Effects of pinealectomy and exogenous melatonin on rat hearts

Therapeutic potential of melatonin in targeting molecular pathways of organ fibrosis

Fibrosis, the excessive deposition of fibrous connective tissue in an organ in response to injury, is a pathological condition affecting many individuals worldwide. Fibrosis causes the failure of tissue function and is largely irreversible as the disease progresses. Pharmacologic treatment options for organ fibrosis are limited, but studies suggest that antioxidants, particularly melatonin, can aid in preventing and controlling fibrotic damage to the organs. Melatonin, an indole nocturnally released from the pineal gland, is commonly used to regulate circadian and seasonal biological rhythms and is indicated for treating sleep disorders. While it is often effective in treating sleep disorders, melatonin's anti-inflammatory and antioxidant properties also make it a promising molecule for treating other disorders such as organ fibrosis. Melatonin ameliorates the necrotic and apoptotic changes that lead to fibrosis in various organs including the heart, liver, lung, and kidney. Moreover, melatonin reduces the infiltration of inflammatory cells during fibrosis development. This article outlines the protective effects of melatonin against fibrosis, including its safety and potential therapeutic effects. The goal of this article is to provide a summary of data accumulated to date and to encourage further experimentation with melatonin and increase its use as an anti-fibrotic agent in clinical settings.

Mitochondrial Melatonin: Beneficial Effects in Protecting against Heart Failure

Cardiovascular disease is the cause of physical infirmity and thousands of deaths annually. Typically, during heart failure, cardiomyocyte mitochondria falter in terms of energy production and metabolic processing. Additionally, inflammation and the accumulation of non-contractile fibrous tissue contribute to cardiac malfunction. Melatonin, an endogenously produced molecule, experimentally reduces the initiation and progression of atherosclerotic lesions, which are often the basis of coronary artery disease. The current review critically analyzes published data related to the experimental use of melatonin to forestall coronary artery pathologies. Collectively, these studies document melatonin's anti-atherosclerotic actions in reducing LDL oxidation and triglyceride levels, lowering endothelial malfunction, limiting adhesion molecule formation, preventing macrophage polarization to the M1 pro-inflammatory phenotype, changing cellular metabolism, scavenging destructive reactive oxygen species, preventing the proliferation and invasion of arterial smooth muscle cells into the lesioned area, restricting the ingrowth of blood vessels from the vasa vasorum, and solidifying the plaque cap to reduce the chance of its rupture. Diabetic hyperglycemia, which aggravates atherosclerotic plaque formation, is also inhibited by melatonin supplementation in experimental animals. The potential value of non-toxic melatonin as a possible inhibitor of cardiac pathology in humans should be seriously considered by performing clinical trials using this multifunctional molecule.

Current Insights and Future Directions in the Treatment of Heart Failure with Preserved Ejection Fraction

Heart failure is a clinical syndrome associated with poor quality of life, substantial healthcare resource utilization, and premature mortality, in large part related to high rates of hospitalizations. The clinical manifestations of heart failure are similar regardless of the ejection fraction. Unlike heart failure with reduced ejection fraction, there are few therapeutic options for treating heart failure with preserved ejection fraction. Molecular therapies that have shown reduced mortality and morbidity in heart failure with reduced ejection have not been proven to be effective for patients with heart failure and preserved ejection fraction. The study of pathophysiological processes involved in the production of heart failure with preserved ejection fraction is the basis for identifying new therapeutic means. In this narrative review, we intend to synthesize the existing therapeutic means, but also those under research (metabolic and microRNA therapy) for the treatment of heart failure with preserved ejection fraction.

A surgical modification in the technique of rat pinealectomy

BACKGROUND

Several experimental intents require pineal gland removal. The main challenge of the pinealectomy surgical procedure is the hemorrhage due to the transverse sinus torn. The study aimed to modify the rat pinealectomy surgical procedure to reduce the risk of bleeding and the mortality rate.

METHODS

Adult male rats experienced pinealectomy surgery. A mini-drill was used to remove a small skull area in the junction of the lambda and sagittal sutures. The pineal gland was removed using a curved-head hook. Animals experienced intensive post-surgical care. Locomotion, cerebellar motor function, working memory, and anxiety were evaluated 2 weeks after pinealectomy by the open field, rotarod, Y maze, and the elevated plus maze, respectively.

RESULTS

Surgical modification reduced the bleeding risk and animal mortality rate. No significant alteration was found in locomotion and working memory. However, the pinealectomy was anxiogenic and decreased entry to the open arm. The cerebellar motor performance did not change in the rotarod test. Hematoxylin-Eosin staining of removed tissue confirmed the histology of the pineal gland.

CONCLUSION

Advantages of this technique were removing a small skull area, modifying the hook insertion point to prevent damaging the brain veins, reducing the bleeding risk and the mortality rate. Surgery modification was associated with a decreased final number of animals used. Regardless of the melatonin shortage, pinealectomy affects different organs, which should be considered in the research study design.

Evidence for the Benefits of Melatonin in Cardiovascular Disease

The pineal gland is a neuroendocrine gland which produces melatonin, a neuroendocrine hormone with critical physiological roles in the circadian rhythm and sleep-wake cycle. Melatonin has been shown to possess anti-oxidant activity and neuroprotective properties. Numerous studies have shown that melatonin has significant functions in cardiovascular disease, and may have anti-aging properties. The ability of melatonin to decrease primary hypertension needs to be more extensively evaluated. Melatonin has shown significant benefits in reducing cardiac pathology, and preventing the death of cardiac muscle in response to ischemia-reperfusion in rodent species. Moreover, melatonin may also prevent the hypertrophy of the heart muscle under some circumstances, which in turn would lessen the development of heart failure. Several currently used conventional drugs show cardiotoxicity as an adverse effect. Recent rodent studies have shown that melatonin acts as an anti-oxidant and is effective in suppressing heart damage mediated by pharmacologic drugs. Therefore, melatonin has been shown to have cardioprotective activity in multiple animal and human studies. Herein, we summarize the most established benefits of melatonin in the cardiovascular system with a focus on the molecular mechanisms of action.

Melatonin ameliorates PM2.5 -induced cardiac perivascular fibrosis through regulating mitochondrial redox homeostasis

Fine particulate matter (PM2.5 ) exposure is correlated with the risk of developing cardiac fibrosis. Melatonin is a major secretory product of the pineal gland that has been reported to prevent fibrosis. However, whether melatonin affects the adverse health effects of PM2.5 exposure has not been investigated. Thus, this study was aimed to investigate the protective effect of melatonin against PM2.5 -accelerated cardiac fibrosis. The echocardiography revealed that PM2.5 had impaired both systolic and diastolic cardiac function in ApoE-/- mice. Histopathological analysis demonstrated that PM2.5 induced cardiomyocyte hypertrophy and fibrosis, particularly perivascular fibrosis, while the melatonin administration was effective in alleviating PM2.5 -induced cardiac dysfunction and fibrosis in mice. Results of electron microscopy and confocal scanning laser microscope confirmed that melatonin had restorative effects against impaired mitochondrial ultrastructure and augmented mitochondrial ROS generation in PM2.5 -treated group. Further investigation revealed melatonin administration could significantly reverse the PM2.5 -induced phenotypic modulation of cardiac fibroblasts into myofibroblasts. For the first time, our study found that melatonin effectively alleviates PM2.5 -induced cardiac dysfunction and fibrosis via inhibiting mitochondrial oxidative injury and regulating SIRT3-mediated SOD2 deacetylation. Our findings indicate that melatonin could be a therapy medicine for prevention and treatment of air pollution-associated cardiac diseases.

The effect of melatonin on cardio fibrosis in juvenile rats with pressure overload and deregulation of HDACs

The effect of melatonin on juveniles with cardio fibrosis is poorly understood. We investigated whether HDACs participate in the anti-fibrotic processes regulated by melatonin during hypertrophic remodeling. Abdominal aortic constriction (AAC) was employed in juvenile rats resulting in pressure overload-induced ventricular hypertrophy and melatonin was subsequently decreased via continuous light exposure for 5 weeks after surgery. AAC rats displayed an increased cross-sectional area of myocardial fibers and significantly elevated collagen deposition compared to sham-operated rats, as measured by HE and Masson Trichrome staining. Continuous light exposure following surgery exacerbated the increase in the cross-sectional area of myocardial fibers. The expression of HDAC1, HDAC2, HDAC3, HDAC4 and HDAC6 genes were all significantly enhanced in AAC rats with light exposure relative to the other rats. Moreover, the protein level of TNF-α was also upregulated in the AAC light exposure groups when compared with the sham. However, Smad4 protein expression was unchanged in the juveniles' hearts. In contrast, beginning 5 weeks after the operation, the AAC rats were treated with melatonin (10 mg/kg, intraperitoneal injection every evening) or vehicle 4 weeks, and sham rats were given vehicle. The changes in the histological measures of cardio fibrosis and the gene expressions of HDAC1, HDAC2, HDAC3, HDAC4 and HDAC6 were attenuated by melatonin administration. The results reveal that melatonin plays a role in the development of cardio fibrosis and the expression of HDAC1, HDAC2, HDAC3, HDAC4 and HDAC6 in cardiomyocytes.

Melatonin promotes reduction in TNF levels and improves the lipid profile and insulin sensitivity in pinealectomized rats with periodontal disease

AIM

This study aimed to investigate the effects of melatonin (ME) on insulin resistance (IR) and signaling (IS), proinflammatory cytokine levels, and lipid profiles in pinealectomyzed (PNX) rats with periodontal disease (PD).

MAIN METHODS

One hundred and forty-four rats (age = 40 days) were distributed into 8 groups: 1) control (CN); 2) PD only; 3) PNX only; 4) PNX and PD (PNXPD); 5) CN treated with ME (CNM); 6) PD treated with ME (PDM); 7) PNX treated with ME(PNXM); 8) PNX and PD treated with ME(PNXPDM). The PNX groups were subjected to pinealectomy at 40 and at 60 days of age. The animals were then subjected to PD induction in the mandibular first molars. After PD induction, the ME replacement therapy (MERT-5 mg/kg body weight) was performed using water for 28 days. After this period, the plasma concentration of glucose, insulin, TNF, IL-6, triglycerides, total cholesterol, HDL-cholesterol, LDL-cholesterol, and VLDL-cholesterol and the HOMA-IR index were determined. Akt serine phosphorylation status in the white adipose tissue, gastrocnemius muscle, and rat liver were also evaluated.

KEY FINDINGS

PD, PNX, and PNXPD groups showed an increase in IR with elevated plasma levels of insulin and TNF compared to CN group. PNX and PNXPD groups presented alteration in lipid profile compared to CN group. MERT improved all of the analyzed parameters. No difference was observed in the IS among different groups.

SIGNIFICANCE

The results suggest that MERT efficiently prevents IR, improves lipid profile, and increases plasma levels of insulin and TNF in PD and PNX rats.

Melatonin in Heart Failure: A Promising Therapeutic Strategy?

Heart failure is a multifactorial clinical syndrome characterized by the inability of the heart to pump sufficient blood to the body. Despite recent advances in medical management, poor outcomes in patients with heart failure remain very high. This highlights a need for novel paradigms for effective, preventive and curative strategies. Substantial evidence supports the importance of endogenous melatonin in cardiovascular health and the benefits of melatonin supplementation in various cardiac pathologies and cardiometabolic disorders. Melatonin plays a crucial role in major pathological processes associated with heart failure including ischemic injury, oxidative stress, apoptosis, and cardiac remodeling. In this review, available evidence for the role of melatonin in heart failure is discussed. Current challenges and possible limitations of using melatonin in heart failure are also addressed. While few clinical studies have investigated the role of melatonin in the context of heart failure, current findings from experimental studies support the potential use of melatonin as preventive and adjunctive curative therapy in heart failure.

Melatonin: Protection against age-related cardiac pathology

Aging is a complex and progressive process that involves physiological and metabolic deterioration in every organ and system. Cardiovascular diseases are one of the most common causes of mortality and morbidity among elderly subjects worldwide. Most age-related cardiovascular disorders can be influenced by modifiable behaviours such as a healthy diet rich in fruit and vegetables, avoidance of smoking, increased physical activity and reduced stress. The role of diet in prevention of various disorders is a well-established factor, which has an even more important role in the geriatric population. Melatonin, an indoleamine with multiple actions including antioxidant properties, has been identified in a very large number of plant species, including edible plant products and medical herbs. Among products where melatonin has been identified include wine, olive oil, tomato, beer, and others. Interestingly, consumed melatonin in plant foods or melatonin supplementation may promote health benefits by virtue of its multiple properties and it may counteract pathological conditions also related to cardiovascular disorders, carcinogenesis, neurological diseases and aging. In the present review, we summarized melatonin effects against age-related cardiac alterations and abnormalities with a special focus on heart ischemia/reperfusion (IR) injury and myocardial infarction.

Melatonin: the dawning of a treatment for fibrosis?

Fibrosis is a common occurrence following organ injury and failure. To date, there is no effective treatment for this condition. Melatonin targets numerous molecular pathways, a consequence of its antioxidant and anti-inflammatory actions that reduce excessive fibrosis. Herein, we review the multiple protective effects of melatonin against fibrosis. There exist four major phases of the fibrogenic response including primary injury to the organ, activation of effector cells, the elaboration of extracellular matrix (ECM) and dynamic deposition. Melatonin regulates each of these phases. Additionally, melatonin reduces fibrosis levels in numerous organs. Melatonin exhibits its anti-fibrosis effects in heart, liver, lung, kidney, and other organs. In addition, adhesions which occur following surgical procedures are also inhibited by melatonin. The information reviewed here should be significant to understanding the protective role of melatonin against fibrosis, contribute to the design of further experimental studies related to melatonin and the fibrotic response and shed light on a potential treatment for fibrosis.

Pinealectomy aggravates acute pancreatitis in the rat

Melatonin, a pineal indoleamine, protects the pancreas against acute damage; however, the involvement of the pineal gland in the pancreatoprotective action of melatonin is unknown. The primary aim of this study was to determine the effects of pinealectomy on the course of acute caerulein-induced pancreatitis (AP) in rats. AP was induced by a subcutaneous infusion of caerulein (25 μg/kg) into pinealectomized or sham-operated animals. Melatonin (5 or 25 mg/kg) was given via intraperitoneal (ip) injection 30 min prior to the induction of AP. The pancreatic content of the lipid peroxidation products malondialdehyde and 4-hydroxynonenal (MDA + 4HNE) and the activity of an antioxidative enzyme, glutathione peroxidase (GSH-Px), were measured in each group of rats. Melatonin blood levels were measured by radioimmunoassay (RIA). In the sham-operated rats, AP was confirmed with histological examination and manifested as pancreatic edema and an increase in the blood lipase level (by 1,500%). In addition, the pancreatic content of MDA+ 4HNE was increased by 200%, and pancreatic glutathione peroxydase (GSH-Px) activity was reduced by 40%. Pinealectomy significantly aggravated the histological manifestations of AP, reduced the GSH-Px activity and markedly augmented the levels of MDA+ 4HNE in the pancreas of rats with or without AP as compared to sham-operated animals. Melatonin was undetectable in the blood of the pinealectomized rats with or without AP. Treatment with melatonin (25 mg/kg, ip) prevented the development of AP in the sham-operated rats and significantly reduced pancreatic inflammation in the animals previously subjected to pinealectomy. In conclusion, pineal melatonin contributes to the pancreatic protection through the activation of the antioxidative defense mechanism in pancreatic tissue as well as its direct antioxidant effects.

Remodelling of the heart and vessels in experimental hypertension: advances in protection

Left ventricular hypertrophy (LVH), despite its adaptive nature, increases cardiovascular morbidity and mortality. Novel approaches for protection against pathological heart remodelling are presented in this supplement. Melatonin diminishes myocardial fibrosis in rats exposed to continuous light and N-nitro-L-arginine-methyl ester (L-NAME) treatment and reduces production of endothelium-derived constricting factors in L-NAME-induced hypertension. Melatonin, because of its extraordinary antioxidant and scavenging properties, benefits for endothelium and sympatholytic action, may prove to be a useful protective drug against heart remodelling. In hypertension induced by relative aldosteronism, the correction of macro and micronutrient dyshomeostasis appears to act beneficially within pathological myocardial remodelling. Alterations in the signal cascade of pathological myocardial growth, including humoral stimuli, receptors, intracellular messengers or transcriptional factors, may be favourably modified at different levels. Inhibition of nuclear factor kappa B (NF-kappaB) potentiates hypertension development, enhances oxidative load, increases the cross-sectional area of the aorta and reduces nitric oxide (NO) synthase activity in L-NAME hypertension. It is suggested that NF-kappaB may play a protective rather than a deleterious role in the haemodynamically overloaded circulation. Compound 21, a recently developed peptide angiotensin II type 2 (AT2) receptor agonist, offers a novel approach in investigating the role of AT2 receptors in the protection of the hypertensive heart. A novel NO donor, L-419, with its intrinsic protection of NO, improves the entire NO signalling cascade and thus favourably influencing the response of the left ventricle to haemodynamic overload. LVH prevention or regression should be considered a therapeutic success only when, along with hypertrophied mass reduction, an improvement of the heart structure, function, metabolism and electrical stability is achieved.

Prolonged melatonin administration in 6-month-old Sprague-Dawley rats: metabolic alterations

The aim of this work was to evaluate the effect of prolonged melatonin administration on chosen metabolic and hormonal variables in male and female Sprague-Dawley rats. Melatonin was administered in tap water (4 microg/ml) daily from the 6th month of age. Rats were fed a standard type of diet ad libitum and were kept in a light regimen L:D--12:12h. The experiment was terminated after 12 weeks of melatonin administration. Melatonin decreased body mass during the whole experiment in females and from the 42nd day of the experiment in males. Relative heart muscle weight in females and absolute/relative thymus weight in males were increased after melatonin administration. Melatonin decreased glycaemia, heart muscle glycogen concentration in females and liver glycogen concentration in both sexes. Serum insulin concentration in males was decreased; serum corticosterone concentration was increased in both males and females. Serum triacylglycerol and heart muscle cholesterol concentration in females were decreased, however in males serum and heart muscle cholesterol concentration was increased. Liver phospholipid concentration in females was decreased and heart muscle phospholipid concentration in males was increased. Melatonin increased malondialdehyde concentration in heart muscle in males and in liver in both sexes. Melatonin induced prominent sex-dependent changes in both carbohydrate and lipid metabolism.

Does pinealectomy affect the recovery rate after spinal cord injury?

Previous reports documented demonstrated that melatonin, a free radical scavenger, is important in protecting against oxidative stress-induced tissue damage after spinal cord injury (SCI). This study was undertaken to investigate the effects of pinealectomy (PX) and administration of exogenous melatonin after SCI in rats. These animals were randomized into six groups, each having 12 rats. Group 1 underwent laminectomy alone. Group 2 underwent laminectomy followed by SCI and received no medication. Group 3 underwent laminectomy followed by SCI and received melatonin. Group 4 underwent PX and laminectomy alone. Group 5 underwent PX and laminectomy followed by SCI and received no medication. Group 6 underwent PX and laminectomy followed by SCI and received melatonin. Melatonin (100 mg/kg) was given intraperitoneally immediately after trauma to the rats in the groups 3 and 6. PX caused a significant increase in the malondialdehyde (MDA), nitrite oxide (NO), glutathione (GSH), xanthine oxidase (XO) levels and decrease in GSH levels as compared with the control group. Trauma to the spinal cord results in significantly higher oxidative stress. Melatonin administration significantly reduced MDA, XO and NO levels, and increased GSH levels in the spinal cord after trauma. Exogenous melatonin treatment after trauma attenuated tissue lesion area and accelerated motor recovery rate. These findings suggest that reduction in endogenous melatonin after PX makes the rats more vulnerable to trauma and exogenous melatonin administration has an important neuroprotective effect on the level of the spinal cord.

Cardiovascular diseases: protective effects of melatonin

This brief review considers some of the cardiac diseases and conditions where free radicals and related reactants are believed to be causative. The report also describes the beneficial actions of melatonin against oxidative cardiovascular disorders. Based on the data available, melatonin seems to have cardioprotective properties via its direct free radical scavenger and its indirect antioxidant activity. Melatonin efficiently interacts with various reactive oxygen and reactive nitrogen species (receptor independent actions) and it also upregulates antioxidant enzymes and downregulates pro-oxidant enzymes (receptor-dependent actions). Moreover, melatonin enters all cells and subcellular compartments and crosses morphophysiologic barriers. These findings have implications for the protective effects of melatonin against cardiac diseases induced by oxidative stress. Melatonin attenuates molecular and cellular damages resulting from cardiac ischemia/reperfusion in which destructive free radicals are involved. Anti-inflammatory and antioxidative properties of melatonin are also involved in the protection against a chronic vascular disease, atherosclerosis. The administration of melatonin, as a result of its antioxidant features, has been reported to reduce hypertension and cardiotoxicity induced by clinically used drugs. The results described herein help to clarify the beneficial effects of melatonin against these conditions and define the potential clinical applicability of melatonin in cardiovascular diseases.

Protective role of aminoguanidine on gentamicin-induced acute renal failure in rats

The toxicity of aminoglycosides including gentamicin (GEN), the most widely used drug in this category, is believed to be related to the generation of reactive oxygen species (ROS) in the kidney. Aminoguanidine (AG) is known as an effective antioxidant and its free radical scavenger effects may protect GEN-induced acute renal failure (ARF). Therefore, this study was focused on investigating the possible protective effect of AG against GEN-induced nephrotoxicity in an in vivo rat model. We investigated the effects of AG on GEN-induced changes in renal tissue malondialdehyde (MDA) levels; nitric oxide (NO) generation; glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), and catalase (CAT) activities; glutathione (GSH) content; serum creatinine (Cr) and blood urea nitrogen (BUN) levels. Morphological changes in the kidney were also examined using light microscopy. GEN administration to control group rats increased renal MDA and NO levels but decreased GSH-Px, SOD, CAT activities and GSH content. AG administration with GEN injection resulted in significantly decreased MDA, NO generation and increased GSH-Px, SOD, CAT activities and GSH content when compared with GEN alone. Serum levels of Cr and BUN significantly increased as a result of nephrotoxicity. Also, AG significantly decreased Cr and BUN levels. Morphological changes in the kidney, including tubular necrosis, intracellular edema, glomerular and basement membrane alterations were evaluated qualitatively. Both biochemical findings and histopathological evidence showed that administration of AG reduced the GEN-induced kidney damage. We propose that AG acts in the kidney as a potent scavenger of free radicals to prevent the toxic effects of GEN both at the biochemical and histological level.

Efficacy of melatonin as protectant against oxidative stress and structural changes in liver tissue in pinealectomized rats

Previous observations demonstrated that physiological levels of melatonin, the pineal secretory product, are important in protecting against oxidative stress-induced tissue damage. We investigated the effects of pinealectomy and administration of exogenous melatonin on liver tissue in rats. Pinealectomized (Px) and sham-operated (non-Px) rats were used. We evaluated structural changes, reduced glutathione (GSH) levels and malondialdehyde (MDA) levels. Rats were divided into three groups (10 rats in each group): control (non-Px), Px+vehicle and Px+melatonin (4 mg/kg given daily intraperitoneally for 10 days). Liver GSH levels were significantly lower in Px rats than in the control group. Melatonin administration significantly increased GSH levels (p < 0.05). Px caused a significant increase in MDA levels as compared with the control group and melatonin administration to Px rats significantly reduced MDA levels in the liver (p < 0.05). Sinusoidal dilatation to a varying degree developed in all Px rats. Severity of mononuclear cell infiltration and sinusoidal congestion were lower in Px+melatonin group than in the Px group. These findings suggest that a significant increase in oxidative and structural changes occur in rat livers after pinealectomy, which can be diminished by melatonin treatment.