Tumour necrosis factor alpha promotes secretion of 14-3-3η by inducing necroptosis in macrophages

Abstract

Background 14-3-3η is an intracellular protein also detected in the serum and synovial fluid of patients with rheumatoid arthritis (RA). It is closely related to disease activity and anti-cyclic citrullinated peptide antibody levels. However, the main source of 14-3-3η and the mechanism of its release into the extracellular space remain unclear. Addressing these two points was the main goal of the current study. Methods The source of 14-3-3η was investigated by immunostaining RA synovial tissue. Fibroblast-like synoviocytes, CD4+ cells, and macrophages were selected as candidates among the various cell types in the synovial tissue. Phosphorylation of mixed-lineage kinase domain-like pseudokinase (MLKL) and cell death of macrophages were studied by phalloidin staining and electron microscopy after stimulation with an oxidative stress inducer (diamide) or tumour necrosis factor (TNF)-α. Extracellular 14-3-3η protein levels were examined by western blotting. Results Macrophages from the synovial tissue from RA, but not osteoarthritis, showed dense and widespread cytoplasmic staining for the 14-3-3η protein, co-localized with peptidylarginine deiminase 4. Swelling and membrane rupture of macrophages were induced by treatment with TNF-α, but not interleukin (IL) 6/soluble IL-6 receptor (sIL-6R). Increased MLKL phosphorylation followed by necroptosis was also induced in TNF-α-stimulated macrophages. Necrostatin-1, a necroptosis inhibitor, antagonized MLKL phosphorylation. High levels of 14-3-3η were detected in the culture supernatants of macrophages stimulated with diamide and TNF-α, but not IL-6/sIL-6R. Conclusions Macrophages that highly express 14-3-3η undergo TNF-α-induced necroptosis with damage to the cellular structure, resulting in the secretion of 14-3-3η into the extracellular space. The current study provides a novel mechanism for 14-3-3η level increase in the RA synovial fluid.

Impending radiographic erosive progression over the following year in a cohort of consecutive patients with inflammatory polyarthritis: prediction by serum biomarkers

“…Fort their part, each positive biomarker contributed individually and synergistically to RR for REP (up to 20.0 in visits of non-erosive patients), while in already erosive patients, all biomarkers High-14-3-3η (≥0.50 ng/mL) thus appears to play the role of an amplifier interacting with High-CRP (and inflamed joints), consistent with the proposed role of extracellular 14-3-3η as an enhancer for the release of proteolytic enzymes and proinflammatory cytokines, such as TNFα. 22 23 As activation of osteoclasts causing bone erosions may result from multiple direct and indirect mechanisms, the direct impact of 14-3-3η may be blunted in the presence of existing definite erosions. Our results also support the interest of identifying novel variable RA biomarkers not correlated with current lines of division of RA, such as seropositivity or inflammation.…”

Cell-Free DNA in Rheumatoid Arthritis

“…In addition to neutrophils, various cell types, including macrophages, monocytes, and FLS, are believed to release cfDNA in RA (Figure 1). Treatment with TNF-α induced necroptosis in macrophages from synovial tissue from patients with RA but not from patients with OA [61]. Furthermore, serum from RA patients induced GSDMD-dependent pyroptosis in monocytes, which was associated with disease activity and the elevation of cfDNA levels in SF and peripheral blood [62].…”

Citrullinated Histone H3 Mediates Sepsis-Induced Lung Injury Through Activating Caspase-1 Dependent Inflammasome Pathway

“…This indicates that CitH3 and/or H3 may activate multiple cell death pathways besides Caspase-1 mediated cell death. Actually, the high concentration of TNF-α released after treatment with CitH3 and H3 can also induced other lytic cell death like necroptosis ( 53 ). Interestingly, a recent study showed that prolonged exposure of myeloid cells to DAMPs like oxLDLs can induce cell to switch between cell death pathways ( 54 ).…”