AUTHOR=Tanaka Koji , Matsumoto Shoji , Yamada Takeshi , Yamasaki Ryo , Suzuki Makoto , Kido Mizuho A. , Kira Jun-Ichi TITLE=Reduced Post-ischemic Brain Injury in Transient Receptor Potential Vanilloid 4 Knockout Mice JOURNAL=Frontiers in Neuroscience VOLUME=14 YEAR=2020 URL=https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2020.00453 DOI=10.3389/fnins.2020.00453 ISSN=1662-453X ABSTRACT=Background and Purpose

In the acute phase of ischemia-reperfusion, hypoperfusion associated with ischemia and reperfusion in microvascular regions and disruption of the blood–brain barrier (BBB) contribute to post-ischemic brain injury. We aimed to clarify whether brain injury following transient middle cerebral artery occlusion (tMCAO) is ameliorated in Transient receptor potential vanilloid 4 knockout (Trpv4–/–) mice.

Methods

tMCAO was induced in wild-type (WT) and Trpv4–/– mice aged 8–10 weeks. Ischemia-induced lesion volume was evaluated by 2,3,5-triphenyltetrazolium chloride staining at 24 h post-tMCAO. Tissue water content and Evans blue leakage in the ipsilateral hemisphere and a neurological score were evaluated at 48 h post-tMCAO. Transmission electron microscopy (TEM) was performed to assess the morphological changes in microvasculature in the ischemic lesions at 6 h post-tMCAO.

Results

Compared with WT mice, Trpv4–/– mice showed reduced ischemia-induced lesion volume and reduced water content and Evans blue leakage in the ipsilateral hemisphere alongside milder neurological symptoms. The loss of zonula occludens-1 and occludin proteins in the ipsilateral hemisphere was attenuated in Trpv4–/– mice. TEM revealed that parenchymal microvessels in the ischemic lesion were compressed and narrowed by the swollen endfeet of astrocytes in WT mice, but these effects were markedly ameliorated in Trpv4–/– mice.

Conclusion

The present results demonstrate that TRPV4 contributes to post-ischemic brain injury. The preserved microcirculation and BBB function shortly after reperfusion are the key neuroprotective roles of TRPV4 inhibition, which represents a promising target for the treatment of acute ischemic stroke.