Mammalian sperm have to undergo capacitation to fertilize the egg. At the molecular level, capacitation involves cAMP synthesis, protein kinase A activation, and downstream increase in tyrosine phosphorylation. In addition, during capacitation, mammalian sperm actively generate reactive oxygen species (ROS). It has been proposed that ROS modulate phosphorylation pathways; however, the crosstalk between these signaling processes is not well-understood. In the present study, we used loss- and gain-of-function approaches to evaluate the interconnection between ROS and phosphorylation. We showed that BSA and HCO₃⁻, but not Ca²⁺, in the capacitation media are required for ROS production. The synergic effect of these compounds was neither mediated by HCO₃⁻ stimulation of cAMP synthesis nor by BSA-induced cholesterol efflux. The capacitation-induced ROS generation was blocked in the presence of superoxide dismutase (SOD), catalase, and apocynin. However, none of these compounds affected cAMP-dependent or tyrosine phosphorylation. On the other hand, the addition of NADPH to the media induced ROS generation in sperm incubated in the absence of BSA and HCO₃⁻ without upregulating cAMP-dependent or tyrosine phosphorylation signaling. Most interestingly, catalase, but not SOD, blocked in vitro fertilization suggesting a role for H₂O₂ in this process.

中文翻译：

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cAMP 依赖性磷酸化途径的激活与小鼠精子获能过程中 ROS 的产生无关

哺乳动物的精子必须经过获能才能使卵子受精。在分子水平上，获能涉及 cAMP 合成、蛋白激酶 A 激活和下游酪氨酸磷酸化的增加。此外，在获能过程中，哺乳动物精子会主动产生活性氧 (ROS)。有人提出 ROS 调节磷酸化途径；然而，这些信号过程之间的串扰并没有被很好地理解。在本研究中，我们使用损失和获得功能的方法来评估 ROS 和磷酸化之间的相互联系。我们表明，在获能介质中，产生 ROS 需要BSA 和 HCO ₃ ^-而不是 Ca ^{2+ 。}这些化合物的协同作用都不是由 HCO _3介导的⁻刺激 cAMP 合成或 BSA 诱导的胆固醇流出。在超氧化物歧化酶 (SOD)、过氧化氢酶和夹竹桃麻素的存在下，获能诱导的 ROS 生成被阻断。然而，这些化合物均不影响 cAMP 依赖性或酪氨酸磷酸化。另一方面，在培养基中添加 NADPH 会诱导在没有 BSA 和 HCO ₃ ^-的情况下培养的精子中产生 ROS，而不会上调 cAMP 依赖性或酪氨酸磷酸化信号。最有趣的是，过氧化氢酶而不是 SOD 阻止了体外受精，这表明 H ₂ O ₂在这个过程中的作用。