2019 Volume 44 Issue 9 Pages 633-641
Asian Sand Dust-Particulate Matter (ASD-PM) aerosol brings large amounts of wind-eroded soil particles containing high concentrations of metallic components caused by industrialization and vehicles. Proinflammatory and cytotoxic cytokines trigger local inflammatory responses and cause a systematically high incidence of cardiovascular and other diseases. Tenascin C (Tn-C) is known to be expressed in damaged tissue or in a developmental stage of tissue. In this study, we examined the expression of Tn-C and Fibronectin in human cancer-cell lines and in liver tissue of mice treated with ASD-PM to investigate the inflammatory and cell-damage effects of ASD-PM. In our in vivo study, mice were intratracheally instilled with saline suspensions of ASD-PM particles. Instillation of these particles was repeated twice a week for 12 weeks and the liver tissues were stained with hematoxylin, eosin, and Masson’s trichrome, and we carried out an IF. Tn-C expression in liver tissues was detected by RT-PCR and western blot analysis. In the results, the expression of Tn-C increased in a dose-dependent manner in both RNA and Immunofluorescence assay (IF). In our in vitro study, A549 and Hep3B cell lines were incubated in culture media with Transforming Growth Factor-Beta1(TGF-β1) and ASD-PM. Immunofluorescence microscopy images showed a two times stronger expression of fluorescence in the ASD-treated group than in that treated with TGF-β1. They also showed a stronger expression of Tn-C in proportion to the concentration of ASD-PM. We confirmed that ASD-PM when inhaled formally migrated to other organs and induced Tn-C expression. ASD-PM containing metals causes expression of Tn-C in liver tissue in proportion to the concentration of ASD-PM.
Asian sand dust-Particulate matter (ASD-PM) aerosol, usually originating from eastern China and Mongolia, periodically brings large amounts of wind-borne soil particles and spreads over wide areas of several East Asian countries, such as Korea, Japan, and China (Chen et al., 2004), and threatens the health of several East Asian peoples. In recent years, the incidence of ASD-PM has remarkably increased, and the concentration of metallic components in ASD-PM has also been highly increased by severe air pollution caused by accelerating industrialization and the increase in the number of vehicles. ASD-PM is composed of mainly soil, ocean salt, and other crustal elements, such as Ca, Mg, Al, and Fe (Cheng et al., 2005; Yeo et al., 2010). ASD-PM aerosol is made by wind erosion and mostly consists of sulfur dioxide and nitrogen dioxide, which increase the chances of respiratory and cardiac-related diseases (Wong et al., 2002). In fact, the increase in human exposure to ASD-PM exposure has resulted in a high incidence of pneumonia, conjunctivitis, and allergic rhinitis (Chen et al., 1998; Yang et al., 2005; Chang et al., 2006) and has been reported to be relevant to the onset of cardiac diseases (Kang et al., 2012). In addition, ASD-PM gives rise to the symptoms of pharyngitis and asthma in healthy people and oxidative damage to DNA at the molecular biological level (Kim et al., 2003; Hwang et al., 2010; Yeo et al., 2010). ASD-PM exposure produces a significant increase in IL-6, IL-8, and RANTES and, because of the production of cytokines, strongly activates eosinophils (Shin et al., 2013).
Liver fibrosis, with its high morbidity and death rate, is a primary source of medical problems. The last stage of liver fibrosis, liver cirrhosis, is characterized by a small lump on the liver and changes in liver function (Fattovich et al., 1997; Friedman, 2003; Tsukada et al., 2006). Unlike liver cirrhosis, there is abundant proof that liver fibrosis is treatable and reversible (Arthur, 2002). Liver fibrosis is caused by chronic damage accumulated by Extracellular Matrix (ECM) proteins, such as collagen, tenascin, fibronectin, and decorin, which have shown up in all types of chronic liver diseases. Excessive ECM accumulation in the liver is caused by chronic repetition of repair reactions and damage by drug, toxic substances, auto-immune reaction, and infection by the Hepatitis B or Hepatitis C virus (Xu et al., 2005; Kamal et al., 2006; Fujiwara et al., 2008).
Tenascin-C (Tn-C) is a 180-250kDa glycoprotein from ECM made up of six monomers linked by a disulfide bond (Erickson and Taylor, 1987; Vaughan et al., 1987). The expression of Tn-C is increased during the chronic state, which is caused by repeated damage and recovery stages and damaged tissue or development (Jones and Jones, 2000; Giblin and Midwood, 2015; Bhattacharyya et al., 2016).
There are many studies about its symptoms and ASD-PM itself, but few about Tn-C expression as a fibrotic effect that ASD-PM causes. In order to study the effects of ASD-PM on several tissues, mainly of the circulatory system, we applied ASD-PM to mouse and human cell lines at different levels and investigated the expression of Tn-C and fibronectin in human cancer-cell lines and mouse liver tissue.
A total of 45 male C57BL/6 mice (three weeks of age, body weight between 24 and 29 g) were purchased from Dae Han Biolink Co., Ltd. (Umsung, Chungbuk, Korea) and were maintained in conventional conditions for a week before the experiment. The mice were fed a diet (Cargill Agri Purina, Inc., Sungnam, Gyeonggi-do, Korea) and were given tap water for hydration. They were housed in an animal facility maintained at 20 ± 2°C with 40 ± 10% humidity and a 12 hr alternate light/dark cycle. Mice were cared for according to the Guideline of the Korean Food & Drug Administration (KFDA) and the National Institute of Health (NIH) Guidelines for the Care and Use of Laboratory Animals. This animal study was approved by the Panel on Laboratory Animal Care of Gachon University (GIACUCR-011).
From April to June 2006, when the ASD-PM storms occurred, ASD-PM particles were collected from the roof of Gachon University of Medicine and Science, Korea, with a particle collector (HV500F, Sibata, Saitama, Japan) and prepared as previously described (Hwang et al., 2010) .
C57BL/6 mice (four weeks of age) were randomly divided into four groups (n = 36): Saline, ASD 0.1, 0.2, or 0.4 mg/mL in Saline.
The control mice received only saline twice a week for 12 weeks. The groups were instilled intratracheally with saline or saline suspension of 0.1, 0.2, or 0.4 mg/kg of ASD-PM particles twice a week for 12 weeks. All intratracheal instillation was carried out by the tongue-pull method. One day after the last intratracheal administration, the mice were sacrificed in accordance with the NIH guidelines.
A human hepatocellular carcinoma-cell line (Hep3B) obtained from the Korean Cell Line Bank (KCLB) was cultured in RPMI1640 with 10% fetal bovine serum (FBS, BRL, Paisley, UK) and maintained in a humidified atmosphere of 37°C, 5% CO2. When the cells were 70% confluent, the medium was replaced by RPMI1640, supplemented with 10% FBS, 2 mM L-glutamine, 10 mM HEPES pH 7.0, and 2 mM penicillin/streptomycin (Sigma-Aldrich, St. Louis, MO, USA). After 48 hr, the medium was replaced by serum-free RPMI1640 with recombinant TGF-β1 (R&D Systems, Minneapolis, MN, USA) and ASD-PM.
Cell treatments were as follows: TGF-β1 (0.5 ng/mL, 1 ng/mL, 2 ng/mL), ASD-PM (10 ng/mL, 20 ng/mL) and incubated for 2 hr, 24 hr. For the control treatment, phosphate-buffered saline (PBS) and cell culture media was given to the cells.
For histological analyses, the mice were anesthetized by administering isoflurane (Ilsung Pharmaceuticals Co., Seoul, Korea). After opening the abdomen, liver tissues were immediately fixed in 10% buffered formalin and embedded in paraffin. Liver sections (5 μm) were deparaffinized in xylene tissue sections and dehydrated in 100%, 95%, 90%, 80%, and 70% ethanol, for 5 min each, before finally being rinsed with distilled water. These sections were stained with hematoxylin & eosin (H&E) and Masson’s trichrome (MT, HT15-1KT, Sigma). MT staining was done using the MT stain kit (Sigma) in accordance with the manufacturer’s instructions. Pathological analysis of inflammatory cells and collagen was done using a Nikon ECLIPSE light microscope (Nikon Co., Tokyo, Japan). Image analysis was also performed using ImageJ software (http://rsb.info.nih.gov/ij).
For fluorescence microscopy studies, cells were plated on eight-well slide glass and coverslips (75 × 25 mm 1, and 18 × 18 mm 0.16, Superior Marienfeld, Germany). The eight-well slide glass was washed with PBS, and cells were fixed with 4% paraformaldehyde in PBS containing 0.1% triton X-100 and 0.1% BSA for 3 min at room temperature (RT). Primary antibodies, incubated with Tenascin-C, Fibronnectin, and TGF-β1 (1:500, Santa Cruz Biotechnology, Inc., Santa Cruz, CA, USA) diluted in 1% BSA were kept overnight at 4°C. After several washes with PBS, the samples were incubated with fluorescent-conjugated secondary antibodies (1:500 for FITC-conjugated anti-rabbit, 1:200 for Alexa Fluor 488-conjugated anti-rabbit, and 1:200 for green oregon-conjugated anti-mouse immunoglobulins) for 1 hr at RT and embedded in Vectahield with DAPI (Vector Laboratories, Burlingame, CA, USA). Cells were visualized by an Olympus BX-60 microscope with the appropriate filters. A blue signal represents the nuclear DNA staining with DAPI. Finally, the slides were dehydrated and mounted. Image analysis was done using ImageJ software (http://rsb.info.nih.gov/ij). Representative images were taken with a Spot 4.3 digital camera and software and edited in Adobe Photoshop.
Liver tissues were grinded and lysed in buffer (Pro-prep, iNtRON) for 30 min. After centrifugation for 5 min at 14,000 rpm, the supernatant protein was collected. The concentrations were measured by Bradford assay, and 5 ug of cell extracts were applied to each lane along with a protein marker (Santa Cruz). They were separated by standard electrophoresis using 10% acrylamide separating gels and 4% stacking gels. After that, they were transferred to a polyvinylidene difluoride (PVDF) membrane. The membranes were incubated with anti- Tn-C, Fibronectin, and actin primary antibody (Santa Cruz) at the dilution of 1:1000 and detected using a western detection solution (ECL, Amersham Life Science). The OD ratio of Tn-C and fibronectin expression was estimated by using Molecular imaging system IS-4000 MM pro (Kodak, Rochester, NY, USA).
Total RNAs were extracted in mice livers according to the manual specification using a TRI reagent RNA extraction kit (Fluka, Buchs, Switzerland). The concentration of total RNAs was measured by nano-drop spectrophotometry. RT-PCR analysis was performed for Tn-C and Fibronectin mRNA. Each sample was reverse-transcribed to cDNA for 1 hr at 42°C using a cDNA synthesis kit (Promega, Madison, WI, USA). PCR was done using the following primers: Tn-C ((Forward primer:5’- ATCGTTACCGCCTCAACTACA-3’; Reverse primer: 5’-TGTTCCATCCACAGTCACCA-3’) [321 bp]); Fibronectin (sense sequence, 5-CAA TGC CCT TCC TGT TCT GC-3; anti-sense sequence, 5-GTG GAC GGC GTA GGC TTC TT-3 [452 bp]); and glyceraldehyde-3-phosphate dehydrogenase (GAPDH; sense sequence, 5- GTG GAT ATT GTT GCC ATC AAT GAC C -3; anti-sense sequence, 5- GCC CCA GCC TTC TTC ATG GTG GT -3 [270 bp]); all purchased from Bioneer (Daejeon, Korea).
The GAPDH was used to verify that equal amounts of RNA were used for reverse transcription and PCR amplification from different experimental conditions. Products were electrophoresed on a 2.0% NuSieve GTG-agarose (Cambrex Bio Science, Rockland, ME, USA) gel and visualized by staining with Safeview nucleic acid (Applied Biological Materials Inc, Vancouver, BC, Canada). The gels were certified using a Molecular Imager ChemiDoc XRS+ (Bio-Rad).
Data analyses were done using version 5.0.1 of the Statview software program (SAS Institute, Cary, NC, USA). Observed values are presented as box plots in the figures, with the largest and smallest observed values. The median value is located within the box plot. We calculated the differences between the groups using the t-test (Statview version 5.0.1, SAS Institute). Probability values of p < 0.05 were considered to be statistically significant.
We investigated the expression pattern of Tn-C induced by TGF-β1 in a lung cancer-cell line, A549 (Adenocarcinomic human alveolar basal epithelial cell) and in a liver cancer-cell line, Hep3B (Hepatocellular carcinoma cell). Cell lines were treated with 1 ng/mL or 2 ng/mL of TGF-β1 for 2 hr and compared to Tn-C expression (Fig. 1). In the A549 cell line, Tn-C expressions was increased six times (p < 0.05) and eight times (p < 0.01) in 1 ng/mL and 2 ng/mL, concentration of TGF-β1 respectively compared to the control. Also, in the Hep3B cell line, Tn-C expression was increased four times (p < 0.05) and six times (p < 0.01), respectively. In both A549 and Hep 3B cell lines, Tn-C expressions showed a significant increase that depended on the TGF-β1 concentration compared with the control.
Comparison of Tenascin-C expression in cell lines A549 (A,B,C,D) and Hep3B (E,F,G,H) treated with Transforming growth factor (TGF-β1). Cell lines were supplement-starved in serum-free RPMI1640 for 24 hr and subsequently stimulated for 2 hr with recombinant TGF-β1 (B,F, 1.0 ng/mL; C, G, 2 ng/mL), and compared with unstimulated controls (A, E). Immunofluorescence analysis was done as detailed in “Methods” with ImageJ software. *p < 0.02, control vs TGF-β1 treated with 1 ng/mL. †p < 0.01, control vs TGF-β1 treated with 2 ng/mL.
We examined the expression patterns of TGF-β1 and Tn-C induced by ASD-PM for 24 hr in the Hep3B cell line. Expression of TGF-β1 was significantly increased by four times at 10 ng/mL (p < 0.05), 4.5 times at 20 ng/mL (p < 0.05), and six times at 40 ng/mL (p < 0.01) of ASD-PM compared to the control (Fig. 2A-E). Also, expression of Tn-C showed significant increases of 9.4 times at 10 ng/mL (p < 0.05), 7.5 times at 20 ng/mL (p < 0.05), and 15 times at 40 ng/mL (p < 0.01) of ASD-PM compared with the unstimulated control (Fig. 2F-J).
Expression of TGF-β1 (A,B,C,D,E) and Tenascin-C (Tn-C) (F,G,H,I,J) in Hep3B treated with ASD-PM. Cell lines were supplement-starved in serum-free RPMI1640 for 24 hr and subsequently stimulated for 24 hr with ASD-PM (B, G,10 ng/mL; C, H, 20 ng/mL; D, I, 40 ng/mL), and compared with unstimulated controls (A,F). Immunofluorescence analysis was done as detailed in “Methods” with ImageJ software (x 100). *p < 0.02 control vs ASD 10. †p < 0.01 control vs ASD 20. ‡ p < 0.01 control vs ASD 40. ≠ p < 0.02 ASD 20 vs ASD 40.
Fibronectin expression was detected in the Hep3B cell line treated with TGF-β1 for 2 hr or ASD-PM for 24 hr at each different concentration. TGF-β1 was treated with 0.5, 1, or 2 ng/mL to Hep3B for 2 hr and fibronectin was significantly expressed at two times at 0.5 ng/mL (p < 0.05), four times at 1 ng/mL (p < 0.001), and three times at 2 ng/mL (p < 0.01) compared to the control (Fig. 3A-E). ASD-PM was treated with 10, 20, or 40 ng/mL to Hep3B for 24 hr. Expression of fibronectin was detected as significantly increased at 2.5 times at 20 ng/mL (p < 0.05) and 4.5 times at 40 ng/mL (p < 0.001) but not at 10 ng/mL of ASD-PM, compared with the unstimulated control (Fig. 3F-J).
Expression of Fibronectin (FND) in Hep3B treated with TGF-β1 (A, B, C, D, E) or ASD-PM (F, G, H, I, J). Cell lines were supplement-starved in serum-free RPMI1640 for 24 hr and subsequently stimulated for 2 hr with recombinant TGF-β1 (B, 0.5 ng/mL; C, 1 ng/mL; D, 2 ng/mL, *p < 0.001 control vs TGF-β1, 0.5. †p < 0.0001 control vs TGF-β1, 1. ‡ P < 0.0001 control vs TGF-β1, 2. ≠ p < 0.001 TGF-β1, 0.5 vs TGF-β1, 1) for 24 hr with ASD-PM (G, 10 ng/mL; H, 20 ng/mL; I, 40 ng/mL, *p < 0.001 control vs ASD20. †p < 0.0001 ASD 10 vs ASD 40. ‡ p < 0.0001 control vs ASD20. ≠ p < 0.0001 ASD 10 vs ASD 40) and compared with unstimulated controls (A, F). Immunofluorescence analysis was done as detailed in “Methods” with ImageJ software.
Mice were serially treated with several concentrations of ASD-PM (0.1 mg/kg/mL, 0.2 mg/kg/mL, or 0.4 mg/kg/mL) from 4 to 12 weeks by instilled intratracheal injection. Expressions of Tn-C gene or protein were investigated in liver tissues at 4, 8, and 12 weeks by RT-PCR (Fig. 4A). Gene expression of Tn-C was detected weakly fot 0.2 and 0.4 mg/kg/mL of ASD-PM at week 4, but was expressed significantly at 0.2 and 0.4 mg/kg/mL at week 8. At 12 weeks, Tn-C genes were also expressed at 0.1 mg/kg/mL and gradually increased with the concentration of ASD-PM (0.1 mg/kg/mL, 0.2 mg/kg/mL, and 0.4 mg/kg/mL) (Fig. 4A).
Tn-C gene mRNA expression in mice liver tissue treated with ASD-PM of different concentrations and periods. Expression of Tn-C cDNA was analyzed by Real-Time PCR (A), confirmed by electrophoresis (B). The data were normalized to GAPDH mRNA levels (C).* < 0.0001, † < 0.0001, ‡ < 0.0001, # < 0.0006).
We detected Tn-C compared to GAPDH expression in ASD-PM instilled intratracheally in mice at 4, 8 and 12 weeks of treatment with ASD-PM (control saline, 0.1 mg/kg/mL, 0.2 mg/kg/mL, or 0.4 mg/kg/mL). Tn-C expression was not detected in the control and low dose (0.1 mg/mL) at 4th week groups, and was weakly expressed at the higher concentrations of 0.2 and 0.4 mg/kg/mL at the 4th week. Expression was significantly expressed at 0.2 and 0.4 mg/kg/mL at 8 weeks. Tn-C expression was observed from the low concentration (0.1 mg/kg/mL) at 12 weeks. Tn-C expression was increased about four-fold for 0.4 mg/kg/mL at 12 weeks. The expression pattern gradually increased as the concentration of yellow dust increased and was significantly expressed (Fig. 4B, C).
Mice tissues after 4, 8, and 12 weeks of ASD-PM treatment were stained with Masson Trichrome (Masson, HT15-1KT, Sigma-Aldrich, 050M4337) to investigate the fibrosis of liver tissue. We used Accustain Trichrome stain and ImageJ software to measure the proportion of blue area to the total.
Stained mouse liver tissues compared to the non-exposed control group at 8 weeks of ASD-PM treatment increased 1.5 times the collagen blue areas and at 12 weeks increased to twice the blue areas. As a result, the ratio of Masson Trichrome-stained blue areas increased significantly because of the concentration of ASD-PM and the increasing number of weeks. As a result, when the ASD-PM was inhaled into the respiratory tract, the collagen blue areas in the liver tissue gradually increased in proportion to the increase of ASD-PM concentration (Fig. 5, 6).
Figure shows mouse liver tissue after four weeks of treatment. A: non-exposed control group. C, D: mice exposed to 20 ng/mL ASD-PM for four weeks. E, F: mice exposed to 20 ng/mL ASD for eight weeks. G, H: mice exposed to 20 ng/mL ASD for 12 weeks ASD-PM. The graph (B) on the right presents a proportion of collagen expression to total area. Mean value of A, C, D, E, F, G and H are presented accordingly. We used Accustain Trichrome stain (Masson, HT15-1KT, Sigma-Aldrich, 050M4337), and ImageJ software to measure the proportion of blue area in the total.
Transformation of healthy to fibrotic tissue. A proposed sequence of a stepwise remodeling of the ECM that induced alterations in the composition of the ECM and effects on cell phenotype in tissue fibrosis. As an alternative pathway, circulating cells such as transdifferentiate into liver fibroblasts, promoting fibrosis into TGF-β, transforming growth factor-β; LPS, cytokines, etc.
Tn-C is an extracellular matrix that is highly expressed during embryo development, but expressed much less in normal conditions (Young et al., 1994). Tn-C reappears under pathological conditions, such as infection, vascular hypertension, myocardial infarction, or tumor formation (Weller et al., 1991; Zhao and Young, 1995; Kalembey et al., 1997; Imanaka-Yoshida et al., 2001; Kalembey et al., 2003; Sato et al., 2012).
In this study, we examined the expression of Tn-C and Fibronectin in human cancer-cell lines and liver tissue of mice treated with ASD-PM to investigate the inflammatory and cell-damage effects from ASD-PM. A549 and Hep3B lines were treated with TGF-β1 and compared to Tn-C and Fibronectin expression. Tn-C expressions increased four times (p < 0.05) and eight times (p < 0.01) compared to the control. Fibronectin expressions increased four times (p < 0.05) compared to the control. In both A549 and Hep 3B cell lines, Tn-C and Fibronectin expressions showed a significant increase that depended on the TGF-β1 concentration compared with the control (Figs. 1, 2, 3). Our study demonstrates the role of Tn-C expression induced by TGF-β1 and indirected with liver cell line. We have shown that expression of Tn-C increases in A549 and Hep3B cell lines and plays an important role in the development of ECM (Extracellular Matrix Production).
Although there were no similar results, many studies have reported that TGF-β1 increases the expression of α-SMA and increases the differentiation of the ECM (Pearson et al., 1988; Jinnin et al., 2004; Schiller et al., 2004). In our previous study, comparing GB (Gobi, N 44° 21. 515’, E 109° 21. 168’; Shine Us Khudag, Mongolia) with ASD, GB is the main ingredient of silicon quartz and has shown a significant increase in the expression of cytokines (Shin et al., 2013).
Recent papers have shown allergy and various respiratory diseases result from long-term exposure to the yellow dust combined with increased in metal ions caused by industrialization (Kwon et al., 2002; Mori et al., 2003; Ichinose et al., 2008; Lee et al., 2009; Kanatani et al., 2010; Watanabe et al., 2011; Shin et al., 2013; Honda et al., 2014).
We treated mice with ASD-PM for twice a week for 4, 8, or 12 weeks and analyzed the Tn-C expression. Tn-C expressions were increased four times (p < 0.05) and eight times (p < 0.01) compared to the control (Fig. 4). Fibronectin expressions were increased 4 times (p < 0.05) compared to the control. In both A549 and Hep 3B cell lines, Tn-C and Fibronectin expressions showed a significant increase that depended on the TGF-β1 concentration compared with the control (Figs. 2, 3). As a result of treatment with ASD-PM at twice a week at concentrations of 0, 0.1, 0.2, or 0.4 mg/kg/mL for 4, 8 and 12 weeks, the expression of Tn-C was weakly expressed in the ASD-PM-untreated control group for 12 weeks, and no clear expression was observed in the electrophoretic bands. The expression of Tn-C was increased in a concentration-dependent manner in the group treated with ASD-PM for 12 weeks. In particular, when RT-PCR was done on mRNA expression, the expression of Tn-C gradually increased in accordance with the treatment period and the concentration of the treatment group.
Our study demonstrates the role of Tn-C expression induced by TGF-β1 and indirected with liver cell. We have shown that expression of Tn-C increases in A549 and Hep3B cell lines and plays an important role in the development of ECM (Extracellular Matrix Production). Although there are no studies directly related to the expression of Tn-C by ASD in previous reports, the expression of Tn-C activates MMP-9 expression through the TLR4 pathway and increases expression of ECM, leading to liver damage. Thus, the expression of Tn-C by ASD-PM is thought to affect liver fibrosis, as in the above (Mackie et al., 1988; Miyazaki et al., 1993; Kuriyama et al., 2011). In addition, the expression of tenascin in liver was increased by the effect of acute liver injury induced by treatment with CCl4, and many studies have been carried out on the correlation between Tn-C expression and liver fibrosis as well as liver cancer (Van Eyken et al., 1992; Gallai et al., 1996; El-Karef et al., 2007).
In this study, we examined the effect of ASD-PM inflow through the respiratory system on other organs. Expression of Tn-C by ASD-PM-containing substances was about twice the expression of Tn-C induced by TGF-β1 treatment. This result showed that ASD-PM affects the liver by increasing Tn-C expression by various mixtures contained in the dust (Fig. 6). When ASD-PM was treated for a long period, we found liver tissues to be worse. If ASD-PM continues to be inhaled, the degree of fibrosis will be accelerated gradually. In the mouse experiment, ASD-PM not only affected the fibrosis of the lung, but also gradually affected the liver fibrosis and other organs.
The accumulation of extracellular matrix proteins, such as Tn-C, by wound-healing mechanisms changes the structure of the liver and, if this process is repeated, can lead to chronic liver fibrosis. Thus, the above results show that long-term exposure to ASD-PM may affect other organs, such as the liver, rather than acting only in the respiratory tract. Recently, automobile growth, urban expansion, and industrialization have changed the composition of fine dust, resulting in mixed PM. PM that is inhaled into the respiratory tract and enter the body may cause changes in the expression factors, which may affect other organs.
This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science, and Technology (2015-0023538)
The authors declare that there is no conflict of interest.