Evaluation and Inhibition of Efflux Pumps Expressed on the Blood Ocular Barrier

描述（由申请人提供）：血眼屏障（BOB）使药物通过全身途径递送至眼组织成为一项具有挑战性的任务。外排蛋白的作用， 如P-糖蛋白（P-gp）和多药耐药蛋白（MRP），作为BOB的主要成分，已经在体外得到很好的证实。然而，关于基质的血液至眼睛渗透的临床意义的研究尚未报道。了解P-gp和MRP的体内屏障特性，并开发非侵入性策略来克服它们在BOB介导的外排，可以通过全身途径改善眼部药物递送。这将有助于避免与直接玻璃体内给药相关的缺点。该提议基于新的假设，即眼外排泵的功能活性可以通过局部共同施用抑制剂而被显著阻断，因此将增强外排蛋白底物的血液至眼睛的渗透。在我们使用家兔作为动物模型的探索性研究中，已经证明了这种方法的可行性。在本申请中，我们提出评估，首先， 时间，体内眼外排蛋白（P-gp和mrp 1）的屏障性质的大小 在野生型和P-gp和mrp 1敲除大鼠中。该提案还试图进一步阐明局部抑制BOB表达的外排蛋白的新策略的各个方面，包括抑制的程度和持续时间以及局部制剂组分的作用。将局部途径的有效性与抑制剂给药的全身途径进行比较，抑制剂给药是一种常用于阻断血脑屏障上的外排蛋白的方法。因此，该项目的具体目标是：（a）使用P-gp（mdr 1a）和mrp 1敲除和野生型大鼠评价相对于药物施用的全身途径的眼外排蛋白屏障的大小，（B）确定通过全身性抑制剂共同给药抑制眼外排蛋白的有效性，和（c）描述与全身途径相比，局部途径应用抑制剂的效率。这些研究的结果将提供更深入的了解体内眼外排泵的屏障特性。预期抑制剂的局部应用将导致显著的 提高全身给药的外排蛋白底物的眼组织浓度。这将打开通过全身途径有效治疗眼部疾病如眼内炎、葡萄膜炎和眼内肿瘤的可能性。它还可以提供克服在一些眼内细菌感染和眼部肿瘤中遇到的耐药性的手段，因为局部施用的抑制剂还可以阻断在这些细胞中上调的多药耐药蛋白。因此，预计这些研究的结果将为眼部药物递送提供新的科学见解，并改善治疗选择和结果。

DESCRIPTION (provided by applicant): The blood-ocular barriers (BOB) make drug delivery to the ocular tissues, through the systemic route, a challenging task. The role of efflux proteins, such as P-glycoprotein (P-gp) and multidrug resistant proteins (MRPs), as major components of the BOB has already been well established in vitro. However, studies investigating their clinical implication, with respect to blood to eye penetration of substrates, have not been reported as yet. An understanding of the in vivo barrier characteristics of P-gp and MRP and development of noninvasive strategies to overcome efflux mediated by them, at the BOB, could improve ocular drug delivery through the systemic route. This would help avoid the drawbacks associated with direct intravitreal administration. This proposal is based on the novel hypothesis that the functional activity of the ocular efflux pumps can be significantly blocked through topical co-administration of inhibitors and will thus enhance the blood to eye penetration of efflux protein substrates. The feasibility of this approach has been demonstrated in our exploratory studies using rabbits as the animal model. In the current application we propose to evaluate, for the first time, the magnitude of the barrier properties of the ocular efflux proteins (P-gp and mrp1) in vivo in wild type and in P-gp and mrp1 knockout rats. The proposal also seeks to further elucidate the various facets of the novel strategy of localized inhibition of the efflux proteins expressed o the BOB with respect to extent and duration of inhibition and effect of topical formulation components. The effectiveness of the topical route will be compared to the systemic route of inhibitor administration, an approach commonly used to block efflux proteins on the blood-brain barrier. Thus, the specific aims of this project are to: (a) evaluate the magnitude of the ocular efflux protein barrier with respect to the systemic route of drug administration using P-gp (mdr1a) and mrp1 knockout and wild type rats, (b) establish the effectiveness of inhibiting the ocular efflux proteins through systemic inhibitor co-administration and (c) delineate the efficiency of the topical route of inhibitor application compared to the systemic route. Results from these studies will provide a deeper insight into the barrier properties of the ocular efflux pumps in vivo. It is expected that topical application of the inhibitors will lead to significantly enhanced ocular tissue concentrations of the systemically administered efflux protein substrates. This will open up the possibility of effectively treating ocular conditions such as endophthalmitis, uveitis and intraocular tumors through the systemic route. It may also provide a means to overcome the drug resistance encountered in some intraocular bacterial infections and ocular tumors, since the topically administered inhibitors may also block the multidrug resistant proteins up-regulated in these cells. It is thus expected that the results from these studies will provide new scientific insights into ocular drug delivery and improve therapeutic options and outcomes.