Estrogen modulation of endosome-associated toll-like receptor 8: an IFNα-independent mechanism of sex-bias in systemic lupus erythematosus.

Females of child-bearing age are more resistant to infectious disease and have an increased risk of systemic lupus erythematosus (SLE). We hypothesized that estrogen-induced gene expression could establish an immunoactivated state which would render enhanced defense against infection, but may be deleterious in autoimmune development. Using peripheral blood mononuclear cells (PBMCs), we demonstrate enhanced responses with immunogen stimulation in the presence of 17ß-estradiol (E2) and gene array analyses reveal toll-like receptor 8 (TLR8) as an E2-responsive candidate gene. TLR8 expression levels are up-regulated in SLE and PBMCs stimulated with TLR8 agonist display a female sex-biased, E2-sensitive response. Moreover, we identify a putative ERα-binding region near the TLR8 locus and blocking ERα expression significantly decreases E2-mediated TLR8 induction. Our findings characterize TLR8 as a novel estrogen target gene that can lower the inflammatory threshold and implicate an IFNα-independent inflammatory mechanism that could contribute to higher SLE incidence in women.

Aberrant muscle antigen exposure in mice is sufficient to cause myositis in a Treg cell-deficient milieu.

OBJECTIVE: Myositis is associated with muscle-targeted inflammation and is observed in some Treg cell-deficient mouse models. Because an autoimmune pathogenesis has been strongly implicated, the aim of this study was to investigate the hypothesis that abnormal exposure to muscle antigens, as observed in muscle injury, can induce autoimmune-mediated myositis in susceptible hosts. METHODS: FoxP3 mutant (scurfy) mice were mated to synaptotagmin VII (Syt VII) mutant mice, which resulted in a new mouse strain that combines impaired membrane resealing with Treg cell deficiency. Lymphocyte preparations from double-mutant mice were adoptively transferred intraperitoneally, with or without purified Treg cells, into recombination-activating gene 1 (RAG-1)-null recipients. Lymph node cells from mice with the FoxP3 mutation were transferred into RAG-1-null mice either 1) intraperitoneally in conjunction with muscle homogenate or purified myosin protein or 2) intramuscularly with or without cotransfer of purified Treg cells. RESULTS: FoxP3-deficient mouse lymph node cells transferred in conjunction with myosin protein or muscle homogenate induced robust skeletal muscle inflammation. The infiltrates consisted predominantly of CD4+ and CD8+ T cells, a limited number of macrophages, and no B cells. Significant inflammation was also seen in similar experiments using lymph node cells from FoxP3/Syt VII double-mutant mice but was absent in experiments using adoptive transfer of FoxP3 mutant mouse cells alone. The cotransfer of Treg cells completely suppressed myositis. CONCLUSION: These data, derived from a new, reproducible model, demonstrate the critical roles of Treg cell deficiency and aberrant muscle antigen exposure in the priming of autoreactive cells to induce myositis. This mouse system has multifaceted potential for examining the interplay in vivo between tissue injury and autoimmunity.

Novel estrogen target gene ZAS3 is overexpressed in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypic, inflammatory autoimmune disease characterized by significant gender bias. Previous studies have established a role for hormones in SLE pathogenesis, including the sex hormone estrogen. Estrogen regulates gene expression by translocating estrogen receptors (ER) α and ß into the nucleus where they induce transcription by binding to estrogen response elements (EREs) of target genes. The ZAS3 locus encodes a signaling and transcriptional molecule involved in regulating inflammatory responses. We show that ZAS3 is significantly up-regulated in SLE patients at both the protein and mRNA levels in peripheral blood mononuclear cells (PBMCs). Furthermore, estrogen stimulates the expression of ZAS3 in vitro in several leukocyte and breast cancer cell lines of both human and murine origin. In vivo estrogen treatment mediates induction of tissue specific ZAS3 expression in several lymphoid organs in mice. Estrogen stimulation also significantly up-regulates ZAS3 expression in primary PBMCs, while treatment with testosterone has no effect. Mechanistically, estrogen induces differential ERα binding to putative EREs within the ZAS3 gene and ERα knockdown with siRNA prevents estrogen induced ZAS3 up-regulation. In contrast, siRNA targeting IFNα has no effect. These data demonstrate that ZAS3 expression is directly regulated by estrogen and that ZAS3 is overexpressed in lupus. Since ZAS3 has been shown to regulate inflammatory pathways, its up-regulation by estrogen could play a critical role in female-biased autoimmune disorders.