Fig. 6
Inducible MMP-9 expression reduces LPS-induced IL-6 secretion in RAW264.7 cells without affecting Il6 mRNA levels. RAW264.7 cells were transduced with a doxycycline (Dox)-inducible MMP-9 expression vector (pLVX-Tet-On-mMMP-9). (A) MMP-9 enzymatic activity in the conditioned medium was assessed by zymography following Dox induction (1 µg/mL for 24 h). (B) Intracellular MMP-9 protein levels were evaluated by immunoblotting. (C–F) Cells were either co-treated with Dox and LPS (100 ng/mL) for 24 h or pretreated with Dox for 16 h prior to LPS stimulation. Gene expression levels of Mmp9, Il6, and Tnf were measured by quantitative PCR using Rpl19 as internal control. (D) ELISA determined IL-6 secretions in conditioned medium. Data are presented as mean ± SEM (n = 3–6 per group). Statistical analyses were performed using unpaired t-tests. *P < 0.05, **P < 0.01 vs. control; ns: not significant. m: marker.
