ABCG2 contributes to the development of gout and hyperuricemia in a genome-wide association study

Abstract

Although many genome-wide association studies (GWASs) of hyperuricemia or gout have been reported, the related genetic factors and the mechanisms from hyperuricemia to gouty attack remain unclear. This study aimed to identify genetic factors and pathogenesis of gout from hyperuricemia by genome-wide association study (GWAS). 747 gout patients, 747 hyperuricemia and 2071 age-matched controls were recruited and analyzed with Affymetrix 650 K chip to find the related genetic variants. The functions of the related genes were investigated in an endothelial cell (EC) with urate crystal stimulation. The GWAS results showed 36 SNPs to be strongly associated with gout compared to controls (all p-values < 10^-7). Whereas the rs2231142 in ABCG2 gene had significant associations between gout and controls, between gout and hyperuricemia, and between hyperuricemia and controls (all p-values < 10^-7), and the ORs were 4.34, 3.37 and 2.15 (all p-values < 0.001) after adjustment of potential confounders, respectively. The cell model showed significantly higher IL-8 release from EC combined with ABCG2 knockdown. We concluded that ABCG2 gene contributed to hyperuricemia but also gout, and that it was involved in the inflammation dysregulation via augmented IL-8 release in EC.

Figure 1

The Manhattan plot displays p-values of SNPs from 23 pairs of chromosomes and mitochondria and shows the genes on chromosome 4 were the hot spot for gout-susceptible genes (A). The log (1/p) of SNPs associated with gout compared to normal control in chromosome 4 (B). It showed two spots positioned near in 1 × 10⁷ (SLC2A9 gene) and in region of 8 × 10⁷ and 9 × 10⁷ near or in MEPE, SPP1 PKD2 and ABCG2 genes involved in gout occurrence.

Figure 2

The linkage disequilibrium (LD) maps. Figure A is the result of comparing gout to normal control ignoring rs2231142 genotype, while Figure B1, B2 and B3 displays the same LD maps with different rs2231142 genotypes, namely GG, GT, and TT, respectively. Parenthesis indicates the gene name and position. Green line blocks the SNPs of the same genes.

Figure 3

PMA-primed THP-1 and endothelial cell line EA. HY296 were used under conditions of with or without ABCG2 gene knockdown (ABCG2 RNAi). It showed IL-8 released was significantly higher from ABCG2 knockdown EA. HY296 cell after urate stimulation (p < 0.05), but not in PMA-primed THP-1 cells (p > 0.05) (A). The IL-1β release did not show significant increases either in THP-1 or EA. HY296 cells even under the condition of ABCG2 knockdown or urate stimulation (both p-values > 0.05) (B). A co-culture of THP-1 and EA. HY296 showed the releases of both IL-8 and IL-1β were significantly increased after urate stimulation and ABCG2 knockdown (both p-values < 0.05) (C and D). *p < 0.05.