Enhancing glymphatic function with very low-intensity ultrasound via the transient receptor potential vanilloid-4-aquaporin-4 pathway

Recently, the glymphatic system has been proposed as a mechanism for waste clearance from the brain parenchyma. Glymphatic dysfunction has been associated with several neurological diseases such as Alzheimer’s disease, traumatic brain injury, and stroke. Therefore, it may be an important target for therapeutic interventions. In this study, we demonstrated that very low intensity ultrasound (VLIUS) (center frequency = 1 MHz; pulse repetition frequency = 1 kHz; duty factor = 1%, and spatial peak temporal average intensity [I spta ] = 3.68 mW/cm 2 ; duration = 5 min) could significantly enhance the influx of cerebrospinal fluid tracers into the perivascular spaces of the brain and also facilitate interstitial substance clearance from the brain parenchyma. Notably, no evidence of brain damage was observed after VLIUS stimulation. We also demonstrated that VLIUS enhanced the glymphatic influx via the transient receptor potential vanilloid-4-aquaporin-4 pathway in the astrocytes. This mechanism may provide insights into VLIUS-regulated glymphatic function that modifies the natural course of central nervous system disorders related to waste clearance dysfunction. One Sentence Summary Very low-intensity ultrasound enhances glymphatic influx via the TRPV4-AQP4 pathway in the astrocytes, without observable brain damage.