Oxidative Stress in Infertility

Reproductive failure is a substantial public health apprehension and globally totally underestimated public health issue. Oxidative stress has an impact on reproductive processes like spermatogenesis, ovulation, steroidogenesis, and reproductive functions, the disturbance of which may contribute to infertility. In the male reproductive system, a small level of reactive oxygen species (ROS) generation is necessary for sperm function like cross-linking of sperm chromatin and induction of sperm capacitation. Spermatozoa are highly vulnerable to elevated levels of ROS due to the presence of extraordinarily high levels of polyunsaturated fatty acids in their membranes and a limited level of intracellular antioxidants. Therefore, excessively high ROS levels are detrimental to sperm function. Hence, ROS are a double-edged sword; small quantities are required for normal sperm functions, while high levels negatively affect sperm membrane integrity, mitochondria, enzymes, DNA, and male hormones, thus leading to male infertility. In the female germ line, excessive ROS can disturb the growth and development of oocytes, the quality of oocytes, and the sequence of events in ovulation and embryo development, disrupt hormone balance, and impair implantation and fertilization leading to infertility. Factors that can contribute to oxidative stress in the female reproductive system include aging, contact with environmental toxins, unhealthy lifestyle habits like smoking and excessive alcohol consumption, and certain pathological conditions like endometriosis and polycystic ovary syndrome (PCOS). This chapter discusses the cause-and-effect relationship including mechanisms that involve ROS in impacting male and female reproduction and contribution to infertility with selected insights into the vital modulatory roles of antioxidants.