TP53 mutations coincide with the ectopic expression of activation-induced cytidine deaminase in the fibroblast-like synoviocytes derived from a fraction of patients with rheumatoid arthritis

The Association between Inefficient Repair of DNA Double-Strand Breaks and Common Polymorphisms of the HRR and NHEJ Repair Genes in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation affecting up to 2.0% of adults around the world. The molecular background of RA has not yet been fully elucidated, but RA is classified as a disease in which the genetic background is one of the most significant risk factors. One hallmark of RA is impaired DNA repair observed in patient-derived peripheral blood mononuclear cells (PBMCs). The aim of this study was to correlate the phenotype defined as the efficiency of DNA double-strand break (DSB) repair with the genotype limited to a single-nucleotide polymorphism (SNP) of DSB repair genes. We also analyzed the expression level of key DSB repair genes. The study population contained 45 RA patients and 45 healthy controls. We used a comet assay to study DSB repair after in vitro exposure to bleomycin in PBMCs from patients with rheumatoid arthritis. TaqMan SNP Genotyping Assays were used to determine the distribution of SNPs and the Taq Man gene expression assay was used to assess the RNA expression of DSB repair-related genes. PBMCs from patients with RA had significantly lower bleomycin-induced DNA lesion repair efficiency and we identified more subjects with inefficient DNA repair in RA compared with the control (84.5% vs. 24.4%; OR 41.4, 95% CI, 4.8-355.01). Furthermore, SNPs located within the RAD50 gene (rs1801321 and rs1801320) increased the OR to 53.5 (95% CI, 4.7-613.21) while rs963917 and rs3784099 (RAD51B) to 73.4 (95% CI, 5.3-1011.05). These results were confirmed by decision tree (DT) analysis (accuracy 0.84; precision 0.87, and specificity 0.86). We also found elevated expression of RAD51B, BRCA1, and BRCA2 in PBMCs isolated from RA patients. The findings indicated that impaired DSB repair in RA may be related to genetic variations in DSB repair genes as well as their expression levels. However, the mechanism of this relation, and whether it is direct or indirect, needs to be elucidated.

Mutant p53R211* ameliorates inflammatory arthritis in AIA rats via inhibition of TBK1-IRF3 innate immune response

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune inflammation disease characterized by imbalance of immune homeostasis. p53 mutants are commonly described as the guardian of cancer cells by conferring them drug-resistance and immune evasion. Importantly, p53 mutations have also been identified in RA patients, and this prompts the investigation of its role in RA pathogenesis.

METHODS

The cytotoxicity of disease-modifying anti-rheumatic drugs (DMARDs) against p53 wild-type (WT)/mutant-transfected RA fibroblast-like synoviocytes (RAFLSs) was evaluated by MTT assay. Adeno-associated virus (AAV) was employed to establish p53 WT/R211* adjuvant-induced arthritis (AIA) rat model. The arthritic condition of rats was assessed by various parameters such as micro-CT analysis. Knee joint samples were isolated for total RNA sequencing analysis. The expressions of cytokines and immune-related genes were examined by qPCR, ELISA assay and immunofluorescence. The mechanistic pathway was determined by immunoprecipitation and Western blotting in vitro and in vivo.

RESULTS

Among p53 mutants, p53R213* exhibited remarkable DMARD-resistance in RAFLSs. However, AAV-induced p53R211* overexpression ameliorated inflammatory arthritis in AIA rats without Methotrexate (MTX)-resistance, and our results discovered the immunomodulatory effect of p53R211* via suppression of T-cell activation and T helper 17 cell (Th17) infiltration in rat joint, and finally downregulated expressions of pro-inflammatory cytokines. Total RNA sequencing analysis identified the correlation of p53R211* with immune-related pathways. Further mechanistic studies revealed that p53R213*/R211* instead of wild-type p53 interacted with TANK-binding kinase 1 (TBK1) and suppressed the innate immune TBK1-Interferon regulatory factor 3 (IRF3)-Stimulator of interferon genes (STING) cascade.

CONCLUSIONS

This study unravels the role of p53R213* mutant in RA pathogenesis, and identifies TBK1 as a potential anti-inflammatory target.

The off-target effects of AID in carcinogenesis

Activation-induced cytidine deaminase (AID) plays a crucial role in promoting B cell diversification through somatic hypermutation (SHM) and class switch recombination (CSR). While AID is primarily associated with the physiological function of humoral immune response, it has also been linked to the initiation and progression of lymphomas. Abnormalities in AID have been shown to disrupt gene networks and signaling pathways in both B-cell and T-cell lineage lymphoblastic leukemia, although the full extent of its role in carcinogenesis remains unclear. This review proposes an alternative role for AID and explores its off-target effects in regulating tumorigenesis. In this review, we first provide an overview of the physiological function of AID and its regulation. AID plays a crucial role in promoting B cell diversification through SHM and CSR. We then discuss the off-target effects of AID, which includes inducing mutations of non-Igs, epigenetic modification, and the alternative role as a cofactor. We also explore the networks that keep AID in line. Furthermore, we summarize the off-target effects of AID in autoimmune diseases and hematological neoplasms. Finally, we assess the off-target effects of AID in solid tumors. The primary focus of this review is to understand how and when AID targets specific gene loci and how this affects carcinogenesis. Overall, this review aims to provide a comprehensive understanding of the physiological and off-target effects of AID, which will contribute to the development of novel therapeutic strategies for autoimmune diseases, hematological neoplasms, and solid tumors.

Long noncoding RNA H19 alleviates inflammation in osteoarthritis through interactions between TP53, IL-38, and IL-36 receptor

Aims

Osteoarthritis (OA) is a common degenerative joint disease characterized by chronic inflammatory articular cartilage degradation. Long noncoding RNAs (lncRNAs) have been previously indicated to play an important role in inflammation-related diseases. Herein, the current study set out to explore the involvement of lncRNA H19 in OA.

Methods

Firstly, OA mouse models and interleukin (IL)-1β-induced mouse chondrocytes were established. Expression patterns of IL-38 were determined in the synovial fluid and cartilage tissues from OA patients. Furthermore, the targeting relationship between lncRNA H19, tumour protein p53 (TP53), and IL-38 was determined by means of dual-luciferase reporter gene, chromatin immunoprecipitation, and RNA immunoprecipitation assays. Subsequent to gain- and loss-of-function assays, the levels of cartilage damage and proinflammatory factors were further detected using safranin O-fast green staining and enzyme-linked immunosorbent assay (ELISA) in vivo, respectively, while chondrocyte apoptosis was measured using Terminal deoxynucleotidyl transferase dUTP Nick-End Labeling (TUNEL) in vitro.

Results

IL-38 was highly expressed in lentivirus vector-mediated OA mice. Meanwhile, injection of exogenous IL-38 to OA mice alleviated the cartilage damage, and reduced the levels of proinflammatory factors and chondrocyte apoptosis. TP53 was responsible for lncRNA H19-mediated upregulation of IL-38. Furthermore, it was found that the anti-inflammatory effects of IL-38 were achieved by its binding with the IL-36 receptor (IL-36R). Overexpression of H19 reduced the expression of inflammatory factors and chondrocyte apoptosis, which was abrogated by knockdown of IL-38 or TP53.

Conclusion

Collectively, our findings evidenced that upregulation of lncRNA H19 attenuates inflammation and ameliorates cartilage damage and chondrocyte apoptosis in OA by upregulating TP53, IL-38, and by activating IL-36R.

Cite this article: Bone Joint Res 2022;11(8):594–607.

ATP spreads inflammation to other limbs through crosstalk between sensory neurons and interneurons

Neural circuits between lesions are one mechanism through which local inflammation spreads to remote positions. Here, we show the inflammatory signal on one side of the joint is spread to the other side via sensory neuron-interneuron crosstalk, with ATP at the core. Surgical ablation or pharmacological inhibition of this neural pathway prevented inflammation development on the other side. Mechanistic analysis showed that ATP serves as both a neurotransmitter and an inflammation enhancer, thus acting as an intermediary between the local inflammation and neural pathway that induces inflammation on the other side. These results suggest blockade of this neural pathway, which is named the remote inflammation gateway reflex, may have therapeutic value for inflammatory diseases, particularly those, such as rheumatoid arthritis, in which inflammation spreads to remote positions.

The p53 status in rheumatoid arthritis with focus on fibroblast-like synoviocytes

P53 is a transcription factor that regulates many signaling pathways like apoptosis, cell cycle, DNA repair, and cellular stress responses. P53 is involved in inflammatory responses through the regulation of inflammatory signaling pathways, induction of cytokines, and matrix metalloproteinase expression. Also, p53 regulates immune responses through modulating Toll-like receptors expression and innate and adaptive immune cell differentiation and maturation. P53 is a modulator of the apoptosis and proliferation processes through regulating multiple anti and pro-apoptotic genes. Rheumatoid arthritis (RA) is categorized as an invasive inflammatory autoimmune disease with irreversible deformity of joints and bone resorption. Different immune and non-immune cells contribute to RA pathogenesis. Fibroblast-like synoviocytes (FLSs) have been recently introduced as a key player in the pathogenesis of RA. These cells in RA synovium produce inflammatory cytokines and matrix metalloproteinases which results in synovitis and joint destruction. Besides, hyper proliferation and apoptosis resistance of FLSs lead to synovial hyperplasia and bone and cartilage destruction. Given the critical role of p53 in inflammation, apoptosis, and cell proliferation, lack of p53 function (due to mutation or low expression) exerts a prominent role for this gene in the pathogenesis of RA. This review focuses on the role of p53 in different mechanisms and cells (specially FLSs) that involved in RA pathogenesis.

Network pharmacology modeling identifies synergistic interaction of therapeutic and toxicological mechanisms for Tripterygium hypoglaucum Hutch

Background

Tripterygium hypoglaucum Hutch (THH) both has prominent efficacy and unwarranted toxicity in the treatment of autoimmune diseases. Nevertheless, its pharmacological and toxicological profiles still remain to be elucidated. In the current study, the network pharmacology approach was applied to identify synergistic interaction and mechanism of efficacy and toxicity for THH from a holistic perspective.

Methods

The compounds from THH were collected using literature retrieval and relevant databases. After the production of putative therapeutic targets for dominant diseases and harmful targets of adverse reactions (ADRs) induced by THH, the protein-protein interactions (PPIs), topological analysis and pathway enrichment were established to distinguish the hub targets and pathways. Additionally, the binding activity of candidate ingredients with core targets were revealed by molecular docking simulation.

Results

A total of eight bioactive components in THH were enrolled, and 633 targets were responsible for rheumatoid arthritis (RA), 1067 targets were corresponding to systemic lupus erythematosus (SLE), 1318 targets of ADRs were obtained. The results of enrichment analysis among THH-RA, THH-SLE and THH-ADR networks indicated that pathway in cancer, hepatitis B, rheumatoid arthritis, and PI3K-Akt signaling pathway might participate in THH for treating RA and SLE. Besides, the mechanism of ADRs that induced by THH were associated with viral carcinogenesis, p53 signaling pathway, PI3K-Akt signaling pathway, and so on. Whereas, these active ingredients of THH exerted the superior binding activities with crucial targets including STAT3, VEGFA, TP53 and MMP9 that functioned synergistically efficacy and toxicity as observed via molecular docking simulation.

Conclusion

The present research preliminarily interpreted the synergistic interaction of therapeutic and toxicological mechanisms for THH through the comprehensive analysis of relationship and binding activity between primary components and core targets, providing a feasible and promising approach to facilitate the development of toxic and irreplaceable herbs.

Bmi1 Regulates IκBα Degradation via Association with the SCF Complex

Bmi1 is a polycomb group protein and regulator that stabilizes the ubiquitination complex PRC1 in the nucleus with no evidently direct link to the NF-κB pathway. In this study, we report a novel function of Bmi1: its regulation of IκBα ubiquitination in the cytoplasm. A deficiency of Bmi1 inhibited NF-κB-mediated gene expression in vitro and a NF-κB-mediated mouse model of arthritis in vivo. Mechanistic analysis showed that Bmi1 associated with the SCF ubiquitination complex via its N terminus and with phosphorylation by an IKKα/β-dependent pathway, leading to the ubiquitination of IκBα. These effects on NF-κB-related inflammation suggest Bmi1 in the SCF complex is a potential therapeutic target for various diseases and disorders, including autoimmune diseases.

Anti-apoptotic roles for the mutant p53R248Q through suppression of p53-regulated apoptosis-inducing protein 1 in the RA-derived fibroblast-like synoviocyte cell line MH7A

We previously reported that somatic mutations in the p53 gene accumulated at a higher frequency in AID(activation induced cytidine deaminase)(+) RA-FLS, which may result in the malfunction of p53, causing the tumor-like properties of RA-FLS. Among the p53 mutations identified from 3 sources of AID(+) RA-FLS, we focused on the p53R248Q mutation because it was reported to enhance the invasiveness of lung cancer cells and to have dominant-negative activity for pro-apoptotic molecules. We obtained cDNA encoding the p53R248Q mutant and introduced it into the MH7A RA-FLS cell line. P53R248Q dramatically suppressed the expression of the pro-apoptotic molecule p53AIP1 even under oxidative stress, which normally upregulates p53AIP1, leading to apoptosis. Moreover, overexpression of p53AIP1 increased apoptosis, whereas p53AIP1 knockdown rescued the cells from apoptosis. Together, these studies indicate the critical role of p53AIP1 under DNA damaging stresses for cell fate determination in RA-FLS containing the p53R248Q mutation.

Household income is associated with the p53 mutation frequency in human breast tumors

BACKGROUND

A study from Scotland reported that the p53 mutation frequency in breast tumors is associated with socio-economic deprivation.

METHODS

We analyzed the association of the tumor p53 mutational status with tumor characteristics, education, and self-reported annual household income (HI) among 173 breast cancer patients from the greater Baltimore area, United States.

RESULTS

p53 mutational frequency was significantly associated with HI. Patients with < $15,000 HI had the highest p53 mutation frequency (21%), followed by the income group between $15,000 and $60,000 (18%), while those above $60,000 HI had the fewest mutations (5%). When dichotomized at $60,000, 26 out of 135 patients in the low income category had acquired a p53 mutation, while only 2 out of 38 with a high income carried a mutation (P < 0.05). In the adjusted logistic regression analysis with 3 income categories (trend test), the association between HI and p53 mutational status was independent of tumor characteristics, age, race/ethnicity, tobacco smoking and body mass. Further analyses revealed that HI may impact the p53 mutational frequency preferentially in patients who develop an estrogen receptor (ER)-negative disease. Within this group, 42% of the low income patients (< $15,000 HI) carried a mutation, followed by the middle income group (21%), while those above $60,000 HI did not carry mutations (Ptrend < 0.05).

CONCLUSIONS

HI is associated with the p53 mutational frequency in patients who develop an ER-negative disease. Furthermore, high income patients may acquire fewer p53 mutations than other patients, suggesting that lifetime exposures associated with socio-economic status may impact breast cancer biology.

Regulation of DNA methylation in rheumatoid arthritis synoviocytes

Rheumatoid arthritis (RA) is a chronic inflammatory disease in which fibroblast-like synoviocytes (FLS) exhibit an aggressive phenotype. Although the mechanisms responsible are not well defined, epigenetic determinants such as DNA methylation might contribute. DNA methyltransferases (DNMTs) are critical enzymes that establish and maintain DNA methylation. We evaluated whether proinflammatory cytokines might contribute to differential DNA methylation previously described in RA FLS through altered DNMT expression. FLS were obtained from RA and osteoarthritis (OA) synovium at the time of total joint replacement. Gene expression was determined by quantitative real-time PCR and protein expression by Western blot analysis. DNMT activity was measured with a functional assay, and global methylation was determined by an immunoassay that detects methylcytosine. Resting expression of DNMT1, -3a, and -3b mRNA were similar in RA and OA FLS. Western blot showed abundant DNMT1 and DNMT3a protein. Exposure to IL-1 decreased DNMT1 and DNMT3a mRNA expression in FLS. Dose responses demonstrated decreased DNMT expression at concentrations as low as 1 pg/ml of IL-1. DNMT mRNA levels decreased rapidly, with significant suppression after 2-8 h of IL-1 stimulation. IL-1 stimulation of OA FLS did not affect methylation of LINE1 sites but led to demethylation of a CHI3L1 locus that is hypomethylated in RA FLS. Chronic IL-1 stimulation also mimicked the effect of a DNMT inhibitor on FLS gene expression. Exposure to proinflammatory mediators reversibly alters DNA methylation in FLS by decreasing DNMT expression and function. These data suggest that IL-1 can potentially imprint cells in chronic inflammatory diseases.

DNA methylome signature in rheumatoid arthritis

OBJECTIVES

Epigenetics can influence disease susceptibility and severity. While DNA methylation of individual genes has been explored in autoimmunity, no unbiased systematic analyses have been reported. Therefore, a genome-wide evaluation of DNA methylation loci in fibroblast-like synoviocytes (FLS) isolated from the site of disease in rheumatoid arthritis (RA) was performed.

METHODS

Genomic DNA was isolated from six RA and five osteoarthritis (OA) FLS lines and evaluated using the Illumina HumanMethylation450 chip. Cluster analysis of data was performed and corrected using Benjamini-Hochberg adjustment for multiple comparisons. Methylation was confirmed by pyrosequencing and gene expression was determined by qPCR. Pathway analysis was performed using the Kyoto Encyclopedia of Genes and Genomes.

RESULTS

RA and control FLS segregated based on DNA methylation, with 1859 differentially methylated loci. Hypomethylated loci were identified in key genes relevant to RA, such as CHI3L1, CASP1, STAT3, MAP3K5, MEFV and WISP3. Hypermethylation was also observed, including TGFBR2 and FOXO1. Hypomethylation of individual genes was associated with increased gene expression. Grouped analysis identified 207 hypermethylated or hypomethylated genes with multiple differentially methylated loci, including COL1A1, MEFV and TNF. Hypomethylation was increased in multiple pathways related to cell migration, including focal adhesion, cell adhesion, transendothelial migration and extracellular matrix interactions. Confirmatory studies with OA and normal FLS also demonstrated segregation of RA from control FLS based on methylation pattern.

CONCLUSIONS

Differentially methylated genes could alter FLS gene expression and contribute to the pathogenesis of RA. DNA methylation of critical genes suggests that RA FLS are imprinted and implicate epigenetic contributions to inflammatory arthritis.

A pro-inflammatory role for A20 and ABIN family proteins in human fibroblast-like synoviocytes in rheumatoid arthritis

Circuit of chronic inflammation in the joints of rheumatoid arthritis (RA) starts from the production of inflammatory cytokines by fibroblast-like synoviocytes (FLS) stimulated by TNFα produced by inflammatory cells mainly composed of macrophages. In this context, TNFα/NF-κB pathway plays an essential role for the transcription of pro-inflammatory cytokines. Here we show that the kinetics of pro-inflammatory cytokine genes induced by TNFα in FLS from RA was synchronized with that of A20, ABIN1, and ABIN3 that have been thought as negative regulators for NF-κB activation. Furthermore, based on this finding, we could tentatively categorize the RA-FLS into two groups; TNFα low-responder and high-responder FLS. The high responders that have abundant mRNA levels of NF-κB inhibitory molecules were also accompanied with the marked induction of the pro-inflammatory cytokines by the stimulation with TNFα. The low responders RA-FLS did not show this property, nor did FLS from osteoarthritis. Phosphorylation dependent degradation of IκBα as well as NF-κB activation upon stimulation with TNFα was significantly enhanced in the high-responder FLS lines. Surprisingly, single transfection of each NF-κB inhibitor was enough to facilitate the transcription of pro-inflammatory cytokines, suggesting that there is an unknown pro-inflammatory function for A20 and ABIN family proteins in RA-FLS.