Fig. 4. CD147 negatively regulates NOD2-mediated NF-B activation and IL8 release. (A) NOD2-dependent MDP-induced activation of NF-B was determined by dual-luciferase assay. Overexpression of full-length CD147 (FL) or its intracellular domain (IC), but not of the extracellular domain (EC) lead to a decrease of NOD2-dependent NF-B activation. (RLU, relative light units; vc, vector control; ^**P<0.01 for transfection of CD147 constructs versus vc). (B) Overexpression of full-length CD147 impairs NOD2-dependent IL8 release in a dose-dependent manner. HEK293 cells were transiently transfected with pcDNA4-Xpress-NOD2 and increasing amounts of pEGFP-N1-CD147 and were left untreated or were treated with MDP. Supernatants were assayed for IL8 by enzyme-linked immunosorbent assay. Transfection with empty vector pEGFP-N1 served as control (indicated by `–'). Data represent the mean ± s.d. of three independent experiments (^**P<0.01 for transfection of CD147 construct versus control).