Antioxidant capacity is correlated with steroidogenic status of the corpus luteum during the bovine estrous cycle

The investigation of the effects of vitamin A, vitamin E, and β-carotene plus vitamin E on some fertility parameters in ewes

This study was aimed at investigating the effects of vitamin A (VITA), vitamin E (VITE), and combined β-carotene plus vitamin E (βCAR+VITE) injections on some fertility parameters in ewes. Estrus synchronization was performed by treating the ewes with intravaginal FGA sponges impregnated with 30 mg of fluorogestone acetate. On the days of the insertion and withdrawal of the intravaginal sponges, groups VITA, VITE, and βCAR+VITE were administered with 500 000 IU of vitamin A, 50 mg of vitamin E, and a combination of β-carotene plus vitamin E, respectively. The ewes in the control group (C) were maintained for control purposes. Statistically significant differences were determined between groups VITA and βCAR+VITE, groups VITE and βCAR+VITE, and groups C and βCAR+VITE, as well as groups VITE and C, groups VITA and C for the multiple birth rates. While significant differences were determined between groups VITA and C, groups VITE and C, and groups βCAR+VITE and C for the lambing rates, it was ascertained that the ratio of newborn lambs to delivered ewes (litter size) significantly differed between groups VITA and βCAR+VITE, groups VITA and C, groups VITE and βCAR+VITE, groups VITE and C, and groups βCAR+VITE and C. The highest MDA level and lowest GSH level were determined on day 20 after mating in the control group. In conclusion, it is suggested that both multiple birth rates and litter size can be increased by the combined administration of β-carotene and vitamin E.

High β ‐ carotene concentration in plasma enhances cyclic progesterone production in nonpregnant Japanese Black cows

β-Carotene is an essential nutrient in cattle reproduction. The objective of this study was to evaluate the effect of β-carotene supplementation on ovarian activities throughout the estrous cycle in nonpregnant Japanese Black cows. The estrous cycles of eight nonpregnant Japanese Black cows were synchronized using a double synch protocol, and the cows were divided into two groups. The cows in the β-carotene (BC) group received supplementation with 1000 mg/day β-carotene for 46 days including the synchronization period. The cows in the control (C) group did not receive β-carotene supplementation. The results showed that β-carotene supplementation at 1000 mg/day was sufficient to maintain a high plasma β-carotene concentration and increase the plasma retinol concentration and that β-carotene supplementation had no significant effects on the dominant follicle diameter, total number of estrus behaviors, or length of the estrous cycle. In contrast, the areas under the P₄ concentration curves in the BC group were higher than those obtained for the C group. In conclusion, a high plasma β-carotene concentration in Japanese Black cows promotes P₄ production in the luteal phase of the estrous cycle and total P₄ production throughout the estrous cycle without changing the length of the estrous cycle.

Pathological Role of Reactive Oxygen Species on Female Reproduction

Oxidative stress (OS), a clinical predicament characterized by a shift in homeostatic imbalance among prooxidant molecules embracing reactive oxygen species (ROS) and reactive nitrogen species (RNS), along with antioxidant defenses, has been established to play an indispensable part in the pathophysiology of subfertility in both human males and females. ROS are highly reactive oxidizing by-products generated during critical oxygen-consuming processes or aerobic metabolism. A healthy body system has its own course of action to maintain the equilibrium between prooxidants and antioxidants with an efficient defense system to fight against ROS. But when ROS production crosses its threshold, the disturbance in homeostatic balance results in OS. Besides their noxious effects, literature studies have depicted that controlled and adequate ROS concentrations exert physiologic functions, especially that gynecologic OS is an important mediator of conception in females. Yet the impact of ROS on oocytes and reproductive functions still needs a strong attestation for further analysis because the disruption in prooxidant and antioxidant balance leads to abrupt ROS generation initiating multiple reproductive diseases such as polycystic ovary syndrome (PCOS), endometriosis, and unexplained infertility in addition to other impediments in pregnancy such as recurrent pregnancy loss, spontaneous abortion, and preeclampsia. The current article elucidates the skeptical state of affairs created by ROS that influences female fertility.

Loss of luteal sensitivity to luteinizing hormone underlies luteolysis in cattle: A hypothesis

By virtue of the secretion of progesterone (P4), corpus luteum (CL) is important not only for normal cyclicity but also for conception and continuation of pregnancy in female mammals. Luteolysis (also called luteal regression) is defined as loss of the capacity to synthesize and secrete P4 followed by the demise of the CL. There is strong evidence that sequential pulses of prostaglandin F2α (PGF) secreted from the uterus near the end of luteal phase induces luteolysis in farm animals. Loss of luteal sensitivity to luteinizing hormone (LH) at the end of menstrual cycle has been reported to be critical for initiation of luteolysis in primates, however this has not been investigated in farm animals. A closer observation of the published real-time profiles of circulating hormones (P4, LH, and PGF) and their inter-relationships around the time of the beginning of spontaneous luteolysis in cattle revealed- 1) A natural pulse of PGF causes a transient P4 suppression lasting a couple of hours followed by a rebound in P4 concentration, 2) The P4 secretions that occur in response to LH pulses before the beginning of luteolysis (i.e., preluteolysis) either fail or do so to a lesser extent during luteolysis indicating a loss of sensitivity to LH, and 3) The loss of sensitivity coincides with the beginning of luteolysis (i.e., transition), and apparently luteolysis does not initiate until there is loss of sensitivity to LH. The CL is sensitive to LH during preluteolysis, and the LH-stimulated P4-dependent and/or independent local survival mechanisms maintain the steroidogenic capability and viability of the CL until the very end of preluteolysis. Luteolysis does not appear to initiate with the PGF pulse(s) that occur during this period. With the loss of sensitivity to LH at the transition, however, a progressive decline in P4 begins initiating luteolysis. Also, the survival mechanisms become compromised making the CL less viable. The uterine PGF pulses that occur after the beginning of luteolysis induces increase in the local luteolytic factors, which contribute to further luteolysis, more importantly, structural luteolysis with ultimate demise of the CL. Therefore, I hypothesize that the loss of luteal sensitivity to LH underlies luteolysis in cattle. The hypothesis not only unifies the basic mechanism of luteolysis in a farm animal and primates but also provides a perspective to view luteolysis as a process rather than a factor-mediated event. A novel unified working model for luteolysis in a farm animal and primates is described. A better understanding of the luteal physiology including how responsiveness to LH diminishes in aging CL would help in the development of novel strategies in modulating CL structure-function to improve and/or control fertility in humans as well as in animals.

GPx8 Expression in Rat Oocytes, Embryos, and Female Genital Organs During Preimplantation Period of Pregnancy

This study aimed to detect the presence of glutathione peroxidase 8 (GPx8) in rat during preimplantation period of pregnancy. Females were killed on first (D1), third (D3), and fifth (D5) day of pregnancy. The presence of GPx8 in embryos was detected under the confocal microscope, the presence of GPx8 in genital organs was confirmed immunohistochemically, and the amount of GPx8 was determined using densitometry. We found that GPx8 is dispersed in the cytoplasm of oocytes, while after fertilization, it is concentrated in granules. From 4-cell stage till blastocyst, GPx8 reaction was found in the perinuclear region. In the ovary, GPx8 was seen in granulosa-lutein cells, in plasma of blood vessels, and inside Graafian follicles. In oviduct, GPx8 was detected in the plasma and in the extracellular matrix (ECM). Moreover, epithelial cells of isthmus were positive. In uterus, GPx8 was observed in the uterine glands, in the plasma, and in ECM. On D5, the enzyme disappeared from the uterine glands and appeared in fibroblasts. Densitometry revealed that the highest amount of GPx8 was on D1 and subsequently declined. To our knowledge, this is the first paper describing GPx8 presence in the oocytes, preimplantation embryos, and female genital organs in mammals. Our results improve the understanding of antioxidant enzymes presence during pregnancy in defense against oxidative stress, which is considered to be one of the main causes of infertility.

Trafficking of cholesterol from lipid droplets to mitochondria in bovine luteal cells: Acute control of progesterone synthesis

The corpus luteum is a transient endocrine gland that synthesizes and secretes the steroid hormone, progesterone, which is vital for establishment and maintenance of pregnancy. Luteinizing hormone (LH) via activation of protein kinase A (PKA) acutely stimulates luteal progesterone synthesis via a complex process, converting cholesterol via a series of enzymatic reactions, into progesterone. Lipid droplets in steroidogenic luteal cells store cholesterol in the form of cholesterol esters, which are postulated to provide substrate for steroidogenesis. Early enzymatic studies showed that hormone sensitive lipase (HSL) hydrolyzes luteal cholesterol esters. In this study, we tested whether HSL is a critical mediator of the acute actions of LH on luteal progesterone production. Using LH-responsive bovine small luteal cells our results reveal that LH, forskolin, and 8-Br cAMP-induced PKA-dependent phosphorylation of HSL at Ser563 and Ser660, events known to promote HSL activity. Small molecule inhibition of HSL activity and siRNA-mediated knock down of HSL abrogated LH-induced progesterone production. Moreover, western blotting and confocal microscopy revealed that LH stimulates phosphorylation and translocation of HSL to lipid droplets. Furthermore, LH increased trafficking of cholesterol from the lipid droplets to the mitochondria, which was dependent on both PKA and HSL activation. Taken together, these findings identify a PKA/HSL signaling pathway in luteal cells in response to LH and demonstrate the dynamic relationship between PKA, HSL, and lipid droplets in luteal progesterone synthesis.

The antioxidative enzyme SOD2 is important for physiological persistence of corpora lutea in lynxes

Corpora lutea (CL) are transient endocrine glands supporting pregnancy by progesterone production. They develop at the site of ovulation from the remaining follicle, are highly metabolically active and undergo distinct, transformative processes during their lifetime. In contrast to other species, CL of lynxes do not regress at the end of cycle, but remain functionally active (persist) for years. Reactive oxygen species (ROS) and anti-oxidative enzymes are described to be important for the functionality of CL. We examined ten anti-oxidative enzymes in fresh and persistent CL of lynxes as well as in domestic cat CL of different luteal stages. The gene expression profiles, especially those of SOD1 and SOD2, showed some remarkable differences between CL stages during non-pregnant and pregnant cycles of domestic cats and between fresh and persistent CL of lynxes. Lynx gene expression profiles of SODs were confirmed by western blot analysis, immunohistochemistry and activity assays. SOD2 was characterized by a conspicuous high expression and enzyme activity exclusively in persistent CL. We suggest that SOD2 is required to detoxify potential elevated superoxide anion levels by producing H₂O₂ in the physiologically persistent CL. This product might also act as a signaling molecule, securing the CL from apoptosis and insuring long-term luteal cell survival.

Heat exposure affected the reproductive performance of pregnant mice: Enhancement of autophagy and alteration of subcellular structure in the corpus luteum

To investigate whether autophagy and subcellular changes are involved in the corpus luteum after heat exposure, a total of 30 early pregnant mice were divided equally into heat stress (HS) and non-HS (NHS) groups (n = 15). Mice in the HS group were exposed to 40.5 ± 0.2 ℃ for 7 consecutive days. Ovaries were collected for immunohistochemistry (IHC), western blot (WB) analysis and transmission electron microscopy (TEM). Serum was collected to determine progesterone by RIA and uteri were collected to count the implantation sites. Results showed that heat exposure increased rectal temperature, decreased body weight and number of implantation sites. WB analysis revealed that ovarian expression of LC3B and Atg7 was up-regulated, while p62 was down-regulated in the HS group. IHC results demonstrated that ovarian staining intensity of LC3B was more intense in the HS group than that of the NHS group. LC3B was mainly localized in the granulosa cells, oocytes and luteal steroidogenic cells of the HS group. TEM results revealed double-layered separated membranes indicative of autophagosomes in the luteal steroidogenic cells of the HS group. Moreover, TEM showed that the mitochondrial cristae became dearth, structure-less, swollen after HS. Additionally, the nucleus expanded and accumulation of lipid droplets increased after HS. Results also showed that heat exposure decreased serum progesterone level and ovarian P450scc expression. These results indicate that HS enhanced autophagy and altered the subcellular structure of luteal steroidogenic cells, which may contribute to interfering with the maintenance of luteal function in early pregnant mice.

Peroxiredoxin I maintains luteal function by regulating unfolded protein response

BACKGROUND

Mounting evidence shows that ROS regulation by various antioxidants is essential for the expression of enzymes involved in steroidogenesis and maintenance of progesterone production by the corpus luteum (CL). However, the underlying mechanisms of peroxiredoxin 1 (PRDX1), an antioxidant enzyme, in luteal function for progesterone production in mice have not been reported. The aim of this study was to evaluate the functional link between PRDX1 and progesterone production in the CL of Prdx1 knockout (K/O) mice in the functional stage of CL.

METHODS

The expression pattern of the unfolded protein response (UPR) signaling pathways, endoplasmic reticulum (ER) stress-induced apoptosis related genes and peroxiredoxins 1 (PRDX1) were investigated by western blotting analysis in CL tissue of 10 weeks mice during functional stage of CL. The protein levels of these genes after ER-stress inducer tunicamycin (Tm), ER-stress inhibitor tauroursodeoxycholic acid (TUDCA) and ROS scavenger, N-acetylcysteine (NAC) stimulation by intraperitoneal (i.p) injection were also investigated in CL tissue of wild type (WT) mice. Finally, we examined progesterone production and UPR signaling related gene expression in CL tissue of Prdx1 K/O mice.

RESULTS

We demonstrated that PRDX1 deficiency in the functional stage activates the UPR signaling pathways in response to ER stress-induced apoptosis. Interestingly, CL number, serum progesterone levels, and steroidogenic enzyme expression in Prdx1 K/O mice decreased significantly, compared to those in wild type mice. Levels of UPR signaling pathway markers (GRP78/BIP, P50ATF6, and phosphorylated (p)-eIF2) and ER-stress associated apoptotic factors (CHOP, p-JNK, and cleaved caspase-3) were dramatically increased in the CL tissue of Prdx1 K/O mice. In addition, administration of the NAC, reduced progesterone production and activated ER-stress-induced UPR signaling in the CL tissue obtained from the ovary of Prdx1 K/O mice. Taken together, these results indicated that reduction in serum progesterone levels and activation of ER-stress-induced UPR signaling are restored by NAC injection in the CL of Prdx1 K/O mice.

CONCLUSION

These observations provide the first evidence regarding the basic mechanisms connecting PRDX1 and progesterone production in the functional stage of CL.

GSTA1 Expression Is Correlated With Aldosterone Level in KCNJ5-Mutated Adrenal Aldosterone-Producing Adenoma

CONTEXT

KCNJ5 mutation is a major cause of aldosterone-producing adenomas (APAs). The development of APA apart from KCNJ5 mutation is less investigated.

OBJECTIVE

To investigate other mechanisms affecting aldosterone secretion apart from KCNJ5.

PATIENTS AND METHODS

Six pairs of KCNJ5-mutated, high and low aldosterone-secreting APAs, five non-KCNJ5-mutated APAs, and four normal adrenal glands were assayed by Affymetrix GeneChip Human Transcriptome Array 2.0. A total of 113 APA samples were investigated to explore the expression of glutathione-S-transferase A1 (GSTA1). H295R cells were used to verify the function of GSTA1.

RESULTS

GSTA1 was the top gene downregulated in high-aldosterone KCNJ5-mutated APAs. GSTA1 was also downregulated in KCNJ5-mutated APAs compared with wild-type KCNJ5 APAs. Accordingly, mutant KCNJ5 decreased GSTA1 messenger RNA and protein expression levels. GSTA1 overexpression suppressed aldosterone secretion whether in wild-type or mutant KCNJ5 H295R cells. Adding ethacrynic acid or silencing of GSTA1 increased aldosterone secretion by increasing reactive oxygen species (ROS), superoxide, H2O2 levels, and Ca2+ influx. The expression of the transcription factors NR4A1, NR4A2, and CAMK1 and intracellular Ca2+ were significantly upregulated by GSTA1 inhibition. The reduced form of NAD phosphate oxidase inhibitor or H2O2 scavenger or blocking calmodulin or calcium channels could significantly reduce aldosterone secretion in GSTA1-inhibited cells.

CONCLUSIONS

(1) GSTA1 expression is reversely correlated with aldosterone level in KCNJ5-mutated APAs, (2) GSTA1 regulates aldosterone secretion by ROS and Ca2+ signaling, and (3) KCNJ5 mutation downregulates GSTA1 expression, and overexpression of GSTA1 reverses increased aldosterone in KCNJ5-mutated adrenal cells.

Role of oxidant–antioxidant balance in reproduction of domestic animals

Reproductive process leads to dynamic changes in metabolism and energy consumption, which may be responsible for the excessive production of free radicals (oxidants) that are generated during the physiological process of oxygen consumption. As the ovary is a metabolically active organ, it produces oxidants. Growing follicles, granulose cells of Graffian follicles and ovulated follicles all produce both enzymatic and non-enzymatic antioxidants to preserve themselves from the oxidative damage of oxidants. Oxidants and antioxidants are involved in several reproductive functions such as the regulation of follicular fluid environment, folliculogenesis, steroidogenesis, corpus luteum function, and luteolysis. In this article, the currently available literature is reviewed in relation to the roles of oxidants and oxidative stress in both normal and abnormal reproductive physiological processes.

Circulating leptin and NF-κB activation in peripheral blood mononuclear cells across the menstrual cycle

Using the menstrual cycle as a model, this study focused on longitudinal changes and associations within a physiological network known to play a role in female fertility, including, as biologically active nodes, NF-κB, leptin and adiponectin, β-carotene, adipose tissue, and progesterone. In 28 women, leptin, adiponectin, β-carotene, and progesterone concentrations, NF-κB p65 and p50 activation in peripheral blood mononuclear cells (known to possess estrogen, progesterone and leptin receptors), total body fat (TBF) and subcutaneous adipose tissue (SAT) mass were determined at early (T1) and late follicular (T2) and mid (T3) and late (T4) luteal phase. Leptin and adiponectin concentrations were higher, while NF-κB p65 activation was lower at T3 compared with T1. NF-κB p65 activation was inversely related to leptin concentrations at T1, T3, and T4. β-Carotene was inversely related to leptin (T1,T2,T4) and SAT (T1,T3,T4). NF-κB p50 activation was inversely related to TBF (T4) and SAT (T3,T4), and leptin was positively related to TBF and SAT (T1-T4). Progesterone was inversely related to leptin (T2,T3), adiponectin (T3), TBF (T3,T4), and SAT (T2,T3,T4). By providing evidence of luteal phase-specific reduced NF-κB p65 activation in women under physiological conditions, this study bridges the gap between existing evidence of a Th1-Th2 immune response shift induced by reduced NF-κB p65 activation and a Th1-Th2 shift previously observed at luteal phase. For the first time, inverse regressions suggest inhibitory effects of leptin on NF-κB p65 activation at luteal phase, along with inhibitory effects of leptin as well as adiponectin on progesterone production in corpus luteum. © 2016 The Authors BioFactors published by Wiley Periodicals, Inc. on behalf of International Union of Biochemistry and Molecular Biology. 24(4):376-387, 2016.

Induction of the expressions of antioxidant enzymes by luteinizing hormone in the bovine corpus luteum

Luteoprotective mechanisms of luteinizing hormone (LH) involved in the maintenance of bovine corpus luteum (CL) function have not been completely clarified. Since antioxidant enzymes are well documented as antiapoptotic factors in the CL of many mammals, we hypothesized that the luteoprotective action of LH is mediated by stimulating the local production and action of antioxidant enzymes. To test the above hypothesis, in the present study, we examined the mechanisms involved in the luteoprotective actions of LH. Cultured bovine luteal cells obtained from the CL at the mid-luteal stage (days 8–12 of the estrous cycle) were treated with LH (10 ng/ml), onapristone (OP; a specific progesterone receptor antagonist, 100 μM) and diethyldithiocarbamate [DETC; an inhibitor of superoxide dismutase (SOD), 100 μM] for 24 h. LH in combination with or without OP significantly increased the mRNA and protein expressions of manganese SOD (Mn-SOD) and catalase (CATA) and SOD activity. While LH alone significantly increased the mRNA and protein expressions of SOD containing copper and zinc (Cu,Zn-SOD), OP in combination with or without LH significantly decreased the mRNA and protein expressions of Cu,Zn-SOD. In addition, Cu,Zn-SOD, Mn-SOD and CATA mRNA expressions were higher at the mid luteal phase than the other luteal phases. LH in combination with DETC significantly decreased LH-increased cell viability. The overall results suggest that LH increases cell viability by LH-increased antioxidant enzymes, resulting in maintenance of CL function during the luteal phase in cattle.

N-acetylcysteine impairs survival of luteal cells through mitochondrial dysfunction

N-acetylcysteine (NAC) is known as an antioxidant and used for mucus viscosity reduction. However, this drug prevents or induces cell death depending on the cell type. The response of steroidogenic luteal cells to NAC is unknown. Our data shows that NAC can behave as an antioxidant or prooxidant in dependency on the concentration and mitochondrial energization. NAC elevated the flowcytometric-measured portion of hypodiploid (dying) cells. This rise was completely abolished by aurintricarboxylic acid, an inhibitor of topoisomerase II. NAC increased the secretion of nitric oxide and cellular nitrotyrosine. An image analysis indicated that cells pretreated with NAC and loaded with DHR showed a fluorescent structure probably elicited by the oxidative product of DHR, rhodamine 123 that sequesters mitochondrially. Pretreating luteal cells with NAC or adding NAC directly to mitochondrial fractions followed by assessing the mitochondrial transmembrane potential difference (Deltapsi) by the JC-1 technique demonstrated a marked decrease in Deltapsi. A protonophore restored Deltapsi and rotenone (an inhibitor of respiratory chain complex I) inhibited mitochondrial recovering. Thus, in steroidogenic luteal cells from healthy mature corpus luteum, NAC impairs cellular survival by interfering with mitochondrial metabolism. The protonophore-induced recovering of NAC-provoked decrease in Deltapsi indicates that an ATP synthase-favored route of H(+) re-entry to the matrix is essentially switched off by NAC while other respiratory chain complexes remain intact. These data may be important for therapeutic timing of treatments with NAC. (c) 2010 International Society for Advancement of Cytometry.

Changes in luteal cells distribution, apoptotic rate, lipid peroxidation levels and antioxidant enzyme activities in buffalo (Bubalus bubalis) corpus luteum

Buffalo (Bubalus bubalis) is known for its weak/silent estrous behaviour, lower conception rate and longer inter-calving interval as compared to cattle. Understanding the kinetics and functional properties of luteal cells may be helpful to improve reproductive efficiency in the buffalo. Hence the present study was designed to assess the size and distribution of steroidogenic luteal cells along with biochemical properties during different phases of corpus luteum (CL) in the buffalo. The ovaries collected from the local abattoir were classified into three phases, early, mid and late, based on the morphological appearance of the CL as well as the follicles in the ovary. The proportion (%) of the luteal cells (>10microm diameter) increased (P<0.01) from early (30.7+/-1.3) to mid (36.30+/-1.6), and then decreased (P<0.01) in late luteal (31.46+/-1.8) phases. Percentage of small luteal cells (10-20microm diameter) was higher (P<0.05) in early (58.47+/-0.61) and mid (61.29+/-0.67) than late luteal (37.18+/-1.50) phases of CL. However, the percentage of large luteal cells (20-50microm diameter) was higher (P<0.05) only in late (62.82+/-1.50) than early (41.53+/-0.61) and mid (38.71+/-0.67) phases of CL. The average size (microm) of the large luteal cells increased (P<0.05) from early (25.46+/-0.62) to mid (27.15+/-0.5) and late (28.86+/-0.47) luteal phases. The percentage of luteal cells expressing in situ DNA fragmentation was significantly (P<0.05) higher in the late luteal (41.17+/-5.8) than mid-luteal (21.15+/-4.9) phase of the CL. In the early stage, half of the steroidogenic luteal cells had significantly (P<0.05) less 3beta-HSD activity than the other two phases. In the mid stage, the steroidogenic luteal cells had significantly higher (P<0.05) intense 3beta-HSD activity than the other two phases. Further in the late phase, a significant (P<0.05) reduction in intense 3beta-HSD activity was observed in the large luteal cells. The lipid peroxidation (micromol/g of CL) levels were significantly (P<0.05) higher in late luteal (3.46+/-0.2) than the mid-luteal (1.43+/-0.16) phases. The superoxide dismutase and catalase enzyme levels (U/mg of protein) were also significantly (P<0.05) higher in late luteal (0.9+/-0.015 and 3.37+/-0.45, respectively) than the mid-luteal (0.1+/-0.01 and 2.34+/-0.3, respectively) phases. In contrast, the GPx activity (U/mg of protein) decreased significantly (P<0.05) from mid-luteal (1.85+/-0.4) to late luteal (1.22+/-0.2) phases. The present study suggests that (i) the decrease in progesterone levels in late CL may be associated with loss of 3beta-HSD activity in large luteal cells and (ii) demise of the buffalo CL may be mediated by apoptosis despite the high levels of luteal antioxidant enzymes.

Short-term intake of beta-carotene-supplemented diets enhances ovarian function and progesterone synthesis in goats

The effect of beta-carotene supplementation upon luteal activity, measured as number (CLT) and volume (VLT) of corpus luteum, and P4 synthesis in goats, was evaluated. Goats (n = 22, 34 months) were randomly assigned to one of two experimental groups: (i) beta-carotene [Beta, n = 10; body weight (BW = 44.8 +/- 1.45 kg), body condition score (BCS = 3.25 +/- 0.07)], and (ii) Control (Control, n = 12; BW = 45.30 +/- 1.32 kg, BCS = 3.33 +/- 0.06). Upon oestrus synchronization, the Beta group received 50 mg of beta-carotene per day during 35 days pre- and 17 days post-ovulation. The day 4, 8, 12 and 16 post-ovulation, blood samples were collected for quantification of serum P4 concentrations by radioimmmunoassay, and transrectal ultrasonographic scanning was performed at day 18 for evaluating CLT and VLT. Overall, CLT and VLT mean were 3.10 and 2211.1 mm(3) respectively. The Beta-goats depicted both the largest values for CLT (p = 0.07) and serum P4 levels (p = 0.05), with no differences (p = 0.53) for VLT between treatments. Results suggest a higher efficiency within the cellular-enzymatic groups defining the steroidogenic pathways in the beta-carotene-supplemented goats, generating a larger P4 synthesis. The last is essential for ovulation of healthy oocytes, maintenance of uterine quiescence, nourishment and survival of the embryo around implantation; all of them of paramount significance during the maternal recognition of pregnancy process.

Antioxidant Protective Mechanisms against Reactive Oxygen Species (ROS) Generated by Mitochondrial P450 Systems in Steroidogenic Cells

Mitochondrial P450 type enzymes catalyze central steps in steroid biosynthesis, including cholesterol conversion to pregnenolone, 11beta and 18 hydroxylation in glucocorticoid and mineralocorticoid synthesis, C-27 hydroxylation of bile acids, and 1alpha and 24 hydroxylation of 25-OH-vitamin D. These monooxygenase reactions depend on electron transfer from NADPH via FAD adrenodoxin reductase and 2Fe-2S adrenodoxin. These systems can function as a futile NADPH oxidase, oxidizing NADPH in absence of substrate, and leak electrons via adrenodoxin and P450 to O(2), producing superoxide and other reactive oxygen species (ROS). The degree of uncoupling depends on the P450 and steroid substrate. Studies with purified proteins and overexpression in cultured cells show consistently that adrenodoxin, but not reductase, is responsible for ROS production that can lead to apoptosis. In the ovary and corpus luteum, antioxidant enzyme activities superoxide dismutase, catalase, and glutathione peroxidase parallel steroidogenesis. Antioxidant beta-carotene, alpha-tocopherol, and ascorbate can protect against oxidative damages of P450 systems. In testis Leydig cells, steroidogenesis is associated with aging of the steroidogenic capacity.

Analysis of gene expression in non-regressed and regressed bovine corpus luteum tissue using a customized ovarian cDNA array

The lifespan of the bovine corpus luteum (CL) is an important factor in the control of normal ovarian cyclicity and the establishment and maintenance of pregnancy. There is increasing evidence that CL lifespan is regulated by alternative expression of genes that promote or inhibit luteolysis. To gain further insights into these events a 434 character ovarian cDNA array comprising genes attributed to key aspects of CL function including more than 100 anonymous expressed sequence tags (ESTs) was constructed and screened with alpha(33)P dATP labeled RNA isolated from non-regressed (n=6) and regressed (n=6) CL tissue. Significance analysis of microarrays (SAM) identified 15 genes that changed expression 1.7-fold or more with a false discovery rate of <5%. The differentially expressed genes encoded enzymes involved in steroid biosynthesis and oxygen radical metabolism and proteins involved in extracellular matrix remodeling, apoptosis and cell structure. Results for five of the differentially expressed genes including matrix gla protein and collagen alpha1(I) (extracellular matrix), glutathione-S-transferase alpha I (oxygen metabolism), clusterin (apoptosis) and scavenger receptor BI (steroid biosynthesis) were confirmed by Northern blot analysis and found to be significantly different (P<0.01) between non-regressed and regressed CL tissue. Collectively this study identified genes with recognized roles in CL regression, genes with potential roles in this process and genes whose function have yet to be defined in this event.

Changes in activities of superoxide dismutase, nitric oxide synthase, glutathione-dependent enzymes and the incidence of apoptosis in sheep corpus luteum during the estrous cycle

Anti-oxidative enzymes play a role in protecting cells from oxidative stress-induced cell death. The present study was conducted to evaluate whether the anti-oxidant and pro-oxidant enzymatic capacities of the sheep corpus luteum (CL) are correlated with steroidogenic and structural status of the gland during the estrous cycle. Steroidogenic activity, apoptosis and superoxide dismutase (SOD1 and SOD2), nitric oxide synthase (NOS), glutathione peroxidase (GPX), glutathione reductase (GSR) and glutathione S-transferase (GST) activities were determined in the CL at specific developmental stages of the luteal phase. The intensity of apoptotic DNA fragmentation, characteristic of physiological cell death, was much greater in CL at late luteal phase than at early and mid-luteal phase, concomitantly with the diminution in the plasma progesterone concentrations from mid-to late luteal phase. SOD1 and GPX activities increased from early to mid-luteal phase, and increased further at late luteal phase. SOD2 and GST activities were not different between early and mid-luteal phase, but increased at late luteal phase. GSR activity was not different between any luteal phase examined. NOS activity decreased from early to mid- and late luteal phase. These results show that the activities of SOD1, SOD2, NOS, GPX, GSR and GST in the sheep CL are subject to major changes during the estrous cycle, and that the anti-oxidant and pro-oxidant enzymatic capacities of luteal cells are not correlated with cell steroidogenic status and integrity during the late luteal phase.

Metformin prevents glucose-induced protein kinase C-beta2 activation in human umbilical vein endothelial cells through an antioxidant mechanism

Hyperglycemia determines the vascular complications of diabetes through different mechanisms: one of these is excessive activation of the isoform beta2 of protein kinase C (PKC-beta2). Metformin, a widely used antidiabetic agent, is associated with decreased cardiovascular mortality in obese type 2 diabetic patients. Therefore, we assessed the role of metformin in glucose-induced activation of PKC-beta2 and determined the mechanism of its effect in human umbilical venous endothelial cells grown to either normo- (5 mmol/l) or hyperglycemia (10 mmol/l) and moderately and acutely exposed to 25 mmol/l glucose. We studied PKC-beta2 activation by developing adenovirally expressed chimeras encoding fusion protein between green fluorescent protein (GFP) and conventional beta2 isoform (PKC-beta2-GFP). Glucose (25 mmol/l) induced the translocation of PKC-beta2-GFP from the cytosol to the membrane in cells grown to hyperglycemia but not in those grown in normal glucose medium. Metformin (20 micromol/l) prevented hyperglycemia-induced PKC-beta2-GFP translocation. We also assessed oxidative stress under the same conditions with a 4-((9-acridine-carbonyl)amino)-2,2,6,6-tetramethylpiperidin-oxyl,free radical (TEMPO-9-AC) fluorescent probe. We observed significantly increased radical oxygen species production in cells grown in hyperglycemia medium, and this effect was abolished by metformin. We show that in endothelial cells, metformin inhibits hyperglycemia-induced PKC-beta2 translocation because of a direct antioxidant effect. Our data substantiate the findings of previous large intervention studies on the beneficial effect of this drug in type 2 diabetic patients.

Reactive oxygen species in ovarian physiology

Cells living under aerobic conditions always face oxygen paradox. Oxygen is necessary for cells to maintain their lives. However, reactive oxygen species such as superoxide radical ( ), hydroxyl radical (OH^-) and hydrogen peroxide (H₂O₂) are generated from oxygen and damage cells. Oxidative stress occurs as a consequence of excessive production of reactive oxygen species and impaired antioxidant defense systems. Antioxidant enzymes include: superoxide dismutase (SOD), which is a specific enzyme to scavenge superoxide radicals; copper-zinc SOD, located in the cytosol; and manganese SOD, located in the mitochondria. Both types of SOD belong to the first enzymatic step to scavenge superoxide radicals. It has been reported that a number of local factors such as cytokines, growth factors and eicosanoids are involved in the regulation of ovarian function, in addition to gonadotropins and ovarian steroid hormones. Since reactive oxygen species are generated and SOD is expressed in the ovary, there is a possibility that reactive oxygen species and SOD work as local regulators of ovarian function. The present review reports that reactive oxygen species and their scavenging systems play important roles in several processes of reproductive physiology, including follicular development, oocyte maturation, ovulation, corpus luteum function and follicular atresia. (Reprod Med Biol 2005; 4: 31- 45).

Involvement of Pro-Inflammatory Cytokines, Mediators of Inflammation, and Basic Fibroblast Growth Factor in Prostaglandin F2α-Induced Luteolysis in Bovine Corpus Luteum1

The process of luteolysis requires very subtly modulated coordination of different factors and regulation systems. Immune cells and cytokines were shown to be relevant for bovine luteolysis. The aim of this study was to investigate the detailed pattern of mRNA expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNFalpha), TNF receptor type 1 (TNF-R1), interleukin 1beta (IL-1beta), and interferon gamma (IFNgamma), and of the inducible nitric oxide synthase (iNOS) and the basic fibroblast growth factor (FGF-2) during prostaglandin (PG) F(2alpha)-induced luteolysis in the bovine corpus luteum (CL). In addition, the mRNA expression for the LH-receptor (LH-R) and the steroidogenic enzyme p450scc was determined. Cows in the midluteal phase (Days 8-12) were injected with the PGF(2alpha) analogue cloprostenol, and CL were collected by transvaginal ovariectomy before and 2, 4, 12, 48, and 64 h after PGF(2alpha) injection. Conventional and real-time reverse transcription polymerase chain reaction RT-PCR (LightCycler) using SYBR Green I detection were employed to determine the mRNA expression for the investigated factors. All cytokines were significantly up-regulated during induced luteolysis. LH-R and p450scc mRNA were down-regulated (P < 0.05) during structural luteolysis (after 12 h), and p450scc in addition at 2 h after PGF(2alpha) (P < 0.05). FGF-2 expression increased (P < 0.001) during functional luteolysis (until 12 h after PGF(2alpha)) and diminished thereafter. The mRNA expression for iNOS decreased (P < 0.05) after induction of luteolysis. In conclusion, cytokines may be involved not only in structural but also in functional luteolysis and the deprivation of luteal survival factors, leading to a situation where apoptosis can occur. FGF-2 may participate in the suppression of cytokine-induced iNOS mRNA expression and in the prevention of an inflammatory reaction in the surrounding tissues.

Vitamin A and beta-carotene levels in plasma, corpus luteum and follicular fluid of cyclic and pregnant cattle

This study was carried out to examine the relationship between the corpus luteum (CL) weight, CL and follicle diameters and progesterone, beta-carotene and vitamin A levels in reproductive organs of cattle obtained from the slaughterhouse. The beta-carotene and vitamin A levels were determined in plasma, CL and follicular fluid (FF) using a spectrophotometric method at different stages of the oestrous cycle (n=40) and at 3-6 months of pregnancy (n=10). The diameters of the CL and follicle were measured using ultrasonography. Plasma progesterone concentrations were determined by an enzyme immunoassay method. The vitamin A levels of the plasma, CL and FF were not related to each other. The highest plasma vitamin A levels were observed in the proestrus and oestrus, at which periods follicular activity dominates. The vitamin A levels in the CL and FF were negatively related to the weight and diameter of the CL and the diameter of follicle, respectively. In contrast to vitamin A, beta-carotene concentrations of plasma, CL and FF were significantly correlated with each other. The highest beta-carotene levels in the plasma, CL and FF were found during pregnancy when there is maximal luteal function, and the beta-carotene level of the CL was significantly correlated with the weight and diameter of CL. Furthermore, the intrafollicular beta-carotene level was negatively correlated with the follicle diameter. There was a positive correlation between plasma progesterone level and the weight and diameter of the CL, but a negative correlation between plasma progesterone level and follicle diameter. Moreover, plasma, FF and CL beta-carotene levels were positively correlated with plasma progesterone levels. This study revealed that beta-carotene levels in the plasma, CL and FF were influenced by the stage of the oestrous cycle or the pregnancy and were related to bovine luteal function without depending on vitamin A.

Effect of cyclodextrin-encapsulated beta-carotene on progesterone production by bovine luteal cells

Experiments were conducted to examine the effect of cyclodextrin-encapsulated beta-carotene on basal or cholesterol (cyclodextrin-encapsulated), LH and dibutyryl cyclic AMP (dbcAMP)-stimulated progesterone production by bovine corpus luteum cells isolated from mid-luteal heifer ovaries by collagenase digestion. Cells were cultured with serum-free DMEM/Ham's F12 medium in serum pre-treated plastic culture dishes for periods of up to 11 days. Medium was replaced after 24h and thereafter every 48 h. Beta-carotene was added to cultures in a carrier molecule, dimethyl-beta-cyclodextrin, to facilitate dissolution. All treatments were started on day 3 of culture. Treatment of cells with 1 or 2 micromol/l beta-carotene resulted in sharp inhibition of progesterone production. On the contrary, treatment of cells with 0.1 micromol/l beta-carotene resulted in significant stimulation (P<0.05) of both basal and cholesterol-stimulated progesterone secretion. The effect of beta-carotene on LH or dbcAMP-stimulated progesterone production was also examined. Treatment of cells with LH or dbcAMP always resulted in stimulation of progesterone secretion (P<0.001). However, cells treated with LH plus beta-carotene or dbcAMP plus beta-carotene both produced significantly (P<0.01) less progesterone relative to those cells treated with LH or dbcAMP alone on days 7, 9 and 11 of culture. These results indicate that beta-carotene can enhance luteal steroidogenesis when present at low concentrations but is inhibitory at higher concentrations and that encapsulation of beta-carotene in cyclodextrin is an effective method of supplying it to cells in culture.

Levels and subcellular distributions of detoxifying enzymes in the ovarian corpus luteum of the pregnant and non-pregnant pig

The levels and subcellular distribution of enzymes involved in defenses against reactive oxygen superoxide dismutase (SOD; E.C.1.15.1.1), glutathione peroxidase (GPX; E.C.1.11.1.9), catalase (CAT; E.C.1.11.1.6), and DT-diaphorase (DT; E.C.1.6.99.2) and of the conjugating enzymes glutathione transferase (GST; E.C.2.5.1.18) and p-sulphotransferase (p-ST; E.C.2.8.2.1) in the corpus luteum of ovaries from pregnant and non-pregnant pigs were investigated. In addition, non-protein thiols and glutathione reductase (GRD; E.C.1.6.4.2) were examined in the same manner. The total cytosolic activities of CAT, DT, GRD, and p-ST were significantly increased, whereas total GST activity was decreased in the pregnant corpus luteum compared to the corresponding activities in non-pregnant corpus luteum. In the case of the mitochondrial fraction from pregnant corpus luteum, GPX and GRD displayed significant increases in specific activity. Upon subfractionation of the mitochondrial fraction (i.e. mitoplast preparation), SOD activity was distributed equally between the mitoplasts and the supernatant. CAT and GPX activities were mainly recovered in the supernatant, while the major GRD activity pelleted with the mitoplasts. Microsomes from pregnant corpus luteum demonstrated increased specific GPX activity and decreased SOD activity compared to the non-pregnant corpus luteum. No differences in the non-protein thiol levels in the cytosolic, mitochondrial, or microsomal fractions from the corpus luteum were observed between non-pregnant and pregnant sows.