Retinoid X receptor and peroxisome proliferator-activated receptor-gamma agonists cooperate to inhibit matrix metalloproteinase gene expression

The PPARgamma and RXR ligands rosiglitazone and LG268 may act through similar mechanisms, inhibiting MMP-1 and MMP-13 transcription. Combinatorial treatment activates each partner of the RXR:PPARgamma heterodimer and inhibits IL-1-beta-induced expression of MMP-1 and MMP-13 more effectively than either compound alone. We conclude that the efficacy of combined treatment with lower doses of each drug may minimize potential side effects of treatment with these compounds.

We used real-time reverse transcription-polymerase chain reaction to measure LG268- and rosiglitazone-mediated inhibition of MMP gene transcription in IL-1-beta-treated SW-1353 chondrosarcoma cells. An in vitro collagen destruction assay was a functional readout of MMP collagenolytic activity. Luciferase reporter assays tested the function of a putative regulatory element in the promoters of MMP-1 and MMP-13, and chromatin immunoprecipitation (ChIP) assays detected PPARgamma and changes in histone acetylation at this site. Post-translational modification of RXR and PPARgamma by small ubiquitin-like modifier (SUMO) was assayed with immunoprecipitation and Western blot.

Rosiglitazone inhibited MMP-1 and MMP-13 expression in IL-1-beta-treated SW-1353 cells at the mRNA and heterogeneous nuclear RNA levels and blunted IL-1-beta-induced collagen destruction in vitro. Combining LG268 and rosiglitazone had an additive inhibitory effect on MMP-1 and MMP-13 transcription and collagenolysis. IL-1-beta inhibited luciferase expression in the MMP reporter assay, but rosiglitazone and LG268 had no effect. ChIP indicated that treatment with IL-1-beta, but not LG268 and rosiglitazone, increased PPARgamma at the proximal promoters of both MMPs. Finally, rosiglitazone or LG268 induced 'cross-SUMOylation' of both the target receptor and its binding partner, and IL-1-beta-alone had no effect on SUMOylation of RXR and PPARgamma but antagonized the ligand-induced SUMOylation of both receptors. Conclusions: The PPARgamma and RXR ligands rosiglitazone and LG268 may act through similar mechanisms, inhibiting MMP-1 and MMP-13 transcription. Combinatorial treatment activates each partner of the RXR:PPARgamma heterodimer and inhibits IL-1-beta-induced expression of MMP-1 and MMP-13 more effectively than either compound alone. We conclude that the efficacy of combined treatment with lower doses of each drug may minimize potential side effects of treatment with these compounds.