Effect of cigarette smoke extract on P-glycoprotein function in primary cultured and newly developed alveolar epithelial cells

ABCB1 expression is increased in human first trimester placenta from pregnant women classified as overweight or obese

Obesity has become a global health challenge also affecting reproductive health. In pregnant women, obesity increases the risk of complications such as preterm birth, macrosomia, gestational diabetes, and preeclampsia. Moreover, obesity is associated with long-term adverse effects for the offspring, including increased risk of cardiovascular and metabolic diseases and neurodevelopmental difficulties. The underlying mechanisms are far from understood, but placental function is essential for pregnancy outcome. Transporter proteins P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) are important for trans-placental transport of endogenous substances like lipids and cortisol, a key hormone in tissue maturation. They also hold a protective function protecting the fetus from xenobiotics (e.g. pharmaceuticals). Animal studies suggest that maternal nutritional status can affect expression of placental transporters, but little is known about the effect on the human placenta, especially in early pregnancy. Here, we investigated if overweight and obesity in pregnant women altered mRNA expression of ABCB1 encoding P-gp or ABCG2 encoding BCRP in first trimester human placenta. With informed consent, 75 first trimester placental samples were obtained from women voluntarily seeking surgical abortion (< gestational week 12) (approval no.: 20060063). Villous samples (average gestational age 9.35 weeks) were used for qPCR analysis. For a subset (n = 38), additional villi were snap-frozen for protein analysis. Maternal BMI was defined at the time of termination of pregnancy. Compared to women with BMI 18.5-24.9 kg/m² (n = 34), ABCB1 mRNA expression was significantly increased in placenta samples from women classified as overweight (BMI 25-29.9 kg/m², n = 18) (p = 0.040) and women classified as obese (BMI ≥ 30 kg/m², n = 23) (p = 0.003). Albeit P-gp expression did not show statistically significant difference between groups, the effect of increasing BMI was the same in male and female pregnancies. To investigate if the P-gp increase was compensated, we determined the expression of ABCG2 which was unaffected by maternal obesity (p = 0.291). Maternal BMI affects ABCB1 but not ABCG2 mRNA expression in first trimester human placenta. Further studies of early placental function are needed to understand how the expression of placental transport proteins is regulated by maternal factors such as nutritional status and determine the potential consequences for placental-fetal interaction.

Steroid Resistance Associated with High MIF and P-gp Serum Levels in SLE Patients

Approximately 30% of patients with systemic lupus erythematosus (SLE) present steroid resistance (SR). Macrophage migration inhibition factor (MIF) and P-glycoprotein (P-gp) could be related to SR. This work aims to evaluate the relationship between MIF and P-pg serum levels in SR in SLE. Methods: Case−control study including 188 SLE patients who were divided into two groups (90 in the steroid-resistant group and 98 in the steroid-sensitive (SS) group) and 35 healthy controls. MIF and P-gp serum levels were determined by ELISA. Multivariable logistic regression and chi-squared automatic interaction detection (CHAID) were used to explore risk factors for SR. Results: The steroid-resistant group presented higher MIF and P-gp serum levels in comparison with the SS (p < 0.001) and reference (p < 0.001) groups. MIF correlated positively with P-gp (rho = 0.41, p < 0.001). MIF (≥15.75 ng/mL) and P-gp (≥15.22 ng/mL) were a risk factor for SR (OR = 2.29, OR = 5.27). CHAID identified high P-gp as the main risk factor for SR and high MIF as the second risk factor in those patients with low P-gp. Conclusions: An association between MIF and P-gp serum levels was observed in SR. CHAID identified P-gp ≥ 15.22 ng/mL as the main risk factor for SR. More studies are needed to validate these results.

The Role of ABC Transporters in Lipid Metabolism and the Comorbid Course of Chronic Obstructive Pulmonary Disease and Atherosclerosis

Chronic obstructive pulmonary disease (COPD) ranks among the leading causes of morbidity and mortality worldwide. COPD rarely occurs in isolation and is often combined with various diseases. It is considered that systemic inflammation underlies the comorbid course of COPD. The data obtained in recent years have shown the importance of violations of the cross-links of lipid metabolism and the immune response, which are links in the pathogenesis of both COPD and atherosclerosis. The role of lipid metabolism disorders in the pathogenesis of the comorbid course of COPD and atherosclerosis and the participation of ATP-binding cassette (ABC) transporters in these processes is discussed in this article. It is known that about 20 representatives of a large family of ABC transporters provide lipid homeostasis of cells by moving lipids inside the cell and in its plasma membrane, as well as removing lipids from the cell. It was shown that some representatives of the ABC-transporter family are involved in various links of the pathogenesis of COPD and atherosclerosis, which can determine their comorbid course.

Effects of Genetic Polymorphisms of Drug Transporter ABCB1 (MDR1) and Cytochrome P450 Enzymes CYP2A6, CYP2B6 on Nicotine Addiction and Smoking Cessation

Objectives

To determine the effects of genetic polymorphisms of ABCB1 (MDR1), CYP2A6, CYP2B6 on smoking status, and clinical outcomes of smoking cessation therapies in a Turkish population.

Methods

130 smokers and 130 non-smokers were recruited. Individuals who never smoked were described as non-smokers. 130 smokers were treated with nicotine replacement therapy (NRT) (n = 40), bupropion (n = 47), bupropion + NRT (n = 15), and varenicline (n = 28). Smokers were checked by phone after 12 weeks of treatment whether they were able to quit smoking or not. Genotyping and phenotyping were performed.

Results

Cessation rates were as follows; 20.0% for NRT, 29.8% for bupropion, 40.0% for bupropion + NRT, 57.1% for varenicline (p = 0.013). The frequency of ABCB1 1236TT-2677TT-3435TT haplotype was significantly higher in non-smokers as compared to smokers (21.5% vs. 10.8, respectively; p = 0.018). Neither smoking status nor smoking cessation rates were associated with genetic variants of CYP2A6 (p = 0.652, p = 0.328, respectively), or variants of CYP2B6 (p = 0.514, p = 0.779, respectively).

Conclusion

Genetic variants of the drug transporter ABCB1 and the 1236TT-2677TT-3435TT haplotype was significantly associated with non-smoking status. Neither ABCB1 nor CYP2A6, CYP2B6 genetic variants were associated with smoking cessation rates at the 12th week of drug treatment.

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.

Suppression of P-glycoprotein by cigarette smoke extract in human lung-derived A549/P-gp cells

Effect of long-term treatment with cigarette smoke extract (CSE) on the function and expression of P-glycoprotein (P-gp) in lung alveolar epithelial cells was examined using A549/P-gp cell line expressing P-gp. CSE treatment suppressed P-gp activity in a concentration- and treatment time-dependent manner. The suppression of P-gp activity by CSE was irreversible for at least 96 h after removal of CSE. In addition, CSE treatment suppressed the expression of P-gp mRNA and protein. In order to understand the mechanisms underlying P-gp suppression by CSE, the role of reactive oxygen species (ROS) was examined. CSE treatment increased intracellular ROS level, and suppressed catalase activity. α-Tocopherol suppressed ROS production by CSE, and ameliorated the suppression of P-gp activity by CSE, suggesting that ROS is involved in CSE-induced suppression of P-gp. The role of intracellular signaling pathways such as the nuclear factor κB and mitogen-activated protein kinase pathways was also examined. Among these pathways, the involvement of extracellular signal-regulated kinase (ERK) pathway was suggested. Taken together, long-term CSE treatment may suppress P-gp via modulation of ROS level and ERK pathway in alveolar epithelial cells.

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.