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.

Pulmonary fibrosis is a progressive and lethal disorder. Although the precise mechanisms of pulmonary fibrosis are not fully understood, oxidant/antioxidant and Th1/Th2 balances may play an important role in many of the processes of inflammation and fibrosis. The transcription factor Nrf2 acts as a critical regulator for various inflammatory and immune responses by controlling oxidative stress. We therefore investigated the protective role of Nrf2 against the development of pulmonary fibrosis.

We previously demonstrated that the transcription factor NF-E2-related factor2 (Nrf2), expressed abundantly in non-small-cell lung cancer (NSCLC) cells, plays a pivotal role in the proliferation and chemoresistance of NSCLC. Here we show that Nrf2-mediated NSCLC cell proliferation is dually regulated by epidermal growth factor receptor (EGFR) signaling and an Nrf2 repressor protein Keap1 (Kelch-like ECH-associated protein-1). NSCLC cells expressing wild-type EGFR and Keap1 genes show enhanced proliferation on stimulation with EGFR ligand under non-stress conditions. Exposure to cigarette smoke extract (CSE) enhanced cell proliferation by modification of the Nrf2/Keap1 interaction. Although EGFR-tyrosine kinase inhibitor (TKI) inhibited the proliferation of these cells, exposure to CSE attenuated its efficacy. In NSCLC cells with Keap1 gene mutations, Nrf2 was constitutively activated owing to dysfunction of Keap1 and cells proliferated independently of EGFR signaling. Furthermore, EGFR-TKI was unable to inhibit their proliferation. In NSCLC cells with EGFR gene mutations, Nrf2 was constitutively activated by EGFR signaling. In these cells, proliferation was largely dependent on the EGFR signaling pathway. Although these cells were highly sensitive to EGFR-TKI, exposure to CSE or knockdown of Keap1 mRNA reduced sensitivity to EGFR-TKI. We found a case of NSCLC showing resistance to EGFR-TKI despite having EGFR-TKI-sensitive EGFR gene mutation because of dysfunctional mutation in Keap1 gene. Results indicate that oxidative stress reduces the anticancer effects of EGFR-TKI in wild-type Keap1 NSCLC cells. Analysis of Keap1 dysfunction may become a novel molecular marker to predict resistance to EGFR-TKI in NSCLC cells having EGFR-TKI-sensitive EGFR mutations. Finally, as the downstream molecule of both EGFR and Keap1 signaling, Nrf2 is an important molecular target for the treatment of NSCLC, where cells have mutations in EGFR, KRAS or Keap1 genes.

Influenza virus is a common respiratory tract viral infection. Although influenza can be fatal in patients with chronic pulmonary diseases such as chronic obstructive pulmonary disease, its pathogenesis is not fully understood. The Nrf2-mediated antioxidant system is essential to protect the lungs from oxidative injury and inflammation. In the present study, we investigated the role of Nrf2 in protection against influenza virus-induced pulmonary inflammation after cigarette smoke exposure with both in vitro and in vivo approaches. For in vitro analyses, peritoneal macrophages isolated from wild-type and Nrf2 -deficient mice were treated with poly(I:C) and/or cigarette smoke extract. For in vivo analysis, these mice were infected with influenza A virus with or without exposure to cigarette smoke. In Nrf2 -deficient macrophages, NF-κB activation and the induction of its target inflammatory genes were enhanced after costimulation with cigarette smoke extract and poly(I:C) compared with wild-type macrophages. The induction of antioxidant genes was observed for the lungs of wild-type mice but not those of Nrf2 -deficient mice after cigarette smoke exposure. Cigarette smoke-exposed Nrf2 -deficient mice showed higher rates of mortality than did wild-type mice after influenza virus infection, with enhanced peribronchial inflammation, lung permeability damage, and mucus hypersecretion. Lung oxidant levels and NF-κB-mediated inflammatory gene expression in the lungs were also enhanced in Nrf2 -deficient mice. Our data indicate that the antioxidant pathway controlled by Nrf2 is pivotal for protection against the development of influenza virus-induced pulmonary inflammation and injury under oxidative conditions.

Candidaspecies are the most common source of nosocomial invasive fungal infections. Previous studies have indicated that T-helper immune response is the critical host factor for susceptibility toCandidainfection. The transcription factor GATA-3 is known as the master regulator for T-helper type 2 (Th2) differentiation. We therefore investigated the role of GATA-3 in the host defense against systemicCandidainfection using GATA-3-overexpressing transgenic mice. The survival of GATA-3-overexpressing mice afterCandidainfection was significantly lower than that of wild-type mice.Candidaoutgrowth was significantly increased in the kidneys of GATA-3-overexpressing mice, compared with wild-type mice. The levels of various Th2 cytokines, including interleukin-4 (IL-4), IL-5, and IL-13, were significantly higher while the level of Th1 cytokine gamma interferon was significantly lower in the splenocytes of GATA-3-overexpressing mice afterCandidainfection. Recruitment of macrophages into the peritoneal cavity in response toCandidainfection and their phagocytic activity were significantly lower in GATA-3-overexpressing mice than in wild-type mice. Exogenous administration of gamma interferon to GATA-3-overexpressing mice significantly reducedCandidaoutgrowth in the kidney and thus increased the survival rate. Administration of gamma interferon also increased the recruitment of macrophages into the peritoneal cavity in response toCandidainfection. These results indicate that overexpression of GATA-3 modulates macrophage antifungal activity and thus enhances the susceptibility to systemicCandidainfection, possibly by reducing the production of gamma interferon in response toCandidainfection.