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Publication Date

2008-12-05

Availability

UM campus only

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Molecular Cell and Developmental Biology (Medicine)

Date of Defense

2008-11-18

First Committee Member

Carlos T. Moraes

Second Committee Member

Pedro J.I. Salas

Third Committee Member

Matthias Salathe

Fourth Committee Member

Gregory E. Conner

Abstract

In airway epithelia, lactoperoxidase (LPO) constitutes an important anti-microbial system to protect the host against infection and inflammation. LPO uses hydrogen peroxide and thiocyanate anion to form the biocidal compound, hypothiocyanite. The rate-limiting factor is hydrogen peroxide substrate availability. This study was conducted to identify the major source of hydrogen peroxide and to characterize its regulation in the human airway. Two homologues of the phagocytic NADPH oxidase, Duox1 and Duox2, were shown to be highly expressed and functional in human airway epithelial cells re-differentiated at the air liquid interface (ALI). Duox activity is regulated by intracellular calcium concentration via its two EF-hand motifs. A rise of intracellular calcium concentration exhibited kinetics that correlated with increase of Duox-generated hydrogen peroxide production, which was inhibited by DPI, a NADPH oxidase inhibitor. Additionally, the involvement of Duox activity in the LPO system was investigated. Bacterial products such as flagellin or inflammatory mediators were used to challenge ALI cultures. As a result, mRNAs from Duox2, LPO and DUOXA2, but not Duox1, were up-regulated in response to stimuli. This study provided new information about the regulation of the anti-microbial LPO system in innate immune host defense.

Keywords

Lentivures; Reactive Oxygen Species; Interferon

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