Early life stress sensitizes rats to angiotensin II-induced hypertension and vascular inflammation in adult life

Abstract

Maternal separation during early life is an established chronic behavioral model of early life stress in rats. It is known that perinatal adverse environments increase activity of the renin-angiotensin (Ang) system, specifically Ang II, in adulthood. The aim of this study was to investigate whether the effects of early life stress augment the sensitivity of the Ang II pathway. Using Wistar Kyoto rats, the maternal separation (MS) protocol was performed by separating approximately half of the male pups from their mother 3 h/d from days 2 to 14 of life. Pups remaining with the mother at all times were used as controls. Maternal separation did not influence the plasma basal parameters, such as blood glucose, insulin, Ang II, Ang 1-7 and plasma renin activity. Furthermore, body weight, blood pressure, and heart rate were similar in MS and control rats. The acute pressor response to Ang II was not different in anesthetized MS and control rats. However, the chronic infusion of Ang II (65 ng/min SC) elicited an exaggerated hypertensive response in MS compared with control rats (P<0.05). Surprisingly, HR was dramatically increased during the second week of Ang II infusion in MS compared with control rats (P<0.05). This enhanced Ang II sensitivity was accompanied by a greater vascular inflammatory response in MS versus control rats. Chronic Ang II infusion increased vascular wall structure in both groups similarly. These data indicate that early life stress sensitizes rats to an increased hemodynamic and inflammatory response during Ang II-induced hypertension.

Figure 1

Change in blood pressure (MAP) and heart rate (HR) in anesthetized rats in response to i.v. bolus of ang II with increasing doses in MS (open bars) and C (black bars) rats, n=5.

Figure 2

MAP (panel 2A) and HR (panel 2B) in non-infused (baseline; prior to ang II infusion) and ang II-infused telemetry implanted MS (▲, dashed line) (n=7) and C rats (■, solid line) (n=8). Data is expressed as 12 hour average. On the x-axis: white bar represents 6:00 a.m. to 6:00 p.m. period; black bar represents 6:00 p.m. to 6:00 a.m. period. * p <0.05 vs. baseline; + p <0.05 vs. C.

Figure 3

Localization of inflammatory cells in aortic tissue from ang II-infused rats. Panels 3A and 3B: representative micrographs of CD68 positive cells in ang II-infused control, C (3A) and maternally separated, MS (3B) rats, respectively. Panels 3C and 3D: representative micrographs of CD3 positive cells in ang II-infused control, C (3C) and maternally separated, MS (3D) rats, respectively. Arrows point to CD68 or CD3 positive cells in the endothelium (En) or adventitia (Adv).

Figure 4

Quantitation of inflammatory cells in the thoracic aorta from vehicle and ang II-infused rats. Panel A: CD68 positive cells in ang II-infused C (n=5) and MS (n=9) rats; vehicle-infused C (n=4) and MS (n=4) rats. Panel B: CD3 positive cells in ang II-infused C (n=6) and MS (n=5) rats; vehicle-infused C (n=4) and MS (n=4) rats. E: Endothelium, Adv: Adventitia. * p <0.05 vs. vehicle. + p <0.05 vs. C.