Research Notes: Melatonin

FEBS J. 2007 Mar 20.
Attenuation of cardiac mitochondrial dysfunction by melatonin in septic mice.
Escames G, Lopez LC, Ortiz F, Lopez A, Garcia JA, Ros E, Acuna-Castroviejo D.
Instituto de Biotecnologia, Departamento de Fisiologia, Universidad de Granada, Spain.

The existence of an inducible mitochondrial nitric oxide synthase has been recently related to the nitrosative/oxidative damage and mitochondrial dysfunction that occurs during endotoxemia. Melatonin inhibits both inducible nitric oxide synthase and inducible mitochondrial nitric oxide synthase activities, a finding related to the antiseptic properties of the indoleamine. Hence, we examined the changes in inducible nitric oxide synthase/inducible mitochondrial nitric oxide synthase expression and activity, bioenergetics and oxidative stress in heart mitochondria following cecal ligation and puncture-induced sepsis in wild-type (iNOS(+/+)) and inducible nitric oxide synthase-deficient (iNOS(-/-)) mice. We also evaluated whether melatonin reduces the expression of inducible nitric oxide synthase/inducible mitochondrial nitric oxide synthase, and whether this inhibition improves mitochondrial function in this experimental paradigm. The results show that cecal ligation and puncture induced an increase of inducible mitochondrial nitric oxide synthase in iNOS(+/+) mice that was accompanied by oxidative stress, respiratory chain impairment, and reduced ATP production, although the ATPase activity remained unchanged. Real-time PCR analysis showed that induction of inducible nitric oxide synthase during sepsis was related to the increase of inducible mitochondrial nitric oxide synthase activity, as both inducible nitric oxide synthase and inducible mitochondrial nitric oxide synthase were absent in iNOS(-/-) mice. The induction of inducible mitochondrial nitric oxide synthase was associated with mitochondrial dysfunction, because heart mitochondria from iNOS(-/-) mice were unaffected during sepsis. Melatonin treatment blunted sepsis-induced inducible nitric oxide synthase/inducible mitochondrial nitric oxide synthase isoforms, prevented the impairment of mitochondrial homeostasis under sepsis, and restored ATP production. These properties of melatonin should be considered in clinical sepsis.

Neuro Endocrinol Lett. 2006 Oct.
Melatonin restores the mitochondrial production of ATP in septic mice.
Lopez LC, Escames G, Ortiz F, Ros E, Acuna-Castroviejo D.
Instituto de Biotecnologia, Departamento de Fisiologia, Universidad de Granada, Granada, Spain.

OBJECTIVES: To evaluate the changes in the mitochondrial ATP production during sepsis and the participation of iNOS in these changes. We also assessed the effect of melatonin administration in this experimental paradigm. METHODS: The activity of ATPase, the level of adenine nucleotides, and the ATP production were measured in mitochondria of diaphragm and hind leg skeletal muscle of wild type (iNOS+/+) and knockout iNOS (iNOS-/-) mice. Three experimental groups were done: control group; group of septic mice induced by cecal ligation and puncture (CLP), and group of septic mice treated with melatonin. Mice were killed 24 hours after CLP. Melatonin was administrated in four doses (30 mg/kg b.w.) as follows: 30 min before CLP (i.p.) and 30 min, 4 h and 8 h after CLP (s.c.). RESULTS: Mitochondrial production of ATP decreased in iNOS+/+ but not in iNOS-/- mice after sepsis. No changes in the ATPase activity were found in any group. Melatonin treatment normalized the production of ATP in iNOS+/+ mice, without affecting iNOS-/- animals. CONCLUSIONS: The reduction of the ATP production in iNOS+/+ but not in iNOS-/- mice suggest the participation of iNOS in the impairment of mitochondrial function in the former. Because ATPase was unaffected by sepsis, it is suggested the ATP deficit depended on the sepsis-induced respiratory chain damage. The normalization of the production of ATP with melatonin may explain the reduction of the mortality reported elsewhere in experimental and clinical sepsis after treatment with the indoleamine.

Child Care Health Dev. 2006 Sep.
Randomized controlled trial of melatonin for children with autistic spectrum disorders and sleep problems.
Garstang J, Wallis M.
Coventry Primary Care Trust, Coventry, UK.

Background: Melatonin is often used for autistic children with sleep disorders, despite a lack of published evidence in this population. Methods: A randomized, placebo-controlled double-blind crossover trial of melatonin was undertaken in 11 children with autistic spectrum disorder (ASD). Results: Seven children completed the trial. Sleep latency was 2.6 h [95% confidence intervals (CI) 2.28-2.93] baseline, 1.91 h (95% CI 1.78-2.03) with placebo and 1.06 h (95% CI 0.98-1.13) with melatonin. Wakings per night were 0.35 (95% CI 0.18-0.53) baseline, 0.26 (95% CI 0.20-0.34) with placebo and 0.08 (95% CI 0.04-0.12) with melatonin. Total sleep duration was 8.05 h (95% CI 7.65-8.44) baseline, 8.75 h (95% CI 8.56-8.98) with placebo and 9.84 h (95% CI 9.68-9.99) with melatonin. Conclusions: Although the study was small owing to recruitment difficulties, it still provides evidence of effectiveness of melatonin in children with sleep difficulties and ASD, which we predict a larger study would confirm.

Int J Biochem Cell Biol. 2006 Feb.
Identification of an inducible nitric oxide synthase in diaphragm mitochondria from septic mice: its relation with mitochondrial dysfunction and prevention by melatonin.
Lopez LC, Escames G, Tapias V, Utrilla P, Leon J, Acuna-Castroviejo D.
Departamento de Fisiologia, Facultad de Medicina, Instituto de Biotecnologia, Universidad de Granada, Avenida de Madrid, 11, Granada, Spain.

Sepsis provokes an induction of inducible nitric oxide synthase (iNOS) and melatonin down-regulates its expression and activity. Looking for an inducible mtNOS isoform, we induced sepsis by cecal ligation and puncture in both normal and iNOS knockout mice and studied the changes in mtNOS activity. We also studied the effects of mtNOS induction in mitochondrial function, and the role of melatonin against induced mtNOS and mitochondrial dysfunction. The activity of mtNOS and nitrite levels significantly increased after sepsis in iNOS+/+ mice. These animals showed a significant inhibition of the respiratory chain activity and an increase in mitochondrial oxidative stress, reflected in the disulfide/glutathione ratio, glutathione redox cycling enzymes activity and lipid peroxidation levels. Interestingly, mtNOS activity remained unchanged in iNOS-/- septic mice, and mitochondria of these animals were unaffected by sepsis. Melatonin administration to iNOS+/+ mice counteracted mtNOS induction and respiratory chain failure, restoring the redox status. The results support the existence of an inducible mtNOS that is likely coded by the same gene as iNOS. The results also suggest that sepsis-induced mtNOS is responsible for the increase of mitochondrial impairment due to oxidative stress in sepsis, perhaps due to the high production of NO. Melatonin treatment prevents mitochondrial failure at the same extent as the lack of iNOS gene.

J Pineal Res. 2006 Jan.
Melatonin counteracts inducible mitochondrial nitric oxide synthase-dependent mitochondrial dysfunction in skeletal muscle of septic mice.
Escames G, Lopez LC, Tapias V, Utrilla P, Reiter RJ, Hitos AB, Leon J, Rodriguez MI, Acuna-Castroviejo D.
Departamento de Fisiologia, Instituto de Biotecnologia, Universidad de Granada, Granada, Spain.

Mitochondrial nitric oxide synthase (mtNOS) produces nitric oxide (NO) to modulate mitochondrial respiration. Besides a constitutive mtNOS isoform it was recently suggested that mitochondria express an inducible isoform of the enzyme during sepsis. Thus, the mitochondrial respiratory inhibition and energy failure underlying skeletal muscle contractility failure observed in sepsis may reflect the high levels of NO produced by inducible mtNOS. The fact that mtNOS is induced during sepsis suggests its relation to inducible nitric oxide synthase (iNOS). Thus, we examined the changes in mtNOS activity and mitochondrial function in skeletal muscle of wild-type (iNOS(+/+)) and iNOS knockout (iNOS(-/-)) mice after sepsis. We also studied the effects of melatonin administration on mitochondrial damage in this experimental paradigm. After sepsis, iNOS(+/+) but no iNOS(-/-) mice showed an increase in mtNOS activity and NO production and a reduction in electron transport chain activity. These changes were accompanied by a pronounced oxidative stress reflected in changes in lipid peroxidation levels, oxidized glutathione/reduced glutathione ratio, and glutathione peroxidase and reductase activities. Melatonin treatment counteracted both the changes in mtNOS activity and rises in oxidative stress; the indole also restored mitochondrial respiratory chain in septic iNOS(+/+) mice. Mitochondria from iNOS(-/-) mice were unaffected by either sepsis or melatonin treatment. The data suggest that inducible mtNOS, which is coded by the same gene as that for iNOS, is responsible for mitochondrial dysfunction during sepsis. The results also suggest the use of melatonin for the protection against mtNOS-mediated mitochondrial failure.

Arzneimittelforschung. 2006.
Beneficial effects of melatonin on diaphragmatic contractility and fatigability in Escherichia coli endotoxemic rats.
Kurcer Z, Iraz M, Kelesyilmaz N, Kilic N, Olmez E.
Department of Pharmacology, Faculty of Medicine, Harran University, Sanliurfa, Turkey.

Sepsis impairs diaphragmatic contractility and endurance capacity and increases diaphragmatic fatigability. Several investigations have shown that administration of a number of free radical scavengers, such as N-acetylcysteine (NAC), protects the diaphragm from the development of endotoxin-mediated diaphragmatic dysfunction. The aim of this study was to evaluate the effects of melatonin (CAS 73-31-4), a naturally occurring potent antioxidant, on diaphragmatic contractility and lipid peroxidation as a marker of oxidative stress in endotoxemic rats. Rats were randomly divided into four groups: control group, endotoxemic group, melatonin group and endotoxemic plus melatonin group. Melatonin was administered by intraperitoneal injection 30 min before endotoxin inoculation to animals. Diaphragmatic function and malondialdehyde (MDA) level analysis as an indicator of lipid peroxidation were assessed 17 h after endotoxin or saline inoculation. Endotoxemia decreased the development of diaphragm fatigue and diaphragmatic MDA levels. The effects of endotoxemia on diaphragmatic contractions and fatigability were reversed and returned to control levels by melatonin administration. However, melatonin did not prevent the increase in muscle MDA content. In conclusion, the present study demonstrated that melatonin attenuated the endotoxin-induced impairment of diaphragm function. This effect of melatonin does not seem to be related to its antioxidant properties.

FASEB J. 2003 May.
Melatonin counteracts lipopolysaccharide-induced expression and activity of mitochondrial nitric oxide synthase in rats.
Escames G, Leon J, Macias M, Khaldy H, Acuna-Castroviejo D.
Departamento de Fisiologia, Instituto de Biotecnologia, Universidad de Granada, Granada, Spain.
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Mitochondrial nitric oxide synthase (mtNOS) is expressed constitutively, although it might be induced. Nitric oxide (NO) is a physiological regulator of mitochondrial respiration. Melatonin prevents mitochondrial oxidative damage and inhibits iNOS expression induced by bacterial lipopolysaccharide (LPS). The loss of melatonin with age may be related to the age-dependent mitochondrial damage. Thus, we examined the protective role of melatonin against the effects of LPS on mtNOS and on respiratory complexes activity in liver and lung mitochondria from young and old rats. The activity of mtNOS in control lung was low and did not change with age. LPS administration (10 mg/kg, i.v.) significantly increased mtNOS expression and activity and NO production in lung mitochondria, and the effect was greater in old rats. LPS administration also reduced the age-dependent decrease of the respiratory complexes I and IV. Melatonin administration (60 mg/kg, i.p.) prevented the LPS toxicity, decreasing mitochondrial NOS activity and NO production. Melatonin also counteracted LPS-induced inhibition of complexes I and IV. In general, the actions of melatonin were stronger in older animals than in younger ones. The results suggest that an inducible component of mtNOS, together with mitochondrial damage, occurs during sepsis, and melatonin prevents the mitochondrial failure that occurs during endotoxemia.

Dev Med Child Neurol. 1998 Mar.
Sleep dysfunction in Rett syndrome: a trial of exogenous melatonin treatment.
McArthur AJ, Budden SS. Department of Psychiatry, Oregon Health Sciences University, Portland, USA.

Nine girls with Rett syndrome (mean age, 10.1 years) were monitored 24 hours a day over a period of 10 weeks using wrist actigraphy. Baseline sleep-wake patterns were assessed for 1 week. Subsequently, patients underwent a 4-week melatonin treatment period in a double-blind, placebo-controlled, crossover protocol that employed a 1-week washout between treatment trials. Melatonin doses ranged from 2.5 to 7.5 mg, based upon individual body weight. Baseline sleep quality was poor compared with healthy children. At baseline the group demonstrated a low sleep efficiency (mean [+/- SE], 68.0+/-3.9%), long sleep-onset latency (42.1+/-12.0 minutes), and a short and fragmented total sleep time (7.5+/-0.3 hours; 15+/-2 awakenings per night). Melatonin significantly decreased sleep-onset latency to (mean +/- SE) 19.1+/-5.3 minutes (P<0.05) during the first 3 weeks of treatment. While the variability of individual responsiveness was high, melatonin appeared to improve total sleep time and sleep efficiency in the patients with the worse baseline sleep quality. Finally, a 4-week administration of melatonin appears to be a safe treatment as no adverse side effects were detected, yet long-term effects of chronic melatonin use in pediatric patients are unknown at this time.