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Am J Physiol Lung Cell Mol Physiol. 2015 Sep 15;309(6):L543-51. doi: 10.1152/ajplung.00289.2014. Epub 2015 Jul 31.

Smart imaging of acute lung injury: exploration of myeloperoxidase activity using in vivo endoscopic confocal fluorescence microscopy.

Author information

1
Soins Intensifs Médicaux, Département de Médecine; Centre de Recherche Clinique du CHUS;
2
Centre de Recherche Clinique du CHUS; Centre d'Imagerie Moléculaire de Sherbrooke; and.
3
Centre de Recherche Clinique du CHUS; Laboratoire de Chimie Médicinale, Institut de Pharmacologie de Sherbrooke Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
4
Soins Intensifs Médicaux, Département de Médecine; Centre de Recherche Clinique du CHUS; Centre d'Imagerie Moléculaire de Sherbrooke; and Olivier.Lesur@USherbrooke.ca.

Abstract

The pathophysiology of acute lung injury (ALI) is well characterized, but its real-time assessment at bedside remains a challenge. When patients do not improve after 1 wk despite supportive therapies, physicians have to consider open lung biopsy (OLB) to identify the process(es) at play. Sustained inflammation and inadequate repair are often observed in this context. OLB is neither easy to perform in a critical setting nor exempt from complications. Herein, we explore intravital endoscopic confocal fluorescence microscopy (ECFM) of the lung in vivo combined with the use of fluorescent smart probe(s) activated by myeloperoxidase (MPO). MPO is a granular enzyme expressed by polymorphonuclear neutrophils (PMNs) and alveolar macrophages (AMs), catalyzing the synthesis of hypoclorous acid, a by-product of hydrogen peroxide. Activation of these probes was first validated in vitro in relevant cells (i.e., AMs and PMNs) and on MPO-non-expressing cells (as negative controls) and then tested in vivo using three rat models of ALI and real-time intravital imaging with ECFM. Semiquantitative image analyses revealed that in vivo probe-related cellular/background fluorescence was associated with corresponding enhanced lung enzymatic activity and was partly prevented by specific MPO inhibition. Additional ex vivo phenotyping was performed, confirming that fluorescent cells were neutrophil elastase(+) (PMNs) or CD68(+) (AMs). This work is a first step toward "virtual biopsy" of ALI without OLB.

KEYWORDS:

endoscopic confocal fluorescence microscopy; inflammation; lung; macrophages; myeloperoxidase; polymorphonuclear neutrophils

PMID:
26232301
DOI:
10.1152/ajplung.00289.2014
[Indexed for MEDLINE]
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