Frequency of surgery and hospital admissions for communicable diseases in a high- and middle-income setting.

BACKGROUND: In high-income countries, non-communicable diseases drive the demand for surgical healthcare. Middle-income countries face a double disease burden, of both communicable and non-communicable disease. The aim of this study was to describe the role of surgery for the in-hospital care of infectious conditions in the high-income country Sweden and the middle-income country South Africa. METHODS: A retrospective cohort study was performed of 1.4 million infectious disease admissions. The study populations were the entire population of Sweden, and a cohort of 3.5 million South Africans with private healthcare insurance, during a 7-year interval. The outcome measures were frequency of surgical procedures across a spectrum of diseases, and sex and age during the medical care event. RESULTS: Some 8.1 per cent of Swedish and 15.7 per cent of South African hospital admissions were because of infectious disease. The proportion of infectious disease admissions that were associated with surgery was constant over time: 8.0 (95 per cent c.i. 7.9 to 8.1) per cent in Sweden and 21.1 (21.0 to 21.2) per cent in South Africa. The frequency of surgery was 2.6 (2.6 to 2.7) times greater in South Africa, and 2.2 (2.2 to 2.3) times higher after standardization for age, sex and disease category. CONCLUSION: The study suggests that surgical care is required to manage patients with communicable diseases, even in high-income settings with efficient prevention and functional primary care. These results further stress the importance of scaling up functional surgical health systems in low- and middle-income countries, where the disease burden is distinguished by infectious disease.

Studies on Synthetic and Natural Melanin and Its Affinity for Fe(III) Ion.

In this work, we measured the metal-binding sites of natural and synthetic dihydroxyindole (DHI) melanins and their respective interactions with Fe(III) ions. Besides the two acid groups detected for the DHI system: catechol (Cat) and quinone-imine (QI), acetate groups were detected in the natural oligomer by potentiometric titrations. At acidic pH values, Fe(III) complexation with synthetic melanin was detected in an Fe(OH)(CatH(2)Cat) interaction. With an increase of pH, three new interactions occurred: dihydroxide diprotonated catechol, Fe(OH)(2)(CatH(2)Cat)(-), dihydroxide monoprotonated catechol, [Fe(OH)(2)(CatHCat)](2-), and an interaction resulting from the association of one quinone-imine and a catechol group, [Fe(OH)(2)(Qi(-))(CatHCat)](3-). In the natural melanin system, we detected the same interactions involving catechol and quinone-imine groups but also the metal interacts with acetate group at pH values lower than 4.0. Furthermore, interactions in the synthetic system were also characterized by infrared spectroscopy by using the characteristic vibrations of catechol and quinone-imine groups. Finally, scanning electronic microscopy (SEM) and energy-dispersive X-ray (EDS) analysis were used to examine the differences in morphology of these two systems in the absence and presence of Fe(III) ions. The mole ratio of metal and donor atoms was obtained by the EDS analysis.

High rate of hypothyroidism among patients treated for multidrug-resistant tuberculosis in Lesotho.

BACKGROUND: Hypothyroidism is a known side effect of treatment for multidrug-resistant tuberculosis (MDR-TB), but it is considered to be rare. Hypothyroidism has vague and non-specific symptoms, and can be easily missed by clinicians. OBJECTIVE: To report the high rate of hypothyroidism in a cohort of MDR-TB patients in Lesotho and to describe our approach to diagnosis and management. DESIGN: A retrospective study of 212 patients who initiated treatment for MDR-TB in Lesotho between 27 July 2007 and 24 March 2009 was performed. RESULTS: Among 186 patients screened, 129 (69%) had hypothyroidism, defined as at least one documented thyroid-stimulating hormone (TSH) result > 10.0 mIU/l; 100 (54%) patients had a maximum TSH > 20.0 mIU/l. At 93 days after starting MDR-TB treatment, half of the patients had developed hypothyroidism. CONCLUSION: Hypothyroidism may be more common during MDR-TB treatment than previously recognized. Screening all patients, even those without symptoms, for hypothyroidism within 2-3 months of starting MDR-TB treatment should be considered until prospective studies can inform screening guidelines.

Programmatic management of multidrug-resistant tuberculosis: models from three countries.

BACKGROUND: Although multidrug-resistant tuberculosis (MDR-TB) is a major global health problem, there is a gap in programmatic treatment implementation. METHODS: This study describes MDR-TB treatment models in three countries--Peru, Russia and Lesotho-- using qualitative data collected over a 13-year period. RESULTS: A program analysis is presented for each country focusing on baseline medical care, initial implementation and program evolution. A pattern analysis revealed six overarching themes common to all three programs: 1) importance of baseline assessments, 2) early identification of key collaborators, 3) identification of initial locus of care, 4) minimization of patient-incurred costs, 5) targeted interventions for vulnerable populations and 6) importance of technical assistance and funding. Site commonalities and differences in each of these areas were analyzed. CONCLUSIONS: It is recommended that all programs providing MDR-TB treatment address these six areas during program development and implementation.

Development of the gubernaculum during testicular descent in the rat.

Gubernacular elongation during inguinoscrotal testicular descent and cremaster muscle development remains poorly described in mammals. The role of the genitofemoral nerve (GFN) remains elusive. We performed detailed histological analysis of testicular descent in normal rats to provide a comprehensive anatomical description for molecular studies. Fetuses and neonatal male offspring (5-10 per group) from time-mated Sprague-Dawley dams (embryonic days 15, 16, and 19; postnatal days 0, 2, and 8) were prepared for histology. Immunohistochemistry was performed for nerves (Class III tubulin, Tuj1) and muscle (desmin). At embryonic days 15 and 16, the gubernaculum and breast bud are adjacent and both supplied by the GFN. By embryonic day 19, the breast bud has regressed and the gubernacular swelling reaction is completed. Postnatally, the gubernacular core regresses, except for a cranial proliferative zone. The cremaster is continuous with internal oblique and transversus abdominis. By postnatal day 2 (P2), the gubernaculum has everted, locating the proliferative zone caudally and the residual mesenchymal core externally. Eversion creates the processus vaginalis, with the everted gubernaculum loose in subcutaneous tissue but still remote from the scrotum. By P8, the gubernaculum has nearly reached the scrotum with fibrous connections attaching the gubernaculum to the scrotal skin. A direct link between GFN, gubernaculum, and breast bud suggests that the latter may be involved in gubernacular development. Second, the cremaster muscle is continuous with abdominal wall muscles, but most of its growth occurs in the distal gubernacular tip. Finally, gubernacular eversion at birth brings the cranial proliferative zone to the external distal tip, enabling gubernacular elongation similar to a limb bud.

Substance P and vasoactive intestinal peptide are reduced in right transverse colon in pediatric slow-transit constipation.

BACKGROUND: Slow-transit constipation (STC) is recognized in children but the etiology is unknown. Abnormalities in substance P (SP), vasoactive intestinal peptide (VIP) and nitric oxide (NO) have been implicated. The density of nerve fibers in circular muscle containing these transmitters was examined in colon from children with STC and compared to other pediatric and adult samples. METHODS: Fluorescence immunohistochemistry using antibodies to NO synthase (NOS), VIP and SP was performed on colonic biopsies (transverse and sigmoid colon) from 33 adults with colorectal cancer, 11 children with normal colonic transit and anorectal retention (NAR) and 51 with chronic constipation and slow motility in the proximal colon (STC). The percentage area of nerve fibers in circular muscle containing each transmitter was quantified in confocal images. KEY RESULTS: In colon circular muscle, the percentage area of nerve fibers containing NOS > VIP > SP (6 : 2 : 1). Pediatric groups had a higher density of nerve fibers than adults. In pediatric samples, there were no regional differences in NOS and VIP, while SP nerve fiber density was higher in sigmoid than proximal colon. STC children had lower SP and VIP nerve fiber density in the proximal colon than NAR children. Twenty-three percent of STC children had low SP nerve fiber density. CONCLUSIONS & INFERENCES: There are age-related reductions in nerve fiber density in human colon circular muscle. NOS and VIP do not show regional variations, while SP nerve fiber density is higher in distal colon. 1/3 of pediatric STC patients have low SP or VIP nerve fiber density in proximal colon.

Economic risk factors for HIV infection among women in rural Haiti: implications for HIV prevention policies and programs in resource-poor settings.

AIMS: The goals of this study were to (1) estimate the prevalence of HIV infection among women accessing services at a women's health center in rural Haiti and (2) to identify economic risk factors for HIV infection in this population. METHODS: Women who accessed healthcare services at this center between June 1999 and December 2002 were recruited to participate. The analysis was based on data from a case-control study of sexually transmitted diseases (STDs) in rural Haiti. HIV prevalence in the study population was 4%. RESULTS: In multivariate analyses, partner occupation was associated with HIV infection in women, with mechanic (OR 9.0, 95% CI 1.8-45) and market vendor (OR 4.2, 95% CI 1.6-11) reflecting the strongest partner occupational risk factors. Partner's occupation as a farmer reduced the risk of infection in women by 60% (95% CI 0.14-1.1). Factors indicating low socioeconomic status (SES), such as food insecurity (OR 2.0, 95% CI 0.75-5.6) and using charcoal for cooking (OR 1.7, 95% CI 0.72-3.8) suggested an association with HIV infection. CONCLUSIONS: Given pervasive gender inequality in Haiti, women's economic security often relies on their partners' income earning activities. Our findings show that although factors reflecting poverty are associated with HIV-positive status, stronger associations are observed for women whose partners indicated a more secure occupation (e.g., mechanic or market vendor). Policies and programs that expand access to education and economic opportunities for women and girls may have long-term implications for HIV prevention in Haiti and other resource-poor settings.

Cells deficient in the base excision repair protein, DNA polymerase beta, are hypersensitive to oxaliplatin chemotherapy.

A significant proportion of human cancers overexpress DNA polymerase beta (Pol beta), the major DNA polymerase involved in base excision repair. The underlying mechanism and biological consequences of overexpression of this protein are unknown. We examined whether Pol beta, expressed at levels found in tumor cells, is involved in the repair of DNA damage induced by oxaliplatin treatment and whether the expression status of this protein alters the sensitivity of cells to oxaliplatin. DNA damage induced by oxaliplatin treatment of HCT116 and HT29 colon cancer cells was observed to be associated with the stabilization of Pol beta protein on chromatin. In comparison with HCT116 colon cancer cells, isogenic oxaliplatin-resistant (HCT-OR) cells were found to have higher constitutive levels of Pol beta protein, faster in vitro repair of a DNA substrate containing a single nucleotide gap and faster repair of 1,2-GG oxaliplatin adduct levels in cells. In HCT-OR cells, small interfering RNA knockdown of Pol beta delayed the repair of oxaliplatin-induced DNA damage. In a different model system, Pol beta-deficient fibroblasts were less able to repair 1,2-GG oxaliplatin adducts and were hypersensitive to oxaliplatin treatment compared with isogenic Pol beta-expressing cells. Consistent with previous studies, Pol beta-deficient mouse fibroblasts were not hypersensitive to cisplatin treatment. These data provide the first link between oxaliplatin sensitivity and DNA repair involving Pol beta. They demonstrate that Pol beta modulates the sensitivity of cells to oxaliplatin treatment.

Decrease in nerve fibre density in human sigmoid colon circular muscle occurs with growth but not aging.

BACKGROUND: Studies in animals suggest that enteric neurons decrease in density or number with increasing age. Neurons containing nitric oxide (NO), vasoactive intestinal peptide (VIP) and Substance P (SP) have been implicated. In human large intestine, NO-utilizing neurons decrease during childhood or early adulthood but it is not known if the innervation of the muscle changes. This study examined the density of nerve fibres containing these transmitters in sigmoid colon circular muscle from children and adults. METHODS: Fluorescence immunohistochemistry using antibodies to neuronal NO synthase (nNOS), VIP and SP was performed on sigmoid colon from 18 adults with colorectal cancer, two children with familial adenomatous polyposis, and normal colon from nine children with Hirschsprung's disease. The percentage area of immunoreactive (IR) nerve fibres containing each transmitter in circular muscle was quantified in confocal images. KEY RESULTS: In the adult sigmoid colon circular muscle, the percentage area of nerve fibres containing nNOS>VIP>SP (6 : 2 : 1). Paediatric groups had significantly higher percentage area of nerve fibres containing nNOS, VIP or SP-IR than adults, with the decrease in nerve fibre density occurring from birth to 30 years. Circular muscle thickness increased between 12 and 30 years. Total nerve fibre area remained constant, while the muscle increased in thickness. CONCLUSIONS & INFERENCES: In human sigmoid colon circular muscle, there are reductions in nNOS-, VIP- and SP-IR nerve fibre density with growth from newborn to late adolescence but little further change with aging. The reduction in nerve density is due to an increase in circular muscle thickness rather than a loss of nerve fibres.

Booster seat laws and child fatalities: a case-control study.

A case-control study examined, primarily, the association between booster seat laws and fatalities among children in frontal collisions and, secondarily, the association between booster seat laws and reported restraint use, and restraint use and child fatalities. Children who died in a crash in the US were cases, and children who survived a fatal crash were controls. Subjects were child passengers (4-8 years old) in the Fatality Analysis Reporting System Database, 1995-2005. In states with a booster seat law, children were less likely to die than in states without a law (OR 0.80; 95% CI 0.66 to 0.98). They were also more likely to be restrained (adjusted OR 1.59; 95% CI 1.21 to 2.09) and were more likely to be correctly restrained (adjusted OR 4.44; 95% CI 3.18 to 6.20). It is concluded that booster seat laws are associated with a decrease in child deaths and an increase in correct restraint use among children involved in a fatal crash in the USA.

First-trimester increase in oxidative stress and risk of small-for-gestational-age fetus.

OBJECTIVE: Investigation of increased oxidative stress in early pregnancy and association with an increased risk of small-for-gestational-age (SGA) fetus. DESIGN: Longitudinal case-control study. SETTING: University Hospitals of Leicester NHS Trust, Leicester, UK. POPULATION: Low-risk pregnant women with no current or pre-existing medical illness were recruited at a large teaching hospital from 2004 to 2006. METHODS: Recruitment performed at the time of the dating ultrasound scan (12+/-2 weeks of gestation). Spot urine samples collected at 12+/-2 and 28+/-2 weeks of gestation were analysed for 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) by liquid chromatography with tandem mass spectrometry). SGA was defined as birthweight <10th centile based on customised centile calculator (www.gestation.net). This identified the cases (n=55), whereas controls (n=55) were mothers whose babies were appropriate for gestational age (AGA, birthweight 10th-90th centile). Statistical analysis was performed using GraphPad Prism v.5. The relationship between maternal urinary 8-oxodG at different gestations and customised SGA was investigated by nonparametric tests. MAIN OUTCOME MEASURES: Customised SGA and AGA pregnancies. RESULTS: Urinary 8-oxodG concentrations were significantly increased in pregnancies with subsequent SGA compared with concentrations in normal pregnancies; 12 weeks: 2.8 (interquartile range [IQR] 1.96-3.67) versus 2.2 (IQR 1.26-3.28) pmol 8-oxodG/micromol creatinine (P=0.0007); 28 weeks: 2.21 (IQR 1.67-3.14) versus 1.68 (IQR 1.16-2.82) pmol 8-oxodG/micromol creatinine (P<0.0002). Concentrations decreased significantly between week 12 and 28 (P=0.04 and P=0.02 for controls and cases). CONCLUSIONS: In this study, urinary 8-oxodG at 12 and 28 weeks were elevated in SGA compared with AGA pregnancies. This may reflect early placental changes predating clinical features of SGA.

Preclinical toxicokinetic evaluation of phortress [2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole lysylamide dihydrochloride] in two rodent species.

BACKGROUND AND AIMS: The 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole prodrug Phortress exerts potent and selective antitumour activity in vitro and in vivo. Preclinical toxicokinetic studies in 2 rodent species were undertaken to determine Phortress' maximum tolerated dose and advise a safe starting dose for clinical evaluation. METHODS: Plasma pharmacokinetic parameters were determined by high-performance liquid chromatography and fluorescence detection following Phortress administration to mice (10 mg/kg, intravenously on days 1 and 8). Phortress (20 mg/kg, on days 1 and 8) was administered to CYP1A1/betaGAL reporter mice; tissues were examined macro- and microscopically. Toxicological and pharmacodynamic endpoints were examined in organs of rodents receiving Phortress (10 mg/kg or 20 mg/kg, on days 1 and 8). CYP1A1 expression and Phortress-derived DNA adducts were determined in lungs and livers (on days 11 and 36). RESULTS: No accumulation of Phortress was detected in murine plasma. beta-Galactosidase activity inferred Phortress-derived induction of cyp1a1 transcription in the livers of transgenic mice; no total body weight loss was encountered in these animals. However, a fall in lung:body weight and kidney:body weight ratios, raised serum alkaline phosphatase levels and hepatic histopathological disturbances in animals receiving 20 mg/kg Phortress indicate organ sites of potential toxicity. CYP1A1 protein was induced transiently in the lungs of both species and in the livers of rats. Elimination of hepatic DNA adducts and rat pulmonary adducts was evident; however, murine pulmonary adducts persisted. CONCLUSION: Rodent preclinical toxicology established that mice represent the more sensitive rodent species, resolving a maximum tolerated dose of 10 mg/kg Phortress.

Effect of vitamin levels on biomarkers of exposure and oxidative damage-the EXPAH study.

DNA adducts are markers of carcinogen exposure and of their biological effect; they have been shown to be related to mutagenesis, and therefore they could be a predictive biomarker of human cancer. The objective of this study was to assess if there is a relationship between vitamins A, C, and E, which are known to play a significant role as free radical scavengers and antioxidant agents, and biomarkers of genotoxicity and oxidative stress. Three hundred and fifty-six subjects from Czech Republic, Slovak Republic and Bulgaria, who completed a questionnaire on dietary information and had a measurement of plasma A, C, E vitamins, DNA adduct levels (benzo[a]pyrene (B[a]P) and bulky (DNA-Tot) DNA adducts) and oxidative damage (cyclic pyrimidopurinone N-1,N2 malondialdehyde-2 deoxyguanosine (M1dG) and 8-oxo-7,8-dihydro-2_deoxyguanosine (8-oxodG)) were analyzed. A significant inverse correlation was observed between plasma vitamin levels and both benzo[a]pyrene (B[a]P) and bulky DNA adducts. Vitamin A was also significantly inversely correlated with M1dG, a marker of oxidative damage. The associations were stronger in non-smokers than in smokers. Dietary intake of certain antioxidants such as vitamins is associated with reduced levels of markers of DNA damage (B[a]P and DNA-Tot) and oxidation (M1dG and 8-oxodG) measured in peripheral white blood cells. This could contribute to the protective role of such a dietary pattern on cancer risk. The protective effect of dietary vitamins is less evident in smokers.

Expanding global HIV treatment: case studies from the field.

In the last 25 years, human immunodeficiency virus (HIV) has become the leading infectious killer of adults globally, with an estimated 44 million people infected with the virus worldwide. Most of these individuals live in poor regions of the world, particularly sub-Saharan Africa. Although a great deal of work has been done in identifying and treating individuals with the disease, there has been little action to date to address the complex socioeconomic factors that lie at the heart of this global pandemic. Understanding and responding to such factors is of paramount importance if HIV infection is to be managed in a meaningful way. This article explores the social context of people living with HIV in three different geographic and epidemiologic settings and highlights the social factors that shape and define an individual's risk of acquiring HIV. It also discusses unique programs aimed at addressing the complex realities of the world in which HIV thrives. These programs can act as models of HIV prevention and treatment.

Treating multidrug-resistant tuberculosis in Tomsk, Russia: developing programs that address the linkage between poverty and disease.

Tuberculosis (TB) and multidrug-resistant TB (MDR-TB) are diseases of poverty. Because Mycobacterium tuberculosis exists predominantly in a social space often defined by poverty and its comorbidities--overcrowded or congregate living conditions, substance dependence or abuse, and lack of access to proper health services, to name a few--the biology of this organism and of TB drug resistance is intimately linked to the social world in which patients live. This association is demonstrated in Russia, where political changes in the 1990s resulted in increased socioeconomic inequality and a breakdown in health services. The effect on TB and MDR-TB is reflected both in terms of a rise in TB and MDR-TB incidence and increased morbidity and mortality associated with the disease. We present the case example of Tomsk Oblast to delineate how poverty contributed to a growing MDR-TB epidemic and increasing socioeconomic barriers to successful care, even when available. The MDR-TB pilot project implemented in Tomsk addressed both programmatic and socioeconomic factors associated with unfavorable outcomes. The result has been a strengthening of the overall TB control program in the region and improved case-holding for the most vulnerable patients. The model of MDR-TB care in Tomsk is applicable for other resource-poor settings facing challenges to TB and MDR-TB control.

Styrene-oxide N-terminal valine haemoglobin adducts as biomarkers of occupational exposure to styrene.

Styrene is widely used in the production of various plastics, synthetic rubber and resins. Occupational exposure occurs mainly via inhalation and relatively high exposure occurs due to its use in manual application techniques. The aim of this study was to evaluate if SO-Hb adducts are a suitable biomarker for assessing occupational exposure to styrene. Seventy-five reinforced plastic workers and 77 control subjects were studied. In the selected population the main urinary styrene metabolites and the styrene oxide N-terminal valine (SO-Hb) adducts in human globin were quantified. The levels of SO-Hb adducts were significantly higher (p<0.01) in the exposed subjects (5.98pmol/g globin) when compared with controls (2.59pmol/g globin) and a significant difference was found in levels of SO-Hb adducts between non-smokers and smokers among the control group. From our data we conclude that SO-Hb adduct measurement is a sensitive and specific means of assessing exposure to styrene at the occupational and environmental level.

Adverse reactions among patients being treated for MDR-TB in Tomsk, Russia.

BACKGROUND AND SIGNIFICANCE: Treatment of multidrug-resistant tuberculosis (MDR-TB) is challenging because of the toxicity of second-line medications. Little is known about whether adverse events impact treatment outcome. METHODS: We conducted a retrospective case series of 244 MDR-TB patients enrolled in Tomsk between 10 September 2000 and 10 September 2002. Adverse reactions were determined by laboratory data and/or clinical criteria. A multiple logistic regression model was performed to determine whether the occurrence of adverse reactions was associated with poor treatment outcome. RESULTS: In this cohort, 76.0% were cured, 6.6% failed, 4.9% died and 11.5% defaulted. Adverse events were observed in 73.3% of patients, occurring in 74.8% of patients who were adherent (taking at least 80% of prescribed doses) and 59.1% of non-adherent individuals (P = 0.11). The impact of adverse events on outcome was modified by non-adherence; among adherent patients, the occurrence of any adverse reaction was associated with treatment cure (adjusted odds ratio 3.24, 95% confidence interval 1.56-6.70). CONCLUSION: Adverse reactions occurred frequently in MDR-TB patients in Tomsk, Russia, but did not negatively impact treatment outcome. The occurrence of adverse reactions among adherent patients was associated with treatment cure.

Styrene-oxide N-terminal valine haemoglobin adducts in reinforced plastic workers: possible influence of genetic polymorphism of drug-metabolising enzymes.

Styrene is one of the most important organic chemicals used worldwide. In humans, styrene metabolism involves oxidation by cytochrome P450 monooxygenases (CYPs) to styrene-7,8-oxide, an epoxide thought to be responsible for the genotoxic effects of styrene exposure, and detoxification by means of epoxide hydrolase (mEH) and glutathione S-transferases (GSTs). The objective of this study was to investigate if genetic polymorphisms of metabolic enzymes modulate the level of urinary styrene metabolites and styrene oxide adducts with N-terminal valine of human globin (SO-Hb) in 75 workers occupationally exposed to styrene and 77 unexposed controls. The mean air concentration of styrene in the breathing zone of workers (30.4ppm) was higher than the threshold limit value of 20ppm recommended by the American Conference of Governmental Industrial Hygienists (ACGIH), and the biological exposure index adopted by the ACGIH for exposure to styrene prior to the next shift (MA+PGA=400mg/g creatinine) was exceeded, indicating that styrene exposure for this group of workers was higher than recommended. A highly significant correlation was observed between styrene concentration in the breathing zone and the MA+PGA in urine of workers (r=0.85, P<0.001). The levels of SO-Hb adducts in exposed workers were significantly increased as compared with controls, although no difference was observed between subjects stratified as high and medium exposure categories based on MA+PGA excretion. Regarding the effect of the genetic polymorphisms we found that the level of SO-Hb adducts might be modulated by the predicted mEH enzymatic activity in the exposed workers. From our data we conclude that SO-Hb adduct measurement is a complementary method to MA+PG measurement for assessing exposure to styrene at occupational and environmental levels, which reflects a more extensive exposure period.

In vitro genotoxicity of PAH mixtures and organic extract from urban air particles part II: human cell lines.

Principal aims of this study were at first, to find a relevant human derived cell line to investigate the genotoxic potential of PAH-containing complex mixtures and second, to use this cell system for the analysis of DNA adduct forming activity of organic compounds bound onto PM10 particles. Particles were collected by high volume air samplers during summer and winter periods in three European cities (Prague, Kosice, and Sofia), representing different levels of air pollution. The genotoxic potential of extractable organic matter (EOM) was compared with the genotoxic potential of individual carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) as well as their artificial mixtures. Metabolically competent human hepatoma HepG2 cells, confluent cultures of human diploid lung fibroblasts (HEL), and the human monocytic leukemia cell line THP-1 were used as models. DNA adducts were analyzed by (32)P-postlabeling. The total DNA adduct levels induced in HepG2 cells after exposure to EOMs were higher than in HEL cells treated under the same conditions (15-190 versus 2-15adducts/10(8) nucleotides, in HepG2 and HEL cells, respectively). THP-1 cells exhibited the lowest DNA adduct forming activity induced by EOMs (1.5-3.7adducts/10(8) nucleotides). A direct correlation between total DNA adduct levels and c-PAH content in EOM was found for all EOMs in HepG2 cells incubated with 50microg EOM/ml (R=0.88; p=0.0192). This correlation was even slightly stronger when B[a]P content in EOMs and B[a]P-like adduct spots were analyzed (R=0.90; p=0.016). As THP-1 cells possess a limited metabolic capacity for most c-PAHs to form DNA reactive intermediates and are also more susceptible to toxic effects of PAHs and various EOM components, this cell line seemed to be an inappropriate system for genotoxicity studies of PAH-containing complex mixtures. The seasonal variability of genotoxic potential of extracts was stronger than variability among the three localities studied. In HepG2 cells, the highest DNA adduct levels were induced by EOM collected in Prague in the winter period, followed by Sofia and Kosice. However, in the summer sampling period, the order was quite opposite: Kosice>Sofia>Prague. When the EOM content per m(3) of air was taken into consideration in order to compare real exposures of humans to genotoxic compounds in all three localities, extracts from respirable dust particles collected in Sofia exhibited the highest genotoxicity regardless of the sampling period. The results indicate that most of DNA adducts detected in cells incubated with EOMs have their origin in low concentrations of c-PAHs representing 0.03-0.17% of EOM total mass. Finally, our results suggest that HepG2 cells have a metabolic capacity for PAHs similar to human hepatocytes and represent therefore the best in vitro model for investigating the genotoxic potential of complex mixtures containing PAHs among the three cell lines tested in this study.