As shown in Fig. 2, MTT assay demonstrated that the total extract and GTF did not show significant reduction of cell viability at the tested concentrations when incubated in SW1353 chondrocytes. However, 50 μg/mL of n-butanol fraction reduced viability (7.0%), and 200 μg/mL of GDF slightly reduced viability (5.1%), but the results are not statistically significant. GDF/F4 showed cytotoxicity Luminespib mouse at 30 μg/mL (53.0%). Therefore, all other experiments of n-butanol fraction, GDF, and GDF/F4

fractions were carried out at lower concentrations than indicated. When the MMP-13 downregulatory effects of these preparations were compared in SW1353 cells, the crude extract (up to 300 μg/mL) and GTF (up to 200 μg/mL) failed to downregulate MMP-13 expression (Fig. 3A and 3B). By contrast, the n-butanol fraction (30 μg/mL) showed significant inhibition of MMP-13 expression ( Fig. 3C). In particular, GDF and PS-341 in vitro GDF/F4 showed clear inhibition at 10–100 μg/mL and 5–20 μg/mL, respectively, without cytotoxic effects ( Fig. 3D and 3E). Dexamethasone (10μM) used as a reference agent strongly inhibited MMP-13 expression as expected. These results indicate that n-butanol fraction, GDF, and GDF/F4 possess MMP-13 downregulatory activity, with GDF/F4 having the strongest inhibition of MMP-13 induction among the preparations tested. Next, the cellular mechanisms of MMP-13

downregulation by GDF/F4, the strongest downregulator, Thalidomide were examined. In SW1353 cells, IL-1β treatment induced MMP-13 expression. Previously, this induction in IL-1β-treated SW1353 cells was found to be mediated, at least in part, via activation of transcription factors, such as NF-κB, activator protein-1 (AP-1), and STAT-1/2 [12] and [14]. Among upstream kinases, p38 MAPK and JAK activation were importantly involved [12]. When the effects on MAPK pathways were examined, GDF/F4 inhibited the activation of p38 MAPK and JNK at 20 μg/mL. Among the transcription factors, the activation

of STAT-1/2 was blocked, but not that of NF-κB and AP-1 (Fig. 4). Thus, it is suggested that GDF/F4 downregulates MMP-13 expression by blocking the activation of multiple points including MAPKs and the transcription factor, STAT-1/2. To establish the cartilage protective effect of the new preparation, rabbit cartilage tissue culture was employed. IL-1α treatment of rabbit cartilage induced MMPs, which degraded the matrix materials and released large amounts of GAG into the media for a 3-day culture (Fig. 5). Under this condition, GDF/F4 inhibited GAG release (30.6% and 19.3%) from rabbit cartilage at 30μM and 50μM, respectively, whereas the reference compound, diclofenac (30μM), showed strong inhibition (64.1%) as expected. However, Korean Red ginseng total ethanol extract did not protect the GAG release at 200 μg/mL under the same experimental conditions.