RESUMEN
A toxicological evaluation of a umami flavour compound, 2-(((3-(2,3-dimethoxyphenyl)-1H-1,2,4-triazol-5-yl)thio)methyl)pyridine (S3643; CAS 902136-79-2), was completed for the purpose of assessing its safety for use in food and beverage applications. S3643 undergoes extensive oxidative metabolism in vitro with rat microsomes producing the S3643-sulfoxide and 4'-hydroxy-S3643 as the major metabolites. In incubations with human microsomes, the O-demethyl-S3643 and S3643-sulfoxide were produced as the major metabolites. In pharmacokinetic studies in rats, the S3643-sulfoxide represents the dominant biotransformation product. S3643 was not found to be mutagenic or clastogenic in vitro, and did not induce micronuclei in CHO-WBL cells. In subchronic oral toxicity studies in rats, the no-observed-adverse-effect-level (NOAEL) for S3643 was 100 mg/kg bw/day (highest dose tested) when administered in the diet for 90 consecutive days.
RESUMEN
Toxicological evaluations of two N-alkyl benzamide umami flavour compounds, N-(heptan-4-yl)benzo[d][1,3]dioxole-5-carboxamide (S807, CAS 745047-51-2) and (R)-N-(1-methoxy-4-methylpentan-2-yl)-3,4-dimethylbenzamide (S9229, CAS 851669-60-8), were completed for the purpose of assessing their safety for use in food and beverage applications. Both S807 and S9229 undergo rapid oxidative metabolism by both rat and human liver microsomes in vitro. In pharmacokinetic studies in rats, the systemic exposure to S9229 on oral administration is very low at all doses (% F < 1%), while that of S807 demonstrated a non-linear dose dependence. In metabolism studies in rats, hydroxylation of the C-4 aryl methyl group was found to be the dominant metabolic pathway for S9229. The dominant metabolic pathway for S807 in the rat involved oxidative scission of the methylenedioxy moiety to produce the corresponding 3,4-dihydroxybenamide which is further converted by Phase II metabolic enzymes to the 3- and 4-O-methyl ethers as well as their corresponding glucuronides. Both S807 and S9229 were not found to be mutagenic or clastogenic in vitro, and did not induce micronuclei in polychromatic erythrocytes in vivo. In a subchronic oral toxicity study in rats, the no-observed-effect-level (NOEL) for S807 was 20 mg/kg bw/day when administered in the diet for 13 weeks. The no-observed-adverse-effect-level (NOAEL) for S9229 in rats was 100 mg/kg bw/day (highest dose tested) when administered in the diet for 28 consecutive days.
RESUMEN
A toxicological evaluation of 4-amino-5-(3-(isopropylamino)-2,2-dimethyl-3-oxopropoxy)-2-methylquinoline-3-carboxylic acid(S9632; CAS 1359963-68-0), a flavour with modifying properties,was completed for the purpose of assessing its safety for use in food and beverage applications. No Phase I biotransformations of S9632 were observed in rat or human microsomes in vitro, and in rat pharmacokinetic studies, the compound was poorly orally bioavailable and rapidly eliminated. S9632 was not found to be mutagenic or clastogenic in vitro, and did not induce micronuclei or indicate interactions with the mitotic spindle in an in vivo mouse micronucleus assay at oral doses up to 2000 mg/kg. In subchronic oral toxicity studies in rats, the NOEL was 100 mg/kg/day (highest dose tested) for S9632 when administered as a food ad-mix for 90 consecutive days. Furthermore, S9632 demonstrated a lack of maternal toxicity, as well as adverse effects on fetal morphology at the highest dose tested, providing a NOEL of 1000 mg/kg/day for both maternal toxicity and embryo/fetal development when administered orally during gestation to pregnant rats.
RESUMEN
A toxicological evaluation of a novel cooling agent, 2-(4-methylphenoxy)-N-(1H-pyrazol-3-yl)-N-(2-thienylmethyl) acetamide (S2227; CAS 1374760-95-8), was completed for the purpose of assessing its safety for use in food and beverage applications. S2227 undergoes rapid oxidative metabolism in vitro, and in rat and dog pharmacokinetic studies is rapidly converted to its component carboxylic acid and secondary amine. S2227 was not found to be mutagenic or clastogenic in vitro, and did not induce micronuclei in polychromatic erythrocytes in vivo. The secondary amine hydrolysis product, N-(2-thienylmethyl)-1H-pyrazol-3-amine (M179), was also evaluated for genotoxicity. In subchronic oral toxicity studies in rats, the no-observed-adverse-effect-level (NOAEL) for S2227 was 100 mg/kg/day (highest dose tested) when administered by oral gavage for 90 consecutive days. Furthermore, S2227 demonstrated a lack of maternal toxicity, as well as adverse effects on fetal morphology at the highest dose tested, providing a NOAEL of 1000 mg/kg/day for both maternal toxicity and embryo/fetal development when administered orally during gestation to pregnant rats.
RESUMEN
DNA damage response (DDR) to double strand breaks is coordinated by 3 phosphatidylinositol 3-kinase-related kinase (PIKK) family members: the ataxia-telangiectasia mutated kinase (ATM), the ATM and Rad3-related (ATR) kinase and the catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs). ATM and ATR are central players in activating cell cycle checkpoints and function as an active barrier against genome instability and tumorigenesis in replicating cells. Loss of ATM function is frequently reported in various types of tumors, thus placing more reliance on ATR for checkpoint arrest and cell survival following DNA damage. To investigate the role of ATR in the G2/M checkpoint regulation in response to ionizing radiation (IR), particularly when ATM is deficient, cell lines deficient of ATM, ATR, or both were generated using a doxycycline-inducible lentiviral system. Our data suggests that while depletion of ATR or ATM alone in wild-type human mammary epithelial cell cultures (HME-CCs) has little effect on radiosensitivity or IR-induced G2/M checkpoint arrest, depletion of ATR in ATM-deficient cells causes synthetic lethality following IR, which correlates with severe G2/M checkpoint attenuation. ATR depletion also inhibits IR-induced autophagy, regardless of the ATM status, and enhances IR-induced apoptosis particularly when ATM is deficient. Collectively, our results clearly demonstrate that ATR function is required for the IR-induced G2/M checkpoint activation and subsequent survival of cells with ATM deficiency. The synthetic lethal interaction between ATM and ATR in response to IR supports ATR as a therapeutic target for improved anti-cancer regimens, especially in tumors with a dysfunctional ATM pathway.