Neuropeptide Y regulates a vascular gateway for hematopoietic stem and progenitor cells
Pratibha Singh, … , Theresa A. Guise, Louis M. Pelus
Pratibha Singh, … , Theresa A. Guise, Louis M. Pelus
Published November 13, 2017
Citation Information: J Clin Invest. 2017;127(12):4527-4540. https://doi.org/10.1172/JCI94687.
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Research Article

Neuropeptide Y regulates a vascular gateway for hematopoietic stem and progenitor cells

Abstract

Endothelial cells (ECs) are components of the hematopoietic microenvironment and regulate hematopoietic stem and progenitor cell (HSPC) homeostasis. Cytokine treatments that cause HSPC trafficking to peripheral blood are associated with an increase in dipeptidylpeptidase 4/CD26 (DPP4/CD26), an enzyme that truncates the neurotransmitter neuropeptide Y (NPY). Here, we show that enzymatically altered NPY signaling in ECs caused reduced VE-cadherin and CD31 expression along EC junctions, resulting in increased vascular permeability and HSPC egress. Moreover, selective NPY2 and NPY5 receptor antagonists restored vascular integrity and limited HSPC mobilization, demonstrating that the enzymatically controlled vascular gateway specifically opens by cleavage of NPY by CD26 signaling via NPY2 and NPY5 receptors. Mice lacking CD26 or NPY exhibited impaired HSPC trafficking that was restored by treatment with truncated NPY. Thus, our results point to ECs as gatekeepers of HSPC trafficking and identify a CD26-mediated NPY axis that has potential as a pharmacologic target to regulate hematopoietic trafficking in homeostatic and stress conditions.

Authors

Pratibha Singh, Jonathan Hoggatt, Malgorzata M. Kamocka, Khalid S. Mohammad, Mary R. Saunders, Hongge Li, Jennifer Speth, Nadia Carlesso, Theresa A. Guise, Louis M. Pelus

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Figure 6

NPY3-36 reduces EC contact and increases permeability.

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NPY3-36 reduces EC contact and increases permeability. (A) Measurement o...
(A) Measurement of dextran-FITC permeability across confluent BMEC monolayers treated with G-CSF, G-CSF plus diprotin A, G-CSF plus diprotin A with NPY, or G-CSF plus diprotin A with NPY3-36 for 24 hours (mean ± SEM; n = 2 experiments, 3 mice/experiment). P ≤ 0.05 compared with vehicle treated mice and †P ≤ 0.05 compared with G-CSF–treated mice, by 1-way ANOVA with Sidak’s multiple comparisons test. (B and C) Measurement of vascular permeability in calvarial BM from mice treated with G-CSF, G-CSF plus diprotin A, or G-CSF plus diprotin A with NPY3-36. (B) Representative intravital 2-photon images of calvarial BM from vehicle- or G-CSF–treated mice and representative average fluorescence intensity ratio for each vessel/interstitial space in vehicle- and G-CSF–treated mice. (C) Average increase in vascular permeability compared with vehicle control (mean ± SEM; n = 4–6 mice/group, each assayed individually). 1-way ANOVA with Sidak’s multiple comparisons test was used to determine the P values and *P < 0.05 compared with G-CSF treated mice was considered significant. (D) Intravital 2-photon image analysis of the distance between individual ECs in isolectin B4–labeled evaluable vessels in BM from mice treated with G-CSF, G-CSF plus diprotin A, or G-CSF plus diprotin A with NPY3-36 (mean ± SEM; n = 4 mice/group; ≥15 fields/mouse). 1-way ANOVA with Sidak’s multiple comparisons test was used to determine the P value and P ≤ 0.05 was considered significant. (E) CD31 and VE-cadherin expression on BM SECs from WT mice treated with G-CSF and from CD26–/– mice treated with G-CSF, G-CSF plus NPY, or G-CSF plus NPY3-36 (mean ± SEM; n = 4 mice/group). (F) CD31 and VE-cadherin expression on BM SECs from mice treated with G-CSF alone or in combination with selective NPYR2 (BIIE 0246) or NPYR5 (CGP 71683 hydrochloride) antagonists (mean ± SEM; n = 4 mice/group). (E and F) *P < 0.05 compared with vehicle treated WT mice and †P ≤ 0.05 compared with G-CSF–treated WT mice, by 1-way ANOVA with Sidak’s multiple comparisons test. (G) Model of NPY3-36-regulated vascular permeability and HSPC egress from BM. In response to G-CSF, CD26 expression and activity are enhanced on BMECs, which converts NPY into NPY3-36 and shifts NPY signaling on ECs from the NPY1 receptors that enforce vascular integrity to the NPY2 and NPY5 receptors that downregulate CD31 and VE-cadherin along endothelial gap junctions, resulting in increased vascular permeability and enhanced HSPC transendothelial egress.