**7. Effect of oxidative stress on male reproductive system**

Oxidative stress is a state which causes disproportion between systemic reactive oxygen species and detoxifying capability of biological system to neutralize the reactive intermediates, also called antioxidant defenses. Spermatozoa have antioxidant defense mechanism that quench the ROS and therefore protects the cells of gonads and mature spermatozoa from oxidative damage [32]. Statistics from United States depicted that the major cause of male infertility is ROS. In 30–40% of infertile men's seminal plasma, there is an increase in the level of ROS [33]. In spermatozoa ROS are generated by two methods.


The production of ROS at the level of mitochondria is the chief source. Large concentration of mitochondria is present in spermatozoa because of a constant need of energy to spermatozoa for motility. In semen, presence of nonfunctional spermatozoa considerably increases the level of ROS that in turn impair the function of mitochondria and motility of sperm. In human spermatozoa, ROS which is produced in large concentration is O2 <sup>−</sup>. It reacts with itself to generate H2O2 by dismutation. H2O2 and O2 <sup>−</sup> generates most destructive and reactive OH<sup>−</sup> by Haber-Weiss reaction in the presence of iron and copper. OH<sup>−</sup> affects the function of sperm by disrupting the fluidity of membrane [35, 36]. Recent studies depicting that O2 production in spermatozoa showed the presence of calcium dependent NADPH oxidase also called NOX5 has been residing in acrosomal and midpiece region of spermatozoa [37]. Initially the NOX5 resides in human testis. It is activated upon binding of calcium to its cytosolic domain and causes conformational changes in cells [35]. ROS is generated during the normal metabolism of cells. Under physiological conditions the mitochondrial respiration is the chief source of superoxide anion radicals. Quality of sperm and function is affected by the high concentration of ROS and is potentially toxic.

### **8. Sources of reactive oxygen species in seminal plasma**

The production of ROS in the seminal plasma originated from different endogenous and exogenous pathways. Ejaculate of human contains varieties of mature and immature cells, epithelial cells, leukocytes and round cells. Of these, leukocytes, immature spermatozoa, macrophages and neutrophils are considered to be the main endogenous source. Others life style practices as: excessive alcohol consumption, smoking and environmental factors (e.g., toxins and radiations) may contribute to exogenous ROS production [38–40].

### **8.1 Endogenous sources of ROS**

### *8.1.1 Leukocytes*

Peroxidase-positive leukocytes include polymorphonuclear leukocytes in about 50–60% and macrophages 20–30%. Peroxidase-positive leukocytes originates in large proportion from prostrate and seminal vesicles of male. These main sources of ROS are activated by different intracellular and extracellular responses such as inflammation and infection. The latest can produce 100 times reactive oxygen species than normal and also increase the secretion of NADPH through hexose monophosphate shunt [41, 42]. There is a decrease in the level of antioxidant superoxide dismutase and an increase in the concentration of proinflammatory cytokines, which can lead to the increased level of ROS and respiratory burst ultimately leading to formation of oxidative species OS. OS will than cause the damage of sperm if the concentration of seminal leukocytes is abnormally high [43]. Although in phagocytic clearance and immuno surveillance of unhealthy (abnormal) sperm, leukocytes and ROS play a decisive role. Inflammatory changes are depicted in the testes of smokers due to increased concentration of leukocyte activated free radicals. These leukocytes overcome the protective action of antioxidants and lead to oxidative stress. OS causes severe single and double stranded breaks in DNA by changing sperm chromatin integrity, modification of bases, deletions and rearrangement of chromosome [7].

### *8.1.2 Immature spermatozoa*

During the process of spermatogenesis, the developing spermatozoa expel their cytoplasmic content to prepare itself for the process of fertilization. Due to the arrest in spermiogenesis, the abnormal spermatozoa retained excess of cytoplasm around the midpiece. This condition is referred as excess residual cytoplasm (ERC). By virtue of hexose monophosphate shunt the ERC activates the NADPH system, which is used as a source of electron by spermatozoa for production of ROS and OS [30]. Therefore, ERC affects the morphology, motility and fertilization potential of sperm which can lead to infertility [44].

### *8.1.3 Varicocele*

Varicocele is a condition of abnormal enlargement of vein in scrotum, i.e., in the plexus pampiniformis situated throughout the spermatic cord. It is considered to be an etiology of male infertility, because varicocele is found in 19–40% of male partners in infertile couples. Current evidence suggested that oxidative stress is the central element contributing to infertility in men with varicocele [45]. Varicocele arises when damage occurs in valves into the spermatic vein(s) resulting in dysfunction and retrograde blood flow into scrotum from abdomen creating an inappropriate

**33**

*Insights of Sperm Pathology and Its Association with Infertility*

environment for development of sperm. Several studies reveal that oxidative stress also leads to varicocele in male, which occurs due to decrease in the concentration of antioxidants. It results in the deterioration of structure of cell membrane and in the DNA integrity. Nitric oxide is a lipophilic molecule which is presented in the spermatic vein of varicocele patient. Both NO and superoxide might cause a damage

Radiation, a natural source of energy, has a considerable effect on humans. Several studies have been depicted that radiation emitted from mobile phone increases the concentration of ROS in human semen resulting in impaired sperm quality [47, 48]. *In vitro* studies showed that in human, spermatozoa electromagnet radiation urges the production of ROS and damages of DNA. These changes further diminish the vitality and motility of sperm cells [49]. Due to the presence of varieties of charged molecules in the cytosol the flow of electron along the internal membrane of cells can be negatively affected by these radio frequency electromagnet radiations, and therefore interferes with the functions of the cell and the

Toxins which are discharged from industrial products and structural materials accumulates in the body of human and increases the production of ROS in the testes. This might result in the negative impact on the structure and function of sperm [51]. Phthalates which are found in the plastics objects used for industrial and domestic's purpose have been found to impair the spermatogenesis process and causes DNA damages in spermatozoa. Moreover, it has been studied that those laborers who were continuously exposed to metal toxins such as chromium, mercury, manganese and cadmium were more probable to have diminished quality of

Tobacco is familiar to be one of the major causes of worldwide death. It has been

reported that more than 4000 toxic chemical compounds have been present in cigarettes which includes nitrosamines, alkaloids and inorganic molecules. In the semen of smokers some of those chemicals were depicted to be the source of imbalance between antioxidant and ROS [41]. This disproportion between the ROS level and antioxidant adversely affects the overall quality of semen. It has been depicted that smoking increases by 48% the concentration of seminal leukocytes and 107% the ROS level in semen [52]. Due to the substantial increase in the level of 8-OHdG which is also a biomarker of oxidative damage, a decrease of the antioxidant level in seminal plasma, like vitamin C and vitamin E occurs, thus causing more risk of oxidative damage [40]. A study performed on smokers found an increased concentration of lead and cadmium in their semen and blood, which led to increase the production of ROS with a decrease in the motility of the sperm [53]. Moreover, the spermatozoa of smoker were substantially more prone to acid mediated denaturation as compare to nonsmoker spermatozoa which led to DNA strand break [54]. Furthermore, it was shown that prolonged smoking damages sperm DNA and

*DOI: http://dx.doi.org/10.5772/intechopen.90950*

in spermatozoa [46].

*8.2.1 Radiation*

organelles [50].

*8.2.2 Toxins*

*8.2.3 Smoking*

**8.2 Exogenous sources of ROS**

sperm, sperm count, density and volume [50].

apoptosis which results in male infertility.

environment for development of sperm. Several studies reveal that oxidative stress also leads to varicocele in male, which occurs due to decrease in the concentration of antioxidants. It results in the deterioration of structure of cell membrane and in the DNA integrity. Nitric oxide is a lipophilic molecule which is presented in the spermatic vein of varicocele patient. Both NO and superoxide might cause a damage in spermatozoa [46].

## **8.2 Exogenous sources of ROS**

## *8.2.1 Radiation*

*Innovations in Assisted Reproduction Technology*

exogenous ROS production [38–40].

**8.1 Endogenous sources of ROS**

rangement of chromosome [7].

sperm which can lead to infertility [44].

*8.1.2 Immature spermatozoa*

*8.1.1 Leukocytes*

**8. Sources of reactive oxygen species in seminal plasma**

The production of ROS in the seminal plasma originated from different endogenous and exogenous pathways. Ejaculate of human contains varieties of mature and immature cells, epithelial cells, leukocytes and round cells. Of these, leukocytes, immature spermatozoa, macrophages and neutrophils are considered to be the main endogenous source. Others life style practices as: excessive alcohol consumption, smoking and environmental factors (e.g., toxins and radiations) may contribute to

Peroxidase-positive leukocytes include polymorphonuclear leukocytes in about 50–60% and macrophages 20–30%. Peroxidase-positive leukocytes originates in large proportion from prostrate and seminal vesicles of male. These main sources of ROS are activated by different intracellular and extracellular responses such as inflammation and infection. The latest can produce 100 times reactive oxygen species than normal and also increase the secretion of NADPH through hexose monophosphate shunt [41, 42]. There is a decrease in the level of antioxidant superoxide dismutase and an increase in the concentration of proinflammatory cytokines, which can lead to the increased level of ROS and respiratory burst ultimately leading to formation of oxidative species OS. OS will than cause the damage of sperm if the concentration of seminal leukocytes is abnormally high [43]. Although in phagocytic clearance and immuno surveillance of unhealthy (abnormal) sperm, leukocytes and ROS play a decisive role. Inflammatory changes are depicted in the testes of smokers due to increased concentration of leukocyte activated free radicals. These leukocytes overcome the protective action of antioxidants and lead to oxidative stress. OS causes severe single and double stranded breaks in DNA by changing sperm chromatin integrity, modification of bases, deletions and rear-

During the process of spermatogenesis, the developing spermatozoa expel their

Varicocele is a condition of abnormal enlargement of vein in scrotum, i.e., in the plexus pampiniformis situated throughout the spermatic cord. It is considered to be an etiology of male infertility, because varicocele is found in 19–40% of male partners in infertile couples. Current evidence suggested that oxidative stress is the central element contributing to infertility in men with varicocele [45]. Varicocele arises when damage occurs in valves into the spermatic vein(s) resulting in dysfunction and retrograde blood flow into scrotum from abdomen creating an inappropriate

cytoplasmic content to prepare itself for the process of fertilization. Due to the arrest in spermiogenesis, the abnormal spermatozoa retained excess of cytoplasm around the midpiece. This condition is referred as excess residual cytoplasm (ERC). By virtue of hexose monophosphate shunt the ERC activates the NADPH system, which is used as a source of electron by spermatozoa for production of ROS and OS [30]. Therefore, ERC affects the morphology, motility and fertilization potential of

**32**

*8.1.3 Varicocele*

Radiation, a natural source of energy, has a considerable effect on humans. Several studies have been depicted that radiation emitted from mobile phone increases the concentration of ROS in human semen resulting in impaired sperm quality [47, 48]. *In vitro* studies showed that in human, spermatozoa electromagnet radiation urges the production of ROS and damages of DNA. These changes further diminish the vitality and motility of sperm cells [49]. Due to the presence of varieties of charged molecules in the cytosol the flow of electron along the internal membrane of cells can be negatively affected by these radio frequency electromagnet radiations, and therefore interferes with the functions of the cell and the organelles [50].

### *8.2.2 Toxins*

Toxins which are discharged from industrial products and structural materials accumulates in the body of human and increases the production of ROS in the testes. This might result in the negative impact on the structure and function of sperm [51]. Phthalates which are found in the plastics objects used for industrial and domestic's purpose have been found to impair the spermatogenesis process and causes DNA damages in spermatozoa. Moreover, it has been studied that those laborers who were continuously exposed to metal toxins such as chromium, mercury, manganese and cadmium were more probable to have diminished quality of sperm, sperm count, density and volume [50].

### *8.2.3 Smoking*

Tobacco is familiar to be one of the major causes of worldwide death. It has been reported that more than 4000 toxic chemical compounds have been present in cigarettes which includes nitrosamines, alkaloids and inorganic molecules. In the semen of smokers some of those chemicals were depicted to be the source of imbalance between antioxidant and ROS [41]. This disproportion between the ROS level and antioxidant adversely affects the overall quality of semen. It has been depicted that smoking increases by 48% the concentration of seminal leukocytes and 107% the ROS level in semen [52]. Due to the substantial increase in the level of 8-OHdG which is also a biomarker of oxidative damage, a decrease of the antioxidant level in seminal plasma, like vitamin C and vitamin E occurs, thus causing more risk of oxidative damage [40]. A study performed on smokers found an increased concentration of lead and cadmium in their semen and blood, which led to increase the production of ROS with a decrease in the motility of the sperm [53]. Moreover, the spermatozoa of smoker were substantially more prone to acid mediated denaturation as compare to nonsmoker spermatozoa which led to DNA strand break [54]. Furthermore, it was shown that prolonged smoking damages sperm DNA and apoptosis which results in male infertility.

**Figure 4.** *Demonstration of various factors responsible for male infertility (origin).*

### *8.2.4 Alcohol consumption*

Alcohol is widely known as the inducer of ROS and it interferes with the antioxidant defense mechanism of the body, mainly in the liver. Acetaldehyde which is the byproduct of ethanol metabolism, may react with protein and lipids forming the ROS, and may lead to damages in DNA, protein and lipids at the molecular level. The excessive consumption of alcohol is linked with a decrease in the concentration of normal sperm in asthenozoospermia patients [55] (**Figure 4**).
