Differential Effects of Specific Deletion of the Dopamine D2 Receptor in Renal Proximal Tubules of Male and Female Mice

Abstract

Previous work from our laboratory showed that the dopamine D2 receptor (D2R) in the kidney has a direct and significant role in normal blood pressure (BP) control and negative regulation of renal inflammation and injury, indicating that the D2R has protective effects in the kidney by limiting the inflammatory and fibrotic reactions. In mice, renal‐restricted silencing of D2R expression results in renal fibrosis and end organ damage that is reversed by renal‐restricted rescue of D2R expression. The D2R is expressed in renal proximal and distal convoluted tubules. To delineate the role of the proximal tubule in the D2R‐mediated regulation of renal inflammation and injury, and blood pressure we generated Drd2 fl/fl, PSGLT2::Cre+ mice (D2R PT−/−) that lack D2R only in the renal proximal tubule and Drd2 fl/fl, PSGLT2::Cre‐ (D2R PT+/+) mice that do not have the deletion. Mice were genotyped for Drd2 fl/fl and a smaller amplicon representing the Cre deletion mutant. Immunohistochemistry for D2R and a brush border membrane marker confirmed the absence of D2R mainly in the S1 and S2 segments of the renal proximal tubule of D2R PT−/−. BP measured under anesthesia showed that male D2R PT−/− had higher BP than male D2R PT+/+ mice (113±1 vs 102±1 mmHg, n=4/group; P<0.05). The renal expression of the inflammatory markers TNFα (2.6±0.09 vs 1.0±0.03 fold; P<0.05) and TGFβ (2.2±0.19 vs 1.0±0.06; P<0.05), as well as the extracellular matrix proteins Col1a1 (2.0±0.15 vs 1.0±0.06; P<0.05) and Fn1 (2.0±0.11 vs 1.0±0.06; P<0.05), were all increased in male D2R PT−/−, relative to male D2R PT+/+ mice. Sirius Red staining of kidney sections also showed increased (0.52±0.01 vs 0.35±0.01 %; P<0.05) areas of renal cortical fibrosis in male D2R PT−/− mice. Moreover, the renal expression of the inflammatory and pro‐apoptotic marker NGAL (5.9±0.54 vs 1.0±0.03; P<0.05) and the cell proliferation marker Ki‐67 (1.6±0.10 vs 1.0±0.03; P<0.05) were increased in male D2R PT−/− mice. In contrast to the increased BP of male D2R PT−/− mice, BPs in female D2R PT−/− and female D2R PT+/+ mice (103±5 vs 105±3; n=4/group) were similar. The renal expressions of TNFα and TGFβ were increased to the same extent (about 2‐fold) in female D2R PT−/− and male D2R PT−/− mice. The renal expression of Fn1 was increased to a lesser extent (1.4‐fold) in female D2R PT−/− than male D2R PT−/− mice while the renal expression of Col1a1 was not increased in female D2R PT−/− mice. NGAL was increased to a lesser extent (3.1‐fold) while Ki‐67 was increased to a greater extent (9.3‐fold) in female than male D2R PT−/− mice. Our results show that the proximal tubular deletion of the D2R increases BP and markers of extracellular matrix and injury in male D2R PT−/− mice but to a lesser extent or not at all in female D2R PT−/− mice. However, D2R PT deletion increased the markers of inflammation to similar levels in male and female D2R PT−/− mice. Female D2R PT−/− mice had a marked increase in renal Ki‐67, suggesting that the milder effect of the renal D2R deletion in female mice may be related to an increase in cell proliferation.Support or Funding InformationUS National Institutes of Health, R01DK090918, P01HL074940, P01HL068686, R01HL092196, R37HL023081, and R01DK039308This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.