Volatile nitrosamines and tobacco-specific nitrosamines in the smoke of Thai cigarettes: a risk factor for lung cancer and a suspected risk factor for liver cancer in Thailand

A critical review of advances in tumor metabolism abnormalities induced by nitrosamine disinfection by-products in drinking water

Intensified sanitation practices amid the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak might result in the increased release of chloramine disinfectants into surface water, significantly promoting the formation of nitrosamine disinfection by-products (DBPs) in drinking water. Unfortunately, these nitrosamine DBPs exhibit significant genotoxic, carcinogenic, and mutagenic properties, whereas chlorinating disinfectants remain in global practice. The current review provides valuable insights into the occurrence, identification, contamination status, exposure limits, and toxicity of the new unregulated disinfection by-products (nitrosamine DBPs) in drinking water. As a result, concentrations of nitrosamine DBPs far exceed allowable limits in drinking water, and prolonged exposure has the potential to cause metabolic disorders, a critical step in tumor initiation and progression. Importantly, based on recent research, we have concluded the role of nitrosamines DBPs in different metabolic pathways. Remarkably, nitrosamine DBPs can induce chronic inflammation and initiate tumors by activating sphingolipid and polyunsaturated fatty acid metabolism. Regarding amino acid and nucleotide metabolism, nitrosamine DBPs can inhibit tryptophan metabolism and de novo nucleotide synthesis. Moreover, inhibition of de novo nucleotide synthesis fails to repair DNA damage induced by nitrosamines. Additionally, the accumulation of lactate induced by nitrosamine DBPs may act as a pivotal signaling molecule in communication within the tumor microenvironment. However, with the advancement of tumor metabolomics, understanding the role of nitrosamine DBPs in causing cancer by inducing metabolic abnormalities significantly lags behind, and specific mechanisms of toxic effects are not clearly defined. Urgently, further studies exploring this promising area are needed.

Long-Term Effects of Cigarette Smoking on All-Cause Mortality and Cardiovascular Outcomes in Thai Population: Results From a 30-Year Cohort Study

Despite the overwhelming evidences on the health consequences of smoking, studies in Asian population in low-to-middle income countries are very limited. Baseline data of a prospective cohort study were collected in year 1985. Endpoints regarding all-cause mortality and major adverse cardiovascular events (MACE) were followed for 30 years. Cox proportional hazard models were used for analysis. Participants had an average age of 43 years, 23% were female, and 43% were current smokers. All-cause mortality was significantly higher in ex-smokers (hazard ratio [HR] 1.32) and current smokers (HR 1.70) when compared with never smokers. Participants with any history of smoking had significantly higher risk of developing MACE. Furthermore, all-cause death, cardiovascular death, and MACE increased with increasing pack years. Statistically significant dose-response relationships were established. Therefore, cigarette smoking increased the risk of all-cause mortality, cardiovascular mortality, and MACE in Thai population. Results emphasized the importance of tobacco control in Thailand.

A Low-Cost, High-Throughput Digital Image Analysis of Stain Patterns on Smoked Cigarette Filter Butts to Estimate Mainstream Smoke Exposure

Standard machine smoking protocols provide useful information for examining the impact of design parameters, such as filter ventilation, on mainstream smoke delivery. Unfortunately, their results do not accurately reflect human smoke exposure. Clinical research and topography devices in human studies yield insights into how products are used, but a clinical setting or smoking a cigarette attached to such a device may alter smoking behavior. To better understand smokers' use of filtered cigarette products in a more natural environment, we developed a low-cost, high-throughput approach to estimate mainstream cigarette smoke exposure on a per-cigarette basis. This approach uses an inexpensive flatbed scanner to scan smoked cigarette filter butts and custom software to analyze tar-staining patterns. Total luminosity, or optical staining density, of the scanned images provides quantitative information proportional to mainstream smoke-constituent deliveries on a cigarette-by-cigarette basis. Duplicate sample analysis using this new approach and our laboratory's gold-standard liquid chromatography/tandem mass spectrometry (LC/MS/MS) solanesol method yielded comparable results (+7% bias) from the analysis of 20 commercial cigarettes brands (menthol and nonmentholated). The brands varied in design parameters such as length, filter ventilation, and diameter. Plots correlating the luminosity to mainstream smoked-nicotine deliveries on a per-cigarette basis for these cigarette brands were linear (average R2 > 0.91 for nicotine and R2 > 0.83 for the tobacco-specific nitrosamine NNK), on a per-brand basis, with linearity ranging from 0.15 to 3.00 mg nicotine/cigarette. Analysis of spent cigarette filters allows exposures to be characterized on a per-cigarette basis or a "daily dose" via summing across results from all filter butts collected over a 24 h period. This scanner method has a 100-fold lower initial capital cost for equipment than the LC/MS/MS solanesol method and provides high-throughput results (~200 samples per day). Thus, this new method is useful for characterizing exposure related to filtered tobacco-product use.

Chemical Risk Factors of Primary Liver Cancer: An Update

Primary liver cancer has the sixth highest incidence and fourth highest cancer mortality worldwide. Hepatitis B is the leading cause of liver cancer, though its incidence is decreasing with vaccination. Alcohol is the leading cause of liver transplant, cirrhosis, and cancer in the developed world, and is projected to surpass hepatitis B as the leading hepatic cancer etiology worldwide. Tobacco smoking has shown a positive association with liver cancer in a majority of studies, though not all. Aflatoxin, a mycotoxin produced by Aspergillus, is estimated to account for 3–20% of global liver cancer cases, 40% of which occur in sub-Saharan Africa. These statistics are confounded by the prevalence of hepatitis B, which may have a synergistic effect on hepatic carcinogenesis. Aflatoxin is ingested and likely inhaled from agricultural products, placing farmers, food processors, and textile workers in developing nations at risk. Vinyl-chloride is used in the production of PVC plastics and causes rare liver angiosarcoma, hepatocellular carcinoma, and other neoplasms. Arsenic and cadmium are naturally-occurring, hepatocarcinogenic metals with high occupational exposure in industries involving coal, metals, plastics, and batteries. Millions of laborers in waste-disposal and manufacturing are exposed to organic solvents and N-nitrosamines, which vary from carcinogenic (group 1) to possibly carcinogenic (group 2B) in their IARC designation. Insecticide DDT is possibly hepatocarcinogenic (group 2B), though continues to be used for malaria control in the developing world. While suggested by case reports, anabolic steroids and oral contraceptives have not been shown to increase liver cancer risk in large studies.

Tramadol-induced hepato- and nephrotoxicity in rats: Role of Curcumin and Gallic acid as antioxidants

Tramadol is an analgesic used to treat moderate to severe pain caused by cancer, osteoarthritis, and other musculoskeletal diseases. Cytochrome P450 system metabolizes tramadol and induces oxidative stress in different organs. Therefore, the present study aims at investigating the changes in the activities and the protein expressions of CYPs isozymes (2E1, 3A4, 2B1/2), antioxidants status, free radicals levels after pretreatment of rats with Curcumin and/or Gallic as single- and/or repeated-doses before administration of tramadol. In repeated-dose treatments of rats with tramadol, the activities of cytochrome P450, cytochrome b5, and NADPH-cytochrome-c-reductase, and the antioxidant enzymes including glutathione reductase, glutathione peroxidase, glutathione S-transferase, catalase, superoxide dismutase, and levels of glutathione were inhibited in the liver and the kidney of rats. Interestingly, such changes caused by tramadol restored to their normal levels after pretreatment of rats with either Curcumin and/or Gallic acid. On the other hand, repeated-dose treatment of rats with tramadol increased the activities of both dimethylnitrosamine N-demethylase I (DMN-dI), and aryl hydrocarbon hydroxylase (AHH) compared to the control group. However, pretreatment of rats with Curcumin and/or Gallic acid prior to administration of tramadol restored the inhibited DMN-dI activity and its protein expression (CYP 2E1) to their normal levels. On the other hand, tramadol inhibited the activity of ethoxycoumarin O-deethylase (ECOD) and suppressed its protein marker expression (CYP2B1/2), whereas Curcumin, Gallic acid and/or their mixture restored such changes to their normal levels. In conclusion, Curcumin and/or Gallic acid alleviated the adverse effects caused by tramadol. In addition, patients should be advice to take Curcumin and/or Gallic acid prior to tramadol treatment to alleviate the hepatic and renal toxicities caused by tramadol.

The interaction of arsenic and N-butyl-N-(4-hydroxybutyl)nitrosamine on urothelial carcinogenesis in mice

The bladder is an important organ for the storage of excreted water and metabolites. If metabolites with carcinogenic characteristics are present in urine, the urothelial lining of the bladder could be damaged and genetically altered. In this study, we analyzed the interaction of arsenic and N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) on mouse bladder carcinogenesis. Our previous study found that arsenic affects BBN-altered urothelial enzymatic activity, protein expression, DNA oxidation and global DNA CpG methylation levels. In this study, two mouse models were used. First, after administering a co-treatment of BBN and arsenic for 20 weeks, BBN alone led to a urothelial carcinoma formation of 20%, and arsenic promoted a BBN-induced urothelial carcinoma formation of 10%. The protein expression of GSTM1, GSTO1, NQO1, and p21 did not change by arsenic along with the BBN co-treatment, but the Sp1 expression increased. In the second mouse model, BBN was a pretreatment promoter; arsenic dose-dependently deteriorated BBN-promoted dysplasia by 10% and 40% at 10 ppm and 100 ppm, respectively. Conversely, BBN pretreatment also accelerated arsenic-induced dysplasia by 30%. The urothelial carcinogenic effect reversed after ceasing BBN for a period of 20 weeks. In summary, three conclusions were drawn from this study. The first is the mutual promotion of arsenic and BBN in bladder carcinogenesis. Second, arsenic dosages without bladder carcinogenicity (10 ppm) or with slight carcinogenicity (100 ppm) promote BBN-induced mice bladder cancer progression. Finally, the dysplastic urothelium had reverted to near-normal morphology after ceasing BBN intake for 20 weeks, providing a good suggestion for people who want to quit smoking.

Helicobacter Species are Possible Risk Factors of Cholangiocarcinoma

Several infectious agents are considered to be causes of cancer in human, mainly hepatitis B and C viruses, high-risk human pailloma viruses, Helicobacter pylori, Clonorchis sinensis, and Opisthorchis viverrini. Here we described the evident research and the association between Helicobacter spp. and biliary tract cancer particularly cholangiocarcinoma (CCA). Global epidemiological studies have suggested that Helicobacter spp. are possible risk factors for biliary tract diseases. Molecular studies support a linkage of Helicobacter spp. with CCA development. H. pylori, H. bilis, and H. hepaticus, are found in CCA, but the most common species are H. pylori and H. bilis. The type of CCA are associated with Helicobacter spp. include extrahepatic CCA, and common bile duct cancer. Up to the present, however, the results from different regions, materials and methods, sub-sites of cancer, and controls have not been consistent, thus introducing heterogeneity. Therefore, a comparison between co-Helicobacter spp.-CCA in the countries with low and high incident of CCA is required to settle the question. Furthermore, clarifying variation in the role of Helicobacter species in this CCA, including pathogenesis of CCA through enhanced biliary cell inflammation and proliferation, is necessary.

Reactive oxygen species mediate Epstein-Barr virus reactivation by N-methyl-N'-nitro-N-nitrosoguanidine

N-nitroso compounds (NOCs) and Epstein-Barr virus (EBV) reactivation have been suggested to play a role in the development of nasopharyngeal carcinoma (NPC). Although chemicals have been shown to be a risk factor contributing to the carcinogenesis of NPC, the underlying mechanism is not fully understood. We demonstrated recently that N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) enhances the genomic instability and tumorigenicity of NPC cells via induction of EBV reactivation. However, the mechanisms that trigger EBV reactivation from latency remain unclear. Here, we address the role of ROS in induction of EBV reactivation under MNNG treatment. EBV reactivation was induced in over 70% of EBV-positive NA cells and the promoter of Rta (Rp) was activated after MNNG treatment. Inhibitor experiments revealed ATM, p38 MAPK and JNK were activated by ROS and involved in MNNG-induced EBV reactivation. Significantly, ROS scavengers N-acetyl-L-cysteine (NAC), catalase and reduced glutathione inhibited EBV reactivation under MNNG and H₂O₂ treatment, suggesting ROS mediate EBV reactivation. The p53 was essential for EBV reactivation and the Rp activation by MNNG. Moreover, the p53 was phosphorylated, translocated into nucleus, and bound to Rp following ROS stimulation. The results suggest ROS play an important role in initiation of EBV reactivation by MNNG through a p53-dependent mechanism. Our findings demonstrate novel signaling mechanisms used by NOCs to induce EBV reactivation and provide a novel insight into NOCs link the EBV reactivation in the contribution to the development of NPC. Notably, this study indicates that antioxidants might be effective for inhibiting N-nitroso compound-induced EBV reactivation and therefore could be promising preventive and therapeutic agents for EBV reactivation-associated malignancies.

Quantitation of urinary volatile nitrosamines from exposure to tobacco smoke

A sensitive and selective method was developed and validated to detect six volatile nitrosamines (N-nitrosodimethylamine, N-nitrosomethylethylamine, N-nitrosodiethylamine, N-nitrosopiperidine, N-nitrosopyrrolidine and N-nitrosomorpholine) in human urine. This method uses a liquid-liquid extraction cartridge followed by analysis with gas chromatography-tandem mass spectrometry (GC-MS-MS) and quantification based on isotopic dilution. This is the first GC-MS-MS method reported for measuring volatile nitrosamines in human urine. This method reduces the sample volume required in other methods from 5-25 to 2 mL. The limits of detection (2.62, 1.99, 2.73, 0.65, 0.25, 3.66 pg/mL, respectively) were better than existing methods, largely because of improved positive chemical ionization achieved by using ammonia gas and reducing background noise. Using nitrogen as the collision gas allowed the confirmation transition in the low mass region to be monitored. The analysis of human urine using this validated method is accurate (relative bias of 0-19%) and precise (relative standard deviation of 0.2-18% over two months of analyses). The validated method was applied to 100 urine samples and the levels of all six volatile nitrosamines were reported for the first time in urine specimens collected from smokers and nonsmokers, with smoking status determined by urinary cotinine measurement. Among 100 smokers and nonsmokers, the levels of three analytes (N-nitrosodimethylamine, N-nitrosomethylethylamine and N-nitrosopiperidine) were significantly higher in smokers than nonsmokers (p < 0.05).

The synergistic effect of chemical carcinogens enhances Epstein-Barr virus reactivation and tumor progression of nasopharyngeal carcinoma cells

Seroepidemiological studies imply a correlation between Epstein-Barr virus (EBV) reactivation and the development of nasopharyngeal carcinoma (NPC). N-nitroso compounds, phorbols, and butyrates are chemicals found in food and herb samples collected from NPC high-risk areas. These chemicals have been reported to be risk factors contributing to the development of NPC, however, the underlying mechanism is not fully understood. We have demonstrated previously that low dose N-methyl-N’-nitro-N-nitrosoguanidine (MNNG, 0.1 µg/ml) had a synergistic effect with 12-O-tetradecanoylphorbol-13-acetate (TPA) and sodium butyrate (SB) in enhancing EBV reactivation and genome instability in NPC cells harboring EBV. Considering that residents in NPC high-risk areas may contact regularly with these chemical carcinogens, it is vital to elucidate the relation between chemicals and EBV and their contributions to the carcinogenesis of NPC. In this study, we constructed a cell culture model to show that genome instability, alterations of cancer hallmark gene expression, and tumorigenicity were increased after recurrent EBV reactivation in NPC cells following combined treatment of TPA/SB and MNNG. NPC cells latently infected with EBV, NA, and the corresponding EBV-negative cell, NPC-TW01, were periodically treated with MNNG, TPA/SB, or TPA/SB combined with MNNG. With chemically-induced recurrent reactivation of EBV, the degree of genome instability was significantly enhanced in NA cells treated with a combination of TPA/SB and MNNG than those treated individually. The Matrigel invasiveness, as well as the tumorigenicity in mouse, was also enhanced in NA cells after recurrent EBV reactivation. Expression profile analysis by microarray indicates that many carcinogenesis-related genes were altered after recurrent EBV reactivation, and several aberrations observed in cell lines correspond to alterations in NPC lesions. These results indicate that cooperation between chemical carcinogens can enhance the reactivation of EBV and, over recurrent reactivations, lead to alteration of cancer hallmark gene expression with resultant enhancement of tumorigenesis in NPC.

Risk factors for gallbladder cancer and cholangiocarcinoma: similarities, differences and updates

INTRODUCTION

Far-ranging variation in the incidence of gallbladder cancer (GBC) and cholangiocarcinoma (CCA) in different geographic regions on the globe may reflect the risk factor distribution for these tumors

METHODS

The authors give a comprehensive review on the known risk factors for GBC and CCA, and analyze both similarities and differences between the risk factors for the two main types of biliary cancer

DISCUSSION AND CONCLUSION

Leading risk factors for GBC include gallstones, female gender, and advancing age. Primary sclerosing cholangitis, nitrosamine exposure, choledochal cysts, Clonorchis sinensis and Opisthorchis viverrini represent important risk factors for CCA, although a specific risk factor cannot be identified for many patients. While both cancers affect mostly individuals in their sixth decade or older, CCA has a male predominance and GBC--a predilection for females. Although the current level of understanding of the molecular pathogenesis of GBC and CCA at the interface with specific risk factors is significantly lower than for other gastrointestinal malignancies, it continues to evolve and may soon open new avenues for the therapy of biliary cancers.

[Determination of tobacco-specific N'-nitrosamines in mainstream smoke from Japanese cigarettes]

OBJECTIVES

Mainstream smoke from cigarettes contains tobacco-specific N'-nitrosamines (TSNAs) listed as Group 1 and 3 carcinogens by the International Agency for Research on Cancer (IARC). Herein, we report on a method of measuring the concentrations of TSNAs in mainstream smoke from the ten top-selling Japanese cigarette brands using an ISO regime by International Organization for Standardization (ISO) and HCI regime of Health Canada.

METHODS

Tar in mainstream smoke was collected on a Cambridge filter pad using a smoking machine. The filter pad was immersed in 40 mL of ammonium acetate (pH 6.8) and shaken for 30 min. The extract was then loaded into a C18 column. After washing with 5 mL of 10% methanol and eluting with 5 mL of 70% methanol, the eluate was concentrated to 1 mL for LC-MS/MS analysis.

RESULTS

The concentrations of TSNAs in all cigarette brands were higher when determined using the HCI regime than when determined using the ISO regime. Furthermore, the concentrations of TSNAs measured using both the ISO and HCI regimes showed negligible correlation to the tar and nicotine concentrations indicated on package labels. The cigarette samples used in the study were categorized into four classes: ultralow-, low-, medium-, and high-yield brands, which corresponded to 1, 3-6, 8-10, and 14 mg tar/cigarette, respectively. The concentration of TSNAs in ultralow-yield cigarettes was 210 ng/cigarette, as measured using the HCI regime, which was nearly equal to that in high-yield cigarettes (180 ng/cigarette).

CONCLUSIONS

Exposure to TSNAs from mainstream smoke from ultralow-yield cigarettes is comparable to that from high-yield cigarettes. To properly evaluate the risk of smoking, not only the concentrations of tar and nicotine but also those of other chemicals, including TSNAs, should be printed on package labels.

Alteration of galectin-1 during tumorigenesis of Opisthorchis viverrini infection-induced cholangiocarcinoma and its correlation with clinicopathology

Galectin-1 is a beta-galactoside-binding lectin to function in cell adhesion, proliferation, differentiation, and might be involved in tumor progression and metastasis. In the present study, the expression kinetics of galectin-1 during the tumorigenesis of a parasite Opisthorchis viverrini infection-induced cholangiocarcinoma (CCA) was investigated in model animal hamsters, and the expression was confirmed in human CCA cases. It was found that galectin-1 was overexpressed at mRNA and protein levels with the tumor progression. The mRNA expression was elevated in very early stage during tumorigenesis and the increase was time dependent. Galectin-1 protein expression profiles indicated that the increased expression was mainly located in the epithelium of extensively proliferated and hyperplasia small bile ducts at early stage of CCA development in model animal and mainly in the extensive tumor stroma tissues in both model animals and human CCA cases at later stage. The analysis of correlation of the overexpression with clinicopathology in human cases suggested that high expression of galectin-1 was associated with advanced stage and metastasis and with shorter cumulative overall survival of the patients. Multivariate Cox regression analysis revealed that galectin-1 expression was of independent prognostic significance for CCA. Our results suggest that galectin-1 is likely involved in the tumorigenesis and expected to serve as a tumor stroma marker in diagnosis and prediction of metastasis and poor prognosis of the opisthorchiasis-associated CCA.

Advances in diagnosis, treatment and palliation of cholangiocarcinoma: 1990-2009

Several advances in diagnosis, treatment and palliation of cholangiocarcinoma (CC) have occurred in the last decades. A multidisciplinary approach to this disease is therefore recommended. CC is a relatively rare tumor and the main risk factors are: chronic inflammation, genetic predisposition and congenital abnormalities of the biliary tree. While the incidence of intra-hepatic CC is increasing, the incidence of extra-hepatic CC is trending down. The only curative treatment for CC is surgical resection with negative margins. Liver transplantation has been proposed only for selected patients with hilar CC that cannot be resected who have no metastatic disease after a period of neoadjuvant chemo-radiation therapy. Magnetic resonance imaging/magnetic resonance cholangiopancreatography, positron emission tomography scan, endoscopic ultrasound and computed tomography scans are the most frequently used modalities for diagnosis and tumor staging. Adjuvant therapy, palliative chemotherapy and radiotherapy have been relatively ineffective for inoperable CC. For most of these patients biliary stenting provides effective palliation. Photodynamic therapy is an emerging palliative treatment that seems to provide pain relief, improve biliary patency and increase survival. The clinical utility of other emerging therapies such as transarterial chemoembolization, hepatic arterial chemoinfusion and high intensity intraductal ultrasound needs further study.

Association of Programmed Cell Death Factor 4 (PDCD4) with Hepatocellular Carcinoma and Smoking in a Chinese Male Population

Programmed cell death factor 4 (PDCD4) is one of the genes that has been found to be up-regulated during apoptosis and loss of PDCD4 expression has been found in many kinds of progressive carcinomas. The objective of this study was to investigate the interactions between PDCD4 and smoking status in hepatocellular carcinoma. This case-controlled study included 68 Chinese male patients with hepatocellular carcinoma who were classified as smokers or non-smokers according to their pack-years of smoking status. Samples were obtained from carcinoma and normal tissues and examined using Western blotting. The results indicated that levels of PDCD4 were significantly lower in hepatocellular carcinoma tissues compared with normal tissues and that, in normal tissue, PDCD4 levels in smokers were significantly lower than in non-smokers.

Improving MCM-41 as a Nitrosamines Trap through a One-Pot Synthesis

Copper oxide was incorporated into MCM-41 by a one-pot synthesis under acidic conditions to prepare a new mesoporous nitrosamines trap for protection of the environment. The resulting composites were characterized by XRD, N2 adsorption-desorption, and H2 temperature-programmed reduction techniques, and their adsorption capabilities were assessed in the gaseous adsorption of N-nitrosopyrrolidine (NPYR). The adsorption isotherms were consistent with the Freundlich equation. The copper salt was deposited onto MCM-41 during the evaporation stage and was fixed on the host in the calcination process that followed. MCM-41 was able to capture NPYR in air below 373 K but not at 453 K. Loading of copper oxide on MCM-41 greatly improved its adsorption capability at elevated temperatures. The influence of the incorporation of copper into MCM-41 samples and the adsorption behavior of these samples are discussed in detail.

Protective role of dietary fibre on N-nitrosopyrrolidine-induced toxicity in hypercholesterolemic rats

N-nitrosopyrrolidine (NPYR) is an important carcinogen, frequently present in the environment and food chain. Oral administration of NPYR to experimental rats evoked severe biochemical and pathological changes. In the present investigation, the protective role of dietary fibre on NPYR-induced toxicity in hypercholesterolemic rats was studied. Supplementation of chickpea seed coat fibre in the diet reduced the hepato-toxic effects of NPYR, as evident from the decreased hepatic degeneration and improved liver weight index compared to control. Administration of NPYR resulted in an increase in the osmotic fragility of erythrocytes in the experimental animals. The antioxidant potential of experimental animals decreased in the NPYR-fed group, which was evident from the increased in vitro lipid peroxidation (LPO) of erythrocytes. However, chickpea seed coat fibre considerably reduced the peroxidative damage done by NPYR. Administration of NPYR resulted in a substantial and significant increase in LPO in all tissues, to a varying degree, though the effect was maximum in the case of the liver. Inclusion of chickpea seed coat fibre considerably reduced the peroxidative damage caused by NPYR in all tissues. The effect of NPYR administration on antioxidant potential was variable in different tissues, but the effect was reduced considerably on inclusion of chickpea seed coat fibre in the diet, providing reasonable protection against NPYR-induced oxidative stress, and, hence, its toxicity. Histopathological analysis of different tissues (heart, liver, lungs, spleen and kidneys) showed mild to severe pathological changes among the control and experimental groups. However, the pathological effects of NPYR administration were markedly reduced with the addition of chickpea seed coat fibre in the diet.

Lung cancer in Asian women-the environment and genes*

The mortality rate of lung cancer in Asian women has increased significantly in the past few decades. Environmental factors include tobacco smoke (active and environmental), other indoor pollutions (cooking oil vapours, coal burning, fungus spores), diet, and infections. Active tobacco smoking is not the major factor. The relative risk of lung cancer among non-smoking women ever exposed to environmental smoke from their husbands was 1.20 from a meta-analysis. Cooking oil vapours associated with high temperature wok cooking and indoor coal burning for heating and cooking in unvented homes, particularly in rural areas, are risk factors for Chinese women. Chronic benign respiratory diseases due to the fungus Microsporum canis probably accounts for the high incidence of lung cancer in northern Thai women at Sarapee. Diets rich in fruits, leafy green vegetables, and vitamin A are protective, while cured meat (Chinese sausage, pressed duck and cured pork), deep-fried cooking, and chili increased the risk. Tuberculosis is associated with lung cancer. Also, a Taiwanese study showed that the odds ratio of papillomavirus (HPV) 16/18 infection in non-smoking female lung cancer patients was 10.1, strongly suggesting a causative role. Genetic factors have also been studied in Chinese women, including human leucocyte antigens, K-ras oncogene activation, p53 mutation, polymorphisms of phase I activating enzymes (cytochrome P450, N-acetyltransferase slow acetylator status), and phase II detoxifying enzymes (glutathione-S-transferases, N-acetyltransferase rapid acetylator status). New molecular screening technology would facilitate identification of molecular targets for future studies. The interaction between environmental and genetic factors should also be further elucidated.

Application of toxicological risk assessment principles to the chemical constituents of cigarette smoke

OBJECTIVE

To provide a hazard prioritisation for reported chemical constituents of cigarette smoke using toxicological risk assessment principles and assumptions. The purpose is to inform prevention efforts using harm reduction.

DATA SOURCES

International Agency for Research on Cancer Monographs; California and US Environmental Protection Agency cancer potency factors (CPFs) and reference exposure levels; scientific journals and government reports from the USA, Canada, and New Zealand.

STUDY SELECTION

This was an inclusive review of studies reporting yields of cigarette smoke constituents using standard ISO methods.

DATA EXTRACTION

Where possible, the midpoint of reported ranges of yields was used.

DATA SYNTHESIS

Data on 158 compounds in cigarette smoke were found. Of these, 45 were known or suspected human carcinogens. Cancer potency factors were available for 40 of these compounds and reference exposure levels (RELs) for non-cancer effects were found for 17. A cancer risk index (CRI) was calculated by multiplying yield levels with CPFs. A non-cancer risk index (NCRI) was calculated by dividing yield levels with RELs. Gas phase constituents dominate both CRI and NCRI for cigarette smoke. The contribution of 1,3-butadiene (BDE) to CRI was more than twice that of the next highest contributing carcinogen (acrylonitrile) using potencies from the State of California EPA. Using those potencies from the USEPA, BDE ranked third behind arsenic and acetaldehyde. A comparison of CRI estimates with estimates of smoking related cancer deaths in the USA showed that the CRI underestimates the observed cancer rates by about fivefold using ISO yields in the exposure estimate.

CONCLUSIONS

The application of toxicological risk assessment methods to cigarette smoke provides a plausible and objective framework for the prioritisation of carcinogens and other toxicant hazards in cigarette smoke. However, this framework does not enable the prediction of actual cancer risk for a number of reasons that are discussed. Further, the lack of toxicology data on cardiovascular end points for specific chemicals makes the use of this framework less useful for cardiovascular toxicity. The bases for these priorities need to be constantly re-evaluated as new toxicology information emerges.

Narcotic drugs change the expression of cytochrome P450 2E1 and 2C6 and other activities of carcinogen-metabolizing enzymes in the liver of male mice

Drug-metabolizing enzymes play a great role in the bioactivation and also detoxification of zenobiotics and carcinogens such as N-nitrosamines and polycyclic aromatic hydrocarbons (PAHs). Therefore, the present study was undertaken to investigate the effect of narcotic drugs such as cannabis (hashish) and diacetylmorphine (heroin) on the activity of N-nitrosodimethylamine N-demethylase I [NDMA-dI], arylhydrocarbon [benzo(a)pyerne] hydroxylase [AHH], cytochrome P450 (CYP), cytochrome b(5), NADPH-cytochrome c reductase, glutathione-S-transferase, and levels of glutathione and thiobarbituric acid-reactive substances (TBARS). In addition, the present study showed the influence of hashish and heroin after single (24 h) and repeated-dose treatments (4 consecutive days) on the expression of cytochrome P450 2E1 (CYP 2E1) and cytochrome P450 2C6 (CYP 2C6). The expression of CYP 2E1 was slightly induced after single-dose and markedly induced after repeated dose-treatments of mice with hashish (10 mg kg(-1) body weight). Contrarily, heroin markedly induced the expression of CYP 2C6 after single-dose and potentially reduced this expression after repeated-dose treatments. It is believed that N-nitrosamines are activated principally by CYP 2E1 and in support of this, the activity of NDMA-dI was found to be increased after single- and repeated-dose treatments of mice with hashish by 23 and 41%, respectively. In addition, single- and repeated-dose treatments of mice with hashish increased: (1) the total hepatic content of CYP by 112 and 206%, respectively; (2) AHH activity by 110 and 165%, respectively; (3) NADPH-cytochrome c reductase activity by 21 and 98%, respectively; (4) and glutathione level by 81 and 173%, respectively. Also, single-dose treatments of mice with heroin increased the total hepatic content of CYP, AHH, NADPH-cytochrome c reductase, and glutathione level by 126, 72, 39, 205%, respectively. However, repeated dose-treatments of mice with heroin did not change such activities except cytochrome c reductase activity increased by 20%. Interestingly, the level of free radicals, TBARS, was potentially decreased after single or repeated-dose treatments with either hashish or heroin. It is clear from this study that the effects of hashish are different from those of heroin on the above mentioned enzymes particularly after repeated dose treatments. It is concluded that hashish induced the expression of CYP 2E1 and other carcinogen-metabolizing enzymes activities, and this induction could potentiate the deleterious effects of N-nitrosamines and aromatic hydrocarbons, e.g. benzo(a)pyrene, upon the liver and probably other organs. Such alterations may also change the therapeutic actions of other drugs, which are primarily metabolized by the P450 system, when administered to peoples using hashish or heroin.

The influence of very low doses of N-nitrosodimethylamine (NDMA) on the apoptosis of rat neutrophils in vivo. The role of reactive oxygen species

N-nitrosodimethylamine (NDMA) causes the apoptosis of neutrophils in vitro experiments. This compound also has the ability to stimulate neutrophils for the production of reactive oxygen species. It has been decided to examine more closely whether the apoptosis of neutrophils by NDMA is caused by the influence of the radicals produced by these cells and whether the stimulation to undergo apoptosis of neutrophils is caused by NDMA in either the original form or by its metabolites. The experiment was conducted on rats. The animals were administered a one-time dose of NDMA intragastrically, 1.5 mg/kg. The research was conducted 1,2,4,12 h consecutively following NDMA administration. The concentration of NDMA in blood was evaluated by means of the gas chromatography method. The neutrophils were isolated from blood by means of differential centrifugation. Respiratory burst was assessed in cells, by means of the cytochrome c reduction method. The percentage of cells revealing morphological properties of apoptosis was determined under the fluorescent microscope. It has been observed that the activation of the respiratory burst is caused mainly by non-metabolised NDMA. Probably the non-metabolised molecules of this compound also have a decisive role in the initiation of apoptosis of neutrophils. It can be assumed that the main factor responsible for the apoptosis of neutrophil rats following a one-time NDMA administration is the induction of respiratory burst in neutrophils by this compound.

Environmental, cultural and social changes and their influence on parasite infections

The changes taking place within the societies, cultures and the environments in which we live are massive and complex. By referring to simple epidemiological models it is possible to build an objective framework with which to look at these changes in terms of their likely impact on the epidemiology of parasitic diseases within human communities. These parameters are listed for hosts and both micro- and macroparasites, as are epidemiologically significant cultural, social and environmental variables. Changes in these variables may be either detrimental or beneficial to human health and may, in addition, interact in complex ways. Examples of the complexity of changes which can influence epidemiology are provided for a cultural template of the population living in the north-east of Thailand.

Increase in mortality rates from intrahepatic cholangiocarcinoma in England and Wales 1968-1998

BACKGROUND

The age standardised mortality rate per 100 000 population for all causes of liver tumours (International Classification of Disease 9 (ICD-9) 155) has almost doubled in England and Wales during the period 1979-1996. We further analysed the mortality statistics to determine which anatomical subcategories were involved.

METHODS

Mortality statistics for liver tumours of ICD-9 155, 156, and subcategories, and for tumours of the pancreas (ICD-9 157), in England and Wales were investigated from the Office for National Statistics, London, from 1968 to 1996 inclusive. Data for 1997 and 1998 were also available on intrahepatic cholangiocarcinomas.

RESULTS

There has been a marked rise in age standardised mortality rates for intrahepatic cholangiocarcinoma. Since 1993, it represents the commonest recorded cause of liver tumour related death in England and Wales. This is evident in age groups older than 45 years. In contrast, mortality trends from other primary liver tumours, including hepatocellular carcinoma, were unremarkable.

CONCLUSIONS

The observed increase in mortality from intrahepatic cholangiocarcinoma may represent better case ascertainment and diagnosis due to improved diagnostic imaging, use of image guided biopsies, or increased use of ERCP. However, the trend started before ERCP was introduced nationally, mortality rates have continued to increase steadily thereafter, and there is no clear evidence that diagnostic transfers easily explains the findings. Alternatively, these observations may represent a true increase in intrahepatic bile duct tumours. Epidemiological studies are required to determine whether there is any geographical clustering of cases around the UK.

"IARC Group 2B carcinogens" reported in cigarette mainstream smoke

In the third and final part of a series surveying the international literature on the "IARC carcinogens" in cigarette mainstream smoke, the "IARC Group 2B carcinogens" are reviewed. A search of the published literature shows that of 227 chemical components classified as Group 2B, that is, "possible carcinogens," by the International Agency for Research on Cancer (IARC), 48 have previously been reported in cigarette mainstream smoke. Owing to its highly interactive molecular nature, removal from or inhibition of a given mutagenic or carcinogenic chemical within the complex aerosol mixture cannot reliably be predicted to reduce either the overall mutagenicity or carcinogenicity. However, in the absence of experimental data demonstrating an increase in adverse biological activity resulting from removal or inhibition of a potentially carcinogenic constituent, negation of the activity of the potential carcinogen may be considered as a desirable circumstance.

"IARC group 2B Carcinogens" reported in cigarette mainstream smoke

In the third and final part of a series surveying the international literature on the "IARC carcinogens" in cigarette mainstream smoke, the "IARC Group 2B carcinogens" are reviewed. A search of the published literature shows that of 227 chemical components classified as Group 2B, that is, "possible carcinogens," by the International Agency for Research on Cancer (IARC), 48 have previously been reported in cigarette mainstream smoke. Owing to its highly interactive molecular nature, removal from or inhibition of a given mutagenic or carcinogenic chemical within the complex aerosol mixture cannot reliably be predicted to reduce either the overall mutagenicity or carcinogenicity. However, in the absence of experimental data demonstrating an increase in adverse biological activity resulting from removal or inhibition of a potentially carcinogenic constituent, negation of the activity of the potential carcinogen may be considered as a desirable circumstance.