Comparison of barrier properties of outer blood-retinal barrier models - Human stem cell-based models as a novel tool for ocular drug discovery.

The retinal pigment epithelial (RPE) cell monolayer forms the outer blood-retinal barrier and has a crucial role in ocular pharmacokinetics. Although several RPE cell models are available, there have been no systematic comparisons of their barrier properties with respect to drug permeability. We compared the barrier properties of RPE secondary cell lines (ARPE19, and ARPE19mel) and both primary (hfRPE) and stem-cell derived RPE (hESC-RPE) cells by investigating the permeability of nine drugs (aztreonam, ciprofloxacin, dexamethasone, fluconazole, ganciclovir, ketorolac, methotrexate, voriconazole, and quinidine) across cell monolayers.

Mechanisms of cellular retention of melanin bound drugs: Experiments and computational modeling.

Melanin binding of drugs is known to increase drug concentrations and retention in pigmented eye tissues. Even though the correlation between melanin binding in vitro and exposure to pigmented eye in vivo has been shown, there is a discrepancy between rapid drug release from melanin particles in vitro and the long in vivo retention in the pigmented tissues. We investigated mechanisms and kinetics of pigment-related drug retention experimentally using isolated melanin particles from porcine retinal pigment epithelium and choroid, isolated porcine eye melanosomes, and re-pigmented ARPE-19 cells in a dynamic flow system.

Retraction: Hellinen et al. Retinal Pigment Epithelial Cell Line with Fast Differentiation and Improved Barrier Properties. 2019, , 412.

The published article [...

Retraction: Hellinen et al. Drug Flux across RPE Cell Models: The Hunt for an Appropriate Outer Blood-Retinal Barrier Model for Use in Early Drug Discovery. 2020, , 176.

The published article [...

Inhibition of prolyl oligopeptidase: A promising pathway to prevent the progression of age-related macular degeneration.

Dry age-related macular degeneration (AMD) is a currently untreatable vision threatening disease. Impaired proteasomal clearance and autophagy in the retinal pigment epithelium (RPE) and subsequent photoreceptor damage are connected with dry AMD, but detailed pathophysiology is still unclear. In this paper, we discover inhibition of cytosolic protease, prolyl oligopeptidase (PREP), as a potential pathway to treat dry AMD.

Biopharmaceutics of Topical Ophthalmic Suspensions: Importance of Viscosity and Particle Size in Ocular Absorption of Indomethacin.

Eye drops of poorly soluble drugs are frequently formulated as suspensions. Bioavailability of suspended drug depends on the retention and dissolution of drug particles in the tear fluid, but these factors are still poorly understood. We investigated seven ocular indomethacin suspensions (experimental suspensions with two particle sizes and three viscosities, one commercial suspension) in physical and biological tests.

Microscale Thermophoresis as a Screening Tool to Predict Melanin Binding of Drugs.

Interactions between drugs and melanin pigment may have major impacts on pharmacokinetics. Therefore, melanin binding can modify the efficacy and toxicity of medications in ophthalmic and other disease of pigmented tissues, such as melanoma. As melanin is present in many pigmented tissues in the human body, investigation of pigment binding is relevant in drug discovery and development.

The effect of prolyl oligopeptidase inhibitors on alpha-synuclein aggregation and autophagy cannot be predicted by their inhibitory efficacy.

Previous studies have shown that prolyl oligopeptidase (PREP) negatively regulates autophagy and increases the aggregation of alpha-synuclein (αSyn), linking it to the pathophysiology of Parkinson's disease. Our earlier results have revealed that the potent small molecular PREP inhibitor KYP-2047 is able to increase autophagy and decrease dimerization of αSyn but other PREP inhibitors have not been systematically studied for these two protein-protein interaction mediated biological functions of PREP. In this study, we characterized these effects for 12 known PREP inhibitors with IC-values ranging from 0.

Prodrug Approach for Posterior Eye Drug Delivery: Synthesis of Novel Ganciclovir Prodrugs and in Vitro Screening with Cassette Dosing.

Because of poor ocular drug bioavailability, intravitreal injections have become the gold standard for drug delivery to the posterior eye. The prodrug approach can be used for optimizing the biopharmaceutical properties of intravitreal drugs. The preclinical screening of prodrugs' properties, such as hydrolysis and bioconversion, should be conducted in a resource-efficient way for an extensive set of synthesized compounds with validated methods.

Drug Flux Across RPE Cell Models: The Hunt for An Appropriate Outer Blood-Retinal Barrier Model for Use in Early Drug Discovery.

The retinal pigment epithelial (RPE) cell monolayer forms the outer blood-retinal barrier and has a crucial role in ocular pharmacokinetics. Although several RPE cell models are available, there have been no systematic comparisons of their barrier properties with respect to drug permeability. We compared the barrier properties of several RPE secondary cell lines (ARPE19, ARPE19mel, and LEPI) and both primary (hfRPE) and stem-cell derived RPE (hESC-RPE) cells by investigating the permeability of nine drugs (aztreonam, ciprofloxacin, dexamethasone, fluconazole, ganciclovir, ketorolac, methotrexate, voriconazole, and quinidine) across cell monolayers.

Quantitative Protein Expression in the Human Retinal Pigment Epithelium: Comparison Between Apical and Basolateral Plasma Membranes With Emphasis on Transporters.

Purpose: Retinal pigment epithelium (RPE) limits the xenobiotic entry from the systemic blood stream to the eye. RPE surface transporters can be important in ocular drug distribution, but it has been unclear whether they are expressed on the apical, basal, or both cellular surfaces. In this paper, we provide quantitative comparison of apical and basolateral RPE surface proteomes.

Characterization of artificially re-pigmented ARPE-19 retinal pigment epithelial cell model.

Melanin pigment has a significant role in ocular pharmacokinetics, because many drugs bind at high extent to melanin in the retinal pigment epithelial cells. Most retinal pigment epithelial cell lines lack pigmentation and, therefore, we re-pigmented human ARPE-19 cells to generate a pigmented cell model. Melanosomes from porcine retinal pigment epithelium were isolated and co-incubated with ARPE-19 cells that spontaneously phagocytosed the melanosomes.

Retinal Pigment Epithelial Cell Line with Fast Differentiation and Improved Barrier Properties.

Retinal pigment epithelium (RPE) acts as an outer blood-retinal barrier that limits the access of circulating xenobiotics to the eye. In addition, the RPE limits posterior elimination of intravitreally injected drugs to circulation. Thus, permeation in the RPE has a significant effect on ocular pharmacokinetics.

Expression, activity and pharmacokinetic impact of ocular transporters.

The eye is protected by several tissues that limit the permeability and entry of potentially harmful substances, but also hamper the delivery of drugs in the treatment of ocular diseases. Active transport across the ocular barriers may affect drug distribution, but the impact of drug transporters on ocular drug delivery is not well known. We have collected and critically reviewed the literature for ocular expression and activity of known drug transporters.

Implications of melanin binding in ocular drug delivery.

Pigmented ocular tissues contain melanin within the intracellular melanosomes. Drugs bind to melanin at varying extent that ranges from no binding to extensive binding. Binding may lead to drug accumulation to the pigmented tissues and prolonged drug retention in the melanin containing cells.