科研之友
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摘要
Background: Tobacco-related chronic lung diseases are characterized by alterations in lung architecture leading to decreased lung function. Knowledge of the exact mechanisms involved in tobacco-induced tissue remodeling and inflammation remains incomplete. We hypothesize that nicotine stimulates the expression of extracellular matrix proteins, leading to relative changes in lung matrix composition, which may affect immune cells entering the lung after injury. Methods: Pulmonary fibroblasts from wildtype and alpha 7 nicotinic acetylcholine receptor knockout (alpha 7KO) mice were exposed to nicotine and examined for collagen type 1 mRNA and protein expression. Testing the potential role on immune cell function, pulmonary fibroblasts were retained in culture for 120 h. The fibroblasts were eliminated by osmotic lysis and the remaining matrix-coated dishes were washed thoroughly. U937 cells were incubated on the matrix-coated dishes for 24 h followed by evaluation of IL-1 beta gene expression. Wildtype or alpha 7KO C57BL/6 mice (female, 8-12 weeks) were fed normal diet and exposed to nicotine in their drinking water (100 mu g/ml) for 8-12weeks. Lungs were processed for mRNA, protein, and histology. Statistical significance was determined at p <= .05 by two-tailed test or 2-way ANOVA with Bonferroni posttest. Results: We found that nicotine stimulated collagen type I mRNA and protein expression in a dose-dependent manner and up to 72 h in primary lung fibroblasts. The stimulatory effect of nicotine was inhibited in alpha 7KO primary lung fibroblasts. Testing the potential role of these events on immune cell function, U937 monocytic cells were cultured atop matrices derived from nicotine-treated lung fibroblasts. These cells expressed more IL-1 beta than those cultured atop matrices derived from untreated fibroblasts, and antibodies against the alpha 2 beta 1 collagen integrin receptor inhibited the effect. Nicotine also stimulated fibroblast proliferation via MEK-1/ERK, unveiling a potentially amplifying pathway. In vivo, nicotine increased collagen type I expression was detected in wildtype, but not in alpha 7KO mice. Wildtype mice showed increased collagen staining in lung, primarily around the airways. Conclusions: These observations suggest that nicotine stimulates fibroblast proliferation and their expression of collagen type I through alpha 7 nAChRs, thereby altering the relative composition of the lung matrix without impacting the overall lung architecture; this may influence inflammatory responses after injury.
- 出版日期2017-6-2
