Journal of Pineal Research最新文献

Cecon E, Ivanova A, Luka M, Gbahou F, Friederich A, Guillaume JL, Keller P, Knoch K, Ahmad R, Delagrange P, Solimena M, Jockers R. Detection of recombinant and endogenous mouse melatonin receptors by monoclonal antibodies targeting the C-terminal domain. J Pineal Res. 2018 Nov 26:e12540. doi:10.1111/jpi.12540

In Figure 3B, lanes for NT and mMT1 for antibody mAB-H04 were incorrect. In Figure 3C, lanes for NT and hMT2 for antibodies mAB-A84 and mAB-I81 were incorrect (switched image of NT lane with hMT2 lane in both cases). In Figure 3D, lanes for NT and rMT2 for mAB-84 were incorrect. All the incorrect lanes correspond to lanes without any specific signals, which resulted in an erroneous assembly of lanes at the final stage of the figure preparation. None of these errors has any impact on the conclusion of the article. Original western blots and the corrected figure is provided.

We apologize for this error.

The labeled ligand commonly employed in competition binding studies for melatonin receptor ligands, 2-[¹²⁵I]iodomelatonin, showed slow dissociation with different half-lives at the two receptor subtypes. This may affect the operational measures of affinity constants, which at short incubation times could not be obtained in equilibrium conditions, and structure–activity relationships, as the K_i values of tested ligands could depend on either interaction at the binding site or the dissociation path. To address these issues, the kinetic and saturation binding parameters of 2-[¹²⁵I]iodomelatonin as well as the competition constants for a series of representative ligands were measured at a short (2 h) and a long (20 h) incubation time. Concurrently, we simulated by molecular modeling the dissociation path of 2-iodomelatonin from MT₁ and MT₂ receptors and investigated the role of interactions at the binding site on the stereoselectivity observed for the enantiomers of the subtype-selective ligand UCM1014. We found that equilibrium conditions for 2-[¹²⁵I]iodomelatonin binding can be reached only with long incubation times, particularly for the MT₂ receptor subtype, for which a time of 20 h approximates this condition. On the other hand, measured K_i values for a set of ligands including agonists, antagonists, nonselective, and subtype-selective compounds were not significantly affected by the length of incubation, suggesting that structure–activity relationships based on data collected at shorter time reflect different interactions at the binding site. Molecular modeling simulations evidenced that the slower dissociation of 2-iodomelatonin from the MT₂ receptor can be related to the restricted mobility of a gatekeeper tyrosine along a lipophilic path from the binding site to the membrane bilayer. The enantiomers of the potent, MT₂-selective agonist UCM1014 were separately synthesized and tested. Molecular dynamics simulations of the receptor–ligand complexes provided an explanation for their stereoselectivity as due to the preference shown by the eutomer at the binding site for the most abundant axial conformation adopted by the ligand in solution. These results suggest that, despite the slow-binding kinetics occurring for the labeled ligand, affinity measures at shorter incubation times give robust results consistent with known structure–activity relationships and with interactions taken at the receptor binding site.

Stability of metabolites in harsh environments such as drought, temperature, and light suggest their untapped potential in processes the plants utilize in mitigation of abiotic and biotic stresses. Such metabolites could be nonspecific to microorganisms, plants, or animals. Many of the indoleamines are ubiquitous throughout species and have been shown to mitigate a wide range of stresses. We tested the role of indoleamine metabolites via exogenous application of the precursor tryptophan (TRP) on strawberry due to the short reproductive life cycle and its temperate traits. Seasonal responses appeared to be perturbed with exogenous application of TRP as a combination of foliar (3 mg/L) and ground drench (100 mg/L) or ground drench only (100 mg/L). The treatment yielded growth stimulatory responses besides mitigating stress, that is, short photoperiod and cold temperature. Plants preparing into dormancy reverted to produce green foliage and flowers that set fruit in unfavorable climate in the month of November where the untreated plants senesced. Analyses of the endogenous indoleamines in flowers and fruits of the treated plants indicated that the titers and ratios of the metabolites NAS, 2-hydroxymelatonin, and N(1)-acetyl-N(2)-formyl-5-methoxykynuramine assisted in the stress mitigation. The ASMT and M2H gene regulations emphasized the stability of intermediate metabolites of TRP. The TDC and T5H regulation explained the detection of a rare to find compound, 5-hydroxytryptophan, in strawberry. This is the first report on detection of eight indoleamines in strawberry alongside the regulatory genes in the indoleamine pathway. Inclining climate crisis demands climate-resilient plants in quick time and the indoleamine toolkit may offer the opportunity to develop simple and effective practices to manage stress tolerance in plants.

Several myeloid cell leukemia sequence 1 protein (MCL1) inhibitors including S64315 have undergone clinical testing for leukemia. Because of the toxicities after MCL1 inhibition, including hematopoietic, hepatic, and cardiac toxicities, there is substantial interest in finding agents that can sensitize leukemia cells to these MCL1 inhibitors. Melatonin is a chronobiotic that promotes chemo-induced cancer cell death while protecting normal cells from cytotoxic effects. In this study, we found melatonin sensitizes over 10 leukemia cell lines to the MCL1 inhibitors S63845 (S64315 analog) and A-1210477. Further studies demonstrate that melatonin sensitizes Jurkat cells to S63845 and A-1210477 independent of melatonin receptors MT1 and MT2, but through multiple mechanisms, including upregulating the death receptor pathway, increasing mitochondrial reactive oxygen species (ROS), inhibiting nuclear factor-κB (NF-κB) signaling, and causing cell cycle arrest. First, death receptor pathway inhibition only slightly diminishes the melatonin sensitization of S63845, while inhibiting mitochondrial ROS partially reduces the S63845/melatonin combination-induced apoptosis and depletion of the mitochondrial pathway totally abolishes it, indicating that both death receptor and mitochondrial apoptosis pathways are involved. Second, transcriptome sequencing analysis found that NF-κB signaling is downregulated by melatonin that inhibition of NF-κB signaling by parthenolide also dramatically sensitizes Jurkat cells to S63845. Third, melatonin induces G1 cell cycle arrest and upregulates NOXA while NOXA knockdown diminishes the sensitization to S63845 by melatonin. In addition, a xenograft model suggests that melatonin in combination with S63845 causes shrinkage of leukemic deposit while S63845 or melatonin monotherapy only has limited effects. Thus, our results demonstrate that melatonin efficiently sensitizes various leukemia to the MCL1 inhibitors, potentially allowing the usage of lower doses.

Women typically sleep and wake earlier than men and have been shown to have earlier circadian timing relative to the light/dark cycle that synchronizes the clock. A potential mechanism for earlier timing in women is an altered response of the circadian system to evening light. We characterized individual-level dose–response curves for light-induced melatonin suppression using a within-subjects protocol. Fifty-six participants (29 women, 27 men; aged 18–30 years) were exposed to a range of light illuminances (10, 30, 50, 100, 200, 400, and 2000 lux) using melatonin suppression relative to a dim control (<1 lux) as a marker of light sensitivity. Women were free from hormonal contraception. To examine the potential influence of sex hormones, estradiol and progesterone was examined in women and testosterone was examined in a subset of men. Menstrual phase was monitored using self-reports and estradiol and progesterone levels. Women exhibited significantly greater melatonin suppression than men under the 400-lux and 2000-lux conditions, but not under lower light conditions (10–200 lux). Light sensitivity did not differ by menstrual phase, nor was it associated with levels of estradiol, progesterone, or testosterone, suggesting the sex differences in light sensitivity were not acutely driven by circulating levels of sex hormones. These results suggest that sex differences in circadian timing are not due to differences in the response to dim/moderate light exposures typically experienced in the evening. The finding of increased bright light sensitivity in women suggests that sex differences in circadian timing could plausibly instead be driven by a greater sensitivity to phase-advancing effects of bright morning light.

Seed germination (SG) is the first stage in a plant's life and has an immense importance in sustaining crop production. Abiotic stresses reduce SG by increasing the deterioration of seed quality, and reducing germination potential, and seed vigor. Thus, to achieve a sustainable level of crop yield, it is important to improve SG under abiotic stress conditions. Melatonin (MEL) is an important biomolecule that interplays in developmental processes and regulates many adaptive responses in plants, especially under abiotic stresses. Thus, this review specifically summarizes and discusses the mechanistic basis of MEL-mediated SG under abiotic stresses. MEL regulates SG by regulating some stress-specific responses and some common responses. For instance, MEL induced stress specific responses include the regulation of ionic homeostasis, and hydrolysis of storage proteins under salinity stress, regulation of C-repeat binding factors signaling under cold stress, starch metabolism under high temperature and heavy metal stress, and activation of aquaporins and accumulation of osmolytes under drought stress. On other hand, MEL mediated regulation of gibberellins biosynthesis and abscisic acid catabolism, redox homeostasis, and Ca²⁺ signaling are amongst the common responses. Nonetheless factors such as endogenous MEL contents, plant species, and growth conditions also influence above-mentioned responses. In conclusion, MEL regulates SG under abiotic stress conditions by interacting with different physiological mechanisms.

Temporal signals such as light and temperature cycles profoundly modulate animal physiology and behaviour. Via endogenous timing mechanisms which are regulated by these signals, organisms can anticipate cyclic environmental changes and thereby enhance their fitness. The pineal gland in fish, through the secretion of melatonin, appears to play a critical role in the circadian system, most likely acting as an element of the circadian clock system. An important output of this circadian clock is the locomotor activity circadian rhythm which is adapted to the photoperiod and thus determines whether animals are diurnal or nocturnal. By using a genetically modified zebrafish strain known as Tg (Xla.Eef1a1:Cau.asip1)iim04, which expresses a higher level of the agouti signalling protein 1 (Asip1), an endogenous antagonist of the melanocortin system, we observed a complete disruption of locomotor activity patterns, which correlates with the ablation of the melatonin daily rhythm. Consistent with this, in vitro experiments also demonstrated that Asip1 inhibits melatonin secretion from the zebrafish pineal gland, most likely through the melanocortin receptors expressed in this gland. Asip1 overexpression also disrupted the expression of core clock genes, including per1a and clock1a, thus blunting circadian oscillation. Collectively, these results implicate the melanocortin system as playing an important role in modulating pineal physiology and, therefore, circadian organisation in zebrafish.

Circadian misalignment (CM) caused by shift work can increase the risk of mood impairment. However, the pathological mechanisms underlying these deficits remain unclear. In the present study, we used long-term variable photoperiod (L-VP) in wild-type mice to better simulate real-life shift patterns and study its effects on the prefrontal cortex (PFC) and hippocampus, which are closely related to mood function. The results showed that exposure to L-VP altered the activity/rest rhythms of mice, by eliciting phase delay and decreased amplitude of the rhythms. Mice with CM developed anxiety and depression-like manifestations and the number of mature oligodendrocytes (OL) was reduced in the medial prefrontal cortex and hippocampal CA1 regions. Mood impairment and OL reduction worsened with increased exposure time to L-VP, while normal photoperiod restoration had no effect. Mechanistically, we identified upregulation of Bmal1 in the PFC and hippocampal regions of CM mice at night, when genes related to mature OL and myelination should be highly expressed. CM mice exhibited significant inhibition of the protein kinase B (AKT)/mTOR signaling pathway, which is directly associated to OL differentiation and maturation. Furthermore, we demonstrated in the OL precursor cell line Oli-Neu that overexpression of Bmal1 inhibits AKT/mTOR pathway and reduces the expression of genes OL differentiation. In conclusion, BMAL1 might play a critical role in CM, providing strong research evidence for BMAL1 as a potential target for CM therapy.

Melatonin is a molecule ubiquitous in nature and involved in several physiological functions. In the brain, melatonin is converted to N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK) and then to N1-acetyl-5-methoxykynuramine (AMK), which has been reported to strongly enhance long-term object memory formation. However, the synthesis of AMK in brain tissues and the underlying mechanisms regarding memory formation remain largely unknown. In the present study, young and old individuals from a melatonin-producing strain, C3H/He mice, were employed. The amount of AMK in the pineal gland and plasma was very low compared with those of melatonin at night; conversely, in the hippocampus, the amount of AMK was higher than that of melatonin. Indoleamine 2, 3-dioxygenase (Ido) mRNA was expressed in multiple brain tissues, whereas tryptophan 2,3-dioxygenase (Tdo) mRNA was expressed only in the hippocampus, and its lysate had melatonin to AFMK conversion activity, which was blocked by the TDO inhibitor. The expression levels of phosphorylated cAMP response element binding protein (CREB) and PSD-95 in whole hippocampal tissue were significantly increased with AMK treatment. Before increasing in the whole tissue, CREB phosphorylation was significantly enhanced in the nuclear fraction. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, we found that downregulated genes in hippocampus of old C3H/He mice were more enriched for long-term potentiation (LTP) pathway. Gene set enrichment analysis showed that LTP and neuroactive receptor interaction gene sets were enriched in hippocampus of old mice. In addition, Ido1 and Tdo mRNA expression was significantly decreased in the hippocampus of old mice compared with young mice, and the decrease in Tdo mRNA was more pronounced than Ido1. Furthermore, there was a higher decrease in AMK levels, which was less than 1/10 that of young mice, than in melatonin levels in the hippocampus of old mice. In conclusion, we first demonstrated the Tdo-related melatonin to AMK metabolism in the hippocampus and suggest a novel mechanism of AMK involved in LTP and memory formation. These results support AMK as a potential therapeutic agent to prevent memory decline.

Age-related sleep and circadian rhythm disturbances may be due to altered nonvisual photoreception. Here, we investigated the temporal dynamics of light-induced melatonin suppression in young and older individuals. In a within-subject design study, young and older participants were exposed for 60 min (0030-0130 at night) to nine narrow-band lights (range: 420−620 nm). Plasma melatonin suppression was calculated at 15, 30, 45, and 60 min time intervals. Individual spectral sensitivity of melatonin suppression and photoreceptor contribution were predicted for each interval and age group. In young participants, melanopsin solely drove melatonin suppression at all time intervals, with a peak sensitivity at 485.3 nm established only after 15 min of light exposure. Conversely, in older participants, spectral light-driven melatonin suppression was best explained by a more complex model combining melanopsin, S-cone, and M-cone functions, with a stable peak (~500 nm) at 30, 45, and 60 min of light exposure. Aging is associated with a distinct photoreceptor contribution to melatonin suppression by light. While in young adults melanopsin-only photoreception is a reliable predictor of melatonin suppression, in older individuals this process is jointly driven by melanopsin, S-cone, and M-cone functions. These findings offer new prospects for customizing light therapy for older individuals.