Gene-specific chromatin damage in human spermatozoa can be blocked by antioxidants that target mitochondria.
Incubation of gradient purified human spermatozoa, which are routinely maintained in media prior to IVF and intracytoplasmic sperm injection (ICSI), induced DNA strand breaks (up to 89 nicks x 10(-3) bp) and chromatin release. Unlike highly dispersed Alu repeat sequences, the centromeric heterochromatin was much less susceptible to endonuclease attack. In addition to chromatin release, the permeability of the sperm membrane was altered as evidenced by reduced accessibility of sperm nuclei to decondensation factors in mouse embryo extracts. Hybridization of cDNA microarrays with DNA released from spermatozoa revealed a consistent hypersensitivity of certain genes to endogenous cleavage including TP53, VHL (tumour suppressors), BRCA1 (breast cancer), NOS1 (neurotransmitter), PECAM1, FLT1 (angiogenesis) and CDKN1C (cell cycle/imprinted). N-tert-butyl hydroxylamine (NTBH), a derivative of the anti-teratogenic alpha-phenyl-N-t-butyl nitrone (PBN) and synthetic superoxide dismutase (SOD)/catalase mimetics inhibited chromatin release and sustained or dissipated relative mitochondrial membrane potential. Together, these results show a link between the hyperactivation of sperm mitochondria and chromosomal damage of specific genes in vitro, and that the potential risk of disruption of paternally contributed genes can be circumvented by antioxidants which are known to target mitochondria.
Lamond
Scott
S
Department of Obstetrics and Gynaecology, St George's Hospital Medical School, Cranmer Terrace, London SW17 ORE, UK.
Watkinson
Michael
M
Rutherford
Tim
T
Laing
Ken
K
Whiting
Andrew
A
Smallwood
Alan
A
Nargund
Geeta
G
Campbell
Stuart
S
Banerjee
Subhasis
S
D020087:Alu Elements; D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002503:Centromere / Q000648:ultrastructure; D002843:Chromatin / Q000378:metabolism / Q000648:ultrastructure*; D004249:DNA Damage; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism; D005434:Flow Cytometry; D006570:Heterochromatin / Q000378:metabolism; D006801:Humans; D008297:Male; D008564:Membrane Potentials; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D008956:Models, Chemical; D020411:Oligonucleotide Array Sequence Analysis; D013094:Spermatozoa / Q000378:metabolism / Q000648:ultrastructure*; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
D000975:Antioxidants; D002843:Chromatin; D018076:DNA, Complementary; D006570:Heterochromatin; D002374:Catalase; D013482:Superoxide Dismutase; D004253:DNA Nucleotidylexotransferase; D004720:Endonucleases