Modulation of the immune response in rheumatoid arthritis with strategically released rapamycin

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease, which is associated with symptoms, including synovial membrane inflammatory pain, joint synovitis and stiffness. However, there are no effective methods available to cure this disease. In the present study, rapamycin was used to modulate immunity in RA. To limit the cytotoxicity of rapamycin, rapamycin was loaded into well‑characterized biocompatible nanoparticles. In vitro, rapamycin particles downregulated the activation of dendritic cell surface markers, including CD80+ and CD40+, upon interacting with macrophages. The rapamycin particles reduced the secretion of inflammatory cytokines, including interleukin (IL)‑6, tumor necrosis factor (TNF) and IL‑1β, which are characteristic of RA. In vivo, the rapamycin particles decreased the symptoms of RA in mice, and the production of inflammatory cytokines was associated with the occurrence of RA. The present study partially revealed the interactions between rapamycin and two types of immune cell in RA disease, and may potentially offer a solution to improve the treatment of RA.

Figure 1.

Characterization of rapamycin-loaded nanoparticles. (A) Scanning electron microscopy revealing the morphology of the rapamycin-loaded particles. (B) Size distribution of rapamycin particles. The particles had a diameter of 165±35 nm. (C) Release profile of rapamycin from particles in PBS.

Figure 2.

Effects of soluble rapamycin and rapamycin particles on splenocyte viability. Rapamycin had a marginal effect on cell viability. Rapamycin loaded in particles (orange bars) has less effect on cell viability, compared with soluble rapamycin (blue bars).

Figure 3.

Rapamycin particles regulate dendritic cell activation. The activation of (A) CD80 and (B) CD40 markers by different samples was examined. Cells were treated with LPS, NP or LPS+rapamycin particles. Cells with no treatment were used as a control. *P<0.05. LPS, lipopolysaccharide; Rapa, rapamycin; NP, empty particles.

Figure 4.

Production of cytokines from macrophages with different treatments. Secretion of (A) IL-6, (B) TNF and (C) IL1-β from macrophages with different treatments. The cells were treated with LPS, LPS+NP or LPS+rapamycin particles. Cells with no treatment were used as a control. *P<0.05 and **P<0.01. IL, interleukin; TNF, tumor necrosis factor; LPS, lipopolysaccharide; Rapa, rapamycin; NP, empty particles.

Figure 5.

In vivo assessment of rapamycin particles in the RA model. (A) Clinical scores of Naïve mice, mice treated with empty NP and mice treated with rapamycin particles. Mice treated with rapamycin particles had lower clinical scores, compared with those in the other two groups. (B) Weights of mice. Naïve mice and mice treated with NP were used as controls, which exhibited reduced weight over time. (C) TNF, (D) IL-6 and (E) IL-10 were present in the sera of mice. *P<0.05 and **P<0.01. RA, rheumatoid arthritis; Naïve, untreated; NP, empty particles; Rapa/NP mice with RA and rapamycin particle treatment; TNF, tumor necrosis factor; IL, interleukin.