Eloisa Gitto

Actions of Melatonin in the Reduction of Oxidative Stress

Melatonin was discovered to be a direct free radical scavenger less than 10 years ago. Besides its ability to directly neutralize a number of free radicals and reactive oxygen and nitrogen species, it stimulates several antioxidative enzymes which increase its efficiency as an antioxidant. In terms of direct free radical scavenging, melatonin interacts with the highly toxic hydroxyl radical with a rate constant equivalent to that of other highly efficient hydroxyl radical scavengers. Additionally, melatonin reportedly neutralizes hydrogen peroxide, singlet oxygen, peroxynitrite anion, nitric oxide and hypochlorous acid. The following antioxidative enzymes are also stimulated by melatonin: superoxide dismutase, glutathione peroxidase and glutathione reductase. Melatonin has been widely used as a protective agent against a wide variety of processes and agents that damage tissues via free radical mechanisms.

Effects of Melatonin Treatment in Septic Newborns

Free radicals have been implicated in the pathogenesis of neonatal sepsis and its complications. This study was conducted to determine the changes in the clinical status and the serum levels of lipid peroxidation products [malondialdehyde (MDA) and 4-hydroxylalkenals (4-HDA)] in 10 septic newborns treated with the antioxidant melatonin given within the first 12 h after diagnosis. Ten other septic newborns in a comparable state were used as “septic” controls, while 10 healthy newborns served as normal controls. A total of 20 mg melatonin was administered orally in two doses of 10 mg each, with a 1-h interval. One blood sample was collected before melatonin administration and two additional blood samples (at 1 and 4 h) were collected after melatonin administration to assess serum levels of lipid peroxidation products. Serum MDA + 4-HDA concentrations in newborns with sepsis were significantly higher than those in healthy infants without sepsis; in contrast, in septic newborns treated with melatonin there was a significant reduction (p < 0.05) of MDA + 4-HDA to the levels in the normal controls at both 1 and 4 h (p < 0.05). Melatonin also improved the clinical outcome of the septic newborns as judged by measurement of sepsis-related serum parameters after 24 and 48 h. Three of 10 septic children who were not treated with melatonin died within 72 h after diagnosis of sepsis; none of the 10 septic newborns treated with melatonin died. To our knowledge, this is the first study where melatonin was given to human newborns.

Oxidative stress of the newborn in the pre- and postnatal period and the clinical utility of melatonin

Abstract:  Newborns, and especially those delivered preterm, are probably more prone to oxidative stress than individuals later in life. Also during pregnancy, increased oxygen demand augments the rate of production of reactive oxygen species (ROS) and women, even with normal pregnancies, experience elevated oxidative stress and lipid peroxidation compared with nonpregnant women. Also, there appears to be an increase in ROS generation in the placenta of pre‐eclamptic women. In comparison with healthy adults, newborn infants have lower levels of plasma antioxidants such as vitamin E, β‐carotene, and sulphydryl groups, lower levels of plasma metal binding proteins including ceruloplasmin and transferrin, and reduced activity of erythrocyte superoxide dismutase. This review summarizes conditions of newborns where there is elevated oxidative stress. Included in this group of conditions is asphyxia, respiratory distress syndrome and sepsis and the review also summarizes the literature related to clinical trials of antioxidant therapies and of melatonin, a highly effective antioxidant and free radical scavenger. The authors document there is general agreement that short‐term melatonin therapy may be highly effective and that it has a remarkably benign safety profile, even when neonates are treated with pharmacological doses. Significant complications with long‐term melatonin therapy in children and adults also have not been reported. None of the animal studies of maternal melatonin treatment or in postnatal life have shown any treatment‐related side effects. The authors conclude that treatment with melatonin might result in a wide range of health benefits, improved quality of life and reduced healthcare costs and may help reduce complications in the neonatal period.

Causes of Oxidative Stress in the Pre- and Perinatal Period

Oxidative stress may be defined as an imbalance between pro-oxidant and antioxidant forces resulting in an overall pro-oxidant insult. Pregnancy is a physiological state accompanied by a high energy demand of many bodily functions and an increased oxygen requirement. Because of the increased intake and utilization of oxygen, augmented levels of oxidative stress would be expected. Arguments for a role of oxidative stress/oxidative lipid derivatives in the pathogenesis of preeclampsia are documented in many papers and evidence continues to accumulate that oxidative stress is a mediator of endothelial dysfunction and thus contributes to the cardiovascular complications of preeclampsia. Also other conditions, such as toxic substance exposure, smoking and asphyxia likewise induce oxidative stress. The oxidized lipid products generated as a consequence of these conditions are highly reactive and cause damage to cells and cell membranes. Thus, increased oxidative stress accompanied by reduced endogenous defences may play a role in the pathogenesis of a number of diseases in the newborn.

Increased levels of malondialdehyde and nitrite/nitrate in the blood of asphyxiated newborns : reduction by melatonin

Free radicals have been implicated in the pathogenesis of neonatal asphyxia and its complications. This study measured a product of lipid peroxidation, malondialdehyde, and the nitrite/nitrate levels in the serum of 20 asphyxiated newborns before and after treatment with the antioxidant melatonin given within the first 6 hr of life. Ten asphyxiated newborns received a total of 80 mg of melatonin (8 doses of 10 mg each separated by 2‐hr intervals) orally. One blood sample was collected before melatonin administration and two additional blood samples (at 12 and 24 hr) were collected after giving melatonin. A third group of healthy newborn children served as controls. Serum malondialdehyde and nitrite+nitrate concentrations in newborns with asphyxia before treatment were significantly higher than those in infants without asphyxia. In the asphyxiated newborns given melatonin, there were significant reductions in malondialdehyde and nitrite/nitrate levels at both 12 and 24 hr. Three of the 10 asphyxiated children not given melatonin died within 72 hr after birth; none of the 10 asphyxiated newborns given melatonin died. The results indicate that the melatonin may be beneficial in the treatment of newborn infants with asphyxia. The protective actions of melatonin in this study may relate to the antioxidant properties of the indole as well as to the ability of melatonin to increase the efficiency of mitochondrial electron transport.

Oxidative Stress in Obesity: A Critical Component in Human Diseases

Obesity, a social problem worldwide, is characterized by an increase in body weight that results in excessive fat accumulation. Obesity is a major cause of morbidity and mortality and leads to several diseases, including metabolic syndrome, diabetes mellitus, cardiovascular, fatty liver diseases, and cancer. Growing evidence allows us to understand the critical role of adipose tissue in controlling the physic-pathological mechanisms of obesity and related comorbidities. Recently, adipose tissue, especially in the visceral compartment, has been considered not only as a simple energy depository tissue, but also as an active endocrine organ releasing a variety of biologically active molecules known as adipocytokines or adipokines. Based on the complex interplay between adipokines, obesity is also characterized by chronic low grade inflammation with permanently increased oxidative stress (OS). Over-expression of oxidative stress damages cellular structures together with under-production of anti-oxidant mechanisms, leading to the development of obesity-related complications. The aim of this review is to summarize what is known in the relationship between OS in obesity and obesity-related diseases.

Protective effects of melatonin in ischemic brain injury

Recent studies have demonstrated that melatonin is a scavenger of oxyradicals and peroxynitrite and an inhibitor of nitric oxide (NO) production. NO, peroxynitrite (formed from NO and superoxide anion), and poly (ADP‐Ribose) synthetase (PARS) have been implicated as mediators of neuronal damage following focal ischemia. In the present study, we have investigated the effects of melatonin treatment in Mongolian gerbils subjected to cerebral ischemia. Treatment of gerbils with melatonin (10 mg kg−1, 30 min before reperfusion and 1, 2, and 6 hr after reperfusion) reduced the formation of post‐ischemic brain edema, evaluated by water content. Melatonin also attenuated the increase in the brain levels malondialdehyde (MDA) and the increase in the hippocampus of myeloperoxidase (MPO) caused by cerebral ischemia. Positive staining for nitrotyrosine was found in the hippocampus of Mongolian gerbils subjected to cerebral ischemia. Hippocampus tissue sections, from Mongolian gerbils subjected to cerebral ischemia, also showed positive staining for PARS. The degrees of staining for nitrotyrosine and for PARS were markedly reduced in tissue sections obtained from animals that received melatonin. Melatonin treatment increased survival and reduced hyperactivity linked to neurodegeneration induced by cerebral ischemia and reperfusion. Histological observations of the pyramidal layer of CA‐1 showed a reduction of neuronal loss in animals that received melatonin. These results show that melatonin improves brain injury induced by transient cerebral ischemia.

Early indicators of chronic lung disease in preterm infants with respiratory distress syndrome and their inhibition by melatonin.

Abstract:  Improved survival from advances in neonatal care has resulted in an increased number of infants at risk for chronic lung disease (CLD). Recently, it was reported that inflammatory mediators such as interleukin (IL)‐1β, IL‐6, tumor necrosis factor (TNF)‐α and IL‐8 are present in higher concentrations in lung lavage from babies who develop CLD. Previously, we found that melatonin reduced the rises in proinflammatory cytokines (IL‐6, IL‐8 and TNF‐α) and nitrite/nitrate levels in the serum of preterm newborns with respiratory distress syndrome (RDS). The values correlated with gestational age and iatrogenic trauma in the form of oxygen exposure and mechanical ventilation. Increased concentrations of proinflammatory cytokines may, therefore, be the most valuable early indicator of developing CLD and these measurements may assist in selecting infants for interventions such as melatonin treatment or more selective blockage of components of inflammation. In the current study, we extend the original observations and report results in which 120 newborns diagnosed with RDS were either treated with melatonin (60 children) or given placebo (60 children). The cytokine measures were consistent with the previously reported findings and showed that melatonin reduced these values and also lowered nitrite/nitrate levels in serum of newborns with respiratory distress. Furthermore, when nonmelatonin‐treated newborns who developed CLD (eight infants) were examined separately, they had levels of IL‐6, IL‐8, TNF‐α and nitrite/nitrate values much higher than those in children who did not develop CLD. Two of the nonmelatonin‐treated newborns died while no children who received melatonin died. Melatonin was well tolerated by the newborns.

Effects of tempol, a membrane-permeable radical scavenger, in a gerbil model of brain injury.

There is evidence that the excessive generation of reactive-oxygen radicals contributes to the brain injury associated with transient, cerebral ischemia. This study investigates the effects of tempol, a small, water-soluble molecule, that crosses biological membranes, on the brain injury caused by bilateral occlusion and reperfusion of both common carotid arteries in the gerbil (BCO). Treatment of gerbils with tempol (30 mg/kg i.p. at 30 min prior to reperfusion and at 1 and 6 h after the onset of reperfusion) reduced the formation of post-ischemic brain oedema. Tempol also attenuated the increase in the cerebral levels of malondialdehyde (MDA) and the hippocampal levels of myeloperoxidase (MPO) caused by cerebral ischemia and reperfusion. The immunohistochemical analysis of the hippocampal region of brains subjected to ischemia-reperfusion exhibited positive staining for nitrotyrosine (an indicator of the generation of peroxynitrite) and poly(ADP-ribose) synthetase (PARS) (an indicator of the activation of this nuclear enzyme secondary to single strand breaks in DNA). In gerbils subjected to BCO, which were treated with tempol, the degree of staining for nitrotyrosine and PARS was markedly reduced. Tempol increased survival and reduced the hyperactivity (secondary to the ischemia-induced neurodegeneration) caused by cerebral ischemia and reperfusion. The loss of neurons from the pyramidal layer of the CA1 region caused by ischemia and reperfusion was also attenuated by treatment of gerbils with tempol. This is the first evidence that the membrane-permeable, radical scavenger tempol reduces the cerebral injury caused by transient, cerebral ischemia in vivo.

Correlation among cytokines, bronchopulmonary dysplasia and modality of ventilation in preterm newborns: improvement with melatonin treatment.

Abstract:  Improved survival because of advances in neonatal care has resulted in an increased number of infants at risk for chronic lung disease. Even though the etiology of lung injury is multifactorial, recent animal and clinical data indicate that pulmonary damage depends in large part on the ventilatory strategies used. Ventilator‐associated lung injury was believed to result from the use of high pressure, thus, the term barotraumas. This trauma is believed to involve free‐radical damage. Oxidant injury is a serious cause of lung injury. In the present study, 110 newborns with respiratory distress syndrome were studied; 55 were treated with melatonin and the other 55 with placebo. All the subjects were mechanically ventilated with or without guaranteed volume. Proinflammatory cytokines [interleukin (IL)‐6, IL‐8 and tumor necrosis factor (TNF)‐α] were measured in tracheobronchial aspirate and the clinical outcome was evaluated. Melatonin treatment reduced the proinflammatory cytokines and improved the clinical outcome. The beneficial action of melatonin presumably related to its antioxidative actions.