| Abstract: | 雌性素(E2)具保護心血管功能，但對心肌細胞的保護機轉仍清楚。近，由於心肌細胞內雌性素接受體(ERα及ERβ)的發現,及COS 細胞中ER 可直接與胞膜上胰島素接受體(IGF-IR)結合，並活化MEK-ERK 訊息途徑，人禁想E2-ER 與IGF-I-IGF-IR在調控心肌細胞功能的關性。且究竟E2-ER 是透過傳統基因性(核內，genomic，slow) 作用或非基因性(膜上，non-genomic，fast)作用調控心肌細胞，值得深究。由於病性心肌肥大為心肌猝死主因，但病性心肌肥大及心肌猝死的分子機轉所知多。目前僅知，IGF-I經IGF-IR 活化IP3K-AKT/PKB 為心肌細胞存活之主要途徑，同時調控心肌細胞大小，可能為生性肥大的主要機轉。IGF-I 並可經IRS-1 活化Ras-Raf-MEK-ERK 調控心臟內非心肌細胞增生。因此，E2-ER 與IGF-I-IGF-IR 的交互作用在心肌保護的角色，急待發掘。已知G proteins coupled receptor (GPCR)之ligands,包括血管增壓素(Ang-II)，為高血壓主因之一，因與鈣子活化、促進心肌肥大之Calcineurin-NFAT 途徑及影響細胞凋亡之PKC 及JNK 有關，所以與病性心肌肥大及猝死關係密。另發現血球中TNFα之基因表現及血液中TNFα蛋白含顯著上升而TGF1β蛋白含減少與病人心肌衰竭極相關，在經抑制TNFα治後，心肌衰竭即改善。而IL6(interleukine-6)並與穩定型冠動脈疾病患者死亡有關，且可經活化MEK5-ERK5 誘發擴張性心肌症，活化P38-STAT1 引發心肌細胞凋亡。而雌性素因具有快速低細胞鈣子內的非基因性功能、及抑制停經後婦發炎細胞激素的產生，ER 可經抑制發炎轉譯因子NFκB 的基因表現，而可能有心肌血管保護功能。因此雌性素與病性心肌病的關係確實值得進一步探討。我們結果並發現:1.腹動脈結紮大白鼠、E2-ER 可經活化IGF-I receptor 及IGF-Igene expression 而維持心肌細胞survival,亦可壓制calcineurin-NFAT3，而延緩病性肥大,纖維化生成及心肌凋亡(附E2-paper)。2.而IGF-IR 阻斷的心肌細胞，除引發胚胎基因IGF-II大表現(圖2)，IGF-II 並與Ang-II 發生加成作用，導致G 蛋白及鈣子-calcineurin-NFAT3過活化，導致心肌細胞加成肥大(圖1)、DNA 斷(圖3)、細胞凋亡(圖4) 及核破濃染(圖5 )。但E2 是否直接具阻斷心肌細胞凋亡作用，透過基因性或非基因性達成，及其影響的基因種及透過之機轉，均急待解答。
It has been proposed that estrogen has the function to protect cardiovascular, but the mechanism is not fully understood. Recently, the estrogen receptors (alpha&beta) were observed in the cardiomyocytes , and the interaction of estrogen receptors (ERs) and membrane insulin-like growth factor receptor (IGF-IR) was also reported in CHO cells, which result in the potentiation MEK-ERK signal pathway. Consequently, if the cardioprotective effects result from the cross talking of E2 and IGF-I pathways has been causing much attentions, and the roles of E2-ER genomic and non-genomic effects should be addressed. As we know, pathiological cardiohypertrophy always leads to the cardiac sudden death (CSD), but the molecular mechanism of hypertrophy and how exactly it leads to CSD is unclear. According to previous studies, IGF-I, a survival factor, activates PI3K-AKT/PKB pathway via IGF-IR. This is not only resulting in cell survival but also regulating the size of cardiomyocyte during physiological hypertrophy. Furthermo e, IGF-I also activates Ras-Raf-MEK-ERK mediated through IRS-1 to promote the proliferation of non-cardiomyocyte in the heart. Therefore, to reveal the cross regulation of E2-ER genomic and non-genomic effects on IGF-I pathways is urgent and important for elucidating the mechanism of E2 cardio-protective effects. However, hypertension, a risk factor for cardiac diseases, is mediated in part by G-protein coupled receptors (GPCRs) and is the response to ligand (e.g. angiotein-II etal) binding on the surface of vessel GPCRs. Angiotensin-II and GPCRs also get involved in cardiac hypertrophy mediated by calcium influx and calcineurin-NFAT pathway activation, which will lead cell to apoptosis by activated PKC and JNK via calcineurin as well. Therefore, the GPCRs could play a key role, for cardiac hypertrophy and CSD as well. Besides, TNFalphagene overexpressed and protein elevated in congestive heart failure patients, accompanied with high IL-6 and TGF1beta reduction. IL-6 related to the mortality of unstable coron y artery diseases as well. IL-6 not only activate MEK5-ERK5 to induce dilated cardiac-myopathy, but also trigger P38-STAT1 activities to cause cardiomyocytes apotosis. However, E2 not only has non-genomic effect can rapidly reduce the calcium influx in cardiomyocytes, but also inhibit inflammation proteins in postmenopausal women, and ER even cross talk and suppress proinflammatory transcription factore NFkappaB which might indeed contribute the cardioprotective effects of estrogen. Sprague-Dawley rats were ovariectomized (OVX) one month before complete coarctation of the abdominal aorta (COX) with or without E2 treatment (100 ng/kg) and sacrificed 4 or 8 days later. Based on our findings, the up-regulation of IGF-I signaling and suppression of calcineurin/NFAT-3 pathway may be plausible mechanisms for the cardiac protective effects of E2(enclosed E2-paper1).We even applied primary cardiomyocytes of rat heart and transforming neonatal rat heart cell-line, H9C2 and skeletal C2C12myocyte-like cells in serum-free medium, and added Ang-II with or without antisense IGF-I and IGF-IR antibodies. Results show that AngII and IGF-I resistant induced both cardiomyocytes hypertrophy and apoptosis. Which included the size enlarged (fig1), DNA fragmented (fig3), nuclei concentrated (fig5), Bad and cytochrom-c proteins elevated as well (fig4). In addition, all the Ang-II effects were fortified by IGF-I resistant. However, cardiomyocytes hypertrophy induced by IGF-I resistant was reversed after IGF-II antibodies treated. At the mean time, the upregulation of IGF-II gene expression and protein production were observed under IGF-I resistant (fig2). In summary, our results indicated that cardiomyocy s hypertrophy and apoptosis caused by Ang-II was augmented by IGF-I resistant, which probably comes from IGF-II up-regulation, and calcium-calcineurin activation. |
