title: BH4 peptide derived from Bcl-xL and Bax-inhibitor peptide suppresses apoptotic mitochondrial changes in heat stressed bovine oocytes.
abstract: Mitochondria play an important role in the integration and transmission of cell death signals mediated by the Bcl-2 family proteins. Experiments were conducted to determine whether the anti-apoptotic peptides BH4 domain of Bcl-xL (TAT-BH4) and Bax inhibitor peptide (BIP) suppresses heat stress (HS) injury in oocytes by reduction of apoptotic-like events. Cumulus-oocyte complexes (COCs) were matured at 39 degrees C (control) or 41 degrees C (HS) for 21 hr then placed in maturation medium containing 0 or 100 microM BIP in water and 0 or 1 microM TAT-BH4 in dimethyl sulfoxide (DMSO), or a combination of both peptides (BIP + BH4). Peptide effects on embryo development, DNA fragmentation, mitochondrial membrane potential (Delta(Psi)m), and mitochondrial DNA (mtDNA) copy number were measured. All groups were fertilized and cultured in vitro at 39 degrees C for 8 days. Compared to control, HS-treated oocytes induced a decrease in embryo development (P < 0.05), increase in proportion of TUNEL-positive chromatin in oocytes and blastocysts (P < 0.05), and loss of oocyte Delta(Psi)m (P < 0.001). In the presence of BIP or BIP + BH4, development of HS-treated oocytes into blastocysts was increased (P < 0.05). Conversely, COCs matured with TAT-BH4 at 41 degrees C showed reduced embryonic development (P < 0.05). Exposure of HS-treated to each or both peptides resulted in a reduction of TUNEL frequency in oocytes and blastocysts cells derived from these oocytes (P < 0.05). The loss of Delta(Psi)m in HS-treated oocytes was not restored by exposure to BIP + BH4 and there was no effect in mtDNA copy number. In conclusion, the present results show that HS-induced apoptosis in bovine oocytes involves Bax and BH4 domain-dependent pathways.
authors.affiliation: Centre de Recherche en Reproduction Animale, Université de Montréal, St-Hyacinthe, QC J2S7C6, Canada.
authors.forename: Paolete
authors.initials: P
authors.lastname: Soto
authors.forename: Lawrence C
authors.initials: LC
authors.lastname: Smith
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001755:Blastocyst / Q000187:drug effects / Q000502:physiology; D002417:Cattle; D054885:Cumulus Cells / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects; D004272:DNA, Mitochondrial; D018628:Gene Dosage / Q000187:drug effects; D006358:Hot Temperature; D020287:In Situ Nick-End Labeling; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects*; D009842:Oligopeptides / Q000494:pharmacology*; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology*; D013312:Stress, Physiological
chemical_list: C539791:Bax-inhibiting peptide, BIP; D004272:DNA, Mitochondrial; D009842:Oligopeptides; D010455:Peptides; C540574:TAT-BH4 peptide