Systems Toxicology Analysis Of Cardiovascular And Respiratory Endpoints From ApoE-/- Mice Showed Similar Effects After Switching To A Candidate Modified Risk Tobacco Product: THS 2.2, Or To Smoking Cessation
Presented at SRNT 2015 21st Annual Meeting
Cigarette smoking is a risk factor for chronic obstructive pulmonary disease (COPD) and cardiovascular disease (CVD). ApoE-deficient mice are prone to developing premature atherosclerosis and emphysema making them an ideal model in which both pathologies can be assessed simultaneously. We evaluated the effects of cigarette smoke (CS) from a reference conventional cigarette (3R4F) and aerosol from THS 2.2, a candidate modified risk tobacco product (cMRTP). ApoE-/- mice were exposed for up to 8 months to an aerosol from 3R4F or from (THS 2.2) 3 hours/day, 5 days/week to a target nicotine concentration of 30 µg/l. After 2 months exposure to CS, cessation and switching groups were further exposed for up to 6 months to fresh air, or THS 2.2 aerosol, respectively. A battery of markers of disease progression were investigated including atherosclerotic plaque formation, pulmonary inflammation (cell infiltration, cytokine levels), pulmonary function and lung emphysema. Exposure to CS induced time-dependent molecular, physiological and inflammatory responses in the lungs of ApoE-/- mice consistent with emphysematous changes. The size of atherosclerotic plaques measured in the aortic arches was higher in CS-exposed animals compared to both sham and cMRTP-exposed animals at all timepoints. Micro computed tomographic (micro CT) images of aortic arches after 8 months of exposure showed a larger plaque volume in 3R4F-exposed animals compared to sham, cessation or cMRTP-exposed mice. Significant changes in the lung transcriptome of ApoE-/- mice were observed in response to 3R4F-exposure compared to the gene expression levels of sham-exposed mice, while smoking cessation and switching to THS2.2 resulted in lower activation levels compared to 3R4F. Both smoking cessation and switching to the cMRTP aerosol halted the rate of disease development as assessed by inflammatory, histopathological and molecular endpoints, typically within 1 to 3 months post switching/cessation. Our work demonstrates the power of using the ApoE-/- mouse model to study comorbidities associated with cigarette smoking and investigate the mechanisms underlying the benefits of smoking cessation or switching to a cMRTP.