Vascular α1A Adrenergic Receptors as a Potential Therapeutic Target for IPAD in Alzheimer's Disease

Drainage of interstitial fluid from the brain occurs via the intramural periarterial drainage (IPAD) pathways along the basement membranes of cerebral capillaries and arteries against the direction of blood flow into the brain. The cerebrovascular smooth muscle cells (SMCs) provide the motive force for driving IPAD, and their decrease in function may explain the deposition of amyloid-beta as cerebral amyloid angiopathy (CAA), a key feature of Alzheimer's disease. The alpha-adrenoceptor subtype alpha(1A)is abundant in the brain, but its distribution in the cerebral vessels is unclear. We analysed cultured human cerebrovascular SMCs and young, old and CAA human brains for (a) the presence of alpha(1A) receptor and (b) the distribution of the alpha(1A)receptor within the cerebral vessels. The alpha(1A) receptor was present on the wall of cerebrovascular SMCs. No significant changes were observed in the vascular expression of the alpha(1A)-adrenergic receptor in young, old and CAA cases. The pattern of vascular staining appeared less punctate and more diffuse with ageing and CAA. Our results show that the alpha(1A)-adrenergic receptor is preserved in cerebral vessels with ageing and in CAA and is expressed on cerebrovascular smooth muscle cells, suggesting that vascular adrenergic receptors may hold potential for therapeutic targeting of IPAD.