Anti-Inflammatory Effects of Hypophyllanthin and Niranthin Through Downregulation of NF-κB/MAPKs/PI3K-Akt Signaling Pathways

Hypophyllanthin (HYP) and niranthin (NIR) are major lignans in Phyllanthus spp. and have been shown to possess strong anti-inflammatory activity. In this study, we investigated the anti-inflammatory effects and the underlying molecular mechanisms of HYP and NIR in in vitro cellular model of LPS-induced U937 macrophages. The effects of HYP and NIR on the production of prostaglandin E-2 (PGE(2)), cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 beta (IL-1 beta) were measured by using ELISA, Western blot, and qRT-PCR. The expressions of signaling molecules related to nuclear factor-kappa B (NF-kappa B), mitogen-activated protein kinases (MAPKs), and phosphatidylinositol 3'-kinase-Akt (PI3K-Akt) signaling pathways were examined. The role of NF-kappa B, MAPKs, and Akt signaling pathways was confirmed by using specific inhibitors (BAY 11-7082, U0126, SB202190, SP600125, and LY294002) mediated suppression of TNF-alpha and COX-2 production. HYP and NIR significantly inhibited the protein and gene levels of COX-2 as well as the downstream signaling products of PGE(2), TNF-alpha, and IL-1 beta. HYP and NIR also suppressed the inhibitors of kappa B (I kappa B), IkB kinases (Ikk alpha/beta), NF-kappa B phosphorylation, and I kappa B degradation. HYP suppressed the phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK), and p38 while NIR only suppressed JNK and ERK but did not have effect on p38. These results demonstrate that HYP and NIR downregulated COX-2, TNF-alpha, and IL-1 beta gene expressions in U937 macrophages by interfering with the activation of NF-kappa B, MAPKs, and Akt. In conclusion, these lignans have potential to be developed as anti-inflammatory agents targeting the NF-kappa B, MAPK, and PI3K-Akt pathways.