Therapeutic time window and dose dependence of xenon delivered via echogenic liposomes for neuroprotection in stroke

Aims: Neurologic impairment following ischemic injury complicates the quality of life for stroke survivors. Xenon (Xe) has favorable neuroprotective properties to modify stroke. Xe delivery is hampered by a lack of suitable administration strategies. We have developed Xe-containing echogenic liposomes (Xe-ELIP) for systemic Xe delivery. We investigated the time window for Xe-ELIP therapeutic effect and the most efficacious dose for neuroprotection. Molecular mechanisms for Xe neuroprotection were investigated.

Methods: Xenon-containing echogenic liposomes were created by a previously developed pressurization-freezing method. Following right middle cerebral artery occlusion (2 h), animals were treated with Xe-ELIP at 2, 3, or 5 h to determine time window of therapeutic effect. The neuroprotectant dosage for optimal effect was evaluated 3 h after stroke onset. Expression of brain-derived neurotrophic factor (BDNF), protein kinase B (Akt), and mitogen-activated protein kinases (MAPK) was determined.

Results: Xenon-containing echogenic liposomes administration for up to 5 h after stroke onset reduced infract size. Treatment groups given 7 and 14 mg/kg of Xe-ELIP reduced infarct size. Behavioral outcomes corresponded to changes in infarct volume. Xe-ELIP treatment reduced ischemic neuronal cell death via activation of both MAPK and Akt. Elevated BDNF expression was shown following Xe-ELIP delivery.

Conclusion: This study demonstrates the therapeutic efficacy of Xe-ELIP administered within 5 h after stroke onset with an optimal dosage range of 7-14 mg/kg for maximal neuroprotection.