Kesherwani Varun, Agrawal Sandeep K
Division of Neurosurgery, Department of Surgery, University of Nebraska Medical Center, Omaha, NE 68198-6250, USA.
Neurol Res. 2012 Jun;34(5):504-11. doi: 10.1179/1743132812Y.0000000038. Epub 2012 May 30.
Calcium overloading is responsible for initiating the cell death in neuronal tissue after hypoxic injury. Inositol 1,4,5-triphosphate receptors (IP3Rs) is an important calcium channel which regulates cellular calcium homeostasis. IP3R1 is widely expressed in brain and spinal tissue. In the present study, we have studied the regulation of IP3R1 in hypoxic/reperfusion injury of spinal cord dorsal column in vitro.
Dorsal columns were isolated from the spinal cord of adult rats and injury was induced by exposing to hypoxic condition for 1 hour. After injury, reperfusion was carried out for 0, 2, 4, and 8 hours. Tissues were collected and processed for western blotting, immunohistochemistry and real-time PCR.
In the present study, we have found increased expression of IP3R1 after hypoxic/reperfusion injury of spinal cord dorsal column in vitro. Maximum expression of IP3R1 has been seen at 4 hours after hypoxia. Double immunofluorescence studies show the localization of IP3R1 in axons and astrocytes. Further identifying the signaling pathway involved in the regulation, we found Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) inhibitor KN-62 and c-Jun N-terminal kinase (JNK) inhibitor SP600125 reduced the expression of IP3R1 suggesting the role of CaMKII and JNK in the regulation of IP3R1 expression. We did not find role of ERK and p38 in the regulation IP3R1 expression in hypoxic/reperfusion injury of dorsal column in vitro.
The result presented in this study showed that IP3R1 expression is increased in hypoxic/reperfusion injury of spinal cord white matter and it is regulated by the CaMKII-JNK pathway.
钙超载是缺氧性损伤后神经元组织细胞死亡的起始原因。肌醇1,4,5 -三磷酸受体（IP3Rs）是调节细胞钙稳态的重要钙通道。IP3R1在脑和脊髓组织中广泛表达。在本研究中，我们在体外研究了脊髓背柱缺氧/再灌注损伤中IP3R1的调控机制。
从成年大鼠脊髓中分离出背柱，通过暴露于缺氧条件1小时诱导损伤。损伤后，分别进行0、2、4和8小时的再灌注。收集组织并进行蛋白质免疫印迹、免疫组织化学和实时聚合酶链反应检测。
在本研究中，我们发现在体外脊髓背柱缺氧/再灌注损伤后IP3R1表达增加。缺氧后4小时观察到IP3R1的表达最高。双重免疫荧光研究显示IP3R1定位于轴突和星形胶质细胞中。为进一步确定参与调控的信号通路，我们发现钙/钙调蛋白依赖性蛋白激酶II（CaMKII）抑制剂KN - 62和c - Jun氨基末端激酶（JNK）抑制剂SP600125可降低IP3R1的表达，提示CaMKII和JNK在IP3R1表达调控中的作用。我们未发现细胞外信号调节激酶（ERK）和p38在体外背柱缺氧/再灌注损伤中对IP3R1表达调控的作用。
本研究结果表明，脊髓白质缺氧/再灌注损伤中IP3R1表达增加，且受CaMKII - JNK信号通路调控。
