Tze Khee Chan

Metabolomics Investigation Reveals Metabolite Mediators Associated with Acute Lung Injury and Repair in a Murine Model of Influenza Pneumonia

Influenza virus infection (IVI) can cause primary viral pneumonia, which may progress to acute lung injury (ALI) and respiratory failure with a potentially fatal outcome. At present, the interactions between host and influenza virus at molecular levels and the underlying mechanisms that give rise to IVI-induced ALI are poorly understood. We conducted a comprehensive mass spectrometry-based metabolic profiling of serum, lung tissue and bronchoalveolar lavage fluid (BALF) from a non-lethal mouse model with influenza A virus at 0, 6, 10, 14, 21 and 28 days post infection (dpi), representing the major stages of IVI. Distinct metabolite signatures were observed in mice sera, lung tissues and BALF, indicating the molecular differences between systematic and localized host responses to IVI. More than 100 differential metabolites were captured in mice sera, lung tissues and BALF, including purines, pyrimidines, acylcarnitines, fatty acids, amino acids, glucocorticoids, sphingolipids, phospholipids, etc. Many of these metabolites belonged to pulmonary surfactants, indicating IVI-induced aberrations of the pulmonary surfactant system might play an important role in the etiology of respiratory failure and repair. Our findings revealed dynamic host responses to IVI and various metabolic pathways linked to disease progression, and provided mechanistic insights into IVI-induced ALI and repair process.

Vitamin E Isoform γ-Tocotrienol Downregulates House Dust Mite–Induced Asthma

Inflammation and oxidative damage contribute to the pathogenesis of asthma. Although corticosteroid is the first-line treatment for asthma, a subset of patients is steroid resistant, and chronic steroid use causes side effects. Because vitamin E isoform γ-tocotrienol possesses both antioxidative and anti-inflammatory properties, we sought to determine protective effects of γ-tocotrienol in a house dust mite (HDM) experimental asthma model. BALB/c mice were sensitized and challenged with HDM. Bronchoalveolar lavage (BAL) fluid was assessed for total and differential cell counts, oxidative damage biomarkers, and cytokine levels. Lungs were examined for cell infiltration and mucus hypersecretion, as well as the expression of antioxidants and proinflammatory biomarkers. Sera were assayed for IgE and γ-tocotrienol levels. Airway hyperresponsiveness in response to methacholine was measured. γ-Tocotrienol displayed better free radical–neutralizing activity in vitro and inhibition of BAL fluid total, eosinophil, and neutrophil counts in HDM mouse asthma in vivo, as compared with other vitamin E isoforms, including α-tocopherol. Besides, γ-tocotrienol abated HDM-induced elevation of BAL fluid cytokine and chemokine levels, total reactive oxygen species and oxidative damage biomarker levels, and of serum IgE levels, but it promoted lung-endogenous antioxidant activities. Mechanistically, γ-tocotrienol was found to block nuclear NF-κB level and enhance nuclear Nrf2 levels in lung lysates to greater extents than did α-tocopherol and prednisolone. More importantly, γ-tocotrienol markedly suppressed methacholine-induced airway hyperresponsiveness in experimental asthma. To our knowledge, we have shown for the first time the protective actions of vitamin E isoform γ-tocotrienol in allergic asthma.

Aeroallergens Induce Reactive Oxygen Species Production and DNA Damage and Dampen Antioxidant Responses in Bronchial Epithelial Cells

Exposure to environmental allergens is a major risk factor for asthma development. Allergens possess proteolytic activity that is capable of disrupting the airway epithelium. Although there is increasing evidence pointing to asthma as an epithelial disease, the underlying mechanism that drives asthma has not been fully elucidated. In this study, we investigated the direct DNA damage potential of aeroallergens on human bronchial epithelial cells and elucidated the mechanisms mediating the damage. Human bronchial epithelial cells, BEAS-2B, directly exposed to house dust mites (HDM) resulted in enhanced DNA damage, as measured by the CometChip and the staining of DNA double-strand break marker, γH2AX. HDM stimulated cellular reactive oxygen species production, increased mitochondrial oxidative stress, and promoted nitrosative stress. Notably, expression of nuclear factor erythroid 2–related factor 2–dependent antioxidant genes was reduced immediately after HDM exposure, suggesting that HDM altered antioxidant responses. HDM exposure also reduced cell proliferation and induced cell death. Importantly, HDM-induced DNA damage can be prevented by the antioxidants glutathione and catalase, suggesting that HDM-induced reactive oxygen and nitrogen species can be neutralized by antioxidants. Mechanistic studies revealed that HDM-induced cellular injury is NADPH oxidase (NOX)-dependent, and apocynin, a NOX inhibitor, protected cells from double-strand breaks induced by HDM. Our results show that direct exposure of bronchial epithelial cells to HDM leads to the production of reactive oxygen and nitrogen species that damage DNA and induce cytotoxicity. Antioxidants and NOX inhibitors can prevent HDM-induced DNA damage, revealing a novel role for antioxidants and NOX inhibitors in mitigating allergic airway disease.

Vitamin E isoform γ-tocotrienol protects against emphysema in cigarette smoke-induced COPD

Abstract Inflammation and oxidative stress contribute to emphysema in COPD. Although corticosteroids are the standard of care for COPD, they do not reduce oxidative stress, and a subset of patients is steroid‐resistant. Vitamin E isoform &ggr;‐tocotrienol possesses both anti‐inflammatory and anti‐oxidative properties that may protect against emphysema. We aimed to establish the therapeutic potential of &ggr;‐tocotrienol in cigarette smoke‐induced COPD models in comparison with prednisolone. BALB/c mice were exposed to cigarette smoke for 2 weeks or 2 months. &ggr;‐Tocotrienol and prednisolone were given orally. Bronchoalveolar lavage (BAL) fluid and lung tissues were assessed for inflammation, oxidative damage, and regulation of transcription factor activities. Emphysema and lung function were also evaluated. &ggr;‐Tocotrienol dose‐dependently reduced cigarette smoke‐induced BAL fluid neutrophil counts and levels of cytokines, chemokines and oxidative damage biomarkers, and pulmonary pro‐inflammatory and pro‐oxidant gene expression, but restored lung endogenous antioxidant activities. &ggr;‐Tocotrienol acted by inhibiting nuclear translocation of STAT3 and NF‐&kgr;B, and up‐regulating Nrf2 activation in the lungs. In mice exposed to 2‐month cigarette smoke, &ggr;‐tocotrienol ameliorated bronchial epithelium thickening and destruction of alveolar sacs in lungs, and improved lung functions. In comparison with prednisolone, &ggr;‐tocotrienol demonstrated better anti‐oxidative efficacy, and protection against emphysema and lung function in COPD. We revealed for the first time the anti‐inflammatory and antioxidant efficacies of &ggr;‐tocotrienol in cigarette smoke‐induced COPD models. In addition, &ggr;‐tocotrienol was able to attenuate emphysematous lesions and improve lung function in COPD. &ggr;‐Tocotrienol may have therapeutic potential for the treatment of COPD. Graphical abstract Figure. No caption available. HighlightsOne puff of cigarette smoke (CS) has 1015 radicals to induce lung inflammation.Vitamin E isoform &ggr;‐tocotrienol is an antioxidant with anti‐inflammatory properties.Oral &ggr;‐tocotrienol abated airway inflammation and oxidative stress in CS‐induced COPD.&ggr;‐Tocotrienol also protected against emphysema and lung function impairment.&ggr;‐Tocotrienol inhibited transcription factors NF‐&kgr;B and STAT3, and activated Nrf2.

O21 - The role of DNA damage and repair in allergic airway inflammation

Extensive DNA damage and inefficient DNA repair might be responsible for some of the pathogenic features in patients suffering from asthma. To determine whether DNA adducts can be used as a “dosimeter” for asthma disease severity, we measured the DNA adducts level in lung of mouse with house dust mite (HDM)-induced allergic airway inflammation, as the disease progresses. Apoptosis of airway epithelial cells is one of the most critical pathophysiological factors in the development of chronic asthma. As repairing of DNA lesions is important in preventing apoptosis, we propose that DNA repair plays an important pathophysiologic role in regulating lung epithelial cell DNA damage response.