16 research outputs found
Platelets interact with CD169+ macrophages and cDC1 and enhance liposome-induced CD8+ T cell responses
Historically platelets are mostly known for their crucial contribution to hemostasis, but there is growing understanding of their role in inflammation and immunity. The immunomodulatory role of platelets entails interaction with pathogens, but also with immune cells including macrophages and dendritic cells (DCs), to activate adaptive immune responses. In our previous work, we have demonstrated that splenic CD169+ macrophages scavenge liposomes and collaborate with conventional type 1 DCs (cDC1) to induce expansion of CD8+ T cells. Here, we show that platelets associate with liposomes and bind to DNGR-1/Clec9a and CD169/Siglec-1 receptors in vitro. In addition, platelets interacted with splenic CD169+ macrophages and cDC1 and further increased liposome internalization by cDC1. Most importantly, platelet depletion prior to liposomal immunization resulted in significantly diminished antigen-specific CD8+ T cell responses, but not germinal center B cell responses. Previously, complement C3 was shown to be essential for platelet-mediated CD8+ T cell activation during bacterial infection. However, after liposomal vaccination CD8+ T cell priming was not dependent on complement C3. While DCs from platelet-deficient mice exhibited unaltered maturation status, they did express lower levels of CCR7. In addition, in the absence of platelets, CCL5 plasma levels were significantly reduced. Overall, our findings demonstrate that platelets engage in a cross-talk with CD169+ macrophages and cDC1 and emphasize the importance of platelets in induction of CD8+ T cell responses in the context of liposomal vaccination
The BRAF pseudogene functions as a competitive endogenous RNA and induces lymphoma in vivo
SummaryResearch over the past decade has suggested important roles for pseudogenes in physiology and disease. In vitro experiments demonstrated that pseudogenes contribute to cell transformation through several mechanisms. However, in vivo evidence for a causal role of pseudogenes in cancer development is lacking. Here, we report that mice engineered to overexpress either the full-length murine B-Raf pseudogene Braf-rs1 or its pseudo âCDSâ or â3âČ UTRâ develop an aggressive malignancy resembling human diffuse large B cell lymphoma. We show that Braf-rs1 and its human ortholog, BRAFP1, elicit their oncogenic activity, at least in part, as competitive endogenous RNAs (ceRNAs) that elevate BRAF expression and MAPK activation in vitro and in vivo. Notably, we find that transcriptional or genomic aberrations of BRAFP1 occur frequently in multiple human cancers, including B cell lymphomas. Our engineered mouse models demonstrate the oncogenic potential of pseudogenes and indicate that ceRNA-mediated microRNA sequestration may contribute to the development of cancer
Republication de : Nouveautés dans le traitement pharmacologique du choc cardiogénique
PTEN Controls Junction Lengthening and Stability during Cell Rearrangement in Epithelial Tissue
International audienc
Platelets are hyperactivated but show reduced glycoprotein VI reactivity in COVID-19 patients
Platelets are Hyperactivated but Show Reduced Glycoprotein VI Reactivity in COVID-19 Patients
Comparison of inhibitory effects of irreversible and reversible Btk inhibitors on platelet function
All irreversible Bruton tyrosine kinase (Btk) inhibitors including ibrutinib and acalabrutinib induce platelet dysfunction and increased bleeding risk. New reversible Btk inhibitors were developed, like MKâ1026. The mechanism underlying increased bleeding tendency with Btk inhibitors remains unclear. We investigated the effects of ibrutinib, acalabrutinib and MKâ1026 on platelet function in healthy volunteers, patients and Btkâdeficient mice, together with offâtarget effects on tyrosine kinase phosphorylation. All inhibitors suppressed GPVIâ and CLECâ2âmediated platelet aggregation, activation and secretion in a doseâdependent manner. Only ibrutinib inhibited thrombus formation on vWFâcoâcoated surfaces, while on collagen this was not affected. In blood from Btkâdeficient mice, collagenâinduced thrombus formation under flow was reduced, but preincubation with either inhibitor was without additional effects. MKâ1026 showed less offâtarget effects upon GPVIâinduced TK phosphorylation as compared to ibrutinib and acalabrutinib. In ibrutinibâtreated patients, GPVIâstimulated platelet activation, and adhesion on vWFâcoâcoated surfaces were inhibited, while CLECâ2 stimulation induced variable responses. The dual inhibition of GPVI and CLECâ2 signalling by Btk inhibitors might account for the increased bleeding tendency, with ibrutinib causing more highâgrade bleedings due to additional inhibition of plateletâvWF interaction. As MKâ1026 showed less offâtarget effects and only affected activation of isolated platelets, it might be promising for future treatment
The Platelet Lipidome Is Altered in Patients with COVID-19 and Correlates with Platelet Reactivity
Background âActivated platelets have been implicated in the proinflammatory and prothrombotic phenotype of coronavirus disease 2019 (COVID-19). While it is increasingly recognized that lipids have important structural and signaling roles in platelets, the lipidomic landscape of platelets during infection has remained unexplored. Objective âTo investigate the platelet lipidome of patients hospitalized for COVID-19. Methods âWe performed untargeted lipidomics in platelets of 25 patients hospitalized for COVID-19 and 23 noninfectious controls with similar age and sex characteristics, and with comparable comorbidities. Results âTwenty-five percent of the 1,650 annotated lipids were significantly different between the groups. The significantly altered part of the platelet lipidome mostly comprised lipids that were less abundant in patients with COVID-19 (20.4% down, 4.6% up, 75% unchanged). Platelets from COVID-19 patients showed decreased levels of membrane plasmalogens, and a distinct decrease of long-chain, unsaturated triacylglycerols. Conversely, platelets from patients with COVID-19 displayed class-wide higher abundances of bis(monoacylglycero)phosphate and its biosynthetic precursor lysophosphatidylglycerol. Levels of these classes positively correlated with ex vivo platelet reactivity-as measured by P-selectin expression after PAR1 activation-irrespective of disease state. Conclusion âTaken together, this investigation provides the first exploration of the profound impact of infection on the human platelet lipidome, and reveals associations between the lipid composition of platelets and their reactivity. These results warrant further lipidomic research in other infections and disease states involving platelet pathophysiology
The host response in different aetiologies of community-acquired pneumonia
Background: Community-acquired pneumonia (CAP) can be caused by a variety of pathogens, of which Streptococcus pneumoniae, Influenza and currently SARS-CoV-2 are the most common. We sought to identify shared and pathogen-specific host response features by directly comparing different aetiologies of CAP. Methods: We measured 72 plasma biomarkers in a cohort of 265 patients hospitalized for CAP, all sampled within 48 hours of admission, and 28 age-and sex matched non-infectious controls. We stratified the biomarkers into several pathophysiological domains- antiviral response, vascular response and function, coagulation, systemic inflammation, and immune checkpoint markers. We directly compared CAP caused by SARS-CoV-2 (COVID-19, n=39), Streptococcus pneumoniae (CAP-strep, n=27), Influenza (CAP-flu, n=22) and other or unknown pathogens (CAP-other, n=177). We adjusted the comparisons for age, sex and disease severity scores. Findings: Biomarkers reflective of a stronger cell-mediated antiviral response clearly separated COVID-19 from other CAPs (most notably granzyme B). Biomarkers reflecting activation and function of the vasculature showed endothelial barrier integrity was least affected in COVID-19, while glycocalyx degradation and angiogenesis were enhanced relative to other CAPs. Notably, markers of coagulation activation, including D-dimer, were not different between the CAP groups. Ferritin was most increased in COVID-19, while other systemic inflammation biomarkers such as IL-6 and procalcitonin were highest in CAP-strep. Immune checkpoint markers showed distinctive patterns in viral and non-viral CAP, with highly elevated levels of Galectin-9 in COVID-19. Interpretation: Our investigation provides insight into shared and distinct pathophysiological mechanisms in different aetiologies of CAP, which may help guide new pathogen-specific therapeutic strategies. Funding: This study was financially supported by the Dutch Research Council, the European Commission and the Netherlands Organization for Health Research and Development