Blood pressure lowering enhances cerebrospinal fluid efflux to the systemic circulation primarily via the lymphatic vasculature
Jukkola, Jari; Kaakinen, Mika; Singh, Abhishek; Moradi, Sadegh; Ferdinando, Hany; Myllylä, Teemu; Kiviniemi, Vesa; Eklund, Lauri (2024-01-26)
BioMed Central
26.01.2024
Jukkola, J., Kaakinen, M., Singh, A. et al. Blood pressure lowering enhances cerebrospinal fluid efflux to the systemic circulation primarily via the lymphatic vasculature. Fluids Barriers CNS 21, 12 (2024). https://doi.org/10.1186/s12987-024-00509-9
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https://creativecommons.org/licenses/by/4.0/
© The Author(s) 2024. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:oulu-202402151781
https://urn.fi/URN:NBN:fi:oulu-202402151781
Tiivistelmä
Abstract
Background:
Inside the incompressible cranium, the volume of cerebrospinal fluid is directly linked to blood volume: a change in either will induce a compensatory change in the other. Vasodilatory lowering of blood pressure has been shown to result in an increase of intracranial pressure, which, in normal circumstances should return to equilibrium by increased fluid efflux. In this study, we investigated the effect of blood pressure lowering on fluorescent cerebrospinal fluid tracer absorption into the systemic blood circulation.
Methods:
Blood pressure lowering was performed by an i.v. administration of nitric oxide donor (sodium nitroprusside, 5 µg kg−1 min−1) or the Ca2+-channel blocker (nicardipine hydrochloride, 0.5 µg kg−1 min−1) for 10, and 15 to 40 min, respectively. The effect of blood pressure lowering on cerebrospinal fluid clearance was investigated by measuring the efflux of fluorescent tracers (40 kDa FITC-dextran, 45 kDa Texas Red-conjugated ovalbumin) into blood and deep cervical lymph nodes. The effect of nicardipine on cerebral hemodynamics was investigated by near-infrared spectroscopy. The distribution of cerebrospinal fluid tracers (40 kDa horse radish peroxidase,160 kDa nanogold-conjugated IgG) in exit pathways was also analyzed at an ultrastructural level using electron microscopy.
Results:
Nicardipine and sodium nitroprusside reduced blood pressure by 32.0 ± 19.6% and 24.0 ± 13.3%, while temporarily elevating intracranial pressure by 14.0 ± 7.0% and 18.2 ± 15.0%, respectively. Blood pressure lowering significantly increased tracer accumulation into dorsal dura, deep cervical lymph nodes and systemic circulation, but reduced perivascular inflow along penetrating arteries in the brain. The enhanced tracer efflux by blood pressure lowering into the systemic circulation was markedly reduced (− 66.7%) by ligation of lymphatic vessels draining into deep cervical lymph nodes.
Conclusions:
This is the first study showing that cerebrospinal fluid clearance can be improved with acute hypotensive treatment and that the effect of the treatment is reduced by ligation of a lymphatic drainage pathway. Enhanced cerebrospinal fluid clearance by blood pressure lowering may have therapeutic potential in diseases with dysregulated cerebrospinal fluid flow.
Background:
Inside the incompressible cranium, the volume of cerebrospinal fluid is directly linked to blood volume: a change in either will induce a compensatory change in the other. Vasodilatory lowering of blood pressure has been shown to result in an increase of intracranial pressure, which, in normal circumstances should return to equilibrium by increased fluid efflux. In this study, we investigated the effect of blood pressure lowering on fluorescent cerebrospinal fluid tracer absorption into the systemic blood circulation.
Methods:
Blood pressure lowering was performed by an i.v. administration of nitric oxide donor (sodium nitroprusside, 5 µg kg−1 min−1) or the Ca2+-channel blocker (nicardipine hydrochloride, 0.5 µg kg−1 min−1) for 10, and 15 to 40 min, respectively. The effect of blood pressure lowering on cerebrospinal fluid clearance was investigated by measuring the efflux of fluorescent tracers (40 kDa FITC-dextran, 45 kDa Texas Red-conjugated ovalbumin) into blood and deep cervical lymph nodes. The effect of nicardipine on cerebral hemodynamics was investigated by near-infrared spectroscopy. The distribution of cerebrospinal fluid tracers (40 kDa horse radish peroxidase,160 kDa nanogold-conjugated IgG) in exit pathways was also analyzed at an ultrastructural level using electron microscopy.
Results:
Nicardipine and sodium nitroprusside reduced blood pressure by 32.0 ± 19.6% and 24.0 ± 13.3%, while temporarily elevating intracranial pressure by 14.0 ± 7.0% and 18.2 ± 15.0%, respectively. Blood pressure lowering significantly increased tracer accumulation into dorsal dura, deep cervical lymph nodes and systemic circulation, but reduced perivascular inflow along penetrating arteries in the brain. The enhanced tracer efflux by blood pressure lowering into the systemic circulation was markedly reduced (− 66.7%) by ligation of lymphatic vessels draining into deep cervical lymph nodes.
Conclusions:
This is the first study showing that cerebrospinal fluid clearance can be improved with acute hypotensive treatment and that the effect of the treatment is reduced by ligation of a lymphatic drainage pathway. Enhanced cerebrospinal fluid clearance by blood pressure lowering may have therapeutic potential in diseases with dysregulated cerebrospinal fluid flow.
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- Avoin saatavuus [42971]
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