No abstract

No abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease leading to joint destruction. Cytokines play a key role in its pathogenesis. They contribute to the induction and maintenance of inflammation and thus provide therapeutic targets. Many cytokines are involved in RA, and this review focuses on a few critical ones: tumor necrosis factor (TNF), interleukin (IL)-6, IL-1, IL-17, and GM-CSF. TNF and IL-6 are both well-established targets in RA treatment, and new biologic agents are reaching the market. IL-1 represents a more complex cytokine as results in humans do not reach those in animal models. IL-17 and GM-CSF are cytokines representing new targets either as early treatment or in non-responders to other biologics. The interaction between cytokines and their signaling pathways are the basis for the development of new strategies with small molecules or bispecific antibodies. Clearly, the targeting of cytokines has been a major progress in RA treatment, but many issues remain open. Although remission can be better achieved, reactivation of the disease too often occurs upon treatment discontinuation. Better understanding and targeting of chronicity remains a goal to achieve in the future.

BackgroundDuring chronic inflammation, immune cells, notably Th17 cells, infiltrate the inflammatory site and interact with local mesenchymal cells. Applied to rheumatoid arthritis (RA), the aim is to study the interactions between synoviocytes and peripheral blood mononuclear cells (PBMC) with a focus on the Th17 pathway and to identify a mechanism which leads to high IL-17 secretion with an interest on podoplanin.MethodsPBMC from healthy donors and RA patients were co-cultured with RA synoviocytes during 48 h, in the presence or not of phytohemagglutinin. An antibody against podoplanin was used in co-culture. Cytokine production (IL-6, IL-1β and IL-17) was measured by ELISA and cell staining (CD3, CD4, IL-17 and podoplanin) by flow cytometry.ResultsIn control conditions, IL-6 and IL-1β production was increased in PBMC-synoviocyte co-culture compared to PBMC alone (p = 0.02). No additional effect was observed with PBMC activation. Flow cytometry analysis showed no difference in the percentage of Th17 cells in activated PBMC alone or with synoviocytes (p = 0.4), indicating that Th17 differentiation requires only T cell activation. Conversely, IL-17 production was highly increased in co-cultures with activated PBMC vs. activated PBMC alone (p = 0.002). Transwell experiments confirm that cell-cell contact was critical for IL-17 secretion. The incubation of either PBMC or synoviocytes with an anti-podoplanin antibody decreased IL-17 secretion by 60 % (p = 0.008).ConclusionsInteractions between resting PBMC and synoviocytes are sufficient to induce IL-6 and IL-1β production. Both PBMC activation and cell interactions are needed to induce a high IL-17 secretion. Podoplanin contributes at the level of both lymphocytes and synoviocytes.

Summary In the context of psoriasis, T helper type 17 (Th17) cells infiltrate the inflammatory site and interact with local mesenchymal cells, including skin fibroblasts. The aim of this work was to study the interactions of skin‐derived fibroblasts with peripheral blood mononuclear cells (PBMC) with a focus on the Th17 pathway and to identify a mechanism which leads to a high interleukin (IL)−17 secretion. A co‐culture system between PBMC and skin fibroblasts was developed. Healthy and patient PBMC were added to non‐lesional or lesional skin fibroblasts at a 5:1 ratio for 48 h in the presence or not of activation with phytohaemagglutinin (PHA). Monocytes were removed or not by adherence before the co‐culture. An anti‐podoplanin antibody was also used during the co‐culture. Cytokine production (IL‐8, IL‐6, IL‐1β and IL‐17) was measured by enzyme‐linked immunosorbent assay (ELISA) and cell staining (CD3, CD4, IL‐17 and podoplanin) by flow cytometry. Without T cell receptor (TCR) activation, IL‐8, IL‐6 and IL‐1β production increased in PBMC‐fibroblast co‐culture compared to PBMC alone. No additional effect was observed with TCR activation, with no difference in the Th17 cell percentage in activated‐PBMC alone or co‐cultured. Conversely, IL‐17 production was increased highly only in co‐cultures between control and patient activated‐PBMC and skin fibroblasts. Removal of monocytes decreased cytokine production, notably that of IL‐17. Addition of an anti‐podoplanin antibody decreased IL‐17 secretion by 60%. Interactions between resting PBMC and fibroblasts induce the IL‐8, IL‐6 and IL‐1β production. PBMC activation and cell interactions are critical for a high IL‐17 secretion. Podoplanin contributes largely to this massive IL‐17 secretion.

Background: IL-17A has effects on several cell types and is a therapeutic target in several inflammatory diseases. IL-17F shares 50% homology and biological activities with IL-17A. It is now of interest to target both cytokines. The objective was to compare the IL-17A and IL-17F effect on cytokine production by RA synoviocytes, and to extend to other cells. Methods: Cells (RA synoviocytes, psoriasis skin fibroblasts, endothelial cells, myoblasts, and hepatocytes) were cultured in the presence or not of: IL-17A, IL-17F, TNF, IL-1β alone or their combinations, IL-17A/TNF, IL-17A/IL-1β, IL-17A/TNF/IL-1β, IL-17F/TNF, IL-17F/IL-1β, and IL-17F/TNF/IL-1β. All experiments were performed in parallel to reduce variability. After 48 h, supernatants were recovered and IL-6 and IL-8 levels were measured by ELISA. Results: IL-17A and IL-17F alone increased significantly IL-6 and IL-8 productions by synoviocytes, with a stronger effect for IL-17A. For IL-6 production, TNF or IL-1β alone had the largest effect on myoblasts (5-fold increase), while for IL-8 production, it was on skin fibroblasts (5-fold increase). The IL-17A/TNF synergistic increase was observed on all cells for IL-6; and for IL-8, except for endothelial cells. For IL-17F/TNF, except with endothelial cells, a synergistic effect was also observed, but less powerful than with IL-17A/TNF. IL-17A/IL-1β or IL-17F/IL-1β effect was cell-type dependent, with an additive effect for synoviocytes (1.6 and 2-fold increase, respectively for IL-6, and 1.8 and 2-fold increase, respectively for IL-8) and a synergistic effect for hepatocytes (3.8 and 4.2-fold increase, respectively for IL-6, and 6 and 2-fold increase, respectively for IL-8). The three-cytokine combination induced an additive effect for synoviocytes and a synergistic effect for skin fibroblasts. Conclusion: IL-17A and IL-17F acted similarly by inducing pro-inflammatory cytokine secretion, with a stronger response intensity with IL-17A. Their activities were potentiated by the combination with TNF and IL-1β, with an effect dependent on the cell type.

BackgroundDuring rheumatoid arthritis (RA), steroids and biotherapies are used alone and combined. Efficacy has been established in clinical trials but their differential effects at the cellular level are less documented. The aim was to study these cellular effects using an in vitro model with synoviocytes interacting with peripheral blood mononuclear cells (PBMC) to reproduce the interactions in the RA synovium.MethodsActivated-PBMC were cocultured with RA synoviocytes during 48 h. A dose–response of methylprednisolone (MP) was tested and different biotherapies (Infliximab, Etanercept, Adalimumab, Tocilizumab, Abatacept, and Rituximab) were added alone or in combination with MP. Cytokine production (IL-17, IL-6, IL-1β, IFN-γ and IL-10) was measured by ELISA.ResultsAddition of MP to cocultures inhibited the production of all cytokines. The response to the biotherapies alone was treatment-dependent. IL-17 production was inhibited only by Tocilizumab (p = 0.004), while IL-6 was decreased only by Infliximab (p ≤ 0.002). IL-1β level was affected in all conditions (p ≤ 0.03). IFN-γ production was mainly decreased by Infliximab (p = 0.004) and IL-10 by Infliximab and Tocilizumab (p ≤ 0.004). The combination MP and biotherapies did not induce an additional effect on pro-inflammatory cytokine inhibition. The combination MP and biotherapies induced a higher IL-10 secretion than MP alone, mainly with Rituximab.ConclusionSteroids inhibited the secretion of all cytokines, and low doses were as potent. The anti-inflammatory effect of biotherapies was dependent on their mechanism of action. MP and biotherapy combination did not enhance the inhibitory effect on pro-inflammatory cytokines but could have a beneficial effect by increasing IL-10 production.

No abstract