GluR6-containing KA receptor mediates the activation of p38 MAP kinase in rat hippocampal CA1 region during brain ischemia injury

Our previous study showed that kainate (KA) receptor subunit GluR6 played an important role in ischemia-induced MLK3 and JNK activation and neuronal degeneration through the GluR6-PSD95-MLK3 signaling module. However, whether the KA receptors subunit GluR6 is involved in the activation of p38 MAP kinase during the transient brain ischemia/reperfusion (I/R) in the rat hippocampal CA1 subfield is still unknown. In this present study, we first evaluated the time-course of phospho-p38 MAP kinase at various time-points after 15 min of ischemia and then observed the effects of antagonist of KA receptor subunit GluR6, GluR6 antisence oligodeoxynucleotides on the phosphorylation of p38 MAP kinase induced by I/R. Results showed that inhibiting KA receptor GluR6 or suppressing the expression of KA receptor GluR6 could down-regulate the elevation of phospho-p38 MAP kinase induced by I/R. These drugs also reduced the phosphorylation of MLK3, MKK3/MKK6, MKK4, and MAPKAPK2. Additionally, our results indicated administration of three drugs, including p38 MAP kinase inhibitor before brain ischemia significantly decreased the number of TUNEL-positive cells detected at 3 days of reperfusion and increased the number of the surviving CA1 pyramidal cells at 5 days of reperfusion after 15 min of ischemia. Taken together, we suggest that GluR6-contained KA receptors can mediate p38 MAP kinase activation through a kinase cascade, including MLK3, MKK3/MKK6, and MKK4 and then induce increased phosphorylation of MAPKAPK-2 during ischemia injury and ultimately result in neuronal cell death in the rat hippocampal CA1 region.