Prostaglandin f2alpha treatment in vivo, but not in vitro, stimulates protein kinase C-activated superoxide production by nonsteroidogenic cells of the rat corpus luteum

Comparison of Soluble and Liposome Encapsulated, Sustained Release Latanoprost for Focal Adipose Reduction

Background: To address the lack of non-cytotoxic, non-surgical options to treat undesirable focal adiposity of the face, we propose use of the anti-glaucoma medication and prostaglandin F2α analogue latanoprost, which has a well-described side effect of periorbital adipose shrinkage. Objective: To evaluate the safety and efficacy of soluble and liposomal latanoprost for focal fat reduction. Approach: To compare efficacy, single administrations of either the FDA-approved cytolytic drug deoxycholic acid (DOCA), latanoprost, or liposomal latanoprost were injected into ob/ob mouse inguinal fat pads. Study outcomes included mouse weight, inguinal fat pad volume, architecture, and cytotoxicity. Results: Both DOCA and soluble latanoprost significantly reduced inguinal fat pad volume whereas liposome encapsulation reduced inguinal fat pad volume insignificantly over the 14-day study period. Hematoxylin and eosin demonstrated effective reduction in adipocyte volume without histologic evidence of cytolysis or inflammation whereas DOCA caused dermal ulcerations, adipocyte lysis, and increased tissue inflammation. Conclusion: Latanoprost reduced fat volume without inducing cell lysis or inflammation.

Interplay between nitric oxide and gonadotrophin-releasing hormone in the neuromodulation of the corpus luteum during late pregnancy in the rat

BACKGROUND

Nitric oxide and GnRH are biological factors that participate in the regulation of reproductive functions. To our knowledge, there are no studies that link NO and GnRH in the sympathetic ganglia. Thus, the aim of the present work was to investigate the influence of NO on GnRH release from the coeliac ganglion and its effect on luteal regression at the end of pregnancy in the rat.

METHODS

The ex vivo system composed by the coeliac ganglion, the superior ovarian nerve, and the ovary of rats on day 21 of pregnancy was incubated for 180 min with the addition, into the ganglionic compartment, of L-NG-nitro arginine methyl ester (L-NAME), a non-selective NO synthase inhibitor. The control group consisted in untreated organ systems.

RESULTS

The addition of L-NAME in the coeliac ganglion compartment decreased NO as well as GnRH release from the coeliac ganglion. In the ovarian compartment, and with respect to the control group, we observed a reduced release of GnRH, NO, and noradrenaline, but an increased production of progesterone, estradiol, and expression of their limiting biosynthetic enzymes, 3β-HSD and P450 aromatase, respectively. The inhibition of NO production by L-NAME in the coeliac ganglion compartment also reduced luteal apoptosis, lipid peroxidation, and nitrotyrosine, whereas it increased the total antioxidant capacity within the corpora lutea.

CONCLUSION

Collectively, the results indicate that NO production by the coeliac ganglion modulates the physiology of the ovary and luteal regression during late pregnancy in rats.

Luteolysis and the Auto-, Paracrine Role of Cytokines From Tumor Necrosis Factor α and Transforming Growth Factor β Superfamilies

Successful pregnancy establishment demands optimal luteal function in mammals. Nonetheless, regression of the corpus luteum (CL) is absolutely necessary for normal female cyclicity. This dichotomy relies on intricate molecular signals and rapidly activated biological responses, such as angiogenesis, extracellular matrix (ECM) remodeling, or programmed cell death. The CL establishment and growth after ovulation depend not only on the luteinizing hormone-mediated endocrine signal but also on a number of auto-, paracrine interactions promoted by cytokines and growth factors like fibroblast growth factor 2, vascular endothelial growth factor A, and tumor necrosis factor α (TNF), which coordinate vascularigenesis and ECM reorganization as well as steroidogenesis. With the organ fully developed, the release of the uterine prostaglandin F2α activates luteolysis, an intricate process supported by intraluteal interactions that ensure the loss of steroidogenic function (functional luteolysis) and the involution of the organ (structural luteolysis). This chapter provides an overview of the local action of cytokines during luteal function, with particular emphasis on the role of TNF and transforming growth factor β superfamilies during luteolysis.

Prostaglandin F2α regulates the expression of uterine activation proteins via multiple signalling pathways

Prostaglandin F2α (PGF2A) has multiple roles in the birth process in addition to its vital contractile role. Our previous study has demonstrated that PGF2A can modulate uterine activation proteins (UAPs) in cultured pregnant human myometrial smooth muscle cells (HMSMCs). The objective of this study was to define the signalling pathways responsible for PGF2A modulation of UAPs in myometrium. It was found that PGF2A stimulated the expression of (GJA1) connexin 43 (CX43), prostaglandin endoperoxide synthase 2 (PTGS2) and oxytocin receptor (OTR) in cultured HMSMCs. The inhibitors of phospholipase C (PLC) and protein kinase C (PKC) blocked PGF2A-stimulated expression of CX43. The inhibitors of ERK, P38 and NFκB also blocked the effect of PGF2A on CX43 expression, whereas PI3K and calcineurin/nuclear factor of activated T-cells (NFAT) pathway inhibitors did not reverse the effect of PGF2A on CX43. For PTGS2 and OTR, PLC, PI3K, P38 and calcineurin/NFAT signalling pathways were involved in PGF2A action, whereas PKC and NFκB signalling were not involved. In addition, PGF2A activated NFAT, PI3K, NFκB, ERK and P38 signalling pathways. Our data suggest that PGF2A stimulates CX43, PTGS2 and OTR through divergent signalling pathways.

Roles of antioxidant enzymes in corpus luteum rescue from reactive oxygen species-induced oxidative stress

Progesterone produced by the corpus luteum (CL) regulates the synthesis of various endometrial proteins required for embryonic implantation and development. Compromised CL progesterone production is a potential risk factor for prenatal development. Reactive oxygen species (ROS) play diverse roles in mammalian reproductive biology. ROS-induced oxidative damage and subsequent adverse developmental outcomes constitute important issues in reproductive medicine. The CL is considered to be highly exposed to locally produced ROS due to its high blood vasculature and steroidogenic activity. ROS-induced apoptotic cell death is involved in the mechanisms of CL regression that occurs at the end of the non-fertile cycle. Luteal ROS production and propagation depend upon several regulating factors, including luteal antioxidants, steroid hormones and cytokines, and their crosstalk. However, it is unknown which of these factors have the greatest contribution to the maintenance of CL integrity and function during the oestrous/menstrual cycle. There is evidence to suggest that antioxidants play important roles in CL rescue from luteolysis when pregnancy ensues. As luteal phase defect impacts fertility by preventing implantation and early conceptus development in livestock and humans, this review attempts to address the importance of ROS-scavenging antioxidant enzymes in the control of mammalian CL function and integrity. The corpus luteum (CL) is a transient endocrine organ that develops after ovulation from the ovulated follicle during each reproductive cycle. The main function of the CL is the production and secretion of progesterone which is necessary for embryonic implantation and development. Compromised CL progesterone production is a potential risk factor for prenatal development and pregnancy outcomes. Reactive oxygen species (ROS), which are natural by-products of cellular respiration and metabolism, play diverse roles in mammalian reproductive biology. ROS-induced oxidative damage and subsequent development of adverse pregnancy outcomes constitute important issues in reproductive medicine. Before the end of the first trimester, a high rate of human and animal conceptions end in spontaneous abortion and most of these losses occur at the time of implantation in association with ROS-induced oxidative damage. Every cell in the body is normally able to defend itself against the oxidative damage caused by the ROS. The cellular antioxidant enzymes constitute the first line of defence against the toxic effects of ROS. The CL is considered to be highly exposed to locally produced ROS due to its high blood vasculature and metabolic activity. There is now evidence to suggest that cellular antioxidants play important roles in CL rescue from regression when pregnancy ensues. As defective CL function impacts fertility by preventing implantation and early conceptus development in livestock and humans, this review attempts to address the importance of antioxidant enzymes in the control of mammalian CL function and integrity.

Prostaglandin F2α (PGF2α) stimulates PTGS2 expression and PGF2α synthesis through NFKB activation via reactive oxygen species in the corpus luteum of pseudopregnant rats

This study was undertaken to investigate how prostaglandin F2α (PGF2α) increases PGF2α synthesis and PTGS2 expression in the corpus luteum of pseudopregnant rats. We further investigated the molecular mechanism by which PGF2α stimulates PTGS2 expression. PGF2α (3 mg/kg) or phosphate buffer as a control was injected s.c. on day 7 of pseudopregnancy. Ptgs2 mRNA expression and PGF2α concentrations in the corpus luteum were measured at 2, 6, and 24 h after PGF2α injection. PGF2α significantly increased Ptgs2 mRNA expression at 2 h and luteal PGF2α concentrations at 24 h. PGF2α significantly decreased serum progesterone levels at all of the times studied. Simultaneous administration of a selective PTGS2 inhibitor (NS-398, 10 mg/kg) completely abolished the increase in luteal PGF2α concentrations induced by PGF2α. PGF2α increased NFKB p65 protein expression in the nucleus of luteal cells 30 min after PGF2α injection, and electrophoretic mobility shift assay revealed that PGF2α increased binding activities of NFKB to the NFKB consensus sequence of the Ptgs2 gene promoter. Simultaneous administration of both superoxide dismutase and catalase to scavenge reactive oxygen species (ROS) inhibited the increases of nuclear NFKB p65 protein expression, lipid peroxide levels, and Ptgs2 mRNA expression induced by PGF2α. In conclusion, PGF2α stimulates Ptgs2 mRNA expression and PGF2α synthesis through NFKB activation via ROS in the corpus luteum of pseudopregnant rats.

The NOX family of ROS-generating NADPH oxidases: physiology and pathophysiology

For a long time, superoxide generation by an NADPH oxidase was considered as an oddity only found in professional phagocytes. Over the last years, six homologs of the cytochrome subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the phagocyte NADPH oxidase itself (NOX2/gp91(phox)), the homologs are now referred to as the NOX family of NADPH oxidases. These enzymes share the capacity to transport electrons across the plasma membrane and to generate superoxide and other downstream reactive oxygen species (ROS). Activation mechanisms and tissue distribution of the different members of the family are markedly different. The physiological functions of NOX family enzymes include host defense, posttranlational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. NOX enzymes also contribute to a wide range of pathological processes. NOX deficiency may lead to immunosuppresion, lack of otoconogenesis, or hypothyroidism. Increased NOX activity also contributes to a large number or pathologies, in particular cardiovascular diseases and neurodegeneration. This review summarizes the current state of knowledge of the functions of NOX enzymes in physiology and pathology.

The molecular control of corpus luteum formation, function, and regression

The corpus luteum (CL) is one of the few endocrine glands that forms from the remains of another organ and whose function and survival are limited in scope and time. The CL is the site of rapid remodeling, growth, differentiation, and death of cells originating from granulosa, theca, capillaries, and fibroblasts. The apparent raison d'etre of the CL is the production of progesterone, and all the structural and functional features of this gland are geared toward this end. Because of its unique importance for successful pregnancies, the mammals have evolved a complex series of checks and balances that maintains progesterone at appropriate levels throughout gestation. The formation, maintenance, regression, and steroidogenesis of the CL are among the most significant and closely regulated events in mammalian reproduction. During pregnancy, the fate of the CL depends on the interplay of ovarian, pituitary, and placental regulators. At the end of its life span, the CL undergoes a process of regression leading to its disappearance from the ovary and allowing the initiation of a new cycle. The generation of transgenic, knockout and knockin mice and the development of innovative technologies have revealed a novel role of several molecules in the reprogramming of granulosa cells into luteal cells and in the hormonal and molecular control of the function and demise of the CL. The current review highlights our knowledge on these key molecular events in rodents.

Changes in the Expression of Steroidogenic and Antioxidant Genes in the Mouse Corpus Luteum During Luteolysis1

Luteal cell death plays a key role in the regulation of the reproductive process in all mammals. It is also known that prostaglandin (PG) F 2alpha is one of the main factors that cause luteal demise; still, the effects of PGF 2alpha on luteal gene transcription have not been fully explored. Using microarray and reverse transcription-polymerase chain reaction, we have profiled gene expression in the corpus luteum (CL) of wild-type and PGF 2alpha receptor knockout mice on Day 19 of pregnancy. Western blot analysis of selected genes was also performed. Because luteolysis has been shown to be associated with increased oxygen radical production and decreased progesterone synthesis, we report here changes observed in the expression of antioxidant and steroidogenic genes. We found that luteal cells express all genes necessary for progesterone synthesis, whether or not they had undergone luteolysis; however, an increase in mRNA levels of enzymes involved in androgen production, along with a decrease in the expression of enzymes implicated in estrogen synthesis, was observed. We also identified six genes committed to the elimination of free radical species that are dramatically down-regulated in the CL of wild-type animals with respect to PGF 2alpha receptor knockout mice. Similar changes in the expression of steroidogenic and antioxidant genes were found in the CL of wild-type animals between Days 15 and 19 of pregnancy. It is proposed that an increase in the androgen:estrogen biosynthesis ratio, along with a significantly reduced expression of free radical scavenger proteins, may play an important role in the luteolytic process.

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).

Expression patterns of cytokines, p53 and nitric oxide synthase isoenzymes in corpora lutea of pseudopregnant rabbits during spontaneous luteolysis

The gene expressions for macrophage chemoattractant protein-1 (MCP-1), interleukin (IL)-1β, IL-2 and p53 were examined by semi-quantitative RT-PCR in corpora lutea (CL) of rabbits during spontaneous luteolysis at days 13, 15, 18 and 22 of pseudopregnancy. In the same luteal tissue, total activity of nitric oxide (NO) synthase (NOS) and genes for both endothelial (eNOS) and inducible (iNOS) isoforms were also analysed. From day 13 to 15, MCP-1 and IL-1βmRNA levels rose (P≤ 0.01) almost 2-fold, and the transcript for p53 almost 8-fold, but then all dropped (P≤ 0.05) from day 18 onward. IL-2 mRNA abundance was higher (P≤ 0.01) on day 13 and then gradually declined. During luteolysis, eNOS mRNA decreased 40% (P≤ 0.05) by day 15, but thereafter remained unchanged, while iNOS mRNA was barely detectable and did not show any clear age-related pattern throughout the late luteal stages. Total NOS activity progressively increased (P≤ 0.01) from day 13 to 18 of pseudopregnancy and then dropped to the lowest (P≤ 0.01) levels on day 22. Luteal progesterone content also declined during CL regression from 411 to 17 pg/mg found on days 13 and 22 respectively, in parallel with the decrease in blood progesterone concentrations. These data further support a physiological role of NO as modulator of luteal demise in rabbits. Locally, luteal cytokines may be involved in the up-regulation of NOS activity, while downstream NO may inhibit steroroidogenesis and induce expression of p53 gene after removal of the protective action of progesterone.

Uncoupling protein 2, but not uncoupling protein 1, is expressed in the female mouse reproductive tract

Uncoupling proteins (UCPs) are transporters of the inner mitochondrial membrane. Whereas UCP1 is uniquely present in brown adipose tissue where it uncouples respiration from ATP synthesis and activates respiration and heat production, UCP2 is present in numerous tissues, and its exact function remains to be clarified. Two sets of data provided the rationale for this study: (i) the intriguing report that UCP1 is present in uterus of mice (Nibbelink, M., Moulin, K., Arnaud, E., Duval, C., Penicaud, L., and Casteilla, L. (2001) J. Biol. Chem. 276, 47291-47295); and (ii) an observation that Ucp2(-/-) female mice (homozygous matings) have smaller litters compared with Ucp2(+/+) animals (S. Rousset and A.-M. Cassard-Doulcier, unpublished observations). These data prompted us to examine the expression of UCP1 and UCP2 in the reproductive tract of female mice. Using wild type, Ucp1(-/-) mice, and Ucp2(-/-) mice, we were unable to detect UCP1 in uterus of mice with appropriate antibodies, and we conclude that the signal assigned to UCP1 by others was neither UCP1 nor UCP2. Using a polyclonal antibody against UCP2 and tissues from Ucp2(-/-) mice as controls, UCP2 was detected in ovary, oviduct, and uterus. Expression of Ucp2 mRNA was also observed in ovary and uterus using in situ hybridization analysis. Bone marrow transplantation experiments revealed that the UCP2 signal of the ovary was restricted to ovarian cells. UCP2 level in ovary decreased during follicular growth and increased during the pre-ovulatory period, during which aspects of an inflammatory process are known to exist. Because UCP2 down-regulates reactive oxygen species, a role in the regulation of inflammatory events linked to the preparation of ovulation is suggested.

Control of ascorbic acid efflux in rat luteal cells: role of intracellular calcium and oxygen radicals

In luteal cells, prostaglandin (PG)F2a mobilizes intracellular calcium concentration ([Ca]i), generates reactive oxygen species (ROS), depletes ascorbic acid (AA) levels, inhibits steroidogenesis, and ultimately induces cell death. We investigated the hypothesis that [Ca]i mobilization stimulates ROS, which results in depletion of cellular AA in rat luteal cells. We used a self-referencing AA-selective electrode that noninvasively measures AA flux at the extended boundary layer of single cells and fluorescence microscopy with fura 2 and dichlorofluorescein diacetate (DCF-DA) to measure [Ca]i and ROS, respectively. Menadione, a generator of intracellular superoxide radical (O2-), PGF2a, and calcium ionophore were shown to increase [Ca]i and stimulate intracellular ROS. With calcium ionophore and PGF2a, but not menadione, the generation of ROS was dependent on extracellular calcium influx. In unstimulated cells there was a net efflux of AA of 121.5 +/- 20.3 fmol x cm-1 x s-1 (mean +/- SE, n = 8), but in the absence of extracellular calcium the efflux was significantly reduced (10.3 +/- 4.9 fmol x cm-1 x s-1; n = 5, P < 0.05). PGF2a and menadione stimulated AA efflux, but calcium ionophore had no significant effect. These data suggest two AA regulatory mechanisms: Under basal conditions, AA efflux is calcium dependent and may represent recycling and maintenance of an antioxidant AA gradient at the plasma membrane. Under luteolytic hormone and/or oxidative stress, AA efflux is stimulated that is independent of extracellular calcium influx or generation of ROS. Although site-specific mobilization of calcium pools and ROS cannot be ruled out, the release of AA by PGF2a-stimulated luteal cells may occur through other signaling pathways.

Concomitant induction of apoptosis and expression of monocyte chemoattractant protein-1 in cultured rat luteal cells by nuclear factor-kappaB and oxidative stress

It has previously been shown that expression of monocyte chemoattractant protein (mcp)-1 and apoptosis of luteal cells occur concomitantly during the estrous cycle in the rat corpus luteum; however, luteal cells containing mcp-1 mRNA did not seem to be apoptotic. In the present study, the relationship between the induction of apoptosis and mcp-1 expression in cultures of dispersed rat luteal cells was examined. Both apoptosis and mcp-1 expression were spontaneously induced in cultured luteal cells in a manner inhibitable by antioxidative reagents or an inhibitor of nuclear translocation of nuclear factor-kB. However, the cells containing mcp-1 mRNA were distinct from those undergoing apoptosis, and the inhibition of apoptosis by the pan-caspase inhibitor z-VAD-fmk did not influence the induction of mcp-1 expression. These results collectively indicate that oxidative stress simultaneously, but independently, induces apoptosis and mcp-1 expression in luteal cells through the activation of nuclear factor-kB. This phenomenon might help to explain how monocytes/macrophages accumulate in regressive corpora lutea where their target apoptotic cells exist.

Effect of local interaction of reactive oxygen species with prostaglandin F(2alpha) on the release of progesterone in ovine corpora lutea in vivo

Prostaglandin (PG) F(2alpha) is implicated in the process of luteal regression in many species, and has been shown to increase the generation of reactive oxygen species. In this study, the role of reactive oxygen species in the local regulatory mechanisms of functional luteolysis in the ewe was examined. In Experiment 1, we studied local effects of hydrogen peroxide (H(2)O(2)) and its interaction with PGF(2alpha) on P secretion in ovine corpus luteum (CL) in vivo. For this purpose, a microdialysis system (MDS) was used, where only the cells surrounding the capillary membrane in the microenvironment of the CL are exposed to these factors, and the P secretory ability of the CL is maintained as if intact. The study used a multiple CL model to implant the MDS, enabling us to examine in parallel several experimental infusions into the MDS implanted in different CLs (one MDS line per CL) developed after superovulation in one ewe. On Day 8 after GnRH treatment, the MDS were implanted into multiple CL in both ovaries of six ewes. A 4-h infusion with PGF(2alpha) (10(-6)M) at 8-12 h slightly increased P release during infusion, while a 4-h infusion with H(2)O(2) (10(-3)M) at 20-24 h decreased P release at 27-38 h. A pre-infusion with PGF(2alpha) for 4h at 8-12h, followed by infusion of H(2)O(2) at 20-24 h rapidly decreased the P release at 20-40 h (P<0.05); this decrease occurred 7h earlier than in the CL treated with H(2)O(2) alone. In Experiment 2, by utilizing the MDS we also applied free radical scavengers to examine their possible weakening effect on the inhibition of P secretion in the microenvironment within the regressing CL induced by PGF(2alpha) treatment. On Day 8 after estrus, the MDS were implanted into the CL (single CL model, two MDS lines per CL). Infusion of free radical scavengers, superoxide dismutase (SOD;50mg/ml)+catalase (CAT; 10mg/ml), at 0-28 h first increased P release until 12 h (P<0.05), and consequently delayed the decrease in P release until 30 h after administration of PGF(2alpha) i.m. (P<0.05). The present results support the concept that the leading pathway from PGF(2alpha) induces an increase of reactive oxygen species in luteolysis in the ewe.

Analysis of luteal tissue inhibitor of metalloproteinase-1, -2, and -3 during prostaglandin F(2alpha)-induced luteolysis

Increased matrix metalloproteinase (MMP) expression and activities help to mediate tissue involution through increasing extracellular matrix remodeling and promoting dedifferentiation and, ultimately, apoptosis. Therefore, we hypothesized that prostaglandin (PG) F(2alpha) administration would decrease expression of the tissue inhibitor of metalloproteinase (TIMP)-1, -2, and -3 and effectively increase the MMP:TIMP ratio, leading to glandular involution. In experiment 1, we tested the effects of PGF(2alpha) administration (Day 10 postestrus; Day 0 = estrus) on luteal TIMP-1, -2, and -3 mRNA and protein expression. Corpora lutea were collected at 0, 15, or 30 min or at 1, 2, 4, 6, 12, 24, and 48 h following PGF(2alpha) administration (n = 3-9 animals/time point). Following PGF(2alpha) administration, TIMP-1 mRNA levels decreased (P < 0.05) at 1 and 2 h relative to 0 h (controls), then increased to levels greater than controls at 4 and 6 h. In contrast, TIMP-2 and -3 mRNA levels did not decrease following PGF(2alpha) administration. The TIMP-1, -2, and -3 proteins were localized to large luteal cells (LLCs) within control (untreated) tissues. However, histodepletion of TIMP-1 within LLCs was evident within 30 min (earliest time point collected) following PGF(2alpha) injection and continued through 48 h. Luteal concentration of TIMP-1, as determined by RIA, was decreased (P < 0.05) by 15 min (earliest time point collected) following PGF(2alpha) administration and remained low through 48 h. In contrast, TIMP-2 and -3 immunolocalization was not altered by PGF(2alpha) administration. Experiment 2 was conducted to determine if PGF(2alpha) could initiate the preceding changes in TIMP-1 in early (Day 3) corpora lutea that can bind PGF(2alpha) but are refractory to its luteolytic effects. Serum concentrations of progesterone and luteal concentrations of TIMP-1 mRNA and protein were similar at 0 and 6 h after PGF(2alpha) injection on Day 3 postestrus. These data suggest that an early and sustained effect of PGF(2alpha) is the specific depletion of TIMP-1 within LLCs that are capable of responding to the luteolytic action of PGF(2alpha). This action may increase the MMP:TIMP-1 ratio, creating an environment that favors extracellular matrix degradation and, thereby, facilitates both functional and structural regression.

Dependence on prolactin of the luteolytic effect of prostaglandin F2alpha in rat luteal cell cultures

Luteal regression is a multistep, prolonged process, and long-term luteal cultures are required for studying it in vitro. Cell suspensions from ovaries of superovulated rats were enriched with steroidogenic cells, seeded on laminin or fibronectin, and maintained in defined medium for up to 10 days. Progesterone secretion was much lower than that of 20alpha-dihydroprogesterone, a product of 20alpha-hydroxysteroid dehydrogenase (20alpha-HSD). Prolactin added throughout the incubation period gradually increased the percent progesterone out of total progestins to fourfold, while reducing 20alpha-HSD mRNA by 73%. Luteinizing hormone accelerated the establishment of higher percent progesterone by prolactin but by itself had no effect. Prolactin did not increase total progestin production or cytochrome P450 side-chain cleavage (P450(scc)) mRNA. Cell viability was unaffected by prolactin and/or LH. Prostaglandin F2alpha (PGF2alpha) was added 7-8 days after seeding. In prolactin-treated cells, PGF2alpha reduced steroidogenesis after 4-45 h, and at 45 h total progestins and P450(scc) mRNA were reduced by 45%. At 8-45 h PGF2alpha reduced the percent progesterone out of total progestins, and at 45 h 20alpha-HSD mRNA was doubled. In contrast, in prolactin-deprived cultures, PGF2alpha had little effect on total progestins or 20alpha-HSD mRNA but doubled P450(scc) mRNA. Phospholipase C activity was stimulated by PGF2alpha regardless of prolactin. Thus, when prolactin-treated, our cultures are a good model for mature corpora lutea challenged with PGF2alpha; the finding that without prolactin PGF2alpha has an alternative set of actions could help in identifying the signaling pathways of PGF2alpha responsible for its luteolytic effects.

Reactive oxygen species up-regulates cyclooxygenase-2, p53, and Bax mRNA expression in bovine luteal cells

Reactive oxygen species (ROS) are well-established modulators of luteal cell apoptosis in the estrous cycle. The objective of this study was to clarify the molecular mechanisms of luteolysis by characterizing the levels and regions of mRNAs involved in ROS-induced luteal cell apoptosis. Stimulation of bovine luteal cells by H2O2 resulted in the induction of apoptotic nuclear condensation and Caspase-3 activation. In addition, a marker for oxidative stress-damaged DNA, 8-hydroxy-2'-deoxyguanosine, was highly accumulated in the large luteal cells prepared from the late estrous stage. Reverse transcription polymerase chain reaction and Northern blot analysis demonstrated that mRNAs of cyclooxygenase (COX)-2, p53, and Bax were highly accumulated in the H2O2-treated cells. In situ hybridization revealed that these mRNAs were most abundantly expressed in the large luteal cells. These findings suggest that enhancement of ROS in the bovine corpus luteum induces expression of COX-2, p53, and Bax mRNAs, resulting in activation of the signaling pathway for luteal-cell apoptosis.

Endocrine-regulated and protein kinase C-dependent generation of superoxide by rat preovulatory follicles

The ovulatory LH surge results in follicular inflammation with an increase in cytokines and PGs. Reactive oxygen species (ROS) are also produced during inflammatory processes. To study ROS generation during the ovulatory cascade, preovulatory follicles were dissected from immature female rats primed with PMSG. Follicles were isolated, and ROS generation was assessed by luminol-amplified chemiluminescence. Immature rat granulosa cells were also subjected to luminometry after isolation from immature rats treated with diethylstilbestrol. Phorbol ester-stimulated ROS generation by follicular cells was completely suppressed by superoxide dismutase and the NADPH/NADH oxidase inhibitor diphenylene iodonium bisulfate, whereas catalase was without effect. Fractionation of granulosa cells with an antibody against leukocyte common antigen-1 showed that leukocyte-enriched cells produced more than 95% of the superoxide measured. In vivo treatment with LH produced a 5-fold increase in phorbol-stimulated superoxide production by isolated follicles. This response was maximal within 4 h and was blocked by indomethacin. In vivo administration of PGE(2) and PGF(2alpha) did not reverse the blockade by indomethacin; however, isolated follicles incubated with PGE(2) produced a time-dependent increase in phorbol-stimulated superoxide generation. Thus, a superoxide generator is present in the preovulatory follicle that is leukocytic in origin, hormone regulated, and activated by a protein kinase C-dependent pathway. The regulated generation of superoxide by preovulatory follicles may indicate a role for ROS in the periovulatory period.

Prostaglandin f(2alpha) induces distinct physiological responses in porcine corpora lutea after acquisition of luteolytic capacity

This study examines differences in intracellular responses to cloprostenol, a prostaglandin (PG)F(2alpha) analog, in porcine corpora lutea (CL) before (Day 9 of estrous cycle) and after (Day 17 of pseudopregnancy) acquisition of luteolytic capacity. Pigs on Day 9 or Day 17 were treated with saline or 500 microgram cloprostenol, and CL were collected 10 h (experiment I) or 0.5 h (experiment III) after treatment. Some CL were cut into small pieces and cultured to measure progesterone and PGF(2alpha) secretion. In experiment I, progesterone remained high and PGF(2alpha) low in luteal incubations from either Day 9 or Day 17 saline-treated pigs. Cloprostenol increased PGF(2alpha) production 465% and decreased progesterone production 87% only from Day 17 luteal tissue. Cloprostenol induced prostaglandin G/H synthase (PGHS)-2 mRNA (0.5 h) and protein (10 h) in both groups. In cell culture, cloprostenol or phorbol 12, 13-didecanoate (PDD) (protein kinase C activator), induced PGHS-2 mRNA in luteal cells from both groups. However, acute cloprostenol treatment (10 min) decreased progesterone production and increased PGF(2alpha) production only from Day 17 luteal cells. Thus, PGF(2alpha) production is induced by cloprostenol in porcine CL with luteolytic capacity (Day 17) but not in CL without luteolytic capacity (Day 9). However, this change in PGF(2alpha) production is not explained by a difference in induction of PGHS-2 mRNA or protein.

Eicosatetraynoic and eicosatriynoic acids, lipoxygenase inhibitors, block meiosis via antioxidant action

We previously showed that nordihydroguaiaretic acid (NDGA) and other antioxidants inhibit the resumption of meiosis in oocyte-cumulus complexes (OCC) and denuded oocytes (DO). Because NDGA is well known to be an inhibitor of lipoxygenases (LOX), we assessed whether other LOX inhibitors influence spontaneous germinal vesicle breakdown (GVBD) in OCC and DO. Spontaneous GVBD in rat OCC obtained from preovulatory follicles was significantly and reversibly inhibited by the minimum effective doses of 80 and 100 microM 5,8,11, 14-eicosatetraynoic acid (ETYA) and 5,8,11-eicosatriynoic acid (ETI), respectively. In DO, GVBD was significantly inhibited by 100 microM ETYA or ETI. The minimum effective concentrations of ETYA and ETI for inhibition of GVBD in either OCC or DO are approximately 30- to 50-fold higher than the concentrations necessary to inhibit LOX activity by 50% in intact cells. Because we previously showed that NDGA and other antioxidants inhibit the spontaneous resumption of meiosis, we assessed whether ETYA and ETI may act similarly as scavengers of reactive oxygen species (ROS). Luminol-amplified chemiluminescence showed that 50 microM of either ETYA or ETI markedly and significantly reduced ROS generated with 10 mM 2, 2'-azobis(2-amidinopropane)dihydrochloride (AAPH). Moreover, incubation of DO with 30 mM AAPH reversed the inhibition of GVBD produced by 100 microM ETYA or ETI. These findings support the conclusion that ETYA and ETI inhibit oocyte maturation by acting as antioxidants rather than by inhibiting LOX.