Project description:Previous studies have shown that smoking induces oxidative stress and inflammation, known factors that coincide with the development and progression of lung toxicity in response to crystalline silica exposure. Nevertheless, the precise role of tobacco smoke exposure on the lung response to tobacco smoke exposure and the underlying mechanisms remain largely elusive. Therefore, the objective of the present study was to determine the effect of smoking, if any, on silica-induced pulmonary toxicity and the underlying molecular mechanisms. Pulmonary toxicity and lung gene expression profiles were determined in rats exposed to air, crystalline silica, tobacco smoke, or crystalline silica plus tobacco smoke. Silica exposure resulted in significant pulmonary toxicity which was further exacerbated by tobacco smoke exposure in the rats. Significant differences in the gene expression profiles were detected in the lungs of the rats exposed to tobacco smoke, silica or a combination of both compared with the air exposed control rats.
Project description:Our previous studies have shown that tobacco smoke exposure exacerbated the lung response to crystalline silica exposure in rats. The objective of the present study, a follow-up to our previous study, was to determine the effect of tobacco smoke exposure cessation on the lung response to crystalline silica exposure in the rats. Rats were exposed to air, crystalline silica (1 week followed by a 1 year progression/recovery period with no exposure), tobacco smoke (6 months of exposure followed by 6 months of recovery with no exposure), or crystalline silica (1 week) plus tobacco smoke (6 months of exposure followed by 6 months of recovery with no exposure). Lung toxicity was determined at the end of the 1-year progression/recovery period in all 4 groups of the rats. Silica exposure resulted in significant lung toxicity which was further exacerbated by tobacco smoke exposure in the rats. Cessation of cigarette smoke exposure did not result in reversal of the silica-induced lung toxicity despite exacerbation of the toxicity by tobacco smoke.
Project description:Previous studies have shown that smoking induces oxidative stress and inflammation, known factors that coincide with the development and progression of silicosis. Nevertheless, the precise role of cigarette smoke exposure in silicosis and the underlying mechanisms are not clearly understood. Therefore, the objective of the present study was to determine the effect of smoking, if any, on silica-induced pulmonary response and the underlying mechanisms. Pulmonary toxicity and lung gene expression profiles were determined in male Fischer 344 rats exposed to air, crystalline silica, cigarette smoke or cigarette smoke plus crystalline silica. Silica exposure resulted in significant pulmonary toxicity which was further exacerbated by cigarette smoke exposure in the rats. Significant differences in the gene expression profiles were detected in the lungs of the rats exposed to cigarette smoke, silica or a combination of both compared with the control rats.
Project description:Exposure to crystalline silica results in serious health effects, most notably, silicosis and cancer. An understanding of the silica-induced lung toxicity is critical for the intervention and/or prevention of its adverse health effects. Rats were exposed by inhalation to air or crystalline silica (15 mg/m3, 6 hours/day for 5 days). At post-exposure time intervals of 1, 3, 6, 9, 12, and 18 months, the control and silica exposed rats were euthanized, and lung toxicity and gene expression profiles determined. Histological changes indicative of lung toxicity detected in the silica exposed rats included infiltration of neutrophils, thickening of alveolar epithelium, and fibrosis. Significant increases in lactate dehydrogenase activity, number of phagocytes, and inflammatory cytokine levels were detected in the bronchoalveolar lavage (BAL) obtained from the silica exposed rats compared with the corresponding time-matched controls. Significant changes in lung gene expression profiles, corresponding to the changes in the lung toxicity parameters analyzed, were detected in the silica exposed rats. The BAL parameters of toxicity and inflammation peaked at the 12-months post-exposure time interval and declined subsequently. However, lung fibrosis continued to progress being highest at the 18-month post-exposure time interval. These results suggest that inflammation may be required for the initiation but not for the progression and/or maintenance of lung fibrosis in response to silica exposure in the rats.
Project description:The effect, if any, of age on the pulmonary toxicity induced by Min-U-Sil 5 crystalline silica exposure was investigated in rats. As part of the study, the changes in global gene expression profiles in the blood and lungs of the animals were determined. To conduct these studies, to determine if age influences the pulmonary response to crystalline silica exposure, two different age groups of healthy, male F344 rats were used. In this study the old age group of rats (12 months old at the time of exposure) was exposed to either air or crystalline silica (Min-U-Sil 5) (15 mg/m3, 6 hours/day, 5 days) by whole body inhalation. The old age group of rats simulates a group of workers who would be 45 to 50 years old. At two crystalline silica post-exposure time periods (1-day and 6-months) animals were euthanized and pulmonary inflammatory, cytotoxic, and oxidant responses were determined. Analysis of bronchoalveolar lavage parameters of toxicity such as oxidant generation and inflammation revealed significant changes in pulmonary toxicity in the crystalline silica exposed rats compared with the time-matched, air exposed control rats. The blood gene expression profiles showed only minimal changes, at both the time points, in the crystalline silica exposed rats compared with the controls. Specifically, no genes were significantly differentially expressed (fold change >1.5 and FDR p<0.05) in the one-day post-exposure group and only 6 genes were significantly differentially expressed in the 6-month post-exposure group. However, the lung gene expression profiles showed substantial changes in the crystalline silica exposed animals at both one-day and 6-month post-exposure. Specifically, there were a total of 325 genes significantly differentially expressed (fold change >1.5 and FDR p<0.05) at the one-day post-exposure group and 3348 genes significantly differentially expressed at the 6-month post-exposure. The data obtained from the present study demonstrated that crystalline silica inhalation exposure, under the conditions employed in the present study, resulted in significant changes in lung toxicity parameters and lung gene expression profile in the rats at both 1-day and 6-month post-exposure.
Project description:Occupational exposure to crystalline silica results in serious health effects, most notably, silicosis and cancer. A proper understanding of the mechanism(s) underlying the initiation and progression of silica-induced pulmonary toxicity is critical for the intervention and/or prevention of the adverse health effects associated with crystalline silica exposure. Rats were exposed to crystalline silica by inhalation at a concentration of 15 mg/m3, 6 hours/day, 5 days/week for 3, 6 or 12 weeks. At the end of each exposure time point, toxicity and global gene expression changes were determined in the lungs. In general, silica exposure resulted in pulmonary toxicity that was dependent on the duration of silica exposure. A significant and silica exposure time-dependent increase in lactate dehydrogenase activity and accumulation of alveolar macrophages and infiltrating neutrophils in the bronchoalveolar lavage fluid suggested crystalline silica-induced pulmonary toxicity in the rats. Histological changes indicative of pulmonary toxicity were detectable only in the lungs of rats that were exposed to silica for 6- or 12-weeks. Minimal, sub-acute pulmonary inflammation consisting mainly of macrophage accumulation and infiltration of neutrophils was seen in 2 out of 8 rats in the 6-week silica exposure group. Chronic active inflammation, type II pneumocyte hyperplasia, and fibrosis were detected following 12-weeks of silica exposure in all rat lungs. In addition, crystalline silica was visible in the lungs of the rats belonging to the 12-week exposure group. A significant increase in the number of neutrophils seen in the blood indicated silica-induced systemic inflammation in the rats. Microarray analysis of the global gene expression profiles of the rat lungs detected significant differential expression (FDR p <0.05 and fold change >1.5) of 38, 77 and 99 genes in the rats exposed to silica for 3-, 6- and 12-weeks, respectively, compared to the time-matched controls. Bioinformatics analysis of the differentially expressed genes identified significant enrichment of functions, networks and pathways related to inflammation, cancer, oxidative stress, fibrosis and tissue remodeling in the lungs of the silica exposed rats. Collectively, the results of our study provided insights into the molecular mechanisms underlying pulmonary toxicity following sub-chronic exposure to silica in rats.
Project description:Occupational exposure to crystalline silica results in serious health effects, most notably, silicosis and cancer. A proper understanding of the mechanism(s) underlying the initiation and progression of silica-induced pulmonary toxicity is critical for the intervention and/or prevention of the adverse health effects associated with crystalline silica exposure. Rats were exposed to crystalline silica by inhalation at a concentration of 15 mg/m3, 6 hours/day, 5 days/week for 3, 6 or 12 weeks. At the end of each exposure time point, toxicity and global gene expression changes were determined in the lungs. In general, silica exposure resulted in pulmonary toxicity that was dependent on the duration of silica exposure. A significant and silica exposure time-dependent increase in lactate dehydrogenase activity and accumulation of alveolar macrophages and infiltrating neutrophils in the bronchoalveolar lavage fluid suggested crystalline silica-induced pulmonary toxicity in the rats. Histological changes indicative of pulmonary toxicity were detectable only in the lungs of rats that were exposed to silica for 6- or 12-weeks. Minimal, sub-acute pulmonary inflammation consisting mainly of macrophage accumulation and infiltration of neutrophils was seen in 2 out of 8 rats in the 6-week silica exposure group. Chronic active inflammation, type II pneumocyte hyperplasia, and fibrosis were detected following 12-weeks of silica exposure in all rat lungs. In addition, crystalline silica was visible in the lungs of the rats belonging to the 12-week exposure group. A significant increase in the number of neutrophils seen in the blood indicated silica-induced systemic inflammation in the rats. Microarray analysis of the global gene expression profiles of the rat lungs detected significant differential expression (FDR p <0.05 and fold change >1.5) of 38, 77 and 99 genes in the rats exposed to silica for 3-, 6- and 12-weeks, respectively, compared to the time-matched controls. Bioinformatics analysis of the differentially expressed genes identified significant enrichment of functions, networks and pathways related to inflammation, cancer, oxidative stress, fibrosis and tissue remodeling in the lungs of the silica exposed rats. Collectively, the results of our study provided insights into the molecular mechanisms underlying pulmonary toxicity following sub-chronic exposure to silica in rats. 36 samples were analyzed in this experiment. 6 rats were exposed to crystalline silica by inhalation 15 mg/m3, 6 hours/day, 5 days, 3 weeks. 6 rats were exposed to crystalline silica by inhalation 15 mg/m3, 6 hours/day, 5 days, 6 weeks. 6 rats were exposed to crystalline silica by inhalation 15 mg/m3, 6 hours/day, 5 days, 12 weeks. 18 rats served as controls (6 for each 3 week, 6 week, and 12 week exposure) and were exposed to air during treatment times. Lung gene expression profiling was performed using RNA isolated from rat lung samples.