Review links vaping to lung disease but highlights major evidence gaps

PURPOSE OF REVIEW: The prevalence of cannabis and nicotine vaporizer use appears to be increasing, but their effects on the respiratory system are incompletely elucidated. This review brings together clinical, pathologic, and molecular knowledge describing airway disease, acute lung injury syndromes, and structural lung injury resulting from nicotine and cannabis vaporizer use. RECENT FINDINGS: We describe consistent epidemiologic associations of nicotine vaporizer use with obstructive lung disease, bronchitis, emphysema, and constrictive bronchiolitis; cannabis vaporizer use is more frequently associated with acute lung injury and airway disease symptoms. At a molecular level, nicotinic receptor activation drives collagen deposition, epithelial barrier dysfunction, and impaired mucociliary clearance; cannabinoid receptor activation has effects on airway inflammation, epithelial integrity, and immune cell function. Oxidative stress and mitochondrial dysfunction likely mediate effects of nicotine and cannabis vaporizer exposure through receptor-independent mechanisms. Use of nicotine and cannabis vaporizers affects clinical pulmonary disease through a variety of converging molecular and cellular mechanisms in the respiratory epithelium. Significant knowledge gaps remain, particularly with regard to molecular investigations of cannabis vaporizer use and dual nicotine-cannabis vaporizer use. Future investigations integrating molecular mechanisms of disease with clinical and histopathologic outcomes are necessary to better characterize the effects of these increasingly impactful public health risks.