Testing the effects of a selective calpain-2 inhibitor on spontaneous recurrent seizures in mouse models of epilepsy

This work investigates the role of calpain-2 activation in seizure-induced neuropathology using mouse models of epilepsy. The study employed conditional calpain-2 knock-out (C2CKO) mice on a C57/Bl6 background and a selective calpain-2 inhibitor to dissect the contribution of prolonged calpain-2 activity to downstream pathological events following kainic acid (KA)-induced seizures. In C57/Bl6 mice 7 days after KA-induced seizures, marked neurodegeneration was evident across hippocampal subfields, with particular vulnerability of mossy cells in the hilus of the dentate gyrus. Notably, calpain-2 activation persisted in mossy cells at this 7-day time point, implicating sustained calpain-2 activity in the evolution of post-seizure neuropathology.

In contrast, mice lacking calpain-2 (C2CKO) and C57/Bl6 mice treated with a selective calpain-2 inhibitor for the week following seizure initiation did not show calpain activation, astroglial and microglial activation, neurodegeneration, or cognitive impairment. These findings indicate that calpain-2 activation is necessary for several hallmark pathological processes that follow status epilepticus in this model. The investigators also examined molecular substrates of calpain-2–mediated damage and found that levels of the potassium chloride cotransporter 2 (KCC2) were decreased in mossy cells 7 days after seizures; importantly, this decrease in KCC2 was prevented either by calpain-2 genetic deletion or by selective pharmacological inhibition. The preservation of KCC2 suggests a plausible mechanistic link between calpain-2 activity and impaired ion homeostasis or inhibitory signaling after seizures, mechanisms that could contribute to both neuronal degeneration and functional deficits.

Collectively, the experiments presented demonstrate that prolonged calpain-2 activation plays a critical role in neuropathology following seizures, affecting neuronal survival, glial activation, molecular regulators of neuronal function, and cognitive outcomes. The parallel protective effects observed with genetic deletion and with a selective calpain-2 inhibitor support the specificity of calpain-2’s contribution and indicate that pharmacological targeting of calpain-2 has translational potential. The authors conclude that a selective calpain-2 inhibitor could represent a therapeutic approach to mitigate seizure-induced neuropathology.

These results, reported in Neurobiology of Disease, provide preclinical evidence that calpain-2 is a key mediator of post-seizure brain injury in this mouse model and justify further exploration of selective calpain-2 inhibition as a strategy to prevent or reduce the long-term neurological consequences of severe seizures.