Ario Conti

Role of the pineal gland in immunity. Circadian synthesis and release of melatonin modulates the antibody response and antagonizes the immunosuppressive effect of corticosterone.

Inhibition of synthesis of the pineal neurohormone melatonin (MEL) in mice, by administration of propranolol (PRO) in the evening, and daily injections of p-chlorophenylalanine (PCPA), resulted in a significant depression of the primary antibody response to sheep red blood cells (SRBC). Spleen cells from these mice showed a reduced reactivity against antigens in the autologous mixed lymphocyte reaction (AMLR). In contrast, alloreactivity remained normal. Reconstitution of the night-time peak of plasma MEL by evening injections to the mice completely reversed the suppression of the humoral response and the AMLR. MEL administration was able to antagonize the depression of antibody production induced by corticosterone in vivo. These results suggest that the pineal gland has important immunomodulatory functions through its cyclic, circadian release of MEL.

Pineal Melatonin, Its Fundamental Immunoregulatory Role in Aging and Cancer

A closely interwoven network of immune and neuroendocrine mechanisms protects our organism against a variety of environmental threats. Derangements of neuroendocrine functions such as those associated with or caused by failure to cope with stressful events or “distress” may lead in turn to an impairment of immunologic functions and possibly to an increased incidence of infections, autoimmune diseases and cancer.’.’ As a matter of fact, functional connections and feedback loops between the immune and the neuroendocrine systems are being increasingly Thus, primary defects in the neuroendocrine system or psychologic disturbances may adversely affect the immunologic machinery. The opposite is also true. In the case of aging, for example, the associated decline of both psychic and immune performance might, therefore, be triggered either by primary psycho-neuroendocrinologic or by immune alterations. The pineal gland is a fundamental modulator of the entire neuroendocrine system. The pineal gland functions as a true “biologic clock” secreting in a circadian fashion its main neurohormone melatonin or N-acetyl-5-methoxytryptamine. Melatonin synthesis and release is regulated mainly by the light-dark cycle with a peak during the night, darkness hours.’.* However, other environmental variables such as temperature, humidity and, perhaps, pheromones and magnetism may influence its rhythm.’.’ Also various physiopathologic states can affect melatonin rhythms. For example, in man alterations of melatonin production have been associated, amongst other things, with aging and cancer. In particular, low or impaired melatonin production has been described in aging’ and various modifications of the melatonin rhythm have been found in cancer patients.” We have recently found that the circadian synthesis and release of melatonin exerts an important immunomodulatory Melatonin appears to be a physiologic “upregulator” of the immune system and to operate via the endogenous opioid system (EOS) on antigen-activated cells.12*” Here we report further on other immunologic

The pineal neurohormone melatonin stimulates activated CD4+, Thy-1+ cells to release opioid agonist(s) with immunoenhancing and anti-stress properties

In previous studies we showed that in mice the pineal gland modulates the immune response via the circadian synthesis and release of melatonin. Exogenous melatonin proved also to exert immunoenhancing effects and to counteract completely the immunologic effect of acute stress. Melatonin was active only in vivo, in mice primed with T-dependent antigens and its effects on the primary antibody response and thymus weight were abolished by the specific opioid antagonist naltrexone. Here we demonstrate that physiologic concentrations of melatonin stimulate, in vitro, activated L3T4+ (CD4+) cells to release opioid agonist(s) that can reproduce in vivo the immunoenhancing and anti-stress effects on thymus cellularity and antibody production of melatonin and compete with specific binding of [3H]naloxone to mouse brain membranes. Similar results were obtained when mitogen-activated human immunocompetent cells were incubated with melatonin. In the human model the results were, however, less consistent than those obtained with murine cells, in that only four out of ten blood donors provided cells that were responsive to melatonin. This finding elucidates the mechanism of a novel immuno-neuroendocrine connection with relevant implications for our understanding of the neuroendocrine factors that may influence the immune response in vivo in normal and stressful situations. In addition, it opens new perspectives in a wide range of research fields.

The Pineal Gland and the Circadian, Opiatergic, Immunoregulatory Role of Melatonin

Earlier work in our laboratory led to the proposition that lymphocyte products act as messengers to the central nervous system.’ Those findings, which have been recently confirmed and extended,’,’ originated from the observation that antigens evoke specific and rapid hormonal responses early after injection into mice. We could demonstrate that the interference with those endocrine changes by a combination of psychotropic drugs specifically depressed humoral and cellular immune responseseh In the course of those studies, however, the idea progressively emerged that another basic modulator of neuroendocrine mechanisms, namely the pineal gland, plays a fundamental role in neuroimmunomodulation besides the better known hypothalamicpituitary system.’ The pineal gland functions as a neuroendocrine “transducer” by translating the most basic environmental information (photic, thermic, magnetic) into signals which modulate most neuroendocrine mechanisms.’.* This remarkable task seems to be accomplished via the circadian synthesis and release of melatonin (N-acetyl-5-methoxytryptamine), the most studied and best known pineal neurohormone. Melatonin is synthesized and released upon activation of pineal beta-adrenergic receptors in man and most vertebrates during the nocturnal, dark hours and maintains a consistently regular circadian rhythm? In humans, alterations of this rhythm have been associated with sleep disturbances, anxiety states, affective disorders, and psychosomatic diseases.I0.I1 Scant experimental findings exist on a possible connection between the pineal gland and the lymphohemopoietic system.” It has been reported that immune reactivity and circulating lymphocytes fluctuate according to a circadian r h ~ t h m , ’ ~ ’ ~ although the significance of these variations is not clear. Evidence for an inhibitory role of the pineal gland on carcinogenesis and tumor growth has also been reported (reviewed in Ref. 16). Recently, our early pharmacologic studies on the pineal-immune system connections’ have been replicated by other authors and our results have been confirmed.”

HPLC-ED measurement of endogenous catecholamines in human immune cells and hematopoietic cell lines

A rapid and simple HPLC-ED method is described to identify and measure catecholamines (CTs) and their major metabolites in immune cells. Using this method, intracellular CTs were quantified in human peripheral blood mononuclear cells (PBMCs), T and B lymphocytes, monocytes and granulocytes. Immune cell subsets were separated by density gradient centrifugation and immunomagnetic cell sorting. CTs were also found in the human hematopoietic cell lines NALM-6 (pre-B) and (in smaller amounts) in Jurkat (T lymphoblastoid) and U937 (promonocytic). In cultured PBMCs, intracellular CTs were reduced by both the tyrosine hydroxylase inhibitor alpha-methyl-p-tyrosine and the chromaffin granule depletant reserpine. In NALM-6 cells, both alpha-methyl-p-tyrosine and the dopamine-beta-hydroxylase inhibitor disulfiram reduced intracellular CTs, supporting the presence of active synthetic pathways in these cells. Since sympathoadrenergic mechanisms play a key role in the interactions between the immune system and the nervous system, these findings may be relevant for a better understanding of the neuro-immune network.

Beta-endorphin and dynorphin mimic the circadian immunoenhancing and anti-stress effects of melatonin.

We have recently demonstrated that the pineal neurohormone melatonin can enhance immune reactivity in normal mice and counteract the effects of acute stress or corticosterone treatment on antibody production, thymus weight and anti-viral resistance. These remarkable immunopharmacologic effects of melatonin were abolished by naltrexone, suggesting an involvement of the endogenous opioid system. Here we compared the immunopharmacologic action of beta-endorphin, dynorphin 1-13, leu-enkephalin and metenkephalin with that of melatonin in restraint-stressed or prednisolone-treated mice and in normal nonstressed animals. We found that beta-endorphin and dynorphin 1-13 can mimic the immunoenhancing and antistress effect of melatonin. However, at variance with the pineal neurohormone, these opioids were effective in umprimed mcie, too. We found also that restraint stress or prednisolone treatment decreases the immunopharmacologic potency of beta-endorphin and augments that of dynorphin 1-13. In fact, at the doses used, beta-endorphin enhanced the antibody response in normal but not in stressed or prednisolone-treated mice, while dynorphin 1-13 was effective only in counteracting the effect of stress or prednisolone treatment. Most interestingly, all these effects proved to be dependent on the time of administration, i.e. showed a circadian rhythm in analogy with the effects of melatonin. Again, naltrexone abolished all the opioid effects, indicating that their action was exerted via opioid receptors. These findings have important scientific and practical implications.

Anti-Stress Role of the Melatonin-Immuno-Opioid Network: Evidence for a Physiological Mechanism Involving T Cell-Derived, Immuno-Reactive β-Endorphin and Met-Enkephalin Binding to Thymic Opioid Receptors

Our previous work showed that the pineal neurohormone melatonin induces activated T lymphocytes to release opioid peptides with immunoenhancing and anti-stress properties. Here we present evidence that these peptides crossreact with anti-beta-endorphin and anti-met-enkephalin antisera, and bind specifically to thymic opioid receptors. Furthermore, the same antisera injected in prednisolone treated mice prevented the normal recovery of thymus cellularity and of the capacity to mount a primary antibody response against T-dependent antigens. Surgical pinealectomy, i.e. inhibition of endogenous melatonin and absence of antigen activation negated the effect of such antisera demonstrating the physiological relevance of this melatonin-immuno-opioids network. It is proposed that function of this network may be that of driving a correct immune recovery after the depression caused by the elevated corticosteroids level associated with immune responses and/or stressful situations.

Role of pineal melatonin and melatonin-induced-immuno-opioids in murine leukemogenesis

The relationship between the pineal gland, melatonin and melatonin-induced-immuno-opioids with the response of C57BI/6 mice to A-RadLV induced T cell lymphomas was investigated. Mice were injected at day 0 with A-RadLV and from day 10 they were treated chronically with melatonin 4 mg/kg body weight, naltrexone 1 mg/kg or phosphate buffered saline, throughout the experiment. In another protocol, groups of mice were a) surgical pinealectomized at day-14, b) functional pinealectomized (24:24 hours light) from day -20 and c) sham pinealectomized. At day 0 each group was inoculated intrathymically with A-RadLV. The results show that melatonin accelerated (p < 0.005) leukemogenesis whereas the surgical pinealectomy and the functional pinealectomy delayed it (p < 0.005 andp < 0.01). Moreover, the action of melatonin was blocked by naltrexone (p < 0.005), indicating the involvement of melatonin-induced-immuno-opioids in the development of the lymphomas.

Botany and Pharmacognosy of the Cacao Tree

Cacao trees originated in river valleys of South America and, by the seventh century AD, the Mayan Indians had brought them north into Mexico. Apart from the Mayans, many other Central American Indians including the Aztecs and the Toltecs seem to have at first domesticated and then cultivated cacao trees, and the word “chocolate” (the beverage) derives from xhocolatl (approximate spelling) or cacahuatl, both originating from the Aztec language. There are several mixtures of cacao described in ancient texts, for ceremonial, medicinal and culinary purposes. Some mixtures included maize, chili, vanilla (Vanilla planifolia), peanut butter and honey. Archaeological evidence of the use of cacao, while relatively sparse, has come from the recovery of whole cacao beans in Uaxactun, Guatemala and from the preservation of wood fragments of the cacao tree at the Belize sites (ex British Honduras). In addition, analysis of residues from ceramic vessels has found traces of theobromine and caffeine in early formative vessels from Puerto Escondido, Honduras (1100–900 BC) and in middle formative vessels from Colha, Belize (600–400 BC) [1], [2].

The pineal neurohormone melatonin and its physiologic opiatergic immunoregulatory role

The pineal gland functions as a neuroendocrine transducer that coordinate the organism response to changing environmental stimuli such as light and temperature. The main and best known pineal neurohormone is melatonin that is synthesized and released in a circadian fashion with a peak during the night darkness hours. We have recently reported that melatonin exerts important immuno regulatory functions. Here we describe the astonishing property of exogenous melatonin which is able to counteract completely the depressive effect of anxiety-restraint stress and/or of corticosterone on thymus weight, andibody production and antiviral responses. This effect seems to be mediated by antigen-activated T cells via an opiatergic mechanism.