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Transcriptomics in whole-blood cells of Buruli ulcer patients identifies a signature of inflammation

ABSTRACT: Mycolactone, a lipid-like toxin, is the major virulence factor of Mycobacterium ulcerans, the etiological agent of Buruli ulcer. Its involvement in lesions development has been widely described in early stages of the disease, through its cytotoxic and immunosuppressive activities, but less is known about later stages. Here, we revisit the role of mycolactone in disease outcome and provide the first demonstration of the pro-inflammatory potential of this toxin. We found that the mycolactone-containing mycobacterial extracellular vesicles produced by M. ulcerans induced the production of IL-1β, a potent pro-inflammatory cytokine, in a TLR2-dependent manner, targeting NLRP3/1 inflammasomes. We showed our data to be relevant in a physiological context. The in vivo injection of these mycolactone-containing vesicles induced a strong local inflammatory response and tissue damages, which were prevented by corticosteroids. Finally, several soluble pro-inflammatory factors, including IL-1β, were detected in infected tissues from mice and Buruli ulcer patients. Our results revisit Buruli ulcer pathophysiology by giving a new insight, thus paving the way for development of new therapeutic strategies, taking account the pro-inflammatory potential of mycolactone.

ORGANISM(S): Homo sapiens

PROVIDER: GSE157350 | GEO | 2020/12/29

REPOSITORIES: GEO

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Project description:BACKGROUND: Cryopyrin-Associated Periodic Syndrome (CAPS) is an autoinflammatory condition consequence of monoallelic variants in the NLRP3 gene that exacerbate IL-1β production. These variants are gain-of-function, but the exact regulatory mechanism of the NLRP3 CAPS-inflammasome is not well yet understood. It is considered as a hypersensitive inflammasome triggered by cell priming, but patients with CAPS and animal disease models present inflammatory flares in the absence of external triggers.OBJECTIVES: To study the regulation and activation of the NLRP3 inflammasome in CAPS.METHODS: CAPS derived blood samples and genetically modified macrophages expressing different NLRP3 CAPS-associated variants were used to assess NLRP3 function dissociated from cell priming and cell metabolism.RESULTS: We found that CAPS-associated variants constitutively result in active NLRP3 inflammasomes, that induce a basal cleavage of gasdermin D, IL-18 release and pyroptosis. The constitutive active NLRP3 inflammasome was blocked by MCC950 and was dependent on NLRP3 expression level, being further regulated by deubiquitination. We also showed that activation of NF-κB with lipopolysaccharide or other endogenous host-derived molecules (palmitate, S100A9 or IL-6) further modulated the activation of the NLRP3 CAPS inflammasome and expanded the repertoire of molecules secreted from CAPS macrophages to IL-1β, IL-1α, HMGB1, cystatin B and the P2X7 receptor, identifying novel proteins involved in CAPS pathogenesis. NLRP3 inflammasomes with CAPS associated variants affected the immunometabolism of the myeloid compartment and impaired glycolysis.CONCLUSIONS: These findings demonstrate that NLRP3 CAPS-associated variants form a constitutive active inflammasome that induce basal pyroptosis and IL-18 release without cell priming, suggesting a priming-independent mechanism for the initiation of CAPS flares characterized with a profound affection in the immunometabolism.

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Transcriptomics in whole-blood cells of Buruli ulcer patients identifies a signature of inflammation

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