Evaluation of anti-tumour properties of two depsidones - Unguinol and Aspergillusidone D - in triple-negative MDA-MB-231 breast tumour cells.

There is an ongoing search for new compounds to lower the mortality and recurrence of breast cancer, especially triple-negative breast cancer. Naturally occurring depsidones, extracted from the fungus Aspergillus, are known for their wide range of biological activities such as cytotoxicity, aromatase inhibition, radical scavenging, and antioxidant properties. Research showed the potential of depsidones as a treatment option for hormone receptor-positive breast cancer treatment, yet its effects on hormone receptor-negative breast cancer are still unkown. This study, therefore, investigated the potential of two depsidones (Unguinol and Aspergillusidone D) to induce apoptosis, cell cycle arrest and cytotoxicity, and reduce cell proliferation in the triple-negative MDA-MB-231 breast cancer cell line. Results were compared with the effects of the cytostatic drug doxorubicin, antimitotic agent colchicine and endogenous hormones 17ß-estradiol, testosterone and dihydrotestosterone. The cytostatic drugs and hormones affected the MDA-MB-231 cell line comparable to other studies, showing the usefulness of this model to study the effects of depsidones on a triple-negative breast cancer cell line. At sub µM levels, Unguinol and Aspergillusidone D did not influence cell proliferation, while cell viability was reduced at concentrations higher than 50 µM. Both depsidones induced apoptosis, albeit not statistically significantly. In addition, Unguinol induced cell cycle arrest in MDA-MB-231 cells at 100 µM. Our research shows the potential of two depsidones to reduce triple-negative breast cancer cell survival. Therefore, this group of compounds may be promising in the search for new cancer treatments, especially when looking at similar depsidones.

Alterations in dimethylnitrosamine-induced lethality and acute hepatotoxicity in rats during dietary thiamin, riboflavin and pyridoxine deficiencies.

The effects of dietary thiamin, riboflavin and pyridoxine deficiencies on dimethylnitrosamine-induced lethality and hepatotoxicity were investigated in the rat. Development of deficiencies was monitored by growth rate, food intake, ratio of liver weight to body weight and the biochemical parameters (thiamin diphosphate effects for thiamin deficiency, glutathione reductase activity coefficient for riboflavin deficiency and erythrocyte glutamate-oxaloacetate transaminase activity for pyridoxine deficiency). Thiamin deficiency slightly increased the acute toxicity of dimethylnitrosamine as observed by the lowering of the LD50 dose and the greater increase in the serum glutamate-oxaloacetate transaminase and serum glutamate-pyruvate transaminase levels. Riboflavin deficiency, on the other hand, slightly increased the LD50 dose of dimethylnitrosamine and resulted in less dimethylnitrosamine-induced damage to the liver. Pyridoxine deficiency did not affect the lethal dose nor significantly alter the transaminases levels.

Ethanol enhances the formation of endogenously and exogenously derived adducts in rat hepatic DNA.

To investigate the role of ethanol in chemically-induced carcinogenesis, we exposed Wistar rats to ethanol, either as an acute dose or for prolonged periods in a liquid diet and looked for effects on endogenously and exogenously derived DNA adducts. Changes in the cytochrome P450 protein (CYP 2E1) and its catalytic demethylase activity were also followed in order to provide a sequence of relatively well understood changes that are associated with free radical production and, therefore, potentially capable of affecting DNA. The exocyclic DNA adducts, ethenodeoxyadenosine (varepsilondA) and ethenodeoxycytidine (varepsilondC), known to arise from oxidative stress and lipid peroxidation (LPO) sources, were detected in the liver DNA of Wistar rats at background concentrations of 4-6 (varepsilondA) and 25-35 (varepsilondC) adducts per 10(9) parent bases. When rats were given either an acute dose of ethanol (5g/kg, i.g.) or exposed for 1 week to ethanol in a liquid diet (5%, w/v), etheno adduct levels were increased approximately 2-fold and this was statistically significant for varepsilondC (P<0.05 and P<0.02, respectively) for the two separate treatments.In N-nitrosodimethylamine (NDMA)-treated rats, acute ethanol treatment significantly increased the level of O(6)-methylguanine (O(6)-MeG) in hepatic DNA and this was paralleled by a decrease in O(6)-alkylguanine DNA alkyltransferase (ATase) activity; immunohistochemistry confirmed this increase of O(6)-MeG in both hepatic and renal nuclei. When rats were given ethanol in the diet and treated with NDMA, O(6)-MeG levels in hepatic DNA increased at 1 week which coincided with the peak of CYP 2E1-dependent NDMA-demethylase activity. Single cell gel electrophoresis of liver cells showed that after 1 week of exposure to ethanol, there was a small but significant increase in the frequency of DNA strand breaks induced by NDMA (P<0.05); after 4 weeks the increase was 1.4-fold (P<0.01). Our results indicate that exposures to ethanol, which resulted in blood ethanol concentrations similar to those seen in chronic alcoholics and increased levels of expression of the CYP 2E1 protein can exacerbate the DNA damaging effects of endogenous and exogenous alkylating agents. These observations provide indications of possible mechanisms for the carcinogenic or co-carcinogenic action of ethanol.

Effects of pyridoxine deficiency on the metabolism of N-nitrosodimethylamine in the rat.

The alteration in the metabolic activation of N-nitrosodimethylamine (NDMA) was investigated in the rat during dietary pyridoxine deficiency. The in vitro metabolism of NDMA by demethylase system was measured in both liver and kidney microsomes. The profile of the kidney enzyme appears similar to that of the liver indicating that at least two forms of isozymes with the low and the high Km's are present. Pyridoxine deficiency significantly increased the activity of NDMA-demethylase of both organs. The increase in the activity of NDMA-demethylase induced by dietary pyridoxine deficiency can be reversed by supplementation of pyridoxine (500 micrograms), i.p., daily for two consecutive days. The increase in the NADPH cytochrome c reductase activity was observed after 6 weeks on pyridoxine-deficient diet.

Exposure to benzene in various susceptible populations: co-exposures to 1,3-butadiene and PAHs and implications for carcinogenic risk.

Exposure to benzene in human populations can occur in various work-related settings in which benzene is used or produced, or from traffic emissions resulting from incomplete combustion of fossil fuel, or from other sources. Two scenarios of benzene exposure were studied in 4 susceptible groups in Thailand. The first scenario is work-related exposures primarily to benzene, with the study subjects consisting of petrochemical laboratory workers and gasoline service station attendants, who are exposed at levels of 78.32 and 360.84 microg/m(3), respectively. The second scenario is traffic-related exposure and exposure to incense smoke, where co-exposures to other pollutants occurs, with the study groups consisting of school children attending schools in the city center and exposed to traffic emissions, and temple workers exposed to incense smoke. The individual benzene exposure levels were approximately 19.38 microg/m(3) in city school children and 45.90 microg/m(3) in temple workers. Co-exposures to 1,3-butadiene and polycyclic aromatic hydrocarbons (PAHs) generated from the same sources occurred in the second exposure scenario. 8-OHdG, DNA strand breaks and DNA repair capacity were measured as biomarkers of early effects of carcinogenic compound exposure. Petrochemical laboratory workers and gasoline service stations attendants had significantly higher levels of DNA strand breaks and significantly lower DNA repair capacity compared to controls, while gasoline service station attendants also had significantly higher levels of 8-OHdG than controls. City school children had significantly higher levels of PAH-DNA adducts, 8-OHdG, and DNA strand breaks and significantly lower levels of DNA repair capacity compared to rural children. Temple workers also had significantly higher levels of 8-OHdG and DNA strand breaks and significantly lower levels of DNA repair capacity compared to controls. In all of the study groups, the levels of benzene exposure correlated significantly with 8-OHdG levels, DNA strand breaks, and DNA repair capacity. In school children, PAH levels also correlated significantly with 8-OHdG levels, DNA strand breaks and DNA repair capacity. In temple workers, 1,3-butadiene levels correlated significantly with 8-OHdG and DNA strand breaks, but not with DNA repair capacity, while in the school children they did not correlate significantly with 8-OHdG or DNA strand breaks, and correlated marginally significantly with DNA repair capacity (deletions per metaphase). Multivariate regression analysis identified total PAHs concentrations converted to B[a]P equivalents as the only factor significantly affecting 8-OHdG levels, and total PAHs concentrations converted to B[a]P equivalents, as well as 1,3-butadiene concentrations as the factors significantly affecting DNA repair capacity in the school children. PAHs concentration was identified as the factor most significantly affecting DNA strand breaks in temple workers, followed by benzene concentrations, while DNA repair capacity was also significantly influenced by PAHs concentrations.

Ethanol modulates rat hepatic DNA repair functions.

To further explore how ethanol may act at the DNA level, studies have been made of DNA repair mechanisms in male Wistar rats given ethanol either as an acute intragastric dose (5 g/kg) or continuously in a liquid diet (5% w/v) to provide 36% of the caloric intake. These treatments generate significant levels of free radicals with evidence of damage to DNA. The acute ethanol dose significantly inhibited O(6)-alkylguanine-DNA alkyltransferase (ATase) activity by 21-32% throughout the 24-h post-treatment period and this was confirmed by immunohistochemical detection of the ATase protein in hepatic nuclei. Twelve hours after the ethanol treatment, the activities of the DNA glycosylases, alkylpurine-DNA-N-glycosylase (APNG) and 8-oxoguanine-DNA glycosylase (OXOG glycosylase) were each increased by approximately 44%. In contrast, when given chronically via the liquid diet, ethanol initially had no effect on ATase activity, but after 4 weeks ATase activity was increased by 40%. Following ethanol withdrawal, ATase activity remained elevated for at least 12 h, but, by 24 h, the activity had fallen to the uninduced control level. DNA glycosylase activities were again affected differently. After 1 week of dietary ethanol exposure, there was no effect on APNG activity but it was inhibited by 19% at 4 weeks. OXOG glycosylase activity, on the other hand, was increased by 53% after 1 week, but decreased by 40% after 4 weeks. Although some of these changes in DNA repair capacity were relatively small, over time, their potential impact on the repair of endogenous or exogenous alkylation and/or oxidation damage in DNA would be substantial. These studies indicate possible mechanisms for the co-carcinogenic effects of ethanol.

Ethanol-induced free radicals and hepatic DNA strand breaks are prevented in vivo by antioxidants: effects of acute and chronic ethanol exposure.

Ethanol was given to male Wistar rats as an acute dose (5 g/kg) or continuously at 5% (w/v) in a liquid diet to provide 36% of the caloric requirement. Free radicals generated in the liver were collected as a stable adduct in bile following the in vivo administration of the spin trapping agent alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN; 700 mg/kg). [1-(13)C]ethanol was used to confirm the formation of the 1-hydroxyethyl radical and to demonstrate that this was ethanol-derived in the case of the single-dose treatment. Free radical production increased up to 1h after the acute dose and then plateaued over the next 30 min. During chronic exposure to ethanol, free radical generation increased significantly after 1 week and then declined again to remain at a low level over the next 2 weeks; this transient increase corresponded closely with the induction of cytochrome P-450 2E1 (CYP 2E1) in response to ethanol feeding. Single-cell electrophoresis was used to investigate effects on DNA. After an acute dose of ethanol, the frequency of single-strand breaks increased from 1 h to peak at 6 h but then declined again to control values by 12 h. During the chronic exposure, an increase in the frequency of DNA breaks was seen at 3 days, reached a peak at 1 week and then decreased slowly over the next 5 weeks. The effects of antioxidants on these parameters was investigated after an acute dose of ethanol. Pre-treatment with vitamin C (400 mg/kg, i.p., daily for 5 days) or vitamin E (100 mg/kg, i.p., for 5 days) prior to the administration of ethanol (5 g/kg) inhibited generation of the 1-hydroxyethyl-POBN adduct by 30 and 50%, respectively, and both agents prevented the increased frequency of DNA single-strand breaks caused by ethanol. The significance of the temporal coincidence of changes in the above parameters in response to ethanol is discussed.