Circulating natural killer cells in retired asbestos cement workers

Biological responses to asbestos inhalation and pathogenesis of asbestos-related benign and malignant disease

Asbestos comprises a group of fibrous minerals that are naturally occurring in the environment. Because of its natural properties, asbestos gained popularity for commercial applications in the late 19th century and was used throughout the majority of the 20th century, with predominant use in the construction, automotive, and shipbuilding industries. Asbestos has been linked to a spectrum of pulmonary diseases, such as pleural fibrosis and plaques, asbestosis, benign asbestos pleural effusion, small cell lung carcinoma, non-small cell lung carcinoma, and malignant mesothelioma. There are several mechanisms through which asbestos can lead to both benign and malignant disease, and they include alterations at the chromosomal level, activation of oncogenes, loss of tumor suppressor genes, alterations in cellular signal transduction pathways, generation of reactive oxygen and nitrogen species, and direct mechanical damage to cells from asbestos fibers. While known risk factors exist for the development of asbestos-related malignancies, there are currently no effective means to determine which asbestos-exposed patients will develop malignancy and which will not. There are also no established screening strategies to detect asbestos-related malignancies in patients who have a history of asbestos exposure. In this article, we present a case that highlights the different biological responses in human hosts to asbestos exposure.

Cytokine alteration and speculated immunological pathophysiology in silicosis and asbestos-related diseases

This review is partly composed of the presentation "Cytokine alteration and speculated immunological pathophysiology in silicosis and asbestos-related diseases" delivered during the symposium "Biological effects of fibrous and particulate substances and related areas" organized by the Study Group of Fibrous and Particulate Studies of the Japanese Society of Hygiene and held at the 78th Annual Meeting in Kumamoto, Japan. In this review, we briefly introduce the results of recent immunological analysis using the plasma of silica and asbestos-exposed patients diagnosed with silicosis, pleural plaque, or malignant mesothelioma. Thereafter, experimental background and speculation concerning the immunological pathophysiology of silica and asbestos-exposed patients are discussed.

Diagnostic relevance of the determination of lymphocyte subpopulations in environmental medicine

Earlier hopes that determination of lymphocyte subpopulations might become a strong diagnostic tool in environmental medicine have not been fulfilled in recent years. Analysis of the scientific literature rather shows that there are only few examples for environmental exposures causing reproducible shifts of lymphocyte subpopulations. Moreover, current knowledge suggests that "environmental diseases" are not associated with characteristic changes of subpopulation patterns. If lymphocyte subpopulations are analyzed, each diagnostic step, including indication, sample handling, analytic procedure and data-interpretation, should adhere to good quality criteria. Taking all together, the determination of lymphocyte subpopulations in the context of environmental medicine comes under category IV of the criteria of the Commission for Methods and Quality Assurance in Environmental Medicine of the German federal health authority (Robert Koch-Institute; RKI): "A procedure cannot be recommended because there is not sufficient information to justify it" (here: no solid trends in epidemiological examinations), "and because theoretical considerations speak against an application" (here: high physiological variability and missing exposure or substance specificity).

Plasma malondialdehyde and erythrocyte glutathione levels in workers with cement dust-exposure [corrected]

BACKGROUND

Chronic exposure to cement dust has been reported to lead to several health problems. Acute and chronic exposure to quartz are associated with the provocation of an inflammatory response and triggers an extensive host defense mechanism. These inflammatory reactions result in the secretions of cytokines, eicosanoids, lytic enzymes, chemotactic factors and reactive oxygen species (ROS). This study was designed to investigate the plasma oxidant and antioxidant status in cement plant workers.

METHODS

Forty-eight non-smoker volunteer male cement plant workers and 28 non-smoker volunteer office male workers (control) aged between 27 and 56 were recruited. The concentrations of plasma malondialdehyde (p-MDA), and the erythrocyte glutathione (GSH) were measured in both groups. Pulmonary function tests, and exposed free silica fractions were also measured in different working places.

RESULTS

Plasma MDA levels were found to be increased, while erythrocyte GSH levels to be decreased in cement workers (p < 0.001). Although no statistically significance was observed, pulmonary function tests were found to be decreased in cement workers. A negative correlation was observed between MDA levels and FEV1 and FEV1% levels. Although no statistically significant difference was found, MDA levels were found to be increased and GSH levels decreased in the working areas where silisium dioxide concentrations were found to be higher.

CONCLUSIONS

In conclusion, the results presented in this study show that direct measurement of plasma MDA and erythrocyte GSH could be accepted as an indicator of oxidative injury in workers exposed to cement dust.

Immunomodulatory effects of mineral fibres in occupationally exposed workers

In the context of a large-scale molecular epidemiology study, the possible immunomodulatory effects of mineral fibres, in workers occupationally exposed to asbestos, rockwool and glass fibres, were examined. In each plant, 61, 98 and 80 exposed workers and 21, 43 or 36 control clerical subjects, respectively, were recruited. In the case of the asbestos-exposed subjects, an additional town-control group of 49 people was included. Evidence of pulmonary fibrosis was found in 42% of the asbestos-exposed workers, while evidence of pleural fibrosis was found in 24%. The asbestos-exposed cohort had significantly decreased forced vital capacity of lungs as well as forced expiratory volume per first second. Our findings indicate that exposure to all three types of fibres examined modulates to different degrees the immune response. Suppression of T-cell immunity and to a lesser extent, B-cell immunity was found in the case of workers from a former asbestos cement plant, while stimulation of T-cell response was observed in rockwool workers, and stimulation of T- and B-cell response was seen in glass fibre workers. Depression of the percentage of lymphocyte subpopulation of CD 16+56 (natural killer cells) in peripheral blood was found in glass fibre workers. Statistical analysis showed increased levels of proinflammatory cytokines (IL-6 asbestos; IL-8 all three fibres), expression of adhesion molecule L-selectin on granulocytes and monocytes (asbestos), levels of soluble adhesion molecules (SAMs) in sera (ICAM-1 all three fibres; E-selectin glass fibres), increased levels of immunoglobulin E (asbestos and rockwool) and elevated expression of activation markers on eosinophils (CD66b asbestos, glass fibres; CD69 asbestos). Significant correlations were observed between lymphocyte proliferation and markers of DNA damage and repair. Increased levels of proinflammatory cytokines, SAMs, immunoglobulin E and elevated expression of activation markers on eosinophils was found in people with symptoms of hypersensitivity and an elevated inflammatory status.

The level of antioxidant enzymes, plasma vitamins C and E in cement plant workers

BACKGROUND

Chronic exposure to cement dust has been reported to lead to several health problems. This study was designed to investigate the plasma oxidant and antioxidant status in cement plant workers and control subjects.

METHODS

Twenty-eight volunteer male cement plant workers and 30 volunteer office male workers (control) aged 29-54 years participated. The concentration of plasma vitamin C (P-VC), plasma vitamin E (P-VE), plasma malondialdehyde (P-MDA), and the activity of erythrocyte superoxide dismutase (E-SOD), plasma glutathione peroxidase (P-GSH-Px), and some serum biochemical parameters were measured in both groups.

RESULTS

The levels of MDA (175%), ALT (61%), and AST (39%) were significantly increased, while total RBC count (12%), Hb (11%) vitamin E (51%), C (35%), SOD (44%), and GSH-Px (51%) activities were markedly decreased, and the levels of urea, protein, and albumin triglyceride and cholesterol were almost the same in cement plant workers versus the control subjects.

CONCLUSION

Cement workers are exposed to more oxidative stress compared to control subjects. To overcome these oxidative stresses, supplementation of antioxidant vitamins, such as alpha-tocopherol and ascorbic acid, may be beneficial. In addition, proper precaution to protect workers could prevent serious health problems.

5-lipoxygenase regulates malignant mesothelial cell survival: involvement of vascular endothelial growth factor

Evidence indicates that lipoxygenases (LO) may play a role in cancer cell survival. We show that human malignant pleural mesothelial (MM) cells, but not normal mesothelial (NM) cells, express a catalytically active 5-LO. Pharmacological or genetic inhibition of MM cell 5-LO determined nucleosome formation and induced a DNA fragmentation pattern typical of apoptosis. This was completely reversed by exogenously added 5(S)-HETE but not by 12(S)-, 15(S)-HETE, or leukotriene (LT)B4. A 5-LO antisense oligonucleotide potently and time-dependently reduced vascular endothelial growth factor (VEGF) mRNA and constitutive VEGF accumulation in the conditioned media of MM cells. When NM cells were transfected with a 5-LO cDNA, basal and arachidonic acid-induced VEGF formation increased consistently by 6- and 12-fold, respectively. This was associated with a significant increase in DNA synthesis that was counteracted by a specific anti-VEGF antibody. Arachidonic acid and 5(S)-HETE also potently stimulated the activity of a VEGF promoter construct. Thus, 5-LO is a key regulator of MM cell proliferation and survival via a VEGF-related circuit.