iMS-Bmal1-/- mice show evident signs of sarcopenia that are counteracted by exercise and melatonin therapies.

Sarcopenia is an age-related disease characterized by a reduction in muscle mass, strength, and function and, therefore, a deterioration in skeletal muscle health and frailty. Although the cause of sarcopenia is still unknown and, thus, there is no treatment, increasing evidence suggests that chronodisruption, particularly alterations in Bmal1 clock gene, can lead to those deficits culminating in sarcopenia. To gain insight into the cause and mechanism of sarcopenia and the protective effect of a therapeutic intervention with exercise and/or melatonin, the gastrocnemius muscles of male and female skeletal muscle-specific and inducible Bmal1 knockout mice (iMS-Bmal1-/- ) were examined by phenotypic tests and light and electron microscopy. Our results revealed a disruption of the normal activity/rest rhythm, a drop in skeletal muscle function and mass, and increased frailty in male and female iMS-Bmal1-/- animals compared to controls. A reduction in muscle fiber size and increased collagenous tissue were also detected, accompanied by reduced mitochondrial oxidative capacity and a compensatory shift towards a more oxidative fiber type. Electron microscopy further supports mitochondrial impairment in mutant mice. Melatonin and exercise ameliorated the damage caused by loss of Bmal1 in mutant mice, except for mitochondrial damage, which was worsened by the latter. Thus, iMS-Bmal1-/- mice let us to identify Bmal1 deficiency as the responsible for the appearance of sarcopenia in the gastrocnemius muscle. Moreover, the results support the exercise and melatonin as therapeutic tools to counteract sarcopenia, by a mechanism that does not require the presence of Bmal1.

Zebrafish as a Human Muscle Model for Studying Age-Dependent Sarcopenia and Frailty.

Currently, there is an increase in the aging of the population, which represents a risk factor for many diseases, including sarcopenia. Sarcopenia involves progressive loss of mass, strength, and function of the skeletal muscle. Some mechanisms include alterations in muscle structure, reduced regenerative capacity, oxidative stress, mitochondrial dysfunction, and inflammation. The zebrafish has emerged as a new model for studying skeletal muscle aging because of its numerous advantages, including histological and molecular similarity to human skeletal muscle. In this study, we used fish of 2, 10, 30, and 60 months of age. The older fish showed a higher frailty index with a value of 0.250 ± 0.000 because of reduced locomotor activity and alterations in biometric measurements. We observed changes in muscle structure with a decreased number of myocytes (0.031 myocytes/µm2 ± 0.004 at 60 months) and an increase in collagen with aging up to 15% ± 1.639 in the 60-month group, corresponding to alterations in the synthesis, degradation, and differentiation pathways. These changes were accompanied by mitochondrial alterations, such as a nearly 50% reduction in the number of intermyofibrillar mitochondria, 100% mitochondrial damage, and reduced mitochondrial dynamics. Overall, we demonstrated a similarity in the aging processes of muscle aging between zebrafish and mammals.

Inflamma-miRs Profile in Myelodysplastic Syndrome Patients.

Etiological factors involved in myelodysplastic syndrome (MDS) include immunologic, oxidative stress and inflammatory factors, among others, and these are targets for microRNAs (miRNs). Here, we evaluated whether some miRNs may affect tumor development comparing untreated and 5-azacitidine (5-AZA) MDS-treated patients. Peripheral blood samples were collected from 20 controls and 24 MDS patients, and selected miRNs related to redox balance and inflammation (inflamma-miRs), including miR-18a, miR-21, miR-34a and miR-146a, were isolated and measured by quantitative real-time polymerase chain reaction (qRTPCR). A differential expression profile of miRNs was detected in untreated MDS patients and the 5-AZA group. Inflammation increases miRNs and, specifically, miR-18a, miR-21 and miR-34a were significantly overexpressed in untreated MDS, compared to controls. However, we did not observe any miRN profile alteration during the progression of the disease. On the other hand, 5-AZA treatment tends to restore miRN expression levels. Relating to prognostic risk factors, high-risk MDS groups (high Revised International Prognostic Scoring System (IPSS-R), high cytogenetic risk, high molecular risk (HMR) mutations) tended to be related with higher expression levels of miR-18a and miR-34a. Higher miRN expression is correlated with lower glutathione peroxidase activity, while they are related with a higher profile of pro-inflammatory cytokines (IL-2, IL-6, IL-8, TNF-α). Although our study was limited by the low number of MDS patients included, we identified miRN deregulation involved in MDS development that could regulate redox sensors and inflammatory responses. Finally, 5-AZA treatment is related with lower miRN expression levels in MDS patients.

A phase II, single-center, double-blind, randomized placebo-controlled trial to explore the efficacy and safety of intravenous melatonin in surgical patients with severe sepsis admitted to the intensive care unit.

To determine whether IV melatonin therapy improves redox status and inflammatory responses in surgical patients with severe sepsis, a unicenter, phase II double-blind, randomized, placebo-controlled trial was carried out. The study included patients with severe sepsis marked by infectious systemic inflammatory response syndrome (SIRS), associated with organ dysfunction, hypoperfusion or hypotension requiring surgical intervention. IV melatonin at a daily dose of 60 mg, which was dissolved in 500 ml of 5% dextrose serum, was continuously administered to the patients for over 30 min starting on the day of the diagnoses during a 5-day period. A total of 14 patients received a placebo treatment and 15 melatonin doses. Redox status decreased in melatonin-treated patients during the 5 days of treatment as compared to the placebo-treated patients. Procalcitonin performed better in the melatonin group, whose neutrophil to lymphocyte ratio was also significantly reduced, resulting in an improved evolution of the disease. Moreover, hospital stays decreased by 19.60% from 26.64 days for the placebo group to 21.42 days for the melatonin group. The placebo group recorded five mortalities, as compared to three for the melatonin group. IV melatonin administration improved the course of the disease in surgical patients with severe sepsis, with no side effects. Additional studies with higher doses of melatonin and a long duration of therapy need to be carried out to assess its clinical use.

The NLRP3 inflammasome: contributions to inflammation-related diseases.

The NOD-like receptor protein 3 (NLRP3) inflammasome is a protein complex that regulates innate immune responses by activating caspase-1 and the inflammatory cytokines interleukin (IL)-1ß and IL-18. Multiple studies have demonstrated the importance of the NLRP3 inflammasome in the development of immune and inflammation-related diseases, including arthritis, Alzheimer's disease, inflammatory bowel disease, and other autoimmune and autoinflammatory diseases. This review first explains the activation and regulatory mechanism of the NLRP3 inflammasome. Secondly, we focus on the role of the NLRP3 inflammasome in various inflammation-related diseases. Finally, we look forward to new methods for targeting the NLRP3 inflammasome to treat inflammation-related diseases, and provide new ideas for clinical treatment.

Role of Melatonin in Cancer: Effect on Clock Genes.

The circadian clock is a regulatory system, with a periodicity of approximately 24 h, that generates rhythmic changes in many physiological processes. Increasing evidence links chronodisruption with aberrant functionality in clock gene expression, resulting in multiple diseases, including cancer. In this context, tumor cells have an altered circadian machinery compared to normal cells, which deregulates the cell cycle, repair mechanisms, energy metabolism and other processes. Melatonin is the main hormone produced by the pineal gland, whose production and secretion oscillates in accordance with the light:dark cycle. In addition, melatonin regulates the expression of clock genes, including those in cancer cells, which could play a key role in the numerous oncostatic effects of this hormone. This review aims to describe and clarify the role of clock genes in cancer, as well as the possible mechanisms of the action of melatonin through which it regulates the expression of the tumor's circadian machinery, in order to propose future anti-neoplastic clinical treatments.

The Relationship between Clock Genes, Sirtuin 1, and Mitochondrial Activity in Head and Neck Squamous Cell Cancer: Effects of Melatonin Treatment.

The circadian clock is a regulatory system, with a periodicity of approximately 24 h, which generates rhythmic changes in many physiological processes, including mitochondrial activity. Increasing evidence links chronodisruption with aberrant functionality in clock gene expression, resulting in multiple diseases such as cancer. Melatonin, whose production and secretion oscillates according to the light-dark cycle, is the principal regulator of clock gene expression. In addition, the oncostatic effects of melatonin correlate with an increase in mitochondrial activity. However, the direct links between circadian clock gene expression, mitochondrial activity, and the antiproliferative effects of melatonin in cancers, including head and neck squamous cell carcinoma (HNSCC), remain largely unknown. In this study, we analyzed the effects of melatonin on HNSCC cell lines (Cal-27 and SCC9), which were treated with 500 and 1000 µM melatonin. We found that the antiproliferative effect of melatonin is not mediated by the Bmal1 clock gene. Additionally, high doses of melatonin were observed to result in resynchronization of oscillatory circadian rhythm genes (Per2 and Sirt1). Surprisingly, the resynchronizing effect of melatonin on Per2 and Sirt1 did not produce alterations in the oscillation of mitochondrial respiratory activity. These results increase our understanding of the possible antiproliferative mechanisms in melatonin in the treatment of head and neck squamous cell carcinoma and suggest that its antiproliferative effects are independent of clock genes but are directly related to mitochondrial activity.

Salivary Melatonin Rhythm and Prostate Cancer: CAPLIFE Study.

PURPOSE: We analyzed the association between salivary melatonin rhythm and prostate cancer (PCa). MATERIALS AND METHODS: A total of 40 PCa cases and 41 controls from the CAPLIFE study were analyzed to determine the salivary melatonin rhythm through 6 saliva samples. Amplitude (maximum melatonin peak) was categorized as low or high using the cutoff point median of the controls. Acrophase (time of maximum melatonin peak) was classified as early or late using the same criteria. In addition, the following data were collected: characteristics related to sleep habits, and clinical and sociodemographic information. Melatonin rhythms were represented for cases and controls and analyzed according to urinary symptoms, tumor aggressiveness and tumor extension. Variations in melatonin levels were estimated using generalized estimating equations on the ln-transformed values. To estimate the association between amplitude, acrophase and PCa, adjusted odds ratio (aOR) and 95% CI were calculated using logistic regression models. RESULTS: The mean age was 67.0 years (SD 7.3) for cases and 67.5 (SD 5.5) for controls. Melatonin levels were always lower in PCa cases than in controls. On average, melatonin levels in cases were -64.0% (95% CI -73.4, -51.4) than controls. PCa cases had lower amplitude, 26.0 pg/ml (SD 27.8) vs 46.3 pg/ml (SD 28.2; p <0.001). A high amplitude was associated with a decreased risk of PCa, aOR=0.31 (95% CI 0.11, 0.86), while a late acrophase could be increased risk of PCa, aOR=2.36 (95% CI 0.88, 6.27). CONCLUSIONS: Patients with PCa always had lower melatonin levels than men without PCa, independent of urinary symptomatology or extension and aggressiveness of the tumor.

Melatonin drives apoptosis in head and neck cancer by increasing mitochondrial ROS generated via reverse electron transport.

The oncostatic effects of melatonin correlate with increased reactive oxygen species (ROS) levels, but how melatonin induces this ROS generation is unknown. In the present study, we aimed to elucidate the two seemingly opposing actions of melatonin regarding its relationship with free radicals. We analyzed the effects of melatonin on head and neck squamous cell carcinoma cell lines (Cal-27 and SCC-9), which were treated with 0.5 or 1 mM melatonin. We further examined the potential effects of melatonin to induce ROS and apoptosis in Cal-27 xenograft mice. Here we report that melatonin mediates apoptosis in head and neck cancer by driving mitochondrial reverse electron transport (RET) to induce ROS production. Melatonin-induced changes in tumoral metabolism led to increased mitochondrial activity, which, in turn, induced ROS-dependent mitochondrial uncoupling. Interestingly, mitochondrial complex inhibitors, including rotenone, abolished the ROS elevation indicating that melatonin increased ROS generation via RET. Melatonin also increased membrane potential and CoQ10 H2 /CoQ10 ratio to elevate mitochondrial ROS production, which are essential conditions for RET. We found that genetic manipulation of cancer cells with alternative oxidase, which transfers electrons from QH2 to oxygen, inhibited melatonin-induced ROS generation, and apoptosis. RET restored the melatonin-induced oncostatic effect, highlighting the importance of RET as the site of ROS production. These results illustrate that RET and ROS production are crucial factors in melatonin's effects in cancer cells and establish the dual effect of melatonin in protecting normal cells and inducing apoptosis in cancer cells.

The Zebrafish, an Outstanding Model for Biomedical Research in the Field of Melatonin and Human Diseases.

The zebrafish has become an excellent model for the study of human diseases because it offers many advantages over other vertebrate animal models. The pineal gland, as well as the biological clock and circadian rhythms, are highly conserved in zebrafish, and melatonin is produced in the pineal gland and in most organs and tissues of the body. Zebrafish have several copies of the clock genes and of aanat and asmt genes, the latter involved in melatonin synthesis. As in mammals, melatonin can act through its membrane receptors, as with zebrafish, and through mechanisms that are independent of receptors. Pineal melatonin regulates peripheral clocks and the circadian rhythms of the body, such as the sleep/wake rhythm, among others. Extrapineal melatonin functions include antioxidant activity, inducing the endogenous antioxidants enzymes, scavenging activity, removing free radicals, anti-inflammatory activity through the regulation of the NF-κB/NLRP3 inflammasome pathway, and a homeostatic role in mitochondria. In this review, we introduce the utility of zebrafish to analyze the mechanisms of action of melatonin. The data here presented showed that the zebrafish is a useful model to study human diseases and that melatonin exerts beneficial effects on many pathophysiological processes involved in these diseases.

Age and Chronodisruption in Mouse Heart: Effect of the NLRP3 Inflammasome and Melatonin Therapy.

Age and age-dependent inflammation are two main risk factors for cardiovascular diseases. Aging can also affect clock gene-related impairments such as chronodisruption and has been linked to a decline in melatonin synthesis and aggravation of the NF-κB/NLRP3 innate immune response known as inflammaging. The molecular drivers of these mechanisms remain unknown. This study investigated the impact of aging and NLRP3 expression on the cardiac circadian system, and the actions of melatonin as a potential therapy to restore daily rhythms by mitigating inflammaging. We analyzed the circadian expression and rhythmicity of clock genes in heart tissue of wild-type and NLRP3-knockout mice at 3, 12, and 24 months of age, with and without melatonin treatment. Our results support that aging, NLRP3 inflammasome, and melatonin affected the cardiac clock genes expression, except for Rev-erbα, which was not influenced by genotype. Aging caused small phase changes in Clock, loss of rhythmicity in Per2 and Rorα, and mesor dampening of Clock, Bmal1, and Per2. NLRP3 inflammasome influenced the acrophase of Clock, Per2, and Rorα. Melatonin restored the acrophase and the rhythm of clock genes affected by age or NLRP3 activation. The administration of melatonin re-established murine cardiac homeostasis by reversing age-associated chronodisruption. Altogether, these results highlight new findings about the effects aging and NLRP3 inflammasome have on clock genes in cardiac tissue, pointing to continuous melatonin as a promising therapy to placate inflammaging and restore circadian rhythm in heart muscle. Additionally, light microscopy analysis showed age-related morphological impairments in cardiomyocytes, which were less severe in mice lacking NLRP3. Melatonin supplementation preserved the structure of cardiac muscle fibers in all experimental groups.

Impact of sound levels on physiological and consciousness state of cardiovascular patients.

BACKGROUND: Patients treated in intensive care units (ICUs) experience life-threatening medical conditions but some external factors in ICUs do not help or even adversely affect and complicate their evolution. Among others, such factors include noise pollution due to alarms and medical clinical equipment, as well as the activities of the health care personnel themselves. AIM: This study aimed to evaluate the influence of elevated sound levels on physiological variables and the consciousness state of patients treated in a cardiovascular area in an ICU. DESIGN: A longitudinal study with several observations was carried out during 1 month in the cardiovascular area of an ICU of a third-level hospital in southern Spain. METHODS: Sound levels were monitored in different work shifts and patients' physiological data and consciousness status were recorded. Generalized additive mixed models (GAMMs) were developed to detect the variability of the sound levels together with the vital parameters of the patients in the ICU. RESULTS: Thirty-eight patients were included. The mean sound level was 54.09 dBA. The GAMM sound levels analysis showed a significant increase in sound levels from 4:30 p.m. to 8:00 p.m. (1.83 dBA; P < .001) and 8:00 p.m. to 11:30 p.m. (3.06 dBA; P < .001). An increase in heart rate (3.66 bpm; P < .001), respiratory rate (2.62 rpm; P < .001) and the Glasgow Coma Scale (0.50 units; P = .002) was detected during the 4:30 p.m.-8:30 p.m. CONCLUSIONS: Elevated sound levels in cardiovascular ICUs seem to influence positively the physiological and consciousness status of patients. Given the importance of the findings for patient safety, future intervention studies are recommended. RELEVANCE TO CLINICAL PRACTICE: The finding of this study could translate into structural changes in ICU facilities, as well as the development of clinical practice guidelines that influence the behaviour of health care professionals.

Clinical trial to test the efficacy of melatonin in COVID-19.

The pharmacological properties of melatonin are well known. However, there is noticeable the lack of clinical trials that confirm the efficacy, security, absence of side effects in the short and long term, and the effective doses of melatonin. This point is especially important in diseases with high morbidity and mortality including COVID-19. There is not treatment for COVID-19, and several anti-inflammatory and antiviral molecules are being tested, and different vaccines are in preparation. Although the SARS-CoV-2 pandemic is apparently improving, it is expected new resurges next fall. Thus, looking for an effective treatment of COVID-19 is mandatory. Melatonin has significant anti-inflammatory, antioxidant, and mitochondrial protective effects, and its efficacy has been demonstrated in multiple experimental models of disease and in a clinical trial in sepsis. Because COVID-19 courses with a severe septic response, multiple reviews proposing melatonin as a treatment for COVID-19 have been published. Nevertheless, there is a lack of experimental and clinical data on the use of melatonin on SARS-CoV-2 infection. Accordingly, we designed a clinical trial with an injectable formulation of melatonin for intravenous perfusion in ICU patients suffering from COVID-19 that has been just approved by the Spanish Agency of Medicines and Medical Devices (AEMPS). The trial will allow by the first time understand the doses and efficacy of melatonin against COVID-19.

Retinoid-related orphan nuclear receptor alpha (RORα)-deficient mice display morphological testicular defects.

The role of retinoid-related orphan receptor, one of the transcription factors reported in testis, in testicular function is unclear, so this study was performed to evaluate the qualitative and quantitative changes in the testicular structure of RORα-deficient mice using light-, electron-microscopy, and immunohistochemistry. Among the most striking alterations observed in the testis of the mutant mice were hypospermatogenesis, marked reduction in volume proportions of interstitial tissues and number of Leydig cells, significant decrease in the diameter of seminiferous tubules and height of their epithelium, vacuolation in the epithelium of the seminiferous tubules with occurrence of mast cells, appearance of delay spermiation signs, and changes in sperm morphology. Moreover, the testis of mutant mice showed symplasts, in addition to appearance of multinucleated giant bromophenol-positive cells. ATPase activity was limited to spermatogonia and some primary spermatocytes, with higher alkaline phosphatase expression. Stronger vimentin reaction was immunolocalized to spermatogonia, spermatids, Leydig cells, and Sertoli cells. The expression of CD117 (C-kit, stem cell growth factor receptor) was limited to spermatogonia, primary spermatocytes, and Leydig cells. Seminiferous tubules showed overexpression of vascular endothelial growth factor (VEGF). Transmission electron microscopy examination of the mutant mice revealed abnormal Sertoli cells, hypertrophied spermatogonia, spermatocytes with degenerated mitochondria, and incompletely developed sperms. In conclusion, RORα is one of the essential proteins that regulate testicular structure.

Targeting NLRP3 (Nucleotide-Binding Domain, Leucine-Rich-Containing Family, Pyrin Domain-Containing-3) Inflammasome in Cardiovascular Disorders.

Inflammation is an important innate immune response to infection or tissue damage. Inflammasomes are involved in the onset and development of inflammation. The NLRP3 (nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3) inflammasome is the best-characterized inflammasome. Recent evidence has indicated the importance of the NLRP3 inflammasome in the pathophysiology of cardiovascular disorders. To further understand the roles of the NLRP3 inflammasome in the cardiovascular system, we provide a comprehensive overview and discuss the remaining questions. First, a summary of NLRP3 inflammasome in the cardiovascular system is introduced. Then, the associations between NLRP3 inflammasome and cardiovascular disorders are presented. Finally, we discuss existing problems and potential directions with this issue. The information compiled here summarizes recent progress, thus potentially aiding in the understanding of the NLRP3 inflammasome in cardiovascular disorders, designing experimental and clinical research about the NLRP3 inflammasome, and promoting therapeutics for cardiovascular disorders.

Protective Effects of Melatonin on the Skin: Future Perspectives.

When exposed to hostile environments such as radiation, physical injuries, chemicals, pollution, and microorganisms, the skin requires protective chemical molecules and pathways. Melatonin, a highly conserved ancient molecule, plays a crucial role in the maintenance of skin. As human skin has functional melatonin receptors and also acts as a complete system that is capable of producing and regulating melatonin synthesis, melatonin is a promising candidate for its maintenance and protection. Below, we review the studies of new metabolic pathways involved in the protective functions of melatonin in dermal cells. We also discuss the advantages of the topical use of melatonin for therapeutic purposes and skin protection. In our view, endogenous intracutaneous melatonin production, together with topically-applied exogenous melatonin and its metabolites, represent two of the most potent defense systems against external damage to the skin.

Combination of melatonin and rapamycin for head and neck cancer therapy: Suppression of AKT/mTOR pathway activation, and activation of mitophagy and apoptosis via mitochondrial function regulation.

Head and neck squamous cell carcinoma (HNSCC) clearly involves activation of the Akt mammalian target of rapamycin (mTOR) signalling pathway. However, the effectiveness of treatment with the mTOR inhibitor rapamycin is often limited by chemoresistance. Melatonin suppresses neoplastic growth via different mechanisms in a variety of tumours. In this study, we aimed to elucidate the effects of melatonin on rapamycin-induced HNSCC cell death and to identify potential cross-talk pathways. We analysed the dose-dependent effects of melatonin in rapamycin-treated HNSCC cell lines (Cal-27 and SCC-9). These cells were treated with 0.1, 0.5 or 1 mmol/L melatonin combined with 20 nM rapamycin. We further examined the potential synergistic effects of melatonin with rapamycin in Cal-27 xenograft mice. Relationships between inhibition of the mTOR pathway, reactive oxygen species (ROS), and apoptosis and mitophagy reportedly increased the cytotoxic effects of rapamycin in HNSCC. Our results demonstrated that combined treatment with rapamycin and melatonin blocked the negative feedback loop from the specific downstream effector of mTOR activation S6K1 to Akt signalling, which decreased cell viability, proliferation and clonogenic capacity. Interestingly, combined treatment with rapamycin and melatonin-induced changes in mitochondrial function, which were associated with increased ROS production, increasing apoptosis and mitophagy. This led to increase cell death and cellular differentiation. Our data further indicated that melatonin administration reduced rapamycin-associated toxicity to healthy cells. Overall, our findings suggested that melatonin could be used as an adjuvant agent with rapamycin, improving effectiveness while minimizing its side effects.

Melatonin, clock genes and mitochondria in sepsis.

After the characterization of the central pacemaker in the suprachiasmatic nucleus, the expression of clock genes was identified in several peripheral tissues including the immune system. The hierarchical control from the central clock to peripheral clocks extends to other functions including endocrine, metabolic, immune, and mitochondrial responses. Increasing evidence links the disruption of the clock genes expression with multiple diseases and aging. Chronodisruption is associated with alterations of the immune system, immunosenescence, impairment of energy metabolism, and reduction of pineal and extrapineal melatonin production. Regarding sepsis, a condition coursing with an exaggerated response of innate immunity, experimental and clinical data showed an alteration of circadian rhythms that reflects the loss of the normal oscillation of the clock. Moreover, recent data point to that some mediators of the immune system affects the normal function of the clock. Under specific conditions, this control disappears reactivating the immune response. So, it seems that clock gene disruption favors the innate immune response, which in turn induces the expression of proinflammatory mediators, causing a further alteration of the clock. Here, the clock control of the mitochondrial function turns off, leading to a bioenergetic decay and formation of reactive oxygen species that, in turn, activate the inflammasome. This arm of the innate immunity is responsible for the huge increase of interleukin-1ß and entrance into a vicious cycle that could lead to the death of the patient. The broken clock is recovered by melatonin administration, that is accompanied by the normalization of the innate immunity and mitochondrial homeostasis. Thus, this review emphasizes the connection between clock genes, innate immunity and mitochondria in health and sepsis, and the role of melatonin to maintain clock homeostasis.

Melatonin Mitigates Mitochondrial Meltdown: Interactions with SIRT3.

Melatonin exhibits extraordinary diversity in terms of its functions and distribution. When discovered, it was thought to be uniquely of pineal gland origin. Subsequently, melatonin synthesis was identified in a variety of organs and recently it was shown to be produced in the mitochondria. Since mitochondria exist in every cell, with a few exceptions, it means that every vertebrate, invertebrate, and plant cell produces melatonin. The mitochondrial synthesis of melatonin is not photoperiod-dependent, but it may be inducible under conditions of stress. Mitochondria-produced melatonin is not released into the systemic circulation, but rather is used primarily in its cell of origin. Melatonin's functions in the mitochondria are highly diverse, not unlike those of sirtuin 3 (SIRT3). SIRT3 is an NAD+-dependent deacetylase which regulates, among many functions, the redox state of the mitochondria. Recent data proves that melatonin and SIRT3 post-translationally collaborate in regulating free radical generation and removal from mitochondria. Since melatonin and SIRT3 have cohabitated in the mitochondria for many eons, we predict that these molecules interact in many other ways to control mitochondrial physiology. It is predicted that these mutual functions will be intensely investigated in the next decade and importantly, we assume that the findings will have significant applications for preventing/delaying some age-related diseases and aging itself.

Melatonin administration to wild-type mice and nontreated NLRP3 mutant mice share similar inhibition of the inflammatory response during sepsis.

The NLRP3 inflammasome is involved in the innate immune response during inflammation. Moreover, melatonin blunts the NF-κB/NLRP3 connection during sepsis. Thus, we compared the roles of the NLRP3 inflammasome and/or melatonin treatment in the septic response of wild-type and NLRP3-/- mice. Mouse myocardial tissue was used for this purpose. The nuclear turnover of NF-κB was enhanced during sepsis, with an increase in TNFα, iNOS, and pro-IL-1ß. The lack of inflammasome in NLRP3-/- mice significantly reduced that response and blunted IL-1ß maturation due to the lack of caspase-1. Clock and Bmal1 did not change in both mouse strains, enhancing Chrono expression in mutants. RORα, which positively regulates Bmal1, was enhanced at a similar extend in both mouse strains, whereas the expression of the Bmal1 repressor, Rev-Erbα, increased in WT but was depressed in NLRP3-/- mice. Nampt, transcriptionally controlled by Bmal1, increased in WT mice together with Sirt1, whereas they remained unchanged in NLRP3-/- mice. Melatonin treatment reduced the septic response in a comparable manner as did the lack of NLRP3, but unlike the latter, it normalized the clock genes turnover through the induction of RORα and repression of Rev-Erbα and Per2, leading to enhanced Nampt and Sirt1. The lack of NLRP3 inflammasome converts sepsis to a moderate inflammatory disease and identifies NLRP3 as a main target for the treatment of sepsis. The efficacy of melatonin in counteracting the NLRP3 inflammasome activation further confirms the indoleamine as a useful therapeutic drug against this serious condition.