(21) Evaluation of Potential Mechanisms of SUDEP in a Mouse Model of Dravet Syndrome

Dravet syndrome (DS) is a genetic epilepsy disorder, the majority resulting from mutations in the sodium channel Scn1a gene. Sudden Unexplained Death in Epilepsy (SUDEP) occurs in up to 50% of DS patients. Risk factors for SUDEP have been identified, but mechanisms are not fully understood. We hypothesize that astrocyte-mediated post-ictal neuroinflammatory damage in the medulla may contribute to respiratory dysfunction. Further, neuroinflammation arising from astrocyte activation in medullary respiratory control centers may be a novel cause of post-ictal apnea and sudden death. In response to CNS insults, astrocytic activation can lead to the production and release of pro-inflammatory cytokines. However, there is little known about the activation of astrocytes in the medulla in models of seizures and epilepsy and how it may contribute to mortality in epilepsy. Further, understanding the role of astrocytes may provide insight to mechanisms of SUDEP in DS and can promote the development of therapies to prevent fatal outcomes.

Methods:

The objective of these studies is to compare neuroinflammation of heterozygous mice with a mutation (A1783V) in Scn1a (HET) to wild-type (WT). Glial fibrillary acidic protein (GFAP) expression, used as a marker of astrocyte activation, was determined in the rostral ventrolateral medulla (RVLM) using immunohistochemistry. This respiratory control center is among several that contribute to post-insult breathing control. Fluorescence intensity was compared in HET vs WT of post-natal age 14-16 (P14-16). The presence of the pro-inflammatory cytokines TNFα and IL-6 mRNA in forebrain and hindbrain were determined using quantitative polymerase chain reaction (qPCR) and was compared between HET and WT of P24-27 animals. 

Results:

There is no significant difference in GFAP expression in the RVLM of Het animals compared to WT at P14-16. There was greater TNFα and IL-6 mRNA in the hindbrain of ~P25 HET animals compared to WT, and such differences were not observed between HET and WT forebrain.

Conclusions:

These results suggest that neuroinflammation, particularly in the hindbrain, may be involved in SUDEP in Dravet Syndrome. Further studies are necessary to better determine the involvement of various respiratory nuclei as well as glial cells in this neuroinflammation as it pertains to sudden death in Dravet Syndrome.

Funding: Please list any funding that was received in support of this abstract.: This work was supported by University of Utah College of Pharmacy.