Protection of Cigarette Smoke‐Induced Lung Injury in Guinea Pigs by Inhalation of Aerosolic All‐Trans Retinoic Acid

Abstract

Both mainstream (MS) and secondhand (SH) cigarette smoking are known to cause abnormality in lung function. We reported earlier that both MS and SH cigarette smoke exposure to guinea pigs caused lung injury associated with accumulation of retinol. The accumulation of retinol in lung was later found to be associated with a decrease in the levels of retinoic acid implying an abnormality in lung retinoid metabolism and signaling. The objective of the present study was to investigate whether inhalation of aerosolic all‐trans retinoic acid (ATRA) immediately smoke exposure can protect against lung damage. Four weeks old male guinea pig were exposed twice daily for 6 weeks to MS or SH smoke from 3 1R3F cigarettes. The sham control group (SC) received a treatment identical to smoke‐exposed groups but in the absence of cigarettes. Four animals from each group received either aerosolic ATRA (2.78mM) or vehicle twice for 20 min/day after smoke exposure. Morphological analysis of lungs showed deleterious alterations in the morphology of the lungs in both MS and SH groups. ATRA treatment showed significant protection against lung damage; however the protection was more evident in MS than SH groups. The mechanism by which ATRA aerosol protects lung against deleterious effects of cigarette smoke is under investigation. (Supported by NIH grant: 1R03HL095419–01A1).