P-glycoprotein inhibition promotes prednisone retention in human sinonasal polyp explants

Nanotechnology-enabled topical delivery of therapeutics in chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a chronic inflammatory disease of the paranasal sinuses which represents a significant health burden due to its widespread prevalence and impact on patients' quality of life. As the molecular pathways driving and sustaining inflammation in CRS become better elucidated, the diversity of treatment options is likely to widen significantly. Nanotechnology offers several tools to enhance the effectiveness of topical therapies, which has been limited by factors such as poor drug retention, mucosal permeation and adhesion, removal by epithelial efflux pumps and the inability to effectively penetrate biofilms. In this review, we highlight the successful application of nanomedicine in the field of CRS therapeutics, discuss current limitations and propose opportunities for future work.

Pathogenesis of Nasal Polyposis: Current Trends

Chronic Rhinosinusitis (CRS) is characterized by edema of the sub-epithelial layers, but, only specific types of CRS are developing polyps. Nasal polyposis may develop under different pathogenetic mechanisms rendering the typical macroscopic classification of CRS, with or without nasal polyps, rather deficient. Currently, we approach nasal polyposis, in terms of diagnosis and treatment, according to its endotype, which means that we focus on the specific cells and cytokines that are participating in its pathogenesis. It appears that the molecular procedures that contribute to polyp formation, initiating with a Th-2 response of the adaptive immune system, are local phenomena occurring in the sub-epithelial layers of the mucosa. Several hypotheses are trying to approach the etiology that drives the immune response towards Th-2 type. Extrinsic factors, like fungi, Staphylococcus superantigens, biofilms, and altered microbiome can contribute to a modified and intense local reaction of the immune system. Some hypotheses based on intrinsic factors like the elimination of Treg lymphocytes, low local vitamin-D levels, high levels of leukotrienes, epithelial to mesenchymal transition (EMT) induced by hypoxia, and altered levels of NO, add pieces to the puzzle of the pathogenesis of nasal polyposis. Currently, the most complete theory is that of epithelial immune barrier dysfunction. Intrinsic and extrinsic conditions can damage the epithelial barrier rendering sub-epithelial layers more vulnerable to invasion by pathogens that trigger a Th-2 response of the adaptive immune system. Th2 cytokines, subsequently, induce the accumulation of eosinophils and IgE together with the remodeling of the stroma in the sub-epithelial layers leading, eventually, to the formation of nasal polyps.

Topical Administration of Verapamil in Poly(ethylene glycol)-Modified Liposomes for Enhanced Sinonasal Tissue Residence in Chronic Rhinosinusitis: Ex Vivo and In Vivo Evaluations

Verapamil is a calcium channel blocker that holds promise for the therapy of chronic rhinosinusitis (CRS) with and without nasal polyps. The verapamil-induced side effects limit its tolerated dose via the oral route, underscoring the usefulness of localized intranasal administration. However, the challenge to intranasal administration is mucociliary clearance, which diminishes localized dose availability. To overcome this challenge, verapamil was loaded into a mucoadhesive cationic poly(ethylene glycol)-modified (PEGylated) liposomal carrier. Organotypic nasal explants were exposed to verapamil liposomes under flow conditions to mimic mucociliary clearance. The liposomes resulted in significantly higher tissue residence compared with the free verapamil control. These findings were further confirmed in vivo in C57BL/6 mice following intranasal administration. Liposomes significantly increased the accumulation of verapamil in nasal tissues compared with the control group. The developed tissue-retentive verapamil liposomal formulation is considered a promising intranasal delivery system for CRS therapy.

Mechanisms and pathogenesis of chronic rhinosinusitis

Chronic rhinosinusitis (CRS) is a heterogeneous disease characterized by local inflammation of the upper airways and is historically divided into 2 main phenotypes: CRS with nasal polyps and CRS without nasal polyps. Inflammation in CRS is mainly characterized by 3 endotypes based on elevation of canonical lymphocyte cytokines: type (T) 1 (T1) by TH1 cytokine IFN-γ, T2 by TH2 cutokines IL-4, IL-5, and IL-13, and T3 by TH17 cytokines including IL-17. Inflammation in both CRS without nasal polyps and CRS with nasal polyps is highly heterogeneous, and the frequency of various endotypes varies geographically around the world. This finding complicates establishment of a unified understanding of the mechanisms of pathogenesis in CRS. Sinonasal epithelium acts as a passive barrier, and epithelial barrier dysfunction is a common feature in CRS induced by endotype-specific cytokines directly and indirectly. The sinonasal epithelium also participates in both innate immunity via recognition by innate pattern-recognition receptors and promotes and regulates adaptive immunity via release of chemokines and innate cytokines including thymic stromal lymphopoietin. The purpose of this review was to discuss the contribution of the epithelium to CRS pathogenesis and to update the field regarding endotypic heterogeneity and various mechanisms for understanding pathogenesis in CRS.

Modulation of nose-to-brain delivery of a P-glycoprotein (MDR1) substrate model drug (quinidine) in rats

During the last decades several new drug formulations were developed to target the central nervous system (CNS) from the nasal cavity. However, in these studies less attention was paid to the possible drug-drug interactions in case of multi-drug therapy. In our pilot study first we compared a nasal solution and a nasal gel to demonstrate their distribution in the nasal cavity (3D printed rat skull model and histology). Due to the aspiration induced high mortality at administration of nasal solution the study was continued only with the gel formulation of quinidine. The aim of our experiments was to identify the possible functional role of P-glycoprotein (P-gp) in the drug absorption in nasal cavity and to test drug-drug interactions at nose-to-brain delivery. Therefore, a P-gp substrate model drug, quinidine was tested by intranasal (IN) administration in presence of PSC-833 (specific P-gp inhibitor) given intravenously (IV) or IN and adrenaline (IN) at low (50 ng) or high (20 μg) dose. In control animals the brain penetration of quinidine was at the level of detection limit, but in combination therapy with IV PSC-833 the brain levels increased dramatically, similarly to high dose IN adrenalin, where due to vasoconstriction peripheral distribution was blocked. These results indicate that P-gp has an important role in drug absorption and efflux at nasal cavity, while adrenaline is also able to modify the penetration profile of the P-gp substrate model drug at nasal application as it decreases nose-to-blood absorption, letting more quinidine to reach the brain along with the nasal nerves.

Pharmacological characterization of the 3D MucilAir™ nasal model

The preclinical evaluation of nasally administered drug candidates requires screening studies based on in vitro models of the nasal mucosa. The aim of this study was to evaluate the morpho-functional characteristics of the 3D MucilAir™ nasal model with a pharmacological focus on [ATP]-binding cassette (ABC) efflux transporters. We initially performed a phenotypic characterization of the MucilAir™ model and assessed its barrier properties by immunofluorescence (IF), protein mass spectrometry and examination of histological sections. We then focused on the functional expression of the ABC transporters P-glycoprotein (P-gp), multidrug resistance associated protein (MRP)1, MRP2 and breast cancer resistance protein (BCRP) in bidirectional transport experiments. The MucilAir™ model comprises a tight, polarized, pseudo-stratified nasal epithelium composed of fully differentiated ciliated, goblet and basal cells. These ABC transporters were all expressed by the cell membranes. P-gp and BCRP were both functional and capable of actively effluxing substrates. The MucilAir™ model could consequently represent a potent tool for evaluating the interaction of nasally administered drugs with ABC transporters.

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.

Risks and management of long-term corticosteroid use in chronic rhinosinusitis

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the use and risks of long-term corticosteroids in the management of chronic rhinosinusitis (CRS).

RECENT FINDINGS

Long-term use of systemic corticosteroids is not indicated in the management of CRS due to the associated side effects and potential complications. Therefore, recent research has focused on the safety and efficacy of topical corticosteroid, particularly second-generation corticosteroids, and their modes of administration. Second-generation corticosteroids are more potent and have less systemic bioavailability than their first-generation counterparts. However, caution must be taken with concomitant use of more than two types of corticosteroids (topical, systemic, inhaled etc.) and also with their dosage and frequency of administration to avoid adrenal suppression, growth suppression in children, elevated intraocular pressure or epistaxis. Research is ongoing into therapies that may reduce corticosteroid resistance which has been demonstrated in some nasal polyps.

SUMMARY

Corticosteroids play an essential role in the management of CRS; however, use must be tailored to the patient-specific disease and requires ongoing review and regular reevaluation by their physician.

Pharmacological Characterization of the RPMI 2650 Model as a Relevant Tool for Assessing the Permeability of Intranasal Drugs

The RPMI 2650 cell line has been described as a potent model of the human nasal mucosa. Nevertheless, pharmacological data are still insufficient, and the role of drug efflux transporters has not been fully elucidated. We therefore pursued the pharmacological characterization of this model, initially investigating the expression of four well-known adenosine triphosphate [ATP]-binding cassette (ABC) transporters (P-glycoprotein (P-gp), multidrug resistance associated protein (MRP)1, MRP2, and breast cancer resistance protein (BCRP)) by means of ELISA and immunofluorescence staining. The functional activity of the selected transporters was assessed by accumulation studies based on specific substrates and inhibitors. We then performed standardized bidirectional transport experiments under air-liquid interface (ALI) culture conditions, using four therapeutic compounds of local intranasal relevance in upper airway diseases. Protein expression of P-gp, MRP1, MRP2, and BCRP was detected at the membrane of the RPMI 2650 cells. In addition, all four transporters exhibited functional activity at the cellular level. In the bidirectional transport experiments, the RPMI 2650 model was able to accurately discriminate the four therapeutic compounds according to their physicochemical properties. The ABC transporters tested did not play a major role in the efflux of these compounds at the barrier level. In conclusion, the RPMI 2650 model represents a promising tool for assessing the nasal absorption of drugs on the basis of preclinical pharmacological data.

Expression of P-glycoprotein in excised human nasal mucosa and optimized models of RPMI 2650 cells

To assess the transmucosal drug transport in the development of medications for intranasal administration, cellular in vitro models are preferred over the use of animal tissues due to inter-species variations and ethical concerns. With regard to the distribution of active agents and multidrug resistance, the ABC transporter P-glycoprotein plays a major role in several mammalian tissues. The present study compares the expression of this efflux pump in optimized in vitro models based on the human RPMI 2650 cell line with specimens of human turbinate mucosa. The presence of the ABCB1 gene was investigated at the mRNA and protein levels using RT-PCR and Western blot analysis in differently cultured RPMI 2650 cells and excised human nasal epithelium. Furthermore, the localization and activity of P-gp was examined by immunohistochemical staining and functionality assays using different substrates in both in vitro and ex vivo models. Both mRNA and protein expression of P-gp was found in all studied models. Furthermore, transporter functionality was detected in both RPMI 2650 cell culture models and excised human mucosa. The results demonstrated a highly promising comparability between RPMI 2650 models and explants of human nasal tissue concerning the influence of MDR1 on drug disposition. The RPMI 2650 cell line might become a useful tool in preclinical trials to improve reproducibility and achieve greater applicability to humans of experimental data regarding passive diffusion and active efflux of drug candidates.