Contribution du cerf de Virginie aux variations spatio-temporelles de la régénération du thuya occidental au Québec et au Nouveau-Brunswick

Les cervidés peuvent moduler la composition, la structure et les fonctions des écosystèmes forestiers qu'ils occupent. En broutant de manière sélective la régénération forestière, ils influencent l'abondance des espèces d'arbres du sous-bois, pouvant mener à un faible recrutement des espèces d'arbres consommées. Cependant, l'impact des cervidés est généralement étudié à fine échelle, rendant difficile la généralisation des connaissances actuelles à l'échelle de l'aire de distribution commune d'un cervidé et d'une espèce d'arbre. De plus, le comportement alimentaire des cervidés est directement influencé par la distribution spatiale des ressources, mais aussi indirectement par la distribution des prédateurs ou des types d'habitats où ils perçoivent un risque de prédation plus élevé, ces derniers étant qualifiés de paysages de la peur. L'évitement de certaines zones risquées par les cervidés pourrait mener à la création d'aires où la pression de broutement est faible, et donc créer des zones de régénération forestière à l'abri du broutement pour les espèces d'arbres sélectionnées dans l'alimentation. Les objectifs de cette étude étaient de déterminer à large échelle l'impact de la variation spatio-temporelle de l'abondance du cerf de Virginie (Odocoileus virginianus) sur le recrutement du thuya occidental (Thuja occidentalis L.), une espèce d'arbre hautement sélectionnée, et d'évaluer si les routes forestières influencent le broutement du cerf de Virginie en générant un paysage de la peur. En utilisant des données écoforestières et de suivi de la grande faune à l'échelle du Québec et du Nouveau-Brunswick, nous avons détecté un effet négatif de l'abondance de cerfs et de la proximité à un ravage sur le recrutement des gaules de thuya. Nous avons constaté que la pression de broutement locale a aussi un impact négatif sur l'abondance de semis. Dans un deuxième temps, nous avons mesuré une faible pression de broutement à proximité de routes forestières, suggérant qu'elles peuvent représenter un paysage de la peur pour le cerf de Virginie. Cependant, puisque la régénération de thuya n'y était pas plus abondante, nous ne pouvons pas conclure que les routes forestières permettent la création de zones de régénération forestière à l'abri du broutement dans le contexte de notre étude.By selectively feeding on forest regeneration, cervids influence the abundance of understory species, which can lead to recruitment failure for the consumed species. However, the impact of cervids on regeneration is generally studied at fine scales, making it difficult to generalize the current knowledge at the scale of the distribution range of co-occurring cervid and tree species. In addition, the foraging behavior of cervids is directly influenced by the spatial distribution of resources but also indirectly by the distribution of predators or of habitat types where they perceive a higher predation risk, the latter being qualified as a landscape of fear. The avoidance of risky zones by cervids could then lead to the creation of areas where browsing pressure is low, therefore providing safe spots for forest regeneration, especially for highly selected species. The objectives of this study were to determine over a broad scale the effect of the spatio-temporal variation of white-tailed deer (Odocoileus virginianus) abundance on northern white cedar (Thuja occidentalis L.) recruitment, a highly selected species, and evaluate if forest roads influence white-tailed deer browsing by creating a landscape of fear. By joining distinct forest and wildlife databases at the scale of Québec and New Brunswick, we detected a negative impact of deer abundance and proximity to deeryard on the recruitment of cedar saplings. We found that local browsing pressure also has a negative impact on the abundance of seedlings. Subsequently, we measured a low browsing pressure near forest roads, suggesting that they can represent a landscape of fear for deer. However, since cedar regeneration was not more abundant near forest roads, we cannot conclude that they allow the creation of safe spots for forest regeneration in the context of the present study

Étude de la capacité d'hyperaccumulation de cadmium en sol contaminé de Brassica juncea et de Helianthus annuus en comparaison avec Thlaspi caerulescens

Affiche présentée dans le cadre du Colloque de l'ARC, «Des racines et des ailes pour la recherche collégiale», dans le cadre du 85e Congrès de l’Acfas, Université McGill, Montréal, les 8 et 9 mai 2017.Le deuxième prix a été décerné à Béatrice Capolla et Todor Minchev, au concours des Prix étudiants 2016-2017 de l'ARC.Le cadmium est un métal lourd absorbé par les plantes lorsqu’il se trouve en trop grande concentration dans le sol. D’où son entrée dans la chaîne alimentaire, qui induit des troubles physiologiques. Sa pré-sence dans le sol est surtout due à l’extraction minière du zinc et à la production industrielle, et son retrait est souvent difficile. La phytoremédiation devient alors intéressante. Thlaspi caerulescens est une petite plante utilisée en Europe en extraction de métaux lourds. Mais elle présente des caractéristiques envahissantes, limitant son usage au Québec. Des plantes naturalisées ou indigènes telles que Helianthus annuus et Brassica juncea sont d'autres candidates potentielles. Des groupes de six à huit réplicats de chaque espèce ont été exposés à un sol contaminé pendant 39 jours. Par la suite, des tissus cibles ont été digérés à l’acide selon un protocole du Centre d'expertise en analyse environnementale du Québec avant d’être analysés par spectrométrie à émission de plasma d’argon. Les résultats démontrent une différence significative entre la concentration de cadmium trouvée dans les tissus de B. juncea contaminés par rapport aux témoins, indiquant une capacité de phytoextraction. Chez H. annuus, la différence a été observée dans les racines plutôt que dans les feuilles, indiquant une capacité de phytostabilisation. Toutefois, aucune espèce n’a réussi à atteindre la concentration de T. caerulescens, compensant plutôt avec une biomasse plus élevée

Surface antibody changes protein corona both in human and mouse serum but not final opsonization and elimination of targeted polymeric nanoparticles

Background: Nanoparticles represent one of the most important innovations in the medical field. Among nanocarriers, polymeric nanoparticles (PNPs) attracted much attention due to their biodegradability, biocompatibility, and capacity to increase efficacy and safety of encapsulated drugs. Another important improvement in the use of nanoparticles as delivery systems is the conjugation of a targeting agent that enables the nanoparticles to accumulate in a specific tissue. Despite these advantages, the clinical translation of therapeutic approaches based on nanoparticles is prevented by their interactions with blood proteins. In fact, the so-formed protein corona (PC) drastically alters the biological identity of the particles. Adsorbed activated proteins of the complement cascade play a pivotal role in the clearance of nanoparticles, making them more easily recognized by macrophages, leading to their rapid elimination from the bloodstream and limiting their efficacy. Since the mouse is the most used preclinical model for human disease, this work compared human and mouse PC formed on untargeted PNPs (uPNPs) and targeted PNPs (tPNPs), paying particular attention to complement activation. Results: Mouse and human serum proteins adsorbed differently to PNPs. The differences in the binding of mouse complement proteins are minimal, whereas human complement components strongly distinguish the two particles. This is probably due to the human origin of the Fc portion of the antibody used as targeting agent on tPNPs. tPNPs and uPNPs mainly activate complement via the classical and alternative pathways, respectively, but this pattern did not affect their binding and internalization in macrophages and only a limited consumption of the activity of the human complement system was documented. Conclusions: The results clearly indicate the presence of complement proteins on PNPs surface but partially derived from an unspecific deposition rather than an effective complement activation. The presence of a targeting antibody favors the activation of the classical pathway, but its absence allows an increased activation of the alternative pathway. This results in similar opsonization of both PNPs and similar phagocytosis by macrophages, without an impairment of the activity of circulating complement system and, consequently, not enhancing the susceptibility to infection. Graphical abstract: [Figure not available: see fulltext.

Bispecific antibodies targeting tumor-associated antigens and neutralizing complement regulators increase the efficacy of antibody-based immunotherapy in mice.

The efficacy of antibody-based immunotherapy is due to the activation of apoptosis, the engagement of antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity (CDC). We developed a novel strategy to enhance CDC using bispecific antibodies (bsAbs) that neutralize the C-regulators CD55 and CD59 to enhance C-mediated functions. Two bsAbs (MB20/55 and MB20/59) were designed to recognize CD20 on one side. The other side neutralizes CD55 or CD59. Analysis of CDC revealed that bsAbs could kill 4 to 25 times more cells than anti-CD20 recombinant antibody in cell lines or cells isolated from patients with chronic lymphocytic leukemia. The pharmacokinetics of the bsAbs was evaluated in a human-SCID model of Burkitt lymphoma. The distribution profile of bsAbs mimics the data obtained by studying the pharmacokinetics of anti-CD20 antibodies, showing a peak in the tumor mass 3-4 days after injection. The treatment with bsAbs completely prevented the development of human/SCID lymphoma. The tumor growth was blocked by the activation of the C cascade and by the recruitment of macrophages, PMN and NK cells. This strategy can easily be applied to the other anti-tumor C-fixing antibodies currently used in the clinic or tested in preclinical studies using the same vector with the appropriate modifications

A new approach for the treatment of CLL using chlorambucil/hydroxychloroquine-loaded anti-CD20 nanoparticles

Current approaches for the treatment of chronic lymphocytic leukemia (CLL) have greatly improved the prognosis for survival, but some patients remain refractive to these therapeutic regimens. Hence, in addition to reducing the long-term sideeffects of therapeutics for all leukemia patients, there is an urgent need for novel therapeutic strategies for difficult-to-treat leukemia cases. Due to the cytotoxicity of drugs, the major challenge currently is to deliver the therapeutic agents to neoplastic cells while preserving the viability of non-malignant cells. In this study, we propose a therapeutic approach in which high doses of hydroxychloroquine and chlorambucil were loaded into biodegradable polymeric nanoparticles coated with an anti-CD20 antibody.We first demonstrated the ability of the nanoparticles to target and internalize in tumor B-cells. Moreover, these nanoparticles could kill not only p53-mutated/deleted leukemia cells expressing a low amount of CD20, but also circulating primary cells isolated from chronic lymphocytic leukemia patients. The safety of these nanoparticles was also demonstrated in healthy mice, and their therapeutic effects were shown in a new model of aggressive leukemia. These results showed that anti-CD20 nanoparticles containing hydroxychloroquine and chlorambucil can be effective in controlling aggressive leukemia and provided a rationale for adopting this approach for the treatment of other B-cell disorders. [Figure not available: see fulltext.

Constitutive psgl-1 correlates with cd30 and tcr pathways and represents a potential target for immunotherapy in anaplastic large t-cell lymphoma

Due to the high expression of P-selectin glycoprotein ligand-1 (PSGL-1) in lymphoprolif-erative disorders and in multiple myeloma, it has been considered as a potential target for humoral immunotherapy, as well as an immune checkpoint inhibitor in T-cells. By investigating the expression of SELPLG in 678 T-and B-cell samples by gene expression profiling (GEP), further supported by tissue microarray and immunohistochemical analysis, we identified anaplastic large T-cell lymphoma (ALCL) as constitutively expressing SELPLG at high levels. Moreover, GEP analysis in CD30+ ALCLs highlighted a positive correlation of SELPLG with TNFRSF8 (CD30-coding gene) and T-cell receptor (TCR)-signaling genes (LCK, LAT, SYK and JUN), suggesting that the common dysreg-ulation of TCR expression in ALCLs may be bypassed by the involvement of PSGL-1 in T-cell activation and survival. Finally, we evaluated the effects elicited by in vitro treatment with two anti-PSGL-1 antibodies (KPL-1 and TB5) on the activation of the complement system and induction of apoptosis in human ALCL cell lines. In conclusion, our data demonstrated that PSGL-1 is specifically enriched in ALCLs, altering cell motility and viability due to its involvement in CD30 and TCR signaling, and it might be considered as a promising candidate for novel immunotherapeutic approaches in ALCLs

Targeting CD34(+) cells of the inflamed synovial endothelium by guided nanoparticles for the treatment of rheumatoid arthritis

Despite the advances in the treatment of rheumatoid arthritis (RA) achieved in the last few years, several patients are diagnosed late, do not respond to or have to stop therapy because of inefficacy and/or toxicity, leaving still a huge unmet need. Tissue-specific strategies have the potential to address some of these issues. The aim of the study is the development of a safe nanotechnology approach for tissue-specific delivery of drugs and diagnostic probes. CD34 + endothelial precursors were addressed in inflamed synovium using targeted biodegradable nanoparticles (tBNPs). These nanostructures were made of poly-lactic acid, poly-caprolactone, and PEG and then coated with a synovial homing peptide. Immunofluorescence analysis clearly demonstrated their capacity to selectively address CD34 + endothelial cells in synovial tissue obtained from human, mouse, and rat. Biodistribution studies in two different animal models of rheumatoid arthritis (antigen-induced arthritis/AIA and collagen-induced arthritis/CIA) confirmed the selective accumulation in inflamed joints but also evidenced the capacity of tBNP to detect early phases of the disease and the preferential liver elimination. The therapeutic effect of methotrexate (MTX)-loaded tBNPs were studied in comparison with conventional MTX doses. MTX-loaded tBNPs prevented and treated CIA and AIA at a lower dose and reduced administration frequency than MTX. Moreover, MTX-loaded tBNP showed a novel mechanism of action, in which the particles target and kill CD34 + endothelial progenitors, preventing neo-angiogenesis and, consequently, synovial inflammation. tBNPs represent a stable and safe platform to develop highly-sensitive imaging and therapeutic approaches in RA targeting specifically synovial neo-angiogenesis to reduce local inflammation

Targeted chitosan nanobubbles as a strategy to down-regulate microRNA-17 into B-cell lymphoma models

IntroductionMicroRNAs represent interesting targets for new therapies because their altered expression influences tumor development and progression. miR-17 is a prototype of onco-miRNA, known to be overexpressed in B-cell non-Hodgkin lymphoma (B-NHL) with peculiar clinic-biological features. AntagomiR molecules have been largely studied to repress the regulatory functions of up-regulated onco-miRNAs, but their clinical use is mainly limited by their rapid degradation, kidney elimination and poor cellular uptake when injected as naked oligonucleotides.MethodsTo overcome these problems, we exploited CD20 targeted chitosan nanobubbles (NBs) for a preferential and safe delivery of antagomiR17 to B-NHL cells.ResultsPositively charged 400 nm-sized nanobubbles (NBs) represent a stable and effective nanoplatform for antagomiR encapsulation and specific release into B-NHL cells. NBs rapidly accumulated in tumor microenvironment, but only those conjugated with a targeting system (antiCD20 antibodies) were internalized into B-NHL cells, releasing antagomiR17 in the cytoplasm, both in vitro and in vivo. The result is the down-regulation of miR-17 level and the reduction in tumor burden in a human-mouse B-NHL model, without any documented side effects.DiscussionAnti-CD20 targeted NBs investigated in this study showed physico-chemical and stability properties suitable for antagomiR17 delivery in vivo and represent a useful nanoplatform to address B-cell malignancies or other cancers through the modification of their surface with specific targeting antibodies

Complement as a biological tool to control tumor growth

Deposits of complement components have been documented in several human tumors suggesting a potential involvement of the complement system in tumor immune surveillance. In vitro and in vivo studies have revealed a double role played by this system in tumor progression. Complement activation in the cancer microenvironment has been shown to promote cancer growth through the release of the chemotactic peptide C5a recruiting myeloid suppressor cells. There is also evidence that tumor progression can be controlled by complement activated on the surface of cancer cells through one of the three pathways of complement activation. The aim of this review is to discuss the protective role of complement in cancer with special focus on the beneficial effect of complement-fixing antibodies that are efficient activators of the classical pathway and contribute to inhibit tumor expansion as a result of MAC-mediated cancer cell killing and complement-mediated inflammatory process. Cancer cells are heterogeneous in their susceptibility to complement-induced killing that generally depends on stable and relatively high expression of the antigen and the ability of therapeutic antibodies to activate complement. A new generation of monoclonal antibodies are being developed with structural modification leading to hexamer formation and enhanced complement activation. An important progress in cancer immunotherapy has been made with the generation of bispecific antibodies targeting tumor antigens and able to neutralize complement regulators overexpressed on cancer cells. A great effort is being devoted to implementing combined therapy of traditional approaches based on surgery, chemotherapy and radiotherapy and complement-fixing therapeutic antibodies. An effective control of tumor growth by complement is likely to be obtained on residual cancer cells following conventional therapy to reduce the tumor mass, prevent recurrences and avoid disabilities

USE OF IMMUNE-NANOPARTICLES CONTAINING CHEMOTHERAPEUTIC AGENTS FOR THE TREATMENT OF B-CELL MALIGNANCIES

2013/2014B-cell malignancies are a heterogeneous group of clinical conditions including indolent diseases such as Chronic Lymphocytic Leukemia (CLL) and highly aggressive lymphoproliferative disorders such as Burkitt’s lymphoma. B-cell malignancies treatments take advantage of dose-intensive chemotherapeutic regimens and immunotherapy via monoclonal antibodies. Unfortunately, they may lead to insufficient tumor distribution of therapeutic agents and cause several adverse effects. Thus, we propose a novel therapeutic approach for the treatment of CLL and Burkitt’s lymphoma in which high-doses of the association of hydroxychloroquine and chlorambucil (HCQ/CLB) or fludarabine were loaded inside biodegradable nanoparticles (BNPs) coated with an anti-CD20 antibody. First of all, a Burkitt’s lymphoma cell line (BJAB), two CLL cell lines (MEC1 and EHEB) and cells purified from patients’ blood samples were used to confirm CD20 expression and to assess BNPs binding and internalization. These studies demonstrated BNPs ability to bind malignant B cells and to enter inside cells in a process different from endocytosis. Then, BNPs therapeutic effect was evaluated by MTT test, AnnV/PI assay and western blot to put in evidence apoptosis induction and autophagy inhibition. These experiments demonstrated drugs-loaded BNPs ability to kill malignant B cells with comparable effects than those obtained with free drugs whereas empty BNPs were practically ineffective. In vivo BNPs characterization included the evaluation of their toxicity, biodistribution and therapeutic effect. C57/BL mice were used to evaluate BNPs toxicity which was studied considering survival, loss of body weight and several tissue markers in the blood. Mice receiving 8 injections of free HCQ+CLB died in this experiment whereas animals challenged with the same amount of drugs encapsulated inside BNPs did not show toxic effects suggesting BNPs safety. The importance of antiCD20 antibody in the homing of BNPs was confirmed by in vivo Time-Domain Optical Imaging performed in localized B-cell malignancy-bearing mice. This analysis suggested the ability of antiCD20-conjugated BNPs to specifically target tumor B-cells, with a pick after 24-48 hours. On the contrary, untargeted BNPs localization inside tumor was significantly decreased. In this analysis it was also evident that the liver is the main site of BNPs’ elimination while in the other organs the presence of fluorescent BNPs was very low. Finally, BNPs ability to treat a new xenograft human/SCID leukemia and Burkitt’s lymphoma mouse model was studied. Drugs-loaded BNPs were able to improve HCQ/CLB efficacy in vivo allowing the cure of treated all Burkitt’s lymphoma-bearing mice and 3 out of 7 leukemia-bearing animals. All these data together put the basis for the potential use of BNPs in the treatment of B-cell malignancies.I tumori a cellule B sono un gruppo eterogeneo di patologie che comprendono sia malattie indolenti, come la leucemia linfatica cronica (LLC), sia aggressive, come il linfoma di Burkitt. Il trattamento delle patologie a cellule B prevede sia l’utilizzo di chemioterapici (agenti alchilanti e analoghi delle purine) che di anticorpi monoclonali. Nonostante la varietà di terapie esistenti, l’efficacia di questi farmaci è limitata dalla mancata specificità per le cellule tumorali e dall’induzione di gravi effetti collaterali. Per ovviare ai limiti delle terapie attuali, è stato quindi proposto l’utilizzo di nanoparticelle coniugate con un anticorpo antiCD20, specifico per le cellule B, e contenenti alte concentrazioni di chemioterapici (idrossiclorochina e clorambucile o fludarabina). Le nanoparticelle sono state caratterizzate in vitro e in vivo durante questo progetto di dottorato. Inizialmente sono stati effettuati studi in vitro al fine di valutare l’espressione del CD20 sulla superficie di una linea cellulare di linforma di Burkitt (BJAB), due linee di LLC (MEC1 e EHEB) e cellule purificate da campioni di sangue di pazienti affetti da LLC. In seguito, il legame e l’internalizzazione delle nanoparticelle a queste cellule sono stati dimostrati suggerendo anche come le nanoparticelle vengano internalizzate attraverso un meccanismo diverso dall’endocitosi. L’effetto terapeutico in vitro delle nanoparticelle è stato valutato con test MTT, AnnessinaV/PI e tramite western blot al fine di evidenziare l’induzione di apoptosi e l’inibizione dell’autofagia, meccanismi attraverso cui i farmaci utilizzati sono noti agire. Questi esperimenti hanno dimostrato che le nanoparticelle cariche di chemioterapici sono in grado di uccidere le cellule B tumorali con effetti paragonabili a quelli ottenuti da pari concentrazioni di farmaci liberi dimostrando come il processo di produzione delle nanoparticelle non influisca sull’efficacia dei chemioterapici. Al contrario, nanoparticelle vuote non sono in grado di uccidere le cellule dimostrando la mancata tossicità dei polimeri da cui sono costituite. Dopo aver confermato il legame e l’internalizzazione delle nanoparticelle che inducono la morte delle cellule B tumorali, sono stati effettuati esperimenti in vivo tra cui studi di tossicità al fine di valutare eventuali effetti collaterali indotti dal trattamento, studi di biodistribuzione e la valutazione degli effetti terapeutici. Gli studi di tossicità sono stati effettuati in topi sani valutando parametri quali la perdita di peso, la sopravvivenza e la tossicità sistemica. Nanoparticelle cariche di farmaci presentano un profilo tossicologico sicuro mentre pari dosi di farmaci liberi inducono la morte di tutti gli animali trattati. Questi esperimenti dimostrano quindi come l’inserimento di farmaci all’interno di nanoparticelle prevenga gli effetti collaterali normalmente indotti dai chemioterapici. Secondariamente, sono stati effettuati studi di biodistribuzione di nanoparticelle coniugate o meno con un anticorpo antiCD20. Questi studi effettuati tramite Optical Imaging dimostrano come nanoparticelle coniugate con l’anticorpo antiCD20 si localizzino preferenzialmente nella massa tumorale in 24-48 ore in quantità maggiore rispetto a nanoparticelle non coniugate con l’anticorpo. Inoltre, da queste analisi risulta evidente come il fegato sia il maggiore sito di eliminazione delle nanoparticelle mentre in altri organi la presenza di nanoparticelle è molto bassa. Infine, un modello disseminato di linfoma di Burkitt e un modello di LLC sono stati sviluppati in topi SCID (Severe Combined ImmunoDeficiency) iniettando rispettivamente cellule BJAB intraperitoneo e cellule MEC1 endovena. I modelli sono stati caratterizzati e utilizzati per valutare la potenziale applicazione delle nanoparticelle nel trattamento di queste patologie. Questi studi hanno dimostrato come le nanoparticelle siano in grado di aumentare l’efficacia dei chemioterapici e di curare tutti i topi affetti da linfoma di Burkitt e 3/7 topi affetti da leucemia. Concludendo, questi risultati suggeriscono la potenziale applicazione delle nanoparticelle cariche di chemioterapici nel trattamento di LLC e linfoma di Burkitt.XXVII Ciclo198