(S)‐roscovitine, a CDK inhibitor, decreases cerebral edema and modulates AQP4 and α1‐syntrophin interaction on a pre‐clinical model of acute ischemic stroke

Abstract

Cerebral edema is one of the deadliest complications of ischemic stroke for which there is currently no pharmaceutical treatment. Aquaporin‐4 (AQP4), a water‐channel polarized at the astrocyte endfoot, is known to be highly implicated in cerebral edema. We previously showed in randomized studies that (S)‐roscovitine, a cyclin‐dependent kinase inhibitor, reduced cerebral edema 48 h after induction of focal transient ischemia, but its mechanisms of action were unclear. In our recent blind randomized study, we confirmed that (S)‐roscovitine was able to reduce cerebral edema by 65% at 24 h post‐stroke (t test, p = .006). Immunofluorescence analysis of AQP4 distribution in astrocytes revealed that (S)‐roscovitine decreased the non‐perivascular pool of AQP4 by 53% and drastically increased AQP4 clusters in astrocyte perivascular end‐feet (671%, t test p = .005) compared to vehicle. Non‐perivascular and clustered AQP4 compartments were negatively correlated (R = −0.78; p < .0001), suggesting a communicating vessels effect between the two compartments. α1‐syntrophin, AQP4 anchoring protein, was colocalized with AQP4 in astrocyte endfeet, and this colocalization was maintained in ischemic area as observed on confocal microscopy. Moreover, (S)‐roscovitine increased AQP4/α1‐syntrophin interaction (40%, MW p = .0083) as quantified by proximity ligation assay. The quantified interaction was negatively correlated with brain edema in both treated and placebo groups (R = −.57; p = .0074). We showed for the first time, that a kinase inhibitor modulated AQP4/α1‐syntrophin interaction, and was implicated in the reduction of cerebral edema. These findings suggest that (S)‐roscovitine may hold promise as a potential treatment for cerebral edema in ischemic stroke and as modulator of AQP4 function in other neurological diseases.