Melatonin: reducing the toxicity and increasing the efficacy of drugs

The effect of orally administered melatonin on tissue accumulation and toxicity of cadmium in mice

The aim of this study was to determine whether an oral administration of melatonin, a known antioxidant, free radical scavenger and metal chelator, influences tissue accumulation and toxicity of cadmium (Cd) in mice exposed subchronically to the metal. The animals received drinking water containing 50 microg Cd/mL only or with additional 2, 4 or 6 microg/mL melatonin for 8 weeks. Melatonin co-treatment brought about a dose-dependent decrease in the renal, hepatic and intestinal Cd concentrations, and the renal and hepatic metallothionein levels followed a pattern similar to that of the Cd accumulation. Histopathological changes occurred only in the kidneys (glomerular swelling and focal tubular degeneration) in all mice from the Cd alone group. In mice co-treated with melatonin, only slight (2 microg/mL melatonin) or no damage (4 and 6 microg/mL melatonin) was seen. The Cd and melatonin treatments did not affect renal lipid peroxidation and iron concentration. These data indicate that orally administered melatonin together with Cd reduces tissue accumulation of this metal; in particular, the reduction of renal Cd accumulation by melatonin is probably responsible for the prevention of Cd-induced injury in this organ.

Taurine protects against methotrexate-induced toxicity and inhibits leukocyte death

The efficacy of methotrexate (MTX), a widely used cytotoxic chemotherapeutic agent, is often limited by severe side effects and toxic sequelae. Regarding the mechanisms of these side effects, several hypotheses have been put forward, among which oxidative stress is noticeable. The present study was undertaken to determine whether taurine, a potent free radical scavenger, could ameliorate MTX-induced oxidative injury and modulate immune response. Following a single dose of methotrexate (20 mg/kg), either saline or taurine (50 mg/kg) was administered for 5 days. After decapitation of the rats, trunk blood was obtained and the ileum, liver, and kidney were removed to measure malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity, and collagen content, as well as histological examination. Our results showed that MTX administration increased the MDA, MPO activity, and collagen contents and decreased GSH levels in all tissues (P < 0.001), while these alterations were reversed in taurine-treated group (P < 0.05-0.01). Elevated (P < 0.001) TNF-alpha level observed following MTX treatment was depressed with taurine (P < 0.01). Oxidative burst of neutrophils stimulated by phorbol myristate acetate was reduced in saline-treated MTX group (P < 0.001), while taurine abolished this effect. Similarly, flow cytometric measurements revealed that leukocyte apoptosis and cell death were increased in MTX-treated animals, while taurine reversed these effects (P < 0.05). Reduced cellularity in bone marrow samples of MTX-treated group (P < 0.01) was reversed back to control levels in taurine-treated rats. Severe degeneration of the intestinal mucosa, liver parenchyma, glomerular, and tubular epithelium observed in saline-treated group was improved by taurine treatment. In conclusion, it appears that taurine protects against methotrexate-induced oxidant organ injury and inhibits leukocyte apoptosis and may be of therapeutic potential in alleviating the systemic side effects of chemotherapeutics.

Effects of intraperitoneal vitamin E, melatonin and aprotinin on leptin expression in the guinea pig eye during experimental uveitis

PURPOSE

To observe ultrastructural changes and leptin expression in the guinea pig eye during experimental uveitis (EU) and the effects of vitamin E, melatonin and aprotinin on leptin expression.

METHODS

Thirty male guinea pigs were randomly classified into five groups. Group 1 was the control group. Groups 2, 3, 4 and 5 received intravitreal injections of bovine serum albumin (BSA) to induce EU. At the same time on the third day, groups 3 (EU + vitamin E), 4 (EU + melatonin) and 5 (EU + aprotinin) received intraperitoneal vitamin E (150 mg/kg), melatonin (10 mg/kg) and aprotinin (20,000 IU/kg), respectively. On the sixth day, histopathological and clinical scoring of inflammation were performed, and leptin expression was investigated in the retina, choroid, sclera, episclera and cornea, and compared.

RESULTS

There was a remarkable increase in leptin expression in the retina, choroid, sclera and episclera in the EU group. Leptin expression in the treatment groups was similar to that in the control group. At light and electron microscopic levels, ganglion cells were oedematous and inner plexiform layer thickness had increased in the EU group retinas. Oedema was decreased in the treatment groups. Comparison of the EU and treatment groups revealed significant differences histopathologically and clinically.

CONCLUSION

Experimental uveitis causes an increase in leptin expression in the retina, choroid, sclera and episclera of guinea pigs. Vitamin E, melatonin and aprotinin inhibit this increase. Leptin seems to be closely related to ocular inflammation.

On the role of melatonin in skin physiology and pathology

Melatonin has been experimentally implicated in skin functions such as hair growth cycling, fur pigmentation, and melanoma control, and melatonin receptors are expressed in several skin cells including normal and malignant keratinocytes, melanocytes, and fibroblasts. Melatonin is also able to suppress ultraviolet (UV)-induced damage to skin cells and shows strong antioxidant activity in UV exposed cells. Moreover, we recently uncovered expression in the skin of the biochemical machinery involved in the sequential transformation of l-tryptophan to serotonin and melatonin. Existence of the biosynthetic pathway was confirmed by detection of the corresponding genes and proteins with actual demonstration of enzymatic activities for tryptophan hydroxylase, serotonin N-acetyl-transferase, and hydroxyindole-O-methyltransferase in extracts from skin and skin cells. Initial evidence for in vivo synthesis of melatonin and its metabolism was obtained in hamster skin organ culture and in one melanoma line. Therefore, we propose that melatonin (synthesized locally or delivered topically) could counteract or buffer external (environmental) or internal stresses to preserve the biological integrity of the organ and to maintain its home-ostasis. Furthermore, melatonin could have a role in protection against solar radiation or even in the management of skin diseases.

Superoxide-dependent Oxidation of Melatonin by Myeloperoxidase

Myeloperoxidase uses hydrogen peroxide to oxidize numerous substrates to hypohalous acids or reactive free radicals. Here we show that neutrophils oxidize melatonin to N(1)-acetyl-N(2)-formyl-5-methoxykynuramine (AFMK) in a reaction that is catalyzed by myeloperoxidase. Production of AFMK was highly dependent on superoxide but not hydrogen peroxide. It did not require hypochlorous acid, singlet oxygen, or hydroxyl radical. Purified myeloperoxidase and a superoxide-generating system oxidized melatonin to AFMK and a dimer. The dimer would result from coupling of melatonin radicals. Oxidation of melatonin was partially inhibited by catalase or superoxide dismutase. Formation of AFMK was almost completely eliminated by superoxide dismutase but weakly inhibited by catalase. In contrast, production of melatonin dimer was enhanced by superoxide dismutase and blocked by catalase. We propose that myeloperoxidase uses superoxide to oxidize melatonin by two distinct pathways. One pathway involves the classical peroxidation mechanism in which hydrogen peroxide is used to oxidize melatonin to radicals. Superoxide adds to these radicals to form an unstable peroxide that decays to AFMK. In the other pathway, myeloperoxidase uses superoxide to insert dioxygen into melatonin to form AFMK. This novel activity expands the types of oxidative reactions myeloperoxidase can catalyze. It should be relevant to the way neutrophils use superoxide to kill bacteria and how they metabolize xenobiotics.

Reintroduction to nutrition and cancer treatment

OBJECTIVES

To review what constitutes optimal nutrition for the cancer patient.

DATA SOURCES

Conventional nutrition, botanical and biomedical journals and texts, electronic media, databases, and abstracts.

CONCLUSION

Optimal nutrition is neither a complementary nor alternative treatment, but is the fundamental groundwork for the creation of the most favorable cancer treatment outcomes as presented in numerous study findings and journal articles. The two main topics of this article are (1) general food choices and decisions that can affect treatment outcomes; and (2) a brief look at the specific scientific application of individual nutrients to affect a positive impact on treatment, protection of healthy cells and tissues, side-effect mitigation, and quality of life for cancer patients.

IMPLICATIONS FOR NURSING PRACTICE

It is critical for health care providers to both acknowledge and apply the principles of nutrition for cancer patients both in general and as part of a therapeutic regimen. It is important for nursing staff to understand that nutritional elements can promote or detract from cancer treatment and recovery.

Selective CCK-A but not CCK-B receptor antagonists inhibit HT-29 cell proliferation: synergism with pharmacological levels of melatonin

Some data suggest that cholecystokinin (CCK) receptor agonists stimulate the growth of colon cancer. Melatonin, an endogenous indoleamine with strong antioxidant properties, displays antiproliferative and proapoptotic properties both in vivo or in vitro in several types of tumors. We used HT-29 human colon cancer cells, expressing CCK receptors, to test the antiproliferative effects of several antagonists of CCK-A and/or CCK-B and their possible synergism with melatonin. HT-29 cells were cultured in RPMI 1640 medium supplemented with fetal bovine serum at 37 degrees C. Cell proliferation was assessed by the incorporation of [3H]-thymidine into DNA. Annexin V-FITC plus propidium iodine were used for flow cytometry apoptosis/necrosis evaluation. The following drugs were tested: gastrin (CCK-B agonist); CCK-8s (CCK-A agonist); proglumide (CCK-A plus CCK-B antagonist); lorglumide (CCK-A antagonist); PD 135,158 (CCK-B antagonist and weak CCK-A agonist); devazepide or L 364,718 (CCK-A antagonist); L 365,260 (CCK-B antagonist), and melatonin. The results shown a lack of effects of gastrin on HT-29 cell proliferation, whereas CCK-8s induced proliferation at high doses. The order of the antiproliferative effect of the other drugs was devazepide > lorglumide > proglumide. These drugs produce cell death mainly inducing apoptosis. Melatonin showed strong antiproliferative effect at millimolar concentrations, and it induced apoptotic cell death. Melatonin generally enhanced the antiproliferative effects of devazepide, lorglumide and proglumide and increased the proglumide-induced apoptosis. These results suggest that melatonin and CCK-A antagonists are useful for controlling human colon cancer cell growth in culture and in combined therapy significantly increases their efficiency.

Tissue-plasminogen activator-induced ischemic brain injury is reversed by melatonin: role of iNOS and Akt

In vivo studies showed that tissue-plasminogen activator (t-PA) may aggravate neuronal injury after focal cerebral ischemia. We hypothesized that t-PA impairs survival-promoting cell signaling in the ischemic brain, which may be reversed by a neuroprotectant, i.e. melatonin. We examined the effects of t-PA (10 mg/kg, i.v.), administered alone or in combination with melatonin (4 mg/kg, i.p.), on ischemic injury, inducible nitric oxide synthase (iNOS) expression as well as Akt, Bcl-X(L) and caspase-3 signaling following 90 min of intraluminal middle cerebral artery (MCA) occlusion in mice. t-PA, delivered immediately after reperfusion onset, increased infarct volume at 24 hr after MCA occlusion, in accordance with previous findings. Melatonin reduced infarct size when administered alone and reversed the t-PA-induced brain injury. Immunohistochemical studies showed that t-PA treatment was associated with an accumulation of iNOS positive cells in ischemic brain areas, which was abolished after co-delivery of melatonin. Western blots revealed that t-PA decreased phosphorylated Akt levels, but did not influence Bcl-X(L) expression and caspase-3 activity in ischemic brain lysates. Co-treatment with melatonin restored phosphorylated Akt levels, increased Bcl-X(L) expression and reduced caspase-3 activity. We provide evidence that t-PA-induced brain injury is accompanied by an activation of iNOS and inhibition of phosphatidylinositol-3 kinase/Akt. That melatonin reversed these signaling changes and the t-PA-induced brain injury makes this indole attractive as an add-on treatment with thrombolytics.

Protective effect of melatonin and omeprazole against alendronat-induced gastric damage

Alendronate causes serious gastrointestinal adverse effects. We aimed to investigate if free radicals have any role in the damage induced by alendronate and if melatonin or omeprazole is protective against this damage. Rats were administered 20 mg/kg alendronate by gavage for 4 days, either alone or following treatment with melatonin or omeprazole. On the last day, following drug administration, pilor ligation was performed, and 2 hr later rats were killed and stomachs were removed. Gastric acidity and tissue ulcer index values, lipid peroxidation, and myeloperoxidase and glutathione levels, as well as the histologic appearance of the stomach tissues, were determined. Chronic oral administration of alendronate induced significant gastric damage, increasing lipid peroxidation and myeloperoxidase activity, while tissue glutathione levels decreased. Treatment with omeprazole or melatonin prevented this damage as well as the changes in biochemical parameters, and melatonin appeared to be more efficient than omeprazole in protecting the mucosa. Intraperitoneal administration of alendronate did not cause much gastric irritation. Findings of the present study suggest that alendronate induces oxidative gastric damage by a local irritant effect and that melatonin and omeprazole are protective against this damage due to their antioxidant properties.

Effect of the preventive-therapeutic administration of melatonin on mammary tumour-bearing animals

Melatonin has been reported to be involved in the feedback between neuroendocrine and immune functions and to exert oncostatic actions. Likewise, this hormone seems to lengthen life span in healthy animals. As of present, most studies have analysed the therapeutic effect of melatonin on cancer growth, but few have tested the preventive effect of melatonin in reducing the risk of cancer. Thus, the aim of this study was to evaluate the preventive-therapeutic effects of melatonin on rats with DMBA-induced mammary tumours, and to examine the effect of melatonin on the first line of cell defence against cancer (macrophages and NK cells) and on some of the neuroendocrine factors that are involved in the development of tumours (prolactin and catecholamines). Melatonin treatment (5 mg/day/animal) began one month prior to DMBA (9,10-dimethyl-1,2-benzanthracene) administration to females Sprague Dawley rats. It was found that the treatment led to an increase in survival and in latency time in the tumour-bearing rats. Although the melatonin treatment did not influence either the phagocytic capacity of macrophages or the number of peripheral blood NK cells, it did stabilise the levels of prolactin by returning the concentrations of this hormone to those of the healthy animals. We conclude that melatonin can exert an oncostatic action, lengthening the survival time of mammary tumour-bearing animals, and suggest that this effect is due, at least in part, to regulating the neuroendocrine parameters of tumour-bearing animals, bringing them closer to their optimal physiological status.

On the role of melatonin in skin physiology and pathology

Melatonin has been experimentally implicated in skin functions such as hair growth cycling, fur pigmentation, and melanoma control, and melatonin receptors are expressed in several skin cells including normal and malignant keratinocytes, melanocytes, and fibroblasts. Melatonin is also able to suppress ultraviolet (UV)-induced damage to skin cells and shows strong antioxidant activity in UV exposed cells. Moreover, we recently uncovered expression in the skin of the biochemical machinery involved in the sequential transformation of l-tryptophan to serotonin and melatonin. Existence of the biosynthetic pathway was confirmed by detection of the corresponding genes and proteins with actual demonstration of enzymatic activities for tryptophan hydroxylase, serotonin N-acetyl-transferase, and hydroxyindole-O-methyltransferase in extracts from skin and skin cells. Initial evidence for in vivo synthesis of melatonin and its metabolism was obtained in hamster skin organ culture and in one melanoma line. Therefore, we propose that melatonin (synthesized locally or delivered topically) could counteract or buffer external (environmental) or internal stresses to preserve the biological integrity of the organ and to maintain its home-ostasis. Furthermore, melatonin could have a role in protection against solar radiation or even in the management of skin diseases.

Melatonin and nitric oxide: two required antagonists for mitochondrial homeostasis

The presence of nitric oxide (NO* ) in the mitochondria led to analysis of its source and functions in mitochondrial homeostasis. Studies have revealed the existence of a mtNOS isoform with similar features to nNOS, with some post-traslational modifications, although without the typical signal peptide responsible for addressing proteins to mitochondrion. This isoform may account for the physiological production of NO* related to the respiratory control. During inflammatory conditions there is an excess of NO* in the mitochondria responsible for an increase in reactive oxygen and nitrogen species in sufficient amounts to compromise mitochondrial function. These conditions led to the discovery of the presence of an inducible mtNOS isoform with kinetic properties similar to iNOS. Experiments with knockout mice lacking either nNOS or iNOS further confirmed the existence of these two mtNOS isoforms in mitochondria. Although the increase in NO* in sepsis by inducible mtNOS may have important regulatory functions including the redistribution of oxygen into other pathways under hypoxia, it causes the production of excess NO* that is deleterious for the cell. Melatonin, an endogenous antioxidant, regulates mitochondrial respiration and bioenergetics and protects mitochondria from excess NO* by controlling the activity of mtNOS.

Exogenous melatonin enhances bile flow and ATP levels after cold storage and reperfusion in rat liver: implications for liver transplantation

Although the use of melatonin in the transplantation field has been suggested, it has not been previously tested in a liver cold-storage model. We used a rat liver model to study (a) the dose-dependent effect of melatonin on bile production, and (b) the potential of melatonin to improve liver function after cold-storage. Male Wistar rats were perfused with Krebs-Henseleit bicarbonate buffer (KHB) at 37 degrees C without or with 25, 50, 100 and 200 microM melatonin. Each dose of melatonin stimulated bile production. For cold-storage studies, livers were flushed with either University of Wisconsin (UW) or Celsior solution and stored for 20 hr at 4 degrees C. Reperfusion (120 min) was performed with KHB at 37 degrees C. In subsequent studies, 100 microM melatonin were added to the perfusate during the reperfusion period. ATP and melatonin levels in the tissue were measured. Bile analysis was performed by measuring melatonin, bilirubin and gamma-glutamyl transpeptidase (gamma-GT) levels in the fluid. A dose-dependent increase in bile secretion, associated with an enhanced melatonin and bilirubin levels in the bile were observed. Also, tissue levels of melatonin increased in a dose-dependent manner. When melatonin was added during the reperfusion period, bile production and bile bilirubin levels increased both with UW and Celsior solutions. The analysis of gamma-GT in the bile showed an increase in the Celsior-preserved liver and the addition of melatonin to the perfusate reduced this effect. Tissue ATP levels were higher when melatonin was added to the perfusion medium. Higher levels of melatonin in bile than in tissue were found. In conclusion, we demonstrate that melatonin improves significantly the restoration of liver function after cold-storage and reperfusion.

Effects of melatonin on wortmannin-induced tau hyperphosphorylation

AIM

To explore the underlying mechanism of tau hyperphosphorylation in an Alzheimeros-affected brain and the possible arresting strategies.

METHODS

MTT(3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide), crystal violet assay, phase-contrast, dead end colorimetric apoptosis detection system (TUNEL) and electron microscopy were used to detect cell viability, morphology and apoptosis. Western blot, 32P-labeling and the detection of malondialdehyde level and superoxide dismutase activity were used respectively for the phosphorylation level of tau, the activity of glycogen synthase kinase (GSK-3), and oxidative stress measurement.

RESULTS

Exposure of the cells to wortmannin resulted in an obvious lipid peroxidation, reduction of cell viability, cell process retraction, and plasma vacuolation, but with no obvious cell apoptosis. We also found that preincubation of the cells with melatonin or vitamin E attenuated differentially wortmannin-induced oxidative stress as well as GSK-3 overactivation and tau hyperphosphorylation.

CONCLUSION

Wortmannin is an effective tool for reproducing Alzheimer-like tau hyperphosphorylation cell model and melatonin/vitamin E can effectively protect the cells from wortmannin-induced impairments.

Melatonin ameliorates bladder damage induced by cyclophosphamide in rats

Cyclophosphamide (CP), an alkylating antineoplastic agent, has potential urotoxicity including causing hemorrhagic cystitis (HC). HC is now accepted as a non-infectious inflammation and the pathogenesis of HC includes cytokine production which leads to inducible nitric oxide synthase (iNOS) induction. Moreover, overproduction of reactive oxygen species (ROS) during inflammation leads to extensive oxidative stress, cellular injury and apoptosis/necrosis via several mechanisms. Based on these facts, the aim of this study was to evaluate the protective effects of melatonin as an antioxidant, iNOS inhibitor and peroxynitrite scavenger against CP-induced urinary bladder damage. A total of 30 male Sprague-Dawley rats were divided into four groups. Three groups received a single dose of CP (100 mg/kg) intraperitoneally with the same times. Group 2 received CP only, group 3 received 5 mg/kg/day and group 4 received 10 mg/kg/day melatonin before and the day after CP administration. Group 1 served as the control. Increased iNOS induction, bladder malonyldialdehyde (MDA) levels and urinary nitrite-nitrate excretion were encountered in the CP-only group leading to severe cystitis. Melatonin exhibited significant protection against CP-induced cystitis by diminishing bladder oxidative stress and blocking iNOS and peroxynitrite production. Oxidants may have a major role in the pathogenesis of CP-induced cystitis and iNOS is an important mediator leading to peroxynitrite production. Melatonin ameliorates bladder damage induced by CP.

Preventive and curative effect of melatonin on mammary carcinogenesis induced by dimethylbenz[a]anthracene in the female Sprague-Dawley rat

Introduction

It has been well documented that the pineal hormone, melatonin, which plays a major role in the control of reproduction in mammals, also plays a role in the incidence and growth of breast and mammary cancer. The curative effect of melatonin on the growth of dimethylbenz [a]anthracene-induced (DMBA-induced) mammary adenocarcinoma (ADK) has been previously well documented in the female Sprague–Dawley rat. However, the preventive effect of melatonin in limiting the frequency of cancer initiation has not been well documented.

Methods

The aim of this study was to compare the potency of melatonin to limit the frequency of mammary cancer initiation with its potency to inhibit tumor progression once initiation, at 55 days of age, was achieved. The present study compared the effect of preventive treatment with melatonin (10 mg/kg daily) administered for only 15 days before the administration of DMBA with the effect of long-term (6-month) curative treatment with the same dose of melatonin starting the day after DMBA administration. The rats were followed up for a year after the administration of the DMBA.

Results

The results clearly showed almost identical preventive and curative effects of melatonin on the growth of DMBA-induced mammary ADK. Many hypotheses have been proposed to explain the inhibitory effects of melatonin. However, the mechanisms responsible for its strong preventive effect are still a matter of debate. At least, it can be envisaged that the artificial amplification of the intensity of the circadian rhythm of melatonin could markedly reduce the DNA damage provoked by DMBA and therefore the frequency of cancer initiation.

Conclusion

In view of the present results, obtained in the female Sprague–Dawley rat, it can be envisaged that the long-term inhibition of mammary ADK promotion by a brief, preventive treatment with melatonin could also reduce the risk of breast cancer induced in women by unidentified environmental factors.

Melatonin prevents the free radical and MADD metabolic profiles induced by antituberculosis drugs in an animal model

The objective was to determine the effect of combined antituberculosis (anti-TB) drug therapy and an antioxidant, melatonin, on the free radical and organic acid profiles in an experimental rat model. A combined anti-TB drug, Rifater, consisting of 12.0 mg rifampicin, 0.8 mg isoniazid, and 23.0 mg pyrazinamide and 18.56 microg melatonin/kg body weight per day (corresponding to average physiological human intake) were orally administered to Sprague-Dawley rats. Hydroxyl radical production was monitored by quantifying 2,3-dihydroxybenzoic acid produced after intraperitonial sodium salicylate injections. Organic acid extractions and gas chromatography-coupled mass spectrometry analyses were performed on collected urine samples. The results show hydroxyl radicals (P = 0.0019) and organic acids (P-value range: 0.037 to <0.001), characteristic of a multiple acyl-CoA dehydrogenase defect (MADD), were elevated with Rifater treatment and these elevations were significantly lowered with melatonin pretreatment (P-value range: 0.031 to <0.001), probably because of its inherent antioxidant activity. We conclude that hydroxyl radical production and an increased organic acid profile induced by anti-TB medication indicates inhibition of the electron transport chain. We also conclude that free radicals leading to clinical symptoms associated with an MADD metabolic profile induced by anti-TB treatment could be alleviated by melatonin intervention.

Protective role of caffeic acid phenethyl ester (cape) on gentamicin-induced acute renal toxicity in rats

The toxicity of gentamicin (GEN) in the kidney seems to relate to the generation of reactive oxygen species (ROS). Caffeic acid phenethyl ester (CAPE) has been demonstrated to have antioxidant, free radical scavenger and anti-inflammatory effects. It has been proposed that antioxidant maintain the concentration of reduced glutathione (GSH) may restore the cellular defense mechanisms and block lipid peroxidation thus protect against the toxicity of wide variety of nephrotoxic chemicals. We investigated the effects of CAPE on GEN-induced changes in renal malondialdehyde (MDA), a lipid peroxidation product, nitric oxide (NO) generation, superoxide dismutase (SOD), catalase (CAT) activities, GSH content, blood urea nitrogen (BUN) and serum creatinine (Cr) levels. Morphological changes in the kidney were also examined. A total of 32 rats were equally divided into four groups which were: (1) control, (2) injected with intraperitoneally (i.p.) GEN, (3) injected with i.p. GEN+CAPE and (4) injected with i.p. CAPE. GEN administration to control rats increased renal MDA and NO generation but decreased SOD and CAT activities, and GSH content. CAPE administration with GEN injections caused significantly decreased MDA, NO generation and increased SOD, CAT activities and GSH content when compared with GEN alone. Serum level of BUN and Cr significantly increased as a result of nephrotoxicity. CAPE also, significantly decreased serum BUN and Cr levels. Morphological changes in the kidney due to GEN, including tubular necrosis, were evaluated qualitatively. In addition, CAPE reduced the degree of kidney tissue damage induced by GEN. Both biochemical findings and histopathological evidence showed that administration of CAPE reduced the GEN-induced kidney damage. Our results indicated that CAPE acts in the kidney as a potent scavenger of free radicals to prevent the toxic effects of GEN both at the biochemical and histological level. Thus, CAPE could be effectively combined with GEN treatment.

Effects of add-on melatonin administration on antioxidant enzymes in children with epilepsy taking carbamazepine monotherapy: a randomized, double-blind, placebo-controlled trial

PURPOSE

Melatonin has been shown to exhibit antioxidant, antiexcitotoxic, and free radical-scavenging properties in various animal models. The study was designed to assess its effects on the blood levels of antioxidant enzymes in children with epilepsy receiving carbamazepine (CBZ).

METHODS

In a double-blind, randomized, parallel-group, placebo-controlled trial, we assessed the effect of add-on melatonin (6-9 mg/day for 14 days) on the antioxidant enzymes glutathione peroxidase (GPx) and glutathione reductase (GRd) in 31 children with epilepsy receiving CBZ monotherapy, who were seizure free at least for the last 6 months. The interaction of melatonin with CBZ and its active metabolite, carbamazepine-10, 11-epoxide (CBZ-E), also was studied.

RESULTS

An increase in GRd activity was noted in the melatonin group as compared with a decrease of the same enzyme in the placebo group. Changes in GPx activity failed to reach statistical significance. No significant changes were found in the serum levels of CBZ and CBZ-E in either group.

CONCLUSIONS

The study suggests that melatonin exerts antioxidant activity in patients with epilepsy receiving CBZ therapy.

Protective effect of chelerythrine on gentamicin-induced nephrotoxicity

Despite their beneficial effects, aminoglycosides including gentamicin (GEN) have considerable nephrotoxic side-effects. The toxicity of GEN at the level of the kidney seems to relate to the generation of reactive oxygen species (ROS). ROS have been reported to be involved in the activation of protein kinase C (PKC). The unique structural aspects of PKC cause it to function as a sensor for oxidative stress. It seems likely that the increased NAD(P)H oxidase-derived superoxide (O2) production is at least in part mediated by PKC. We investigated the effects of chelerythrine, a commonly used PKC inhibitor, on GEN-induced changes of renal malondialdehyde (MDA), nitric oxide (NO) generation, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activities, glutathione (GSH) content, and serum creatinine (Cr), blood urea nitrogen (BUN) levels. Morphological changes in the kidney were also examined. GEN administration to control rats increased MDA and NO generation but decreased CAT, SOD and GSH-Px activities, and GSH content. Chelerythrine administration with GEN caused significantly decreased MDA, NO generation and increased CAT, SOD and GSH-Px activities, and GSH content when compared with GEN alone. Chelerythrine also significantly decreased serum Cr and BUN levels. Morphological changes in the kidney including tubular necrosis were evaluated qualitatively. Both biochemical findings and histopathological evidence showed that administration of chelerythrine reduced the GEN-induced kidney damage. We propose that chelerythrine acts in the kidney as a potent scavenger of free radicals to prevent the toxic effects of GEN via the inhibition of a PKC pathway.

Protective effects of MESNA (2-mercaptoethane sulphonate) against acetaminophen-induced hepatorenal oxidative damage in mice

Acetaminophen, a widely used analgesic and antipyretic, is known to cause hepatic and renal injury in humans and experimental animals when administered in high doses. It was reported that these toxic effects of acetaminophen are due to oxidative reactions that take place during its metabolism. In this study we aimed to investigate the possible beneficial effect of 2-mercaptoethane sulphonate (MESNA), an antioxidant agent, against acetaminophen toxicity in mice. Balb-c mice were injected i.p. with: vehicle (the control group); a single dose of 150 mg kg(-1) MESNA (MES group); a single dose of 900 mg kg(-1) i.p. acetaminophen (AA4h and AA24h groups); and MESNA, at a dose of 150 mg kg(-1) after acetaminophen injection (AA4h-MES and AA24h-MES groups). The MESNA injection was repeated once more 12 h after the first injection in the AA24h-MES group. Blood urea nitrogen, serum creatinine, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in blood and glutathione (GSH) and malondialdehyde (MDA) levels, myeloperoxidase (MPO) activity and collagen contents in liver and kidney tissues were measured. Tissues also were examined microscopically. Blood urea nitrogen and serum creatinine, which were increased significantly (P < 0.001) following acetaminophen treatment were decreased significantly (P < 0.05-0.001) after treatment with MESNA. The ALT and AST levels were also increased significantly (P < 0.001) after acetaminophen treatment but were not reduced with MESNA. Acetaminophen treatment caused a significant (P < 0.05-0.001) decrease in GSH levels whereas MDA levels and MPO activity were increased in both tissues. These changes were reversed by MESNA treatment. Collagen contents of the liver and kidney tissues were increased by acetaminophen treatment (P < 0.001) and reversed back to the control levels with MESNA. Our results imply that acetaminophen causes oxidative damage in hepatic and renal tissues and that MESNA, via its antioxidant effects, protects these tissues. Therefore, its therapeutic role as a 'tissue injury-limiting agent' must be elucidated further in drug-induced oxidative damage.

Protective effects of melatonin against carbon tetrachloride hepatotoxicity in rats

Melatonin is an indolamine, mainly secreted by the pineal gland into the blood of mammalian species. The potential for protective effects of melatonin on carbon tetrachloride (CCl(4))-induced acute liver injury in rats was investigated in this work. CCl(4) exerts its toxic effects by generation of free radicals; it was intragastrically administered to male Wistar rats (4 g kg(-1) body weight) at 20 h before the animals were decapitated. Melatonin (15 mg kg(-1) body weight) was administered intraperitoneally three times: 30 min before and at 2 and 4 h after CCl(4) injection. Rats injected with CCl(4) alone showed significant lipid and hydropic dystrophy of the liver, massive necrosis of hepatocytes, marked increases in free and conjugated bilirubin levels, elevation of hepatic enzymes (alanine aminotransferase and aspartate aminotransferase) in plasma, as well as NO accumulation in liver and in blood. Melatonin administered at a pharmacological dose diminished the toxic effects of CCl(4). Thus it decreased both the structural and functional injury of hepatocytes and clearly exerted hepatoprotective effects. Melatonin administration also reduced CCl(4)-induced NO generation. These findings suggest that the effect of melatonin on CCl(4)-induced acute liver injury depends on the antioxidant action of melatonin.

Signal transduction pathways involved in melatonin-induced neuroprotection after focal cerebral ischemia in mice

Because of its favorable action profile in humans, melatonin is a particularly interesting candidate as a neuroprotectant in acute ischemic stroke. Until now, the signaling mechanisms mediating melatonin's neuroprotective actions remained essentially uninvestigated. Herein, we examined the effects of melatonin, administered either orally for 9 wk as a stroke prophylactic (4 mg/kg/day) or intraperitoneally immediately after reperfusion onset (4 mg/kg), on the activation of signal transduction pathways in mice submitted to 90 min of intraluminal middle cerebral artery occlusion, followed by 24 hr of reperfusion. In these studies, melatonin significantly reduced ischemic infarct size by approximately 30-35%, as compared with animals receiving diluent (sham) treatment, independent of whether the indole was administered prior to or after ischemia. Under both conditions, animals receiving melatonin exhibited elevated phosphorylated Akt levels in their brains, as determined by Western blots. Additionally, phosphorylation levels of mitogen-activated protein kinase/extracellular-regulated kinase (ERK)-1/-2 and Jun kinase (JNK)-1/-2 were increased following prophylactic, but not acute, melatonin treatment. Our data suggest a role of phosphatidyl inositol-3 kinase/Akt signaling in acute melatonin-induced neuroprotection, while ERK-1/-2 and/or JNK-1/-2 rather appear to be involved in melatonin's long-term effects.

Comparison of chemopreventive effects of Vitamin E plus selenium versus melatonin in 7,12-dimethylbenz(a)anthracene-induced mouse brain damage

In this work, the protective effect of Vitamin E plus selenium (Vit E+Se) and melatonin against 7,12-dimethylbenz(a)anthracene (7,12-DMBA)-induced changes in superoxide dismutase (SOD), glutathione peroxidase (GSHPx), catalase (CAT) and carbonic anhydrase (CA) activities and malonedialdehyde (MDA) levels of mouse brain were compared. 12-month old mice were divided into four groups each including 10 animals. The first group served as control group. The second group was treated with 7,12-DMBA (20 mg/(kg day)). The third group was treated with 7,12-DMBA and Vitamin E (90 microg/(individual day)) and selenium (1.8 microg/(individual day)) simultaneously. The fourth group was treated with 7,12-DMBA and melatonin (4.2 mg/(kg day)) simultaneously. Treatment continued for 21 days after which the mice were sacrificed and brain homogenates were prepared. 7,12-DMBA treated group exhibited significantly decreased levels of brain SOD, GSHPx, CAT and CA activities and increased MDA levels as compared to control. Vitamin E+Se fully or partially restored enzyme inhibition except for SOD. Lipid peroxidation was also reduced in Vitamin E+Se treated group. Melatonin provided a better protection for SOD, GSHPx and CAT, and a plausible protection for CA activity. Protection against lipid peroxidation measured as MDA in melatonin treated group was appreciable although slightly lesser than the protection provided by Vitamin E+Se. The results imply that Vitamin E+Se and melatonin both provide chemoprevention against 7,12-DMBA-induced oxidative stress in mouse brain.

Prophylactic use of melatonin protects against focal cerebral ischemia in mice: role of endothelin converting enzyme-1

Melatonin has previously been shown to be neuroprotective in rodent models of ischemic stroke. Herein, we tested whether this antioxidant may also be suitable for prophylactic use against stroke. To clarify this issue, melatonin was administrated orally for 9 wk (4 mg/kg/day) in mice and its effects on subsequent injury development after 90 min of intraluminal middle cerebral artery (MCA) occlusion were tested. To evaluate its neuroprotective properties, the protective actions of prophylactic melatonin were compared with both acute melatonin (4 mg/kg, i.p.) administration and with a diluent (sham)-treated control condition. MCA occlusion resulted in reproducible ischemia, as revealed by laser Doppler flowmetry; this was followed by a rapid restoration of blood flow immediately after reperfusion onset. Laser Doppler flow values after reperfusion onset were moderately elevated by melatonin, both when the indole was given prophylactically and when acutely administrated after stroke. In control animals, reproducible brain infarcts were observed 24 hr after reperfusion onset. Treatment with melatonin significantly reduced the infarct size by approximately 30-35%, independent of whether the indole was given prophylactically before or acutely after ischemia. To test whether brain protection involved vascular mechanisms, as suggested earlier, the effects of melatonin on endothelin converting enzyme-1 (ECE-1) levels were studied using Western blots. Interestingly, delivery of melatonin was accompanied by a marked inhibition of ECE-1 levels, which was similarly seen after both acute and chronic melatonin treatment. Our data suggest that melatonin, given at pharmacological doses, may be suitable as a prophylaxis against stroke. Tissue protection may involve an inhibition of ECE-1, which improves vasodilation, after ischemia.

Melatonin, human aging, and age-related diseases

The worldwide prolongation of the mean life expectancy has resulted in a rapid increase of the size of the elderly population (over the age of 60), both in numbers and as a proportion of the whole. As a consequence, increasing the number of potential beneficiaries of health and pension funds, mainly those aged 65 and over raises many social and economic problems since they are supported by a relatively smaller number of potential contributors, i.e. those in the economically active ages between 18 and 64. Therefore, there is a search for any therapeutic agent improving quality of life in the elderly. A role for melatonin as such a compound was recently suggested. In this survey, data on the possible role of melatonin in human aging and age-related diseases are briefly presented. Undoubtedly the aging process is multi-factorial, and no single factor has been identified which satisfactorily explains the phenomenon. Although many theories relating the pineal gland and its secretory product melatonin to aging have been proposed, the role of this agent in the aging process is still unclear. However, for several reasons it seems reasonable to postulate a role for melatonin in this process. Melatonin levels decline gradually over the life-span and may be related to lowered sleep efficacy, very often associated with advancing age, as well as to deterioration of many circadian rhythms. Melatonin exhibits immunomodulatory properties, and a remodeling of immune system function is an integral part of aging. Finally, because melatonin is a potent free radical scavenger, its deficiency may result in reduced antioxidant protection in the elderly which may have significance not only for aging per se but also may contribute to the incidence or severity of some age-related diseases. Presently available data do not allow us to conclude that melatonin may have a role in extending normal longevity. However, although melatonin cannot be recognized as 'rejuvenating' agent, some of its actions may be beneficial for the aging process. Administration of melatonin may improve temporal organization in advanced age. Moreover, it has beneficial effects on sleep as well as age-related diseases. Although recommendations of melatonin supplementation in elderly should be considered, there is a need for extensive studies on the use of melatonin in order to improve the quality of life in advanced age.

Melatonin protects against ionizing radiation-induced oxidative damage in corpus cavernosum and urinary bladder in rats

The objective of this study was to examine the potential radioprotective properties of pharmacological doses of melatonin on corpus cavernosum and bladder tissues of whole-body irradiated (IR) rats. A total of 32 male Sprague-Dawley rats were exposed to irradiation performed with a LINAC which produced 6 MV photons at a focus 100 cm distant from the skin. Under ketamine anesthesia, each rat received a single whole-body dose of 800 cGy. Immediately before and after IR, rats were treated with either saline or melatonin (20 and 10 mg/kg, i.p.) and decapitated at 12 hr after exposure to irradiation. Another group of rats was followed for 72 hr after IR, where melatonin injections were repeated once daily. Tissue levels of malondialdehyde (MDA), an index of lipid peroxidation, and glutathione (GSH), a key antioxidant, were estimated in corpus cavernosum and urinary bladder. Tissues were also examined microscopically. The results demonstrate that both 12 and 72 hr following IR, tissue levels of MDA were elevated (P < 0.001), while GSH levels were reduced (P < 0.01) in both tissues. On the other hand, melatonin reversed these changes significantly (P < 0.05-0.01), concomitant with the improvement in histological appearances. Our results show that whole-body irradiation causes oxidative damage in the tissues of the genitourinary system. As melatonin administration reversed oxidative organ injury, as assessed by biochemical and histopathological findings, it is suggested that supplementing cancer patients with adjuvant therapy of melatonin may have some benefit for successful radiotherapy.

Circadian rhythms, oxidative stress, and antioxidative defense mechanisms

Endogenous circadian and exogenously driven daily rhythms of antioxidative enzyme activities and of low molecular weight antioxidants (LMWAs) are described in various phylogenetically distant organisms. Substantial amplitudes are detected in several cases, suggesting the significance of rhythmicity in avoiding excessive oxidative stress. Mammalian and/or avian glutathione peroxidase and, as a consequence, glutathione reductase activities follow the rhythm of melatonin. Another hint for an involvement of melatonin in the control of redox processes is seen in its high-affinity binding to cytosolic quinone reductase 2, previously believed to be a melatonin receptor. Although antioxidative protection by pharmacological doses of melatonin is repeatedly reported, explanations of these findings are still insufficient and their physiological and chronobiological relevance is not yet settled. Recent data indicate a role of melatonin in the avoidance of mitochondrial radical formation, a function which may prevail over direct scavenging. Rhythmic changes in oxidative damage of protein and lipid molecules are also reported. Enhanced oxidative protein modification accompanied by a marked increase in the circadian amplitude of this parameter is detected in the Drosophila mutant rosy, which is deficient in the LMWA urate. Preliminary evidence for the significance of circadian rhythmicity in diminishing oxidative stress comes from clock mutants. In Drosophila, moderately enhanced protein damage is described for the arrhythmic and melatonin null mutant per0, but even more elevated, periodic damage is found in the short-period mutant per(s), synchronized to LD 12:12. Remarkably large increases in oxidative protein damage, along with impairment of tissue integrity and--obviously insufficient--compensatory elevations in protective enzymes are observed in a particularly vulnerable organ, the Harderian gland, of another short-period mutant tau, in the Syrian hamster. Mice deficient in the per2 gene homolog are reported to be cancer-prone, a finding which might also relate to oxidative stress. In the dinoflagellate Lingulodinium polyedrum [Gonyaulax polyedra], various treatments that cause oxidative stress result in strong suppressions of melatonin and its metabolite 5-methoxytryptamine (5-MT) and to secondary effects on overt rhythmicity. The glow maximum, depending on the presence of elevated 5-MT at the end of subjective night, decreases in a dose-dependent manner already under moderate, non-lethal oxidative stress, but is restored by replenishing melatonin. Therefore, a general effect of oxidative stress may consist in declines of easily oxidizable signaling molecules such as melatonin, and this can have consequences on the circadian intraorganismal organization and expression of overt rhythms. Recent findings on a redox-sensitive input into the core oscillator via modulation of NPAS2/BMAL1 or CLK/BMAL1 heterodimer binding to DNA indicate a direct influence of cellular redox balance, including oxidative stress, on the circadian clock.

Hypochlorous acid-induced oxidative stress in Chinese hamster B14 cells: viability, DNA and protein damage and the protective action of melatonin

This study provides further evidence for the toxicity of hypochlorous acid (HOCl) in mammalian cells. Using the Chinese hamster B14 cell line, a significant decrease in cell viability was demonstrated after exposure to 100-200 microM HOCl for 1 h. Loss of viability was accompanied by a slight increase in DNA damage as shown by the Comet assay and by oxidation of cellular thiols. Exposure of B14 cells, erythrocyte membranes and human serum albumin to HOCl resulted in an extensive protein carbonyl accumulation. Thus, the cytotoxicity of HOCl may be due to both protein damage (carbonyl formation and oxidation of protein thiol groups) and DNA damage. The well-known antioxidant melatonin interacted with the oxidant and significantly protected cells during HOCl exposure, diminishing its cytotoxic effects and reducing protein carbonyl generation.

Melatonin protects SH-SY5Y neuroblastoma cells from calyculin A-induced neurofilament impairment and neurotoxicity

Hyperphosphorylation of cytoskeletal proteins seen in Alzheimer's disease is most probably the result of an imbalanced regulation in protein kinases and protein phosphatases (PP) in the affected neurons. Previous studies have revealed that PP-2A and PP-1 play important roles in the pathogenesis. Employing human neuroblastoma cells, we found that 10 nM calyculin A (CA), a selective inhibitor of PP-2A and PP-1, significantly increased phosphorylation and accumulation of neurofilament (NF) in the cells. Levels of NF-M (middle chain) and NF-L (light chain) mRNA decreased after CA treatment. Additionally, CA led to a decreased cell viability determined by MTT and crystal violet assay. Melatonin efficiently protects the cell from CA-induced alterations in NF hyperphosphorylation and accumulation, suppressed NF gene expression as well as decreased cell viability. It is concluded that inhibition of PP-2A/PP-1 by CA induces abnormalities in NF metabolism and cell survival, and melatonin efficiently arrests the lesions.

Melatonin as a new drug for improving oocyte quality

Background:  Although recent technical advances have benefited infertile couples, inadequate embryo development as a result of poor quality oocytes still contributes to infertility. The purpose of the present study was to evaluate melatonin as a drug for improving oocyte quality in such cases. Methods:  Twenty-seven women from whom fewer than three fertilized embryos were grown and who failed to fall pregnant in previous treatment cycles were enrolled in the current prospective clinical study. Subjects took 1 mg or 3 mg tablets of melatonin orally at 22:00 h from the fifth day of the previous menstrual cycle to the day they were injected with human chorionic gonadotropin. The numbers of mature follicles, retrieved oocytes, degenerate oocytes, and fertilized embryos were compared to their previous data without melatonin (the control cycle). Results:  Intrafollicular melatonin concentrations were significantly increased, and intrafollicular lipid peroxide concentrations showed a tendency towards lower levels in the 3 mg melatonin treatment cycles compared with the control cycles. The number of degenerate oocytes was significantly reduced, and the number of fertilized embryos showed a tendency towards an increase in the 3 mg cycle compared to the control cycle. Three women succeeded in falling pregnant. Conclusion:  Melatonin is likely to become the drug of choice for improving oocyte quality in women who cannot fall pregnant because of poor quality oocytes. (Reprod Med Biol 2003; 2: 139-144).

Agents ameliorating or augmenting experimental gentamicin nephrotoxicity: some recent research

Despite its nephrotoxic potential, the aminoglycoside antibiotic gentamicin (GM) is still considered to be an important agent against life-threatening infections. The goal of reducing or protecting against its nephrotoxicity has attracted much effort and attention during the last decade. This article reviews some of the literature published during the last decade on the effects of agents that ameliorate or augment GM nephrotoxicity. Notable among the ameliorating agents are antioxidant agents. These include different classes of compounds that include beta blockers (e.g. carvedilol), superoxide dismutase mimetic agents (e.g. M40403), hormones (e.g. melatonin), iron chelators (e.g. deferrioxamine), vitamins (vitamin C and E) and medicinal plants (e.g. garlic). Other ameliorating agents include antibiotics (e.g. ceftriaxone), antiplatelet drugs (e.g. trapidil) and Ca++ agents that may augment GM nephrotoxicity include cyclosporin and the Ca++-channel blocker verapamil.

Protective effect of melatonin against fractionated irradiation-induced epiphyseal injury in a weanling rat model

The effects of melatonin, a free-radical scavenger and a general antioxidant, on radiation-induced growth plate injury have not been studied previously. The purpose of this study was to determine the potential benefits of sparing longitudinal bone growth by fractionated radiotherapy alone compared with pretreatment with melatonin that provides differential radioprotection of normal cells. Weanling 4-wk-old (75-100 g) male Sprague-Dawley rats were randomly assigned to one of three groups: Group R received fractionated radiation alone (n = 8); groups M5 (n = 8) and M15 (n = 7) received 5 or 15 mg/kg melatonin prior to fractionated radiation, respectively. The distal femur and proximal tibia in the right leg of each animal were exposed to a therapeutic X-irradiation dose (25 Gy total in three fractions) with the contralateral left leg as the non-irradiated control. Melatonin was administered intraperitoneally to the animals 30 min before radiation exposure. Six weeks after treatment, the rats were killed and the lower limbs disarticulated, skeletonized, radiographed, and bone growth was calculated based on measurement of the bone lengths. Fractionated radiation resulted in a mean percent overall limb growth loss of 41.2 +/- 9.5 and a mean percent overall limb discrepancy of 11.2 +/- 2.2. The administration of 5 or 15 mg/kg melatonin before each of the three fractions of radiotherapy reduced the mean percent overall limb growth loss to 33.9 +/- 5.8 and 32.2 +/- 4.5, respectively, and the mean percent overall limb discrepancy to 9.4 +/- 1.6 and 8.9 +/- 1.1, respectively; these values were significantly different compared with irradiation alone (range: P = 0.01-0.04). When compared with Group R, the growth arrest recovered by 5 or 15 mg/kg melatonin was 19.7 and 24.1% for the tibia, 7 and 18.6% for the femur, and 17.7 and 21.8% for the total limb, respectively. These results support further investigation of melatonin in combination with fractionation for potential use in growing children requiring radiotherapy to the extremity for malignant tumors.

Melatonin protects against myocardial doxorubicin toxicity in rats: role of physiological concentrations

Doxorubicin (Dox) is a widely used antineoplastic drug. Oxygen radical-induced injury of membrane lipids is considered to be the most important factor responsible for the development of Dox-induced cardiotoxicity. The pineal secretory product, melatonin, is known to be a potent free radical scavenger and its pharmacological concentrations have been shown to reduce Dox-induced cardiac damage. However, the physiological role of melatonin in the prevention of this damage is unknown. We investigated physiological and pharmacological effects of melatonin on Dox-induced changes in the levels of malondialdehyde (MDA), a lipid peroxidation product, and morphological changes in heart. Rats were pinealectomized (Px) or sham-operated (control) 2 months before the studies. Melatonin was administered [4 mg/kg, intraperitoneally (i.p.)] 1 hr before or 24 hr after the administration of a single dose of Dox (20 mg/kg, i.p.) and continued for 2 days. The levels of MDA Dox was found to be significantly higher in the Px rats (55.9 +/- 0.6 nmol/g tissue) than intact control animals (42.6 +/- 0.4). Dox administration to Px and non-Px rats significantly increased the MDA levels. Pre- and post-treatment with melatonin in both Px and intact rats significantly reduced MDA levels. Morphological changes parallelled the MDA alterations. These findings strongly suggest that both physiological and pharmacological concentrations of melatonin are important in protecting the heart from Dox-induced damage in rats. It would seem valuable to test melatonin in clinical trials for prevention of possible heart damage associated with Dox.

Melatonin ameliorates oxidative organ damage induced by acute intra-abdominal compartment syndrome in rats

Acutely increased intra-abdominal pressure (IAP) can lead to multiple organ failure. As blood flow to intra-abdominal organs is reduced by high venous resistance, ischemia-reperfusion (I/R) injury plays an important role in the pathogenesis of abdominal compartment syndrome (ACS) following IAP. Melatonin, a secretory product of the pineal gland, is known to have free radical scavenging and antioxidative properties in several oxidative processes. The objective of this study was to examine the potential protective properties of melatonin on the oxidative organ damage in a rat model of ACS. Under ketamine anesthesia, an arterial catheter was inserted intraperioneally (i.p.) and using an aneroid manometer connected to the catheter, IAP was kept at 20 mmHg (ischemia group; I) for 1 hr. In the ischemia/reperfusion (I/R) group, pressure applied for an hour was decompressed and a 1-hr reperfusion period was allowed. In another IR group, melatonin was administered (10 mg/kg, i.p.) immediately before the decompression of IAP. The results demonstrate that tissue levels of malondialdehyde (MDA) and myeloperoxidase activity (MPO; index of tissue neutrophil infiltration) were elevated, while glutathione (GSH; a key to antioxidant) levels were reduced in both I and I/R groups (P < 0.05-0.001). Melatonin treatment in I/R rats reversed these changes (P < 0.01-0.001). Moreover, melatonin given to the I/R group reduced the elevations in serum aspartate aminotransferase, alanine aminotransferase and blood urea nitrogen levels and abolished the increase in serum creatinine levels. Our results indicate that melatonin, because of antioxidant and free radical scavenging properties, ameliorates reperfusion-induced oxidative organ damage. In conclusion, the results of the present study suggest that the therapeutic value of melatonin as a 'reperfusion injury-limiting' agent must be considered in ACS.

Amikacin-induced acute renal injury in rats: protective role of melatonin

It is well established that some agents such as aminoglycosides generate free oxygen radicals, leading to an increased oxireductase production, which in turn increases tissue toxicity. The aim of this study is to test whether melatonin, the chief secretory product of the pineal gland and a highly effective antioxidant and free radical scavenger, reduces the nephrotoxicity caused by amikacin (AK). Herein, we investigated the physiologic and pharmacological role of melatonin in influencing AK-induced nephrotoxicity. For this, pinealectomized (Px) and sham operated (non-Px) rats were used. Both AK and melatonin were administered to all groups. We investigated the effects of melatonin on AK-induced changes in levels of malondialdehyde (MDA), a lipid peroxidation product, glutathione (GSH), an antioxidant whose levels are influenced by oxidative stress, and blood urea nitrogen (BUN) and serum creatine (Cr) levels. Morphologic changes in the kidney were also examined by using light microscopy. MDA levels were found to be higher in Px than in non-Px AK-treated animals. Melatonin administration to Px rats reduced MDA levels. In relative to non-Px rats, Px animals treated with AK had significantly lower GSH concentrations while melatonin administration elevated GSH levels in the kidney; however, this stimulatory effect of melatonin was not observed in non-Px AK-treated rats. Treatment with AK alone resulted in significantly higher plasma Cr and BUN levels. Repeated administration of melatonin prevented the AK-induced elevation of plasma Cr and BUN levels. Morphologic damage to renal tubules as a result of AK was more severe in the renal cortex than in the medulla. The damage to the kidney induced by AK was reversed by melatonin in the Px rats. In conclusion, these results show that physiologic melatonin concentrations are important in reducing AK-induced renal damage, while pharmacologic concentrations of melatonin did not add to the beneficial effect.

Protective effects of melatonin, vitamin E and N-acetylcysteine against acetaminophen toxicity in mice: a comparative study

Acetaminophen (AA) is a commonly used analgesic and antipyretic drug; however, when used in high doses, it causes fulminant hepatic necrosis and nephrotoxic effects in both humans and experimental animals. It has been reported that the toxic effects of AA are the result of oxidative reactions that take place during its metabolism. In this study we investigated if melatonin, vitamin E or N-acetylcysteine (NAC) are protective against AA toxicity in mice. The doses of the antioxidants used were as follows: melatonin (10 mg/kg), vitamin E (30 mg/kg) and NAC (150 mg/kg). Blood urea nitrogen (BUN), serum creatinine, alanine aminotransferase (ALT), aspartate aminotransferase (AST) levels in blood, and glutathione (GSH), malondialdehyde (MDA), oxidized protein levels and myeloperoxidase (MPO) activity in liver and kidney tissues were measured. BUN and serum creatinine, ALT and AST levels which were increased significantly following AA treatment decreased significantly after pretreatment with either vitamin E, melatonin or NAC; however, they were not reduced to control levels. ALT and AST levels were significantly higher at 4 hr compared with the 24 hr levels after AA administration. However, BUN and creatinine levels were significantly elevated only at 24 hr. GSH levels were reduced while MDA, MPO and oxidized protein levels were increased significantly following AA administration. These changes were reversed by pretreatment with either melatonin, vitamin E or NAC. Liver toxicity was higher at 4 hr, whereas nephrotoxicity appeared to be more severe 24 hr after treatment with AA. Vitamin E was the least efficient agent in reversing AA toxicity while melatonin, considering it was given as at lower dose than either vitamin E or NAC, was the most effective. This may be the result of the higher efficacy of melatonin in scavenging various free radicals and also because of its ability in stimulating the antioxidant enzymes.

Five years survival in metastatic non-small cell lung cancer patients treated with chemotherapy alone or chemotherapy and melatonin: a randomized trial

Numerous experimental data have documented the oncostatic properties of melatonin. In addition to its potential direct antitumor activity, melatonin has proved to modulate the effects of cancer chemotherapy, by enhancing its therapeutic efficacy and reducing its toxicity. The increase in chemotherapeutic efficacy by melatonin may depend on two main mechanisms, namely prevention of chemotherapy-induced lymphocyte damage and its antioxidant effect, which has been proved to amplify cytotoxic actions of the chemotherapeutic agents against cancer cells. However, the clinical results available at present with melatonin and chemotherapy in the treatment of human neoplasms are generally limited to the evaluation of 1-year survival in patients with very advanced disease. Thus, the present study was performed to assess the 5-year survival results in metastatic non-small cell lung cancer patients obtained with a chemotherapeutic regimen consisting of cisplatin and etoposide, with or without the concomitant administration of melatonin (20 mg/day orally in the evening). The study included 100 consecutive patients who were randomized to receive chemotherapy alone or chemotherapy and melatonin. Both the overall tumor regression rate and the 5-year survival results were significantly higher in patients concomitantly treated with melatonin. In particular, no patient treated with chemotherapy alone was alive after 2 years, whereas a 5-year survival was achieved in three of 49 (6%) patients treated with chemotherapy and melatonin. Moreover, chemotherapy was better tolerated in patients treated with melatonin. This study confirms, in a considerable number of patients and for a long follow-up period, the possibility to improve the efficacy of chemotherapy in terms of both survival and quality of life by a concomitant administration of melatonin. This suggests a new biochemotherapeutic strategy in the treatment of human neoplasms.

Melatonin: clinical relevance

This chapter reviews the neural connections between the retinas and the pineal gland and summarizes the role of the light:dark cycle and the biological clock, i.e. the suprachiasmatic nuclei, in regulating pineal melatonin synthesis and secretion. The cellular mechanisms governing the nocturnal production of melatonin are described together with the way in which the misuse of light interferes with the circadian melatonin cycle and the total quantity of the indole generated. The chapter describes the nature of the membrane melatonin receptors and their signal transduction mechanisms in peripheral organs. The clinical implications and potential uses of melatonin in terms of influencing the biological clock (e.g. sleep and jet lag), immune function, and cancer initiation and growth are noted. Additionally, the chapter includes a description of the newly discovered free radical scavenging and antioxidant activities of melatonin; it also includes a list of clinical situations in which melatonin has been used with beneficial effects.

Antioxidant activity of melatonin in Chinese hamster ovarian cells: changes in cellular proliferation and differentiation

Melatonin is an endogenously generated molecule with free radical scavenging and antioxidant properties. Here, we studied the antiproliferative role of melatonin and other antioxidants on transformed Chinese hamster ovarian cells. Melatonin reduces cell proliferation in a dose- and time-dependent manner. Natural antioxidants which appear in edible plants including resveratrol and vitamin E mimicked the effect of melatonin. Flow cytometer analysis revealed that melatonin treatment reduces the number of cells in S-phase and increases cells in both G0/G1 and G2/M gaps. In addition, melatonin, as well as trolox, caused a clear morphological change by inducing the cells to become spindle shaped and fibroblast-like. Its effect is a reversible phenomenon that disappeared when melatonin was withdrawn from the culture medium. GSH levels are increased after melatonin treatment but pharmacologically blockade of GSH synthesis did not abolish melatonin's antiproliferative effect. Reduction of cell proliferation and the apparent induction of cell differentiation overlapped with melatonin's ability to change the intracellular redox state of CHO cells. We conclude that the cellular redox state may be involved in cellular transformation caused by antioxidants such as melatonin and trolox.