Sandrine Truchet

The human and livestock pathogen Staphylococcus aureus poses a major clinical challenge due to antibiotic treatment failure. Its resilience is mainly attributed to antibiotic resistance and tolerance mechanisms related to persistence. Here we investigate how two infection-relevant conditions, milk and serum, shape S. aureus pathogenic properties and capacity to withstand environmental stresses. Milk- versus serum-grown bacteria show gross differences in envelope physical properties, membrane fatty acid composition and rigidity, and pigment production, and display distinct proteomic profiles. Compared to growth in serum, S. aureus grown in milk exhibits extreme resistance to ROS damage, marked antimicrobial tolerance, and accelerated killing in a larval infection model. High level S. aureus pigmentation in whole milk is stimulated by milk lipids, and is responsible for high ROS resistance. The remarkable robustness of S. aureus in a milk biotope may signal the need to adjust antibiotic regimens when treating mastitis infections in humans and livestock.

Campylobacter jejuni is a foodborne pathogen that adheres to and invades the epithelial cells of the human intestinal tract. The extracellular vesicles (EVs) of C. jejuni have an important impact during pathogenicity but their role in invasion of the host intestinal epithelial cells remain largely unknown. In vitro models lack the complexity of tissue and fail to accurately replicate the dynamic interactions between EVs and human intestinal epithelial cells, while animal infection models have species-specific differences that limit their translational relevance and are associated with ethical concerns. To bridge this gap, we propose a microfluidic platform integrated with an impedimetric sensor to monitor C. jejuni EV interactions with human intestinal epithelial Caco-2 cells. When cultured in this microfluidic device, Caco-2 cells underwent spontaneous 3D morphogenesis and were spatially organised into spheroid-like structures. By combining impedance spectroscopy and microscopic observation, the platform allowed direct monitoring of cellular spatial growth and sensitive detection of their interaction with EVs. Although functional assays revealed that the C. jejuni EVs killed Caco-2 cells cultured on plates, 3D Caco-2 spheroids showed significantly greater resistance to both C. jejuni secretome and EVs. The physiological relevance of the model was confirmed by TEER measurements that suggested that Campylobacter EVs difused paracellularly. The developed microfluidic device is a promising platform for investigating host‒microbe interactions and may have a broad impact on biomedical research on gastroenteritis.

Shadoo belongs to the prion protein family, an evolutionary conserved and extensively studied family due to the implication of PrP in Transmissible Spongiform Encephalopathies. However, the biological function of these genes remains poorly understood. While Sprn-knockdown experiments suggested an involvement of Shadoo during mouse embryonic development, Sprn-knockout experiments in 129Pas/C57BL/6J or 129Pas/FVB/NCr mice did not confirm it. In the present study, we analyzed the impact of Sprn gene invalidation in a pure FVB/NJ genetic background, using a zinc finger nuclease approach. The in-depth analysis of the derived knockout transgenic mice revealed a significant increase in embryonic lethality at early post-implantation stages, a growth retardation of young Sprn-knockout pups fed by wild type mice and a lactation defect of Sprn-knockout females. Histological and transcriptional analyses of knockout E7.5 embryos, E14.5 placentas and G7.5 mammary glands revealed specific roles of the Shadoo protein in mouse early embryogenesis, tissue development and differentiation with a potential antagonist action between PrP and Shadoo. This study thus highlights the entanglement between the proteins of the prion family.

In peripherally acquired prion diseases, prions move through several tissues of the infected host, notably in the lymphoid tissue, long before the occurrence of neuroinvasion. Accumulation can even be restricted to the lymphoid tissue without neuroinvasion and clinical disease. Several experimental observations indicated that the presence of differentiated follicular dendritic cells (FDCs) in the lymphoid structures and the strain type are critical determinants of prion extraneural replication. In this context, the report that granulomatous structures apparently devoid of FDCs could support prion replication raised the question of the requirements for prion lymphotropism. The report also raised the possibility that nonlymphoid tissue-tropic prions could actually target these inflammatory structures. To investigate these issues, we examined the capacity of closely related prions, albeit with opposite lymphotropism (or FDC dependency), for establishment in experimentally-induced granuloma in ovine PrP transgenic mice. We found a positive correlation between the prion capacity to accumulate in the lymphoid tissue and granuloma, regardless of the prion detection method used. Surprisingly, we also revealed that the accumulation of prions in granulomas involved lymphoid-like structures associated with the granulomas and containing cells that stain positive for PrP, Mfge-8 but not CD45 that strongly suggest FDCs. These results suggest that the FDC requirement for prion replication in lymphoid/inflammatory tissues may be strain-dependent.

Compelling evidence supports a tight link between oxidative stress and protein aggregation processes, which are noticeably involved in the development of proteinopathies, such as Alzheimer’s disease, Parkinson’s disease, and prion disease. The literature is tremendously rich in studies that establish a functional link between both processes, revealing that oxidative stress can be either causative, or consecutive, to protein aggregation. Because oxidative stress monitoring is highly challenging and may often lead to artefactual results, cutting-edge technical tools have been developed recently in the redox field, improving the ability to measure oxidative perturbations in biological systems. This review aims at providing an update of the previously known functional links between oxidative stress and protein aggregation, thereby revisiting the long-established relationship between both processes.

Extracellular vesicles (EVs) are biological vectors that can modulate the metabolism of target cells by conveying signalling proteins and genomic material. The level of EVs in plasma is significantly increased in cardiometabolic diseases associated with obesity, suggesting their possible participation in the development of metabolic dysfunction. With regard to the poor definition of adipocyte‐derived EVs, the purpose of this study was to characterise both qualitatively and quantitatively EVs subpopulations secreted by fat cells. Adipocyte‐derived EVs were isolated by differential centrifugation of conditioned media collected from 3T3‐L1 adipocytes cultured for 24 h in serum‐free conditions. Based on morphological and biochemical properties, as well as quantification of secreted EVs, we distinguished two subpopulations of adipocyte‐derived EVs, namely small extracellular vesicles (sEVs) and large extracellular vesicles (lEVs). Proteomic analyses revealed that lEVs and sEVs exhibit specific protein signatures, allowing us not only to define novel markers of each population, but also to predict their biological functions. Despite similar phospholipid patterns, the comparative lipidomic analysis performed on these EV subclasses revealed a specific cholesterol enrichment of the sEV population, whereas lEVs were characterised by high amounts of externalised phosphatidylserine. Enhanced secretion of lEVs and sEVs is achievable following exposure to different biological stimuli related to the chronic low‐grade inflammation state associated with obesity. Finally, we demonstrate the ability of primary murine adipocytes to secrete sEVs and lEVs, which display physical and biological characteristics similar to those described for 3T3‐L1. Our study provides additional information and elements to define EV subtypes based on the characterisation of adipocyte‐derived EV populations. It also underscores the need to distinguish EV subpopulations, through a combination of multiple approaches and markers, since their specific composition may cause distinct metabolic responses in recipient cells and tissues.