Sex-Specific Modulation of Renal Dopamine Receptor Expression by DRD2 Single-Nucleotide Polymorphisms (SNPs) and Hormonal Factors

Background: The involvement of renal dopamine, through the dopamine D2 receptor (D2R), in maintaining water, electrolyte balance, and blood pressure has a critical role in homeostasis in mammals. We have reported that the D2R is essential in preventing inflammation and kidney injury. In humans, the DRD2 gene has several polymorphisms. The presence of specific single nucleotide polymorphisms (SNPs), such as rs6276 and rs6277 (DRD2 SNPs), correlates with decreased D2R expression and activity, and is associated with increased blood pressure and susceptibility to hypertension. Human renal proximal tubule cells (hRPTCs) carrying these DRD2 SNPs show a proinflammatory and profibrotic phenotype, which differs between sexes and is influenced by hormones in the culture medium. Exploring how hormonal factors modulate these responses could provide insights into sex-specific differences in renal physiology and pathophysiology. Methods: This study was designed to investigate the factors influencing D2R expression in hRPTCs. We used four different hRPTC lines, genotyped for the absence (WT) or presence of SNPs and categorized by sex (male: M WT, M SNPs; female: F WT, F SNPs). We measured D2R expression levels and investigated the involvement of transcription factors Nurr1, ATF4, and Sp1, and the androgen receptor (AR), all known to bind to the DRD2 promoter. Results: D2R expression in male and female hRPTCs was greater in WT than SNPs cells. Expression of Nurr1 and Sp1 was similar in all cell lines. However, there were differences in ATF4 expression. While expressions were similar in F WT and F SNPs cells (1.3±0.1 vs 1.0±0.1; n= 3-5; p=0.199), a notable disparity was observed between M WT and M SNPs (1.0±0.1 vs 2.4±0.1; n= 3-5; p<0.001). AR expression was lower in female WT and SNP cells (0.77±0.09 and 0.8±0.1, respectively) than their male counterparts (1.10±0.10 and 1.56±0.04). Dihydrotestosterone (DHT) (5 nM/24 hr) decreased D2R expression in F WT cells (1.2±0.10 vs. 0.72±0.05; n=10-13; p<0.001) and M WT cells, (0.97±0.06 vs. 0.70±0.090; n=10-13, p<0.001), relative to vehicle treatment. DHT had no effect in cells with SNPs, F or M. Conclusion: These findings highlight the sex-dependent regulation of renal D2R expression and suggest potential importance of SNPs on gene promoter binding sites and responses to hormones. Funding: NIDDK Support