Melatonin and mitochondrial function

Melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in leukocytes from elderly humans

The mechanisms regulating neutrophil apoptosis are basically unaffected by the aging process. However, a significant impairment of cell survival occurs in elderly individuals following neutrophil challenge with pro-inflammatory stimuli, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). The goal of the present study was to prove the effects of melatonin supplementation on apoptosis induced by calcium signaling in human leukocytes from elderly volunteers. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin, and/or the calcium mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (fMLP), induced mitochondrial membrane depolarization, caspase activation, phosphatidylserine (PS) externalization, and DNA fragmentation in leukocytes from both young and elderly volunteers, although such effects were much more evident in aged leukocytes. Importantly, melatonin treatment substantially preserved mitochondrial membrane potential, reversed caspase activation, reduced PS exposure and forestalled DNA fragmentation in leukocytes from both age groups. In conclusion, melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in aged leukocytes and may counteract, at the cellular level, age-related degenerative phenomena linked to oxidative stress.

Synergism between melatonin and atorvastatin against endothelial cell damage induced by lipopolysaccharide

The beneficial effects of atorvastatin are based on both cholesterol-dependent and independent mechanisms. The latter probably include the ability of the estatin to enhance the expression of endothelial nitric oxide synthase (eNOS) and to cause a vasodilatation. In turn, the antioxidant and anti-inflammatory actions of melatonin are related to its vascular protection. In the present study, we investigated the efficacy of the combination of melatonin plus atorvastatin against endothelial cell damage induced by inflammation and oxidative stress injury. Human umbilical vein endothelial cells (HUVEC) were cultured with bacterial lipopolysaccharide (LPS) in the presence or absence of melatonin and/or atorvastatin. LPS inhibited eNOS mRNA and protein expression, which was reversed by atorvastatin and, to a lesser extent, by melatonin. Together, melatonin + atorvastatin induced higher eNOS protein expression than either compound alone. Melatonin, but not atorvastatin, reduced free radical generation, lipid peroxidation, and interleukin-6 levels induced by LPS. In the presence of atorvastatin, the effects of melatonin were maintained or even improved. These data suggest that melatonin improves the beneficial effects of atorvastatin and reduces its side effects in endothelial cells during inflammation and under conditions of oxidative stress.

Melatonin as a natural ally against oxidative stress: a physicochemical examination

Oxidative stress has been proven to be related to the onset of a large number of health disorders. This chemical stress is triggered by an excess of free radicals, which are generated in cells because of a wide variety of exogenous and endogenous processes. Therefore, finding strategies for efficiently detoxifying free radicals has become a subject of a great interest, from both an academic and practical points of view. Melatonin is a ubiquitous and versatile molecule that exhibits most of the desirable characteristics of a good antioxidant. The amount of data gathered so far regarding the protective action of melatonin against oxidative stress is overwhelming. However, rather little is known concerning the chemical mechanisms involved in this activity. This review summarizes the current progress in understanding the physicochemical insights related to the free radical-scavenging activity of melatonin. Thus far, there is a general agreement that electron transfer and hydrogen transfer are the main mechanisms involved in the reactions of melatonin with free radicals. However, the relative importance of other mechanisms is also analyzed. The chemical nature of the reacting free radical also has an influence on the relative importance of the different mechanisms of these reactions. Therefore, this point has also been discussed in detail in the current review. Based on the available data, it is concluded that melatonin efficiently protects against oxidative stress by a variety of mechanisms. Moreover, it is proposed that even though it has been referred to as the chemical expression of darkness, perhaps it could also be referred to as the chemical light of health.

Protective effects of melatonin against oxidative stress in flow cytometry-sorted buffalo sperm

Previous reports of the ability of melatonin to scavenge a variety of toxic oxygen and nitrogen-based reactants suggest that melatonin could be an effective antioxidant for protecting sperm. In this study, flow cytometry and laser tweezers Raman spectroscopy were used to evaluate the effect of melatonin on buffalo sperm quality to optimize sperm sex-sorting procedures. In fresh sperm incubated in the presence or absence of melatonin (10(-4)  m) for 1, 24, 48 h or 72 h at 27°C, the mitochondrial activity was significantly higher than in a non-melatonin control (p < 0.05). Also, during the flow-sorting process, sperm in melatonin-supplemented groups had higher (p < 0.05) mitochondrial activity than the control. The intensity of Raman spectra from sperm frozen in media supplemented with melatonin was significantly weaker than that for non-melatonin-treated groups, except for a band at 1302 per cm. Thus, melatonin helps to protect buffalo sperm from reactive oxygen species induced by staining, sorting and freezing and increases semen quality after the freezing-thawing processes. Furthermore, the results indicate the high potential of the laser tweezers Raman spectroscopy technique for rapid, effective and non-invasive assessment of the quality of sperm cells.

Melatonin combats molecular terrorism at the mitochondrial level

The intracellular environmental is a hostile one. Free radicals and related oxygen and nitrogen-based oxidizing agents persistently pulverize and damage molecules in the vicinity of where they are formed. The mitochondria especially are subjected to frequent and abundant oxidative abuse. The carnage that is left in the wake of these oxygen and nitrogen-related reactants is referred to as oxidative damage or oxidative stress. When mitochondrial electron transport complex inhibitors are used, e.g., rotenone, 1-methyl-1-phenyl-1,2,3,6-tetrahydropyridine, 3-nitropropionic acid or cyanide, pandemonium breaks loose within mitochondria as electron leakage leads to the generation of massive amounts of free radicals and related toxicants. The resulting oxidative stress initiates a series of events that leads to cellular apoptosis. To alleviate mitochondrial destruction and the associated cellular implosion, the cell has at its disposal a variety of free radical scavengers and antioxidants. Among these are melatonin and its metabolites. While melatonin stimulates several antioxidative enzymes it, as well as its metabolites (cyclic 3-hydroxymelatonin, N¹-acetyl-N²-formyl-5-methoxykynuramine and N¹-acetyl-5-methoxykynuramine), likewise effectively neutralize free radicals. The resulting cascade of reactions greatly magnifies melatonin's efficacy in reducing oxidative stress and apoptosis even in the presence of mitochondrial electron transport inhibitors. The actions of melatonin at the mitochondrial level are a consequence of melatonin and/or any of its metabolites. Thus, the molecular terrorism meted out by reactive oxygen and nitrogen species is held in check by melatonin and its derivatives.

Canolol: a promising chemical agent against oxidative stress

The OOH radical scavenging activity of canolol (CNL) has been studied in aqueous and lipid solutions, using the density functional theory. CNL is predicted to react about 3.6 times faster in aqueous solution than in lipid media. The overall rate coefficients are predicted to be 2.5 × 10(6) and 6.8 × 10(5) M(-1) s(-1), respectively. The OOH radical scavenger activity of canolol is predicted to be similar to that of carotenes, higher than that of allicin, and much higher than that of melatonin. Branching ratios for the different channels of reaction are reported for the first time. It was found that the reactivity of canolol toward OOH radicals takes place almost exclusively by H atom transfer from the phenolic moiety in canolol, regardless of the polarity of the environment. Taking into account that the reactivity of peroxyl radicals is significantly lower than that of other reactive oxygen species, canolol is proposed to be a very good antioxidant.

Reactive oxygen species in the regulation of synaptic plasticity and memory

The brain is a metabolically active organ exhibiting high oxygen consumption and robust production of reactive oxygen species (ROS). The large amounts of ROS are kept in check by an elaborate network of antioxidants, which sometimes fail and lead to neuronal oxidative stress. Thus, ROS are typically categorized as neurotoxic molecules and typically exert their detrimental effects via oxidation of essential macromolecules such as enzymes and cytoskeletal proteins. Most importantly, excessive ROS are associated with decreased performance in cognitive function. However, at physiological concentrations, ROS are involved in functional changes necessary for synaptic plasticity and hence, for normal cognitive function. The fine line of role reversal of ROS from good molecules to bad molecules is far from being fully understood. This review focuses on identifying the multiple sources of ROS in the mammalian nervous system and on presenting evidence for the critical and essential role of ROS in synaptic plasticity and memory. The review also shows that the inability to restrain either age- or pathology-related increases in ROS levels leads to opposite, detrimental effects that are involved in impairments in synaptic plasticity and memory function.

Potential utility of melatonin as an antioxidant during pregnancy and in the perinatal period

Reactive oxygen species (ROS) play a critical role in the pathogenesis of various diseases during pregnancy and the perinatal period. Newborns are more prone to oxidative stress than individuals later in life. During pregnancy, increased oxygen demand augments the rate of production of ROS and women, even during normal pregnancies, experience elevated oxidative stress compared with non-pregnant women. ROS generation is also increased in the placenta during preeclampsia. Melatonin is a highly effective direct free-radical scavenger, indirect antioxidant, and cytoprotective agent in human pregnancy and it appears to be essential for successful pregnancy. This suggests a role for melatonin in human reproduction and in neonatal pathologies (asphyxia, respiratory distress syndrome, sepsis, etc.). This review summarizes current knowledge concerning the role for melatonin in human pregnancy and in the newborn. Numerous studies agree that short-term melatonin therapy is highly effective in reducing complications during pregnancy and in the neonatal period. No significant toxicity or treatment-related side effects with long-term melatonin therapy in children and adults have been reported. Treatment with melatonin might result in a wide range of health benefits, including improved quality of life and reduced healthcare costs.

Melatonin in mitochondrial dysfunction and related disorders

Mitochondrial dysfunction is considered one of the major causative factors in the aging process, ischemia/reperfusion (I/R), septic shock, and neurodegenerative disorders like Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). Increased free radical generation, enhanced mitochondrial inducible nitric oxide (NO) synthase activity, enhanced NO production, decreased respiratory complex activity, impaired electron transport system, and opening of mitochondrial permeability transition pore all have been suggested as factors responsible for impaired mitochondrial function. Melatonin, the major hormone of the pineal gland, also acts as an antioxidant and as a regulator of mitochondrial bioenergetic function. Both in vitro and in vivo, melatonin was effective for preventing oxidative stress/nitrosative stress-induced mitochondrial dysfunction seen in experimental models of PD, AD, and HD. In addition, melatonin is known to retard aging and to inhibit the lethal effects of septic shock or I/R lesions by maintaining respiratory complex activities, electron transport chain, and ATP production in mitochondria. Melatonin is selectively taken up by mitochondrial membranes, a function not shared by other antioxidants. Melatonin has thus emerged as a major potential therapeutic tool for treating neurodegenerative disorders such as PD or AD, and for preventing the lethal effects of septic shock or I/R.

Critical diaphragm failure in sudden infant death syndrome

Sudden infant death syndrome (SIDS) is the leading cause of death in infants between the ages of 1 and 12 months in developed countries. SIDS is by definition a diagnosis of exclusion, and its mechanism of action is unknown. The SIDS-Critical Diaphragm Failure (CDF) hypothesis postulates that the cause of death in SIDS is respiratory failure caused by CDF. Four principal risk factors contribute to CDF in young infants: undeveloped respiratory muscles, non-lethal infections, prone resting position, and REM sleep. Even relatively minor infections can cause an acute and significant reduction in diaphragm force generation capacity that in conjunction with other risk factors can precipitate CDF. CDF-induced acute muscle weakness leaves few, if any pathological marks on the affected tissue.Understanding the underlying mechanism of SIDS may help in formulating new approaches to child care that can help to further reduce the incidence of SIDS.

Melatonin induces neural SOD2 expression independent of the NF-kappaB pathway and improves the mitochondrial population and function in old mice

Aging is commonly defined as a physiological phenomenon associated with morphological and functional deleterious changes in which oxidative stress has a fundamental impact; therefore, readjusting the oxidative balance should have beneficial effects. In our study, we tested the antioxidant melatonin in old mouse brains and showed positive effects at the cellular and mitochondrial levels. Melatonin attenuated β-amyloid protein expression and α-synuclein deposits in the brain compared to aged group. Furthermore, oxidative stress was increased by aging and induced the nuclear translocation of nuclear factor-kappa B (NF-κB), which was suppressed by melatonin treatment. The antioxidant mitochondrial expression, superoxide dismutase 2 (SOD2), was increased in both control and melatonin-treated old mice, despite the different activation states of the NF-κB pathway. The NF-κB pathway was activated in the old mice, which may be explained by this group's response to the increased oxidative insult; this insult was inhibited in melatonin-treated animals, showing this group an increase in active mitochondria population that was not observed in old group. We also report that melatonin is capable of restoring the mitochondrial potential of age-damaged neurons. In conclusion, melatonin's beneficial effects on brain aging are linked to the increase in mitochondrial membrane potential and SOD2 expression, which probably reduces the mitochondrial contribution to the oxidative stress imbalance.

Update on the use of melatonin in pediatrics

Melatonin, an endogenously produced indoleamine, is a highly effective antioxidant, free radical scavenger, and a primary circadian regulator. Melatonin has important antioxidant properties owing to direct and indirect effects. It directly scavenges reactive oxygen and reactive nitrogen species, prevents molecular oxidation, improves mitochondrial physiology, and restores glutathione homeostasis. Its indirect antioxidant effects stem from its ability to stimulate the activities of the enzymes involved in the glutathione cycling and production. Melatonin, by reducing free radical damage, may be an effective protective agent for the fetus as it is in adults. Several clinical studies on melatonin have shown that it reduces oxidative stress in human newborns with sepsis, hypoxic distress, or other conditions, where there is excessive free radical generation. A role of melatonin in infant development has also been suggested. Pineal dysfunction may be associated with deleterious outcomes in infants and may contribute to an increased prevalence of sudden infant death syndrome. Delayed melatonin production is evident in infants who had experienced an apparent life-threatening event. Melatonin has been used as a pharmacologic treatment for insomnias associated with shift work, jet lag, and delayed sleep onset in adults for decades. In children as well, melatonin has value as a sleep-promoting agent. Evidence suggests that melatonin has utility as an analgesic agent presumably related to its ability to release β-endorphin. The data support the notion that melatonin, or one of its analogs, might find use as an anesthetic agent in children.

The effect of melatonin against FK506-induced renal oxidative stress in rats

BACKGROUND

Nephrotoxicity is an important side effect of FK506 and oxidative stress has been considered as one of the possible mechanisms. The present investigation examines the ability of melatonin to protect against FK506-induced renal oxidative stress.

METHODS

Thirty rats were divided into 3 groups (n = 10 each group). Group A was the sham group. Group B received 14 days FK506 (5 mg/kg/d, intraperitoneally [i.p.]) and group C received FK506 (5 mg/kg/d, i.p.) together with melatonin (4 mg/kg, i.p.) for 14 days. Kidney tissues were harvested to determine the tissue levels of malondialdehyde (MDA), total nitrite and nitric oxide (NO), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6).

RESULTS

In group C, the levels of TNF-α, IL-6, and NO were lower than in the group B (P < .01, P < .03, and P < .04, respectively) and although MDA levels were lower than in group B, the differences were not statistically significant (P > .05).

CONCLUSION

These results suggest that melatonin has protective effect against FK506-induced renal oxidative stress.

Melatonin, cardiolipin and mitochondrial bioenergetics in health and disease

Melatonin is a natural occurring compound with well-known antioxidant properties. Melatonin is ubiquitously distributed and because of its small size and amphiphilic nature, it is able to reach easily all cellular and subcellular compartments. The highest intracellular melatonin concentrations are found in mitochondria, raising the possibility of functional significance for this targeting with involvement in situ in mitochondrial activities. Mitochondria, the powerhouse of the cell, are considered to be the most important cellular organelles to contribute to degenerative processes mainly through respiratory chain dysfunction and formation of reactive oxygen species, leading to damage to mitochondrial proteins, lipids and DNA. Therefore, protecting mitochondria from oxidative damage could be an effective therapeutic strategy against cellular degenerative processes. Many of the beneficial effects of melatonin administration may depend on its effect on mitochondrial physiology. Cardiolipin, a phospholipid located at the level of inner mitochondrial membrane is known to be intimately involved in several mitochondrial bioenergetic processes as well as in mitochondrial-dependent steps of apoptosis. Alterations to cardiolipin structure, content and acyl chain composition have been associated with mitochondrial dysfunction in multiple tissues in several physiopathological situations and aging. Recently, melatonin was reported to protect the mitochondria from oxidative damage by preventing cardiolipin oxidation and this may explain, at least in part, the beneficial effect of this molecule in mitochondrial physiopathology. In this review, we discuss the role of melatonin in preventing mitochondrial dysfunction and disease.

Melatonin as a therapeutic tool in ophthalmology: implications for glaucoma and uveitis

Several lines of evidence support the view that increased free radical generation and altered nitric oxide (NO) metabolism play a role in the pathogenesis of highly prevalent ocular diseases, such as glaucoma and uveitis. Data are discussed indicating that melatonin, being an efficient antioxidant that displays antinitridergic properties, has a promising role in the treatment of these ocular dysfunctions. Melatonin synthesis occurs in the eye of most species, and melatonin receptors are localized in different ocular structures. In view of the fact that melatonin lacks significant adverse collateral effects even at high doses, the application of melatonin could potentially protect ocular tissues by effectively scavenging free radicals and excessive amounts of NO generated in the glaucomatous or uveitic eye.

The protective effect of melatonin on methamphetamine-induced calpain-dependent death pathway in human neuroblastoma SH-SY5Y cultured cells

Methamphetamine (METH) is a potent psychostimulant drug that may cause neuronal cell degeneration. The underlying mechanisms of METH-induced neuronal toxicity remains poorly understood. In this study, we investigated an important role of calpain-dependent cascades in methamphetamine-induced toxicity in human dopaminergic neuroblastoma SH-SY5Y cultured cell lines. In addition, the protective effect of melatonin against METH-induced calpain-dependent death pathway was also investigated. The results of this study show that METH significantly decreased cell viability and tyrosine hydroxylase phosphorylation in SH-SY5Y cultured cells. Melatonin reversed the toxic effect of METH by inducing cell viability. In addition, melatonin was able to restore the reduction in mitochondrial function and phosphorylation of tyrosine hydroxylase in SH-SY5Y treated cells. An induction of calpain expression and activity but a reduction of calpain inhibitor (calpastatin) protein levels were observed in SH-SY5Y cells treated with METH but these effects were diminished by melatonin. These results implicated calpain-dependent death pathways in the processes of METH-induced toxicity and also indicated that melatonin has the capacity to reverse this toxic effect in SH-SY5Y cultured cells.

Differential effects of melatonin on amyloid-beta peptide 25-35-induced mitochondrial dysfunction in hippocampal neurons at different stages of culture

beta-Amyloid (Abeta) is strongly involved in the pathogenesis of Alzheimer's disease (AD), and mitochondria play an important role in neurodegenerative disorders. To determine whether any different effect of melatonin on cultured neurons treated with Abeta in vitro and which may be produced through its different action on mitochondria at different stages of culture, we investigated the damage of cultured rat hippocampal neurons mitochondrial function induced by Abeta in young neurons [days in vitro 10 (DIV 10)] and senescent neurons (DIV 25) and the protective effect of melatonin. Rat hippocampal neurons were incubated with amyloid-beta peptide 25-35 (Abeta25-35) alone or pretreatment with melatonin. Cell viability, mitochondrial membrane potential (Deltapsim), ATP and the activity of the respiratory chain complexes were measured. Data showed that Abeta25-35 caused a reduction in Deltapsim, inhibited the activity of the respiratory chain complexes and led to ATP depletion, melatonin attenuated Abeta25-35-induced mitochondrial impairment in young neurons, whereas melatonin had no effect on Abeta25-35-induced mitochondrial damage in senescent neurons. These results demonstrate that melatonin has differential effect on Abeta25-35-induced mitochondrial dysfunction at different stages of culture and suggest that melatonin is useful for the prevention of AD, rather than treatment.

Bladder dysfunction in a new mutant mouse model with increased superoxide--lack of nitric oxide?

PURPOSE

Nitric oxide mediates urethral smooth muscle relaxation and may also be involved in detrusor activity control. Mice with mutation in the Immp2l gene have high superoxide ion levels and a consequent decrease in the bioavailable amount of nitric oxide. We studied bladder function in this mouse model.

MATERIAL AND METHODS

Young male mutants at ages 4 to 6 months, old female mutants at age 18 months and healthy WT age matched controls were used. The detrusor contractile response to carbachol and electrical field stimulation was tested in isolated detrusor strips in organ baths. In vivo bladder function was evaluated by cystometry in conscious animals.

RESULTS

Young male mutants had significantly lower micturition and higher post-void residual volume than WT controls. They had pronounced voiding difficulty and strained when initiating micturition. Detrusor contractile responses to carbachol and electrical field stimulation were similar in mutant and WT mice. Old female mutant mice had lower bladder capacity and micturition volume, and higher micturition frequency and bladder-to-body weight ratio than WT controls. In the in vitro study detrusor strips from mutants showed a lower maximum response to carbachol.

CONCLUSIONS

Mice with mutation in the Immp2l gene have bladder dysfunction, mainly characterized by emptying abnormalities in young males and increased detrusor activity in old females. Detrusor function was preserved in young males and impaired in old females. These animals are a natural model of oxidative stress with low bioavailable nitric oxide. Thus, they are interesting tools in which to evaluate the role of these conditions on bladder dysfunction.

Treatment of mitochondrial disorders

Treatment of mitochondrial disorders (MIDs) is a challenge since there is only symptomatic therapy available and since only few randomized and controlled studies have been carried out, which demonstrate an effect of some of the symptomatic or supportive measures available. Symptomatic treatment of MIDs is based on mainstay drugs, blood transfusions, hemodialysis, invasive measures, surgery, dietary measures, and physiotherapy. Drug treatment may be classified as specific (treatment of epilepsy, headache, dementia, dystonia, extrapyramidal symptoms, Parkinson syndrome, stroke-like episodes, or non-neurological manifestations), non-specific (antioxidants, electron donors/acceptors, alternative energy sources, cofactors), or restrictive (avoidance of drugs known to be toxic for mitochondrial functions). Drugs which more frequently than in the general population cause side effects in MID patients include steroids, propofol, statins, fibrates, neuroleptics, and anti-retroviral agents. Invasive measures include implantation of a pacemaker, biventricular pacemaker, or implantable cardioverter defibrillator, or stent therapy. Dietary measures can be offered for diabetes, hyperlipidemia, or epilepsy (ketogenic diet, anaplerotic diet). Treatment should be individualized because of the peculiarities of mitochondrial genetics. Despite limited possibilities, symptomatic treatment should be offered to MID patients, since it can have a significant impact on the course and outcome.

Improving the effect of incubation and oxidative stress on thawed spermatozoa from red deer by using different antioxidant treatments

Antioxidants could improve sperm media, extending the viability of spermatozoa and protecting their DNA. The protective ability of lipoic acid, melatonin, Trolox and crocin was tested on red deer spermatozoa incubated at 37°C. Cryopreserved spermatozoa were thawed and incubated with 1 mM or 0.1 mM of each antioxidant, with or without oxidative stress (100 μM Fe2+). Motility (CASA), viability, mitochondrial membrane potential and acrosomal status were assessed. Lipoperoxidation (malondialdehyde production), intracellular reactive oxygen species (ROS) and DNA status (TUNEL) were checked at 4 h. Incubation alone increased ROS and decreased motility. Oxidative stress intensified these effects, increasing lipoperoxidation and DNA damage. Lipoic acid had little protective effect, whereas 1 mM melatonin showed limited protection. Trolox lowered ROS and lipoperoxidation both in oxidised and non-oxidised samples. In oxidised samples, Trolox prevented DNA and acrosomal damage, and ameliorated motility. Crocin at 1 mM showed similar results to Trolox, but noticeably stimulated motility and had no effect on lipoperoxidation. In a second experiment, a broader range of crocin and melatonin concentrations were tested, confirming the effects of crocin (positive effects noticeable at 0.5–0.75 mM), but showing an increase in lipoperoxidation at 2 mM. Melatonin was increasingly effective at 2.5 and 5 mM (ROS, lipoperoxidation and DNA status). Crocin seems a promising new antioxidant, but its particular effects on sperm physiology must be further studied, especially the consequences of motility stimulation and confirming its effect on lipoperoxidation. Melatonin might be useful at relatively high concentrations, compared to Trolox.

Mitochondria, oxidative stress, and temporal lobe epilepsy

Mitochondrial oxidative stress and dysfunction are contributing factors to various neurological disorders. Recently, there has been increasing evidence supporting the association between mitochondrial oxidative stress and epilepsy. Although certain inherited epilepsies are associated with mitochondrial dysfunction, little is known about its role in acquired epilepsies such as temporal lobe epilepsy (TLE). Mitochondrial oxidative stress and dysfunction are emerging as key factors that not only result from seizures, but may also contribute to epileptogenesis. The occurrence of epilepsy increases with age, and mitochondrial oxidative stress is a leading mechanism of aging and age-related degenerative disease, suggesting a further involvement of mitochondrial dysfunction in seizure generation. Mitochondria have critical cellular functions that influence neuronal excitability including production of adenosine triphosphate (ATP), fatty acid oxidation, control of apoptosis and necrosis, regulation of amino acid cycling, neurotransmitter biosynthesis, and regulation of cytosolic Ca(2+) homeostasis. Mitochondria are the primary site of reactive oxygen species (ROS) production making them uniquely vulnerable to oxidative stress and damage which can further affect cellular macromolecule function, the ability of the electron transport chain to produce ATP, antioxidant defenses, mitochondrial DNA stability, and synaptic glutamate homeostasis. Oxidative damage to one or more of these cellular targets may affect neuronal excitability and increase seizure susceptibility. The specific targeting of mitochondrial oxidative stress, dysfunction, and bioenergetics with pharmacological and non-pharmacological treatments may be a novel avenue for attenuating epileptogenesis.

Melatonin prevents oxidative stress-mediated mitochondrial permeability transition and death in skeletal muscle cells

Oxidative stress-induced mitochondrial dysfunction plays a crucial role in the pathogenesis of a wide range of diseases including muscle disorders. In this study, we demonstrate that melatonin readily rescued mitochondria from oxidative stress-induced dysfunction and effectively prevented subsequent apoptosis of primary muscle cultures prepared from C57BL/6J mice. In particular, melatonin (10(-4)-10(-6) m) fully prevented myotube death induced by tert-butylhydroperoxide (t-BHP; 10 microm-24 hr) as assessed by acid phosphatase, caspase-3 activities and cellular morphological changes. Using fluorescence imaging, we showed that the mitochondrial protection provided by melatonin was associated with an inhibition of t-BHP-induced reactive oxygen species generation. In line with this observation, melatonin prevented t-BHP-induced mitochondrial depolarization and mitochondrial permeability transition pore (PTP) opening. This was associated with a highly reduced environment as reflected by an increased glutathione content and an increased ability to maintain mitochondrial pyridine nucleotides and glutathione in a reduced state. Using isolated mitochondria, in a similar manner as cyclosporin A, melatonin (10(-8)-10(-6) m) desensitized the PTP to Ca(2+) and prevented t-BHP-induced mitochondrial swelling, pyridine nucleotide and glutathione oxidation. In conclusion, our findings suggest that inhibition of the PTP essentially contributes to the protective effect of melatonin against oxidative stress in myotubes.

Reducing oxidative/nitrosative stress: a newly-discovered genre for melatonin

The discovery of melatonin and its derivatives as antioxidants has stimulated a very large number of studies which have, virtually uniformly, documented the ability of these molecules to detoxify harmful reactants and reduce molecular damage. These observations have clear clinical implications given that numerous age-related diseases in humans have an important free radical component. Moreover, a major theory to explain the processes of aging invokes radicals and their derivatives as causative agents. These conditions, coupled with the loss of melatonin as organisms age, suggest that some diseases and some aspects of aging may be aggravated by the diminished melatonin levels in advanced age. Another corollary of this is that the administration of melatonin, which has an uncommonly low toxicity profile, could theoretically defer the progression of some diseases and possibly forestall signs of aging. Certainly, research in the next decade will help to define the role of melatonin in age-related diseases and in determining successful aging. While increasing life span will not necessarily be a goal of these investigative efforts, improving health and the quality of life in the aged should be an aim of this research.

Melatonin protects against heart ischemia-reperfusion injury by inhibiting mitochondrial permeability transition pore opening

Melatonin, a well-known antioxidant, has been shown to protect against ischemia-reperfusion myocardial damage. Mitochondrial permeability transition pore (MPTP) opening is an important event in cardiomyocyte cell death occurring during ischemia-reperfusion and therefore a possible target for cardioprotection. In the present study, we tested the hypothesis that melatonin could protect heart against ischemia-reperfusion injury by inhibiting MPTP opening. Isolated perfused rat hearts were subjected to global ischemia and reperfusion in the presence or absence of melatonin in a Langerdoff apparatus. Melatonin treatment significantly improves the functional recovery of Langerdoff hearts on reperfusion, reduces the infarct size, and decreases necrotic damage as shown by the reduced release of lactate dehydrogenase. Mitochondria isolated from melatonin-treated hearts are less sensitive than mitochondria from reperfused hearts to MPTP opening as demonstrated by their higher resistance to Ca(2+). Similar results were obtained following treatment of ischemic-reperfused rat heart with cyclosporine A, a known inhibitor of MPTP opening. In addition, melatonin prevents mitochondrial NAD(+) release and mitochondrial cytochrome c release and, as previously shown, cardiolipin oxidation associated with ischemia-reperfusion. Together, these results demonstrate that melatonin protects heart from reperfusion injury by inhibiting MPTP opening, probably via prevention of cardiolipin peroxidation.

The melatonin-producing system is fully functional in retinal pigment epithelium (ARPE-19)

Since melatonin production has been documented in extrapineal and extraneuronal tissues, we investigated the expression of molecular elements of the melatoninergic system in human RPE cells (ARPE-19). The expression of key enzymes for melatonin synthesis: tryptophan hydroxylases (TPH1 and TPH2); arylalkylamine N-acetyltransferase (AANAT) and hydroxyindole-O-methyltransferase (HIOMT) was detected in ARPE-19 cells using RT-PCR. TPH1 and AANAT proteins were detected in ARPE by Western blotting, while sequential metabolism of tryptophan, serotonin and N-acetylserotonin to melatonin was shown by RP-HPLC. We also demonstrated, by means of RT-PCR, that ARPE expressed mRNA encoding the melatonin receptors: MT2 (but not MT1), two isoforms of nuclear receptor (RORalpha1 and RORalpha4/RZR1), and quinone oxidoreductase (NQO2). By analogy with other peripheral tissues, for example the skin, the expression of these metabolic elements in RPE cells suggests that the RPE represents an additional source of melatonin in the eye, to regulate local homeostasis and prevent from oxidative damage in intra-, auto- and/or paracrine fashions.

Protection against cognitive deficits and markers of neurodegeneration by long-term oral administration of melatonin in a transgenic model of Alzheimer disease

The neurohormone melatonin has been reported to exert anti-beta-amyloid aggregation, antioxidant, and anti-inflammatory actions in various in vitro and animal models. To comprehensively determine the potential for long-term melatonin treatment to protect Alzheimer's transgenic mice against cognitive impairment and development of beta-amyloid (Abeta) neuropathology, we administered melatonin (100 mg/L drinking water) to APP + PS1 double transgenic (Tg) mice from 2-2.5 months of age to their killing at age 7.5 months. A comprehensive behavioral battery administered during the final 6 weeks of treatment revealed that Tg mice given melatonin were protected from cognitive impairment in a variety of tasks of working memory, spatial reference learning/memory, and basic mnemonic function; Tg control mice remained impaired in all of these cognitive tasks/domains. Immunoreactive Abeta deposition was significantly reduced in hippocampus (43%) and entorhinal cortex (37%) of melatonin-treated Tg mice. Although soluble and oligomeric forms of Abeta1-40 and 1-42 were unchanged in the hippocampus and cortex of the same melatonin-treated Tg mice, their plasma Abeta levels were elevated. These Abeta results, together with our concurrent demonstration that melatonin suppresses Abeta aggregation in brain homogenates, are consistent with a melatonin-facilitated removal of Abeta from the brain. Inflammatory cytokines such as tumor necrosis factor (TNF)-alpha were decreased in hippocampus (but not plasma) of Tg+ melatonin mice. Finally, the cortical mRNA expression of three antioxidant enzymes (SOD-1, glutathione peroxidase, and catalase) was significantly reduced to non-Tg levels by long-term melatonin treatment in Tg mice. Thus, melatonin's cognitive benefits could involve its anti-Abeta aggregation, anti-inflammatory, and/or antioxidant properties. Our findings provide support for long-term melatonin therapy as a primary or complementary strategy for abating the progression of Alzheimer disease.

Sustained anti-β-adrenergic effect of melatonin in guinea pig heart papillary muscle

OBJECTIVE

Anti-ss-adrenergic actions of several substances influence heart function significantly. The anti-ss-adrenergic effect of melatonin was investigated, with special attention to protein kinase C (PKC) and nitric oxide (NO).

DESIGN

Guinea pig papillary muscles were exposed to melatonin (500 pM) for 15 min and 20 min washout. Contractile force was measured during a bolus of isoproterenol (300 nM) given before melatonin, at the end of melatonin-exposure and after washout. In separate experiments blockers of PKC, NO-synthase (NOS) and melatonin receptors were added, or forskolin (10 microM) substituted for isoproterenol.

RESULTS

Melatonin significantly reduced the increase in contractile force in response to isoproterenol, both when present and after melatonin-washout. The reduction was unaffected by inhibition of PKC, while inhibition of melatonin receptors or NOS seemed to abolish the effect. Melatonin induced a sustained but not acute reduction of contractile force response with forskolin stimulation. This was abolished by NOS-inhibition.

CONCLUSION

Receptor-mediated immediate and sustained anti-ss-adrenergic effects of melatonin were demonstrated in contractile function. A role for NO in the response was indicated, while a role for PKC was not verified.

Protective role of melatonin against the mercury induced oxidative stress in the rat thyroid

Present study investigated the protective role of melatonin (MLT, 5mg/kg body wt., ip) against the long term effects of mercuric chloride (MC; 2 and 4 mg/kg body wt., po) in the thyroid gland of the rats through certain antioxidative indices like superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione (GSH), catalase (CAT) and lipid peroxidation (LPO), other biochemical parameters such as succinate dehydrogenase (SDH), adenosine triphosphatase (ATPase), acid phosphatase (ACPase) and alkaline phosphatase (ALPase) were also measured. Antioxidative enzymes and other parameters showed a significant reduction while LPO and mercury levels increased significantly in a dose dependent manner in MC treated animals as compared to control groups. Co-treatment with MLT revealed no significant effect on antioxidative and metabolic indices in the thyroid gland of rats. The results of present study thus strongly suggest that mercury affected antioxidant defense system and other metabolic enzymes of thyroid. Co-administration of melatonin exerted a protective effect against mercury induced endocrine toxicity.

Melatonin reduces induction of Bax, caspase and cell death in methamphetamine-treated human neuroblastoma SH-SY5Y cultured cells

Several studies demonstrated that methamphetamine (MA)-treated human neuroblastoma cells exhibit increased oxidative stress, which regulates intracellular signaling cascades leading to cell death. Melatonin has a potential as a direct free radical scavenger and protects against cell death caused by MA. The objective of this study was to investigate the neuroprotective properties of melatonin on MA-induced induction of death signaling cascade and neuronal cell degeneration in human neuroblastoma SH-SY5Y cultured cells. The results of the present study demonstrate that MA significantly reduced cell viability in SH-SY5Y cultured cells. Desipramine, a monoamine uptake blocker, and melatonin reversed the toxic effect of MA in reducing cell viability. Induction of Bax, Bcl-2 and cleaved caspase-3 protein levels were observed in SH-SY5Y cultured cells treated with MA, whereas the induction of Bax and cleaved caspase-3 was diminished by melatonin. Visualization of the induction of Bax using immunofluorescence but a reduction in mitochondrial sites using red-fluorescent mitochondria-staining dye was more obviously apparent in MA-treated cells than in untreated control cells and, again, this effect was abolished by melatonin. These findings demonstrate important roles of Bax and caspase in death signaling cascade, and the protective effects of melatonin in MA-treated SH-SY5Y cells.

Antioxidant and anti-apoptotic effect of melatonin on the vestibular hair cells of rat utricles

OBJECTIVES

Aminoglycosides are commonly used antibiotic agents, and they are known to generate free oxygen radicals within the inner ear and to cause vestibulo-cochlear toxicity and permanent damage to the sensory hair cells and neurons. Melatonin, a pineal secretory product, has the properties of being a powerful direct and indirect antioxidant. The aim of the present study was to prove the antioxidant effect of melatonin against gentamicin-induced ototoxicty.

METHODS

The utricular maculae of Sprague-Dawley rats were prepared from postnatal day 2-4, and these maculae were were divided into 6 groups as follows: 1) control, 2) melatonin only, 3) gentamicin only, and 4), 5), and 6) gentamicin plus melatonin (10, 50, and 100 microM, respectively). To count the number of hair cells, 5 utricles from each group were stained with phalloidin-FITC on the 1st, 4th, and 7th days after drug administration. Reactive oxygen species (ROS) was assessed by using the fluorescent probe hydrofluorescent diacetate acetyl ester. The caspase-3 activity was also examined with using the fluorescent caspase-3 substrate and performing Western blotting.

RESULTS

The result of this study showed that gentamicin induced the loss of utricular hair cells, and this loss of hair cells was significantly attenuated by co-administration of melatonin. Melatonin reduced ROS production and caspase-3 activation in the gentamicin treated utricular hair cells.

CONCLUSION

Our findings conclusively reveal that melatonin has protective effects against gentamicin-induced hair cell loss in the utricles of rat by inhibiting both ROS production and caspase-3 activity.

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

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, beta-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.

Melatonin restores impaired contractility in aged guinea pig urinary bladder

Urinary bladder disturbances are frequent in the elderly population but the responsible mechanisms are poorly understood. This study evaluates the effects of aging on detrusor myogenic contractile responses and the impact of melatonin treatment. The contractility of bladder strips from adult, aged and melatonin-treated guinea pigs was evaluated by isometric tension recordings. Cytoplasmatic calcium concentration ([Ca(2+)](i)) was estimated by epifluorescence microscopy of fura-2-loaded isolated detrusor smooth muscle cells, and the levels of protein expression and phosphorylation were quantitated by Western blotting. Aging impairs the contractile response of detrusor strips to cholinergic and purinergic agonists and to membrane depolarization. The impaired contractility correlates with increased [Ca(2+)](i) in response to the stimuli, suggesting a reduced Ca(2+)sensitivity. Indeed, the agonist-induced contractions in adult strips were sensitive to blockade with Y27362, an inhibitor of Rho kinase (ROCK) and GF109203X, an inhibitor of protein kinase C (PKC), but these inhibitors had negligible effects in aged strips. The reduced Ca(2+) sensitivity in aged tissues correlated with lower levels of RhoA, ROCK, PKC and the two effectors CPI-17 and MYPT1, and with the absence of CPI-17 and MYPT1 phosphorylation in response to agonists. Interestingly, melatonin treatment restored impaired contractility via normalization of Ca(2+) handling and Ca(2+) sensitizations pathways. Moreover, the indoleamine restored age-induced changes in oxidative stress and mitochondrial polarity. These results suggest that melatonin might be a novel therapeutic tool to palliate aging-related urinary bladder contractile impairment.

Melatonin attenuates calpain upregulation, axonal damage and neuronal death in spinal cord injury in rats

Multiple investigations in vivo have shown that melatonin (MEL) has a neuroprotective effect in the treatment of spinal cord injury (SCI). This study investigates the role of MEL as an intervening agent for ameliorating Ca(2+)-mediated events, including activation of calpain, following its administration to rats sustaining experimental SCI. Calpain, a Ca(2+)-dependent neutral protease, is known to be involved in the pathogenesis of SCI. Rats were injured using a standard weight-drop method that induced a moderately severe injury (40 g.cm force) at T10. Sham controls received laminectomy only. Injured animals were given either 45 mg/kg MEL or vehicle at 15 min post-injury by intraperitoneal injection. At 48 hr post-injury, spinal cord (SC) samples were collected. Immunofluorescent labelings were used to identify calpain expression in specific cell types, such as neurons, glia, or macrophages. Combination of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) and double immunofluorescent labelings was used to identify apoptosis in specific cells in the SC. The effect of MEL on axonal damage was also investigated using antibody specific for dephosphorylated neurofilament protein (dNFP). Treatment of SCI animals with MEL attenuated calpain expression, inflammation, axonal damage (dNFP), and neuronal death, indicating that MEL provided neuroprotective effect in SCI. Further, expression and activity of calpain and caspse-3 were examined by Western blotting. The results indicated a significant decrease in expression and activity of calpain and caspse-3 in SCI animals after treatment with MEL. Taken together, this study strongly suggested that MEL could be an effective neuroprotective agent for treatment of SCI.

Molecular mechanisms involved in the hormonal prevention of aging in the rat

Previous data from our group have provided support for the role of GH, melatonin and estrogens in the prevention of aging of several physiological parameters from bone, liver metabolism, vascular activity, the central nervous system (CNS), the immune system and the skin. In the present work data on the molecular mechanisms involved are presented. A total of 140 male and female rats have been submitted to different treatments over 10 weeks, between 22 and 24 months of age. Males have been treated with GH and melatonin. Females were divided in two groups: intact and castrated at 12 months of age. The first group was treated with GH and melatonin and the second with the two latter compounds and additionally with estradiol and Phytosoya. Aging was associated with a reduction in the number of neurons of the hylus of the dentate gyrus of the hippocampus and with a reduction of neurogenesis. GH treatment increased the number of neurons but did not increase neurogenesis thus suggesting a reduction of apoptosis. This was supported by the reduction in nucleosomes and the increase in Bcl2 observed in cerebral homogenates together with an increase in sirtuin2 and a reduction of caspases 9 and 3. Melatonin, estrogen and Phytosoya treatments increased neurogenesis but did not enhance the total number of neurons. Aging induced a significant increase in mitochondrial nitric oxide in the hepatocytes, together with a reduction in the mitochondrial fraction content in cytochrome C and an increase of this compound in the cytosolic fraction. Reductions of glutathione peroxidase and glutathione S-transferase were also detected, thus indicating oxidative stress and possibly apoptosis. Treatment for 2.5 months of old rats with GH and melatonin were able to significantly and favourably affect age-induced deteriorations, thus reducing oxidative damage. Keratinocytes obtained from old rats in primary culture showed an increase in lipoperoxides, caspases 8 and 3 as well as a reduction in Bcl2 leading to enhanced number of nucleosomes that was also restored upon treatments with GH and melatonin. In conclusion, GH and melatonin treatment seem to have beneficial effects against age-induced damage in the CNS the liver and the skin through molecular mechanisms reducing oxidative stress and apoptosis.

Endomorphins and morphine limit anoxia-reoxygenation-induced brain mitochondrial dysfunction in the mouse

The protection of brain mitochondria from oxidative stress is an important therapeutic strategy against ischemia-reperfusion injury and neurodegenerative disorders. Isolated brain mitochondria subjected to a 5 min period of anoxia followed by 5 min reoxygenation mirrored the effect of oxidative stress in the brain. The present study attempts to evaluate the protective effects of endomorphin 1 (EM1), endomorphin 2 (EM2), and morphine (Mor) in an in vitro mouse brain mitochondria anoxia-reoxygenation model. Endomorphins (EM1/2) and Mor were added to mitochondria prior to anoxia or reoxygenation. EM1/2 and Mor markedly improved mitochondrial respiratory activity with a decrease in state 4 and increases in state 3, respiratory control ratio (RCR) and the oxidative phosphorylation efficiency (ADP/O ratio), suggesting that they may play a protective role in mitochondria. These drugs inhibited alterations in mitochondrial membrane fluidity, lipoperoxidation, and cardiolipin (CL) release, which indicates protection of the mitochondrial membranes from oxidative damage. The protective effects of these drugs were concentration-dependent. Furthermore, these drugs blocked the enhanced release of cytochrome c (Cyt c), and consequently inhibited the cell apoptosis induced by the release of Cyt c. Our results suggest that EM1/2 and Mor effectively protect brain mitochondria against oxidative stresses induced by in vitro anoxia-reoxygenation and may play an important role in the prevention of deleterious effects during brain ischemia-reperfusion and neurodegenerative diseases.

Melatonin and the hair follicle

Melatonin, the chief secretory product of the pineal gland, has long been known to modulate hair growth, pigmentation and/or molting in many species, presumably as a key neuroendocrine regulator that couples coat phenotype and function to photoperiod-dependent environmental and reproductive changes. However, the detailed effects and mechanisms of this surprisingly pleiotropic indole on the hair follicle (HF) regarding growth control and pigmentation have not yet been completely understood. While unspecific melatonin binding sites have long been identified (e.g., in goat and mouse HFs), specific melatonin membrane MT2 receptor transcripts and both protein and mRNA expression for a specific nuclear melatonin binding site [retinoid-related orphan receptor alpha (RORalpha)] have only recently been identified in murine HFs. MT1, known to be expressed in human skin cells, is not transcribed in mouse skin. After initial enzymologic data from hamster skin related to potential intracutaneous melatonin synthesis, it has recently been demonstrated that murine and human skin, namely human scalp HFs in anagen, are important sites of extrapineal melatonin synthesis. Moreover, HF melatonin production is enhanced by catecholamines (as it classically occurs in the pineal gland). Melatonin may also functionally play a role in hair-cycle control, as it down-regulates both apoptosis and estrogen receptor-alpha expression, and modulates MT2 and RORalpha expression in murine skin in a hair-cycle-dependent manner. Because of melatonin's additional potency as a free radical scavenger and DNA repair inducer, the metabolically and proliferatively highly active anagen hair bulb may also exploit melatonin synthesis in loco as a self-cytoprotective strategy.

Association of ischemia-modified albumin and melatonin in patients with ST-elevation myocardial infarction

INTRODUCTION

It has been proposed that reactive oxygen species (ROS) generated during myocardial ischemia-reperfusion modify the N-terminus of serum albumin resulting in ischemia-modified albumin (IMA) formation. Likewise, several recent publications provide evidence that melatonin, a circadian endogenously produced indolamine, is a direct scavenger of ROS. We sought to investigate the relationship between IMA and melatonin in ST- elevation myocardial infarction (STEMI).

METHODS

We compared IMA and melatonin levels in 27 patients with STEMI undergoing primary angioplasty and 20 age- and gender-matched healthy normal subjects. Blood samples were drawn at 02:00h (night period) and 09:00h (day period) while patients were resting, to assess IMA and melatonin.

RESULTS

In both groups, melatonin concentrations maintained a diurnal variation, but the difference between nocturnal and diurnal levels was less in the STEMI-patients than in the control group (p<0.001). In contrast to findings about melatonin, IMA levels showed no diurnal variations in control subjects. However, the STEMI group showed a diurnal fluctuation with significantly higher levels at 02:00h (p<0.01). The association between IMA and melatonin remained statistically significant after adjustment for cardiovascular risk factors. An inverse correlation between IMA and melatonin at 02:00h and at 09:00h was observed, with respective r-values of -0.42 (p<0.03) and -0.57 (p<0.002).

CONCLUSIONS

Circulating IMA is negatively correlated to melatonin in STEMI-patients. Our results suggest that melatonin might exert a beneficial effect as a radical scavenger in a human model of myocardial ischemia-reperfusion.

Identification of novel modulators of mitochondrial function by a genome-wide RNAi screen in Drosophila melanogaster

Mitochondrial dysfunction is associated with many human diseases. There has not been a systematic genetic approach for identifying regulators of basal mitochondrial biogenesis and function in higher eukaryotes. We performed a genome-wide RNA interference (RNAi) screen in Drosophila cells using mitochondrial Citrate synthase (CS) activity as the primary readout. We screened 13,071 dsRNAs and identified 152 genes that modulate CS activity. These modulators are involved in a wide range of biological processes and pathways including mitochondrial-related functions, transcriptional and translational regulation, and signaling pathways. Selected hits among the 152 genes were further analyzed for their effect on mitochondrial CS activity in transgenic flies or fly mutants. We confirmed a number of gene hits including HDAC6, Rpd3(HDAC1), CG3249, vimar, Src42A, klumpfuss, barren, and smt3 which exert effects on mitochondrial CS activities in vivo, demonstrating the value of Drosophila genome-wide RNAi screens for identifying genes and pathways that modulate mitochondrial function.

Melatonin is able to reduce the apoptotic liver changes induced by aging via inhibition of the intrinsic pathway of apoptosis

We examined the effect of daily melatonin supplementation on liver apoptosis induced by aging in rats. Young (3-month-old) and aged (24-month-old) Wistar rats were supplemented daily with melatonin in their drinking water (20 mg/L) for 4 weeks. Aged rats showed increases in the liver concentration of thiobarbituric acid-reactive substances and in the oxidized/reduced glutathione ratio. These increases were accompanied by apoptotic ultrastructural alterations and increases in cytochrome c mitochondrial release, Bax to Bcl-2 relative expression, and activity of caspase-3. No significant changes were observed in Fas-ligand (Fas-L) expression and caspase-8 activity. Melatonin administration was able to abrogate changes detected in aged rats. Data suggest that liver apoptotic cell death is induced by reactive oxygen species, via the intrinsic signalling pathway, and that the antiapoptotic action provided by melatonin is related to its antioxidant effect, with reduction of cytochrome c release by the modulation of Bcl-2 and Bax genes.

Melatonin protects SK-N-SH neuroblastoma cells from amphetamine-induced neurotoxicity

Several hypotheses regarding the mechanism underlying amphetamine-induced neurotoxicity have been proposed. One of them is based on the observation of free radical formation and oxidative stress produced by auto-oxidation of dopamine (DA). The formation of DA-related reactive oxygen species (ROS) such as superoxide and hydroxyl radicals appears to play an important role in amphetamine-induced neurotoxicity. Melatonin, the main secretory product of pineal gland, is well known for its protective effects that are currently attributed mainly to its radical scavenging and antioxidant properties. The present study was conducted to investigate the protective effects of melatonin on d-amphetamine (AMPH)-induced neurotoxicity in cultured human dopaminergic neuroblastoma SK-N-SH cells. Our data indicate that AMPH significantly reduces cell viability, induces oxidative stress (enhances ROS production and malondialdehyde levels), up-regulates alpha-synuclein expression and decreases intracellular ATP levels. However, pretreatment of SK-N-SH cells with melatonin prevents AMPH-induced loss of cell viability and induction of oxidative stress, while reducing alpha-synuclein expression and increasing ATP production. These results suggest that the antioxidant properties of melatonin may provide a protective mechanism against AMPH-induced neuronal degeneration.