Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Liposomal Targeting of Glucocorticoids to the Synovial Lining during Experimental Arthritis Inhibits M1 Macrophage Activation in Favour of M2 Differentiation.

Hofkens2,  Wouter, Storm3,  Gert, Van Den Berg1,  Wim B., van Lent2,  Peter

Radboud Univ Nijmegen Med Cntr, Nijmegen, The Netherlands
Radboud University Nijmegen Medical Center
Utrecht University

Background and Objective:

Recently we found that systemic delivery of liposomes containing glucocorticoids strongly suppresses joint inflammation during experimental antigen-induced arthritis (AIA). During the course of AIA, macrophages in the synovial lining layer are activated towards a pro-inflammatory ('M1') and in later phases towards an anti-inflammatory ('M2') activation state. M1 macrophages are characterized mainly by an up-regulation of pro-inflammatory cytokines such as TNF-a, IL-1b, IL-6 and IL-12p40 whereas M2 macrophages show an increase in IL-10 expression and expression of membrane markers IL-1 receptor type II (IL-1RII) and CD163. We now explored whether liposomal targeting of synovial lining macrophages with glucocorticoids exerts its effect through M1/M2 macrophage skewing.

Materials and Methods:

Mice with established antigen-induced arthritis (AIA) were treated with a single intravenous injection of 10 mg/kg liposomal prednisolone phosphate (Lip-PLP) or PBS. Naïve mice were injected intra-articularly with IFNg/LPS to induce M1 phenotype and 24 hours thereafter with Lip-PLP or PBS. Mice were sacrificed at day 1 after Lip-PLP treatment and whole knee joints were isolated for histology and synovial biopsies were isolated for RNA analysis. In vitro, murine bone marrow macrophages were differentiated towards M1 phenotype with LPS and IFNg, treated with Lip-PLP and M1/M2 markers characterized by quantitative RT-PCR, LUMINEX and FACS.

Results:

A single intravenous injection with Lip-PLP in mice with established AIA significantly reduced synovial infiltration from control treatment (PBS) within 1 day. At this time point, synovial gene expression was strongly down-regulated by Lip-PLP for the M1 cytokines TNF-a (3.3 fold), IL-1b (10.6 fold), IL-6 (5.6 fold) and IL-12p40 (6.3 fold) compared to PBS treated mice, whereas expression of M2 markers was only slightly down-regulated (IL-10: 2.1 fold and IL-1RII: 1.2 fold) or even up-regulated (CD163: 1.9 fold). Liposomes entered the synovium by blood vessels lying just beneath the lining layer and were directly engulfed by macrophages as detected by gold containing liposomes. To evaluate whether Lip-PLP had a direct effect on M1 macrophages, these cells were induced in vitro by IFNg and LPS and subsequently incubated with Lip-PLP for 24 hours. Lip-PLP suppressed expression of TNF-a, IL-1b, IL-6 and IL-12p40 and induced expression of IL-10, IL-1RII and CD163 in M1 macrophages in vitro suggesting a selective skewing of M1 macrophages towards an M2 phenotype. Local M1 activation and subsequent treatment with Lip-PLP led to a similar gene expression pattern as in the AIA providing cogent evidence for selective skewing of M1 macrophages in favour of the M2 phenotype.

Conclusion:

Systemic delivery of liposomal glucocorticoids during experimental arthritis inhibit M1 macrophages in favour of M2 phenotype in the lining layer and may drive their strong suppressive effect.

To cite this abstract, please use the following information:
Hofkens, Wouter, Storm, Gert, Van Den Berg, Wim B., van Lent, Peter; Liposomal Targeting of Glucocorticoids to the Synovial Lining during Experimental Arthritis Inhibits M1 Macrophage Activation in Favour of M2 Differentiation. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :283
DOI: 10.1002/art.28052

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