Epileptic activity induces rapid ROCK1-dependent astrocyte morphology changes

Long-term changes of the morphology and function of astrocytes are well known to occur in epilepsy and are thought to play an important role in the development and manifestation of the disease. However, the initial astrocytic processes triggered at the onset of status epilepticus or epileptiform activity are less clear. For instance, it remains to be established how quickly epileptic activity induces changes of astrocyte morphology and what the associated molecular cascades is.We used two-photon excitation fluorescence imaging to monitor changes in astrocyte morphology concurrently with the induction of epileptiform activity. Our findings reveal changes of astrocyte morphology within 10-30 minutes in acute hippocampal slices. Further in vitro analysis uncovered a persistent reduction in the volume of peripheral astrocyte processes triggered by epileptiform activity. Additionally, impaired diffusion within and between astrocytes was observed. In vivo experiments demonstrated similarly changed astrocyte morphology within 30 minutes following the induction of status epilepticus. Notably, these observed changes in astrocyte morphology were prevented by inhibiting the Rho GTPase RhoA and the Rho-associated kinase (ROCK). Selective deletion of ROCK1 but not ROCK2 from astrocytes also prevented the morphological changes following the induction of epileptiform activity and reduced epileptiform activity itself.These results indicate that epileptic activity rapidly triggers a ROCK1-dependent alteration in astrocyte morphology, linked to the strength of epileptiform activity. Consequently, our findings suggest that astrocytic ROCK1 signaling represents a maladaptive response of astrocytes to the initiation of epileptic activity.