Lung permeability, antioxidant status, and NO2 inhalation: a selenium supplementation study in rats

Little is known about antioxidant status, selenium status in particular, and lung response to NO2, which acts as a proinflammatory air pollutant. The effects of a low selenium diet (1.3 microg Se/d) with or without selenium supplementation were therefore studied in 128 Wistar rats, 2 mo old, male exposed to either acute (50 ppm, 30 min), intermittent subacute (5 ppm, 6 h/d, 5 d), intermittent long-term NO2 (1 ppm, 10 ppm, 6 h/d, 5 d/wk, 28 d), or normal atmospheric air (controls). Following sacrifice, measurements of lipid peroxidation (thiobarbituric acid-reactive substances, chemiluminescence), antioxidative protective enzymes (glutathione peroxidase [GPx], superoxide dismutase [SOD], glutathione S-transferase [GST], ceruloplasmin), lung damage (lactate dehydrogenase, alkaline and acid phosphatases), lung permeability (total protein, albumin), and inflammation (cell populations), along with the determination of new biomarkers such as CC16 (Clara-cell protein), were performed in serum and bronchoalveolar lavage fluid (BALF). While selenium-supplemented animals had increased GPx activity in serum prior to inhalation experiments, they also had decreased BALF CC16, blood SOD, and GST levels. Nevertheless, the protective role of normal selenium status with respect to NO2 lung toxicity was evident both for long-term and acute exposures, as the increase in BALF total proteins and corresponding decrease in serum (indicating increased lung permeability) was significantly more pronounced in selenium-deficient animals. During the various inhalation experiments, serum CC16 demonstrated its key role as an early marker of increased lung permeability. These findings corroborate the important role of selenium status in NO2 oxidative damage modulation, but also indicate, in view of its negative impact on CC16, a natural anti-inflammatory and immunosuppressor, that caution should be used prior to advocating selenium supplementation.

Mechanistically identified suitable biomarkers of exposure, effect, and susceptibility for silicosis and coal-worker's pneumoconiosis: a comprehensive review

Clinical detection of silicosis is currently dependent on radiological and lung function abnormalities, both late manifestations of disease. Markers of prediction and early detection of pneumoconiosis are imperative for the implementation of timely intervention strategies. Understanding the underlying mechanisms of the etiology of coal workers pneumoconiosis (CWP) and silicosis was essential in proposing numerous biomarkers that have been evaluated to assess effects following exposure to crystalline silica and/or coal mine dust. Human validation studies have substantiated some of these proposed biomarkers and argued in favor of their use as biomarkers for crystalline silica- and CWP-induced pneumoconiosis. A number of "ideal" biological markers of effect were identified, namely, Clara cell protein-16 (CC16) (serum), tumor necrosis factor-alpha (TNF-alpha) (monocyte release), interleukin-8 (IL-8) (monocyte release), reactive oxygen species (ROS) measurement by chemiluminescence (neutrophil release), 8-isoprostanes (serum), total antioxidant levels measured by total equivalent antioxidant capacity (TEAC), glutathione, glutathione peroxidase activity, glutathione S-transferase activity, and platelet-derived growth factor (PDGF) (serum). TNF-alpha polymorphism (blood cellular DNA) was identified as a biomarker of susceptibility. Further studies are planned to test the validity and feasibility of these biomarkers to detect either high exposure to crystalline silica and early silicosis or susceptibility to silicosis in gold miners in South Africa.

Signal transduction pathways involved in particulate matter induced relaxation in rat aorta--spontaneous hypertensive versus Wistar Kyoto rats

Previously we reported that in vivo exposure to ambient particulate matter (PM) induces vasodilatation in rat aorta. The purpose of the current study was to investigate the intracellular messengers involved in PM-elicited vasodilatation in aortas from spontaneous hypertensive (SHR) and normotensive (WKY) rats.

METHODS

The contribution of three different intracellular pathways, i.e. (1) the NO-cGMP pathway, (2) prostanoids signaling and (3) endothelial hyperpolarisation factors were evaluated by using specific inhibitors (NS2028, Diclofenac and high K-concentration/17-ODYA, respectively). Using antagonists of capsaicin- or histamine receptors we tested potential interactions of PM with these receptors. Particle suspensions (EHC-93), particle filtrates (particle-free) and Cu(2+)- or Zn(2+)-containing solutions were used to obtain cumulative dose-response curves of relaxation in normal and endothelium-denuded rings.

RESULTS

Our present data confirm that PM and its soluble components elicit an endothelium-independent vasodilatation in rat aorta rings. The response is mainly linked to the activation of soluble guanylate cyclase (sGC), since its inhibition by NS2028 almost abolished relaxation. Indeed PM suspensions stimulated cGMP production in purified isolated sGC. Neither the receptor nor their signaling pathways played a significant role in the direct relaxation by PM or metals. Vasodilatation responses were significantly higher in SHR than WKY control rats.

CONCLUSION

Our data demonstrate that PM elicits a dose-dependent vasodilatation via activation of sGC in vascular smooth muscles. PM components, including soluble transition metals play a major role in this response. The stronger effect in SHR rats is in accordance with the observation that acute effects of PM are mainly seen in patients with underlying cardiovascular diseases.

Platinum levels in nasal lavage fluid as a biomarker for traffic-related exposure and inflammation in children

Platinum (Pt) is a well-known constituent of particles emitted by catalytic converters during car operation. To evaluate Pt as a potential marker for traffic related particle exposure, we investigated Pt content along with metals vanadium (V) and chromium (Cr) in coarse and fine particulate matter (PM), sampled in four areas with different traffic density, as well as in the nasal lavage (NAL) of 67 children (average age: 6 years) living in these areas. The different sites were characterised by significant differences in air pollutants including PM, NO, NO(2), CO and Cr, but differences in V or Pt were absent. No significant differences in neutrophil and epithelial cell counts or concentrations of the neutrophil chemoattractant interleukin-8 (IL-8) were found in the NAL of children living in the different areas. In addition, the concentrations of V, Cr and Pt, which were detectable in 64%, 73% and 93% of the individuals, respectively, did not differ between the different locations. However, in the NAL of the children, a significant correlation between Pt and the number of neutrophils/ml (r=0.40, p<0.001) as well as of epithelial cells/ml (r=0.41, p<0.001) was found. No relation was present between nasal inflammation and nasal Cr levels, whereas a relatively weak association was observed between V and epithelial cells counts (r=0.30, p=0.018). In conclusion, our data suggests a role for nasal lavage Pt as a candidate biomarker for traffic-related PM, which is able to induce inflammation in the upper respiratory tract.

Temporal variation of hydroxyl radical generation and 8-hydroxy-2'-deoxyguanosine formation by coarse and fine particulate matter

AIMS

To determine the induction of 8-hydroxy-2'-deoxyguanosine (8-OHdG) by fine (<2.5 microm) and coarse (10-2.5 microm) particulate matter (PM) sampled over time at one sampling location, and to relate the observed effects to the hydroxyl radical (*OH) generating activities and transition metal content of these samples, and to meteorological parameters.

METHODS

Weekly samples of coarse and fine PM were analysed for H(2)O(2) dependent *OH formation using electron spin resonance (ESR) and formation of 8-OHdG in calf thymus DNA using an immuno-dotblot assay. Immunocytochemistry was used to determine 8-OHdG formation in A549 human epithelial lung cells. To determine temporal effects, samples from six weeks in summer and six weeks in autumn/winter were compared using ESR and the dotblot assay. Concentrations of leachable V, Cr, Fe, Ni, and Cu were determined by inductively coupled plasma mass spectrometry.

RESULTS

Both PM fractions elicited *OH generation as well as 8-OHdG formation in calf thymus DNA and in A549 cells. 8-OHdG formation in the naked DNA was significantly related to *OH generation, but not to metal concentrations except for copper. A significantly higher *OH generation was observed for coarse PM, but not fine PM collected during the autumn/winter season; this was not due to differences in sampled mass or metal content. Specific weather conditions under which increased *OH formation in the coarse mode was observed suggest that other, as yet unknown, anthropogenic components might affect the radical generating capacity of PM.

CONCLUSIONS

Both coarse and fine PM are able to generate *OH, and induce formation of 8-OHdG. When considered at equal mass, *OH formation shows considerable variability with regard to the fraction of PM, as well as the sampling season. The toxicological implications of this heterogeneity in *OH formation by PM, as can be easily determined by ESR, need further investigation.

Respiratory symptoms, lung function, and nasal cellularity in Indonesian wood workers: a dose-response analysis

OBJECTIVES

It was hypothesised that inflammation plays a dominant part in the respiratory effects of exposure to wood dust. The purpose of this study was to relate the nasal inflammatory responses of workers exposed to meranti wood dust to (a) levels of exposure, (b) respiratory symptoms and (c) respiratory function.

METHODS

A cross sectional study was carried out in 1997 in a woodworking plant that used mainly meranti, among 982 workers exposed to different concentrations of wood dust. Personal sampling (n=243) of inhalable dust measurements indicated mean exposure in specific jobs, and enabled classification of 930 workers in three exposure classes (<2, 2-5, and >5 mg/m(3)) based on job title. Questionnaires were used to screen respiratory symptoms in the entire population. Lung function was measured with two different techniques, conventional flow-volume curves and the forced oscillation technique. Nasal lavage was done to assess inflammation in the upper respiratory tract.

RESULTS

A negative trend between years of employment and most flow-volume variables was found in men, but not in women workers. Current exposure, however, was not related to spirometric outcomes, respiratory symptoms, or nasal cellularity. Some impedance variables were related to current exposure but also with better function at higher exposure.

CONCLUSIONS

Exposure to meranti wood dust did not cause an inflammation in the upper respiratory tract nor an increase of respiratory symptoms or decrease of lung function. These data do not corroborate the hypothesis that inflammation plays a part in airway obstruction induced by wood dust.