YKL-40 serum levels are predicted by inflammatory state, age and diagnosis of idiopathic inflammatory myopathies.

YKL-40 increase according to the aging process, and its functions have been associated with tissue remodeling and systemic inflammation. In Rheumatoid Arthritis (RA) it has been proposed as a possible biomarker of activity and severity, however; in the field of idiopathic inflammatory myopathies (IIM) the role of YKL-40 in IIM is not clear. Thus, we aimed to evaluate if there is an association between the serum levels and muscle tissue expression of YKL-40 with age, IIM phenotype, muscle strength and myositis disease activity. The main finding was that age is the most important variable that affects the YKL-40 serum levels. In muscle biopsy, we observed that YKL-40 is mainly expressed in infiltrating lymphoid cells than in muscle tissue. Using ANCOVA according to the b-coefficients, YKL-40 serum levels are predicted by inflammatory state, age, and IIM diagnosis.

Autoantibodies in the pathogenesis of idiopathic inflammatory myopathies: Does the endoplasmic reticulum stress response have a role?

Idiopathic inflammatory myopathies (IIMs) are a group of rare, acquired autoimmune diseases characterized by profound muscle weakness and immune cell invasion into non-necrotic muscle. They are related to the presence of antibodies known as myositis-specific antibodies and myositis-associated antibodies, which are associated with various IIM phenotypes and the clinical prognosis. The possibility of the participation of other pathological mechanisms involved in the inflammatory response in IIM has been proposed. Such mechanisms include the overexpression of major histocompatibility complex class I in myofibers, which correlates with the activation of stress responses of the endoplasmic reticulum (ER). Taking into account the importance of the ER for the maintenance of homeostasis of the musculoskeletal system in the regulation of proteins, there is probably a relationship between immunological and non-immunological processes and autoimmunity, and an example of this might be IIM. We propose that ER stress and its relief mechanisms could be related to inflammatory mechanisms triggering a humoral response in IIM, suggesting that ER stress might be related to the triggering of IIMs and their auto-antibodies' production.

Impaired muscle strength is associated with ultrastructure damage in myositis.

The muscle fiber ultrastructure in Idiopathic Inflammatory Myopathies (IIM) has been scarcely explored, especially in Inclusion Body Myositis. The aim of this study was to implement the Scanning Electron Microscopy (SEM) in a small cohort of IIM patients, together with the characterization of immunological profile for a better understanding of the pathophysiology. For immunological profile characterization, we identified the presence of autoantibodies (Ro-52, OJ, EJ, PL7, PL12, SRP, Jo-1, PMScl75, PMScl100, Ku, SAE1, NXP2, MDA5, TIF1γ, Mi-2α, Mi-2ß) and quantified cytokines (IL-1ß, IFN-α2, IFN-γ, TNF-α, IL-6, IL-10, IL-12p70, IL-17A, IL-18, IL-23, IL-33) and chemokines (CCL2, CXCL8). The histological analysis was made by hematoxylin-eosin staining while the muscle fiber ultrastructure was characterized by SEM. We observed changes in the morphology and structure of the muscle fiber according to muscle strength and muscle enzymes. We were able to find and describe muscle fiber ultrastructure with marked irregularities, porosities, disruption in the linearity and integrity of the fascicle, more evident in patients with increased serum levels of muscle enzymes and diminished muscle strength. Despite the scarce reports about the use of SEM as a tool in all clinical phenotypes of IIM, our work provides an excellent opportunity to discuss and reframe the clinical usefulness of SEM in the diagnostic approach of IIM.

Geographical Latitude Remains as an Important Factor for the Prevalence of Some Myositis Autoantibodies: A Systematic Review.

The idiopathic inflammatory myopathies (IIM) are characterized by muscular weakness, cutaneous manifestations, muscle damage revealed by increase of muscular enzymes, muscle biopsy, electromyography and changes on magnetic resonance imaging. However, the hallmark of these IIM, is the development of myositis specific antibodies (MSA) or myositis associated antibodies (MAA). The theories about their presence in the serum of IIM is not known. Some studies have suggested that some of these MSA, such as anti-Mi-2 increases according to the intensity of UV radiation. There is scarce information about the environmental factors that might contribute in order to be considered as triggering factors as UV radiation might be. In this review, we analyzed the reported prevalence of MSAs and MAAs regarding to their geographical location and the possible relation with UV radiation. We collected the prevalence data of fifteen MSA and thirteen MAA from 22 countries around the world and we were able to observe a difference in prevalence between countries and continents. We found differences in anti-PL7, anti-Ro52, anti-La and anti-Ku prevalence according to UV radiation level. Otherwise, we observed that anti-Mi-2 prevalence increases near to the Equator meanwhile anti-MJ/NXP2 and anti-ARS prevalence had an opposite behavior increasing their prevalence in the geographical locations farther to the Equator. Our results highlighted the importance to include the UV radiation and other environmental factors in IIM studies, in order to clarify its association with MSA and MAA prevalence as well as its possible role in the immunopathogenesis of these diseases.

Going Further: Comprehensive Disease Control of Rheumatoid Arthritis, Targeting Cytokines and Chemokines.

OBJECTIVES: Mechanism of action of biological and synthetic disease-modifying antirheumatic drugs (DMARDs) includes the inhibition of specific proinflammatory cytokines. This study aimed to elucidate the cytokines and chemokines inhibited by different treatments (conventional synthetic DMARD [csDMARD], biological and targeted synthetic DMARD) in rheumatoid arthritis (RA). METHODS: Fifty-nine RA patients with low disease activity or remission included in a cross-sectional study were classified by treatment in groups: abatacept, certolizumab, rituximab (RTX), tocilizumab, tofacitinib (TOF), baricitinib (BAR), and csDMARD. Cytokine and chemokine serum levels were measured by LEGENDplex Human Inflammation panel. Quantitative variables were compared using Student t or Mann-Whitney U test as appropriate, whereas qualitative variables were compared using χ2 or Fisher exact test. p < 0.05 was considered significant. RESULTS: Certolizumab, RTX, tocilizumab, and TOF showed that most cytokine pathways inhibited: tumor necrosis factor α, interferon γ, interleukin 1ß (IL-1ß), IL-12, IL-18, and IL-23; in addition, csDMARDs showed a similar inhibition patron except for IL-23. Serum level of tumor necrosis factor α pathway was one of the most inhibited being undetectable in RTX, TOF, and BAR groups. Interleukin 6 was shown to be inhibited by abatacept, RTX, and TOF; however, higher levels were observed in 3 patients treated with tocilizumab. Abatacept, certolizumab, RTX, and TOF downregulated IL-10 in this group of patients but remained detectable in almost half of the subjects, with the highest levels in the BAR group. The active pathways that remained the most were CC chemokine ligand 2, IL-8, IL-17, and IL-33. CONCLUSIONS: Understanding the cytokine chemokine pathways inhibition could help rheumatologists to prescribe a tailored therapy using the arsenal of DMARDs for individualized RA treatment in an evidence-based decision manner.