Melatonin decreases human adipose tissue insulin sensitivity.

Melatonin is a pineal hormone that modulates the circadian system and exerts soporific and phase-shifting effects. It is also involved in many other physiological processes, such as those implicated in cardiovascular, endocrine, immune, and metabolic functions. However, the role of melatonin in glucose metabolism remains contradictory, and its action on human adipose tissue (AT) explants has not been demonstrated. We aimed to assess whether melatonin (a pharmacological dose) influences insulin sensitivity in human AT. This will help better understand melatonin administration's effect on glucose metabolism. Abdominal AT (subcutaneous and visceral) biopsies were obtained from 19 participants with severe obesity (age: 42.84 ± 12.48 years; body mass index: 43.14 ± 8.26 kg/m2) who underwent a laparoscopic gastric bypass. AT biopsies were exposed to four different treatments: control (C), insulin alone (I) (10 nM), melatonin alone (M) (5000 pg/mL), and insulin plus melatonin combined (I + M). All four conditions were repeated in both subcutaneous and visceral AT, and all were performed in the morning at 8 a.m. (n = 19) and the evening at 8 p.m. (in a subsample of n = 12). We used western blot analysis to determine insulin signaling (using the pAKT/tAKT ratio). Furthermore, RNAseq analyses were performed to better understand the metabolic pathways involved in the effect of melatonin on insulin signaling. As expected, insulin treatment (I) increased the pAKT/tAKT ratio compared with control (p < .0001). Furthermore, the addition of melatonin (I + M) resulted in a decrease in insulin signaling as compared with insulin alone (I); this effect was significant only during the evening time (not in the morning time). Further, RNAseq analyses in visceral AT during the evening condition (at 8 p.m.) showed that melatonin resulted in a prompt transcriptome response (around 1 h after melatonin addition), particularly by downregulating the insulin signaling pathway. Our results show that melatonin reduces insulin sensitivity in human AT during the evening. These results may partly explain the previous studies showing a decrease in glucose tolerance after oral melatonin administration in the evening or when eating late when endogenous melatonin is present.

Disruption of central and peripheral circadian clocks and circadian controlled estrogen receptor rhythms in night shift nurses in working environments.

Chronic disruption of circadian rhythms by night shift work is associated with an increased breast cancer risk. However, little is known about the impact of night shift on peripheral circadian genes (CGs) and circadian-controlled genes (CCGs) associated with breast cancer. Hence, we assessed central clock markers (melatonin and cortisol) in plasma, and peripheral CGs (PER1, PER2, PER3, and BMAL1) and CCGs (ESR1 and ESR2) in peripheral blood mononuclear cells (PBMCs). In day shift nurses (n = 12), 24-h rhythms of cortisol and melatonin were aligned with day shift-oriented light/dark schedules. The mRNA expression of PER2, PER3, BMAL1, and ESR2 showed 24-h rhythms with peak values in the morning. In contrast, night shift nurses (n = 10) lost 24-h rhythmicity of cortisol with a suppressed morning surge but retained normal rhythmic patterns of melatonin, leading to misalignment between cortisol and melatonin. Moreover, night shift nurses showed disruption of rhythmic expressions of PER2, PER3, BMAL1, and ESR2 genes, resulting in an impaired inverse correlation between PER2 and BMAL1 compared to day shift nurses. The observed trends of disrupted circadian markers were recapitulated in additional day (n = 20) and night (n = 19) shift nurses by measurement at early night and midnight time points. Taken together, this study demonstrated the misalignment of cortisol and melatonin, associated disruption of PER2 and ESR2 circadian expressions, and internal misalignment in peripheral circadian network in night shift nurses. Morning plasma cortisol and PER2, BMAL1, and ESR2 expressions in PBMCs may therefore be useful biomarkers of circadian disruption in shift workers.

Assessment of retinal and choroidal microvasculature in night shift medical workers by OCT angiography.

This study evaluated retinal and choroidal microvascular changes in night shift medical workers and its correlation with melatonin level. Night shift medical workers (group A, 25 workers) and non-night shift workers (group B, 25 workers) were recruited. The images of macula and optic nerve head were obtained by swept-source OCT-angiography. Vessel density of retina, choriocapillaris (CC), choriocapillaris flow deficit (CC FD), choroidal thickness (CT) and choroidal vascularity index (CVI) were measured. 6-sulfatoxymelatonin concentration was analyzed from the morning urine. CC FD and CVI were significantly decreased and CT was significantly increased in group A (all P < 0.05). 6-sulfatoxymelatonin concentration was significantly lower in group A (P < 0.05), which was significantly positively correlated with CC FD size (r = 0.318, P = 0.024) and CVI of the most regions (maximum r-value was 0.482, P < 0.001), and was significantly negatively associated with CT of all regions (maximum r-value was - 0.477, P < 0.001). In night shift medical workers, the reduction of melatonin was significantly correlated with CT thickening, CVI reduction and CC FD reduction, which suggested that they might have a higher risk of eye diseases. CC FD could be a sensitive and accurate indicator to reflect CC perfusion.

In Vitro Effects of Fentanyl on Aortic Viscoelasticity in a Rat Model of Melatonin Deficiency.

Melatonin influences arterial biomechanics, and its absence could cause remodeling of the arterial wall, leading to increased stiffness. Direct effects of fentanyl on the aortic wall have also been observed previously. This study aimed to evaluate in vitro the effects of fentanyl on aortic viscoelasticity in a rat model of melatonin deficiency and to test the hypothesis that melatonin deficiency leads to increased arterial wall stiffness. The viscoelasticity was estimated in strip preparations from pinealectomized (pin, melatonin deficiency) and sham-operated (sham, normal melatonin) adult rats using the forced oscillations method. In the untreated aortic wall pin, the viscoelasticity was not significantly altered. However, combined with 10-9 M fentanyl, the pin increased the natural frequency (f0) and modulus of elasticity (E') compared to the sham-operated. Independently, fentanyl treatment decreased f0 and E' compared separately to untreated sham and pin preparations. The effects of fentanyl were neither dose-dependent nor affected by naloxone, suggesting a non-opioid mechanism. Furthermore, an independent effect of naloxone was also detected in the normal rat aortic wall, resulting in reduced E'. Additional studies are needed that may improve the clinical decisions for pain management and anesthesia for certain patients with co-occurring chronic low levels of blood plasma melatonin and some diseases.

Zygotic Exposure to Venlafaxine Disrupts the Circadian Locomotor Activity Behaviour in Zebrafish Larvae.

The antidepressant venlafaxine, a selective serotonin and norepinephrine reuptake inhibitor, is commonly prescribed to treat major depressive disorder and is found at high concentrations in the aquatic environment. Concerns have been raised related to the health of aquatic organisms in response to this nontargeted pharmaceutical exposure. For instance, we previously demonstrated that exposure to venlafaxine perturbs neurodevelopment, leading to behavioural alterations in zebrafish (Danio rerio). We also observed disruption in serotonin expression in the pineal and raphe, regions critical in regulating circadian rhythms, leading us to hypothesize that zygotic exposure to venlafaxine disrupts the circadian locomotor rhythm in larval zebrafish. To test this, we microinjected zebrafish embryos with venlafaxine (1 or 10 ng) and recorded the locomotor activity in 5-day-old larvae over a 24-h period. Venlafaxine deposition reduced larval locomotor activity during the light phase, but not during the dark phase of the diurnal cycle. The melatonin levels were higher in the dark compared to during the light photoperiod and this was not affected by embryonic venlafaxine deposition. Venlafaxine exposure also did not affect the transcript abundance of clock genes, including clock1a, bmal2, cry1a and per2, which showed a clear day/night rhythmicity. A notable finding was that exposure to luzindole, a melatonin receptor antagonist, decreased the locomotor activity in the control group in light, whereas the activity was higher in larvae raised from the venlafaxine-deposited embryos. Overall, zygotic exposure to venlafaxine disrupts the locomotor activity of larval zebrafish fish during the day, demonstrating the capacity of antidepressants to disrupt the circadian rhythms in behaviour. Our results suggest that disruption in melatonin signalling may be playing a role in the venlafaxine impact on circadian behaviour, but further investigation is required to elucidate the possible mechanisms in larval zebrafish.

Optimizing the Time and Dose of Melatonin as a Sleep-Promoting Drug: A Systematic Review of Randomized Controlled Trials and Dose-Response Meta-Analysis.

Previous studies have reported inconsistent results about exogenous melatonin's sleep-promoting effects. A possible explanation relies on the heterogeneity in administration schedule and dose, which might be accountable for differences in treatment efficacy. In this paper, we undertook a systematic review and meta-analysis of double-blind, randomized controlled trials performed on patients with insomnia and healthy volunteers, evaluating the effect of melatonin administration on sleep-related parameters. The standardized mean difference between treatment and placebo groups in terms of sleep onset latency and total sleep time were used as outcomes. Dose-response and meta-regression models were estimated to explore how time of administration, dose, and other treatment-related parameters might affect exogenous melatonin's efficacy. We included 26 randomized controlled trials published between 1987 and 2020, for a total of 1689 observations. Dose-response meta-analysis showed that melatonin gradually reduces sleep onset latency and increases total sleep time, peaking at 4 mg/day. Meta-regression models showed that insomnia status (ß = 0.50, p < 0.001) and time between treatment administration and the sleep episode (ß = -0.16, p = 0.023) were significant predictors of sleep onset latency, while the time of day (ß = -0.086, p < 0.01) was the only significant predictor of total sleep time. Our results suggest that advancing the timing of administration (3 h before the desired bedtime) and increasing the administered dose (4 mg/day), as compared to the exogenous melatonin schedule most used in clinical practice (2 mg 30 min before the desired bedtime), might optimize the efficacy of exogenous melatonin in promoting sleep.

Comparison between melatonin versus melatonin and photobiomodulation versus photobiomodulation in the treatment of Alopecia X in German Spitz dogs: Clinical, randomized, double-blind, parallel, non-inferiority protocol.

Canine Alopecia X is a non-inflammatory hair loss disorder of unknown etiology that predominantly affects German Spitz dogs. Treatment modalities include hormone and/or melatonin supplementation and low trauma microneedling. Melatonin influences hair growth and pigmentation in several species and presents a low risk of adverse effects when used in dogs with Alopecia X. Photobiomodulation (PBM) is frequently used in human androgenetic alopecia and alopecia areata; despite this, PBM remains unexplored in canine Alopecia X. To address this knowledge gap, sixty dogs of both sexes will be randomly assigned to three groups: (i) melatonin only group (3 mg/Kg, n = 20); (ii) PBM only group (diode laser, wavelength 660nm, 100mw power, with 3 J/point, 2 sessions/week for 3 months, n = 20); (ii) PBM + melatonin group (n = 20). The objective is to determine the potential of PBM alone or in conjunction with melatonin supplementation in promoting hair regrowth (hair density and diameter) by means of dermatoscopy and planimetry over a period of 90 days.

The impact of melatonin on postoperative delirium in geriatric patients after colorectal surgery: a randomized placebo-controlled trial.

BACKGROUND: The current study was designed to evaluate the role of prophylactic melatonin administration in reducing delirium occurrence in elderly patients undergoing colorectal cancer surgeries. METHODS: One hundred patients of both genders undergoing elective colorectal cancer surgeries under general anesthesia were randomly allocated into two equal groups. A treatment group of patients (Melatonin group) received five mg of melatonin the night before surgery, twelve hours before the scheduled surgery time, and an additional five mg of melatonin two hours before surgery. The control group of patients received placebo tablets at the same time points. Delirium score, sedation score, pain score, hemodynamics, oxygen saturation, and blood requirements were recorded. RESULTS: Twenty-eight patients (56%) in the control group versus 18 (36%) in the melatonin group developed delirium (P=0.045), OR=2.26, 95% CI: 1.013-5.05. Five patients (18%) in the control group versus six (33%) in the melatonin group developed delirium on discharge from the recovery room (P=0.749), OR=1.22, 95% CI: 0.34-4.31, while 23 patients (82%) in the control group versus 12 (66%) in the melatonin group developed delirium six hours postoperative (P=0.021), OR=1.705, 95% CI: 1.02-2.81 with higher nursing delirium screening score in the control group 2 (1, 4) versus 1 (0, 2) in the melatonin group (P=0.002), 95% CI: 1.77-2.71. CONCLUSIONS: The prophylactic administration of melatonin may decrease the incidence of postoperative delirium in elderly patients undergoing colorectal surgeries under general anesthesia.

In vitro and in silico analyses reveal the toxicity of metolachlor to grass carp hepatocytes and the antagonism of melatonin.

Due to the widespread use of metolachlor (MET), the accumulation of MET and its metabolites in the environment has brought serious health problems to aquatic organisms. At present, the toxicity of MET on the physiological metabolism of aquatic animals mainly focused on the role of enzymes. There is still a lack of research on the molecular mechanisms of MET hepatotoxicity, especially on antagonizing MET toxicity. Therefore, this study focuses on grass carp hepatocytes (L8824 cells) closely related to toxin accumulation. By establishing a MET exposed L8824 cells model, it is determined that MET exposure induces pyrolytic inflammation of L8824 cells. Subsequent mechanistic studies found that MET exposure induces pyroptosis in L8824 cells through mitochondrial dysfunction, and siCaspase-1 inhibits the MET induced ROS production, suggesting a regulation of ROS-NLRP3- Caspase-1 pyroptotic inflammation cycling center in MET induced injury to L8824 cells. Molecular docking revealed a strong binding energy between melatonin (MT) and Caspase-1. Finally, a model of L8824 cells with MT intervention in MET exposure was established. MT can antagonize the pyroptosis induced by MET exposure in L8824 cells by targeting Caspase-1, thereby restoring mitochondrial function and inhibiting the ROS-pyroptosis cycle. This study discovered targets and mechanisms of MT regulating pyroptosis in MET exposed-L8824 cells, and the results are helpful to provide new targets for the design of MET antidotes.

Protective effect of melatonin on imidacloprid-induced pyroptosis and ferroptosis by mediating peptidoglycan in the gut of the common carp (Cyprinus carpio).

Imidacloprid (IMI) is a contaminant widespread in surface water, causing serious intestinal damage in the common carp. Melatonin (MT), an endogenous indoleamine hormone, plays a crucial role in mitigating pesticide-induced toxicity. Our previous research has demonstrated that MT effectively reduces the production of intestinal microbial-derived signal peptidoglycan (PGN) induced by IMI, thereby alleviating intestinal tight junction injuries in the common carp. In this study, we performed a transcriptomic analysis to explore the effect of MT on the IMI exposure-induced gut damage of the common carp. The results elucidated that the ferroptosis, mitogen-activated protein kinases (MAPKs), and nucleotide oligomerization domain (NOD)-like signaling pathways were significantly associated with IMI exposure and MT treatment. Meanwhile, the exposure to IMI resulted in the formation of pyroptotic bodies and distinct morphological features of ferroptosis, both mitigated with the addition of MT. Immunofluorescence double staining demonstrated that MT abolished the elevated expression of NOD-like receptor thermal protein domain associated protein 3 (NLRP3) and Gasdermin D (GSDMD) induced by IMI, as well as reduced expression of ferritin heavy chains (FTH) and glutathione peroxidase 4 (GPX4) in gut tissues. Subsequently, we found that the exposure to IMI or PGN enhanced the expression of toll-like receptors (TLR) 2 (a direct recognition receptor of PGN) triggering the P38MAPK signaling pathway, thereby aggravating the process of pyroptosis and ferroptosis of cell models. The addition of MT or SB203580 (a P38MAPK inhibitor) significantly reduced pyroptotic cells, and also decreased iron accumulation. Consequently, these results indicate that MT alleviates IMI-induced pyroptosis and ferroptosis in the gut of the common carp through the PGN/TLR2/P38MAPK pathway.

[Advances in the study of the role and mechanisms of endogenous hormones in the development of myopia].

With the increasing prevalence of myopia among adolescents, the pathogenesis of this condition has garnered significant attention. Studies have discovered the expression of various hormone receptors in ocular tissues of both animals and humans. Additionally, changes in hormone levels accompany the development of myopia, although the exact relationships remain inconclusive. This article reviews the potential influences and mechanisms of action of endogenous hormones such as melatonin, serotonin, insulin, glucagon, sex hormones, vitamin D, and prostaglandins in ocular tissues including the retina, choroid, and sclera. It elaborates on the relationship between fluctuations in these hormone levels and the progression of myopia, aiming to provide guidance for exploring targets for myopia prevention and control.

Potential of exogenous melatonin administration to mitigate heat stress induce pathophysiology of chicken.

Melatonin (MT) is an amine hormone secreted by the body that has antioxidant and anti-inflammatory properties. The aim of this study was to investigate pathophysiological protection of MT in heat-stressed chickens. By modelling heat-stressed chickens and treating them with MT. After 21 days of administration, serum antioxidant enzymes, biochemical indices, inflammatory cytokine and heat-stress indices were detected, along with cardiopulmonary function indices and histological observations in chickens. The results show heat-stress induced a decrease (P < 0.05) in body weight and an increase in body temperature, which was reversed after MT intervention. Treatment with MT inhibited (P < 0.05) the secretion of pro-inflammatory factors interleukin-1ß, interleukin-6, tumor necrosis factor α, serum heat shock protein 70, corticosterone, and elevated (P < 0.05) the levels of biochemical factors total protein, albumin, globulin, and increased (P < 0.05) the activities of antioxidant enzymes superoxide dismutase, glutathione peroxidase and catalase in chicken serum caused by heat stress, and the best effect was observed with the medium dose of MT. The heat-stress caused cardiac atrophy and pulmonary congestion, decreased (P < 0.05) the cardiac function indices creatine kinase isoenzyme, cardiac troponin I, angiotensin receptor I, creatine kinase and lung function indices myeloperoxidase, angiotensin-II, heat shock factor I, and increased (P < 0.05) the lung vascular endothelial growth factor II. Sections of the heart and lungs after administration of MT were observed to be more complete with more normal tissue indices. At the same time, compared with heat stress, heart and lung function indices of grade chickens after MT administration were significantly (P < 0.05)reduced and tended to normal levels, and the best effect was observed in the medium-dose MT. In conclusion, heat stress can cause pathophysiological damage in chickens, and 1 mg/kg/d of exogenous melatonin can attenuate this adverse effect.

Melatonin activates Nrf2/HO-1 signalling pathway to antagonizes oxidative stress-induced injury via melatonin receptor 1 (MT1) in cryopreserved mice ovarian tissue.

Our previous research has shown that melatonin (MLT) can reduce cryopreserved ovarian damage in mice. Yet, the molecular mechanism of MLT protection is still unclear. Some studies have shown that melatonin receptor 1 (MT1) is very important for animal reproductive system. To evaluate whether MLT exerts its protective effect on cryopreserved mice ovarian tissue via MT1, we added antagonist of MT1/MT2 (Luzindor) or antagonist of MT2 (4P-PDOT) to the freezing solution, followed by cryopreservation and thawing of ovarian tissue. The levels of total superoxide dismutase (T-SOD), catalase (CAT), nitric oxide (NO) and malondialdehyde (MDA) were detected. Besides, by using RT-PCR and Western blotting, the expression of Bcl-2, Bax and Nrf2/HO-1 signalling pathway-related proteins was detected. These findings demonstrated that compared with the melatonin group, the addition of Luzindor increased apoptosis, NO and MDA activities, decreased CAT and T-SOD activities and inhibited Nrf2/HO-1 signalling pathway. In conclusion, melatonin can play a protective role in cryopreserved ovarian tissue of mice through MT1 receptor.

Comparison of the efficacy of royal jelly and melatonin combinations in experimentally induced wounds in geriatric and young mice.

BACKGROUND: Wound healing involves the repair of skin and other soft tissues after an injury. Royal jelly, a product of bees, possesses antioxidant, anti-inflammatory, antibacterial, and antiviral properties. Melatonin, a circadian indoleamine, is produced in the pineal gland and other organs. This study explores the effects of melatonin and royal jelly, both individually and combined, on wound healing in geriatric and young mice. METHODS: The study includes 90 Balb/C mice divided into ten groups to assess the effects of royal jelly and melatonin on wound healing. Royal jelly was applied topically at a concentration of 300 mg/kg. Melatonin was formulated in a vaseline-based pomade at a concentration of 5 mg/kg. The substances were applied either separately or in combination to wounds created on the mice. RESULTS: Both substances significantly enhanced wound healing at a macroscopic level in both age groups. Melatonin was found to be more effective during the initial wound formation process, whereas royal jelly was more beneficial during the granulation phase. However, significant results at a histopathological level were observed only in geriatric animals. CONCLUSION: The findings suggest a potential new therapeutic approach to enhance wound healing, particularly in elderly individuals. However, these findings need to be supported through further research and clinical trials.

Melatonin mediated tolerance to benzalkonium chloride phytotoxicity through improved growth, photochemical reactions, and antioxidant system in wild-type and snat2 mutant Arabidopsis lines.

Melatonin (Mel) is a phytohormone that plays a crucial role in various plant processes, including stress response. Despite numerous studies on the role of Mel in stress resistance, its significance in plants exposed to benzalkonium chloride (BAC) pollution remains unexplored. BAC, a common antiseptic, poses a threat to terrestrial plants due to its widespread use and inefficient removal, leading to elevated concentrations in the environment. This study investigated the impact of BAC (0.5 mg L-1) pollution on wild-type Col-0 and snat2 knockout mutant Arabidopsis lines, revealing reduced growth, altered water relations, and gas exchange parameters. On the other hand, exogenous Mel (100 µM) treatments mitigated BAC-induced phytotoxicity and increased the growth rate by 1.8-fold in Col-0 and 2-fold in snat2 plants. snat2 mutant seedlings had a suppressed carbon assimilation rate (A) under normal conditions, but BAC contamination led to further A repression by 71% and 48% in Col-0 and snat2 leaves, respectively. However, Mel treatment on stressed plants was successful in improving Fv/Fm and increased the total photosynthesis efficiency by regulating photochemical reactions. Excessive H2O2 accumulation in the guard cells of plants exposed to BAC pollution was detected by confocal microscopy. Mel treatments triggered almost all antioxidant enzyme activities (except POX) in both Arabidopsis lines under stress. This enhanced antioxidant activity, facilitated by foliar Mel application, contributed to the alleviation of oxidative damage, regulation of photosynthesis reactions, and promotion of plant growth in Arabidopsis. In addition to corroborating results observed in many agricultural plants regarding the development of tolerance to environmental stresses, this study provides novel insights into the action mechanisms of Mel under the emerging pollutant benzalkonium chloride.

Melatonin-Regulated Chaperone Binding Protein Plays a Key Role in Cadmium Stress Tolerance in Rice, Revealed by the Functional Characterization of a Novel Serotonin N-Acetyltransferase 3 (SNAT3) in Rice.

The study of the mechanisms by which melatonin protects against cadmium (Cd) toxicity in plants is still in its infancy, particularly at the molecular level. In this study, the gene encoding a novel serotonin N-acetyltransferase 3 (SNAT3) in rice, a pivotal enzyme in the melatonin biosynthetic pathway, was cloned. Rice (Oryza sativa) OsSNAT3 is the first identified plant ortholog of archaeon Thermoplasma volcanium SNAT. The purified recombinant OsSNAT3 catalyzed the conversion of serotonin and 5-methoxytryptamine to N-acetylserotonin and melatonin, respectively. The suppression of OsSNAT3 by RNAi led to a decline in endogenous melatonin levels followed by a reduction in Cd tolerance in transgenic RNAi rice lines. In addition, the expression levels of genes encoding the endoplasmic reticulum (ER) chaperones BiP3, BiP4, and BiP5 were much lower in RNAi lines than in the wild type. In transgenic rice plants overexpressing OsSNAT3 (SNAT3-OE), however, melatonin levels were higher than in wild-type plants. SNAT3-OE plants also tolerated Cd stress, as indicated by seedling growth, malondialdehyde, and chlorophyll levels. BiP4 expression was much higher in the SNAT3-OE lines than in the wild type. These results indicate that melatonin engineering could help crops withstand Cd stress, resulting in high yields in Cd-contaminated fields.

Tailored Melatonin- and Donepezil-Based Hybrids Targeting Pathognomonic Changes in Alzheimer's Disease: An In Vitro and In Vivo Investigation.

A plethora of pathophysiological events have been shown to play a synergistic role in neurodegeneration, revealing multiple potential targets for the pharmacological modulation of Alzheimer's disease (AD). In continuation to our previous work on new indole- and/or donepezil-based hybrids as neuroprotective agents, the present study reports on the beneficial effects of lead compounds of the series on key pathognomonic features of AD in both cellular and in vivo models. An enzyme-linked immunosorbent assay (ELISA) was used to evaluate the anti-fibrillogenic properties of 15 selected derivatives and identify quantitative changes in the formation of neurotoxic ß-amyloid (Aß42) species in human neuronal cells in response to treatment. Among the most promising compounds were 3a and 3c, which have recently shown excellent antioxidant and anticholinesterase activities, and, therefore, have been subjected to further in vivo investigation in mice. An acute toxicity study was performed after intraperitoneal (i.p.) administration of both compounds, and 1/10 of the LD50 (35 mg/kg) was selected for subacute treatment (14 days) with scopolamine in mice. Donepezil (DNPZ) and/or galantamine (GAL) were used as reference drugs, aiming to establish any pharmacological superiority of the multifaceted approach in battling hallmark features of neurodegeneration. Our promising results give first insights into emerging disease-modifying strategies to combine multiple synergistic activities in a single molecule.

Melatonin Delays Arthritis Inflammation and Reduces Cartilage Matrix Degradation through the SIRT1-Mediated NF-κB/Nrf2/TGF-ß/BMPs Pathway.

Cartilage, a flexible and smooth connective tissue that envelops the surfaces of synovial joints, relies on chondrocytes for extracellular matrix (ECM) production and the maintenance of its structural and functional integrity. Melatonin (MT), renowned for its anti-inflammatory and antioxidant properties, holds the potential to modulate cartilage regeneration and degradation. Therefore, the present study was devoted to elucidating the mechanism of MT on chondrocytes. The in vivo experiment consisted of three groups: Sham (only the skin tissue was incised), Model (using the anterior cruciate ligament transection (ACLT) method), and MT (30 mg/kg), with sample extraction following 12 weeks of administration. Pathological alterations in articular cartilage, synovium, and subchondral bone were evaluated using Safranin O-fast green staining. Immunohistochemistry (ICH) analysis was employed to assess the expression of matrix degradation-related markers. The levels of serum cytokines were quantified via Enzyme-linked immunosorbent assay (ELISA) assays. In in vitro experiments, primary chondrocytes were divided into Control, Model, MT, negative control, and inhibitor groups. Western blotting (WB) and Quantitative RT-PCR (q-PCR) were used to detect Silent information regulator transcript-1 (SIRT1)/Nuclear factor kappa-B (NF-κB)/Nuclear factor erythroid-2-related factor 2 (Nrf2)/Transforming growth factor-beta (TGF-ß)/Bone morphogenetic proteins (BMPs)-related indicators. Immunofluorescence (IF) analysis was employed to examine the status of type II collagen (COL2A1), SIRT1, phosphorylated NF-κB p65 (p-p65), and phosphorylated mothers against decapentaplegic homolog 2 (p-Smad2). In vivo results revealed that the MT group exhibited a relatively smooth cartilage surface, modest chondrocyte loss, mild synovial hyperplasia, and increased subchondral bone thickness. ICH results showed that MT downregulated the expression of components related to matrix degradation. ELISA results showed that MT reduced serum inflammatory cytokine levels. In vitro experiments confirmed that MT upregulated the expression of SIRT1/Nrf2/TGF-ß/BMPs while inhibiting the NF-κB pathway and matrix degradation-related components. The introduction of the SIRT1 inhibitor Selisistat (EX527) reversed the effects of MT. Together, these findings suggest that MT has the potential to ameliorate inflammation, inhibit the release of matrix-degrading enzymes, and improve the cartilage condition. This study provides a new theoretical basis for understanding the role of MT in decelerating cartilage degradation and promoting chondrocyte repair in in vivo and in vitro cultured chondrocytes.

Potential Neuroprotective Effect of Melatonin in the Hippocampus of Male BTBR Mice.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder identified by impairments in common social interactions and repetitive behaviors. In ASD patients, substantial morphological alterations have been observed in the hippocampus, which represents an important region for the development of social skills. Melatonin, commonly found in many foods and plants, is also produced by the pineal gland. This indolamine, known to regulate the circadian rhythm, shows antioxidant and anti-inflammatory properties. We therefore hypothesized that melatonin may reduce oxidative stress and inflammation in the hippocampus of ASD patients. We explored our hypothesis using the BTBR mouse, a well-regarded murine transgenic model for ASD. Immediately after weaning, male BTBR and C57BL/6 mice underwent an 8-week treatment with melatonin or vehicle. Later, through immunohistochemistry and the immunoblotting analysis of the hippocampus, we evaluated the overall expression and cellular localization of Nrf2 and SOD1, two enzymes involved in the oxidative stress response. Similarly, we evaluated NLRP3 and NFkB, two mediators of inflammation, and GAD67, an enzyme responsible for the synthesis of GABA. Ultimately, we addressed melatonin's potential to regulate iron metabolism through a DAB-enhanced Perls reaction assay. Results showed melatonin's potential for modulating the analyzed markers in BTBR mice, suggesting a potential neuroprotective effect in ASD patients.