Expression of aryl hydrocarbon receptor, inflammatory cytokines, and incidence of rheumatoid arthritis in Vietnamese dioxin-exposed people

Aryl hydrocarbon receptor gene expression in ankylosing spondylitis and its correlation with interleukin-17, RAR-related orphan receptor gamma t expression, and disease activity indices

Objectives

Considering the role of T helper (Th)17 cells in the pathogenesis of ankylosing spondylitis (AS), the aim of this study was to determine the correlation between aryl hydrocarbon receptor (AHR) gene expression and the expression of Th17-related genes including interleukin (IL)-17 and RAR-related orphan receptor gamma t (RORγt) transcription factor.

Patients and methods

Thirty patients with AS (26 males, 4 females; mean age: 36.1±8.1 years) and 30 age- and sex-matched healthy individuals (26 males, 4 females; mean age: 36.2±14.6 years) were recruited for the case-control study between June 2021 and January 2022. Ribonucleic acid (RNA) was extracted from peripheral blood cells and expression levels of AHR, IL-17, RORγt, and AHR repressor (AHRR) genes were evaluated using real-time polymerase chain reaction technique. The serum level of IL-17 was evaluated with enzyme-linked immunosorbent assay.

Results

The results showed a nonsignificant elevation of AHR, IL-17, and RORγt gene expression in the patient group compared to the control. There was a direct correlation between AHR gene expression and IL-17 and RORγt genes and a negative correlation between AHR and AHRR expression. Moreover, AHR gene expression showed a weak correlation with disease activity indices, including Bath Ankylosing Spondylitis Disease Activity Index, Bath Ankylosing Spondylitis Functional Index, Bath Ankylosing Spondylitis Metrology Index, Bath Ankylosing Spondylitis Global Score, and Ankylosing Spondylitis Quality of Life. Moreover, the serum level of IL-17 was higher in AS patients compared to the healthy group (p=0.02).

Conclusion

Upregulated expression of the AHR gene in ankylosing spondylitis and its correlation with IL-17 and ROR-γ t gene expression suggests that it could be a potential diagnostic and therapeutic target for AS.

Association between combined exposure to dioxins and arthritis among US adults: a cross-sectional study

Dioxins and dioxin-like compounds (DLCs) are common pollutants hazardous to human health. We applied 12 dioxins and DLCs data of 1851 participants (including 484 arthritis patients) from National Health Examination Survey (NHANES) 2001-2004 and quadrupled them into rank variables. Multivariate logistic regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) models were used to explore the relationship between individual or mixed exposure to the pollutants and arthritis after adjusting for multiple covariates. In multivariable logistic regression with an individual dioxin or DLC, almost every chemical was significantly positively associated with arthritis, except PCB66 (polychlorinated biphenyl 66) and 1,2,3,4,6,7,8-heptachlorodibenzofuran (hpcdf). The WQS model indicated that the combined exposure to the 12 dioxins and DLCs was positively linked to arthritis (OR: 1.884, 95% CI: 1.514-2.346), with PCB156 (weighted 0.281) making the greatest contribution. A positive trend between combined exposure and arthritis was observed in the BKMR model, with a posterior inclusion probability (PIP) of 0.987 for PCB156, which was also higher than the other contaminants.

Endocrine-disrupting chemicals and autoimmune diseases

Endocrine-disrupting chemicals (EDCs) widely exist in people's production and life which have great potential to damage human and animal health. Over the past few decades, growing attention has been paid to the impact of EDCs on human health, as well as immune system. So far, researchers have proved that EDCs (such as bisphenol A (BPA), phthalate, tetrachlorodibenzodioxin (TCDD), etc.) affect human immune function and promotes the occurrence and development of autoimmune diseases (ADs). Therefore, in order to better understand how EDCs affect ADs, we summarized the current knowledge about the impact of EDCs on ADs, and elaborated the potential mechanism of the impact of EDCs on ADs in this review.

Elevated Kynurenine Levels in Patients with Primary Sjögren's Syndrome

OBJECTIVE

We aimed to investigate the plasma levels of tryptophan (Trp) and its metabolites in patients with primary Sjögren's syndrome (pSS).

METHODS

The study included 34 pSS patients and 42 healthy individuals, and serum Trp and kynurenine (Kyn) concentrations were measured by liquid chromatography with tandem mass spectrometry. Trp degradation was predicted using the ratio of Kyn and Trp concentrations (Kyn/Trp).

RESULTS

In our study, the mean serum Trp concentration was found to be considerably lower in the pSS group than in the control group (P = .001). The levels of Kyn (P = .019) and the Kyn/Trp ratio (P < .001) were significantly higher in the pSS group than in the control group. The Kyn/Trp ratio was negatively correlated with C-reactive protein (r = -0.369, P = .032).

CONCLUSION

We found that Kyn pathway metabolism was altered in patients with pSS. This suggests that Trp metabolism may be closely linked to the disease pathogenesis of pSS.

Toxic mechanisms of cigarette smoke and heat-not-burn tobacco vapor inhalation on rheumatoid arthritis

Tobacco combustion exposure worsens rheumatoid arthritis (RA). Non-combustible tobacco devices, as heat-not-burn tobacco (HNBT), are emerging as harm reduction to smokers by releasing nicotine and lower combustible tobacco products. Nevertheless, HNBT toxicity remains unclear. Hence, here we investigated the impacts of the tobacco combustible product (cigarette smoke; CS) or HNBT vapor exposures on antigen-induced arthritis (AIA) in C57BL/6 mice. Animals were exposed to airflow, HNBT vapor, or CS during 1 h/twice a day, under the Health Canada Intense (HCI) smoking regime, between days 14 to 20 after the first immunization. At day 21, 16 h after the last exposures, mice were i.a. challenged and the AIA effects were evaluated 24 h later. CS- or HNBT-exposed mice presented equivalent blood nicotine levels. CS exposure worsened articular symptoms, pulmonary inflammation, and expression of lung metallothioneins. Nevertheless, CS or HNBT exposures reduced lymphoid organs' cellularity, splenocyte proliferation and IL-2 secretion. Additional in vitro CS or HNBT exposures confirmed the harmful effects on splenocytes, which were partially mediated by the activation of nicotine/α7nAchR pathway. Associated, data demonstrate the toxic mechanisms of CS or HNBT inhalation at HCI regime on RA, and highlight that further investigations are fundamental to assure the toxicity of emerging tobacco products on the immune system during specific challenges.

Aryl hydrocarbon receptor is essential for the pathogenesis of pulmonary arterial hypertension

Inflammatory signals are thought to be crucial for the pathogenesis of PAH; however, the underlying mechanism is still largely unknown. In this study, we demonstrate that AHR makes a causal contribution to the pathogenesis of PAH, activating a focal inflammatory response in the lungs and promoting infiltration of immune cells from the bone marrow. Furthermore, we found that PAH patients with higher AHR agonistic activity in sera are more susceptible to severe clinical events than those with lower activity. Because conventional therapy for pulmonary hypertension targeting pulmonary artery vasodilation has limited efficacy against severe PAH, the AHR-signaling pathway represents a promising therapeutic target for PAH. In addition, AHR agonistic activity in serum represents a biomarker for PAH.

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by arteriopathy in the small to medium-sized distal pulmonary arteries, often accompanied by infiltration of inflammatory cells. Aryl hydrocarbon receptor (AHR), a nuclear receptor/transcription factor, detoxifies xenobiotics and regulates the differentiation and function of various immune cells. However, the role of AHR in the pathogenesis of PAH is largely unknown. Here, we explore the role of AHR in the pathogenesis of PAH. AHR agonistic activity in serum was significantly higher in PAH patients than in healthy volunteers and was associated with poor prognosis of PAH. Sprague–Dawley rats treated with the potent endogenous AHR agonist, 6-formylindolo[3,2-b]carbazole, in combination with hypoxia develop severe pulmonary hypertension (PH) with plexiform-like lesions, whereas Sprague–Dawley rats treated with the potent vascular endothelial growth factor receptor 2 inhibitors did not. Ahr-knockout (Ahr^−/−) rats generated using the CRISPR/Cas9 system did not develop PH in the SU5416/hypoxia model. A diet containing Qing-Dai, a Chinese herbal drug, in combination with hypoxia led to development of PH in Ahr^+/+ rats, but not in Ahr^−/− rats. RNA-seq analysis, chromatin immunoprecipitation (ChIP)-seq analysis, immunohistochemical analysis, and bone marrow transplantation experiments show that activation of several inflammatory signaling pathways was up-regulated in endothelial cells and peripheral blood mononuclear cells, which led to infiltration of CD4⁺ IL-21⁺ T cells and MRC1⁺ macrophages into vascular lesions in an AHR-dependent manner. Taken together, AHR plays crucial roles in the development and progression of PAH, and the AHR-signaling pathway represents a promising therapeutic target for PAH.

Indirect co-cultivation of HepG2 with differentiated THP-1 cells induces AHR signalling and release of pro-inflammatory cytokines

HepG2 and THP-1 cells, the latter differentiated by phorbol 12-myristate 13-acetate (PMA), were co-cultured and characterized for typical liver-specific functions, such as xenobiotic detoxification, lipid and cholesterol metabolism. Furthermore, liver injury-associated pathways, such as inflammation, were studied. In general, the co-cultivation of these cells produced a pro-inflammatory system, as indicated by increased levels of cytokines (IL-8, TGF-α, IL-6, GM-CSF, G-CSF, TGF-β, and hFGF) in the respective supernatant. Increased expression levels of target genes of the aryl hydrocarbon receptor (AHR), e.g., CYP1A1, CYP1A2 and CYP1B1, were detected, accompanied by the increased enzyme activity of CYP1A1. Moreover, transcriptome analyses indicated a significant upregulation of cholesterol biosynthesis, which could be reduced to baseline levels by lovastatin. In contrast, total de novo lipid synthesis was reduced in co-cultured HepG2 cells. Key events of the adverse outcome pathway (AOP) for fibrosis were activated by the co-cultivation, however, no increase in the concentration of extracellular collagen was detected. This indicates, that AOP should be used with care. In summary, the indirect co-culture of HepG2/THP-1 cells results in an increased release of pro-inflammatory cytokines, an activation of the AHR pathway and an increased enzymatic CYP1A activity.

Elevated kynurenine levels in diffuse cutaneous and anti-RNA polymerase III positive systemic sclerosis

Systemic sclerosis (SSc) is a systemic disease characterized by vasculopathy, progressive fibrosis and autoimmune activation. Tryptophan (Trp) metabolism has been linked to altered immune cell function and to malignancy. We have investigated the role of Trp metabolic pathway in SSc measuring serum Trp, Kynurenine (Kyn) and Trp/Kyn ratio in a cohort of 97 SSc patients and 10 healthy controls. Association with disease characteristics was evaluated. We found that Trp levels in SSc patients were significantly lower compared to HCs. We also found that patients with diffuse cutaneous (dcSSc) had lower levels of Trp compared to limited cutaneous (lcSSc). These results were paralleled by higher levels of Kyn found in SSc patients compared to HCs and significantly lower levels in dcSSc compared to lcSSc. The autoantibody profile was also found to be significantly associated with Kyn and Trp levels as anti-RNA-polymerase III (ARA) positive patients were shown to have lower Trp levels and higher Kyn levels compared with anti-centromere and anti-topoisomerase I positive patients. Moreover, the highest Trp/Kyn was found in ARA+ patients with dcSSc, suggesting that an activation of the Kyn pathway, is more specifically associated with this subset of SSc patients. Stability over time makes these markers of Trp metabolism feasible for SSc stratification.

Natural Products for the Treatment of Autoimmune Arthritis: Their Mechanisms of Action, Targeted Delivery, and Interplay with the Host Microbiome

Rheumatoid arthritis (RA) is a chronic, debilitating illness characterized by painful swelling of the joints, inflammation of the synovial lining of the joints, and damage to cartilage and bone. Several anti-inflammatory and disease-modifying drugs are available for RA therapy. However, the prolonged use of these drugs is associated with severe side effects. Furthermore, these drugs are effective only in a proportion of RA patients. Hence, there is a need to search for new therapeutic agents that are effective yet safe. Interestingly, a variety of herbs and other natural products offer a vast resource for such anti-arthritic agents. We discuss here the basic features of RA pathogenesis; the commonly used animal models of RA; the mainstream drugs used for RA; the use of well-characterized natural products possessing anti-arthritic activity; the application of nanoparticles for efficient delivery of such products; and the interplay between dietary products and the host microbiome for maintenance of health and disease induction. We believe that with several advances in the past decade in the characterization and functional studies of natural products, the stage is set for widespread clinical testing and/or use of these products for the treatment of RA and other diseases.