Piperine inhibits PMA-induced cyclooxygenase-2 expression through downregulating NF-κB, C/EBP and AP-1 signaling pathways in murine macrophages.

Piperine is a major component of black (Piper nigrum Linn) and long (Piper longum Linn) peppers, and is widely used as a traditional food and medicine. It also exhibits a variety of biological activities, which include antioxidant, anti-tumor and anti-pyretic properties. In the present study, we investigated the inhibitory effects of piperine on phorbol 12-myristate 13-acetate (PMA)-induced cyclooxygenase-2 (COX-2) gene expression and analyzed the molecular mechanism of its activity in murine RAW 264.7 macrophages. Piperine dose-dependently decreased PMA-induced COX-2 expression and PGE(2) production, as well as COX-2 promoter-driven luciferase activity. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs, in which specific enhancer elements were mutagenized, revealed that the nuclear factor-κB (NF-κB), CCAAT/enhancer binding protein (C/EBP) and activator protein-1 (AP-1), were the predominant contributors to the effects of piperine. In addition, piperine inhibited PMA-induced NF-κB, C/EBP and c-Jun nuclear translocation. Furthermore, piperine significantly inhibited PMA-induced activation of the Akt and ERK. These findings demonstrate that piperine effectively attenuates COX-2 production, and provide further insight into the signal transduction pathways involved in the anti-inflammatory effects of piperine.

Kim HG ，Han EH ，Jang WS ，Choi JH ，Khanal T ，Park BH ，Tran TP ，Chung YC ，Jeong HG ... -  《-》

Suppression of phorbol-12-myristate-13-acetate-induced tumor cell invasion by piperine via the inhibition of PKCα/ERK1/2-dependent matrix metalloproteinase-9 expression.

Piperine is a major component of black pepper, Piper nigrum Linn, used widely in traditional medicine. Several previous studies reported that piperine possesses various beneficial biological activities including antioxidant, anti-tumor and anti-inflammation properties. In the present study, we investigated the inhibitory effects of piperine on tumor invasion and migration and the possible mechanisms involved using human fibrosarcoma HT-1080 cells. We found that piperine suppresses PMA-enhanced matrix metalloproteinase-9 (MMP-9) expression at the protein, mRNA, and transcriptional levels through the suppression of NF-κB and AP-1 activation without changing the level of tissue inhibitor of metalloproteinase (TIMP)-1. Piperine also inhibits PMA-enhanced membrane-type 1 MMP expression without changing the level of tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2. Piperine inhibited PMA-induced NF-κB and c-Jun nuclear translocation, which are upstream of PMA-induced MMP-9 expression and invasion. Furthermore, piperine strongly repressed the PMA-induced phosphorylation of ERK, which are dependent on the PKCα pathway. In conclusion, we demonstrated that the anti-invasive effects of piperine may occur through inhibition of PKCα and ERK phosphorylation and reduction of NF-κB and AP-1 activation, leading to down-regulation of MMP-9 expression. Thus, piperine has potential as a potent anti-cancer drug in therapeutic strategies for fibrosarcoma metastasis.

Hwang YP ，Yun HJ ，Kim HG ，Han EH ，Choi JH ，Chung YC ，Jeong HG ... -  《-》

1-Bromopropane up-regulates cyclooxygenase-2 expression via NF-κB and C/EBP activation in murine macrophages.

1-Bromopropane (1-BP) has been used in industry as an alternative to ozone-depleting solvents. In the present study, we examined the effect of 1-BP on cyclooxygenase-2 (COX-2) gene expression and analyzed the molecular mechanism of its activity in murine RAW 264.7 macrophages. 1-BP dose-dependently increased COX-2 protein and mRNA levels, as well as COX-2 promoter-driven luciferase activity in macrophages. Additionally, exposure to 1-BP markedly enhanced the production of prostaglandin E(2) (PGE(2)), a major COX-2 metabolite, in macrophages. Transfection experiments with several human COX-2 promoter constructs revealed that 1-BP activated the transcription factors nuclear factor-κB (NF-κB) and CCAAT/enhancer-binding protein (C/EBP), but not AP-1 or the cyclic AMP response element binding protein. Furthermore, Akt and mitogen-activated protein (MAP) kinases were significantly activated by 1-BP. These results demonstrated that 1-BP induced COX-2 expression via NF-κB and C/EBP activation through the Akt/ERK and p38 MAP kinase pathways. These findings provide further insight into the signal transduction pathways involved in the inflammatory effects of 1-BP.

Han EH ，Yang JH ，Kim HK ，Choi JH ，Khanal T ，Do MT ，Chung YC ，Lee KY ，Jeong TC ，Jeong HG ... -  《-》

Dihydro-N-caffeoyltyramine down-regulates cyclooxygenase-2 expression by inhibiting the activities of C/EBP and AP-1 transcription factors.

Dihydro-N-caffeoyltyramine (DHCT), a novel phenolic amide isolated from the root bark of Lycium chinense Miller, has potent antioxidative activity and anti-fungal effects. In the present study, we investigated the effects of DHCT on phorbol 12-myristate 13-acetate (PMA)-induced pro-inflammatory protein cyclooxygenase (COX-2) expression in macrophages. Treatment with DHCT suppressed PMA-mediated induction of COX-2 mRNA and protein. PMA-inducible production of PGE2 was inhibited by DHCT in a dose-dependent manner. Transient transfections and electrophoretic mobility shift assays indicated that the inhibitory effects of DHCT were mediated via CCAAT/enhancer-binding protein (C/EBP) and activator protein 1 (AP-1). DHCT reduced PMA-induced C/EBPbeta protein expression and c-jun/c-fos gene and protein expression. Furthermore, DHCT significantly inhibited PMA-induced activation of the mitogen activated protein (MAP) kinases (ERK and JNK). Thus, DHCT is an effective agent to attenuate COX-2 production mediated by the transcription factors C/EBP and AP-1, and these results enhance our understanding of the anti-inflammatory and anti-cancer properties by DHCT.

Han EH ，Kim JY ，Kim HG ，Choi JH ，Im JH ，Woo ER ，Jeong HG ... -  《-》

Piperine inhibits LPS induced expression of inflammatory mediators in RAW 264.7 cells.

The aim of the present study was to investigate the effects of piperine on the inflammatory responses to lipopolysaccharide (LPS) in RAW264.7 cells and the signal transduction pathways involved. RAW264.7 cells were pretreated with piperine at 10, 50 or 100 μg/ml and subsequently stimulated with LPS (1 μg/ml) for 24 h. We found that piperine inhibited the production of prostaglandin E2 (PGE2) and nitric oxide (NO) induced by LPS. Piperine significantly decreased LPS-stimulated gene expression and production of tumor necrosis factor-alpha (TNF<alpha>), inducible NO synthase (iNOS) and COX-2 in RAW264.7 cells. Piperine inhibited the LPS-mediated activation of nuclear factor-kappa B (NF-kappaB) by suppressing the degradation of inhibitor-κB proteins (IκB) and the translocations of p65 subunit of NF-kB from the cytosol to the nucleus. Our results demonstrate the anti-inflammatory activity of piperine in RAW264.7 cells; suggesting that piperine may be a potential agent in the treatment of inflammation.

Ying X ，Yu K ，Chen X ，Chen H ，Hong J ，Cheng S ，Peng L ... -  《-》