Fig. 6.

OGN promotes TLR4 activation by enhancing MAPK-induced cytokine production. Bone marrow-derived macrophages (BMDMs) from WT and KO mice were isolated and stimulated with LPS (10 ng/ml). a–d LPS stimulation resulted in the blunted induction of pro-inflammatory cytokines TNFα and IL-6 expression (1 h) as well as IL-1β and IL-12 at a later stage (6 h) (c, d). This difference in TLR4 activation was reflected in the lower TNFα and IL-6 expression levels in the medium of OGN-KO BMDMs (e, f). This increased cytokine production was the result of significant induction of MyD88 that was blunted in the OGN-KO BMDMs (g, h). g Western blot analysis and further quantification revealed blunted c-jun, ERK1/2 and JNK phosphorylation in the KO BMDMs, and blunted pNFkB induction (i–l). All experiments were repeated at least twice. n ≥ 3; *p < 0.05; **p < 0.01; ***p < 0.001