A control mechanism for intra-mural peri-arterial drainage via astrocytes: How neuronal activity could improve waste clearance from the brain

• Published in: PloS one Vol. 13; no. 10; p. e0205276
• Main Authors: Diem, Alexandra K, Carare, Roxana O, Weller, Roy O, Bressloff, Neil W
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 04.10.2018; Public Library of Science (PLoS)
• Subjects: Aging; Alzheimer's disease; Arteries; Arterioles; Astrocytes; Basement membranes; Biology; Biology and Life Sciences; Brain; Brain research; Care and treatment; Cognitive ability; Communication; Computational neuroscience; Dementia; Engineering; Exercise; Fluid flow; Health aspects; Hyperemia; Hypotheses; Medicine and Health Sciences; Membranes; Muscles; Neurology; Neurons; Neurophysiology; Neurosciences; Parenchyma; Parenchyma (Botany); Physical activity; Physical fitness; Physical Sciences; Physiology; Potassium; Risk factors; Smooth muscle; Veins & arteries; Wound drainage
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0205276

The mechanisms behind the clearance of soluble waste from deep within the parenchyma of the brain remain unclear. Experimental evidence reveals that one pathway for clearance of waste, termed intra-mural peri-arterial drainage (IPAD), is the rapid drainage of interstitial fluid along basement membranes (BM) of the smooth muscle cells of cerebral arteries; failure of IPAD is closely associated with the pathology of Alzheimer's disease (AD), but its driving mechanism remains unclear. We have previously shown that arterial pulsations generated by the heart beat are not strong enough to drive IPAD. Here we present computational evidence for a mechanism for clearance of waste from the brain that is driven by functional hyperaemia, that is, the dilatation of cerebral arterioles as a consequence of increased nutrient demand from neurons. This mechanism is based on our model for the flow of fluid through the vascular BM. It accounts for clearance rates observed in mouse experiments, and aligns with pathological observations and recommendations to lower the individual risk of AD, such as mental and physical activity. Thus, our neurovascular hypothesis should act as the new working hypothesis for the driving force behind IPAD.