Abstract 668: Inhibition of DNA Methyltransferase Inhibits the Ang II-Induced Increase in Blood Pressure, Vascular Remodeling and Target Organ Damage
Growth signals stimulate DNA methyltransferase (DNMT) expression through extracellular signal-regulated kinases 1/2 (ERK1/2) pathway and that inhibition of ERK1/2 signaling results in repression of DNMT expression and activation of expression of some DNMT-repressed genes. Angiotensin II (Ang II) has been shown to stimulate ERK1/2 signaling in resistance arteries. We hypothesized that Ang II stimulates DNMT expression resulting in methylation and repression of antihypertensive genes such as 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) and that blocking DNMT activity may inhibit Ang II-induced hypertension, vascular remodeling, and target organ damage. C57BL/6J (C57) mice were treated with the specific DNMT inhibitor 5′-aza-2′-deoxycytidine (aza-CdR, 1 mg/kg/day) intraperitoneally for 3 consecutive days before subcutaneous Ang II infusion for 28d at a pressure dose of 0.7 mg/kg/day using Alzet osmotic minipumps. Systolic blood pressure was monitored during this period and tissues were harvested to determine vascular wall thickness, cardiac hypertrophy, and expression and methylation of 11β-HSD2 in arteries and the kidneys. Ang II infusion induced a more than 2-fold increase in DNMT1 expression (n=6, p≤ 0.05). Moreover, blocking DNMT1 activity significantly inhibited the Ang II-induced increase in systolic and diastolic blood pressure (from 102 ± 3 to138 ± 7 for saline-treated vs. 101 ± 4 to 105 ± 6 mm Hg for aza-CdR-treated mice, n=8, p≤ 0.01 for saline vs.aza-CdR in the presence of Ang II treatment). In addition, expression of 11β-HSD2 was inhibited by Ang II treatment. However, expression of 11β-HSD2 was found to be above the background observed in absence of Ang II when Ang II treatment was associated with DNMT activity blockade. Methylation-specific PCR indicated that 11β-HSD2 was methylated in the arteries and kidneys but its Ang II-dependency is still to be determined. Finally when DNMT activity was inhibited, the Ang II-induced increase cardiac hypertrophy (heart/body weight) and wall/lumen ratio in the carotid arteries were significantly inhibited (n= 8, p≤ 0.05). These results suggest that DNA methylation plays a critical role in the coordinate regulation of genes involved in the pathogenesis of hypertension and vascular remodeling.