[P2-101] Enhanced astrocytic Ca2+ signals via IP3R2 contribute to eplileptogenesis after status epilepticus
Introduction: Temporal lobe epilepsy is the most common type of drug-resistant epilepsy partly characterized by astrogliosis, which is thought to contribute to the pathophysiology in epilepsy. However, functional properties of astrocyte in TLE are still unknown. In this study, we investigated astrocytic Ca2+ signals after SE and determined its pathophysiological relevance to epileptogenesis after SE.
Methodology: Pilocarpine was administrated to induce SE in 8-week-old male mice. Astrogliosis was assessed with immunohistochemistry of GFAP at 1, 3, 7 and 28 days after the SE. For functional analysis, Ca2+ imaging were performed from hippocampal slices 4 weeks after SE. Astrocytic Ca2+ were visualized by either GCaMP3, a genetically encoded Ca2+ indicator or Fluo-4.
Results: A significant increase in the area of GFAP-positive astrocytes was found in CA1 from 7 to 28 days after SE, suggesting that astrocytes became “reactive”. Astrocytes displayed significantly larger Ca2+ signals from 25 to 32 days after SE. Tetrodotoxin had no effect the larger Ca2+ signals. Both pharmacological depletion of intracellular Ca2+ stores and genetic deletion of IP3 receptor type2 (IP3R2), a major IP3R in astrocytes, significantly reduced the larger Ca2+ signals of astrocyte after SE. While less dose of pilocarpine induced the second SE at 28 days after the first SE in C57BL/6J mice, equivalent dose of pilocarpine was required to induce the second SE in IP3R2 knockout mice.
Conclusions: These results suggest that astrocytes undergo reactive changes after SE contributing to epilepstogenesis via IP3R2-mediated Ca2+ signals.
Methodology: Pilocarpine was administrated to induce SE in 8-week-old male mice. Astrogliosis was assessed with immunohistochemistry of GFAP at 1, 3, 7 and 28 days after the SE. For functional analysis, Ca2+ imaging were performed from hippocampal slices 4 weeks after SE. Astrocytic Ca2+ were visualized by either GCaMP3, a genetically encoded Ca2+ indicator or Fluo-4.
Results: A significant increase in the area of GFAP-positive astrocytes was found in CA1 from 7 to 28 days after SE, suggesting that astrocytes became “reactive”. Astrocytes displayed significantly larger Ca2+ signals from 25 to 32 days after SE. Tetrodotoxin had no effect the larger Ca2+ signals. Both pharmacological depletion of intracellular Ca2+ stores and genetic deletion of IP3 receptor type2 (IP3R2), a major IP3R in astrocytes, significantly reduced the larger Ca2+ signals of astrocyte after SE. While less dose of pilocarpine induced the second SE at 28 days after the first SE in C57BL/6J mice, equivalent dose of pilocarpine was required to induce the second SE in IP3R2 knockout mice.
Conclusions: These results suggest that astrocytes undergo reactive changes after SE contributing to epilepstogenesis via IP3R2-mediated Ca2+ signals.