Silicon dioxide-induced endoplasmic reticulum stress of alveolar macrophages and its role on the formation of silicosis fibrosis: a review article.

Silicosis is a chronic lung inflammatory disease induced by long-term inhalation of high concentrations of silicon dioxide (SiO2), characterized by pulmonary fibrosis. Inhalation of silica invades alveolar macrophages (AMs) and changes the micro-environment of the cell, resulting in abnormal morphology and dysfunction of the endoplasmic reticulum (ER). Once beyond the range of cell regulation, the endoplasmic reticulum stress (ERS) will occur, which will lead to cell damage, necrosis, and apoptosis, eventually causing silicosis fibrosis through various mechanisms. This is a complex and delicate process accompanied by various macrophage-derived cytokines. Unfortunately, the details have not been systematically summarized yet. In this review, we systematically introduce the basic two processes: the process of inducing ERS by inhaling SiO2 and the process of inducing pulmonary fibrosis by ERS. Moreover, the underlying mechanism of the above two sequential events is also be discussed. We conclude that the ERS of alveolar macrophages caused by silica dust are involved deeply in the pathogenesis of silicosis. Therefore, changing the states of SiO2-induced ERS of macrophage may be an attractive therapeutic target for silicosis fibrosis.

Altered M1/M2 polarization of alveolar macrophages is involved in the pathological responses of acute silicosis in rats in vivo.

Alveolar macrophages play a vital role in the development of acute silicosis, but the dynamic changes of M1 and/or M2 phenotypes have not been elucidated. In this study, acute silicosis models of rat were established by a one-time dusting method, and the rats were sacrificed after 1, 3, 7, 14, and 28 days. The polarity states of macrophages were assessed by measuring the M1/M2 marker genes of alveolar macrophages and the M1/M2 marker proteins in bronchoalveolar lavage fluid. The pathological changes of lung tissues were examined with hematoxylin and Eosin and Masson's trichrome staining. Our results showed that in the early stages, alveolar macrophages were mainly polarized into M1; with time, the polarization of M2 gradually became dominant. Microscopic sections showed significant pathological responses of inflammation and fibrosis. This work suggested that the alteration of alveolar macrophage polarization was involved in the lung pathologic responses to acute silicosis.

Location and dynamic changes of inflammation, fibrosis, and expression levels of related genes in SiO2-induced pulmonary fibrosis in rats in vivo.

Silicosis is a serious occupational disease characterized by pulmonary fibrosis, and its mechanism and progression have not been fully elucidated yet. In this study, silicosis models of rat were established by a one-time dusting method, and the rats were sacrificed after 30, 60, and 120 days (herein referred to as the 30, 60, and 120 days groups, respectively). The rats without dust exposure were used as the control. The lungs were removed to observe pathological changes using hematoxylin and eosin and Masson's trichrome staining and transmission electron microscopy, and the degree of collagen type I and III deposition in the lung was evaluated by enzyme-linked immunosorbent assay. The levels of malondialdehyde and superoxide dismutase were measured by spectrophotometry, and the expression levels of fibrosis-related genes (transforming growth factor beta 1, type I collagen, type III collagen) were assessed by real-time quantitative polymerase chain reaction. The results suggested that the rats in the model groups exhibited obvious collagen fibrosis and that the severity of the lung injury increased as the time after exposure to SiO2 increased. There was a significant response to lung inflammation in the model rats, especially in the 30 days group. The degree of lipid peroxidation in bronchoalveolar lavage fluid cells and lung tissues in experiment group rats significantly increased. Among the three fibrosis-related genes, transforming growth factor beta 1was elevated in both bronchoalveolar lavage fluid cells and lung tissues of the experiment group rats, while collagen type I and III were only elevated in lung tissues. Hence, we concluded that as silicosis progressed, inflammation, fibrosis, and the expression of fibrosis-related genes showed different time-dependent changes and that a number of causal relationships existed among them.

Effects of abnormal expression of fusion and fission genes on the morphology and function of lung macrophage mitochondria in SiO2-induced silicosis fibrosis in rats in vivo.

Silicosis is a serious occupational disease affecting millions of related workers. Many studies showed lung macrophages play an important role in the disease. However, the changes of macrophages are not fully characterized and the mechanisms need further investigations. The objectives of this work were to evaluate the effects of abnormal expression of fusion and fission genes on the morphology and function of lung macrophage mitochondria in SiO2-induced silicosis fibrosis in rats. In this study, the rats were injected with 1 mL of SiO2 suspension (100 mg/mL) into the lungs to establish silicosis models, and killed after 30, 60, and 120 days. The rats which were injected with normal saline (1 mL) into lungs were used as control. The lungs of rats were taken for pathological observation. Lung macrophages were collected to measure the number, activity, level of MDA and SOD, and relative content of fusion (Mfn1, Mfn2) and fission (Fis, DRP) genes. Subsequently, mitochondria were extracted from the macrophages to measure the changes of function, including MDA, SOD, ATP, and ATPase. We found that silica dust inhalation led to the proliferation of collagen fibers in the lung tissue. During this process, the number and activity of macrophages increased, the degree of lipid peroxidation increased, and the expression of mitochondrial fusion and fission genes was abnormal. Moreover, the mitochondrial lipid peroxidation level in macrophages increased, the production of ATP and the activity of ATPase decreased, and the abnormal forms of mitochondria occurred. Our results indicated that the morphology and function of mitochondria in macrophages changed during the progress of silicosis, which were related to the abnormal expression of fusion and fission genes.

[Effects of malathion on testicular spermatogenic function in rats].

OBJECTIVE: To investigate the effects of malathion on the testicular spermatogenic function of male rats and its working mechanism. METHODS: Forty specific pathogen-free male Wistar rats were randomly and equally divided into four groups: three exposure groups and a control group. Malathion was administered orally to male rats in the exposure groups at 33.75, 54, and 108 mg/kg (1/32 LD50, 1/20 LD50, and 1/10 LD50) for 60 days. Rats in the control group received an equal volume of water. The body weights of rats were measured after exposure. The organ weights and coefficients of the testes and epididymes were determined as soon as rats were sacrificed. The sperm motility, counts, and malformation rates were measured in the left epididymis. Histopathological changes, cell apoptosis, and the expression levels of Bcl-2/Bax in the testes of rats were observed using HE staining, terminal deoxynucleotidyl transferase-mediated dUPT-biotin nick end labeling, and immunohistochemistry SABC method. RESULTS: The body weights and the testis weights in the exposure groups were significantly lower than those in the control group (P < 0.01). The exposure groups had significantly lower sperm motility and significantly higher sperm malformation rates than the control group (P < 0.01). The sperm counts were significantly lower in the exposure groups than in the control group (P<0.01). The sperm counts and motility were negatively correlated with exposure dose (r = -0.81, P < 0.01; r = -0.51, P < 0.01), while the sperm malformation rate was positively correlated with exposure dose (r = 0.85, P 0.01). The exposure groups had significantly higher spermatogenic cell apoptosis rates than the control group (P<0.01). The expression level of Bax was significantly higher in the exposure groups than in the control group (P<0.01), while the expression level of Bcl-2 was significantly lower in the exposure groups than in the control group (P < 0.01). Histopathological examination of the testes showed degenerative changes in the seminiferous tubules at various doses along with the increase in malathion exposure dose. CONCLUSION: Malathion affects the testicular spermatogenic function of male rats and its working mechanism may involve cell apoptosis induced by down-regulation of Bcl-2 and up-regulation of Bax.

[Association between GSTP1, GSTM1, GSTT1 genetic polymorphisms and urinary styrene phenyl hydroxyethyl mercapturic acids level].

OBJECTIVE: To investigate the relationship between genetic polymorphisms of glutathione S-transferase P1 (GSTP1), glutathione S-transferase M1 (GSTM1), and glutathione S-transferase T1 (GSTT1) and urinary level of mercapturic acids of styrene (PHEMAs) in workers exposed to styrene. METHODS: One hundred and twenty-six workers exposed to styrene were selected as exposure group, and 150 workers without styrene exposure as the control group; all the workers came from a locomotive shell production factory in Shandong Province, China. The PCR-RFLP technique was applied to analyze the individual genetic polymorphisms of GSTP1; the multiplex PCR technique was used to investigate the genetic polymorphisms of GSTM1 and GSTT1; the relationship between genetic polymorphisms of GSTP1, GSTM1, and GSTT1 and urinary level of PHEMAs in workers exposed to styrene was statistically analyzed. RESULTS: The three genotypes investigated in the study had a distribution in accordance with the Chinese population. With exposure to high- concentration styrene, the individuals carrying GSTP1 (exon5, A105G) AA genotype (wildtype) had a significantly higher urinary level of PHEMAs (43.58 mg/g) than those with mutant genotypes AG (29.769 mg/g) and GG (30.245 mg/g); the urinary level of PHEMAs in individuals carrying wild-type GSTM1 genotype was significantly higher than that in individuals carrying deficient-type GSTM1 genotype (40.197 mg/g vs 28.866 mg/g, P < 0.05); no significant difference in urinary level of PHEMAs was found between individuals carrying wild-type GSTT1 genotype and deficient-type GSTT1 genotype. There was no significant relationship between the three gene polymorphisms and urinary level of PHEMAs in the control group. CONCLUSION: The genetic polymorphisms of GSTP1 and GSTM1 may be related to urinary level of PHEMAs in workers exposed to styrene.