Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland.
Drug Research Program, Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, FI-00014 University of Helsinki, Finland; School of Pharmacy, University of Eastern Finland, P.O. Box 1627, FI-70211 Kuopio, Finland; Institute of Chemistry, St. Petersburg State University, Petergof, St. Petersburg 198504, Russia.
J Control Release. 2018 Aug 10;283:261-268. doi: 10.1016/j.jconrel.2018.05.034. Epub 2018 May 31.
Melanin binding affects drug distribution and retention in pigmented ocular tissues, thereby affecting drug response, duration of activity and toxicity. Therefore, it is a promising possibility for drug targeting and controlled release in the pigmented cells and tissues. Intracellular unbound drug concentrations determine pharmacological and toxicological actions, but analyses of unbound vs. total drug concentrations in pigmented cells are lacking. We studied intracellular binding and cellular drug uptake in pigmented retinal pigment epithelial cells and in non-pigmented ARPE-19 cells with five model drugs (chloroquine, propranolol, timolol, diclofenac, methotrexate). The unbound drug fractions in pigmented cells were 0.00016-0.73 and in non-pigmented cells 0.017-1.0. Cellular uptake (i.e. distribution ratio Kp), ranged from 1.3 to 6300 in pigmented cells and from 1.0 to 25 in non-pigmented cells. Values for intracellular bioavailability, F, were similar in both cells types (although larger variation in pigmented cells). In vitro melanin binding parameters were used to predict intracellular unbound drug fraction and cell uptake. Comparison of predictions with experimental data indicates that other factors (e.g. ion-trapping, lipophilicity-related binding to other cell components) also play a role. Melanin binding is a major factor that leads to cellular uptake and unbound drug fractions of a range of 3-4 orders of magnitude indicating that large reservoirs of melanin bound drug can be generated in the cells. Understanding melanin binding has important implications on retinal drug targeting, efficacy and toxicity.
黑色素结合会影响药物在色素性眼组织中的分布和保留，从而影响药物反应、作用持续时间和毒性。因此，它是在色素细胞和组织中进行药物靶向和控制释放的一种很有前途的可能性。细胞内未结合的药物浓度决定了药物的药理和毒理作用，但缺乏对色素细胞中未结合药物与总药物浓度的分析。我们研究了五种模型药物（氯喹、普萘洛尔、噻吗洛尔、双氯芬酸、甲氨蝶呤）在色素性视网膜色素上皮细胞和非色素性 ARPE-19 细胞中的细胞内结合和细胞摄取。色素细胞中的未结合药物分数为 0.00016-0.73，非色素细胞中的为 0.017-1.0。细胞摄取（即分布比 Kp）在色素细胞中为 1.3-6300，在非色素细胞中为 1.0-25。两种细胞类型的细胞内生物利用度 F 值相似（尽管色素细胞中的变化较大）。体内黑色素结合参数用于预测细胞内未结合药物分数和细胞摄取。预测值与实验数据的比较表明，其他因素（例如离子捕获、与其他细胞成分的亲脂性结合）也起作用。黑色素结合是导致细胞摄取和未结合药物分数在 3-4 个数量级范围内的主要因素，这表明细胞内可以产生大量结合药物的黑色素储备。了解黑色素结合对视网膜药物靶向、疗效和毒性具有重要意义。
