Heme oxygenase-1 (HO-1) protein induction in a mouse model of asthma.

Abstract

Carbon monoxide (CO) is known to be present in measurable quantities in the exhalation of asthmatic patients. Corticosteroid treatment resulted in a decrease in exhaled CO levels in asthmatic patients, raising the possibility that an increase in exhaled CO concentration reflects inflammation of the asthmatic airway. Heme oxygenase-1 (HO-1) protein, also called HSP32, is the rate-limiting enzyme in the catabolism of heme to biliverdin, free iron and CO. However, it is unknown whether an expression of HO-1 within the lung tissue is related to allergic airway inflammation. We studied the expression of HO-1 in lung tissue and bronchoalveolar lavage cells in a mouse model of asthma. Ovalbumin (OVA)-sensitized C57BL/6 mice were challenged with aerosolized OVA. HO-1 positive cells were identified by immunostaining in lung tissue and bronchoalveolar lavage fluid (BALF) after the challenge. HO-1 positive cell numbers increased in the subepithelium of the bronchi after OVA challenge. In cytospin preparations from BALF after OVA challenge, HO-1 was localized to alveolar macrophages. Inside the macrophages, HO-1 reactivity was expressed in the cytoplasm, and the perinuclear region in particular. The expression of HO-1 is increased within the lung tissue in allergic airway inflammation. Measurement of HO-1 activity may be clinically useful in the management of asthma.