The antioxidant behaviour of melatonin and structural analogues during lipid peroxidation depends not only on their functional groups but also on the assay system

Melatonin and the Brain-Heart Crosstalk in Neurocritically Ill Patients-From Molecular Action to Clinical Practice

Brain injury, especially traumatic brain injury (TBI), may induce severe dysfunction of extracerebral organs. Cardiac dysfunction associated with TBI is common and well known as the brain-heart crosstalk, which broadly refers to different cardiac disorders such as cardiac arrhythmias, ischemia, hemodynamic insufficiency, and sudden cardiac death, which corresponds to acute disorders of brain function. TBI-related cardiac dysfunction can both worsen the brain damage and increase the risk of death. TBI-related cardiac disorders have been mainly treated symptomatically. However, the analysis of pathomechanisms of TBI-related cardiac dysfunction has highlighted an important role of melatonin in the prevention and treatment of such disorders. Melatonin is a neurohormone released by the pineal gland. It plays a crucial role in the coordination of the circadian rhythm. Additionally, melatonin possesses strong anti-inflammatory, antioxidative, and antiapoptotic properties and can modulate sympathetic and parasympathetic activities. Melatonin has a protective effect not only on the brain, by attenuating its injury, but on extracranial organs, including the heart. The aim of this study was to analyze the molecular activity of melatonin in terms of TBI-related cardiac disorders. Our article describes the benefits resulting from using melatonin as an adjuvant in protection and treatment of brain injury-induced cardiac dysfunction.

Isobornylchalcones as Scaffold for the Synthesis of Diarylpyrazolines with Antioxidant Activity

The pyrazoline ring is defined as a "privileged structure" in medicinal chemistry. A variety of pharmacological properties of pyrazolines is associated with the nature and position of various substituents, which is especially evident in diarylpyrazolines. Compounds with a chalcone fragment show a wide range of biological properties as well as high reactivity which is primarily due to the presence of an α, β-unsaturated carbonyl system. At the same time, bicyclic monoterpenoids deserve special attention as a source of a key structural block or as one of the pharmacophore components of biologically active molecules. A series of new diarylpyrazoline derivatives based on isobornylchalcones with different substitutes (MeO, Hal, NO2, N(Me)2) was synthesized. Antioxidant properties of the obtained compounds were comparatively evaluated using in vitro model Fe2+/ascorbate-initiated lipid peroxidation in the substrate containing brain lipids of laboratory mice. It was demonstrated that the combination of the electron-donating group in the para-position of ring B and OH-group in the ring A in the structure of chalcone fragment provides significant antioxidant activity of synthesized diarylpyrazoline derivatives.

Melatonin and its metabolites vs oxidative stress: From individual actions to collective protection

Oxidative stress (OS) represents a threat to the chemical integrity of biomolecules including lipids, proteins, and DNA. The associated molecular damage frequently results in serious health issues, which justifies our concern about this phenomenon. In addition to enzymatic defense mechanisms, there are compounds (usually referred to as antioxidants) that offer chemical protection against oxidative events. Among them, melatonin and its metabolites constitute a particularly efficient chemical family. They offer protection against OS as individual chemical entities through a wide variety of mechanisms including electron transfer, hydrogen transfer, radical adduct formation, and metal chelation, and by repairing biological targets. In fact, many of them including melatonin can be classified as multipurpose antioxidants. However, what seems to be unique to the melatonin's family is their collective effects. Because the members of this family are metabolically related, most of them are expected to be present in living organisms wherever melatonin is produced. Therefore, the protection exerted by melatonin against OS may be viewed as a result of the combined antioxidant effects of the parent molecule and its metabolites. Melatonin's family is rather exceptional in this regard, offering versatile and collective antioxidant protection against OS. It certainly seems that melatonin is one of the best nature's defenses against oxidative damage.

Phenolic Melatonin-Related Compounds: Their Role as Chemical Protectors against Oxidative Stress

There is currently no doubt about the serious threat that oxidative stress (OS) poses to human health. Therefore, a crucial strategy to maintain a good health status is to identify molecules capable of offering protection against OS through chemical routes. Based on the known efficiency of the phenolic and melatonin (MLT) families of compounds as antioxidants, it is logical to assume that phenolic MLT-related compounds should be (at least) equally efficient. Unfortunately, they have been less investigated than phenols, MLT and its non-phenolic metabolites in this context. The evidence reviewed here strongly suggests that MLT phenolic derivatives can act as both primary and secondary antioxidants, exerting their protection through diverse chemical routes. They all seem to be better free radical scavengers than MLT and Trolox, while some of them also surpass ascorbic acid and resveratrol. However, there are still many aspects that deserve further investigations for this kind of compounds.

N-acetyl-serotonin protects HepG2 cells from oxidative stress injury induced by hydrogen peroxide

Oxidative stress plays an important role in the pathogenesis of liver diseases. N-Acetyl-serotonin (NAS) has been reported to protect against oxidative damage, though the mechanisms by which NAS protects hepatocytes from oxidative stress remain unknown. To determine whether pretreatment with NAS could reduce hydrogen peroxide- (H₂O₂-) induced oxidative stress in HepG2 cells by inhibiting the mitochondrial apoptosis pathway, we investigated the H₂O₂-induced oxidative damage to HepG2 cells with or without NAS using MTT, Hoechst 33342, rhodamine 123, Terminal dUTP Nick End Labeling Assay (TUNEL), dihydrodichlorofluorescein (H2DCF), Annexin V and propidium iodide (PI) double staining, immunocytochemistry, and western blot. H₂O₂ produced dramatic injuries in HepG2 cells, represented by classical morphological changes of apoptosis, increased levels of malondialdehyde (MDA) and intracellular reactive oxygen species (ROS), decreased activity of superoxide dismutase (SOD), and increased activities of caspase-9 and caspase-3, release of cytochrome c (Cyt-C) and apoptosis-inducing factor (AIF) from mitochondria, and loss of membrane potential (ΔΨ_m). NAS significantly inhibited H₂O₂-induced changes, indicating that it protected against H₂O₂-induced oxidative damage by reducing MDA levels and increasing SOD activity and that it protected the HepG2 cells from apoptosis through regulating the mitochondrial apoptosis pathway, involving inhibition of mitochondrial hyperpolarization, release of mitochondrial apoptogenic factors, and caspase activity.

The role of the sympathetic nervous system in the resuscitative effect of stimulating the central serotonin 1A receptors in haemorrhagic shock in rats

Haemorrhagic shock is a life threatening condition, and, as such, it is important to understand the mechanisms taking part in its reversal. In the 1990s, it was shown that activation of serotonin 1A receptors is responsible for the circulatory decompensation and development of the sympathoinhibitory phase. In previous reports, it was demonstrated that activation of serotonin 1A receptors induces resuscitative effects in haemorrhaged rats. However, the effectory mechanisms still require further investigation. The aim of the present study was to determine whether the sympathetic nervous system participates in the effects of serotonin through central serotonin 1A receptors in haemorrhagic shock in rats. In order to determine the role of the sympathetic nervous system alpha-1-, alpha-2-, and beta-adrenergic receptor agonists - prazosin, yohimbine and propranolol, respectively, were used. We found that stimulation of the central serotonin 1A receptors by the administration of a selective agonist - 8-hydroxy-2-(di-n-propylamino)tetralin, 1-(2,5-dimethoxy-4-iodophenyl)-aminopropane (8-OH-DPAT) into the lateral brain ventricle is connected with the activation of compensation mechanisms leading to the increase in the heart rate and blood pressure. The current results demonstrate that the stimulation of peripheral alpha-1-, alpha-2- and beta-adrenergic receptors plays an essential role in the resuscitative effect triggered by the stimulation of central serotonin 1A receptors.

Metabolism of salvianolic acid A and antioxidant activities of its methylated metabolites

This study investigated the metabolism of salvianolic acid A (SAA) both in vivo and in vitro. Liquid chromatography-mass spectrometry analysis of drug-containing rat bile samples and bile samples hydrolyzed by glucuronidase revealed a series of methylated conjugates of SAA and its glucuronides, as well as the predominance of the methylation pathway of SAA in rats. For the first time, four major methylated metabolites present in vivo were prepared for structure characterization and bioactivity evaluation using in vitro coincubation systems with rat hepatic cytosol protein as the enzyme donor. By using nuclear magnetic resonance imaging and other spectroscopic methods, these metabolites were unambiguously elucidated as 3-O-methyl-SAA (M1), 3'-O-methyl-SAA (M2), 3,3″-O-dimethyl-SAA (M3), and 3',3″-O-dimethyl-SAA (M4), respectively. Along with results from the enzyme inhibition study, selective formation of these meta-O-methylated derivatives indicated that catechol O-methyltransferase (COMT) is responsible for methylated transformation of SAA. All of these metabolites displayed fairly high antioxidant potency against in vitro rat liver lipid peroxidation with half-maximal inhibitory concentrations that were much lower than those of the positive controls and even SAA. Overall, the results from this study demonstrate that SAA is a metabolically unstable compound that undergoes rapid methylation metabolism catalyzed by COMT, and these generated O-methylated metabolites may be largely responsible for its in vivo pharmacological effects.

Protective effect of N-acetylserotonin against acute hepatic ischemia-reperfusion injury in mice

The purpose of this study was to investigate the possible protective effect of N-acetylserotonin (NAS) against acute hepatic ischemia-reperfusion (I/R) injury in mice. Adult male mice were randomly divided into three groups: sham, I/R, and I/R + NAS. The hepatic I/R injury model was generated by clamping the hepatic artery, portal vein, and common bile duct with a microvascular bulldog clamp for 30 min, and then removing the clamp and allowing reperfusion for 6 h. Morphologic changes and hepatocyte apoptosis were evaluated by hematoxylin-eosin (HE) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, respectively. Activated caspase-3 expression was evaluated by immunohistochemistry and Western blot. The activation of aspartate aminotransferase (AST), malondialdehyde (MDA), and superoxide dismutase (SOD) was evaluated by enzyme-linked immunosorbent assay (ELISA). The data show that NAS rescued hepatocyte morphological damage and dysfunction, decreased the number of apoptotic hepatocytes, and reduced caspase-3 activation. Our work demonstrates that NAS ameliorates hepatic IR injury.