Project description:Dendritic cells (DCs) are short-lived immune cells that continuously roam our body in search for foreign or self-antigens. Upon acquisition of antigen, they mature and start migrating to the lymph node to present the antigen to naïve T cells. Depending on the context wherein the antigen is acquired, DCs will mature in a homeostatic or immunogenic manner. So far, the field is lacking proper tools to distinguish between the two maturation states. Most maturation markers are shared between the two states and therefore inappropriate to use. Still, defining the proper maturation type is crucial as it determines how the DCs will instruct the T cells towards antigen expressing cells. In this study, we used a lipid nanoparticle (LNP)-based approach to steer DC maturation pathways in vivo. CITE-seq analysis allowed us to design a panel of flow cytometry markers that reliably annotates the two DC maturation states, as validated in an infection and in a tumor model. Furthermore, the data corroborated that uptake of empty LNPs in DCs induces their homeostatic maturation, in contrast to uptake of mRNA-LNPs or TLR ligand-adjuvanted LNPs, leading to distinct effector T cell outputs. This reveals that LNPs themselves are not being decoded as “danger” by cDC1s, and that the cargo is essential to provide adjuvants activity, which is highly relevant for targeted design of LNP-based therapies.
Project description:Depending on how an antigen is perceived, dendritic cells (DCs) mature in an immunogenic or tolerogenic manner, safeguarding the balance between immunity and tolerance. Whereas the pathways driving immunogenic maturation in response to infectious insults are well characterized, the signals driving tolerogenic maturation in homeostasis are still poorly understood. Here we demonstrate that engulfment of apoptotic cells triggers homeostatic maturation of conventional cDC1s in the spleen. This process can be modeled by engulfment of empty, non-adjuvanted lipid nanoparticles (LNPs), is marked by intracellular accumulation of cholesterol, and highly unique to type 1 DCs. Engulfment of apoptotic cells or cholesterol-rich LNPs leads to activation of the LXR pathway driving cellular cholesterol efflux and repression of immunogenic genes. In contrast, simultaneous engagement of TLR3 to mimic viral infection via administration of poly(I:C)-adjuvanted LNPs represses the LXR pathway, thus delaying cellular cholesterol efflux and inducing genes that promote T cell immunity. These data demonstrate how DCs exploit the conserved cellular cholesterol efflux pathway to regulate induction of tolerance or immunity and reveal that administration of non-adjuvanted cholesterol-rich LNPs is a powerful platform for inducing tolerogenic DC maturation.
Project description:Depending on how an antigen is perceived, dendritic cells (DCs) mature in an immunogenic or tolerogenic manner, safeguarding the balance between immunity and tolerance. Whereas the pathways driving immunogenic maturation in response to infectious insults are well characterized, the signals driving tolerogenic maturation in homeostasis are still poorly understood. Here we demonstrate that engulfment of apoptotic cells triggers homeostatic maturation of conventional cDC1s in the spleen. This process can be modeled by engulfment of empty, non-adjuvanted lipid nanoparticles (LNPs), is marked by intracellular accumulation of cholesterol, and highly unique to type 1 DCs. Engulfment of apoptotic cells or cholesterol-rich LNPs leads to activation of the LXR pathway driving cellular cholesterol efflux and repression of immunogenic genes. In contrast, simultaneous engagement of TLR3 to mimic viral infection via administration of poly(I:C)-adjuvanted LNPs represses the LXR pathway, thus delaying cellular cholesterol efflux and inducing genes that promote T cell immunity. These data demonstrate how DCs exploit the conserved cellular cholesterol efflux pathway to regulate induction of tolerance or immunity and reveal that administration of non-adjuvanted cholesterol-rich LNPs is a powerful platform for inducing tolerogenic DC maturation.
Project description:Expansion of nanotechnology will bring many potential benefits as adversely effects on human health. Protection of the human respiratory system from exposure of volatile nanoparticles has become an emerging health concern. The understanding of the biological processes involved in the development and maintenance of a variety of pathologies is improved by genome-wide approaches. Technical feasibility of this type of experiment has perfected in recent years, but data analysis remains challenging. In this context, gene set analysis has emerged as a fundamental tool for the interpretation of the results. We demonstrate how the use of a combination of gene-by-gene and gene set analyses can enhance the interpretation of results. Gene set analyses are able to distinguish responses due to nanoparticle size also discriminating between long and short time recovery after exposure. Transcription regulation and cell proliferation modulation appear to be an early response while oxidative stress and mitochondrial perturbation are late response. Moreover, smaller the particle higher the effect on inflammatory response and DNA damage activation. By integrating the two approaches, we evidenced the importance of MMP1, MMP9, MMP7 and MMP14 genes in response to Ludox® silica nanoparticles and the involvement apoptosis process in cell viability. This study is based on the treatment of A549 cells with two different silica nanoparticles (SM30, 9 nm of diameter, and AS30, 18 nm of diameter). Treatment with nanoparticles were performed independently. We performed three biological replicates for each condition.
Project description:BackgroundSynthetic amorphous silica nanoparticles (SAS-NPs) are widely employed in pharmaceutics, cosmetics, food and concretes. Workers and the general population are exposed daily via diverse routes of exposure. SAS-NPs are generally recognized as safe (GRAS) by the Food and Drug Administration, but because of their nanoscale size and extensive uses, a better assessment of their immunotoxicity is required. In the presence of immune "danger signals", dendritic cells (DCs) undergo a maturation process resulting in their migration to regional lymph nodes where they activate naive T-cells. We have previously shown that fumed silica pyrogenic SAS-NPs promote the two first steps of the adaptative immune response by triggering DC maturation and T-lymphocyte response, suggesting that SAS-NPs could behave as immune "danger signals". The present work aims to identify the mechanism and the signalling pathways involved in DC phenotype modifications provoked by pyrogenic SAS-NPs. As a pivotal intracellular signalling molecule whose phosphorylation is associated with DC maturation, we hypothesized that Spleen tyrosine kinase (Syk) may play a central role in SAS-NPs-induced DC response.ResultsIn human monocyte-derived dendritic cells (moDCs) exposed to SAS-NPs, Syk inhibition prevented the induction of CD83 and CD86 marker expression. A significant decrease in T-cell proliferation and IFN-γ, IL-17F and IL-9 production was found in an allogeneic moDC:T-cell co-culture model. These results suggested that the activation of Syk was necessary for optimal co-stimulation of T-cells. Moreover, Syk phosphorylation, observed 30 min after SAS-NP exposure, occurred upstream of the c-Jun N-terminal kinase (JNK) Mitogen-activated protein kinases (MAPK) and was elicited by the Src family of protein tyrosine kinases. Our results also showed for the first time that SAS-NPs provoked aggregation of lipid rafts in moDCs and that MβCD-mediated raft destabilisation altered Syk activation.ConclusionsWe showed that SAS-NPs could act as an immune danger signal in DCs through a Syk-dependent pathway. Our findings revealed an original mechanism whereby the interaction of SAS-NPs with DC membranes promoted aggregation of lipid rafts, leading to a Src kinase-initiated activation loop triggering Syk activation and functional DC maturation.