Early life stress in male mice induces superoxide production and endothelial dysfunction in adulthood

Abstract

Early life stress (ELS) is a risk for cardiovascular disease in adulthood although very little mechanistic insight is available. Because oxidative stress and endothelial dysfunction are major contributors to cardiovascular risk, we hypothesized that ELS induces endothelial dysfunction in adult male mice via increased superoxide production. Studies employed a mouse model of ELS, maternal separation with early weaning (MSEW), in which litters were separated from the dam for 4 h/day [postnatal days (PD) 2-5] and 8 h/day (PD6-16), and weaned at PD17. Control litters remained undisturbed until weaning at PD21. When compared with control mice, thoracic aortic rings from adult male MSEW mice displayed significant endothelial dysfunction that was reversed by the superoxide scavenger, polyethylene glycol-superoxide dismutase (PEG-SOD). PEG-SOD-inhibitable superoxide production by aortae from MSEW mice was significantly greater than observed in control aortae, although unaffected by nitric oxide synthase inhibition, suggesting that uncoupled nitric oxide synthase was not responsible for the accelerated superoxide production. Aortic SOD expression, plasma SOD activity, and total antioxidant activity were similar in MSEW and control mice, indicating unaltered antioxidant capacity in MSEW mice. Increased expression of the NADPH oxidase subunits, NOX2 and NOX4, was evident in the aortae of MSEW mice. Moreover, endothelial dysfunction and superoxide production in MSEW mice was reversed with the NADPH oxidase inhibitor, apocynin, indicating increased NADPH oxidase-dependent superoxide production and endothelial dysfunction. The finding that MSEW induces superoxide production and endothelial dysfunction in adult mice may provide a mechanistic link between ELS and adult cardiovascular disease risk.

A model of neglect during postnatal life heightens obesity-induced hypertension and is linked to a greater metabolic compromise in female mice

“…Hence, the MSEW model has been generated with the goal to replicate a consistent phenotype. As adult, mice exposed to MSEW display alterations across several behavioral domains, increases in hyperactivity, anxiety, and depressive- like behavior 34,35,37 .…”

Developmental origins of cardiovascular disease: Impact of early life stress in humans and rodents

“…Selection for low or high care C57BL/6 mothers also has a minimal impact on offspring behavior and stress response (Pedersen et al, 2011). These studies suggest that alternative more severe models of ELS, beyond three hours, combined with early weaning are necessary to induce the ELS-like phenotype in mice (George et al, 2010; Ho et al, 2016). …”

“…These models include restraint stress during gestation days 15 to 21, maternal protein deprivation, and glucocorticoid exposure via dexamethasone administration during gestation (Harris and Seckl, 2011; Igosheva et al, 2004; Mizuno et al, 2013). However, maternal separation (MatSep) and similar models of chronic behavioral stress seem to induce a “first hit” effect that does not change the baseline cardiovascular parameters in young adult rodents, but primes the physiological systems to overreact in response to a secondary stressor or “second hit.”(Ho et al, 2016; Loria et al, 2010b; Sanders and Anticevic, 2007). …”

“…Previously, we have reported impaired blood pressure regulation in rats exposed to 3 hours of maternal separation daily from postnatal day 2–14 (Loria et al, 2013a). Within a murine model, MatSep with early weaning consists of separating the litters for 4 hours per day during postnatal days 2–5 followed by 8 hours per day from postnatal day 6–16 with weaning at day 17 induces vascular endothelial dysfunction and superoxide production thus increasing cardiovascular risk (Ho et al, 2016). …”

Childhood adversity and mechanistic links to hypertension risk in adulthood

“…Though several studies suggest that ROS‐mediated inflammatory and vascular effects play important roles in the development of hypertension, few studies have examined the pathophysiological role of ROS in ELS‐induced CVD risk and associated hypertension. Our group showed that expression of genes encoding NADPH oxidase subunits Nox2 and Nox4 are up‐regulated in aorta from mice exposed to MSEW and that NADPH oxidase inhibition with apocynin improves MSEW‐mediated endothelial dysfunction (Ho et al, ). In contrast, although constrictor responses to acute AngII treatment are exaggerated in aorta from MatSep rats, this phenomenon is unaffected by treatment with apocynin or cell‐permeable SOD, suggesting that other ROS‐dependent pathways may be involved (Loria, Kang, Pollock, & Pollock, ).…”