Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.10.3.1 (tyrosinase)
 9,065 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cultured retinal pigment epithelial (RPE) cells are commonly used as a model of the tissue to study their involvement in visual diseases. Unfortunately, cultured RPE often lose their differentiated phenotype reducing their usefulness as a model of the RPE in vivo. In this study, we used a Ca++-switch protocol to initiate the patterned expression of several phenotypic and functional markers of RPE differentiation. Cultured RPE cells from adult donors were maintained through at least six serial passages prior to assay to minimize their differentiated properties. The cells were then subjected to the Ca++-switch protocol and maintained at confluence for up to 4 months. Paired control and Ca++-switch cells were examined for phenotype, pigmentation, and the expression of tyrosinase, CRABP, myocilin, and bestrophin by western blot analysis. The Ca++-switch protocol led to a rapid restriction of N-cadherin to lateral cell borders, and to expression of tyrosinase by day 4. After 8 weeks, the experimental RPE monolayers began to accumulate visible pigment, and after 12 weeks CRABP expression was observed. Myocilin was observed at 4 months after the Ca++-switch but bestrophin was not detected at any time point. Our results suggest this protocol may drive epithelial morphogenesis in RPE cells. We note two specific differences in cells plated in low Ca++, reduced spreading on the substrate and coordinated development of cadherin adhesion when the Ca++-concentration is returned to normal. Thus, we suggest that this method produces phenotypic changes through multiple cell signalling pathways.
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PMID:Ca++-switch induction of RPE differentiation. 1628 63

Retinal pigment epithelium (RPE) regulates drug transfer between posterior eye segment and blood circulation, but there is no established RPE cell model for drug delivery studies. We evaluated ARPE-19 filter culture model for this purpose. Passive permeability of 6-carboxyfluorescein, betaxolol and FITC-dextran (40kDa) and active transport of 6-carboxyfluorescein, sodium fluorescein, rhodamine 123, cyclosporine A and digoxin in ARPE-19 model were investigated and compared with isolated bovine RPE-choroid tissue. In addition, barrier properties, and mRNA expression of RPE-specific and melanogenesis-related genes (RPE65, VMD2, CRALBP, OTX-2, MITF-A, TRP-1, tyrosinase) were measured in various culture conditions. The filter grown ARPE-19 cell model showed reasonable barrier properties (TER close to 100Omegacm(2)), but its permeability was slightly higher than that of isolated bovine RPE/choroid specimens. In active transport studies the ARPE-19 model mimics qualitatively the permeability profile of bovine RPE-choroid, but ARPE-19 model underestimates the importance of active transport relative to passive diffusion. Long-term filter-cultured ARPE-19 cells expressed various RPE-specific and melanogenesis-related genes at higher levels than the ARPE-19 cells cultured short-term in flasks. ARPE-19 model can be used to study drug permeation processes in the RPE.
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PMID:Filter-cultured ARPE-19 cells as outer blood-retinal barrier model. 2038 30