Abstract 117: Inhibition of DNA Methyltransferase Attenuates Salt-Sensitive Hypertension & Renal Disease in Dahl Salt Sensitive Rats

Abstract

DNA methylation plays a key role in the regulation of gene expression. In the present study, we investigated the impact of changes in DNA methylation in Dahl Salt Sensitive (SS) rats fed a casein-based AIN-76A chow containing low salt (LS) or high salt (HS). In addition to the hypertension and renal damage which occurs following 14 days of HS feeding, we assessed 5-Methylcytosine levels at single-base resolution by reduced representation bisulfite genome sequencing (RRBS) of DNA from the renal outer medulla of SS rats. Several hundred differentially methylated regions (DMRs) were identified between the SS rats on the LS or HS diet. Approximately a quarter of the DMRs were located in transcriptional start site regions, a third in intragenic regions, and the remainder in intergenic regions. To investigate the functional role of methylation in SS hypertension, we administered decitabine (DNA methyltransferase inhibitor, 5mg/kg, ip) or vehicle at Days 0, 3, 5, and 7 during a 14 day HS period. While there was no difference in MAP during the LS period (127±3 vs. 126±6 mmHg, vehicle vs. decitabine, n=9), at the end of 2 weeks of HS there was a significant increase in MAP in the vehicle SS rats compared to the decitabine-treated rats (163±6 vs 141±4 mmHg, p<0.0001 ). This protective effect in MAP in the decitabine-treated group also exhibit a reduction in albumin excretion rate compared to controls (119±19 vs. 182±24 mg/day, p<0.01 ). Upon analysis of the immune cell infiltration profile, there was a reduction in number of CD45+ total leukocytes, CD11b/c+ monocytes/ macrophages, and CD45R+ B cells in the decitabine-treated animals compared to controls. Decitabine administration also significantly reduced renal histological damage as indicated by the presence of outer medullary protein casts compared to vehicle-treated rats (6.8±1.0% vs. 10.6±1.3%, p <0.05). Lastly, methylation rate was significantly reduced in decitabine-treated rats by 40% compared to the control levels. In summary, the inhibition of methylation by decitabine attenuated MAP and markers of renal damage in response to a HS diet suggesting that DNA methylation could be a potential therapeutic target for the treatment of hypertension and renal damage.