Therapeutic time window for conivaptan treatment against stroke-evoked brain edema and blood-brain barrier disruption in mice

Abstract

Background: Ischemic stroke is often complicated by brain edema, disruption of blood-brain barrier (BBB), and uncontrolled release of arginine-vasopressin (AVP). Conivaptan, a V1a and V2 receptor antagonist, reduces brain edema and minimizes damage to the blood-brain barrier after stroke. Most stroke patients do not receive treatment immediately after the onset of brain ischemia. Delays in therapy initiation may worsen stroke outcomes. Therefore, we designed a translational study to explore the therapeutic time window for conivaptan administration.

Methods: Mice were treated with conivaptan beginning 3, 5, or 20 hours after 60-minute focal middle cerebral artery occlusion. Treatments were administered by continuous IV infusion for a total of 48 hours. Brain edema and blood-brain barrier (BBB) disruption were evaluated at endpoint.

Results: Conivaptan therapy initiated at 3 hours following ischemia reduced edema in the ipsilateral hemisphere, which corresponded with improvements in neurological deficits. Stroke-triggered BBB disruption was also reduced in mice when conivaptan treatments were initiated at 3 hours of reperfusion. However, 5 and 20-hour delays of conivaptan administration failed to reduce edema or protect BBB.

Conclusion: Timing of conivaptan administration is important for successful reduction of brain edema and BBB disruption. Our experimental data open new possibilities to repurpose conivaptan, and make an important "bench-to-bedside translation" of the results into clinical practice.

Fig 1. Diagram of experimental design.

Mice underwent 60-minute transient focal brain ischemia by middle cerebral artery occlusion (MCAO) with reperfusion. Treatments with normal saline (NS) or conivaptan were initiated at 3, 5, or 20 hours following MCAO. At the end point (48 hours following MCAO) brain edema, BBB integrity, plasma osmolality, and neurological deficits scoring were assessed in all experimental animals.

Fig 2. Conivaptan reduces brain edema when administered with 3 hour delay.

Mice were subjected to 1-hour MCAO with reperfusion followed by IV treatment initiated at 3, 5, or 20 hours after onset of ischemia. Conivaptan treatment initiated at 3-hour delay reduced brain water content (BWC) in the ipsilateral hemisphere compared to normal saline (NS) treated mice (A). However, 5 or 20-hour delay in treatment initiation failed to reduce brain edema (B and C). Values are mean ± SEM *p ˂ 0.05 vs. NS-treated mice, n = 10 per group.

Fig 3. Conivaptan treatment reduces blood-brain barrier (BBB) breakdown after 3 hour delay.

Evans blue extravasation was measured 48 hours after MCAO in mice treated with conivaptan or normal saline (NS) beginning at 3, 5, or 20 hours after brain ischemia. Conivaptan treatment initiated at 3 hours after MCAO (A) was effective in protecting the BBB integrity. However, 5 and 20-hour delays of treatment initiation did not produce any beneficial effect (B and C). Values are mean and SEM, *p ˂ 0.05 vs NS-treated mice, n = 5–8 per group.