PGE2-EP4 pathway is in charge of LF41-mediated attenuation of hepatic TNF-α expression.
(A) ELISA for PGE2 secretion by the terminal ileum and total PGE2 levels in the liver of mice (n = 8) orally treated either for 10 days with PBS, L-LF41, or H-LF41, or for 3 weeks with PBS or H-LF41. * P < 0.05 PBS. (B) ELISA for hepatic IL-10 protein concentration of mice (n = 8) fed either PBS or H-LF41 for 10 days. P > 0.05 compared to PBS. (C) q-PCR for hepatic Cox1 or Cox2 mRNA levels of mice (n = 8) fed either PBS or H-LF41 for 10 days. Results are expressed as fold change relative to PBS. P > 0.05 compared to PBS. (D) Western blot assay for representative hepatic COX-1 and COX-2 protein levels of mice (n = 4) orally treated with either PBS or H-LF41 for 10 days. Hepatic COX-2 protein levels from a mouse receiving 2 h of stimulation with LPS (0.5 mg/kg BW; single IP injection) were determined as a positive control (left lane). (E) Mice (H-LF41-treated groups: n = 10 per group; PBS-treated groups: n = 8 per group) were pretreated with 10 days of PBS or H-LF41, either alone or combined with administration of either a specific inhibitor for PGE2 receptor EP-4, ONA-AE3-208 (I-EP4), or its vehicle (Vehicle). Hepatic Tnf mRNA levels were assayed by q-PCR 2 h after LPS treatment. Results are expressed as fold change relative to PBS+LPS.* P < 0.05; & P < 0.05 compared to H-LF41+LPS; n.s., non-statistical difference. All values except that of Western blot are shown as mean ± SEM. Results are representative of 2 similar experiments.