Insights into the pathogenesis of psoriatic arthritis from genetic studies

From Psoriasis to Psoriatic Arthritis: Ultrasound Insights Connecting Psoriasis with Subclinical Musculoskeletal Inflammation and the Path to Psoriatic Arthritis

PURPOSE OF REVIEW

This review summarizes the literature about the transition from psoriasis to psoriatic arthritis (PsA), focusing on musculoskeletal ultrasound (MSUS) for detecting subclinical inflammation and its role in diagnosis and triage of high-risk patients.

RECENT FINDINGS

MSUS effectively detects subclinical musculoskeletal inflammation in patients with psoriasis; however, some of these lesions are non-specific and can be found in healthy individuals. Preliminary evidence suggest that subclinical sonographic findings may predict progression to PsA in psoriasis patients. MSUS can also improve referrals' accuracy and its integration in the PsA classification criteria may improve early PsA detection. MSUS is a valuable tool for detecting subclinical abnormalities in psoriasis patients, which indicate an increased likelihood of progressing to PsA. Its integration into referral protocols and clinical use could improve PsA diagnosis. We propose an MSUS-inclusive algorithm for PsA referrals and triage, which requires validation. The potential of early intervention in reducing PsA progression in psoriasis patients with subclinical inflammation remains to be established.

Transcriptome-wide association study identifies new susceptibility genes and pathways for spondyloarthritis

BACKGROUND

Spondyloarthritis (SpA) is a group of multifactorial bone diseases influenced by genetic factors, the environment and lifestyle. However, current studies have found a limited number of SpA-related genes, and the genetic and pathogenic mechanisms of SpA are still unclear.

METHODS

A tissue-specific transcriptome-wide association study (TWAS) of SpA was performed using GWAS (including 3966 SpA patients and 448,298 controls) summary data and gene expression weights of whole blood and skeletal muscle. The SpA-associated genes identified by TWAS were further compared with the differentially expressed genes (DEGs) identified in the SpA gene expression profile acquired from the Gene Expression Omnibus database (GEO, GSE58667). Finally, functional enrichment and annotation analyses of the identified genes were performed.

RESULTS

The TWAS detected 499 suggestive genes associated with SpA in whole blood and skeletal muscle, such as CTNNAL1 (PSM = 3.04 × 10-2, PWB = 9.58 × 10-3). The gene expression profile of SpA identified 20 candidate genes that overlapped in the TWAS data, such as MCM4 (PTWAS = 1.32 × 10-2, PDEG = 2.75 × 10-2) and KIAA1109 (PTWAS = 3.71 × 10-2, PDEG = 4.67 × 10-2). Enrichment analysis of the genes identified by TWAS identified 93 significant GO terms and 33 KEGG pathways, such as mitochondrion organization (GO: 0007005) and axon guidance (hsa04360).

CONCLUSION

We identified multiple candidate genes that were genetically related to SpA. Our study may provide novel clues regarding the genetic mechanism, diagnosis, and treatment of SpA.

The Conundrum of Psoriatic Arthritis: a Pathogenetic and Clinical Pattern at the Midpoint of Autoinflammation and Autoimmunity

Psoriatic arthritis (PsA) is a chronic inflammatory condition characterized by psoriasis, synovitis, enthesitis, spondylitis, and the possible association with other extra-articular manifestations and comorbidities. It is a multifaceted and systemic disorder sustained by complex pathogenesis, combining aspects of autoinflammation and autoimmunity. Features of PsA autoinflammation include the role of biomechanical stress in the onset and/or exacerbation of the disease; the evidence of involvement of the innate immune response mediators in the skin, peripheral blood and synovial tissue; an equal gender distribution; the clinical course which may encounter periods of prolonged remission and overlapping features with autoinflammatory syndromes. Conversely, the role of autoimmunity is evoked by the association with class I major histocompatibility complex alleles, the polyarticular pattern of the disease which sometimes resembles rheumatoid arthritis and the presence of serum autoantibodies. Genetics also provide important insights into the pathogenesis of PsA, particularly related to class I HLA being associated with psoriasis and PsA. In this review, we provide a comprehensive review of the pathogenesis, genetics and clinical features of PsA that endorse the mixed nature of a disorder at the crossroads of autoinflammation and autoimmunity.

Qilongtian ameliorate bleomycin-induced pulmonary fibrosis in mice via inhibiting IL-17 signal pathway

Pulmonary fibrosis (PF) is a special type of pulmonary parenchymal disease, with chronic, progressive, fibrosis, and high mortality. There is a lack of safe, effective, and affordable treatment methods. Qilongtian (QLT) is a traditional Chinese prescription that is composed of Panax notoginseng, Earthworm, and Rhodiola, and shows the remarkable clinical curative effect of PF. However, the mechanism of QLT remains to be clarified. Therefore, we studied the effectivity of QLT in treating Bleomycin (BLM) induced PF mice. 36 C57BL/6 J mice were randomized into the control group, the model group, the low-, medium- and high-dose QLT group, and Pirfenidone group. After establishing a model of pulmonary fibrosis in mice, the control and model groups were infused with a normal saline solution, and the delivery group was infused with QLT. Pulmonary function in the mice from each group was detected. Pulmonary tissue morphologies and collagen deposition were stained by HE and Masson. The content of hydroxyproline (HYP) was detected by alkaline hydrolysis and the mRNA and protein expression of related genes in pulmonary tissues were detected by using q-PCR, ELISA, and Western blot. Our studies have shown that QLT significantly reduced the inflammatory injury, hydroxy-proline content, and collagen deposition of pulmonary tissue in BLM-induced PF mice and down-regulated the cytokine related to inflammation and fibrosis and PF expression on the mRNA and protein level in PF mice. To identify the mechanism of QLT, the Transcriptome was measured and the IL-17 signal pathway was screened out for further research. Further studies indicated that QLT reduced the mRNAs and protein levels of interleukin 17 (IL-17), c-c motif chemokine ligand 12 (CCL12), c-x-c motif chemokine ligand 5 (CXCL5), fos-like antigen 1 (FOSL1), matrix metalloproteinase-9 (MMP9), and amphiregulin (AREG), which are inflammation and fibrosis-related genes in the IL-17 signal pathway. The results indicated that the potential mechanism for QLT in the prevention of PF progression was by inhibiting inflammation resulting in the IL-17 signal pathway. Our study provides the novel scientific basis of QLT and represents new therapeutics for PF in clinical.

MTHFR Gene Polymorphism Association With Psoriatic Arthritis Risk and the Efficacy and Hepatotoxicity of Methotrexate in Psoriasis

Aims

To assess whether MTHFR rs1801131 and rs1801133 SNPs are associated with concomitant psoriatic arthritis (PsA) and investigate the efficacy and hepatotoxicity of MTX in patients with psoriasis in the Han Chinese population.

Methods

This prospective, single-arm, interventional study recruited a total of 309 patients with psoriasis, 163 with psoriatic arthritis and 146 without psoriatic arthritis, who completed a 12-week MTX treatment and 1,031 healthy controls. Patients' characteristics including age, gender, disease duration, height, weight, smoking status, alcohol consumption, medical history, disease severity and liver function test results were accessed and recorded. Single nucleotide polymorphism (SNP) genotyping of rs1801131 and rs1801133 in the MTHFR gene was performed.

Results

The rs1801133 CC genotype was more frequent in patients with PsA than those with PsO and healthy controls (42.3% vs. 28.8% vs. 33.1%, p < 0.05). The 90% reduction from baseline PASI score (PASI 90) response rates to MTX were significantly higher in patients with the rs1801133 TT genotype than those with the CT and CC genotype (33.96% vs. 19.31% vs. 14.41%, OR = 2.76, p = 0.006). The rs1801133 CT+TT genotype was more frequent in PsA patients with abnormal liver function than in those with normal liver function (p < 0.05). In addition, patients with the rs1801131 CT genotype had lower PASI 75 response rates to MTX (OR = 0.49, p = 0.01), and lower risk of ALT elevation (OR = 0.46, p = 0.04).

Conclusions

This study provided some evidence for MTHFR polymorphism association with the risk of PsA and the efficacy and hepatotoxicity of the low-dose MTX in the Chinese population. Given the relatively small sample size and potentially missed diagnosis of PsA, the results from this study warrant further investigation.

Genetic Variants of the NF-κB Pathway: Unraveling the Genetic Architecture of Psoriatic Disease

Psoriasis is a multifactorial genetic disease for which the genetic factors explain about 70% of disease susceptibility. Up to 30–40% of psoriasis patients develop psoriatic arthritis (PsA). However, PsA can be considered as a “disease within a disease”, since in most cases psoriasis is already present when joint complaints begin. This has made studies that attempt to unravel the genetic basis for both components of psoriatic disease enormously difficult. Psoriatic disease is also accompanied by a high burden of comorbid conditions, mainly of the cardiometabolic type. It is currently unclear whether these comorbidities and psoriatic disease have a shared genetic basis or not. The nuclear factor of kappa light chain enhancer of activated B cells (NF-κB) is a transcription factor that regulates a plethora of genes in response to infection, inflammation, and a wide variety of stimuli on several cell types. This mini-review is focused on recent findings that highlight the importance of this pathway both in the susceptibility and in the determinism of some features of psoriatic disease. We also briefly review the importance of genetic variants of this pathway as biomarkers of pharmacological response. All the above may help to better understand the etiopathogenesis of this complex entity.