Abstract
In epidemiologic studies, high intake of β-cryptoxanthin has been associated with a decreased risk of lung cancer, particularly among current smokers. However, data are not available from well-controlled animal studies to examine the effects of β-cryptoxanthin on cigarette smoke-induced lung lesions, and the biological mechanisms by which β-cryptoxanthin might affect lung carcinogenesis. We evaluated the effects of β-cryptoxanthin supplementation on cigarette smoke-induced squamous metaplasia, inflammation, and changes in protein levels of proinflammatory cytokine [tumor necrosis factor alpha (TNFα)] and transcription factors [nuclear factor kappa B (NF-κB) and activator protein-1 (AP-1)], as well as on smoke-induced oxidative DNA damage [8-hydroxy-2'-deoxyguanosine (8-OHdG)] in the lung tissue of ferrets. Thirty-six male ferrets were assigned to cigarette smoke exposure or no exposure and to low-dose, or high-dose β-cryptoxanthin, or no dose (2 × 3 factorial design) for 3 months. β-Cryptoxanthin supplementation dose-dependently increased plasma and lung β-cryptoxanthin levels in ferrets, whereas cigarette smoke exposure lowered plasma and lung β-cryptoxanthin levels. β-Cryptoxanthin at both doses significantly decreased smoke-induced lung squamous metaplasia and inflammation. β-Cryptoxanthin also substantially reduced smoke-elevated TNFα levels in alveolar, bronchial, bronchiolar, and bronchial serous/mucous gland epithelial cells and in lung macrophages. Moreover, β-cryptoxanthin decreased smoke-induced activation of NF-κB, expression of AP-1 and levels of 8-OHdG. The beneficial effects of β-cryptoxanthin were stronger for high-dose β-cryptoxanthin than for low-dose β-cryptoxanthin. Data from this study indicate that β-cryptoxanthin provides a beneficial effect against cigarette smoke-induced inflammation, oxidative DNA damage and squamous metaplasia in the lungs.