| Dust is air pollutant. The occupational dusts usually come from industries of mining, ceramic processing and glass manufacturing, which not only pollute the environment atmosphere, but also affect the health of employees. A number of studies have suggested that long-term exposure to occupational dusts is associated directly or indirectly with the development of occupational diseases including silicosis in workers. Currently, more attention is being paid to the health effect of dusts on cardiovascular system since some studies have indicated that small-sized dusts and components of dusts, especially ultrafine particles can cross the air-blood barrier and then translocate into the systemic circulation after inhaling.Accumulating evidences from epidemiological studies have shown that increased morbidity and mortality from cardiovascular diseases is related to both short- and long-term exposure to dusts. Unfortunately, until now the mechanisms responsible for these cardiovascular effects have not been well-elucidated. The main hypotheses include oxidative stress and inflammation accompanying dust exposure, change of blood constituent and autonomic imbalance, while immune dysfunction and inflammation have been much investigated. The injury of dust on vascular endothelial cell has been demonstrated as the onset of cardiovascular injury and diseases.Our previous epidemiological studies have shown that exposure to different types of dusts, for example tungsten mines, iron miners, tin mines, pottery factories, could result in increased cardiovascular mortality. And the mortalities from cardiovascular diseases are different in workers from different industries.To estimate cardiovascular toxicity of dusts, we collected occupational dusts from four pottery factories and four tungsten mines in JiangXi and HuNan province, different sizes of quartz and carbon black dusts as experimental dusts. Vascular endothelial cells were used as target cells. The study was divided into two parts: (1) the cytotoxicity of occupational dusts from pottery factories and tungsten mines on vascular endothelial cells (2) the effects of size on the cytotoxicity of dust on vascular endothelial cells.Part 1 The cytotoxicity of occupational dusts from pottery factories and tungsten mines on vascular endothelial cellsObjective: To assess direct adverse effects of occupational dusts from pottery factories and tungsten mines on vascular endothelial cells in vitro test.Methods: Human umbilical vein endothelial cells (HUVEC) were used as target cells. HUVEC were then treated with respirable dusts from workplaces in pottery factories (named as A,B,C,D) and tungsten mines (named as E,F,G,H) in concentrations of 25, 50, 100, 200 and 400μg/ml for 24 h. China Standard Quartz was used as control. LDH activity, cell viability, the release of NO and TNF-αwere determined to assess the biological responses of the dust particles.Results: (1) Dose-response relationships between the dust concentrations and the enhancement of LDH activity were found in dusts from all pottery factories, tungsten mines and China Standard Quartz. There were differences of LDH activity induced by dust particle from different pottery factories or tungsten mines. LDH activities induced by occupational dusts of pottery factories were similar to those of tungsten mines, and lower than that of China Standard Quartz.(2) The cell viability decreased with the increase of dust concentrations from 25μg/ml to 400μg/ml. A bit stronger decrease in cell viability was induced by dusts from pottery factories compared with dusts from tungsten mines. Compared with China Standard Quartz, high decreased cell viability was seen in the occupational dusts from pottery factories and tungsten mines at lower dust concentrations (25, 50, 100μg/ml), while at higher dust concentrations (200, 400μg/ml), occupational dusts induced a bit lower decrease of cell viability than that of control.(3) Dose-response relationships between the dust concentrations and release of NO were found in dusts from all pottery factories and tungsten mines. No significant difference of release of NO was observed among the occupational dusts and China Standard Quartz, except for dusts from one mine, which induced higher release of NO than China Standard Quartz.(4) Dose-response relationships between the dust concentrations and release of TNF-αwere found in dusts from all pottery factories and tungsten mines. Occupational dusts induced similar release of TNF-αto China Standard Quartz at lower dust concentrations (25, 50, 100μg/ml). However, higher level of TNF-αwas induced by China Standard Quartz when compared with dusts from workplaces at concentrations of 200 and 400μg/ml.Part 2 The effects of size on the cytotoxicity of dusts on vascular endothelial cellsObjective: To compare biological responses induced by dusts of different size on vascular endothelial cells in vitro test, and further estimate influence of dust diameter on cardiovascular toxicity.Methods: Human umbilical vein endothelial cells (HUVEC) were used as target cells. HUVEC were then treated with dusts of different size in concentrations of 25, 50, 100, 200 and 400μg/ml for 24 h. We collected two types of dust including European Standard Quartz (DQ12) which has three sizes (DQPM1, <1μm; DQPM3~5, 3~5μm; DQPM5, 5μm), and carbon black dust (CB) which has two sizes (CB0.1, <0.1μm; CB1, <1μm). China Standard Quartz was used as control. LDH activity, cell viability, the release of NO and TNF-αwere determined to assess the biological responses of the dusts.Results: (1) Dose-response relationships between the dust concentrations and the enhancement of LDH activity were found in dusts of all sizes. For DQ12, the dust of smaller size induced stronger LDH activity. The ability to increase LDH activity induced by CB0.1 was stronger than CB1 at lower dust concentrations (25, 50, 100μg/ml), while at higher dust concentrations (200, 400μg/ml), CB1 surpassed CB0.1.(2) The cell viability decreased with the increase of dust concentrations from 25μg/ml to 400μg/ml. Among DQ12 samples, the ability of DQPM1 was the strongest, and DQPM5 was the weakest. The ability to decrease cell viability induced by CB0.1 was a bit stronger than CB1 at lower dust concentrations (25, 50, 100μg/ml), while at higher dust concentrations (200, 400μg/ml), CB1 surpassed CB0.1.(3) Dose-response relationships between the dust concentrations and releases of NO were found in dusts of all sizes. No significant difference of NO release was observed among DQ12. And CB0.1 induced a little higher release of NO than CB1 at all dust concentrations.(4) Dose-response relationships between the dust concentrations and release of TNF-αwere found in dusts of all sizes. Significant higher release of TNF-αwas found in dust of smaller size among DQ12 than that of big size dust particles. CB0.1 induced higher release of TNF-αthan CB1 at all other dust concentrations, except that at concentrations of 400μg/ml.In conclusion, occupational dusts from four pottery factories and four tungsten mines could induce the cells injury and the releases of NO and TNF-αfrom HUVEC. And this was in concord with the high cardiovascular mortality in workers exposed to these occupational dusts. The mechanisms responsible for these cardiovascular effects probably included oxidative stress and inflammation.The compositions of dusts play important effect on the shape and function of cell. No significant difference of release of NO and TNF-αwas observed between the occupational dusts and China Standard Quartz, which indicated that except for free silica, other compositions existing in dusts could promote injury on vascular endothelial cells.The injury on vascular endothelial cells was in relation to size of dusts. Dusts of smaller size could induce stronger injury on cells, higher releases of NO and TNF-αfrom vascular endothelial cells. However, size was not the only influencing factors of cardiovascular toxicity. We also observed that dusts of various types (DQPM1 and CB1), even same type of dust from various sources (China Standard Quartz and DQPM3~5), performed different cytotoxicity on HUVEC, although dust sizes were equivalent. This evidence indicated that biological responses of dust should be combined effects of multiple characteristics. Above all, our study could provide basic data for further prevention from dusts and diseases. |
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