While platelets are the cellular mediators of thrombosis, platelets are also immune cells. Platelets interact both directly and indirectly with immune cells, impacting their activation and differentiation, as well as all phases of the immune response. Megakaryocytes (Mks) are the cell source of circulating platelets, and until recently Mks were typically only considered as bone marrow (BM) resident cells. However, platelet producing Mks also reside in the lung, and lung Mks express greater levels of immune molecules compared to BM Mks. We therefore sought to define the immune functions of lung Mks. Using single cell RNA-Seq of BM and lung myeloid enriched cells, we found that lung Mks (MkL) had gene expression patterns that are similar to antigen presenting cells (APC). This was confirmed using imaging and conventional flow cytometry. The immune phenotype of Mks was plastic and driven by the tissue immune environment as evidenced by BM Mks having a MkL like phenotype under the influence of pathogen receptor challenge and lung associated immune molecules, such as IL-33. Our in vitro and in vivo assays demonstrated that MkL internalized and processed both antigenic proteins and bacterial pathogens. Furthermore, MkL induced CD4 + T cell activation in a MHC II dependent manner both in vitro and in vivo. These data indicated that Mks in the lung had key immune regulatory roles dictated in part by the tissue environment.

Lack of endothelial nitric oxide causes endothelial dysfunction and circulating monocyte infiltration, contributing to systemic atheroma plaque formation in arterial territories. Among the different inflammatory products, macrophage-derived foam cells and smooth muscle cells synthesize matrix metalloproteinases (MMPs), playing a pivotal role in early plaque formation and enlargement. We found increased levels of MMP-9 and MMP-13 in human endarterectomies with advanced atherosclerosis, together with significant amounts of extracellular matrix (ECM) metalloproteinase inducer EMMPRIN. To test whether the absence of NO may aggravate atherosclerosis through EMMPRIN activation, double NOS3/apoE knockout (KO) mice expressed high levels of EMMPRIN in carotid plaques, suggesting that targeting extracellular matrix degradation may represent a new mechanism by which endothelial NO prevents atherosclerosis. Based on our previous experience, by using gadolinium-enriched paramagnetic fluorescence micellar nanoparticles conjugated with AP9 (NAP9), an EMMPRIN-specific binding peptide, magnetic resonance sequences allowed non-invasive visualization of carotid EMMPRIN in NOS3/apoE over apoE control mice, in which atheroma plaques were significantly reduced. Taken together, these results point to EMMPRIN as a new therapeutic target of NO-mediated protection against atherosclerosis, and NAP9 as a non-invasive molecular tool to target atherosclerosis.

Toll-like receptor 4 (TLR4) contributes to the pathogenesis of coronary ischemia/reperfusion (IR). To test whether the new TLR4 antagonist, ApTOLL, may prevent coronary IR damage, we administered 0.078 mg/kg ApTOLL or Placebo in pigs subjected to IR, analyzing the levels of cardiac troponins, matrix metalloproteinases, pro-, and anti-inflammatory cytokines, heart function, and tissue integrity over a period of 7 days after IR. Our results show that ApTOLL reduced cardiac troponin-1 24 h after administration, improving heart function, as detected by a significant recovery of the left ventricle ejection fraction (LVEF) and the shortening fraction (FS) cardiac parameters. The extension of necrotic and fibrotic areas was also reduced, as detected by Evans blue/2,3,5-triphenyltetrazolium chloride (TTC) staining, Hematoxylin/Eosine, and Masson Trichrome staining of heart sections, together with a significant reduction in the expression of the extracellular matrix-degrading, matrix metalloproteinase 9. Finally, the expression of the following cytokines, CCL1, CCL2, MIP1-A-B, CCL5, CD40L, C5/C5A, CXCL1, CXCL10, CXCL11, CXCL12, G-CSF, GM-CSF, ICAM-1, INF-g, IL1-a, ILI-b, IL-1Ra, IL2, IL4, IL5, IL6, IL8, IL10, IL12, IL13, IL16, IL17-A, IL17- E, IL18, IL21, IL27, IL32, MIF, SERPIN-E1, TNF-a, and TREM-1, were also assayed, detecting a pronounced decrease of pro-inflammatory cytokines after 7 days of treatment with ApTOLL. Altogether, our results show that ApTOLL is a promising new tool for the treatment of acute myocardial infarction (AMI).