Ascorbate-dependent elevation of mRNA levels for cytochrome P450s induced by polychlorinated biphenyls

Ascorbic Acid and Graphene Oxide Exposure in the Model Organism Acheta domesticus Can Change the Reproduction Potential

The use of nanoparticles in the industry carries the risk of their release into the environment. Based on the presumption that the primary graphene oxide (GO) toxicity mechanism is reactive oxygen species production in the cell, the question arises as to whether well-known antioxidants can protect the cell or significantly reduce the effects of GO. This study focused on the possible remedial effect of vitamin C in Acheta domesticus intoxicated with GO for whole lives. The reproduction potential was measured at the level of Vitellogenin (Vg) gene expression, Vg protein expression, hatching success, and share of nutrition in the developing egg. There was no simple relationship between the Vg gene's expression and the Vg protein content. Despite fewer eggs laid in the vitamin C groups, hatching success was high, and egg composition did not differ significantly. The exceptions were GO20 and GO20 + Vit. C groups, with a shift in the lipid content in the egg. Most likely, ascorbic acid impacts the level of Vg gene expression but does not affect the production of Vg protein or the quality of eggs laid. Low GO concentration in food did not cause adverse effects, but the relationship between GO toxicity and its concentration should be investigated more thoroughly.

Turnabout is fair play: Secondary roles for primary compounds

Chemically based resistance of plants to herbivorous insects is today essentially synonymous with allelochemically based resistance; the importance of plant secondary compounds in determining patterns of host-plant utilization has been established in a wide variety of insect-plant interactions. In contrast, primary metabolites, those involved in fundamental plant physiological processes, are rarely considered to be major determinants of host-plant resistance despite the fact that, as insect nutrients, they can have profound effects on behavior and physiology. The degree to which variation in plant primary metabolism results from the selective impact of herbivory may be greatly underestimated in that the biosynthetic and structural diversity of primary metabolites and the consequences of that diversity on herbivores are rarely taken into account in most studies of insect preference and performance. Qualitative and quantitative variation in the production of primary metabolites can result from herbivore selection pressure if production of primary metabolites is under genetic control and if plant fitness in the presence of herbivores is associated in a predictable way with genetically based primary metabolite variation. Variation in primary metabolism is likely to be particularly effective as a defense against highly oligophagous herbivores with limited mobility, especially those confined to structures containing allelochemicals that could neutralize the benefits associated with compensatory feeding.

Escape from tolerance of organic nitrate by induction of cytochrome P450

The mechanism of organic nitrate tolerance is poorly defined. We studied the rat P450-catalyzed conversion of organic nitrate to nitric oxide (NO) by purified P450 isoforms relationship between P450 expression and nitrate tolerance following continuous infusion of organic nitrates in rats. The hypotensive effect of an nitroglycerin (NTG) bolus injection was abolished in rats that had been previously provided a continuous 48 h infusion of NTG. This effect was accompanied by a gradual but marked decrease in plasma and urinary nitrate levels following a peak at 18-24 h. Nitrate tolerance was reversible; the decline in the hypotensive effect and P450 levels observed after 2 d of continuous infusion was followed by restoration to control levels 2 d after cessation of the infusion. Similarly, the hypotensive action disappeared in P450-depleted, and -inhibited rats. At 48 h after infusion, NTG-induced NO generation of the vessels increased in acetone (a P450 inducer) -pretreated rats. The appearance and disappearance of P450 paralleled the conversion of organic nitrates to NO. Our observations indicate that nitrate tolerance is in large part the result of decreased P450 expression and activity. Interventions that maintain or increase P450 activity may be a strategy to provide relief from ischemic conditions in humans.

Vitamin C attenuates nitrate tolerance independently of its antioxidant effect

In LLC-PK1 kidney epithelial cells, a 5-h pretreatment with glyceryl trinitrate (GTN) resulted in substantial desensitization of the intracellular cyclic GMP response to a subsequent 10-min challenge with GTN (1 microM). GTN-tolerant cells were fully sensitive to the spontaneous nitric oxide (NO) donor spermine NONOate, which does not require enzymatic bioactivation. Cyclic GMP stimulation by GTN was up to 3.1-fold higher when vitamin C (1-10 mM) was present during the pretreatment period. In contrast, other oxygen radical scavengers such as tiron or dimethylsulfoxide and the NO scavenger PTIO left tolerance induction unaltered. Together, our results suggest that reactive oxygen species or NO do not contribute to the development of nitrate tolerance. Tolerance reduction by vitamin C may be due to a stabilizing effect on enzymes involved in the bioconversion of GTN to NO.

Induction of ovalbumin mRNA by ascorbic acid in primary cultures of tubular gland cells of the chicken oviduct

The present study was conducted to investigate the effects of aging and medium supplements on steroid-induced ovalbumin mRNA in primary cultures of tubular gland cells from the chicken oviduct. In experiment 1, the effect of aging was examined by comparing the responsiveness to administration of estrogen and corticosterone in cells derived from laying hens and estrogen-primed chicks. In experiment 2, the effect of supplementing a culture medium with various compounds on the responsiveness to the steroid treatment was examined. In experiment 3, the effect of supplementing with ascorbic acid was tested in the presence or absence of the steroid hormones. The results indicated that the oviduct cells from immature chicks had clearer induction of ovalbumin mRNA by the steroid treatment than did those from laying hens. Among medium supplements, ascorbate increased the steroid responsiveness to a great extent, and fetal calf serum had modest, but long lasting, induction of ovalbumin mRNA. The drastic induction of ovalbumin mRNA by ascorbic acid supplementation was exerted only when the steroid hormones were present in the medium, implying that the effect of ascorbic acid may be auxiliary in steroid-induced transcription of the ovalbumin gene.

Effects of caloric restriction on rodent drug and carcinogen metabolizing enzymes: implications for mutagenesis and cancer

Caloric restriction in rodents results in increased longevity and a decreased rate of spontaneous and chemically induced neoplasia. The low rates of spontaneous neoplasia and other pathologies have made calorically restricted rodents attractive for use in chronic bioassays. However, caloric restriction also alters hepatic drug metabolizing enzyme (DME) expression and so may also alter the biotransformation rates of test chemicals. These alterations in DME expression may be divided into two types: (1) those that are the direct result of caloric restriction itself and are detectable from shortly after the restriction is initiated; (2) those which are the result of pathological conditions that are delayed by caloric restriction. These latter alterations do not usually become apparent until late in the life of the organism. In rats, the largest direct effect of caloric restriction on liver DMEs is an apparent de-differentiation of sex-specific enzyme expression. This includes a 40-70% decrease in cytochrome P450 2C11 (CYP2C11) expression in males and a 20-30% reduction of corticosterone sulfotransferase activity in females. Changes in DME activities that occur late in life in calorically restricted rats include a stimulation of CYP2E1-dependent 4-nitrophenol hydroxylase activity and a delay in the disappearance of male-specific enzyme activities in senescent males. It is probable that altered DME expression is associated with altered metabolic activation of chemical carcinogens. For example the relative expression of hepatic CYP2C11 in ad libitum-fed or calorically restricted rats of different ages is closely correlated with the amount of genetic damage in 2-acetylaminofluorene- or aflatoxin B1-pretreated hepatocytes isolated from rats of the same age and caloric intake. This suggests that altered hepatic drug and carcinogen metabolism in calorically restricted rats can influence the carcinogenicity of test chemicals.