Role of the potassium chloride cotransporter isoform 2-mediated spinal chloride homeostasis in a rat model of visceral hypersensitivity
Role of the potassium chloride cotransporter isoform 2-mediated spinal chloride homeostasis in a rat model of visceral hypersensitivity
复制标题
氯化钾协同转运蛋白亚型 2 介导的脊髓氯稳态在内脏过敏大鼠模型中的作用。
DOI：
10.1152/ajpgi.00313.2014
复制
发表时间：
2015-05-01
影响因子：
4.5
通讯作者：
Yuan, Yao-Zong
中科院分区：
文献类型：
--
作者：
Tang, Dong;Qian, Ai-Hua;Yuan, Yao-Zong
内脏超敏反应是肠易激综合征（IBS）病理生理学的一个重要标志，其机制尚不明确。本研究旨在探讨脊髓阳离子-氯共转运体（CCC）介导的氯离子（Cl(-)）稳态是否参与慢性应激性内脏超敏反应。研究了雄性Wistar大鼠避水应激（was）诱导的慢性内脏过敏反应。采用RT-PCR、Western blotting和免疫组化检测脊髓中CCCs的表达。采用膜片钳法记录成人脊髓切片，评价I层神经元的Cl（-）稳态和Cl（-）挤压能力。通过测量结肠直肠膨胀（CRD）时的腹部退缩反射来估计内脏敏感性。暴露于WAS 10天后，腰骶脊髓背角中K(+)- cl（-）共转运体亚型2 （KCC2）的总蛋白和寡聚形式的水平显著降低，但Na(+)-K(+)- 2cl（-）转运体亚型1 （NKCC1）的水平没有显著降低。KCC2的下调导致腰骶脊髓I层神经元gaba能抑制突触后电流平衡电位的去极化移位和Cl（-）挤压能力受损。急性毒性CRD在假手术大鼠腹胀2小时后破坏了脊髓KCC2的表达和功能，但在WAS大鼠中没有。鞘内注射KCC2抑制剂[（二氢独立基）氧]烷酸对KCC2活性的药理学阻断增强了假手术大鼠内脏伤害性敏感性，但对WAS大鼠没有作用。这些结果表明，KCC2下调介导的脊髓Cl（-）稳态损伤可能在慢性应激性内脏超敏反应中起重要作用。
Visceral hypersensitivity represents an important hallmark in the pathophysiology of irritable bowel syndrome (IBS), of which the mechanisms remain elusive. The present study was designed to examine whether cation-chloride cotransporter (CCC)-mediated chloride (Cl(-)) homeostasis of the spinal cord is involved in chronic stress-induced visceral hypersensitivity. Chronic visceral hypersensitivity was induced by exposing male Wistar rats to water avoidance stress (WAS). RT-PCR, Western blotting, and immunohistochemistry were used to assess the expression of CCCs in the spinal cord. Patch-clamp recordings were performed on adult spinal cord slices to evaluate Cl(-) homeostasis and Cl(-) extrusion capacity of lamina I neurons. Visceral sensitivity was estimated by measuring the abdominal withdrawal reflex in response to colorectal distension (CRD). After 10 days of WAS exposure, levels of both total protein and the oligomeric form of the K(+)-Cl(-) cotransporter isoform 2 (KCC2), but not Na(+)-K(+)-2Cl(-) transporter isoform 1 (NKCC1), were significantly decreased in the dorsal horn of the lumbosacral spinal cord. The downregulation of KCC2 resulted in a depolarizing shifted equilibrium potential of GABAergic inhibitory postsynaptic current and impaired Cl(-) extrusion capacity in lamina I neurons of the lumbosacral spinal cord from WAS rats. Acute noxious CRD disrupted spinal KCC2 expression and function 2 h after the final distention in sham rats, but not in WAS rats. Pharmacological blockade of KCC2 activity by intrathecal injection of a KCC2 inhibitor [(dihydroindenyl)oxy] alkanoic acid enhanced visceral nociceptive sensitivity in sham rats, but not in WAS rats. These results suggest that KCC2 downregulation-mediated impairment of spinal cord Cl(-) homeostasis may play an important role in chronic stress-induced visceral hypersensitivity.