Deficiency of gp91phox Inhibits Allergic Airway Inflammation

Abstract

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, a multienzyme complex, is the major source for production of reactive oxygen species (ROS). ROS are increased in allergic diseases, such as asthma, but the role of ROS in disease pathogenesis remains uncertain. We hypothesized that mice unable to generate ROS via the NADPH oxidase pathway would have decreased allergic airway inflammation. To test this hypothesis, we studied gp91phox 2/2 mice in a model of allergic airway inflammation after sensitization and challenge with ovalbumin. Serum, bronchoalveolar lavage fluid, and lungs were then examined for evidence of allergic inflammation. We found that mice lacking a functional NADPH oxidase complex had significantly decreased ROS production and allergic airway inflammation, compared with wild-type (WT) control animals. To determine the mechanism by which allergic inflammation was inhibited by gp91phox deficiency, we cultured bone marrowderived dendritic cells from WT and gp91phox 2/2 mice and activated them with LPS. IL-12 expression was significantly increased in the gp91phox 2/2 bone marrow-derived dendritic cells, suggesting that the cytokine profile produced in the absence of gp91phox enhanced the conditions leading to T helper (Th) type 1 differentiation, while inhibiting Th2 polarization. Splenocytes from sensitized gp91phox 2/2 animals produced significantly less IL-13 in response to ovalbumin challenge in vitro compared with splenocytes from sensitized WT mice, suggesting that NADPH oxidase promotes allergic sensitization. In contrast, inflammatory cytokines produced by T cells cultured from WT and gp91phox 2/2 mice under Th0, Th1, Th2, and Th17 conditions were not significantly different. This study demonstrates the importance of NADPH oxidase activity and ROS production in a murine model of asthma.Keywords: asthma; allergic airway inflammation; gp91phox; reactive oxygen species; NADPH oxidase Asthma is a significant health problem, affecting up to 300 million children and adults around the world (1). In the United States alone, costs associated with asthma exceed $50 billion each year due to health care use and lost productivity (2). The prevalence of this disease is increasing, without clear etiology (3, 4). Chronic inflammation of the airways is a hallmark of the disease (5), and yet, despite widespread research, the mechanisms of persistent allergic airway inflammation are poorly understood.Reactive oxygen species (ROS) are increased in allergic diseases, such as asthma, and ROS production is associated with airway inflammation and airway hyperresponsiveness (6). Breath condensates from subjects with asthma have been shown to contain increased hydrogen peroxide, an ROS, and 8-isoprostane, an F 2 -isoprostane that is a marker of oxidative stress, compared to control subjects without asthma (7-9). In addition, increased levels of peroxidation products are present in the serum, urine, and lung tissue of patients with asthma compared with those without asthma (10-12). Mice with allergic lung inf...

Facilitation of Allergic Sensitization and Allergic Airway Inflammation by Pollen-Induced Innate Neutrophil Recruitment

“…In the present study, one possible mechanism by which innate recruitment of neutrophils by pollens shifts the immune response to an allergic phenotype upon repeated challenge is induction of a state of sustained oxidative stress in the airways by repeated recruitment of activated ROS-generating neutrophils. This is suggested by reports that mice deficient in gp91phox, the dominant superoxide-generating enzyme in neutrophils, have decreased ROS generation and mount an attenuated allergic inflammatory response to allergen challenge (19). Additionally, chronic oxidative stress can worsen allergic asthma (21)(22)(23)(24), alter dendritic cell function, and modify the Th1/ Th2 balance (25,26).…”

Silymarin Reduces Profibrogenic Cytokines and Reverses Hepatic Fibrosis in Chronic Murine Schistosomiasis

“…It is known that lymphocytes from gp91 phoxϪ/Ϫ mice (deficient in the superoxide production that accompanies the respiratory burst) produce less IL-13 under allergic sensitization (54), indicating that IL-13 production is under ROS control and that antioxidants are able to (A) Analysis of the correlation between IL-13 serum amounts and hepatic hydroxyproline contents in infected nontreated or treated mice. Samples examined for hydroxyproline and IL-13 came from the same pool of mice.…”

Neutrophil recruitment by allergens contribute to allergic sensitization and allergic inflammation

“…Neutrophil are a major source of oxidative stress by their respiratory chain. Because mice deficient in gp91phox showed less Th2 cytokine secretion and allergic inflammation [37], recruitment of ROS-generating neutrophils after allergen challenge may have an important role in subsequent allergic inflammation. Several studies have shown that chronic oxidative stress can worsen allergic asthma [38–41], alter DC function, and modify Th1/Th2 balance [42,43].…”

“…Since neutrophils recruited by intranasal allergen challenge generates sustained ROS in the airways, it is likely that this property of neutrophil promotes allergic inflammation through ROS generation. This is suggested by reports that mice deficient in gp91phox, the dominant superoxide generating enzyme in neutrophils, have decreased ROS, and mount an attenuated allergic inflammatory response to allergen challenge [37]. LTB4 generation from recruited neutrophil to the skin stimulates accumulation of effector CD4 + T cells to OVA-challenged skin, thereby facilitating allergic skin inflammation [23].…”