Glycine Ameliorates Endoplasmic Reticulum Stress Induced by Thapsigargin in Porcine Oocytes

Eicosatrienoic acid enhances the quality of in vitro matured porcine oocytes by reducing PRKN-mediated ubiquitination of CISD2

Oocytes and early embryos are exposed to many uncontrollable factors that trigger endoplasmic reticulum (ER) stress during in vitro culture. Prevention of ER stress is an effective way to improve the oocyte maturation rate and oocyte quality. Increasing evidence suggests that dietary intake of sufficient n-3 polyunsaturated fatty acids (PUFAs) is associated with health benefits, particularly in the domain of female reproductive health. We found that supplementation of eicosatrienoic acid (ETA) during in vitro maturation (IVM) of oocyte significantly downregulated ER stress-related genes. Mitochondria-associated membranes (MAMs) are communications areas between the ER and mitochondria. Inositol 1,4,5-trisphosphate receptor (IP3R) is a key calcium channels in MAMs and, participates in the regulation of many cellular functions. Notably, the MAM area was significantly decreased in ETA-treated oocytes. CDGSH iron sulfur domain 2 (CISD2) is presents in MAMs, but its role in oocytes is unknown. ETA treatment significantly increased CISD2 expression, and siRNA-mediated knockdown of CISD2 blocked the inhibitory effect of ETA on IP3R. Transcriptomic sequencing and immunoprecipitation experiments showed that ETA treatment significantly decreased expression of the E3 ubiquitin ligase PRKN. PRKN induced ubiquitination and degradation of CISD2, indicating that the PRKN-mediated ubiquitin-proteasome system regulates CISD2. In conclusion, our study reveals the mechanism by which ETA supplementation during IVM alleviates mitochondrial calcium overload under ER stress conditions by decreasing PRKN-mediated ubiquitination of CISD2 and facilitating inhibition of IP3R by CISD2/BCL-2. This improves oocyte quality and subsequent embryo developmental competence prior to implantation.

IP3R1 is required for meiotic progression and embryonic development by regulating mitochondrial calcium and oxidative damage

Calcium ions (Ca2+) regulate cell proliferation and differentiation and participate in various physiological activities of cells. The calcium transfer protein inositol 1,4,5-triphosphate receptor (IP3R), located between the endoplasmic reticulum (ER) and mitochondria, plays an important role in regulating Ca2+ levels. However, the mechanism by which IP3R1 affects porcine meiotic progression and embryonic development remains unclear. We established a model in porcine oocytes using siRNA-mediated knockdown of IP3R1 to investigate the effects of IP3R1 on porcine oocyte meiotic progression and embryonic development. The results indicated that a decrease in IP3R1 expression significantly enhanced the interaction between the ER and mitochondria. Additionally, the interaction between the ER and the mitochondrial Ca2+ ([Ca2+]m) transport network protein IP3R1-GRP75-VDAC1 was disrupted. The results of the Duolink II in situ proximity ligation assay (PLA) revealed a weakened pairwise interaction between IP3R1-GRP75 and VDAC1 and a significantly increased interaction between GRP75 and VDAC1 after IP3R1 interference, resulting in the accumulation of large amounts of [Ca2+]m. These changes led to mitochondrial oxidative stress, increased the levels of reactive oxygen species (ROS) and reduced ATP production, which hindered the maturation and late development of porcine oocytes and induced apoptosis. Nevertheless, after treat with [Ca2+]m chelating agent ruthenium red (RR) or ROS scavenger N-acetylcysteine (NAC), the oocytes developmental abnormalities, oxidative stress and apoptosis caused by Ca2+ overload were improved. In conclusion, our results indicated IP3R1 is required for meiotic progression and embryonic development by regulating mitochondrial calcium and oxidative damage.

Cyclosporine A improves the binding of mouse embryos to fibronectin

AIM

The binding of integrin αvβ3 with endometrial fibronectin (FN) promotes the migration of preimplantation embryos in mice. We have previously shown that cyclosporine A (CsA) improves the adhesion and invasion of mouse preimplantation embryos. In this study, we evaluated the roles of calcium ions and downstream signaling factors in the binding of integrin αvβ3 to FN.

METHODS

Female Institute of Cancer Research (ICR) mice were superovulated and mated, and two-cell embryos were harvested from the oviducts and cultured to the blastocyst stage The adhesion and stretching growth of hatched embryos in laminin-coated dishes were evaluated, and integrinβ3 expression was determined using qPCR. Blastocytes were cultured with 0 or 1  μM cyclosporine A (CsA) and the attachment of embryonic integrin αvβ3 to FN120 was observed using a fluorescent bead. To further determine the mechanism, the cells were also incubated with calcium ions and protein kinase C and calmodulin antagonists. The binding of integrin αvβ3 to FN120 was examined via confocal laser scanning microscopy.

RESULTS

The adhesion and stretching growth of peri-implantation embryos were greater and integrinβ3 expression was higher in the 1 μM CsA group than in the 0 μM CsA group (p < 0.05). When incubated with calcium ions and protein kinase C and calmodulin antagonists, the ability of peri-implantation embryos to bind to FN decreased; CsA treatment promoted this binding.

CONCLUSION

This study revealed that CsA up - regulates integrinβ3 expression in peri - implantation embryos and promotes binding to FN via calcium ions, and protein kinase C, and calmodulin. These findings provide evidence supporting the beneficial effect of CsA on the peri - implantation embryo adhesion.

TBBPA causes apoptosis in grass carp hepatocytes involving destroyed ER-mitochondrial function

Tetrabromobisphenol A (TBBPA) is the most-produced brominated flame retardant, which can be found in various industrial and household products. Studies have shown that TBBPA has hepatotoxicity, and could pose a risk to aquatic animals. The endoplasmic reticulum (ER) and mitochondria are two important organelles that are highly dynamic in cells, the homeostasis and orchestrated interactions of which are crucial to maintaining cellular function. The aim of this study was to explore the involvement of ER-mitochondria crosstalk in TBBPA-induced toxicity in aquatic animals' hepatocytes. Herein, we exposed grass carp hepatocytes (L8824 cells) to different concentrations of TBBPA. Our experimental results suggested that TBBPA exposure suppressed cell viability and caused apoptosis of L8824 cells. TBBPA treatment upregulated expressions of ER stress markers, increased reactive oxygen species (ROS) and mitochondrial Ca2+ levels, and reduced mitochondrial membrane potential (MMP) in L8824 cells. However, the pretreatment of 2-aminoethoxydiphenyl borate (2-APB) could alleviate TBBPA-induced cell apoptosis, ER stress, and mitochondrial dysfunction. Additionally, 2-APB pretreat relieved ER-mitochondrial contact and the expression of ER-mitochondrial function-related genes induced by high-dose TBBPA. Taken together, these results indicated that TBBPA caused grass carp hepatocyte apoptosis by destroying ER-mitochondrial crosstalk.

IP3R1 regulates calcium balance in porcine oocyte maturation and early embryonic development

The dynamic balance of Ca2+ in oocytes promotes the recovery of the meiotic arrest phase, consequently promoting oocyte maturation. Hence, the analysis of the maintenance and role of calcium homeostasis in oocytes has important guiding significance for obtaining high-quality eggs and maintaining the development of preimplantation embryos. Inositol 1,4,5-trisphosphate receptors (IP3Rs) are calcium channel proteins that regulate the dynamic balance between the endoplasmic reticulum (ER) and mitochondrial Ca2+. Nevertheless, the expression and role of IP3R in normal pig oocytes have not been reported, and other studies have focused on the role of IP3R in damaged cells. The purpose of this study was to investigate the potential role of IP3R in regulating calcium homeostasis in oocyte maturation and early embryonic development. Our results showed that IP3R1 is stably expressed at different stages of porcine oocyte meiosis, IP3R1 gradually converges to the cortex, and cortical clusters are formed in MII stages. The loss of IP3R1 activity contributeds to the failure of porcine oocyte maturation and cumulus cell expansion, as well as the obstruction of polar body excretion. Further analysis showed that IP3R1 plays an important role in affecting calcium balance by regulating the IP3R1-GRP75-VDAC1 channel between mitochondria and the endoplasmic reticulum (ER) during porcine oocyte maturation. Inhibiting IP3R1 expression-induced ER dysfunction, contributeding to ER calcium concentration ([Ca2+]ER) release outwards into mitochondria and causing mitochondrial free calcium concentration ([Ca2+]m) overload and mitochondrial oxidative stress, which was confirmed by the increase in the level of reactive oxygen species (ROS) and apoptosis. Thereby, IP3R1 plays an important role in affecting calcium balance by regulating the IP3R1-GRP75 -VDAC1 channel between mitochondria and the ER during porcine oocyte maturation, inhibiting IP3R1 expression-induced calcium overload and mitochondrial oxidative stress, and increasing ROS levels and apoptosis.

Astaxanthin protects oocyte maturation against cypermethrin-induced defects in pigs

Cypermethrin (CYP), a pyrethroid insecticide, exerts the detrimental effect on the reproductive system, while astaxanthin (AST), a xanthophyll carotenoid, possesses the powerful antioxidant property and can protect oocyte maturation. However, the toxicity of CYP and the protective role of AST against CYP during oocyte maturation remain unclear. Here, porcine oocytes were applied to investigate the potential effects and underlying mechanisms of CYP and AST during oocyte maturation. This work demonstrated that CYP significantly decreased oocyte maturation rate and subsequent embryo development in a dose-dependent manner (P < 0.05). And, CYP obviously induced the overproduction of reactive oxygen species and the reduction of glutathione content by downregulating the expression of redox genes in oocytes (P < 0.05). Moreover, CYP significantly caused oocyte DNA damage and disturbed the function of endoplasmic reticulum by altering the transcription of DNA damage repair and endoplasmic reticulum stress related genes (P < 0.05). Whereas CYP-exposed oocytes were treated with AST, these defects caused by CYP were significantly ameliorated (P < 0.05). In conclusion, this study demonstrated that CYP exerted the toxic effect on porcine oocytes, while AST effectively alleviated CYP-induced defects. This work provides a potential strategy to prevent pesticide toxicity and protect oocyte maturation in mammalian reproduction.

Xanthoangelol promotes early embryonic development of porcine embryos by relieving endoplasmic reticulum stress and enhancing mitochondrial function

RESEARCH QUESTION

Does the addition of an antioxidant agent, xanthoangelol (XAG), to the culture medium improve in-vitro development of porcine embryos?

DESIGN

Early porcine embryos were incubated in the presence of 0.5 μmol/l XAG in in-vitro culture (IVC) media and analysed using various techniques, including immunofluorescence staining, reactive oxygen species (ROS) detection, TdT-mediated dUTP nick-end labelling (TUNEL), and reverse transcription followed by quantitative polymerase chain reaction (RT-qPCR).

RESULTS

The addition of 0.5 μmol/l XAG to IVC media increased the rate of blastocyst formation, total cell number, glutathione concentrations and proliferative capacity, while reducing reactive oxygen species concentrations, apoptosis and autophagy. In addition, upon XAG treatment, the abundance of mitochondria and mitochondrial membrane potential significantly increased (both P < 0.001), and the genes related to mitochondrial biogenesis (TFAM, NRF1 and NRF2) were significantly up-regulated (all P < 0.001). XAG treatment also significantly increased the endoplasmic reticulum abundance (P < 0.001) and reduced the concentrations of endoplasmic reticulum stress (ERS) marker GRP78 (P = 0.003) and expression of the ERS-related genes EIF2α, GRP78, CHOP, ATF6, ATF4, uXBP1 and sXBP 1 (all P < 0.001).

CONCLUSION

XAG promotes early embryonic development in porcine embryos in vitro by reducing oxidative stress, enhancing mitochondrial function and relieving ERS.

Glutathione Mitigates Meiotic Defects in Porcine Oocytes Exposed to Beta-cypermethrin by Regulating ROS Levels

Beta-cypermethrin (β-CYP) is a commonly used insecticide that is potentially toxic and has adverse effects on the health of both animals and humans. Studies have indicated that β-CYP damages organs like the liver, thyroid, intestinal tract, and uterus. However, the underlying mechanisms that β-CYP affects oocyte quality are poorly understood. According to our research, β-CYP exposure led to the aberrant assembly of spindles and alignment of chromosomes, resulting in porcine oocytes' defective nuclear maturation. Concurrently, β-CYP exposure perturbed the cytoplasmic maturation by disturbing the cortical granules (CGs), endoplasmic reticulum (ER), and mitochondrial integrity. It also led to accumulating reactive oxygen species (ROS) and apoptosis. We found that supplementation with glutathione (GSH) mitigated the meiotic defects induced by β-CYP exposure via regulating ROS levels. Our observations illustrate that β-CYP exposure adversely impacts oocyte meiotic maturation, and taking GSH supplementation is an effective strategy.

Shenxiong glucose injection inhibits oxidative stress and apoptosis to ameliorate isoproterenol-induced myocardial ischemia in rats and improve the function of HUVECs exposed to CoCl2

Background: Shenxiong Glucose Injection (SGI) is a traditional Chinese medicine formula composed of ligustrazine hydrochloride and Danshen (Radix et rhizoma Salviae miltiorrhizae; Salvia miltiorrhiza Bunge, Lamiaceae). Our previous studies and others have shown that SGI has excellent therapeutic effects on myocardial ischemia (MI). However, the potential mechanisms of action have yet to be elucidated. This study aimed to explore the molecular mechanism of SGI in MI treatment. Methods: Sprague-Dawley rats were treated with isoproterenol (ISO) to establish the MI model. Electrocardiograms, hemodynamic parameters, echocardiograms, reactive oxygen species (ROS) levels, and serum concentrations of cardiac troponin I (cTnI) and cardiac troponin T (cTnT) were analyzed to explore the protective effect of SGI on MI. In addition, a model of oxidative damage and apoptosis in human umbilical vein endothelial cells (HUVECs) was established using CoCl₂. Cell viability, Ca²⁺ concentration, mitochondrial membrane potential (MMP), apoptosis, intracellular ROS, and cell cycle parameters were detected in the HUVEC model. The expression of apoptosis-related proteins (Bcl-2, Caspase-3, PARP, cytoplasmic and mitochondrial Cyt-c and Bax, and p-ERK1/2) was determined by western blotting, and the expression of cleaved caspase-3 was analyzed by immunofluorescence. Results: SGI significantly reduced ROS production and serum concentrations of cTnI and cTnT, reversed ST-segment elevation, and attenuated the deterioration of left ventricular function in ISO-induced MI rats. In vitro, SGI treatment significantly inhibited intracellular ROS overexpression, Ca²⁺ influx, MMP disruption, and G2/M arrest in the cell cycle. Additionally, SGI treatment markedly upregulated the expression of anti-apoptotic protein Bcl-2 and downregulated the expression of pro-apoptotic proteins p-ERK1/2, mitochondrial Bax, cytoplasmic Cyt-c, cleaved caspase-3, and PARP. Conclusion: SGI could improve MI by inhibiting the oxidative stress and apoptosis signaling pathways. These findings provide evidence to explain the pharmacological action and underlying molecular mechanisms of SGI in the treatment of MI.

Glycine regulates lipid peroxidation promoting porcine oocyte maturation and early embryonic development

In vitro-cultured oocytes are separated from the follicular micro-environment in vivo and are more vulnerable than in vivo oocytes to changes in the external environment. This vulnerability disrupts the homeostasis of the intracellular environment, affecting oocyte meiotic completion, and subsequent embryonic developmental competence in vitro. Glycine, one of the main components of glutathione (GSH), plays an important role in the protection of porcine oocytes in vitro. However, the protective mechanism of glycine needs to be further clarified. Our results showed that glycine supplementation promoted cumulus cell expansion and oocyte maturation. Detection of oocyte development ability showed that glycine significantly increased the cleavage rate and blastocyst rate during in vitro fertilization (IVF). SMART-seq revealed that this effect was related to glycine-mediated regulation of cell membrane structure and function. Exogenous addition of glycine significantly increased the levels of the anti-oxidant GSH and the expression of anti-oxidant-related genes (glutathione peroxidase 4 [GPX4], catalase [CAT], superoxide dismutase 1 [SOD1], superoxide dismutase 2 [SOD2], and mitochondrial solute carrier family 25, member 39 [SLC25A39]), decreased the lipid peroxidation caused by reactive oxygen species (ROS) and reduced the level of malondialdehyde (MDA) by enhancing the functions of mitochondria, peroxisomes and lipid droplets (LDs) and the levels of lipid metabolism-related factors (peroxisome proliferator activated receptor coactivator 1 alpha [PGC-1α], peroxisome proliferator-activated receptor γ [PPARγ], sterol regulatory element binding factor 1 [SREBF1], autocrine motility factor receptor [AMFR], and ATP). These effects further reduced ferroptosis and maintained the normal structure and function of the cell membrane. Our results suggest that glycine plays an important role in oocyte maturation and later development by regulating ROS-induced lipid metabolism, thereby protecting against biomembrane damage.

Glycine ameliorates MBP-induced meiotic abnormalities and apoptosis by regulating mitochondrial-endoplasmic reticulum interactions in porcine oocytes

Monobutyl phthalate (MBP) is the main metabolite of dibutyl phthalate (DBP) in vivo. MBP has a stable structure, can continuously accumulate in living organisms, and has the potentially to harm animal and human reproductive function. In the ovarian follicle microenvironment, MBP may lead to defects in follicular development and steroid production, abnormal meiotic maturation, impaired ovarian function and other reproductive deficits. In this study, SMART-seq was used to investigate the effects of MBP exposure on the in vitro maturation (IVM) and development of porcine oocytes. The results showed that differentially expressed genes after MBP exposure were enriched in the biological processes cytoskeleton, cell apoptosis, endoplasmic reticulum (ER) and mitochondria. Glycine (Gly) improved the developmental potential of porcine oocytes by regulating mitochondrial and ER function. The effect of Gly in protecting oocytes against MBP-induced damage was studied. The results showed that the addition of Gly significantly decreased the rate of MBP-induced spindle abnormalities, decreased the frequency of MBP-induced mitochondria-associated ER membrane (MAM) interactions, and downregulated the protein and gene expression of the linkage molecules Mitofusin 1 (MFN1) and Mitofusin 2 (MFN2) in the MAM. Additionally, treatment with Gly restored the distribution of the 1,4,5-triphosphate receptor 1 (IP₃R1) and voltage-dependent anion channel 1 (VDAC1), further decreasing the intracellular free calcium concentration ([Ca²⁺]_i) levels and mitochondrial Ca²⁺ ([Ca²⁺]_m) , increasing the ER Ca²⁺ ([Ca²⁺]_ER) levels, and thus significantly increasing the ER levels and mitochondrial membrane potential (ΔΨ m). Gly also decreased the levels of reactive oxygen species (ROS) and increased the levels of Glutathione (GSH), oocyte apoptosis-related indicators (Caspase-3 activity and Annexin V) and oocyte apoptosis-related genes (BAX, Caspase 3 and AIFM1). Our results suggest that Gly can ameliorate microtubule cytoskeleton abnormalities and improve oocyte maturation by reducing the defective mitochondrial-ER interactions caused by MBP exposure in vitro.