κ-opioid receptor is involved in the cardioprotection induced by exercise training

κ-opioid receptor stimulation alleviates rat vascular smooth muscle cell calcification via PFKFB3-lactate signaling

In the present study, the effects and mechanism of action of U50,488H (a selective κ-opioid receptor agonist) on calcification of rat vascular smooth muscle cells (VSMCs) induced by β-glycerophosphate (β-GP) were investigated. VSMCs were isolated and cultured in traditional FBS-based media. A calcification model was established in VSMCs under hyperphosphatemia and intracellular calcium contents. Alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and lactate were detected in cell culture supernatants before and after treatment. Alizarin red staining was used to detect the degree of calcification of VSMCs. Expression levels of key molecules of osteogenic markers, fructose-2,6-biphosphatase 3 (PFKFB3), and proline hydroxylase 2 (PHD2), were determined using western blotting. Further, vascular calcification was induced by vitamin D3 plus nicotine in rats and isolated thoracic aortas, calcium concentration was assessed in rat aortic rings in vitro. We demonstrated that U50,488H inhibited VSMC calcification in a concentration-dependent manner. Moreover, U50,488H significantly inhibited osteogenic differentiation and ALP activity in VSMCs pretreated with β-GP. Further studies confirmed that PFKFB3 expression, LDH level, and lactate content significantly increased during calcification of VSMCs; U50,488H reversed these changes. PHD2 expression showed the opposite trend compared to PFKFB3 expression. nor-BNI or 3-PO abolished U50,488H protective effects. Besides, U50,488H inhibited VSMC calcification in rat aortic rings ex vivo. Collectively, our experiments show that κ-opioid receptor activation inhibits VSMC calcification by reducing PFKFB3 expression and lactate content, providing a potential drug target and strategy for the clinical treatment of vascular calcification.

Mitochondrial Dysfunction and Apoptosis Are Attenuated on κ-Opioid Receptor Activation Through AMPK/GSK-3β Pathway After Myocardial Ischemia and Reperfusion

Previous studies have shown that κ-opioid receptor activation possesses cardioprotection against myocardial ischemia and reperfusion (MI/R) injury. The current study was designed to investigate whether mitochondrial dysfunction after MI/R is regulated by the κ-opioid receptor and to further explore the underlying mechanisms involved. MI/R rat model was established in vivo, and a hypoxia and reoxygenation cardiomyocytes model was used in vitro. Mitochondrial morphology and function as well as myocardial apoptosis were determined. Our data indicated that treatment with U50,488H (a selective κ-opioid receptor agonist) not only reduced apoptosis but also significantly improved mitochondrial morphology and function. These effects were blocked by nor-binaltorphimine (nor-BNI, a selective κ-opioid receptor antagonist), Compound C (an AMPK inhibitor), and AR-A014418 (a GSK3β inhibitor). Moreover, in cardiomyocytes, treatment with U50,488H significantly increased the expression in phosphorylation of AMPK and the phosphorylation of GSK3β. Treatment of cardiomyocytes with AMPKα siRNA decreased the phosphorylation of AMPK and GSK3β. Moreover, AMPK activation resulted in the phosphorylation of GSK3β. Our findings suggested that U50,488H exerted cardioprotective effects by improving mitochondrial morphology and function against MI/R injury through activation of the κ-opioid receptor-mediated AMPK/GSK3β pathway.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Exercise-induced cardiac opioid system activation attenuates apoptosis pathway in obese rats

AIM

To compare the effect of 150 min vs. 300 min of weekly moderate intensity exercise training on the activation of the opioid system and apoptosis in the hearts of a diet-induced obesity model.

METHODS

Male Wistar rats were fed with either control (CON) or high fat (HF) diet for 32 weeks. At the 20th week, HF group was subdivided into sedentary, low (LEV, 150 min·week^-1) or high (HEV, 300 min·week^-1) exercise volume. After 12 weeks of exercise, body mass gain, adiposity index, systolic blood pressure, cardiac morphometry, apoptosis biomarkers and opioid system expression were evaluated.

RESULTS

Sedentary animals fed with HF presented pathological cardiac hypertrophy and higher body mass gain, systolic blood pressure and adiposity index than control group. Both exercise volumes induced physiological cardiac hypertrophy, restored systolic blood pressure and improved adiposity index, but only 300 min·week^-1 reduced body mass gain. HF group exhibited lower proenkephalin, PI3K, ERK and GSK-3β expression, and greater activated caspase-3 expression than control group. Compared to HF, no changes in the cardiac opioid system were observed in the 150 min·week^-1 of exercise training, while 300 min·week^-1 showed greater proenkephalin, DOR, KOR, MOR, Akt, ERK and GSK-3β expression, and lower activated caspase-3 expression.

CONCLUSION

300 min·week^-1 of exercise training triggered opioid system activation and provided greater cardioprotection against obesity than 150 min·week^-1. Our findings provide translational aspect with clinical relevance about the critical dose of exercise training necessary to reduce cardiovascular risk factors caused by obesity.

Post-infarct morphine treatment mitigates left ventricular remodeling and dysfunction in a rat model of ischemia-reperfusion

Following myocardial infarction, the heart undergoes a series of dramatic compensations which may later form a maladaptive picture characterized by ventricular dilation and pump failure. Among several opioid agents, morphine has been shown to confer protection against reperfusion injury and infarct size. Here, we sought to study the cardioprotective effect of post-infarct morphine treatment against left ventricular adverse remodeling. We induced myocardial infarction in male Sprague - Dawley rats by ligating left anterior descending artery and then, treated these animals with three different doses of morphine -0.3, 3 and 10 mg/kg (i.p.). The echocardiographic evaluation depicted improved cardiac performance and lesser chamber dilation in the animals that had received 3 mg/kg of morphine. Next, we studied the effect of 3 mg/kg morphine administration on left ventricular hemodynamics, infarct size, tissue architecture, changes in lung and heart weight, circulating TNF-α level and post-MI mRNA expression of collagen-1, collagen-3, TGF-β, TNF-α, MMP-2 and MMP-9. Five-day morphine administration markedly improved LV function, and also reduced infarct size, myocyte hypertrophy, fibrosis, index of infarct expansion, heart weight and serum TNF-α level. Moreover, morphine alleviated MI-induced increase in wet and dry lung weight. Morphine also altered the mRNA expression of fibrosis-related genes, TNF-α, MMP-2 and MMP-9. In conclusion, post-infarct morphine treatment can mitigate adverse remodeling and cardiac dysfunction after MI. Beside analgesic effect, we may be able to harvest benefits from the antifibrotic and anti-remodeling action of morphine in patients with the acute coronary syndrome.

κ-opioid receptor activation protects against myocardial ischemia-reperfusion injury via AMPK/Akt/eNOS signaling activation

This study aims to investigate the effect of κ-opioid receptor activation on myocardial ischemia and reperfusion(I/R) injury and elucidate the underlying mechanisms. Myocardial I/R rat model and simulated I/R cardiomyocytes model were established. In vivo study showed that U50,488 H improved cardiac function, reduced myocardial infarct size and serum cTnT significantly. The effect of U50,488 H was abolished by nor-BNI(a κ-opioid receptor antagonist), Compound C(an AMPK inhibitor), Akt inhibitor and L-NAME(an eNOS inhibitor). AICAR, an AMPK activator, mimicked the effect of U50,488 H. U50,488 H up-regulated p-AMPK, p-Akt, and p-eNOS, which were abolished by nor-BNI. AICAR increased p-Akt and p-eNOS, which was abolished by Compound C. In vitro study showed that U50,488 H increased p-AMPK, p-Akt, and p-eNOS via κ-OR activation. The effect of U50,488 H on p-AMPK was abolished by compound C, but not Akt inhibitor and L-NAME. The effect of U50,488 H on p-Akt was abolished by compound C and Akt inhibitor, but not L-NAME. AICAR increased p-Akt and p-eNOS, which was abolished by Akt inhibitor, but not L-NAME. U50,488 H and AICAR also increased the viability of cardiomyocytes subjected to simulated I/R, the effects of U50,488 H and AICAR were blocked by nor-BNI, Compound C, Akt inhibitor, and L-NAME, respectively. In conclusion, κ-OR activation confers cardioprotection via AMPK/Akt/eNOS signaling.

Cardioprotective Exercise and Pharmacologic Interventions as Complementary Antidotes to Cardiovascular Disease

Exercise and pharmacologic therapies to prevent and treat cardiovascular disease have advanced largely through independent efforts. Understanding of first-line drug therapies, findings from preclinical animal studies, and the need for research initiatives related to complementary cardioprotective exercise-pharma interventions are reviewed from the premise that contemporary cardioprotective therapies must include adjunctive exercise and lifestyle interventions in addition to pharmacologic agents.