Role of Melatonin in Viral, Bacterial and Parasitic Infections.

In all mammals, the circulating pool of MLTs is synthesized in the pineal gland during the night's darkness hours. Its main function is synchronizing the organism in the photoperiod. In contrast, extra-pineal MLT is synthesized in peripheral organs, does not follow any circadian rhythm or circulate, and plays a detoxifying and cytoprotective role. Circulating MLT may stimulate both innate and acquired immune responses through its circadian action and by activating high-affinity receptors on immunocompetent cells. Extra-pineal MLT may have antioxidant and anti-inflammatory effects that dampen the innate immune response. These two seemingly divergent roles may be considered to be two sides of the same coin. In fact, the integration of both circulating and extra-pineal MLT functions might generate a balanced and effective immune response against microbial pathogens. The studies described in this review investigated the effects of exogenous MLT in various models of infectious diseases using extremely different doses and treatment schedules. None of them evaluated the possibility of integrating the non-circadian anti-inflammatory effect with the circadian immunoenhancing action of MLT. As a consequence, in spite of the fact that most studies agree that MLT has a beneficial effect against infections, it seems difficult to draw any definite conclusion about its possible therapeutic use.

ß2-Adrenergic agonists bias TLR-2 and NOD2 activated dendritic cells towards inducing an IL-17 immune response.

This study tested the hypothesis that activation of ß2-adrenoceptors on DCs influences NOD2 signaling along with its cross-talk with Toll-like receptor-2 resulting in altered Th cell priming ability. Th17 cells are a newly discovered lineage of CD4(+) T cells involved in defense against extracellular bacteria and also implicated in autoimmune disorders. Initiation and polarization of the adaptive immune response is controlled by innate immune recognition mediated by DCs. Previous studies demonstrated that adrenergic receptors modulate cytokine production by DCs and affect their Th cell priming ability. We show that the ß2-adrenoceptor agonist salbutamol enhanced IL-6 production in murine bone marrow-derived DCs stimulated with the nucleotide-binding oligomerization domain 2 ligand muramyl dipeptide. However, when the Toll-like receptor-2 ligand Pam3CysSK4 was added, salbutamol inhibited IL-12 but did not alter IL-6 and IL-23 expression. Gene expression analysis showed that salbutamol inhibited the p40 subunit as well as IL-12p35, while IL-23p19 and IL-6 were stimulated. Therefore, ß2-adrenoceptors modulated cytokine production resulting in a Th17 cell priming cytokine pattern. Indeed, when antigen-pulsed DCs stimulated by muramyl dipeptide or Pam3CysSK4+muramyl dipeptide in the presence of salbutamol were used for in vivo immunization, the resulting Th17/Th1 cell ratio was increased as evaluated by IL-17 and IFN-γ production. In addition, intradermal injection of norepinephrine along with Pam3CysSK4+muramyl dipeptide increased the Th17 response to an immunogenic protein and this effect was reversed by a ß2-adrenoceptor antagonist. Thus, ß2-adrenoceptors may be involved in the regulation of defense against extracellular bacteria and the pathogenesis of inflammatory diseases.

Pinealectomy affects bone mineral density and structure--an experimental study in sheep.

BACKGROUND: Osteoporosis and associated fractures are a major public health burden and there is great need for a large animal model. Melatonin, the hormone of the pineal gland, has been shown to influence bone metabolism. This study aims to evaluate whether absence of melatonin due to pinealectomy affects the bone mass, structure and remodeling in an ovine animal model. METHODS: Female sheep were arranged into four groups: Control, surgically ovariectomized (Ovx), surgically pinealectomized (Px) and Ovx+Px. Before and 6 months after surgery, iliac crest biopsies were harvested and structural parameters were measured using µCT. Markers of bone formation and resorption were determined. To evaluate long term changes after pinealectomy, bone mineral density (BMD) was analyzed at the distal radius at 0, 3, 9, 18 and 30 months. RESULTS: Cancellous bone volume (BV/TV) declined after 6 months by -13.3% Px and -21.5% OvxPx. The bone loss was due to increased trabecular separation as well as decreased thickness. The histomorphometric quantification and determination of collagen degradation products showed increased bone resorption following pinealectomy. Ovariectomy alone results in a transient bone loss at the distal radius followed by continuous increase to baseline levels. The bone resorption activity after pinealectomy causes a bone loss which was not transient, since a continuous decrease in BMD was observed until 30 months. CONCLUSIONS: The changes after pinealectomy in sheep are indicative of bone loss. Overall, these findings suggest that the pineal gland may influence bone metabolism and that pinealectomy can be used to induce bone loss in sheep.

Physiological effects of melatonin: role of melatonin receptors and signal transduction pathways.

Melatonin, an endogenous signal of darkness, is an important component of the body's internal time-keeping system. As such it regulates major physiological processes including the sleep wake cycle, pubertal development and seasonal adaptation. In addition to its relevant antioxidant activity, melatonin exerts many of its physiological actions by interacting with membrane MT1 and MT2 receptors and intracellular proteins such as quinone reductase 2, calmodulin, calreticulin and tubulin. Here we review the current knowledge about the properties and signaling of melatonin receptors as well as their potential role in health and some diseases. Melatonin MT1 and MT2 receptors are G protein coupled receptors which are expressed in various parts of the CNS (suprachiasmatic nuclei, hippocampus, cerebellar cortex, prefrontal cortex, basal ganglia, substantia nigra, ventral tegmental area, nucleus accumbens and retinal horizontal, amacrine and ganglion cells) and in peripheral organs (blood vessels, mammary gland, gastrointestinal tract, liver, kidney and bladder, ovary, testis, prostate, skin and the immune system). Melatonin receptors mediate a plethora of intracellular effects depending on the cellular milieu. These effects comprise changes in intracellular cyclic nucleotides (cAMP, cGMP) and calcium levels, activation of certain protein kinase C subtypes, intracellular localization of steroid hormone receptors and regulation of G protein signaling proteins. There are circadian variations in melatonin receptors and responses. Alterations in melatonin receptor expression as well as changes in endogenous melatonin production have been shown in circadian rhythm sleep disorders, Alzheimer's and Parkinson's diseases, glaucoma, depressive disorder, breast and prostate cancer, hepatoma and melanoma. This paper reviews the evidence concerning melatonin receptors and signal transduction pathways in various organs. It further considers their relevance to circadian physiology and pathogenesis of certain human diseases, with a focus on the brain, the cardiovascular and immune systems, and cancer.

Adrenergic Modulation of Hematopoiesis.

Hematopoiesis produce every day billions of blood cells and takes place in the bone marrow (BM) by the proliferation and differentiation of hematopoietic stem cells (HSC). HSC are found mainly adjacent to the BM vascular sinusoids where endothelial cells and mesenchimal stromal cells promote HSC maintenance by producing a variety of factors. Other cell types that regulate HSC niches include sympathetic nerves, non-myelinating Schwann cells and a variety of mature hematopoietic cells such as macrophages, neutrophils, and megakaryocytes. This review will focus on the role of adrenergic signals, i.e. of catecholamines, in the regulation of the HSC niche. The available evidence is rather controversial possibly due to the fact that adrenergic receptors are expressed by many cellular components of the niche and also by the often neglected observation that catecholamines may be produced and released also by the BM cells themselves. In addition one has to consider that, physiologically, the sympathetic nervous system (SNS) activity follows a circadian rhythmicity as driven by the suprachiasmatic nucleus (SCN) of the hypothalamus but may be also activated by cognitive and non-cognitive environmental stimuli. The adrenergic modulation of hematopoiesis holds a considerable potential for pharmacological therapeutic approaches in a variety of hematopoietic disorders and for HSC transplantation however the complexity of the system demands further studies. Graphical Abstract Sympathetic nerve termini may release NE while mature BM cells may release norepinephrine (NE) and / or epinephrine (E). Both may bind to ß-adrenergic receptor (AR) expressed in nestin+MSC in the hematopoietic stem cell (HSC) niche and regulate the physiological trafficking of HSC by modulating the expression of CXCL12 and SCF. Both NE and E may also activate Lin - c-Kit+ Sca-1+ (LKS) cell via another AR. In addition, NE may also signal to α1-AR expressed in pre-B cells which by TGF-ß secretion might regulate proliferation of their lymphoid progenitors in an autocrine manner and/or inhibit myeloid progenitors.

Sympathetic nervous modulation of the skin innate and adaptive immune response to peptidoglycan but not lipopolysaccharide: involvement of beta-adrenoceptors and relevance in inflammatory diseases.

Disorders of the skin immune activity are implicated in the pathogenesis of acquired inflammatory skin disorders. Inflammatory diseases including psoriasis, atopic dermatitis, lichen planus and vitiligo have also been associated with local alterations of adrenergic mechanisms and emotional stress. Here we show that the beta-adrenergic receptors antagonist propranolol along with peptidoglycan, but not LPS, combined with intradermal injection of a soluble protein, shifted the recall memory response to the Th1 type. The specific beta2-AR antagonist ICI 118,551 did not reproduce this effect suggesting that inhibition of both beta1- and beta2-AR caused the Th1 polarization. The underlying mechanism included enhanced local expression of IFN-gamma, IL-12 and IL-23 as well as of IFN-beta and CXCR3 ligands during the innate phase of the response which resulted in an increase of antigen-positive plasmacytoid dendritic cells (pDCs) in the draining lymph node. In particular, modulation of inflammatory cytokines, and IFN-beta inducible genes expression appeared to involve also the beta1-AR. Plasmacytoid dendritic cells and IL-23 were recently reported to play a central role in the pathogenesis of Th1-sustained inflammatory skin diseases such as psoriasis. Thus, primary beta-adrenoceptors signaling defects or altered sympathetic nervous activity together with selected pattern recognition receptors activation might serve as initiation and/or persistence factors for numerous Th1-sustained inflammatory skin diseases.

Immunomodulation by melatonin: its significance for seasonally occurring diseases.

Melatonin is not only synthesized by the pineal gland but also in many other organs and tissues of the body, particularly by lymphoid organs such as the bone marrow, thymus and lymphocytes. Melatonin participates in various functions of the body, among which its immunomodulatory role has assumed considerable significance in recent years. Melatonin has been shown to be involved in the regulation of both cellular and humoral immunity. Melatonin not only stimulates the production of natural killer cells, monocytes and leukocytes, but also alters the balance of T helper (Th)-1 and Th-2 cells mainly towards Th-1 responses and increases the production of relevant cytokines such as interleukin (IL)-2, IL-6, IL-12 and interferon-gamma. The regulatory function of melatonin on immune mechanisms is seasonally dependent. This fact may in part account for the cyclic pattern of symptom expression shown by certain infectious diseases, which become more pronounced at particular times of the year. Moreover, melatonin-induced seasonal changes in immune function have also been implicated in the pathogenesis of seasonal affective disorder and rheumatoid arthritis. The clinical significance of the seasonally changing immunomodulatory role of melatonin is discussed in this review.

Sympathetic nervous system influence on the innate immune response.

Our studies focused on the sympathetic nervous system (SNS) influence on dendritic cells (DCs), which play a crucial role in the innate immune response. We found that DCs express a variety of adrenergic receptors (ARs) with alpha1-ARs playing a stimulatory and beta2-ARs an inhibitory effect on DCs migration. beta2-ARs in skin and bone marrow-derived DCs when stimulated by bacterial toll-like receptors (TLRs) agonists respond to norepinephrine (NE) by decreased interleukin-12 (IL-12) and increased IL-10 production which in turn downregulates inflammatory cytokine production and CCR7 expression and thus their migration ability leading to reduced T helper-1 (Th1) priming. We also found that contact sensitizers that may induce a predominant Th1 response, do so by inhibiting the local NE turnover in the skin. The SNS seems therefore to contribute in shaping the information conveyed by DCs to T cells and thus in inducing the appropriate adaptive immune response. In this sense, the SNS physiological influence may allow Th2 priming to fight infections sustained by extracellular pathogens and limit the risk for organ-specific autoimmune reactions associated with excessive Th1 priming and inhibition of T regulatory cell functions. More recently, we found that preconditioning of the skin by beta-adrenergic antagonist and the TLR2 agonist S. Aureus peptidoglycan (PGN) may instruct a Th1 adaptive response to a soluble protein antigen. On the contrary, when the TLR4 agonist E. Coli lipopolysaccharide was used, the presence of the beta-adrenergic antagonist was not effective. These effects were consonant with the pattern of TLRs expression shown by epidermal keratinocytes (EKs) but not by skin DCs. As beta-ARs signaling defects together with S. Aureus infections are thought to serve as initiation and/or persistence factors for numerous Th1-sustained autoimmune inflammatory skin diseases, we might have disclosed at least part of the relevant pathogenetic mechanism.

Circadian rhythms: glucocorticoids and arthritis.

Circadian rhythms are driven by biological clocks and are endogenous in origin. Therefore, circadian changes in the metabolism or secretion of endogenous glucocorticoids are certainly responsible in part for the time-dependent changes observed in the inflammatory response and arthritis. More recently, melatonin (MLT), another circadian hormone that is the secretory product of the pineal gland, has been found implicated in the time-dependent inflammatory reaction with effects opposite those of cortisol. Interestingly, cortisol and MLT show an opposite response to the light. The light conditions in the early morning have a strong impact on the morning cortisol peak, whereas MLT is synthesized in a strictly nocturnal pattern. Recently, a diurnal rhythmicity in healthy humans between cellular (Th1 type) or humoral (Th2 type) immune responses has been found and related to immunomodulatory actions of cortisol and MLT. The interferon (IFN)-gamma/interleukin (IL)-10 ratio peaked during the early morning and correlated negatively with plasma cortisol and positively with plasma MLT. Accordingly, the intensity of the arthritic pain varies consistently as a function of the hour of the day: pain is greater after waking up in the morning than in the afternoon or evening. The reduced cortisol and adrenal androgen secretion, observed during testing in rheumatoid arthritis (RA) patients not treated with glucocoticoids, should be clearly considered as a "relative adrenal insufficiency" in the presence of a sustained inflammatory process, and allows Th1 type cytokines to be produced in higher amounts during the late night. In conclusion, the right timing (early morning) for the glucocorticoid therapy in arthritis is fundamental and well justified by the circadian rhythms of the inflammatory mechanisms.

Does melatonin play a disease-promoting role in rheumatoid arthritis?

The pineal neurohormone melatonin (MLT) has been widely shown to exert an immunostimulatory and antiapoptotic role, mainly by acting on Th cells and on T and B cell precursors, respectively. Thus, MLT might favor or promote autoimmune diseases by acting directly on immature and mature immunocompetent cells. In fact, preclinical and clinical evidence point to a disease-promoting role of MLT in rheumatoid arthritis (RA). MLT, whose concentration is increased in serum from RA patients, may act systemically or locally in the inflamed joints. The circadian secretion of MLT with a peak level during the night hours might be strictly correlated with the peculiar daily rhythmicity of the RA symptoms. In rat studies employing Freund's complete mycobacterial adjuvant (FCA) as a model of rheumatoid arthritis, pinealectomized rats turned arthritic and exhibited a significantly less pronounced inflammatory response, which was restored to normal by a low MLT dose and was aggravated by a pharmacological MLT dose, that augmented the inflammatory and immune response. Continued investigation will refine our understanding of these observations, which will possibly translate into improved therapeutic approaches.

The endogenous cannabinoid 2-arachidonoyl glycerol as in vivo chemoattractant for dendritic cells and adjuvant for Th1 response to a soluble protein.

The decision-making mechanisms that determine the choice of the appropriate effector immune response to a microbial challenge are poorly understood. The endocannabinoid 2-arachidonoylglycerol (2-AG), injected intradermally in mice together with a soluble protein and a T helper-2 (Th2) priming Toll-like receptors (TLRs) agonist during primary immunization, shifts the memory response to the Th1 type. This effect can be shown by the enhanced hypersensitivity response and by the Th1 pattern of cytokines production that was abolished by the specific cannabinoid receptor CB2 antagonist SR 144528. 2-AG seems to operate during the innate response by increasing the number of dendritic cells (DCs) migrating to the draining lymph nodes. Expression of CB2 mRNA but not of the protein was higher in immature vs. mature DCs. Consistently, in vitro, 2-AG exerted a potent chemotactic activity on both immature and mature DCs. In conclusion, we suggest that, in vivo, the endocannabinoid 2-AG may act as chemotactic substance capable of recruiting DCs and/or their precursors during the innate immune response that, in presence of a TLR agonist, consequently instruct a Th1-shifted adaptive response. As 2-AG may be induced in tissues by various stimuli at concentrations similar to that used in our study, this evidence might be of a wide-ranging pathophysiological relevance.

Adrenergic modulation of dendritic cells function: relevance for the immune homeostasis.

Dendritic cells (DC) play a key role in determining the appropriate immune response to invading pathogens and tolerance to self antigens. Here I review the evidence that dendritic cell functions may be tuned by the sympathetic nervous system via the local release of norepinephrine. In the presence of antigens or microbial products, such as agonists for Toll-like receptors 2 and 4, norepinephrine inhibits dendritic cell migration, antigen presentation and T-helper cells type 1 priming. This effect, which is mainly mediated by beta-adrenergic receptors in DC and interlukin-10 production, limits potentially damaging reactions and is functional in shaping the appropriate humoral immune response to extracellular pathogens that need antibodies to be neutralized. In addition, the response to contact sensitizers seems to involve a modulation of the local sympathetic activity. Thus, the sympathetic nervous system may play a crucial role in modulating DC function during the innate phase of the immune response. This evidence has many pathophysiological implications and offers new tools for modulating the immune response.

Sympathoadrenergic modulation of hematopoiesis: a review of available evidence and of therapeutic perspectives.

Innervation of the bone marrow (BM) has been described more than one century ago, however the first in vivo evidence that sympathoadrenergic fibers have a role in hematopoiesis dates back to less than 25 years ago. Evidence has since increased showing that adrenergic nerves in the BM release noradrenaline and possibly also dopamine, which act on adrenoceptors and dopaminergic receptors (DR) expressed on hematopoietic cells and affect cell survival, proliferation, migration and engraftment ability. Remarkably, dysregulation of adrenergic fibers to the BM is associated with hematopoietic disturbances and myeloproliferative disease. Several adrenergic and dopaminergic agents are already in clinical use for non-hematological indications and with a usually favorable risk-benefit profile, and are therefore potential candidates for non-conventional modulation of hematopoiesis.

Modulation of skin norepinephrine turnover by allergen sensitization: impact on contact hypersensitivity and T helper priming.

The information gathered by dendritic cells during the innate immune response is determinant for the type and strength of the adaptive response. We showed that the sympathetic neurotransmitter norepinephrine influences dendritic cell migration and T helper priming via alpha- and beta-adrenoceptors. Others have shown that Langerhans cells also express mRNA for beta 1-, beta 2-, and alpha 1A-adrenoceptors and that catecholamines may inhibit the antigen-presenting capability via beta 2-adrenoceptors. Here we report that oxazolone, which induces a predominant T-helper-1-type contact hypersensitivity response, but not fluorescein isothiocyanate, which induces a prevailing T-helper-2-type response, inhibits the local norepinephrine turnover in the skin of mice during the first 8 h of sensitization. Oxazolone also induced higher expression of the inflammatory cytokines interleukin-1 and interleukin-6 mRNA in the skin. Lack or blockade of these cytokines as well as inhibition of prostaglandin synthesis, however, did not influence the oxazolone effect. Only the nonspecific anti-inflammatory steroid dexamethasone could neutralize the effect of oxazolone. Furthermore, fluorescein isothiocyanate but not oxazolone sensitization in the presence of the specific beta 2-adrenoceptor antagonist ICI 118,551 enhanced the consequent contact hypersensitivity response as well as the production of T helper 1 cytokines in draining lymph nodes; conversely T helper 2 cytokines were not affected. Thus, the extent of T helper 1 priming in the adaptive response to a sensitizing agent seems to depend also on its ability to modulate the local sympathetic nervous activity during the innate immune response.

Short exposure of maturing, bone marrow-derived dendritic cells to norepinephrine: impact on kinetics of cytokine production and Th development.

The information gathered by dendritic cells (DC) during the innate immune response to a pathogen is determinant for the type of adaptive response. Here we show that short-term (3 h) exposure of bone marrow-derived DC to norepinephrine (NE), at the beginning of lipopolysaccharide (LPS) or keyhole limpet hemocyanin (KLH) stimulation hampers IL-12 production and increases IL-10 release. The NE effect was mediated by both beta- and alpha2-adrenergic receptors. The capacity of NE-exposed DC to produce IL-12 upon CD40 cross-linking as well as to stimulate allogeneic T-helper (Th) lymphocytes was reduced. Adoptive transfer of NE-exposed DC induced a Th2 slanted response in vivo. Thus, a brief NE exposure of antigen-stimulated DC seems to limit their Th1 polarizing properties. Noteworthy, the ganglionic blocker pentolinium administered in mice before skin sensitization with fluoroscein isothiocyanate (FITC) could increase the Th1-type response in the draining lymph nodes. Our results suggest that the extent of Th differentiation in the response to an antigen might be influenced by the local sympathetic nervous activity in the early phase of dendritic cell stimulation.

Langerhans cells beta 2-adrenoceptors: role in migration, cytokine production, Th priming and contact hypersensitivity.

We showed that norepinephrine (NE) hampers IL-12 and stimulates IL-10 production via adrenoceptors (ARs) in bone marrow-derived dendritic cells (BMDC) influencing their Th priming ability. Others have shown that Langerhans cells (LC) express mRNA for beta1-, beta2- and alpha1(A)-(ARs) and that catecholamines may inhibit the antigen-presenting capability via beta2-ARs. Here, we show that also BMDC express mRNA for beta1-, beta2-, alpha2(A)- and alpha2(C)-ARs. Inhibition of IL-12 is mediated by both beta2- and alpha2(A)-ARs, while stimulation of IL-10 by beta2-ARs only. In addition, LC migration, the contact hypersensitivity response (CHS) and production of IFN-gamma and IL-2 in draining lymph node cells is increased in mice treated topically with the beta2-AR antagonist ICI 118,551 during FITC sensitization. Activation of beta2-ARs in BMDC before adoptive transfer could reduce both migration and CHS response to FITC. Finally, preincubation of BMDC with LPS in presence of the specific beta2-AR agonist salbutamol impaired their chemotactic response to CCL19 and CCL21 and this effect was neutralized by anti-IL-10 mAb. We suggest that the physiological activation of beta2-ARs in DC (LC) results in stimulation of IL-10 which in turn restrains DC (LC) migration influencing antigen presentation and the consequent CHS response.

Melatonin in rheumatoid arthritis: synovial macrophages show melatonin receptors.

The pineal neurohormone melatonin is widely recognized as exerting important immunoenhancing effects that act on specific receptors in immunocompetent cells. This action results in stimulation of cytokine production in lymphocytes and macrophages. Here we report that the nocturnal plasma concentration of melatonin in rheumatoid arthritis (RA) patients is higher than in healthy controls. Furthermore, melatonin is present in the synovial fluid of RA patients and synovial macrophages express a specific binding site. We suggest that melatonin may exert a disease-promoting role in RA.

Oncostatic activity of pineal neuroendocrine treatment with the pineal indoles melatonin and 5-methoxytryptamine in untreatable metastatic cancer patients progressing on melatonin alone.

OBJECTIVE: The recent advances in psycho-neuro-endocrino-immunology have demonstrated the existence of several endogenous neuroendocrine substances, capable of affecting both tumor growth and host anticancer immune defenses. The pineal gland would represent one of the most important organs releasing antiproliferative and immunostimulating substances, the most known of them is melatonin (MLT). However, MLT would not be the only pineal indole provided by antitumor activity. Other pineal indoles, namely 5-methoxytryptamine (5-MTT), would play antitumor effects, by either inhibiting cancer cell proliferation or stimulating the anticancer immunity. Preliminary data have shown that MLT may deserve antitumor activity in the treatment of human neoplasms, whereas at present there are no clear data about 5-MTT. In an attempt to obtain some preliminary data about the anticancer properties of 5-MTT in humans, we have evaluated the efficacy of MLT plus 5-MTT in untreatable advanced cancer patients progressing on MLT alone. METHODS: The study included 73 untreatable advanced solid tumor patients, who had progressed after two months of MLT therapy alone. According to tumor histotype, patients were randomized to receive MLT alone (20 mg/day orally in the evening) or MLT plus 5-MTT (1 mg at noon orally), every day for at least two months. The clinical response was evaluated according to WHO criteria. RESULTS: A partial response (PR) occurred in two patients treated with MLT + 5-MTT and in none of the patients receiving MLT alone. A stable disease (SD) was achieved in only 2/37 patients on MLT therapy alone, and in 8/36 patients receiving MLT plus 5-MTT. Therefore, the percent of non-progressing patients (SD + PR) obtained with MLT plus 5-MTT was significantly higher than that obtained with MLT alone. Moreover, the relief of asthenia and depressant symptoms was significantly higher in patients concomitantly treated with 5-MTT. DISCUSSION: This preliminary study would suggest that the concomitant administration of the less known pineal indole 5-MTT, also provided by antiproliferative and immunomodulating effects, may further amplify the oncostatic activity of the pineal hormone MLT in the palliative and curative therapy of advanced untreatable human solid neoplasms.

Neuroimmunotherapy of untreatable metastatic solid tumors with subcutaneous low-dose interleukin-2, melatonin and naltrexone: modulation of interleukin-2-induced antitumor immunity by blocking the opioid system.

OBJECTIVES: The preliminary applications of the psychoneuroimmunological knowledges to the treatment of human diseases have confirmed the possibility to amplify IL-2-dependent anticancer immunity by the pineal hormone melatonin (MLT) or by opioid antagonist, such as naltrexone (NTX), which act by activating TH1 lymphocytes or suppressing TH2 lymphocytes, respectively. At present, however, there are no data about the immunobiological effects of a concomitant administration of both MLT and NTX on IL-2-induced anticancer immunity. This preliminary study was carried out to evaluate whether the association of NTX may further enhance the lymphocytosis induced by the neuroimmunotherapy with IL-2 plus MLT. MATERIALS & METHODS: The study included 14 consecutive untreatable metastatic solid tumor patients. According to a cross-over randomized study, the patients were treated during two consecutive immunotherapeutic cycles at 21-day intervals with IL-2 plus MLT alone or with IL-2 plus MLT plus NTX. IL-2 was injected subcutaneously at 3 MIU/day for 6 days/week for 4 weeks, MLT was given orally at 20 mg /day in the evening every day, and NTX was given orally at 100 mg in the morning every next day. For the immune evaluation, venous blood samples were drawn before the onset of treatment and at weekly intervals. RESULTS: Lymphocyte mean number significantly increased after both IL-2 plus MLT and IL-2 plus MLT plus NTX. However, the concomitant administration of NTX induced a significantly higher increase in lymphocyte mean number with respect to that achieved with IL-2 plus MLT alone. In contrast, the increase in eosinophil mean number was significantly higher on IL-2 plus MLT alone. CONCLUSIONS: This preliminary study shows that the association of NTX further amplifies the lymphocytosis obtained by IL-2 plus MLT. Since the lymphocytosis represents the most important favourable prognostic variable predicting the anticancer efficacy of IL-2 immunotherapy, it is probable that a cancer neuroimmunotherapy with IL-2 plus both MLT and NTX to activate TH1 and suppress TH2 cells respectively, may deserve more promising results in the treatment of human neoplasms according to the psychoneuroimnunological knowledge.