Temporal characterisation and electrophysiological implications of TBI-induced serine/threonine kinase activity in mouse cortex

Abstract

Traumatic brain injury (TBI) remains the leading cause of death and disability worldwide with no existing effective treatment. The early phase after TBI induction triggers numerous molecular cascades to regulate adaptive processes and cortical network activity. Kinases play a particularly prominent role in modifying peptide substrates, which include ion channels, receptors, transcription factors and inflammatory mediators. This study aimed to better understand the post-injury serine/threonine kinome; (1) Which kinases conduct phosphorylation-induced alterations of target peptides following unilateral TBI in mouse cortex? (2) How do these kinases effectuate pathological network hyperexcitability, which has detrimental long-term outcomes? We used a serine/threonine kinase assay at 4 h, 24 h and 72 h post-TBI to identify hyper-/hypo-active/phosphorylated kinases and peptides in the ipsilateral and contralateral cortical hemispheres relative to sham-operated controls. We pharmacologically mimicked the changes seen in ERK1/2 and PKC kinase activity, and using microelectrode array recordings we explored their significant electrophysiological implications on spontaneous and evoked cortical activity. We then used these findings to manipulate key kinase activity changes at 24 h post-TBI to rescue the hyperexcitability that is seen in the contralateral cortical network at this timepoint back to sham level. The contribution of specific downstream peptide target channel/receptor subunits was also shown. We conclude that volatile kinase activity has potent implications on cortical network activity after the injury and that these kinases and/or their peptide substrates should be more seriously considered as therapeutic targets for the clinical treatment of TBI.