Biology subjects

Camacho, V.

Publications and source records attributed to Camacho, V..

5 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

Glutamine-Dependent Biosynthetic Pathways Fuel Autoreactive T and B Cells in Foxp3 Deficiency-mediated Disease

Foxp3 deficiency causes a profound loss of immune tolerance, unleashing autoreactive T and B cells, lymphoproliferation, cytokine-driven inflammation, and autoantibody production. This autoimmune pathology is fueled by increased glutamine usage, but it remains unresolved whether glutamine is necessary to produce energy, or for biosynthetic pathways leading to inosine and asparagine production. Here, we demonstrate that glutamine utilization supports Foxp3-deficiency mediated disease independently of pathogenic Foxp3-deficient Treg cell energetic reprogramming. Mechanistically, glutamine biosynthetic pathways sustain conventional T cell activation and proinflammatory cytokine production preventing inosine accumulation and signaling, thus implicating adenosine pathway modulation in autoreactive T cell dysregulation. Conversely, autoreactive B cell activation and autoantibody production depend on glutamine-dependent asparagine synthesis, which we reveal as a targetable vulnerability for autoantibody formation. These findings highlight glutamine-driven biosynthetic processes as critical drivers of autoimmunity and reveal distinct metabolic vulnerabilities in autoreactive T and B cells that can be targeted for therapeutic intervention.

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

Inhibition of RhoA-mediated secretory autophagy in megakaryocytes mitigates myelofibrosis in mice

Megakaryocytes (MKs) are large, polyploid cells that contribute to bone marrow homeostasis through the secretion of cytokines such as transforming growth factor {beta}1 (TGF{beta}1). During neoplastic transformation, immature MKs accumulate in the bone marrow where they induce fibrotic remodeling ultimately resulting in myelofibrosis. Current treatment strategies aim to prevent MK hyperproliferation, however, little is understood about the potential of targeting dysregulated cytokine secretion from neoplastic MKs as a novel therapeutic avenue. Unconventional secretion of TGF{beta}1 as well as interleukin 1{beta} (IL1{beta}) via secretory autophagy occurs in cells other than MKs, which prompted us to investigate whether similar mechanisms are utilized by MKs. Here, we identified that TGF{beta}1 strongly co-localized with the autophagy marker light chain 3B in native MKs. Disrupting secretory autophagy by inhibiting the small GTPase RhoA or its downstream effector Rho kinase (ROCK) markedly reduced TGF{beta}1 and IL1{beta} secretion in vitro. In vivo, conditional deletion of the essential autophagy gene Atg5 from the hematopoietic system limited megakaryocytosis and aberrant cytokine secretion in an MPLW515L-driven transplant model. Similarly, mice with a selective deletion of Rhoa from the MK and platelet lineage were protected from progressive fibrosis. Finally, disease hallmarks in MPLW515L-transplanted mice were attenuated upon treatment with the autophagy inhibitor hydroxychloroquine or the ROCK inhibitor Y27632, either as monotherapy or in combination with the JAK2 inhibitor ruxolitinib. Overall, our data indicate that aberrant cytokine secretion is dependent on secretory autophagy downstream of RhoA, targeting of which represents a novel therapeutic avenue in the treatment of myelofibrosis. One Sentence SummaryTGF{beta}1 is released from megakaryocytes via RhoA-mediated secretory autophagy, and targeting this process can alleviate fibrosis progression in a preclinical mouse model of myelofibrosis.

cell biology↗

bioRxiv2018

Agreement between 18F-Florbetapir PET imaging and cerebrospinal fluid Aβ1-42, Aβ1-40, tTau and pTau measured on the LUMIPULSE G fully automated platform

INTRODUCTIONThe development of fully automated immunoassay platforms has improved the technical reliability of cerebrospinal fluid (CSF) biomarkers for Alzheimers disease.\n\nMETHODSWe quantified A{beta}1-42, A{beta}1-40, tTau and pTau levels using the Lumipulse G System in 94 CSF samples from participants of the SPIN cohort with available 18F-Florbetapir imaging. Amyloid scans were assessed visually and through automated quantification. We determined the cutoffs of CSF biomarkers that optimized their agreement with 18F-Florbetapir PET and evaluated concordance between markers of the amyloid category.\n\nRESULTSA{beta}1-42, tTau and pTau (but not A{beta}1-40) and the ratios with A{beta}1-42 had good diagnostic agreement with 18F-Florbetapir PET. As a marker of amyloid pathology, the A{beta}1-42/A{beta}1-40 ratio had higher agreement and better correlation with amyloid PET than A{beta}1-42 alone.\n\nDISCUSSIONCSF biomarkers measured with the Lumipulse G System show good agreement with amyloid imaging. Combination of A{beta}1-42 with A{beta}1-40 increases the agreement between markers of amyloid pathology.

neuroscience↗