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We examined the hypothesis that superoxide mediates infiltration of neutrophils to the airways through nuclear factor (NF)-kappaB and interleukin-8 (IL-8) after acute exposure to cigarette smoke (CS) in vivo. Male Hartley strain guinea pigs were exposed to air or 20 puffs of CS and killed 5 h after the exposure. The differential cell count of bronchoalveolar lavage fluid and specific myeloperoxidase enzyme assay demonstrated that acute exposure to CS caused neutrophil accumulation to the airways and parenchyma, respectively. Acute exposure to CS increased DNA-binding activity of NF-kappaB in the lung. Acute exposure to CS also increased IL-8 messenger RNA (mRNA) expression in the lung. Pretreatment of guinea pigs with recombinant human superoxide dismutase (rhSOD) aerosols reduced the CS-induced neutrophil accumulation to the airways. Both activation of NF-kappaB and increased IL-8 mRNA expression were also inhibited by the pretreatment of rhSOD aerosols. Strong immunoreactivities for p65 and p50 were detected in the nuclei of alveolar macrophages after acute exposure to CS. The signal for IL-8 mRNA expression was demonstrated in the alveolar space after acute exposure to CS. Neither significant immunoreactivities for p65 and p50 nor IL-8 mRNA signals were observed in airway epithelium. These observations suggest that acute exposure to CS initiates superoxide-dependent mechanism that, through NF-kappaB activation and IL-8 mRNA expression, produces infiltration of neutrophils to the airways in vivo. It was also suggested that the alveolar macrophage is one potential source of NF-kappaB activation and IL-8 mRNA expression after acute exposure to CS.

By using a direct, intratracheal inoculation of an adenovirus encoding heme oxygenase 1 (Ad.HO-1), model gene therapy for acute lung injury induced by inhaled pathogen was performed. Data demonstrated that Ad.HO-1 administration is as effective as the pharmacologic upregulation of the endogenous HO-1 gene expression by hemin to attenuate neutrophilic inflammations of the lung after aerosolized lipopolysaccharide (LPS) exposure. Interestingly, immunohistochemical analysis revealed that the HO-1 gene was transferred not only to the airway epithelium, but to the alveolar macrophages (AMs). Moreover, overexpression of exogenous HO-1 in the macrophages provided a high level of endogenous interleukin 10 (IL-10) production from the macrophages, and additional experiments using IL-10 knockout mice demonstrated that the increase in IL-10 in the macrophages was critical for the resolution of neutrophilic migration in the lung after LPS exposure. These results suggest that AMs not only are barriers for efficient gene transfer to the respiratory epithelium, but also represent logical targets for Ad-mediated, direct, in vivo gene therapy strategies for inflammatory disorders in humans.

Heme oxygenase 1 (HO-1) is an inducible enzyme that catalyzes heme to generate bilirubin, ferritin, and carbon monoxide. Because enhanced expression of HO-1 confers protection against many types of cell and tissue damage by modulating apoptotic cell death or cytokine expression profiles, we hypothesized that adenovirus-mediated transfer of HO-1 cDNA and subsequent overexpression of the protein in lung would provide therapeutic benefit in a murine model of bleomycin-induced pulmonary fibrosis. In C57BL/6 mice, HO-1 overexpression clearly suppressed the development of fibrotic changes and was associated with enhanced interferon gamma production in lung and reduced numbers of respiratory epithelial cells with damaged DNA. However, HO-1 overexpression did not prevent pulmonary fibrosis induced by agonistic anti-Fas antibody inhalation in C57BL/6 or ICR mice, a strain known to develop pulmonary fibrosis via the Fas-Fas ligand (FasL) pathway. Consistent with the concept that HO-1 overexpression prevents fibrosis via a pathway independent of Fas-FasL interaction, Ad.HO-1 administration prevented bleomycin-induced pulmonary fibrosis in gld/gld mice, which express nonfunctional FasL. These observations suggest that using HO-1 overexpression strategies to treat idiopathic pulmonary fibrosis, or fibrotic disorders of other target organs, by attenuating apoptotic cell death likely would be effective in clinical situations.

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