Oxidative Stress and its impact on sperm DNA
The word “stress” immediately brings thoughts of pressure and tension. However, what is oxidative stress? It is described as “caused by an imbalance between production and accumulation of reactive oxygen species (ROS) in cells and tissues and the ability of a biological system to detoxify these reaction products.” So what role does oxidative stress play in male infertility?
Some factors such as varicocele, hypogonadism (failure of testes to function properly), cryptorchidism (undescended testicles) and genes can cause infertility. However, in about 25% of the infertile male population, the cause is idiopathic or not known.
Research has shown that oxidative stress can be one of the reasons for male infertility. Increased ROS with less antioxidant defence results in redox (reduction-oxidation) imbalance. Due to the high amount of unsaturated fatty acids found in their cell membranes, spermatozoa are affected by the damaging effects of ROS. Intracellular oxidative burden is caused which leads to lipid peroxidation resulting in cell damage, reduced membrane integrity with increased absorption, structural DNA damage, reduced sperm motility and even apoptosis (death of cells).
Some levels of ROS are required for sperm maturity, sperm capacitation (the functional changes of spermatozoa to enable penetration and fertilization), reaction of acrosome (release of egg-penetrating enzymes), hyperactivation (vital for fertilization as it is required for penetration) and sperm-oocyte (paternal components combining with the female germ cell) function. ROS is important in cell signaling and homeostasis (regulation of variables so that internal conditions retain stability and constancy).
However, excessive ROS submerges the neutralizing competence of antioxidants in the seminal plasma, the fluid which transports the ejaculated spermatozoa from the testes to the oocyte. It disrupts the fluidity leading to loss of motility. It also increases damaging chemical and structural modifications to sperm nuclear DNA. This DNA damage can be significant to both the mitochondrial (circular) and nuclear (linear) genomes of spermatozoa. Excessive ROS attacks the DNA bases, destabilizing the molecule and creating conditions that eventually result in DNA fragmentation.
Endogenous sources of ROS in semen are leukocytes (white blood cells) and abnormal spermatozoa. External factors that can increase oxidative stress are obesity, high-fat diets including sugar and processed foods, exposure to pollution, radiation or pesticides/industrial chemicals, smoking, alcohol intake and certain medications. The obvious counteraction would be to reduce weight, exercise more, eat more antioxidant-rich food, lower stress levels, cut down or give up smoking and alcohol and get sufficient sleep.
Many studies have proved that oxidative stress causes sperm DNA damage. There are now various tests available to measure the degree of such DNA fragmentation, such as the SCSA (sperm chromatin structure assay), SCD (sperm chromatin dispersion test), TUNEL, and Comet assay (single cell gel electrophoresis).
We, at Andrology Center, carry out the DFI (DNA fragmentation index) testing, which shows the levels of damage to the sperm DNA, using the SCSA (sperm chromatin structure assay) test. We are the only laboratory in India authorised to carry out the authentic SCSA test. Our laser equipment is of exceptional standard and with the special technology we have, we can guarantee accurate results. This is a major factor in assisting the physician to recommend the best possible treatment to the patient.
