The lung tumor promoter, butylated hydroxytoluene (BHT), causes chronic inflammation in promotion-sensitive BALB/cByJ mice but not in promotion-resistant CXB4 mice

Abstract

An inflammatory response accompanies the reversible pneumotoxicity caused by butylated hydroxytoluene (BHT) administration to mice. Lung tumor formation is promoted by BHT administration following an initiating agent in BALB/cByJ mice, but not in CXB4 mice. To assess the contribution of inflammation to this differential susceptibility, we quantitatively characterized inflammation after one 150 mg/kg body weight, followed by three weekly 200 mg/kg ip injections of BHT into male mice of both strains. This examination included inflammatory cell infiltrate and protein contents in bronchoalveolar lavage (BAL) fluid, cyclooxygenase (COX)-1 and COX-2 expression in lung extracts, and PGE 2 and PGI 2 production by isolated bronchiolar Clara cells. BAL macrophage and lymphocyte numbers increased in BALB mice ( P<0.0007 and 0.02, respectively), as did BAL protein content ( P<0.05), COX-1 and COX-2 expression ( P<0.05 for each), and PGI 2 production ( P<0.05); conversely, these indices were not perturbed by BHT in CXB4 mice. BALB mice fed aspirin (400 mg/kg of chow) for two weeks prior to BHT treatment had reduced inflammatory cell infiltration. Our results support a hypothesis that resistance to BHT-induced inflammation in CXB4 mice accounts, at least in part, for the lack of effect of BHT on lung tumor multiplicity in this strain.