ABSTRACT
BACKGROUND: Urolithin A (URA) is an intestinal microbiota metabolic product from ellagitannin-containing foods with multiple biological activities. However, its role in autoimmune diseases is largely unknown. Here, for first time, we demonstrate the therapeutic effect of URA in an experimental autoimmune encephalomyelitis (EAE) animal model. METHODS: Therapeutic effect was evaluated via an active and passive EAE animal model in vivo. The function of URA on bone marrow-derived dendritic cells (BM-DCs), T cells, and microglia were tested in vitro. FINDINGS: Oral URA (25 mg/kg/d) suppressed disease progression at prevention, induction, and effector phases of preclinical EAE. Histological evaluation showed that significantly fewer inflammatory cells, decreased demyelination, lower numbers of M1-type microglia and activated DCs, as well as reduced infiltrating Th1/Th17 cells were present in the central nervous system (CNS) of the URA-treated group. URA treatment at 25 µM inhibited the activation of BM-DCs in vitro, restrained Th17 cell differentiation in T cell polarization conditions, and in a DC-CD4+ T cell co-culture system. Moreover, we confirmed URA inhibited pathogenicity of Th17 cells in adoptive EAE. Mechanism of URA action was directly targeting Aryl Hydrocarbon Receptor (AhR) and modulating the signaling pathways. INTERPRETATION: Collectively, our study offers new evidence that URA, as a human microbial metabolite, is valuable to use as a prospective therapeutic candidate for autoimmune diseases.
Subject(s)
Coumarins/pharmacology , Encephalomyelitis, Autoimmune, Experimental/etiology , Encephalomyelitis, Autoimmune, Experimental/metabolism , Receptors, Aryl Hydrocarbon/metabolism , Animals , Biomarkers , Coumarins/chemistry , Disease Models, Animal , Disease Susceptibility , Encephalomyelitis, Autoimmune, Experimental/drug therapy , Encephalomyelitis, Autoimmune, Experimental/pathology , Female , Immunohistochemistry , Mice , Models, Molecular , Molecular Targeted Therapy , Receptors, Aryl Hydrocarbon/antagonists & inhibitors , Receptors, Aryl Hydrocarbon/chemistry , Receptors, Aryl Hydrocarbon/genetics , Structure-Activity RelationshipABSTRACT
Multiple sclerosis (MS) is a CNS autoimmune disease characterized by demyelination and inflammatory infiltration with a high disability rate. Increasing evidence has demonstrated the importance of gut microbiota as an environmental risk factor in MS and its animal model experimental autoimmune encephalomyelitis (EAE). Diet is the main determinant of gut microbiota composition and function, which greatly affects the shaping of microbial structure. Pomegranate peel, a waste product in the production of juice, is rich in health-promoting compounds. However, its individual constituents, immunoregulatory activities, and action associated with bacterial diversity in the gut microbiota are largely unknown. Here, the main nutrient ingredients of pomegranate peel extract (PPE) were identified as phenols, flavonoids, amino acids, carbohydrates, fatty acids, lipids, nucleotides, organic acids, alcohols, and vitamins via metabolomics evaluation. We found, for the first time, oral PPE (100 mg/kg/day) not only effectively relieves EAE, inhibits CNS inflammatory factor infiltration and myelin loss, but also reshapes gut microbiota. Furthermore, recipient EAE mice with fecal transplantation from the PPE-treated donor delayed the disease development significantly. 16S rRNA gene sequencing revealed the increased gut microbiota richness in PPE-treated group. Among them, Lactobacillaceae enriched significantly, while Alcaligenaceae and Acidaminococcacea decreased remarkably. In conclusion, our data demonstrated that gut microbiota mediated the beneficial effects of oral PPE on EAE, and provided new ideas for developing the prebiotic value of pomegranate peel for the treatment of autoimmune diseases.
Subject(s)
Bacteria/drug effects , Encephalomyelitis, Autoimmune, Experimental/drug therapy , Gastrointestinal Microbiome/drug effects , Multiple Sclerosis/drug therapy , Plant Extracts/administration & dosage , Pomegranate/chemistry , Waste Products/analysis , Animals , Bacteria/classification , Bacteria/genetics , Bacteria/growth & development , Disease Models, Animal , Encephalomyelitis, Autoimmune, Experimental/microbiology , Female , Fruit/chemistry , Humans , Mice , Mice, Inbred C57BL , Multiple Sclerosis/microbiology , Plant Extracts/chemistryABSTRACT
T helper 17 (Th17) cells that express interleukin-17 (IL-17) play a key role in various inflammatory diseases, such as multiple sclerosis (MS), and its animal model experimental autoimmune encephalomyelitis (EAE). The retinoic acid receptor-related orphan receptors γt (RORγt) have an indispensable effect on the differentiation of this cell type, and are thus considered a valuable target in the treatment of Th17-related disorders. In this study, we found that eriodictyol (EDT), a natural flavonoid abundant in citrus fruits and peanuts, was located directly in the binding pocket of RORγt, and induced a conformational change that resulted in the effective suppression of the receptor's activity, thus offering insight into the transcriptional inhibition of RORγt-dependent genes. Consistent with this, EDT dose-dependently (5-10 µM) blocked murine Th17 differentiation, and markedly reduced IL-17A secretion in vitro. Furthermore, this compound has been found to have novel properties for directly inhibiting Th1 cell development and promoting Treg cell differentiation at high doses (≥10 µM). EDT administration significantly decreased the clinical severity in the EAE model, with inhibited demyelination and reduced inflammatory responses in the periphery and in the central nervous system (CNS). In the adoptive transfer model, EDT also remarkably suppressed the Th17 cell infiltration and pathogenicity. Collectively, our data demonstrated that EDT, as an agent for the pharmacological inhibition of RORγt, has great potential for immunomodulation, and for use in the treatment of Th17-mediated autoimmune disease.
