Bitter taste receptor activation by cholesterol and an intracellular tastant.

Bitter taste sensing is mediated by type 2 taste receptors (TAS2Rs (also known as T2Rs)), which represent a distinct class of G-protein-coupled receptors1. Among the 26 members of the TAS2Rs, TAS2R14 is highly expressed in extraoral tissues and mediates the responses to more than 100 structurally diverse tastants2-6, although the molecular mechanisms for recognizing diverse chemicals and initiating cellular signalling are still poorly understood. Here we report two cryo-electron microscopy structures for TAS2R14 complexed with Ggust (also known as gustducin) and Gi1. Both structures have an orthosteric binding pocket occupied by endogenous cholesterol as well as an intracellular allosteric site bound by the bitter tastant cmpd28.1, including a direct interaction with the α5 helix of Ggust and Gi1. Computational and biochemical studies validate both ligand interactions. Our functional analysis identified cholesterol as an orthosteric agonist and the bitter tastant cmpd28.1 as a positive allosteric modulator with direct agonist activity at TAS2R14. Moreover, the orthosteric pocket is connected to the allosteric site via an elongated cavity, which has a hydrophobic core rich in aromatic residues. Our findings provide insights into the ligand recognition of bitter taste receptors and suggest activities of TAS2R14 beyond bitter taste perception via intracellular allosteric tastants.

Molecular basis for selective activation of DREADD-based chemogenetics.

Designer receptors exclusively activated by designer drugs (DREADDs) represent a powerful chemogenetic technology for the remote control of neuronal activity and cellular signalling1-4. The muscarinic receptor-based DREADDs are the most widely used chemogenetic tools in neuroscience research. The Gq-coupled DREADD (hM3Dq) is used to enhance neuronal activity, whereas the Gi/o-coupled DREADD (hM4Di) is utilized to inhibit neuronal activity5. Here we report four DREADD-related cryogenic electron microscopy high-resolution structures: a hM3Dq-miniGq complex and a hM4Di-miniGo complex bound to deschloroclozapine; a hM3Dq-miniGq complex bound to clozapine-N-oxide; and a hM3R-miniGq complex bound to iperoxo. Complemented with mutagenesis, functional and computational simulation data, our structures reveal key details of the recognition of DREADD chemogenetic actuators and the molecular basis for activation. These findings should accelerate the structure-guided discovery of next-generation chemogenetic tools.

Structure, function and pharmacology of human itch GPCRs.

The MRGPRX family of receptors (MRGPRX1-4) is a family of mas-related G-protein-coupled receptors that have evolved relatively recently1. Of these, MRGPRX2 and MRGPRX4 are key physiological and pathological mediators of itch and related mast cell-mediated hypersensitivity reactions2-5. MRGPRX2 couples to both Gi and Gq in mast cells6. Here we describe agonist-stabilized structures of MRGPRX2 coupled to Gi1 and Gq in ternary complexes with the endogenous peptide cortistatin-14 and with a synthetic agonist probe, respectively, and the development of potent antagonist probes for MRGPRX2. We also describe a specific MRGPRX4 agonist and the structure of this agonist in a complex with MRGPRX4 and Gq. Together, these findings should accelerate the structure-guided discovery of therapeutic agents for pain, itch and mast cell-mediated hypersensitivity.

Ligand recognition and allosteric modulation of the human MRGPRX1 receptor.

The human MAS-related G protein-coupled receptor X1 (MRGPRX1) is preferentially expressed in the small-diameter primary sensory neurons and involved in the mediation of nociception and pruritus. Central activation of MRGPRX1 by the endogenous opioid peptide fragment BAM8-22 and its positive allosteric modulator ML382 has been shown to effectively inhibit persistent pain, making MRGPRX1 a promising target for non-opioid pain treatment. However, the activation mechanism of MRGPRX1 is still largely unknown. Here we report three high-resolution cryogenic electron microscopy structures of MRGPRX1-Gαq in complex with BAM8-22 alone, with BAM8-22 and ML382 simultaneously as well as with a synthetic agonist compound-16. These structures reveal the agonist binding mode for MRGPRX1 and illuminate the structural requirements for positive allosteric modulation. Collectively, our findings provide a molecular understanding of the activation and allosteric modulation of the MRGPRX1 receptor, which could facilitate the structure-based design of non-opioid pain-relieving drugs.

TLT-1 Promotes Platelet-Monocyte Aggregate Formation to Induce IL-10-Producing B Cells in Tuberculosis.

The immunoregulation of platelets and platelet-monocyte aggregates (PMAs) is increasingly recognized, but it roles in tuberculosis (TB) remain to be elucidated. In this study, we found that CD14+CD41+ PMAs were increased in peripheral blood of patients with active TB. CD14+CD41+ PMAs highly expressed triggering receptors expressed on myeloid cells (TREMs)-like transcript-1 (TLT-1), P-selectin (CD62P), and CD40L. Our in vitro study found that platelets from patients with active TB aggregate with monocytes to induce IL-1ß and IL-6 production by monocytes. Importantly, we identified that TLT-1 was required for formation of PMAs. The potential TLT-1 ligand was expressed and increased on CD14+ monocytes of patients with TB determined by using TLT-1 fusion protein (TLT-1 Fc). Blocking of ligand-TLT-1 interaction with TLT-1 Fc reduced PMA formation and IL-1ß and IL-6 production by monocytes. Further results demonstrated that PMAs induced IL-10 production by B cells (B10) dependent on IL-1ß, IL-6, and CD40L signals in a coculture system. Moreover, TLT-1 Fc treatment suppressed B10 polarization via blocking PMA formation. Taking all of these data together, we elucidated that TLT-1 promoted PMA-mediated B10 polarization through enhancing IL-1ß, IL-6, and CD40L origin from PMAs, which may provide potential targeting strategies for TB disease treatment.

Structure of the glucagon receptor in complex with a glucagon analogue.

Class B G-protein-coupled receptors (GPCRs), which consist of an extracellular domain (ECD) and a transmembrane domain (TMD), respond to secretin peptides to play a key part in hormonal homeostasis, and are important therapeutic targets for a variety of diseases. Previous work has suggested that peptide ligands bind to class B GPCRs according to a two-domain binding model, in which the C-terminal region of the peptide targets the ECD and the N-terminal region of the peptide binds to the TMD binding pocket. Recently, three structures of class B GPCRs in complex with peptide ligands have been solved. These structures provide essential insights into peptide ligand recognition by class B GPCRs. However, owing to resolution limitations, the specific molecular interactions for peptide binding to class B GPCRs remain ambiguous. Moreover, these previously solved structures have different ECD conformations relative to the TMD, which introduces questions regarding inter-domain conformational flexibility and the changes required for receptor activation. Here we report the 3.0 Å-resolution crystal structure of the full-length human glucagon receptor (GCGR) in complex with a glucagon analogue and partial agonist, NNC1702. This structure provides molecular details of the interactions between GCGR and the peptide ligand. It reveals a marked change in the relative orientation between the ECD and TMD of GCGR compared to the previously solved structure of the inactive GCGR-NNC0640-mAb1 complex. Notably, the stalk region and the first extracellular loop undergo major conformational changes in secondary structure during peptide binding, forming key interactions with the peptide. We further propose a dual-binding-site trigger model for GCGR activation-which requires conformational changes of the stalk, first extracellular loop and TMD-that extends our understanding of the previously established two-domain peptide-binding model of class B GPCRs.

Chlorogenic acid, rutin, and quercetin from Lysimachia christinae alleviate triptolide-induced multi-organ injury in vivo by modulating immunity and AKT/mTOR signal pathway to inhibit ferroptosis and apoptosis.

Drug-induced organ injury is one of the key factors causing organ failure and death in the global public. Triptolide (TP) is the main immunosuppressive component of Tripterygium wilfordii Hook. f. (Leigongteng, LGT) for the first-line management of autoimmune conditions, but it can cause serious multi-organ injury. Lysimachia christinae (Jinqiancao, JQC) is a detoxifying Chinese medicine and could suppress LGT's toxicity. It contains many immune enhancement and organ protection components including chlorogenic acid (CA), rutin (Rut), and quercetin (Que). This study aimed to explore the protection of combined treatments of these organ-protective ingredients of JQC on TP-induced liver, kidney, and heart injury and initially explore the mechanisms. Molecular docking showed that CA, Rut, and Que bounded protein kinase B (AKT)/mechanistic target of rapamycin (mTOR) pathway-related molecules intimately and might competitively antagonize TP. Corresponding in vivo results showed that the combination activated TP-inhibited protein of AKT/mTOR pathway, and reversed TP-induced excessive ferroptosis (excessive Fe 2+ and lipid peroxidation malondialdehyde accumulation, decreased levels of antioxidant enzymes catalase, glutathione peroxidase, glutathione-s transferase, reduced glutathione, and superoxide dismutase, and down-regulated P62/nuclear factor erythroid-2-related factor 2/heme oxygenase-1 pathway), and apoptosis (activated apoptotic factor Fas and Bax and inhibited Bcl-2) in the organ of mice to varying degrees. In conclusion, the combined treatments of CA, Rut, and Que from JQC inhibited TP-induced multi-organ injury in vivo, and the mechanism may largely involve immunomodulation and activation of the AKT/mTOR pathway-mediated cell death reduction including ferroptosis and apoptosis inhibition.

TARM-1 Is Critical for Macrophage Activation and Th1 Response in Mycobacterium tuberculosis Infection.

T cell-interacting activating receptor on myeloid cells 1 (TARM-1) is a novel leukocyte receptor expressed in neutrophils and macrophages. It plays an important role in proinflammatory response in acute bacterial infection, but its immunomodulatory effects on chronic Mycobacterium tuberculosis infections remain unclear. TARM-1 expression was significantly upregulated on CD14high monocytes from patients with active pulmonary tuberculosis (TB) as compared that on cells from patients with latent TB or from healthy control subjects. Small interfering RNA knockdown of TARM-1 reduced expression levels of proinflammatory cytokines IL-12, IL-18, IL-1ß, and IL-8 in M. tuberculosis-infected macrophages, as well as that of HLA-DR and costimulatory molecules CD83, CD86, and CD40. Moreover, TARM-1 enhanced phagocytosis and intracellular killing of M. tuberculosis through upregulating reactive oxygen species. In an in vitro monocyte and T cell coculture system, blockade of TARM-1 activity by TARM-1 blocking peptide suppressed CD4+ T cell activation and proliferation. Finally, administration of TARM-1 blocking peptide in a mouse model of M. tuberculosis infection increased bacterial load and lung pathology, which was associated with decreased macrophage activation and IFN-γ production by T cell. Taken together, these results, to our knowledge, demonstrate a novel immune protective role of TARM-1 in M. tuberculosis infection and provide a potential therapeutic target for TB disease.

Association of systemic immune-inflammation index (SII) and aggregate index of systemic inflammation (AISI) with thyroid nodules in patients with type 2 diabetes mellitus: a retrospective study.

OBJECTIVE: This retrospective study aimed to investigate the association between TNs and the systemic immune-inflammation index (SII) and the aggregate index of systemic inflammation (AISI) in patients with T2DM. METHODS: A total of 370 T2DM patients, who were admitted to Dongzhimen Hospital between January 2020 and March 2023, were included in this retrospective study. Binary logistic regression models with multivariable adjustment were employed to assess the relationship between SII, AISI quartiles, and TNs. Furthermore, receiver operating characteristic (ROC) curve analysis was performed to assess the diagnostic accuracy of SII and AISI in identifying T2DM patients with TNs. RESULTS: Age, diabetes duration, diabetic nephropathy (DN), SII, and AISI demonstrated significant positive associations with TNs. Compared to the first quartile of SII, the second, third, and fourth quartiles showed increased risks of TNs with hazard ratios (HRs) of 1.578 (0.883-2.820), 2.279 (1.257-4.131), and 3.626 (1.931-6.810), respectively (P < 0.001). Similar results were observed for AISI and TNs. ROC curve analysis revealed that SII and AISI exhibited a high discriminatory capability for identifying TNs in the overall and male participant group, whereas the significance among females was not discernible. CONCLUSIONS: This study provides evidence that SII and AISI are independent risk factors for TNs, suggesting that elevated SII and AISI levels may contribute to the development of TNs in patients with T2DM particularly among male individuals.

Untargeted metabolomics reveals hepatic metabolic disorder in the BTBR mouse model of autism and the significant role of liver in autism.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, and the etiology is unknown. Metabolic dysfunction is present in patients with ASD. In the current study, untargeted metabolomics was employed to screen the differential metabolites in the liver of BTBR mouse model of autism, and MetaboAnalyst 4.0 was used for metabolic pathway analysis. Mice were killed, and liver samples were collected for untargeted metabolomics analysis and examination of histopathology. Finally, 12 differential metabolites were identified. The intensities of phenylethylamine, 4-Guanidinobutanoic acid, leukotrieneD4, and SM(d18:1/24:1(15Z)) were significantly upregulated (p < .01), and the intensities of estradiol, CMP-N-glycoloylneuraminate, retinoyl ß-glucuronide,4-phosphopantothenoylcysteine, aldophosphamide, taurochenodesoxycholic acid, taurocholic acid, and dephospho-CoA were significantly downregulated (p < .01) in the BTBR group compared with C57 control group, indicating that differences between BTBR and C57 groups were observed in metabolic patterns. Disturbed pathways of the BTBR mice involved lipid metabolism, retinol metabolism, and amino acid and energy metabolism, revealing that bile acid-mediated activation of LXRα might contribute to metabolic dysfunction of lipid and leukotriene D4 produced by the activation of 5-LOX led to hepatic inflammation. Pathological changes in the liver tissue, such as hepatocyte vacuolization, and small amounts of inflammatory and cell necrosis, further supported metabolomic results. Moreover, Spearman's rank correlation revealed that there is a strong relationship between metabolites across liver and cortex, suggesting liver may exert action by connecting peripheral and neural systems. These findings were likely to be of pathological importance or a cause/consequence of autism, and may provide insight into key metabolic dysfunction to target potential therapeutic strategies relating to ASD.

Robo4 inhibits gamma radiation-induced permeability of a murine microvascular endothelial cell by regulating the junctions.

BACKGROUND: Hematopoietic stem cell transplantation involves irradiation preconditioning which causes bone marrow endothelial cell dysfunction. While much emphasis is on the reconstitution of hematopoietic stem cells in the bone marrow microenvironment, endothelial cell preservation is indispensable to overcome the preconditioning damages. This study aims to ascertain the role of Roundabout 4 (Robo4) in regulating irradiation-induced damage to the endothelium. METHODS: Microvascular endothelial cells were treated with γ-radiation to establish an endothelial cell injury model. Robo4 expression in the endothelial cells was manipulated employing lentiviral-mediated RNAi and gene overexpression technology before irradiation treatment. The permeability of endothelial cells was measured using qPCR, immunocytochemistry, and immunoblotting to analyze the effect on the expression and distribution of junctional molecules, adherens junctions, tight junctions, and gap junctions. Using Transwell endothelial monolayer staining, FITC-Dextran permeability, and gap junction-mediated intercellular communication (GJIC) assays, we determined the changes in endothelial functions after Robo4 gene manipulation and irradiation. Moreover, we measured the proportion of CD31 expression in endothelial cells by flow cytometry. We analyzed variations between two or multiple groups using Student's t-tests and ANOVA. RESULTS: Ionizing radiation upregulates Robo4 expression but disrupts endothelial junctional molecules. Robo4 deletion causes further degradation of endothelial junctions hence increasing the permeability of the endothelial cell monolayer. Robo4 knockdown in microvascular endothelial cells increases the degradation and delocalization of ZO-1, PECAM-1, occludin, and claudin-5 molecules after irradiation. Conversely, connexin 43 expression increases after silencing Robo4 in endothelial cells to induce permeability but are readily destroyed when exposed to 10 Gy of gamma radiation. Also, Robo4 knockdown enhances Y731-VE-cadherin phosphorylation leading to the depletion and destabilization of VE-cadherin at the endothelial junctions following irradiation. However, Robo4 overexpression mitigates irradiation-induced degradation of tight junctional proteins and stabilizes claudin-5 and ZO-1 distribution. Finally, the enhanced expression of Robo4 ameliorates the irradiation-induced depletion of VE-cadherin and connexin 43, improves the integrity of microvascular endothelial cell junctions, and decreases permeability. CONCLUSION: This study reveals that Robo4 maintains microvascular integrity after radiation preconditioning treatment by regulating endothelial permeability and protecting endothelial functions. Our results also provided a potential mechanism to repair the bone marrow vascular niche after irradiation by modulating Robo4 expression.

LncRNA-WAKMAR2 regulates expression of CLDN1 to affect skin barrier through recruiting c-Fos.

BACKGROUND: Chronic actinic dermatitis (CAD) is an immune-mediated photo-allergic skin disease. In the clinic, the treatment of this disease is hampered by the lack of proper understanding of the skin barrier dysfunction mechanism. OBJECTIVE: To illuminate the mechanism of skin barrier dysfunction in CAD. METHODS: Transcriptome sequencing and protein profiling were used to detect skin barrier injury-related genes. RNA pull down, a promoter-reporter gene assay, and chromatin isolation by RNA purification-sequencing were used to elucidate the effect of WAKMAR2 in skin barrier functionality. RESULTS: Transcriptome sequencing from patient's tissues showed a significantly decreased expression of WAKMAR2. Down-regulation of WAKMAR2 destroyed the keratinocyte barrier. Moreover, WAKMAR2 can directly bind to the c-Fos protein. This novel long non-coding RNA (LncRNA)-protein complexes were targeted to the CLDN1 promotor. Overexpression of WAKMAR2 enhanced the promoter activity of CLDN1, while the addition of AP-1 inhibitor could reverse this phenomenon. Furthermore, our in vivo results suggested that expression of WAKMAR2 was required for the repair of skin damage in mice induced by ultraviolet irradiation. CONCLUSIONS: We identified a crucial LncRNA (WAKMAR2) for the protection of the skin barrier in vitro and in vivo. Mechanically, it can specifically interact with c-Fos protein for the regulation of CLDN1, a finding which could be applied for CAD treatment.

N-Acetylcysteine improves oocyte quality through modulating the Nrf2 signaling pathway to ameliorate oxidative stress caused by repeated controlled ovarian hyperstimulation.

CONTEXT: N -acetyl-cysteine (NAC) is a potent antioxidant that can be used for many gynecological diseases such as polycystic ovary syndrome and endometriosis. Controlled ovarian hyperstimulation (COH) is a critical step in infertility treatment. Our previous clinical studies have shown that repeated COH led to oxidative stress in follicle fluid and ovarian granulosa cells. AIMS: In this study, we investigated whether NAC could inhibit oxidative stress in mice caused by repeated COH and improve the mitochondrial function of oocytes. METHODS: Female Institute of Cancer Research (ICR) mice were randomly assigned into three groups: normal group, model (repeated COH) group, NAC group. We examined the morphology, number and quality of mitochondria. The mechanism of regulation of nuclear factor erythroid 2-related factor 2 (Nrf2) by NAC to ameliorate oxidative stress was also investigated. KEY RESULTS: Repeated COH caused oxidative damage in ovaries and oocytes and decreased oocyte quality, while NAC prevented oxidative damage and increased oocyte mitochondrial function. In in vitro experiments, it was verified that NAC can promote the nuclear translocation of Nrf2, which transcriptionally activates the expression of superoxide dismutase and glutathione peroxidase, which removed excessive reactive oxygen species that causes mitochondria damage. CONCLUSIONS: The results suggest that NAC raises mitochondrial function in oocytes and improves oocyte quality through decreasing oxidative stress in mice with repeated COH. The underlying mechanism is related to the regulation of the Nrf2 signaling pathway. IMPLICATION: This study provides a meaningful foundation for the future clinical application of NAC during repeated COH.

Protective effect of C-phycocyanin and apo-phycocyanin subunit on programmed necrosis of GC-1 spg cells induced by H2 O2.

C-phycocyanin (C-PC) is an effective antioxidant and has an important value in medical research. Oxidative stress is considered to be one of the main underlying mechanisms of cell death, and reducing oxidative stress is one of the strategies to enhance germ cell viability. Herein, we investigated the protective effect and the mechanism of C-PC and apo-phycocyanin subunit on oxidative stress damage induced by H2 O2 in GC-1 spg cells. C-PC genes were cloned into the pGEX-4T-1 vectorand transformed into Escherichia coli BL21 to achieve the efficient expression of C-PC subunit. GC-1 spg cells were treated with 600 µM H2 O2 for 24 h to establish the oxidative stress damage model. Cell viability was detected by CCK-8. The degree of oxidative stress was detected by testing Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities and glutathione (GSH) and Malondialdehyde (MDA) levels. Reactive oxygen species (ROS) was evaluated utilizingby 2', 7'-dichlorofluorescent-diacetate (DCFH-DA). Mitochondrial membrane potential was determined by JC-1. Cell necrosis rate was detected by Annexin V-FITC/PI. Expression of protein was detected by western blot. We found that C-PC and GST-CPC ß significantly inhibited H2 O2 -induced oxidative damage of GC-1 spg cells, improved the ability of antioxidation, reduced ROS overproduction, and mitochondrial membrane potential loss, and inhibited the RIP-1/RIP-3/ p-MLKL signaling pathway to reduce the necrosis rate. The results demonstrated that C-PC played a protective role against H2 O2 -induced cell damage, especially its ß subunit. This study provides a theoretical basis for C-PC as a potential protective agent of reproductive system.

Extending the Structural View of Class B GPCRs.

The secretin-like class B family of G protein-coupled receptors (GPCRs) are key players in hormonal homeostasis. Recent structures of various receptors in complex with a variety of orthosteric and allosteric ligands provide fundamental new insights into the function and mechanism of class B GPCRs, including: (i) ligand-induced changes in the relative orientation of the extracellular and transmembrane receptor domains; (ii) intramolecular interaction networks that stabilize conformational changes to accommodate intracellular G protein binding; and (iii) allosteric modulation of receptor activation. This review provides a comprehensive analysis of the structural, biochemical, and pharmacological data on class B GPCRs for understanding ligand-receptor interaction and modulation mechanisms and assessing the potential implications for drug discovery for the secretin-like GPCR family.

Risk factors for severe and critically ill COVID-19 patients: A review.

The pandemic of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused an unprecedented global social and economic impact, and high numbers of deaths. Many risk factors have been identified in the progression of COVID-19 into a severe and critical stage, including old age, male gender, underlying comorbidities such as hypertension, diabetes, obesity, chronic lung diseases, heart, liver and kidney diseases, tumors, clinically apparent immunodeficiencies, local immunodeficiencies, such as early type I interferon secretion capacity, and pregnancy. Possible complications include acute kidney injury, coagulation disorders, thoromboembolism. The development of lymphopenia and eosinopenia are laboratory indicators of COVID-19. Laboratory parameters to monitor disease progression include lactate dehydrogenase, procalcitonin, high-sensitivity C-reactive protein, proinflammatory cytokines such as interleukin (IL)-6, IL-1ß, Krebs von den Lungen-6 (KL-6), and ferritin. The development of a cytokine storm and extensive chest computed tomography imaging patterns are indicators of a severe disease. In addition, socioeconomic status, diet, lifestyle, geographical differences, ethnicity, exposed viral load, day of initiation of treatment, and quality of health care have been reported to influence individual outcomes. In this review, we highlight the scientific evidence on the risk factors of severity of COVID-19.

Activation-Induced Cell Death of Mucosal-Associated Invariant T Cells Is Amplified by OX40 in Type 2 Diabetic Patients.

Mucosal-associated invariant T (MAIT) cells play a key role in local and systemic immune responses. Studies suggest that type 2 diabetes (T2D) is associated with alterations in the human MAIT cell response. However, the mechanisms that regulate the survival and homeostasis of human MAIT cells are poorly defined. In this study, we demonstrate that the costimulatory TNF superfamily receptor OX40 was highly expressed in MAIT cells of patients with T2D. Compared with OX40-negative MAIT cells, OX40-positive MAIT cells showed a high activation and a memory phenotype. Surprisingly, OX40 expression was negatively correlated with the frequency of MAIT cells in the peripheral blood of T2D patients. Increased cleaved caspase-3 levels were observed in OX40+-expressing MAIT cells in T2D patients. In vitro, activated OX40 signaling by recombinant OX40L protein promoted caspase-3 activation and apoptosis of MAIT cells. Inhibition of caspase-3 restored apoptosis of MAIT cells induced by OX40 signaling. These results identify OX40 as an amplifier of activation-induced cell death of human blood MAIT cells and shed new light on the regulation of MAIT cells in the phase of immune responses in T2D.

Effects of quercetin on the alterations of serum elements in chronic unpredictable mild stress-induced depressed rats.

Depression is a common and serious psychiatric disorder, but current conventional antidepressants have limited efficacy and significant side effects. Thus, better antidepressants are urgently needed. This study aimed to investigate the antidepressant-like effects and potential mechanism of quercetin by evaluating the changes of serum elements in chronic unpredictable mild stress (CUMS) rats. Based on the results of the sucrose preference test (SPT), 96 rats were randomly assigned to six groups: control, different dosages of quercetin (10 and 50 mg/kg·bw, respectively), depressed, and different dosages quercetin plus depressed groups. After 8 weeks of CUMS modeling, rat serum was collected. Fifteen elements in serum were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), and related enzyme indicators, antioxidant indicators, and inflammatory cytokines were detected to further explore the potential mechanism. Besides, the accuracy and precision of the method were evaluated. The results showed that the levels of iron (Fe), copper (Cu), and calcium (Ca) in serum significantly increased (p ≤ 0.001), while the levels of magnesium (Mg), zinc (Zn), selenium (Se), and cobalt (Co) significantly decreased (p ≤ 0.001) in depressed group compared with the control group. The levels of the remaining eight elements did not change significantly. When high-dose quercetin was administered to depressed rats, the levels of the above seven elements significantly restored (p ≤ 0.001). This study suggests that quercetin (50 mg/kg·bw) has a regulatory effect on serum elements in CUMS rats, which may be mediated by reducing oxidative stress, inhibiting inflammation, and regulating a variety of neurotransmitter systems.

Metabolomics analysis of the effects of quercetin on renal toxicity induced by cadmium exposure in rats.

This study aims to explore the protective effects of quercetin against cadmium-induced nephrotoxicity utilizing metabolomics methods. Male Sprague-Dawley rats were randomly assigned to six groups: control, different dosages of quercetin (10 and 50 mg/kg·bw, respectively), CdCl2 (4.89 mg/kg·bw) and different dosages quercetin plus CdCl2 groups. After 12 weeks, the kidneys were collected for metabolomics analysis and histopathology examination. In total, 11 metabolites were confirmed, the intensities of which significantly changed (up-regulated or down-regulated) compared with the control group (p < 0.00067). These metabolites include xanthosine, uric acid (UA), guanidinosuccinic acid (GSA), hypoxanthine (Hyp), 12-hydroxyeicosatetraenoic acid (tetranor 12-HETE), taurocholic acid (TCA), hydroxyphenylacetylglycine (HPAG), deoxyinosine (DI), ATP, formiminoglutamic acid (FIGLU) and arachidonic acid (AA). When high-dose quercetin and cadmium were given to rats concurrently, the intensities of above metabolites significantly restored (p < 0.0033 or p < 0.00067). The results showed quercetin attenuated Cd-induced nephrotoxicity by regulating the metabolism of lipids, amino acids, and purine, inhibiting oxidative stress, and protecting kidney functions.