Pesquisadores ligados ao German Cancer Research Center, a Universidade de Regensburg e ao Massachusetts General Hospital publicaram, recentemente, no Arthritis & Rheumatism, um estudo em que procuraram investigar a hipótese de que proteases envolvidas na destruição articular são, in vivo, marcadores sensíveis para avaliação precoce da resposta ao tratamento em modelo murino de artrite reumatóide.
Utilizando um marcador “inteligente” fluorescente ativado pela atividade da protease, os pesquisadores examinaram a presença e a distribuição da fluorescência em articulações artríticas de camundongos portadores de artrite induzida por colágeno através de estudos de imunofluorescência e histológicos. Proteases cujos alvos eram locais de ligação Lisina-Lisina, incluindo catepsina B, ativavam o marcador fluorescente. Dados sobre o controle do tratamento foram obtidos após a administração de metotrexate.
Vinte e quatro horas após a administração endovenosa dos marcadores fluorescentes com sensores de proteases, articulações acometidas nas patas e nos dedos dos animais apresentaram intensidade significativamente maior de fluorescência, comparadas às articulações de animais saudáveis. Fluorescência a partir do marcador de protease e imunohistoquímica positiva para catepsina B foram localizados na maioria das células presentes na sinóvia inflamada. Em animais tratados com metotrexate 35mg/kg 48 horas antes da administração de marcadores fluorescentes, a resposta com fluorescência foi significativamente menor (patas inflamadas = 50%; dedos inflamados = 70%), comparada à resposta verificada em animais saudáveis.
Portanto, os pesquisadores concluíram que marcadores fluorescentes ativados por proteases são sensíveis para detecção de enzimas em articulações artríticas, podendo servir para monitorização de tratamento com drogas anti-reumáticas.
In vivo imaging of protease activity in arthritis: A novel approach for monitoring treatment Response - Arthritis & Rheumatism; 2004; 50(8): 2459-2465
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In vivo imaging of protease activity in arthritis: A novel approach for monitoring treatment response
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| Andreas Wunder 1 2, Ching-Hsuan Tung 2, Ulf Müller-Ladner 3, Ralph Weissleder 2, Umar Mahmood 2 * |
1German Cancer Research Center, Heidelberg, Germany
2Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts
3University of Regensburg, Regensburg, Germany
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| email: Umar Mahmood (mahmood@helix.mgh.harvard.edu) |
*Correspondence to Umar Mahmood, MGH-CMIR 5408, Building 149, 13th Street, Charlestown, MA 02129
Funded by:
NIH; Grant Number: P50-CA-86355, R24-CA-92782, R01-EB-001872
German Cancer Research Center
German Research Society; Grant Number: DFG Mu 1383/3-3
Objective |
| Sensitive noninvasive strategies for monitoring treatment response in rheumatoid arthritis (RA) would be valuable for facilitating appropriate therapy and dosing, evaluating clinical outcome, and developing more effective drugs. Because different proteases are highly up-regulated in RA and contribute significantly to joint destruction, in the present study we investigated whether such enzymes are suitable in vivo imaging biomarkers for early evaluation of treatment response in a murine model of RA. |
Methods |
Using a protease-activated near-infrared fluorescence (NIRF) imaging  smart probe, we examined the presence and distribution of fluorescence in arthritic joints of mice with collagen-induced arthritis by both noninvasive fluorescence imaging and histology. Proteases that target the Lys-Lys cleavage site, including cathepsin B, activate probe fluorescence. Treatment monitoring data were obtained following methotrexate (MTX) therapy. |
Results |
| Twenty-four hours after intravenous injection of the protease sensor, affected toes and paws of arthritic mice showed significantly higher fluorescence intensity than did toes and paws of healthy mice. Fluorescence from the protease probe and cathepsin B antibody histologic staining were localized in the vast majority of cells in the inflamed synovium. In arthritic animals treated with MTX (35 mg of MTX/kg 48 hours prior to probe injection), a significantly lower fluorescent signal (inflamed paws 50%, inflamed toes 70%) was observed as compared with untreated arthritic animals. |
Conclusion |
| Protease-activated NIRF probes are sensitive means of imaging the presence of target enzymes in arthritic joints and can be used for early monitoring of treatment response to antirheumatic drugs such as MTX. |
