Reducing nitrosamine contamination in cutting fluids

Mitoquinol mesylate (MITOQ) attenuates diethyl nitrosamine-induced hepatocellular carcinoma through modulation of mitochondrial antioxidant defense systems

Diethyl nitrosamine (DEN) induced cirrhosis-hepatocellular carcinoma (HCC) model associates cancer progression with oxidative stress and mitochondrial dysfunction. This study investigated the effects of mitoquinol mesylate (MitoQ), a mitochondrial-targeted antioxidant on DEN-induced oxidative damage in HCC Wistar rats. Fifty male Wistar rats were randomly divided into five groups. Healthy control, DEN, and MitoQ groups were orally administered exactly 10 mg/kg of distilled water, DEN, and MitoQ, respectively for 16 weeks. Animals in the MitoQ + DEN group were pre-treated with MitoQ for a week followed by co-administration of 10 mg/kg each of MitoQ and DEN. DEN + MitoQ group received DEN for 8 weeks, then co-administration of 10 mg/kg each of DEN and MitoQ till the end of 16th week. Survival index, tumour incidence, hematological profile, liver function indices, lipid profile, mitochondrial membrane composition, mitochondrial respiratory enzymes, and antioxidant defense status in both mitochondrial and post-mitochondrial fractions plus expression of antioxidant genes were assessed. In MitoQ + DEN and DEN + MitoQ groups, 80% survival occurred while tumour incidence decreased by 60% and 40% respectively, compared to the DEN-only treated group. Similarly, MitoQ-administered groups showed a significant (p < 0.05) decrease in the activities of liver function enzymes while hemoglobin concentration, red blood cell count, and packed cell volume were significantly elevated compared to the DEN-only treated group. Administration of MitoQ to the DEN-intoxicated groups successfully enhanced the activities of mitochondrial F1F0-ATPase and succinate dehydrogenase; and up-regulated the expression and activities of SOD2, CAT, and GPx1. Macroscopic and microscopic features indicated a reversal of DEN-induced hepatocellular degeneration in the MitoQ + DEN and DEN + MitoQ groups. These data revealed that MitoQ intervention attenuated DEN-induced oxidative stress through modulation of mitochondrial antioxidant defense systems and alleviated the burden of HCC as a chemotherapeutic agent.

Quantitative analysis of source and fate of N-nitrosamines and their precursors in an urban water system in East China

The source and fate of N-nitrosamines and their precursors in terms of formation potential (FP) was investigated quantitatively in the city level for the first time. Different sources of nitrosamines and their precursors were investigated in one city in the Yangtze River delta, China. The source water located downstream of the city contained 8.4 ng/L of N-nitrosodimethyamine (NDMA) and 153 ng/L of NDMA FP. The contribution of each discharge source was evaluated based on the concentration, the river water flux, and the amount of wastewater discharges. Textile printing and dyeing wastewater, and electroplating industrial wastewater contained high concentration of nitrosamines and were important discharge sources. Taking NDMA and NDMA FP attenuation by photolysis and biodegradation into consideration, the mass load calculation showed upstream surface water brought about 13 ± 4% of NDMA and 21 ± 3% of NDMA FP to downstream source water. Local wastewater discharges contributed 30 ± 8% of NDMA and 17 ± 2% of NDMA FP to downstream source water. Endogenous formation via amino acids metabolism could contribute 36% of NDMA FP (maximum) to downstream source water. Overall, this study provides a protocol for quantitative evaluation of the nitrosamine contribution to urban water supply from different contamination sources.

Subchronic dermal toxicity study of triethanolamine in C3H/HeJ mice

Triethanolamine (TEA) was applied to the skin of male and female C3H mice (15 per sex per dose group) three times weekly for 95 days (37 applications). TEA was administered at concentrations of 0 (acetone vehicle), 10, 33 and 100% (undiluted) in a volume of 50 microliters. The approximate daily doses of TEA were 0.14, 0.46 or 2.0 g/kg per male and 0.16, 0.54 or 2.3 g/kg per female, respectively. The animals were weighted weekly and observed for clinical signs including skin irritation. 10 mice per sex per dose group were designated for clinical chemistry and haematology at terminal killing. Complete autopsies were performed, and the liver, kidneys, brain, heart, spleen, thymus and testes were weighted. Histopathology was performed on tissues from control and high-dose mice and on target organs. Treatment-related effects were limited to a slight epidermal hyperplasia at the site of application at all TEA concentrations. The results indicate that TEA caused a mild local reaction at all concentrations tested, but did not cause systemic toxicity under these conditions.

Cytochrome P-450-dependent catabolism of triethanolamine in Rhodotorula mucilaginosa

The yeast Rhodotorula mucilaginosa was able to grow in media containing triethanolamine or diethanolamine as the sole nitrogen source. During growth in the presence of triethanolamine, extracts of yeast cells contained increased levels of cytochrome P-450 dependent monooxygenase which catalyzed the oxidative N-dealkylation of aminoalcohols. Formation of diethanolamine, ethanolamine and glyoxylate from triethanolamine was demonstrated, and the identity of the products was verified by thin layer chromatography. These observations suggested the following scheme of triethanolamine catabolism: triethanolamine----diethanolamine + glycolaldehyde, diethanolamine----ethanolamine + glycolaldehyde, ethanolamine----NH3 + glycolaldehyde----glycolate----glyoxylate----glycerate pathway.

Persistence of N-nitrosodiethanolamine contamination in American metal-working lubricants

The potent carcinogen N-nitrosodiethanolamine (NDELA) was discovered as a contaminant of commercial metal-working lubricants over a decade ago. To determine whether or not improvements in industrial practice suggested in the meantime have eliminated this contamination from United States products, a selection of cutting fluids obtained from the current marketplace was analysed for NDELA content. All six semi-synthetic fluids examined contained NDELA at levels ranging from 0.5 to 4.3 ppm. Three of six petroleum-based lubricants and five of six synthetics also contained significant NDELA (when analysed at a detection limit of 0.03 ppm), at levels of up to 0.16 and 55 ppm, respectively. The mean concentrations were 1.5 ppm for the semi-synthetics, 0.07 ppm for the petroleum-based products, and 11.4 ppm for the synthetic metal-working fluids. While these levels are far below the values of 1-2% by weight (10,000-20,000 ppm) found in some contaminated products 13 years ago, they may nevertheless pose a continuing health risk for the machinists who work with them.