Ahmed E. Hegab

Nrf2‐deficient mice are highly susceptible to cigarette smoke‐induced emphysema

Inflammation, protease/anti‐protease imbalance and oxidative stress play important roles in the pathogenesis of emphysema. Nrf2 counteracts oxidative tissue damage and inflammation through transcriptional activation via the anti‐oxidant responsive element (ARE). To clarify the protective role of Nrf2 in the development of emphysema, the susceptibility of Nrf2‐knockout mice to cigarette smoke (CS)‐induced emphysema was examined. In Nrf2‐knockout mice, emphysema was first observed at 8 weeks and exacerbated by 16 weeks following CS‐exposure, whereas no pathological abnormalities were observed in wild‐type mice. Neutrophilic lung inflammation and permeability lung damage were significantly enhanced in Nrf2‐knockout mice 8 weeks after CS‐exposure. Importantly, neutrophil elastase activity in bronchoalveolar lavage fluids was markedly higher in Nrf2‐knockout mice preceding the pronounced neutrophil accumulation. The expression of secretory leukoprotease inhibitor, a potent inhibitor of neutrophil elastase, was inducible in wild‐type, but not in Nrf2‐knockout mice. This protease/anti‐protease imbalance, together with the lack of inducible expression of ARE‐regulated anti‐oxidant/anti‐inflammatory genes, may explain the predisposition of Nrf2‐knockout mice to neutrophilic inflammation. Indeed, specific activators of Nrf2 induced the expression of the SLPI gene in macrophages. These results indicate that Nrf2 protects against the development of emphysema by regulating not only the oxidant/anti‐oxidant balance, but also inflammation and the protease/anti‐protease balance.

Transcription Factor Nrf2 Plays a Pivotal Role in Protection against Elastase-Induced Pulmonary Inflammation and Emphysema

Emphysema is one of the major pathological abnormalities associated with chronic obstructive pulmonary disease. The protease/antiprotease imbalance and inflammation resulting from oxidative stress have been attributed to the pathogenesis of emphysema. Nrf2 is believed to protect against oxidative tissue damage through the transcriptional activation of a battery of antioxidant enzymes. In this study, we investigated the protective role of Nrf2 in the development of emphysema using elastase-induced emphysema as our model system. We found that elastase-provoked emphysema was markedly exacerbated in Nrf2-knockout (KO) mice compared with wild-type mice. The severity of emphysema in Nrf2-KO mice correlated intimately with the degree of lung inflammation in the initial stage of elastase treatment. The highly inducible expression of antioxidant and antiprotease genes observed in wild-type alveolar macrophages was significantly attenuated in the lungs of Nrf2-KO mice. Interestingly, transplantation of wild-type bone marrow cells into Nrf2-KO mice retarded the development of initial lung inflammation and subsequent emphysema, and this improvement correlated well with the appearance of macrophages expressing Nrf2-regulated antiprotease and antioxidant genes. Thus, Nrf2 appears to exert its protective effects through the transcriptional activation of antiprotease and antioxidant genes in alveolar macrophages.

Suppression of eosinophilic airway inflammation by treatment with α-galactosylceramide

To clarify the essential role of NKT cells in allergy, we investigated the contribution of NKT cells to the pathogenesis of eosinophilic airway inflammation using α‐galactosylceramide (α‐GalCer), a selective ligand for NKT cells. Although continuous administration of α‐GalCer during ovalbumin (OVA) sensitization increased OVA‐specific IgE levels and worsened eosinophil inflammation, a single administration of α‐GalCer at the time of OVA challenge completely prevented eosinophilic infiltration in wild‐type mice. This inhibitory effect of α‐GalCer was associated with a decrease in airway hyperresponsiveness, an increase in IFN‐γ, and decreases in IL‐4, IL‐5 and IL‐13 levels in the bronchoalveolar lavage fluids. Analysis of lung lymphocytes revealed that production of IFN‐γ increased in NK cells, but not in T or NKT cells, following α‐GalCer administration. Induction of vascular cell adhesion molecule‐1 in the lungs of wild‐type mice was also significantly attenuated by treatment with α‐GalCer. These effects of α‐GalCer were abrogated in Jα281–/– mice, which lack NKT cells, and in wild‐type mice treated with anti‐IFN‐γ Ab. Hence, our data indicate that α‐GalCer suppresses allergen‐induced eosinophilic airway inflammation, possibly by inducing a Th1 bias that results in inhibition of eosinophil adhesion to the lung vessels.

Treatment with α-Galactosylceramide Attenuates the Development of Bleomycin-Induced Pulmonary Fibrosis

Pulmonary fibrosis is an end-stage disorder for which efficacious therapeutic options are not readily available. Although its pathogenesis is poorly understood, pulmonary fibrosis occurs as a result of various inflammations. NKT cells modulate inflammation because of their ability to produce large amounts of cytokines by stimulation with their glycolipid ligand. In the present study, we investigated the effects of α-galactosylceramide (α-GalCer), a selective NKT cell ligand, on the development of bleomycin-induced pulmonary fibrosis. Treatment of mice with α-GalCer prolonged their survival under bleomycin administration by attenuating the development of pulmonary fibrosis. The protective effects of α-GalCer were associated with an increase in the pulmonary level of IFN-γ and a decrease in the pulmonary level of fibrogenic cytokines such as TGF-β and connective tissue growth factor. The initial pulmonary inflammation caused by bleomycin was also attenuated by α-GalCer with the reduction of the macrophage inflammatory protein-2 level. The protective effects of α-GalCer were markedly reduced in mice lacking NKT cells or as a result of treatment with anti-IFN-γ Ab. These results suggest that α-GalCer suppresses bleomycin-induced acute pulmonary inflammation and thus attenuates the development of pulmonary fibrosis possibly by regulating several cytokine levels.

Promoter activity of human tissue inhibitor of metalloproteinase 2 gene with novel single nucleotide polymorphisms

Objective:  The single nucleotide polymorphism (SNP) −418G > C in the TIMP2 gene promoter region has been shown to be associated with in chronic obstructive pulmonary disease (COPD). The purpose of this study was to search for novel single nucleotide polymorphism (SNP) in the TIMP2 promoter region around the −418G > C locus, and to investigate whether any of these SNP, including −418G > C, had an influence on TIMP2 transcription activity.

Genetics of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a complex disease that results from the interaction of multiple genetic and environmental factors. Different approaches have been used to identify the genetic factors: genome-wide linkage study, gene expression profiling, candidate gene association study, and genome-wide association study. Although many genes responsible for susceptibility to COPD have been reported, most of them have not been replicated in other study populations. Difficulty in replication is attributed to the genetic and phenotypic heterogeneity of the disease as well as the small influence of each gene on the development of the disease. A more precise definition is required for the characterization of different COPD phenotypes such as emphysema and small airway disease. A combination of several approaches using the improved phenotypes will lead to detection of novel susceptibility genes and new therapeutic targets.