ABSTRACT
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.
Subject(s)
CCAAT-Enhancer-Binding Proteins/metabolism , Cyclooxygenase 2/metabolism , Macrophages/drug effects , NF-kappa B/metabolism , Up-Regulation/drug effects , Animals , Cell Line , Cyclooxygenase 2/genetics , Gene Expression/drug effects , Hydrocarbons, Brominated/pharmacology , Macrophages/metabolism , Mice , Polymerase Chain Reaction , Promoter Regions, Genetic , Protein Kinases/metabolism , Signal Transduction/drug effects , Transcription Factors/geneticsABSTRACT
In the present work, we investigated the protective effects of the ethanol extract of Aralia continentalis roots (AC) on tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity in a cultured Hepa1c1c7 cell line and in mouse liver. Pretreatment with AC prior to the administration of t-BHP significantly prevented the increase in serum levels of hepatic enzyme markers (ALT, AST) and lipid peroxidation and reduced oxidative stress, as measured by glutathione content, in the liver. Histopathological evaluation of the livers also revealed that AC reduced the incidence of liver lesions. The in vitro study showed that AC significantly reduced t-BHP-induced oxidative injury in Hepa1c1c7 cells, as determined by cell cytotoxicity, intracellular glutathione content, lipid peroxidation, reactive oxygen species (ROS) levels, and caspase-3 activation. Also, AC up-regulated phase II genes including heme oxygenase-1 (HO-1), NAD(P)H:quinone reductase, and glutathione S-transferase. Moreover, AC induced Nrf2 nuclear translocation and ERK1/2 and p38 activation, pathways that are involved in inducing Nrf2 nuclear translocation. Taken together, these results suggest that the protective effects of AC against t-BHP-induced hepatotoxicity may, at least in part, be due to its ability to scavenge ROS and to regulate the antioxidant enzyme HO-1 via the ERK1/2 and p38/Nrf2 signaling pathways.
Subject(s)
Aralia/chemistry , Liver/drug effects , Oxidative Stress/drug effects , Plant Extracts/pharmacology , tert-Butylhydroperoxide/toxicity , Animals , Caspase 3/metabolism , Cell Line , Chemical and Drug Induced Liver Injury/pathology , Chemical and Drug Induced Liver Injury/prevention & control , Glutathione/metabolism , Lipid Peroxidation/drug effects , Liver/enzymology , Liver/metabolism , Male , Mice , Mice, Inbred ICR , Oxidation-Reduction , Random Allocation , Reactive Oxygen Species/metabolism , Signal Transduction , tert-Butylhydroperoxide/antagonists & inhibitorsABSTRACT
Dichlorodiphenyltrichloroethane (DDT) has been used as an insecticide to prevent the devastation of malaria in tropical zones. However, many reports suggest that DDT may act as an endocrine disruptor and may have possible carcinogenic effects. Cyclooxygenase-2 (COX-2) acts as a link between inflammation and carcinogenesis through its involvement in tumor promotion. In the present study, we examined the effect of o,p'-DDT on COX-2 gene expression and analyzed the molecular mechanism of its activity in murine RAW 264.7 macrophages. Exposure to o,p'-DDT markedly enhanced the production of prostaglandin E(2) (PGE(2)), a major COX-2 metabolite, in murine macrophages. Furthermore, o,p'-DDT dose-dependently increased the levels of COX-2 protein and mRNA. Transfection with human COX-2 promoter construct, electrophoretic mobility shift assays and DNA-affinity protein-binding assay experiments revealed that o,p'-DDT activated the activator protein 1 (AP-1) and cyclic AMP response element (CRE) sites, but not the NF-kappaB site. Phosphatidylinositol 3 (PI3)-kinase, its downstream signaling molecule, Akt, and mitogen-activated protein kinases (MAPK) were also significantly activated by the o,p'-DDT-induced AP-1 and CRE activation. These results demonstrate that o,p'-DDT induced COX-2 expression via AP-1 and CRE activation through the PI3-K/Akt/ERK, JNK, and p38 MAP kinase pathways. These findings provide further insight into the signal transduction pathways involved in the carcinogenic effects of o,p'-DDT.
