Upregulation of P-glycoprotein expression by ophthalmic drugs in different corneal in-vitro models.

Objectives: The purpose of this study was to analyse P-glycoprotein (P-gp) expression in different human in-vitro cornea models (HCE-T epithelial model and Hemicornea construct) after stimulation with P-gp substrates (rhodamine 123, levofloxacin and acebutolol).

Methods: The influence of P-gp substrates on mRNA expression was analysed using reverse transcriptase polymerase chain reaction (PCR) and real-time PCR. The effect of stimulation on the transporter functionality was estimated with a digoxin efflux assay.

Multidrug resistance-associated protein (MRP1, 2, 4 and 5) expression in human corneal cell culture models and animal corneal tissue.

Preclinical studies addressing the transcorneal absorption of ophthalmic drugs are mainly performed using ex vivo animal corneas and in vitro corneal cell culture models, leaving open the question of transferability to humans in an in vivo situation. While passive drug absorption through corneal tissue is well understood, little is known about the expression of transporter proteins and active drug transport in human and animal corneas as well as corneal cell culture models. Therefore, the aim of this study was to conduct an expression analysis of four multidrug resistance-associated proteins (MRP1, 2, 4 and 5) in various in vitro and ex vivo corneal models, leading to a better understanding of the comparability of different corneal models regarding drug absorption and transferability to humans.

Expression analysis of MDR1, BCRP and MRP3 transporter proteins in different in vitro and ex vivo cornea models for drug absorption studies.

Ocular drug absorption studies are required for the development of new drugs or drug delivery systems for eye treatment. Such preclinical investigations on transcorneal drug absorption are performed ex vivo with the excised corneas of experimental animals or in vitro using corneal cell culture models. The data currently available on the expression of ABC transporter proteins in corneal tissue is limited or contradictory.

In vitro cell culture models to study the corneal drug absorption.

Introduction: Many diseases of the anterior eye segment are treated using topically applied ophthalmic drugs. For these drugs, the cornea is the main barrier to reaching the interior of the eye. In vitro studies regarding transcorneal drug absorption are commonly performed using excised corneas from experimental animals.

Nonclassical export pathway: overexpression of NCE102 reduces protein and DNA damage and prolongs lifespan in an SGS1 deficient Saccharomyces cerevisiae.

In this study, we used our recently developed screening method, Bud-Scar-based Screening (BSS), to screen a yeast cDNA expression library in an SGS1 deletion BY4742 yeast strain. One gene involved in a nonclassical export pathway, NCE102, was found to extend the life span of Deltasgs1 yeast. Deletion of NCE102 in a wild type yeast strain increased its sensitivity to oxidative stress upon diethylmaleate (DEM) treatment but did not shorten its lifespan, indicating that this gene is not essential in determining yeast lifespan.