黃芩類黃酮改善低氧誘導肺動脈平滑肌細胞鉀離子通道的抑制表現

Scutellaria baicalensis Flavonoids Improve Hypoxia-Induced Potassium Channels Dysfunction in Pulmonary Arterial Smooth Muscle Cell

張勝璭(Chang-Kun Chang)

指導教授 ： 吳炳男

高雄醫學大學/醫學院/藥理學科研究所/碩士(2011年)

摘要

低氧會造成肺動脈收縮與肺動脈高壓的形成有密切的關係。有許多證據都顯示出當暴露在低氧的環境下，鉀離子通道會被抑制進而使得細胞內鈣離子濃度增加，鈣離子濃度的上昇是造成肺動脈收縮及肺動脈平滑肌細胞增生一個很重要的因素。而本次的研究中我們主要目的是探討一個目前已被研究岀具有多種藥理作用的傳統中藥黃芩其分離岀的類黃酮純化物能否預防低氧造成的肺動脈收縮功能變差及肺動脈細胞增生與鉀離子通道被抑制的情形，並進一步研究其中所參與的機轉。實驗中所使用的肺動脈平滑肌細胞是由Wistar大鼠所取出的肺動脈培養而得。之後將肺動脈細胞置於設定條件為1% O2低氧環境的培養箱中2或4小時來誘導鉀離子通道蛋白抑制現象。
在離體肺動脈張力實驗中發現低氧誘導4小時之後，肺動脈收縮功能明顯的變差，而黃芩類黃酮可以預防這個現象。而在細胞實驗中也觀察到低氧的確會誘導肺動脈平滑肌細胞增生及抑制細胞上KV2.1 、KV1.5和BKCa等鉀離子通道的表現，而這種細胞增生及鉀離子通道被抑制的情形也能在前給予黃芩類黃酮後獲得改善。另外由實驗結果發現低氧誘導細胞增生及鉀離子通道被抑制的現象可以被PKC的抑制劑chelerythrine或是PKA的活化劑8-Br-cAMP反轉，且黃芩類黃酮也能預防因PKC的活化劑PMA及PKA的抑制劑KT5720所造成的鉀離子表現抑制現象。
綜合以上結果我們推測黃芩類黃酮之所以能改善因低氧所造成血管收縮功能變差的情形、抑制低氧所造成的細胞增生及預防鉀離子通道抑制的現象，其主要可能是透過抑制PKC及活化PKA路徑所致，而這個發現將來或許可以應用在改善低氧所造成的肺動脈高壓上。

關鍵字

黃芩 ； 鉀離子 ； 低氧

並列摘要

Hypoxia causes contraction of pulmonary arteries (PAs), which may play a key role in pulmonary arterial hypertension (PAH). Recent evidence suggests that exposure to hypoxia inhibits K+-channel activity resulting in the enhancement of intracellular Ca2+ concentration ([Ca2+]i). Ca2+ is a major trigger for pulmonary vasoconstriction and a stimulus for pulmonary arterial smooth muscle cells (PASMCs) proliferation. Three flavonoids baicalin, baicalein and wogonin (isolated from Scutellaria baicalensis) have been widely used in cardiovascular dysfunction and inflammation.
This study aimed to investigate the underlying mechanism of these 3 flavonoids prevention of hypoxia-induced vessel reactivity decrease, K+-channel inhibition and proliferation in PASMCs. PASMCs were primary cultured from Wistar rats and placed in the hypoxic chamber under 1% O2 for 2-4 hours to suppress K+-channel.
In isolated PA experiments, hypoxia-induced (4 h) PA contraction was weaker than the control and this response was ameliorated by pretreating flavonoids. In PASMCs study, the protein levels of voltage-gated K+ channels (KV2.1 and KV1.5) and large-conductance Ca2+-activated K+ (BKCa) channel were reduced under hypoxic states, and these proteins were reversed by pretreating flavonoids. These flavonoids could also attenuate the hypoxia-induced PASMCs proliferation. Hypoxia-induced K+-channel suppression and PASMCs proliferation were reversed by the PKC inhibitor chelerythrine (1 μM) and PKA activator 8-Br-cAMP (100 μM). Enhanced K+-channel proteins of flavonoids were attenuated by the PKC activator PMA (1 μM) and the PKA inhibitor KT5720 (1 μM).
In light of these results, we suggest that 3 flavonoids prevention of hypoxia-induced vessel reactivity reduction and K+-channel inhibition and cell proliferation in PAs could be due to the involvement of PKC and PKA pathways. Finally, we suggest that 3 flavonoids would be used in the control of hypoxia-induced PAH.

並列關鍵字

Scutellaria baicalensis Georgi ； potassium channel ； hypoxia

參考文獻

參考文獻

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