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Integrin VLA-4 as a PET imaging biomarker of hyper-adhesion in transgenic sickle mice.

ABSTRACT: In sickle cell disease (SCD), very late antigen-4 (VLA-4 or integrin ?4?1) mediates the adhesion of reticulocytes to inflamed, proinflammatory endothelium, a key process in promoting vaso-occlusive episodes (VOEs). We hypothesized that a radionuclide tracer targeting VLA-4 could be harnessed as a positron emission tomography (PET) imaging biomarker of VOEs. We tested the VLA-4 peptidomimetic PET tracer 64Cu-CB-TE1A1P-PEG4-LLP2A (64Cu-LLP2A) for imaging hyper-adhesion-associated VOEs in the SCD Townes mouse model. With lipopolysaccharide (LPS)-induced VOEs, 64Cu-LLP2A uptake was increased in the bone marrow of the humeri and femurs, common sites of VOEs in SCD mice compared with non-SCD mice. Treatment with a proven inhibitor of VOEs (the anti-mouse anti-P-selectin monoclonal antibody [mAb] RB40.34) during LPS stimulation led to a reduction in the uptake of 64Cu-LLP2A in the humeri and femurs to baseline levels, implying blockade of VOE hyper-adhesion. Flow cytometry with Cy3-LLP2A demonstrated an increased percentage of VLA-4-positive reticulocytes in SCD vs non-SCD mice in the bone and peripheral blood after treatment with LPS, which was abrogated by anti-P-selectin mAb treatment. These data, for the first time, show in vivo imaging of VLA-4-mediated hyper-adhesion, primarily of SCD reticulocytes, during VOEs. PET imaging with 64Cu-LLP2A may serve as a valuable, noninvasive method for identifying sites of vaso-occlusion and may provide an objective biomarker of disease severity and anti-P-selectin treatment efficacy in patients with SCD.

SUBMITTER: Perkins LA

PROVIDER: S-EPMC7479956 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Integrin VLA-4 as a PET imaging biomarker of hyper-adhesion in transgenic sickle mice.

Perkins Lydia A LA Nyiranshuti Lea L Little-Ihrig Lynda L Latoche Joseph D JD Day Kathryn E KE Zhu Qin Q Tavakoli Sina S Sundd Prithu P Novelli Enrico M EM Anderson Carolyn J CJ

Blood advances 20200901 17

In sickle cell disease (SCD), very late antigen-4 (VLA-4 or integrin α4β1) mediates the adhesion of reticulocytes to inflamed, proinflammatory endothelium, a key process in promoting vaso-occlusive episodes (VOEs). We hypothesized that a radionuclide tracer targeting VLA-4 could be harnessed as a positron emission tomography (PET) imaging biomarker of VOEs. We tested the VLA-4 peptidomimetic PET tracer 64Cu-CB-TE1A1P-PEG4-LLP2A (64Cu-LLP2A) for imaging hyper-adhesion-associated VOEs in the SCD T ...[more]

PMID: 32882004

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Project description:RationaleCyclic GMP (cGMP) is an important intracellular signaling molecule in the cardiovascular system, but its spatiotemporal dynamics in vivo is largely unknown.ObjectiveTo generate and characterize transgenic mice expressing the fluorescence resonance energy transfer-based ratiometric cGMP sensor, cGMP indicator with an EC50 of 500 nmol/L (cGi500), in cardiovascular tissues.Methods and resultsMouse lines with smooth muscle-specific or ubiquitous expression of cGi500 were generated by random transgenesis using an SM22α promoter fragment or by targeted integration of a Cre recombinase-activatable expression cassette driven by the cytomegalovirus early enhancer/chicken β-actin/β-globin promoter into the Rosa26 locus, respectively. Primary smooth muscle cells isolated from aorta, bladder, and colon of cGi500 mice showed strong sensor fluorescence. Basal cGMP concentrations were < 100 nmol/L, whereas stimulation with cGMP-elevating agents such as 2-(N,N-diethylamino)-diazenolate-2-oxide diethylammonium salt (DEA/NO) or the natriuretic peptides, atrial natriuretic peptide, and C-type natriuretic peptide evoked fluorescence resonance energy transfer changes corresponding to cGMP peak concentrations of ≈ 3 µmol/L. However, different types of smooth muscle cells had different sensitivities of their cGMP responses to DEA/NO, atrial natriuretic peptide, and C-type natriuretic peptide. Robust nitric oxide-induced cGMP transients with peak concentrations of ≈ 1 to > 3 µmol/L could also be monitored in blood vessels of the isolated retina and in the cremaster microcirculation of anesthetized mice. Moreover, with the use of a dorsal skinfold chamber model and multiphoton fluorescence resonance energy transfer microscopy, nitric oxide-stimulated vascular cGMP signals associated with vasodilation were detected in vivo in an acutely untouched preparation.ConclusionsThese cGi500 transgenic mice permit the visualization of cardiovascular cGMP signals in live cells, tissues, and mice under normal and pathological conditions or during pharmacotherapy with cGMP-elevating drugs.

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Dataset Information

Integrin VLA-4 as a PET imaging biomarker of hyper-adhesion in transgenic sickle mice.

Publications

Integrin VLA-4 as a PET imaging biomarker of hyper-adhesion in transgenic sickle mice.

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