非转录激活的 PI3K/Akt 信号转导介导了雌激素受体 β 在大鼠延髓头端腹外侧区激活后的降压作用。

BACKGROUND: Estrogen acts on the rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons are located, to elicit vasodepressor effects via an estrogen receptor (ER)β-dependent mechanism. We investigated in the present study nontranscriptional mechanism on cardiovascular effects following activation of ERβ in the RVLM, and delineated the involvement of phosphatidylinositol 3-kinase (PI3K)/serine/threonine kinase (Akt) signaling pathway in the effects. METHODS: In male Sprague-Dawley rats maintained under propofol anesthesia, changes in arterial pressure, heart rate and sympathetic neurogenic vasomotor tone were examined after microinjection bilaterally into RVLM of 17β-estradiol (E2β) or a selective ERα or ERβ agonist. Involvement of ER subtypes and PI3K/Akt signaling pathway in the induced cardiovascular effects were studied using pharmacological tools of antagonists or inhibitors, gene manipulation with antisense oligonucleotide (ASON) or adenovirus-mediated gene transfection. RESULTS: Similar to E2β (1 pmol), microinjection of ERβ agonist, diarylpropionitrile (DPN, 1, 2 or 5 pmol), into bilateral RVLM evoked dose-dependent hypotension and reduction in sympathetic neurogenic vasomotor tone. These vasodepressive effects of DPN (2 pmol) were inhibited by ERβ antagonist, R,R-tetrahydrochrysene (50 pmol), ASON against ERβ mRNA (250 pmol), PI3K inhibitor LY294002 (5 pmol), or Akt inhibitor (250 pmol), but not by ERα inhibitor, methyl-piperidino-pyrazole (1 nmol), or transcription inhibitor, actinomycin D (5 or 10 nmol). Gene transfer by microinjection into bilateral RVLM of adenovirus encoding phosphatase and tensin homologues deleted on chromosome 10 (5 × 10(8) pfu) reversed the vasodepressive effects of DPN. CONCLUSIONS: Our results indicate that vasodepressive effects following activation of ERβ in RVLM are mediated by nongenomic activation of PI3K/Akt signaling pathway. This study provides new insight in the intracellular signaling cascades involved in central vasodepressive functions of estrogen.

背景：雌激素通过雌激素受体（ER）β依赖的机制作用于延髓头端腹外侧区（RVLM），从而引起血管舒张作用。本研究旨在探讨 RVLM 中 ERβ激活后对心血管的非转录机制，并阐明磷脂酰肌醇 3-激酶（PI3K）/丝氨酸/苏氨酸激酶（Akt）信号通路在该作用中的参与情况。

方法：在丙泊酚麻醉下维持的雄性 Sprague-Dawley 大鼠中，观察双侧 RVLM 微注射 17β-雌二醇（E2β）或选择性 ERα或 ERβ激动剂后动脉压、心率和交感神经血管紧张度的变化。使用拮抗剂或抑制剂、反义寡核苷酸（ASON）或腺病毒介导的基因转染的基因操作来研究 ER 亚型和 PI3K/Akt 信号通路在诱导心血管效应中的作用。

结果：类似于 E2β（1 pmol），双侧 RVLM 微注射 ERβ激动剂二芳基丙腈（DPN，1、2 或 5 pmol）引起剂量依赖性低血压和交感神经血管紧张度降低。DPN（2 pmol）的这些血管舒张作用被 ERβ拮抗剂 R,R-四氢苊（50 pmol）、针对 ERβ mRNA 的 ASON（250 pmol）、PI3K 抑制剂 LY294002（5 pmol）或 Akt 抑制剂（250 pmol）抑制，但不受 ERα 抑制剂甲基-哌啶基-吡唑（1 nmol）或转录抑制剂放线菌素 D（5 或 10 nmol）抑制。通过双侧 RVLM 微注射腺病毒转染编码磷酸酶和张力蛋白同源物缺失 10 号染色体（5×10^8 空斑形成单位），逆转了 DPN 的血管舒张作用。

结论：我们的结果表明，RVLM 中 ERβ 激活后的血管舒张作用是通过 PI3K/Akt 信号通路的非基因组激活介导的。本研究为雌激素中枢性血管舒张功能涉及的细胞内信号级联提供了新的见解。