Functional expression of P2X4 receptor in capillary endothelial cells of the cochlear spiral ligament and its role in regulating the capillary diameter.
Functional expression of P2X4 receptor in capillary endothelial cells of the cochlear spiral ligament and its role in regulating the capillary diameter.
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P2X4受体在耳蜗螺旋韧带毛细血管内皮细胞中的功能表达及其调节毛细血管直径的作用。
DOI：
10.1152/ajpheart.01035.2010
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Nuttall,AL
中科院分区：
文献类型：
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作者：
Wu,T;Dai,M;Shi,XR;Jiang,ZG;Nuttall,AL
耳蜗侧壁产生耳蜗内电位(EP)，为毛细胞传导电流创造驱动力，是正常听力所必需的。耳蜗侧壁处的血流对维持EP至关重要。EP对低氧的易感性表明，耳蜗侧壁上的血流受到动态而精确的调节，以满足耳蜗侧壁不断变化的代谢需求。已有研究表明，作为一种重要的细胞外信号分子，三磷酸腺苷在调节耳蜗血流量中起着重要作用。然而，三磷酸腺苷诱导局部血流改变的细胞机制还没有被研究。在本研究中，我们证实：1)在螺旋韧带(SL)毛细血管内皮细胞(ECs)表达P2X4受体；2)ATP以剂量依赖的方式在ECs上引起一种特征电流(EC50=0.16 mM)。5-(3-bromophenyl)-1，3-dihydro-2H-benzofuro[3，2-e]-1，4-diazepin-2-one(5-BDBD)、LaCl3、磷酸吡哆醛-6-偶氮苯-2，4-二磺酸四钠水合物(PPADS)和细胞外酸中毒均能抑制∼电流。对α，β-MeATP和2‘-和3’-O-(4-苯甲酰-苯甲酰基)腺苷5‘-三磷酸(α，β)不敏感。3)三磷酸腺苷可引起内皮细胞内钙的一过性增加。4)与上述研究结果一致，1 mM的外淋巴液中的三磷酸腺苷可引起SL毛细血管扩张11.5%。非选择性一氧化氮合酶抑制剂N-ω-硝基-L-精氨酸甲酯盐酸盐(N-NAME)或特异性的P2X4抑制剂5-BDBD可显著阻断这一扩张。这些发现支持我们的假设，即细胞外ATP通过激活内皮细胞中的P2X4来调节耳蜗侧向血流量。
The cochlear lateral wall generates the endocochlear potential (EP), which creates a driving force for the hair cell transduction current and is essential for normal hearing. Blood flow at the cochlear lateral wall is critically important for maintaining the EP. The vulnerability of the EP to hypoxia suggests that the blood flow in the cochlear lateral wall is dynamically and precisely regulated to meet the changing metabolic needs of the cochlear lateral wall. It has been reported that ATP, an important extracellular signaling molecule, plays an essential role in regulating cochlear blood flow. However, the cellular mechanism underlying ATP-induced regional blood flow changes has not been investigated. In the current study, we demonstrate that1) the P2X4 receptor is expressed in endothelial cells (ECs) of spiral ligament (SL) capillaries.2) ATP elicits a characteristic current through P2X4 on ECs in a dose-dependent manner (EC50= 0.16 mM). The ATP current has a reversal potential at ∼0 mV; is inhibited by 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]-1,4-diazepin-2-one (5-BDBD), LaCl3, pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid) tetrasodium salt hydrate (PPADS), and extracellular acidosis; and is less sensitive to α,β-methyleneadenosine 5′-triphosphate (α,β-MeATP) and 2′- and 3′-O-(4-benzoyl-benzoyl) adenosine 5′-triphosphate (BzATP).3) ATP elicits a transient increase of intracellular Ca2+in ECs.4) In accordance with the above in vitro findings, perilymphatic ATP (1 mM) caused dilation in SL capillaries in vivo by 11.5%.Nω-nitro-l-arginine methyl ester hydrochloride (l-NAME), a nonselective inhibitor of nitric oxide synthase, or 5-BDBD, the specific P2X4 inhibitor, significantly blocked the dilation. These findings support our hypothesis that extracellular ATP regulates cochlear lateral blood flow through P2X4 activation in ECs.