Acute Physical Stress Preconditions the Heart Against Ischemia/Reperfusion Injury Through Activation of Sympathetic Nervous System

Abstract

BackgroundStress is defined as a complicated state that related to homeostasis disturbances, over-activity of the sympathetic nervous system and hypothalamus-pituitary-adrenal axis responses. Cardiac preconditioning reduces myocardial damages.ObjectiveThis study was designed to assess the cardioprotective effects of acute physical stress against ischemia/reperfusion (I/R) injury through the activation of the sympathetic nervous system.MethodsThirty-two male Wistar rats were divided into four groups; (1) IR (n = 8): rats underwent I/R, (2) Acute stress (St+IR) (n = 8): physical stress induced 1-hour before I/R, (3) Sympathectomy (Symp+IR) (n = 8): chemical sympathectomy was done 24-hours before I/R and (4) Sympathectomy- physical stress (Symp+St+IR) (n = 8): chemical sympathectomy induced before physical stress and I/R. Chemical sympathectomy was performed using 6-hydroxydopamine (100 mg/kg, sc). Then, the hearts isolated and located in the Langendorff apparatus to induce 30 minutes ischemia followed by 120 minutes reperfusion. The coronary flows, hemodynamic parameters, infarct size, corticosterone level in serum were investigated. P < 0.05 demonstrated significance.ResultsPhysical stress prior to I/R could improve left ventricular developed pressure (LVDP) and rate product pressure (RPP) of the heart respectively, (63 ± 2 versus 42 ± 1.2, p < 0.05, 70 ± 2 versus 43 ± 2.6, p < 0.05) and reduces infarct size (22.16 ± 1.3 versus 32 ± 1.4, p < 0.05) when compared with the I/R alone. Chemical sympathectomy before physical stress eliminated the protective effect of physical stress on I/R-induced cardiac damages (RPP: 21 ± 6.6 versus 63 ± 2, p < 0.01) (LVDP: 38 ± 4.5 versus 43 ± 2.6, p < 0.01) (infarct size: 35 ± 3.1 versus 22.16 ± 1.3, p < 0.01).ConclusionFindings indicate that acute physical stress can act as a preconditional stimulator and probably, the presence of sympathetic nervous system is necessary.

Pré-Condicionamento na Lesão por Isquemia-Reperfusão

“…7,8 Additionally, preconditioning of rats with acute physical stress prior to the IR insult reduced infarct size and improved hemodynamic parameters. 9 Currently, methods to induce ischemia-reperfusion have been used experimentally to assess whether different pharmacological and non-pharmacological therapies are effective in protecting the heart from ischemia and reperfusion injury. However, investigations to evaluate potential drugs, such as atorvastatin, anti-inflammatory medicines, or antioxidants did not result in cardioprotection after myocardial ischemia.…”

“… 7 , 8 Adicionalmente, o pré-condicionamento de ratos com estresse físico agudo anteriormente ao período de isquemia e reperfusão reduziu o tamanho do infarto e melhorou os parâmetros hemodinâmicos. 9 …”

The Role of Sympathetic System as a Therapeutic Option in the Ischemia/Reperfusion Injury

“…In this issue of the Arquivos Brasileiros de Cardiologia, Imani et al 5 assessed the cardioprotective effects of acute physical stress against I/R injury, through the activation of the sympathetic nervous system. They used the isolated heart preparation, with the Langendorff apparatus.…”

“…Physical stress prior to the I/R improved left ventricular developed pressure and reduced infarct size when compared with the I/R alone. 5 In addition, chemical sympathectomy before physical stress eliminated the protective effect of physical stress on I/R-induced cardiac damages. The authors concluded that the presence of the sympathetic nervous system is necessary for the beneficial effects of acute physical stress on I/R injury.…”

“…The authors concluded that the presence of the sympathetic nervous system is necessary for the beneficial effects of acute physical stress on I/R injury. 5…”