Department of Physiology, Pasteur Institute of Iran, Tehran 131694-3551, Islamic Republic of Iran.
Neurosci Bull. 2012 Dec;28(6):729-36. doi: 10.1007/s12264-012-1279-6. Epub 2012 Nov 12.
Understanding the molecular and cellular mechanisms underlying epileptogenesis yields new insights into potential therapies that may ultimately prevent epilepsy. Gap junctions (GJs) create direct intercellular conduits between adjacent cells and are formed by hexameric protein subunits called connexins (Cxs). Changes in the expression of Cxs affect GJ communication and thereby could modulate the dissemination of electrical discharges. The hippocampus is one of the main regions involved in epileptogenesis and has a wide network of GJs between different cell types where Cx30 is expressed in astrocytes and Cx32 exists in neurons and oligodendrocytes. In the present study, we evaluated the changes of Cx30 and Cx32 expression in rat hippocampus during kindling epileptogenesis.
Rats were stereotaxically implanted with stimulating and recording electrodes in the basolateral amygdala, which was electrically stimulated once daily at afterdischarge threshold. Expression of Cx30 and Cx32, at both the mRNA and protein levels, was measured in the hippocampus at the beginning, in the middle (after acquisition of focal seizures), and at the end (after establishment of generalized seizures) of the kindling process, by real-time PCR and Western blot.
Cx30 mRNA expression was upregulated at the beginning of kindling and after acquisition of focal seizures. Then it was downregulated when the animals acquired generalized seizures. Overexpression of Cx30 mRNA at the start of kindling was consistent with the respective initial protein increase. Thereafter, no change was found in protein abundance during kindling. Regarding Cx32, mRNA expression decreased after acquisition of generalized seizures and no other significant change was detected in mRNA and protein abundance during kindling.
We speculate that Cx32 GJ communication in the hippocampus does not contribute to kindling epileptogenesis. The Cx30 astrocytic network localized to perivascular regions in the hippocampus is, however, overexpressed at the initiation of kindling to clear excitotoxic molecules from the milieu.
了解癫痫发生的分子和细胞机制，为可能最终预防癫痫的潜在治疗方法提供新的见解。缝隙连接 (GJ) 在相邻细胞之间形成直接的细胞间通道，由称为连接蛋白 (Cx) 的六聚体蛋白亚基组成。Cx 表达的变化会影响 GJ 通讯，从而调节电放电的传播。海马体是癫痫发生的主要区域之一，具有不同细胞类型之间广泛的 GJ 网络，其中 Cx30 在星形胶质细胞中表达，Cx32 存在于神经元和少突胶质细胞中。在本研究中，我们评估了在点燃癫痫发生过程中大鼠海马体中 Cx30 和 Cx32 表达的变化。
大鼠立体定向植入外侧杏仁核的刺激和记录电极，每天在发作后阈值下对其进行电刺激。在点燃过程的开始、中间（获得局灶性发作后）和结束（获得全身性发作后），通过实时 PCR 和 Western blot 测量海马体中 Cx30 和 Cx32 的 mRNA 和蛋白表达。
Cx30 mRNA 表达在点燃开始和获得局灶性发作后上调。然后，当动物获得全身性发作时，它被下调。在点燃开始时 Cx30 mRNA 的过表达与各自的初始蛋白增加一致。此后，在点燃过程中未发现蛋白质丰度的变化。关于 Cx32，在获得全身性发作后 mRNA 表达下降，在点燃过程中未检测到 mRNA 和蛋白质丰度的其他显著变化。
我们推测海马体中的 Cx32 GJ 通讯不会导致点燃癫痫发生。然而，位于海马体血管周围区域的 Cx30 星形胶质细胞网络在点燃开始时过表达，以清除细胞外环境中的兴奋性毒性分子。
