Inhibition of MMP1, MMP2 and MMP8 by mepacrine

Background

Matrix metalloproteinases (MMPs) play a pivotal role in many diseases. Inhibition of these enzymes is therefore also an important therapeutic target in rheumatoid arthritis and osteoarthritis, in which elevated levels of MMPs contribute to joint destruction. We reported earlier that mepacrine may effect MMPs by interfering with the activation of the transcription factor AP-1. Here we demonstrate that mepacrine may exert certain beneficial effects by suppressing MMP up-regulation in mononuclear cells.

Objective and methods

THP-1 and blood cells freshly isolated by density-gradient centrifugation were used. This cell population was pre-treated with mepacrine and was subsequently stimulated with PMA for 4 hours to induce MMPs. RT-PCR was used to monitor the effect of mepacrine on cytokine- and PMA-induced MMP1, MMP2, MMP3 and MMP8 up-regulation.

Mepacrine has been used successfully to tether certain forms of rheumatic diseases. In order to account for these findings, we investigated possible effects of mepacrine on TNF as well as PMA-induced MMP up-regulation.

Results

Mepacrine dose-dependently inhibited the PMA-induced up-regulation of MMP1, MMP2 and MMP8. The observed effects are specific, since mepacrine did not interfere with MMP3 activation. Western blot and RT-PCR experiments showed that treatment of mononuclear cells (MNCs) with mepacrine blocked the MMP up-regulation at the transcriptional level. Furthermore, electrophoretic mobility shift assays, using the AP-1 consensus element and MNC nuclear extract, demonstrated that, similar to human synovial fibroblast-like cells, mepacrine blocked AP-1-DNA interactions.

Conclusion

These effects of mepacrine on MMP up-regulation in MNCs may contribute to the beneficial effects of this drug seen in the past. To what degree events upstream of AP-1 are affected by mepacrine is currently under investigation.