Hypotensive effects of melatonin in rats: Focus on the model, measurement, application, and main mechanisms

The roles of melatonin and potassium channels in relaxation response to ang 1-7 in diabetic rat isolated aorta

In a circadian cycle, the pineal gland produces and releases melatonin (MEL) into the bloodstream. By activating distinct melatonin receptors, MEL has been shown to variably change vascular endothelial dysfunction (VED) to various vascular beds. This study investigates the interaction of melatonin (MEL) and potassium ion (K+) on angiotensin 1-7 (Ang 1-7) vasorelaxant in streptozotocin (STZ)-induced diabetes mellitus (DM) and non-diabetes mellitus (non-DM) male albino rat aortic rings. The isometric tension of isolated aortic rings was assessed by generating a dose-response curve (DRC) for Ang 1-7 using a PowerLab data acquisition system. Accordingly, three experimental sets were carried out. In the first set the aortic rings were exposed MEL and MEL agonist ramelteon (RAM) and MEL antagonist luzindole (LUZ). In the second set, the aortic rings were exposed to various non-selective calcium activated potassium channel (KCa) blockers, including tetraethylammonium (TEA), a small and large-conductance calcium-activated K+ [(SKCa) and (BKCa)] channels blocker charybdotoxin (ChTx) and intermediate calcium-activated K+ channel (IKCa) blocker clotrimazole (CLT). In the third set, the aortic rings were exposed to various selective K+ channels blockers, including the selective blocker of KATP channel, glibenclamide (Glib), 4-aminopyridine (4-AP), a selective blocker of Kv channels and BaCl2, delayed inward rectifier K+ channels (Kir) blocker. The results highlight the significant role of MEL in modulating vascular reactivity, particularly in the DM aorta. By enhancing the vasorelaxant effects of Ang 1-7 through mechanisms involving its receptors and antioxidant activities, MEL demonstrates its potential to counteract oxidative stress and VED associated with diabetes. These findings advance the understanding of vascular reactivity in diabetes and suggest MEL as a promising therapeutic agent for improving vascular health in diabetic conditions.

Melatonin's Impact on Wound Healing

Melatonin (5-methoxy-N-acetyltryptamine) is an indoleamine compound that plays a critical role in the regulation of circadian rhythms. While melatonin is primarily synthesized from the amino acid tryptophan in the pineal gland of the brain, it can also be produced locally in various tissues, such as the skin and intestines. Melatonin's effects in target tissues can be mediated through receptor-dependent mechanisms. Additionally, melatonin exerts various actions via receptor-independent pathways. In biological systems, melatonin and its endogenous metabolites often produce similar effects. While injuries are common in daily life, promoting optimal wound healing is essential for patient well-being and healthcare outcomes. Beyond regulating circadian rhythms as a neuroendocrine hormone, melatonin may enhance wound healing through (1) potent antioxidant properties, (2) anti-inflammatory actions, (3) infection control, (4) regulation of vascular reactivity and angiogenesis, (5) analgesic (pain-relieving) effects, and (6) anti-pruritic (anti-itch) effects. This review aims to provide a comprehensive overview of scientific studies that demonstrate melatonin's potential roles in supporting effective wound healing.

Artificial light at night suppresses the day-night cardiovascular variability: evidence from humans and rats

Artificial light at night (ALAN) affects most of the population. Through the retinohypothalamic tract, ALAN modulates the activity of the central circadian oscillator and, consequently, various physiological systems, including the cardiovascular one. We summarised the current knowledge about the effects of ALAN on the cardiovascular system in diurnal and nocturnal animals. Based on published data, ALAN reduces the day-night variability of the blood pressure and heart rate in diurnal and nocturnal animals by increasing the nocturnal values of cardiovascular variables in diurnal animals and decreasing them in nocturnal animals. The effects of ALAN on the cardiovascular system are mainly transmitted through the autonomic nervous system. ALAN is also considered a stress-inducing factor, as glucocorticoid and glucose level changes indicate. Moreover, in nocturnal rats, ALAN increases the pressure response to load. In addition, ALAN induces molecular changes in the heart and blood vessels. Changes in the cardiovascular system significantly depend on the duration of ALAN exposure. To some extent, alterations in physical activity can explain the changes observed in the cardiovascular system after ALAN exposure. Although ALAN acts differently on nocturnal and diurnal animals, we can conclude that both exhibit a weakened circadian coordination among physiological systems, which increases the risk of future cardiovascular complications and reduces the ability to anticipate stress.

Potential Neuroprotective Role of Melatonin in Sepsis-Associated Encephalopathy Due to Its Scavenging and Anti-Oxidative Properties

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. The brain is one of the organs involved in sepsis, and sepsis-induced brain injury manifests as sepsis-associated encephalopathy (SAE). SAE may be present in up to 70% of septic patients. SAE has a very wide spectrum of clinical symptoms, ranging from mild behavioral changes through cognitive disorders to disorders of consciousness and coma. The presence of SAE increases mortality in the population of septic patients and may lead to chronic cognitive dysfunction in sepsis survivors. Therefore, therapeutic interventions with neuroprotective effects in sepsis are needed. Melatonin, a neurohormone responsible for the control of circadian rhythms, exerts many beneficial physiological effects. Its anti-inflammatory and antioxidant properties are well described. It is considered a potential therapeutic factor in sepsis, with positive results from studies on animal models and with encouraging results from the first human clinical trials. With its antioxidant and anti-inflammatory potential, it may also exert a neuroprotective effect in sepsis-associated encephalopathy. The review presents data on melatonin as a potential drug in SAE in the wider context of the pathophysiology of SAE and the specific actions of the pineal neurohormone.

Melatonin as a Potential Approach to Anxiety Treatment

Anxiety disorders are the most common mental diseases. Anxiety and the associated physical symptoms may disturb social and occupational life and increase the risk of somatic diseases. The pathophysiology of anxiety development is complex and involves alterations in stress hormone production, neurosignaling pathways or free radical production. The various manifestations of anxiety, its complex pathophysiological background and the side effects of available treatments underlie the quest for constantly seeking therapies for these conditions. Melatonin, an indolamine produced in the pineal gland and released into the blood on a nightly basis, has been demonstrated to exert anxiolytic action in animal experiments and different clinical conditions. This hormone influences a number of physiological actions either via specific melatonin receptors or by receptor-independent pleiotropic effects. The underlying pathomechanism of melatonin's benefit in anxiety may reside in its sympatholytic action, interaction with the renin-angiotensin and glucocorticoid systems, modulation of interneuronal signaling and its extraordinary antioxidant and radical scavenging nature. Of importance, the concentration of this indolamine is significantly higher in cerebrospinal fluid than in the blood. Thus, ensuring sufficient melatonin production by reducing light pollution, which suppresses melatonin levels, may represent an endogenous neuroprotective and anxiolytic treatment. Since melatonin is freely available, economically undemanding and has limited side effects, it may be considered an additional or alternative treatment for various conditions associated with anxiety.