Blood brain barrier dysfunction caused by repeated Endothelin-1 injection leads to irreversible memory impairment.

Abstract

Vascular dysfunction is being increasingly recognized as a major contributor to dementia burden. Repeated occurrence of vascular insults in small vessels results in Blood Brain Barrier (BBB) dysfunction potentially contributing to cognitive impairments. The small vessel infracts is seen as white matter hyperintensities in MRI of many patients. Postmortem studies have shown BBB damage in dementia including AD and accumulation blood-derived proteins as well as loss of BBB associated cells like pericytes. In view of such a scenario we wanted to establish an animal model to study multiple small vessel insults impacting BBB leading to learning and memory deficits. C57/BL6J mice aged 4-5 months was implanted with cannula on left side of the hemisphere. ET-1 (Endothelin- 1), a 21 amino acid vasoconstricting peptide was infused through guide cannula into the intracerebroventricular space of lateral ventricle. Mice were injected for 3 doses of ET-1 at intervals of 3 weeks over a period of 9 weeks. The animals were assessed for associative learning and spatial memory deficits with different behavioral task. Animals were perfused and brain was processed for immunohistochemistry to assess vascular pathology. To simulate the clinical conditions the animals were injected over a period of three weeks to make sure that animal completely recovers from first vascular insult and then subsequent insults were given. There was BBB leakage, discrepancies in the blood vessel integrity and loss of pericytes after multiple ET-1 injection. Further there was significant memory deficits in novel object task, contextual fear conditioning test and Morris water maze. Our results demonstrated that chronic vascular insults cause BBB dysfunction and cognitive deficits seen as memory impairment. We were able to establish that repeated vasoconstriction by ET-1 in small vessels leads to BBB breach resulting in irreversible learning and memory deficits. This animal model could help us to study molecular underpinnings of white matter hyperintensities.