Melatonin and tryptophan counteract lipid peroxidation and modulate superoxide dismutase activity in ringdove heterophils in vivo. Effect of antigen-induced activation and age

L-4-thiazolylalanine (Protinol), a novel non-proteinogenic amino acid, demonstrates epidermal and dermal efficacy with clinically observable benefits

OBJECTIVE

Facial skin undergoes major structural and functional changes as a result of intrinsic and extrinsic factors. The goal of the current work is to demonstrate L-4-thiazolylalaine (L4, Protinol), a non-proteinogenic amino acid shown to stimulate the production of dermal proteins by fibroblasts, is an alternative efficacious topical ingredient for visible signs of ageing.

METHODS

In vitro studies using 3D human skin tissue models were performed to show changes in protein and gene expression of key dermal markers in samples treated with 0.3% L4 compared to vehicle control. In vivo evaluation of skin turnover was measured in volunteers after treatment with L4 compared to retinol. Skin biopsies (n = 30) were taken to investigate epidermal and dermal changes in cases treated with L4 and compared to retinol. Finally, a clinical evaluation (n = 28) was conducted to assess the efficacy of L4 over a base formulation using various ageing parameters within a population of women 46-66 years old with mild-to-moderate wrinkles.

RESULTS

In vitro studies on 3D tissues displayed significant changes in the dermal matrix via an increase in HA and pro-collagen I production and a decrease in the expression of inflammatory genes. In vivo biopsy studies demonstrated that L4 and retinol independently increased epidermal thickness and collagen remodelling significantly more compared with the base formula. Clinical evaluation showed firmer and smoother skin at day 28 post-treatment with L4 over the vehicle control without causing side effects such as redness or irritation.

CONCLUSION

L4 is a novel, multi-functional ingredient which offers a superior alternative to currently available technologies for improving epidermal and dermal parameters that change during ageing and photodamage.

Chemical-genetic interaction landscape of mono-(2-ethylhexyl)-phthalate using chemogenomic profiling in yeast

Integration of chemical-genetic interaction data with biological functions provides a mechanistic understanding of how toxic compounds affect cells. Mono-(2-ethylhexyl)-phthalate (MEHP) is an active metabolite of di-(2-ethylhexyl)-phthalate (DEHP), a commonly used plasticizer. MEHP adversely affects human health causing hepatotoxicity and reproductive toxicity. How MEHP affects cellular physiology is not fully understood. We utilized a genome-wide competitive fitness-based assay called 'chemogenomic profiling' to determine the genetic interaction map of MEHP in Saccharomyces cerevisiae. Gene Ontology enrichment analysis of 218 genes that provide resistance to MEHP indicated that MEHP affects seven cellular processes namely: (1) cellular amino acid biosynthetic process, (2) sterol biosynthetic process, (3) cellular transport, (4) transcriptional and translational regulation, (5) protein glycosylation, (6) cytokinesis and cell morphogenesis and (7) ionic homeostasis. We show that MEHP protects yeast cells from membrane perturbing agents such as amphotericin B, dihydrosphingosine and phytosphingosine. Moreover, we also demonstrate that MEHP compromises the integrity of the yeast plasma membrane and cell wall. Our work provides a basis for further investigation of MEHP toxicity in humans.

Mitochondria: Central Organelles for Melatonin's Antioxidant and Anti-Aging Actions

Melatonin, along with its metabolites, have long been known to significantly reduce the oxidative stress burden of aging cells or cells exposed to toxins. Oxidative damage is a result of free radicals produced in cells, especially in mitochondria. When measured, melatonin, a potent antioxidant, was found to be in higher concentrations in mitochondria than in other organelles or subcellular locations. Recent evidence indicates that mitochondrial membranes possess transporters that aid in the rapid uptake of melatonin by these organelles against a gradient. Moreover, we predicted several years ago that, because of their origin from melatonin-producing bacteria, mitochondria likely also synthesize melatonin. Data accumulated within the last year supports this prediction. A high content of melatonin in mitochondria would be fortuitous, since these organelles produce an abundance of free radicals. Thus, melatonin is optimally positioned to scavenge the radicals and reduce the degree of oxidative damage. In light of the "free radical theory of aging", including all of its iterations, high melatonin levels in mitochondria would be expected to protect against age-related organismal decline. Also, there are many age-associated diseases that have, as a contributing factor, free radical damage. These multiple diseases may likely be deferred in their onset or progression if mitochondrial levels of melatonin can be maintained into advanced age.

Variation in the Markers of Nutritional and Oxidative State in a Long-Lived Seabird: Associations with Age and Longevity

Age-related declines in life-history traits have been widely observed in free-living animals. Several theories link senescence to oxidative stress. The aim of this study was to measure several widely used markers of oxidative and nutritional state in a long-lived seabird, the common gull (Larus canus), in order to assess the suitability of these markers for describing deterioration in physiological condition associated with chronological age and survival. Associations with longevity and individual consistency of these parameters over the years (repeatability) were also assessed. Senescence in fitness parameters was observed during the study period: in females, laying date and clutch mass were related to bird age in a curvilinear manner, with middle-aged birds breeding earlier and laying heavier eggs. The only parameter associated with aging processes was glutathione concentration in erythrocytes, which was lower in female birds with longer life spans. Of indexes of nutritional state, plasma triglyceride concentration showed a between-individual increase with age, suggesting selective mortality of birds with low levels. Additionally, total plasma protein levels of individual males increased with age. The mostly negative results of this study hint that the commonly used parameters of physiological condition and oxidative state used in this study do not adequately reflect an individual's long-term health condition. Alternatively, it is possible that in common gulls, senescence occurs in reproductive mechanisms but not in mechanisms responsible for maintaining an organism's redox balance, consistent with the idea that different aspects of an organism's physiological condition age at different rates. Significant interannual repeatability was detected in three plasma constituents-carotenoids, uric acid, and total protein-all of which can possibly be linked to variation in dietary habits.

Melatonin and its atheroprotective effects: a review

Atherosclerosis is a chronic vascular disease in which oxidative stress and inflammation are commonly implicated as major causative factors. Identification of novel strategies that contribute to plaque stabilization or inhibition represents a continuing challenge for the medical community. The evidence from the last decade highlights that melatonin influences the cardiovascular system, but its mechanisms of action have not been definitively clarified. Melatonin has atheroprotective effects by acting on different pathogenic signaling processes; these result from its direct free radical scavenger activity, its indirect antioxidant properties and its anti-inflammatory actions. In this review, we summarize the many pieces of the puzzle which identified molecular targets for prevention and therapy against the atherosclerotic pathogenic processes and we evaluate the data documenting that melatonin treatment has important actions that protect against atherosclerosis and atherosclerosis-related cardiovascular diseases.

Tryptophan-enriched cereal intake improves nocturnal sleep, melatonin, serotonin, and total antioxidant capacity levels and mood in elderly humans

Melatonin and serotonin rhythms, which exhibit a close association with the endogenous circadian component of sleep, are attenuated with increasing age. This decrease seems to be linked to sleep alterations in the elderly. Chrononutrition is a field of chronobiology that establishes the principle of consuming foodstuffs at times of the day when they are more useful for health, improving, therefore, biorhythms and physical performance. Our aim was to analyze whether the consumption of cereals enriched with tryptophan, the precursor of both serotonin and melatonin, may help in the reconsolidation of the sleep/wake cycle and counteract depression and anxiety in 35 middle-aged/elderly (aged 55-75 year) volunteers in a simple blind assay. Data were collected for 3 weeks according to the following schedule: The control week participants consumed standard cereals (22.5 mg tryptophan in 30 g cereals per dose) at breakfast and dinner; for the treatment week, cereals enriched with a higher dose of tryptophan (60 mg tryptophan in 30 g cereals per dose) were eaten at both breakfast and dinner; the posttreatment week volunteers consumed their usual diet. Each participant wore a wrist actimeter that logged activity during the whole experiment. Urine was collected to analyze melatonin and serotonin urinary metabolites and to measure total antioxidant capacity. The consumption of cereals containing the higher dose in tryptophan increased sleep efficiency, actual sleep time, immobile time, and decreased total nocturnal activity, sleep fragmentation index, and sleep latency. Urinary 6-sulfatoxymelatonin, 5-hydroxyindoleacetic acid levels, and urinary total antioxidant capacity also increased respectively after tryptophan-enriched cereal ingestion as well as improving anxiety and depression symptoms. Cereals enriched with tryptophan may be useful as a chrononutrition tool for alterations in the sleep/wake cycle due to age.

Chrononutrition against oxidative stress in aging

Free radicals and oxidative stress have been recognized as important factors in the biology of aging and in many age-associated degenerative diseases. Antioxidant systems deteriorate during aging. It is, thus, considered that one way to reduce the rate of aging and the risk of chronic disease is to avoid the formation of free radicals and reduce oxidative stress by strengthening antioxidant defences. Phytochemicals present in fruits, vegetables, grains, and other foodstuffs have been linked to reducing the risk of major oxidative stress-induced diseases. Some dietary components of foods possess biological activities which influence circadian rhythms in humans. Chrononutrition studies have shown that not only the content of food, but also the time of ingestion contributes to the natural functioning of the circadian system. Dietary interventions with antioxidant-enriched foods taking into account the principles of chrononutrition are of particular interest for the elderly since they may help amplify the already powerful benefits of phytochemicals as natural instruments with which to prevent or delay the onset of common age-related diseases.

The inhibition of TNF-α-induced leucocyte apoptosis by melatonin involves membrane receptor MT1/MT2 interaction

The pro-apoptotic signalling cascades induced by tumour necrosis factor-alpha (TNF-α) have been intensively studied in multiple cellular systems. So far, it is known that TNF-α can simultaneously activate survival and apoptotic cell death responses. The balance between these signals determines the ultimate response of the cell to TNF-α. Moreover, emerging evidence suggests that melatonin may be involved in the protection of different cell types against apoptosis. Thus, the objective of this study was to evaluate the effect of melatonin on TNF-α-induced apoptosis in human leucocytes. Cells were treated with TNF-α alone or in the presence of cycloheximide (CHX), which promotes caspase-8 activation by eliminating the endogenous caspase-8 inhibitor, c-FLIP. Treatment with TNF-α/CHX led to apoptotic cell death, as ascertained by annexin V/propidium iodide (PI) staining. Likewise, in the presence of CHX, TNF-α stimulation produced cFLIP down-regulation and subsequent caspase-8 activation, thus directly triggering caspase-3 activation and causing Bid truncation and subsequent caspase-9 activation. Conversely, pre-incubation of cells with melatonin inhibited TNF-α-/CHX-evoked leucocyte apoptosis. Similarly, pretreatment of leucocytes with melatonin increased cFLIP protein levels, thereby preventing TNF-α-/CHX-mediated caspase processing. Blockade of melatonin membrane receptor MT1/MT2 or extracellular signal-regulated kinase (ERK) pathway with luzindole or PD98059, respectively, abolished the inhibitory effects of melatonin on leucocyte apoptosis evoked by TNF-α/CHX. In conclusion, the model proposed by these findings is that the MT1/MT2 receptors, which are under the positive control of melatonin, trigger an ERK-dependent signalling cascade that interferes with the anti-apoptotic protein cFLIP modulating the cell life/death balance of human leucocytes.

Aging and vascular dysfunction: beneficial melatonin effects

Aging is characterized by a progressive deterioration of physiological functions and metabolic processes. In aging and in diseases associated with the elderly, the loss of cells in vital structures or organs may be related to several factors. Sirtuin1 (SIRT1) is a member of the sirtuin family of protein deacetylases involved in life span extension; however, its involvement in the aging is not yet completely defined. Recently, melatonin, a pleiotropic molecule, shown to activate SIRT1 in primary neurons of young animals, as well as in aged neurons of a murine model of senescence. Melatonin is known to modulate oxidative stress-induced senescence and pro-survival pathways. We treated 6- and 15-week-old apolipoprotein E (APOE)-deficient mice (APOE 6w and 15w) with two melatonin formulations (FAST and RETARD) to evaluate their anti-aging effect. Morphological changes in vessels (aortic arch) of APOE mice were evaluated SIRT1, p53, endothelial nitric oxide synthase (eNOS), and endothelin-1 (ET-1) markers. We demonstrate that SIRT1 and eNOS decresed in APOE mice between 6 and 15 weeks and that aging induced an elevated expression of p53 and ET-1 in APOE animals. Melatonin improved the impairment of endothelial damage and reduced loss of SIRT1 and eNOS decreasing p53 and ET-1 expression. The RETARD melatonin preparation caused a greater improvement of vessel cytoarchitecture. In summary, we indicate that SIRT1-p53-eNOS axis as one of the important marker of advanced vascular dysfunctions linked to aging. Finally, we suggest that extended-release melatonin (RETARD) provides a more appropriate option for contrasting these dysfunctions compared with rapid release melatonin (FAST) administration.

Dietary L-tryptophan supplementation with reduced large neutral amino acids enhances feed efficiency and decreases stress hormone secretion in nursery pigs under social-mixing stress

Tryptophan (Trp), the rate-limiting substrate of serotonin [5-hydroxytryptoamine (5-HT)] synthesis in the brain, competes with large neutral amino acids (LNAA) to cross the blood-brain barrier. This study was designed to evaluate the effect of L-Trp supplementation on nursery pigs experiencing social-mixing stress and fed diets varying in LNAA concentrations. Forty-eight individually housed barrows at 6 wk of age were randomly allotted to 4 dietary treatments based on a 2 × 2 factorial arrangement, with L-Trp supplementation (0 or 0.6%) and LNAA concentrations (4.5 or 3.8%) as the 2 main factors. Pigs were fed the diets for 7 d. On d 4, pigs within a treatment were paired in a new pen to create social-mixing stress and behavior was recorded for 24 h. Body weight was measured on d 0, 4, 5, and 7. Saliva and blood were collected on d 4 and 7. On d 7, pigs were killed to obtain hypothalami. During the entire period excluding the mixing day (d 5), L-Trp supplementation improved (P < 0.01) feed efficiency of pigs and lowering the LNAA further enhanced (P < 0.05) the effects of L-Trp. Supplementation of 0.6% L-Trp increased (P < 0.001) hypothalamic 5-HT and 5-hydroxyindoleacetic acid. The salivary cortisol concentration was reduced (P < 0.05) by lowering the LNAA. Collectively, lowering the LNAA further enhanced the improvement of feed efficiency by L-Trp supplementation of nursery pigs under social-mixing stress in association with reduced stress hormones, indicating that reducing LNAA in the diet can facilitate the effect of L-Trp on the stress response of pigs.

A jerte valley cherry-based product as a supply of tryptophan

L-Tryptophan (tryptophan) is an essential amino acid in humans. It has important roles as a precursor of different bioactive compounds. Based on previous studies in which tryptophan has been shown to be present in fresh cherries, the aim of the present work was to analyze the tryptophan content of a Jerte Valley cherry-based product. A previously optimized method of analysis of tryptophan was used, ie, high-performance liquid chromatography with fluorescence detection (HPLC/FL). As expected, HPLC/FL technique permitted to detect and quantify the tryptophan content in a different matrix rather than fresh cherries. In fact, the Jerte Valley cherry-based product contained 69.54 ± 10.64 ppm of tryptophan, thereby showing that this product is a good source of tryptophan. In summary, it has been proven that the Jerte Valley cherry-based product is rich in tryptophan and may be indicated as a supply of this essential amino acid as well as having potential health benefits for conditions where tryptophan is necessary.

Melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in leukocytes from elderly humans

The mechanisms regulating neutrophil apoptosis are basically unaffected by the aging process. However, a significant impairment of cell survival occurs in elderly individuals following neutrophil challenge with pro-inflammatory stimuli, such as granulocyte-macrophage colony-stimulating factor (GM-CSF). The goal of the present study was to prove the effects of melatonin supplementation on apoptosis induced by calcium signaling in human leukocytes from elderly volunteers. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin, and/or the calcium mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (fMLP), induced mitochondrial membrane depolarization, caspase activation, phosphatidylserine (PS) externalization, and DNA fragmentation in leukocytes from both young and elderly volunteers, although such effects were much more evident in aged leukocytes. Importantly, melatonin treatment substantially preserved mitochondrial membrane potential, reversed caspase activation, reduced PS exposure and forestalled DNA fragmentation in leukocytes from both age groups. In conclusion, melatonin is able to delay endoplasmic reticulum stress-induced apoptosis in aged leukocytes and may counteract, at the cellular level, age-related degenerative phenomena linked to oxidative stress.

Diets enriched with a Jerte Valley cherry-based nutraceutical product reinforce nocturnal behaviour in young and old animals of nocturnal (Rattus norvegicus) and diurnal (Streptopelia risoria) chronotypes

The decline in melatonin secretion with age seems to be one of the major reasons for increased sleep disruption in older animals. Previously, we showed that the administration with melatonin or its precursor, tryptophan, improved activity/rest rhythms in aged individuals. Here, it was evaluated the effect of a 10-day consumption of a Jerte Valley cherry-based nutraceutical product (patent no. ES2342141B1), which contains high levels of tryptophan, serotonin and melatonin, on the activity/rest rhythms of young and old rats (Rattus norvegicus) and ringdoves (Streptopelia risoria) as representatives of animals with nocturnal and diurnal habits, respectively, and its possible relationship with the serum levels of melatonin and glucose. Total diurnal and nocturnal activity pulses were logged at control, during, and up to 3 days after the treatment. Melatonin and glucose were measured with ELISA and testing kits respectively. In both young and old rats, the intake of the cherry nutraceutical decreased diurnal activity, whereas nocturnal activity increased. The opposite effect was observed for ringdoves. The treatment increased the circulating levels of melatonin in both species and restored the amplitude of the activity rhythm in the old animals to that of the non-treated young groups. The consumption of a Jerte Valley cherry-based nutraceutical product may help to counteract the impaired activity/rest rhythm found in aged animals.

Protective effect of melatonin against human leukocyte apoptosis induced by intracellular calcium overload: relation with its antioxidant actions

Apoptosis or programmed cell death plays a critical role in both inflammatory and immune responses. Recent evidence demonstrates that control of leukocyte apoptosis is one of the most striking immune system-related roles of melatonin. For this reason, this study evaluated the protective effects of melatonin on human leukocyte apoptosis induced by sustained cytosolic calcium increases. Such protective effects are likely mediated by melatonin's free-radical scavenging actions. Treatments with the specific inhibitor of cytosolic calcium re-uptake, thapsigargin (TG), and/or the calcium-mobilizing agonist, N-formyl-methionyl-leucyl-phenylalanine (FMLP), induced intracellular reactive oxygen species (ROS) production, caspase activation as well as DNA fragmentation in human leukocytes. Also, TG- and/or FMLP-induced apoptosis was dependent on both cytosolic calcium increases and calcium uptake into mitochondria, because when cells were preincubated with the cytosolic calcium chelator, dimethyl BAPTA, and the inhibitor of mitochondrial calcium uptake, Ru360, TG- and FMLP-induced apoptosis was largely inhibited. Importantly, melatonin treatment substantially prevented intracellular ROS production, reversed caspase activation, and forestalled DNA fragmentation induced by TG and FMLP. Similar results were obtained by preincubating the cells with another well-known antioxidant, i.e., N-acetyl-L-cysteine. To sum up, depletion of intracellular calcium stores induced by TG and/or FMLP triggers different apoptotic events in human leukocytes that are dependent on calcium signaling. The protective effects resulting from melatonin administration on leukocyte apoptosis likely depend on melatonin's antioxidant action because we proved that this protection is melatonin receptor independent. These findings help to understand how melatonin controls apoptosis in cells of immune/inflammatory relevance.

Biogerontology in Spain: the most significant studies

Here we give an overview of the past and ongoing research in the biology of ageing in Spain. Some of the main topics being investigated are those related to oxidative stress and aging. One of the main findings is the implication of mitochondria in the age-associated oxidative stress. Nutritional modulation of aging is another topic which has been dealt with, and one of the main findings is that methionine restriction has a role in longevity extension. Regarding to hormones and aging, is important to highlight the role of estrogens in protecting females against oxidative stress, and the health-associated effects of melatonin. Finally, molecular biologists have found new age-associated genes by showing changes in longevity of genetically manipulated mice.

Melatonin counteracts alterations in oxidative metabolism and cell viability induced by intracellular calcium overload in human leucocytes: changes with age

Ageing is associated with an increased production of free radicals and alterations in the mechanisms of adaptation to oxidative stress. In fact, the free radical theory of ageing proposes that deleterious actions of free radicals are responsible for the functional deterioration associated with ageing. Moreover, a close relationship exists between calcium homeostasis and oxidative stress. The current work was aimed at proving that intracellular calcium overload induced by N-formyl-methionyl-leucyl-phenylalanine (FMLP) and/or thapsigargin leads to oxidative stress. We additionally examined the effect of melatonin on the levels of reactive oxygen species (ROS) and cell viability in human leucocytes collected from young (20-30-year-old) and elderly (65-75-year-old) individuals under both basal and oxidative stress-induced conditions. Treatments with 10 nM FMLP and/or 1 microM thapsigargin induced a transient increase in cytosolic free-calcium concentration ([Ca(2 + )](c)) in human leucocytes due to calcium release from internal stores, and led in turn to oxidative stress, as assessed by intracellular ROS measurement. Non-treated leucocytes from aged individuals exhibited higher ROS levels and lower rates of cell survival when compared to leucocytes from young individuals. Similar results were obtained in FMLP and/or thapsigargin-treated leucocytes from elderly individuals when compared to those from the young individuals. Melatonin treatment significantly reduced both hydrogen peroxide (H(2)O(2)) and superoxide anion levels, likely due to its free-radical scavenging properties, and enhanced leucocyte viability in both age groups. Therefore, melatonin may be a useful tool for the treatment of disease states and processes where an excessive production of oxidative damage occurs.

Melatonin as a potential tool against oxidative damage and apoptosis in ejaculated human spermatozoa

It is assumed somatic cells can die in the apoptotic, the autophagic, or the necrotic way; however, the mechanisms of sperm death are not clear. Here, ejaculated human spermatozoa were evaluated for apoptosis and reactive oxygen species production in the absence or presence of melatonin, and we concluded that melatonin reverses sperm apoptosis due to its free radical scavenging actions.