Proteasome inhibitor MG132 ameliorates joint pain and the progression of experimental osteoarthritis.
Osteoarthritis is a degenerative joint disease with pain and loss of joint function as major pathological features. Recent studies show that proteasome inhibitors reduce pain in various pathological conditions. We evaluated the effects of MG132, a reversible proteasome inhibitor on pain and joint destruction in a rat model of osteoarthritis. Osteoarthritis was induced by intraarticular injection of monosodium iodoacetate into the rat knee. Knee joint stiffness was scored and nociception was evaluated by mechanical pressure applied to the respective hind paw. Knee joint destruction was assessed by radiological and histological analyses. Expression of matrix metalloproteinase-3 (MMP-3) was analyzed by quantitative reverse transcription polymerase chain reaction in the knee articular cartilage. Expression of substance P (SP) and calcitonin gene-related peptide (CGRP) was studied in the dorsal root ganglia (L4–L6) by quantitative reverse transcription polymerase chain reaction and in the knee joints by immunohistochemistry. Our results indicate that daily treatment of osteoarthritic rats with MG132 significantly increases their mobility while the swelling, pain thresholds, and pathological features of the affected joints were reduced. Furthermore, the upregulated expression of MMP-3, SP, and CGRP in the arthritic rats was normalized by MG132 administration. We conclude that the proteasome inhibitor MG132 reduces pain and joint destruction, probably by involving the peripheral nervous system, and that changes in SP and CGRP expression correlate with alterations in behavioural responses. Our findings suggest that nontoxic proteasome inhibitors may represent a novel pharmacotherapy for osteoarthritis.
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
aDepartment of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm 17176, Sweden
bDepartment of Medicine, Centre for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Solna, Stockholm 17176, Sweden
cDepartment of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, Stockholm 18288, Sweden
dDepartment of Pharmaceutical Biosciences, Uppsala University, Uppsala 75105, Sweden
eDepartment of Neurobiology, Care Sciences and Society, Center for Family and Community Medicine, Karolinska Institutet, Huddinge 14183, Sweden
*Corresponding author. Address: Rheumatology Unit, L8:04, Department of Molecular Medicine and Surgery, Karolinska University Hospital, Stockholm 17176, Sweden. Tel.: +46 735 056601.
Article history: Received 6 December 2010; Received in revised form 30 June 2011; Accepted 1 August 2011.