MMP-9 inhibits IFN-α/β downstream effectors. (A) HepG2 cells (2 × 106) were transfected with pCMV-Tag2B-MMP-9 for 48 h and treated with rhIFN-α (300 IU/ml) for 30 min. (B) HepG2 cells (2 × 106) were transfected with pCMV-Tag2B-MMP-9 for 48 h and treated with rhIFN-α (300 IU/ml) for different times. (C) HepG2 cells (2 × 106) were transfected with pCMV-Tag2B-MMP-9 at different concentrations for 48 h and treated with rhIFN-α for 30 min. (D) HepG2 cells (2 × 106) were treated with rhMMP-9 (50 ng/ml) for 3 h and treated with rhIFN-α for 30 min. (E) HepG2 cells (2 × 106) were transfected with pCMV-Tag2B-MMP-9-wt or pCMV-Tag2B-MMP-9-mut for 48 h and treated with rhIFN-β (10 ng/ml) for 30 min. (F) HepG2 cells (2 × 106) were transfected with siR-MMP-9 (100 nM) for 48 h and treated with rhIFN-α for 30 min. (G) HepG2 cells (2 × 106) were transfected with pHBV1.3 (1 μg) and siR-MMP-9 (100 nM) for 48 h and treated with rhIFN-α for 30 min. For panels A to G, levels of proteins expressed in treated cells were determined by Western blot analyses using the corresponding antibodies, as indicated. (H to J) HepG2 cells (2 × 106) were transfected with pCMV-Tag2B-MMP-9 for 36 h and treated with rhIFN-α (300 IU/ml), rhIFN-β (10 ng/ml), rhIFN-γ (50 ng/ml), and rhIFN-λ1 (100 ng/ml) for 12 h. PKR mRNA (H), OAS1 mRNA (I), and Mx1 mRNA (J) levels were measured by qPCR. (K) HepG2 cells (2 × 106) were transfected with pCMV-Tag2B-MMP-9 for 36 h and treated with rhIFN-α for 12 h. (L) HepG2 cells (2 × 106) were treated with rhMMP-9 (50 ng/ml) for 3 h and treated with rhIFN-α for 12 h. (M) HepG2 cells (2 × 106) were transfected with siR-MMP-9 (100 nM) for 36 h and treated with rhIFN-α for 12 h. (N) HepG2 cells (2 × 106) were cotransfected with pHBV1.3 (1 μg) and siR-MMP-9 (100 nM) for 36 h and treated with rhIFN-α for 12 h. In panels K to N, levels of proteins expressed in treated cells were determined by Western blot analyses using the corresponding antibodies, as indicated. Results show means ± standard deviations (n = 3). ns, nonsignificant; *, P < 0.05.