title: Sex differences in the mechanism of Met5-enkephalin-induced cardioprotection: role of PI3K/Akt.
abstract: Met(5)-enkephalin (ME)-induced cardioprotection occurs via epidermal growth factor receptor (EGFR) transactivation with the subsequent activation of phosphatidylinositol 3-kinase (PI3K). In the present study, we investigated whether there is a sex difference in ME-elicited PI3K signaling. Neonatal murine cardiomyocytes were isolated by collagenase digestion and subjected to 90 min hypoxia and 180 min reoxygenation at 37 degrees C (n = 5 to 7 replicates). PI3K/Akt signaling was interrogated using pharmacological inhibitors and small interfering RNA (siRNA). Cell death was assessed by propidium iodide. More than 300 cells were examined for each treatment. The data are presented as means +/- SE. There was not a sex difference in the basal content of total Akt. ME (100 microM) elicited comparable protection in both sexes. Wortmannin and the nonselective Akt inhibitor IV completely abolished ME-induced protection in male cardiomyocytes but only attenuated protection in female cardiomyocytes. Isoform-selective knockdown of Akt in males with siRNAs against Akt1/2 completely abolished ME-induced cardioprotection, whereas the siRNAs against Akt3 only attenuated protection of approximately 40%. In contrast, in females the siRNAs against Akt1/2 attenuated and against Akt3 eliminated ME-induced cardioprotection. There is not a sex difference in the degree of ME-induced protection, and there is a sex difference in the cardioprotective signaling pathways after the administration of ME; ME-induced cardioprotection in males primarily utilizes a PI3K/Akt1/2 pathway and in females primarily utilizes a PI3K/Akt3 pathway. The incomplete loss of protection in females following the blockade of PI3K suggests that additional factors may facilitate the maintenance or function of activated Akt.
authors.affiliation: Anesthesiology Service, Veterans' Affairs Medical Center, 3710 SW US Veterans Hospital Road, Portland, OR 97239-2999, USA.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Cao
authors.forename: Lijuan
authors.initials: L
authors.lastname: Liu
authors.forename: William
authors.initials: W
authors.lastname: Packwood
authors.forename: Matthias
authors.initials: M
authors.lastname: Merkel
authors.forename: Patricia D
authors.initials: PD
authors.lastname: Hurn
authors.forename: Donna M
authors.initials: DM
authors.lastname: Van Winkle
mesh_terms: D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004744:Enkephalin, Methionine / Q000378:metabolism*; D005260:Female; D008297:Male; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D015428:Myocardial Reperfusion Injury / Q000201:enzymology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D000077191:Wortmannin
chemical_list: D000730:Androstadienes; D002867:Chromones; D004744:Enkephalin, Methionine; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D034741:RNA, Small Interfering; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C514862:Akt1 protein, mouse; C494922:Akt2 protein, mouse; C491753:Akt3 protein, mouse