Search Results (77)

Interferon-γ (IFNγ), a key inflammatory cytokine that orchestrates immune responses, also emerges as a regulator of cellular metabolism; however, in alveolar epithelial cells its impact on amino acid homeostasis remains poorly defined. Here, we investigated the effects of IFNγ on intracellular amino acid content and transmembrane transport in human alveolar epithelial A549 cells, focusing on the contribution of the JAK/STAT/IRF1 signaling axis. To this end, A549 WT and IRF1 knockout (IRF1 KO) cells were used to investigate IRF1 contribution, and baricitinib to evaluate the role of the JAK/STAT pathway. HPLC analysis reveals that in WT, but not in IRF1 KO cells, IFNγ markedly increases the intracellular concentration of many amino acids, including glutamine, glutamate, and several neutral and cationic amino acids, without affecting the cell volume, thus indicating true metabolic accumulation. The measurement of the transmembrane uptake of specific radiolabeled amino acids demonstrates a concomitant increase in transport Systems ASC, A, L, and y⁺ activity; an upregulation of the related transporters ASCT2, SNAT2, LAT1, and CAT1 has also been observed by means of qPCR analysis. Moreover, conditioned medium from SARS-CoV-2 spike-activated macrophages recapitulates IFNγ-driven amino acid remodeling in a JAK/STAT/IRF1-dependent manner. Overall, our findings identify IFNγ as a potent regulator of intracellular amino acid availability in alveolar epithelial cells through the modulation of the activity of membrane transporters. The observed IFNγ-reprogramming is IRF1 dependent, ascribing a crucial role to this transcription factor in linking inflammation and amino acid metabolism. Full article

We study heavy-ion collisions with a focus on pion production using an extended parity doublet model implemented in the “DaeJeon Boltzmann–Uehling–Uhlenbeck” (DJBUU) code. We consider three different systems—¹⁰⁸Sn + ¹¹²Sn, ¹¹²Sn + ¹²⁴Sn, and ¹³²Sn + ¹²⁴Sn—at a beam energy of $E_{\mathrm{beam}}=270$ A MeV, with an impact parameter of 3 fm, and compare our results with the SπRIT data. Since one of the key features of the parity doublet model is the existence of a chiral-invariant mass $m_0$ that contributes to the nucleon mass, we investigate how pion production depends on the chiral-invariant mass in these heavy-ion collisions. We adopt the values of the chiral-invariant mass of 600, 700, and 800 MeV and find that the case with $m_0=800$ MeV best reproduces the experimental data. We also observe that a larger $m_0$ results in a higher maximum baryon density of nuclear matter produced during heavy-ion collisions. Full article

Plant melatonin is widely recognized as a pleiotropic regulator. As a growth-regulating hormone, it extensively participates in various growth and developmental processes and has significant functions in stress responses and disease resistance. Plant melatonin is synthesized primarily through the catalytic actions of five enzymes: TDC (tryptophan decarboxylase), T5H (tryptamine-5-hydroxylase), SNAT (serotonin N-acetyltransferase), ASMT (N-acetylserotonin methyltransferase), and COMT (caffeic acid-O-methyltransferase). There are multiple genes for each of these five enzymes in citrus genomes, however, with the exception of COMT5—whose function has recently been elucidated—and SNAT, which has only been preliminarily identified, the remaining genes have not been unequivocally characterized or functionally annotated. Hence, we carried out a genome-wide analysis of melatonin biosynthesis enzyme-related gene families in trifoliate orange (Poncirus trifoliata), one of the most common citrus rootstock varieties. Through bioinformatics approaches, we identified 96 gene family members encoding melatonin biosynthetic enzymes and characterized their protein sequence properties, phylogenetic relationships, gene structures, chromosomal distributions, and promoter cis-acting elements. Furthermore, by analyzing expression patterns in different tissues and under various stresses, we identified multiple stress-responsive melatonin synthase genes. These genes likely participate in melatonin synthesis under adverse conditions, thereby enhancing stress adaptation. Specifically, PtCOMT5, PtASMT11, and PtTDC9 were significantly induced by low temperature; PtSNAT1, PtSNAT14, PtSNAT18, and PtTDC10 were markedly responsive to drought; and PtASMT15, PtSNAT15, PtASMT16, and PtSNAT3 were strongly induced by ABA. Among them, PtASMT23 expression was induced up to 120-fold under low temperature, while PtSNAT18 showed over 100-fold upregulation under dehydration treatment. These findings strongly suggest that PtASMT23 and PtSNAT18 play critical roles in regulating melatonin biosynthesis in response to cold and drought stress, respectively. Collectively, these findings pinpoint novel genetic targets for enhancing stress resilience in citrus breeding programs and lay the foundation for the functional characterization of specific melatonin biosynthesis pathway gene family members in citrus and other horticultural crop species. Full article

Plant growth regulators of natural origin are becoming increasingly important in crop production to protect plants against various abiotic stresses and often to modulate plant pathological processes. These compounds offer the potential to enhance plant health exogenously by protecting plants against oxidative stress. Melatonin has been studied previously; however, the role of exogenous melatonin in abiotic stress tolerance and the underlying mechanisms are still less understood. In this study, potato plants were grown in vitro to study the effects of exogenous melatonin and ultrasound treatment (latter as an abiotic stress). The measured parameters included morphological data and the concentrations of melatonin and its degradation products, indole-3-acetic acid and salicylic acid, at 0 h, 24 h, 1 week, and 4 weeks after treatment. In addition, the expression levels of the genes responsible for the production of enzymes involved in melatonin synthesis were traced by RT-qPCR analysis. Melatonin added to the culture medium was taken up by the in vitro plantlets, and it participated both in the plant stress reaction and stress mitigation when an abiotic stress reaction was triggered by ultrasound. Among the degradation products, we detected N-acetyl-5-methoxykynuramine, 6-hydroxymelatonin, and 5-methoxytryptamine by UHPLC-MS. Among the enzymes involved in the synthesis of melatonin and indole-3-acetic acid, the expression levels of COMT, SNAT, TSB, TAA, ASMT, TPH, AANAT, ASMT, and TSA were measured and no pattern was observed in response to the treatments. Full article

Bacterial wilt (BW) is a globally serious soil-borne disease in a wide range of plants, caused by diverse strains of Ralstonia solanacearum. However, there are few research reports on melatonin regulating plant resistance against R. solanacearum. N-acetyltransferase SlSNAT2 is a rate-limiting enzyme in plant melatonin synthesis. This study elucidates the mechanisms of SlSNAT2 modulating tomato resistance to BW. SlSNAT2 was expressed in tomato roots, stems, and leaves and induced upon R. solanacearum inoculation. Knocking out SlSNAT2 significantly decreased the melatonin content in CRISPR/Cas9 mutant slsnat2. With R. solanacearum inoculation, the morbidity and disease index value of slsnat2 were significantly higher than those of the tomato wild-type plant Micro-Tom (MT) according to the wilt rate and severity. The chlorophyll levels, photosynthetic rates, and callus deposition quantity in slsnat2 were notably lower while the reactive oxygen species (ROS) level was considerably higher than those in the MT after inoculation. Additionally, the SlSNAT2 deficiency depressed the expression of the mitogen-activated protein kinase (MAPK) pathway genes (SlMPK1, SlMKK2), salicylic acid pathway genes (SlGluA, SlPR-1a), jasmonic acid pathway gene SlPin2, and pathogenesis-related (PR) protein genes (SlPR-STH2a, SlPR-STH2b, SlPR-STH2c, SlPR-STH2d). These results revealed SlSNAT2 enhanced the tomato resistance against R. solanacearum by orchestrating ROS homeostasis, callose deposition, MAPK signaling, hormone pathways, and PR gene transcripts. Full article

Lead (Pb) is a pervasive neurotoxicant with well-documented detrimental effects on the central nervous system, particularly in vulnerable populations such as children. Despite historical recognition of its toxicity, Pb exposure remains a significant public health concern due to its environmental persistence, historical industrial use, and ongoing applications in modern technologies. This review focuses on the mechanisms by which Pb disrupts glutamatergic signaling, a critical pathway for learning, memory, and synaptic plasticity. Pb’s interference with glutamate receptors (ionotropic NMDA and AMPA, as well as metabotropic receptors), transporters (EAATs, VGLUTs, and SNATs), and metabolic pathways (glutamate–glutamine cycle, TCA cycle, and glutathione synthesis) are detailed. By mimicking divalent cations like Ca²⁺ and Zn²⁺, Pb²⁺ disrupts calcium homeostasis, exacerbates excitotoxicity, and induces oxidative stress, ultimately impairing neuronal communication and synaptic function. These molecular disruptions manifest cognitive deficits, behavioral abnormalities, and increased susceptibility to neurodevelopmental and neurodegenerative disorders. Understanding Pb’s impact on glutamatergic neurotransmission offers critical insights into its neurotoxic profile and highlights the importance of addressing its effects on neural function. Full article

Background: Glutamate, a nutritionally non-essential amino acid, is a key intermediate in nitrogen metabolism. Despite more studies on its functional role in intestine health, it remains unknown how glutamate regulates nitrogen metabolism in animals fed a low-protein diet. Methods: Herein, we investigated the effects of glutamate supplementation on colonic amino acid transport, barrier protein expression, microbiota alterations, fecal nitrogen emissions, hepatic amino acid transport, and protein synthesis in weaned rats. Results: We found that protein restriction diminished the mucus thickness, reduced goblet cell numbers, and the expression of EAAT3, y⁺LAT2 in the colon. In contrast, glutamate supplementation reversed these effects, increasing the colon length and enhancing the expression of ZO-1, Occludin, and Claudin-1 in the colon. At the genus level, glutamate increased the abundance of Lactococcus and Clostridia_sensu_stricto_18. Additionally, glutamate supplementation resulted in an increased apparent nitrogen digestibility, reduced the ratio of fecal nitrogen to total nitrogen intake, and increased the ratio of fecal microbial nitrogen to total nitrogen intake. Protein restriction decreased the mRNA level of ATP1A1, EAAT3, SNAT9/2, and ASCT2, and the protein level of p-mTOR, mTOR, p-mTOR/mTOR, and p-p70S6K/p70S6K as well as p-4EBP1/4EBP1 in the liver. These effects were reversed by glutamate supplementation. Conclusions: In conclusion, glutamate supplementation upregulates amino acid transporters and barrier protein expression in the colon, modulates microbiota composition to reduce fecal nitrogen excretion, and enhances amino acid transport and protein synthesis in the liver by activating the mTOR/p70S6K/4EBP1 pathway, which influences nitrogen metabolism in weaned rats fed a low-protein diet. Full article

Serotonin N-acetyltransferase (SNAT) is a crucial enzyme in the melatonin synthesis pathway, playing an essential role in both melatonin biosynthesis and plant resistance to abiotic stress. A bioinformatics approach was employed to identify the members of the citrus SNAT gene family and to analyze their physicochemical properties, gene structure, conserved domains, phylogenetic relationships, and promoter cis-acting elements. Additionally, the tissue-specific expression of trifoliate orange SNAT family members and their expression patterns under stress conditions were examined. This study identified 21 members of the SNAT gene family across five citrus genomes, distributed over five chromosomes, with the majority predicted to localize within chloroplasts. These genes were characterized by having between 1 and 8 exons, 0 and 7 introns, 1 and 2 conserved domains, and 5 and 8 motifs. Phylogenetic analysis classified the genes into four subgroups, demonstrating significant collinearity with SNAT genes in rice. Analysis of the promoter regions revealed 32 cis-acting elements, with those responsive to light, abscisic acid, and drought being the most common. Expression analysis of SNAT genes in trifoliate orange indicated tissue specificity, with the highest expression levels detected in leaves. Quantitative real-time PCR analysis showed that the PtrSNAT1 gene was notably upregulated under various stress conditions, suggesting its role in stress response. Overall, these findings provide critical insights for further functional studies of citrus SNAT genes in relation to abiotic stress responses. Moreover, the PtrSNAT1 gene represents a potential target for developing rootstocks with enhanced resistance to abiotic stress. Full article

Serotonin N-acetyltransferase (SNAT) is a pivotal enzyme for melatonin biosynthesis in all living organisms. It catalyzes the conversion of serotonin to N-acetylserotonin (NAS) or 5-methoxytrypytamine (5-MT) to melatonin. In contrast to animal- and plant-specific SNAT genes, a novel clade of archaeal SNAT genes has recently been reported. In this study, we identified homologues of archaeal SNAT genes in ciliates and dinoflagellates, but no animal- or plant-specific SNAT homologues. Archaeal SNAT homologue from the ciliate Stylonychia lemnae was annotated as a putative N-acetyltransferase. To determine whether the putative S. lemnae SNAT (SlSNAT) exhibits SNAT enzyme activity, we chemically synthesized and expressed the full-length SlSNAT coding sequence (CDS) in Escherichia coli, from which the recombinant SlSNAT protein was purified by Ni²⁺ affinity column chromatography. The recombinant SlSNAT exhibited SNAT enzyme activity toward serotonin (K_m = 776 µM) and 5-MT (K_m = 246 µM) as substrates. Furthermore, SlSNAT-overexpressing (SlSNAT-OE) transgenic rice plants showed higher levels of melatonin synthesis than wild-type controls. The SlSNAT-OE rice plants exhibited delayed leaf senescence and tolerance against treatment with the reactive oxygen species (ROS)-inducing herbicide butafenacil by decreasing hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels, suggesting that melatonin alleviates ROS production in vivo. Full article

The placenta plays a crucial role in nutrient transport and waste exchange between the dam and fetus, sustaining fetal growth. While the positive effects of 25-hydroxyvitamin D₃ (25-OH-D₃) on animal performance have been reported, its impact on placental function remains largely unknown. Therefore, this study aimed to investigate the effects of supplementing 25-OH-D₃ in the diet of primiparous sows on reproductive performance, antioxidant capacity, placental oxidative stress, nutrient transport, and inflammatory response during mid-to-late gestation. A total of 45 healthy Landrace × Yorkshire primiparous sows on day 60 of gestation were selected and randomly allocated to three treatment groups based on body weight and backfat thickness: the control group (corn-soybean meal basal diet), the VD₃ group (basal diet + 2000 IU VD₃), and the 25-OH-D₃ group (basal diet + 50 μg/kg 25-OH-D₃). The results demonstrated that supplementation with 25-OH-D₃ in the diet enhanced sows’ average litter weight and birth weight during mid-to-late gestation. Additionally, plasma malondialdehyde (MDA) concentrations in sows significantly decreased in the VD₃ and 25-OH-D₃ groups (p < 0.05). Furthermore, lower gene expressions of placental HO-1, GPX2, IL-8, and IL-6 were found in the VD₃ or 25-OH-D₃ groups (p < 0.05 or p < 0.10), while higher gene expressions of GLUT1 and SNAT2 in the placenta of sows were observed in the VD₃ and 25-OH-D₃ groups, respectively (p < 0.05). These findings indicate that the supplementation of VD₃ and 25-OH-D₃ in the diet of sows can improve their plasma oxidative stress status, enhance placental antioxidant capacity and nutrient transport, and reduce placental inflammatory responses, with more pronounced improvements in sow performance observed in sows fed diets supplemented with 25-OH-D₃. Full article

The prolactin (PRL) hormone is a major regulator of mammary gland development and lactation. However, it remains unclear whether and how PRL contributes to mammary epithelial cell proliferation and secretion. The Boer and Macheng black crossbred goats are superior in reproduction, meat, and milk, and are popular in Hubei province. To elucidate the mechanisms of PRL on mammary growth and lactation, to improve the local goat economic trade, we have performed studies on these crossbred goats during pregnancy and early lactation, and in goat mammary epithelial cells (GMECs). Here, we first found that the amino acid transporters of SNAT1 and SNAT2 expression in vivo and in vitro were closely associated with PRL levels, the proliferation and secretion of GMECs; knockdown and over-expression of SNAT1/2 demonstrated that PRL modulated the proliferation and lactation of GMECs through regulating SNAT1/2 expression. Transcriptome sequencing and qPCR assays demonstrated the effect of PRL on the transcriptional regulation of SNAT1 and SNAT2 in GMECs. Dual-luciferase reporter gene assays further verified that the binding of the potential PRL response element in the SNAT1/2 promoter regions activated SNAT1/2 transcription after PRL stimulation. Additionally, silencing of either PRLR or STAT5 nearly abolished PRL-stimulated SNAT1/2 promoter activity, suggesting PRLR–STAT5 signaling is involved in the regulation of PRL on the transcriptional activation of SNAT1/2. These results illustrated that PRL modulates the proliferation and secretion of GMECs via PRLR–STAT5-mediated regulation of the SNAT1/2 pathway. This study provides new insights into how PRL affects ruminant mammary development and lactation through regulation of amino acid transporters. Full article

This study investigated the transcriptomic mechanisms underlying melatonin accumulation and the enhancement of salt tolerance in hull-less barley seeds subjected to zinc sulphate stress. Following zinc sulphate treatment, hull-less barley seeds demonstrated increased melatonin accumulation and improved salt tolerance. Through transcriptome analysis, the study compared gene expression alterations in seeds (using the first letter of seed, this group is marked as ‘S’), seeds treated with pure water (as the control group, is marked as ‘C’), and germinated seeds exposed to varying concentrations of zinc sulphate (0.2 mM and 0.8 mM, the first letter of zinc sulphate, ‘Z’, is used to mark groups ‘Z1’ and ‘Z2’). The analysis revealed that 8176, 759, and 622 differentially expressed genes (DEGs) were identified in the three comparison groups S.vs.C, C.vs.Z1, and C.vs.Z2, respectively. Most of the DEGs were closely associated with biological processes, including oxidative-stress response, secondary metabolite biosynthesis, and plant hormone signaling. Notably, zinc sulphate stress influenced the expression levels of Tryptophan decarboxylase 1 (TDC1), Acetylserotonin O-methyltransferase 1 (ASMT1), and Serotonin N-acetyltransferase 2 (SNAT2), which are key genes involved in melatonin synthesis. Furthermore, the expression changes of genes such as Probable WRKY transcription factor 75 (WRKY75) and Ethylene-responsive transcription factor ERF13 (EFR13) exhibited a strong correlation with fluctuations in melatonin content. These findings contribute to our understanding of the mechanisms underlying melatonin enrichment in response to zinc sulphate stress. Full article

Smart Nano-enabled Antiviral Therapeutic (SNAT) is a promising nanodrug that previously demonstrated efficacy in preclinical studies to alleviate SARS-CoV-2 pathology in hamsters. SNAT comprises taxoid (Tx)-decorated amino (NH₂)-functionalized near-atomic size positively charged silver nanoparticles (Tx–[NH₂-AgNPs]). Herein, we aimed to elucidate the molecular mechanism of the viral inhibition and safety of aerosolized SNAT treatment in SARS-CoV-2-infected golden Syrian hamsters. High-resolution transmission electron microscopy (HR-TEM) coupled with energy dispersive spectroscopy (EDS) and ELISAs showed SNAT binds directly to the SARS-CoV-2 virus by interacting with intact spike (S) protein, specifically to S2 subunit. SNAT (≥1 µg/mL) treatment significantly lowered SARS-CoV-2 infections of Calu-3 cells. Extraction-free whole transcriptome assay was used to detect changes in circulatory micronome in hamsters treated intranasally with SNAT (two doses of 10 µg/mL of 2 mL each administered 24 h apart). Uninfected hamsters treated with SNAT had altered circulatory concentrations of 18 microRNAs (8 miRNAs upregulated, 10 downregulated) on day 3 post-treatment compared to uninfected controls. SNAT-induced downregulation of miR-141-3p and miR-200b-3p may reduce viral replication and inflammation by targeting Ythdf2 and Slit2, respectively. Further, SNAT treatment significantly lowered IL-6 expression in infected hamster lungs compared to untreated infected hamsters. Taken together, we demonstrate that SNAT binds directly to SARS-CoV-2 via the S protein to prevent viral entry and propose a model by which SNAT alters the cellular miRNA-directed milieu to promote antiviral cellular processes and neutralize infection. Our results provide insights into the use of low-dose intranasally delivered SNAT in treating SARS-CoV-2 infections in a hamster model. Full article

Both melatonin and hydrogen sulfide (H₂S) mitigate chromium (Cr) toxicity in plants, but the specific interaction between melatonin and H₂S in Cr detoxification remains unclear. In this study, the interaction between melatonin and H₂S in Cr detoxification was elucidated by measuring cell wall polysaccharide metabolism and antioxidant enzyme activity in maize. The findings revealed that exposure to Cr stress (100 μM K₂Cr₂O₇) resulted in the upregulation of L-/D-cysteine desulfhydrase (LCD/DCD) gene expression, leading to a 77.8% and 27.3% increase in endogenous H₂S levels in maize leaves and roots, respectively. Similarly, the endogenous melatonin system is activated in response to Cr stress. We found that melatonin had a significant impact on the relative expression of LCD/DCD, leading to a 103.3% and 116.7% increase in endogenous H₂S levels in maize leaves and roots, respectively. In contrast, NaHS had minimal effects on the relative mRNA expression of serotonin-Nacetyltransferase (SNAT) and endogenous melatonin levels. The production of H₂S induced by melatonin is accompanied by an increase in Cr tolerance, as evidenced by elevated gene expression, elevated cell wall polysaccharide content, increased pectin methylesterase activity, and improved antioxidant enzyme activity. The scavenging of H₂S decreases the melatonin-induced Cr tolerance, while the inhibitor of melatonin synthesis, p-chlorophenylalanine (p-CPA), has minimal impact on H₂S-induced Cr tolerance. In conclusion, our findings suggest that H₂S serves as a downstream signaling molecule involved in melatonin-induced Cr tolerance in maize. Full article

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. Full article