The production of progesterone and 5,6-epoxyeicosatrienoic acid by human granulosa cells

Role of oxylipins in ovarian function and disease: A comprehensive review

Ovaries are essential for healthy female reproduction, with the follicles as their fundamental functional units, which consist of an oocyte and surrounding granulosa cells. The development and formation of follicles in the ovaries are closely linked to reproductive health. Oxylipins refer to oxidative metabolites produced from the oxidation of polyunsaturated fatty acids, either through automatic oxidation or with the help of specific enzymes. They play crucial regulatory roles in the immune system, oxidative stress, and inflammatory reactions and are intimately linked to the development of numerous illnesses, such as diabetes, heart disease, asthma, and Alzheimer's disease. Furthermore, oxylipins have a complex relationship with ovarian function, and both prostaglandins and leukotrienes produced by arachidonic acid affect processes such as follicle growth and development, ovulation, and hormone regulation. The synthesis and metabolism of oxylipins in the ovaries are finely regulated. Oxylipin dysregulation has been linked to various ovarian diseases, including endometriosis, polycystic ovary syndrome, ovarian cancer, and premature ovarian insufficiency. In addition, potential therapeutic targets and interventions targeting the oxylipin pathway for the treatment of ovarian diseases have become a prominent research focus, including regulating the enzymes responsible for oxylipin synthesis, using anti-inflammatory agents, and regulating lipid metabolism. Recent research has been directed towards improving the reproductive outcomes of women with ovarian diseases through this series of interventions. An overview of the role of oxylipins in ovarian function and disease is provided in this article, which will aid researchers in understanding the current state of the field and in identifying future directions.

Inflammation, lipid dysregulation, and transient receptor potential cation channel subfamily V member 4 signaling perpetuate chronic vulvar pain

ABSTRACT

Localized provoked vulvodynia is characterized by chronic vulvar pain that disrupts every aspect of the patient's life. Pain is localized to the vulvar vestibule, a specialized ring of tissue immediately surrounding the vaginal opening involved in immune defense. In this article, we show inflammation is the critical first step necessary for the generation of pain signals in the vulva. Inflammatory stimuli alone or combined with the transient receptor potential cation channel subfamily V member 4 (TRPV4) agonist 4α-phorbol 12,13-didecanoate stimulate calcium flux into vulvar fibroblast cells. Activity is blocked by the TRPV4 antagonist HC067047, denoting specificity to TRPV4. Using lipidomics, we found pro-resolving lipids in the vulvar vestibule were dysregulated, characterized by a reduction in pro-resolving mediators and heightened production of inflammatory mediators. We demonstrate specialized pro-resolving mediators represent a potential new therapy for vulvar pain, acting on 2 key parts of the disease mechanism by limiting inflammation and acutely inhibiting TRPV4 signaling.

Inflammation, lipids, and pain in vulvar disease

Localized provoked vulvodynia (LPV) affects ∼14 million people in the US (9% of women), destroying lives and relationships. LPV is characterized by chronic pain (>3 months) upon touch to the vulvar vestibule, which surrounds the vaginal opening. Many patients go months or years without a diagnosis. Once diagnosed, the treatments available only manage the symptoms of disease and do not correct the underlying problem. We have focused on elucidating the underlying mechanisms of chronic vulvar pain to speed diagnosis and improve intervention and management. We determined the inflammatory response to microorganisms, even members of the resident microflora, sets off a chain of events that culminates in chronic pain. This agrees with findings from several other groups, which show inflammation is altered in the painful vestibule. The vestibule of patients is acutely sensitive to inflammatory stimuli to the point of being deleterious. Rather than protect against vaginal infection, it causes heightened inflammation that does not resolve, which coincides with alterations in lipid metabolism that favor production of proinflammatory lipids and not pro-resolving lipids. Lipid dysbiosis in turn triggers pain signaling through the transient receptor potential vanilloid subtype 4 receptor (TRPV4). Treatment with specialized pro-resolving mediators (SPMs) that foster resolution reduces inflammation in fibroblasts and mice and vulvar sensitivity in mice. SPMs, specifically maresin 1, act on more than one part of the vulvodynia mechanism by limiting inflammation and acutely inhibiting TRPV4 signaling. Therefore, SPMs or other agents that target inflammation and/or TRPV4 signaling could prove effective as new vulvodynia therapies.

Enantioselective residues and toxicity effects of the chiral triazole fungicide hexaconazole in earthworms (Eisenia fetida)

The enantioselective toxic effect and environmental behavior of chiral pesticides have attracted increasing research attention. In this study, the enantioselective toxicity and residues of hexaconazole (HEX) in earthworms (Eisenia fetida) were investigated. In the present study, significant enantioselective degradation characteristics were observed in artificial soil with the R-enantiomer preferentially degrading (p < 0.05); however, no significant enantioselective bioaccumulation was observed in the earthworms (p > 0.05). The acute toxicity of S-(+)-HEX was higher than that of R-(-)-HEX in earthworms, with 48-h LC₅₀ values of 8.62 and 22.35 μg/cm², respectively. At 25 mg/kg, enantiospecific induction of oxidative stress was observed in earthworms; moreover, S-(+)-HEX had a greater influence on the contents of malonaldehyde, cytochrome P450, and 8-hydroxy-2-deoxyguanosine than R-(-)-HEX. These results were consistent with those of the enrichment analysis of differentially expressed genes. The transcriptome sequencing results showed that S-(+)-HEX had a more significant influence on steroid biosynthesis, arachidonic acid metabolism, and cell cycle processes than R-(-)-HEX, leading to abnormal biological function activities. These results indicate that S-(+)-HEX may pose a higher risk to soil organisms than R-(-)-HEX. This study suggests that the environmental risk of chiral pesticides to nontarget organisms should be assessed at the enantiomeric level.

Epoxyeicosatrienoic acids: Emerging therapeutic agents for central post-stroke pain

Central post-stroke pain (CPSP) is chronic neuropathic pain due to a lesion or dysfunction of the central nervous system following cerebrovascular insult. This syndrome is characterized by chronic somatosensory abnormalities including spontaneous pain, hyperalgesia and allodynia, which localize to body areas corresponding to the injured brain region. However, despite its potential to impair activities of daily life and cause mood disorders after stroke, it is probably the least recognized complication of stroke. All currently approved treatments for CPSP have limited efficacy but troublesome side effects. The detailed mechanism underlying CPSP is still under investigation; however, its diverse clinical features indicate excessive central neuronal excitability, which is attributed to loss of inhibition and excessive neuroinflammation. Recently, exogenous epoxyeicosatrienoic acids (EETs) have been used to attenuate the mechanical allodynia in CPSP rats and proven to provide a quicker onset and superior pain relief compared to the current first line drug gabapentin. This anti-nociceptive effect is mediated by reserving the normal thalamic inhibition state through neurosteroid-GABA signaling. Moreover, mounting evidence has revealed that EETs exert anti-inflammatory effects by inhibiting the expression of vascular adhesion molecules, activating NFκB, inflammatory cytokines secretion and COX-2 gene induction. The present review focuses on the extensive evidence supporting the potential of EETs to be a multi-functional therapeutic approach for CPSP. Additionally, the role of EETs in the crosstalk between anti-CPSP and the comorbid mood disorder is reviewed herein.

Dysregulated immunological and metabolic functions discovered by a polygenic integrative analysis for PCOS

RESEARCH QUESTION

Polycystic ovary syndrome (PCOS) is a complex disease and its pathophysiology is still unclear. This polygenic study may provide some clues.

DESIGN

A polygenic, functionome-based study with the ovarian gene expression profiles downloaded from the National Center for Biotechnology Information (NCBI) Gene Expression Omnibus (GEO) database, including 48 PCOS and 181 normal control samples. These profiles were converted to the gene set regularity (GSR) indices, which were computed by the modified differential rank conversion algorithm and were defined by the gene ontology terms.

RESULTS

Machine learning could accurately recognize the patterns of functional regularities between PCOS and normal controls. The significantly aberrant functions in PCOS included transporter activity, catalytic activity, the receptor signalling pathway via signal transducer and activator of transcription (STAT), the cellular metabolic process, and immune response.

CONCLUSION

This study provided a comprehensive view of the dysregulated functions and information for further studies on the management of PCOS.

SIRT2 plays a novel role on progesterone, estradiol and testosterone synthesis via PPARs/LXRα pathways in bovine ovarian granular cells

SIRT2 has been shown to possess NAD⁺-dependent deacetylase and desuccinylase enzymatic activities, it also regulates metabolism homeostasis in mammals. Previous data has suggested that resveratrol, a potential activator of Sirtuins, played a stimulation role in steroidogenesis. Unfortunately, to date, the physiological roles of SIRT2 in ovarian granular cells (GCs) are largely unknown. Here, we studied the function and molecular mechanisms of SIRT2 on steroid hormone synthesis in GCs from Qinchuan cattle. Immunohistochemistry and western blotting showed that SIRT2 was expressed not only in GCs and cumulus cells, but also in oocytes and theca cells. We found that the secretion of progesterone was induced, whereas that of estrogen and testosterone secretion was suppressed by treatment with the SIRT2 inhibitor (Thiomyristoyl or SirReal2) or siRNA. Additionally, the PPARs/LXRα signaling pathways were suppressed by SIRT2 siRNA or inhibitors. The mRNA expression of CYP17, aromatase and StAR was suppressed, but the abundance of CYP11A1 mRNA was induced by SIRT2 inhibition. Furthermore, the PPARα agonist or PPARγ antagonist could mimic the effects of SIRT2 inhibition on hormones levels and gene expression associated with steroid hormone biosynthesis. In turn, those effects were abolished by the LXRα agonist (LXR-623). Together, these data support the hypothesis that SIRT2 regulates steroid hormone synthesis via the PPARs/LXRα pathways in GCs.

Cross-Classification of Human Urinary Lipidome by Sex, Age, and Body Mass Index

Technological advancements in past decades have led to the development of integrative analytical approaches to lipidomics, such as liquid chromatography-mass spectrometry (LC/MS), and information about biogenic lipids is rapidly accumulating. Although several cohort-based studies have been conducted on the composition of urinary lipidome, the data on urinary lipids cross-classified by sex, age, and body mass index (BMI) are insufficient to screen for various abnormalities. To promote the development of urinary lipid metabolome-based diagnostic assay, we analyzed 60 urine samples from healthy white adults (young (c.a., 30 years) and old (c.a., 60 years) men/women) using LC/MS. Women had a higher urinary concentration of omega-3 12-lipoxygenase (LOX)-generated oxylipins with anti-inflammatory activity compared to men. In addition, young women showed increased abundance of poly-unsaturated fatty acids (PUFAs) and cytochrome P450 (P450)-produced oxylipins with anti-hypertensive activity compared with young men, whereas elderly women exhibited higher concentration of 5-LOX-generated anti-inflammatory oxylipins than elderly men. There were no significant differences in urinary oxylipin levels between young and old subjects or between subjects with low and high BMI. Our findings suggest that sex, but neither ages nor BMI could be a confounding factor for measuring the composition of urinary lipid metabolites in the healthy population. The information showed contribute to the development of reliable biomarker findings from urine.

Cylindrospermopsin, a blue-green algal toxin, inhibited human luteinised granulosa cell protein synthesis in vitro

The blue-green algal toxin cylindrospermopsin (CYN) inhibits protein synthesis, and CYP450 enzymes metabolise CYN to cytotoxic endproducts. Human chorionic gonadotrophin (hCG) stimulates the de novo synthesis of StAR and CYP450 aromatase. Human IVF-derived granulosa cells (GC) (n=7) were exposed to 0-5μM CYN±1IU/ml hCG for 2-24h. After 24h pre-culture GC responded to hCG by increasing estradiol 17β (E(2)) and progesterone (P(4)) synthesis. Three micromolar of CYN±1IU/ml hCG for 24h was not cytotoxic and did not affect basal or hCG-stimulated E(2) or P(4) production, but did inhibit protein synthesis (p<0.05, n=4). hCG-stimulated steroidogenesis was not reduced by CYN, suggesting a lack of effect on StAR or CYP450 aromatase protein synthesis. hCG enhanced the effects of CYN on GC protein synthesis. Twenty four hours exposure to 0.1μM CYN did not affect GC, supporting the establishment of a 0.0024μM Guideline level for CYN in public water supplies.

Soluble epoxide hydrolase and epoxyeicosatrienoic acids modulate two distinct analgesic pathways

During inflammation, a large amount of arachidonic acid (AA) is released into the cellular milieu and cyclooxygenase enzymes convert this AA to prostaglandins that in turn sensitize pain pathways. However, AA is also converted to natural epoxyeicosatrienoic acids (EETs) by cytochrome P450 enzymes. EET levels are typically regulated by soluble epoxide hydrolase (sEH), the major enzyme degrading EETs. Here we demonstrate that EETs or inhibition of sEH lead to antihyperalgesia by at least 2 spinal mechanisms, first by repressing the induction of the COX2 gene and second by rapidly up-regulating an acute neurosteroid-producing gene, StARD1, which requires the synchronized presence of elevated cAMP and EET levels. The analgesic activities of neurosteroids are well known; however, here we describe a clear course toward augmenting the levels of these molecules. Redirecting the flow of pronociceptive intracellular cAMP toward up-regulation of StARD1 mRNA by concomitantly elevating EETs is a novel path to accomplish pain relief in both inflammatory and neuropathic pain states.

Inhibition of thromboxane a synthase activity enhances steroidogenesis and steroidogenic acute regulatory gene expression in MA-10 mouse Leydig cells

The cyclooxygenase-2 (COX2)-dependent inhibition of Leydig cell steroidogenesis has been demonstrated. To understand the mechanism for this effect of COX2, the present study examined the role of an enzyme downstream of COX2, namely thromboxane A synthase (TBXAS), in steroidogenesis. Inhibition of TBXAS activity with the inhibitor furegrelate induced a concentration-dependent increase in cAMP-induced steroidogenic acute regulatory (StAR) protein in MA-10 mouse Leydig cells. The increase in StAR protein occurred concomitantly with a significant increase in steroid hormone production. Similar results were obtained in StAR promoter activity assays and RT-PCR analyses of StAR mRNA levels, suggesting that inhibition of TBXAS activity enhanced StAR gene transcription. These observations were corroborated when TBXAS expression was specifically inhibited by RNA interference. Although the RNA interference reduced mRNA levels of TBXAS, it increased StAR mRNA levels, StAR protein, and steroidogenesis. Additional studies indicated that inhibition of TBXAS activity reduced DAX-1 protein, a repressor in StAR gene transcription. In the absence of cAMP, inhibition of TBXAS activity did not induce a significant increase in steroid hormone and StAR protein. However, addition of a low level of cAMP analogs dramatically increased steroidogenesis. Lastly, inhibition of protein kinase A activity essentially abolished the steroidogenic effect of the TBXAS inhibitor. Thus, the results from the present study suggest that a minimal level of protein kinase A activity is required for the steroidogenic effect of the TBXAS inhibitor and that inhibition of TBXAS activity or its expression increase the steroidogenic sensitivity of MA-10 mouse Leydig cells to cAMP stimulation.

Dynamic expression of epoxyeicosatrienoic acid synthesizing and metabolizing enzymes in the primate corpus luteum

Epoxyeicosatrienoic acids (EpETrEs), produced from arachidonic acid via cytochrome P450 (CYP) epoxygenases, regulate inflammation, angiogenesis, cellular proliferation, ion transport and steroidogenesis. EpETrE actions are regulated through their metabolism to diols (dihydroxyeicosatrienoic acids; DiHETrE) via the enzyme soluble epoxide hydrolase (EPHX2). We set out to determine, therefore, whether EpETrE generating (epoxygenases CYP2C8, 2C9, 2C19, 2J2, 1A2 and 3A4) and metabolizing (EPHX2) enzymes are expressed in the primate corpus luteum (CL). CL were isolated from rhesus macaques during the early (day 3-5 post-LH surge), mid (day 6-8), mid-late (day 10-12), late (day 14-16) and very-late (day 17-19: menses) luteal phase of natural menstrual cycles. EPHX2 mRNA levels peaked in mid-late CL (5-fold when compared with early CL, P<0.05) and remained elevated in the late CL. Ablation of pituitary LH secretion and luteal steroid synthesis significantly reduced (P<0.05) EPHX2 mRNA levels in the mid-late CL, with progestin replacement being insufficient to restore its level of expression to control values. EPHX2 protein was localized to large and small luteal cells, as well as vascular endothelial cells. The EpETrE-generating CYP epoxygenase 2J2, 2C9 and 3A4 genes were also expressed in the macaque CL. While CYP2J2 mRNA levels did not significantly change through the luteal phase, CYP2C9 and CYP3A4 levels were significantly (P<0.05) higher in the mid-late phase when compared with the early phase. CYP2C9, 2J2 and 3A4 proteins were each localized to the large luteal cells, with 2C9 and 2J2 also being present in the small luteal, stromal and endothelial cells. These studies demonstrate for the first time that an EpETrE generating and metabolizing system exists in the primate CL, with the latter being regulated by LH and steroid hormone(s).

Identification and Characterization of an Ovary-Selective Isoform of Epoxide Hydrolase1

A novel ovary-selective gene was identified by suppression subtractive hybridization (SSH) that is expressed only during the mouse periovulatory phase of a stimulated estrous cycle. Analysis of the protein encoded by the full-length cDNA revealed that the majority of it, with the exception of the first 44 amino acids, matched soluble epoxide hydrolase (Ephx2, referred to as Ephx2A). By comparing the cDNA sequence of this newly identified variant of soluble epoxide hydrolase (referred to as Ephx2B) with the mouse genome database, an exon was identified that corresponds to its unique 5' cDNA sequence. Through the use of an Ephx2A-specific probe, Northern blot analysis revealed that this mRNA was also expressed in the ovary, with the highest level of expression occurring during the luteal phase of a stimulated estrous cycle. In situ hybridization revealed that Ephx2B mRNA expression was restricted to granulosa cells of preovulatory follicles. Ephx2A mRNA expression, however, was detectable in follicles at different stages of development, as well as in the corpus luteum. Total ovarian epoxide hydrolase activity increased following the induction of follicular development, and remained elevated through the periovulatory and postovulatory stages of a stimulated estrous cycle. The change in enzyme activity paralleled the combined mRNA expression profiles for both Ephx2A and Ephx2B, thus supporting a role for epoxide metabolism in ovarian function.

Cytochrome p450-dependent lipid metabolism in preovulatory follicles

Estrogen biosynthesis and proteolysis are both important processes involved in ovarian follicular development, which may be influenced by cytochrome P450 (CYP)-dependent fatty acid metabolites. However, CYP-dependent lipid metabolism has not been characterized with respect to follicular maturation in vivo. Therefore, follicular fluid was collected in the hours before and after the LH surge in pigs, and concentrations of epoxy, hydroxy, and dihydroxy lipids were measured by liquid chromatography tandem mass spectrometry. Arachidonate oxidation and epoxyeicosatrienoic acid hydrolysis to dihydroxyeicosatrienoic acids (DHETs) were also assessed in thecal and granulosa tissue fractions, and the expression of CYP epoxygenases was evaluated by immunoblots using available antisera. To evaluate soluble epoxide hydrolase (sEH) expression, the porcine sEH was cloned from ovarian tissue, expressed and purified for antibody generation. The follicular fluid oxylipin concentrations ranged from 1-150 nm depending on the compound and estrous stage. The follicular fluid concentrations of CYP-dependent oxylipins increased at estrus, as did sEH expression; however, significant changes in epoxides were not observed, and the 11,12-DHET peak was delayed. The ratio of 14,15-DHET:11,12-DHET across all samples correlated with the log of follicular fluid estradiol concentrations (P < 0.01). Epoxygenase activities were similar in theca and granulosa, varying little with follicular development, whereas the decline of a single CYP2J isoform at ovulation was observed by immunoblots. The sEH activity was higher in granulosa than in theca. Finally, the dynamic changes in follicular CYP-dependent arachidonic acid metabolites and their modulatory function in vascular models suggest roles for these metabolites in follicular maturation, which may include regulation of estradiol biosynthesis and preovulatory remodeling of the follicular wall that should be fully explored in future studies.