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Shock. 2018 Jul 30. doi: 10.1097/SHK.0000000000001226. [Epub ahead of print]

Partial Deletion of Tie2 Affects Microvascular Endothelial Responses to Critical Illness in a Vascular Bed and Organ-Specific Way.

Author information

1
Department of Pathology and Medical Biology, Medical Biology section.
2
Department of Critical Care.
3
Department of Anesthesiology.
4
Department of Pediatrics, Molecular Genetics section, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.

Abstract

Tie2 is a tyrosine kinase receptor that is mainly expressed by endothelial cells. In animal models mimicking critical illness, Tie2 levels in organs are temporarily reduced. Functional consequences of these reduced Tie2 levels on microvascular endothelial behaviour are unknown. We investigated the effect of partial deletion of Tie2 on the inflammatory status of endothelial cells in different organs. Newly-generated heterozygous Tie2 knockout mice (exon 9 deletion, ΔE9/Tie2) exhibiting 50% reduction in Tie2 mRNA and protein, and wild type littermate controls (Tie2), were subjected to hemorrhagic shock and resuscitation (HS + R), or challenged with i.p. lipopolysaccharide (LPS). Kidney, liver, lung, heart, brain, and intestine were analyzed for mRNA levels of adhesion molecules E-selectin, VCAM-1, and ICAM-1, and CD45. Exposure to HS + R did not result in different expression responses of these molecules between organs from Tie2 or Tie2 mice and sham-operated mice. In contrast, the LPS-induced mRNA expression levels of E-selectin, VCAM-1, and ICAM-1, and CD45 in organs were attenuated in Tie2 mice when compared to Tie2 mice in kidney and liver, but not in the other organs studied. Furthermore, reduced expression of E-selectin and VCAM-1 protein, and reduced influx of CD45 cells upon LPS exposure, was visible in a microvascular bed-specific pattern in kidney and liver of Tie2 mice compared to controls. In contrast to the hypothesis that a dysbalance in the Ang/Tie2 system leads to increased microvascular inflammation, heterozygous deletion of Tie2 is associated with an organ-restricted, microvascular bed-specific attenuation of endothelial inflammatory response to LPS.

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