The presence of lipid droplets (LD) and the utilization of fatty acids (FA) as a source of energy are Sertoli cell (SC) putative characteristics. It is well known that SCs can phagocyte and degrade apoptotic germ cells (AGC) resulting in increasing lipid content and ATP levels. A relationship between the regulation of lipid storage and of lipid oxidation in SC might be envisaged. The aim of this study was to analyze whether AGC and FA are able to simultaneously regulate molecular mechanisms involved in lipid storage and in FA oxidation in SC. The experimental model utilized in this study consisted in SC cultures obtained from 20-day-old rats that were co-cultured with AGC or treated with palmitic acid (PA, 500 μM) for 24 and 48 h. AGC and PA increase LD, triacylglycerol (TAG) content and mRNA levels of Plin1, Plin2, Plin3 (proteins involved in TAG storage). Simultaneously, AGC and PA rise the extent of FA oxidation and mRNA levels of Cpt1 and Lcad (proteins involved in FA degradation). Results also show that peroxisome proliferator-activated receptor (PPAR) transcriptional activity, transcription factor which participate in lipid metabolism regulation, increases by AGC and PA treatment in SC. Additionally, the presence of a PPARg antagonist decreases the upregulation of LD content and Plin1 expression. Similarly, the presence of a PPARb/d antagonist reduces the increase in FA oxidation and Cpt1 mRNA levels. Altogether these results suggest that AGC and FA, which probably generate PPAR ligands, regulate lipid storage and fatty acid utilization, contributing to the energy homeostasis in the seminiferous tubules.
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Mariana Regueira, Agostina Gorga, Gustavo Marcelo Rindone, Eliana Herminia Pellizzari, Selva Beatriz Cigorraga, María Noel Galardo, María Fernanda Riera and Silvina Beatriz Meroni
Silvia Sposini and Aylin C Hanyaloglu
Our understanding of G protein-coupled receptor (GPCR) signalling has significantly evolved over the past decade, whereby signalling not only occurs from the plasma membrane but continues, or is reactivated, following internalisation in to endosomal compartments. The spatial organisation of GPCRs is thus essential to decode dynamic and complex signals and to activate specific downstream pathways that elicit the appropriate cellular response. For the gonadotrophin hormone receptors, membrane trafficking has been demonstrated to play a significant role in regulating its signal activity that in turn would impact at physiological and even pathophysiological level. Here, we will describe the developments in our understanding of the role of ‘location’ in gonadotrophin hormone receptor signalling, and how these receptors have unveiled fundamental mechanisms of signal regulation likely to be pertinent for other GPCRs. We will also discuss the potential impact of spatially controlled gonadotrophin hormone receptor signalling in both health and disease, and the therapeutic possibilities this new understanding of these receptors, so key in reproduction, offers.
Pacharawan Deenarn, Punsa Tobwor, Rungnapa Leelatanawit, Somjai Wongtriphop, Jutatip Khudet, Nitsara Karoonuthaisiri, Vanicha Vichai and Wananit Wimuttisuk
The delay in ovarian maturation in farmed black tiger shrimp Penaeus monodon has resulted in the widespread practice of feeding broodstock with the polychaete Perinereis nuntia and their unilateral eyestalk ablation. Although this practice alters fatty acid content in shrimp ovaries and hepatopancreas, its effects on fatty acid regulatory genes are yet to be systematically examined. Here, microarray analysis was performed on hepatopancreas and ovary cDNA collected from P. monodon at different ovarian maturation stages, revealing that 72 and 58 genes in fatty acid regulatory pathways were differentially expressed in hepatopancreas and ovaries respectively. Quantitative real-time PCR analysis revealed that ovarian maturation was associated with higher expression levels of acetyl-CoA acetyltransferase, acyl-CoA dehydrogenase, acyl-CoA oxidase 3 and long-chain fatty acid transport protein 4 in hepatopancreas, whereas the expression levels of 15 fatty acid regulatory genes were increased in shrimp ovaries. To distinguish the effects of different treatments, transcriptional changes were examined in P. monodon with stage 1 ovaries before polychaete feeding, after 1 month of polychaete feeding and after eyestalk ablation. Polychaete feeding resulted in lower expression levels of enoyl-CoA hydratase and acyl-CoA synthetase medium-chain family member 4, while the expression level of phosphatidylinositide phosphatase SAC1 was higher in shrimp hepatopancreas and ovaries. Additionally, eyestalk ablation resulted in a higher expression level of long-chain fatty acid-CoA ligase 4 in both tissues. Together, our findings describe the dynamics of fatty acid regulatory pathways during crustacean ovarian development and provide potential target genes for alternatives to eyestalk ablation in the future.
Jun Yin, Bing Ni, Yi-dong Yang, Zhong-wei Tang, Zhi-qi Gao, Lan Feng, Wei-gong Liao and Yu-qi Gao
Autophagy and apoptosis are interlocked in an extensive crosstalk. Our previous study demonstrated that hypotonic hypoxia-induced marked apoptosis of a spermatocyte-derived cell line (GC-2). However, whether hypoxia-induced apoptosis is mediated by inhibition of autophagy under hypoxic conditions remains unclear. In this study, GC-2 cells were cultured in 1% O2 and harvested at different time points. Autophagy was determined by acridine orange staining, cyto-ID staining, mCherry-GFP-LC3B adenovirus transfection and Western blotting for various autophagy markers. Apoptosis was detected by TUNEL staining, flow cytometry, JC-1 staining and Western blotting of apoptosis-related proteins. We found that hypoxia-induced apoptosis of GC-2 cells through mitochondrial and death receptor pathways and inhibited autophagic flux in GC-2 cells in a time-dependent manner. However, while marked autolysosome formation was observed in GC-2 cells before 24-h culture in hypoxic conditions, apparent apoptosis was observed only after 24-h culture in hypoxic conditions. Caspase-8 siRNA treatment induced cell survival, accompanied by induction of the mature autophagosome, acidic vesicular organelle formation and autophagic flux. Furthermore, Beclin-1 overexpression markedly attenuated the impairment of spermatogenesis in mice by inhibiting apoptosis of spermatocytes. The results of this study demonstrate that hypoxia inhibits autophagy, which further enhances hypoxia-induced apoptosis of mouse spermatocytes by promoting caspase-8 activation in a time-dependent manner, suggesting that combined application of apoptosis inhibition and autophagy activation might be a therapeutic strategy for treating hypoxia-induced male infertility.
Beverly G Reed, Samir N Babayev, Lucy X Chen, Bruce R Carr, R Ann Word and Patricia T Jimenez
MicroRNAs (miRs) are small molecules important for regulation of transcription and translation. The objective was to identify hormonally regulated miRs in human endometrial stromal cells and to determine the impact of the endocrine disruptor, bisphenol A (BPA), on those miRs. miR microarray analysis and multiple confirmatory cell preparations treated with 17β-estradiol (E2) and BPA altered miR-27b, let-7c, let-7e and miR-181b. Further, decidualization downregulated miR-27b. VEGFB and VEGFC were validated as targets of miR-27b. Identification of miR-27b target genes suggests that BPA and E2 downregulate miR-27b thereby leading to upregulation of genes important for vascularization and angiogenesis of the endometrium during the menstrual cycle and decidualization.
Melissa L McCallum, Cindy A Pru, Andrea R Smith, Nicole C Kelp, Marc Foretz, Benoit Viollet, Min Du and James K Pru
Adenosine monophosphate-activated protein kinase (AMPK) is a highly conserved heterotrimeric complex that acts as an intracellular energy sensor. Based on recent observations of AMPK expression in all structures of the female reproductive system, we hypothesized that AMPK is functionally required for maintaining fertility in the female. This hypothesis was tested by conditionally ablating the two catalytic alpha subunits of AMPK, Prkaa1 and Prkaa2, using Pgr-cre mice. After confirming the presence of PRKAA1, PRKAA2 and the active phospho-PRKAA1/2 in the gravid uterus by immunohistochemistry, control (Prkaa1/2 fl/fl) and double conditional knockout mice (Prkaa1/2 d/d) were placed into a six-month breeding trial. While the first litter size was comparable between Prkaa1/2 fl/fl and Prkaa1/2 d/d female mice (P = 0.8619), the size of all subsequent litters was dramatically reduced in Prkaa1/2 d/d female mice (P = 0.0015). All Prkaa1 /2 d/d female mice experienced premature reproductive senescence or dystocia by the fourth parity. This phenotype manifested despite no difference in estrous cycle length, ovarian histology in young and old nulliparous or multiparous animals, mid-gestation serum progesterone levels or uterine expression of Esr1 or Pgr between Prkaa1/2 fl/fl and Prkaa1/2 d/d female mice suggesting that the hypothalamic–pituitary–ovary axis remained unaffected by PRKAA1/2 deficiency. However, an evaluation of uterine histology from multiparous animals identified extensive endometrial fibrosis and disorganized stromal-glandular architecture indicative of endometritis, a condition that causes subfertility or infertility in most mammals. Interestingly, Prkaa1/2 d/d female mice failed to undergo artificial decidualization. Collectively, these findings suggest that AMPK plays an essential role in endometrial regeneration following parturition and tissue remodeling that accompanies decidualization.
Qianrong Qi, Yifan Yang, Kailin Wu and Qingzhen Xie
Recent studies revealed that TMEM16A is involved in several reproductive processes, including ovarian estrogen secretion and ovulation, sperm motility and acrosome reaction, fertilization and myometrium contraction. However, little is known about the expression and function of TMEM16A in embryo implantation and decidualization. In this study, we focused on the expression and regulation of TMEM16A in mouse uterus during early pregnancy. We found that TMEM16A is upregulated in uterine endometrium in response to embryo implantation and decidualization. Progesterone treatment could induce TMEM16A expression in endometrial stromal cells through progesterone receptor/c-Myc pathway, which is blocked by progesterone receptor antagonist or the inhibitor of c-Myc signaling pathway. Inhibition of TMEM16A by small molecule inhibitor (T16Ainh-A01) resulted in impaired embryo implantation and decidualization in mice. Treatment with either specific siRNA of Tmem16a or T16Ainh-A01 inhibited the decidualization and proliferation of mouse endometrial stromal cells. In conclusion, our results revealed that TMEM16A is involved in embryo implantation and decidualization in mice, compromised function of TMEM16A may lead to impaired embryo implantation and decidualization.
Gabriela Hernández-Silva, Marta Durand, Fernando Larrea and Mayel Chirinos
When levonorgestrel (LNG) is given for emergency contraception during the follicular phase, it not only inhibits or delays ovulation, but also induces changes in endometrial secretions that modulate sperm functionality. In order to characterize the female reproductive tract secreted molecules that may affect human spermatozoa, we analyzed changes in the protein content of uterine flushings obtained from women during the periovulatory phase of a control and a LNG-treated menstrual cycle. Lectin affinity analysis and 2D gel electrophoresis of uterine samples showed changes in protein glycosylation patterns and the presence of 31 differentially expressed proteins (8 upregulated and 23 downregulated). Mass spectrometry and Western blot analyses of the differential expressed proteins showed lactotransferrin (LTF) as one of the upregulated molecules by LNG. In this study, LTF exhibited significant dose-related effects on sperm functionality, particularly a decrease of calcium ionophore-induced acrosome reaction and protein tyrosine phosphorylation. Overall, the results indicated that LNG promoted changes in the proteome of uterine secretions that might compromise human sperm capacitation. These data further support the participation of other mechanisms of action of LNG as emergency contraceptive, in addition to those on ovulation.
Roland Abi Nahed, Guillaume Martinez, Jean Pascal Hograindleur, Emilie Le Blévec, Sabine Camugli, Richard Le Boucher, Pierre F Ray, Jessica Escoffier, Eric Schmitt and Christophe Arnoult
For artificial insemination (AI) to be successful, it is essential that sperm delivery be perfectly timed relative to ovulation, as sperm lifespan is limited due to oxidative metabolism induced by capacitation. Extending the window of sperm capacitation could therefore increase sperm lifespan, prolong sperm-fertilizing competence and increase AI efficiency. Hyperpolarization of sperm is a crucial step in capacitation and is induced by activation of the potassium calcium-activated channel subfamily U member 1 (KCNU1, also named Slo3 or KSper). Given the essential role played by KCNU1 in capacitation, this study assessed the impact of its pharmacological inhibition on sperm lifespan. We showed that treatment of murine sperm with sub-micromolar concentrations of clofilium, a specific inhibitor of KCNU1, slowed down capacitation, decreased the rate of acrosome reaction and extended the fertilizing competence of capacitated sperm for 12 h. Clofilium also extended fertilizing competence and motility of bovine-capacitated sperm, and increased the rate of fertilization with sperm capacitated for 24 h by 100%, and the rate of blastocyst formation by 150%. Finally, toxicity experiments showed clofilium to have no impact on sperm DNA and no embryotoxicity at the concentration used to extend sperm lifespan. Our results demonstrate that clofilium prolongs fertilizing competence of aging capacitated sperm in vitro in both rodent and bovine species. To our knowledge, this is the first time the duration of sperm-fertilizing competence is shown to be extended by potassium channels blockers.
Andrée-Anne Saindon and Pierre Leclerc
Sperm adhesion molecule 1 (SPAM1) is a sperm protein possessing a hyaluronidase domain in its N-terminus and a zona pellucida-binding domain in its C-terminus. Our previous studies showed that bovine spermatozoa potentially have 2 SPAM1 isoforms that present different C-terminal domains, different origins (testis and epididymis) and different locations in spermatozoa. In this study, two approaches were taken to characterize the different SPAM1 isoforms. First, 3′-RACE experiments were done to determine the sequence of the 3′ regions of the potential transcripts. Second, by in silico analyses, we aimed to determine whether our antibody that recognizes the N-terminal domain of SPAM1 detects two SPAM1 isoforms or two highly similar, although different, proteins. We found that the 3′ regions of SPAM1 transcripts from bovine testis and caput epididymis were identical. Nevertheless, two transcript variants that differ by 90 nucleotides, encoded by an entire exon, are expressed in both tissues. Only the protein encoded by the longest SPAM1 transcript variant was confirmed in ejaculated bull spermatozoa by mass spectrometry. In silico analyses revealed a highly similar protein to SPAM1, PH-20, that could potentially be recognized by our N-terminal antibody. The presence of PH-20 transcripts was confirmed in bovine testis and the protein is present in ejaculated spermatozoa. Our N-terminal antibody possibly recognizes both SPAM1 and the highly homologous protein PH-20 instead of two SPAM1 isoforms. Identifying the proteins implicated in the fertilization process is crucial in order to elucidate their roles and to better understand the complex process of fertilization.