platelet production, but recent studies indicate functional heterogeneity and immune potential. We found that ~20% of bone marrow MKs express Major Histocompatibility Complex (MHC) II and co-stimulatory receptors CD80, CD86, CD40, and CD83. These MKs process and present antigen to activate T cells ex vivo in an MHC II-dependent manner. MK/T cell interactions induced TGF-{beta}1 secretion and promoted induced Treg differentiation. Prior stimulation of MKs with LPS or Poly I:C was associated with modest Th1-associated CD4+ T cell responses, including IFN-{gamma} and TNF- production, without robust Th17 differentiation. Immunopeptidomics of the murine MK MHC II receptor confirmed occupancy by exogenous peptides, suggesting in vivo functionality. Using a murine model with MK-targeted deletion of MHC II (Pf4-MHC{Delta}/{Delta}), we observed altered TLR signaling and reduced bone marrow TGF-{beta}1. Together, these findings identify MHC II+ MKs as noncanonical antigen-presenting cells with the potential to modulate CD4 T cell responses as part of the immune regulation of the bone marrow niche.

immunology↗

bioRxiv2025

Induction of Moderate DNA Damage Enhances Megakaryopoiesis and Platelet Production

A common side effect of poly-ADP ribose polymerase (PARP) inhibitors is low platelet counts, or thrombocytopenia, presumably mediated through platelet progenitors, megakaryocytes (MKs). MKs are large, hematopoietic cells with a polyploid, multi-lobulated nucleus. While DNA replication in MKs (endomitosis) is well studied, limited investigations have examined the impact of DNA damage and repair inhibition on megakaryopoiesis. To explore PARP inhibitor-induced thrombocytopenia, we treated mice with PARP inhibitors (niraparib and olaparib), which are approved for the treatment of solid tumors. While high-dose niraparib treatment led to thrombocytopenia, consistent with clinical observations, treatment at a lower dosage led to a significant, >1.5-fold increase in both the number of bone marrow MKs and circulating platelets. This increase was accompanied by elevated DNA damage in both MKs and MK progenitors, as measured by both {gamma}H2AX accumulation and comet assays of MKs. Notably, platelets from niraparib-treated mice were functionally normal in their response to ADP, TRAP, and collagen. Gamma-irradiation treatment similarly increased MK and platelet counts in mice, suggesting that moderate DNA damage enhances megakaryopoiesis and increases platelet counts. These data reveal a previously unknown relationship between MKs and DNA damage and present a novel target for triggering enhanced platelet production in vivo. Key PointsO_LITreatment of mice with low dose PARP inhibitors or gamma-irradiation enhances platelet counts. C_LIO_LILow dose PARP inhibitor treatment leads to increased DNA damage in MKs and MK progenitors and enhances bone marrow megakaryopoiesis. C_LI

cell biology↗

bioRxiv2024

ADP-dependent platelet activation is required for thrombus formation during a long-distance flight

The association between venous thromboembolism (VTE) and air travel is well documented. Prolonged exposure to reduced atmospheric pressure and low oxygen levels during flights triggers coagulation disorders, representing the primary risk factor for Deep Vein Thrombosis (DVT), surpassing immobility. In our study, we investigated how long-distance flight conditions affect VTE development in mice exposed to 6h of hypobaric hypoxia or normobaric normoxia after inferior vena cava (IVC) ligation. We observed a pro-thrombotic profile under flight-simulated conditions, characterized by larger thrombi with higher neutrophil and fibrin densities. However, no difference was observed in neutrophil extracellular traps (NETs) or fibrin-positive neutrophils in thrombi between groups, indicating that neutrophils/NETs may not be involved in DVT development during flight. Considering the elevated ADP levels observed at high altitudes, we further assessed thrombus formation in wild-type and P2RY12-deficient mice. Remarkably, thrombus formation was no longer affected by aircraft conditions in P2RY12-deficient or wild type mice treated with clopidogrel. We conclude that ADP-induced platelet activation is involved in the development of DVT during flight, suggesting that the use of P2RY12 inhibitors may be of interest to prevent DVT in susceptible patients.

pathology↗

bioRxiv2023

Efficient megakaryopoiesis and platelet production require phospholipid remodeling and PUFA uptake through CD36

Lipids contribute to hematopoiesis and membrane properties and dynamics, however, little is known about the role of lipids in megakaryopoiesis. Here, a lipidomic analysis of megakaryocyte progenitors, megakaryocytes, and platelets revealed a unique lipidome progressively enriched in polyunsaturated fatty acid (PUFA)-containing phospholipids. In vitro, inhibition of both exogenous fatty acid functionalization and uptake and de novo lipogenesis impaired megakaryocyte differentiation and proplatelet production. In vivo, mice on a high saturated fatty acid diet had significantly lower platelet counts, which was prevented by eating a PUFA-enriched diet. Fatty acid uptake was largely dependent on CD36, and its deletion in mice resulted in thrombocytopenia. Moreover, patients with a CD36 loss-of-function mutation exhibited thrombocytopenia and increased bleeding. Our results suggest that fatty acid uptake and regulation is essential for megakaryocyte maturation and platelet production, and that changes in dietary fatty acids may be a novel and viable target to modulate platelet counts.

cell biology↗