New perspectives in melatonin uses

Contents lists available at Pharmacological Research New perspectives in melatonin uses A. Carpentieri , G. Díaz de Barboza , V. Areco , M. Peralta López , N. Tolosa de Talamoni a Laboratorio "Dr. Fernando Ca˜ nas", Cátedra de Bioquímica y Biología Molecular, Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Córdoba, Argentina b Cátedra de Química Biológica, Facultad de Odontología, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba, Argentina This review summarizes the metabolism, secretion, regulation and sites of action of melatonin. An Received 6 December 2011 updated description of the melatonin receptors, including their signal transduction mechanisms, dis- Accepted 10 January 2012 tribution and characterization of receptor genes, is given. Special emphasis is focused on the clinical aspects and potential uses of melatonin in the sleep-wake rhythms, in the immune function, in can- cer therapy, in neuroprotection against oxidative damage and antioxidant activities in different tissues.
Melatonin receptors Finally, combined effects of melatonin with other drugs are discussed.
Melatonin metabolism 2012 Elsevier Ltd. All rights reserved.
Antioxidant properties Central nervous system Melatonin (MEL) (N-acetyl-5-methoxytryptamine) was discov- Abbreviations: AANAT, N-acetyltransferase; AD, Alzheimer disease; AFMK, N1- ered about fifty years ago and is a compound synthesized by the pineal gland in the human brain. It is also produced in retina, CAT, catalase; CNS, central nervous system; ETC, electron transport chain; thymus, bone marrow, respiratory epithelium, skin, lens, intes- GI, gastrointestinal; GPCR, 7-transmembrane G-protein-coupled receptor; GPx, tine and in other sites Pineal MEL passes freely through glutathione peroxidase; GR, GSH reductase; GSH, glutathione; GSSG, oxidized membranes and distributes in all body compartments, whereas GSH; HIOMT, hydroxyindole-O-methyltransferase; IFN-␣, interferon alpha; IFN- ␥, interferon gamma; IL, interleukin; iNOS, inducible nitric oxide synthase; LOX, retinal MEL apparently acts locally within the eyes partici- lipoxygenase; MDM2, murine double minute-2; MEL, melatonin; MEN, menadione; pates in the regulation of important physiological and pathological mtDNA, mitochondrial DNA; NAS, N-acetylserotonin; NAT, N-acetyltransferase; NO, processes. It is considered a hormone that regulates the circa- nitric oxide; NOS, nitric oxide synthase; PD, Parkinson disease; PLA2, phosholipase dian day–night rhythm and seasonal biorhythm by the classical A2; QR2, quinone reductase 2; RNS, reactive nitrogen species; ROS, reactive oxy- gen species; SCN, suprachiasmatic nucleus; SOD, superoxide dismutase; Th1, Type chronobiology. MEL has been characterized as an effective synchro- 1 helper T lymphocytes; Th2, Type 2 helper T lymphocytes; TNF␣, tumor necrosis nizing agent in several physiological and pathological conditions, factor alpha.
such as in maternal-fetus entrainment in dissociated circa- ∗ Corresponding author at: Cátedra de Bioquímica y Biología Molecular, Facultad dian rhythms induced by a short light–dark cycle addition, de Ciencias Médicas, Universidad Nacional de Córdoba, Pabellón Argentina, 2do.
modulation of immune defense responses, body weight and repro- Piso, Ciudad Universitaria, 5000 Córdoba, Argentina. Tel.: +54 351 4333024; fax: +54 351 4333072.
duction, tumor growth inhibition and anti-jetlag effects have been E-mail address: (N. Tolosa de Talamoni).
recognized is also evidence that MEL could act as a potent 1043-6618/$ – see front matter 2012 Elsevier Ltd. All rights reserved.

A. Carpentieri et al. / Pharmacological Research 65 (2012) 437–444 Fig. 1. Metabolic pathway of melatonin synthesis.
direct antioxidant, as a chemotoxicity reducing agent and a putative cerebrospinal fluid and reaches other body fluids such as bile, cere- anti-aging substance brospinal fluid, saliva, semen, ovarian follicular fluid and amniotic fluid. Small amounts of unmetabolized MEL are excreted in the 1. Structure, metabolism and secretion
The half life of MEL in the serum has been calculated to be MEL is an indoleamine containing two functional groups, which in the range 30–50 min The ability to synthesize MEL is are decisive not only for the receptor binding but also for its rather constant in a given person, but there is marked variability amphiphilicity giving to the molecule the capacity to enter any cell among individuals. There is evidence that MEL levels decrease with compartment or body fluid. Due to its extensive solubility in lipids, increasing age in mammals, including humans. The serum level of MEL easily passes by diffusion from the peripheral circulation to MEL is very low in the first weeks of postnatal life, without diur- other fluids or cells. In serum, 70% of the MEL is bound to albumins nal variation. At six months of life the typical diurnal rhythm of and the remaining 30% diffuses to the surrounding tissues secretion appears, reaching the maximum levels between the third Tryptophan and serotonin are precursors of MEL. Two well char- and sixth years of life. A marked decrease in MEL secretion has acterized enzymes participate in its synthesis: N-acetyltransferase been noted during sexual maturation. At 40–50 years, a noticeable (AANAT), which converts serotonin to N-acetylserotonin (NAS), and decrease in daily MEL synthesis has been observed and after the 70 hydroxyindole-O-methyltransferase (HIOMT), which converts NAS years of age the diurnal rhythm of secretion practically disappears to MEL (The regulation of MEL synthesis is controlled by in most individuals seasonal variation in the synthesis of the light–dark cycle, acting through neural activation of the ante- MEL in humans seems to exist, the levels being higher in winter rior hypothalamus via the axons of retinal ganglion cells running in the optic nerves and forming the retino-hypothalamic tract.
The catabolism of MEL was thought to be almost exclusively Suprachiasmatic nucleus (SCN) is connected with the pineal gland done by the hepatic P450 monooxygenases, followed by conju- through paraventricular nuclei and preganglionic sympathetic neu- gation of the resulting 6-hydroxy-melatonin to give the main rons. Norepinephrine released from postganglionic sympathetic urinary metabolite 6-sulfatoxy-melatonin. This might occur with fibers at pinealocyte membrane stimulates its adrenoceptors lead- the circulating hormone. In contrast, in the central nervous sys- ing to cAMP formation as well as other second messengers, which tem (CNS) the oxidative pyrrole-ring cleavage predominates and stimulate the expression and activity of AANAT, the first-rate limit- no 6-hydroxy-melatonin was detected after MEL injection into the ing enzyme in MEL production non-mammalian vertebrates, cisterna magna, which may be important because much more MEL this enzyme appears to be directly controlled by circadian clock is released via the pineal recess into the cerebrospinal fluid than genes in the pineal gland into the circulation. The primary cleavage product is N1-acetyl-N2- The secretion of MEL has a typical diurnal rhythm. At night formyl-5-methoxykynuramine (AFMK). Several different reactions the synthesis and secretion of MEL are stimulated, reaching a lead to the same product, AFMK, and this pathway contributes to peak value (80–150 pg/mL) between midnight and 3 a.m., while its about one third of the total catabolism. AFMK is converted into concentration during the day is low (10–20 pg/mL) syn- N1-acetyl-5-methoxykynuramine (AMK). AFMK and AMK form thesized in the pineal gland, MEL is secreted into the blood and metabolites by interaction with reactive oxygen and nitrogen A. Carpentieri et al. / Pharmacological Research 65 (2012) 437–444 species. Some other metabolites have been detected, but appar- 4. MEL and mitochondria
ently in minor quantities The lipophilic nature of MEL favors that the indolamine crosses cell membranes to easily reach subcellular compartments includ- 2. MEL receptors
ing mitochondria. MEL interacts with lipid bilayers and stabilizes mitochondrial inner membranes, which may improve the elec- Most actions of MEL are mediated by membrane receptors and tron transport chain (ETC) activity. At a concentration of 1 nM, nuclear sites corresponding to orphan members of the nuclear MEL increases the activity of the complexes I and IV in rat liver receptor superfamily RZR/ROR. Three subtypes of mammalian MEL mitochondria, while 10–100 nM MEL stimulates the activity of receptors have been proposed and cloned. Two of these, MT1 and those complexes in brain mitochondria. When a dose of cyanide MT2, are members of the 7-transmembrane G-protein-coupled decreases the complex IV activity by 50%, MEL counteracts this inhi- receptor (GPCR) family. These two receptors are classified as unique bition. In contrast, when the complex IV is totally inactivated by subtypes based on their molecular structure and chromosomal cyanide, MEL is unable to counteract this inhibition, independently localization. Both of them belong to the class A group of rhodopsin- of its concentration. The previous data suggest that the regulation like GPCRs. They are formed by 350 and 362 aminoacids and their by MEL on the activities of complexes I and IV does not only rely calculated molecular weights are 39 and 40 kDa, respectively. The on its antioxidant properties. MEL has a high reduction potential, gene MTRN1A for the MT1 receptor is located at position 4q35- which suggests that MEL might interact with the components of 1 and the gene MTNR1B for the MT2 receptor at 11q21-22. They the electron transport chain increasing the electron flow, and con- share 60% homology. MT1 has two potential glycosylation sites in sequently, the ATP production the N-terminal region and MT2 has one potential glycosylation site As known, reactive oxygen species (ROS) and reactive nitrogen in the same region. Both receptors involve signaling through inhi- species (RNS) are synthesized as subproducts of the mitochon- bition of cAMP formation and protein kinase A activity, and effects drial electron transport chain, although the main sources of •NO on phospholipase A2 and C, calcium and potassium channels are the reactions catalyzed by nNOS (neuronal nitric oxide syn- MT3, the third receptor, is an enzyme identified as quinone reduc- thase) and the iNOS (inducible nitric oxide synthase). Moderate tase 2 (QR2). Little information exists on nuclear MEL receptors.
levels of •NO are considered favorable for mitochondrial function, Another MEL-related receptor, named GPR50, has also been found whereas high •NO concentrations produce severe ETC dysfunction, in different species including humans 1c, the first type of blocking the respiration in extreme conditions of inflammation MEL receptor discovered, is a receptor subtype expressed in non seems to protect proteins of the ETC and mtDNA from mammalian species is some evidence that MEL receptor ROS/RNS-induced oxidative damage. The hormone limits the loss expression exhibits circadian variation of intramitochondrial GSH, improves the electron transport chain activity and reduces mtDNA damage. It apparently increases the 3. MEL and antioxidant properties
expression and activity of complex IV and the activity of complex I, which improves mitochondrial respiration and increases ATP syn- There is a large body of evidence that MEL is a major scav- enger of both oxygen and nitrogen-based reactive molecules. MEL MEL also regulates the GSH redox status in isolated brain and provokes this effect at both physiological and pharmacological con- liver mitochondria when it is disrupted by oxidative stress. The centrations. Several of its metabolites can also detoxify free radicals indolamine increases the mitochondrial GSH content, decreases and derivatives The indolamine eliminates the decomposi- oxidized GSH (GSSG) and hydroperoxide levels and stimulates the tion products of peroxynitrites, including free hydroxyl radicals and activity of GPx and GSH reductase (GR), which are two enzymes nitrogen dioxide radicals and the carbonate radical in the presence involved in the GSH-GSSG balance et al. of physiological CO2 concentration induces the synthesis demonstrated that micromolecular concentrations of MEL prevent of another intracellular antioxidant, glutathione (GSH), in rabbits calcium dependent cardiolipin peroxidation in mitochondria, thus that exhibit diabetes-induced oxidative stress benefit of protecting against the induction of mitochondrial permeability antioxidant properties of MEL has been shown in patients with transition and cytochrome c release.
rheumatoid arthritis (RA) with infertility in It is of interest that MEL acts as an antiapoptotic agent in elderly patients with primary essential hypertension How- mitochondrial ROS/RNS- mediated cell death, but it also has ever, there is no agreement about the beneficial effects of MEL on proapoptotic effects in several tumor cell lines such as in MCF-7 RA. Instead, MEL has been reported to be a RA promoter due to breast cancer cells suggests that MEL has a potential its capability to act as an immunoenhancing agent and stimula- use to kill cancer cells preserving normal cells.
tor of proinflammatory cytokine release With regards to A direct relationship between the indolamine and aging has the enzymes of the antioxidant system, MEL regulates the expres- not been proven but certain properties of the hormone indicate sion of several genes such as those of superoxide dismutase (SOD) its potential benefit in the elderly. Data obtained in senescence- and glutathione peroxidase (GPx). The hormone influences the accelerated mice have demonstrated that chronic administration enzyme activity and cellular mRNA levels of these proteins under of MEL does not reduces respiratory function, decreases the neu- physiological and oxidant conditions MEL concentration ral and hepatic peroxidation products and the protein carbonyl to up-regulate the enzyme gene expression corresponds to the content in brain physiological night time peak of plasma MEL, whereas higher con- centration does not affect the gene expression. The antioxidant effect of low concentrations of MEL seems to be indirect via up- 5. MEL and immune system
regulation of GPx gene expression and antioxidant activity, while at high concentration the effect is attributed to direct radical scav- A link between MEL from the pineal gland and the immune sys- enging actions. It has been proposed that the ability of MEL to tem in different species, including humans, has been documented up-regulate the antioxidant enzyme involves both membrane and immune system is modulated by different environmental nuclear receptors appears that the stimulation of GPx by MEL signals being light one of them. Although most of the light received is the most consistent effect, while the effect on other enzymes is by the retina goes to the visual cortex, another pathway from the tissue-specific or conditional.
retina relays to the SCN, which forms part of the hypothalamic A. Carpentieri et al. / Pharmacological Research 65 (2012) 437–444 region in the brain hypophysis and the pineal gland are that MEL could be a mediator of acid-induced secretion also involved in neuroendocrine changes induced by the light. MEL of the MEL effects on the GI tract seem to be mediated by MT2 is one of the neuroendocrine hormones that are sensitive to changes receptors the presence of MT1 receptor has been in circadian rhythm. Since MEL is produced not only by the pineal also demonstrated in human gallbladder epithelium from patients gland, but also in the retina and in other parts of the body, the with cholelithiasis and gallbladder carcinoma et al.
immune system might be affected by MEL originated in different shown that MEL inhibits serotonin transporter activity in organs. Besides, human peripheral blood mononuclear cells syn- Caco-2 cells, apparently without mediation of MT1 or MT2 recep- thesize important amounts of MEL, which indicates a potential tors or PKC and cAMP pathways, but the doses used were high. It intracrine and paracrine role of MEL in immune regulation. Mem- is not known if this occurs under physiological conditions. MEL has brane receptors have been found in T and B lymphocytes. MEL also antioxidant properties in the GI system; its concentration in also stimulates cytokine production by human peripheral blood the human liver is suitable for prevention of oxidative damage. In mononuclear cells through nuclear receptors Although the our laboratory, MEL has been found to reverse the inhibition of the mechanism by which MEL enhances the immune response is not intestinal calcium absorption caused by menadione, apparently by clear, it is thought that it may increase phagocytosis and antigen antioxidant mechanisms presentation. In addition, MEL induces T cell differentiation toward MEL receptors have been detected in the pancreas and the the type 1 helper T cells (Th1) phenotype and the activation of the stimulation of pancreatic enzyme secretion by the hormone in a immune system by the indolamine has been shown to be mediated dose-dependent manner has been demonstrated. MEL was also by the regulation of gene expression of cytokines in the spleen, thy- implicated in the pancreatic endocrine function. Pinealectomy pro- mus, lymph nodes and bone marrow killer cell activity duces hyperinsulinemia and increases the triglyceride content in and production are apparently increased by MEL administration the liver of type 2 diabetic rats Endogenous MEL has been either in humans or mice. Although many studies have implicated shown to protect against pancreatitis, probably mediated by MT2 MEL as a positive regulator of immune system, other reports have also suggested that MEL could act as an anti-inflammatory agent through inhibition of immune responses. The anti-inflammatory action is considered to be, at least in part, due to the induction 7. MEL and central nervous system
of type 2 helper T lymphocytes (Th2) producing interleukin (IL)-4 and inhibiting Th1 function has pleiotropic effects on dif- MEL and melatoninergic drugs have hypnotic effects mediated ferent steps of inflammation. It has a pro-inflammatory role at an through MT1 and MT2 receptors, especially those in the SCN, which early phase through activation of pro-inflammatory mediators such acts on the hypothalamic sleep switch. They favor sleep initiation as phosholipase A2 (PLA2), lipoxygenase (LOX) and cytokines such and reset the circadian clock allowing persistent sleep, a require- as IL-1 and tumor necrosis factor alpha (TNF␣). Contrarily, when ment in circadian rhythm sleep alterations. The action of MEL on the inflammatory process proceeds toward the chronic phase, MEL sleep is mainly of a chronobiological nature. The hormone acts in has a negative effect. The antagonist role of MEL on chronic inflam- a dual way, resetting the clock via MT2 receptor and suppressing mation is due to downregulation of mediators such as PLA2, LOX neuronal firing via MT1 receptor. Apparently, the soporific action and cytokines, induction of a survival pathway in leukocytes and of MEL also involves the thalamus. MEL receptors have been found blocking of oxidation by its antioxidant properties in this area and the formation of the spindles is stimulated by MEL could also play a role in the influence of seasonal changes on the hormone. Other areas of the brain seem to be involved in the immune function. In healthy volunteers during autumn/winter the transmission of MEL-dependent responses. It is uncertain to season, the production of IL-6, interferon alpha (IFN-␣) and inter- what extent the thalamus and other brain areas participate in the feron gamma (IFN-␥) was higher. The seasonal changes in immune sleep promotion as compared to the hypothalamic via MEL functions appear to be mediated by alterations in duration of MEL treatment to patients with severe CNS dysfunction and MEL defi- secretion. In this sense, changes in mood and behavior such as in ciency is not sufficient to mitigate sleep difficulties. In addition, the seasonal affective disorder have been associated with seasonal CNS destruction causing sleep fragmentation and loss of circadian changes in cytokines like IL-6, IFN-␣ or the balance between Th1 rhythmicity, allows spindle formation. MEL has a different mode and Th2 responses of action as compared to other hypnotics such as benzodiazepins and z-drugs, which produce a more generalized CNS depression through GABA receptors. Only very high pharmacological doses 6. MEL and the gastrointestinal (GI) tract
of MEL can produce generalized sedative effects or even narcotic effects but mediated by other mechanisms, such as antiexcita- MEL is also produced in high amount in the enteroendocrine tory suppression of calcium signaling and inhibition of neuronal cells of GI mucosa. The amount of MEL in the gut is about 400 times NO synthase. The major obstacle for the use of MEL in primary larger than the content of MEL in the pineal gland pro- chronic insomnia is that the half life of circulation is extremely duction in the GI tract does not follow a circadian rhythm as occurs short, 20–30 min and even less (eventually it could last up to a max- in the pineal gland, but it responds to the periodicity of food intake imum of 45 min). MEL promotes sleep initiation but improves sleep rich in tryptophan a pinealectomy, serum levels of maintenance only marginally. Part of this problem has been solved, MEL do not maintain a rhythm according to the light–dark cycle, at least in part, by drugs that prolong the release of MEL and the but values are not too low at daytime because of the contribution melatoninergic agonists with longer half-life of MEL by the extra-pineal sources, mainly the GI tract Neurodegenerative diseases such as Alzheimer disease (AD) and The main enzymes of MEL synthesis, AANAT and HIOMT, have Parkinson disease (PD) are age-related disorders that share mito- also been detected in GI mucosa, supporting the hypothesis that in chondrial dysfunction, oxidative/nitrosative stress and apoptosis the gut MEL is synthesized from l-tryptophan present in food in different areas of the brain. Patients with AD have a reduc- The function of gut MEL is not clear yet because the intestine is tion in MEL levels both in blood and cerebrospinal fluid, which not only source but also sink of MEL, brought by the circulation is even present in preclinical stages MEL's cognitive bene- Decreases in motility and increases in mucosal blood flow fits have been demonstrated either in AD patients or in AD mice.
have been observed It has been also demonstrated that Low levels of mRNA of SOD-1, GPx and catalase were found in hip- luminal MEL stimulates duodenal HCO − secretion, which suggests pocampus from MEL treated AD mice In PD model animals, A. Carpentieri et al. / Pharmacological Research 65 (2012) 437–444 MEL normalizes complex I activity from electron transport chain various organs such as heart, kidney and bone marrow in the course and oxidative status in mitochondria from substantia nigra and of chemotherapy and radiotherapy. This protective effect of MEL striatum and reduces mitochondrial inducible nitric oxide synthase administration might allow treating patients more effectively using decreasing nitric oxide radicals and preventing the inhibition of higher doses of cytostatic drugs and radiation, which by themselves complex IV by this radical treatment improved the quality could damage the organs involved it has been shown of sleep in patients with Parkinson idea that MEL is favor- that MEL synergistically with vitamin D down-regulates Akt and able in PD patients or PD animal models is controversial. Willis et al.
MDM2 leading to growth inhibition of breast cancer cells that the light exposure at the bed time reduces the In studies in which gastric damage was induced by severity of PD symptoms, whereas the MEL intracerebroventricu- indomethacin acetylsalicylic acid MEL prevented lar implants increased its severity. Further studies about the use of or reduced the gastric mucosal lesion. In addition, the combination MEL in the PD treatment are needed.
of MEL with anti-ulcer drugs such as ranitidine and omeprazole reduces the doses and minimizes the side effects The pathophysiology of primary headache has been partially 8. MEL and cancer
attributed to desynchrony and dysfunction of the whole or part of the retino-hypothalamic-pineal axis synchronizing ability There is abundant evidence indicating that MEL is involved of MEL together with its antioxidant and anti-inflammatory prop- in preventing tumor initiation, promotion, and progression. The erties, make this indolamine effective to decrease the frequency increased incidence of breast, endometrial and colorectal cancer or totally suppress headache of different kinds (migraine, cluster seen in nurses and in other night shift workers suggests a possible headache, etc.) allowing the patient to reduce the consumption of link between diminished secretion of MEL and increased exposure to light during nightime This evidence and the antioxidant The use of MEL alone or in combination with other effective and anti or proapoptotic action of MEL and its relationship with agents has been reported to diminish collateral damage in sev- the endocrine and immune systems led to examine the effect of eral psychiatric disorders. Anxiolytic, sedative, anticonvulsant and the hormone on tumor cells. Recent human and animal studies anti-hypertensive effects of MEL may be helpful in the treatment have shown that MEL also has important oncostatic properties by of depression with inhibitors of monoaminooxidase. A combina- altering the expression of anti-cancer cytokines IL-2 and IL-12 in tion of MEL with lithium or valproate was more effective than human neoplasms of 1 nM MEL to MCF-7 cell culture either lithium or valproate alone in bipolar syndrome patients. MEL inhibits proliferation the expression of proapoptotic has also protective properties against haloperidol adverse effect in proteins such as p53 and p21 reduces their metastatic schizophrenia patients should be noted that many of the potential due to increased expression of E-cadherin and ␤ beneficial effects of MEL are associated with the improvement of proteins antiproliferative effects on human breast cancer sleep disorders that are very frequent in several neuropsychiatric cells seem to be mediated by MT1 receptor, which suggests that MEL or its analogs could be used as potential antitumoral agents The administration of MEL alone is successful in the treatment of circadian system disorders such as jet lag, shift work, some The finding of MEL binding sites in human colon tissue suggested sleeps disturbances, etc. In these cases MEL acts as a synchronizer, a possible role of MEL in colorectal cancer. Schernhammer et al. entraining the human activity circadian rhythms according to a have found increased risk of colorectal cancer in nurses subjected to phase-response curve shift work, which was attributed to the suppression of MEL produc- As shown in MEL is a pleiotropic molecule and its tion by nocturnal lighting. Farriol et al. demonstrated that administration to humans and animals at both physiological and MEL was able to inhibit cell growth in CT-26 cells, a cell line derived pharmacological concentrations seems to be non-toxic. Since MEL from a murine colon carcinoma. Although MEL had no effect on cell has a wide therapeutic range, it can be administered in differ- growth at low doses, a significant and progressive suppression of ent doses according to the expected effects. The ability of MEL to DNA synthesis was found with high doses of the indolamine. The scavenge ROS is one of the explanations for the reduction of side authors concluded that MEL exerted its anti-proliferative action effects produced by some pharmacological agents such as onco- through a non-hormone dependent mechanism, because no recep- static, antinflammatory, antiepilepsic drugs these cases, the tors were involved in the cell line selected. The oncostatic effect doses of MEL range from 10 to 50 mg, much higher than physiolog- of MEL on colon cancer was demonstrated to be mediated through ical level, in order to counteract the high amounts of free radicals MT2 receptors and through its binding to nuclear RZR/ROR ␣ recep- Finally, an illustrative list of some recent in vivo and in vitro studies exemplifying the effects of the combination 9. Combined effects of MEL with other drugs
of MEL with other drugs. As demonstrated, MEL can be useful in the treatment of a wide variety of diseases improving their effi- The effect of MEL in the presence of other drugs has been cacy while reducing the side effects in order to enhance life quality.
studied in different tissues. Several findings support the hypoth- This broad therapeutic spectrum makes MEL a potential therapeu- esis that MEL enhances the effect of chemotherapy on colorectal tic tool in combination with other traditional therapies and opens carcinoma. Cerea et al. the effect of the simultane- a promising field of research in the pharmacological area.
ous administration of MEL and the cytotoxic drug CPT-11 in 30 patients with metastatic colorectal carcinoma. It was found that co-administration of MEL (20 mg/day at bedtime) with CPT-11 was 10. Remarks
more effective in controlling the disease than administration of CPT-11 alone. It has also been shown that 1 mM MEL potentiates MEL is a hormone produced in the pineal gland mainly at night flavone-induced apoptosis in HT-29 human colon cancer cells time, but is also synthesized by other tissues being the intestine the by increasing the level of oxidizable substrates that can be incor- main source during the day. Its lipophilic nature makes MEL easily porated into mitochondria in the presence of flavones.
cross all membranes. Most of its actions are mediated by membrane Another relevant aspect related to the application of MEL and nuclear receptors. It has antioxidant and antiapoptotic prop- as adjuvant in tumor therapy includes its protective effect on erties, resulting in the improvement of mitochondrial metabolic

A. Carpentieri et al. / Pharmacological Research 65 (2012) 437–444 Effect of MEL combined with other drugs in the treatment of different diseases. In vivo and in vitro studies.
MEL combined with other drugs or Suppression of seizures in refractory epilepsy in Improvement of wake-sleep Attenuation of aggressive behavior Improvement of subjective sleep quality 2 mg/day at bed time Antiparkinsonian drugs: levodopa, Improvement of subjective sleep quality, sleep amantadine, selegiline, pramipexol quantity and daytime sleepiness Alzheimer disease Increase of daytime wake time and activity levels 3–6 mg/day, at bed time Improvement of rest-activity Increase of apoptosis and inhibition of hepatoma cell 10−5 to 10−8 mol/L Protection of the gastric mucosa decreasing the doses Increase of immune response altered by Trypanosoma 5 to 10 mg/kg b.w.
Enhancement of mycobacterial growth inhibition Gram (−) bacterial infections Attenuation of nephro and ototoxicity produced by 250 ␮g to 10 mg/kg a Clinical trials or case reports.
b In vitro studies.
c Animal studies.
Fig. 2. Effects of melatonin on different tissues and systems. CAT: catalase, ETC: electron transport chain, GPx: glutathione peroxidase, GSH: glutathione, IFN␣: interferon
alpha, IFN␥: interferon gamma, IL: interleukin, iNOS: inducible nitric oxide synthase, LOX: lipoxygenase, MEN: menadione, mtDNA: mitochondrial DNA, NOS: nitric oxide synthase, PLA2: phosholipase A2, RNS: reactive nitrogen species, ROS: reactive oxygen species, SOD1: superoxide dismutase one, Th1: type 1 helper T lymphocytes, Th2: type 2 helper T lymphocytes, TNF-␣: tumor necrosis factor alpha.
A. Carpentieri et al. / Pharmacological Research 65 (2012) 437–444 pathways and ATP production. A potential intracrine and paracrine [18] Tan DX, Manchester LC, Terron MP, Flores LJ, Reiter RJ. One molecule, many role of MEL in immune regulation has been suggested although the derivatives: a never-ending interaction of melatonin with reactive oxygen and nitrogen species. J Pineal Res 2007;42:28–42.
molecular mechanisms involved in the immunoregulatory function [19] Peyrot F, Houee-Levin C, Ducrocq C. Melatonin nitrosation promoted by remain to be elucidated. The action of MEL on sleep is mainly of a NO*2 radical; comparison with the peroxynitrite reaction. Free Radic Res chronobiological nature. One of the major obstacles for the use of [20] Winiarska K, Fraczyk T, Malinska D, Drozak J, Bryla J. Melatonin attenuates MEL in primary chronic insomnia is that the half life of circulation diabetes-induced oxidative stress in rabbits. J Pineal Res 2006;40:168–76.
is extremely short, which has been partially solved by synthesis [21] Forrest CM, Mackay GM, Stoy N, Stone TW, Darlington LG. Inflammatory status of drugs that prolong the release of MEL and the melatoninergic and kynurenine metabolism in rheumatoid arthritis treated with melatonin. Br agonists with longer half-life. MEL's cognitive benefits have been J Clin Pharmacol 2007;64:517–26.
[22] Tamura H, Takasaki A, Miwa I, Taniguchi K, Maekawa R, Asada H, et al. Oxidative demonstrated either in AD patients or in AD mice. Some approaches stress impairs oocyte quality and melatonin protects oocytes from free radical indicate that MEL alone or in combination with other drugs could damage and improves fertilization rate. J Pineal Res 2008;44:280–7.
be used to prevent tumor initiation, promotion, and progression.
[23] Kedziora-Kornatowska K, Szewczyk-Golec K, Czuczejko J, Pawluk H, Van Marke de Lumen K, Kozakiewicz M, et al. Antioxidative effects of melatonin Anti-proliferative effects of MEL on breast and colon cancer cells administration in elderly primary essential hypertension patients. J Pineal Res have been demonstrated, but the underlying mechanisms are not clear yet. Another possible use of MEL alone or combined with other [24] Cutolo M, Maestroni GJ. The melatonin-cytokine connection in rheumatoid arthritis. Ann Rheum Dis 2005;64:1109–11.
drugs would be for treatment of several psychiatric disorders due to [25] Maestroni GJ, Otsa K, Cutolo M. Melatonin treatment does not improve rheuma- its anxiolytic, sedative, anticonvulsant and anti-hypertensive prop- toid arthritis. Br J Clin Pharmacol 2008;65:797–8.
erties. In conclusion, the spectrum of uses of MEL seems to be wide, [26] Rodriguez C, Mayo JC, Sainz RM, Antolín I, Herrera F, Martín V, et al. Regu- lation of antioxidant enzymes: a significant role for melatonin. J Pineal Res although more investigation is needed in order to know better the molecular mechanisms and the possible side effects.
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Dr. Tolosa de Talamoni N. and Carpentieri A. are Members of [29] Dungel P, Mittermayr R, Haindl S, Osipov A, Wagner C, Redl H, et al. Illu- mination with blue light reactivates respiratory activity of mitochondria Career from CONICET. Peralta López M. and Areco V. are recipients inhibited by nitric oxide, but not by glycerol trinitrate. Arch Biochem Biophys of Fellowships from CONICET.
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