Background Cells from the myelo-monocytic lineage are central in Rheumatoid arthritis (RA). They can present arthritogenic peptides, orientate towards Th17 and Th1 commitment, produce pro-inflammatory cytokines (TNFα, IL1, IL6), and differentiate into osteoclasts. Recently, we have shown that synthetic dendrimer aza-bisphosphonate (ABP) could be a potential therapeutic for RA through its specific targeting of monocytes (Mo) (1), alternative activation of Mo (2), suppression of murine arthritis and inhibition of human osteoclastogenesis (3). In RA, activation and maturation of Mo and dendritic cells are thought to be driven, at least in part, by Pattern Recognition Receptors such as TLR4.
Objectives To assess modulation of cytokine production by monocytes and dendritic cells, in response to TLR4 stimulation, in the presence of ABP. To determine dendritic cell maturation profile in the presence of ABP.
Methods Mo and monocyte derived dendritic cells (MoDC) from peripheral blood of healthy donors (n=12) were prepared. Cells were preincubated or not for 1 hour with ABP, then incubated with LPS (as a TLR4 ligand) and interferon γ (IFNγ) for 38 hours. Secretion of TNFα, IL1, IL6, IL12p70, IL10 and IL23 in the culture medium was measured by ELISA and Cytokine Bead Array. MoDC differentiation and subsequent maturation in the presence of LPS were analyzed by flow cytometry using CD80, CD86, CD83 and CD1a surface expression as markers. For statistical analysis, a two-tailed paired t-test was performed if data were normally distributed. Otherwise, the Wilcoxon signed-rank test was used.
Results In activated Mo, TNFα, IL1β and IL23 levels were significantly lower in the presence of ABP. In activated MoDC, ABP promoted IL10 secretion while decreasing dramatically the level of IL12. TNFα and IL6 secretion were significantly lower in the presence of ABP.
LPS driven maturation of MoDC was impaired by ABP treatment, as attested by the significantly lower expression of CD80 and CD86 and impaired induction of CD83.
Conclusions Our data indicate that ABP possesses anti-inflammatory properties on human Mo and MoDC, in a TLR4 stimulation model, by inducing M2 alternative activation of Mo, decreasing the secretion of pro-inflammatory cytokines by Mo, and promoting tolerogenic MoDC through higher IL10 secretion. Our data also suggest that ABP may modulate T helper cells differentiation by decreasing IL-12 and IL-23 secretion and CD80 and CD86 expression.
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Disclosure of Interest Y. Degboé Grant/research support from: Supported by Grants from INSERM-CNRS and Pfizer. Yannick Degboé was supported by a fellowship from Société Française de Rhumatologie for his Master Research work, S. Fruchon: None Declared, C.-O. Turrin: None Declared, A.-M. Caminade: None Declared, R. Poupot: None Declared, A. Cantagrel: None Declared, J.-L. Davignon: None Declared