Jae-Young Park

Melatonin improves the meiotic maturation of porcine oocytes by reducing endoplasmic reticulum stress during in vitro maturation

Under endoplasmic reticulum (ER)‐stress conditions, the unfolded protein response (UPR) generates a defense mechanism in mammalian cells. The regulation of UPR signaling is important in oocyte maturation, embryo development, and female reproduction of pigs. Recent studies have shown that melatonin plays an important role as an antioxidant to improve pig oocyte maturation. However, there is no report on the role of melatonin in the regulation of UPR signaling and ER‐stress during in vitro maturation (IVM) of porcine oocytes. Therefore, the objective of this study was to investigate the antioxidative effects of melatonin on porcine oocyte maturation through the regulation of ER‐stress and UPR signaling. We investigated the changes in the mRNA/protein expression levels of three UPR signal genes (Bip/Grp78, ATF4, P90/50ATF6, sXbp1, and CHOP) on oocytes, cumulus cells, and cumulus‐oocyte complexes (COCs) during IVM (metaphase I; 22 hours and metaphase II; 44 hours) by Western blot and reverse transcription‐polymerase chain reaction analysis. Treatment with the ER‐stress inducer, tunicamycin (Tm), significantly increased expression of UPR markers. Additionally, cumulus cell expansion and meiotic maturation of oocytes were reduced in COCs of Tm‐treated groups (1, 5, and 10 μg/mL). We confirmed the reducing effects of melatonin (0.1 μmol/L) on ER‐stress after pretreatment with Tm (5 μg/mL; 22 hours) in maturing COCs. Addition of melatonin (0.1 μmol/L) to Tm‐pretreated COCs recovered meiotic maturation rates and expression of most UPR markers. In conclusion, we confirmed a role for melatonin in the modulation of UPR signal pathways and reducing ER‐stress during IVM of porcine oocytes.

173 MELATONIN ALLEVIATES THE ENDOPLASMIC RETICULUM STRESS THROUGH THE REGULATING OF UNFOLDING PROTEIN RESPONSE SIGNALING DURING PORCINE OOCYTE MATURATION IN VITRO

Unfolding protein response (UPR) is a defence mechanism during endoplasmic reticulum (ER) stress in mammalian cells. Especially, UPR genes and regulation of reactive oxygen species is involved in ER stress response on porcine oocyte maturation in vitro. Some studies have shown that melatonin treatment results in reducing oxidative stress, a protective function of free radical damage in oocyte maturation and embryo development. Also, melatonin has an important role in reducing reactive oxygen species and ER stress. However, it is unknown how the changes of UPR genes expression levels are affected the porcine oocyte maturation. In addition, there are no reports about ER stress recovery mechanism by melatonin during porcine oocyte maturation. Here, we investigated the UPR signal genes (Bip/Grp78, Atf4, p90/p50Atf6, and Xbp1) and ER-stress mediated apoptosis factors (Chop and Cleaved caspase 3) in porcine oocyte maturation in vitro. Expression of Chop and Cleaved caspase 3 mRNA levels were significantly increased (P<0.01) in matured oocytes (metaphase II; 44h) in vitro. Porcine oocytes were cultured in maturation medium with ER stress inducer, tunicamycin (Tm), and supplemented with various concentrations (1, 5, and 10μgmL-1) of Tm for 0 to 44h. Our results indicated that the proportion of matured oocytes was significantly decreased in Tm-treated groups in a dose-dependent manner (60.1±1.3, 46.5±2.1, and 38.9±5.1% at 1, 5, and 10μgmL-1 of Tm) compared with the control group (76.6±1.9%). Likewise, mRNA expression of UPR regulator genes (Grp78/Bip, Aft4, Xbp1, Chop, and Cleaved caspase 3) was decreased by melatonin treatment (0.1μM, 22-44h) after pretreatment of Tm (5μgmL-1, 0-22h) during oocyte maturation. Our results demonstrated that the roles of melatonin as UPR signaling regulator for reducing ER stress are essential for promotion of porcine oocyte maturation and cumulus cell expansion of cumulus-oocyte complex. Moreover, the current study was initiated to confirm a functional link between effect of melatonin and regulating of UPR signaling in porcine oocytes maturation. These results suggest that melatonin improve the oocyte maturation and cumulus cells expansion by regulating of UPR signal genes against the ER stress during the porcine in vitro maturation process.

172 THE APOPTOTIC EFFECTS OF BISPHENOL A-INDUCED MITOCHONDRIAL-DERIVED REACTIVE OXYGEN SPECIES ON MATURATION OF PORCINE OOCYTES IN VITRO

Bisphenol A (BPA) is well known as oestrogen-like chemical and it is widely used in plastic products. Many studies have reported that BPA exposure has a well-known toxicity effect on reproduction function, such as reducing the number of ovulated oocytes, oocyte quality, and maturation rate. Recently, BPA induced mitochondrial-derived reactive oxygen species (mito-ROS) and disrupted mitochondrial homeostasis by increasing of superoxide anions production. In this study, we investigated how the regulation of mito-ROS production may play a critical role in meiotic maturation and expansion of cumulus cells during the in vitro maturation progression of porcine oocytes. Furthermore, we investigated the toxicity effect of BPA exposure on mitochondrial functions and mito-ROS production during porcine oocyte maturation in vitro. All results were analysed using a 1-way ANOVA followed by Bonferronis and Tukeys Multiple Comparison Test and t-tests. First, porcine oocytes were matured in NCSU-23 medium supplemented with BPA (50, 75, and 100µM) for 44h. Our results indicated that the rates of matured oocytes were significantly decreased by BPA exposure in a dose-dependent manner (69.4±5.1, 50.9±6.3, and 29.9±5.8% for BPA treatments of 50, 75, and 100μM) compared with control group (70.2±7.8%; P<0.05). Next, we confirmed the secretion functions of oocyte and cumulus cell of cumulus-oocyte complex (COC) and ROS production. Cumulus cell secretion factors (has2, tnfaip6, and cx37) mRNA expression in COC were decreased in the BPA-treated (75µM) group. In addition, mRNA expressions of mitochondrial-specific antioxidant enzymes (sod2, P<0.001; prdx3, P<0.01; prdx5, P<0.001) and mitochondrial apoptosis genes (bax and caspase-3, P<0.01) were significantly increased in COC of the BPA-treated (75µM) group. We measured mitochondrial membrane potential and mito-ROS production using JC-1 analysis and Mito-SOX staining, respectively. The BPA treatment caused a rapid decrease of mitochondrial membrane potential maintenance and increase of mito-ROS production in porcine COC. Moreover, mitochondrial-specific ROS scavenger, Mito-Tempo (0.1µM) treatment was significantly increased the meiotic maturation of porcine oocytes compared with control group (78.5±3.5v. 65.8±5.0%; P<0.05). Based on these results, we first confirmed that BPA exposure reduces the meiotic maturation and cumulus cells expansion of COC by increasing mito-ROS production during porcine oocyte maturation in vitro. Therefore, controlling of mito-ROS for mitochondrial function maintenance and apoptosis plays a critical role in improving porcine oocyte maturation in vitro.

Tyrphostin A9 improves blastocyst development in porcine embryos through induction of dynamin-related protein 1-dependent mitochondrial fission

Mitochondrial dynamics are associated with the development of porcine embryos. However, little is known about the effects of mitochondrial dynamics-related genes (Drp1 and pDrp1-Ser616) on early porcine embryo development. Here, we investigated the effect of Drp1-dependent mitochondrial fission signaling on the development of porcine embryos using the mitochondrial fission inducer, tyrphostin A9 (TA9). We determined that TA9 (1μM) treated embryos were increased the mitochondrial functions, blastocyst development rate and quality, as well as decreased mitochondria-specific superoxide and mitochondrial apoptosis. Thus, TA9-induced appropriate mitochondrial fission improved the developmental competence via maintenance of a balance in mitochondrial dynamics in porcine embryo.

Native plants ( Phellodendron amurense and Humulus japonicus ) extracts act as antioxidants to support developmental competence of bovine blastocysts

Objective Phellodendron amurense (P. amurense) and Humulus japonicus (H. japonicus) are closely involved in anti-oxidative response and increasing antioxidant enzymes activities. However, the effects of their extracts on development of preimplantation bovine embryos have not been investigated. Therefore, we investigated the effects of P. amurense and H. japonicus extracts on developmental competence and quality of preimplantation bovine embryos. Methods After in vitro fertilization, bovine embryos were cultured for 7 days in Charles Rosenkrans amino acid medium supplemented with P. amurense (0.01 μg/mL) and H. japonicus (0.01 μg/mL). The effect of this supplementation during in vitro culture on development competence and antioxidant was investigated. Results We observed that the blastocysts rate was significantly increased (p<0.05) in P. amurense (28.9%±2.9%), H. japonicus (30.9%±1.5%), and a mixture of P. amurense and H. japonicus (34.8%± 2.1%) treated groups compared with the control group (25.4%±1.6%). We next confirmed that the intracellular levels of reactive oxygen species (ROS) were significantly decreased (p<0.01) in P. amurense and/or H. japonicus extract treated groups when compared with the control group. Our results also showed that expression of cleaved caspase-3 and apoptotic cells of blastocysts were significantly decreased (p<0.05) in bovine blastocysts derived from both P. amurense and H. japonicus extract treated embryos. Conclusion These results suggest that proper treatment with P. amurense and H. japonicus extracts in the development of preimplantation bovine embryos improves the quality of blastocysts, which may be related to the reduction of ROS level and apoptosis.

Regulation of the Endoplasmic Reticulum Stress by BIP/GRP78 is involved in Meiotic Maturation of Porcine Oocytes In Vitro

ABSTRACT In the present study, we investigated the role of binding immunoglobulin protein/glucose-regulated protein, 78-kDa (BIP/GRP78)-regulated endoplasmic reticulum (ER)-stress on meiotic maturation and cumulus cells expansion in porcine cumulus-oocyte complexes (COCs). Previously, it has been demonstrated that unfolded protein response (UPR)-related genes, such as molecules involved in ER-stress defense mechanisms, were expressed in matured oocytes and cumulus cells during in vitro maturation (IVM) of porcine oocytes. However, BIP/GRP78-mediated regulation of ER stress in porcine oocytes has not been reported. Firstly, we observed the effects of knockdown of BIP/GRP78 (an UPR initiation marker) using porcine-specific siRNAs (#909, #693, and #1570) on oocyte maturation. Among all siRNAs, siRNA #693 significantly reduced the protein levels of UPR marker proteins (BIP/GRP78, ATF4, and P90ATF6) in porcine COCs observed by Western blotting and immunofluorescence analysis. We also observed that the reduction of BIP/GRP78 levels by siRNA#693 significantly inhibited the meiotic maturation of oocytes (siRNA #693: 32.5±10.1% vs control: 77.8±5.3%). In addition, we also checked the effect of ER-stress inhibitors, tauroursodeoxycholic acid (TUDCA, 200 μM) and melatonin (0.1 μM), in BIP/ GRP78-knockdown oocytes. TUDCA and melatonin treatment could restore the expression levels of ER-stress marker proteins (BIP/GRP78, p-eIF2α, eIF2α, ATF4, and P90ATF6) in siRNA #693-transfected matured COCs. In conclusion, these results demonstrated that BIP/GRP78-mediated regulation of UPR signaling and ER stress plays an important role in in vitro maturation of porcine oocytes.

Changes of Ganglioside GM3 Expression in Porcine Oocyte Maturation and Early Embryonic Development In Vitro

Gangliosides exist in glycosphingolipid-enriched domains on the cell membrane and regulate various functions such as adhesion, differentiation, and receptor signaling. Ganglioside GM3 by ST3GAL5 enzyme provides an essential function in the biosynthesis of more complex ganglio-series gangliosides. However, the role of gangliosides GM3 in porcine oocytes during in vitro maturation and early embryo development stage has not yet understood clear. Therefore, we examined ganglioside GM3 expression patterns under apoptosis stress during maturation and preimplantation development of porcine oocytes and embryos. First, porcine oocytes cultured in the NCSU-23 medium for 44 h after H2O2 treated groups (0.01, 0.1, 1 mM). After completion of meiotic maturation, the proportion MII (44 h) was significantly different among control and the H2O2 treated groups (76.8±0.3 vs 69.1±0.4; 0.01 mM, 55.7±1.0; 0.1 mM, 38.2±1.6%; 1 mM, P<0.05). The expressions of ST3GAL5 in H2O2 treated groups were gradually decreased compared with control group. Next, changes of ST3GAL5 expression patterns were detected by using immunofluorescene (IF) staining during preimplantation development until blastocyst. As a result, we confirmed that the expressions of ST3GAL5 in cleaving embryos were gradually decreased (P<0.05) according to the early embryo development progress. Based on these results, we suggest that the ganglioside GM3 was used to the marker as pro-apoptotic factor in porcine oocyte of maturation and early embryo production in vitro, respectively. Furthermore, our findings will be helpful for better understanding the basic mechanism of gangliosides GM3 regulating in oocyte maturation and early embryonic development of porcine in vitro.