Axonal injury and dysfunction are responsible for much of the disability observed following a stroke. Human brain comprises equal proportions of gray matter and white matter and white matter is injured in most strokes. Casein kinase 2 (CK2) is a protein kinase expressed in brain, including white matter, and is regulated by ischemia. We therefore hypothesized that transient CK2 inhibition would protect white matter from ischemic injury.
To assess the impact of CK2 inhibition on axonal electrical activity following oxygen glucose deprivation (OGD), mouse optic nerves (MONs), a pure white matter track, from C57BL/6J were subjected to OGD (1h) while eliciting compound action potentials (CAPs) and exposed to CX-4945, a selective CK2 inhibitor, or control artificial cerebrospinal fluid (ACSF). We observed that CX-4945 preserved CAPs when applied either before or after OGD. Then to determine the impact of CK2 inhibition on glial cell survival following OGD, MONs exposed to OGD that were treated with either CX-4945 or control ACSF were processed for immunohistochemistry. We observed that CX-4945 treatment protected oligodendrocytes from OGD. And finally, to determine if CK2 inhibition protected mitochondrial from OGD, MONs from Thy-1 mito-CFP mice were similarly subjected to OGD in the presence of either CX-4945 or control ACSF. We observed that CX-4945 maintained Thy-1 mito-CFP fluorescence following OGD.
In conclusion, our results suggest that CK2 inhibition preserves axonal function by preserving oligodendrocytes and mitochondrial function following ischemic injury. We propose that CK2 inhibitors, which are currently in phase II-III clinical trials for cancer therapy could be repurposed and provide a novel therapeutic target to protect white matter against ischemic injury, reducing mortality and morbidity and improving recovery following stroke.