Background Systemic lupus erythematosus (SLE) disproportionally affects females (9:1) over males. Despite significant research effort, the exact mechanisms behind this compelling sex bias are undefined. Our prior studies demonstrate a significant role for estrogen receptor alpha (ER) mediated inflammation in the pathogenesis of disease. NZM2410 lupus prone mice, expressing a truncated ER functional knockout, survived longer and had significantly reduced renal disease. Yet, a complete knockout of ER was not protective, suggesting the truncated isoform may be protective with the full-length gene necessary for disease. These findings underscore the importance of defining the role of ER in lupus.
Methods While the hormonal impact of estrogen and ER is well studied, less is known about the transcriptional impact of ER in immunity. Our goal is to identify the molecular mechanisms utilized by liganded ER in regulating the inflammatory milieu. To accomplish this, we have identified ER associated target genes, transcription factors and genes involved in the immune response, histone acetylation, and immune related signaling pathways, and determined differences in expression. B cells isolated from 15 female African American lupus patients and 8 age and race matched healthy controls were used for the analysis. In an effort to further understand the molecular mechanisms behind ER function, we examined the transcriptional effects of ER on the inflammatory response. Transient transfections of full length ER (66 kDa) and a shortened isoform ER46 (lacking the AF-1 activation domain and similar to the truncated ER functional knockout) were initially performed in the human breast cancer cell line MDA-MB-231, which lacks ER.
Results RNA-seq analysis indicates that 64% of ER associated target genes were differentially expressed between the two groups. The majority of these genes were upregulated in lupus patients compared to controls. Genes with increased expression included TLRs, NFB related transcription factors and IL-1. Preliminary results from the transfection experiments indicate that both ER isoforms reduce mRNA expression of the inflammatory cytokines IL-6 and IL-1 twenty-four hours after stimulation with a TLR4 agonist. A decrease in cytokine expression was observed when the short isoform ER46 was overexpressed in relation to ER66. Additional transfections will be carried out in immune relevant cells such as B cells, monocytes, macrophages or dendritic cells.
Conclusions These results support a role for ER in the pathogenesis of SLE via regulation of inflammatory mediators. Future goals include utilizing high throughput sequencing technology to examine the transcriptional impact of ER in monocytes of African American pediatric lupus patients.
Funding Source(s): None
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