| 研究生: |
王忻慈 Wang, Hsin-Tzu |
|---|---|
| 論文名稱: |
活化雌激素貝他增加心臟L型鈣離子通道及誘導新生鼠心臟生理性肥大外表型 Activated ERbeta increases the expression of L-type Ca2+ channel and enhances the hypertrophic phenotype of neonatal rat hearts |
| 指導教授: |
蔡美玲
Tsai, Mei-Ling |
| 學位類別: |
碩士 Master |
| 系所名稱: |
醫學院 - 生理學研究所 Department of Physiology |
| 論文出版年: | 2013 |
| 畢業學年度: | 101 |
| 語文別: | 英文 |
| 論文頁數: | 60 |
| 中文關鍵詞: | 17貝它雌激素 、雌激素接受器貝它 、L-型鈣離子通道 、鈣調控蛋白 、心臟細胞骨架蛋白 、QT間隔 |
| 外文關鍵詞: | 17beta-estradiol, ERbeta, L-type Ca2+ channel, calcium-handling protein, cardiac cytoskeleton proteins, QT interval |
| 相關次數: | 點閱:106 下載:1 |
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自著床後的懷孕期間,雌激素(E2)的濃度不斷的上升直到分娩。同時心臟發育從胚胎期到剛出生持續改變它的生長型態,由分裂(增加細胞數目)至分化(加大細胞面積),但不增加心臟與身體之重量比。因此,本研究假設:雌激素具有誘導生理性心臟肥大的能力。目前研究顯示E2可作用至兩種接受器,分別是ERα和ERβ。在成熟小鼠中,剃除體內ERβ增加L型鈣離子通道(L-type Ca2+ channel)電流,延長心臟週期,並誘導心臟肥大但剃除體內ERβ對L型鈣離子通道(L-type Ca2+ channel)電流與心臟形態並無影響。然而在實驗室先前的實驗結果顯示,的ERβ蛋白表現量隨著心臟的成熟而下降,所以推測新生鼠ERβ表現量高的情況下會影響L型鈣離子通道,進而誘導出生理性心臟肥大。因此本研究的目的是利用DPN,探討活化ERβ是否增加L-type Ca2+ channel,引發新生鼠生理性心臟肥大表現型。新生大鼠皮下注射DPN (20 µg/ kg/ day) 一連七天當作是本研究的動物實驗模式。另外,由大鼠胚胎心臟分離出的H9c2 (心臟前驅細胞)當作細胞實驗模式,進一步去證實動物實驗模式。維他命A酸(retinoic acid), 白血病抑制因子(leukemia inhibitory factor)以及異丙腎上腺素(isoproterenol)改變細胞型態且增加L-type Ca2+ channel以及細胞骨架蛋白( α-sarcomeric actinin,β-tubulin)蛋白表現量,顯示出心臟肥大的早期外表型。以上這些作為細胞模式的正向控制組。實驗結果顯示,雌激素和DPN並不會影響新生鼠的心跳,心臟和體重。但是相較於E2,DPN會影響心電圖之心臟週期(QT interval) ,使其與心跳呈逆相關,增加在Lead I肢導之R+S波。另外也增加鈣處置蛋白(calcium-handling protein)及細胞骨架蛋白(cytoskeletal proteins)的表現。Nifedipine (L-type Ca2+ channel blocker) 不讓細胞外鈣離子流入,DPN促進nifedipine抑制的Lead I肢導S 波以及R+S 波以及抑制nifedipine促進的心跳速率。H9c2培養在低血清濃度下七天,生長型態像是retinoic acid, leukemia inhibitory factor以及isoproterenol的組別,長度增加但寬度不變的非同心肥大,並且增加ER蛋白表現,促進L-type Ca2+ channel和 α-sarcomeric actinin,β-tubulin的蛋白表現量。在tamoxifen (ER αand ERβ 拮抗劑, 10-8 M)或PHTPP (ERβ 拮抗劑, 10-7 M)存在下會降低DPN的促進L-type Ca2+ channel的作用。另外ERβshRNA 抑制L-type Ca2+ channel的蛋白表現。利用全細胞膜片箝制技術(whole-cell patch clamp method)偵測DPN所促進的L-type Ca2+ channel電流。本研究之細胞及動物實驗的結果顯示,在長時間活化ERβ,促使鈣處置蛋白以及細胞骨架蛋白表現量增加,推論雌激素貝他扮演著啟動初期生理性心臟肥大的能力。
With the elevation of 17 β-estradiol (E2) from implantation to parturition during pregnancy, cardiac development from the embryonic to neonatal stages changes its growth pattern from hyperplasia to hypertrophy without increasing the ratio of heart to body weight. It is possible that E2 may induce cardiac hypertrophy in neonatal hearts. Now, two estrogen receptors are discovered. Deletion of ERβ increases the current of the L-type calcium channel, prolongs the duration of the cardiac cycle, and induces cardiac hypertrophy in adult mice but depletion of ERβ does not Our preliminary data showed higher levels of ERβ protein in pre-pubertal hearts than those in adult hearts. Therefore, the purpose of the study was to determine whether activation of ERβ by DPN increased the expression of L-type Ca2+ channels and enhanced the hypertrophic phenotype of neonatal hearts. Neonatal SD rats were injected with DPN (20 µg/kg/day) subcutaneously for 7 days. H9c2 derived from cardiac tissue-derived cardiomyoblasts were used to confirm our study in neonatal rats. A 7-day treatment with retinoic acid (RA), LIF, or isoproterenol which changed cell morphology and increased the expression of α-actinin and L-type calcium channel showed early sign of hypertrophic growth. Those were used as our positive controls in vitro. Our results indicated that both E2 and DPN did not affect heart rate, heart weight, and body weight. Compared with E2, DPN improved the inverse correlation between heart rate and the duration of an electrical cycle of the heart (QTc), enlarged the amplitude of the QRS complex in Lead I, and increased the relative abundance of calcium handling proteins and cytoskeletal proteins. Co-treatment with nifedipine increased the amplitude of the S wave in Lead I and heart rate. A 7-day culture with DPN in vitro, changed cell morphology as RA, LIF, or ISO without altering cell size and increased the protein expressions of ER β,L-type Ca2+ channel, α-actinin, and β-tubulin. Co-treatment with tamoxifen (ER αand ER β antagonist, 10-8M) or PHTPP (an ER βantagonist, 10-8M) lowered the positive effect of DPN on the expression of L-type Ca2+ channel protein expression. Knockdown of ER βinhibited L-type Ca2+ channel protein expression as well. Whole-cell patch clamp showed the increased current of L-type Ca2+ channel by DPN enhanced. These in vivo and in vitro results showed the increases of calcium-handling proteins, cytoskeletal proteins, calcium current, and the amplitude of the QRS complex in Lead I with the increased expression of ERβ suggesting the role of ER β in initiating early development of cardiac hypertrophy.
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