Cao Zhiping, Liu Lijuan, Packwood William, Merkel Matthias, Hurn Patricia D, Van Winkle Donna M
Anesthesiology Service, Veterans' Affairs Medical Center, 3710 SW US Veterans Hospital Road, Portland, OR 97239-2999, USA.
Am J Physiol Heart Circ Physiol. 2008 Jan;294(1):H302-10. doi: 10.1152/ajpheart.00845.2007. Epub 2007 Nov 2.
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.
蛋氨酸脑啡肽（ME）诱导的心脏保护作用通过表皮生长因子受体（EGFR）转活化及随后的磷脂酰肌醇3激酶（PI3K）激活而发生。在本研究中，我们调查了ME诱导的PI3K信号传导中是否存在性别差异。通过胶原酶消化分离新生小鼠心肌细胞，并在37℃下进行90分钟缺氧和180分钟复氧处理（n = 5至7个重复样本）。使用药理学抑制剂和小干扰RNA（siRNA）研究PI3K/Akt信号传导。通过碘化丙啶评估细胞死亡。每种处理检查超过300个细胞。数据以平均值±标准误表示。总Akt的基础含量不存在性别差异。ME（100μM）在两性中诱导出相当的保护作用。渥曼青霉素和非选择性Akt抑制剂IV完全消除了ME在雄性心肌细胞中诱导的保护作用，但仅减弱了雌性心肌细胞中的保护作用。用针对Akt1/2的siRNA对雄性Akt进行亚型选择性敲低完全消除了ME诱导的心脏保护作用，而针对Akt3的siRNA仅减弱了约40%的保护作用。相比之下，在雌性中，针对Akt1/2的siRNA减弱了，而针对Akt3的siRNA消除了ME诱导的心脏保护作用。ME诱导的保护程度不存在性别差异，且在给予ME后心脏保护信号通路存在性别差异；ME在雄性中诱导的心脏保护主要利用PI3K/Akt1/2途径，而在雌性中主要利用PI3K/Akt3途径。PI3K阻断后雌性保护作用未完全丧失表明可能有其他因素促进活化Akt的维持或功能。
