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.

The Bacterial Effector Protein YopM Reduces Bone Destruction in Rheumatoid Arthritis (RA).

Bertrand1,  Jessica, Ruter3,  Christian, Scharnert3,  Julia, Schmidt3,  Alexander, Pap2,  Thomas

Institute for Experimental Musculoskeletal Medicine, Münster, Germany
Institute for Experimental Musculoskeletal Medicine
Institute for Infectiology ZMBE


Bone marrow macrophages (BMM) are precursors of osteoclasts, which mediate the degradation of bone during rheumatoid arthritis (RA). The yersinia outer protein M (YopM) is an effector protein of Yersinia species that is able to enter host cells by membrane penetration. In the cell YopM mediates down-regulation of inflammatory responses. We investigated whether YopM has the potential to act as a "self-delivering" immune therapeutic agent by reducing the inflammation and joint destruction linked to RA.


We analysed the penetration of recombinant YopM into BMMs by confocal laserscanning microscopy and studied the effects of YopM on osteoclastogenesis using an in vitro osteoclast formation assay. To unravel the signaling pathways involved in the effects of YopM, we investigated the activation of MAP-kinases (ERK, AKT and p-38) and NF-KB signaling by Western Blot analysis. With respect to a potential in vivo application of YopM, we injected YopM intra articular and intravenous of wildtype and hTNFtg mice and monitored its distribution by fluorescence reflection imaging (FRI). Additionaly, we treated hTNFtg mice, as animal model for RA, with YopM and recorded clinical parameters (weight, grip strength and paw swelling). Finally, we analysed the destruction of bone and cartilage histologically compared to untreated hTNFtg mice and wildtype mice.


As seen in confocal scanning microscopy, YopM penetrated the cell membrane of BMMs and accumulated near the nucleus. Studying the signaling pathways affected by YopM, we found that YopM reduced the TNF alpha induced activation of NF-KB by reducing the phosphorylation of IkB alpha. TNF alpha mediated phosphorylation of MAP kinases were not altered by YopM. Most interestingly, we found a strong reduction of osteoclast formation by YopM. Incubation of BMMs with YopM led to a 90% reduction in osteoclasts precursors and osteoclasts. YopM-Cy5 injected intra-articular into the knee joints of a mouse was detectable whithout a systemic distribution of YopM during a time period of 72 hours. Analysing the clinical parameters of RA in hTNFtg mice, we observed a delay of onset of paw swelling in mice treated with YopM. At histological analysis of the hind paws, we found reduced bone destruction and inflammation in YopM treated hTNFtg mice in comparison to untreated hTNFtg mice.


These results suggest that YopM has the potential to reduce inflammation and bone destruction in vivo. Therefore YopM may constitute a novel therapeutic principle for the treatment of RA.

To cite this abstract, please use the following information:
Bertrand, Jessica, Ruter, Christian, Scharnert, Julia, Schmidt, Alexander, Pap, Thomas; The Bacterial Effector Protein YopM Reduces Bone Destruction in Rheumatoid Arthritis (RA). [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1130
DOI: 10.1002/art.28897

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