Serum levels of interleukin-34 and clinical correlation in patients with primary Sjögren's syndrome

Significance of IL-34 and SDC-1 in the pathogenesis of RA cells and preclinical models

IL-34 shares a common receptor with M-CSF, while it can bind to other distinct receptors including protein-tyrosine phosphatase zeta (PTPζ), and syndecan1 (SDC-1). In physiological conditions, IL-34 has a critical role in the maintenance and development of Langerhans and microglial cells in part through PTPζ ligation. Conversely, in autoimmune diseases such as rheumatoid arthritis (RA), SDC-1-induced phosphorylation of M-CSFR was responsible for the pathological effect of IL-34 in patient cells and/or preclinical models. Intriguingly, enrichment of IL-34 is strongly linked to rheumatoid factor (RF), disease activity score (DAS)28, erythrocyte sedimentation rate (ESR), c-reactive protein (CRP), and radiographic progression. In parallel, IL-34-induced naïve cell reprogramming into glycolytic RA CD14+CD86+GLUT1+ macrophage was dysregulated via M-CSFR or SDC-1 antibody therapy. Moreover, the inflammatory and erosive imprints of IL-34 arthritic mice were mitigated by glucose uptake inhibition and SDC-1, or RAG deficiency through nullifying macrophage metabolic rewiring and their ability to advance Th1/Th17 cell polarization. Consistently, IL-34-/- and SDC-1-/- mice could effectively impair CIA joint inflammation, osteoclast formation, and neovascularization by restraining monocyte infiltration as well as suppressing the inflammatory macrophage and T effector cell reconfiguration via metabolic deactivation. In conclusion, targeting IL-34/SDC-1 signaling, or its interconnected metabolites can uniquely intercept the crosstalk between glycolytic RA myeloid and lymphoid cells and their ability to trigger arthritis.

Increased serum interleukin-34 levels as a novel diagnostic and prognostic biomarker in patients with acute ischemic stroke

BACKGROUND

Recent data reveal that interleukin-34 (IL-34) can drive inflammatory response, thereby participating in the pathogenesis of inflammatory diseases. However, the potential effect of IL-34 in acute ischemic stroke (AIS) remains unknown. The purpose of this study was to explore whether the levels of serum IL-34 were correlated with clinical severity or prognosis in AIS patients.

METHODS

In this prospective cohort study, serum IL-34 levels were detected in 150 healthy controls and 155 AIS patients. Univariate and multivariate logistic regression analysis were conducted to investigate the effect of IL-34 on the diagnosis and prognosis of AIS. ROC curve was utilized to evaluate predictive values for IL-34.

RESULTS

Serum IL-34 levels at admission were significantly higher in AIS patients than those in the healthy controls. Univariate and multivariate logistics regression analysis showed that IL-34 was an independent predictor of occurrence and functional outcome of AIS. The ROC curve demonstrated that IL-34 had a good predictive effect on the diagnosis and prognosis of AIS.

CONCLUSIONS

IL-34 can be used as a novel and independent diagnostic and predicting prognostic biomarker in AIS.

The twin cytokines interleukin-34 and CSF-1: masterful conductors of macrophage homeostasis

Macrophages are specialized cells that control tissue homeostasis. They include non-resident and tissue-resident macrophage populations which are characterized by the expression of particular cell surface markers and the secretion of molecules with a wide range of biological functions. The differentiation and polarization of macrophages relies on specific growth factors and their receptors. Macrophage-colony stimulating factor (CSF-1) and interleukine-34 (IL-34), also known as "twin" cytokines, are part of this regluatory landscape. CSF-1 and IL-34 share a common receptor, the macrophage-colony stimulating factor receptor (CSF-1R), which is activated in a similar way by both factors and turns on identical signaling pathways. However, there is some discrete differential activation leading to specific activities. In this review, we disscuss recent progress in understanding of the role of the twin cytokines in macrophage differentiation, from their interaction with CSF-1R and the activation of signaling pathways, to their implication in macrophage polarization of non-resident and tissue-resident macrophages. A special focus on IL-34, its involvement in pathophsyiological contexts, and its potential as a theranostic target for macrophage therapy will be proposed.