Central Angiotensin-(1-7) Treatment Attenuates ERK 1/2 Expression and Oxidative Stress in the Dorsal Medulla of Betamethasone-Exposed Sheep That Associates With Improved Blood Pressure and Baroreflex Sensitivity.

Fetal exposure to betamethasone (BMX) that is routinely administered to women threatening premature delivery may lead to deleterious long-term effects on the central cardiovascular system. In the adult offspring of BMX-exposed sheep, we demonstrate increased mean arterial pressure (MAP) and attenuated baroreflex sensitivity (BRS). These responses are associated with dysregulation of the brain renin-angiotensin system (RAS) reflecting lower medullary expression of Angiotensin-(1-7) [Ang-(1-7)] and its beneficial actions. Moreover, mitogen activated protein kinase (MAPK), a key signaling cascade implicated in cardiovascular dysfunction and stimulation of oxidative stress is increased in the brain dorsomedial medulla (DMM). We hypothesize that loss of Ang-(1-7) tone with BMX is an underlying mechanism for the programming effects to increase MAPK and oxidative stress. Thus, we examined whether intracerebroventricular treatment with Ang-(1-7) that lowers MAP and improves BRS will impact MAPK signaling and downstream generation of reactive oxygen species (ROS). MAPK activation as detected by the ratio of phospho-ERK 1/2 to total ERK densities was significantly reduced by >80% in the Ang-(1-7)-treated BMX sheep as compared to the CSF-treated BMX controls (0.20 ± 0.07 vs 1.04 ± 0.31; p = 0.01, N=4/group). Ang-(1-7) treatment was associated with lower expression of two indices of ROS including 4-HNE (0.23 ± 0.03 vs. 0.31 ± 0.03 p = 0.03) and protein carbonyl content (9.95 ± 0.69 vs 15.94 ± 3.49; p = 0.07). Finally, regression analysis revealed that phospho-ERK 1/2 expression positively correlated with ROS (4-HNE) (r = 0.816; p = 0.01). The 4-HNE content also trended positively with MAP (r = 0.659, p = 0.08), but exhibited a negative correlation with BRS (r = -0.831; p = 0.01). We conclude that reduced central Ang-(1-7) tone may contribute to the chronic dysregulation of the MAPK and ROS signaling pathways within the DMM following BMX exposure. Moreover, Ang-(1-7) may constitute a potential therapeutic approach to improve autonomic dysfunction by attenuating both MAPK and ROS pathways. HD 047584.