Alveolar type II epithelial (AEII) cells regulate lung inflammatory response and, simultaneously, they are a target of environmental carcinogenic factors. We employed an in vitro model of rat AEII cells, the RLE-6TN cell line, in order to analyze the interactive effects of tumor necrosis factor-α (TNF-α), a cytokine which plays a key role in the initiation of inflammatory responses in the lung, and benzo[a]pyrene (BaP), a highly carcinogenic polycyclic aromatic hydrocarbon. TNF-α strongly augmented the formation of stable BaP diol epoxide-DNA adducts in AEII cells, which was associated with enhanced p53-Ser15 phosphorylation and decreased cell survival. The increased genotoxicity of BaP was associated with altered expression of cytochrome P450 (CYP) enzymes involved in its bioactivation, a simultaneous suppression of CYP1A1 and enhancement of CYP1B1 expression. Importantly, BaP and TNF-α acted synergistically to upregulate key inflammatory regulators in AEII cells, including the expression of inducible NO synthase and cyclooxygenase-2 (COX-2), and enhanced prostaglandin E2 production and expression of proinflammatory cytokines, such as TNF-α, interleukin-1β and interleukin-6. We observed that BaP and TNF-α together strongly activated p38 kinase, a principal regulator of inflammatory response. SB202190, a specific p38 inhibitor, prevented induction of both COX-2 and proinflammatory cytokines, thus confirming that p38 activity was crucial for the observed inflammatory reaction. Taken together, our data demonstrated, for the first time, that a proinflammatory cytokine and an environmental PAH may interact to potentiate both DNA damage and the inflammatory response in AEII cells, which may occur through coordinated upregulation of p38 activity.
- MeSH
- adukty DNA metabolismus MeSH
- aktivace enzymů účinky léků MeSH
- apoptóza účinky léků MeSH
- aromatické hydroxylasy genetika metabolismus MeSH
- benzopyren metabolismus toxicita MeSH
- buněčné linie MeSH
- cytochrom P-450 CYP1A1 genetika metabolismus MeSH
- fosforylace účinky léků MeSH
- inhibitory proteinkinas farmakologie MeSH
- karcinogeny životního prostředí toxicita MeSH
- krysa rodu rattus MeSH
- mediátory zánětu metabolismus MeSH
- messenger RNA metabolismus MeSH
- mitogenem aktivované proteinkinasy p38 antagonisté a inhibitory metabolismus MeSH
- mutageny toxicita MeSH
- nádorový supresorový protein p53 metabolismus MeSH
- pneumocyty účinky léků imunologie metabolismus MeSH
- posttranslační úpravy proteinů účinky léků MeSH
- proliferace buněk účinky léků MeSH
- regulace genové exprese účinky léků MeSH
- TNF-alfa metabolismus MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Benzo[a]pyrene (BaP) is a ubiquitous environmental pollutant, which may contribute to the development of human cancer. The ultimate carcinogenic BaP metabolite produced by cytochrome P450 enzymes (CYP), such as CYP1A1 and CYP1B1, anti-BaP-7,8-diol-9,10-epoxide, binds covalently to DNA and causes mutations. The levels of various CYP isoforms can be significantly modulated under inflammatory conditions. As the chronic inflammation is known to contribute to carcinogenesis, we investigated interactions of a major proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), and BaP in regulation of the expression of CYP1A1/1B1 and induction of DNA damage in rat liver epithelial WB-F344 cells. TNF-alpha enhanced induction of CYP1B1, while it simultaneously suppressed the BaP-induced CYP1A1 expression. The observed deregulation of CYP1 induction was found to be associated with a significantly enhanced formation of DNA adducts. The elevated DNA damage corresponded with increased phosphorylation of p53 tumor suppressor at Ser-15 residue, enhanced accumulation of cells in the S-phase of cell cycle and potentiation of BaP-induced apoptosis. Inhibition of CYP1B1 by fluoranthene significantly decreased both the formation of DNA adducts and the induction of apoptosis in WB-F344 cells treated with BaP and TNF-alpha, thus suggesting that this isoform might be responsible for genotoxic effects of BaP in nonparenchymal liver cells. Our results seem to indicate that inflammatory conditions might enhance genotoxic effects of carcinogenic polycyclic aromatic hydrocarbons through upregulation of CYP1B1 expression.
- MeSH
- aromatické hydroxylasy metabolismus MeSH
- benzopyren toxicita MeSH
- buněčné linie MeSH
- epitelové buňky enzymologie účinky léků MeSH
- financování organizované MeSH
- játra enzymologie účinky léků MeSH
- krysa rodu rattus MeSH
- synergismus léků MeSH
- TNF-alfa farmakologie MeSH
- upregulace MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- mužské pohlaví MeSH
- zvířata MeSH
Non-dioxin-like polychlorinated biphenyls (NDL-PCBs) have been shown to act as tumor promoters in liver; however, the exact mechanisms of their action are still only partially understood. One of the interesting effects of NDL-PCBs is the acute inhibition of gap junctional intercellular communication (GJIC), an effect, which has been often found to be associated with tumor promotion. As previous studies have suggested that NDL-PCB-induced disruption of lipid signalling pathways might correspond with GJIC inhibition, we investigated effects of PCBs on the release of arachidonic acid (AA) in the rat liver epithelial WB-F344 cell line, a well-established model of liver progenitor cells. We found that both 2,2',4,4'-tetrachlorobiphenyl (PCB 47) and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), but not the dioxin-like, non-ortho-substituted, 3,3',4,4',5-pentachlorobiphenyl (PCB 126), induce a massive release of AA. The AA release, induced by PCB 153, was partially inhibited by extracellular signal-regulated kinases 1/2 (ERK1/2) signalling inhibitor, U0126, and by cytosolic phospholipase A(2) (cPLA(2)) inhibitor, AACOCF(3). Although PCB 153 induced both ERK1/2 and p38 activation, the specific p38 kinase inhibitor, SB203580, had no effect on AA release. Inhibitors of other phospholipases, including phosphatidylcholine-specific phospholipase C or phosphatidylinositol-specific phospholipase C, were also without effect. Taken together, our findings suggest that the AA release, induced by non-dioxin-like PCBs in liver progenitor cell line, is partially mediated by cytosolic PLA(2) and regulated by ERK1/2 kinases. Our results suggest that more attention should be paid to cell signalling pathways regulated by AA or eicosanoids after PCB exposure, which might be involved in their toxic effects.
- MeSH
- buněčné linie MeSH
- cytosolické fosfolipasy A2 metabolismus účinky léků MeSH
- epitelové buňky metabolismus účinky léků MeSH
- financování organizované MeSH
- játra cytologie metabolismus účinky léků MeSH
- kmenové buňky metabolismus účinky léků MeSH
- krysa rodu rattus MeSH
- kyseliny arachidonové metabolismus MeSH
- látky znečišťující životní prostředí toxicita MeSH
- mitogenem aktivovaná proteinkinasa 1 metabolismus účinky léků MeSH
- mitogenem aktivovaná proteinkinasa 3 metabolismus účinky léků MeSH
- polychlorované bifenyly farmakologie toxicita MeSH
- potkani inbrední F344 MeSH
- signální transdukce účinky léků MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
Various liver diseases lead to an extensive inflammatory response and release of a number of proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha). This cytokine is known to play a major role in liver regeneration as well as in carcinogenesis. We investigated possible interactions of TNF-alpha with ligands of the aryl hydrocarbon receptor (AhR) and known liver carcinogens, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and coplanar 3,3',4,4',5-pentachlorobiphenyl (PCB 126). These compounds have been previously found to disrupt cell cycle control in contact-inhibited rat liver WB-F344 cells, an in vitro model of adult liver progenitor cells. TNF-alpha itself had no significant effect on the proliferation/apoptosis ratio in the WB-F344 cell line. However, it significantly potentiated proliferative effects of low picomolar range doses of both TCDD and PCB 126, leading to an increase in cell numbers, as well as an increased percentage of cells entering the S-phase of the cell cycle. The combination of TNF-alpha with low concentrations of AhR ligands increased both messenger RNA (mRNA) and protein levels of cyclin A, a principle cyclin involved in disruption of contact inhibition. TNF-alpha temporarily inhibited AhR-dependent induction of cytochrome P450 1A1 (CYP1A1). In contrast, TNF-alpha significantly enhanced induction of CYP1B1 at both mRNA and protein levels, by a mechanism, which was independent of nuclear factor-kappaB activation. These results suggest that TNF-alpha can significantly amplify effects of AhR ligands on deregulation of cell proliferation control, as well as on expression of CYP1B1, which is involved in metabolic activation of a number of mutagenic compounds.
- MeSH
- aromatické hydroxylasy genetika metabolismus MeSH
- cytochrom P-450 CYP1A1 genetika metabolismus MeSH
- epitelové buňky enzymologie účinky léků MeSH
- financování organizované MeSH
- fixní kombinace léků MeSH
- játra cytologie MeSH
- karcinogeny metabolismus toxicita MeSH
- kmenové buňky enzymologie MeSH
- krysa rodu rattus MeSH
- kultivované buňky MeSH
- lékové interakce MeSH
- ligandy MeSH
- polychlorované bifenyly metabolismus toxicita MeSH
- polychlorované dibenzodioxiny metabolismus toxicita MeSH
- potkani inbrední F344 MeSH
- proliferace buněk účinky léků MeSH
- regulace genové exprese enzymů účinky léků MeSH
- TNF-alfa farmakologie MeSH
- vztah mezi dávkou a účinkem léčiva MeSH
- zvířata MeSH
- Check Tag
- krysa rodu rattus MeSH
- zvířata MeSH
