Biomedical subjects

Lisa M Kamendulis

Publications and source records attributed to Lisa M Kamendulis.

7 recordsLinked to original sources

PubMed2002

Comparative effects of phthalate monoesters on gap junctional intercellular communication and peroxisome proliferation in rodent and primate hepatocytes.

Several phthalate esters, compounds used as plasticizers in a variety of commercial products, have been shown to induce hepatic tumors in rodents. In this study, the comparative effects of phthalate monoesters on inhibition of gap junctional intercellular communication and induction of peroxisomal beta-oxidation were assessed in primary cultured hepatocytes from rats, mice, hamsters, cynomolgus monkeys, and humans. A human liver cell line was also utilized. Eight monoesters examined included mono-2-ethylhexyl phthalate (MEHP), mono-n-octyl phthalate (MNOP), mono-isononyl phthalate (MINP, 3 types, -1, -2, and -3), mono-isoheptyl phthalate (MIHP), mono-isodecyl phthalate (MIDP), and mono-(heptyl, nonyl, undecyl) phthalate (M711P). Gap junctional intercellular communication was measured 4 and 24 h after treatment by lucifer yellow dye coupling. Gap junctional intercellular communication was inhibited in rat and mouse hepatocytes by all eight monoesters in a concentration-dependent manner. In most cases, gap junctional intercellular communication was significantly reduced at the lowest concentrations tested (50 pM). Inhibition of gap junctional intercellular communication in rodent cells was substantially reversed within 24 h of monoester removal. In contrast, cell-to-cell communication was not inhibited in hamster, cynomolgus, or human hepatocytes or in a human liver cell line at any concentration examined. In rat hepatocytes, peroxisomal beta-oxidation was elevated after treatment with MEHP, MINP, MIHP, and MIDP but not MNOP or M711P, and with all but MIHP in mouse hepatocytes. The eight phthalates produced no marked change on peroxisomal beta-oxidation in hepatocytes from other species. These data provide additional evidence that the toxicological effects of phthalate esters are species specific.

Adult↗

PubMed2002

Effects of 2-butoxyethanol on hepatic oxidative damage.

2-Butoxyethanol has been reported to induce an increase in liver tumors in male B6C3F1 mice following chronic inhalation while rats, similarly treated, showed no increase in liver tumors. The mechanism for the selective induction of cancer in mouse liver is unknown, however, 2-butoxyethanol has been shown to induce hemolysis in mice, resulting in an accumulation of hemosiderin (iron) in the liver. Previous studies by our group and others have shown that mouse liver compared to other rodent species has a lower antioxidant capacity and appears to be more susceptible to chemically-induced oxidative damage. Since iron is known to produce hydroxyl radicals (through the Fenton reaction), we have proposed that the 2-butoxyethanol-induced iron overload (through hemolysis) may contribute to the induction of liver neoplasia in the mouse. In the present studies, 2-butoxyethanol induced oxidative stress in the liver of mice following 7-day treatment by gavage. These studies also examined whether 2-butoxyethanol, 2-butoxy acetic acid (a major metabolite of 2-butoxyethanol) or iron (FeSO(4)) produced oxidative stress in mouse and rat hepatocytes. Oxidative stress was examined by measuring oxidative DNA damage (OH8dG), lipid peroxidation (MDA formation) and cellular vitamin E concentrations. Neither 2-butoxyethanol or 2-butoxyacetic acid induced changes in the oxidative stress parameters examined in either rat or mouse hepatocytes. In contrast, FeSO(4) produced a dose-related increase in OH8dG and MDA and a decrease in vitamin E levels following 24 h treatment. Mouse hepatocytes were more sensitive than rat hepatocytes to the oxidative damage induced by the FeSO(4). FeSO(4)-induced oxidative stress was not increased by co-treatment of FeSO(4) with either 2-butoxyethanol or 2-butoxy acetic acid. These results support the proposal that the induction of hepatic oxidative stress by 2-butoxyethanol in vivo occurs secondary to induction of hemolysis and iron deposition in the liver rather than as a direct action of 2-butoxyethanol or its main metabolite, 2-butoxy acetic acid.

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2002

Acrylamide-induced cellular transformation.

Acrylamide is a monomer of polyacrylamide, whose products are used in biochemistry, the manufacture of paper, water treatment, and as a soil stabilizer. While polymeric acrylamide is nontoxic, the monomer can cause several toxic effects and has the potential for human occupational exposure. While acrylamide is not mutagenic in prokaryotic mutagenesis assays, chronic acrylamide treatment in rodents has been shown to produce tumors in both rats and mice. The mechanism for the induction of tumors by acrylamide is not known. In the present study, we examined the possibility that acrylamide might induce cellular transformation, using Syrian hamster embryo (SHE) cell morphological transformation as well as potential mechanisms for the cellular transformation. Results showed that treatment with 0.5 mM and higher concentrations of acrylamide continuously for 7 days induced morphological transformation. Cotreatment with acrylamide and N-acetyl-L-cysteine (NAC), a sulfhydryl group donor, resulted in the reduction of acrylamide-induced morphological transformation in SHE cells. Cotreatment with 1-aminobenzotriazole (ABT), a nonspecific P450 inhibitor, and acrylamide produced no change in morphological transformation when compared to acrylamide treatment only. Cotreatment with acrylamide and DL-buthionone-[S,R]-sulfoximine (BSO), a selective inhibitor of gamma-glutamylcysteine synthetase, increased the percent of morphologically transformed colonies compared to acrylamide treatment alone. Acrylamide reduced GSH levels in SHE cells, and cotreatment with acrylamide and NAC prevented the acrylamide-induced reduction of GSH. BSO treatment with acrylamide enhanced the depletion of GSH. These results suggest that acrylamide itself, but not oxidative P450 metabolites of acrylamide appear to be involved in acrylamide-induced cellular transformation and that cellular thiol status (possibly GSH) is involved in acrylamide-induced morphological transformation.

Acetylcysteine↗

PubMed2002

Mechanisms for the induction of oxidative stress in Syrian hamster embryo cells by acrylonitrile.

Chronic administration of acrylonitrile to rats resulted in an increase in the incidence of glial neoplasms of the brain. Recent studies have shown that acrylonitrile induces oxidative stress in rat brain and cultured rat glial cells. Acrylonitrile also induces morphological transformation concomitant with an increase in the formation of oxidized DNA in Syrian Hamster Embryo (SHE) cells in a dose-dependent manner. The mechanism for the induction of oxidative stress in SHE cells remains unresolved. The present study examined the effects of acrylonitrile on enzymatic and nonenzymatic antioxidants in SHE cells. SHE cells were treated with subcytolethal doses of acrylonitrile (0, 25, 50, and 75 microg/ml) for 4, 24, and 48 h. Acrylonitrile (50 microg/ml and 75 microg/ml) increased the amount of reactive oxygen species in SHE cells at all time points. Glutathione (GSH) was depleted and catalase and superoxide dismutase activities were significantly decreased in SHE cells after 4 h of treatment. The inhibition of these antioxidants was temporal, returning to control values or higher after 24 and 48 h. Xanthine oxidase activity was increased following 24 and 48 h treatment with acrylonitrile. 1-aminobenzotriazole, a suicidal P450 enzyme inhibitor, attenuated the effects of acrylonitrile on catalase and xanthine oxidase in SHE cells, suggesting that P450 metabolism is required for acrylonitrile to produce its effects on these enzymes. Additional studies showed that in the absence of metabolic sources acrylonitrile had no effect on either catalase or superoxide dismutase activity. These results suggest that the induction of oxidative stress by acrylonitrile involves a temporal decrease in antioxidants and increase in xanthine oxidase activity that is mediated by oxidative metabolism of acrylonitrile.

Acrylonitrile↗

PubMed2002

Mechanisms of 2-butoxyethanol carcinogenicity: studies on Syrian Hamster Embryo (SHE) cell transformation.

Previous studies showed that 2-butoxyethanol increased liver tumors in B6C3F1 mice following chronic exposure. While the mechanism of 2-butoxyethanol-induced liver carcinogenicity has not been defined, 2-butoxyethanol has been shown to induce hemolysis in rodents via 2-butoxyacetic acid, the major metabolite of 2-butoxyethanol. This toxic effect, coupled with the observation that continued treatment with 2-butoxyethanol results in hemosiderin deposition in the liver, has led to our hypothesis that liver carcinogenicity by 2-butoxyethnaol is mediated via oxidative stress (iron catalyzed) and Kupffer cell activation. The present study used Syrian Hamster Embryo (SHE) cell transformation, a surrogate in vitro model for carcinogenesis in vivo, to examine whether 2-butoxyethanol, 2-butoxyacetic acid, or iron (ferrous sulfate) produced cell transformation. SHE cells were treated with either 2-butoxyethanol (0.5-20 mM), 2-butoxyacetic acid (0.5-20 mM), or ferrous sulfate (0.5-75 microg/ml) for 7 days. 2-Butoxyethanol and 2-butoxyacetic acid did not induce cellular transformation. In contrast, treatment with ferrous sulfate (2.5 and 5.0 microg/ml) increased morphological transformation. Cotreatment of ferrous sulfate with the antioxidants alpha-tocopherol (vitamin E) or (-)-epigallocatechin-3-gallate (EGCG) prevented ferrous sulfate-induced transformation, suggesting the involvement of oxidative stress in SHE cell transformation. The level of oxidative DNA damage (OH8dG) increased following ferrous sulfate treatment in SHE cells; additionally, using single cell gel electrophoresis (comet assay), ferrous sulfate treatment produced an increase in DNA damage. Both DNA lesions were decreased by cotreatment of ferrous sulfate with antioxidants. These data support our proposal that iron, produced indirectly through hemolysis, and not 2-butoxyethanol or its metabolite 2-butoxyacetic acid, is responsible for the observed carcinogenicity of 2-butoxyethanol.

Animals↗

PubMed2002

Morphological transformation and oxidative stress induced by cyanide in Syrian hamster embryo (SHE) cells.

Cyanide is a well-established poison known for its rapid lethal action and toxicity. Although long-term mammalian studies examining the carcinogenic potential of cyanide have not been previously reported, cyanide was reported to be positive in Salmonella typhimurium mutagenesis assay and induced aneuploidy in Drosophila. To further evaluate the carcinogenic potential of cyanide, the ability of cyanide to induce morphological transformation in Syrian hamster embryo (SHE) cells was studied. Cyanide induced a dose-dependent increase in morphological transformation in SHE cells following a 7-day continuous treatment. A significant increase in transformation was observed at potassium cyanide doses of 200 microM and greater. Transformation induced by cyanide was inhibited in a dose-related manner by vitamin E, suggesting a role of oxidative stress in the induction of morphological transformation by cyanide. Further, it was shown that 500 microM cyanide induced oxidative DNA damage in SHE cells, evidenced by the formation of 8-hydroxy-2'-deoxyguanosine (50-66% increase over control). The induction of oxidative stress by cyanide involved an early and temporal inhibition of antioxidant enzymes (catalase and superoxide dismutase) as well as an increased production of reactive oxygen species (1.5- to 2.0-fold over control).

8-Hydroxy-2'-Deoxyguanosine↗

PubMed2002

Hepatic effects of 2-butoxyethanol in rodents.

Chronic inhalation of 2-butoxyethanol resulted in an increase in liver hemangiosarcomas and hepatic carcinomas in male mouse liver. No increase in liver neoplasia was observed in similarly exposed male and female rats or female mice. We proposed that the production of liver neoplasia in the male mouse is the result of oxidative damage secondary to the hemolytic deposition of iron in the liver. This occurs selectively in the male mouse and leads either directly or indirectly to liver neoplasia. To address this proposal, male B6C3F1 mice and male F344 rats were treated with 2-butoxyethanol (via daily gavage; five times per week) at doses of 0, 225, 450, and 900 mg/kg/day (mice) and 0, 225, and 450 mg/kg/day (rats) respectively. Following treatment for 7, 14, 28, and 90 days, DNA synthesis, oxidative damage, hematocrit, and iron deposition were measured in the livers. An increase in hemolysis (measured by a decrease in hematocrit and increase in relative spleen weight) was observed in 2-butoxyethanol-treated rats and mice in a dose-dependent manner. An increase in the percentage of iron-stained Kupffer cells was observed following treatment with 450 and 900 mg/kg of 2-butoxyethanol in mice and 225 and 450 mg/kg of 2-butoxyethanol in rats. A biphasic increase in oxidative damage (8-hydroxydeoxyguanosine and malondialdehyde) was seen in mouse liver after 7 and 90 days of treatment with 2-butoxyethanol, whereas no increases were observed in treated rat liver. Vitamin E levels were reduced by 2-butoxyethanol treatment in both mice and rat liver; however, the basal level of vitamin E was approximately 2.5-fold higher in rat than in mouse liver. A similar biphasic induction of DNA synthesis was seen following 2-butoxyethanol treatment in the mouse. In the mouse liver, increased DNA synthesis was observed in hepatocytes at 90 days and in endothelial cells at 7 and 14 days at all doses. No change in DNA synthesis was seen in 2-butoxyethanol-treated rat liver. No apparent differences in apoptosis and mitosis in the liver were observed in mouse and rat liver between 2-butoxyethanol treatment groups and untreated controls. These results suggest that DNA synthesis, possibly from oxidative stress or Kupffer cell activation, occurs selectively in the mouse liver, primarily in endothelial cells (a target of 2-butoxyethanol neoplasia), following exposure to 2-butoxyethanol.

8-Hydroxy-2'-Deoxyguanosine↗