Oxidants, Antioxidants, and Impact of the Oxidative Status in Male Reproduction

Ralf Henkel, Luna Samanta, Ashok Agarwal

• Publisher: Academic Press
• Year: 2018
• Print ISBN: 9780128125014
• eBook ISBN: 9780128125670
• Topic: Medicine
• Subtopic: Endocrinology & Metabolism

Oxidants, Antioxidants and Impact of the Oxidative Status in Male Reproduction is an essential reference for fertility practitioners and research and laboratory professionals interested in learning about the role of reactive oxygen species in sperm physiology and pathology. The book focuses on unravelling the pathophysiology of oxidative stress mediated male infertility, recruiting top researchers and clinicians to contribute chapters. This collection of expertise delves into the physico-chemical aspects of oxidative stress, including a new focus on reductive stress. Furthermore, the inclusion of clinical techniques to determine oxidative stress and the OMICS of reductive oxidative stress are also included.This is a must-have reference in the area of oxidative stress and male reproductive function.- Offers comprehensive information on oxidative stress and its role in male reproduction, including new therapeutic approaches- Deals with current approaches to oxidative stress using OMICS platform- Designed for fertility practitioners, reproductive researchers, and laboratory professionals interested in learning about the role of reactive oxygen species in sperm physiology and pathology

Part I

Basic Aspects

Outline

1. Chapter 1.1. Life Under Aerobic Conditions
2. Chapter 1.2. The Oxidant Paradox
3. Chapter 1.3. From Past to Present: An Historical Overview of the Concept of Spermatozoa, Reactive Oxygen Species, and Male-Factor Infertility
4. Chapter 1.4. Basic Aspects of Oxidative Stress in Male Reproductive Health
5. Chapter 1.5. Leukocytes as a Cause of Oxidative Stress
6. Chapter 1.6. Human Spermatozoa and Interactions With Oxidative Stress
7. Chapter 1.7. Causes of Reductive Stress in Male Reproduction
8. Chapter 1.8. Physiological Role of Reactive Oxygen Species in Male Reproduction

Chapter 1.1

Life Under Aerobic Conditions

Kristian Leisegang School of Natural Medicine, University of the Western Cape, Bellville, South Africa

Abstract

Following the rise of prokaryote life dependent on anaerobic respiration, oxygen was produced as a toxic by-product. This steadily and significantly contributed to the formation of an oxygen-rich environment that resulted in a shift in atmospheric and oceanic redox status. This necessitated the evolution of aerobic respiration, and mitochondria seemingly arose independently of bacterial life before becoming incorporated into eukaryote cells. Aerobic respiration allowed for a significant increase in adenosine triphosphate production, which is critical to meet the energy demands required for complex multicellular life to evolve. This molecular process also results in a leakage of potentially toxic reactive oxygen species (ROS) from the mitochondria. Although ROS have evolved as critical molecular and cellular regulators, excessive ROS damages cellular molecules and components. Therefore, endogenous antioxidants evolved as an important regulator of the redox state within the cellular environment in order to optimize the beneficial roles of redox biology.

Keywords

Aerobic respiration; Antioxidants; Evolution; Great oxygenation event; Mitochondria; Reactive oxygen species

Introduction

Biology on earth has had a significant impact on planetary evolution. This is prominently evident through planetary redox evolution due to changing atmospheric and oceanic gaseous environments [1]. In the modern era, climate change is based on the evolutionary recent rapid rise of CO₂ in the atmosphere, significantly driven by Homo sapiens' influence through industrialization and unrestricted utilization of fossil fuel (carbonaceous) resources [2]. However, in the ancient organic rich environment of the late Archean (4–2.5 Ga: giga anuum = 1 billion years ago) and Proterozoic (2.5–0.5 Ga) periods, significant climate change occurred in which the atmosphere was being polluted by rising oxygen (O₂) concentrations [2]. Although a rapid rise of O₂ is evident in the records, it remains a challenge for geobiologists to fully understand the role of biological life in the oxygenation of the planet. This is due to scarce access to the well-preserved rocks from these times as well as a poor biological record of early biota [1]. However, it is evident that biological life significantly contributed to the changing environment, in which aerobic respiration evolved as a prominent event for the development of multicellular organisms due to the ability to produce energy more efficiently [1,2].

The Great Oxygenation Event

The early biosphere of earth, around 3.8 Ga in which life arose, is generally accepted to have been a low O₂ environment [2] dominated by carbon dioxide (CO₂) and nitrogen (N₂). This chemical composition would have created an environment with mild reducing conditions, providing the main energy source for exclusively unicellular organisms consisting mainly of hyperthermophiles [1,3]. These organisms utilized chemical sources of energy through metabolic CO₂ assimilation mechanisms, and from this photosynthesis appears to have arisen early in the evolution of life. O₂ is a toxic molecular by-product of this anaerobic respiration [3]. Following this, geographical evidence suggests a significant global rise in atmospheric O₂ approximately 2.3 Ga, known as the Great Oxygenation Event (GOE) [4]. In addition to biological life, environmental and climatic events such as glaciations and intense continental weathering that resulted in oxidation of the ocean surface water also contributed to the rise in O₂ levels [5].

However, as early as 3 Ga, there was an atmospheric change in which oxygenic photosynthesis (oxygenic phototrophy) evolved through ancient cyanobacteria as a significant microbial biochemical innovation, providing the most significant source of modern atmospheric O₂ concentrations [6]. Following the GOE, a final rise in atmospheric O₂ was observed approximately 0.5 Ga [1].

It is clear, therefore, that the biological production of O₂ dramatically modified the environment into the Proterozoic period, resulting in more oxidizing conditions compared to that of the Archean period [1,7]. Importantly, the associated change in the environmental redox state modified the bioavailability of metals, including iron, copper and molybdenum [8]. The bioavailability of O₂ provided early biota with an oxidant environment, which arguably necessitated the evolution of aerobic respiration [8].

Biological Life and Environmental Evolution

The emergence of O₂ in the evolution of Earth required at least one biological pathway to have been active and present, as abiotic generation of O₂ (e.g., photodissociation of water vapor with hydrogen escaping to space) would have been too ineffective [9]. With abiotic production of O₂ from water via UV light considered as a minor contributor, it is proposed that biological photosynthesis in cyanobacteria and photosynthetic eukaryotes greatly contributed to modern atmospheric O₂ levels [10].

In addition to oxygenic photosynthesis, biological sources of O₂ generation include reactive oxygen species (ROS) detoxification, chlorate generation, and nitrogen-driven anaerobic methane oxidation [9]. O₂ production from detoxification of ROS is generally regarded to have evolved after oxygenic photosynthesis, and initial mechanisms of defense to ROS were physical barriers as opposed to enzymatic antioxidant systems [11]. Although there is some debate, aerobic respiration would have likely evolved after that of oxygen photosynthesis [1]. However, prior to this evolution, O₂ may have been produced by chemosynthetic sources, such as possible nitrite anaerobic methane oxidation by oxygenic bacteria, primordial chlorate metabolism by microbial chlorate dismutation, catalase-like enzymes converting radioactivity produced peroxides, or via nitric oxide dismutation on volcanic nitric oxide in the presence of abundant oceanic iron to release environmental oxygen [12]. Increased subaerial volcanic activity further provided oxidized gases such...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributors
• Foreword
• Preface
• Introduction
• Part I. Basic Aspects
• Part II. Clinical Aspects
• Part III. Clinical Methods to Determine and Treat Oxidative Stress
• Part IV. Current Approaches: The OMICS
• Index