Impact of angiotensin II receptor antagonism on the sex-selective dysregulation of cardiovascular function induced by in utero dexamethasone exposure.

In utero exposure to glucocorticoids in late gestation programs changes in cardiovascular function. The objective of this study was to determine the degree to which angiotensin II mediates sex-biased changes in autonomic function as well as basal and stress-responsive cardiovascular function following in utero glucocorticoid exposure. Pregnant rats were administered the synthetic glucocorticoid dexamethasone (Dex; 0.4 mg/kg/day sc) or vehicle on gestation days 18-21. Mean arterial pressure, heart rate, and heart rate variability (HRV) were measured via radiotelemetry in freely moving, conscious adult rats. To evaluate the impact of stress, rats were placed in a restraint tube for 20 min. In a separate cohort of rats, restraint stress was performed before and after chronic treatment with the angiotensin type 1 receptor antagonist, losartan (30 mg/kg/day ip). Frequency domain analysis of HRV was evaluated, and data were integrated into low-frequency (LF, 0.20-0.75 Hz) and high-frequency (HF, 0.75-2.00 Hz) bands. Prenatal Dex resulted in an exaggerated pressor and heart rate response to restraint in female offspring that was attenuated by prior losartan treatment. HF power was higher in vehicle-exposed female rats compared with Dex females. Following losartan, HF power was equivalent between female vehicle and Dex-exposed rats. In utero exposure to Dex produced female-biased alterations in stress-responsive cardiovascular function, which may be indicative of a reduction in parasympathetic activity. Moreover, these findings suggest this autonomic dysregulation may be mediated, in part, by long-term changes in renin-angiotensin signaling.NEW & NOTEWORTHY Our findings reveal the involvement of angiotensin II on sex-selective cardiovascular function and autonomic changes in adult offspring exposed to dexamethasone during the last 4 days of gestation. We show that angiotensin II receptor blockade reverses the exaggerated pressor and heart rate response to acute restraint stress and the autonomic dysregulation observed in female, but not male, offspring exposed to dexamethasone in utero.

Persistent change in cardiac fibroblast physiology after transient ACE inhibition.

Transient angiotensin-converting enzyme (ACE) inhibition induces persistent changes that protect against future nitric oxide synthase (NOS) inhibitor-induced cardiac fibrosis and inflammation. Given the role of fibroblasts in mediating these effects, the present study investigates whether prior ACE inhibition produced persistent changes in cardiac fibroblast physiology. Adult male spontaneously hypertensive rats (SHRs) were treated with vehicle (C+L) or the ACE inhibitor, enalapril (E+L) for 2 wk followed by a 2-wk washout period and a subsequent 7-day challenge with the NOS inhibitor N(ω)-nitro-l-arginine methyl ester. A third set of untreated SHRs served as controls. At the end of the study period, cardiac fibroblasts were isolated from control, C+L, and E+L left ventricles to assess proliferation rate, collagen expression, and chemokine release in vitro. After 7 days of NOS inhibition, there were areas of myocardial injury but no significant change in collagen deposition in E+L and C+L hearts in vivo. In vitro, cardiac fibroblasts isolated from C+L but not E+L hearts were hyperproliferative, demonstrated increased collagen type I gene expression, and an elevated secretion of the macrophage-recruiting chemokines monocyte chemoattractant protein-1 and granulocyte macrophage-colony stimulating factor. These findings demonstrate that in vivo N(ω)-nitro-l-arginine methyl ester treatment produces phenotypic changes in fibroblasts that persist in vitro. Moreover, this is the first demonstration that transient ACE inhibition can produce a persistent modification of the cardiac fibroblast phenotype to one that is less inflammatory and fibrogenic. It may be that the cardioprotective effects of ACE inhibition are related in part to beneficial changes in cardiac fibroblast physiology.