Expression of tumor necrosis factor-like weak inducer of apoptosis and fibroblast growth factor-inducible 14 in patients with polymyositis and dermatomyositis

TWEAK and Fn14 are overexpressed in immune-mediated necrotizing myopathy: implications for muscle damage and repair

OBJECTIVES

TNF-like weak inducer of apoptosis (TWEAK) and its sole receptor fibroblast growth factor-inducible 14 (Fn14) are involved in various inflammatory conditions. This study was performed to investigate the potential role of TWEAK/Fn14 in immune-mediated necrotizing myopathy (IMNM).

METHODS

Muscle biopsies from patients with IMNM (n = 37) and controls (n = 11) were collected. Human muscle cells were treated with TWEAK in vitro. Muscle biopsies and cultured muscle cells were analysed by immunostaining and quantitative PCR. Serum levels of TWEAK and Fn14 were detected by ELISA.

RESULTS

TWEAK and Fn14 were overexpressed in IMNM muscle biopsies. The percentage of Fn14-positive myofibers correlated with disease severity, myonecrosis, regeneration and inflammation infiltrates. Fn14-positive myofibers tended to be surrounded or invaded by CD68+ macrophages. TWEAK treatment had a harmful effect on cultured muscle cells by inducing the production of multiple chemokines and pro-inflammatory cytokines. Serum Fn14 levels were increased in patients with IMNM and correlated with muscle weakness.

CONCLUSIONS

TWEAK/Fn14 signalling was activated in IMNM, most likely aggravating muscle damage via amplifying inflammatory response and macrophages chemotaxis. Fn14 seems to be a biomarker for assessing disease severity in IMNM. In addition, Fn14 may also contribute to muscle injury repair.

Involvement of the cytokine TWEAK in the pathogenesis of psoriasis vulgaris, pustular psoriasis, and erythrodermic psoriasis

Psoriasis is a common chronic inflammatory dermatitis in which various cytokines play a detrimental role. The cytokine tumor necrosis factor-related weak inducer of apoptosis (TWEAK) is involved in the pathogenesis of multiple inflammatory disorders. However, the potential role of TWEAK in various subtypes of psoriasis has not been studied in depth. To investigate whether the levels of TWEAK are associated with clinical traits and the levels of some known psoriasis-related cytokines, such as interleukin (IL)-17A, IL-22, interferon (IFN)-γ, and IL-36γ, 20 patients with psoriasis vulgaris (PV), 8 patients with pustular psoriasis (PP), 8 patients with erythrodermic psoriasis (EP), and 20 healthy controls (HCs) were recruited into this study. The levels of serum cytokines were detected by commercial enzyme-linked immunosorbent assay kits. The average levels of TWEAK, IL-17A, IL-22, IFN-γ, and IL-36γ were significantly higher in the psoriasis groups than in the HC group. Furthermore, there was a statistically significant correlation between TWEAK and IL-17A/IFN-γ in PV and IL-36γ in EP, but there was no correlation between TWEAK and IL-22 in any subtype of psoriasis. This study suggests that TWEAK may have a role in the pathogenesis of PV, PP, and EP via synergy with IL-17A, IFN-γ, or IL-36γ, but not with IL-22.

Fn14 Deficiency Ameliorates Anti-dsDNA IgG-Induced Glomerular Damage in SCID Mice

Many studies have demonstrated that anti-dsDNA IgG is closely associated with lupus nephritis. Recently, it was found that activation of the fibroblast growth factor-inducible 14 (Fn14) signaling pathway damages glomerular filtration barrier in MRL/lpr lupus-prone mice. However, MRL/lpr mice have high titers of serum autoantibodies other than anti-dsDNA IgG. The aim of this study was to further explore the effect of Fn14 deficiency on anti-dsDNA IgG-induced glomerular damage in severe combined immunodeficiency (SCID) mice that have no endogenous IgG. Fn14 deficiency was generated in SCID mice. The murine hybridoma cells producing control IgG or anti-dsDNA IgG were intraperitoneally injected into mice. In two weeks, the urine, serum, and kidney tissue samples were harvested from mice at sacrifice. It showed that the injection of anti-dsDNA IgG, but not control IgG hybridoma cells, induced proteinuria and glomerular damage in SCID mice. Between the wild-type (WT) and knockout (KO) mice injected with anti-dsDNA IgG hybridoma cells, the latter showed a decrease in both proteinuria and glomerular IgG deposition. The histopathological changes, inflammatory cell infiltration, and proinflammatory cytokine production were also attenuated in the kidneys of the Fn14-KO mice upon anti-dsDNA IgG injection. Therefore, Fn14 deficiency effectively protects SCID mice from anti-dsDNA IgG-induced glomerular damage.

TWEAK/Fn14 Activation Participates in Skin Inflammation

Tumor necrosis factor- (TNF-) like weak inducer of apoptosis (TWEAK) participates in multiple biological activities via binding to its sole receptor-fibroblast growth factor-inducible 14 (Fn14). The TWEAK/Fn14 signaling pathway is activated in skin inflammation and modulates the inflammatory responses of keratinocytes by activating nuclear factor-κB signals and enhancing the production of several cytokines, including interleukins, monocyte chemotactic protein-1, RANTES (regulated on activation, normal T cell expressed and secreted), and interferon gamma-induced protein 10. Mild or transient TWEAK/Fn14 activation contributes to tissular repair and regeneration while excessive or persistent TWEAK/Fn14 signals may lead to severe inflammatory infiltration and tissue damage. TWEAK also regulates cell fate of keratinocytes, involving the function of Fn14-TNF receptor-associated factor-TNF receptor axis. By recruiting inflammatory cells, promoting cytokine production, and regulating cell fate, TWEAK/Fn14 activation plays a pivotal role in the pathogenesis of various skin disorders, such as psoriasis, atopic dermatitis, cutaneous vasculitis, human papillomavirus infection and related skin tumors, and cutaneous autoimmune diseases. Therefore, the TWEAK/Fn14 pathway may be a potential target for the development of novel therapeutics for skin inflammatory diseases.

Elevated Serum Levels of Soluble CD163 in Polymyositis and Dermatomyositis: Associated with Macrophage Infiltration in Muscle Tissue

Objective.

To investigate serum levels of soluble CD163 (sCD163) in patients with polymyositis (PM) and dermatomyositis (DM), and to correlate these to clinical manifestations and laboratory data.

Methods.

Serum levels of sCD163 were detected in 24 patients with PM, 84 patients with DM, and 46 healthy controls by using the ELISA method. Immunohistochemistry staining of macrophage infiltration in muscle tissue using anti-CD163 monoclonal antibody was conducted on muscle biopsy specimens from 13 patients with PM and 17 with DM.

Results.

Serum levels of sCD163 were significantly increased in patients compared with healthy controls (p < 0.001). Patients with interstitial lung disease (ILD) had statistically higher sCD163 levels than patients without ILD (p < 0.001). High serum sCD163 levels were associated with increased incidence of antinuclear antibody (p < 0.05), higher serum levels of immunoglobulin G (p < 0.01) and immunoglobulin A (p < 0.05), and increased erythrocyte sedimentation rates (p < 0.01). Serum sCD163 levels were inversely correlated with CD3+ T cell counts in peripheral blood of patients (r = −0.306, p < 0.01). Cross-sectional assessment and longitudinal study revealed a significant correlation between serum sCD163 levels and disease activity. Patients with high serum sCD163 levels showed a higher incidence of CD163+ macrophage infiltration in muscle tissue than patients with normal sCD163 levels (chi-square value = 10.804, p < 0.01).

Conclusion.

Serum levels of sCD163 were significantly elevated and correlated with disease severity in patients with PM/DM, suggesting serum sCD163 as a promising biomarker in the disease evaluation of PM/DM. Our finding of elevated serum sCD163 levels associated with muscle macrophage infiltration highlights the role activated macrophage plays in the pathogenesis of PM/DM.

A new look at rheumatology in China--opportunities and challenges

In the past two decades, Chinese rheumatology has developed rapidly in terms of both clinical practice and basic research. Many rheumatology departments and divisions have been established, creating positions for more residents to join rheumatology practices. Numerous studies of rheumatic diseases have been published in recent years by Chinese rheumatologists and immunologists, supported by government funding that has dramatically increased over the past few years. These studies are focused mainly on epidemiology, mechanisms, early diagnosis and interventions of rheumatic diseases. Increasing numbers of national and international scientific activities in China, including research collaborations, education programmes and conferences have greatly helped the development of rheumatology. In this APLAR series article, the major, high-impact studies and latest developments in Chinese rheumatology are reviewed.