Before fertilization, spermatozoa undergo a crucial maturation step called capacitation, which is a unique event regulates the sperm’s ability for successful fertilization. The capacitation process takes place as the spermatozoa pass through the female reproductive tract (FRT). Dihydrolipoamide dehydrogenase (DLD) protein is a post-pyruvate metabolic enzyme, exhibiting reactive oxygen species (ROS) production which causes capacitation. Additionally, other vital functions of DLD in buffalo spermatozoa are hyperactivation and acrosome reaction. DLD produces the optimum amount of ROS required to induce capacitation process in FRT. Depending on physiological or pathophysiological conditions, DLD can either enhance or attenuate the production of reactive oxygen species (ROS). Aim of this study was to investigate whether changes in the production of ROS in sperm cells can impact their ability to fertilize by triggering the capacitation and acrosome reaction. In this study, abundance of DLD protein was quantified between high (n = 5) and low fertile bull (n = 5) spermatozoa. It was found that compared to high-fertile (HF) bulls, low-fertile (LF) bulls exhibited significantly (P < 0.05) higher DLD abundances. Herein, we optimised the MICA concentration to inhibit DLD function, spermatozoa were treated with MICA in time (0, 1, 2, 3, 4, and 5 h) and concentrations (1, 2.5, 5, and 10 mmol/L) dependent manner. Maximum DLD inhibition was found to be at 4 h in 10 mmol/L MICA concentration, which was used for further experimentation in HF and LF. Based on DLD inhibition it was seen that LF bull spermatozoa exhibited significantly (P < 0.05) higher ROS production and acrosome reaction in comparison to the HF bull spermatozoa. The kinematic parameters of the spermatozoa such as percent total motility, velocity parameters (VCL, VSL, and VAP) and other parameters (BCF, STR, and LIN) were also decreased in MICA treated spermatozoa in comparison to the control (capacitated) spermatozoa. The present study provides an initial evidence explaining the buffalo bull spermatozoa with higher DLD abundance undergo early capacitation, which subsequently reduces their capacity to fertilize.

中文翻译：

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水牛精子中较高丰度的 DLD 蛋白会导致 ROS 产生增加，从而导致精子早期获能并降低受精能力


在受精之前，精子经历一个关键的成熟步骤，称为获能，这是调节精子成功受精能力的独特事件。当精子通过女性生殖道 (FRT) 时，就会发生获能过程。二氢硫辛酰胺脱氢酶 (DLD) 蛋白是一种丙酮酸后代谢酶，会产生活性氧 (ROS)，从而导致获能。此外，DLD 在水牛精子中的其他重要功能是过度激活和顶体反应。 DLD 产生诱导 FRT 获能过程所需的最佳量的 ROS。根据生理或病理生理条件，DLD 可以增强或减弱活性氧 (ROS) 的产生。本研究的目的是调查精子细胞中 ROS 产生的变化是否会通过触发获能和顶体反应来影响其受精能力。在这项研究中，对高生育力公牛 (n = 5) 和低生育力公牛 (n = 5) 精子之间 DLD 蛋白的丰度进行了定量。结果发现，与高繁殖力 (HF) 公牛相比，低繁殖力 (LF) 公牛表现出显着 (P< 0.05) 更高的 DLD 丰度。在此，我们优化了 MICA 浓度以抑制 DLD 功能，用 MICA 处理精子的时间（0、1、2、3、4 和 5 小时）和浓度（1、2.5、5 和 10 mmol/L）依赖性方式。在 10 mmol/L MICA 浓度下，4 小时发现最大 DLD 抑制，用于 HF 和 LF 的进一步实验。基于 DLD 抑制，可以看出，与 HF 公牛精子相比，LF 公牛精子表现出显着（P< 0.05）更高的 ROS 产生和顶体反应。 与对照（获能）精子相比，经 MICA 处理的精子的精子运动学参数，如总活力百分比、速度参数（VCL、VSL 和 VAP）和其他参数（BCF、STR 和 LIN）也有所降低。本研究提供了初步证据，解释了具有较高 DLD 丰度的水牛精子经历早期获能，从而降低了其受精能力。