The reverse roles of transient receptor potential canonical channel-3 and -6 in neuronal death following pilocarpine-induced status epilepticus

Abstract

Transient receptor potential canonical channel (TRPC) is a nonselective cation channel permeable to Ca(2+), which is expressed in many cell types, including neurons. However, the alterations in TRPC receptor expressions in response to status epilepticus (SE) have not been explored. Therefore, the present study was designated to elucidate the roles of TRPC3 and TRPC6 in neuronal death following SE. In non-SE animals, TRPC3 and TRPC6 immunoreactivity was abundantly detected in the dendrites of pyramidal cells and the cell bodies of dentate granule cells. Following SE, TRPC3 expression was significantly elevated in CA1-, CA3 pyramidal cells, and dentate granule cells, while TRPC6 expression was reduced in these regions. Pyrazole-3 (a TRPC3 inhibitor) effectively prevented up-regulation of neuronal TRPC3 expression induced by SE. Hyperforin (a TRPC6 activator) effectively prevented down-regulation of neuronal TRPC6 expression induced by SE. In addition, both Pyr3 and hyperforin effectively protected neuronal damages from SE. Therefore, the present study yields novel information regarding the role of TRPC3 and 6 in epileptogenic insults and suggests that TRPC 3 and 6 may be involved in neurodegeneration following SE.

Fig. 1

TRPC3 expression in the hippocampus following SE. a Non-SE animal. Bar = 400 (panel 1) and 50 μm (panel 2–4). b One day-post SE animals. Bar = 400 (panel 1) and 50 μm (panel 2–4). c Three days-post SE animals. Bar = 400 (panel 1) and 50 μm (panel 2–4). d One week-post SE animals. Bar = 400 (panel 1) and 50 μm (panel 2–4). e Quantitative analysis of TRPC3 expression in the hippocampus following SE (mean ± SEM). Significant differences from vehicle-treated groups (*p < 0.05 vs. non-SE animals). DG dentate granule cell layer; CA1 pyramidal cell layer; CA3 pyramidal cell layer

Fig. 2

Effect of TRPC3 inhibitor (Pyr3) on neuronal death in the hippocampus following SE. a, b Non-SE animals; c, d three days-post SE animals treated with vehicle; e, f three days-post SE animals treated with Pyr-3. b, d, f High magnification of CA1 pyramidal cells. Panels 1, 2, 3, and 4 are TRPC3, NeuN, DAPI counterstaining, and merge images, respectively. Bar = 400 (a, c, e) and 12.5 μm (b, d, f). g Quantitative analysis of TRPC3 expression in the hippocampus following SE (mean ± SEM). Significant differences from non-SE animals and vehicle-treated animals (* and # p < 0.05 vs. non-SE animals and vehicle-treated animals, respectively)

Fig. 3

TRPC6 expression in the hippocampus following SE. a Non-SE animal. Bar = 400 (panel 1) and 50 μm (panel 2–4). b One day-post SE animals. Bar = 400 (panel 1) and 50 μm (panel 2–4). c Three days-post SE animals. Bar = 400 (panel 1) and 50 μm (panel 2–4). d One week-post SE animals. Bar = 400 (panel 1) and 50 μm (panel 2–4). e Quantitative analysis of TRPC6 expression in the hippocampus following SE (mean ± SEM). Significant differences from vehicle-treated groups (*p < 0.05 vs. non-SE animals). DG dentate granule cell layer; CA1 pyramidal cell layer; CA3 pyramidal cell layer

Fig. 4

Effect of TRPC6 activator (hyperforin) on neuronal death in the hippocampus following SE. a, b Non-SE animals; c, d three days-post SE animals treated with vehicle; e, f three days-post SE animals treated with hyperforin. b, d, f High magnification of CA1 pyramidal cells. Panels 1, 2, 3, and 4 are TRPC3, NeuN, DAPI counterstaining, and merge images, respectively. Bar = 400 (a, c, e) and 12.5 μm (b, d, f). g Quantitative analysis of TRPC6 expression in the hippocampus following SE (mean ± SEM). Significant differences from non-SE animals and vehicle-treated animals (* and # p < 0.05 vs. non-SE animals and vehicle-treated animals, respectively)

Fig. 5

Effects of Pyr3 and hyperforin on neuronal damages in the hippocampus following SE. a Vehicle-treated animals; b pyr3-treated animals; c hyperforin-treated animals. Bar = 20 μm. (d–f) Quantitative analysis of FJB positive neurons in the hippocampus following SE (mean ± SEM). Significant differences from vehicle-treated animals (*p < 0.05 vs. non-SE animals). DH dentate hilar cell; CA1 pyramidal cell; CA3 pyramidal cell