Dexamethasone-induced activation of heat shock response ameliorates seizure susceptibility and neuroinflammation in mouse models of Lafora disease

Abstract

Heat shock response (HSR) is a conserved cytoprotective pathway controlled by the master transcriptional regulator, the heat shock factor 1 (HSF1), that activates the expression of heat shock proteins (HSPs). HSPs, as chaperones, play essential roles in minimizing stress-induced damages and restoring proteostasis. Therefore, compromised HSR is thought to contribute to neurodegenerative disorders. Lafora disease (LD) is a fatal form of neurodegenerative disorder characterized by the accumulation of abnormal glycogen as Lafora bodies in neurons and other tissues. The symptoms of LD include progressive myoclonus epilepsy, dementia, and cognitive deficits. LD is caused by the defects in the gene coding laforin phosphatase or the malin ubiquitin ligase. Laforin and malin are known to work upstream of HSF1 and are essential for the activation of HSR. Herein, we show that mice deficient for laforin or malin show reduced levels of HSF1 and their targets in their brain tissues, suggesting compromised HSR; this could contribute to the neuropathology in LD. Intriguingly, treatment of LD animals with dexamethasone, a synthetic glucocorticoid analogue, partially restored the levels of HSF1 and its targets. Dexamethasone treatment was also able to ameliorate the neuroinflammation and susceptibility to induced seizures in the LD animals. However, dexamethasone treatment did not show a significant effect on Lafora bodies or autophagy defects. Taken together, the present study establishes a role for HSR in seizure susceptibility and neuroinflammation and dexamethasone as a potential antiepileptic agent, suitable for further studies in LD.