Wutou decoction attenuates rheumatoid arthritis by modulating the Ahr/LOC101928120/SHC1 pathway.

CONTEXT: Wutou decoction (WTD) is a Chinese herbal formula alleviating rheumatoid arthritis (RA). SHC adaptor protein 1 (SHC1) regulates apoptosis, inflammation, and the production of reactive oxygen species (ROS). The LOC101928120 gene is located near the SHC1 gene. Bioinformatics analysis showed that the long non-coding RNA LOC101928120 binds to histone deacetylase HDAC1 that might regulate SHC1 expression. The LOC101928120 gene might be targeted by the transcriptional factor Aryl hydrocarbon receptor (Ahr). OBJECTIVE: This study determines the involvement of the Ahr/LOC101928120/SHC1 pathway in WTD alleviation of RA. MATERIALS AND METHODS: Wistar rats were injected with complete Freund's adjuvant in the hind footpad to construe the RA model. WTD (9.8 g/kg/day) was administered intragastrically for 15 days. The CHON-001 chondrocyte cells were treated with IL-1ß (10 ng/mL) alone or in combination with WTD (1 µg/mL). A RNA pull-down assay was performed to determine the interaction between LOC101928120 and HDAC1. Ahr targeting the LOC101928120 gene was detected using luciferase reporter and chromatin immunoprecipitation assays. RESULTS: WTD alleviated the swelling of the hind paw in rats with RA and suppressed the chondrocyte apoptosis and ROS production caused by IL-1ß. WTD decreased SHC1 but increased LOC101928120 in IL-1ß-treated chondrocytes. SHC1 knockdown and LOC101928120 overexpression also showed the protection. However, LOC101928120 knockdown attenuated the protective effects of WTD. WTD stimulated Ahr, which promoted LOC101928120 transcription. LOC101928120 recruited HDAC1 to the promoter region of the SHC1 gene, thereby decreasing SHC1. DISCUSSION AND CONCLUSION: This study revealed a new mechanism by which WTD alleviates RA by modulating the Ahr/LOC101928120/SHC1 pathway.

AhR and IDO1 in pathogenesis of Covid-19 and the "Systemic AhR Activation Syndrome:" a translational review and therapeutic perspectives.

Covid-19 is the acute illness caused by SARS-CoV-2 with initial clinical symptoms such as cough, fever, malaise, headache, and anosmia. After entry into cells, corona viruses (CoV) activate aryl hydrocarbon receptors (AhRs) by an indoleamine 2,3-dioxygenase (IDO1)-independent mechanism, bypassing the IDO1-kynurenine-AhR pathway. The IDO1-kynurenine-AhR signaling pathway is used by multiple viral, microbial and parasitic pathogens to activate AhRs and to establish infections. AhRs enhance their own activity through an IDO1-AhR-IDO1 positive feedback loop prolonging activation induced by pathogens. Direct activation of AhRs by CoV induces immediate and simultaneous up-regulation of diverse AhR-dependent downstream effectors, and this, in turn, results in a "Systemic AhR Activation Syndrome" (SAAS) consisting of inflammation, thromboembolism, and fibrosis, culminating in multiple organ injuries, and death. Activation of AhRs by CoV may lead to diverse sets of phenotypic disease pictures depending on time after infection, overall state of health, hormonal balance, age, gender, comorbidities, but also diet and environmental factors modulating AhRs. We hypothesize that elimination of factors known to up-regulate AhRs, or implementation of measures known to down-regulate AhRs, should decrease severity of infection. Although therapies selectively down-regulating both AhR and IDO1 are currently lacking, medications in clinical use such as dexamethasone may down-regulate both AhR and IDO1 genes, as calcitriol/vitamin D3 may down-regulate the AhR gene, and tocopherol/vitamin E may down-regulate the IDO1 gene. Supplementation of calcitriol should therefore be subjected to epidemiological studies and tested in prospective trials for prevention of CoV infections, as should tocopherol, whereas dexamethasone could be tried in interventional trials. Because lack of physical exercise activates AhRs via the IDO1-kynurenine-AhR signaling pathway increasing risk of infection, physical exercise should be encouraged during quarantines and stay-at-home orders during pandemic outbreaks. Understanding which factors affect gene expression of both AhR and IDO1 may help in designing therapies to prevent and treat humans suffering from Covid-19.

Activation of the aryl hydrocarbon receptor suppresses sensitization in a mouse peanut allergy model.

Food allergy is an increasing health problem in Western countries. Previously, it has been shown that the intensity of food allergic reactions can be regulated by regulatory T (T(reg)) cells. In addition, it has been shown that activation of the aryl hydrocarbon receptor (AhR) regulates T-cell responses by induction of T(reg) cells. Therefore, we hypothesized that activation of the AhR pathway can suppress development of food allergic responses through the induction of T(reg) cells. This was investigated by using a mouse model for peanut allergy. C3H/HeOuJ mice (AhR(b)(-2)) were sensitized to peanut by administering peanut extract (PE) by gavage in the presence of cholera toxin and were treated with the prototypical AhR ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (0.6, 1.7, 5, and 15 µg/kg body weight) on days 3 and 11 orally. The functional role of CD4(+)CD25(+)Foxp3(+) T(reg) cells was investigated by depleting these cells with anti-CD25 mAb during sensitization to PE. TCDD treatment dose dependently suppressed sensitization to peanut (PE-specific IgE, IgG1, and IgG2a and PE-induced IL-5, IL-10, and IL-13, respectively). The percentage, but not the number, of CD4(+)CD25(+)Foxp3(+) T(reg) cells dose dependently increased by AhR activation in both spleen and mesenteric lymph nodes. Depletion of CD4(+)CD25(+)Foxp3(+) T(reg) cells markedly reversed the suppressive effect of TCDD on PE-specific antibody levels and PE-induced IL-5, IL-10, and IL-13 cytokine production. Present data demonstrate for the first time that activation of the AhR by TCDD suppressed the development of Th2-mediated food allergic responses. A functional shift within the CD4(+) cell population toward CD4(+)CD25(+)Foxp3(+) T(reg) cells appeared to underlie this effect. This suggests that the AhR pathway might provide potential therapeutic targets to treat food allergic diseases.

Evodiamine as a novel antagonist of aryl hydrocarbon receptor.

Evodiamine, the major bioactive alkaloid isolated from Wu-Chu-Yu, has been shown to interact with a wide variety of proteins and modify their expression and activities. In this study, we investigated the interaction between evodiamine and the aryl hydrocarbon receptor (AhR). Molecular modeling results revealed that evodiamine directly interacted with the AhR. Cytosolic receptor binding assay also provided the evidence that evodiamine could interact with the AhR with the K(i) value of 28.4±4.9nM. In addition, we observed that evodiamine suppressed the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced nuclear translocation of the AhR and the expression of CYP1A1 dose-dependently. These results suggested that evodiamine was able to bind to the AhR as ligand and exhibit antagonistic effects.

Evaluation of human liver slices and reporter gene assays as systems for predicting the cytochrome p450 induction potential of drugs in vivo in humans.

PURPOSE: The aim of the study was to investigate the feasibility of predicting human in vivo cytochrome P450 (CYP) induction properties of drugs using in vitro methods. METHODS: The CYP induction potential of compounds was tested in human liver slices and in reporter gene assays for the aryl hydrocarbon receptor (AhR) and the pregnane X receptor (PXR). RESULTS: In human liver slices, CYP activities decreased dramatically over the experimental period, whereas mRNA levels could reliably be used to investigate CYP1A, 2C9, and 3A4 induction. However, the interindividual variations and demanding experimentation limit the use of liver slices in screening programs. Reporter gene assays are robust and reliable assays, amenable to high throughput screening. Several compounds activated AhR. The relevance of this activation, however, needs to be further investigated since there are no clear reports on drugs inducing CYP1A in vivo. The results from the PXR assay could be used to correctly classify compounds with known CYP3A induction properties when relating in vivo AUCtot to PXR EC50 values. CONCLUSIONS: Liver slices are a valuable model to study the regulation of a larger number of enzymes by single compounds. The PXR reporter gene assay could be used as a reliable screening method to predict CYP3A induction in vivo.

Ontogenetic development, sexual differentiation, and effects of Aroclor 1254 exposure on expression of the arylhydrocarbon receptor and of the arylhydrocarbon receptor nuclear translocator in the rat hypothalamus.

Interaction of polychlorinated biphenyls (PCBs) with the aryl hydrocarbon receptor (AhR)/nuclear translocator (ARNT) system might interfere with the mechanisms controlling the sexual differentiation of the developing hypothalamus. The aim of this study was to evaluate the presence of AhR/ARNT in brain cells and the developmental profile of their expression in the hypothalamus of male and female rats during the perinatal period. Brain accumulation of the main PCB congeners after prenatal exposure to Aroclor 1254 and its influence on hypothalamic expression of AhR/ARNT was also assessed. The results show that: (a) AhR and ARNT are expressed both in neurons and in glia; (b) AhR expression progressively increases in the developing hypothalamus particularly in males, while ARNT is relatively constant in both sexes; (c) the prenatal administration of Aroclor to dams produces a differential accumulation of PCBs, depending on the chlorine atom number, and stimulates AhR expression only in the male hypothalamus. In conclusion, the developing male hypothalamus might be more sensitive to disrupting potential of PCBs.

Black tea extract suppresses transformation of aryl hydrocarbon receptor induced by dioxin.

Dioxins cause various adverse effects through binding to an aryl hydrocarbon receptor (AhR) and transformation of the receptor. In this study, we investigated whether black tea extract suppresses AhR transformation. Dried black tea leaves were extracted with 75% ethanol, and the extract was pretreated to the rat liver cytosol fraction 10 min prior to addition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Transformed AhR was detected by electrophoretic gel mobility shift assay. Black tea extract suppressed AhR transformation in a dose-dependent manner, and the IC50 value against 1 nM TCDD-induced AhR transformation was 8.9 microg/ml. The result suggests that intake of black tea has a potential to suppress the AhR transformation, leading protection from dioxin toxicity.

Anthocyan does not suppress transformation of aryl hydrocarbon receptor induced by dioxin.

Dioxins cause a variety of toxic effects through transformation of a cytosolic aryl hydrocarbon receptor (AhR). We have previously demonstrated that certain natural flavones and flavonols at the dietary levels suppress AhR transformation. In this study, we investigated whether 5 anthocyanidins, 15 anthocyanins, and protocatechuic acid suppress AhR transformation in mouse hepatoma Hepa-1c1c7 cells. All the compounds tested here at 5 microM unexpectedly failed to suppress the transformation induced by 0.1 nM TCDD, indicating that anthocyan does not have a potential to prevent dioxin toxicity.

Differences in inducibility of CYP1A1-mRNA by benzimidazole compounds between human and mouse cells: evidences of a human-specific signal transduction pathway for CYP1A1 induction.

Three benzimidazole compounds, omeprazole (OP), thiabendazole (TBZ), and lansoprazole (LP), were compared with respect to the induction of CYP1A1-mRNA in human hepatoma cells, HepG2. OP was the most potent inducer among the three compounds, but LP was found to be a weak inducer. Induction by TBZ was at an intermediate level. None of these compounds induced CYP1A1-mRNA in a mouse hepatoma cell line, Hepa-1. The transient expression of mouse Cyp1a1-CAT gene into HepG2 cells showed that OP treatment of the transfectants induced CAT activity to the same degree as 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment. Therefore, the cellular factors in human cells were able to work on the mouse regulatory element. The expression of human aryl hydrocarbon (Ah) receptor in the mouse Hepa-1 mutant cell line cl-19, which is defective in Ah receptor, did not increase the induction level of CYP1A1-mRNA by OP treatment. When the cultured medium of HepG2 cells in the presence of OP was added to the mouse Hepa-1 cell culture medium, CYP1A1-mRNA was not induced in Hepa-1 cells. It is thus concluded that metabolites of OP in human cells are not the ligands for the human Ah receptor. Therefore, in human cells, but not mouse cells, there must be an OP-sensitive activation factor for the human Ah receptor.