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Nucleic acid-sensing toll-like receptors: Important players in Sjogren's syndrome.

ABSTRACT: Sjögren's syndrome (SS) is a chronic systemic autoimmune disease that affects the salivary and lacrimal glands, as well as other organ systems like the lungs, kidneys and nervous system. SS can occur alone or in combination with another autoimmune disease, such as systemic lupus erythematosus (SLE) or rheumatoid arthritis. The etiology of SS is unknown but recent studies have revealed the implication of the activation of innate immune receptors, including Toll-like receptors (TLRs), mainly through the detection of endogenous nucleic acids, in the pathogenesis of systemic autoimmune diseases. Studies on SS mouse models suggest that TLRs and especially TLR7 that detects single-stranded RNA of microbial or endogenous origin can drive the development of SS and findings in SS patients corroborate those in mouse models. In this review, we will give an overview of the function and signaling of nucleic acid-sensing TLRs, the interplay of TLR7 with TLR8 and TLR9 in the context of autoimmunity, summarize the evidence for the critical role of TLR7 in the pathogenesis of SS and present a possible connection between SARS-CoV-2 and SS.

SUBMITTER: Alexopoulou L

PROVIDER: S-EPMC9659959 | biostudies-literature | 2022

REPOSITORIES: biostudies-literature

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Nucleic acid-sensing toll-like receptors: Important players in Sjögren's syndrome.

Alexopoulou Lena L

Frontiers in immunology 20221031

Sjögren's syndrome (SS) is a chronic systemic autoimmune disease that affects the salivary and lacrimal glands, as well as other organ systems like the lungs, kidneys and nervous system. SS can occur alone or in combination with another autoimmune disease, such as systemic lupus erythematosus (SLE) or rheumatoid arthritis. The etiology of SS is unknown but recent studies have revealed the implication of the activation of innate immune receptors, including Toll-like receptors (TLRs), mainly throu ...[more]

PMID: 36389822

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Project description:Streptococcus pyogenes is a major human pathogen causing a variety of diseases ranging from common pharyngitis to life-threatening soft tissue infections and sepsis. Microbial nucleic acids, especially bacterial RNA, have recently been recognized as a major group of pathogen-associated molecular patterns (PAMPs) involved in the detection of Streptococcus pyogenes via endosomal Toll-like receptors (TLRs) in vitro. However, the individual contribution and cooperation between TLRs as well as cell-type and strain specific differences in dependency on nucleic acid detection during S. pyogenes infection in vitro have not been clarified in detail. Moreover, the role of particularly bacterial RNA for the defense of S. pyogenes infection in vivo remains poorly defined. In this study, we report that in all investigated innate immune cells involved in the resolution of bacterial infections, including murine macrophages, dendritic cells and neutrophils, recognition of S. pyogenes strain ATCC12344 is almost completely dependent on nucleic acid sensing via endosomal TLRs at lower MOIs, whereas at higher MOIs, detection via TLR2 plays an additional, yet redundant role. We further demonstrate that different S. pyogenes strains display a considerable inter-strain variability with respect to their nucleic acid dependent recognition. Moreover, TLR13-dependent recognition of S. pyogenes RNA is largely non-redundant in bone marrow-derived macrophages (BMDMs), but less relevant in neutrophils and bone marrow-derived myeloid dendritic cells (BMDCs) for the induction of an innate immune response in vitro. In vivo, we show that a loss of nucleic acid sensing blunts early recognition of S. pyogenes, leading to a reduced local containment of the bacterial infection with subsequent pronounced systemic inflammation at later time points. Thus, our results argue for a crucial role of nucleic acid sensing via endosomal TLRs in defense of S. pyogenes infection both in vitro and in vivo.

Project description:The genome of vertebrates contains endogenous retroviruses (ERVs) that have resulted from ancestral infections by exogenous retroviruses. ERVs are germline encoded, transmitted in a Mendelian fashion and account for about 8% of the human and 9.9% of the murine genome, respectively1, 2. By spontaneous activation and reintegration ERVs may cause insertional mutagenesis and thus participate in the process of malignant transformation or progression of tumor growth3, 4. However, if the innate immune system is able to recognize and control ERVs has not yet been elucidated. Here we report that, in vitro, nucleic-acid sensing TLRs on dendritic cells are activated by retroviral RNA and DNA from infected cells in vitro. Infection of TLR competent wild type mice with murine leukemia virus (MuLV)-like ERV isolates results in non-canonical gene upregulation, independent of type I IFN. In vivo, TLR3, -7 and -9 triple deficient mice (TLR379-/-) and mice with non functional TLR3, 7 and 9 signaling due to a mutation in UNC93B develop spontaneous ERV-induced viremia. More importantly, in TLR379-/- mice ERV-induced viremia correlates with acute T cell lymphoblastic leukemia (T-ALL). Multiple independent TLR379-/- T cell leukemia lines produce infectious MuLV of endogenous origin. These cell lines display de novo retroviral integration into the Nup214 or Notch1 gene locus leading to gene dysregulation that is reminiscent of aberrant Nup214 and Notch1 expression in human T-ALLs5. Overall, our results demonstrate that in addition to their role in innate immune defense against exogenous pathogens, TLR3,-7, and -9 may be essential for the control of endogenous retroviral mediated T-cell lymphomagenesis. The data covers two data sets. The data set covers two comparisons of the expression profile from old and young TLR379-/- knockout. Spleen was taken from and old wild type (C57BL/6 background) to compare it against an old TLR379-/- knockout and also from an young wild type (C57BL/6 background) to compare it against a young TLR379-/- knockout. The second experiment includes three replicates of the wild type, the Baki-1MuLV infected C57BL/6, and the Sendai infected C57BL/6.

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Nucleic acid-sensing toll-like receptors: Important players in Sjogren's syndrome.

Publications

Nucleic acid-sensing toll-like receptors: Important players in Sjögren's syndrome.

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