Social defeat stress induces myocardial injury by modulating inflammatory factors

Protective effect of naringin against radiation-induced heart disease in rats via Sirt1/NF-κB signaling pathway and endoplasmic reticulum stress

This study was designed to explore the protective effect and mechanism of naringin (NG) on radiation-induced heart disease (RIHD) in rats. Rats were divided into four x-ray (XR) irradiation groups with different absorbed doses (0/10/15/20 Gy), or into three groups (control, XR, and XR + NG groups). Subsequently, the ultrasonic diagnostic apparatus was adopted to assess and compare the left ventricular ejection fraction (LVEF), left ventricular fractional shortening (LVFS), left ventricular internal diameter at end diastole (LVIDd), and left ventricular internal diameter at end systole (LVIDs) in rats. Hematoxylin-eosin (H&E) staining and Masson staining were applied to detect the pathological damage and fibrosis of heart tissue. Western blot was used to measure the expression levels of myocardial fibrosis-related proteins, endoplasmic reticulum stress-related proteins, and Sirt1 (silent information regulator 1)/NF-κB (nuclear factor kappa-B) signaling pathway-related proteins in cardiac tissues. Additionally, enzyme-linked immunosorbent assay was utilized to detect the activities of pro-inflammatory cytokines, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) in cardiac tissue. The results showed that NG treatment significantly attenuated the 20 Gy XR-induced decline of LVEF and LVFS and the elevation of LVIDs. Cardiac tissue damage and fibrosis caused by 20 Gy XR were significant improved after NG treatment. Meanwhile, in rats irradiated by XR, marked downregulation was identified in the expressions of fibrosis-related proteins (Col I, collagen type I; α-SMA, α-smooth muscle actin; and TGF-β1, transforming growth factor-beta 1) and endoplasmic reticulum stress-related proteins (GRP78, glucose regulatory protein 78; CHOP, C/EBP homologous protein; ATF6, activating transcription factor 6; and caspase 12) after NG treatment. Moreover, NG treatment also inhibited the production of pro-inflammatory cytokines [interleukin-6, interleukin-1β, and monocyte chemoattractant protein-1 (MCP-1)], reduced the expression of MDA, and promoted the activities of SOD and CAT. Also, NG treatment promoted Sirt1 expression and inhibited p65 phosphorylation. Collectively, XR irradiation induced cardiac injury in rats in a dose-dependent manner. NG could improve the cardiac injury induced by XR irradiation by inhibiting endoplasmic reticulum stress and activating Sirt1/NF-κB signaling pathway.

Repeated witness social stress causes cardiomyocyte contractile impairment and intracellular Ca2+ derangement in female rats

The impact of psychosocial stressors on cardiovascular health in women is of growing interest in both the popular and scientific literature. Rodent models are useful for providing direct experimental evidence of the adverse cardiovascular consequences of psychosocial stressors, yet studies in females are scarce. Here, we investigated the effects of repeated exposure to witness social defeat stress (WS) on cardiomyocyte contractile function and intracellular Ca2+ homeostasis in young adult wild-type Groningen female rats. Female rats bore witness to an aggressive social defeat episode between two males for nine consecutive days or were exposed to a control procedure. Stress-related behaviors were assessed during the first and last WS/control exposure. Twenty-four hours after the last exposure, plasma corticosterone levels were measured, and cardiomyocytes were isolated for analyses of contractile properties and Ca2+ transients, and expression levels of proteins involved in intracellular Ca2+dynamics. The results show an impairment of the intrinsic cardiac mechanical properties and prolonged intracellular Ca2+decay in WS female rats showing social stress-related behavioral (larger amounts of burying behavior) and neuroendocrine (elevated plasma corticosterone levels) phenotypes. Further, the results implicate alterations in the sarcoplasmic reticulum Ca2+-ATPase/phospholamban complex in the contractile defects described in cardiomyocytes of WS female rats. In conclusion, this study highlights the utility of the WS model as an ethologically relevant social stressor for investigating pathophysiological processes that occur in the heart of female subjects and may increase vulnerability to social stress-related cardiovascular risk.

Decline of cardiomyocyte contractile performance and bioenergetic function in socially stressed male rats

Chronic social stress has been epidemiologically linked to increased risk for cardiovascular disease, yet the underlying pathophysiological mechanisms are still largely elusive. Mitochondrial (dys)function represents a potential intersection point between social stress exposure and (mal)adaptive cardiac responses. In this study, we used a rodent model of social stress to study the extent to which alterations in the cellular mechanical properties of the heart were associated with changes in indexes of mitochondrial function. Male adult rats were exposed to repeated episodes of social defeat stress or left undisturbed (controls). ECG signals were recorded during and after social defeat stress. Twenty-four hours after the last social defeat, cardiomyocytes were isolated for analyses of mechanical properties and intracellular Ca²⁺ dynamics, mitochondrial respiration, and ATP content. Results indicated that social defeat stress induced potent cardiac sympathetic activation that lasted well beyond stress exposure. Moreover, cardiomyocytes of stressed rats showed poor contractile performance (e.g., slower contraction and relaxation rates) and intracellular Ca²⁺ derangement (e.g., slower Ca²⁺ clearing), which were associated with indexes of reduced reserve respiratory capacity and decreased ATP production. In conclusion, this study suggests that repeated social stress provokes impaired cardiomyocyte contractile performance and signs of altered mitochondrial bioenergetics in the rat heart. Future studies are needed to clarify the causal link between cardiac and mitochondrial functional remodeling under conditions of chronic social stress.