Background/Purpose: Liver X receptor alpha (LXRA, NR1H3) and beta (LXRB, NR1H2) can influence macrophage biology by modulation of lipid metabolism and by effects on innate immunity. The recent studies have reported that LXRs are involved in regulation of inflammation and immune responses.  In our previous data, we have identified five polymorphisms (-1851 T>C, -1830 T>C, -1003 G>A, -840 C>A and -115 G>A) including one novel SNPs (-1003 G>A) in the NR1H3 gene. Especially, the -1830 T>C promoter polymorphism was significantly different in genotype analysis and clinical manifestations. This study evaluated the functional effect of the NR1H3 promoter polymorphism on systemic lupus erythematosus.

Methods: The promoter activity was analyzed by luciferase reporter assay in Hep3B cells and COS-7 cells. To investigate the effects of the stimulation, we used a functional assay of transcriptional activity and B cell proliferation assay with lipopolysaccharide, GW3965 and T0901317. The mRNA expression of NR1H3 gene according to the genotype was analyzed by RT-PCR and quantitative real-time PCR. To investigate whether the genetic polymorphism changed a transcription factor binding, we performed an electrophoretic mobility shift assay (EMSA).

Results: Luciferase activity of the constructs containing -1830 C was lower than that of the constructs containing -1830 T (p=0.009). Moreover, promoter activity of the -1830 C was less enhanced compared to that of the -1830 T in GW3965 and T0901317 treated cells (p=0.034 and p<0.001, respectively). Proliferation of -1830 TC type was increased compared to that of -1830 TT type in basal, GW3965 and T0901317 treated B cells from SLE patients (p=0.011, p= 0.040 and p=0.017, respectively). The -1830 TC type B cells displayed lower NR1H3 mRNA expression level than the -1830 TT type B cells in both SLE and NC. Moreover, NR1H3 expression level significantly different between genotypes in real-time PCR. In both SLE and NC, the -1830 TC type was an approximately 1.8-fold decrease than the -1830 TT type. EMSA using nuclear extracts prepared from Hep3B cells revealed a specific band with the -1830 T probe, but not with the -1830 C probe. We performed a competition assay using GATA-3 probes, and found that the shifted band corresponding to the -1830 T probe was completely competed for by the unlabeled GATA-3 probe. The -1830 T specific band was also competed by anti-GATA-3 antibodies but not supershifted.

Conclusion: These results suggest that the NR1H3 gene -1830 T>C promoter polymorphism may be involved in regulation of NR1H3 expression.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/functional-effect-of-nr1h3-lxra-promoter-polymorphisms-in-korean-patients-with-systemic-lupus-erythematosus/