Role of integrin α2 in methotrexate-induced epithelial-mesenchymal transition in alveolar epithelial A549 cells

Methotrexate (MTX) is widely used to treat various diseases. However, it induces adverse reactions like serious lung injury, including pulmonary fibrosis. Increasing evidence suggests that epithelial-mesenchymal transition (EMT) in injured alveolar epithelium contributes to the development of the pathophysiological state of the lung. We demonstrated that MTX induced EMT in cultured alveolar epithelial cell lines. Integrin-mediated signaling is considered a significant factor in recognizing the EMT process. However, the relationship between MTX-induced EMT and integrin family members is poorly understood. In the present study, we aimed to clarify the role of integrin in MTX-induced EMT in A549 and NCI-H1299 (H1299) cells by focusing on the integrin alpha 2 (ITGA2) subunit, selected based on our microarray analysis. MTX treatment for 72 h significantly increased the mRNA and cell surface expression of ITGA2 in both cell lines. However, this upregulation by MTX was suppressed by co-treatment with SB431542 and folic acid, which are inhibitors of MTX-induced EMT in A549 cells. The mRNA expression levels of EMT-related genes were more affected in the MTX-treated A549 cells with high ITGA2 expression than in those with low ITGA2 expression. Finally, E7820, an ITGA2 inhibitor, suppressed MTX-induced EMT-related phenotypic changes, such as morphology and mRNA and protein expression of α-smooth muscle actin, a representative EMT marker. These findings suggest that ITGA2 may play a key role in MTX-induced EMT in alveolar epithelial cells.

A Liquid Chromatography-Mass Spectrometry Method to Study the Interaction between Membrane Proteins and Low-Molecular-Weight Compound Mixtures

Molecular interaction analysis is an essential technique for the study of biomolecular functions and the development of new drugs. Most current methods generally require manipulation to immobilize or label molecules, and require advance identification of at least one of the two molecules in the reaction. In this study, we succeeded in detecting the interaction of low-molecular-weight (LMW) compounds with a membrane protein mixture derived from cultured cells expressing target membrane proteins by using the size exclusion chromatography-mass spectrometry (SEC-MS) method under the condition of 0.001% lauryl maltose neopentyl glycol as detergent and atmospheric pressure chemical ionization. This method allowed us to analyze the interaction of a mixture of medicinal herbal ingredients with a mixture of membrane proteins to identify the two interacting ingredients. As it does not require specialized equipment (e.g., a two-dimensional liquid chromatography system), this SEC-MS method enables the analysis of interactions between LMW compounds and relatively high-expressed membrane proteins without immobilization or derivatization of the molecules.

Effect of Corticosteroids on Peptide Transporter 2 Function and Induction of Innate Immune Response by Bacterial Peptides in Alveolar Epithelial Cells

In the lung alveolar region, the innate immune system serves as an important host defense system. We recently reported that peptide transporter 2 (PEPT2) has an essential role in the uptake of bacterial peptides and induction of innate immune response in alveolar epithelial cells. In this study, we aimed to clarify the effects of corticosteroids on PEPT2 function and PEPT2-dependent innate immune response. NCI-H441 (H441) cells were used as an in vitro model of human alveolar type II epithelial cells, and the effects of dexamethasone (DEX) and budesonide (BUD) on the transport function of PEPT2 and the innate immune response induced by bacterial peptides were examined. PEPT2 function, estimated by measuring β-alanyl-Nε-(7-amino-4-methyl-2-oxo-2H-1-benzopyran-3-acetyl)-L-lysine (β-Ala-Lys-AMCA) uptake in H441 cells, was suppressed by treatment with DEX and BUD in a concentration- and time-dependent manner. The suppression of PEPT2 function was partially recovered by a glucocorticoid receptor antagonist. The expression of PEPT2 and nucleotide-binding oligomerization domain 1 (NOD1) mRNAs was suppressed by treatment with DEX and BUD, while PEPT2 protein level was not changed by these treatment conditions. Additionally, the increased mRNA expression of interleukin (IL)-8 and the increased secretion of IL-8 into the culture medium induced by bacterial peptides were also suppressed by treatment with these corticosteroids. Taken together, these results clearly suggest that corticosteroids suppress PEPT2 function and bacterial peptide-induced innate immune response in alveolar epithelial cells. Therefore, PEPT2- and NOD1-dependent innate immune response induced by bacterial peptides in the lung alveolar region may be suppressed during the inhaled corticosteroid therapy.

Characterization of miR-34a-Induced Epithelial-Mesenchymal Transition in Non-Small Lung Cancer Cells Focusing on p53

Background: Epithelial–mesenchymal transition (EMT), a phenotypic conversion of the epithelial to mesenchymal state, contributes to cancer progression. Currently, several microRNAs (miRNAs) are associated with EMT-mediated cancer progression, but the contribution of miR-34a to EMT in cancer cells remains controversial. The present study aimed to clarify the role of miR-34a in the EMT-related phenotypes of human non-small cell lung cancer (NSCLC) cell lines, A549 (p53 wild-type) and H1299 (p53-deficient). Methods: The miR-34a mimic and p53 small interfering RNA (siRNA) were transfected into the cells using Lipofectamine, and the obtained total RNA and cell lysates were used for real-time polymerase chain reaction and Western blotting analysis, respectively. Results: The introduction of the miR-34a mimic led to an increase in the mRNA and protein expression levels of α-smooth muscle actin (α-SMA), a mesenchymal marker gene, in A549, but not in H1299 cells. Additionally, miR-34a-induced the upregulation of p53 activity and migration was observed in A549, but not in H1299 cells. However, under the p53-knockdown condition, only α-SMA upregulation by miR-34a was abolished. Conclusion: These findings indicate a close relationship between p53 and miR-34a-induced EMT in p53-wild type NSCLC cells, which provides novel insights about the role of miR-34a in EMT-like phenotypic changes in NSCLC.

Functional expression of equilibrative and concentrative nucleoside transporters in alveolar epithelial cells

Equilibrative nucleoside transporters (ENTs) and concentrative nucleoside transporters (CNTs) mediate the cellular uptake of nucleosides and nucleobases across the plasma membrane and play important roles in the salvage pathways of nucleotide synthesis. However, information about nucleoside transport systems in the lung alveolar epithelial cells is limited. Therefore, in the present study, we examined the function and expression of nucleoside transporters using primary cultured alveolar type II cells and transdifferentiated type I-like cells. The uptake of uridine, a substrate for ENTs and CNTs, in type II and type I-like cells was time, temperature, and concentration dependent, and was inhibited by other nucleoside transporter substrates such as adenosine. Uridine uptake in both cells was insensitive to nanomolar concentrations of NBMPR, a potent ENT1 inhibitor, while it was inhibited by higher concentrations of NBMPR, suggesting that ENT2, but not ENT1, is involved in uridine uptake in these cells. Additionally, uridine uptake was higher in the presence of Na⁺ than in the absence of Na + and was partially inhibited by a CNT inhibitor phloridzin in these cells, suggesting that CNT is also involved in uridine uptake. In both cells, the mRNA expression of ENT1, ENT2, CNT2, and CNT3 was observed. Finally, the activity of uridine uptake was considerably higher in type II cells than in type I-like cells. In addition, the mRNA expression of ENT2, CNT2, and CNT3, but not ENT1, was lower in type I-like cells than in type II cells. These findings would help understand the functional roles of equilibrative and concentrative nucleoside transporters in alveolar epithelial cells.

Evaluation on epithelial-mesenchymal state and microRNAs focusing on isolated alveolar epithelial cells from bleomycin injured rat lung

Several studies using bleomycin (BLM)-induced lung injury rat model revealed that epithelial-mesenchymal transition (EMT) contributes to pulmonary fibrosis. Conversely, microRNAs (miRNAs) are considered as useful markers of various diseases. In the present study, we aimed to characterize the EMT state through focusing on alveolar epithelial cells and identify the miRNAs that can be used as markers to predict pulmonary fibrosis using a BLM-induced lung injury rat model. Intratracheal administration of BLM increased hydroxyproline, a component of collagen, in lung tissues at day 14, but not at day 7. However, BLM induced EMT at day 7, which was accompanied with increased mRNA expression of α-smooth muscle actin, a representative EMT marker, in alveolar epithelium, thereby suggesting that EMT occurs prior to pulmonary fibrosis in alveolar epithelial cells. Using this rat model, the expression levels of several EMT-associated miRNAs were examined, and miR-222 was found to be upregulated in alveolar epithelial cells as well as bronchoalveolar lavage fluid from day 3. Our findings indicate that EMT in alveolar epithelial cells may occur before pulmonary fibrosis, and miR-222 may be used as a potential marker for early prediction of pulmonary fibrosis.

Direct N1-Selective Alkylation of Hydantoins Using Potassium Bases

Hydantoins, including the antiepileptic drug phenytoin, contain an amide nitrogen and an imide nitrogen, both of which can be alkylated. However, due to the higher acidity of its proton, N³ can be more easily alkylated than N¹ under basic conditions. In this study, we explored methods for direct N¹-selective methylation of phenytoin and found that conditions using potassium bases [potassium tert-butoxide (^tBuOK) and potassium hexamethyldisilazide (KHMDS)] in tetrahydrofuran (THF) gave N¹-monomethylated phenytoin in good yield. The applicable scope of this reaction system was found to include various hydantoins and alkyl halides. To explore the function of methylated hydantoins, the effects of a series of methylated phenytoins on P-glycoprotein were examined, but none of methylated products showed inhibitory activity toward rhodamine 123 efflux by P-glycoprotein.

miR-484: A Possible Indicator of Drug-Induced Pulmonary Fibrosis

BACKGROUND

Drug-induced lung injury leads to serious lung diseases, such as pulmonary fibrosis. We demonstrated in an alveolar epithelial cell line A549/ABCA3 that certain microRNAs were associated with bleomycin induced epithelial-mesenchymal transition (EMT) which is closely related to pulmonary fibrosis. In this study, we focused on the role of miR-484 in drug-induced EMT using A549/ABCA3 cells and a mouse lung injury model.

METHODS

The expression of EMT-related genes and miR-484 was detected by real-time polymerase chain reaction. miR-484-targeted proteins were analyzed by Western blot. Pulmonary fibrosis mouse model was prepared by the intratracheal administration of BLM. As miR-484 is known to target SMAD2 and zinc finger E-box binding homeobox 1 (ZEB1), which are the well-known EMT-related transcription factors, we assessed the effects of a miR-484 inhibitor or mimic on the mRNA/protein expression of both the factors.

RESULTS

We found that bleomycin significantly suppressed the intracellular expression and extracellular release of miR-484 in A549/ABCA3 cells. Moreover, the miR-484 mimic and inhibitor showed no drastic effects on the expression of the EMT-related transcription factors. In addition, the miR-484 mimic had no effect on the bleomycin-induced altered mRNA expression of the α-smooth muscle actin, a representative EMT marker. This suggested that miR-484 did not directly contribute to bleomycin-induced EMT in A549/ABCA3 cells. In contrast, the significant decrease in miR-484 expression in the lung tissue or plasma of bleomycin-administered mice suggested that miR-484 expression was closely correlated with bleomycin-induced lung injury.

CONCLUSIONS

These findings indicate that miR-484 could be a novel diagnostic indicator for drug-induced pulmonary fibrosis.

Differential mechanisms underlying methotrexate-induced cell death and epithelial-mesenchymal transition in A549 cells

Epithelial-mesenchymal transition (EMT), a biological process through which epithelial cells transdifferentiate into mesenchymal cells, is involved in several pathological events, such as cancer progression and organ fibrosis. So far, we have found that methotrexate (MTX), an anticancer drug, induced EMT in the human A549 alveolar adenocarcinoma cell line. However, the relationship between EMT and the cytotoxicity induced by MTX remains unclear. In this study, we compared the processes of MTX-induced EMT and apoptosis in A549 cells. Q-VD-Oph, a caspase inhibitor, suppressed MTX-induced apoptosis, but not the increase in mRNA expression of α-smooth muscle actin (SMA), a representative EMT marker. In addition, SB431542, an EMT inhibitor, did not inhibit MTX-induced apoptosis. By using isolated clonal cells from wild-type A549 cells, the induction of EMT and apoptosis by MTX in each clone was analyzed, and no significant correlation was observed between the MTX-induced increase in α-SMA mRNA expression and the proportion of cells undergoing apoptosis. Furthermore, the increase in the mRNA expression of α-SMA was well correlated with cyclin-dependent kinase inhibitor 1A, a cell cycle arrest marker, but not with BCL-2 binding component 3 and Fas cell surface death receptor, which are both pro-apoptotic factors, indicating that the MTX-induced EMT may be related to cell cycle arrest, but not to apoptosis. These findings suggested that different mechanisms were involved in the MTX-induced EMT and apoptosis.

Transport of ribavirin in human myelogenous leukemia cell line K562

The anticancer effect of ribavirin, a purine nucleoside analogue, has been studied using cultured cancer cells such as the human myelogenous leukemia cell line K562. In order to exert its pharmacological effect, ribavirin has to enter cancer cells. However, there is little information concerning the transport mechanism of ribavirin into K562 cells. In this study, therefore, we examined the uptake mechanism of ribavirin in K562 cells. The uptake of ribavirin in K562 cells was time- and temperature-dependent, and was saturable with a Km value of 1.5 mM. Ribavirin uptake was inhibited by nucleosides such as adenosine and uridine, and by inhibitors of equilibrative nucleoside transporter 1 (ENT1) such as S-(4-nitrobenzyl)-6-thioinosine and dipyridamole in a concentration-dependent manner. In addition, the expression of ENT1 mRNA in K562 cells was confirmed by real-time PCR. On the other hand, Na⁺-dependence of ribavirin uptake was not observed, suggesting the involvement of ENT1, but not Na⁺-dependent concentrative nucleoside transporters, in ribavirin uptake in K562 cells. Treatment of K562 cells with sodium butyrate induced erythroid differentiation, but ribavirin uptake activity and sensitivity of the uptake to various inhibitors were not different between native and differentiated K562 cells. These results suggest that ribavirin uptake into K562 cells is mainly mediated by ENT1, which may have a pivotal role in anticancer effect of ribavirin.

[Investigation of Drug-induced Lung Injury for the Development of a Novel Therapeutic Approach]

The development of serious lung diseases, such as pulmonary fibrosis, is associated with several drugs. A recent study has shown that the epithelial-mesenchymal transition (EMT) plays an essential role in the development of pulmonary fibrosis. However, the mechanisms underlying drug-induced EMT in alveolar epithelial cells have not been characterized. The present study showed that methotrexate (MTX), a drug known to cause lung injury, induced EMT-like phenotypic changes in an A549 cell model of the alveolar epithelium. We also found that the transforming growth factor (TGF)-β1-mediated signaling pathway was associated with MTX-induced EMT. In addition, our results showed that certain secreted factors and microRNAs, a class of small noncoding RNAs, may be involved in MTX-induced EMT. The effects of COA-Cl, a novel synthetic small molecule, on TGF-β1-induced EMT were evaluated to determine the therapeutic potential of COA-Cl against drug-induced lung injury. COA-Cl significantly suppressed TGF-β1-induced EMT-like phenotypic changes, as evidenced by the inhibition of EMT-related transcription factors. Furthermore, MTX-induced EMT was completely suppressed by co-treatment with folic acid. Thus, these compounds may be promising therapeutic agents against drug-induced lung injury. In conclusion, the present study elucidated mechanisms underlying drug-induced EMT and highlighted a potential novel therapeutic approach to drug-induced lung diseases.

Effect of transforming growth factor-β1 on functional expression of monocarboxylate transporter 1 in alveolar epithelial A549 cells

Epithelial-mesenchymal transition (EMT) contributes to the development of severe lung diseases, such as pulmonary fibrosis. Recently, it has been reported that EMT involves complex metabolic reprogramming triggered by several factors including transforming growth factor (TGF-β1) and that monocarboxylate transporter (MCT1) plays an essential role in these metabolic changes. The aim of the present study was to clarify the functional expression of MCT1 during TGF-β1-induced EMT in alveolar epithelial A549 cells. The transport function of MCT1 in A549 cells was examined using [³H]γ-hydroxybutyrate (GHB) and [³H] lactic acid (LA) as substrates and α-cyano-4-hydroxycinnamate (CHC), lactic acid, phloretin, and AR-C155858 (AR) as inhibitors of MCT1. EMT was induced by treating the cells with TGF-β1. mRNA and protein expression levels were analyzed using real-time PCR and Western blotting, respectively. Time-, temperature-, and pH-dependent GHB and LA uptake were observed in A549 cells. CHC, lactic acid, phloretin, and AR significantly inhibited the uptake of GHB in a concentration-dependent manner, suggesting that MCT1 is primarily responsible for transport of monocarboxylates such as GHB and LA in A549 cells. TGF-β1 treatment significantly enhanced GHB and LA uptake as well as the mRNA and protein expression levels of MCT1 in A549 cells. These changes were neutralized by co-treatment with SB431542, an inhibitor for the TGF-β1 signaling pathway. CHC and AR had no effect on TGF-β1-induced EMT-related gene expression changes. Here, we have clearly characterized functional expression of MCT1 in A549 cells and have shown that MCT1 may be upregulated via the TGF-β1 signaling pathway.

Anticancer Drug-Induced Epithelial-Mesenchymal Transition via p53/miR-34a axis in A549/ABCA3 Cells

PURPOSE. Several anticancer drugs including bleomycin (BLM) and methotrexate (MTX) cause serious lung diseases such as pulmonary fibrosis. Although evidences showing the association of epithelial-mesenchymal transition (EMT) with pulmonary fibrosis are increasing, the mechanism underlying anticancer drug-induced EMT has been poorly understood. On the other hand, miR-34a, a non-coding small RNA, has been highlighted as a key factor to regulate EMT in lung. In this study, we elucidated the role of miR-34a in anticancer drug-induced EMT using A549/ABCA3 cells as a novel type II alveolar epithelium model. METHODS. Expression levels of α-smooth muscle actin (α-SMA) mRNA, miR-34a, and p53 were evaluated by real-time PCR and western blot analysis, respectively. RESULTS. BLM and MTX induced EMT-like morphological changes and increase in mRNA expression level of α-SMA, an EMT marker. Also, both drugs increased the expression level of miR-34a. Furthermore, mRNA expression level of α-SMA was enhanced by introduction of miR-34a mimic into A549/ABCA3 cells. To examine the mechanism underlying drug-induced enhancement of miR-34a expression, we focused on p53/miR-34a axis. Both drugs upregulated protein expression of p53, an inducer of miR-34a, as well as phosphorylation of Ser15 in p53. CONCLUSIONS. These findings indicated that p53/miR-34a axis may contribute to anticancer drug-induced EMT in type II alveolar epithelial cells.

Association of cell cycle arrest with anticancer drug-induced epithelial-mesenchymal transition in alveolar epithelial cells

Many drugs exert serious cytotoxic effects on pulmonary tissues. Although several reports have shown an association of epithelial-mesenchymal transition (EMT) with anticancer drug-induced lung injury, mechanisms of these effects are poorly understood. In the present study, we evaluated mechanisms of anticancer drug-induced EMT, with a focus on involvement of cell cycle arrest. We found that methotrexate (MTX) altered mRNA expression levels of many genes as determined by microarray analysis. Gene set enrichment analysis revealed that cell cycle arrest pathways may be associated with MTX-induced EMT. In addition, thymidine (THY) and nocodazole (NOC), which induce cell cycle arrest at S-phase and G2/M-phase, increased mRNA expression levels of α-smooth muscle actin (SMA), an EMT marker. Furthermore, α-SMA protein expression in cells arrested at S- and G2/M-phases by MTX and paclitaxel (PTX) was significantly higher than that in cells at G1. Notably, co-treatment of cells with THY or NOC and EMT-inducing anticancer drugs did not result in additional upregulation of α-SMA mRNA expression. These findings suggested that cell cycle arrest may be closely associated with anticancer drug-induced EMT in alveolar epithelial cells.

Reduced folate carrier-mediated methotrexate transport in human distal lung epithelial NCl-H441 cells

Objectives

We had previously found that reduced folate carrier (RFC; SLC19A1) is mainly involved in an influx of transport of methotrexate (MTX), a folate analogue, using alveolar epithelial A549 cells. Therefore, we examined MTX uptake in NCl-H441 (H441) cells, another in vitro alveolar epithelial model, focusing on the localization of RFC in the present study.

Methods

Transport function of RFC in H441 cells was studied using [3H]MTX.

Key findings

The uptake of MTX was increased remarkably after pretreatment of the cell monolayer with ethylenediaminetetraacetic acid (EDTA) in H441 cells but not in A549 cells, indicating the contribution of the basolaterally located transporter. In addition, folic acid and thiamine monophosphate, RFC inhibitors, inhibited the uptake of MTX from the basolateral side of the H441 cells. In order to compare the function of RFC on the apical and basolateral sides of the cells, the uptake of MTX from each side was examined using a Transwell chamber. Intracellular MTX amounts from the basolateral side were found to be significantly higher than those from the apical side.

Conclusions

These findings suggest that the distribution of MTX in the lung alveolar epithelial cells may be mediated by basolaterally located RFC in alveolar epithelial cells.

P-gp modulating effect of Azadirachta indica extract in multidrug-resistant cancer cell lines

The extract of Azadirachta indica, commonly known as neem, has found extensive use in traditional medicine for treating various human diseases. In this study, the effect of the 50% ethanol extract of A. indica (AI01) on P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) was examined using MDR cell lines, specifically paclitaxel-resistant HepG2 (PR-HepG2) and doxorubicin (DOX)-resistant (DR) colon-26 cells. 96-h treatment of the two cell lines with AI01 (30 μg/mL) showed no effect on the expression of P-gp mRNA (human MDR1 and mouse mdr1b) and protein, while AI01 increased the accumulation of rhodamine 123, a P-gp substrate, in both PR-HepG2 and DR-colon-26 cells. The cytotoxic effects of 48-h treatment with AI01 on the viability of PR-HepG2 and DR-colon-26 cells were not observed. Therefore, 30 μg/mL AI01 may have no cytotoxic and P-gp-inducing effects. Finally, AI01 potentiated the sensitivity of PR-HepG2 and DR-colon-26 cell lines to DOX by 8.6- and 15.3-fold, respectively. These findings suggest that A. indica may be a promising source for a new class of P-gp modulators without cytotoxic/P-gp induction effects.

Transport of AOPP-Albumin into Human Alveolar Epithelial A549 Cell

PURPOSE

Alveolar clearance of proteins, such as albumin, plays an essential role in recovery from lung injuries. Albumin is known to be oxidized by reactive oxygen species (ROS), leading to generation of advanced oxidation protein products (AOPP)-albumin in the alveolar lining fluid. In this study, we aimed to characterize the uptake of FITC-labeled AOPP-albumin (FITC-AOPP-albumin) into human alveolar epithelial cell line, A549.

METHODS

FITC-AOPP-albumin uptake into A549 cells and its effect of ROS generation was evaluated using fluorescence spectrometer and flow cytometry, respectively.

RESULTS

FITC-AOPP-albumin was taken up by A549 cells in a time- and temperature-dependent fashion, and showed saturation kinetics with a Km value of 0.37 mg/mL. The uptake of FITC-AOPP-albumin was suppressed by phenylarsine oxide, a clathrin-mediated endocytosis inhibitor, but not by indomethacin and nystatin, caveolae-mediated endocytosis inhibitors, or 5-(N-ethyl-N-isopropyl) amiloride, a macropinocytosis inhibitor. AOPP-albumin induced ROS generation in A549 cells, suggesting that alveolar clearance of AOPP-albumin should be important to prevent further ROS generation.

CONCLUSION

AOPP-albumin is transported into alveolar epithelial cells through clathrin-mediated endocytosis, which may be important to prevent further ROS generation. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

Folic acid prevents methotrexate-induced epithelial-mesenchymal transition via suppression of secreted factors from the human alveolar epithelial cell line A549

Methotrexate (MTX) often induces serious lung diseases such as pulmonary fibrosis. Although MTX is known to be a folic acid (FA) antagonist, the effect of FA on MTX-induced lung injury remains unclear. Recent studies indicate that epithelial-mesenchymal transition (EMT) is involved in pulmonary fibrosis. Here, we aimed to clarify the effect of FA on MTX-induced EMT in human alveolar epithelial cell line A549 using conditioned medium (CM). CM was prepared from the supernatants of A549 cells treated with MTX in the absence (CMM) or presence (CMMF) of FA. FA suppressed EMT-like morphological changes and elevated mRNA/protein expression levels of α-smooth muscle actin induced by MTX in A549 cells. In addition, CMM induced EMT-like phenotypical changes, whereas CMMF had no effect on the phenotype of A549 cells, indicating that FA may suppress MTX-induced EMT via inhibiting the secretion of certain factors into the supernatant of the cells. Furthermore, FA also prevented CMM-induced EMT-like phenotypical changes in A549 cells. These findings indicate that FA may be a useful pharmaceutical for MTX-induced lung injury.

Nicotine transport in lung and non-lung epithelial cells

AIMS

Nicotine is rapidly absorbed from the lung alveoli into systemic circulation during cigarette smoking. However, mechanism underlying nicotine transport in alveolar epithelial cells is not well understood to date. In the present study, we characterized nicotine uptake in lung epithelial cell lines A549 and NCI-H441 and in non-lung epithelial cell lines HepG2 and MCF-7.

MATERIALS AND METHODS

Characteristics of [³H]nicotine uptake was studied using these cell lines.

KEY FINDINGS

Nicotine uptake in A549 cells occurred in a time- and temperature-dependent manner and showed saturation kinetics, with a Km value of 0.31mM. Treatment with some organic cations such as diphenhydramine and pyrilamine inhibited nicotine uptake, whereas treatment with organic cations such as carnitine and tetraethylammonium did not affect nicotine uptake. Extracellular pH markedly affected nicotine uptake, with high nicotine uptake being observed at high pH up to 11.0. Modulation of intracellular pH with ammonium chloride also affected nicotine uptake. Treatment with valinomycin, a potassium ionophore, did not significantly affect nicotine uptake, indicating that nicotine uptake is an electroneutral process. For comparison, we assessed the characteristics of nicotine uptake in another lung epithelial cell line NCI-H441 and in non-lung epithelial cell lines HepG2 and MCF-7. Interestingly, these cell lines showed similar characteristics of nicotine uptake with respect to pH dependency and inhibition by various organic cations.

SIGNIFICANCE

The present findings suggest that a similar or the same pH-dependent transport system is involved in nicotine uptake in these cell lines. A novel molecular mechanism of nicotine transport is proposed.

Role of miR-34a in TGF-β1- and Drug-Induced Epithelial-Mesenchymal Transition in Alveolar Type II Epithelial Cells

Epithelial-mesenchymal transition (EMT) of alveolar type II epithelial cells may play an important role in the pulmonary fibrosis induced by drugs such as bleomycin (BLM) and methotrexate (MTX). In this study, we examined the role of microRNAs (miRNAs) in drug-induced EMT using RLE/Abca3, a cell line having alveolar type II cell-like phenotype. Based on the screening using miRNA microarray analysis, it was found that the expression of some miRNAs, such as miR-34a, was increased by transforming growth factor (TGF)-β1 and BLM. An increase in miR-34a expression due to TGF-β1, BLM, and MTX was also observed in real-time PCR analysis. Therefore, miR-34a was focused upon in further studies. The expression of nectin-1 mRNA and protein, a possible target of miR-34a, was decreased by the treatment with TGF-β1, BLM, and MTX. In addition, when RLE/Abca3 cells were transfected with miR-34a mimic, the expression of nectin-1 mRNA and Abca3 mRNA, another target of miR34a, decreased significantly. Furthermore, the mRNA expression of cytokeratin 19, an epithelial marker, decreased, whereas that of α-smooth muscle actin, a mesenchymal marker, increased in the cells transfected with miR-34a mimic. These results suggest that miR-34a is involved in drug-induced EMT in alveolar epithelial cells, and possibly in lung fibrosis.

Effect of Curcuma comosa extracts on the functions of peptide transporter and P-glycoprotein in intestinal epithelial cells

Curcuma comosa has been widely used as a herbal medicine in Thailand; however, it remains unclear whether C. comosa influences the absorption of drugs that are substrates for the transporters in the small intestine. In this study, we investigated the effect of C. comosa extracts on the functioning of peptide transporter 1 (PEPT1), an influx transporter, and P-glycoprotein (P-gp), an efflux transporter, in Caco-2 cells and rat intestine. In Caco-2 cells, the ethanolic extract of C. comosa (CCE) lowered the uptake of glycylsarcosine (Gly-Sar), a PEPT1 substrate, while it enhanced the uptake of rhodamine 123 (Rho123), a P-gp substrate, in a concentrationdependent manner. In addition, CCE inhibited apical-to-basal transport of Gly-Sar and basal-to-apical transport of Rho123. Furthermore, the absorption of cephalexin, another PEPT1 substrate, and the exsorption of Rho123 across the rat intestine were inhibited by CCE. Conversely, CCW, the hot water extract of C. comosa, suppresses the function of PEPT1 but not of P-gp in Caco-2 cells. These results suggest that C. comosa used as a herbal medicine in Thailand may affect the intestinal absorption of certain drugs.

Methotrexate-Induced Epithelial-Mesenchymal Transition in the Alveolar Epithelial Cell Line A549

PURPOSE

Methotrexate (MTX) therapy of certain cancers and rheumatoid arthritis often induces serious interstitial lung complications including pulmonary fibrosis. In this study, we investigated the epithelial-mesenchymal transition (EMT) induced by MTX and by transforming growth factor (TGF)-β1 in the human alveolar epithelial cell line A549 in order to develop new strategies for the prevention of EMT.

METHODS

First, we examined the effect of TGF-β1 and MTX on cell morphology and the expression of EMT-related mRNAs in A549 cells. Then, the effects of SB431542 (SB), a potent inhibitor of TGF-β receptor kinase, and a neutralizing antibody for TGF-β1 on the phenotypic changes of A549 cells induced by TGF-β1 and MTX were examined.

RESULTS

After incubation with TGF-β1 and MTX, the mRNA expression of epithelial markers such as cytokeratin 19 was reduced, while that of mesenchymal markers such as α-smooth muscle actin was increased. SB suppressed the development of morphological changes and partially rescued alterations in mRNA expression of EMT markers induced by MTX. In addition, the enhancement of SMAD2 phosphorylation by MTX was also prevented by SB. On the other hand, EMT-related changes induced by MTX were not affected by a neutralizing antibody for TGF-β1.

CONCLUSION

We have demonstrated that phenotypic changes of A549 cells induced by MTX are partly mediated by a TGF-β1-related intracellular signaling pathway, although TGF-β1 itself is not directly involved in this process.

Modulation of P-glycoprotein function and multidrug resistance in cancer cells by Thai plant extracts

The effects of ethanol extracts from Thai plants belonging to the families of Annonaceae, Rutaceae, and Zingiberaceae on P-glycoprotein (P-gp) function and multidrug resistance were examined in paclitaxel-resistant HepG2 (PR-HepG2) cells. All the extracts tested, significantly increased the accumulation of [3H]paclitaxel, a P-gp substrate, in the cells. Among nine extracts, Z01 and Z02, extracts from Curcuma comosa and Kaempferia marginata (Zingiberaceae family), respectively, potently increased the accumulation. In addition, Z01 and Z02 increased the accumulation of other P-gp substrates, rhodamine 123 and doxorubicin, in PR-HepG2 cells in a concentration-dependent manner. Increased accumulation of rhodamine 123 and doxorubicin by Z01 and Z02 was also confirmed by confocal laser scanning microscopy. The effect of Z01 and Z02 pretreatment on the expression of MDR1 mRNA was also examined. The expression of MDR1 mRNA was not affected by the treatment of PR-HepG2 cells with these extracts for 48 hours. Cytotoxicity of paclitaxel was examined by XTT and protein assays in the absence and presence of Z02. Z02 potentiated the cytotoxicity of paclitaxel in PR-HepG2 cells. These results suggest that Curcuma comosa and Kaempferia marginata belonging to Zingiberaceae are useful sources to search for new P-gp modulator(s) that can be used to overcome multidrug resistance of cancer cells.

Effect of Thai plant extracts on P-glycoprotein function and viability in paclitaxel-resistant HepG2 cells

The effects of ethanol extracts from Thai plants on P-glycoprotein (P-gp) function and cell viability were examined using paclitaxel-resistant HepG2 (PR-HepG2) cells. KP018 from Ellipeiopsis cherrevensis and AT80 from Ancistrocladus tectorius increased both rhodamine 123, a typical P-gp substrate, and [(3)H]paclitaxel uptake in PR-HepG2 cells. However, some extracts such as MT80 from Microcos tomentosa increased rhodamine 123, but not [(3)H]paclitaxel, uptake, while MM80 from Micromelum minutum increased only [(3)H]paclitaxel uptake. Thus, the effects of extracts of Thai plants on rhodamine 123 uptake were not necessarily the same as those on [(3)H]paclitaxel uptake. Purified compounds such as bergapten did not affect the uptake of either substrate. KP018, AT80, and MM80 increased [(3)H]paclitaxel uptake and decreased the cell viability in a concentration-dependent manner. Among these extracts, KP018 showed the most potent cytotoxicity. The cytotoxic potency of KP018 on PR-HepG2 cells was similar to that on wild-type HepG2 cells, and was not potentiated by verapamil. At concentrations resulting in no cytotoxicity, AT80 and MM80 potentiated paclitaxel-induced cytotoxicity in PR-HepG2 cells. These results indicate that K018 may be a useful source to search for a new anticancer drug, while AT80 and MM80 may be useful as modulators of P-gp-mediated multidrug resistance in cancer cells.

Cytogenetic damage and cell-mediated immunity in pneumoconiosis

The International Agency for Research on Cancer (IARC) determined that crystalline silica inhaled from occupational sources should be classified as carcinogenic to humans and upgraded it from group 2A to group 1. It has also been found that silicosis may be associated with cancer of various organs and with autoimmune diseases. We studied both the cytogenetic effects and the influence on cell-mediated immunity of mineral dust inhalation in patients with pneumoconiosis, including silicosis. The frequency of sister chromatid exchanges and micronucleus in the pneumoconiosis group were significantly higher than in the controls, suggesting a cytogenetic influence of the occupationally inhaled dust. Alterations in the immunoregulatory T cells were observed in the pneumoconiosis groups, suggesting that inhaled mineral dust may cause immunotoxic effects. Based on these findings, we can consider that cytogenetic damages and immunoregulatory abnormalities in pneumoconiosis patients may play a role in the pathogenesis of various cancers and autoimmune diseases associated with pneumoconiosis.

Mineral dust exposure and systemic diseases

Based on clinical and immunological studies, we have proposed the hypothesis that occupational dust exposure might cause not only pneumoconiosis but also autoimmune diseases and malignancies of various organs such as neoplasms of lymphatic and hematopoietic tissues and gastric cancer. Evidence from cohort studies of pneumoconiotic patients in Japan, copper miners, and stone masons support our hypothesis. The carcinogenicity and cytotoxic effect of inhaled dust on immune cells are considered to contribute to the development of these diseases.

[Progressive pulmonary fibrosis in a case of Sjögren's syndrome with asbestos exposure]

A 62-year-old man had an occupational history of exposure to asbestos for 27 years (1947-1974). Dry mouth, dry eyes and swollen gums were noted in 1974. Sjögren's syndrome was diagnosed in 1975. The chest radiograph in 1984 showed bilateral pleural thickening and small reticular opacities in the left lower lung field. In 1990, he complained of dyspnea and cough, and diffuse interstitial pneumonia was diagnosed. While being treated for diffuse interstitial pneumonia, pulmonary fibrosis progressed rapidly, and advanced pulmonary fibrosis was obvious in 1992. Laboratory data showed hyper gamma-globulinemia (36.8%) and a high level of IgG (3772 mg/dl) in 1976. These values decreased to within the normal ranges during the subsequent clinical course. The results of lymphocyte subset counts in 1988 were normal. With the progression of diffuse interstitial pneumonia in 1990, the lymphocyte subset counts showed a low percentage of CD4 (19.2%), a low CD4/8 ratio (0.46), and a low percentage of CD20 (26.8%). In 1992, as pulmonary fibrosis progressed despite treatment, the disorder of lymphocyte subsets became worse. The CD4 percentage was very low (5.0%), as was the CD4/8 ratio (0.08), and the percentage of CD20 (1.4%); the CD8 percentage was high (64.7%), as was the percentage of Leu 7 (49.0%). These immunologic and pulmonary changes could be not explained by Sjögren's syndrome. Determining what factor induced these changes is difficult, but asbestos exposure is a likely cause.