Oxidative stress, DNA damage and the Y chromosome

Recent advances in understanding of male infertility have implicated two ma jor causative factors, oxidative stress and Y chromosome deletions. A major cause of oxidative stress appears to be the high rate of reactive oxygen s pecies generation associated with the retention of excess residual cytoplas m in the sperm midpiece. Other possible causes include the redox cycling of xenobiotics, and antioxidant depletion or apoptosis. Oxidative stress indu ces peroxidative damage in the sperm plasma membrane and DNA damage in both the mitochondrial and nuclear genomes. Nuclear DNA damage in the germ line of the father may be associated with pathology in the offspring, including childhood cancer and infertility. Gene deletions on the non-recombining re gion of the Y chromosome account for the infertility observed in about 15% of patients with azoospermia and 5-10% of subjects with severe oligozoosper mia. The Y chromosome is particularly susceptible to gene deletions because of the inability of the haploid genome to deploy recombination repair in r etrieving lost genetic information. Aberrant recombination, defective chrom atin packaging, abortive apoptosis and oxidative stress may all be involved in the aetiology of DNA damage in the germ line. The factors responsible f or Y chromosome deletions in spermatozoa remain unresolved but may be one f acet of a central reproductive problem: controlling the amount of oxidative stress experienced by germ cells during their differentiation and maturati on in the male reproductive tract.