High expression of pro-inflammatory cytokine genes IL-1β and IL-1R2 upon TLR4 activation in Takayasu arteritis

A pilot study of childhood-onset Takayasu arteritis using whole exome sequencing suggests oligogenic inheritance involving classical complement, collagen, and autoinflammatory pathways

Takayasu arteritis (TA) is a chronic granulomatous inflammatory disease affecting the aorta and its branches. Paediatric TA (pTA) may present from 6 months after birth till the adolescent age group. Genetics and pathogenesis of pTA are not fully understood. Earlier studies reported monogenic mutation in NOD2, XIAP, and STAT1 genes in patients with pTA. TA, a relatively rare disease, is more common in geographical pockets, including India. We hypothesized that South Asian patients with pTA, namely, those of Indian subcontinent origin, may have clinically relevant and unique pathogenic variants involving one or more genes, especially those linked to genetically driven vasculitic illnesses, including autoinflammatory pathologies. Children with pTA fulfilling EULAR/PRINTO/PReS classification criteria and presenting with clinical symptoms to the Paediatric Rheumatology clinic of Christian Medical College, Vellore, were included. Blood samples were collected after getting informed consent from parents or guardians and assent forms from children. DNA was extracted from whole blood using the Qiagen DNA extraction kit. Initially, the common variant in Indian population, namely, ADA2 c.139G > A; p.Gly47Arg, was screened, followed by whole exome sequencing. Fourteen children were recruited for the study. Median age of patients was 11 years (4 months-14 years) with a male-to-female ratio of 4:10. Distribution of angiographic subsets by Numano's classification of included children were as follows: type 5 (n = 7), type 4 (n = 5), and type 3 (n = 2). We identified novel variants in ten different genes. This include variants in genes of classical complement pathway, namely, C2, C3, C6, C7, and C9, and other genes, namely, CYBA, SH3BP2, GUCY2C, CTC1, COL5A1, and NLPR3. Two of 14 patients have heterozygous pathogenic variants; this implies that combination of heterozygous variants in C3 and COL5A1 might lead to disease development, suggesting digenic inheritance. One patient has a homozygous variant in CYBA. None of the patients were identified to have ADA2 variants. Whole exome sequencing reveals combination of rare variants in genes C3, COL5A1, and CYBA associated with disease development in children with Takayasu Arteritis. Key Points • We identified novel variants in genes of classical complement pathway, namely, C2, C3, C6, C7, and C9, and other genes, namely, CYBA, SH3BP2, GUCY2C, CTC1, COL5A1, and NLPR3. • Two of 14 patients have heterozygous pathogenic variants in C3 and COL5A1; this may have implications in disease development, suggesting digenic inheritance. • One patient has homozygous variant in CYBA. • None of the patients were identified to have ADA2 variants.

A Glimpse into Humoral Response and Related Therapeutic Approaches of Takayasu's Arteritis

Takayasu's arteritis (TAK) manifests as an insidiously progressive and debilitating form of granulomatous inflammation including the aorta and its major branches. The precise etiology of TAK remains elusive, with current understanding suggesting an autoimmune origin primarily driven by T cells. Notably, a growing body of evidence bears testimony to the widespread effects of B cells on disease pathogenesis and progression. Distinct alterations in peripheral B cell subsets have been described in individuals with TAK. Advancements in technology have facilitated the identification of novel autoantibodies in TAK. Moreover, emerging data suggest that dysregulated signaling cascades downstream of B cell receptor families, including interactions with innate pattern recognition receptors such as toll-like receptors, as well as co-stimulatory molecules like CD40, CD80 and CD86, may result in the selection and proliferation of autoreactive B cell clones in TAK. Additionally, ectopic lymphoid neogenesis within the aortic wall of TAK patients exhibits functional characteristics. In recent decades, therapeutic interventions targeting B cells, notably utilizing the anti-CD20 monoclonal antibody rituximab, have demonstrated efficacy in TAK. Despite the importance of the humoral immune response, a systematic understanding of how autoreactive B cells contribute to the pathogenic process is still lacking. This review provides a comprehensive overview of the biological significance of B cell-mediated autoimmunity in TAK pathogenesis, as well as insights into therapeutic strategies targeting the humoral response. Furthermore, it examines the roles of T-helper and T follicular helper cells in humoral immunity and their potential contributions to disease mechanisms. We believe that further identification of the pathogenic role of autoimmune B cells and the underlying regulation system will lead to deeper personalized management of TAK patients. We believe that further elucidation of the pathogenic role of autoimmune B cells and the underlying regulatory mechanisms holds promise for the development of personalized approaches to managing TAK patients.

Emerging Role of the IL-36/IL-36R Axis in Multiple Inflammatory Skin Diseases

IL-36 is a most recent member of the IL-1 cytokine family, primarily expressed at barrier sites of the body such as the skin, lungs, and intestine. It plays a vital role in inflammation and is implicated in the development of various cutaneous; intestinal; and pulmonary disorders, including psoriasis, inflammatory bowel disease, and chronic obstructive pulmonary disease. IL-36 comprises 4 isoforms: the proinflammatory IL-36α, IL-36β, and IL-36γ and the anti-inflammatory IL-36R antagonist. An imbalance between proinflammatory and anti-inflammatory IL-36 isoforms can contribute to the inflammatory fate of cells and tissues. IL-36 cytokines signal through an IL-36R heterodimer mediating their function through canonical signaling cacade, including the NF-B pathway. Prominent for its role in psoriasis, IL-36 has recently been associated with disease mechanisms in atopic dermatitis, hidradenitis suppurativa, neutrophilic dermatoses, autoimmune blistering disease, and Netherton syndrome. The major cutaneous source of IL-36 cytokines is keratinocytes, pointing to its role in the communication between the epidermis, innate (neutrophils, dendritic cells) immune system, and adaptive (T helper [Th]1 cells, Th17) immune system. Thus, cutaneous IL-36 signaling is crucial for the immunopathological outcome of various skin diseases. Consequently, the IL-36/IL-36R axis has recently been recognized as a promising drug target for the treatment of inflammatory disorders beyond psoriasis. This review summarizes the current update on IL-36 cytokines in inflammatory skin diseases.

Animal models for large vessel vasculitis - The unmet need

Our understanding of the pathogenesis of large vessel vasculitis (LVV) are mainly achieved by studying the arteries taken from temporal artery biopsy in giant cell arteries (GCA) or surgical or autopsy specimens in Takayasu arteritis (TAK). These artery specimens provide invaluable information about pathological changes in these conditions that GCA and TAK are similar but are distinctly different in immune cell infiltrate and distribution of inflammatory cells in anatomical locations. However, these specimens of established arteritis do not provide information of the arteritis initiation and early events which are impossible to obtain in human artery specimens. Animal models for LVV are needed but not available. Here, several approaches are proposed for experimentation to generate animal models to aid in delineating the interaction of immune reaction with arterial wall components.

Transcriptome profiling of abdominal aortic tissues reveals alterations in mRNAs of Takayasu arteritis

Takayasu arteritis (TA) is a chronic granulomatous vasculitis involving in the main branches of aorta. Previous studies mainly used peripheral blood and some vascular tissues but seldom studies have sequenced vascular tissues. Here in this study, we aimed to explore the alterations of mRNA in TA by performing bulk RNA sequencing. A total of 14 abdominal aortic tissues including 8 from renal transplantation and 6 from patient with TA undergoing bypass surgeries. Bulk RNA sequencing were performed and after the quality control, a total of 1897 transcripts were observed to be significantly differently (p < 0.05 and Log2FC > 1) expressed between the TA and control group, among which 1,361 transcripts were in TA group and 536 in the Control group. Reactome Pathway Enrichment Comparison analysis revealed interleukin-10 signaling and signaling by interleukins were highly expressed in TA group. Besides, extracellular matrix organization was also observed in this group. WGCNA and PPI obtained 26 core genes which were highly correlated with the clinical phenotype. We then also perform deconvolution of the bulk RNA-seq data by using the scRNA-seq dataset and noticed the high proportion of smooth muscle cells in our dataset. Additionally, immunohistochemical staining confirmed our bioinformatic analysis that TA aortic tissues express high levels of IL-1R1 and IL-1R2. Briefly, this study revealed critical roles of interleukins in TA pathogenesis, and SMCs may also participate in the reconstruction in vessel wall at late stage of TA.

Identification of the Association Between Toll-Like Receptors and T-Cell Activation in Takayasu’s Arteritis

To explore the relationships between Toll-like receptors (TLRs) and the activation and differentiation of T-cells in Takayasu’s arteritis (TAK), using real-time fluorescence quantitative polymerase chain reaction, mRNA abundance of 29 target genes in peripheral blood mononuclear cells (PBMCs) were detected from 27 TAK patients and 10 healthy controls. Compared with the healthy control group, the untreated TAK group and the treated TAK group had an increased mRNA level of TLR2 and TLR4. A sample-to-sample matrix revealed that 80% of healthy controls could be separated from the TAK patients. Correlation analysis showed that the inactive-treated TAK group exhibited a unique pattern of inverse correlations between the TLRs gene clusters (including TLR1/2/4/6/8, BCL6, TIGIT, NR4A1, etc) and the gene cluster associated with T-cell activation and differentiation (including TCR, CD28, T-bet, GATA3, FOXP3, CCL5, etc). The dynamic gene co-expression network indicated the TAK groups had more active communication between TLRs and T-cell activation than healthy controls. BCL6, CCL5, FOXP3, GATA3, CD28, T-bet, TIGIT, IκBα, and NR4A1 were likely to have a close functional relation with TLRs at the inactive stage. The co-expression of TLR4 and TLR6 could serve as a biomarker of disease activity in treated TAK (the area under curve/sensitivity/specificity, 0.919/100%/90.9%). The largest gene co-expression cluster of the inactive-treated TAK group was associated with TLR signaling pathways, while the largest gene co-expression cluster of the active-treated TAK group was associated with the activation and differentiation of T-cells. The miRNA sequencing of the plasma exosomes combining miRDB, DIANA-TarBase, and miRTarBase databases suggested that the miR-548 family miR-584, miR-3613, and miR-335 might play an important role in the cross-talk between TLRs and T-cells at the inactive stage. This study found a novel relation between TLRs and T-cell in the pathogenesis of autoimmune diseases, proposed a new concept of TLR-co-expression signature which might distinguish different disease activity of TAK, and highlighted the miRNA of exosomes in TLR signaling pathway in TAK.

Fecal S100A12 in Takayasu arteritis predicts disease activity and intestinal involvement

Gastrointestinal involvement in Takayasu Arteritis (TA) requires invasive or expensive diagnostic studies. Instead a fecal biomarker can be used as an initial screening test. In this context, S100A12 is promising as an established biomarker in intestinal inflammation and its role in TA pathogenesis. As such we aimed to test the feasibility of fecal S100A12 as a means of the fecal biomarker in gastrointestinal involvement in TA in this pilot study. Our study population consisted of 30 TA patients and 14 control patients with non-inflammatory arthralgia. Patients with inflammatory or infectious gastrointestinal tract diseases, or used oral antibiotics or NSAIDs for the 3 weeks were excluded. Vasculitis involvements were determined with cross-sectional radiologic studies. TA disease activity was evaluated per Indian Takayasu's Activity Score (2010) criteria and vascular involvements were classified according to Numano classification. ELISA test was used to determine fecal S100A12 levels. Fecal S100A12 levels were higher in TA patients when compared to the controls (37.9 ng/ml vs. 12.5 ng/ml p = 0.038). ESR and CRP levels were also higher in the TA group, however not correlated with fecal S100A12. Among TA patients, fecal S100A12 levels were higher inactive ones with ITAS2010 > 1 (72.9 ng/ml vs. 16.7 ng/ml p = 0.016) correlated with total ITAS2010 scores. (R = 0.52 p = 0.003). TA patients with abdominal symptoms had higher fecal S100A12 levels when compared to the remaining TA population (327.8 ng/ml vs. 28.0 ng/ml p = 0.003). However, fecal S100A12 levels in patients with or without mesenteric vessel involvement did not differ. Fecal S100A12 shows promise as a fecal biomarker to screen intestinal ischemia and inflammatory bowel disease in TA patients.