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Female Bias in Systemic Lupus Erythematosus is Associated with the Differential Expression of X-Linked Toll-Like Receptor 8.

McDonald G, Cabal N, Vannier A, Umiker B, Yin RH, Orjalo AV, Johansson HE, Han JH, Imanishi-Kari T - Front Immunol (2015)

Bottom Line: Here, we show the results of our investigation into the role of Tlr8 expression in SLE pathogenesis in 564Igi females.Bone marrow-derived macrophages from 564Igi females have a significant increase in Tlr8 expression compared to male-derived cells, and RNA fluorescence in situ hybridization data suggest that Tlr8 may escape X-inactivation in female-derived macrophages.These results propose a model by which females may be more susceptible to SLE pathogenesis due to inefficient inactivation of Tlr8.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Physiology and Pathobiology, Tufts University , Boston, MA , USA.

ABSTRACT
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of anti-nuclear antibodies. SLE is one of many autoimmune disorders that have a strong gender bias, with 70-90% of SLE patients being female. Several explanations have been postulated to account for the severity of autoimmune diseases in females, including hormonal, microbiota, and gene dosage differences. X-linked toll-like receptors (TLRs) have recently been implicated in disease progression in females. Our previous studies using the 564Igi mouse model of SLE on a Tlr7 and Tlr9 double knockout background showed that the presence of Tlr8 on both X chromosomes was required for the production of IgG autoantibodies, Ifn-I expression and granulopoiesis in females. Here, we show the results of our investigation into the role of Tlr8 expression in SLE pathogenesis in 564Igi females. Female mice have an increase in serum pathogenic anti-RNA IgG2a and IgG2b autoantibodies. 564Igi mice have also been shown to have an increase in neutrophils in vivo, which are major contributors to Ifn-α expression. Here, we show that neutrophils from C57BL/6 mice express Ifn-α in response to 564 immune complexes and TLR8 activation. Bone marrow-derived macrophages from 564Igi females have a significant increase in Tlr8 expression compared to male-derived cells, and RNA fluorescence in situ hybridization data suggest that Tlr8 may escape X-inactivation in female-derived macrophages. These results propose a model by which females may be more susceptible to SLE pathogenesis due to inefficient inactivation of Tlr8.

No MeSH data available.


Related in: MedlinePlus

Tlr8 RNA co-localizes with Xist RNA. (A–F) BMDM from C57BL/6 and 564Igi mice were stained for the presence of Xist and (A)Tlr7 and Tlr8 exonic mRNA, (B)Eif2s3x intronic mRNA, (C)Tlr7 intronic and exonic mRNA or (D–F)Tlr8 intronic and exonic mRNA using fluorescent probes. (A) An example of increased Tlr8 mRNA compared to Tlr7 mRNA in female BMDM. (B) Two examples of escaped X-inactivation of Eif2s3x. (C) An example of normal X-inactivation of Tlr7. (D) An example of potential escaped X-inactivation of Tlr8 in C57BL/6 female BMDM. (E) An example of potential escaped X-inactivation of Tlr8 in 564Igi female BMDM. 1/800 cells (~0.1%) show this staining pattern. The insert shows the Xist-cloud with the Tlr8 and weak Eif2s3x signals. (F) An example of normal X-inactivation of Tlr8 in C57BL/6 female BMDM. The probes used in each set of images are shown underneath. Intronic (int) probes detect nuclear pre-mRNA before splicing. Exonic (ex) probes also detect cytoplasmic mature mRNA after splicing. White arrowheads show target RNA expression from active X chromosome. White arrows show target RNA expression from inactivated X chromosome.
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Figure 5: Tlr8 RNA co-localizes with Xist RNA. (A–F) BMDM from C57BL/6 and 564Igi mice were stained for the presence of Xist and (A)Tlr7 and Tlr8 exonic mRNA, (B)Eif2s3x intronic mRNA, (C)Tlr7 intronic and exonic mRNA or (D–F)Tlr8 intronic and exonic mRNA using fluorescent probes. (A) An example of increased Tlr8 mRNA compared to Tlr7 mRNA in female BMDM. (B) Two examples of escaped X-inactivation of Eif2s3x. (C) An example of normal X-inactivation of Tlr7. (D) An example of potential escaped X-inactivation of Tlr8 in C57BL/6 female BMDM. (E) An example of potential escaped X-inactivation of Tlr8 in 564Igi female BMDM. 1/800 cells (~0.1%) show this staining pattern. The insert shows the Xist-cloud with the Tlr8 and weak Eif2s3x signals. (F) An example of normal X-inactivation of Tlr8 in C57BL/6 female BMDM. The probes used in each set of images are shown underneath. Intronic (int) probes detect nuclear pre-mRNA before splicing. Exonic (ex) probes also detect cytoplasmic mature mRNA after splicing. White arrowheads show target RNA expression from active X chromosome. White arrows show target RNA expression from inactivated X chromosome.

Mentions: It has been shown that 564Igi females with two normal copies of Tlr8, one on each X chromosome, express Tlr8 approximately twofold higher than 564Igi females carrying only one copy of Tlr8 (15). These data led to the hypothesis that inefficient X-inactivation may be responsible for the significant increase in Tlr8 expression in female BMDM. To examine this possibility, we used RNA-FISH to detect the presence of Tlr7 and Tlr8 exonic mature mRNA in BMDM from C57BL/6 males and females. In female BMDM, there appears to be more Tlr8 transcript than in male BMDM (Figure 5A), consistent with the RT-qPCR data (Figures 4C,D).


Female Bias in Systemic Lupus Erythematosus is Associated with the Differential Expression of X-Linked Toll-Like Receptor 8.

McDonald G, Cabal N, Vannier A, Umiker B, Yin RH, Orjalo AV, Johansson HE, Han JH, Imanishi-Kari T - Front Immunol (2015)

Tlr8 RNA co-localizes with Xist RNA. (A–F) BMDM from C57BL/6 and 564Igi mice were stained for the presence of Xist and (A)Tlr7 and Tlr8 exonic mRNA, (B)Eif2s3x intronic mRNA, (C)Tlr7 intronic and exonic mRNA or (D–F)Tlr8 intronic and exonic mRNA using fluorescent probes. (A) An example of increased Tlr8 mRNA compared to Tlr7 mRNA in female BMDM. (B) Two examples of escaped X-inactivation of Eif2s3x. (C) An example of normal X-inactivation of Tlr7. (D) An example of potential escaped X-inactivation of Tlr8 in C57BL/6 female BMDM. (E) An example of potential escaped X-inactivation of Tlr8 in 564Igi female BMDM. 1/800 cells (~0.1%) show this staining pattern. The insert shows the Xist-cloud with the Tlr8 and weak Eif2s3x signals. (F) An example of normal X-inactivation of Tlr8 in C57BL/6 female BMDM. The probes used in each set of images are shown underneath. Intronic (int) probes detect nuclear pre-mRNA before splicing. Exonic (ex) probes also detect cytoplasmic mature mRNA after splicing. White arrowheads show target RNA expression from active X chromosome. White arrows show target RNA expression from inactivated X chromosome.
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Figure 5: Tlr8 RNA co-localizes with Xist RNA. (A–F) BMDM from C57BL/6 and 564Igi mice were stained for the presence of Xist and (A)Tlr7 and Tlr8 exonic mRNA, (B)Eif2s3x intronic mRNA, (C)Tlr7 intronic and exonic mRNA or (D–F)Tlr8 intronic and exonic mRNA using fluorescent probes. (A) An example of increased Tlr8 mRNA compared to Tlr7 mRNA in female BMDM. (B) Two examples of escaped X-inactivation of Eif2s3x. (C) An example of normal X-inactivation of Tlr7. (D) An example of potential escaped X-inactivation of Tlr8 in C57BL/6 female BMDM. (E) An example of potential escaped X-inactivation of Tlr8 in 564Igi female BMDM. 1/800 cells (~0.1%) show this staining pattern. The insert shows the Xist-cloud with the Tlr8 and weak Eif2s3x signals. (F) An example of normal X-inactivation of Tlr8 in C57BL/6 female BMDM. The probes used in each set of images are shown underneath. Intronic (int) probes detect nuclear pre-mRNA before splicing. Exonic (ex) probes also detect cytoplasmic mature mRNA after splicing. White arrowheads show target RNA expression from active X chromosome. White arrows show target RNA expression from inactivated X chromosome.
Mentions: It has been shown that 564Igi females with two normal copies of Tlr8, one on each X chromosome, express Tlr8 approximately twofold higher than 564Igi females carrying only one copy of Tlr8 (15). These data led to the hypothesis that inefficient X-inactivation may be responsible for the significant increase in Tlr8 expression in female BMDM. To examine this possibility, we used RNA-FISH to detect the presence of Tlr7 and Tlr8 exonic mature mRNA in BMDM from C57BL/6 males and females. In female BMDM, there appears to be more Tlr8 transcript than in male BMDM (Figure 5A), consistent with the RT-qPCR data (Figures 4C,D).

Bottom Line: Here, we show the results of our investigation into the role of Tlr8 expression in SLE pathogenesis in 564Igi females.Bone marrow-derived macrophages from 564Igi females have a significant increase in Tlr8 expression compared to male-derived cells, and RNA fluorescence in situ hybridization data suggest that Tlr8 may escape X-inactivation in female-derived macrophages.These results propose a model by which females may be more susceptible to SLE pathogenesis due to inefficient inactivation of Tlr8.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Physiology and Pathobiology, Tufts University , Boston, MA , USA.

ABSTRACT
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of anti-nuclear antibodies. SLE is one of many autoimmune disorders that have a strong gender bias, with 70-90% of SLE patients being female. Several explanations have been postulated to account for the severity of autoimmune diseases in females, including hormonal, microbiota, and gene dosage differences. X-linked toll-like receptors (TLRs) have recently been implicated in disease progression in females. Our previous studies using the 564Igi mouse model of SLE on a Tlr7 and Tlr9 double knockout background showed that the presence of Tlr8 on both X chromosomes was required for the production of IgG autoantibodies, Ifn-I expression and granulopoiesis in females. Here, we show the results of our investigation into the role of Tlr8 expression in SLE pathogenesis in 564Igi females. Female mice have an increase in serum pathogenic anti-RNA IgG2a and IgG2b autoantibodies. 564Igi mice have also been shown to have an increase in neutrophils in vivo, which are major contributors to Ifn-α expression. Here, we show that neutrophils from C57BL/6 mice express Ifn-α in response to 564 immune complexes and TLR8 activation. Bone marrow-derived macrophages from 564Igi females have a significant increase in Tlr8 expression compared to male-derived cells, and RNA fluorescence in situ hybridization data suggest that Tlr8 may escape X-inactivation in female-derived macrophages. These results propose a model by which females may be more susceptible to SLE pathogenesis due to inefficient inactivation of Tlr8.

No MeSH data available.


Related in: MedlinePlus