Influence of aging and growth hormone on different members of the NFkB family and IkB expression in the heart from a murine model of senescence-accelerated aging.

Inflammation is related to several pathological processes. The aim of this study was to investigate the protein expression of the different subunits of the nuclear factor Kappa b (NFkBp65, p50, p105, p52, p100) and the protein expressions of IkB beta and alpha in the hearts from a murine model of accelerated aging (SAM model) by Western blot. In addition, the translocation of some isoforms of NFkB from cytosol to nuclei (NFkBp65, p50, p52) and ATP level content was studied. In addition we investigated the effect of the chronic administration of growth hormone (GH) on these age-related parameters. SAMP8 and SAMR1 mice of 2 and 10 months of age were used (n = 30). Animals were divided into five experimental groups: 2 old untreated (SAMP8/SAMR1), 2 young control (SAMP8/SAMR1) and one GH treated-old groups (SAMP8). Age-related changes were found in the studied parameters. We were able to see decreases of ATP level contents and the translocation of the nuclear factor kappa B p50, p52 and p65 from cytosol to nuclei in old SAMP8 mice together with a decrease of IKB proteins. However p100 and p105 did not show differences with aging. No significant changes were recorded in SAMR1 animals. GH treatment showed beneficial effects in old SAMP8 mice inducing an increase in ATP levels and inhibiting the translocation of some NFkB subunits such as p52. Our results supported the relation of NFkB activation with enhanced apoptosis and pro-inflammatory status in old SAMP8 mice and suggested a selective beneficial effect of the GH treatment, which was able to partially reduce the incidence of some deleterious changes in the heart of those mice.

Melatonin in the oral cavity: physiological and pathological implications.

BACKGROUND AND OBJECTIVES: The purpose of this article was to summarize what is known about the function of melatonin in the oral cavity. MATERIAL AND METHODS: Databases were searched for the relevant published literature to 30 November, 2013. The following search items were used in various combinations: melatonin, gingiva, periodontium, inflammation, herpes, alveolar bone, periodontal ligament, dental implants, xerostomia, methacrylate, chlorhexidine, cancer. The literature uncovered is summarized herein. RESULTS: Salivary melatonin levels exhibit a circadian rhythm with highest values at night. Melatonin has both receptor-mediated and receptor-independent actions in cells of the oral cavity. Melatonin is released into the saliva by the acinar cells of the major salivary glands and via the gingival fluid. Functions of melatonin in the oral cavity are likely to relate primarily to its anti-inflammatory and antioxidant activities. These actions may suppress inflammation of the gingiva and periodontium, reduce alveolar bone loss, abrogate herpes lesions, enhance osteointegration of dental implants, limit oral cancer, and suppress disorders that have a free radical component. Sublingual melatonin tablets or oral melatonin sprays and topical melatonin-containing gel, if used on a regular basis, may improve overall oral health and reduce mucosal lesions. CONCLUSION: Collectively, the results indicate that endogenously-produced and exogenously-applied melatonin are beneficial to the oral cavity.

Melatonin synthetic analogs as nitric oxide synthase inhibitors.

Nitric oxide (NO), which is produced by oxidation of L-arginine to L-citrulline in a process catalyzed by different isoforms of nitric oxide synthase (NOS), exhibits diverse roles in several physiological processes, including neurotransmission, blood pressure regulation and immunological defense mechanisms. On the other hand, an overproduction of NO is related with several disorders as Alzheimer's disease, Huntington's disease and the amyotrophic lateral sclerosis. Taking melatonin as a model, our research group has designed and synthesized several families of compounds that act as NOS inhibitors, and their effects on the excitability of N-methyl-D-aspartate (NMDA)-dependent neurons in rat striatum, and on the activity on both nNOS and iNOS were evaluated. Structural comparison between the three most representative families of compounds (kynurenines, kynurenamines and 4,5-dihydro-1H-pyrazole derivatives) allows the establishment of structure-activity relationships for the inhibition of nNOS, and a pharmacophore model that fulfills all of the observed SARs were developed. This model could serve as a template for the design of other potential nNOS inhibitors. The last family of compounds, pyrrole derivatives, shows moderate in vitro NOS inhibition, but some of these compounds show good iNOS/nNOS selectivity. Two of these compounds, 5-(2-aminophenyl)-1H-pyrrole-2-carboxylic acid methylamide and cyclopentylamide, have been tested as regulators of the in vivo nNOS and iNOS activity. Both compounds prevented the increment of the inducible NOS activity in both cytosol (iNOS) and mitochondria (i-mtNOS) observed in a MPTP model of Parkinson's disease.

Melatonin and its agonists in pain modulation and its clinical application.

Melatonin, the hormone of darkness has many physiological functions in the body and also exerts a number of pharmacological effects. Most of these actions of melatonin are mediated through melatonin membrane receptors like MT1/MT2 receptors or through nuclear orphan receptors like RZR/ROR receptors or through calcium binding proteins in the cytosol. The finding that pain perception is circadian in nature has prompted many to suggest that "pain modulation" is one of the most important physiological functions of melatonin. By using a number of animal models of pain perception, it has been found that melatonin exerts antinociceptive and antiallodynic effects. Number of studies has shown that melatonin modulates pain perception by acting through opioid receptors, NMDA receptors and G-protein, and they have been analyzed using specific antagonists like naloxone or NMDA-G protein receptor antagonists. Recently it has been shown that melatonin exerts its antinociceptive effects through MT1 and MT2 melatonergic receptors located in the dorsal region of the spinal cord as well as in various parts of the brain concerned with pain modulation. Evidences for this have been obtained by using common melatonergic receptor antagonist like luzindole or specific MT2 receptor antagonist like 4P-PDOT or K-185. In a few clinical studies undertaken during surgery, melatonin has been shown to have analgesic effects. Melatonin is emerging as a new analgesic drug with a novel mechanism of actions and has the potential to be used as a natural pain killer in inflammatory, neuropathic pain conditions and also during surgical procedures.

Melatonin reduces membrane rigidity and oxidative damage in the brain of SAMP8 mice.

We evaluated the autophagy-lysosomal pathway and membrane fluidity in brain cells and mitochondrial membranes obtained from senescence-accelerated (SAMP(8)) and senescence-resistant (SAMR(1)) mice at 5 and 10 months of age. Moreover, we studied whether chronic treatment from age 1 to 10 months with melatonin stabilizes membrane fluidity. Fluidity was measured by polarization changes of 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene-p-toluene sulfonate. Results showed that in untreated animals at 5 months of age, synaptosomal and mitochondrial fluidity was decreased in SAMP(8) compared to SAMR(1), as was the cathepsin D/B ratio, indicating dysfunction of the autophagy-lysosomal pathway. Moreover, we detected synaptosomal rigidity and programmed cell death capability in both groups at 10 months of age. Mitochondrial fluidity, however, did not show a significant age-dependent change but was lower in SAMP(8) than in SAMR(1) at the 5- and 10-month time points. Melatonin administration prevented rigidity in the mitochondrial membrane and seemed to decrease age-related autophagy-lysosomal alterations. These data suggest that melatonin may act to slow down the aging process because of its ability to enhance membrane fluidity and maintain structural pathways.

Melatonin, a potential therapeutic agent for smooth muscle-related pathological conditions and aging.

Increases or decreases in the contractile response of smooth muscle underlie important pathological conditions such as hypertension, incontinence and altered gastrointestinal transit. These disorders are also frequently encountered in the aged population. Oxidative stress and inflammation are key features in the initiation, progression, and clinical manifestations of smooth muscle disorders. Melatonin, the major secretory product of the pineal gland, has free radical scavenging and antioxidative properties and protects against oxidative insult. Recently, widespread interest has grown regarding the apparent protective effects of melatonin on smooth muscle dysfunction. "In vitro" studies have shown that melatonin decreased vascular tone of vascular beds from control, hypertensive or aged animals, through the reduction of adrenergic contraction and the increase in acetylcholine-induced relaxation. "In vivo", melatonin also attenuates sympathetic tone by direct activation of melatonin receptors, scavenging free radicals or increasing NO availability in the central nervous system. In the gastrointestinal tract, melatonin treatment improves age-related impairments in gallbladder contractility and prevents deleterious effects of cholecystitis on smooth muscle and the enteric nervous system through suppression of oxidative stress. In addition, melatonin improves colonic transit time in constipation-predominant IBS patients. Melatonin is also able to restore impaired contractility of the detrusor muscle from old animals through normalization of Ca(2+) dependent and independent contraction, mitochondrial polarity, neuromuscular function and oxidative stress, which would explain the effects of melatonin counteracting cystometric changes in senescent animals. It also reverses bladder damage following ischemia/reperfusion. In conclusion, melatonin may be a promising candidate for future research of agents that modulate smooth muscle motility.

Derivados de 4, 5-DIHIDRO-1H-PIRAZOL como inhibidores selectivos de nNOS: Síntesis y relaciones estructura-actividad / 4, 5-DIHYDRO-1H-PYRAZOLE as nNOS selective inhibitors: Synthesis and structure-activity relationship

INTRODUCCIÓN: La oxido nítrico sintasa (NOS) es la enzima que cataliza la biosíntesis de óxido nítrico (NO) a partir de L-arginina. 1 Hasta el momento, se han descubierto cuatro isoformas:2 nNOS, iNOS, eNOS y mtNOS. El NO es un biomensajero relacionado con importantes funciones fisiológicas. 3Sin embargo, se ha demostrado que una sobreproducción de NO por la nNOS está implicada en procesos neurodegenerativos. 4 Este hecho justifica la necesidad terapéutica de encontrar inhibidores selectivos de la nNOS que permitan luchar contra enfermedades tales como Alzheimer, Parkinson, esclerosis lateral amiotrófica y corea de Huntington. Nuestro grupo de investigación ha sintetizado y evaluado una serie de derivados kinurenínicos 5 1 y kinurenamínicos 6 2 como agentes neuroprotectores que resultaron desprovistos de actividad inhibitoria frente a la enzima kinurenina-3-hidroxilasa (KYN3OH), lo que demuestra que su actividad neuroprotectora se debe a la inhibición de la nNOS. OBJETIVO: Basándonos en estos antecedentes, hemos sintetizado y realizado la evaluación biológica in vitrofrente a las isoformas nNOS e iNOS de una serie de derivados de 4,5-dihidro-1H-pirazol con estructura general 3, con objeto de encontrar inhibidores selectivos de alguna de estas isoformas. METODOLOGÍA: Tomando como referencia los derivados kinurenínicos y kinurenamínicos, hemos sintetizado los análogos rígidos con un resto de 4,5-dihidro-1H-pirazol. Además de la restricción conformacional, se han llevado a cabo otras modificaciones, como la introducción de distintos sustituyentes en el anillo aromático y la modificación del grupo acilo en el anillo de pirazolina(AU)

CONCLUSIÓN /DISCUSIÓN: Todos los compuestos ensayados inhiben nNOS. La inhibición de iNOS es ínfima en la mayoría de los casos, por lo que se pueden considerar selectivos, y no hay inhibición de KYN3OH. Por consiguiente, el potencial neuroprotector de estos derivados se debe únicamente a la inhibición de nNOS(AU)

INTRODUCTION: Nitric Oxide Synthase (NOS) is the enzyme which catalyses the biosynthesis of Nitric Oxide (NO)from L-arginine 1. Four NOS isoforms have been described: 2 nNOS, iNOS, eNOS and mtNOS. NO is a biological messenger involved in several physiologic processes. 3 However, an over production of NO by nNOS produces neurotoxicity which has been associated with various neurological disorders 4.Therefore, it is necessary to found nNOS inhibitors to fight pathologies such as Alzheimer’s disease, Parkinson, amyotrophic lateral sclerosis and Huntington’s disease. In previous papers, our research group have described the synthesis of a series of kynurenine 5 1 and kynurenamine 6 2 derivatives as neuroprotective agents which are not active versus kynurenine-3-hydroxylase (KYN3OH). This fact demonstrates that their neuroprotective activity is only due to then NOS inhibition. 2 3 OBJECTIVE: Basing on these precedents, we have developed and evaluated in vivo, versus nNOS and iNOS, a series of 4,5-dihydro-1H-pyrazole derivatives with general structure 3 in order to find new selective compounds. METHODOLOGY: Taking kynurenine and kynurenamine derivatives as reference, we have synthesized rigid analogous with a ring of 4,5-dihydro-1H-pyrazole . Besides the conformacional restriction, other modification shave been carried out, as the introduction of different substituents in the aromatic ring and the modification of the acyl group in the pyrazoline ring . CONCLUSION /DISCUSION: All compounds inhibit nNOS. In most of cases, the inhibition of iNOS is negligible. Thus, they can be considered selective. On the other hand, there is no KYN3OH inhibition. Consequently, the neuroprotective potential of these derivatives is due only to the inhibition of nNOS(AU)

[Melatonin, synthetic analogs, and the sleep/wake rhythm]. / Melatonina, analogos sinteticos y el ritmo sueno/vigilia.

INTRODUCTION: Melatonin, a widespread hormone in the animal kingdom, is produced by several organs and tissues besides the pineal gland. Whilst extrapineal melatonin behaves as a cytoprotective molecule, the pineal produces the hormone in a rhythmic manner. The discovery of melatonin in 1958, and the characterization of its synthesis somewhat later, let to the description of its photoperiodic regulation and its relationship with the biological rhythms such as the sleep/wake rhythm. DEVELOPMENT: The suprachiasmatic nuclei are the anatomical seat of the biological clock, represented by the clock genes, which code for the period and frequency of the rhythms. The photoperiod synchronizes the activity of the auprachiasmatic biological clock, which in turn induces the melatonin's rhythm. The rhythm of melatonin, peaking at 2-3 am, acts as an endogenous synchronizer that translates the environmental photoperiodic signal in chemical information for the cells. The sleep/wake cycle is a typical biological rhythm synchronized by melatonin, and the sleep/wake cycle alterations of chronobiological origin, are very sensitive to melatonin treatment. Taking advantage of the chronobiotic and antidepressive properties of melatonin, a series of synthetic analogs of this hormone, with high interest in insomnia, are now available. CONCLUSIONS: Melatonin is a highly effective chronobiotic in the treatment of chronobiological alterations of the sleep/wake cycle. From a pharmacokinetic point of view, the synthetic drugs derived from melatonin are interesting tools in the therapy of these alterations.

Melatonina, análogos sintéticos y el ritmo sueño/vigilia / Melatonin, synthetic analogs, and the sleep/wake rhythm

Resumen. Introducción. La melatonina, una hormona ampliamente distribuida en el reino animal, se produce en numerosos órganos y tejidos además de la glándula pineal. Mientras que la melatonina extrapineal tiene funciones de protección celular, la pineal se encarga de su producción rítmica. La caracterización de la melatonina en 1958 y la identificación de su síntesis permitieron describir su regulación fotoperiódica y su relación con los ritmos biológicos, entre otros, el ritmo sueño/vigilia. Desarrollo. Los núcleos supraquiasmáticos son la sede anatómica del reloj biológico, representado por los genes reloj, que codifican para el período y la frecuencia de los ritmos. El fotoperíodo sincroniza la actividad del reloj biológico en los núcleos supraquiasmáticos, que a su vez inducen el ritmo de melatonina. Este ritmo, con un pico máximo hacia las dos o tres de la madrugada, actúa como un sincronizador endógeno que permite traducir la señal fotoperiódica ambiental en información química que las células del organismo pueden leer. El ciclo sueño/vigilia es un caso típico de ritmo biológico sincronizado por la melatonina, y las alteraciones del ciclo sueño/vigilia de origen cronobiológico responden muy bien a esta sustancia. Aprovechando las propiedades cronobióticas y antidepresivas de la melatonina, han aparecido recientemente diversos análogos sintéticos de ésta, de gran interés en la clínica del insomnio. Conclusiones. La melatonina es un cronobiótico de gran eficacia en el tratamiento de las alteraciones cronobiológicas del ciclo sueño/vigilia. Los fármacos sintéticos derivados de la melatonina representan una herramienta terapéutica muy interesante desde el punto de vista farmacocinético para el tratamiento de dichas alteraciones (AU)

Summary. Introduction. Melatonin, a widespread hormone in the animal kingdom, is produced by several organs and tissues besides the pineal gland. Whilst extrapineal melatonin behaves as a cytoprotective molecule, the pineal produces the hormone in a rhythmic manner. The discovery of melatonin in 1958, and the characterization of its synthesis somewhat later, let to the description of its photoperiodic regulation and its relationship with the biological rhythms such as the sleep/wake rhythm. Development. The suprachiasmatic nuclei are the anatomical seat of the biological clock, represented by the clock genes, which code for the period and frequency of the rhythms. The photoperiod synchronizes the activity of the auprachiasmatic biological clock, which in turn induces the melatonin’s rhythm. The rhythm of melatonin, peaking at 2-3 am, acts as an endogenous synchronizer that translates the environmental photoperiodic signal in chemical information for the cells. The sleep/wake cycle is a typical biological rhythm synchronized by melatonin, and the sleep/wake cycle alterations of chronobiological origin, are very sensitive to melatonin treatment. Taking advantage of the chronobiotic and antidepressive properties of melatonin, a series of synthetic analogs of this hormone, with high interest in insomnia, are now available. Conclusions. Melatonin is a highly effective chronobiotic in the treatment of chronobiological alterations of the sleep/wake cycle. From a pharmacokinetic point of view, the synthetic drugs derived from melatonin are interesting tools in the therapy of these alterations (AU)

Melatonin protects the mitochondria from oxidative damage reducing oxygen consumption, membrane potential, and superoxide anion production.

The role of melatonin in improving mitochondrial respiratory chain activity and increasing ATP production in different experimental conditions has been widely reported. To date, however, the mechanism(s) involved are largely unknown. Using high-resolution respirometry, fluorometry and spectrophotometry we studied the effects of melatonin on normal mitochondrial functions. Mitochondria were recovered from mouse liver cells and incubated in vitro with melatonin at concentrations ranging from 1 nm to 1 mm. Melatonin decreased oxygen consumption concomitantly with its concentration, inhibited any increase in oxygen flux in the presence of an excess of ADP, reduced the membrane potential, and consequently inhibited the production of superoxide anion and hydrogen peroxide. At the same time it maintained the efficiency of oxidative phosphorylation and ATP synthesis while increasing the activity of the respiratory complexes (mainly complexes I, III, and IV). The effects of melatonin appeared to be due to its presence within the mitochondria, since kinetic experiments clearly showed its incorporation into these organelles. Our results support the hypothesis that melatonin, together with hormones such as triiodothyronine, participates in the physiological regulation of mitochondrial homeostasis.

Melatonin increases following convulsive seizures may be related to its anticonvulsant properties at physiological concentrations.

Melatonin ( N-acetyl-5-methoxytryptamine, aMT) is an indoleamine produced by several organs and tissues including the pineal gland. Melatonin (aMT) modulates the activity of the brain, mainly acting on both GABA and glutamate receptors. Previous studies have shown the participation of melatonin in the control of convulsive crises, suggesting that aMT concentration increases during seizures, and that patients with seizures of diverse origins show an alteration of the aMT rhythm. However, what is not known is the duration of the aMT response to seizures, and whether aMT changes during seizures could be a marker of the disease. For this reason, the serum levels of aMT in 54 children with a convulsive crisis, febrile and epileptic, were analyzed during the crisis, as well as at 1 h and 24 hours after the seizure. The results show that aMT significantly increases during the seizure (Day group, 75.64+/-45.91 and Night group, 90.69+/-51.85 pg/mL), with normal values being recovered 1 h later (Day group, 26.33+/-10.15 and Night group, 27.78+/-7.82 pg/mL) and maintained for up to 24 hours, when the circadian variation of aMT returns to the normal acrophase. Due to the interindividual variation of aMT levels among healthy people, a single determination of the indoleamine concentration is not a suitable marker of the existence of a convulsive crisis unless the circadian profile of aMT secretion in the patient is known. The results obtained also support the view that the stimulation of aMT production by the convulsive crisis may participate in the response of the organism against the seizures.

Melatonin expression in periodontal disease.

BACKGROUND AND OBJECTIVE: It was the purpose of this study to examine the relationship between periodontal diseases and melatonin level. MATERIAL AND METHODS: Forty-six patients with periodontal disease, together with 26 age- and gender-matched healthy controls, were included. Periodontal status was assessed using the Community Periodontal Index. Plasma and salivary melatonin levels were determined using specific commercial radioimmunoassays, whereas lymphocyte subpopulations (e.g. CD3, CD4, CD8, C19 and natural killer cells) were analyzed using flow cytometry. RESULTS: Patients with periodontal disease had significantly (p < 0.001) lower plasma (9.46 +/- 3.18 pg/mL) and saliva (2.55 +/- 0.99 pg/mL) melatonin levels than healthy control patients (14.33 +/- 4.05 and 4.22 +/- 0.87 pg/mL, respectively). A biphasic relationship was observed between plasma melatonin levels and Community Periodontal Indices. The plasma melatonin level was reduced in patients with a lower Community Periodontal Index value (1 or 2) and increased in patients with a higher Community Periodontal Index value (3 or 4). Salivary melatonin parallels the changes of plasma melatonin. The higher the Community Periodontal Index, the older the patient and the higher the total lymphocyte counts. CD4 concentrations also increased as the disease worsened. CONCLUSION: The results obtained from this study suggest that melatonin could act as a protective function in fighting periodontal infection. However, further studies in this area are encouraged.

Melatonin administration prevents cardiac and diaphragmatic mitochondrial oxidative damage in senescence-accelerated mice.

Cardiac and diaphragmatic mitochondria from male SAMP8 (senescent) and SAMR1 (resistant) mice of 5 or 10 months of age were studied. Levels of lipid peroxidation (LPO), glutathione (GSH), GSH disulfide (GSSG), and GSH peroxidase and GSH reductase (GRd) activities were measured. In addition, the effect of chronic treatment with the antioxidant melatonin from 1 to 10 months of age was evaluated. Cardiac and diaphragmatic mitochondria show an age-dependent increase in LPO levels and a reduction in GSH:GSSG ratios. Chronic treatment with melatonin counteracted the age-dependent LPO increase and GSH:GSSG ratio reduction in these mitochondria. Melatonin also increased GRd activity, an effect that may account for the maintenance of the mitochondrial GSH pool. Total mitochondrial content of GSH increased after melatonin treatment. In general, the effects of age and melatonin treatment were similar in senescence-resistant mice (SAMR1) and SAMP8 cardiac and diaphragmatic mitochondria, suggesting that these mice strains display similar mitochondrial oxidative damage at the age of 10 months. The results also support the efficacy of long-term melatonin treatment in preventing the age-dependent mitochondrial oxidative stress.

Binding properties and immunolocalization of a fatty acid-binding protein in Giardia lamblia.

We describe here a fatty acid-binding protein (FABP) isolated and purified from the parasitic protozoon Giardia lamblia. The protein has a molecular mass of 8 kDa and an isoelectric point of 4.96. A Scatchard analysis of the data at equilibrium revealed a dissociation constant of 3.12 x 10(-8) M when the labeled oleic acid was displaced by a 10-fold greater concentration of unlabeled oleic acid. Testosterone, sodium desoxycholate, taurocholate, metronidazol, and alpha-tocopherol, together with butyric, arachidonic, palmitic, retinoic, and glycocholic acids, were also bound to the protein. Assays with polyclonal antibodies revealed that the protein is located in the ventral disk and also appears in the dorsal membrane, the cytoplasm, and in the vicinity of the lipid vacuoles.

Relación del óxido nítrico con el síndrome de isquemia/reperfusión en el pinzamiento aórtico / The relationship between nitric oxide and ischemia-reperfusion syndrome in aortic clamping

El pinzamiento aórtico (PA) provoca un síndrome de isquemia/ reperfusión (SIR) de consecuencias multiorgánicas, que actualmente se relaciona con el daño provocado por radicales libres y sustancias proinflamatorias. El estrés oxidativo (EO) producido daña las membranas celulares y al endotelio, y se puede afectar la sínte-sis de óxido nítrico (NO). Objetivos. 1. Medir los niveles de lipoperoxidación (LPO) de las membranas: indicador del EO. 2. Valorar la influencia del PA en los niveles plasmáticos de NO. 3. Relacionar los niveles de NO con la LPO. 4. Valorar la relación entre la distribución de NO/LPO y la morbimortalidad de la cirugía aórtica. Pacientes y métodos. 21 pacientes con patología oclusiva aortoiliaca y 17 aneurismas, sometidos a un PA electivo. Se obtuvieron 10 muestras de sangre para las determinaciones bioquímicas (NO/LPO). Se recogieron las complicaciones sistémicas postoperatorias de cada paciente. Se analizaron los datos en función de la pertenencia a cada grupo. Resultados. El PA produce en ambos grupos un aumento de la LPO y de los niveles de NO. Cuando el EO es excesivo (LPO), descienden los niveles de NO al reaccionar con los radicales libres. La acumulación de mayor número de complicaciones postoperatorias se produce en aquellos pacientes con mayores niveles de LPO y descenso de NO. Conclusiones. El EO secunda-rio al PA provoca una alteración en la fisiología del NO. La reperfusión estimula la síntesis de NO, que en casos extremos contribuye a aumentar el daño oxidativo. Existe una relación clara entre los niveles de LPO, de NO y la morbimortalidad asociada a esta cirugía

Introduction. Aortic clamping (AC) gives rise to an ischemia-reperfusion syndrome (IRS), with consequences affecting a number of organs, which is currently linked to the damage caused by free radicals and proinflammatory substances. The oxidative stress (OS) produced damages cell membranes and the endothelium, and the synthesis of nitric oxide (NO) may also be involved. Aims. 1. To measure the levels of lipoperoxidation (LPO) in the membranes: an OS indicator. 2. To evaluate the influence of AC on levels of NO in plasma. 3. To establish the relation between NO and LPO. 4. To evaluate the relation between the distribution of NO/LPO and the rates of morbidity and mortality in aortic surgery. Patients and methods. The study included 21 patients with an aortoiliac occlusive pathology and 17 aneurysms, who were submitted to elective AC. 10 blood samples were obtained for bio-chemical analysis (NO/LPO). The post-operative systemic complications of each patient were noted. The data were analysed according to which group they belonged to. Results. AC produced an increase in LPO and levels of NO in both groups. When OS is excessive (LPO), NO levels drop as it reacts with the free radicals. A greater number of post-operative complications occur in patients who have higher levels of LPO and reduced NO. Conclusions. OS secondary to AC gives rise to an alteration in NO physiology. Reperfusion stimulates the synthesis of NO, which in extreme cases plays a part in increasing oxidative damage. There is a relationship between LPO and NO levels and the rates of morbidity and mortality associated to this intervention

Mechanisms of N-methyl-D-aspartate receptor inhibition by melatonin in the rat striatum.

N-methyl-D-aspartate (NMDA) receptor activation comprises multiple regulatory sites controlling Ca2+ influx into the cell. NMDA-induced increases in intracellular [Ca(+2)] lead to nitric oxide (NO) production through activation of neuronal NO synthase (nNOS). Melatonin inhibits either glutamate or NMDA-induced excitation, but the mechanism of this inhibition is unknown. In the present study, the mechanism of melatonin action in the rat striatum was studied using extracellular single unit recording of NMDA-dependent neuronal activity with micro-iontophoresis. Melatonin inhibited neuronal excitation produced by either NMDA or L-arginine. The effects of both NMDA and L-arginine were blocked by nitro-L-arginine methyl ester, suggesting that nNOS participates in responses to NMDA. However, excitation of NMDA-sensitive neurones induced by the NO donor sodium nitroprusside was only slightly modified by melatonin. Melatonin iontophoresis also counteracted excitation induced by tris(2-carboxyethyl)phosphine hydrochloride, showing that the redox site of the NMDA receptor may be a target for melatonin action. The lack of effects of the membrane melatonin receptor ligands luzindole, 4-phenyl-2-propionamidotetralin and 5-methoxycarbonylamino-N-acetyltryptamine, and the nuclear melatonin ligand, CGP 52608, a thiazolidine dione, excluded the participation of known membrane and nuclear receptors for melatonin. The data suggest that inhibition of NMDA-dependent excitation by melatonin involves both nNOS inhibition and redox site modulation.

Melatonin improves deferoxamine antioxidant activity in protecting against lipid peroxidation caused by hydrogen peroxide in rat brain homogenates.

Deferoxamine (DF) is an antioxidant molecule because of its ability to chelate iron. This study compared the ability of DF alone or in combination with melatonin, 5-methoxytryptophol or pinoline in preventing lipid peroxidation due to hydrogen peroxide (H(2)O(2)) in rat brain homogenates. Malondialdehyde (MDA) and 4-hydroxyalkenals (4-HDA) in the homogenates were measured as indices of lipid peroxidation. Incubation of homogenates with DF reduced, in a dose-dependent manner, MDA+4-HDA formation due to H(2)O(2). When melatonin, 5-methoxytryptophol or pinoline were added to the incubation medium, the efficacy of DF in preventing lipid peroxidation was enhanced. These cooperative effects between DF, melatonin, and related pineal products may be important in protecting tissues from the oxidative stress due to iron overload.