Effects of arachidonic acid and indomethacin on sister-chromatid exchange induction by polycyclic aromatic hydrocarbons in mammalian cell lines

Final Report on the Safety Assessment of Arachidonic Acid

Arachidonic Acid is an essential, polyunsaturated, fatty acid that is used as a surfactant-cleansing agent and a surfactant-emulsifying agent in cosmetic formulations. Arachidonic Acid is well absorbed from the gastrointestinal tract and the circulatory system; it distributes rapidly into the lipid compartment of the body and is rapidly converted to phospholipid by the liver.

Arachidonic Acid may alter the cutaneous immune response; in one study, the effect was more pronounced at lower test concentrations than at higher. Application of Arachidonic Acid to mouse skin produced edema and inflammation, with high dosages possibly causing ulceration of the skin. Arachidonic Acid has mutagenic potential. In a 24 h single insult patch test, a formulation containing 0.04% Arachidonic Acid was not a skin irritant.

The safety of use of this ingredient in cosmetic products has not been documented and substantiated. It cannot be concluded that Arachidonic Acid is safe for use in cosmetic products until the needed additional safety test data have been obtained and evaluated. If the requested skin absorption data indicate that absorption occurs, immunomodulatory data, carcinogenicity and photocarcinogenicity data, human irritation, sensitization, and photosensitization data may also be required.

Apricot attenuates oxidative stress and modulates of Bax, Bcl-2, caspases, NFκ-B, AP-1, CREB expression of rats bearing DMBA-induced liver damage and treated with a combination of radiotherapy

We evaluated the ability of apricot to attenuate apoptosis and oxidative stress developed during the process of 7,12-dimethylbenz[a]anthracene (DMBA) and radiotherapy in the liver of rats bearing liver damage. Fifty female Wistar rats were divided into 7 groups; (i) normal control rats; (ii) rats fed with standard diet with apricot (20%), (ii) rats fed with standard diet and administrated 6 gray radiotherapy with Co 60 device applied to a single fraction, (iv) rats fed with standard diet and administered intraperitoneally DMBA (20mg/kg), (v) rats fed with standard diet and administered DMBA and 6 gray radiotherapy, (vi) rats fed with standard rat diet and administered DMBA and supplemented apricot, (vii) rats fed with standard diet supplemented apricot administered DMBA and radiotherapy (RT) for 6weeks. Expression of Bax, caspase 3, and glutathione activity decreased in the liver but liver expression of NF-κB, AP-1, CREB, Bcl-2 and ALT, AST, 5'NT, MDA, NO levels increased in DMBA-induced liver damage rats. In conclusion, the results suggest that apricot supplementation and irradiation given in combination, offer maximum protection against DMBA-induced hepatic carcinogenesis.

In vivo Comet assay on isolated kidney cells to distinguish genotoxic carcinogens from epigenetic carcinogens or cytotoxic compounds

The objective of this study was to determine the ability of the alkaline in vivo Comet assay (pH>13) to distinguish genotoxic carcinogens from epigenetic carcinogens when performed on freshly isolated kidney cells and to determine the possible interference of cytotoxicity by assessing DNA damage induced by renal genotoxic, epigenetic or toxic compounds after enzymatic isolation of kidney cells from OFA Sprague-Dawley male rats. The ability of the Comet assay to distinguish (1) genotoxicity versus cytotoxicity and (2) genotoxic versus non-genotoxic (epigenetic) carcinogens, was thus investigated by studying five known genotoxic renal carcinogens acting through diverse mechanisms of action, i.e. streptozotocin, aristolochic acids, 2-nitroanisole, potassium bromate and cisplatin, two rodent renal epigenetic carcinogens: d-limonene and ciclosporine and two nephrotoxic compounds: streptomycin and indomethacin. Animals were treated once with the test compound by the appropriate route of administration and genotoxic effects were measured at the two sampling times of 3-6 and 22-26h after treatment. Regarding the tissue processing, the limited background level of DNA migration observed in the negative control groups throughout all experiments demonstrated that the enzymatic isolation method implemented in the current study is appropriate. On the other hand, streptozotocin, 20mg/kg, used as positive reference control concurrently to each assay, caused a clear increase in the mean Olive Tail Moment median value, which allows validating the current methodology. Under these experimental conditions, the in vivo rodent Comet assay demonstrated good sensitivity and good specificity: all the five renal genotoxic carcinogens were clearly detected in at least one expression period either directly or indirectly, as in the case of cisplatin: for this cross-linking agent, the significant decrease in DNA migration observed under standard electrophoresis conditions was clearly amplified when the duration of electrophoresis was increased up to 40min. In contrast, epigenetic and nephrotoxic compounds failed to induce any signifcant increase in DNA migration. In conclusion, the in vivo rodent Comet assay performed on isolated kidney cells could be used as a tool to investigate the genotoxic potential of a test compound if neoplasic/preneoplasic changes occur after subchronic or chronic treatments, in order to determine the role of genotoxicity in tumor induction. Moreover, the epigenetic carcinogens and cytotoxic compounds displayed clearly negative responses in this study. These results allow excluding a DNA direct-acting mechanism of action and can thus suggest that a threshold exists. Therefore, the current in vivo rodent Comet assay could contribute to elucidate an epigenetic mechanism and thus, to undertake a risk assessment associated with human use, depending on the exposure level.

Genetic toxicities of human teratogens

Birth defects cause a myriad of societal problems and place tremendous anguish on the affected individual and his or her family. Current estimates categorize about 3% of all newborn infants as having some form of birth defect or congenital anomaly. As more precise means of detecting subtle anomalies become available this estimate, no doubt, will increase. Even though birth defects have been observed in newborns throughout history, our knowledge about the causes and mechanisms through which these defects are manifested is limited. For example, it has been estimated that around 20% of all birth defects are due to gene mutations, 5-10% to chromosomal abnormalities, and another 5-10% to exposure to a known teratogenic agent or maternal factor [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis. Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500; K. Nelson, L.B. Holmes Malformations due to presumed spontaneous mutations in newborn infants, N. Engl. J. Med. 320 (1989) 19-23.]. Together, these percentages account for only 30-40%, leaving the etiology of more than half of all human birth defects unexplained. It has been speculated that environmental factors account for no more than one-tenth of all congenital anomalies [D.A. Beckman, R.L. Brent, Mechanisms of teratogenesis, Ann. Rev. Pharmacol. Toxicol. 24 (1984) 483-500]. Furthermore, since there is no evidence in humans that the exposure of an individual to any mutagen measurably increases the risk of congenital anomalies in his or her offspring' [J.F. Crow, C. Denniston, Mutation in human populations, Adv. Human Genet. 14 (1985) 59-121; J.M. Friedman, J.E. Polifka, Teratogenic Effects of Drugs: A Resource for Clinicians (TERIS). The John Hopkins University Press, Baltimore, 1994], the mutagenic activity of environmental agents and drugs as a factor in teratogenesis has been given very little attention. Epigenetic activity has also been given only limited consideration as a mechanism for teratogenesis. As new molecular methods are developed for assessing processes associated with teratogenesis, especially those with a genetic or an epigenetic basis, additional environmental factors may be identified. These are especially important because they are potentially preventable. This paper examines the relationships between chemicals identified as human teratogens (agents that cause birth defects) and their mutagenic activity as evaluated in one or more of the established short-term bioassays currently used to measure such damage. Those agents lacking mutagenic activity but with published evidence that they may otherwise alter the expressions or regulate interactions of the genetic material, i.e. exhibit epigenetic activity, have likewise been identified. The information used in making these comparisons comes from the published literature as well as from unpublished data of the U.S. National Toxicology Program (NTP).

Effects of indomethacin and arachidonic acid on sister chromatid exchange induction by styrene and styrene-7,8-oxide

Styrene is converted into styrene-7,8-oxide in human lymphocyte cultures, in a reaction probably mediated by oxyhemoglobin. As a consequence, styrene induces sister-chromatid exchanges (SCEs) in whole-blood lymphocyte cultures without exogenous metabolic activation systems. Another metabolic pathway that could be involved in the metabolism of styrene is cooxidation by prostaglandin-endoperoxide synthase (PES). To study the role of PES in the metabolism of styrene, human whole-blood lymphocyte cultures were treated for the entire culture time of 72 h with styrene (0.5 and 1 mM) or styrene-7,8-oxide (50 and 100 microM), in the presence and absence of 75 or 150 microM indomethacin (an inhibitor of PES) and arachidonic acid (substrate of PES). Indomethacin potentiated SCE induction by both styrene and styrene-7,8-oxide; a slight but statistically significant enhancement (16-32%; p < 0.05-0p < 0.001) was observed in all treatments with styrene and at 150 microM indomethacin in the case of styrene-7,8-oxide. At 150 microM, arachidonic acid induced a 15-20% suppression (p < 0.01) in SCE induction by both styrene (1 mM only) and styrene-7,8-oxide (100 microM only). Indomethacin or arachidonic acid did not alone influence the frequency of SCEs. The results suggest that PES acts as an inactivation route for styrene and styrene-7,8-oxide in human whole-blood lymphocyte cultures, possibly through PES-mediated binding to glutathione.

Effects of indomethacin and arachidonic acid on sister chromatid exchange induction by styrene and styrene-7,8-oxide

Styrene is converted into styrene-7,8-oxide in human lymphocyte cultures, in a reaction probably mediated by oxyhemoglobin. As a consequence, styrene induces sister-chromatid exchanges (SCEs) in whole-blood lymphocyte cultures without exogenous metabolic activation systems. Another metabolic pathway that could be involved in the metabolism of styrene is cooxidation by prostaglandin-endoperoxide synthase (PES). To study the role of PES in the metabolism of styrene, human whole-blood lymphocyte cultures were treated for the entire culture time of 72-h with styrene (0.5 and 1 mM) or styrene-7,8-oxide (50 and 100 microM), in the presence and absence of 75 or 150 microM indomethacin (an inhibitor of PES) and arachidonic acid (substrate of PES). Indomethacin potentiated SCE induction by both styrene and styrene-7,8-oxide; a slight but statistically significant enhancement (16-32%; p < 0.05-p < 0.001) was observed in all treatments with styrene and at 150 microM indomethacin in the case of styrene-7,8-oxide. At 150 microM, arachidonic acid induced a 15-20% suppression (p < 0.01) in SCE induction by both styrene (1 mM only) and styrene-7,8-oxide (100 microM only). Indomethacin or arachidonic acid did not alone influence the frequency of SCEs. The results suggest that PES acts as an inactivation route for styrene and styrene-7,8-oxide in human whole-blood lymphocyte cultures, possibly through PES-mediated binding to glutathione.

Sister-chromatid exchange: second report of the Gene-Tox Program

This paper reviews the ability of a number of chemicals to induce sister-chromatid exchanges (SCEs). The SCE data for animal cells in vivo and in vitro, and human cells in vitro are presented in 6 tables according to their relative effectiveness. A seventh table summarizes what is known about the effects of specific chemicals on SCEs for humans exposed in vivo. The data support the concept that SCEs provide a useful indication of exposure, although the mechanism and biological significance of SCE formation still remain to be elucidated.

Anticlastogenicity in cultured mammalian cells

Basic and applied research on anticlastogenicity has not only revealed valuable evidence on the mechanisms governing the induction of chromosomal aberrations by environmental mutagens, but also contributed effective ideas on a practical employment of this knowledge for the protection of individuals at risk. Considering the basic role played by chromosomal anomalies in oncogenesis, additional weight must be attributed to studies on anticlastogenicity. The employment of human cells in this kind of study dates back to 1969/70, while classical mammalian cell systems were used only later on. Various modes of application of both clastogens and anticlastogens (AC) were examined, but simultaneous addition to the cultures of both reagents was the most favored way. A wide spectrum of cytogenetic endpoints can be studied, but differences can be demonstrated with regard to efficacy of inhibitors on different types of cytogenetic changes, e.g., open breaks vs. rearrangements, but also vs. SCEs. Depending on their mode of influence on this spectrum, ACs can be arranged in various categories which are of practical importance, for instance, with regard to their oncogenic potential. A wide variety of factors was shown to influence AC action, e.g., time and mode of application of the test substances, physiologic and metabolic features of the cell types studied, type and mechanism of the clastogen used, etc. The addition of S9 mix can drastically change the patterns of efficacy of the ACs. The combined application of two or more ACs, as far as investigated, apparently neither potentiates nor even merely adds their effects.

Effects of polyunsaturated fatty acids and of their oxidation products on cell survival

The stimulatory, cytostatic and cytotoxic effects of polyunsaturated fatty acids, prostaglandins, thromboxanes, hydroperoxy fatty acids, hydroxy fatty acids and leukotrienes on normal and tumor cells are described. Their effects are related to the ability of the cells to undergo lipid peroxidation. The significance of controlled peroxidation of selected polyunsaturated fatty acids in the control of tumor development is examined. It is suggested that selected polyunsaturated fatty acids if used at appropriate concentrations may have a protective role against cancer development by inducing and/or mediating cytotoxic reactions in malignant cells directly or indirectly through the intermediacy of immune cells.