The pineal hormone melatonin in hematology and its potential efficacy in the treatment of thrombocytopenia

Recent experimental studies suggested that hematopoietic cell proliferation and differentiation are under a neuroendocrine control and that they change in relation to the 24-hour period. Moreover, it has been shown that the pineal hormone melatonin (MLT) plays a role in mediating the influence of the psychoendocrine system and of the lighting conditions on the hematopoiesis. Finally, MLT has appeared to regulate hematopoietic cell growth by influencing apoptosis-related mechanisms. In particular, preliminary studies have shown that the pineal hormone MLT may determine some benefits in blood cell disorders, mainly platelet diseases. On this basis, a pilot phase II study of MLT therapy was performed in patients suffering from persistent thrombocytopenia due to different causes. The study included 14 patients, and thrombocytopenia was due to bone metastatic involvement in 5, hypersplenism in 3, myelodysplastic syndrome in 3, DIC in 1, genetic factors in 1, and Werlhof's disease in the last case. MLT was given orally at 20 mg/day in the evening for 2 months. No MLT-related toxicity occurred. A normalization of platelet number was achieved in 8/14 (57%), and platelet mean number significantly increased on MLT therapy. This preliminary study would suggest that MLT may be effective in the treatment of thrombocytopenia due to different reasons, for which no effective standard therapy is available.     

Daily variations in pineal melatonin concentrations in inbred and outbred mice

Magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and magnetic resonance spectroscopy (MRS) were successively recorded in a 3-year-old girl with the acute hemiplegia syndrome. She was admitted to our hospital with complaints of fever, loss of consciousness and right side dominant clonic convulsions evolving into status epilepticus, and then recovered with sequelae of aphasia and right hemiparesis. Electroencephalography showed a generalized slow rhythm at the onset, and very low activities on the left hemisphere in the follow-up records. Brain CT and MRI revealed edema of the left hemisphere initially, followed by left side dominant brain atrophy. No cerebral vascular lesion was detected by magnetic resonance angiography. N-Isopropyl-[123I]-iodoamphetamine SPECT showed marked hypoperfusion of the left hemisphere accompanied by crossed cerebellar diaschisis. MRS at the initial stage detected decreased N-acetyl-aspartic acid and increased lactic acid signals in the bilateral hemisphere, which subsequently normalized only on the right side. These findings suggested brain damage and neural cell death in the left cerebral hemisphere, caused by acute encephalopathy. SPECT and MRS are useful new techniques to study the pathophysiology of the acute hemiplegia syndrome.     

Treatment of cancer-related thrombocytopenia by low-dose subcutaneous interleukin-2 plus the pineal hormone melatonin: a biological phase II study

Despite the platelet production in response to IL-2, cancer immunotherapy with IL-2 tends to induce thrombocytopenia, which probably depends on an enhanced peripheral destruction. On the basis of our previous studies, this effect may be neutralized by a concomitant administration of the pineal hormone melatonin (MLT). This study was performed to investigate the influence of an immunotherapeutic combination with low-dose IL-2 and MLT on platelet number in advanced cancer patients showing persistent thrombocytopenia. The study included 14 advanced solid tumor patients, affected by thrombocytopenia due to different causes (portal hypertension: 9; previous chemotherapies: 3; DIC: 2). IL-2 was injected at 3 million IU/day subcutaneously for 6 days/week for 4 weeks, in association with MLT (40 mg/day orally). A normalization of platelet number occurred in 10/14 (71%) patients, and platelet mean number significantly increased on treatment. No important therapy-related toxicity was observed. This preliminary study would suggest that the concomitant administration of MLT is able not only to neutralize IL-2-induced thrombocytopenia, but also to increase platelet number in thrombocytopenic cancer patients.     

Differences in isoproterenol-stimulated melatonin production by perifused rat pineal glands: time dependent effects and role of enantiomeric forms

The perifusion of rat pineal glands removed at different times of the light-dark cycle showed a greater beta adrenergic-stimulated production of melatonin in glands obtained at the beginning of either the light or the dark stage. The effect of isoproterenol was found dependent upon its enantiomeric forms (-, +/-, +). The relative order of potency was (-) > (+/-) > (+) enantiomer. These results show that the response of pineal beta-adrenergic receptors to isoproterenol is stereospecific and circadian stage dependent.     

Rest-activity rhythm of the blind mole rat Spalax ehrenbergi under different lighting conditions

The mole rat is a solitary, subterranean and photoperiodic rodent. We investigated its rest activity behavior under several lighting conditions, complemented our observations with light-induced c-fos expression, and compared the activity behavior of two chromosomal forms (2n = 58 and 60). The 26 mole rats had a clear overall preference for activity in the light or dark period, but prolonged recordings in five individuals showed that the initial preference was not stable in the nocturnal animals, they became diurnal. A 6-h advance of the light-dark (LD) cycle induced a shift of activity and the previous LD preference was reestablished. The large daily variability of activity onset did not allow this study to determine whether the animals were entrained to the LD cycle upon release into constant darkness (DD) or whether activity had been masked by light. The period of the motor activity rhythm in DD free ran in more than 50% of the animals. No differences in activity were observed between the two karyotypes. Immunohistochemistry for c-fos expression in the nucleus suprachiasmaticus at different circadian times showed that c-fos was induced only in animals exposed to a 1-h light pulse during the subjective night, but not during the subjective day or in control animals in the absence of a light pulse. The large intra- and inter-individual variability in daily motor activity both in LD and in DD suggest only a weak photic entrainment of the circadian clock to light of approximately 100 lux, and possibly a weak regulation of behavior by the circadian clock.     

Direct effects of the pineal hormone melatonin on testosterone synthesis of Leydig cells in Djungarian hamsters (Phodopus sungorus) in vitro

Leydig cells of adult Djungarian hamsters, stimulated with luteinizing hormone (LH), were co-incubated with melatonin at various concentrations in a primary culture system. Testosterone secretion was only affected by melatonin when cells were stimulated with LH. Maximal suppression was observed at low doses of LH (0.5 ng/ml). These effects are at least partially mediated through the adenylate cyclase system, since melatonin was able to reduce forskolin-stimulated testosterone secretion. These results indicate that the time between pulses of LH can be considered to be most highly effective for tonic melatonin actions.     

Sigma receptor modulation of noradrenergic-stimulated pineal melatonin biosynthesis in rats

Because sigma receptors are richly concentrated in the rat pineal gland, the present study was performed to investigate their possible role in the modulation of melatonin production. To this purpose, we assessed in vivo the effects of the sigma-receptor ligands 1,3-di(2-tolyl)guanidine and (+)-N-allylnormetazocine on the rat pineal gland activity during either the daytime or the nighttime. Compared with vehicle, 1,3-di(2-tolyl)guanidine and (+)-N-allylnormetazocine potentiated the enhancement of N-acetyltransferase activity and pineal melatonin content induced by isoproterenol administration during the daytime, whereas they did not affect the diurnal basal biosynthetic activity of the gland. Conversely, at night, 1,3-di(2-tolyl)guanidine and (+)-N-allylnormetazocine enhanced significantly the physiological increases in both pineal N-acetyltransferase activity and melatonin levels. This enhancement was prevented by pretreatment with rimcazole, a specific sigma-receptor antagonist. These findings suggest that, in rats, the activation of pineal sigma-receptor sites does not affect the biosynthetic activity of the pineal gland during daytime, whereas it potentiates the production of melatonin when the gland is noradrenergically stimulated either by isoproterenol administration or by the endogenously released norepinephrine at nighttime.     

Circadian melatonin and young-to-old pineal grafting postpone aging and maintain juvenile conditions of reproductive functions in mice and rats

Chronic, night administration of melatonin to aging mice and transplantation of a young pineal gland into the thymic rudiment of older mice and rats have been studied with the aim of evaluating their effects on aging of gonadal, sexual, and reproductive functions. Both melatonin administration and young-to-old pineal grafting positively affect size and function of testes and maintenance of juvenile hippocampal and testicular LHRH-receptors and beta-adrenergic receptors in the tests of old rats and mice. These results demonstrate that a pineal-directed circadian function and cyclicity is fundamental for the regulation of sexual, reproductive physiology, and that proper intervention with melatonin may potentially postpone aging of both neural and gonadal sexual function.     

Regulation mechanism of melatonin rhythm in the pineal gland by light: experimental studies by in vivo microdialysis

Light has dual effects on the pineal melatonin; one is the entrainment of the circadian rhythm and the other is suppression of the melatonin synthesis. It is not known whether the entraining and suppressing effects of light are mediated by the same pathway or not. To elucidate the mechanism of the dual effects of light, (1) the sensitivity of the retina, (2) effects of acetylcholine agonist and, (3) the arrhythmicity induced by longterm continuous light, were studied by measuring melatonin continuously from a single rat by means of in vivo microdialysis. Pineal melatonin was suppressed by light more strongly at the late dark phase than at midnight, and by green light (520nm) than by red light (660nm). Pineal melatonin measured by microdialysis was decreased rapidly by a short light exposure and the melatonin rhythm was shifted on the following days. Microinjection of cholinergic agonist, carbachol, into the suprachiasmatic nucleus neither suppressed nor entrained the pineal melatonin rhythm. Immediately after the blinding, rats showed the circadian rhythm in pineal melatonin which had been abolished under long-term continuous light. While, it took several days for the locomotor rhythm to reappear. It is concluded that, (1) suppression of the pineal melatonin by light depends on the circadian phase and on the wavelength of light, (2) the threshold for light suppression is lower than that for phase-shift, (3) the melatonin rhythm starts to phase-shift on the following day of light pulse. (4) Acetylcholine is unlikely to be involved in the photic transmission both to the circadian clock and to the pineal, (5) arrhythmicity induced by long-term continuous light seems to be due to masking for the melatonin rhythm, and to uncoupling from the clock for the locomotor rhythm.     

Presence of melatonin in plasma and urine or pinealectomized rats

Melatonin was shown to occur in rat plasma and urine after pinealectomy by bioassay, radioimmunoassay, and thin-layer chromatography. Total daily excretion of melatonin in pinealectomized rats was about 20% of control. Light-dark rhythms of plasma melatonin levels and urinary excretion rates disappeared after pinealectomy.     

Endocrine effects of the pineal gland and neutralization of circulating melatonin and N-acetylserotonin

Adrenocortical function was studied in rats after shampinealectomy, pinealectomy, or immunization against melatonin and N-acetylserotonin (NAS). Pineals were stimulated to increase melatonin synthesis by blinding or exposure to 23 h of darkness daily. Blinding elevated morning corticosterone levels without altering the corticosterone response to novelty stimulation. Among blinded animals, pinealectomy partially reversed and immunization completely reversed the elevations in morning steroid levels. Exposure to short daily photoperiods flattened the diurnal corticosterone rhythm. Pinealectomy did not affect morning corticosterone levels but reduced evening corticosterone levels. More importantly, immunization resulted in reduced corticosterone levels throughout the diurnal cycle. These findings suggest that melatonin and (or) NAS may be involved in the regulation of resting diurnal adrenocortical function.     

HPLC detection of serotonin within the rat cochlea

This study was performed to analyse the cochlear concentrations of serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), their sources and modifications induced by noise exposure. Superior cervical ganglionectomy did not modify these concentrations. However, removal of the blood by aortic perfusion reduced significantly (about 76%) the cochlear concentration of 5-HT without affecting the 5-HIAA concentration. These results indicate that blood constitutes an important source of 5-HT to the cochlea, opposite to the superior cervical ganglion. Exposure to noise at 90 dB SPL did not modify the total cochlear concentrations of 5-HT and 5-HIAA, or the concentrations remaining after removal of the blood, suggesting that 5-HT could have a modulatory role in the cochlea distinct from that of olivocochlear neurotransmitters.     

Inconsistent suppression of nocturnal pineal melatonin synthesis and serum melatonin levels in rats exposed to pulsed DC magnetic fields

The purpose of these experiments was to determine whether the exposure of rats at night to pulsed DC magnetic fields (MF) would influence the nocturnal production and secretion of melatonin, as indicated by pineal N-acetyltransferase (NAT) activity (the rate limiting enzyme in melatonin production) and pineal and serum melatonin levels. By using a computer-driven exposure system, 15 experiments were conducted. MF exposure onset was always during the night, with the duration of exposure varying from 15 to 120 min. A variety of field strengths, ranging from 50 to 500 microT (0.5 to 5.0 G) were used with the bulk of the studies being conducted using a 100 microT (1.0 G) field. During the interval of DC MF exposure, the field was turned on and off at 1-s intervals with a rise/fall time constant of 5 ms. Because the studies were performed during the night, all procedures were carried out under weak red light (intensity of <5 microW/cm2). At the conclusion of each study, a blood sample and the pineal gland were collected for analysis of serum melatonin titers and pineal NAT and melatonin levels. The outcome of individual studies varied. Of the 23 cases in which pineal NAT activity, pineal melatonin, and serum melatonin levels were measured, the following results were obtained; in 5 cases (21.7%) pineal NAT activity was depressed, in 2 cases (8.7%) studies pineal melatonin levels were lowered, and in 10 cases (43.5%) serum melatonin concentrations were reduced. Never was there a measured rise in any of the end points that were considered in this study. The magnitudes of the reductions were not correlated with field strength (i.e., no dose-response relationships were apparent), and likewise the reductions could not be correlated with the season of the year (experiments conducted at 12-month intervals under identical exposure conditions yielded different results). Duration of exposure also seemed not to be a factor in the degree of melatonin suppression. The inconsistency of the results does not permit the conclusion that pineal melatonin production or release are routinely influenced by pulsed DC MF exposure. In the current series of studies, a suppression of serum melatonin sometimes occurred in the absence of any apparent change in the synthesis of this indoleamine within the pineal gland (no alteration in either pineal NAT activity or pineal melatonin levels). Because melatonin is a direct free radical scavenger, the drop in serum melatonin could theoretically be explained by an increased uptake of melatonin by tissues that were experiencing augmented levels of free radicals as a consequence of MF exposure. This hypothetical possibly requires additional experimental documentation.     

Development of 11 beta-hydroxysteroid dehydrogenase expression in the rat cochlea

Spontaneous coronary dissection is rare and the diagnosis is usually post-mortem. Less than 60 cases have been diagnosed at coronary angiography. The authors report, to the best of their knowledge, the first case of multiple spontaneous coronary artery dissections in a type IV Ehlers-Danlos syndrome in a young woman admitted to hospital for acute myocardial infarction. She had a previous history of regressive complete tetraplegia due to dissection of the basilar artery and episodes of dizziness related to a dissecting aneurysm of the left vertebral artery. The diagnosis of type IV Ehlers-Danlos syndrome was established after skin biopsy had shown typical histological changes. The patient died several months later after an acute abdominal syndrome probably related to dissection of the aorta. An autopsy was refused by her family. The authors believe this to be the first case of spontaneous coronary dissection related to a type IV Ehlers-Danlos syndrome.     

Autonomic regulation of melatonin synthesis through intrinsic glutaminergic systems in mammalian pineal glands]

Prospects for the search for thrombolytic compositions on the basis of short-term and long-term acting plasminogen activators were shown. These will be useful as potential ambulance remedies for effective prehospital treatment. Combined proteolysis by plasminogen activators with complementary action mechanisms and significantly different pharmacokinetic behavior was suggested for this purpose.     

Presence of atrial natriuretic peptide in two desert rodents: comparison with rat

Atrial natriuretic peptide (ANP) was characterized and assayed in plasmas, hearts, and brains of two Algerian desert rodents, Psammomys obesus and Meriones libycus along with vasopressin, which was assayed in hypophyses and hypothalami. Using reverse-phase high-performance liquid chromatography and radioimmunoassay, we showed, in plasmas and hearts of both species of desert rats, the presence of peptides similar to rat N- and C-terminal ANP but in lower amounts than in Wistar rats. Conversely, C-terminal ANP was abundantly detected in hypophyses from Meriones libycus rats. As these peptides, through their diuretic and natriuretic activities, are involved in body fluid regulation and electrolyte balance, the reduction of ANP stores in both plasmas and hearts suggests that diuresis and natriuresis are lowered in both species of mammals adapted to arid environments. This could occur because of the vasopressin-mediated adaptation, but also in response to the low ANP involvement in hydro-osmotic regulations, even in Psammomys, which has a dietary salt loading. On the other hand, the higher C-terminal ANP contents in the hypophysis of Meriones than in Psammomys and Wistar rats remain to be understood.     

Multiple sclerosis: the role of puberty and the pineal gland in its pathogenesis

Epidemiological studies demonstrate that the incidence of multiple sclerosis (MS) is age-dependent being rare prior to age 10, unusual prior to age 15, with a peak in the mid 20s. It has been suggested that the manifestation of MS is dependent upon having passed through the pubertal period. In the present communication, I propose that critical changes in pineal melatonin secretion, which occur in temporal relationship to the onset of puberty, are intimately related to the timing of onset of the clinical manifestations of MS. Specifically, it is suggested that the fall in melatonin secretion during the prepubertal period, which may disrupt pineal-mediated immunomodulation, may stimulate either the reactivation of the infective agent or increase the susceptibility to infection during the pubertal period. Similarly, the rapid fall in melatonin secretion just prior to delivery may account for the frequent occurrence of relapse in MS patients during the postpartum period. In contrast, pregnancy, which is associated with high melatonin concentrations, is often accompanied by remission of symptoms. Thus, the presence of high melatonin levels may provide a protective effect, while a decline in melatonin secretion may increase the risk for the development and exacerbation of the disease. The melatonin hypothesis of MS may explain other epidemiological and clinical phenomena associated with the disease such as the low incidence of MS in the black African and American populations, the inverse correlation with sun light and geomagnetic field exposure, the occurrence of relapses in relation to seasonal changes and fluctuations in mood, and the association of MS with affective illness and malignant disease. Therapeutically, this hypothesis implies that application of bright light therapy or the use of other major synchronizers of circadian rhythms such as sleep deprivation or application of external weak magnetic fields may be beneficial in the treatment and/or prophylaxis of relapses in the disease.