Free Radicals in Andrology
Reactive oxygen species (ROS) are highly reactive oxidizing agents that, at physiologic levels, play an essential role in the health and well-being of aerobic organisms. When supraphysiological levels of ROS are produced or when the cells’ antioxidant def
- PDF / 677,319 Bytes
- 21 Pages / 439.37 x 666.14 pts Page_size
- 47 Downloads / 212 Views
Free Radicals in Andrology Ashok Agarwal and Ahmad Majzoub
1.1
Introduction
Infertility is a condition associated with major medical and social preoccupation. A male etiology is responsible for nearly half the cases of infertility [1] and is caused by alterations in sperm concentration, motility, and/or morphology [2]. Recent advances in the field of infertility have greatly influenced our understanding of the different circumstances attributing to male factor infertility. While environmental, physiological, and genetic influences were recognized, at the molecular level, oxidative stress (OS) resulting from the imbalance between oxidants and reductants appears to be a common denominator impairing sperm function and delaying pregnancy. Reactive oxygen species (ROS) are highly reactive oxidizing agents that can, at supraphysiological levels, have a potential toxic effect on sperm quality and function [3]. Like other free radicals, ROS contain unpaired electrons triggering a tendency for strong reactivity with other compounds. Moreover, they typically incite a chain reaction exposing a vicious circle type of activity. Under normal physiological circumstances, ROS are products of natural oxygen metabolism acting as vital signaling molecules. However, excessive levels of ROS can be
A. Agarwal, PhD, HCLD (*) American Center for Reproductive Medicine, Department of Urology, Cleveland Clinic, Cleveland, OH 44195, USA Lerner College of Medicine, Andrology Center and American Center for Reproductive Medicine, 10681 Carnegie Avenue, Desk X11, Cleveland, OH 44195, USA e-mail: [email protected]; http://www.ClevelandClinic.Org/ReproductiveResearchCenter A. Majzoub, MD American Center for Reproductive Medicine, Department of Urology, Cleveland Clinic, Cleveland, OH 44195, USA © Springer International Publishing Switzerland 2017 G. Balercia et al. (eds.), Antioxidants in Andrology, Trends in Andrology and Sexual Medicine, DOI 10.1007/978-3-319-41749-3_1
1
2
A. Agarwal and A. Majzoub
Fig. 1.1 Factors contributing to oxidative stress-induced male infertility (Copyright license provided)
produced secondary to a variety of environmental exposures and pathologic processes (Fig. 1.1) resulting in several disease entities such as neurodegenerative disease, vascular disease, cancer, and infertility. To minimize the hazardous effects of excessive ROS levels, a number of endogenous enzymatic and nonenzymatic antioxidants exist scavenging or neutralizing excess ROS.
1
Free Radicals in Andrology
3
Like all other living cells, spermatozoa require oxygen for survival. However, excessive exposure to oxygen metabolites can alter normal sperm function and vitality [3, 4]. Several reports have confirmed the presence of high ROS levels in the semen of 25–40 % of infertile men [5, 6]. Negative correlations were detected between ROS levels and normal sperm morphology as well as with measures of sperm DNA fragmentation [7, 8]. Spermatozoa are predominantly vulnerable to the damage caused by excessive ROS because their plasma membranes cont
Data Loading...
