Abstract 252: Renal Rescue of D2R Function in Mice Using an AAV9 Vector Reverses the Renal Injury and High Blood Pressure Induced by D2R Silencing in the Kidney

Abstract

Lack or downregulation of dopamine D2 receptor (D2R) function in mice increases the vulnerability to renal inflammation. Recent studies from our laboratory showed that long-term (28 days) selective down regulation of D2R in one kidney in mice with two intact kidneys increases systolic blood pressure and the expression of inflammatory and injury markers. We hypothesized that rescuing D2R function by re-expressing the receptor in the kidney of mice with D2R silencing will reduce renal inflammation and injury, and normalize blood pressure. To test our hypothesis we silenced D2R expression by the renal subcapsular infusion of D2RsiRNA and then we rescued the silenced D2R expression using retrograde ureteral infusion of AAV9 vector carrying wild-type D2R (D2RAAV). Mice were treated with non-silencing siRNA (NS siRNA) or D2RsiRNA (3 μg/day, n=6 per group) using 28 day osmotic minipumps. Fourteen days following the initiation of siRNA treatment, each group was treated with control AAV (CAAV) or D2RAAV (n=3 per group, 1e+11 viral genome particles per mouse). Fourteen days following AAV administration, blood pressure was recorded and organs were collected. D2R expression was decreased in D2RsiRNA-treated kidneys compared with NS siRNA-treated kidneys (immunoblotting: 54 ± 0.8 vs 100± 22 %; P<0.05). D2RAAV treatment increased D2R expression (7.5 -11 fold; P<0.01) in both D2R and NS siRNA-treated mice. Mice treated with D2RsiRNA+CAAV had increased systolic blood pressure (121±3 mmHg; P<0.05) in comparison with mice treated with D2RsiRNA+D2RAAV (100±6 mm Hg) (rescued mice), NS siRNA +CAAV (101±4 mm Hg), or NS siRNA +D2RAAV (101±1 mm Hg). The expression of TGF-β was higher in the mice treated with D2RsiRNA+CAAV than in D2R rescued mice (D2RsiRNA+D2RAAV) (100±22 vs 54± 11%; P<0.05). The number of cells positive for the marker of proliferation ki-67 was higher in kidneys of D2RsiRNA+CAAV mice than in D2RsiRNA+D2RAAV (32± 5 vs 15±2 per field; P<0.01). In conclusion, these results demonstrate that increased blood pressure and renal injury due to D2R silencing could be rescued by over expression of D2R using AAV9 vector in the kidney. Furthermore, these data confirms the protective effects of renal D2R and may provide the basis for designing novel therapies for kidney disease.