Understanding Lung Deposition of Alpha-1 Antitrypsin in Acute Experimental Mouse Lung Injury Model Using Fluorescence Microscopy.

Mengmeng Wang,Haojing Rong,Denise M O’Hara,Vuong Nguyen,Shawn P O’Neil,Jane Owens,Xianfeng Li,Jianqing Chen,Yutian Zhan,Brahma Ghosh

doi:10.1155/2016/5768312

Mengmeng Wang, Haojing Rong + Show 8 more

Open Access

https://doi.org/10.1155/2016/5768312

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Abstract

Human plasma-derived α1-antitrypsin (AAT) delivered by intravenous infusion is used as augmentation therapy in patients with emphysema who have a genetic mutation resulting in deficiency of AAT. Inhalation is an alternative route of administration that can potentially increase the efficacy and convenience of treatment. This study was conducted to determine whether delivery to the lungs, initially via the intratracheal (IT) route of administration, would deliver efficacious levels of a recombinant AAT (rAAT) to the site of action in the lungs in mice. 125I-radiolabeled rAAT, fluorophore-conjugated rAAT (rAAT-Alexa488), and NE680 (neutrophil elastase 680, a silent fluorescent substrate of neutrophil elastase which fluoresces in the near-infrared range upon activation by neutrophil elastase) were used to characterize the pharmacokinetics and tissue distribution profile, distribution of rAAT within the lung, and efficacy of rAAT to inhibit neutrophil elastase at the site of action, respectively. The study has demonstrated that rAAT was able to gain access to locations where neutrophil elastase was localized. The histochemical quantification of rAAT activity relative to dose at the site of action provided here will improve confidence in predicting the human dose via the inhalation route.

Highlights

Human α1-antitrypsin (AAT) is a serine proteinase inhibitor produced primarily by hepatocytes, macrophages, and bronchial epithelial cells [1]
The accompanying AAT plasma deficiency leaves the lungs exposed to neutrophil elastase, resulting in premature emphysema [7], which can be relieved by IV infusion of human plasma-derived AAT [8]
Preliminary predictive modeling suggested that the site of action is in the pulmonary alveolar interstitium and epithelium lining fluid (ELF) and that delivery of sufficient concentrations of functional AAT to inhibit neutrophil elastase will lead to the rescue of AAT deficiency in the lungs

Summary

Introduction

Human α1-antitrypsin (AAT) is a serine proteinase inhibitor produced primarily by hepatocytes, macrophages, and bronchial epithelial cells [1]. Preliminary predictive modeling suggested that the site of action is in the pulmonary alveolar interstitium and epithelium lining fluid (ELF) and that delivery of sufficient concentrations of functional AAT to inhibit neutrophil elastase will lead to the rescue of AAT deficiency in the lungs (data not shown). Hubbard et al [12] have examined the pulmonary absorption of an aerosol of yeast-produced human recombinant α1-antitrypsin in sheep and demonstrated that aerosolized AAT was deposited on the epithelial surface and diffused across the alveolar epithelium. To evaluate pulmonary rAAT concentrations in the LPS/fMLP-induced ALI mouse model, fluorophore-labeled rAAT was administered via the IT route and the magnitude and biodistribution of rAAT were investigated using fluorescence microscopy on lung cryosections. The functional activity of rAAT delivered to the lung was evaluated by measuring the magnitude of NE680 fluorescence by fluorescence microscopy

Experimental Procedures

Immunohistochemistry and Fluorescence Microscopy

Results

Discussion