Effects of Exposure to Incense Smoke on Airway Function: An in Vitro and in Vivo Study

Recent clinical studies have suggested that inhalation of incense smoke (IS) may result in impaired lung function and asthma. However, there is little experimental evidence to link IS with airway dysfunction. Using mouse and cell culture models, we evaluated the effects of IS exposure on airway function, such as airway hyperresponsiveness (AHR), expression of multiple epithelial tight junction (TJ)- and adherens junction-associated mRNAs and proteins in the lungs, and the barrier function of bronchial epithelial cells assessed by transepithelial electronic resistance (TEER). Exposure of BALB/c mice to IS increased AHR and inflammatory macrophage recruitment to BALF; reduced claudin-1, -2, -3, -7, -10b, -12, -15, and -18, occludin, zonula occludens-1 [ZO-1], and E-cadherin mRNA expression; and caused discontinuity of claudin-2 and ZO-1 protein immunostaining in lung tissue. IS extract dose-dependently decreased TEER and increased reactive oxygen species production in bronchial epithelial cell cultures. Treatment with N-acetyl-l-cysteine, but not glucocorticosteroids or long-acting β2-agonists, prevented the detrimental effects of IS. IS exposure can be problematic for respiratory health, as evidenced by AHR, increased recruitment of inflammatory macrophages and disruption of TJ proteins in the lung, and damage to epithelial barrier integrity. However, antioxidants may be useful for the treatment of IS-induced airway dysfunction.