Constitutive expression of p-glycoprotein in normal lung alveolar epithelium and functionality in primary alveolar epithelial cultures

P-glycoprotein (P-gp)-driven cancer drug resistance: biological profile, non-coding RNAs, drugs and nanomodulators

Drug resistance has compromised the efficacy of chemotherapy. The dysregulation of drug transporters including P-glycoprotein (P-gp) can mediate drug resistance through drug efflux. In this review, we highlight the role of P-gp in cancer drug resistance and the related molecular pathways, including phosphoinositide 3-kinase (PI3K)-Akt, phosphatase and tensin homolog (PTEN) and nuclear factor-κB (NF-κB), along with non-coding RNAs (ncRNAs). Extracellular vesicles secreted by the cells can transport ncRNAs and other proteins to change P-gp activity in cancer drug resistance. P-gp requires ATP to function, and the induction of mitochondrial dysfunction or inhibition of glutamine metabolism can impair P-gp function, thus increasing chemosensitivity. Phytochemicals, small molecules and nanoparticles have been introduced as P-gp inhibitors to increase drug sensitivity in human cancers.

Dynamics of Endothelial Cell Diversity and Plasticity in Health and Disease

Endothelial cells (ECs) are vital structural units of the cardiovascular system possessing two principal distinctive properties: heterogeneity and plasticity. Endothelial heterogeneity is defined by differences in tissue-specific endothelial phenotypes and their high predisposition to modification along the length of the vascular bed. This aspect of heterogeneity is closely associated with plasticity, the ability of ECs to adapt to environmental cues through the mobilization of genetic, molecular, and structural alterations. The specific endothelial cytoarchitectonics facilitate a quick structural cell reorganization and, furthermore, easy adaptation to the extrinsic and intrinsic environmental stimuli, known as the epigenetic landscape. ECs, as universally distributed and ubiquitous cells of the human body, play a role that extends far beyond their structural function in the cardiovascular system. They play a crucial role in terms of barrier function, cell-to-cell communication, and a myriad of physiological and pathologic processes. These include development, ontogenesis, disease initiation, and progression, as well as growth, regeneration, and repair. Despite substantial progress in the understanding of endothelial cell biology, the role of ECs in healthy conditions and pathologies remains a fascinating area of exploration. This review aims to summarize knowledge and concepts in endothelial biology. It focuses on the development and functional characteristics of endothelial cells in health and pathological conditions, with a particular emphasis on endothelial phenotypic and functional heterogeneity.

How to use an in vitro approach to characterize the toxicity of airborne compounds

As part of the development of new approach methodologies (NAMs), numerous in vitro methods are being developed to characterize the potential toxicity of inhalable xenobiotics (gases, volatile organic compounds, polycyclic aromatic hydrocarbons, particulate matter, nanoparticles). However, the materials and methods employed are extremely diverse, and no single method is currently in use. Method standardization and validation would raise trust in the results and enable them to be compared. This four-part review lists and compares biological models and exposure methodologies before describing measurable biomarkers of exposure or effect. The first section emphasizes the importance of developing alternative methods to reduce, if not replace, animal testing (3R principle). The biological models presented are mostly to cultures of epithelial cells from the respiratory system, as the lungs are the first organ to come into contact with air pollutants. Monocultures or cocultures of primary cells or cell lines, as well as 3D organotypic cultures such as organoids, spheroids and reconstituted tissues, but also the organ(s) model on a chip are examples. The exposure methods for these biological models applicable to airborne compounds are submerged, intermittent, continuous either static or dynamic. Finally, within the restrictions of these models (i.e. relative tiny quantities, adhering cells), the mechanisms of toxicity and the phenotypic markers most commonly examined in models exposed at the air-liquid interface (ALI) are outlined.

High and Low Levels of ABCB1 Expression Are Associated with Two Distinct Gene Signatures in Lung Tissue of Pulmonary TB Patients with High Inflammation Activity

P-glycoprotein (encoded by the ABCB1 gene) has a dual role in regulating inflammation and reducing chemotherapy efficacy in various diseases, but there are few studies focused on pulmonary TB patients. In this study, our objective was to identify a list of genes that correlate with high and low levels of ABCB1 gene expression in the lungs of pulmonary TB patients with different activity of chronic granulomatous inflammation. We compared gene expression in two groups of samples (with moderate and high activity of tuberculomas) to identify their characteristic gene signatures. Gene expression levels were determined using quantitative PCR in samples of perifocal area of granulomas, which were obtained from 65 patients after surgical intervention. Subsequently, two distinct gene signatures associated with high inflammation activity were identified. The first signature demonstrated increased expression of HIF1a, TGM2, IL6, SOCS3, and STAT3, which correlated with high ABCB1 expression. The second signature was characterized by high expression of TNFa and CD163 and low expression of ABCB1. These results provide insight into various inflammatory mechanisms and association with P-gp gene expression in lung tissue of pulmonary TB patients and will be useful in the development of a host-directed therapy approach to improving the effectiveness of anti-TB treatment.

Regulation of ABC transporters by sex steroids may explain differences in drug resistance between sexes

Drug efficacy is dependent on the pharmacokinetics and pharmacodynamics of therapeutic agents. Tight junctions, detoxification enzymes, and drug transporters, due to their localization on epithelial barriers, modulate the absorption, distribution, and the elimination of a drug. The epithelial barriers which control the pharmacokinetic processes are sex steroid hormone targets, and in this way, sex hormones may also control the drug transport across these barriers. Thus, sex steroids contribute to sex differences in drug resistance and have a relevant impact on the sex-related efficacy of many therapeutic drugs. As a consequence, for the further development and optimization of therapeutic strategies, the sex of the individuals must be taken into consideration. Here, we gather and discuss the evidence about the regulation of ATP-binding cassette transporters by sex steroids, and we also describe the signaling pathways by which sex steroids modulate ATP-binding cassette transporters expression, with a focus in the most important ATP-binding cassette transporters involved in multidrug resistance.

PET imaging to assess the impact of P-glycoprotein on pulmonary drug delivery in rats

Several drugs approved for inhalation for the treatment of pulmonary diseases are substrates of the adenosine triphosphate-binding cassette (ABC) transporter P-glycoprotein (P-gp). P-gp is expressed in the apical membrane of pulmonary epithelial cells and could play a role in modulating the pulmonary absorption and distribution of inhaled drugs, thereby potentially contributing to variability in therapeutic response and/or systemic side effects. We developed a new in vivo experimental approach to assess the functional impact of P-gp on the pulmonary delivery of inhaled drugs in rats. By using positron emission tomography (PET) imaging, we measured the intrapulmonary pharmacokinetics of the model P-gp substrates (R)-[¹¹C]verapamil ([¹¹C]VPM) and [¹¹C]-N-desmethyl-loperamide ([¹¹C]dLOP) administered by intratracheal aerosolization in three rat groups: wild-type, Abcb1a/b^(-/-) and wild-type treated with the P-gp inhibitor tariquidar. Lung exposure (AUC_{lung_right}) to [¹¹C]VPM was 64% and 50% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b^(-/-) rats, respectively, compared to untreated wild-type rats. For [¹¹C]dLOP, AUC_{lung_right} was 59% and 34% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b^(-/-) rats, respectively. Our results show that P-gp can affect the pulmonary disposition of inhaled P-gp substrates, whereby a decrease in P-gp activity may lead to lower lung exposure and potentially to a decrease in therapeutic efficacy. Our study highlights the potential of PET imaging with intratracheally aerosolized radiotracers to assess the impact of membrane transporters on pulmonary drug delivery, in rodents and potentially also in humans.

Development of physiologically-based pharmacokinetic models for standard of care and newer tuberculosis drugs

Tuberculosis (TB) remains a global health problem and there is an ongoing effort to develop more effective therapies and new combination regimes that can reduce duration of treatment. The purpose of this study was to demonstrate utility of a physiologically‐based pharmacokinetic modeling approach to predict plasma and lung concentrations of 11 compounds used or under development as TB therapies (bedaquiline [and N‐desmethyl bedaquiline], clofazimine, cycloserine, ethambutol, ethionamide, isoniazid, kanamycin, linezolid, pyrazinamide, rifampicin, and rifapentine). Model accuracy was assessed by comparison of simulated plasma pharmacokinetic parameters with healthy volunteer data for compounds administered alone or in combination. Eighty‐four percent (area under the curve [AUC]) and 91% (maximum concentration [C_max]) of simulated mean values were within 1.5‐fold of the observed data and the simulated drug‐drug interaction ratios were within 1.5‐fold (AUC) and twofold (C_max) of the observed data for nine (AUC) and eight (C_max) of the 10 cases. Following satisfactory recovery of plasma concentrations in healthy volunteers, model accuracy was assessed further (where patients’ with TB data were available) by comparing clinical data with simulated lung concentrations (9 compounds) and simulated lung: plasma concentration ratios (7 compounds). The 5th–95th percentiles for the simulated lung concentration data recovered between 13% (isoniazid and pyrazinamide) and 88% (pyrazinamide) of the observed data points (Am J Respir Crit Care Med, 198, 2018, 1208; Nat Med, 21, 2015, 1223; PLoS Med, 16, 2019, e1002773). The impact of uncertain model parameters, such as the fraction of drug unbound in lung tissue mass (fu_mass), is discussed. Additionally, the variability associated with the patient lung concentration data, which was sparse and included extensive within‐subject, interlaboratory, and experimental variability (as well interindividual variability) is reviewed. All presented models are transparently documented and are available as open‐source to aid further research.

In vitro and ex vivo models in inhalation biopharmaceutical research - advances, challenges and future perspectives

Oral inhalation results in pulmonary drug targeting and thereby reduces systemic side effects, making it the preferred means of drug delivery for the treatment of respiratory disorders such as asthma, chronic obstructive pulmonary disease or cystic fibrosis. In addition, the high alveolar surface area, relatively low enzymatic activity and rich blood supply of the distal airspaces offer a promising pathway to the systemic circulation. This is particularly advantageous when a rapid onset of pharmacological action is desired or when the drug is suffering from stability issues or poor biopharmaceutical performance following oral administration. Several cell and tissue-based in vitro and ex vivo models have been developed over the years, with the intention to realistically mimic pulmonary biological barriers. It is the aim of this review to critically discuss the available models regarding their advantages and limitations and to elaborate further which biopharmaceutical questions can and cannot be answered using the existing models.

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.

Abdulbaqi I, Parumasivam T, Mohtar N, A. Wahab H. Advances in Nanocarriers for Effective Delivery of Docetaxel in the Treatment of Lung Cancer: An Overview

Docetaxel (DCX) is a highly effective chemotherapeutic drug used in the treatment of different types of cancer, including non-small cell lung cancer (NSCLC). The drug is known to have low oral bioavailability due to its low aqueous solubility, poor membrane permeability and susceptibility to hepatic first-pass metabolism. To mitigate these problems, DCX is administered via the intravenous route. Currently, DCX is commercially available as a single vial that contains polysorbate 80 and ethanol to solubilize the poorly soluble drug. However, this formulation causes short- and long-term side effects, including hypersensitivity, febrile neutropenia, fatigue, fluid retention, and peripheral neuropathy. DCX is also a substrate to the drug efflux pump P-glycoprotein (P-gp) that would reduce its concentration within the vicinity of the cells and lead to the development of drug resistance. Hence, the incorporation of DCX into various nanocarrier systems has garnered a significant amount of attention in recent years to overcome these drawbacks. The surfaces of these drug-delivery systems indeed can be functionalized by modification with different ligands for smart targeting towards cancerous cells. This article provides an overview of the latest nanotechnological approaches and the delivery systems that were developed for passive and active delivery of DCX via different routes of administration for the treatment of lung cancer.

Recent progress in layered double hydroxides as a cancer theranostic nanoplatform

Layered double hydroxide (LDH) has been a big challenge in exploring new hybrid materials by intercalating inorganic, organic, or bio molecules into their lamellar lattice, those which often showed dual functions from each other or new mutative properties. Recently, nano-bio convergence technology becomes one of the most extensively studied research fields in the view point of developing advanced drugs and diagnostic agents to fight against disease and eventually to improve the lives of human beings. Therefore, LDH as one of the nanomaterials have been intensively investigated not only as biocompatible drug delivery vehicle for cancer chemotherapy but also as diagnostic and imaging agents. In the present review, we have attempted to summarize theranostic functions of drug-LDH hybrid nanoparticles including their synthetic methods, physico-chemical and biological properties, and their unique mechanism overcoming drug resistance, and targeting properties based on in vitro and finally in vivo results. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > in vivo Nanodiagnostics and Imaging.

Phototoxic effectiveness of zinc phthalocyanine tetrasulfonic acid on MCF-7 cells with overexpressed P-glycoprotein

The development of multidrug resistance is often associated with the over-expression of P-glycoprotein (P-gp). This protein prevents drug accumulation and extrudes them out of the cell before they reach the intended target. The aim of this study was to develop an in vitro MCF-7 cell line with increased expression of P-gp and test the phototoxicity of a novel photoactivated zinc phthalocyanine tetrasulfonic acid (ZnPcS4) on these cells. The over-expressed P-gp MCF-7 cells (MCF-7/DOX) were developed from wildtype (WT) MCF-7 cells by a stepwise continuous exposure of the WT cells to different concentrations of Doxorubicin (DOX) (0.1 - 1 μM) over a period of 4 months. The P-gp expression was measured using flow cytometry, immunofluorescence and enzyme immunoassay. To verify whether zinc phthalocyanine-mediated photodynamic therapy (ZnPcS4 - PDT) is effective in MCF-7/DOX, we studied the subcellular localization, phototoxicity and nuclear damage. The flow cytometry result showed two distinct peaks of P-gp positive and negative expression in MCF-7/DOX cell population, which correlates with the ELISA-based assay (p˂0.001). The ME16C (Normal breast cells) was used as control. The localization studies showed that ZnPcS4 have greater affinity for lysosome than mitochondria. Phototoxicity results indicated that photoactivated zinc phthalocyanine decreased the cell proliferation and viability as the drug and laser light dosages increased to 16 μM and 20 J/cm² respectively. PDT-induced cytotoxicity using lactose dehydrogenase (LDH) enzyme leakage as measure did not increase likewise. The ZnPcS4-induced PDT was less effective for MCF-7/DOX cells which could be attributed to decreased retention of ZnPcS4 in major cellular organelles due to the presence of increased drug efflux P-gp. The current findings suggest that, increased P-gp expression, a characteristic of multidrug resistance together with other related intrinsic mechanisms might contribute to render MCF-7/DOX cells less sensitive to ZnPcS4-induced phototoxicity.

A Breath of Fresh Air in the Fog of Antimicrobial Resistance: Inhaled Polymyxins for Gram-Negative Pneumonia

Despite advancements in therapy, pneumonia remains the leading cause of death due to infectious diseases. Novel treatment strategies are desperately needed to optimize the antimicrobial therapy of patients suffering from this disease. One such strategy that has recently garnered significant attention is the use of inhaled antibiotics to rapidly achieve therapeutic concentrations directly at the site of infection. In particular, there is significant interest in the role of inhaled polymyxins for the treatment of nosocomial pneumonia, including ventilator-associated pneumonia, due to their retained activity against multi-drug resistant Gram-negative pathogens, including Acinetobacter baumannii and Pseudomonas aeruginosa. This review will provide a comprehensive overview of the pharmacokinetic/pharmacodynamic profile, clinical outcomes, safety, and potential role of inhaled polymyxins in clinical practice.

Effect of age on the pharmacokinetics and distribution of tulathromycin in interstitial and pulmonary epithelial lining fluid in healthy calves

OBJECTIVE To compare the plasma pharmacokinetics of tulathromycin between 3-week-old (preweaned) and 6-month-old (weaned) calves and to characterize the distribution of tulathromcyin into pulmonary epithelial lining fluid (PELF) and interstitial fluid (ISF) of preweaned and weaned calves following SC administration of a single dose (2.5 mg/kg). ANIMALS 8 healthy 3-week-old and 8 healthy 6-month-old Holstein steers. PROCEDURES A jugular catheter and SC ultrafiltration probe were aseptically placed in the neck of each calf before tulathromycin administration. Blood, ISF, and bronchoalveolar lavage fluid samples were collected at predetermined times before and after tulathromycin administration for quantification of drug concentration. A urea dilution method was used to estimate tulathromycin concentration in PELF from that in bronchoalveolar lavage fluid. Tulathromycin-plasma protein binding was determined by in vitro methods. Plasma pharmacokinetics were determined by a 2-compartment model. Pharmacokinetic parameters and drug concentrations were compared between preweaned and weaned calves. RESULTS Clearance and volume of distribution per fraction of tulathromycin absorbed were significantly greater for weaned calves than preweaned calves. Tulathromycin-plasma protein binding was significantly greater for weaned calves than preweaned calves. Maximum PELF tulathromycin concentration was significantly greater than the maximum plasma and maximum ISF tulathromycin concentrations in both groups. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that age affected multiple pharmacokinetic parameters of tulathromycin, likely owing to physiologic changes as calves mature from preruminants to ruminants. Knowledge of those changes may be useful in the development of studies to evaluate potential dose adjustments during treatment of calves with respiratory tract disease.

P-glycoprotein and chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a heterogeneous definition that includes different disease states that usually are associated with abnormal inflammatory responses. Besides being prevalent, the mechanisms involved in its pathogenesis are not clear and there are few therapeutic options with tolerable side effects. P-glycoprotein (P-gp) is an efflux pump responsible of extruding xenobiotics and cellular metabolites from multiple cell types. It has been widely studied in the cancer field, due to its ability to confer resistance to chemotherapy. It also promotes Type 2 helper T-cell polarizing cytokine secretion in CRS and may represent a potential target to differentiate subtypes of CRS and personalize treatment. This state-of-the-art review explores current knowledge on the participation of P-gp in the pathogenesis of CRS, the P-gp inhibition as a novel targeted therapeutic strategy and the exosomal P-gp test, a non-invasive biomarker that can represent an important advance in the field of rhinology.

Toxicity of orally inhaled drug formulations at the alveolar barrier: parameters for initial biological screening

Oral delivery is the most common mode of systemic drug application. Inhalation is mainly used for local therapy of lung diseases but may also be a promising route for systemic delivery of drugs that have poor oral bioavailability. The thin alveolar barrier enables fast and efficient uptake of many molecules and could deliver small molecules and proteins, which are susceptible to degradation and show poor absorption by oral application. The low rate of biotransformation and proteolytic degradation increases bioavailability of drugs but accumulation of not absorbed material may impair normal lung function. This limitation is more relevant for compounds that should be systematically active because higher doses have to be applied to the lung. The review describes processes that determine absorption of orally inhaled formulations, namely dissolution in the lung lining fluid and uptake and degradation by alveolar epithelial cells and macrophages. Dissolution testing in simulated lung fluid, screening for cytotoxicity and pro-inflammatory action in respiratory cells and study of macrophage morphology, and phagocytosis can help to identify adverse effects of pulmonary formulations.

The Differential Absorption of a Series of P-Glycoprotein Substrates in Isolated Perfused Lungs from Mdr1a/1b Genetic Knockout Mice can be Attributed to Distinct Physico-Chemical Properties: an Insight into Predicting Transporter-Mediated, Pulmonary Specific Disposition

PURPOSE

To examine if pulmonary P-glycoprotein (P-gp) is functional in an intact lung; impeding the pulmonary absorption and increasing lung retention of P-gp substrates administered into the airways. Using calculated physico-chemical properties alone build a predictive Quantitative Structure-Activity Relationship (QSAR) model distinguishing whether a substrate's pulmonary absorption would be limited by P-gp or not.

METHODS

A panel of 18 P-gp substrates were administered into the airways of an isolated perfused mouse lung (IPML) model derived from Mdr1a/Mdr1b knockout mice. Parallel intestinal absorption studies were performed. Substrate physico-chemical profiling was undertaken. Using multivariate analysis a QSAR model was established.

RESULTS

A subset of P-gp substrates (10/18) displayed pulmonary kinetics influenced by lung P-gp. These substrates possessed distinct physico-chemical properties to those P-gp substrates unaffected by P-gp (8/18). Differential outcomes were not related to different intrinsic P-gp transporter kinetics. In the lung, in contrast to intestine, a higher degree of non-polar character is required of a P-gp substrate before the net effects of efflux become evident. The QSAR predictive model was applied to 129 substrates including eight marketed inhaled drugs, all these inhaled drugs were predicted to display P-gp dependent pulmonary disposition.

CONCLUSIONS

Lung P-gp can affect the pulmonary kinetics of a subset of P-gp substrates. Physico-chemical relationships determining the significance of P-gp to absorption in the lung are different to those operative in the intestine. Our QSAR framework may assist profiling of inhaled drug discovery candidates that are also P-gp substrates. The potential for P-gp mediated pulmonary disposition exists in the clinic.

Endocytic Uptake, Transport and Macromolecular Interactions of Anionic PAMAM Dendrimers within Lung Tissue

Purpose

Polyamidoamine (PAMAM) dendrimers are a promising class of nanocarrier with applications in both small and large molecule drug delivery. Here we report a comprehensive evaluation of the uptake and transport pathways that contribute to the lung disposition of dendrimers.

Methods

Anionic PAMAM dendrimers and control dextran probes were applied to an isolated perfused rat lung (IPRL) model and lung epithelial monolayers. Endocytosis pathways were examined in primary alveolar epithelial cultures by confocal microscopy. Molecular interactions of dendrimers with protein and lipid lung fluid components were studied using small angle neutron scattering (SANS).

Results

Dendrimers were absorbed across the intact lung via a passive, size-dependent transport pathway at rates slower than dextrans of similar molecular sizes. SANS investigations of concentration-dependent PAMAM transport in the IPRL confirmed no aggregation of PAMAMs with either albumin or dipalmitoylphosphatidylcholine lung lining fluid components. Distinct endocytic compartments were identified within primary alveolar epithelial cells and their functionality in the rapid uptake of fluorescent dendrimers and model macromolecular probes was confirmed by co-localisation studies.

Conclusions

PAMAM dendrimers display favourable lung biocompatibility but modest lung to blood absorption kinetics. These data support the investigation of dendrimer-based carriers for controlled-release drug delivery to the deep lung.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-017-2190-7) contains supplementary material, which is available to authorized users.

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

The effect of cigarette smoke extract (CSE) on P-glycoprotein (P-gp) function in the distal lung is unclear. In this study, we first examined the expression and function of P-gp and the effect of CSE in rat primary cultured alveolar epithelial cells. The expression of P-gp protein was observed in type I-like cells, but not in type II cells. In type I-like cells, rhodamine 123 (Rho123) accumulation was enhanced by various P-gp inhibitors such as verapamil and cyclosporine A. In addition, the expression of P-gp mRNAs, mdr1a and mdr1b, as well as P-gp activity increased along with the transdifferentiation. When type I-like cells were co-incubated with CSE, P-gp activity was suppressed. Next, we attempted to clarify the effect of CSE on P-gp function in human-derived cultured alveolar epithelial cells. For this purpose, we isolated an A549 clone (A549/P-gp) expressing P-gp, because P-gp expression in native A549 cells was negligible. In A549/P-gp cells, P-gp was functionally expressed, and the inhibitory effect of CSE on P-gp was observed. These results suggested that smoking would directly suppress P-gp activity, and that A549/P-gp cell line should be a useful model to further study the effect of xenobiotics on P-gp function in the alveolar epithelial cells.

Effect of MDR1 gene polymorphisms on mortality in paraquat intoxicated patients

Paraquat is a fatal herbicide following acute exposure. Previous studies have suggested that multidrug resistance protein 1 (MDR1) might help remove paraquat from the lungs and the kidney. MDR1 single-nucleotide polymorphisms (SNPs) are involved in the pharmacokinetics of many drugs. The purpose of this study was to determine whether MDR1 SNPs were associated with the mortality in paraquat intoxicated patients. We recruited 109 patients admitted with acute paraquat poisoning. They were genotyped for C1236T, G2677T/A, and C3435T single-nucleotide polymorphisms (SNPs) of MDR1 gene. Their effects on mortality of paraquat intoxicated patients were evaluated. Overall mortality rate was 66.1%. Regarding the C1236T of the MDR1 gene polymorphism, 21 (19.3%) had the wild type MDR1 while 88 (80.7%) had homozygous mutation. Regarding the C3435T MDR1 gene polymorphism, 37(33.9%) patients had the wild type, 23 (21.1%) had heterozygous mutation, and 49 (45.0%) had homozygous mutation. Regarding the G2677T/A MDR1 gene polymorphism, 38 (34.9%) patients had the wild type, 57 (52.3%) had heterozygous mutation, and 14 (12.8%) had homozygous mutation. None of the individual mutations or combination of mutations (two or three) of MDR1 SNP genotypes altered the morality rate. The mortality rate was not significantly different among SNP groups of patients with <4.0 μg/mL paraquat. In conclusion, MDR1 SNPs have no effect on the mortality rate of paraquat intoxicated patients.

Inhaled Antibiotics for Gram-Negative Respiratory Infections

Gram-negative organisms comprise a large portion of the pathogens responsible for lower respiratory tract infections, especially those that are nosocomially acquired, and the rate of antibiotic resistance among these organisms continues to rise. Systemically administered antibiotics used to treat these infections often have poor penetration into the lung parenchyma and narrow therapeutic windows between efficacy and toxicity. The use of inhaled antibiotics allows for maximization of target site concentrations and optimization of pharmacokinetic/pharmacodynamic indices while minimizing systemic exposure and toxicity. This review is a comprehensive discussion of formulation and drug delivery aspects, in vitro and microbiological considerations, pharmacokinetics, and clinical outcomes with inhaled antibiotics as they apply to disease states other than cystic fibrosis. In reviewing the literature surrounding the use of inhaled antibiotics, we also highlight the complexities related to this route of administration and the shortcomings in the available evidence. The lack of novel anti-Gram-negative antibiotics in the developmental pipeline will encourage the innovative use of our existing agents, and the inhaled route is one that deserves to be further studied and adopted in the clinical arena.

Preparation, in vitro and in vivo evaluation of polymeric nanoparticles based on hyaluronic acid-poly(butyl cyanoacrylate) and D-alpha-tocopheryl polyethylene glycol 1000 succinate for tumor-targeted delivery of morin hydrate

Herein, we describe the preparation of a targeted cellular delivery system for morin hydrate (MH), based on a low-molecular-weight hyaluronic acid-poly(butyl cyanoacrylate) (HA-PBCA) block copolymer. In order to enhance the therapeutic effect of MH, D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS) was mixed with HA-PBCA during the preparation process. The MH-loaded HA-PBCA “plain” nanoparticle (MH-PNs) and HA-PBCA/TPGS “mixed” nanoparticles (MH-MNs) were concomitantly characterized in terms of loading efficiency, particle size, zeta potential, critical aggregation concentration, and morphology. The obtained MH-PNs and MH-MNs exhibited a spherical morphology with a negative zeta potential and a particle size less than 200 nm, favorable for drug targeting. Remarkably, the addition of TPGS resulted in about 1.6-fold increase in drug-loading. The in vitro cell viability experiment revealed that MH-MNs enhanced the cytotoxicity of MH in A549 cells compared with MH solution and MH-PNs. Furthermore, blank MNs containing TPGS exhibited selective cytotoxic effects against cancer cells without diminishing the viability of normal cells. In addition, the cellular uptake study indicated that MNs resulted in 2.28-fold higher cellular uptake than that of PNs, in A549 cells. The CD44 receptor competitive inhibition and the internalization pathway studies suggested that the internalization mechanism of the nanoparticles was mediated mainly by the CD44 receptors through a clathrin-dependent endocytic pathway. More importantly, MH-MNs exhibited a higher in vivo antitumor potency and induced more tumor cell apoptosis than did MH-PNs, following intravenous administration to S180 tumor-bearing mice. Overall, the results imply that the developed nanoparticles are promising vehicles for the targeted delivery of lipophilic anticancer drugs.

Biopharmaceutical characterization of nebulized antimicrobial agents in rats: 1. Ciprofloxacin, moxifloxacin, and grepafloxacin

The aim of this study was to evaluate the biopharmaceutical characteristics of three fluoroquinolones (FQs), ciprofloxacin (CIP), moxifloxacin (MXF), and grepafloxacin (GRX), after delivery via a nebulized aerosol to rats. Bronchoalveolar lavages (BAL) were conducted 0.5, 2, 4, and 6 h after FQ intravenous administration and nebulized aerosol delivery to estimate epithelial lining fluid (ELF) drug concentrations. Plasma drug concentrations were also measured, and profiles of drug concentrations versus time after intravenous administration and nebulized aerosol delivery were virtually superimposable, attesting for rapid and complete systemic absorption of FQs. ELF drug concentrations were systematically higher than corresponding plasma drug concentrations, whatever the route of administration, and average ELF-to-unbound plasma drug concentration ratios post-distribution equilibrium did not change significantly between the ways of administration and were equal: 4.0 ± 5.3 for CIP, 12.6 ± 7.3 for MXF, and 19.1 ± 10.5 for GRX (means ± standard deviations). The impact of macrophage lysis on estimated ELF drug concentrations was significant for GRX but reduced for MXF and CIP; therefore, simultaneous pharmacokinetic modeling of plasma and ELF drug concentrations was only performed for the latter two drugs. The model was characterized by a fixed volume of ELF (VELF), passive diffusion clearance (QELF), and active efflux clearance (CLout) between plasma and ELF, indicating active efflux transport systems. In conclusion, this study demonstrates that ELF drug concentrations of these three FQs are several times higher than plasma drug concentrations, probably due to the presence of efflux transporters at the pulmonary barrier level, but no biopharmaceutical advantage of FQ nebulization was observed compared with intravenous administration.

Potential for layered double hydroxides-based, innovative drug delivery systems

Layered Double Hydroxides (LDHs)-based drug delivery systems have, for many years, shown great promises for the delivery of chemical therapeutics and bioactive molecules to mammalian cells in vitro and in vivo. This system offers high efficiency and drug loading density, as well as excellent protection of loaded molecules from undesired degradation. Toxicological studies have also found LDHs to be biocompatible compared with other widely used nanoparticles, such as iron oxide, silica, and single-walled carbon nanotubes. A plethora of bio-molecules have been reported to either attach to the surface of or intercalate into LDH materials through co-precipitation or anion-exchange reaction, including amino acid and peptides, ATPs, vitamins, and even polysaccharides. Recently, LDHs have been used for gene delivery of small molecular nucleic acids, such as antisense, oligonucleotides, PCR fragments, siRNA molecules or sheared genomic DNA. These nano-medicines have been applied to target cells or organs in gene therapeutic approaches. This review summarizes current progress of the development of LDHs nanoparticle drug carriers for nucleotides, anti-inflammatory, anti-cancer drugs and recent LDH application in medical research. Ground breaking studies will be highlighted and an outlook of the possible future progress proposed. It is hoped that the layered inorganic material will open up new frontier of research, leading to new nano-drugs in clinical applications.

Gaining the Upper Hand on Pulmonary Drug Delivery

Asthma, Chronic Obstructive Pulmonary Disease (COPD) and Cystic Fibrosis (CF) are all pulmonary diseases which are characterized by chronic inflammation and an increase in mucus production. Excess mucus in the airways correlates with pathophysiology such as a decline in lung function and prolonged bacterial infections. New drugs to treat these chronic respiratory diseases are currently being developed and include both inhaled and orally administered compounds. Whilst oral drugs may be easier to administer, they are more prone to side-effects due to higher bioavailability. Inhaled compounds may show reduced bioavailability, but face their own unique challenges. For example, thick mucus in the respiratory tracts of asthma, CF and COPD patients can act as a physical barrier that impedes drug delivery. Mucus also contains a high number of enzymes and proteases that may degrade compounds before they reach their site of action. Furthermore, some classes of drugs are rapidly absorbed across the respiratory epithelia into systemic circulation, which may limit their duration of action and/or cause off-target effects. This review discusses some of the different treatment options that are currently available and the considerations that need to be taken into account to produce new therapies for the treatment of chronic respiratory diseases.

Clinical experimentation with aerosol antibiotics: current and future methods of administration

Currently almost all antibiotics are administered by the intravenous route. Since several systems and situations require more efficient methods of administration, investigation and experimentation in drug design has produced local treatment modalities. Administration of antibiotics in aerosol form is one of the treatment methods of increasing interest. As the field of drug nanotechnology grows, new molecules have been produced and combined with aerosol production systems. In the current review, we discuss the efficiency of aerosol antibiotic studies along with aerosol production systems. The different parts of the aerosol antibiotic methodology are presented. Additionally, information regarding the drug molecules used is presented and future applications of this method are discussed.

Selectivity in the impact of P-glycoprotein upon pulmonary absorption of airway-dosed substrates: a study in ex vivo lung models using chemical inhibition and genetic knockout

P-glycoprotein (P-gp) mediated efflux is recognised to alter the absorption and disposition of a diverse range of substrates. Despite evidence showing the presence of P-gp within the lung, relatively little is known about the transporter's effect upon the absorption and distribution of drugs delivered via the pulmonary route. Here, we present data from an intact isolated rat lung model, alongside two isolated mouse lung models using either chemical or genetic inhibition of P-gp. Data from all three models show inhibition of P-gp increases the extent of absorption of a subset of P-gp substrates (e.g. rhodamine 123 and loperamide) whose physico-chemical properties are distinct from those whose pulmonary absorption remained unaffected (e.g. digoxin and saquinavir). This is the first study showing direct evidence of P-gp mediated efflux within an intact lung, a finding that should warrant consideration as part of respiratory drug discovery and development as well as in the understanding of pulmonary pharmacokinetic (PK)-pharmacodynamic (PD) relationships.

New insights in the production of aerosol antibiotics. Evaluation of the optimal aerosol production system for ampicillin-sulbactam, meropenem, ceftazidime, cefepime and piperacillin-tazobactam

BACKGROUND

Several aerosol antibiotics are on the market and several others are currently being evaluated. Aim of the study was to evaluate the aerosol droplet size of five different antibiotics for future evaluation as an aerosol administration.

MATERIALS AND METHODS

The nebulizers Sunmist(®), Maxineb(®) and Invacare(®) were used in combination with four different "small <6 ml" residual cups and two "large <10 ml" with different loadings 2-4-6-8 ml (8 ml only for large residual cups) with five different antibiotic drugs (ampicilln-sulbactam, meropenem, ceftazidime, cefepime and piperacillin-tazobactam). The Mastersizer 2000 (Malvern) was used to evaluate the produced droplet size from each combination

RESULTS

Significant effect on the droplet size produced the different antibiotic (F=96.657, p<0.001) and the residual cup design (F=68.535, p<0.001) but not the different loading amount (p=0.127) and the nebulizer (p=0.715). Interactions effects were found significant only between antibiotic and residual cup (F=16.736, p<0.001). No second order interactions were found statistically significant.

CONCLUSION

Our results firstly indicate us indirectly that the chemical formulation of the drug is the main factor affecting the produced droplet size and secondly but closely the residual cup design.

Drug Resistance Mechanisms in Non-Small Cell Lung Carcinoma

Lung cancer is the most commonly diagnosed cancer in the world. “Driver” and “passenger” mutations identified in lung cancer indicate that genetics play a major role in the development of the disease, progression, metastasis and response to therapy. Survival rates for lung cancer treatment have remained stagnant at ~15% over the past 40 years in patients with disseminated disease despite advances in surgical techniques, radiotherapy and chemotherapy. Resistance to therapy; either intrinsic or acquired has been a major hindrance to treatment leading to great interest in studies seeking to understand and overcome resistance. Genetic information gained from molecular analyses has been critical in identifying druggable targets and tumor profiles that may be predictors of therapeutic response and mediators of resistance. Mutated or overexpressed epidermal growth factor receptor (EGFR) and translocations in the echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) genes (EML4-ALK) are examples of genetic aberrations resulting in targeted therapies for both localized and metastatic disease. Positive clinical responses have been noted in patients harboring these genetic mutations when treated with targeted therapies compared to patients lacking these mutations. Resistance is nonetheless a major factor contributing to the failure of targeted agents and standard cytotoxic agents. In this review, we examine molecular mechanisms that are potential drivers of resistance in non-small cell lung carcinoma, the most frequently diagnosed form of lung cancer. The mechanisms addressed include resistance to molecular targeted therapies as well as conventional chemotherapeutics through the activity of multidrug resistance proteins.

Evaluation of layers of the rat airway epithelial cell line RL-65 for permeability screening of inhaled drug candidates

A rat respiratory epithelial cell culture system for in vitro prediction of drug pulmonary absorption is currently lacking. Such a model may however enhance the understanding of interspecies differences in inhaled drug pharmacokinetics by filling the gap between human in vitro and rat in/ex vivo drug permeability screens. The rat airway epithelial cell line RL-65 was cultured on Transwell inserts for up to 21 days at an air-liquid (AL) interface and cell layers were evaluated for their suitability as a drug permeability measurement tool. These layers were found to be morphologically representative of the bronchial/bronchiolar epithelium when cultured for 8 days in a defined serum-free medium. In addition, RL-65 layers developed epithelial barrier properties with a transepithelial electrical resistance (TEER) >300 Ω cm(2) and apparent (14)C-mannitol permeability (P(app)) values between 0.5-3.0 × 10(-6)cm/s; i.e., in the same range as established in vitro human bronchial epithelial absorption models. Expression of P-glycoprotein was confirmed by gene analysis and immunohistochemistry. Nevertheless, no vectorial transport of the established substrates (3)H-digoxin and Rhodamine123 was observed across the layers. Although preliminary, this study shows RL-65 cell layers have the potential to become a useful in vitro screening tool in the pre-clinical development of inhaled drug candidates.

Spatial expression and functionality of drug transporters in the intact lung: objectives for further research

This commentary provides a background appraising evidence in the intact lung on the spatial expression of drug transporters and, where available, evidence in the intact lung of the impact, or otherwise, that such transporters can have upon pulmonary drug absorption and disposition. Ultimately drug discovery and development scientists will wish to identify in a 'pulmonary' context the effect of disease upon transporter function, the potential for drug transporters to contribute to drug-drug interactions and to inter-individual variation in drug handling and response. The rate and extent of lung epithelial permeation of drugs involve an interplay between the dose and the deposition site of drug within the lung and physiological variables operational at the epithelial-luminal interface. Amongst the latter variables is the potential impact of active transporter processes which may well display regio-selective characteristics along the epithelial tract. In pulmonary tissues the spatial pattern of drug transporter expression is generally poorly defined and the functional significance of transporters within the intact lung is explored in only a limited manner. Active transporters in the lung epithelium may affect airway residence times of drug, modulate access of drug to intracellular targets and to submucosal lung tissue, and potentially influence airway to systemic drug absorption profiles. Transporters in the lung tissue may also have the capacity to mediate uptake of drug from the systemic circulation resulting in drug accumulation in the lung. Transporters have physiological roles and new drug candidates while not necessarily serving as transport substrates may modulate transporter activity and hence physiology. The commentary highlights a series of recommendations for further work in pulmonary drug transporter research.

Surfactant protein A (SP-A)-tacrolimus complexes have a greater anti-inflammatory effect than either SP-A or tacrolimus alone on human macrophage-like U937 cells

Intratracheal administration of immunosuppressive agents to the lung is a novel treatment after lung transplantation. Nanoparticles of tacrolimus (FK506) might interact with human SP-A, which is the most abundant lipoprotein in the alveolar fluid. This study was undertaken to determine whether the formation of FK506/SP-A complexes interferes with FK506 immunosuppressive actions on stimulated human macrophage-like U937 cells. We found that SP-A was avidly bound to FK506 (K(d) = 35 ± 4nM), as determined by solid phase-binding assays and dynamic light scattering. Free FK506, at concentrations ≤ 1 μM, had no effect on the inflammatory response of LPS-stimulated U937 macrophages. However, coincubation of FK506 and SP-A, at concentrations where each component alone did not affect LPS-stimulated macrophage response, significantly inhibited LPS-induced NF-κB activation and TNF-alpha secretion. Free FK506, but not FK506/SP-A, functioned as substrate for the efflux transporter P-glycoprotein. FK506 bound to SP-A was delivered to macrophages by endocytosis, since several endocytosis inhibitors blocked FK506/SP-A anti-inflammatory effects. This process depended partly on SP-A binding to its receptor, SP-R210. These results indicate that FK506/SP-A complexes have a greater anti-inflammatory effect than either FK506 or SP-A alone and suggest that SP-A strengthened FK506 anti-inflammatory activity by facilitating FK506 entrance into the cell, overcoming P-glycoprotein.

Drug transporters in the lung--do they play a role in the biopharmaceutics of inhaled drugs?

The role of transporters in drug absorption, distribution and elimination processes as well as in drug-drug interactions is increasingly being recognised. Although the lungs express high levels of both efflux and uptake drug transporters, little is known of the implications for the biopharmaceutics of inhaled drugs. The current knowledge of the expression, localisation and functionality of drug transporters in the pulmonary tissue and the few studies that have looked at their impact on pulmonary drug absorption is extensively reviewed. The emphasis is on transporters most likely to affect the disposition of inhaled drugs: (1) the ATP-binding cassette (ABC) superfamily which includes the efflux pumps P-glycoprotein (P-gp), multidrug resistance associated proteins (MRPs), breast cancer resistance protein (BCRP) and (2) the solute-linked carrier (SLC and SLCO) superfamily to which belong the organic cation transporter (OCT) family, the peptide transporter (PEPT) family, the organic anion transporter (OAT) family and the organic anion transporting polypeptide (OATP) family. Whenever available, expression and localisation in the intact human tissue are compared with those in animal lungs and respiratory epithelial cell models in vitro. The influence of lung diseases or exogenous agents on transporter expression is also mentioned.

Lack of difference in pulmonary absorption of digoxin, a P-glycoprotein substrate, in mdr1a-deficient and mdr1a-competent mice

Although in-vitro experiments have suggested that P-glycoprotein (P-gp) may have an important influence on the disposition of inhaled drugs, the effect of P-gp on absorption from the lung in-vivo has not been reported previously. The aim of this study was to compare the pulmonary absorption of digoxin, a well-characterised substrate for P-gp, in mdr1a (–/–) (P-gp-deficient) and mdr1a (+/+) (P-gp-competent) mice. Digoxin was administered by intratracheal instillation over 3–4 s, a method demonstrated to result in dispersion of the dose to all regions of the lung. Drug distribution was determined in the lungs, plasma, brain, heart, liver and kidney of individual mice after 5, 10, 30, 60 and 90 min. Digoxin was cleared rapidly from the lung after intratracheal administration. No differences were observed in the maximum serum concentrations between mdr1a (+/+) and mdr1a (–/–) mice (37.8 ± 6.9 and 38.8 ± 15.8 ng mL−1, respectively). The serum concentration versus time profiles were similar in both strains; the area under the drug serum concentration versus time curve (AUC) was 2010 and 1812 ng mL−1 min in mdr1a (–/–) and mdr1a (+/+) mice, respectively. For organs harvested at the end of the experiment (90 min), the only significant difference between the strains was the markedly elevated concentration of digoxin in the brains of mdr1a (–/–) mice. In conclusion, digoxin is rapidly absorbed from the mouse lung following tracheal instillation, with no difference in the rate or extent of absorption between mdr1a-deficient and -competent mice. This suggests that, in contrast to the scenario suggested by in-vitro data, P-gp in the respiratory epithelium may have little influence on the disposition of drugs that are well absorbed from the lung.

In-vitro respiratory drug absorption models possess nominal functional P-glycoprotein activity

Objectives

The P-glycoprotein (P-gp) efflux pump is known to be present within several major physiological barriers including the brain, kidney, intestine and placenta. However, the function of P-gp in the airways of the lung is unclear. The purpose of this study was to use the highly specific P-gp inhibitor GF120918A to investigate the activity of the P-gp transporter in the airways to determine whether P-gp could influence inhaled drug disposition.

Methods

P-gp activity was measured as a change in digoxin transport in the presence of GF120918A in normal human bronchial epithelial (NHBE) cells, Calu-3 cell layers and the ex-vivo rat lung.

Key findings

The efflux ratios (ERs) in NHBE and Calu-3 cells were between 0.5 and 2, in contrast to 10.7 in the Caco-2 cell control. These low levels of GF120918A-sensitive polarised digoxin transport were measured in the absorptive direction in NHBE cells (ER = 0.5) and in the secretory direction in Calu-3 cells (ER = 2), but only after 21 days in culture for both cell systems and only in Calu-3 cells at passage &gt;50. The airspace to perfusate transfer kinetics of digoxin in the ex-vivo rat lung were unchanged in the presence of GF120918A.

Conclusions

These results demonstrated that although low levels of highly culture-dependent P-gp activity could be measured in cell-lines, these should not be interpreted to mean that P-gp is a major determinant of drug disposition in the airways of the lung.

RT-PCR analysis of ABC, SLC and SLCO drug transporters in human lung epithelial cell models

Objectives

Carrier-mediated transport mechanisms play crucial roles in drug absorption and elimination processes, as well as in the transport of endogenous molecules affecting cellular regulation and function. In this study we used RT-PCR analysis to characterise the mRNA transcript expression of a wide range of membrane carrier transporters in several in-vitro lung epithelial cell models. Transporters studied included: 11 ATP-binding cassette (ABC) transporters, 11 solute carrier (SLC) transporters and 9 solute carrier organic anion (SLCO) transporters.

Methods

The cell culture models included both established cell lines (A549, Calu-3, 16HBE14o-, BEAS-2B) and freshly isolated lung epithelial cells in primary culture (human bronchial and alveolar epithelial cells).

Key findings

The expression profiles of several clinically relevant drug transporters were characterised using RT-PCR analysis. Our results showed differential transporter expression in cell culture models from different regions of the lung and also highlighted disparities when comparing lung cell lines with primary cell culture models. Differences in transporter expression between cell models of pulmonary and gastrointestinal origin were also noted.

Conclusions

The information will guide and validate the use of in-vitro lung epithelial cell lines in the study of pulmonary administered drugs and candidate molecules.