The clinical neuroimmunotherapeutic role of melatonin in oncology

Nonlinear study of indolamines: A hidden property that might have possible implications in neurodegeneration

Indolamines (e.g., serotonin and melatonin) are tryptophan-derived class of neurotransmitters and neuromodulators that play crucial roles in mood regulation, sleep-wake cycles, and gastrointestinal functions. These biogenic amines exert their effects by binding to specific receptors in the central nervous system, influencing neuronal activity and signalling cascades. Indolamines are vital in maintaining homeostasis, and imbalances in their levels have been implicated in various neurological and psychiatric disorders. Hence, in the present study, we have investigated the nonlinear properties of indolamines under a continuous wave (CW) and pulsed laser excitation using the closed-aperture (CA) Z-scan technique. The CA Z-scan is a cost-effective and sensitive analytical tool for investigating nonlinear properties. It is observed that indolamines show negative refractive and positive absorptive nonlinearity under in vitro physiological conditions. The origin of nonlinearity is ascribed to the thermo-optical effect governed by the saturated atomic absorption and molecular orientation mechanisms under CW and pulsed laser excitation, respectively. The strength of nonlinearity is found to vary linearly with the concentration of indolamines. Overall, serotonin possesses stronger nonlinearity than melatonin. The maximum nonlinearity (refractive index (n2) & absorption coefficient (β)) for melatonin under CW and pulsed laser excitations are (-1.266 × 10-12 m2W-1 and -1.883 × 10-17 m2W-1) & (8.046 × 10-8 mW-1 and 1.516 × 10-13 mW-1), respectively. Meanwhile, the maximum n2 and β under pulsed laser excitation for serotonin are obtained as -3.195 × 10-17 m2W-1 and 6.149 × 10-12 mW-1, respectively. The outcome of the results may be utilized in understanding processes mediated by indolamines and designing therapeutic interventions.

Oncostatic activities of melatonin: Roles in cell cycle, apoptosis, and autophagy

Melatonin, the major secretory product of the pineal gland, not only regulates circadian rhythms, mood, and sleep but also has actions in neoplastic processes which are being intensively investigated. Melatonin is a promising molecule which considered a differentiating agent in some cancer cells at both physiological and pharmacological concentrations. It can also reduce invasive and metastatic status through receptors MT1 and MT2 cytosolic binding sites, including calmodulin and quinone reductase II enzyme, and nuclear receptors related to orphan members of the superfamily RZR/ROR. Melatonin exerts oncostatic functions in numerous human malignancies. An increasing number of studies report that melatonin reduces the invasiveness of several human cancers such as prostate cancer, breast cancer, liver cancer, oral cancer, lung cancer, ovarian cancer, etc. Moreover, melatonin's oncostatic activities are exerted through different biological processes including antiproliferative actions, stimulation of anti-cancer immunity, modulation of the cell cycle, apoptosis, autophagy, the modulation of oncogene expression, and via antiangiogenic effects. This review focuses on the oncostatic activities of melatonin that targeted cell cycle control, with special attention to its modulatory effects on the key regulators of the cell cycle, apoptosis, and telomerase activity.

Adverse Events Associated with Melatonin for the Treatment of Primary or Secondary Sleep Disorders: A Systematic Review

BACKGROUND

Melatonin is widely available either on prescription for the treatment of sleep disorders or as an over-the-counter dietary supplement. Melatonin has also recently been licensed in the UK for the short-term treatment of jetlag. Little is known about the potential for adverse events (AEs), in particular AEs resulting from long-term use. Concern has been raised over the possible risks of exposure in certain populations including pre-adolescent children and patients with epilepsy or asthma.

OBJECTIVES

The aim of this systematic review was to assess the evidence for AEs associated with short-term and longer-term melatonin treatment for sleep disorders.

METHODS

A literature search of the PubMed/Medline database and Google Scholar was conducted to identify randomised, placebo-controlled trials (RCTs) of exogenous melatonin administered for primary or secondary sleep disorders. Studies were included if they reported on both the types and frequencies of AEs. Studies of pre-term infants, studies of < 1 week in duration or involving single doses of melatonin and studies in languages other than English were excluded. Findings from open-label studies that raised concerns relating to AE reports in patients were also examined. Studies were assessed for quality of reporting against the Consolidated Standards of Reporting Trials (CONSORT) checklist and for risk of bias against the Cochrane Collaboration risk-of-bias criteria.

RESULTS

37 RCTs met criteria for inclusion. Daily melatonin doses ranged from 0.15 mg to 12 mg. Subjects were monitored for up to 29 weeks, but most studies were of much shorter duration (4 weeks or less). The most frequently reported AEs were daytime sleepiness (1.66%), headache (0.74%), other sleep-related AEs (0.74%), dizziness (0.74%) and hypothermia (0.62%). Very few AEs considered to be serious or of clinical significance were reported. These included agitation, fatigue, mood swings, nightmares, skin irritation and palpitations. Most AEs either resolved spontaneously within a few days with no adjustment in melatonin, or immediately upon withdrawal of treatment. Melatonin was generally regarded as safe and well tolerated. Many studies predated publication of the CONSORT checklist and consequently did not conform closely to the guidelines. Similarly, only eight studies were judged 'good' overall with respect to the Cochrane risk-of-bias criteria. Of the remaining papers, 16 were considered 'fair' and 13 'poor' but publication of almost half of the papers preceded that of the earliest version of the guidelines.

CONCLUSION

Few, generally mild to moderate, AEs were associated with exogenous melatonin. No AEs that were life threatening or of major clinical significance were identified. The scarcity of evidence from long-term RCTs, however, limits the conclusions regarding the safety of continuous melatonin therapy over extended periods. There are insufficient robust data to allow a meaningful appraisal of concerns that melatonin may result in more clinically significant adverse effects in potentially at-risk populations. Future studies should be designed to comply with appropriate quality standards for RCTs, which most past studies have not.

Tissue regeneration: Impact of sleep on stem cell regenerative capacity

The circadian rhythm orchestrates many cellular functions, such as cell division, cell migration, metabolism and numerous intracellular biological processes. The physiological changes during sleep are believed to promote a suitable microenvironment for stem cells to proliferate, migrate and differentiate. These effects are mediated either directly by circadian clock genes or indirectly via hormones and cytokines. Hormones, such as melatonin and cortisol, are secreted in response to neural optic signals and act in harmony to regulate many biological functions during sleep. Herein, we correlate the effects of the main circadian genes on the expression of certain stem cell genes responsible for the regeneration of different tissues, including bone, cartilage, skin, and intestine. We also review the effects of different hormones and cytokines on stem cell activation or suppression and their relationship to the day/night cycle. The correlation of circadian rhythm with tissue regeneration could have implications in understanding the biology of sleep and tissue regeneration and in enhancing the efficacy and timing of surgical procedures.

Effect of occupational EMF exposure from radar at two different frequency bands on plasma melatonin and serotonin levels

OBJECTIVE

To delineate the effect of chronic electromagnetic field (EMF) exposure from radar on plasma melatonin and serotonin levels in occupationally exposed military personnel.

SUBJECTS AND METHODS

A total of 166 male military personnel participated in the study out of which only 155 joined for blood draw. They were divided into three sets: Control group (n = 68), exposure group I (n = 40) exposed to 8-12 GHz and exposure group II (n = 58) working with radar at 12.5-18 GHz frequency. The three groups were further split into two groups according to their years of service (up to 10 years and > 10 years) in order to investigate the effect of years of exposure from radar. Melatonin and serotonin levels were estimated by enzyme immunoassay in fasting blood samples collected from 06:00-07:00 h. EMF measurements were recorded at different locations using Satimo EME Guard 'Personal Exposure Meter' and Narda 'Broad Band Field Meter'.

RESULTS

The group I exposed population registered a minor though not significant decrease in plasma melatonin concentration while the other group II exposed population registered statistically significant decline in melatonin concentration when compared with controls. Highly significant increase in plasma serotonin levels was found in exposure group II when compared to control whereas marginal non-significant rise was also registered in exposure group I in comparison to control. Exposure in terms of length of service up to 10 years did not produce any significant effect in the indoleamine levels in both the exposure groups when they were compared with their respective control groups. Whereas, length of service greater than 10 years was observed to decrease and increase respectively the melatonin and serotonin concentration significantly in exposure group II but not in exposure group I. However, correlation test did not yield any significant association between years of service and melatonin or serotonin levels respectively in both the exposure sets I and II. No significant association was observed between melatonin and serotonin levels as well.

CONCLUSION

The study showed the EMF ability to influence plasma melatonin and serotonin concentration in radar workers, significantly in 12.5-18 GHz range with service period greater than 10 years.

Melatonin attenuates the TLR4-mediated inflammatory response through MyD88- and TRIF-dependent signaling pathways in an in vivo model of ovarian cancer

Background

Toll-like receptors (TLRs) are effector molecules expressed on the surface of ovarian cancer (OC) cells, but the functions of the TLR2/TLR4 signaling pathways in these cells remain unclear. Melatonin (mel) acts as an anti-inflammatory factor and has been reported to modulate TLRs in some aggressive tumor cell types. Therefore, we investigated OC and the effect of long-term mel therapy on the signaling pathways mediated by TLR2 and TLR4 via myeloid differentiation factor 88 (MyD88) and toll-like receptor-associated activator of interferon (TRIF) in an ethanol-preferring rat model.

Methods

To induce OC, the left ovary of animals either consuming 10% (v/v) ethanol or not was injected directly under the bursa with a single dose of 100 μg of 7,12-dimethylbenz(a)anthracene (DMBA) dissolved in 10 μL of sesame oil. The right ovaries were used as sham-surgery controls. After developing OC, half of the animals received i.p. injections of mel (200 μg/100 g b.w./day) for 60 days.

Results

Although mel therapy was unable to reduce TLR2 levels, it was able to suppress the OC-associated increase in the levels of the following proteins: TLR4, MyD88, nuclear factor kappa B (NFkB p65), inhibitor of NFkB alpha (IkBα), IkB kinase alpha (IKK-α), TNF receptor-associated factor 6 (TRAF6), TRIF, interferon regulatory factor 3 (IRF3), interferon β (IFN-β), tumor necrosis factor alpha (TNF-α), and interleukin (IL)-6. In addition, mel significantly attenuated the expression of IkBα, NFkB p65, TRIF and IRF-3, which are involved in TLR4-mediated signaling in OC during ethanol intake.

Conclusion

Collectively, our results suggest that mel attenuates the TLR4-induced MyD88- and TRIF-dependent signaling pathways in ethanol-preferring rats with OC.

Protective effects of melatonin in reducing oxidative stress and in preserving the fluidity of biological membranes: a review

Free radicals generated within subcellular compartments damage macromolecules which lead to severe structural changes and functional alterations of cellular organelles. A manifestation of free radical injury to biological membranes is the process of lipid peroxidation, an autooxidative chain reaction in which polyunsaturated fatty acids in the membrane are the substrate. There is considerable evidence that damage to polyunsaturated fatty acids tends to reduce membrane fluidity. However, adequate levels of fluidity are essential for the proper functioning of biological membranes. Thus, there is considerable interest in antioxidant molecules which are able to stabilize membranes because of their protective effects against lipid peroxidation. Melatonin is an indoleamine that modulates a wide variety of endocrine, neural and immune functions. Over the last two decades, intensive research has proven this molecule, as well as its metabolites, to possess substantial antioxidant activity. In addition to their ability to scavenge several reactive oxygen and nitrogen species, melatonin increases the activity of the glutathione redox enzymes, that is, glutathione peroxidase and reductase, as well as other antioxidant enzymes. These beneficial effects of melatonin are more significant because of its small molecular size and its amphipathic behaviour, which facilitates ease of melatonin penetration into every subcellular compartment. In the present work, we review the current information related to the beneficial effects of melatonin in maintaining the fluidity of biological membranes against free radical attack, and further, we discuss its implications for ageing and disease.

Characterization of chemically induced ovarian carcinomas in an ethanol-preferring rat model: influence of long-term melatonin treatment

Ovarian cancer is the fourth most common cause of cancer deaths among women, and chronic alcoholism may exert co-carcinogenic effects. Because melatonin (mel) has oncostatic properties, we aimed to investigate and characterize the chemical induction of ovarian tumors in a model of ethanol-preferring rats and to verify the influence of mel treatment on the overall features of these tumors. After rats were selected to receive ethanol (EtOH), they were surgically injected with 100 µg of 7,12-dimethyl-benz[a]anthracene (DMBA) plus sesame oil directly under the left ovarian bursa. At 260 days old, half of the animals received i.p. injections of 200 µg mel/100 g b.w. for 60 days. Four experimental groups were established: Group C, rats bearing ovarian carcinomas (OC); Group C+EtOH, rats voluntarily consuming 10% (v/v) EtOH and bearing OC; Group C+M, rats bearing OC and receiving mel; and Group C+EtOH+M, rats with OC consuming EtOH and receiving mel. Estrous cycle and nutritional parameters were evaluated, and anatomopathological analyses of the ovarian tumors were conducted. The incidence of ovarian tumors was higher in EtOH drinking animals 120 days post-DMBA administration, and mel efficiently reduced the prevalence of some aggressive tumors. Although mel promoted high EtOH consumption, it was effective in synchronizing the estrous cycle and reducing ovarian tumor mass by 20%. While rats in the C group displayed cysts containing serous fluid, C+EtOH rats showed solid tumor masses. After mel treatment, the ovaries of these rats presented as soft and mobile tissues. EtOH consumption increased the incidence of serous papillary carcinomas and sarcomas but not clear cell carcinomas. In contrast, mel reduced the incidence of sarcomas, endometrioid carcinomas and cystic teratomas. Combination of DMBA with EtOH intake potentiated the incidence of OC with malignant histologic subtypes. We concluded that mel reduces ovarian masses and the incidence of adenocarcinomas in ethanol-deprived rats.

A reinterpretation of the pathogenesis and cure of cancer according to the psychoneuroimmunological discoveries

The recent discoveries in the oncological researches have demonstrated that the prognosis of the neoplastic diseases depends on not only the biological characteristics of tumors, including oncogene expression and growth factor receptor activity, but also on the immune status of cancer patients. This is because the well-documented importance of the anticancer immunity in the initiation of the tumor that is mainly modulated by lymphocytes. In addition, the knowledge on the interactions between the immune and neuroendocrine systems has demonstrated that the immune responses are physiologically under a psychoneuroendocrine control. In particular, it has been confirmed that the activation of the brain opioid tone may suppress the generation of an effective anticancer immunity, whereas it is stimulated by other neuroendocrine structure, namely the pineal gland, through the release of at least two indole hormones with anticancer activity, melatonin and 5-methoxytryptamine, exerting both antiproliferative and immunostimulatory effects. By investigating the immune and neuroendocrine functions in cancer patients, it has been observed that cancer progression is associated with a progressive decline in the pineal function, which would constitute the main cancer-related endocrine deficiency, and the occurrence of the irreversible immune alterations. The most prognostically important factors would consist of a diminished endogenous production of anticancer cytokines, such as IL-2 and IL-12, as well as an abnormally enhanced secretion of cytokines provided by suppressive effect on the anticancer immunity, namely IL-14, TGF-beta, and IL-6. The psychoneuroimmunotherapeutic approach in the treatment of cancer would simply consist of the corrections of the various endocrine and immune cancer-related alterations in an attempt to re-establish the neuroimmune condition of the health status.

Principles of psychoneuroendocrinoimmunotherapy of cancer

Recent advances in the knowledge of the mechanisms responsible for antitumor immunity have stimulated the elaboration of new cancer immunotherapeutic strategies. Moreover, more recent discoveries have demonstrated that immune responses are under a physiological modulatory control played by several neuroendocrine pathways, which explain the differences between the in vivo and in vitro immune responses. While until a few years ago the evaluation of the immune status of cancer patients was substantially established on the basis of clinical empirical criteria, recent discoveries of the antitumor cytokine network have allowed the biochemical bases of anticancer immunity to be defined, leading to new anticancer immunotherapeutic strategies, on the basis of patient neuroendocrine and neuroimmune status, in an attempt to correct the great number of cancer-related alterations on the basis of knowledge of the physiopathology of anticancer immunity. The rationale for cancer neuroimmunotherapy consists of the possibility to enhance the efficacy of the various immunotherapeutic strategies by a concomitant administration of antitumor cytokines (namely IL-2), in addition to neuroendocrine endogenous molecules (namely the pineal indole hormones), able to stimulate the anticancer immunoresponse by amplifying the anticancer reaction and/or by counteracting the generation of immunosuppressive events.

The importance of spirituality in supportive care

Background:

It has been shown that the pineal gland plays a fundamental role in mediating either the spiritual perception or the anticancer immunity by stimulating the endogenous production of anticancer cytokine interleukin (IL)-2.

Objective:

The present study was performed to evaluate the impact of a spiritual approach consisting of Kriya Yoga program alone or in association with melatonin (MLT) or low-dose IL-2 plus MLT on the survival time in a group of metastatic cancer patients with life expectancy less than 1 year.

Materials and Methods:

A case-control study was carried out in 240 patients (M/F: 146/94; median age: 62 years, range: 34-71, suffering from non-small-cell lung cancer or gastrointestinal tumors) who were subdivided into 6 groups of 40 patients, treated with supportive care alone as a control group, supportive care plus Yoga, MLT alone, MLT plus Yoga, inteleukin-2 plus MLT, or IL-2 plus MLT plus Yoga.

Results:

The best results in terms of increased survival time were obtained by the association between neuroimmunotherapy with MLT plus IL-2 and Yoga program (2 years), which was significantly longer with respect to that achieved by supportive care alone, Yoga alone, or IL-2 plus MLT alone (1 year).

Conclusions:

This study would suggest that a spiritual therapeutic approach may improve the survival time of untreatable metastatic solid tumor patients.

Therapeutic Actions of Melatonin in Cancer: Possible Mechanisms

Melatonin is a phylogenetically well-preserved molecule with diverse physiological functions. In addition to its well-known regulatory control of the sleep/wake cycle, as well as circadian rhythms generally, melatonin is involved in immunomodulation, hematopoiesis, and antioxidative processes. Recent human and animal studies have now shown that melatonin also has important oncostatic properties. Both at physiological and pharmacological doses melatonin exerts growth inhibitory effects on breast cancer cell lines. In hepatomas, through its activation of MT 1 and MT2 receptors, melatonin inhibits linoleic acid uptake, thereby preventing the formation of the mitogenic metabolite 1,3-hydroxyoctadecadienoic acid. In animal model studies, melatonin has been shown to have preventative action against nitrosodiethylamine (NDEA)-induced liver cancer. Melatonin also inhibits the growth of prostate tumors via activation of MT1 receptors thereby inducing translocation of the androgen receptor to the cytoplasm and inhibition of the effect of endogenous androgens. There is abundant evidence indicating that melatonin is involved in preventing tumor initiation, promotion, and progression. The anticarcinogenic effect of melatonin on neoplastic cells relies on its antioxidant, immunostimulating, and apoptotic properties. Melatonin's oncostatic actions include the direct augmentation of natural killer (NK) cell activity, which increases immunosurveillance, as well as the stimulation of cytokine production, for example, of interleukin (IL)-2, IL-6, IL-12, and interferon (IFN)-γ. In addition to its direct oncostatic action, melatonin protects hematopoietic precursors from the toxic effect of anticancer chemotherapeutic drugs. Melatonin secretion is impaired in patients suffering from breast cancer, endometrial cancer, or colorectal cancer. The increased incidence of breast cancer and colorectal cancer seen in nurses and other night shift workers suggests a possible link between diminished secretion of melatonin and increased exposure to light during nighttime. The physiological surge of melatonin at night is thus considered a “natural restraint” on tumor initiation, promotion, and progression.

Melatonin Induces Akt Phosphorylation through Melatonin Receptor- and PI3K-Dependent Pathways in Primary Astrocytes

Melatonin has been reported to protect neurons from a variety of neurotoxicity. However, the underlying mechanism by which melatonin exerts its neuroprotective property has not yet been clearly understood. We previously demonstrated that melatonin protected kainic acid-induced neuronal cell death in mouse hippocampus, accompanied by sustained activation of Akt, a critical mediator of neuronal survival. To further elucidate the neuroprotective action of melatonin, we examined in the present study the causal mechanism how Akt signaling pathway is regulated by melatonin in a rat primary astrocyte culture model. Melatonin resulted in increased astrocytic Akt phosphorylation, which was significantly decreased with wortmannin, a specific inhibitor of PI3K, suggesting that activation of Akt by melatonin is mediated through the PI3K-Akt signaling pathway. Furthermore, increased Akt activation was also significantly decreased with luzindole, a non-selective melatonin receptor antagonist. As downstream signaling pathway of Akt activation, increased levels of CREB phoshorylation and GDNF expression were observed, which were also attenuated with wortmannin and luzindole. These results strongly suggest that melatonin exerts its neuroprotective property in astrocytes through the activation of plasma membrane receptors and then PI3K-Akt signaling pathway.

Melatonin the "light of night" in human biology and adolescent idiopathic scoliosis

Melatonin "the light of night" is secreted from the pineal gland principally at night. The hormone is involved in sleep regulation, as well as in a number of other cyclical bodily activities and circadian rhythm in humans. Melatonin is exclusively involved in signalling the 'time of day' and 'time of year' (hence considered to help both clock and calendar functions) to all tissues and is thus considered to be the body's chronological pacemaker or 'Zeitgeber'. The last decades melatonin has been used as a therapeutic chemical in a large spectrum of diseases, mainly in sleep disturbances and tumours and may play a role in the biologic regulation of mood, affective disorders, cardiovascular system, reproduction and aging. There are few papers regarding melatonin and its role in adolescent idiopathic scoliosis (AIS). Melatonin may play a role in the pathogenesis of scoliosis (neuroendocrine hypothesis) but at present, the data available cannot clearly support this hypothesis. Uncertainties and doubts still surround the role of melatonin in human physiology and pathophysiology and future research is needed.

Melatonin inhibits the expression of the inducible isoform of nitric oxide synthase and nuclear factor kappa B activation in rat skeletal muscle

This study investigated whether the induction of inducible nitric oxide synthase (iNOS) produced by acute exercise in rat skeletal muscle could be prevented by melatonin and whether iNOS down-regulation was related to inhibition of nuclear factor kappaB (NF-kappaB) activation. Male Wistar rats received melatonin i.p. at a dose of 1.0 mg/kg body weight 30 min before being exercised for 60 min on a treadmill at a speed of 25 m/min and a 10% slope. Exercise caused a significant induction of iNOS protein levels and a marked activation of NF-kappaB that were significantly prevented in rats treated with melatonin. Exercise also resulted in increased IkappaB kinasealpha (IKKalpha) and phosphorylated IkappaBalpha protein levels, whereas IkappaBalpha content decreased. These effects were blocked by melatonin administration. The increase in the muscle concentration of thiobarbituric acid reactive substances and in the oxidized/reduced glutathione ratio induced by exercise was partially prevented by melatonin. Our data indicate that melatonin has potent protective effects against damage caused by acute exercise in rat muscle, preventing oxidative stress, NF-kappaB activation and iNOS over-expression. These findings support the view that melatonin treatment, by abolishing the IKK/NF-kappaB signal transduction pathway, might block the production of noxious mediators involved in the inflammatory process.

Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in advanced non-small-cell lung cancer patients with low performance status

BACKGROUND

The prognosis of low performance status (PS) patients with advanced non-small-cell-lung cancer (NSCLC) is dismal. In these patients, we have determined the survival, clinical benefits, and toxicity of a multidrug regimen, based on cyclophosphamide and biotherapeutical agents.

METHODS

Patients with a diagnosis of stage IIIB or stage IV NSCLC, no previous surgery or chemoradiotherapy, and an Eastern Cooperative Oncology Group (ECOG) PS equal to or greater than 2 received a daily combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide.

RESULTS

Twenty-eight (28) patients were enrolled. The median age was 64 years (range, 35-74). The PS was 2 and 3 in 78.6% and 21.4% of patients, respectively. The median overall survival (intent-to-treat analysis) was 12.9 months (range, 1.5-33.5 months), The overall survival rates at 1 and 2 years were 51.2% and 21.1%, respectively. The side-effects were very mild, mostly consisting of diarrhoea, nausea/vomiting, and drowsiness of grade 1-2. Most patients experienced an improvement of both respiratory (cough and dyspnoea) and general (pain, fatigue, and insomnia) symptoms.

CONCLUSIONS

Low PS patients with advanced NSCLC may benefit from a combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide, in terms of survival and quality of life, with very low side-effects.

Sustained activation of Akt by melatonin contributes to the protection against kainic acid-induced neuronal death in hippocampus

In the present study, the underlying protective mechanism of melatonin on kainic acid (KA)-induced excitotoxicity was examined in the hippocampus of mice. KA, administered intracerebroventricularly (i.c.v.), induced marked neuronal cell death with concurrent microglial activation and subsequent induction of inducible nitric oxide synthase (iNOS) in the hippocampus. Histopathological analysis demonstrated that melatonin (10 mg/kg), administered 1 hr prior to KA, attenuated KA-induced death of pyramidal neurons in the CA3 region. Melatonin obviously suppressed KA-induced microglial activation and consequent iNOS expression that were determined by increased immunoreactivities of microglial marker OX-6 and iNOS, respectively. Increased phosphorylation of Akt in pyramidal neurons was observed as early as 2 hr after administration of melatonin. Further, melatonin resulted in increased expression of astroglial glial cell line-derived neurotrophic factor (GDNF), which started to appear approximately 6 hr after administration of melatonin. The results of the present study demonstrate that melatonin exerts its neuroprotective action against KA-induced excitotoxicity both through the activation of neuronal Akt and via the direct action on hippocampal neurons and through the increased expression of astroglial GDNF, which subsequently activates neuronal PI3K/Akt pathway. Therefore, the present study suggests that melatonin, pineal secretory product, is potentially useful in the treatment of acute brain pathologies associated with excitotoxic neuronal damage such as epilepsy, stroke, and traumatic brain injury.

Evaluation of the relationship between inducible nitric oxide synthase (iNOS) activity and effects of melatonin in experimental osteoporosis in the rat

Inducible nitric oxide synthase (iNOS) plays a critical role in the pathogenesis of osteoporosis. iNOS generates nitric oxide (NO), a free radical contributing to the imbalance between bone formation and resorption caused by estrogen depletion. Melatonin is the major product of the pineal gland which is known to diminish iNOS expression and NO production significantly. The aim of this study was to determine the distribution of iNOS and the amount of apoptotic cells after melatonin treatment in ovariectomized rats. Since previous studies have shown that constitution of bone formation is primarily sustained in nucleus pulposus and epiphyseal cartilage, experiments were carried out on nucleus pulposus and epiphyseal cartilage; additional quantitation of osteoblasts and osteoclasts were evaluated on vertebral area as well. Vertebral sections of ovariectomized rats were obtained from formalin-fixed and parafin-embedded blocks. iNOS expression and quantitation of apoptotic cells in nucleus pulposus and epiphyseal cartilage were evaluated using indirect immunoperoxidase and TUNEL techniques, respectively. The number of osteoclasts and osteoblasts in trabecular bone was determined using histomorphometry. Ovariectomy increased iNOS expression and the number of apoptotic cells in nucleus pulposus and epiphyseal cartilage, whereas a 4-week treatment with melatonin (10 mg/kg/day) resulted in the reduction of both effects. These data indicate that there is strong influence of melatonin application on expression of iNOS, apoptosis, osteoclast and osteoblast numbers after ovariectomy. In conclusion, melatonin besides its usual use as an antiaging hormone, may also be an effective hormone in treatment of bone changes in estrogen deficiency states.

Melatonin improves sleep in asthma: a randomized, double-blind, placebo-controlled study

Disturbed sleep is common in asthma. Melatonin has sleep-inducing activity and reportedly affects smooth muscle tone and inflammation. The aim of this study was to evaluate the effect of melatonin on sleep in patients with mild and moderate asthma. This was a randomized, double-blind, placebo-controlled study. Twenty-two consecutive women with asthma were randomized to receive melatonin 3 mg (n = 12) or placebo (n = 10) for 4 weeks. Sleep quality and daytime somnolence were assessed by the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Scale, respectively. Pulmonary function was assessed by spirometry. Use of relief medication, asthma symptoms, and morning and evening peak expiratory flow rate were recorded daily. Melatonin treatment significantly improved subjective sleep quality, as compared with placebo (p = 0.04). No significant difference in asthma symptoms, use of relief medication and daily peak expiratory flow rate was found between groups. We conclude that melatonin can improve sleep in patients with asthma. Further studies looking into long-term effects of melatonin on airway inflammation and bronchial hyperresponsiveness are needed before melatonin can be recommended in patients with asthma.

Melatonin as a radioprotective agent: a review

Melatonin (N-acetyl-5-methoxytryptamine), the chief secretory product of the pineal gland in the brain, is well known for its functional versatility. In hundreds of investigations, melatonin has been documented as a direct free radical scavenger and an indirect antioxidant, as well as an important immunomodulatory agent. The radical scavenging ability of melatonin is believed to work via electron donation to detoxify a variety of reactive oxygen and nitrogen species, including the highly toxic hydroxyl radical. It has long been recognized that the damaging effects of ionizing radiation are brought about by both direct and indirect mechanisms. The direct action produces disruption of sensitive molecules in the cells, whereas the indirect effects ( approximately 70%) result from its interaction with water molecules, which results in the production of highly reactive free radicals such as *OH, *H, and e(aq)- and their subsequent action on subcellular structures. The hydroxyl radical scavenging ability of melatonin was used as a rationale to determine its radioprotective efficiency. Indeed, the results from many in vitro and in vivo investigations have confirmed that melatonin protects mammalian cells from the toxic effects of ionizing radiation. Furthermore, several clinical reports indicate that melatonin administration, either alone or in combination with traditional radiotherapy, results in a favorable efficacy:toxicity ratio during the treatment of human cancers. This article reviews the literature from laboratory investigations that document the ability of melatonin to scavenge a variety of free radicals (including the hydroxyl radical induced by ionizing radiation) and summarizes the evidence that should be used to design larger translational research-based clinical trials using melatonin as a radioprotector and also in cancer radiotherapy. The potential use of melatonin for protecting individuals from radiation terrorism is also considered.

Melatonin ameliorates ionizing radiation-induced oxidative organ damage in rats

This study was designed to study the effects of the potential radioprotective properties of pharmacological doses of melatonin against organ damage induced by whole-body irradiation (IR) in rats. A total of 32 male Sprague-Dawley rats were exposed to irradiation performed with a LINAC producing 6 MV photons at a focus 100 cm distant from the skin. Under ketamine anaesthesia, 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 mg/kg and 10 mg/kg, i.p.) and decapitated at 12-h after exposure to irradiation. Another group of rats was followed for 72-h after IR, where melatonin (10 mg/kg, i.p.) injections were repeated once daily. Tissue levels of malondialdehyde (MDA)--an index of lipid peroxidation--, glutathione (GSH)--a key to antioxidant--and myeloperoxidase (MPO) activity--an index of neutrophil infiltration--were estimated in liver, lung, colon and intestinal tissues. The results demonstrate that both 12-h and 72-h following IR, tissue levels of MDA were elevated (p<0.05-0.001), while GSH levels were reduced (p<0.05-0.001) in all organs. On the other hand, melatonin, reduced the levels of MDA and increased the GSH levels significantly, (p<0.05-0.001). MPO activity was increased significantly in the colonic tissue at the both 12-h and 72-h, and in the hepatic tissue at the 72-h following IR, which were reduced by melatonin (p<0.01-0.001). In the lung tissue enzyme activity was decreased at 72nd h of post-irradiation. In conclusion, the increase in MDA levels and MPO activity and the concomitant decrease in GSH levels demonstrate the role of oxidative mechanisms in irradiation-induced tissue damage, and melatonin, by its free radical scavenging and antioxidant properties, ameliorates irradiation-induced organ injury. Thus, supplementing cancer patients with adjuvant therapy of melatonin may have some benefit for successful radiotherapy.

Chronopharmacology of melatonin in mice to maximize the antitumor effect and minimize the rhythm disturbance effect

The influence of dosing time on the antitumor effect and the rhythm disturbance effect of melatonin (MLT) was investigated in ICR male mice under a light/dark (12:12) cycle. In tumor-bearing mice, the antitumor effect of MLT (1 mg/kg intraperitoneal) was most effective in the dark phase; and the rhythm disturbance effect of MLT on the locomotor activity was more serious in the light phase than in the dark phase. The antitumor effect and the rhythm disturbance effect of MLT increased when the specific binding of MLT receptor in target tissues, tumor or suprachiasmatic nucleus, increased and they decreased when the level decreased. Furthermore, because luzindole, an MT1 and MT2 blocker, caused the antitumor effect or rhythm disturbance effect of MLT to decrease, it is suggested that the time-dependent change of the pharmacological effects of MLT were influenced by that of MLT receptor(s) function. On the other hand, there was no significant dosing time-dependent change of MLT concentration in tumor or brain after injection. Thus, the pharmacokinetic factor does not seem to contribute to the dosing time-dependent effect of MLT. These results suggest that by choosing the most suitable dosing time for MLT, the efficacy of the drug can be increased, and the toxicity of the drug can be decreased in certain experimental and clinical situations.

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.

[Video screen exposure and 6-sulfatoxymelatonin urinary excretion in women]

A study in blind conditions was conducted on 13 women (mean age < 30 years). Six women worked at least four hours per day, five days a week, since more than one month, in front of a video screen constituted the exposed group. Radioimmunoassay of 6-sulfatoxymelatonin was done on urine collected during night. Results were analysed by a non parametric rank-test (Mann-Withney). It was observed an important (- 54%) and significant lower level (p < 0.01) of 6-sulfatoxymelatonin in urine of women exposed to video screen.

Does the pineal gland have a role in the psychological mechanisms involved in the progression of cancer?

Psychological factors, e.g., depression and psychological stress have been implicated in the progress of cancer. Similarly, the pineal gland and its principal secretion, melatonin, are known to influence the initiation and progress of cancer. Furthermore, changes in melatonin secretion have been linked with psychological stress and depression, and both the pineal gland and the cerebral cortex act via the limbic system in producing their effects. Both psychological stress and melatonin affect the immune system, as does the hypothalamus and the autonomic nervous system. The pineal gland has both a direct effect on cancer, and via the immune system. Psychological treatment and melatonin treatment have both been found to alleviate the course of cancer clinically. It is thus hypothesized that the pineal gland, and melatonin, are involved in the mechanism of psychological effects in the promotion of the progress of cancer.

Melatonin: from basic research to cancer treatment clinics

Melatonin, the chief secretory product of the pineal gland, is a direct free radical scavenger, an indirect antioxidant, as well as an important immunomodulatory agent. In both in vitro and in vivo investigations, melatonin protected healthy cells from radiation-induced and chemotherapeutic drug-induced toxicity. Furthermore, several clinical studies have demonstrated the potential of melatonin, either alone or in combination with traditional therapy, to yield a favorable efficacy to toxicity ratio in the treatment of human cancers. This study reviews the literature from laboratory investigations that document the antioxidant and oncostatic actions of melatonin and summarizes the evidence regarding the potential use of melatonin in cancer treatment. This study also provides rationale for the design of larger translational research-based clinical trials.

Melatonin fails to modulate immune parameters influenced by calorie restriction in aging Fischer 344 rats

The aim of this study was to determine if long-term treatment with melatonin (MEL), a purported anti-aging agent, was as effective as calorie restriction (CR) in modulating immune parameters in aging Fischer 344 male rats. Splenic lymphocytes were isolated from 17-month-old rats that, beginning at 6 weeks of age, were treated with MEL (4 or 16 microg/ml in drinking water) and from 17-month-old rats fed ad libitum (AL) or rats fed a CR diet (55% of AL intake). The number of splenic T cell populations and T cell subsets was measured by flow cytometry, the proliferative response of splenocytes to Concanavalin A (Con A) and lipopolysaccharide (LPS) was measured by [(3)H]thymidine incorporation, and the induction of cytokine production (IL-2 and IFN-gamma) was measured by ELISA assay. In addition, the level of the natural killer (NK) cell activity was assessed by fluorimetric assay. CR rats had a higher number of lymphocytes expressing the naïve T cell marker (CD3 OX22) than AL rats (P < 0.05). CR rats also showed greater induction of proliferative response, IL-2 and IFN-gamma levels following Con A simulation, and NK cell activity than AL rats (P < 0.05). MEL-treated rats did not differ from AL rats in any of these parameters or in any other measurement. These results indicate that MEL treatment is unable to modulate immune function in a manner comparable with that of CR.

Role of exogenous melatonin in reducing the cardiotoxic effect of daunorubicin and doxorubicin in the rat

The aim of the studies was to examine the cardioprotective effect of melatonin during the anthracycline administration (daunorubicin, doxorubicin) in rats. Application of these drugs in chemotherapy is limited because of their cardiotoxicity. Rats of Buffalo strain were divided into groups according to the cytostatic drug used, its dose and sequence of administration (single intravenous [i.v.] dose of 10 mg/kg b.w., i.e., acute intoxication; 3 mg/kg b.w. weekly for 3 weeks, subchronic intoxication). Melatonin was administered subcutaneously before and after every injection of a cytostatic drug at a dose of 10 mg/kg b.w. The degree of cardiac muscle cell alterations was examined either histologically (Mean Total Score technique and the Billingham scale), or biochemically (levels of lipid peroxidation markers, malonyldialdehyde, and 4-hydroxyalkenals). Statistically significant decrease in cardiac muscle cell damage was noted with an aid of the Billingham scale after melatonin administration in acutely intoxicated doxorubicin-treated rats (p < 0.001). The similar phenomenon was observed using the Mean Total Score technique in case of acute daunorubicin or doxorubicin (p < 0.01 and p < 0.001, respectively) intoxications. A significant reduction in cardiac muscle cell lesions was detected either by the Billingham scale or by the Mean Total Score technique during subchronic intoxication with either of the anthracyclines when melatonin was given. Biochemical assays revealed significant decreases in malonyldialdehyde and 4-hydroxyalkenals levels following application of melatonin during either acute doxorubicin (p < 0.05) or subchronic daunorubicin (p < 0.01) intoxication. In summary, melatonin was found to exert a protective effect on the cardiac muscle cells, which was particularly evident after acute doxorubicin or subchronic daunorubicin intoxication, using either histological or biochemical methods.

Oncology in neuroimmunomodulation. What progress has been made?

In 1987 in Dubrovnik, Yugoslavia, N.H. Spector named a new discipline: Neuroimmunomodulation. R. Ader called this new discipline psychoneuroimmunomodulation when the major emphysis was on its behavioral aspects. Neuroimmunomodulation (NIM) is devoted to the study of the interactions at different morphologic and functional levels among the immune, nervous, and endocrine systems. In fact, this science is the modern manifestation of an old science: in the words of B.D. Jankovic (1987), "Neuroimmunomodulation is a modern reflection in neurosciences and immunosciences of the ideas and experience of philosophers and ingenious observers of ancient Egypt, Greece, China, India, and other civilizations that the mind is involved in the defense against diseases." Twelve years ago NIM was regarded by many conventional scientists almost as a form of witchcraft. Today it may be the fastest growing area of biomedical science research in the world. Important clinical applications will not be far behind. NIM research has also progressed in the field of oncology research. Topics such as treatment of hormone-dependent cancer with analogues of hypothalamic hormones, the role of opioids and T cells in cancer, stress-cancer-immune connections, the anticancer role of melatonin and cytokines, immunotherapy of cancer, and the role of psychotherapy in cancer patients represent some lines of research that have been or are being investigated by scientists. Some areas remain to be thoroughly investigated such as the influence of physical exercise (sports), music (classical or modern), and/or relaxation techniques (e.g. yoga) on the development of human cancer. This paper reviews the role of NIM in oncology and provides some perspectives for further research and development of clinical applications.

Melatonin attenuates the changes in polyamine levels induced by systemic kainate administration in rat brains

Systemically administered kainate has been demonstrated to induce neuronal damage and changes of the levels of biochemical substances related to neurotoxicity. Polyamines are thought to be important in the generation of edema and neuronal cell loss associated with various type of excitotoxicity. Melatonin exerts potent free radical scavenging, antioxidant, and neuroprotective properties. This study was designed to estimate the effect of exogenous melatonin administration on the changes of polyamine levels in rat brains after systemic administration of kainate. Kainate [10 mg/kg, intraperitoneally (i.p.)] was injected into the rats to produce excitotoxicity. Melatonin (15 mg/kg, i.p.) was administered 1 h before, immediately after, and 1 h after kainate treatment. We examined the polyamine [putrescine (PU), spermidine (SD) and spermine (SM)] levels in the cerebral cortex and hippocampus and neuronal density in the hippocampal CA1 and CA3 subsectors in brain sections. PU levels were increased 8 and 24 h after kainate treatment and the administration of melatonin attenuated these changes. Only minor changes were noted in the levels of the polyamine SD and SM after the kainate treatment. In histology, neuronal injuries in the hippocampal CA1 and CA3 subsectors were examined 3 days after kainate treatment and melatonin reduced the kainate-induced neuronal injuries. Our results show that melatonin inhibits the polyamine responses in the cerebral cortex and hippocampus following kainate-induced excitotoxicity and PU may be responsible for the protective effect of melatonin against kainate-induced excitotoxicity.

MLT and the immune-hematopoietic system

It is now well recognized that a main actor in the continuous interaction between the nervous and immune systems is the pineal hormone MLT. T-helper cells bear G-protein coupled MLT cell membrane receptors and, perhaps, MLT nuclear receptors. Activation of MLT receptors enhances the release of T-helper cell type 1 (Th1) cytokines, such as gamma-interferon and interleukin-2 (IL-2), as well as of novel opioid cytokines which crossreact immunologically with both interleukin-4 (IL-4) and dynorphin B. MLT has been reported also to enhance the production of interleukin-1 (IL-1), interleukin-6 (IL-6) and interleukin-12 (IL-12) in human monocytes. These mediators may counteract stress-induced immunodepression and other secondary immunodeficiencies, protect mice against lethal viral and bacterial diseases, synergize with IL-2 in cancer patients and influence hematopoiesis. In cancer patients, MLT seems to be required for the effectiveness of low dose IL-2 in those neoplasias that are generally resistant to IL-2 alone. Hematopoiesis is apparently influenced by the action of the MLT-induced-opioids (MIO) on kappa-opioid receptors present on stromal bone marrow macrophages. Most interestingly, gamma-interferon and colony stimulating factors (CSFs) may modulate the production of MLT in the pineal gland. A hypothetical pineal-immune-hematopoietic network is, therefore, taking shape. From the immunopharmacological and ethical point of view, clinical studies on the effect of MLT in combination with IL-2 or other cytokines in viral disease including human immunodeficiency virus-infected patients and cancer patients are needed. In conclusion, MLT seems to play a crucial role in the homeostatic interactions between the brain and the immune-hematopoietic system and deserves to be further studied to identify its therapeutic indications and its adverse effects.

Therapeutic potential of melatonin in immunodeficiency states, viral diseases, and cancer

Maintenance of health depends on the ability to respond appropriately to environmental stressors via reciprocal interactions between the body and the brain. In this context, it is well recognized that the pineal hormone melatonin (MLT) plays an important role. T-helper cells bear G-protein-coupled MLT cell membrane receptors and, perhaps, MLT nuclear receptors. Activation of MLT receptors enhances the release of T-helper cell cytokines, such as gamma-interferon and interleukin-2 (IL-2), as well as activation of novel opioid cytokines which crossreact immunologically with both interleukin-4 and dynorphin B. MLT has been reported also to enhance the production of interleukin-1, interleukin-6 and interleukin-12 in human monocytes. These mediators may counteract secondary immunodeficiencies, protect mice against lethal viral and bacterial diseases, synergize with IL-2 against cancer and influence hematopoiesis. Hematopoiesis is influenced by MLT-induced-opioids (MIO) acting on kappa 1-opioid receptors present on bone marrow macrophages. Clinically, MLT could amplify the anti-tumoral activity of low dose IL-2, induce objective tumor regression, and prolong progression-free time and overall survival. MLT seems to be required for the effectiveness of low dose IL-2 in those neoplasias that are generally resistant to IL-2 alone. Similar findings were obtained in a study in which MLT was combined with gamma-interferon in metastatic renal cell carcinoma. In addition, MLT in combination with low-dose IL-2 was able to neutralize the surgery-induced lymphocytopenia in cancer patients. IL-2 treatment in patients results in activation of the immune system and creates the most suitable biological background for MLT. The finding that MLT stimulates IL-12 production from human monocytes only if incubated in presence of IL-2 further supports this concept. On the other hand, high concentrations of MLT have been found in human breast cancer tissue. The MLT concentration, which was 3 orders of magnitude higher than that present in the plasma, correlated positively with good prognostic markers such as estrogen receptor status and nuclear grade. Whether this relates to the immunoneuroendocrine action of MLT remains to be established. Clinical studies are needed on the effect of MLT in combination with IL-2 or other cytokines in cancer patients and viral diseases including HIV-infected patients.

Melatonin metabolite levels in workers exposed to 60-Hz magnetic fields: work in substations and with 3-phase conductors

Melatonin suppression by 50/60-Hz magnetic fields represents a plausible biological mechanism for explaining increased health risks in workers. Personal exposure to magnetic fields and ambient light, and excretion of the melatonin metabolite 6-hydroxymelatonin sulfate (6-OHMS), were measured over 3 consecutive workdays in electric utility workers. There was a magnetic field-dependent reduction in adjusted mean nocturnal and post-work 6-OHMS levels among men working more than 2 hours per day in substation and 3-phase environments and no effect among those working 2 hours or less. No changes were observed among men working in 1-phase environments. The results suggest that circular or elliptical magnetic field polarization, or another factor linked to substations and 3-phase electricity, is associated with magnetic field induced melatonin suppression in humans.

Genotoxicity of paraquat: micronuclei induced in bone marrow and peripheral blood are inhibited by melatonin

The ability of melatonin to influence paraquat-induced genotoxicity was tested using micronucleated polychromatic erythrocytes as an index of damage in both bone marrow and peripheral blood cells of mice. Melatonin (10 mg/kg) or an equal volume of saline were administered intraperitoneally (ip) to mice 30 min prior to an ip injection of paraquat (20 mg/kgx2), and thereafter at 6-h intervals until the conclusion of the study (72 h). The number of the micronucleated polychromatic erythrocytes increased after paraquat administration both in peripheral blood and bone marrow cells. Melatonin administration to paraquat-treated mice significantly reduced micronuclei formation in both peripheral blood and bone marrow cells; these differences were apparent at 24, 48 and 72 h after paraquat administration. The induction of micronuclei was time-dependent with peak values occurring at 24 and 48 h. The reduction in paraquat-related genotoxicity by melatonin is likely due in part to the antioxidant activity of the indole. We did not observe effects of melatonin over paraquat in paraquat+melatonin groups incubated at 0, 60 and 120 min. Mitomycin C, which was used as a positive control, also caused the expected large rises in micronuclei in both bone marrow and peripheral blood cells at 24, 48 and 72 h after its administration.

Effects of ageing and dehydroepiandrosterone administration on pro-opiomelanocortin mRNA expression in the anterior and intermediate lobes of the rat pituitary

There is still controversy about the influence of ageing on the activity of the hypothalamo-pituitary-adrenocortical (HPA) axis in the rat. The first objective of the present study was to evaluate the influence of ageing on the activity of the HPA axis by measuring pituitary proopiomelanocortin (POMC, the precursor of ACTH and alphaH) mRNA levels in the anterior and intermediate lobes in young (50-55-day old) and aged (18-month-old) rats of both sexes. The second goal of the study was to evaluate the effect of 2.5 day administration of dehydroepiandrosterone (DHEA), a steroid precursor which has been shown to improve some ageing-associated deficits. In the young male anterior pituitary, DHEA induced a 17.5% increase in POMC mRNA levels. In aged males, anterior pituitary POMC mRNA levels were 22% lower than those detected in young animals. DHEA treatment produced a 26% increase, then completely restoring mRNA levels when compared to those found in young vehicle-treated males. In the young female, DHEA did not induce any changes in anterior pituitary POMC mRNA. In aged females a 24% reduction in the hybridization signal was observed. This reduction was completely reversed by DHEA which induced a 45% increase over the levels observed in vehicle-treated aged animals. In the intermediate lobe, the results were very similar to those obtained in the anterior lobe, although the observed effects induced by ageing and DHEA were less striking. These results together with previous ones indicating an age-related decrease in corticotropin-releasing hormone (CRH) neuronal activity suggest that ageing is associated with a decrease in HPA axis activity. They also demonstrate that a short-term DHEA treatment can exert a beneficial influence by reversing the decrease in pituitary POMC mRNA expression which occurs as a consequence of ageing.

The effect of melatonin on cellular activation processes in human blood

The pineal hormone melatonin, due to its lipophilic nature, has access to every cell and every part of a cell in the body, suggesting that it could exert effects on blood immune cells. The regulation of the activation of monocytes may be important in a number of diseases, especially pathophysiological conditions associated with inflammatory reactions. Considering this, a study on the effect of melatonin on monocytes in whole blood was carried out. Melatonin added at a final concentration of 5 ng/mL to whole blood in vitro reduced lipopolysaccharide (LPS)-induced tissue factor (TF) activity in monocytes by 55% in blood from a group of subjects with melatonin-sensitive cells. At even lower concentrations of melatonin (20-50 pg/mL) and in the physiological range, a trend of suppressed LPS-induced TF activity by approximately 20% was seen. A further indication of a downregulation of LPS-stimulated monocytes by melatonin was shown by its reduction of LPS-induced tumor necrosis factor (TNF). Twenty to one hundred pg/mL melatonin caused a significant reduction of LPS-induced TNF production by approximately 25-30%. In contrast, melatonin at a final concentration of 10 pg/mL, added to whole blood incubated with LPS and also the phorbol ester, PMA, caused a significant rise of 25%; whereas 100 pg/mL enhanced LPS + PMA-induced TNF by approximately 80% as compared to LPS + PMA alone. These effects were not detectable during the winter darkness of Tromsø (70 degrees N), probably due to the high content of melatonin in the blood even at daytime. These results show that melatonin may have a beneficial effect by suppressing the expression of TF activity in LPS-stimulated monocytes. Furthermore, the results indicate that LPS-induced TF in monocytes of whole blood is independent of protein kinase C (PKC) activation. Melatonin is probably amplifying cellular activation reactions that are PKC-dependent. This may be physiologically important in upregulation of the immune system.

Melatonin administration in tumor-bearing mice (intact and pinealectomized) in relation to stress, zinc, thymulin and IL-2

Melatonin (MEL) may counteract tumors through a direct oncostatic role. MEL is also an antistress agent with immunoenhancing properties against tumors due to a suppressive role of MEL on corticosterone release. Rotational stress (RS) (spatial disorientation) facilitates metastasis progression in mice. Also, MEL counteracts tumors because of its influence on immune responses via the metabolic zinc pool, which, is reduced in tumors and stress. Zinc is required for normal thymic endocrine activity (i.e. thymulin) and interleukin-2 (IL-2) production. Because in vivo data is still controversial, exogenous MEL treatment (22 days in drinking water) in both intact and pinealectomized (px) mice bearing Lewis lung carcinoma leads to significant decrements of metastasis volume, restoration of the negative crude zinc balance, recovery of thymulin activity and increment of IL-2 exclusively in intact and px tumor bearing mice subjected to RS. Significant inverse correlations are found in both stressed intact and px tumor bearing mice after MEL treatment between zinc and corticosterone (r = 0.78, P < 0.01; r = 0.80, P < 0.01, respectively). Positive correlations between zinc and IL-2 (r = 0.75, P < 0.01; r = 0.73, P < 0.01, respectively) or thymulin (r = 0.75, P < 0.01; r = 0.82, P < 0.01, respectively) are observed in same models of mice. These findings suggest a MEL action to decrease metastasis mediated by a possible interplay between zinc and MEL, via corticosterone, with consequent restoration of thymic efficiency and IL-2 production. MEL as an antistress agent with immunoenhancing properties in cancer deserves further consideration.nuclear factor-kb; POMC, proopiomelanocortin; Px, pinealectomized mice; RIA, radioimmunoassay; RS, rotational stress; SDI, stressed intact mice; SDPx, stressed pinealectomized mice; TNF-alpha, tumor necrosis factor-alpha; ZnFTS, active zinc-bound thymulin; ZnFTS + FTS, total thymulin.

Intervention in the aging immune system: Influence of dietary restriction, dehydroepiandrosterone, melatonin, and exercise

The decline in immunologic function with age is associated with an increase in susceptibility to infections and the occurrence of autoimmune diseases and cancers. Hence, the restoration of immunologic function is expected to have a beneficial effect in reducing pathology and maintaining a healthy condition in advanced age. A number of therapeutic strategies have been employed to intervene in the aging immune system. This article reviews the effect of dietary restriction (DR), dehydroepiandrosterone (DHEA) treatment, melatonin (MLT) therapy, and exercise on modulating the immune responses and retarding/reducing immunosenescence. DR has been subject to intensive research and is known to be the most efficacious means of increasing longevity, reducing pathology and enhancing immune function. The circulatory levels of the androgenic hormone DHEA and the pineal hormone MLT decrease with increasing age, and this decrease has been correlated with the age-related decline in the immune system. Therefore, the observation that immunosenescence is associated with low levels of DHEA and MLT has provided a rationale for therapeutic intervention. DHEA treatment and MLT therapy both exhibit immunostimulatory actions and preliminary reports indicate that hormonal (DHEA or MLT) substitution therapy reverses immunosenescence in mice. Similarly, exercise in some studies has been shown to enhance the immune response. However, these findings have not been confirmed by other laboratories. Thus, at the present time, it is difficult to draw any definitive conclusions on the efficacy of DHEA, MLT, and exercise on reversing or restoring the aging immune system.

Melatonin rhythms in mice: role in autoimmune and lymphoproliferative diseases

Production of melatonin (MLT) in the pineal gland (PG) of inbred mice such as C57BI/6J, BALB/c, and AKR strains is still a matter of debate. In a recent study we validated the presence of MLT in the PG of these inbred mice. We found a short-term MLT peak in the middle of the dark period with a pattern that mirrors that found previously in the serum. In another study, based on the known immunoregulatory role of MLT, we investigated the role of the PG and MLT in autoimmune diabetes mellitus type I using, as an experimental model, female nonobese diabetic (NOD) mice. Mice were pinealectomized or treated chronically with MLT (injected subcutaneously or administered via drinking water). We found that neonatal pinealectomy accelerates the development of disease in female NOD mice, whereas exogenous MLT protects animals. This is in spite of the fact that MLT increased the production of insulin autoantibodies (IAA). We conclude that PG and MLT influence the development of autoimmune diabetes, although the mechanism of action needs further investigation.

Specific binding of melatonin by purified cell nuclei from spleen and thymus of the rat

In the present paper, we show that pineal hormone melatonin interacts with purified cell nuclei from rat spleen and thymus. Binding of 2-[125I]iodomelatonin ([125I]melatonin) by cell nuclei fulfills all criteria for binding to a receptor site. Binding exhibited properties such as dependence on time and temperature as well as reversibility, saturability, high affinity, and specificity. Results suggested binding to single classes of binding sites. The dissociation constants (Kd) for the binding sites in the spleen and thymus nuclei were 68 and 102 pM, respectively. These data are in close agreement with data obtained from kinetic studies, in which the kinetically derived values of the dissociation constant in the spleen and thymus nuclei were 166 and 537 pM, respectively. The affinities for melatonin of these nuclear binding sites suggest that they may recognize the physiological concentrations of melatonin in the tissues. Finally, we have demonstrated that binding of [125I]melatonin by the nuclei is displaced by CGP 52608, a specific ligand of the putative nuclear melatonin receptor RZR/ROR. Results strongly suggest that in addition to membrane receptor-related mechanisms, nuclear receptors may be involved in the regulation of immune system by melatonin.

Melatonin inhibits expression of the inducible isoform of nitric oxide synthase in murine macrophages: role of inhibition of NFkappaB activation

The role of melatonin as an immunomodulator is well established. Recent reports showed that melatonin exerts protective effects in septic and hemorrhagic shock and in inflammation. The expression of the inducible isoform of nitric oxide synthase (iNOS) makes an important contribution to the pathophysiology of shock and inflammation. We studied, in cultured murine macrophages, the role of melatonin in the regulation of the expression of iNOS and defined the mode of melatonin's action. Our results show that melatonin, at 1 microM-1 mM, decreased the production of nitrite/nitrate (the breakdown products of NO) as well as the production of 6-keto-prostaglandin F1alpha (the major stable breakdown product of prostacyclin) in macrophages stimulated with bacterial lipopolysaccharide (10 microg/ml). We observed that melatonin reduces iNOS steady-state mRNA levels and iNOS protein expression in the same concentration range (1 microM-1 mM). Melatonin, up to 10 mM, exerted only a slight direct inhibitory effect on iNOS activity. Using iNOS promoter-luciferase constructs, we found that melatonin inhibits iNOS promoter activation. Inhibition of iNOS expression was associated with inhibition of activation of the transcription factor nuclear factor kappa B (NFkappaB). We conclude that melatonin inhibits NO production in immunostimulated macrophages mainly by inhibiting the expression of iNOS. This is due to inhibition of iNOS transcription, in part through inhibition of NFkappaB activation. Inhibition of iNOS-derived NO production by melatonin may contribute to the anti-inflammatory effects of this pineal secretory product.

The photoperiod transducer melatonin and the immune-hematopoietic system

The pineal neurohormone melatonin functionally synchronizes the organism with the photoperiod. It is now well recognized that melatonin also plays an important immunoregulatory role. T-helper cells bear G-protein coupled melatonin cell-membrane receptors and, perhaps, melatonin nuclear receptors. Activation of melatonin receptors enhances the release of T-helper cell type 1 (Th1) cytokines, such as gamma-interferon and interleukin-2, as well as of novel opioid cytokines which crossreact immunologically with both interleukin-4 and dynorphin B. Melatonin has also been reported to enhance the production of interleukin-6 from human monocytes. These mediators may counteract secondary immunodeficiencies, protect mice against lethal viral and bacterial diseases, synergize with interleukin-2 in cancer patients and influence hematopoiesis. Hematopoiesis is apparently influenced by the action of the melatonin-induced opioids on kappa-opioid receptors present on stromal bone marrow cells. Most interestingly, gamma-interferon and colony stimulating factors may modulate the production of melatonin in the pineal gland. A hypothetical pineal-immune-hematopoietic network is, therefore, taking shape. From the immunopharmacological point of view, a call is made for clinical studies on the effect of melatonin in viral disease including human immunodeficiency virus-infected patients and cancer patients. In conclusion, melatonin seems to be an important immunomodulatory hormone which deserves to be further studied to identify its relevance in immune-based diseases, its therapeutic indications, and its adverse effects.

kappa-Opioid receptors in marrow stroma mediate the hematopoietic effects of melatonin-induced opioid cytokines

Melatonin exerts colony-stimulating activity and rescues myeloid progenitors from apoptosis, induced either in vivo or in vitro by cancer chemotherapy compounds in tumor-bearing mice. These effects are mediated mainly by T-helper cell-derived opioid cytokines with an apparent molecular mass of 15 kDa and 67 kDa that are recognized both by anti-interleukin-4 and anti-dynorphin B antibodies. These putative new cytokines were named melatonin-induced-opioid (MIO). The most active and naltrexone-sensitive MIO was the smaller molecule, which was called MIO15 and found to act on an opioid-binding site present in adherent bone marrow cells. However, the hematopoietic action of MIO15 was dependent on the presence of colony-stimulating factors (CSF). To investigate this point, we studied the ability of melatonin to rescue granulocyte/macrophage colony-forming units (GM-CFU) in the bone marrow of tumor-free animals treated with cancer chemotherapeutic compounds. We found that melatonin not only is unable to protect bone marrow GM-CFU unless the mice are transplanted with Lewis lung carcinoma (LLC), but also that melatonin seems to increase the myelotoxicity of cyclophosphamide in tumor-free mice. In both tumor-bearing or healthy mice, the effect of melatonin is negated by naltrexone, indicating the involvement of MIO15. Competition studies classified the target opioid-binding site as a kappa-opioid receptor with low affinity in tumor-free mice and high affinity in LLC-implanted mice. LLC is known to release CSF. Consistently, addition of CSF in the form of lung-conditioned medium (LCM) to adherent bone marrow cells increased the affinity of the kappa-opioid receptor. Addition of antigranulocyte/macrophage colony-stimulating factor (GM-CSF) mAbs neutralized the effect of LCM. In conclusion, the affinity state of the kappa-opioid receptors in stromal bone marrow cells seems to modulate the hematopoietic effect of melatonin and/or MIO15.

Opioidergic innervation of the tree shrew pineal gland: an immunohistochemical study

The tree shrew (Tupaia glis) has been described as a missing link relating primate to insectivore stock. The pineal gland of the tree shrew consists of a superficial pineal and a deep pineal, which are connected by a long and slender pineal stalk. A monoclonal antibody against leu-enkephalin was used in an immunohistochemical investigation of the tree shrew pineal gland. A moderate innervation of leu-enkephalin immunoreactive nerve fibers has been demonstrated in both superficial and deep pineal gland of the tree shrew. The density of the nerve fibers was slightly higher in the superficial pineal than that of the deep one. The number of immunoreactive nerve fibers were observed in the capsule of the pineal gland from where they entered the pineal parenchyma. Only a few immunoreactive fibers were found in the habenular area and the area rostral to the pineal recess, connecting the habenula and the deep pineal. Furthermore, some positive fibers were located in the pineal stalk. There was no evidence of leu-enkephalin immunoreactive intrapineal cells as seen in the other species of mammal. Therefore, the interspecies variation of opioidergic innervation among the mammals may exist. The lack of intrapineal perikarya is interpreted to indicate that the sources of leu-enkephalin nerve fibers were outside the gland. The anatomical location of the leu-enkephalin immunoreactive nerve fibers in the tree shrew pineal gland supports to both central and peripheral pinealopetal pathways in this species.