Dietary butylated hydroxytoluene counteracts with paraquat to reduce the rate of hepatic DNA single strand breaks in senescence-accelerated mice

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Final report on the safety assessment of BHT(1)

BHT is the recognized name in the cosmetics industry for butylated hydroxytoluene. BHT is used in a wide range of cosmetic formulations as an antioxidant at concentrations from 0.0002% to 0.5%. BHT does penetrate the skin, but the relatively low amount absorbed remains primarily in the skin. Oral studies demonstrate that BHT is metabolized. The major metabolites appear as the carboxylic acid of BHT and its glucuronide in urine. At acute doses of 0.5 to 1.0 g/kg, some renal and hepatic damage was seen in male rats. Short-term repeated exposure to comparable doses produced hepatic toxic effects in male and female rats. Subchronic feeding and intraperitoneal studies in rats with BHT at lower doses produced increased liver weight, and decreased activity of several hepatic enzymes. In addition to liver and kidney effects, BHT applied to the skin was associated with toxic effects in lung tissue. BHT was not a reproductive or developmental toxin in animals. BHT has been found to enhance and to inhibit the humoral immune response in animals. BHT itself was not generally considered genotoxic, although it did modify the genotoxicity of other agents. BHT has been associated with hepatocellular and pulmonary adenomas in animals, but was not considered carcinogenic and actually was associated with a decreased incidence of neoplasms. BHT has been shown to have tumor promotion effects, to be anticarcinogenic, and to have no effect on other carcinogenic agents, depending on the target organ, exposure parameters, the carcinogen, and the animal tested. Various mechanism studies suggested that BHT toxicity is related to an electrophillic metabolite. In a predictive clinical test, 100% BHT was a mild irritant and a moderate sensitizer. In provocative skin tests, BHT (in the 1% to 2% concentration range) produced positive reactions in a small number of patients. Clinical testing did not find any depigmentation associated with dermal exposure to BHT, although a few case reports of depigmentation were found. The Cosmetic Ingredient Review Expert Panel recognized that oral exposure to BHT was associated with toxic effects in some studies and was negative in others. BHT applied to the skin, however, appears to remain in the skin or pass through only slowly and does not produce systemic exposures to BHT or its metabolites seen with oral exposures. Although there were only limited studies that evaluated the effect of BHT on the skin, the available studies, along with the case literature, demonstrate no significant irritation, sensitization, or photosensitization. Recognizing the low concentration at which this ingredient is currently used in cosmetic formulations, it was concluded that BHT is safe as used in cosmetic formulations.

A higher oxidative status accelerates senescence and aggravates age-dependent disorders in SAMP strains of mice

The SAM strain of mice is actually a group of related inbred strains consisting of series of SAMP (accelerated senescence-prone, short-lived) and SAMR (accelerated senescence-resistant, longer-lived) strains. Comparing with the SAMR strains, the SAMP strains of mice show a more accelerated senescence process, shorter lifespan, and an earlier onset and more rapid progress of age-associated pathological phenotypes similar to several geriatric disorders observed in humans, including senile osteoporosis, degenerative joint disease, age-related deficits in learning and memory, olfactory bulb and forebrain atrophy, presbycusis and retinal atrophy, senile amyloidosis, immunosenescence, senile lungs, and diffuse medial thickening of the aorta. The higher oxidative stress observed in the SAMP strains of mice are partly caused by mitochondrial dysfunction, and may be one cause of the senescence acceleration and age-dependent alterations in cell structure and function, including neuronal cell degeneration. This senescence acceleration is also observed during senescence/crisis in cultures of isolated fibroblast-like cells from SAMP strains of mice, and was associated with a hyperoxidative status. These observations suggest that the SAM strains are useful tools in the attempt to understand the mechanisms of age-dependent degeneration of cells and tissues, and their aggravation, and to develop clinical interventions.

Spontaneous loss-of-function mutations of the 8-oxoguanine DNA glycosylase gene in mice and exploration of the possible implication of the gene in senescence

8-Oxoguanine is one of the major premutagenic oxidative base legions in vivo and is suspected to play a crucial role in various pathophysiological processes, such as cancer and aging. Mammalian 8-oxoguanine DNA glycosylase (OGG1) is thought to play a major role in the removal of 8-oxoguanine adducts in vivo. We have identified several inbred mouse strains with a spontaneous mutation, OGG1-R336H or double mutations, OGG1-R304W/R336H. R304W mutation caused a complete loss of OGG1 activity, while the R336H mutation led to disruption of nuclear localization of the enzyme although the activity remained normal. Among the double mutants was SAMP1, which exhibits accelerated senescence and short lifespan. We assessed the possible implication of the mutant OGG1 and 8-oxoguanine in aging utilizing SAMP1 mice. SAMP1 retained 1.5- to 1.9-fold increase in 8-oxoguanine level of hepatic nuclear DNA as compared with normal mice, until at least 12 months of age. A genetic association study, however, indicated that the mutant Ogg1 gene per se is not responsible for the accelerated senescence and short lifespan of SAMP1. Mutant OGG1 may be associated with pathologic conditions in other mouse strains.

Age-associated DNA damage is accelerated in the senescence-accelerated mice

We investigated how the DNA status correlates with the aging process in organisms, in different organs and in tissues using two inbred strains of mice, which are genetically related but have different senescence patterns. The SAMP1 mice belong to an accelerated senescence-prone and short lived strain, the other, SAMR1 mice are from an accelerated senescence-resistant and long lived strain. Using the alkaline filter elution technique, pieces of tissues from six organs: lung, intestine, liver, brain, muscle, and heart have been examined for DNA damage, mainly DNA single strand breaks. It was shown that in newborns the DNA damage is minimal, and it was increased significantly with calendric age in all organs in both strains. Although the correlation of DNA damage with aging differed in the different six organs, damage was significantly higher in SAMP1 mice than SAMR1 mice at later life in all organs. This is another remarkable example for the strong correlation of DNA damage and aging process, especially with senescence acceleration.

Genetic analysis of lifespan in hybrid progeny derived from the SAMP1 mouse strain with accelerated senescence

The SAMP1 mouse, a senescence-accelerated mouse prone (SAMP) strain, shows accelerated senescence coupled with a short lifespan as a genetic trait, and has been used in gerontological research. The accelerated senescence and short lifespan of SAMP strains is considered to be under the control of multiple genes. To identify the chromosomal regions encompassing the genes for the accelerated senescence and short lifespan, we performed whole genome scanning with polymorphic marker loci in a progeny from a cross between the SAMP1 strain and normal B10.BR strain. A genetically recessive effect of the amyloidogenic Apoa2(c) allele from SAMP1 on chromosome 1 to shorten the lifespan was demonstrated in the progeny, consistent with the previous report. The recessive effect was observed also at D1Mit67, D5Mit267, D6Mit384 and D19Mit33, suggesting the presence of genes for accelerated senescence in the SAMP strains around these loci. Other markers on chromosomes 8, 14, 16, and 17, however, exhibited a dominant or additive effect to shorten or prolong the lifespan, demonstrating a complex genetic control of the trait.