Studies using structural analogs and inbred strain differences to support a role for quinone methide metabolites of butylated hydroxytoluene (BHT) in mouse lung tumor promotion

Doubly vinylogous and doubly rearomative functionalization of 2-alkyl-3-furfurals

The manuscript describes a straightforward functionalization of 2-alkyl-3-furfurals via simple aminocatalytic conjugate addition. The reaction proceeds through the formation of dearomatized dienamine-like intermediate that undergoes 1,6-addition to 4-alkylidene-2,6-dialkylcyclohexa-2,5-dienones. This process can be described as doubly rearomative as it proceeds with the re-formation of both furan and phenyl aromatic moieties. Target products have been obtained in a highly stereoselective manner, providing an interesting example of 2-alkyl-3-furfural functionalization via doubly vinylogous Michael addition. The mechanism of the reaction has been studied by means of computational methods.

Determination of volatile organic compounds in SW620 colorectal cancer cells and tumor-bearing mice

Early diagnosis and early treatment are important factors in reducing colorectal cancer (CRC) metastasis and mortality. Volatile organic compounds (VOCs) released by the human body have great potential for use in clinical diagnosis and therapeutic monitoring for CRC. The aim of our study was to identify VOCs with high specificity and high sensitivity for CRC and to provide a method for early diagnosis of CRC. Gas chromatography-mass spectrometry (GC-MS) was utilized to analyze metabolites in both the in vivo and in vitro experimental groups. In vivo, VOCs were analyzed in the blood of mice after cell inoculation and tumor resection. In vitro experiments were performed by comparing changes in VOCs in an HCoEpiC cell group, control group, SW620 cell group and Arsenic trioxide + SW620 group. We observed changes in VOCs in a series of CRC SW620 cells in vivo and in vitro. Among these changes, we found that the concentrations of 8 substances, including acetone, increased with tumor growth. Nine substances were found to be significantly elevated in the SW620 cancer cell group compared with the other groups. Only one substance was consumed by the tumor in both the in vivo and in vitro experiments. Our study showed that alkanes, lipids, alcohols, ketones, aldehyde, butylated hydroxytoluene (BHT) and hexamethylcyclotrisiloxane all existed at different levels in SW620 CRC cells compared to those in normal cells. We need more research to further confirm this hypothesis.

Role of Glucuronidation and P450 Oxidation in the Bioactivation of Bromfenac

Bromfenac is a nonsteroidal anti-inflammatory drug that was approved in the United States in 1997. It was withdrawn from clinical use less than one year later, in 1998, due to hepatotoxicity. We investigate the potential of bromfenac to be metabolized to reactive intermediates to further the current understanding of bromfenac bioactivation. Incubations were conducted with hepatocytes and human, rat, and cynomolgus liver microsomes fortified with cofactors and N-acetylcysteine. One thioether adduct of hydroxylated bromfenac and three thioether adducts of hydroxylated bromfenac indolinone were detected in extracts following incubations in liver microsomes fortified with NADPH and UDPGA. These findings demonstrate a bioactivation pathway for bromfenac and contribute to the body of evidence that could advance the understanding of the toxicity associated with bromfenac.

2,6-Di-Tert-Butyl-Hydroxytoluene and Its Metabolites in Foods

2,6-Di-tert-butyl-hydroxytoluene (BHT, E-321) is a synthetic phenolic antioxidant which has been widely used as an additive in the food, cosmetic, and plastic industries for the last 70 y. Although it is considered safe for human health at authorized levels, its ubiquitous presence and the controversial toxicological data reported are of great concern for consumers. In recent years, special attention has been paid to these 14 metabolites or degradation products: BHT-CH₂ OH, BHT-CHO, BHT-COOH, BHT-Q, BHT-QM, DBP, BHT-OH, BHT-OOH, TBP, BHQ, BHT-OH(t), BHT-OH(t)QM, 2-BHT, and 2-BHT-QM. These derived compounds could pose a human health risk from a food safety point of view, but they have been little studied. In this context, this review deals with the occurrence, origin, and fate of BHT in foodstuffs, its biotransformation into metabolites, their toxicological implications, their antioxidant and prooxidant properties, the analytical determination of metabolites in foods, and human dietary exposure. Moreover, noncontrolled additional sources of exposure to BHT and its metabolites are highlighted. These include their carryover from feed to fish, poultry and eggs, their presence in smoke flavorings, their migration from plastic pipelines and packaging to water and food, and their presence in natural environments, from which they can reach the food chain.

Protein damage from electrophiles and oxidants in lungs of mice chronically exposed to the tumor promoter butylated hydroxytoluene

The food additive butylated hydroxytoluene (BHT) promotes tumorigenesis in mouse lung. Chronic BHT exposure is accompanied by pulmonary inflammation and several studies indicate that elevated levels of reactive oxygen species (ROS) are involved in its promoting activity. The link between BHT and elevated ROS involves formation of quinone methide (QM) metabolites; these electrophiles form adducts with a variety of lung proteins including several enzymes that protect cells from oxidative stress. Studies in vitro demonstrated that QM alkylation of cytoprotective enzymes is accompanied by inactivation, so an objective of the present investigation was to determine if inactivation also occurs in vivo. Two groups of mice were exposed to BHT by intraperitoneal injection, one for 10 days and the other for 24 days, and proteins from lung cytosols were examined for damage. Analysis by Western blotting demonstrated that BHT treatment caused substantial increases in protein carbonylation, nitration and adduction by 4-hydroxynonenal, confirming the occurrence of sustained oxidative and nitrosative stress over the treatment period required for tumor promotion. Effects of BHT on the activities and/or levels of a representative group of antioxidant/protective enzymes in mouse lung also were assessed; NAD(P)H:quinone reductase and glutathione reductase were unaffected, however carbonyl reductase activity decreased 50-60%. Superoxide dismutase and glutathione peroxidase activities increased 2- and 1.5-fold, respectively, and glutamate-cysteine ligase catalytic subunit expression increased 32-39% relative to untreated mice. Glutathione S-transferase (GST) activity decreased 50-60% but concentrations of the predominant isoforms, GSTM1 and P1, were not affected. GSTP1 was substantially more susceptible than M1 to adduction and inhibition by treatment with BHT-QM in vitro, suggesting that lower GST activity in mice after BHT treatment is due to adduction of the P1 isoform. The results of this study provide additional insight into mechanisms of BHT-induced oxidative damage and further support a link between inflammation and tumor promotion in mouse lung.

Copper-induced peroxidation of phosphatidylserine-containing liposomes is inhibited by nanomolar concentrations of specific antioxidants

Copper-induced peroxidation of liposomal palmitoyllinoleoyl-phosphatidylcholine (PLPC) is inhibited by alpha-tocopherol at micromolar concentrations. In our previous study we found that when the liposomes contain phosphatidylserine (PS), nanomolar concentrations of Toc were sufficient to inhibit peroxidation. In an attempt to gain understanding of the origin of this extreme antioxidative potency, we tested the antioxidative potency of 36 additional antioxidants and the dependence of their potency on the presence of PS in the liposomes. The results of these studies reveal that only 11 of the tested antioxidants possess similar antioxidative potency to that of Toc. These include trolox, butylated hydroxytoluene (BHT), curcumin, nordihydroguaiaretic acid (NDGA), diethylstilbestrol (DES), 2 of the 13 tested flavonoids (luteolin and 7,3',4'-trihydroxyflavone; T-414), alpha-naphthol, 1,5-, 1,6- and 1,7-dihydroxynaphthalenes (DHNs). Propyl gallate (PG), methyl syringate, rosmarinic acid, resveratrol, other flavonoids, as well as beta-naphthol, 1,2-, 1,3-, 1,4-, 2,3-, 2,6-, and 2,7-DHNs were either moderately antioxidative or pro-oxidative. For liposomes made of PLPC (250 microM) and PS (25 microM) the "lag" preceding copper-induced peroxidation (5 microM copper) was doubled upon addition of 30-130nM of the "super-active" antioxidants. We propose that the mechanism responsible for the extreme antioxidative potency against copper-induced peroxidation in PS-containing liposomes involves replenishment of the antioxidant in a ternary PS-copper-antioxidant complex. Based on structure-activity relationship of the 37 tested antioxidants, the "super-antioxidative potency" is attributed to the recycling of relatively stable semiquinone or semiquinone-like radicals.

Mechanistic basis for inflammation and tumor promotion in lungs of 2,6-di-tert-butyl-4-methylphenol-treated mice: electrophilic metabolites alkylate and inactivate antioxidant enzymes

An established model for mechanistic analysis of lung carcinogenesis involves administration of 3-methylcholanthrene to mice followed by several weekly injections of the tumor promoter 2,6-di-tert-butyl-4-methylphenol (BHT). BHT is metabolized to quinone methides (QMs) responsible for promoting tumor formation. QMs are strongly electrophilic and readily form adducts with proteins. The goal of the present study was to identify adducted proteins in the lungs of mice injected with BHT and to assess the potential impact of these modifications on tumorigenesis. Cytosolic proteins from treated mouse lungs were separated by two-dimensional electrophoresis, adducts detected by immunoblotting, and proteins identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Eight adducts were detected in the lungs of most, or all, of six experimental groups of BALB mice. Of these adducts, several were structural proteins, but others, namely, peroxiredoxin 6 (Prx6), Cu,Zn-superoxide dismutase (SOD1), carbonyl reductase, and selenium-binding protein 1, have direct or indirect antioxidant functions. When the 9000g supernatant fraction of mouse lung was treated with BHT-QM (2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone), substantial lipid peroxidation and increases in hydrogen peroxide and superoxide formation were observed. Studies with human Prx6 and bovine SOD1 demonstrated inhibition of enzyme activity concomitant with adduct formation. LC-MS/MS analysis of digests of adducted Prx6 demonstrated adduction of both Cys 91 and Cys 47; the latter residue is essential for peroxidatic activity. Analysis of QM-treated bovine SOD1 by matrix-assisted laser desorption/ionization time-of-flight MS demonstrated the predominance of a monoadduct at His 78. This study provides evidence that indicates Prx6, SOD1, and possibly other antioxidant enzymes in mouse lung are inhibited by BHT-derived QMs leading to enhanced levels of reactive oxygen species and inflammation and providing a mechanistic basis for the effects of BHT on lung tumorigenesis.

Beta-catenin in the fibroproliferative response to acute lung injury

Resolution of alveolar epithelial/capillary membrane damage after acute lung injury requires coordinated and effective tissue repair to reestablish a functional alveolar epithelial/capillary membrane barrier. We hypothesized that signaling pathways important in lung alveolar bud ontogeny are activated in the recovery and remodeling phases after profound oxidant stress lung injury in a murine model. To test this, we characterized the expression of noncanonical beta-catenin pathway proteins E-cadherin, integrin-linked kinase-1, and beta-catenin in mice undergoing normoxic recovery after exposure to butylated hydroxytoluene (BHT, ionol) and concomitant sublethal (75% O2) hyperoxia. Mice developed early acute lung injury with subsequent inflammation, collagen deposition, interstitial cellular proliferation, and lung architectural distortion. Reduced E-cadherin expression after 6 d of BHT and hyperoxia was accompanied by enhanced expression and nuclear localization of beta-catenin and increased integrin-linked kinase-1 expression during subsequent normoxic recovery. This resulted in increased expression of the cotranscriptional regulators TCF-1 and -3 and cyclin D1. Proliferation of murine lung epithelial-12 cells in vitro after 8 h of treatment with BHT quinone-methide and hyperoxia and 48 h of normoxic recovery was enhanced 2.7-fold compared with vehicle-treated control mice at the same time point. BHT/hyperoxia-exposed mice treated with the pan-caspase inhibitor z-ASP had increased acute lung injury and reduced survival despite the presence of TUNEL-positive cells, suggesting enhanced lung cell necrosis. Beta-catenin expression was reduced in z-ASP-co-treated lungs after BHT/hyperoxia. The noncanonical cadherin-beta-catenin axis is associated with fibroproliferative repair after BHT/hyperoxia exposure and may regulate epithelial proliferation and lung matrix remodeling and repair in response to lung injury.

Immunochemical and Proteomic Analysis of Covalent Adducts Formed by Quinone Methide Tumor Promoters in Mouse Lung Epithelial Cell Lines

Two quinone methide (QM) metabolites of the phenolic antioxidant butylated hydroxytoluene (BHT), 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) and the tert-butyl-hydroxylated derivative (BHTOH-QM), are believed to be responsible for promoting lung tumor formation in mice treated with BHT. QMs are strongly electrophilic and undergo Michael type additions with nucleophiles at the exocyclic methylene to form benzylic thioether adducts. Our goal was to identify intracellular protein targets of these QMs in order to gain insight into their effects on tumorigenesis. Cell line E10 of mouse lung epithelial origin and its spontaneous transformant, the tumorigenic E9 cell line, were treated with BHT-QM or BHTOH-QM, and cellular proteins were analyzed by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Adducted proteins were detected on western blots with polyclonal antibodies developed to a conjugate of BHTOH-QM that recognized adducts of both QMs bound to thiol groups of Cys and side chain amino groups of Lys and His residues. Tryptic digests of immunoreactive proteins were analyzed by HPLC mass spectrometry (LC/MS) and identified by searching protein databases using MS/MS data. In a few cases, adducted peptides in these digests were detected by matrix-assisted laser desorption/ionization time-of-flight MS. A total of 37 immunoreactive proteins were identified including proteins involved in carbohydrate metabolism, nucleic acid synthesis, and RNA and protein processing, in addition to several cytoskeletal and stress-related proteins. About half of the protein adducts were found in both cell lines. Adducts detected only in transformed E9 cells include glutathione S-transferase P1, peroxiredoxin 2, nucleoside diphosphate kinase, and vinculin, whereas several alkylated cytoskeletal proteins such as tubulins, vimentin, calvasculin, and calcyclin were detected exclusively in E10 cells. Several of the proteins modified by BHT-derived QMs have been implicated in various aspects of tumorigenesis and are excellent candidates for further study into the consequences of alkylation on cellular transformation.

Inhibition of glutathione S-transferase P1-1 in mouse lung epithelial cells by the tumor promoter 2,6-di-tert-butyl-4-methylene-2,5-cyclohexadienone (BHT-quinone methide): protein adducts investigated by electrospray mass spectrometry

Oxidation of the food preservative 2,6-di-tert-butyl-4-methylphenol (BHT) by mouse lung cytochrome P450 produces electrophilic quinone methides thought to promote lung tumors in mice by covalent binding to critical proteins. Specific pulmonary targets of 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) have not been identified, however. The present work was undertaken to determine if glutathione S-transferase P1-1 (GSTP1-1) is alkylated by BHT-QM, as this protein is overexpressed in tumors and has important roles in protecting cells from electrophiles and oxidants and in regulating stress kinases. This work was conducted with cell lines C10 and E10 derived from mouse lung epithelia and their spontaneous transformants, the tumorigenic cell lines A5 and E9. Cytosolic GSTs were isolated by affinity chromatography and analyzed by ESI-LC/MS. Ion current chromatograms indicated that GSTP1 predominates over the other isoforms, especially in tumorigenic cells. Treatment with BHT-QM inhibited cytosolic GST activity by 28-44%, and inhibition was exacerbated by depleting intracellular GSH. Alkylation of GSTP1 by BHT-QM was investigated by separating cytosolic proteins with two-dimensional SDS-PAGE and detecting adducts by Western blotting with polyclonal antibodies that recognize the BHT group. The identity of GSTP1 comigrating with immunoreactive material was confirmed by in-gel proteolysis and LC/MS/MS analysis. Human GSTP1 was utilized to investigate the specific residues involved in QM binding. The only peptide adduct detected in digests of monoadducted GSTP1 corresponded to Cys101, whereas adducts at Cys14, Cys47, and Cys101 were identified from the trialkylated protein. Losses of transferase activity were most influenced by alkylation at Cys47, but binding to Cys14 appeared to inhibit the activity further. These findings demonstrate that cytosolic GSTP1 may be a target for BHT-QM resulting in decreased cellular protection from electrophiles and oxidants. Alkylation also may interfere with GSTP1 regulation of stress kinases, thereby influencing phosphorylation and cell growth.

Susceptibility to neoplastic and non-neoplastic pulmonary diseases in mice: genetic similarities

Chronic inflammation predisposes toward many types of cancer. Chronic bronchitis and asthma, for example, heighten the risk of lung cancer. Exactly which inflammatory mediators (e.g., oxidant species and growth factors) and lung wound repair processes (e.g., proangiogenic factors) enhance pulmonary neoplastic development is not clear. One approach to uncover the most relevant biochemical and physiological pathways is to identify genes underlying susceptibilities to inflammation and to cancer development at the same anatomic site. Mice develop lung adenocarcinomas similar in histology, molecular characteristics, and histogenesis to this most common human lung cancer subtype. Over two dozen loci, called Pas or pulmonary adenoma susceptibility, Par or pulmonary adenoma resistance, and Sluc or susceptibility to lung cancer genes, regulate differential lung tumor susceptibility among inbred mouse strains as assigned by QTL (quantitative trait locus) mapping. Chromosomal sites that determine responsiveness to proinflammatory pneumotoxicants such as ozone (O3), particulates, and hyperoxia have also been mapped in mice. For example, susceptibility QTLs have been identified on chromosomes 17 and 11 for O3-induced inflammation (Inf1, Inf2), O3-induced acute lung injury (Aliq3, Aliq1), and sulfate-associated particulates. Sites within the human and mouse genomes for asthma and COPD phenotypes have also been delineated. It is of great interest that several susceptibility loci for mouse lung neoplasia also contain susceptibility genes for toxicant-induced lung injury and inflammation and are homologous to several human asthma loci. These QTLs are described herein, candidate genes are suggested within these sites, and experimental evidence that inflammation enhances lung tumor development is provided.

Metabolism, pharmacokinetics, and protein covalent binding of radiolabeled MaxiPost (BMS-204352) in humans

MaxiPost [(3S)-(+)-(5-chloro-2-methoxyphenyl)-1,3-dihydro-3-fluoro-6-(trifluoromethyl)-2H-indole-2-one); BMS-204352] is an investigational maxi-K channel opener to treat ischemic stroke. This study reports the disposition, metabolism, pharmacokinetics, and protein covalent binding of (14)C-labeled MaxiPost in healthy male volunteers as well as in dogs and rats. After each human subject received a single dose of 10 mg (14)C-labeled BMS-204352 (50 microCi) as a 5-ml intravenous infusion lasting 5 min, the plasma radioactivity concentrations showed a unique profile, wherein the concentration appeared to increase initially, followed by a terminal decline. The mean terminal t(1/2) of plasma radioactivity (259 h) was prolonged compared with that of unchanged parent (37 h). Furthermore, the extractability of radioactivity in plasma decreased over time, reaching approximately 20% at 4 h after dosing. The unextractable radioactivity was covalently bound to plasma proteins through a des-fluoro-des-methyl BMS-204352 lysine adduct. Unchanged BMS-204352 and minor metabolites were identified in plasma extract following protein precipitation. The recovery of the radioactive dose in urine and feces was nearly complete in 14-day collections (approximately 37% in urine and 60% in feces). The N-glucuronide of the parent was the prominent metabolite in urine (16.5% of dose), whereas the parent was a major drug-related component in feces (11% of dose). Similar disposition, metabolism, pharmacokinetic, and protein covalent binding properties of (14)C-labeled BMS-204352 were observed in humans, dogs, and rats.

Protein covalent binding of maxipost through a cytochrome P450-mediated ortho-quinone methide intermediate in rats

(3S)-(+)-(5-Chloro-2-methoxyphenyl)-1,3-dihydro-3-fluoro-6-(trifluoromethyl)-2H-indole-2-one) (MaxiPost, BMS-204352) is a potent and specific opener for maxi-K channels and has potential to prevent and treat ischemic stroke. Following single intravenous doses of [14C]BMS-204352 to rats, only 10 to 12% of radioactivity was extractable from plasma with organic solvents. The unextractable radioactivity remained associated with the proteins (mostly albumin) after SDS-polyacrylamide gel electrophoresis or dialysis. Following acid hydrolysis in 6 M HCl for 24 h at 110 degrees C from plasma proteins collected from nine rats dosed with [14C]BMS-204352, one major radioactive product was isolated and identified as a lysine-adduct of des-fluoro des-O-methyl BMS-204352 by liquid chromatography/mass spectrometry and NMR analyses as well as by comparison with the synthetic analog, lysine-adduct of des-fluoro BMS-204352 (BMS-349821). The covalent binding of BMS-204352 results from the displacement of the ring-fluorine atom of des-O-methyl BMS-204352 with the epsilon-amino group of a lysine residue. Microsomal incubations of [14C]BMS-204352 resulted in low levels of covalent binding of radioactivity to proteins. This in vitro covalent binding required cytochrome P450-reductase cofactor NADPH and was attenuated by glutathione. P4503A inhibitors ketoconazole and troleadomycin selectively prevented the covalent binding in vitro. Based on these observations, a two-step bioactivation process for the protein covalent binding of BMS-204352 was postulated: 1) P4503A-mediated O-demethylation leading to spontaneous release of HF and the formation of an ortho-quinone methide reactive metabolite and 2) nucleophilic addition of the epsilon-amino group of protein lysine residue(s) in protein to form des-fluoro des-O-methyl BMS-204352 lysine adduct.

Responses of tumorigenic and non-tumorigenic mouse lung epithelial cell lines to electrophilic metabolites of the tumor promoter butylated hydroxytoluene

A model system to investigate the promotion phase of pulmonary carcinogenesis involves chronic exposure of carcinogen-initiated mice to the food additive, butylated hydroxytoluene (BHT). Previous studies strongly suggested that this activity is due to the cytochrome p450-catalyzed formation of quinone methides 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) and 6-tert-butyl-2-(1',1'-dimethyl-2'-hydroxy)ethyl-4-methylenecyclohexa-2,5-dienone (BHTOH-QM). The effects of these electrophiles on non-tumorigenic C10 and E10 epithelial cell lines derived from a normal mouse lung explant were compared with effects on their corresponding neoplastic siblings, the A5 and E9 spontaneous transformants, respectively. The tumorigenic cells were more resistant to cell killing, with LC(50) values of 165-180 microM for BHT-QM and 12-22 microM for BHTOH-QM, versus LC(50) values in the non-tumorigenic cells of 105-118 microM and 5.0-6.0 microM, respectively. Constitutive glutathione (GSH) concentrations were 12-20 nmol/10(6) cells, and BHT-QM toxicity was enhanced >2-fold by depleting GSH with buthionine sulfoximine (BSO). Formation of the GSH conjugate of BHT-QM accounted for a substantial fraction of the cellular GSH lost by quinone methide exposure. Enhanced lipid peroxidation and superoxide formation occurred in all cell lines treated with BHT-QM, but both tumorigenic lines contained higher levels of GSH S-transferase and superoxide dismutase (SOD) activities. These data suggest the possibility that BHT-derived quinone methides may exert their promoting effects by inducing oxidative stress; such stress is better tolerated by tumorigenic cells, which have higher levels of antioxidant enzymes. Normal cells are destroyed more readily which allows neoplastic cells to expand their proliferation.

Lung toxicity and tumor promotion by hydroxylated derivatives of 2,6-di-tert-butyl-4-methylphenol (BHT) and 2-tert-butyl-4-methyl-6-iso-propylphenol: correlation with quinone methide reactivity

Acute pulmonary toxicity and tumor promotion by the food additive 2,6-di-tert-butyl-4-methylphenol (BHT) in mice are well documented. These effects have been attributed to either of two quinone methides, 2,6-di-tert-butyl-4-methylenecyclohexa-2,5-dienone (BHT-QM) formed through direct oxidation of BHT by pulmonary cytochrome P450 or a quinone methide formed by hydroxylation of a tert-butyl group of BHT (to form BHTOH) followed by oxidation of this metabolite to BHTOH-QM. BHTOH-QM is a more reactive electrophile compared to BHT-QM due to intramolecular interactions of the side-chain hydroxyl with the carbonyl oxygen. To further examine this bioactivation pathway, an analogue of BHTOH was prepared, 2-tert-butyl-6-(1'-hydroxy-1'-methyl)ethyl-4-methylphenol (BPPOH), that is structurally very similar to BHTOH but forms a quinone methide (BPPOH-QM) capable of more efficient intramolecular hydrogen bonding and, therefore, higher electrophilicity than BHTOH-QM. BPPOH-QM was synthesized and its reactivity with water, methanol, and glutathione determined to be >10-fold higher than that of BHTOH-QM. The conversions of BPPOH and BHTOH to quinone methides in lung microsomes from male BALB/cByJ mice were quantitatively similar, but in vivo the former was pneumotoxic at one-half of the dose required for the latter and one-eighth of the dose required for BHT, as determined by increased lung weight:body weight ratios following a single i.p. injection. Similar differences were found in the doses of BHT, BHTOH, or BPPOH required for tumor promotion after a single initiating dose of 3-methylcholanthrene followed by three weekly injections of the phenol. The downregulaton of calpain II, previously shown to accompany lung tumor promotion by BHT and BHTOH, also occurred with BPPOH. The correlation between biologic activities of these phenols and the reactivities of their corresponding quinone methides provides additional support for the role of BHTOH-QM as the principal metabolite responsible for the effects of BHT on mouse lung.

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

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.