Remote Control of Intracerebral Arteriole Diameter by Capillary TRPV4 and TRPV3 Channels

• Published in: The FASEB journal 2016-04, Vol.30 (S1)
• Main Authors: Dabertrand, Fabrice, Harraz, Osama F, Longden, Thomas A, Brayden, Joseph E, Nelson, Mark T
• Format: Article
• Language: English
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.30.1_supplement.lb780

Abstract only Brain parenchymal arterioles (PAs) terminate to from a dense network of hundreds of miles of capillaries, which are in close apposition to all neurons. Capillary endothelial cells (cECs) are therefore ideally positioned to detect and respond to local neuronal activity. Using a novel intact ex vivo preparation of pressurized PAs and capillaries from mouse, we revealed that application of the postulated neurovascular coupling agent prostaglandin E 2 (PGE 2 ‐1μM) onto capillaries triggered an upstream arteriolar vasodilation (38.6%). We then investigated the hypothesis that activation of EP1 receptors (Gq protein‐coupled PGE 2 receptor) in the cECs initiates a retrograde Ca 2+ signal mediated by transient receptor potential vanilloid (TRPV) cation channels. Selective capillary stimulation with TRPV4 (GSK1016790A‐1 μM) or TRPV3 (Carvacrol‐10 μM) agonists induced upstream PAs dilation (37.9% and 26.2% respectively). Patch clamp electrophysiology performed on acutely isolated cECs from mouse brain confirmed the presence of both TRP channels (TRPV4: 160.3±26.2 pA/pF at +100 mV; and TRPV3: 14.9±1.7 pA/pF at +100 mV). The TRPV4 antagonist HC‐067047 (1 μM) abolished GSK1016790A‐induced currents and upstream arteriolar dilation, while carvacrol‐induced responses were absent in TRPV3 knock out animals, further supporting the role played by both channels in the capillary to arteriole signaling. Finally, using an adeno‐associated virus approach, we transfected cECs with fluorescent Ca 2+ indicator protein GCaMP6f and recorded TRPV4 and TRPV3 channel‐dependent propagating Ca 2+ signals within cECs of the aforementioned pressurized ex vivo preparation. We have previously shown that activation of cEC K IR 2.1 channels by external K + initiates a propagated, regenerative hyperpolarization causing upstream arteriolar dilation, which promotes rapid hyperaemia at the site of the K + increase. Here we present data supporting the presence of a Ca 2+ signaling route, acting in parallel with the electrical pathway, that communicates activation of capillary TRPV4 and TRPV3 channels to dilate upstream PAs. In this model, capillary GqPCR activation would reinforce and sustain electrical signals by providing an additional level of spatial and temporal control over cerebral blood flow. Support or Funding Information Supported by the NIH (R01HL121706, PO1HL‐095488, R37‐DK‐053832; MTN), the Totman Medical Research Trust (MTN), the Fondation Leducq (MTN), the AHA (14POST2048