Evaluation of tissue ascorbic acid status in different hormonal states of female rat

Attenuation of sodium arsenite mediated ovarian DNA damage, follicular atresia, and oxidative injury by combined application of vitamin E and C in post pubertal Wistar rats

Arsenic being a toxic metalloid ubiquitously persists in environment and causes several health complications including female reproductive anomalies. Epidemiological studies documented birth anomalies due to arsenic exposure. Augmented reactive oxygen species (ROS) generation and quenched antioxidant pool are foremost consequences of arsenic threat. On the contrary, Vitamin E (VE) and C (VC) are persuasive antioxidants and conventionally used in toxicity management. Present study was designed to explore the extent of efficacy of combined VE and VC (VEC) against Sodium arsenite (NaAsO2) mediated ovarian damage. Thirty-six female Wistar rats were randomly divided into three groups (Grs) and treated for consecutive 30 days; Gr I (control) was vehicle fed, Gr II (treated) was gavaged with NaAsO2 (3 mg/kg/day), Gr III (supplement) was provided with VE (400 mg/kg/day) & VC (200 mg/kg/day) along with NaAsO2. Marked histological alterations were evidenced by disorganization in oocyte, granulosa cells and zona pellucida layers in treated group. Considerable reduction of different growing follicles along with increased atretic follicles was noted in treated group. Altered activities ofΔ5 3β-Hydroxysteroid dehydrogenase and 17β-Hydroxysteroid dehydrogenase accompanied by reduced luteinizing hormone, follicle-stimulating hormone and estradiol levels were observed in treated animals. Irregular estrous cyclicity pattern was also observed due to NaAsO2 threat. Surplus ROS production affected ovarian antioxidant strata as evidenced by altered oxidative stress markers. Provoked oxidative strain further affects DNA status of ovary. However, supplementation with VEC caused notable restoration from such disparaging effects of NaAsO2 toxicities. Antioxidant and antiapoptotic attributes of those vitamins might be liable for such restoration.

Effects of Low Vitamin C Intake on Fertility Parameters and Pregnancy Outcomes in Guinea Pigs

Identifying how specific nutrients can impact fertility, pregnancy, and neonatal outcomes will yield important insights into the biological mechanisms linking diet and reproductive health. Our study investigates how dietary vitamin C intake affects various fertility parameters and pregnancy and neonatal outcomes in the guinea pig, a natural model of vitamin C dependency. Dunkin Hartley guinea pigs were fed an optimal (900 mg/kg feed) or low (100 mg/kg feed) vitamin C diet ad libitum for at least three weeks prior to mating and throughout pregnancy. We found that animals receiving the low vitamin C diet had an increased number of unsuccessful matings, a higher incidence of foetal reabsorption, and, among pregnancies resulting in delivery at term, produced fewer offspring. Neonates from mothers on the low vitamin C diet had significantly decreased plasma vitamin C concentrations at birth and exhibited mild growth impairments in a sex-dependent manner. We conclude that a diet low of vitamin C induces a state of subfertility, reduces overall fecundity, and adversely impacts both pregnancy outcomes and growth in the offspring. Our study provides an essential foundation for future investigations to determine whether these findings translate to humans. If so, they could have important clinical implications for assisted reproductive technologies and nutritional recommendations for couples trying to conceive, pregnant women, and breastfeeding mothers.

Stress amelioration potential of vitamin C in ruminants: a review

Ruminants, as well as other livestock, can synthesize vitamin C (VC) in their liver, and therefore, dietary requirements from exogenous supplementation are often ignored. However, metabolic demand may be exceeded, leading to a decreased endogenous synthetic capacity of VC following exposure to stressful conditions. Such conditions include high thermal load, limited water intake (induced by water scarcity), physiological status and infectious diseases. The obvious consequences are decreased performance, susceptibility to infections and increased mortality. This review discusses the potential role of vitamin C in ruminants' stress management and summarizes the in vitro and in vivo research to date. The different administration routes, comparative advantages and supplementation outcomes on growth, production parameters and physiological status were also identified. Also, areas where there was a lack of evidence or controversy, including critical literature research gaps, were identified, while the mechanism of VC's actions on significant outcomes was explained.

Inhibition of Stimulated Ascorbic Acid and Luteinizing Hormone-Releasing Hormone Release by Nitric Oxide Synthase or Guanyl Cyclase Inhibitors

Ascorbic acid (AA), an antioxidant, is present in high concentrations in the hypothalamus. Previously, we have shown that AA inhibited stimulated release of luteinizing hormone-releasing hormone (LHRH) from medial basal hypothalami in vitro. We have also demonstrated that cell membrane depolarization by high [K+] media-induced AA release that is blocked by NG-monomethyl-l-arginine, a competitive inhibitor of nitric oxide synthase (NOS), indicating that the release process is mediated by NO. The release of LHRH is also mediated by NO. We hypothesized that AA is a co-transmitter released with classical transmitters from synaptic vesicles that acts to reduce chemically the NO formed, thereby providing feed-forward inhibitory control over LHRH release. Because NO acts by activating guanylyl cyclase (GC) resulting in production of cGMP, in the present investigation we studied the effects of an NOS inhibitor LY 83583 and GC inhibitor, O.D.Q. to further characterize the role of NO in high [K+]-induced AA and LHRH release. Medial basal hypothalami were incubated in 0.5 ml of Krebs-Ringer Bicarbonate buffer or medium containing increased potassium [K+ = 56 mM] for 1 hr or combinations of high [K+] + LY 83583 or O.D.Q. for 1 hr. AA and LHRH released into the incubation medium were measured by high-pressure liquid chromatography and radioimmunoassay, respectively. Cell membrane depolarization with high [K+] produced a significant increase in both AA and LHRH release. A combination of high [K+] + LY 83583 or high [K+] + O.D.Q. decreased basal AA and completely blocked high [K+]-induced AA and LHRH release. As in the case of high [K+], LHRH release induced by the excitatory amino acid N-methyl-d-aspartic acid (NMDA) was blocked by both the inhibitors. NMDA alone failed to alter AA release, but the combined presence of NMDA and the inhibitors totally blocked AA release. Because LY 83583 and O.D.Q. were shown to inhibit NOS and soluble GC, respectively, the data demonstrate that basal and high [K+]-induced AA and high [K+] and NMDA-stimulated LHRH release were mediated by NO by its activation of GC and consequent generation of cGMP.

Impact of polychlorinated biphenyl Aroclor 1254 on testicular antioxidant system in adult rats

To clarify the reproductive toxicity of polychlorinated biphenyl compounds through determination of testicular lipid peroxidation, reactive oxygen species and enzymatic and non-enzymatic antioxidants in rats exposed to Aroclor 1254. Adult male rats were administered Aroclor 1254 at a dose of 2 mg/kg per day ip for 30 days. The rats were sacrificed 24 hours after last dosing and the serum and other tissues collected and processed for relevant determinations. The body weight and the weights of the testis, epididymis, ventral prostate and seminal vesicle and the serum testosterone and estradiol were significantly decreased in Aroclor 1254 treated rats. The testicular lipid peroxidation, hydrogen peroxide and hydroxyl radical were significantly elevated whereas, testicular antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione-S-transferase (GST) and glutathione reductase (GR) were significantly decreased. The non-enzymatic antioxidants, vitamin C and vitamin E, were also decreased. These results suggest that Aroclor 1254 induces an increase in the lipid peroxidation, hydrogen peroxide and hydroxyl radical and diminish in the antioxidant defense system in rats, indicating that the free radical-dependent mechanism may play an important role in the testicular toxicity of polychlorinated biphenyls.

Ascorbic acid treatment elevates follicle stimulating hormone and testosterone plasma levels and enhances sperm quality in albino Wistar rats

BACKGROUND

Infertility issues have been linked to the effect of oxidative reaction in the reproductive system. This study evaluated the effect of ascorbic acid, on fertility parameters of male albino Wistar rats was studied.

MATERIALS AND METHODS

Eighteen albino Wistar rats weighed between 178 g and 241 g were used, randomly assigned into three groups. Group 1 was the control group; oral gavaged 5 ml of distilled water; Groups 2 and 3 were administered medium dose (250 mg/kg) and high dose of ascorbic acid (400 mg/kg), respectively; twice daily for 21 days. Blood samples were obtained by cardiac puncture, and blood serum was obtained for hormonal assay, and the testes were harvested for sperm analysis.

RESULTS

Follicle stimulating hormone levels significantly increased in the high-dose group as compared to both the control and medium dose groups. Luteinizing hormone levels in the medium dose group decreased significantly as compared to the control group. Testosterone significantly increased in both the medium- and high-dose groups as compared to the control group. Sperm motility increased significantly in the high-dose group as compared to both control and medium-dose groups. Percentage sperm concentration decreased significantly in the medium-dose group when compared to the control and increased significantly in the high-dose group as compared to the medium-dose group. For percentage normal morphology, there was a dose-dependent increase in the test groups when compared to control group.

CONCLUSION

These results are indicative of a positive influence of ascorbic acid on male fertility modulators and may therefore, serve as a potential adjuvant treatment for male infertility cases.

Increased TRH and TRH-like peptide release in rat brain and peripheral tissues during proestrus/estrus

Women are at greater risk for major depression, PTSD, and other anxiety disorders. ERβ-selective agonists for the treatment of these disorders are the focus of pharmacologic development and clinical testing. Estradiol and its metabolites contribute to the neuroprotective effects of this steroid class, particularly in men, due to local conversion of testosterone to estiradiol in key brain regions which are predisposed to neurodegenerative diseases. We have used young adult female Sprague-Dawley rats to assess the role of TRH and TRH-like peptides, with the general structure pGlu-X-Pro-NH2 where "X" can be any amino acid residue, as mediators of the neurobiochemical effects of estradiol. The neuroprotective TRH and TRH-like peptides are coreleased with excitotoxic glutamate by glutamatergic neurons which contribute importantly to the regulation of the estrus cycle. The levels of TRH and TRH-like peptides during proestrus and/or estrus in the 12 brain regions analyzed were significantly decreased (due to accelerated release) 106 times but increased only 25 times when compared to the corresponding levels during diestrus days 1 and 2. These changes, listed by brain region in the order of decreasing number of significant decreases (↓) and/or increases (↑), were: striatum (20↓,1↑), medulla oblongata (16↓,2↑), amygdala (14↓,1↑), cerebellum (13↓,1↑), hypothalamus (12↓,1↑), entorhinal cortex (6↓,6↑), posterior cingulate (10↓,1↑), frontal cortex (3↓,5↑), nucleus accumbens (5↓,3↑), hippocampus (5↓,2↑), anterior cingulate (2↓,1↑), and piriform cortex (1↑). In peripheral tissues the corresponding changes were: ovaries (23↓), uterus (16↓,1↑), adrenals (11↓,3↑), and pancreas (1↓,6↑). We conclude that these peptides may be downstream mediators of some of the therapeutic effects of estrogen.

Ascorbic acid supplementation enhances recovery from ethanol induced inhibition of Leydig cell steroidogenesis than abstention in male guinea pigs

The impact of ascorbic acid supplementation against ethanol induced Leydig cell toxicity was studied in guinea pigs. Male guinea pigs were exposed to ethanol (4g/kgb.wt.) for 90 days. After 90 days, ethanol administration was completely stopped and animals in the ethanol group were divided into abstention group and ascorbic acid supplemented group (25mg/100gb.wt.) and those in control group were maintained as control and control+ascorbic acid group. Ethanol administration reduced the serum testosterone and LH (luteinising hormone) levels and elevated estradiol levels. Cholesterol levels in Leydig cell were increased whereas the mRNA and protein expressions of StAR (steroidogenic acute regulatory) protein, cytochrome P450scc (cytochrome p450side chain cleavage enzyme), 3β-HSD (3β-hydroxysteroid dehydrogenase), 17β-HSD (17β-hydroxysteroid dehydrogenase) and LH receptor were drastically reduced. Administration of ascorbic acid resulted in alteration of all these parameters indicating enhanced recovery from ethanol induced inhibition of Leydig cell steroidogenesis. Although abstention could also reduce the inhibition of steroidogenesis, this was lesser in comparison with ascorbic acid supplemented group.

Hormones and antioxidant systems: role of pituitary and pituitary-dependent axes

Oxidative stress, a condition defined as unbalancing between production of free radicals and antioxidant defenses, is an important pathogenetic mechanism in different diseases. Despite the abundant literature, many aspects of hormone role in regulating antioxidant synthesis and activity still remain obscure. Therefore, we reviewed experimental data, in vivo and in vitro, about the effects of the different pituitary- dependent axes on antioxidant levels, trying to give a broad view from hormones which also have antioxidant properties to the classic antioxidants, from the lipophilic antioxidant Coenzyme Q10, strictly related to thyroid function, to total antioxidant capacity, a measure of non-protein non-enzymatic antioxidants in serum and other biological fluids. Taken together, these data underline the importance of oxidative stress in various pituitary-dependent disorders, suggesting a possible clinical usefulness of antioxidant molecules.

Studies on the protective role of vitamin C and E against polychlorinated biphenyl (Aroclor 1254)--induced oxidative damage in Leydig cells

Free radical production and lipid peroxidation are potentially important mediators in testicular physiology and toxicology. Polychlorinated biphenyls (PCBs) are global environmental contaminants that cause disruption of the endocrine system in human and animals. The present study was conducted to elucidate the protective role of vitamin C and E against Aroclor 1254-induced changes in Leydig cell steroidogenesis and antioxidant system. Adult male rats were dosed for 30 days with daily intraperitoneal (ip) injection of 2 mg/kg Aroclor or vehicle (corn oil). One group of rats was treated with vitamin C (100 mg/kg bw/day) while the other group was treated with vitamin E (50 mg/kg bw/day) orally, simultaneously with Aroclor 1254 for 30 days. One day after the last treatment, animals were euthanized and blood was collected for the assay of serum hormones such as luteinizing hormone (LH), thyroid stimulating hormone (TSH), prolactin (PRL), triiodothyronine (T(3)), thyroxine (T(4)), testosterone and estradiol. Testes were quickly removed and Leydig cells were isolated in aseptic condition. Purity of Leydig cells was determined by 3beta-hydroxysteroid dehydrogenase (3beta-HSD) staining method. Purified Leydig cells were used for quantification of cell surface LH receptors and steroidogenic enzymes such as cytochrome P(450) side chain cleavage enzyme (P(450)scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD) and 17beta-hydroxysteroid dehydrogenase (17beta- HSD). Leydig cellular enzymatic antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), gamma-glutamyl transpeptidase (gamma-GT), glutathione-S-transferase (GST) and non-enzymatic antioxidants such as vitamin C and E were assayed. Lipid peroxidation (LPO) and reactive oxygen species (ROS) were also estimated in Leydig cells. Aroclor 1254 treatment significantly reduced the serum LH, TSH, PRL, T(3), T(4), testosterone and estradiol. In addition to this, Leydig cell surface LH receptors, activities of the steroidogenic enzymes such as cytochrome P(450)scc, 3beta-HSD, 17beta-HSD, antioxidant enzymes SOD, CAT, GPX, GR, gamma-GT, GST and non-enzymatic antioxidants such as vitamin C and E were significantly diminished whereas, LPO and ROS were markedly elevated. However, the simultaneous administration of vitamin C and E in Aroclor 1254 exposed rats resulted a significant restoration of all the above-mentioned parameters to the control level. These observations suggest that vitamin C and E have ameliorative role against adverse effects of PCB on Leydig cell steroidogenesis.

Sodium vitamin C cotransporter SVCT2 is expressed in hypothalamic glial cells

Kinetic analysis of vitamin C uptake demonstrated that different specialized cells take up ascorbic acid through sodium-vitamin C cotransporters. Recently, two different isoforms of sodium-vitamin C cotransporters (SVCT1/SLC23A1 and SVCT2/SLC23A2) have been cloned. SVCT2 was detected mainly in choroidal plexus cells and neurons; however, there is no evidence of SVCT2 expression in glial and endothelial cells of the brain. Certain brain locations, including the hippocampus and hypothalamus, consistently show higher ascorbic acid values compared with other structures within the central nervous system. However, molecular and kinetic analysis addressing the expression of SVCT transporters in cells isolated from these specific areas of the brain had not been done. The hypothalamic glial cells, or tanycytes, are specialized ependymal cells that bridge the cerebrospinal fluid with different neurons of the region. Our hypothesis postulates that SVCT2 is expressed selectively in tanycytes, where it is involved in the uptake of the reduced form of vitamin C (ascorbic acid), thereby concentrating this vitamin in the hypothalamic area. In situ hybridization and optic and ultrastructural immunocytochemistry showed that the transporter SVCT2 is highly expressed in the apical membranes of mouse hypothalamic tanycytes. A newly developed primary culture of mouse hypothalamic tanycytes was used to confirm the expression and function of the SVCT2 isoform in these cells. The results demonstrate that tanycytes express a high-affinity transporter for vitamin C. Thus, the vitamin C uptake mechanisms present in the hypothalamic glial cells may perform a neuroprotective role concentrating vitamin C in this specific area of the brain.

GM1 ganglioside attenuates convulsions and thiobarbituric acid reactive substances production induced by the intrastriatal injection of methylmalonic acid

The effects of the administration of monosialoganglioside (GM1) on methylmalonic acid (MMA)-induced convulsions, production of thiobarbituric acid reactive substances (TBARS) and on the striatal content of ascorbic acid and total non-protein thiol (SH) groups were evaluated in adult male rats. Animals received two intraperitoneal injections of GM1 (50 mg/kg) or saline (0.85% NaCl) spaced 24h apart. Thirty minutes after the second GM1 or saline injection, L-MMA (6 micromol) or NaCl (9 micromol) was injected into the right striatum and the animals were observed for the appearance of convulsions for 15 min. The animals were sacrificed and their striatal content of ascorbic acid, SH groups and TBARS was measured. The effect of GM1 on MMA-induced TBARS production in striatal homogenates was also evaluated in vitro.MMA injection caused convulsions (Sal-MMA: 9.8+/-1.4 episodes, which lasted 271+/-48 s) and increased the striatal content of TBARS (Sal-MMA: 149.0+/-11.5 nmol MDA/g tissue), but did not alter total striatal SH or ascorbic acid contents. GM1 pretreatment decreased MMA-induced convulsions (GM1-MMA: 6.3+/-2.0 episodes, which lasted 115.1+/-42.2s) and TBARS increase (GM1-MMA: 102.4+/-19.5 nmol MDA/g tissue). GM1 pretreatment increased ascorbic acid content of the striata (saline-pretreated: 1514+/-75.9; GM1-pretreated: 1878.6+/-102.8 microg ascorbic acid/mg tissue). MMA increased TBARS production in vitro, and GM1 had no effect on such MMA-induced effect. This study provides evidence that GM1 increases striatal ascorbic acid content and decreases MMA-induced neurotoxicity assessed by behavioral and neurochemical parameters.

Oral ascorbic acid increases plasma oestradiol during postmenopausal hormone replacement therapy

OBJECTIVES

To study the possible interaction between ascorbic acid (AA) and oestradiol (E2) in postmenopausal women on hormone replacement therapy (HRT).

METHODS

We studied 25 healthy postmenopausal women who had used percutaneous E2 gel at same dose for 10-12 months, at which time the plasma E2 concentrations were stabilized. The subjects were treated with 1000 mg of AA daily for 3 months and blood samples for assay of AA and E2 were taken at 0, 1 and 3 months.

RESULTS

After 1 month of AA treatment, there was an overall increase of 20.8% in E2 levels in the group as a whole. Greater responses were seen in two subgroups. In women with initially the lowest plasma concentrations of AA (<70 micromol/l), there was an increase of 55% in plasma E2 levels which was close to significance (P=0.063). In another subgroup with initially the lowest E2 levels (<0.20 nmol/l) there was a marked and significant increase (from 0.13 to 0.26 nmol/l) in plasma E2 concentrations (P=0.028).

CONCLUSIONS

Our results support early findings that AA may interact with oestrogen therapy. Possible interaction of AA with E2 at the level of antioxidation is discussed.

Ascorbic acid stimulates gonadotropin release by autocrine action by means of NO

Because high concentrations of ascorbic acid (AA) are found in the adenohypophysis, we hypothesized that it might have an acute effect on the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the gland, particularly because we have reported that AA rapidly inhibits stimulated LH-releasing hormone (LHRH) release from medial basal hypothalamic explants. Incubation of anterior pituitary halves from adult male rats with graded concentrations of AA for 1 h induced highly significant release of both FSH and LH with a minimal effective concentration of 10(-5) M. Release remained on a plateau from 10(-5) to 10(-2) M. When both AA and an effective concentration of LHRH were incubated together, there was no additive response to LHRH and the response was the same as to either compound alone. The FSH and LH release in response to AA was blocked by incubation with N(G)-monomethyl-l-arginine (NMMA) (300 microM), a competitive inhibitor of NO synthase. NMMA also inhibited LHRH-induced LH and FSH release and gonadotropin release in the presence of both LHRH and AA, whereas sodium nitroprusside, a releaser of NO, stimulated LH and FSH release. Membrane depolarization caused by incubation in high potassium (K(+) = 28 or 56 mM) medium stimulated release of FSH, LH, and AA that was blocked by NMMA. We hypothesize that AA is released with FSH and LH from secretory granules. AA is transported back into gonadotropes by the AA transporter and increases intracellular [Ca(2+)]-activating NO synthase that evokes exocytosis of gonadotropins and AA by cGMP.

Ascorbic acid acts as an inhibitory transmitter in the hypothalamus to inhibit stimulated luteinizing hormone-releasing hormone release by scavenging nitric oxide

Because ascorbic acid (AA) is concentrated in synaptic vesicles containing glutamic acid, we hypothesized that AA might act as a neurotransmitter. Because AA is an antioxidant, it might therefore inhibit nitric oxidergic (NOergic) activation of luteinizing hormone-releasing hormone (LH-RH) release from medial basal hypothalamic explants by chemically reducing NO. Cell membrane depolarization induced by increased potassium concentration [K(+)] increased medium concentrations of both AA and LH-RH. An inhibitor of NO synthase (NOS), N(G)-monomethyl-l-arginine (NMMA), prevented the increase in medium concentrations of AA and LH-RH induced by high [K(+)], suggesting that NO mediates release of both AA and LH-RH. Calcium-free medium blocked not only the increase in AA in the medium but also the release of LH-RH. Sodium nitroprusside, which releases NO, stimulated LH-RH release and decreased the concentration of AA in the incubation medium, presumably because the NO released oxidized AA to dehydro-AA. AA (10(-5) to 10(-3) M) had no effect on basal LH-RH release but completely blocked high [K(+)]- and nitroprusside-induced LH-RH release. N-Methyl-d-aspartic acid (NMDA), which mimics the action of the excitatory amino acid neurotransmitter glutamic acid, releases LH-RH by releasing NO. AA (10(-5) to 10(-3) M) inhibited the LH-RH-releasing action of NMDA. AA may be an inhibitory neurotransmitter that blocks NOergic stimulation of LH-RH release by chemically reducing the NO released by the NOergic neurons.

Enhanced oxidative stress in female rat brain after gonadectomy

Oxidative stress, assessed by tissue ascorbate loss following ischemia, is greater in male than female rat brain. The factors mediating this gender difference are unclear. The goal of the present studies was to determine the influence of gonadal sex hormones on this difference. Three weeks prior to experiment, adult Long-Evans male and female rats were gonadectomized for comparison with controls. Ascorbate and glutathione levels were determined in brain and plasma under basal conditions and in brain after one-hour decapitation ischemia, using liquid chromatography with electrochemical detection. Basal ascorbate levels in brain were 6-9% higher in males than in females, whereas plasma levels were 100% higher in males. After gonadectomy, the gender difference in plasma ascorbate levels was lost, while the effect on basal brain levels depended upon region. Ischemia-induced losses in brain ascorbate were three-fold greater in control males compared to control females. Significant losses occurred in frontal cortex, hippocampus, and cerebellum in males during ischemia, whereas loss in females was significant in cerebellum only. After gonadectomy, increased ascorbate loss was seen in all female brain regions, indicating enhanced oxidative stress. This increase eliminated the gender difference in loss; male ascorbate loss was comparatively unaffected by gonadectomy. Glutathione levels and loss were unaffected by either gender or gonadectomy, indicating differences in regulation from that of ascorbate. These findings provide evidence for the hypothesis that protection against oxidative stress is afforded by ovarian sex hormones, thus decreasing the potential for oxidative cell damage in females compared to males.