Circulatory system disease mortality and occupational exposure to radon progeny in the cohort of Newfoundland Fluorspar Miners between 1950 and 2016.

OBJECTIVES: Exposure to ionizing radiation may increase the risk of circulatory diseases, including heart disease. A limited number of cohort studies of underground miners have investigated these associations. We previously reported a positive but non-statistically significant association between radon progeny and heart disease in a cohort of Newfoundland fluorspar miners. In this study, we report updated findings that incorporate 15 additional years of follow-up. METHODS: The cohort included 2050 miners who worked in the fluorspar mines from 1933 to 1978. Statistics Canada linked the personal identifying data of the miners to Canadian mortality data to identify deaths from 1950 to 2016. We used previously derived individual-level estimates of annual radon progeny exposure in working-level months. Cumulative exposure was categorized into quantiles. We estimated relative risks and their 95% confidence intervals using Poisson regression for deaths from circulatory, ischemic heart disease and acute myocardial infarction. Relative risks were adjusted for attained age, calendar year, and the average number of cigarettes smoked daily. RESULTS: Relative to the Newfoundland male population, the standardized mortality ratio for circulatory disease in this cohort was 0.82 (95% CI 0.74-0.91). Those in the highest quantile of cumulative radon progeny exposure had a relative risk of circulatory disease mortality of 1.03 (95% CI 0.76-1.40) compared to those in the lowest quantile. The corresponding estimates for ischemic disease and acute myocardial infarction were 0.99 (95% CI 0.66-1.48), and 1.39 (95% CI 0.84-2.30), respectively. CONCLUSIONS: Our findings do not support the hypothesis that occupational exposure to radon progeny increases the risk of circulatory disease.

Association between exposures to radon and γ-ray radiation and histologic type of lung cancer in Eldorado uranium mining and milling workers from Canada.

BACKGROUND: The authors assessed the association between radon decay products (RDP) exposure and histologic types of incident lung cancer in a cohort of 16,752 (91.6% male) Eldorado uranium workers who were first employed from 1932 to 1980 and were followed through 1969-1999. METHODS: Substantially revised identifying information and RDP exposures were obtained on workers from the Port Radium and Beaverlodge uranium mines and from the Port Hope radium and uranium refinery and processing facility in Canada. Poisson regression was conducted using the National Research Council's Biological Effects of Ionizing Radiation (BEIR) VI-type models to estimate the risks of lung cancer by histologic type from RDP exposures and γ-ray doses. RESULTS: Lung cancer incidence was significantly higher in workers compared with the general Canadian male population. Radiation risks of lung cancer for all histologic types (n = 594; 34% squamous cell, 16% small cell, 17% adenocarcinoma) increased with increasing RDP exposure, with no indication of curvature in the dose response (excess relative risk per 100 working level months = 0.61; 95% confidence interval, 0.39-0.91). Radiation risks did not differ by histologic type (p = .144). The best-fitting BEIR VI-type model included adjustments for the significant modifying effects of time since exposure, exposure rate, and attained age. The addition of γ-ray doses to the model with RDP exposures improved the model fit, but the risk estimates remained unchanged. CONCLUSIONS: The first analysis of radiation risks of lung cancer histologic types in the Eldorado cohort supported the use of BEIR VI-type models to predict the future risk of histologic types of lung cancer from past and current RDP exposures. LAY SUMMARY: Lung cancer survival depends strongly on the cell type of lung cancer. The best survival rates are for patients who have the adenocarcinoma type. This study included 16,752 Eldorado uranium workers who were exposed to radon and γ-ray radiation during 1932-1980, were alive in 1969, and were followed for the development of new lung cancer during 1969-1999. One third of all lung cancers were of the squamous cell type, whereas the adenocarcinoma and small cell types accounted for less than 20% each. Radiation risks of lung cancer among men increased significantly with increasing radon exposure for all cell types, with the highest risks estimated for small cell and squamous cell lung cancers.

Low radon exposures and lung cancer risk: joint analysis of the Czech, French, and Beaverlodge cohorts of uranium miners.

It is well established that high radon exposures increase the risk of lung cancer mortality. The effects of low occupational exposures and the factors that confound and modify this risk are not clear and are needed to inform current radiation protection of miners. The risk of lung cancer mortality at low radon exposures (< 100 working-level months) was assessed in the joint cohort analysis of Czech, French, and Canadian uranium miners, employed in 1953 or later. Statistical analysis was based on linear Poisson regression modeling with grouped cohort survival data. Two sensitivity analyses were used to assess potential confounding from tobacco smoking. A statistically significant linear relationship between radon exposure and lung cancer mortality was found. The excess relative risk per working-level month was 0.022 (95% confidence intervals: 0.013-0.034), based on 408 lung cancer deaths and 394,236 person-years of risk. Time since exposure was a statistically significant modifier; risk decreased with increasing time since exposure. A tendency for a decrease in risk with increasing attained age was observed, but this was not statistically significant. Exposure rate was not found to be a modifier of the excess relative risk. The potential confounding effect of tobacco smoking was estimated to be small and did not substantially change the radon-lung cancer mortality risk estimates. This joint cohort analysis provides strong evidence for an increased risk of lung cancer mortality from low occupational radon exposures. The results suggest that radiation protection measures continue to be important among current uranium miners.

Heparosan-coated liposomes for drug delivery.

Liposomal encapsulation is a useful drug delivery strategy for small molecules, especially chemotherapeutic agents such as doxorubicin. Doxil® is a doxorubicin-containing liposome ("dox-liposome") that passively targets drug to tumors while reducing side effects caused by free drug permeating and poisoning healthy tissues. Polyethylene glycol (PEG) is the hydrophilic coating of Doxil® that protects the formulation from triggering the mononuclear phagocyte system (MPS). Evading the MPS prolongs dox-liposome circulation time thus increasing drug deposition at the tumor site. However, multiple doses of Doxil® sometimes activate an anti-PEG immune response that enhances liposome clearance from circulation and causes hypersensitivity, further limiting its effectiveness against disease. These side effects constrain the utility of PEG-coated liposomes in certain populations, justifying the need for investigation into alternative coatings that could improve drug delivery for better patient quality of life and outcome. We hypothesized that heparosan (HEP; [-4-GlcA-ß1-4-GlcNAc-α1-]n) may serve as a PEG alternative for coating liposomes. HEP is a natural precursor to heparin biosynthesis in mammals. Also, bacteria expressing an HEP extracellular capsule during infection escape detection and are recognized as "self," not a foreign threat. By analogy, coating drug-carrying liposomes with HEP should camouflage the delivery vehicle from the MPS, extending circulation time and potentially avoiding immune-mediated clearance. In this study, we characterize the postmodification insertion of HEP-lipids into liposomes by dynamic light scattering and coarse-grain computer modeling, test HEP-lipid immunogenicity in rats, and compare the efficacy of drug delivered by HEP-coated liposomes to PEG-coated liposomes in a human breast cancer xenograft mouse model.

Expanding glycosaminoglycan chemical space: towards the creation of sulfated analogs, novel polymers and chimeric constructs.

Glycosaminoglycans (GAGs) have therapeutic potential in areas ranging from angiogenesis, inflammation, hemostasis and cancer. GAG bioactivity is conferred by intrinsic structural features, such as disaccharide composition, glycosidic linkages and sulfation pattern. Unfortunately, the in vitro enzymatic synthesis of defined GAGs is quite restricted by a limited understanding of current GAG synthases and modifying enzymes. Our work provides insights into GAG-active enzymes through the creation of sulfated oligosaccharides, a new polysaccharide and chimeric polymers. We show that a C6-sulfonated uridine diphospho (UDP)-glucose (Glc) derivative, sulfoquinovose, can be used as an uronic acid donor, but not as a hexosamine donor, to cap hyaluronan (HA) chains by the HA synthase from the microbe Pasteurella multocida. However, the two heparosan (HEP) synthases from the same species, PmHS1 and PmHS2, could not employ the UDP-sulfoquinovose under similar conditions. Serendipitously, we found that PmHS2 co-polymerized Glc with glucuronic acid (GlcA), creating a novel HEP-like polymer we named hepbiuronic acid [-4-GlcAß1-4-Glcα1-]n. In addition, we created chimeric block polymers composed of both HA and HEP segments; in these reactions GlcA-, but not N-acetylglucosamine-(GlcNAc), terminated GAG acceptors were recognized by their noncognate synthase for further extension, likely due to the common ß-linkage connecting GlcA to GlcNAc in both of these GAGs. Overall, these GAG constructs provide new tools for studying biology and offer potential for future sugar-based therapeutics.

Aging Promotes Sirtuin 3-Dependent Cartilage Superoxide Dismutase 2 Acetylation and Osteoarthritis.

OBJECTIVE: To quantify functional age-related changes in the cartilage antioxidant network in order to discover novel mediators of cartilage oxidative stress and osteoarthritis (OA) pathophysiology. METHODS: We evaluated histopathologic changes of knee OA in 10-, 20-, and 30-month-old male F344BN rats and analyzed cartilage oxidation according to the ratio of reduced to oxidized glutathione. Antioxidant gene expression and protein abundance were analyzed by quantitative reverse transcription-polymerase chain reaction and selected reaction-monitoring mass spectrometry, respectively. Superoxide dismutase 2 (SOD2) activity and acetylation were analyzed by colorimetric enzyme assays and Western blotting, respectively. We examined human OA cartilage to evaluate the clinical relevance of SOD2 acetylation, and we tested age-related changes in the mitochondrial deacetylase sirtuin 3 (SIRT-3) in rats and mice. RESULTS: Cartilage oxidation and OA severity in F344BN rats increased with age and were associated with an increase in SOD2 expression and protein abundance. However, SOD2-specific activity decreased with age due to elevated posttranslational lysine acetylation. Consistent with these findings, SIRT-3 levels decreased substantially with age, and treatment with SIRT-3 increased SOD2 activity in an age-dependent manner. SOD2 was also acetylated in human OA cartilage, and activity was increased with SIRT-3 treatment. Moreover, in C57BL/6J mice, cartilage SIRT-3 expression decreased with age, and whole-body deletion of SIRT-3 accelerated the development of knee OA. CONCLUSION: Our results show that SIRT-3 mediates age-related changes in cartilage redox regulation and protects against early-stage OA. These findings suggest that mitochondrial acetylation promotes OA and that restoration of SIRT-3 in aging cartilage may improve cartilage resistance to oxidative stress by rescuing acetylation-dependent inhibition of SOD2 activity.

Mitochondrial respiration and redox coupling in articular chondrocytes.

INTRODUCTION: Chondrocytes rely primarily on glycolysis to meet cellular energy needs, but recent studies implicate impaired mitochondrial function in osteoarthritis (OA) pathogenesis. Our objectives were to investigate the ability of chondrocytes to upregulate mitochondrial respiration when challenged with a nutrient stress and determine the effect on mediators of chondrocyte oxidative homeostasis. METHODS: Primary bovine chondrocytes were isolated and cultured in alginate beads. Mitochondrial respiration was stimulated by culturing cells with galactose-supplemented media for a period of 1 or 5 days. Metabolic flexibility was assessed by measuring metabolite and enzymatic biomarkers of glycolytic and mitochondrial metabolism. Oxidative homeostasis was assessed by measuring (1) cellular glutathione content and redox homeostasis, (2) rates of nitric oxide and superoxide production, and (3) the abundance and activity of cellular anti-oxidant proteins, especially the mitochondrial isoform of superoxide dismutase (SOD2). The regulatory role of hypoxia-inducible factor 2α (HIF-2α) in mediating the metabolic and redox responses was evaluated by chemical stabilization with cobalt chloride (CoCl2). RESULTS: After 5 days of galactose culture, lactate production and lactate dehydrogenase activity were reduced by 92% (P<0.0001) and 28% (P=0.051), respectively. Conversely, basal oxygen consumption increased 35% (P=0.042) without increasing mitochondrial content. Glutathione redox homeostasis was unaffected by galactose culture. However, the production of nitric oxide and superoxide and the expression and activity of SOD2 were significantly reduced after 5 days in galactose culture. Nuclear protein expression and gene expression of HIF-2α, a transcription factor for SOD2, were significantly downregulated (more than twofold; P<0.05) with galactose culture. CoCl2-mediated stabilization of HIF-2α during the initial galactose response phase attenuated the reduction in SOD2 (P=0.028) and increased cell death (P=0.003). CONCLUSIONS: Chondrocyte metabolic flexibility promotes cell survival during a nutrient stress by upregulating mitochondrial respiration and reducing the rate of reactive nitrogen and oxygen species production. These changes are coupled to a substantial reduction in the expression and activity of the mitochondrial anti-oxidant SOD2 and its pro-catabolic transcription factor HIF-2α, suggesting that an improved understanding of physiologic triggers of chondrocyte metabolic flexibility may provide new insight into the etiology of OA.

Leukemia, lymphoma and multiple myeloma mortality (1950-1999) and incidence (1969-1999) in the Eldorado uranium workers cohort.

Uranium workers are chronically exposed to low levels of radon decay products (RDP) and gamma (γ) radiation. Risks of leukemia from acute and high doses of γ-radiation are well-characterized, but risks from lower doses and dose-rates and from RDP exposures are controversial. Few studies have evaluated risks of other hematologic cancers in uranium workers. The purpose of this study was to analyze radiation-related risks of hematologic cancers in the cohort of Eldorado uranium miners and processors first employed in 1932-1980 in relation to cumulative RDP exposures and γ-ray doses. The average cumulative RDP exposure was 100.2 working level months and the average cumulative whole-body γ-radiation dose was 52.2 millisievert. We identified 101 deaths and 160 cases of hematologic cancers in the cohort. Overall, male workers had lower mortality and cancer incidence rates for all outcomes compared with the general Canadian male population, a likely healthy worker effect. No statistically significant association between RDP exposure or γ-ray doses, or a combination of both, and mortality or incidence of any hematologic cancer was found. We observed consistent but non-statistically significant increases in risks of chronic lymphocytic leukemia (CLL) and Hodgkin lymphoma (HL) incidence and non-Hodgkin lymphoma (NHL) mortality with increasing γ-ray doses. These findings are consistent with recent studies of increased risks of CLL and NHL incidence after γ-radiation exposure. Further research is necessary to understand risks of other hematologic cancers from low-dose exposures to γ-radiation.

Mortality (1950-1999) and cancer incidence (1969-1999) of workers in the Port Hope cohort study exposed to a unique combination of radium, uranium and γ-ray doses.

OBJECTIVES: Uranium processing workers are exposed to uranium and radium compounds from the ore dust and to γ-ray radiation, but less to radon decay products (RDP), typical of the uranium miners. We examined the risks of these exposures in a cohort of workers from Port Hope radium and uranium refinery and processing plant. DESIGN: A retrospective cohort study with carefully documented exposures, which allowed separation of those with primary exposures to radium and uranium. SETTINGS: Port Hope, Ontario, Canada, uranium processors with no mining experience. PARTICIPANTS: 3000 male and female workers first employed (1932-1980) and followed for mortality (1950-1999) and cancer incidence (1969-1999). OUTCOME MEASURES: Cohort mortality and incidence were compared with the general Canadian population. Poisson regression was used to evaluate the association between cumulative RDP exposures and γ-ray doses and causes of death and cancers potentially related to radium and uranium processing. RESULTS: Overall, workers had lower mortality and cancer incidence compared with the general Canadian population. In analyses restricted to men (n=2645), the person-year weighted mean cumulative RDP exposure was 15.9 working level months (WLM) and the mean cumulative whole-body γ-ray dose was 134.4 millisieverts. We observed small, non-statistically significant increases in radiation risks of mortality and incidence of lung cancer due to RDP exposures (excess relative risks/100 WLM=0.21, 95% CI <-0.45 to 1.59 and 0.77, 95% CI <-0.19 to 3.39, respectively), with similar risks for those exposed to radium and uranium. All other causes of death and cancer incidence were not significantly associated with RDP exposures or γ-ray doses or a combination of both. CONCLUSIONS: In one of the largest cohort studies of workers exposed to radium, uranium and γ-ray doses, no significant radiation-associated risks were observed for any cancer site or cause of death. Continued follow-up and pooling with other cohorts of workers exposed to by-products of radium and uranium processing could provide valuable insight into occupational risks and suspected differences in risk with uranium miners.

Lung cancer mortality (1950-1999) among Eldorado uranium workers: a comparison of models of carcinogenesis and empirical excess risk models.

Lung cancer mortality after exposure to radon decay products (RDP) among 16,236 male Eldorado uranium workers was analyzed. Male workers from the Beaverlodge and Port Radium uranium mines and the Port Hope radium and uranium refinery and processing facility who were first employed between 1932 and 1980 were followed up from 1950 to 1999. A total of 618 lung cancer deaths were observed. The analysis compared the results of the biologically-based two-stage clonal expansion (TSCE) model to the empirical excess risk model. The spontaneous clonal expansion rate of pre-malignant cells was reduced at older ages under the assumptions of the TSCE model. Exposure to RDP was associated with increase in the clonal expansion rate during exposure but not afterwards. The increase was stronger for lower exposure rates. A radiation-induced bystander effect could be a possible explanation for such an exposure response. Results on excess risks were compared to a linear dose-response parametric excess risk model with attained age, time since exposure and dose rate as effect modifiers. In all models the excess relative risk decreased with increasing attained age, increasing time since exposure and increasing exposure rate. Large model uncertainties were found in particular for small exposure rates.

Mortality (1950-1999) and cancer incidence (1969-1999) in the cohort of Eldorado uranium workers.

This study assessed the relationship between radon decay product (RDP) exposure and mortality and cancer incidence in a cohort of 17,660 Eldorado uranium workers first employed in 1932-1980 and followed up through 1999. The analysis was based on substantially revised identifying information and dosimetry for workers from the Beaverlodge and Port Radium uranium mines and for the first time includes workers from a radium and uranium refinery and processing facility in Port Hope, Canada. Overall, male workers had lower mortality rates of all causes and all cancers and lower incidence rates of all cancers compared with the general Canadian male population, a likely healthy worker effect. Individual cancer rates were also reduced except for lung cancer mortality (SMR  =  1.31, P < 0.001) and incidence (SIR  =  1.23, P < 0.001). The excess relative risk per 100 WLM (ERR/100 WLM) of lung cancer mortality (N  =  618, ERR/100 WLM  =  0.55, 95% CI: 0.37, 0.78, P < 0.01) and incidence (N  =  626, ERR/100 WLM  =  0.55, 95% CI: 0.37, 0.81, P < 0.001) increased linearly with increasing RDP exposure. Adjustment for effect modification by time since exposure, exposure rate and age at risk resulted in comparable estimates of risk of lung cancer for all three uranium worksites. RDP exposures and γ-ray doses were not associated with any other cancer site or other cause of death. The risk estimates are in agreement with the results of the pooled analysis of 11 miner cohorts and more recent studies of uranium workers. The current analysis provides more precise risk estimates and compares the findings from the mortality study with the incidence study. Future follow-up of the cohort and joint analysis with other uranium miners' studies should shed more light on the effects of low RDP exposures as experienced by current workers as well as help to understand and address the health risks associated with residential radon.

Coronary heart disease mortality and radon exposure in the Newfoundland fluorspar miners' cohort, 1950-2001.

Kreuzer and coworkers recently reported no association between cumulative exposure to radiation and death from cardiovascular disease in a cohort of German uranium miners. Here, we report on the relationship between cumulative exposure to radon progeny and coronary heart disease among Newfoundland fluorspar miners. Previous analyses in this cohort found elevated death rates from coronary heart disease among those with higher cumulative radon exposure. However, this finding was based on a relatively small number of deaths and was not statistically significant. Since then, the follow-up of this cohort has been extended by 10 years until the end of 2001. Among the 2,070 miners in our study, 267 died from coronary heart disease. There was no trend evident between cumulative exposure to radon and the relative risk of death from coronary heart disease (P = 0.63). This finding was unchanged after adjusting for the lifetime smoking status that was available for approximately 54% of the cohort. Similarly, the cumulative radon exposure was found to be unrelated to deaths of the circulatory system, acute myocardial infarction, and cerebrovascular disease. These findings are consistent with those recently reported by Kreuzer and colleagues. We share their view that uncontrolled confounding for other coronary heart disease risk factors hinders the interpretation of the risk estimates.