sample="quota" bates="2060578937" isource="pm" decade="1990" class="ui" date="19980318" TRIP REPORT Subject: 37th Annual Meeting of the Society of Toxicology, Seattle, 1-5 March, 1998. Author: Dr. A. R. Tricker Date: 18th March, 1998 Organizer: Society of Toxicology Participants: ca. 5,000 Other PM staff: 14 in total Proceedings: Toxicological Sciences Vol. 42 (1-S), 1988 Distribution: WSA: Worldwide INFIBO: WRE General Remarks According to the organizers, 5,000 people registered to attend the meeting which had multiple parallel sessions for oral and poster presentations. In total the meeting contained 2,000 presentations and 200 trade stands. About 30 scheduled posters were not presented. It was, evident that considerable interest (and funding) remains in the U.S. for studies involving (I) PCB's - most of which were focused on environment/exposure/risk of female breast cancer, (ii) chlorinated solvents in drinking water, and (ii) exposure to heavy metals - particularly cadmium and lead. Due to the large amount of work presented, this report is only a subjective selection of some of the presentations reporting product and smoking-related issues, inhalation studies, chemical and invitro studies of tobacco smoke constituents, molecular and genetic susceptibility studies of different population groups to specific diseases. Copies of the abstracts (denoted #) are available from the author. Smoking-related presentations The meeting contained 4 posters from the Company on an electrically heated cigarette (#1449, #1450, #1451, #1452) and will not be discussed further. Finch (Lovelace, Albuquerque, NM., #1728) reported a chronic inhalation study in which male and female (F344/Crl rats were exposed to mainstream CS (100 or 250 mg TPM/m³, 6 h/d, 5 d/wk, 30 m, whole-body) and received a single acute nasal exposure to 239PuO2 during week 6. Crude tumor incidences at the end of exposure were as follows: Assuming an approximately linear dose-response relationship between radiation dose (Sham smoke: 3.8 Gy; low smoke exposure: 4.1 Gy; high smoke exposure: 7.6Gy) and crude lung tumor incidence, no explanation could be given for the supperadditive increase in lung neoplasms in animals receiving both exposures. Fung (Rutgers University, Piscataway, NJ., #470) reported induction of CYP1A1 (mRNA, protein and catalytic activity) in lung, liver and kidney of male SD rats exposed to diluted SS or MS of the 2R1 reference cigarette. Rats were exposed to smoke from 3 machine-smoked cigarettes using various experimental protocols (number of exposures, duration of exposure, and time of sacrifice after last exposure). MS was more effective than SS at inducing CYP1A1 activity under most conditions. Induction by SS was observed in lung kidney, and to a lesser extent in liver. Meckley (RJR, #1085) reported a standardized dermal tumor promotion assay protocol for CSC using female CD-1 mice initiated with a single dose of 75 µg DMBA followed by promotion 3 times/wk using 12, 24, 36, 48 and 60 mg 'tar' for 51 weeks. Using groups of 40 mice it was claimed that the protocol can differentiate between different doses of CSC. The 1R4F reference cigarette was used as a source of CSC. The assay protocol was suggested to replace existing protocols using the SENCAR mouse. ETS/Smoking-related presentations Pereg (CHUQ Research Center Ste-Foy, Qc., #1593) reported preliminary data for placental cadmium levels in nonsmokers (geometric mean: 0.026; range 0.024-0.028 µg/kg; n=15), smokers of 1-15 cpd (geometric mean; 0.058; range 0.053-0.064 µg/kg; n=14) and smokers of 15 cpd (geometric mean: 0.080; range 0.072-0.088 µg/kg; n=11). Significant correlation's were claimed between placental cadmium and cpd (Pearson's r=0.61; p 0.01), cotinine in meconium (r=0.87; p 0.001) and placental EROD activity (r=0.61; p 0.001). The study is being extended to 100 subjects and to determine total adducts using 32P-postlabeling. Cadmium levels were claimed (verbally) to be higher in Canadian cigarettes compared to U.S. blend cigarettes. The ultimate study aim is to establish an association between self-reported exposure to ETS and placental cadmium. ( Copy of poster available on request) Howard (University of Nevada, Reno, NV., #744) - 'DNA damage from exposure to environmental tobacco smoke in the workplace'. Some discrepancies in the reported data in the poster and a handout publication at the poster boards were apparent. (Howard et al., Cancer Epidemiol. Biomarkers & Prev., 7, 141-146, 1998). Neglecting these discrepancies, the method used to determine 8-hydroxy-2'-deoxyguanosine as a marker of oxidative stress is known to be prone to artifact formation. The cotinine data was also suspect. ( Publication available on request). These results do not explain the 1000-fold greater susceptibility of mice to 1,3-butadiene. In discussion with Boogaard I heard that Shell's current research concludes that: Only 15% of total hemoglobin-bound material can be identified. C4 lipid peroxidation contributes to background levels of adducts thought to be specific for 1,3-butadiene. Hemoglobin adducts cannot be used to determine occupational exposure to a TWA8 of 2 ppm 1,3-butadiene. Biomonitoring of 1,3-butadiene excretion products (metabolites M1 and M2) cannot differentiate between nonsmokers and smokers of 2 packs/day. Swenberg (University of North Carolina, Chapel Hill, NC., #890) reported data from a series of inhalation studies with SD rats and B6C3F1 mice (20-625 ppm, 6 h/d, 10d, and single 6 h exposure to 1250 pm 1,3-butadiene). Detected levels of hepatic DNA adducts paralleled the increased sensitivity of mice compared to rats for liver cancer. Henderson (Lovelace, Albuquerque, NM., #898) reported a higher frequency of hprt mutant T cells in the spleen of B6C3F1 mice compared to F344 rats exposed to 1,3-butadiene (0, 20, 62.5 and 625 ppm; 6 h/d, 5 d/wk for 4 wk), 1,3- butadiene monoepoxide (o, 2.5 and 25 ppm; 6 h/d, 5 d/wk for 4 wk), and 1,3-butadiene diepoxide (0, 2, and 4 ppm; 6 h/d, 5 d/wk for 4 wk). The diepoxide was concluded to induce hprt mutations, and mice were more sensitive than rats to 1,3-butadiene. Nitrosamines Data was presented by Tricker and Richter (#900) and Smith (#1399) for metabolism of NNK in human lung tissue and isolated lung cell fractions (cell digest, Type II cells and macrophages), respectively. Tricker and Richter compared metabolism in lung and liver of the A/J mouse, F344 rat and man, and concluded that NNK to NNAL reduction accounted for 97% of NNK metabolism in human lung and liver, while significant -hydroxylation occurred in tissues from experimental animals with reduced formation of NNAL. Smith (Queen's University, Kingston, ON., #1399) reported human lung cell fractions primarily metabolize NNK by reduction to NNAL ( 95% of total metabolism). Smith used a single concentration of 4.2 µM NNK with 24-h incubation, separation of metabolite peaks by HPLC fractionation and solid-phase radioactivity monitoring. Neglecting differences in experimental and analytical protocols, both studies indicated 1.5% -hydroxylation of NNK in human lung preparations. Gerde (Lovelace, NM., #901) reported absorption of NNK and B(a)P over canine tracheal epithelium following instillation in the distal trachea. NNK, but not B(a)P, was rapidly absorption over the trachea. Two to 3-fold higher binding of NNK occurred in trachea than observed in distal tissues including lung. No NNK was detected in systemic circulation 18 min after administration. It was concluded that (I) absorption of B(a)P was considerably slower than that of NNK, (ii) NNK absorption over lung epithelial is likely to be so rapid that significant metabolism does not occur in this organ, and (iii) the slower absorption of B(a)P probably induces biological effects at the site-of-entry. Chang (RJR, #899) reported an old study in which NNK-induced O6-methylguanine formation in lung and liver of the A/J mouse was significantly suppressed by inhalation of cigarette smoke. ( Copy available on request) Latropoulos (AHF, #63) presented an extension of a previously published study (Williams et al., Carcinogenesis, 14, 2149-2156, 1993 and 17, 2253-2258, 1996) showing non-linearity of NDEA liver noeplasms in male F344 rats. The NOEL for initiation was 0.5 mmol/kg cumulative dose. ( Copy available on request) Smith (MRC Toxicology Unit, Leicestershire, UK, #64) reported that iron overload (500 mg/kg bw iron dextran) promoted NDEA-initiated GST-P foci in the rat liver. It was suggested that iron might also act as a promoter of human liver cancer. (Study published by Carthew et al., Carcinogenesis, 18, 599-603, 1997, and available on request) Bichet (SANOFI Research, Montpellier, France, #390) reported that N-nitroso-N-methylpiperazine might be a suspect hepatocarcinogen in the rat. The biological activity of this compound in the rat liver was actually reported by Druckrey et al., Z. Krebsforsch., 69, 103-201, 1967 - probably before the presenter was born! Furlong (University of Washington, Seattle, #566) reported that newborn rats and mice have very low paraoxonase (PON1) levels and require about 3 weeks before PON1 expression develops. PON1, also known as arylesterase, is located in HDL particles and may be a genetic susceptibility factor for vascular disease and Gulf War syndrome. The Gin192 Arg amino acid change in PON1 is associated with reduced lipid oxidation. A second silent polymorphism in codon 55 (not fully characterized) does not appear to have a functional effect. Loo (University of Washington, Seattle, #1445) reported a rapid ELISA-based oligonucleotide ligation assay to detect lle104 Val and Ala113 Val polymorphisms in GSTP1. Variant allele frequencies of 33.6% and 10.8% were reported for Val104 and Val113, respectively, among controls. No increase in risk of Parkinson's disease was found for the Val104 allele (OR=0.83; 95% Cl 0.35-1.99) or the Val113 allele (OR=0.93; 95% Cl 0.27-3.22). The same polymorphisms are being investigated for lung and espophageal cancer. Shinde (University of Arkansas for Medical Sciences, AR., #1567) reported a bp-34 (T C) substitution in the 5' promoter region of CYP17 which appears to increase gene expression. Since CYP17 is involved in testosterone biosynthesis, this point mutation may increase androgen levels. Preliminary results indicate an increased risk of prostate cancer in combined heterozygotes and homozygotes men for the variant allele. (This is consistent with the increased androgen level hypothesis) Omiecinsky (University of Washington, Seattle, #567) reported that exon 3 Tyr113 His and exon 4 His139 Arg polymorphisms in microsomal epoxide hydroxylase (mEH) have no significant effect on enzyme function since genotype and function are only weakly correlated. In addition to these two polymorphisms, a further 7 polymorphic sites have been identified, 3 of which impact post-transcription regulation. Failure to consider these new polymorphisms question the validity of previous associations reported for mEH polymorphisms: His139 Arg increases the risk of hepatocellular cancer (McGlynn et al., PNAS 92, 2384, 1995) Tyr113 His increases the risk of ovarian cancer (Lancaster et al., Mol. Car., 17, 160, 1996) Neither polymorphism related to bladder cancer (Brockmöller et al., Cancer Res., 56, 3915, 1996). Polymorphisms of mEH are currently being studied at the University of Washington as genetic risk factors for lung cancer and Parkinson's disease. Maier (University of Cincinnati Medical Center, OH., #1222) presented initial data indicating 10 polymorphic sites in the coding region of the mouse Ah receptor. A further polymorphic site was identified in a non-coding region. Henry (University of Pittsburgh, PA., #91) presented initial data for phenotyping using the 'Pittsburgh cocktail', a mixture of 5 test substrates to determine phenotype for CYP1A1, CYP2C9, CYP2E1, CYP2D6 and NAT2 acetylator status. Although the 'cocktail' was claimed not to result in cross-inhibition of CYP activity, the presented results suggest that significant inhibition of CYP2D6 metabolism occurred since 4 of 18 subjects (22%) were classified as CYP 2D6 PM phenotypes compared to an expected 6-8%. Andersen (University of Washington, Seattle, #83) genotyped expression of CYP2D6 in a human liver bank. Although not mentioned in the abstract, data was presented in the poster to show expression of CYP2D6, CYP2D7 and CYP2D8P in human lung. Paine (University of Michigan, Ann Arbor, MI., #1644) presented data to show that ketoconazole, originally thought to be a mechanism-based inhibitor of CYP3A4, potentially inhibits metabolism by CYP1A1. Moron (University of Colorado, Denver, CO., #1393) reported that the bp609 (C T) point mutation resulting in a Pro187 Ser amino acid exchange in NAD(P)H: quinone oxidoreductase (NQO1) increases in vitro benzene toxicity in human bone marrow cells. Studies using precision-cut tissue slice This model is currently being used in a Philip Morris funded project (Richter and Tricker; #900). Evident from the meeting was a renewed interest in using this model for studying the metabolism and toxicity of various xenobiotics: The above studies used various culture media, incubation times and protocols. It was evident from the combined presentations that each group has their own preferred method and conditions. Comparative studies showed interspecies differences for trans-methylstyryl ketone metabolism by rat, mouse and human liver (Sipes, #1390) and for 2-butoxyethanol metabolism by F344 rat and B6C3F1 mouse liver (Grant, #1624). Grant also reported age-related differences in hepatic metabolism of 2-butoxyethanol. Most studies provided data to confirm vitality of fresh liver slices for 36-96 h. -- End or report --