Remote ischemic preconditioning-induced late cardioprotection: possible role of melatonin-mitoKATP-H2S signaling pathway

Purpose: Remote ischemic preconditioning (RIPC) confers cardioprotection against ischemia reperfusion (IR) injury. However, the precise mechanisms involved in RIPC-induced cardioprotection are not fully explored. The present study was aimed to identify the role of melatonin in RIPC-induced late cardioprotective effects in rats and to explore the role of H2 S, TNF-α and mitoKATP in melatoninmediated effects in RIPC. Methods: Wistar rats were subjected to RIPC in which hind limb was subjected to four alternate cycles of ischemia and reperfusion of 5 min duration by using a neonatal blood pressure cuff. After 24 h of RIPC or ramelteon-induced pharmacological preconditioning, hearts were isolated and subjected to IR injury on the Langendorff apparatus. Results: RIPC and ramelteon preconditioning protected the hearts from IR injury and it was assessed by a decrease in LDH-1, cTnT and increase in left ventricular developed pressure (LVDP). RIPC increased the melatonin levels (in plasma), H2 S (in heart) and decreased TNF-α levels. The effects of RIPC were abolished in the presence of melatonin receptor blocker (luzindole), ganglionic blocker (hexamethonium) and mitochondrial KATP blocker (5-hydroxydecanoic acid). Conclusion: RIPC produce delayed cardioprotection against IR injury through the activation of neuronal pathway, which may increase the plasma melatonin levels to activate the cardioprotective signaling pathway involving the opening of mitochondrial KATP channels, decrease in TNF-α production and increase in H2 S levels. Ramelteon-induced pharmacological preconditioning may also activate the cardioprotective signaling pathway involving the opening of mitochondrial KATP channels, decrease in TNF-α production and increase in H2 S levels.

Protective effects of melatonin in cisplatin-induced cardiac toxicity: possible role of BDNF-TNF-α signaling pathway

Purpose: The present study explored the role of melatonin in cisplatin-induced cardiac injury along with the possible role of brain-derived neurotrophic factor (BDNF) in melatonin-mediated effects. Methods: Wistar rats were administered cisplatin (10 mg/kg), and cardiac injury was assessed by measuring the levels of cardiac troponin (cTnT) and lactate dehydrogenase (LDH-1).The extent of apoptosis was measured by measuring caspase-3 (pro-apoptotic) and Bcl-2 (anti-apoptotic) in hearts. The levels of BDNF, tumour necrosis factor α (TNF-α) and reduced glutathione were measured in heart. Melatonin (5 and 10 mg/kg) was administered for 15 days, and the role of BDNF was identified by co-administering BDNF inhibitor, ANA-12 (0.25 and 0.5 mg/kg). Results: Melatonin attenuated cTnT and LDH-1 levels along with reduction in caspase-3 and increase in Bcl-2. It also increased cisplatin-induced decrease in BDNF, increase in TNF-α and decrease in reduced glutathione levels. Moreover, ANA-12 abolished the cardioprotective effects, anti-inflammatory and antioxidant effects of melatonin suggesting the role of BDNF in melatonin-mediated effects in cisplatin-induced cardiac injury. Conclusions: Melatonin is useful in cisplatin-induced cardiac injury, which may be due to an increase in BDNF, decrease in inflammation and increase in antioxidant activities.

Acutely applied melatonin prevents CCl4-induced testicular lesions in rats: the involvement of the oxidative capacity and arginine metabolism

Abstract Carbon tetrachloride (CCl4) represents an organic chemical that causes reactive oxygen species derived organ disturbances including male infertility. Melatonin (MLT) is a neurohormone with strong antioxidant capacity, involved in numerous physiological processes. In this study we evaluated the capability of MLT, administered in a single dose of 50 mg/kg, to preserve the testicular tissue function after an acute administration of CCl4 to rats. The disturbance in testicular tissue and the effects of MLT after CCl4 exposure were estimated using biochemical parameters that enabled us to determine the tissue (anti)oxidant status and the intensity of arginine/nitric oxide metabolism. Also, the serum levels of testosterone and the histopathological analysis of tissue gave us a better insight into the occurring changes. A significant diminution in tissue antioxidant defences, arginase activity and serum testosterone levels, followed by the increased production of nitric oxide and extensive lipid and protein oxidative damage, was observed in the CCl4-treated group. The application of MLT after the CCl4 caused changes, clearly visible at both biochemical and histological level, which could be interpreted mainly as a consequence of general antioxidant system stimulation and a radical scavenger. On the other hand, the application of MLT exerted a limited action on the nitric oxide signalling pathway.

Melatonin and its neuroimmunological actions

Introduction: Melatonin is a neurohormone, synthesized mainly in the pineal gland, which regulates the circadian rhythm. Objective: To describe the neuroimmunological actions produced by melatonin. Methods: A review on the subject was carried out using articles of free access in the Pubmed database from 2015 to January 2019. Discussion: The effects of melatonin on the wake-sleep cycle are known. Recently it has been shown that this neurohormone can modulate the immune response and reduce seizures in autoimmune and rheumatologic diseases. It induces the pattern of regulatory T lymphocytes and immunomodulatory cytokines maintaining the homeostasis of the internal environment. In the Central Nervous System inhibits the formation of free radicals, has antioxidant functions and can slow neurodegenerative processes. In the peripheral nerves decreases oxidative stress and cellular apoptosis. There are drugs that use melatonin as an active ingredient for its beneficial effects. In Cuba, only the history of a publication on this hormone is collected. Conclusions: Melatonin can be a very useful element in the management of inflammatory and neurological diseases(AU)

Comparison of sexual performance and testicular characteristics of melatonin treated Kivircik and Charollais rams during the non-breeding season / Comparação de desempenho reprodutivo e características testiculares de carneiros Kivircik e Charollais tratados com melatonina durante a estação não reprodutiva

This study was conducted to investigate the effects of melatonin implantation on basic testicular characteristics and reproductive performance of Kivircik and Charollais rams and ewes during the non-breeding season. In this study, 8 Kivircik and 6 Charollais rams were used. Rams were implanted with 54 mg melatonin according to the manufacturer's instructions. At melatonin implantation and at ram introduction the reproductive performance and testicular characteristics were evaluated. Throughout the experimental period, rams were permanently kept outdoors under conditions of natural day length and at ambient temperature. The effects of exogenous melatonin treatments on the reproductive performances of rams and ewes, estrus response, pregnancy rate, litter size and twinning rate of ewes were evaluated in all groups. Libido values were significantly higher in Charollais rams compared to Kivircik rams (P<0.001). Testicular volume (TV) was increased in both ram breeds. Scrotal length (SL) was also increased in both Kivircik and Charollais rams (P<0.01). In conclusion, we showed that the treatment of rams with slow release melatonin implants increased scrotal diameters and testicular volumes in both Kivircik and Charollais rams. Furthermore, melatonin implantation improved the reproductive performances of ewes naturally mated with these melatonin implanted rams during non-breeding season.(AU)

Esse estudo foi conduzido para investigar os efeitos de implantação de melatonina em características testiculares básicas e desempenho reprodutivo de carneiros Kivircik e Charollais durante a estação não reprodutiva. Nesse estudo, oito carneiros Kivircik e 6 Charollais foram utilizados. Foi implantado 54 mg de melatonina nos cordeiros de acordo com as instruções do produtor. Ao implantar a melatonina e à introdução do carneiro, foram avaliados o desempenho reprodutivo e as características testiculares. Ao longo do período experimenta, os cordeiros foram mantidos em ambiente externo sob condições de luz e ritmo circadiano naturais e à temperatura ambiente. O efeito de tratamento com melatonina exógena no desempenho reprodutivo de carneiros e ovelhas, resposta estral, taxa de prenhez, tamanho de ninhada e taxa de gemelaridade foram avaliados em todos os grupos. Valores de libido foram significativamente maiores em Charollais comparados a Kivircik (P<0.001). Volume testicular (VT) estava aumentado em ambas as raças. Comprimento escrotal (CE) também estava aumentado tanto em Kivircik quanto em Charollais (P<0.01). Conclui-se que o tratamento de carneiros com implantes de liberação lenta de melatonina aumentou diâmetro e volume testiculares tanto em carneiros Kivircik quanto em Charollais. Ademais, implantação de melatonina melhorou o desempenho reprodutivo de ovelhas naturalmente cruzadas com esses carneiros implantados com melatonina durante o período não reprodutivo.(AU)

Efeito de diferentes concentrações de melatonina em espermatozoides de carneiros sobre estresse oxidativo após criopreservação / Effect of different concentrations of melatonin to ram spermatozoa on oxidative stress after cryopreservation

Objetivou-se avaliar o efeito da adição de diferentes concentrações de melatonina no sêmen diluído de carneiros após criopreservação. Foram coletados 10 ejaculados de três carneiros adultos (n=30), por meio de vagina artificial para ovinos. Os ejaculados coletados foram diluídos em Tris-Gema de ovo, para a concentração final de 200x106 sptz/mL, mantidos em banho maria a 32°C, e a melatonina adicionada conforme os tratamentos: Controle; 100pM; 100nM; 100µM e 1mM de melatonina. Então, as amostras foram resfriadas em câmara fria a 5°C por duas horas, envasadas em palhetas de 0,5 mL e lacradas. Logo após, foram acondicionadas sob vapores do nitrogênio liquido, por 15 minutos, a 8cm da lâmina líquida e congeladas com nitrogênio líquido. As amostras foram analisadas quanto à motilidade espermática, integridade da membrana plasmática, membrana acrossomal, atividade mitocondrial, quantificação do estresse oxidativo e a capacidade de ligação. As variáveis foram submetidas à análise de variância e as médias foram comparadas pelo teste de Tukey a 5% de probabilidade. A motilidade total e progressiva dos espermatozoides descongelados foi maior nas amostras tratadas com 100pM de melatonina (62,99 e 45,07% respectivamente; P<0,05) quando comparado aos demais tratamentos. A adição das diferentes concentrações de melatonina no sêmen diluído, com exceção da concentração de 1 mM, apresentou maior percentual de células com membrana plasmática íntegra, quando comparadas com o controle (P<0,05). O percentual de espermatozoides com integridade da membrana do acrossoma foi maior no sêmen tratado com 100 pM de melatonina (P<0,05) do que nos demais tratamentos. A alta atividade mitocondrial foi maior nos espermatozoides tratados com 100 pM de melatonina (69,30%; P<0,05). A adição de 100 nM de melatonina reduziu a quantidade de TBARS após a criopreservação (2,84; P<0,05) quando comparado aos demais tratamentos. Após o descongelamento, o número de espermatozoides que se ligaram à membrana perivitelina foi maior nos tratados com 100 pM de melatonina (155,73; P<0,05). Portanto, a adição de melatonina no sêmen diluído pode ser útil para aperfeiçoar a criopreservação do sêmen de ovinos, melhorando as taxas de fertilização por meio da inseminação artificial.(AU)

The aim was to evaluate the effect of adding different concentrations of melatonin in ram semen diluted after cryopreservation. Ten ejaculates were collected0 from three adult ram (n=30) by means of artificial vagina for sheep. The collected samples were diluted in Tris-egg yolk, to a final concentration 200x106 sptz/mL kept in water bath at 32°C, and melatonin added as treatments: control; 100pM; 100nM; 100µM and 1mM melatonin. Then, the samples were cooled in a cold chamber at 5°C for two hours, in straws of 0.5mL and sealed. They were stored under the liquid nitrogen vapor for 15 minutes to 8cm of liquid blade and frozen with liquid nitrogen. Samples were analyzed for sperm motility, membrane integrity, acrosomal membrane, mitochondrial activity, oxidative stress and quantification of the binding capacity. The variables were subjected to analysis of variance and the means were compared by Tukey test at 5% probability. The total and progressive motility of thawed sperm were higher in samples treated with 100pM melatonin (62.99 and 45.07%, respectively; P<0.05) when compared to other treatments. The addition of different concentrations of melatonin in semen diluted with the exception of 1mM concentration, a higher percentage of cells with intact plasma membrane, as compared with the control (P<0.05). The percentage of sperm with acrosome membrane integrity was higher in the semen with 100pM melatonin (P<0.05) than the other treatments. The high mitochondrial activity was higher in spermatozoa treated with 100pM melatonin (69.30%; P<0.05). Addition of 100nM melatonin reduced the amount of TBARS after cryopreservation (2.84, P<0.05) when compared with the other treatments. After thawing, the number of sperm which bind to the perivitelline membrane was higher in the melatonin treated with 100pM (155,73; P<0.05). Therefore, melatonin addition the semen diluted can be useful to enhance the cryopreservation of sheep semen, improving fertilization rates through artificial insemination.(AU)

Efeito da iluminação constante sobre a placenta de ratas: um estudo morfológico, morfométrico e histoquímico / The effect of constant illumination on the placenta in rats: a morphological, morphometric and immunohistochemical study

A presente pesquisa analisou o efeito da iluminação constante sobre a estrutura placentária de ratas, abordando parâmetros morfológicos, morfométricos e histoquímicos. Vinte ratas albinas foram submetidas aos seguintes tratamentos: 12hL/12hE por 60 dias, e acasaladas em seguida (GI); ausência de luz por 60 dias, e acasaladas em seguida (GII); iluminação constante por 60 dias, e acasaladas em seguida (GIII); iluminação constante por 60 dias, acasaladas em seguida e tratadas com melatonina (GIV). O estímulo luminoso foi em torno de 400 lux. A melatonina foi administrada na água (400mg/mL de etanol). Os resultados mostraram que histologicamente o GII apresentou vacuolização das células do trofospongio. Morfometricamente, o GIII apresentou camada do labirinto com redução no número de trofoblastos sinciciais e maior vascularização materno-fetal, hiperplasia e hipertrofia das células trofoblásticas gigantes, uma maior média da área total do disco placentário; porém, na camada de trofospongio, as células trofoblásticas e trofoblastos sinciciais não diferiram nos grupos experimentais. As placentas do GIV foram semelhantes às do GI. Histoquimicamente não houve alterações nas fibras colágenas, elásticas, reticulares e glicosaminoglicanas ácidas. Em conclusão, a iluminação constante promove alterações morfológicas e morfométricas na placenta de ratas, podendo acarretar redução funcional e restrições ao crescimento fetal. Essas alterações são abolidas pela reposição de melatonina.

This study examined the effect of constant illumination on the placental structure of rats, addressing morphological, morphometric and immunohistochemical parameters. 20 albino rats were subjected to the following treatments: GI-12hL/12hE for 60 days and then mated; GII- dark for 60 days and then mated; GIII- constant illumination for 60 days and then mated and GIV- constant light for 60 days, mated and then treated with melatonin. The light stimulus was around 400 lux. Melatonin was administered in water (400 mg / ml ethanol). The results showed that GII had histologically trofospongio vacuolization of cells. Morphometrically, GIII presented a labyrinth layer reduction in the number of syncytial trophoblasts and greater maternal-fetal vasculature, hyperplasia and hypertrophy of trophoblast giant cells, a higher average of the total area of the placenta disk, but in the trofospongio layer, the trophoblast cells and syncytial trophoblasts did not differ between experimental groups. The placentas in GIV were similar to GI. Histochemically there were no changes in the collagen and elastic fibers, reticular and acidic glycosaminoglycans. In conclusion, the constant lighting promotes morphological and morphometric changes in the placenta in rats and may lead to functional reduction and restrictions on fetal growth. These changes are abolished by the melatonin replacement.

Efeito da dexametasona e melatonina exógenas sobre parâmetros sanguíneos, progesterona, carboidratos totais e histomorfometria de órgãos em ratas prenhes / The effect of dexamethasone and exogenous melatonin on blood parameters, progesterone, total carbo hydrates and histomorphometry of organs in pregnant rats

A dexametasona é utilizada em casos de gestação com risco de prematuridade; porém, doses suprafisiológicas podem afetar a embriogênese. A melatonina tem demonstrado prevenir efeitos deletérios dos glicocorticoides. Assim, avaliamos a influência da melatonina sobre efeitos da dexametasona em ratas prenhes através dos seguintes parâmetros: 1. Hemograma e perfil glicídico; 2. Níveis de progesterona; e 3. Histomorfometria e histoquímica. Foram utilizadas 20 ratas divididas nos grupos: I - ratas prenhes que receberam placebo (Controle); II - ratas prenhes tratadas com dexametasona (0,8mg/kg); III - ratas prenhes tratadas com melatonina (0,5mg/kg); IV - ratas prenhes tratadas com dexametasona e melatonina. Todos os tratamentos foram iniciados 10 dias após confirmação do acasalamento até o final da prenhez. O sangue foi coletado no 7º, 14º e 21º dia de prenhez. As dosagens de carboidratos e progesterona foram realizadas pelo método antrona e ELISA, respectivamente. O fígado, rins e adrenais foram analisados histoquímica e morfometricamente. No 7º dia de prenhez, não houve alteração significativa nos parâmetros analisados. Porém, no 14º dia de prenhez, houve aumento significativo do volume de hematócrito, redução do número total de hemácias e leucócitos, neutrofilia, linfopenia, eosinopenia e redução do diâmetro das hemácias nas matrizes tratadas com dexametasona. Esses efeitos permaneceram no 21º dia de prenhez, exceto para o hematócrito, o qual reduziu. Verificou-se ainda redução significativa dos níveis de glicose (21º dia de prenhez) e progesterona (14º e 21º dia de prenhez). Não houve alteração nos parâmetros morfométricos e histoquímico no fígado, rins e adrenais. A dexametasona na dosagem de 0,8mg/kg, administrada a partir do terço médio da prenhez, produz alterações hematológicas, bioquímicas e hormonais em ratas, sendo prevenidas pela melatonina; porém não afeta o fígado, rins e adrenais quanto aos parâmetros morfométricos e histoquímicos.

Dexamethasone is used in cases of pregnancy with prematurity risk. However, it may affect the embryogenesis when used in supraphysiological doses. Melatonin has been shown to prevent the deleterious effects of glucocorticoids. Therefore, the influence of melatonin on the effects of dexamethasone on pregnant rats was evaluated through the following parameters: 1. Hemogram and glucose profile; 2. Progesterone levels; 3. Histomorphometry and histochemistry analyses. Twenty female rats were divided into the following groups: I - rats that received placebo (Control); II - rats treated with dexamethasone (0.8mg/kg); III - rats treated with melatonin (0.5mg/kg); IV - rats treated with dexamethasone and melatonin. All treatments started 10 days after confirmation of mating and lasted until the end of the pregnancy. Blood samples were collected on the 7th, 14th, and 21st day. Carbohydrate and progesterone levels were determined with the antrona and ELISA method, respectively. The liver, kidneys, and adrenal glands were analyzed morphometrically and histochemically. On the 7th day of pregnancy there were no significant changes in the parameters analyzed. However, at 14 days of pregnancy there was a significant increase of hematocrit, reducing the total number of erythrocytes and leukocytes, neutrophilia, lymphopenia, eosinopenia and reduced diameter of red blood cells in rats treated with dexamethasone. These effects remained on the 21st of day of pregnancy, except for the hematocrit, which was reduced. There was also a significant reduction in glucose levels (21st day) and progesterone (14th and 21st days). There was no change in the histochemical and morphometric parameters in the liver, kidneys and adrenals. Dexamethasone at a dosage of 0.8mg/kg administered from the middle third of pregnancy produces hematological, biochemical and hormonal changes in rats, being prevented by melatonin, but does not affect the liver...

Ação da melatonina sobre a dinâmica sanguínea de ratas prenhes e sobre a histogênese do baço e do timo da prole / The action of melatonin on the blood dynamics of pregnant rats and on the histogenesis of the spleen and thymus of offspring

Investigou-se a influência da melatonina sobre o hemograma de ratas prenhes e dos filhotes e sobre a histogênese e morfometria do baço e do timo dos filhotes. A melatonina foi administrada na dose 0,5mg/kg de peso corporal, dissolvida em 0,1mL de etanol e diluída em 0,3mL de solução salina. Para análise do hematócrito, contagem total de hemácias e contagem total e diferencial dos leucócitos, amostras de sangue foram coletadas no sétimo, 14ºe 21ºdias de prenhez e aos 10 dias de nascimento dos filhotes. Cortes histológicos do baço e do timo da prole foram utilizados para histoquímica e morfometria. A ausência da melatonina promoveu alterações no hemograma apenas no terço final da gestação, sem interferir no hemograma dos filhotes, e induziu modificações morfológicas e morfométricas no timo e no baço nos primeiros dias de vida dos filhotes. Concluiu-se que a melatonina materna é importante para a modulação do hemograma em ratas prenhes e para o desenvolvimento normal do baço e do timo dos filhotes.

We investigated the influence of melatonin on the hemogram of pregnant rats and puppies, and on the histogenesis and morphology of the spleen and thymus of puppies. Melatonin was administered at a dose 0.5mg/kgbody weight, dissolved in 0.1mL of ethanol and diluted in 0.3mL of saline. For hematocrit analysis, total erythrocyte count and total and differential leukocyte count, blood samples were collected on the 7th, 14th and 21st days of pregnancy and the offspring at 10 days of birth. Histological sections of spleen and thymus of the offspring were used for histochemistry and morphometry. The absence of melatonin promoted changes in blood count only in the final third of gestation, without interfering with the hemogram of the puppies, and induced morphological and morphometric changes in the thymus and spleen in the first days of life of the puppies. It was concluded that maternal melatonin is important for the modulation of the blood count in pregnant rats and the normal development of the spleen and thymus of the offspring.

The therapeutic effect of a pulsed electromagnetic field on the reproductive patterns of male Wistar rats exposed to a 2.45-GHz microwave field

INTRODUCTION: Environmental exposure to man-made electromagnetic fields has been steadily increasing with the growing demand for electronic items that are operational at various frequencies. Testicular function is particularly susceptible to radiation emitted by electromagnetic fields. OBJECTIVES: This study aimed to examine the therapeutic effects of a pulsed electromagnetic field (100 Hz) on the reproductive systems of male Wistar rats (70 days old). METHODS: The experiments were divided into five groups: microwave sham, microwave exposure (2.45 GHz), pulsed electromagnetic field sham, pulsed electromagnetic field (100 Hz) exposure, and microwave/pulsed electromagnetic field exposure. The animals were exposed for 2 hours/day for 60 days. After exposure, the animals were sacrificed, their sperm was used for creatine and caspase assays, and their serum was used for melatonin and testosterone assays. RESULTS: The results showed significant increases in caspase and creatine kinase and significant decreases in testosterone and melatonin in the exposed groups. This finding emphasizes that reactive oxygen species (a potential inducer of cancer) are the primary cause of DNA damage. However, pulsed electromagnetic field exposure relieves the effect of microwave exposure by inducing Faraday currents. CONCLUSIONS: Electromagnetic fields are recognized as hazards that affect testicular function by generating reactive oxygen species and reduce the bioavailability of androgen to maturing spermatozoa. Thus, microwave exposure adversely affects male fertility, whereas pulsed electromagnetic field therapy is a non-invasive, simple technique that can be used as a scavenger agent to combat oxidative stress.

A study of melatonin levels and stress in female shift workers.

The aim of this study was to determine the relationship between saliva melatonin and stress levels in Thai female shift workers. Five older (38.4 +/- 1.82) and five younger (21.4 +/- 0.55) female workers voluntarily participated in this study. All participants worked both morning and night shifts at a glass manufacturing factory. Saliva was collected every three hours at the workplace and at the subjects' houses to examine melatonin profiles. The Mann-Whitney U test and the Wilcoxon signed ranks test were used. There was a significant (p < 0.05) difference between melatonin levels in younger and older subjects when measured during the night shift at 19:00. Differences between melatonin levels during the morning and night shifts in the older group were significant at 07:00 and at 19:00 in younger subjects (p < 0.05). Normal stress and mild stress were found. No significant differences in melatonin levels were found between workers with normal and mild stress levels. The onset time of increasing saliva melatonin was at 19:00, both in women working the morning shift and in those working the night shift. Peak melatonin production occurred at 22:00 for the night shift in both groups. During the morning shifts, the peak times were at 04:00 and 01:00 (in the younger and older groups, respectively), usually between 02:00 and 04:00. These findings show that melatonin levels in female shift workers adapted according to the shift worked, especially in the older group. Health surveillance programs should therefore be established to prevent further negative health effects for female shift workers.

La melatonina: una revisión de su farmacología / Melotonin: review of pharmacology

La melatonina es una hormona de la glándula pineal, cuya secreción está bajo la influencia del ciclo de luz-oscuridad. Su mayor concentración, en plasma, se encuentra durante la noche, por lo qu se cree que juega un papel en la regulación del sueño. en dosis farmacológicas, puede actuar como facilitador del sueño e hipnótico. Además, algunos estudios muestran que podría tener un papel en el tratamiento de la sintomatología del "jet lag". Sus efectos antigonadales, aunque aún controversiales, podrían ser importantes en algunas patologías.