Effect of steroidogenesis on ascorbic acid content and uptake in isolated adrenal cells

Vitamin C deficiency alters the transcriptome of the rat brain in a glucocorticoid-dependent manner, leading to microglial activation and reduced neurogenesis

Vitamin C (VitC) is maintained at high concentrations in the brain and is an essential micronutrient for brain function. VitC deficiency leads to neuropsychiatric scurvy, which is characterized by depression and cognitive impairment. However, the molecular mechanism by which mild VitC deficiency impairs brain function is currently unknown. In the present study, we conducted RNA sequencing analysis and found that a short-term VitC deficiency altered the brain transcriptome in ODS rats, which cannot synthesize VitC. Bioinformatic analysis indicated that VitC deficiency affected the expression of genes controlled by the glucocorticoid receptor in the brain. We confirmed an increased secretion of glucocorticoids from the adrenal gland during VitC deficiency. We found that non-neuronal cells, including microglia, which are resident immune cells in the brain, changed their transcriptional patterns in response to VitC deficiency. Immunohistochemical analysis revealed that the quiescent ramified microglia transform into the activated amoeboid microglia during three weeks of VitC deficiency. The morphological activation of microglia was accompanied by increased expression of proinflammatory cytokines such as interleukin-6 in the hippocampus. Furthermore, VitC deficiency decreased the number of newly born neurons in the dentate gyrus of the hippocampus, suggesting that VitC was required for adult neurogenesis that plays a crucial role in learning and memory. Our findings may provide insights into the molecular mechanisms underlying the maintenance of normal brain function by adequate levels of VitC.

Compound 48/80 causes oxidative stress in the adrenal gland of rats through mast cell degranulation

Rats were intraperitoneally treated once with compound 48/80 (C48/80), a mast cell degranulator, (0.75 mg/kg). Serum serotonin, histamine and corticosterone levels increased 0.5 h after C48/80 treatment, but their increases were reduced thereafter. Adrenal total ascorbic acid (ascorbic acid plus dehydroascorbic acid), ascorbic acid and dehydroascorbic acid levels decreased 0.5, 3 or 6 h after C48/80 treatment, adrenal lipid peroxide level increased at 3 and 6 h, adrenal non-protein-SH level decreased at 3 and 6 h and adrenal beta-tocopherol level decreased at 3 h. Ketotifen, a mast cell stabilizer (1 mg/kg) administered intraperitoneally at 0.5 h before C48/80 treatment, attenuated all these changes found in the serum and adrenal at 3 h after treatment, while beta-tocopherol (250 mg/kg), administered orally at 0.5 h after C48/80 treatment, attenuated all these changes in the adrenal tissue. These results indicate that C48/80 causes oxidative stress in rat adrenal gland through mast cell degranulation.

Vitamin C is an important cofactor for both adrenal cortex and adrenal medulla

The adrenal gland is among the organs with the highest concentration of vitamin C in the body. Interestingly, both the adrenal cortex and the medulla accumulate such high levels of ascorbate. Ascorbic acid is a cofactor required both in catecholamine biosynthesis and in adrenal steroidogenesis. Here we provide an overview on the role of vitamin C in the adrenal cortex and medulla derived from in vitro and in vivo studies. In addition, recent insights gained from an animal model with a deletion in the gene for the ascorbic acid transporter will be summarized. Mutant mice lacking the plasma membrane ascorbic acid transporter (SVCT2) have severely reduced tissue levels of ascorbic acid and die soon after birth. There is a significant decrease of tissue catecholamine levels in the adrenals. On the ultrastructural level, adrenal chromaffin cells in SVCT2 null mice show depletion of catecholamine storage vesicles, signs of apoptosis, and increased glycogen storage. Decreased plasma levels of corticosterone and altered morphology of mitochondrial membranes indicate additional effects of the deficiency on adrenal cortical function. The data derived from these animal models and various cell culture studies confirm a crucial role for vitamin C for both the adrenal cortex as well as the adrenal medulla further underlining the interdependence of the two endocrine systems united in one gland.

Influences of wet feeding and supplementation with ascorbic acid on performance and carcass composition of broiler chicks exposed to a high ambient temperature

In two experiments was investigated whether feeding with an air-dry feed mixed with different amounts of water and/or supplemental ascorbic acid affect performance and carcass compositions of broilers exposed to a high ambient temperature (35 to 37 degrees C for 8 h/d and thermoneutral for 16 h/d). In the first trial, 64 one-week-old male broiler chicks were fed ad libitum in four dietary treatment groups for a 6-week period. Experimental mash diets were prepared by mixing a maize-soybean based standard broiler starter or finisher with tap water in the ratios of 0.0:1.0, 0.5:1.0, 1.0:1.0 and 1.5:1.0 (water:air-dry feed, w/w). More water in the diet increased BWG, DMI, abdominal fat and carcass weight, carcass CP, crude fat, but it deteriorated DM conversion efficiency. In the second experiment, 64 one-week-old male broiler chicks were given air-dry or wet (water:feed, 1.5:1) starter or finisher diets without or with ascorbic acid supplementation (0 and 250 mg/kg air-dry feed, resp.) ad libitum for a 6-week period. Ascorbic acid supplementation increased BWG, carcass weight and carcass CP significantly, while reducing carcass crude fat content. However, feeding broilers with a diet mixed with water in a ratio of 1.5:1.0 increased BWG, DMI, carcass weight and carcass lipid markedly, but deteriorated DM conversion efficiency. There was also a significant interaction between ascorbic acid and wet feeding, whereby ascorbic acid supplementation induced a significant reduction in carcass lipid contents of broilers fed on air-dry diets but not on wet diets. It is concluded that wet feeding, especially an addition of 150% water to produce a porridge like consistency, improved growth performance by increasing fat, ash and protein deposition in the body, while reducing DM conversion efficiency. It is also concluded that under heat stress supplemental ascorbic acid in air-dry diets stimulates broiler performance but not in wet diets.

Effects of supplemental ascorbic acid on the energy conversion of broiler chicks during heat stress and feed withdrawal

The objectives of this study were 1) to determine the effects of supplemental ascorbic acid (AA) on the energy conversion of broiler chicks maintained at thermoneutral and potential heat stress temperatures using indirect convective calorimetry; and 2) to determine whether changes in energy conversion are reflected in changes in lipid metabolism. In Experiment 1, 120 2-d-old cockerels, housed in two identical environmental chambers, were maintained under constant light (2.0 +/- 0.2 fc) and recommended thermal conditions (29.6 +/- 0.8 C; 33.4 +/- 8.0% RH) and consumed water and feed ad libitum. Beginning on Day 8 posthatch, one-half of the birds inside each chamber were randomly assigned and received feed supplemented with AA. Beginning on Day 9 posthatch, the temperature inside one chamber was increased to 34 C whereas the other chamber remained thermoneutral. This design resulted in four treatments: 1) thermoneutral (TN: 27.7 +/- 0.8 C; 40.9 +/- 9.4% RH) and 0 mg AA/kg feed (ppm); 2) TN and 150 ppm AA; 3) heat stress (H: 33.8 +/- 0.5 C; 43.3 +/- 7.4% RH) and 0 ppm AA; or 4) H and 150 ppm AA. Also beginning on Day 9 posthatch, birds were randomly assigned to one of three identical, indirect convective calorimeters designed to accommodate TN or H. Oxygen consumption, carbon dioxide production, respiratory quotient, and heat production were evaluated daily for 8 h, through Day 17 posthatch. Following calorimetric measurement, birds were returned to their respective caging unit/chamber for the remainder of the study. Weight gain, feed intake, and gain: feed were also measured over the 9-d study. Heat exposure depressed (P < 0.05) weight gain, feed intake, and gain:feed. Ascorbic acid increased (P < 0.10) weight gain. Oxygen consumption and carbon dioxide and heat production per kilogram0.75 decreased (P < 0.05) with age with no change in the respiratory quotient. Heat exposure lowered (P < 0.001) the respiratory quotient. A temperature by AA interaction was detected in which heat-exposed birds expressed lower (P < 0.10) respiratory quotients when consuming the AA-supplemented diet. In Experiment 2, 18 2-d-old cockerels, housed in an environmental chamber, were maintained under constant light and recommended thermal conditions (29.3 +/- 0.4 C; 41.4 +/- 3.3% RH) and consumed water and feed ad libitum. On Day 9 posthatch, birds were deprived of feed for 24 h with ad libitum access to water supplemented with either 0 or 400 mg AA/L. Blood samples were obtained from each bird before and after feed withdrawal and supplementation. Supplemented birds exhibited elevated (P < 0.01) plasma AA, levels that were not affected by feed deprivation. Feed deprivation increased (P < 0.0001) plasma beta-hydroxybutyrate with no effect of AA, and decreased (P < 0.05) plasma triglycerides in the unsupplemented birds. A feed withdrawal by AA interaction was detected in which plasma triglycerides remained elevated in birds supplemented with AA. These data suggest that supplemental AA influences body energy stores that are used for energy purposes during periods of reduced energy intake.

Self-selection of ascorbic acid in coloured foods by heat-stressed broiler chicks

Female broiler chicks were given red and green supplemented (200 mg ascorbic acid (AA)/kg) and unsupplemented foods on alternate days for 8 days under heat-stressed and unstressed conditions. After this training period, the birds were given access to both foods, and the intake of each was monitored. In both heated treatments the intake of the supplemented food was significantly higher (p < 0.05) than of the unsupplemented food (800 vs. 518 g/14 days), although in the unheated groups significantly more of the unsupplemented food was eaten (756 vs. 639 g/14 days). Birds were unable to select for AA when neither food was coloured, even when they were presented continuously in the same positions in the cage. It is concluded that chicks can learn to associate the colour of the food with its AA content and that they select proportions of supplemented and unsupplemented foods appropriate for their needs, as influenced by environmental temperature.

The influence of NADPH-dependent lipid peroxidation on the progesterone biosynthesis in human placental mitochondria

In an in vitro system consisting of human term placental mitochondria and an NADPH-generating system plus Fe2+, significant lipid peroxidation was observed along with a concomitant inhibition of progesterone biosynthesis. This inhibition could be markedly blocked by Mn2+, superoxide dismutase and dimethylfuran, inhibitors of NADPH-dependent lipid peroxidation. In addition, it has been found that malondialdehyde formation is accompanied by a corresponding decrease in placental mitochondrial cytochrome P-450 content. Inhibitors of lipid peroxidation also prevent the loss of cytochrome P-450, further demonstrating a direct relationship between NADPH-dependent lipid peroxidation and degradation of cytochrome P-450 in cell-free systems. These measurements provide the first evidence that the inhibition of progesterone biosynthesis by a NADPH-dependent lipid peroxidation in placental mitochondria is a consequence of cytochrome P-450 degradation due to lipid peroxidation.

Effect of calf housing on plasma ascorbate and endocrine and immune function

The effect of housing calves in indoor metal pens (1.2 m x 1.2 m) or commercial calf hutches was determined on plasma concentration of cortisol, antibodies, and ascorbate. Six calves per treatment were deprived of colostrum, assigned randomly to treatment, and fed a commercial milk replacer until 56 d of age. Calves housed in hutches had higher plasma IgG concentrations than calves in pens at 42 and 56 d of age. Housing had no effect on plasma IgM concentration. Antibody titers to keyhole limpet hemocyanin injected at 14 and 28 d of age were higher in hutch-housed calves from 21 to 56 d of age. Calves housed in hutches also had lower plasma cortisol concentrations, although cortisol decreased with age in both treatment groups. Plasma ascorbate and ascorbate plus dehydroascorbate were higher in hutch-housed calves. Regression analysis indicated a positive relationship between plasma ascorbate and IgG in metal penhoused calves and a negative relationship in hutch-housed calves. Housing in 1.2 m x 1.2 m metal pens decreases cortisol, plasma ascorbate, IgG, and specific antibody titers in dairy calves relative to calves housed in hutches.

Effect of environmental stress on the ascorbic acid requirement of laying hens

An experiment with a factorial arrangement of treatment (3 by 2 by 2 by 2) was conducted to determine the effect of ascorbic-acid supplementation (0, 100, and 200 ppm) on the performance of two commercial layer strains housed at a density of either 3 or 4 birds per cage and relative humidities (RH) of 40% or 60%. The hens were subjected to a continuous heat stress of 31.1 degrees C for the 3-mo experimental period. As a comparison with an unstressed control group, an additional group of hens was housed at 23.9 degrees C and 40% RH and was fed the diet without ascorbic-acid supplementation. Mortality was reduced by ascorbic-acid supplementation. Shell weight per unit surface area showed a small increase with the added ascorbic acid. Values (in Haugh units) were increased by ascorbic-acid supplementation at the 200 ppm level and by the lower relative humidity. The higher RH reduced egg production by 4.16% and changed feed efficiency from 2.29 to 2.45 g of feed intake per gram of egg mass. There were differences in blood pH, blood CO2, blood HCO3-, and blood and adrenal ascorbic-acid levels due to the housing temperature. The higher RH produced blood-chemistry changes that were typical of respiratory alkalosis, which has been shown to occur in layers at high temperatures. Higher cage density, on the other hand, showed no change in the HCO3 level; but blood pCO2 was increased while blood pH was decreased. These results demonstrate that ascorbic-acid supplementation can be effective in reducing laying-hen mortality due to environmental stress and has small influences on egg quality.

Relationship between mitochondrial lipid peroxidation and alpha-tocopherol levels in the guinea-pig adrenal cortex

Lipid peroxidation in mitochondria from the functionally distinct inner (zona reticularis) and outer (zona fasciculata + zona glomerulosa) zones of the guinea-pig adrenal cortex was investigated. Ferrous ion (Fe2+)-induced lipid peroxidation was far greater in inner than outer zone mitochondria. Ascorbic acid similarly initiated lipid peroxidation to a greater extent in inner zone mitochondrial preparations. Differences in the unsaturated fatty acid content of inner and outer zone mitochondria could not account for the regional differences in lipid peroxidation. Total fatty acid concentrations were greater in the outer than in the inner zone, and the relative amounts of each fatty acid were similar in the two zones. However, mitochondrial concentrations of alpha-tocopherol, an antioxidant known to inhibit lipid peroxidation, were approx. 5-times greater in the outer than inner zone. The results demonstrate that there are regional differences in mitochondrial lipid peroxidation in the adrenal cortex which may be attributable to differences in alpha-tocopherol content. Thus, alpha-tocopherol may serve to protect outer zone mitochondrial enzymes from the consequences of lipid peroxidation and thereby contribute to some of the functional differences between the zones of the adrenal cortex.

Regional differences in microsomal lipid peroxidation and antioxidant levels in the guinea pig adrenal cortex

Lipid peroxidation (LP) and antioxidant levels were studied in the chromatically distinct inner (zona reticularis) and outer (zona fasciculata + zona glomerulosa) zones of the guinea pig adrenal cortex. Ferrous ion (Fe2+) produced a concentration-dependent (10(-5) to 10(-3) M) stimulation of microsomal LP in both zones, but LP, as estimated by malonaldehyde production, was far greater in the inner zone. Although cytosolic ascorbic acid content was similar in the two zones, microsomal tocopherol levels were approx 4 times greater in the outer than inner zone. Subphysiological concentrations of ascorbic acid, like Fe2+, initiated LP to a greater extent in inner than outer zone microsomes; optimal stimulation of LP by ascorbic acid occurred at concentrations of 100-200 microM in both zones. Physiological concentrations of ascorbic acid (1-5 mM), by contrast, did not initiate LP and, in fact, markedly inhibited Fe2+-induced LP in both inner and outer zone microsomal preparations. Outer zone microsomes were more sensitive to the antioxidant effects of ascorbic acid than were inner zone preparations. Addition of alpha-tocopherol to inner zone microsomal suspensions inhibited Fe2+-induced LP. The results indicate that there are regional differences in adrenocortical LP which may be caused by differences in tocopherol content. alpha-Tocopherol may serve important antioxidant functions within the adrenal cortex, thereby contributing to the functional zonation of the gland.

Effect of adrenocorticotropin and dietary ascorbic acid on cutaneous basophil hypersensitivity to phytohemagglutinin in chickens

Two trials were conducted to assess the effects of adrenocorticotropin (ACTH) and dietary ascorbic acid (AA) on cutaneous basophil hypersensitivity (CBH) to phytohemagglutinin (PHA-P) in chickens. Broiler chicks received AA at levels of 0, 150, or 300 mg/kg of feed (ppm) continuous from hatching. At 6 to 7 wk of age, birds from each AA group received either 2 IU ACTH/100 g of body weight, 4% gelatin, or no ACTH or gelatin injections. Injections were given 12 h prior to, at the time of, and at 12 and 24 h after an intradermal wattle injection with PHA-P. Responses to PHA-P were determined as wattle indices. Injections of ACTH reduced body weight gain in both trials and decreased relative bursa weight in Trial 1. Injections of ACTH and dietary AA increased plasma cholesterol in both trials. Peak CBH wattle response occurred at 24 h post PHA-P injection. Injections of ACTH decreased mean wattle index at 18 and 36 h post PHA-P injection in Trial 1 and 18 and 24 h post PHA-P injection in Trial 2. The addition of AA ameliorated the ACTH-mediated suppression of CBH in a dose-related manner.

The function of NADH-semidehydroascorbate reductase and ascorbic acid in corticosteroid hydroxylation

We have demonstrated in rat adrenal (Natarajan, R.D. and Harding, B.W. (1985) J. Biol. Chem. 260, 3902-3905) that NADH-semidehydroascorbate reductase and ascorbate participate in an electron transport pathway (ETP) supplying reducing equivalents from NADH to cytochrome P-450scc. Here, we demonstrate that this ascorbate dependent ETP also supplies reducing equivalents to cytochrome P-450(11 beta/18) in both rat adrenal and bovine adrenal cortex. The activity is dependent upon addition of catalase or upon 'cold shock' treatment of isolated mitochondria. Comparison of the rates of 11 beta- and 18-hydroxylation supported by this ETP and by the classical pathway supported by various TCA cycle intermediates suggests that in vivo the ascorbate dependent pathway may be essential for maximal flow of reducing equivalents to the mitochondrial hydroxylases. Partial reconstitution of the ascorbate dependent 11 beta/18-hydroxylase activity was achieved with purified bovine outer mitochondrial and inner mitochondrial membranes fortified with supernatant from sonified mitochondria all preincubated with phosphatidyl choline. These preparations no longer require catalase or 'cold shock' treatment. Ascorbate and NADH-semidehydroascorbate reductase are unable to support 17 alpha- or 21-hydroxylase activity in isolated bovine adrenal cortical microsomes whether incubated with purified outer mitochondrial membranes or not.

Evidence of rebound effect with ascorbic acid

The urinary excretion pattern of ascorbic acid in two subjects who had been taking a large amount of ascorbic acid (10 g per day) and later reverted to a small intake (125 mg per day) is described. The ascorbic acid concentration in the 24-hour urine samples was measured over a 40-day collection of this period. The mean urinary ascorbic acid excretion during the loading period of the two subjects was about 2 g per day. Upon termination of the high intake of ascorbic acid, urinary ascorbic acid excretion dropped to presupplementation levels within 6 days. Urinary ascorbic acid of the two subjects continued to decrease to below basal level, and remained at abnormally low levels for 10 and 12 days respectively. We hypothesize that the high intake of ascorbic acid has induced the formation of increased amounts of enzymes that help convert the ascorbic acid into other substances and that these substances are valuable. Some possible physiological actions of these ascorbic acid metabolites are discussed.

Effects of lipid peroxidation on adrenal microsomal monooxygenases

Incubation of guinea pig adrenal microsomes with 10(-6) M ferrous (Fe2+) ion and adrenal cytosol initiated high levels of lipid peroxidation as measured by the production of malonaldehyde. Cytosol or Fe2+ alone had little effect on microsomal malonaldehyde formation. When microsomes were incubated in the presence of Fe2+ and cytosol, malonaldehyde levels continued to increase for at least 60 min. Accompanying the lipid peroxidation was a decline in adrenal microsomal monooxygenase activities. The rates of metabolism of xenobiotics (benzphetamine demethylase, benzo[a]pyrene hydroxylase) as well as steroids (21-hydroxylation) decreased as malonaldehyde levels increased. In addition, cytochrome P-450 levels, NADPH- and NADH-cytochrome c reductase activities, and substrate interactions with cytochrome(s) P-450 decreased as lipid peroxidation progressed. Inhibition of lipid peroxidation by increasing microsomal protein concentrations during the incubation period prevented the changes in microsomal metabolism. Malonaldehyde had no direct effects on adrenal microsomal enzyme activities. The results indicate that lipid peroxidation may have significant effects on adrenocortical function, diminishing the capacity for both xenobiotic and steroid metabolism.

Ascorbic acid accumulation by cultured rat adrenocortical cells

The influence of adrenocorticotrophin (ACTH) on radiolabeled ascorbic acid (AA) accumulation by adrenocortical cells was examined in primary cultures of collagenase dissociated glands from adult male rats. The cells were ACTH responsive by morphological and steroidogenic criteria. After 5 d in AA-free medium, cells pretreated with 100 mU/ml ACTH for 3 d took up two to three times more AA over a 2 h period than did untreated controls (4.0 to 10.0 nmol versus 1.7 to 3.4 nmol AA/micrograms DNA). In contrast, ACTH administered on Day 6 concurrently with AA inhibited AA accumulation compared to cultures exposed to AA alone. This acute inhibitory effect of ACTH was in the order of 30% in cultures pretreated with ACTH for 3 d but was not significant (7%) without ACTH pretreatment. The results show that ACTH has distinct long term stimulatory and acute inhibitory effects on AA accumulation by adrenocortical cells and suggest that both maximal AA accumulation and the responsiveness to acute inhibition of AA accumulation by ACTH may depend on the maintenance of the differentiated state of the adrenal cortex.

Hormonal regulation of the adrenocortical cell

Monolayer cultures of bovine and human adrenocortical cells have been used to study regulation of growth and function. Homogeneous bovine adrenocortical cells exhibit a finite life span of approximately 60 generations in culture. Full maintenance of differentiated function (steroid hormone synthesis) requires an inducer such as ACTH and antioxidizing conditions. Full induction of differentiated function occurs only when cellular hypertrophy is stimulated by growth factors such as fibroblast growth factor and serum. ACTH and other agents that increase cellular cAMP inhibit replication but do not block growth factor-induced cellular hypertrophy. ACTH and growth factors together result in a hypertrophied, hyperfunctional cell. Replication ensues only when desensitization to the growth inhibitory effects of ACTH occurs. Cultures of the definitive and fetal zones of the human fetal adrenal cortex synthesize the steroids characteristic of the two zones in vivo. ACTH stimulates production of dehydroepiandrosterone (DHA), the major steroid product of the fetal zone, and of cortisol, the characteristic steroid product of the definitive zone. Prolonged ACTH treatment of fetal zone cultures results in a preferential increase in cortisol production so that the pattern of steroid synthesis becomes that of the definitive zone. The preferential increase in cortisol production by fetal Zone cultures results from induction of 3 beta-hydroxysteroid dehydrogenase, delta 4,5 isomerase activity, which is limiting in fetal zone cells. ACTH thus causes a phenotypic change in fetal zone cells to that of definitive zone cells. In both bovine and human adrenocortical cells, the principal effect of ACTH is to induce full expression of differentiated function. This occurs only under conditions where growth substances and nutrients permit full amplification.