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Updated: Jan 26, 2026
A Mouse Model for Pathogen-induced Chronic Inflammation at Local and Systemic Sites
Published on: August 8, 2014
Subantimicrobial Dose Doxycycline Worsens Chronic Arthritis-Induced Bone Microarchitectural Alterations in a Mouse
Ádám Horváth1,2, Bálint Botz2,3, Tamás Kiss1,2
1Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary.
Abstract:
Background: Rheumatoid arthritis (RA) is a chronic inflammatory joint disease hallmarked by irreversible damage of cartilage and bone. Matrix metalloproteinases (MMPs) involved in connective tissue remodeling play an important role in this process. Numerous MMPs have been examined in humans and animals, but their functions are still not fully understood. Therefore, we investigated the role of MMPs in the K/BxN serum-transfer model of RA with the broad-spectrum MMP inhibitor subantimicrobial dose doxycycline (SDD) using complex in vivo and in vitro methodolgy. Methods: Chronic arthritis was induced by repetitive i.p. injections of K/BxN serum in C57BL/6J mice. SDD was administered daily in acidified drinking water (0.5 mg/mL, 80 mg/kg) during the 30 days experimental period. Mechanonociceptive threshold of the paw was evaluated by aesthesiometry, grasping ability by grid test, arthritis severity by scoring, neutrophil myeloperoxidase activity by luminescence, vascular hyperpermeability and MMP activity by fluorescence in vivo imaging and the latter also by gelatin zymography, bone structure by micro-computed tomography (micro-CT). Plasma concentrations of doxycycline were determined by liquid chromatography-mass spectrometry analysis. Results: K/BxN serum induced significant inflammatory signs, mechanical hyperalgesia, joint function impairment, increased myeloperoxidase activity and vascular hyperpermeability. Significant increase of MMP activity was also observed both in vivo and ex vivo with elevation of the 57-60, 75, and 92 kDa gelatinolytic isoforms in the arthritic ankle joints, but neither MMP activity nor any above described functional parameters were influenced by SDD. Most importantly, SDD significantly reduced bone mineral density in the distal tibia and enhanced the Euler number in the ankle. Arthritis-induced microarchitectural alterations demonstrating increased irregularity and cancellous bone remodeling, such as increased Euler number was significantly elevated by SDD in both regions. Conclusion: We showed increase of various MMP activities in the joints by in vivo fluorescence imaging together with ex vivo zymography, and investigated their functional significance using the broad-spectrum MMP inhibitor SDD in the translational RA model. This is the first demonstration that SDD worsens arthritis-induced bone microarchitectural alterations, but it appears to be independent of MMP inhibition.
Insights
Subantimicrobial dose doxycycline (SDD) did not inhibit matrix metalloproteinases (MMPs) in a rheumatoid arthritis model. Instead, SDD worsened bone damage, suggesting effects beyond MMP inhibition in arthritis.
Area of Science:
- Rheumatology
- Pharmacology
- Biochemistry
Background:
- Rheumatoid arthritis (RA) is a chronic inflammatory joint disease causing irreversible cartilage and bone damage.
- Matrix metalloproteinases (MMPs) are implicated in RA pathogenesis through connective tissue remodeling.
- The precise roles of various MMPs in RA remain incompletely understood.
Purpose of the Study:
- To investigate the role of MMPs in the K/BxN serum-transfer model of RA.
- To evaluate the effects of the broad-spectrum MMP inhibitor, subantimicrobial dose doxycycline (SDD), on RA progression.
- To elucidate the functional significance of MMPs in RA using in vivo and in vitro methodologies.
Main Methods:
- Chronic arthritis was induced in C57BL/6J mice via K/BxN serum injections.
- Subantimicrobial dose doxycycline (SDD) was administered daily.
- Evaluated parameters included mechanonociceptive thresholds, joint function, neutrophil myeloperoxidase activity, vascular hyperpermeability, MMP activity (in vivo imaging and zymography), and bone structure (micro-CT).
Main Results:
- K/BxN serum induced significant inflammatory signs, pain, joint dysfunction, and increased myeloperoxidase activity and vascular hyperpermeability.
- MMP activity, including specific gelatinolytic isoforms, increased in arthritic joints.
- SDD did not influence MMP activity or the observed functional parameters of arthritis.
- Crucially, SDD exacerbated bone mineral density reduction and altered bone microarchitecture, indicated by an increased Euler number, independent of MMP inhibition.
Conclusions:
- Increased MMP activity was confirmed in the joints during experimental RA using in vivo and ex vivo methods.
- The broad-spectrum MMP inhibitor SDD did not ameliorate RA symptoms or MMP activity.
- This study demonstrates for the first time that SDD worsens arthritis-induced bone microarchitectural damage, independent of MMP inhibition.
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