Background/Purpose: Liver X receptorsare established sensors of lipid and cholesterol homeostasis. The recent studies have reported that LXRs are involved in regulation of inflammation and immune responses. We attempted to identify single nucleotide polymorphisms (SNPs) of the NR1H3 and NR1H2 genes, associated with the susceptibility to SLE in Korean populations.

Methods: Blood samples were collected from Korean SLE patients (n=300) and normal healthy controls (NC, n=217). Also, replication samples were collected from Korean SLE patients (n=160) and NC (n=143). SNPs were genotyped using SNaPSHOT assay. 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. To investigate whether the genetic polymorphism changed a transcription factor binding, we performed an electrophoretic mobility shift assay.

Results: We have identified five polymorphisms (-1851 T>C and -1830 T>C in the promoter region, -1003 G>A, -840 C>A and -115 G>A in the intron 1 region) including one novel SNPs (-1003 G>A) in the NR1H3 gene. Two SNPs in the NR1H3 gene, -840 C>A and -115 G>A, showed the complete linkage disequilibrium. There was significant difference in the -1830 T>C polymorphism (co: p=0.001), -1003 G>A polymorphism (co: p=0.002), -115 G>A polymorphism (co: p<0.001) between SLE and NC. These results were consistent with those of replication samples. Three common haplotypes for four polymorphisms were constructed: HT1 [TTGG], HT2 [CTGG] and HT3 [TCAA]. There was significant difference between SLE and NC in the observed haplotype HT1 [TTGG] (co: p=0.033) and HT3 [TCAA] (co: p=0.008). In the -1830 T>C polymorphism, arthritis was significantly more common in the SLE patients with the -1830 C allele (p=0.005). The -1003 G>A polymorphism was significantly associated with oral ulcer (p=0.039), arthritis (p=0.006), anti-dsDNA (p=0.041) and elevated triglyceride (p=0.007). The -115 G>A polymorphism was significantly associated with oral ulcer (p=0.024), arthritis (p=<0.001) and elevated triglyceride (p=0.011). Luciferase activity of the constructs containing -1830 Cand -1003 A was lower than that of the constructs containing -1830 T and -1003 G (p=0.009 and p=0.030, respectively). Moreover, promoter activity of the -1830 C and -1003 A was less enhanced when compared to that of the -1830 T and -1003 G in GW3965 and T0901317 treated cells (p=0.034 and p<0.001, respectively). Proliferation of -1830 TC type was increased when 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). We found that transcription factor GATA-binding protein 3 (GATA3) protein preferentially bound the -1830 T promoter.

Conclusion: These results suggest that the NR1H3 gene genetic polymorphisms may be associated with disease susceptibility and clinical manifestations of SLE in Korean population. Specially, -1830 T>C polymorphism within NR1H3 promoter region may be involved in regulation of NR1H3 expression.