Investigating the in vivo effects of cannabis smoke exposure on lung innate immunity

Abstract

Cannabis is widely used for recreational and medicinal purposes. Inhalation of cannabis smoke is the predominant method of drug consumption, exposing the lungs to THC and CBD, as well as a plethora of toxic combustion products. Clinical observations suggest that cannabis smoking contributes to the development of respiratory symptoms and may play a role in the pathogenesis of inflammatory lung disease. However, the association between cannabis smoke, dysregulated pulmonary immunity, and the development of lung disease is inconclusive. To improve our understanding of this relationship, we developed novel mouse models to investigate the effect of cannabis smoke exposure on lung immunity. Using compositionally relevant cannabis strains, we established a mouse model of cannabis smoke exposure and validated that it delivers cannabis smoke by measuring cannabis smoke-associated metabolites in the blood. In our initial lung immune characterization, we demonstrated that acute cannabis smoke exposure induces modest changes to innate immune cellularity in the airways and lung tissue. Specifically, lung macrophage subpopulations were proportionally altered following smoke exposure. As well, we demonstrated that lung disease-associated mediators, including MDC, TARC, and VEGF, were dysregulated in cannabis smoke-exposed lung tissue. In addition to our initial characterization, we established a first-of-its-kind concurrent cannabis smoke exposure and influenza infection model. Using this model, we demonstrated that cannabis smoke exposure exacerbates weight loss following influenza infection. These increases in weight loss corresponded with dysregulated cellular responses and immune mediator expression. Cell types involved in early innate immune signaling, such as macrophages and dendritic cells, were significantly affected by concurrent exposure and infection. Additionally, anti-viral mediators. including IFNγ, IP-10, RANTES, and TNFα, were decreased in cannabis smoke-exposed, infected lung tissue. Collectively, we defined two novel models of cannabis smoke exposure that can be leveraged in future investigations on the inflammatory effects and associated health outcomes of cannabis smoke.