Melatonin and clinical application

A review of the different publications dealing with melatonin in humans shows that this field has been very active in the last few years. Normative melatonin values have been defined. Various relationships between melatonin and other traits have been studied, such as sleep, circadian rhythm, surgical stress and anaesthesia. Age-related melatonin studies and melatonin during depression and other psychiatric disorders have been reviewed. Finally, some studies have been performed to use melatonin as a medication for sleep disturbance in depression, for jet-lag and as a skin protector for ultraviolet light.

New actions of melatonin on tumor metabolism and growth

Melatonin is an important inhibitor of cancer growth promotion while the essential polyunsaturated fatty acid, linoleic acid is an important promoter of cancer progression. Following its rapid uptake by tumor tissue, linoleic acid is oxidized via a lipoxygenase to the growth-signaling molecule, 13-hydroxyoctadecadienoic acid (13-HODE) which stimulates epidermal growth factor (EGF)-dependent mitogenesis. The uptake of plasma linoleic acid and its metabolism to 13-HODE by rat hepatoma 7288CTC, which expresses both fatty acid transport protein and melatonin receptors, is inhibited by melatonin in a circadian-dependent manner. This inhibitory effect of melatonin is reversible with either pertussis toxin, forskolin or cAMP. While melatonin inhibits tumor linoleic acid uptake, metabolism and growth, pinealectomy or constant light exposure stimulates these processes. Thus, melatonin and linoleic acid represent two important environmental signals that interact in a unique manner to regulate tumor progression and ultimately the host-cancer balance.

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.

Vitamin A deficiency reduces the responsiveness of pineal gland to light in Japanese quail (Coturnix japonica)

Synthesis of melatonin in pineal gland is under the control of light environment. The recent finding of the presence of rhodopsin-like photopigment (pinopsin) and retinal in the avian pinealocytes has led to a hypothesis that vitamin A is involved in photoresponses of the pineal gland. We have thus analyzed the effect of vitamin A deficiency on the regulatory system of melatonin synthesis in the pineal gland of Japanese quail. Depletion of vitamin A from Japanese quails was attained by feeding them with a vitamin A-free diet supplemented with retinoic acid. In the vitamin A-deficient birds, diurnal rhythm in melatonin production persisted such that the phase of the wave was similar to that seen in the control birds. However, the amplitude of the nighttime surge of pineal melatonin was damped by vitamin A deficiency. When the control birds were briefly exposed to light at night, pineal melatonin dropped to the daytime level. In contrast, only slight decrease was observed in the vitamin A-deficient quails. The light responsiveness was restored after feeding the vitamin A-deficient quails with the control diet for 1 week. These results indicate that vitamin A plays essential roles in maintaining sufficient responsiveness of the avian pineal gland to photic input.

I. Role of the pineal gland in multiple sclerosis: a hypothesis

Despite intensive research over the past several decades, the etiology and pathogenesis of multiple sclerosis (MS) remain elusive. The last 20 years have seen only meager advances in the treatment of the disease in part because too much attention has been devoted to the process of demyelination and its relationship to the neurologic symptoms and recovery of the disease. A host of biological phenomena associated with the disease involving interactions among genetic, environmental, immunologic, and hormonal factors, cannot be explained on the basis of demyelination and, therefore, require refocusing attention on alternative explanations, one of which implicates the pineal gland as the pivotal mover of the disease. This review summarizes the evidence linking dysfunction of the pineal gland with the epidemiology, pathogenesis, clinical manifestations, and course of the disease. The pineal hypothesis of MS also provided the impetus for the development of a novel and highly effective therapeutic modality, one that involves the transcranial application of AC pulsed electromagnetic fields in the picotesla flux density.

[Significance of melatonin in malignant diseases]

The review summarizes experimental and preliminary clinical findings relating to the application of melatonin in malignancy to allow a differential discussion concerning its potential therapeutic use in cancer patients. In vivo experiments show that melatonin inhibits chemically induced, as well as spontaneous rodent tumors, but is mostly ineffective in controlling the growth of undifferentiated transplantable tumors. Some human and murine in vitro cancer cell lines are inhibited by physiological concentrations of melatonin, but the majority of the tested cell lines is resistant to melatonin or can be inhibited at pharmacological doses only. In individual cases melatonin was reported to stimulate cell growth. The molecular mechanisms of how melatonin affects the proliferation of cancer cells under in vivo and in vitro conditions are mostly unknown and their elucidation will require further basic research to determine the therapeutic potential of melatonin. From a theoretical point of view substitution therapy with melatonin might be worthwhile since a progressive decline of pineal melatonin secretion is observed parallel to the growth of the primary tumor in breast and prostate cancer. The mechanisms involved in this depression are at present poorly understood but do not appear to be identical among species so that similar results in animal experiments are of limited applicability to humans. First clinical experience with melatonin in the treatment of cancer patients has been confined to adjuvant therapies at advanced and terminal stages of malignancy and have yielded certain encouraging results. It is imperative to verify these preliminary data applying double-blind protocols and future therapeutic trials of melatonin in patients with early-stage malignant disease should be contemplated. Evidence exists that the role of the pineal gland in malignancy may not be confined to melatonin since potent antineoplastic fractions of yet unknown chemical structure have been detected which are capable of inhibiting in vitro cell lines resistant to melatonin.

[Melatonin and coronary heart disease]

The observation of raised nocturnal urinary norepinephrine excretion in patients with coronary heart disease (CHD), together with results of animal experiments showing a suppression of sympathetic activity by melatonin, were the reasons for this investigation. In 15 patients with CHD and 10 controls the concentrations of serum melatonin, serotonin and N-acetylserotonin were determined in samples gained by venopuncture at 14.00 h and 02.00 h. The melatonin secretion was significantly lower at 02.00 h in the patients with CHD than in the controls. Moreover the serotonin concentration was significantly lower at 14.00 h in the patients with CHD, and somewhat, but not significantly, lower at 02.00 h than in the controls. On the other hand, the serum concentrations of N-acetylserotonin showed a tendency towards higher levels in the CHD patients than in the controls. The causes and consequences of the diminished secretion during the night in patients with CHD are discussed.

[Changes in the 24-hour rhythm of plasma melatonin in patients with liver cirrhosis--relation to sleep architecture]

OBJECTIVE

To assess the 24 hr plasma melatonin profile as a marker of the output rhythm from the circadian clock and to study sleep diaries as reflection of subjective sleep quality in patients with liver cirrhosis.

DESIGN

Prospective cohort study.

PATIENTS

A total of 14 subjects, 7 non-alcoholic cirrhotics and 7 age-, sex-, and educationally-matched controls. Exclusion criteria were factors that could affect melatonin levels (intercontinental travel, shift work, therapy with betablockers or corticosteroids).

MEASUREMENTS

Plasma melatonin was measured every 30 min for 24 hr by radioimmuno assay and sleep recordings by polysomnography. Neuropsychological testing included visual reaction time. Trailmaking test A and B and the Digit Symbol Test. Sleep diaries were kept for the week prior to admission.

RESULTS

Time of onset of melatonin rise was displaced from 19:50 +/- 26 min in the controls to 21:30 +/- 13 min (p = 0.013) in patients with liver cirrhosis. The time of peak melatonin levels was consistently and significantly delayed from 00:36 +/- 33 min in controls to 5:36 +/- 29 min (p < 0.001) in patients. Cirrhotic subjects showed markedly elevated melatonin levels during daytime, when melatonin is normally absent. Polysomnographic tracings showed no differences in patients and controls, but sleep diaries indicated more frequent nocturnal awakenings (p = 0.05) and daytime naps.

CONCLUSIONS

A marked alteration of plasma melatonin rhythm is found in cirrhotic patients with subclinical hepatic encephalopathy. This disruption may reflect changes in the output of the circadian pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. It is possible that some of the metabolic disturbances that lead to hepatic encephalopathy may also alter the function of the biological "clock".

[6-sulfatoxymelatonin in women with secondary amenorrhea]

We evaluated the overnight urinary excretion of 6-sulfatoxymelatonin in a group of 347 women (range: 18-69 years). 26 women (range 20-29 years) with normogonadotrophic, hypoestrogenemic amenorrhoea (WHO II) were selected and compared with a group of 26 women menstruating normally (range: 19-30 years) with respect to urinary 6-sulfatoxymelatonin excretion, serum 17 beta-estradiol levels and response to the thyroid releasing hormone (TRH) test. Patients with hyperprolactinemia, hyperandrogenemia, thyroid dysfunction and weight problems were excluded. 6-sulfatoxymelatonin was found to be significantly higher in the amenorrhoeic women than in the controls (p < 0.000001). In the amenorrhoeic patients a statistically significant inverse correlation was found between serum 17 beta-estradiol levels and urinary 6-sulfatoxymelatonin excretion. A positive correlation was obtained between the thyroid stimulation hormone (TSH) value measured at 20 minutes after stimulation and 6-sulfatoxymelatonin excretion. Further clinical research in this field is required to evaluate its clinical impact, especially in patients with secondary amenorrhea.

Anticancer neuroimmunomodulation by pineal hormones other than melatonin: preliminary phase II study of the pineal indole 5-methoxytryptophol in association with low-dose IL-2 and melatonin

Despite several years of experimental observations, the clinical application of the neuroimmunomodulation is still at the beginning. The pineal gland plays a main role in mediating the link between psychoneuroendocrine and immune systems. Melatonin (MLT), which is the main pineal hormone produced during the night, has appeared to amplify IL-2 anticancer activity. Other pineal hormones, however, would have immunomodulatory activity, in particular 5-methoxytryptophol (5-MTT), which is mainly produced during the light phase of the day. Previous clinical studies have shown that low-dose IL-2 plus MLT may have therapeutic efficacy in advanced cancer patients with neoplasms generally resistant to IL-2 alone, with a tumor regression rate generally less than 20% and an acceptable toxicity. The present study was carried out to evaluate the efficacy of low-dose IL-2 in association with both MLT and 5-MTT. The study included 14 untreatable advanced solid tumor patients (lung cancer: 4; gastric cancer: 3; mesothelioma: 2; hepatocarcinoma: 2; pancreatic cancer: 1; melanoma: 1; colon cancer: 1). IL-2 was injected subcutaneously at 3 MIU/day for 6 days/week for 4 weeks, by repeating a second cycle after a 21- day rest period. Both MLT and 5-MTT were given orally at 40 mg/day in the evening and at 1 mg/day at noon. The clinical results, as evaluated by WHO criteria after each cycle, consisted of partial response (PR) in 4/14 (29%) (lung cancer: 2; hepatocarcinoma: 1; mesothelioma: 1), stable disease (SD) in 6 and progressive disease in the last 4 patients. The treatment was extremely well tolerated in all patients, and in particular no fever greater than 38 degrees C occurred. These preliminary results show that the neuroimmunotherapy with low-dose IL-2 plus two pineal hormones, MLT and 5-MTT, is a well tolerated and potentially effective cancer therapy of untreatable advanced solid tumor patients, with results apparently superior with respect to those previously described with IL-2 plus MLT alone.

[The conjoint relationships of the epiphysis and hippocampus in the shaping of the reaction to stress]

Pinealectomy and electrolytic destruction in different directions changed the behaviour of rats in a conflict situation and the temporal organization of forced swimming. Combination of both kinds of surgery decreased the behavioural shifts produced by the hippocampal lesions. It is suggested that the anti-stressor properties of the pineal gland can be realized through changes in the hippocampal function state.

Influence of the pineal gland on the expression of experimental allergic encephalomyelitis: possible relationship to the aquisition of multiple sclerosis

Experimental allergic encephalomyelitis (EAE), a T-cell mediated autoimmune disease, is widely considered as an animal model of multiple sclerosis (MS). It is believed that breakdown of the blood brain barrier (BBB) reflects the initial mechanism in the induction of EAE. It has been reported that while neonatally pinealectomized Wistar rats develop extensive pathological changes and severe neurologic deficits upon induction of EAE with allogeneic spinal cord in adjuvant, adult rats pinealectomized at 6 weeks of age appeared resistant to the induction of EAE. These findings suggest that: (a) the pineal gland influences the expression of EAE and, by inference, the integrity of the BBB; and (b) there is an age-related window of susceptibility to the development of EAE possibly related to the level of maturation of the pineal gland and functional integrity of the BBB. This age-related susceptibility to the development of EAE in rats may be relevant to the timing of aquisition of MS where a viral infection in childhood is thought to initiate the induction of autosensitization to myelin antigens. More specifically, it is suggested that the viral infection associated with the development of MS most likely is acquired in infancy prior to the establishment of the melatonin circadian rhythms between 3 and 9 months of age.

Nocturnal serum melatonin profile in major depression in children and adolescents

BACKGROUND

In major depression, biological rhythm disturbances in sleep, appetite, and mood suggest dysregulation in neuroendocrine functions, possibly in the pineal gland. In this study, pineal gland function was examined by measuring nocturnal serum melatonin levels during both wakefulness and sleep in depressed children and adolescents.

METHODS

Twenty-two youths aged 8 to 17 years primarily with major depression were compared with 19 controls. Blood samples were drawn every half hour from 6 PM to 7 AM. Nocturnal serum melatonin levels were measured by radioimmunoassay.

RESULTS

The overall nocturnal serum melatonin profile from 6 PM to 7 AM was significantly higher (mean +/- SD, 0.18 +/- 0.14 nmol/L) in the depressed group than in the controls [mean +/- SD, 0.15 +/- 0.10 nmol/L, F(1,26) = 4.37, P < .05]. In dim light, when the subjects were awake, no difference existed between the 2 groups. After lights-out, from 10 PM to 7 AM, the melatonin profile rose in both groups; however, the depressed group had a significantly higher increase (mean +/- SD, 0.24 +/- 0.14 nmol/L) than the controls [mean +/- SD, 0.18 +/- 0.07 nmol/L, F(1,26) = 4.93, mean square error = 0.11, P = .04]. Post hoc analysis showed a significantly higher melatonin profile in depressed subjects without psychosis (n = 15) than in depressed subjects with psychosis (n = 7) or in the controls.

CONCLUSIONS

Measuring the overall nocturnal serum melatonin profile during darkness may help to differentiate children and adolescents with major depression without psychosis from those with psychosis and from controls.

The pineal gland and cancer

The pineal gland is considered today as one of the main organs involved in the transduction process which converts environmental light information into an endocrine response. The gland and its hormone melatonin seem to be important chronoimmunomodulators, and a reduction of the latter was associated with experimental and clinical immunodeficiencies and over the control of the neoplastic process. Moreover, melatonin can be an oncostatic or oncostimulating hormone, depending on the timing of its administration. The melatonin circadian rhythm is altered in cancer patients, and this rhythm could be modified as a consequence of certain therapies. Also Electromagnetic Fields (EMF) can affect the pineal function, perhaps working as synchronizers or, as this paper proposes, also through action of the "antenna effect" suggested for artificial human models, with a major energetic transfer over the cephalic area. The pineal could play an important role in the appearance and development of some forms of apparently EMF-related cancers.

Increased melatonin levels after hemorrhagic shock in male and female C3H/HeN mice

Although hemorrhagic shock leads to significant alterations of several hormones, e.g. ACTH, corticosterone and beta-endorphin, it is not known whether plasma melatonin levels are affected under this condition and if so, whether the effects are comparable in males and females. Using a radioimmunoassay, it was found that plasma melatonin levels were significantly increased in male and proestrus female C3H/HeN mice immediately after hemorrhagic shock. However, in male mice, by two hours after hemorrhage and resuscitation, plasma melatonin returned to levels comparable to those seen in control and sham-operated animals. Proestrus female mice, on the other hand, showed significantly increased plasma melatonin levels at two hours after surgery when compared to unoperated control animals. Although the significance and biological role of the transient increased plasma melatonin levels after hemorrhagic shock remain to be determined, it appears that the pineal gland and/or an extrapineal source of melatonin, of both male and proestrus female mice responds to severe hypotension by increased release of melatonin.

Thirty years of human pineal research: do we know its clinical relevance?

A role for melatonin in humans is becoming evident in an increasing number of clinical situations. Marked variations in the magnitude of the nocturnal melatonin peak are observed throughout the human lifespan. The highest levels occur in children and then fall during puberty and further during adulthood. A negative correlation between circulating melatonin and sex steroids has been observed in a number of instances, and appears to be independent of concomitant gonadotrophins. No clear melatonin pattern has been observed in pituitary tumors, but in large lesions that involve the hypothalamus, a reduced nocturnal rise has been reported. Reported effects of exogenously administered melatonin are variable, probably reflecting differences in dose and timing; a slight stimulation of prolactin, as well as a partial inhibition of gonadotrophins, has been reported, which explains its utility as an oral contraceptive, associated with a progestogen. A potential clinical use of melatonin as an oncostatic drug still awaits confirmation, although experimental data firmly support this possibility. The indole has also been used to hasten entrainment of subjects travelling across various time zones, and has been found to be specially useful in eastward travel. Finally, changes in the normal melatonin circadian pattern have been reported in psychiatric diseases and in sudden infant death syndrome.

Lack of association between thyroid and pineal responses to antidepressant treatment

With antidepressant treatment for major depression there are decreases in thyroid hormone levels and increases in pineal function. We have conducted a study to examine whether there is a relationship between pineal and thyroid hormone measures as well as between hormone measures and response to treatment in patients treated with desipramine. Measures of thyroid activity included thyroxine, triiodothyronine, T3 resin uptake, and TSH. Pineal function was determined by measurement of 6-suphatoxymelatonin in three consecutive 8 hour pools. Hormone measures as well as Hamilton depression scores were obtained prior to treatment and at the end of 5 weeks of treatment. As in previous studies, thyroid measures decreased, pineal activity increased, and Hamilton scores decreased significantly with treatment. No correlations were found between these measures, suggesting that if there is a relationship between them it is not a direct one.

Melatonin replacement corrects sleep disturbances in a child with pineal tumor

A child with a germ cell tumor involving the pineal region had marked suppression of melatonin secretion associated with severe insomnia. Exogenous melatonin (3 mg in the evening) for 2 weeks restored sleep continuity, as demonstrated by objective monitoring of rest-activity cycles. This case report provides direct evidence of the essential role of melatonin in normal sleep.

The pineal gland, cataplexy, and multiple sclerosis

Since the discovery of melatonin as the principal hormone of the pineal gland in 1963, scientists have come to recognize that melatonin is a "master hormone" involved in the control of circadian rhythms and other biological functions. Although little is known about the influence of the pineal gland on motor control, important clues may be obtained by considering the pattern of melatonin secretion during the sleep cycles and particularly during rapid eye movement (REM) sleep when melatonin plasma levels are at their lowest. Since REM sleep is characterized by the occurrence of profound atonia which results in an almost complete paralysis of striated muscles, it is suggested that there might be a causal relationship between inhibition of melatonin secretion during REM sleep and the development of REM sleep atonia. This relationship is supported by the findings that melatonin regulates the activity of brainstem serotonin (5-HT) neurons which characteristically cease to fire during REM sleep and which faciliate the development of REM sleep atonia. Moreover, as the muscular atonia of REM sleep is physiologically and pharmacologically indistinguishable from cataplexy, it is possible that the pineal gland also influences to the development of cataplexy. Cataplexy is an ancillary symptom of narcolepsy and also occurs in multiple sclerosis (MS). In fact, it is believed that several of the neurological symptoms experienced by patients with MS such as weakness in the legs, feeling of collapsing knees, paroxysmal sudden falling, weakness in the neck, extreme fatigue, intermittent paresthesias, slurring of speech and intermittent blurring of vision, which often are exacerbated by stress and other emotional influences, may reflect the manifestations of cataplexy. Thus, several of the clinical features of MS may reflect a dissociated state of wakefulness and sleep and may improve by the administration of anticataplectic drugs.

Serum melatonin in multiple myeloma: natural brake or epiphenomenon?

Melatonin (MEL), the main hormone produced by the pineal gland, seems to exert antineoplastic activity both in vitro and in vivo. Moreover, several studies reported increased melatonin blood levels in cancer patients. Plasma melatonin concentrations were determined in 46 patients with multiple myeloma and in 31 age matched healthy subjects (57.8 +/- 6.9 versus 55.2 +/- 8.9 years). Venous blood was drawn between 7.30 and 9.30 a.m. and melatonin was assayed using a commercially available radioimmunoassay. The data were analysed by Student's t test and results reported as mean values +/- standard deviation. The patients with multiple myeloma showed significantly higher mean melatonin serum levels than healthy subjects (21.6 +/- 13.5 versus 12.1 +/- 4.8 pg/ml; p < 0.001). This behaviour could actually represent a phenomenon secondary to an altered endocrine-metabolic balance caused by an increased demand of the developing tumor. On the other hand, the increased melatonin secretion might be considered as a compensatory mechanism due to its antimitotic action and therefore as an effort to secrete substances capable of regulating neoplastic growth.

Diurnal variations in vision and relations to circadian melatonin secretion in multiple sclerosis

It has long been recognized that symptoms of multiple sclerosis (MS) wax and wane with fluctuations occurring on an hour to-hour basis throughout a 24 hour period. It has been proposed that changes in circadian core body temperature, which alter axonal conductivity, may account for the fluctuations of symptoms in MS. A 51-year-old man with MS is reported in whom visual acuity deteriorated throughout the course of the day only to improve again at night between 10:00 p.m. and 2:00 a.m. These changes in vision were unrelated to rest or physical activity, but appeared to coincide with the circadian secretion of melatonin which is coupled to the circadian temperature rhythms. Since melatonin lowers body temperature, it is hypothesized that the nocturnal rise in melatonin secretion was related to improvement in vision in this patient. This hypothesis is supported by the observation that administration of melatonin (3 mg, orally) at 2:00 p.m., when the patient experienced severe blurring of vision, resulted within 15 minutes in a dramatic improvement in visual acuity and in normalization of the visual evoked potential latency after stimulation of the left eye. Moreover, since the pineal gland is a thermoregulatory organ which functions to prevent excessive rise of body temperature, it is possible that since MS is associated with dysfunction of the pineal gland, these patients may experience diminished capacity to eliminate heat at rest or during physical activity with resultant elevation of body temperatures which may further compromise neurologic functions by causing failure of axonal conduction.