Tracheal Morphologic and Protein Alterations Following Short-Term Cigarette Mainstream Smoke Exposure to Rats

A short-term 5-day nose-only cigarette smoke exposure study was conducted in Fisher 344rats to identify smoke-induced tracheal protein changes. Groups of 10 male and female 5week old rats were assigned to 1 of 4 exposure groups. Animals received filtered air, or75, 200 or 400 mg total particulate matter (TPM)/m³ of diluted 3R4F Kentuckyreference cigarette mainstream smoke. Exposures were conducted for 3 hrs/day, for 5consecutive days. Tracheas from half the rats were processed for pathology, and tracheasfrom the other half of the rats frozen immediately for proteomics. We hypothesized thatsmoke will activate tracheal inflammatory, apoptotic, proliferative, and stress-inducedpathways. Mucosal epithelial toxicity from the inhaled material was evidenced by ciliashortening and loss of tracheal mucosal epithelium in smoke-exposed animals. Mucosalthinning occurred in all smoke-exposed groups with hyperplastic reparative responses inthe 200 and 400 mg TPM/m³ groups. Tracheal lysates from control vs. treatedanimals were screened for 800 proteins using antibody-based microarray technology andsubsequently the most changed proteins evaluated by Western blot. Tracheal proteinsexpressed at high levels that were markedly increased or decreased by smoke exposuredepended on dose and gender and included caspase 5, ERK 1/2 and p38. Signaling pathwayscommon between the morphologic and protein changes were stress, apoptosis, cell cyclecontrol, cell proliferation and survival. Changes in identified proteins affected by smokeexposure were associated with tracheal mucosal pathology, may induce functional trachealchanges, and could serve as early indicators of tracheal damage and associateddisease.