Abstract
Hypertension is characterized by a pro-inflammatory status, including redox imbalance and increased levels of pro-inflammatory cytokines, which may be exacerbated after heat exposure. However, the effects of heat exposure, specifically in individuals with inflammatory chronic diseases such as hypertension, are complex and not well understood. This study compared the effects of heat exposure on plasma cytokine levels and redox status parameters in 8 hypertensive (H) and 8 normotensive (N) subjects (age: 46.5±1.3 and 45.6±1.4 years old, body mass index: 25.8±0.8 and 25.6±0.6 kg/m2, mean arterial pressure: 98.0±2.8 and 86.0±2.3 mmHg, respectively). They remained at rest in a sitting position for 10 min in a thermoneutral environment (22°C) followed by 30 min in a heated environmental chamber (38°C and 60% relative humidity). Blood samples were collected before and after heat exposure. Plasma cytokine levels were measured using sandwich ELISA kits. Plasma redox status was determined by thiobarbituric acid reactive substances (TBARS) levels and ferric reducing ability of plasma (FRAP). Hypertensive subjects showed higher plasma levels of IL-10 at baseline (P<0.05), although levels of this cytokine were similar between groups after heat exposure. Moreover, after heat exposure, hypertensive individuals showed higher plasma levels of soluble TNF receptor (sTNFR1) and lower TBARS (P<0.01) and FRAP (P<0.05) levels. Controlled hypertensive subjects, who use angiotensin-converting-enzyme inhibitor (ACE inhibitors), present an anti-inflammatory status and balanced redox status. Nevertheless, exposure to a heat stress condition seems to cause an imbalance in the redox status and an unregulated inflammatory response.
Highlights
Systemic arterial hypertension is characterized by endothelial dysfunction, vascular injury [1], and chronic inflammation [2], which includes increased pro-inflammatory cytokines such as interleukin 1-b (IL1-b), tumor necrosis factor (TNF-a) and interleukin 6 (IL-6)
Taking into account that hypertensive subjects have chronic inflammation, which is associated with development of elevated blood pressure and future risk of myocardial infarction, atherosclerosis and cardiovascular death [8,14,15], and that heat exposure interferes with inflammatory and redox status, this study aimed to investigate the effects of heat exposure on plasma cytokine levels and redox status parameters in hypertensive subjects
There was an increase in the sTNFR1 plasma level in hypertensive subjects (Po0.01) after heat exposure, which was significantly higher compared to the sTNFR1 level in normotensive subjects (Po0.05)
Summary
Systemic arterial hypertension is characterized by endothelial dysfunction, vascular injury [1], and chronic inflammation [2], which includes increased pro-inflammatory cytokines such as interleukin 1-b (IL1-b), tumor necrosis factor (TNF-a) and interleukin 6 (IL-6). These cytokines affect the function of vascular endothelium-derived factors involved in blood pressure (BP) regulation [1,3,4]. Previous studies have demonstrated that heat stress exposure can increase both pro- and anti-inflammatory cytokines in human and animal models [9,10]. The effects of heat exposure in individuals with chronic inflammatory diseases, such as hypertension, are complex and not completely understood
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