miR-217 Mediates the Protective Effects of the Dopamine D2 Receptor on Fibrosis in Human Renal Proximal Tubule Cells

Lack or downregulation of the dopamine D2 receptor (D2R) increases the vulnerability to renal in independent of blood pressure in mice, Common single nucleotide polymorphisms (SNPs) rs6276, 6277, and 1800497 in the human D2R gene are associated with decreased receptor expression/function and hypertension, Human renal proximal tubule cells from subjects carrying these SNPs have decreased D2R expression and increased expression of profibrotic factors and production of extracellular matrix proteins. We tested the hypothesis that the D2R mediates these effects by regulating micro-RNA expression. In cells carrying D2R SNPs, micro-RNAs (miRs)-217, miR-224, miR-335, and miR1265 were downregulated, whereas miR-1290 was upregulated >4-fold compared with those carrying D2R wild-type alleles, However, only miR-217 was directly regulated by D2R expression. In cells carrying D2R wild-type, miR-217 inhibitor increased the expression of transforming growth factor (TGF)-beta 1, matrix metalloproteinase 3, fibronedin and collagen 1 a, whereas miR-217 mimic had the opposite effect, In cells carrying D2R SNPs, miR-217 mimic also decreased the expression of TGF beta 1 and its targets. Win5a, a miR-217 target, was increased in cells carrying D2R SNPs and decreased by miR-217 mimic but increased by miR-217 inhibitor in both cell types. In cells carrying D2R wild-type, Wnt5a treatment increased TGF beta 1 while silencing Ror2, a Wnt5a receptor, decreased TGF beta 1 and blunted the Wnt5ainduced increase in cells carrying D2R wild-type, Our results show that renal proximal tubule cells from subjects carrying D2R SNPs resulting in D2R downregulation have increased TGF beta 1 that is mediated by decreased regulation of the miR217-Wnt5a-Ror2 pathway.