Lung inflammation after exposure to nonfibrous silicates increases with chelatable [Fe3+]

Annual trends in occurrence of submicron particles in ambient air and health risk posed by particle bound metals

Risk analysis is highly important in toxicology and public health studies. Health risk related to exposure to toxic metals of PM1 was assessed. Concentrations of 13 heavy metals, adsorbed to submicron particulate matter PM1 were experimentally examined but only 12 metals were found at detectable levels inside IIT Kanpur campus in 2008-2009 for all months excluding June and October. A total of 90 samples collected for 8 h sampling time by a single stage round nozzle, grease impaction substrate based impactor type PM1 sampler were analysed by ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry). Results showed daily average PM1 concentration is 102.46 ± 35.9 μg/m(3) and metal concentration followed the trend: Ca > Fe > Mg > Zn > Pb > Cu > Cr > Ni > Se > Cd > V > As. Contamination level assessment using geo-accumulation index showed Ca, Fe and Mg exhibited non contamination whereas metals like Cr, Zn, As, Cd, Pb, Se, Ni and Cu exhibited ranges from moderate to extreme contamination. Ingestion is found to be the major exposure pathway for heavy metals. Non-carcinogenic health risk assessment for Pb, Cd and Cr (HI > 1) signified strong chances of adverse impact on children whereas adults are well under safe limit. Cancer Risk for adults and children followed the same decreasing order, Cr(VI)>Cd > Ni > As > Pb. It was found to be higher than permissible limits (10(-6)) for adults and children both.

Degradation of damaged proteins: the main function of the 20S proteasome

Cellular proteins are exposed to oxidative modification and other forms of damage through oxidative stress and disease, and as a consequence of aging. This oxidative damage results in loss and/or modification of protein function, which in turn compromises cell function and may even cause cell death. Therefore, the removal of damaged proteins is extremely important for the maintenance of normal cell function. The 20S proteasome functions primarily as a system for removal of such damaged proteins. Unlike the 26S proteasome, the 20S proteasome exhibits a high degree of selectivity in degrading the oxidized, or otherwise damaged, forms of cell proteins. The 20S proteasome is broadly distributed throughout the cell and has a range of specific functions in different organelles, which are controlled through a number of proteasome regulators. It is also activated, and its synthesis is induced, under conditions of enhanced oxidative stress, thus permitting greater removal of damaged proteins.

Toxic elements in tobacco and in cigarette smoke: inflammation and sensitization

Biochemically and pathologically, there is strong evidence for both atopic and nonatopic airway sensitization, hyperresponsiveness, and inflammation as a consequence of exposure to tobacco mainstream or sidestream smoke particulate. There is growing evidence for the relation between exposure to mainstream and sidestream smoke and diseases resulting from reactive oxidant challenge and inflammation directly as a consequence of the combined activity of neutrophils, macrophages, dendritic cells, eosinophils, basophils, as a humoral immunological consequence of sensitization, and that the metal components of the particulate play a role in adjuvant effects. As an end consequence, carcinogenicity is a known outcome of chronic inflammation. Smokeless tobacco has been evaluated by the IARC as a group 1 carcinogen. Of the many harmful constituents in smokeless tobacco, oral tissue metallothionein gradients suggest that metals contribute to the toxicity from smokeless tobacco use and possibly sensitization. This work reviews and examines work on probable contributions of toxic metals from tobacco and smoke to pathology observed as a consequence of smoking and the use of smokeless tobacco.

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.

Surface reactivity, cytotoxicity, and transforming potency of iron-covered compared to untreated refractory ceramic fibers

Untreated and iron-coated refractory ceramic fibers (RCFs) 1, 3, and 4 were examined for their potential to generate free radicals and to catalyze hydrogen peroxide decomposition in cell-free assays and were compared for cytotoxic and transforming potencies in Syrian hamster embryo (SHE) cell system. Coating with a high quantity of iron increased the capability of RCFs to generate hydroxyl radicals and to catalyze the decomposition of hydrogen peroxide. In the SHE cells, the untreated RCFs had varying ability to induce inhibition of cell proliferation, cytotoxicity (as measured by the colony-forming efficiency, CE) and morphological transformation, in a concentration-dependent manner. According to cytotoxic and transforming potencies, they ranged as follows: RCF3 > RCF1 > RCF4. The lethal concentration 50 (LC50; decrease of CE to 50% of controls after 7 d of treatment) expressed per number of RCF3 and RCF1/cm(2) of culture dish was 2.5 x 10(4) and 3.7 x 10(4), respectively, whereas RCF4 was not cytotoxic up to the highest concentration tested (23.7 x 10(4) fibers/cm(2)). At LC50, RCF3 was 1.4-fold more transforming than RCF1, and the weakest, RCF4, induced less than 1% transformation. Iron coating of RCF1 and RCF3 markedly attenuated their cytostatic, cytotoxic, and transforming potencies without a linear concentration-transformation relationship. In contrast, iron coating of RCF4 affected slightly its low transforming potency, although the growth inhibitory effect was reduced. The observed decrease rather than increase in the cytotoxic and transforming potencies of the active samples RCF1 and RCF3 by their coating with large amounts of ferric iron suggests that it is not the quantity or any form of iron on the surface of fibers but the iron, even in trace, in a particular redox and coordinate state that might play a role in the fiber's surface reactivity with regard to the biological material. Surface chemical functions involved in the interaction with the cell could be inactivated by the deposition of a high quantity of Fe(III) on the surface of fibers. Physicochemical studies correlated to biological effects is an approach for understanding the properties of solids related to a given biological response and for elucidating the cellular and molecular mechanisms.

Iron regulates xanthine oxidase activity in the lung

The iron chelator deferoxamine has been reported to inhibit both xanthine oxidase (XO) and xanthine dehydrogenase activity, but the relationship of this effect to the availability of iron in the cellular and tissue environment remains unexplored. XO and total xanthine oxidoreductase activity in cultured V79 cells was increased with exposure to ferric ammonium sulfate and inhibited by deferoxamine. Lung XO and total xanthine oxidoreductase activities were reduced in rats fed an iron-depleted diet and increased in rats supplemented with iron, without change in the ratio of XO to total oxidoreductase. Intratracheal injection of an iron salt or silica-iron, but not aluminum salts or silica-zinc, significantly increased rat lung XO and total xanthine oxidoreductase activities, immunoreactive xanthine oxidoreductase, and the concentration of urate in bronchoalveolar fluid. These results suggest the possibility that the production of uric acid, a major chelator of iron in extracellular fluid, is directly influenced by iron-mediated regulation of the expression and/or activity of its enzymatic source, xanthine oxidase.

Importance of soluble metals and reactive oxygen species for cytokine release induced by mineral particles

The mechanisms for particle-induced health effects are not well understood, but inflammation seems to be of importance. Previously, we have shown that stone quarry particles with various mineral and metal content differed widely in potency to induce inflammatory cytokines (IL-6, IL-8 and TNF-alpha) in different types of lung cells. In this study we investigated if the observed cytokine responses were associated with the soluble or insoluble components of the stone particles and if there was a relationship between the differential cytokine release and generation of reactive oxygen species (ROS). Exposure of the human alveolar cell line A549 to the different particle leachates (pH 7.4 and 4.0) did not induce corresponding differential increases in the IL-8 release as observed with whole particles. Increase in ROS production, measured as dichlorofluorescein-fluorescence, was only demonstrated after exposure of A549 cells to the pH 4.0 extract from basalt. Furthermore, generation of ROS was found in neutrophils but not in A549 cells and primary macrophages after exposure to suspensions of the solid particles. However, no obvious differences in potency among the different particles were demonstrated. In summary, other mechanisms than particle-induced ROS formation seem to be responsible for the differential induction of IL-8. Furthermore, our findings indicate that the differential ability to induce IL-8 release in lung cells is attributed to the solid components of the stone particles.