ABSTRACT
UNLABELLED: The protective effect of an antioxidant, Vitamin E (dl-alpha-tocopherol, 100 mg/kg/day, 8 days p.o. in vivo and 10 and 50 microM in vitro) was tested against PCB-induced neurotoxicity. IN VIVO STUDIES: Microdialysis was used to investigate changes in the striatal extracellular dopamine level and in p-nNOS expression in PCB-treated (Aroclor 1254, 10 microg/ml, 2 microl/min, 5 h; 6 microg was infused by microdialysis probe) rats. IN VITRO STUDIES: Cell viability and levels of p-nNOS expression were observed in PCB-treated (Aroclor 1254, 5 microg/ml) immortalized dopaminergic cell line (CATH.a cells). RESULTS: Treatment with PCB: (1) decreased the extracellular dopamine level in rat striatum, (2) increased p-nNOS expression both in rat striatal tissue and in CATH.a cells, (3) reduced the cell viability of, and (4) increased LDH release by CATH.a cells. However, Vitamin E showed a protective effect against PCB-induced toxicity and downregulation of the extracellular dopamine level. These results indicate that Vitamin E may have neuroprotective effects by inhibiting PCB-induced nNOS phosphorylation.
Subject(s)
Dopamine/metabolism , Endocrine Disruptors , Neurotoxicity Syndromes/prevention & control , Nitric Oxide Synthase Type I/metabolism , Polychlorinated Biphenyls/toxicity , Vitamin E/pharmacology , Administration, Oral , Animals , Cell Culture Techniques , Cell Survival/drug effects , Chromatography, High Pressure Liquid , Corpus Striatum/drug effects , Corpus Striatum/metabolism , Immunoblotting , Male , Microdialysis , Neurotoxicity Syndromes/etiology , Neurotoxicity Syndromes/metabolism , Nitric Oxide Synthase Type I/drug effects , Phosphorylation/drug effects , Polychlorinated Biphenyls/antagonists & inhibitors , Rats , Rats, Sprague-Dawley , Time Factors , Up-Regulation/drug effects , Vitamin E/administration & dosage , Vitamin E/therapeutic useABSTRACT
Excessive nitric oxide production by inducible nitric oxide synthase (iNOS) in stimulated inflammatory cells is thought to be a causative factor of cellular injury in cases of inflammation. In recent studies, it has been shown that kahweol, coffee-specific diterpene, exhibit chemoprotective effects. In this study, we investigated the effects of kahweol on the production of and the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. The nitrite production induced by LPS was markedly reduced in a dose-dependent manner. In addition, kahweol suppressed the expression of iNOS protein and iNOS mRNA. Since iNOS transcription has been shown to be under the control of the transcription factor, NF-kappaB, the effects of kahweol on NF-kappaB activation were examined. Transient transfection experiments showed that kahweol inhibited NF-kappaB-dependent transcriptional activity. Moreover, electrophoretic mobility shift assay experiments indicated that kahweol blocked the LPS-induced activation of NF-kappaB. The results of these studies suggest that the suppression of the transcriptional activation of iNOS by kahweol might be mediated through the inhibition of NF-kappaB activation. Taken together, the results of our study provide evidence that kahweol possess an anti-inflammatory potential, which constitutes a previously unrecognized biologic activity, and which may provide new insights into the inflammatory process.