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Cancer cells, relative to normal cells, demonstrate increased sensitivity to glucose deprivation-induced cytotoxicity. To determine if oxidative stress mediated by O2•− and hydroperoxides contributed to the differential susceptibility of human epithelial cancer cells to glucose deprivation, oxidation of dihydroethidine (DHE; for O2•−) and 5-(and-6)-carboxy-2', 7'-dichlorodihydrofluorescein diacetate (CDCFH2; for hydroperoxides) were measured in human colon and breast cancer cells (HT29, HCT116, SW480, MB231) and compared to normal human cells (FHC, 33Co, HMEC). Cancer cells showed significant increases in DHE (2–20 fold) and CDCFH2 (1.8–10 fold) oxidation, relative to normal cells that were more pronounced in the presence of the mitochondrial electron transport chain blocker, antimycin A. Furthermore, HCT116 and MB231 cells were more susceptible to glucose deprivation-induced cytotoxicity and oxidative stress, relative to 33Co and HMEC. HT-29 cells were also more susceptible to 2-deoxyglucose-(2DG)-induced cytotoxicity, relative to FHC. Over expression of manganese superoxide dismutase and mitochondrially targeted catalase significantly protected HCT116 and MB231 cells from glucose deprivation-induced cytotoxicity and oxidative stress, as well as protecting HT-29 cells from 2DG-induced cytotoxicity. These results show cancer cells (relative to normal cells) demonstrate increased steady-state levels of reactive oxygen species (ROS, i.e. O2•− and H2O2) that contribute to differential susceptibility to glucose deprivation-induced cytotoxicity and oxidative stress. These studies support the hypotheses that cancer cells increase glucose metabolism to compensate for excess metabolic production of ROS as well as that inhibition of glucose and hydroperoxide metabolism may provide a biochemical target for selectively enhancing cytotoxicity and oxidative stress in human cancer cells.

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This work tested the hypotheses that splanchnic oxidant generation is important in determining heat tolerance and that inappropriate.NO production may be involved in circulatory dysfunction with heat stroke. We monitored colonic temperature (T(c)), heart rate, mean arterial pressure, and splanchnic blood flow (SBF) in anesthetized rats exposed to 40 degrees C ambient temperature. Heating rate, heating time, and thermal load determined heat tolerance. Portal blood was regularly collected for determination of radical and endotoxin content. Elevating T(c) from 37 to 41.5 degrees C reduced SBF by 40% and stimulated production of the radicals ceruloplasmin, semiquinone, and penta-coordinate iron(II) nitrosyl-heme (heme-.NO). Portal endotoxin concentration rose from 28 to 59 pg/ml (P < 0.05). Compared with heat stress alone, heat plus treatment with the nitric oxide synthase (NOS) antagonist N(omega)-nitro-L-arginine methyl ester (L-NAME) dose dependently depressed heme-.NO production and increased ceruloplasmin and semiquinone levels. L-NAME also significantly reduced lowered SBF, increased portal endotoxin concentration, and reduced heat tolerance (P < 0.05). The NOS II and diamine oxidase antagonist aminoguanidine, the superoxide anion scavenger superoxide dismutase, and the xanthine oxidase antagonist allopurinol slowed the rates of heme-.NO production, decreased ceruloplasmin and semiquinone levels, and preserved SBF. However, only aminoguanidine and allopurinol improved heat tolerance, and only allpourinol eliminated the rise in portal endotoxin content. We conclude that hyperthermia stimulates xanthine oxidase production of reactive oxygen species that activate metals and limit heat tolerance by promoting circulatory and intestinal barrier dysfunction. In addition, intact NOS activity is required for normal stress tolerance, whereas overproduction of.NO may contribute to the nonprogrammed splanchnic dilation that precedes vascular collapse with heat stroke.

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-The purpose of this study was to characterize intestinal permeability changes over a range of physiologically relevant body temperatures in vivo and in vitro. Initially, FITC-dextran (4,000 Da), a large fluorescent molecule, was loaded into the small intestine of anesthetized rats. The rats were then maintained at ϳ37°C or heated over 90 min to a core body temperature of ϳ41, ϳ41.5, or ϳ42.5°C. Permeability was greater in the 42.5°C group compared with the 37, 41, or 41.5°C groups. Histological analysis revealed intestinal epithelial damage in heated groups. Everted intestinal sacs were then used to further characterize hyperthermia-induced intestinal permeability and to study the potential role of oxidative and nitrosative stress. Increased permeability to 4,000-Da FITC-dextran in both small intestinal and colonic sacs was observed at a temperature of 41.5-42°C compared with 37°C, along with widespread intestinal epithelial damage. Administration of antioxidant enzyme mimics or a nitric oxide synthase inhibitor did not reduce permeability due to heat stress, and tissue concentrations of a lipid peroxidation product were not altered by heat stress, suggesting that oxidative and nitrosative stress were not likely mediators of this phenomenon in vitro. In conclusion, hyperthermia produced increased permeability and marked intestinal epithelial damage both in vivo and in vitro, suggesting that thermal disruption of epithelial membranes contributes to the intestinal barrier dysfunction manifested with heat stress. intestine; heat stress; free radicals; nitric oxide; FITC-dextran