Deficit of mitochondria-derived ATP during oxidative stress impairs mouse MII oocyte spindles

Abstract

Although the role of oxidative stress in maternal aging and infertility has been suggested, the underlying mechanisms are not fully understood. The present study is designed to determine the relationship between mitochondrial function and spindle stability in metaphase II (MII) oocytes under oxidative stress. MII mouse oocytes were treated with H 2 O 2 in the presence or absence of permeability transition pores (PTPs) blockers cyclosporin A (CsA). In addition, antioxidant N-acetylcysteine (NAC), F 0 /F 1 synthase inhibitor oligomycin A, the mitochondria uncoupler carbonyl cyanide 4-trifluoromethoxyphenylhydrazone (FCCP) or thapsigargin plus 2.5 mM Ca 2+ (Th+2.5 mM Ca 2+ ) were used in mechanistic studies. Morphologic analyses of oocyte spindles and chromosomes were performed and mitochondrial membrane potential (∆Ψm), cytoplasmic free calcium concentration ([Ca 2+ ] c ) and cytoplasmic ATP content within oocytes were also assayed. In a time-and H 2 O 2 dose-dependent manner, disruption of meiotic spindles was found after oocytes were treated with H 2 O 2 , which was prevented by pre-treatment with NAC. Administration of H 2 O 2 led to a dissipation of ∆Ψm, an increase in [Ca 2+ ] c and a decrease in cytoplasmic ATP levels. These detrimental responses of oocytes to H 2 O 2 treatment could be blocked by pre-incubation with CsA. Similar to H 2 O 2 , both oligomycin A and FCCP dissipated ∆Ψm, decreased cytoplasmic ATP contents and disassembled MII oocyte spindles, while high [Ca 2+ ] c alone had no effects on spindle morphology. In conclusion, the decrease in mitochondria-derived ATP during oxidative stress may cause a disassembly of mouse MII oocyte spindles, presumably due to the opening of the mitochondrial PTPs.

Mitochondrial functions on oocytes and preimplantation embryos

“…The similar conditions between the maternal age-related aneuploidy and drugexposure aneuploidy suggest that mitochondrial dysfunction affects spindle formation and the segregation of chromosomes during the maturation of aged oocyte (Eichenlaub-Ritter, 1998). Oxidative stress can also influence the oocyte spindle assembly (Tarín, 1996), because oxidative stress may trigger mPT pore opening and decrease ATP content in oocytes (Zhang et al, 2006). It is therefore not surprising that injection of cytoplasm may improve embryo quality and support the embryo development (Cohen et al, 1998).…”

“…Mitochondria form aggregates with the smooth endoplasmic reticulum (SER), Cummins et al, 1997;Cox and Spradling, 2003;Mitochondrial distribution Wilding et al, 2001Torner et al, 2004;Nishi et al, 2003Mitochondrial movement van Blerkom, 1991Cox and Spradling, 2003;mtDNA content Reynier et al, 2001Spikings et al, 2007mtDNA mutation Yesodi et al, 2002Hsieh et al, 2004Mitochondrial polarity van Blerkom et al, 2003 2007 Function in calcium regulation Machaty et al, 1997;Krisher, 2004;Whitaker, 2008 Mitochondrial dysfunction Tarín, 1996;Eichenlaub-Ritter, 1998;Yin et al, 1998;Ottolenghi et al, 2004;Thouas et al, 2004;Zhang et al, 2006Mitochondria transfer Pinkert et al, 1997Malter and Cohen, 2002;Kong et al, 2004;Yi et al, 2007 a Studies involved in oocytes and embryos and these aggregates are apparently involved in the energy production and deposition before fertilization (Torner et al, 2004). Mammalian oocyte maturation relies not only on a high level of ATP for nuclear envelope breakdown, but also on intracellular calcium, which is derived from the endoplasmic reticulum (ER) and mitochondria (Krisher, 2004).…”

SIRT4 is essential for metabolic control and meiotic structure during mouse oocyte maturation

“…Thus, mitochondrial status has been recognized as an important factor determining mammalian oocyte quality. In particular, the factors associated with mitochondrial metabolism, such as ATP, ROS, and pyruvate dehydrogenase complex (PDH), are required for proper spindle assembly and chromosome alignment in oocyte meiosis (Choi et al., 2007; Johnson, Freeman, Gardner, & Hunt, 2007; Zhang, Wu, Lu, Guo, & Ma, 2006). …”

A novel form of ataxia oculomotor apraxia characterized by oxidative stress and apoptosis resistance

“…There is good evidence that oxidative stress causes mitochondrial dysfunction and lowered levels of ATP. 36,37 Thus, the increased levels of ROS/RNS observed in ATL2ABR cells might be responsible for the depleted levels of ATP observed here. Alternatively, the hyperactivation of PARP-1 in ATL2ABR cells, which appears to be due to increased levels of ROS/RNS, would be expected to consume both NAD and ATP resulting in reduced amounts of both.…”