ABSORPTION MECHANISMS FOR PEPTIDE/PROTEIN DRUGS VIA LUNG

生物技术的进步正在催生对人类健康大有可为的新型多肽/蛋白质药物。不幸的是，口服给药通常在输送此类药物时无效，必须通过非肠道途径服用。近年来，经肺给药已显示出相当大的潜力作为全身给药的替代途径。因此，在这项建议中，我们的长期目标是阐明多肽和蛋白质药物通过肺泡上皮吸收的机制，肺泡上皮表面必须发生药物从肺空气中的吸收。虽然动物实验表明，蛋白质/多肽药物的肺部给药具有良好的生物利用度，但吸收机制和途径几乎是未知的。与肺给药有关的生物工程问题包括制剂形式、给药途径和跨上皮转运。其中，我们选择描绘可能在跨肺泡上皮吸收多肽/蛋白质药物方面占优势的特定机制。我们将利用原代培养的大鼠肺泡上皮细胞单层作为体外模型，以二/三肽、粒细胞集落刺激因子和人生长激素为模型药物。我们建议：1)描述模型蛋白药物通过肺泡上皮屏障吸收的机制和途径(即细胞旁扩散、液相跨细胞作用、受体介导和/或吸附跨细胞作用)；2)研究通过跨肺泡上皮屏障促进蛋白药物吸收的潜在机制；3)研究多肽药物如何通过肺泡上皮吸收；4)确定物理化学变量对蛋白质/多肽药物通过肺泡上皮吸收的刺激作用。通过利用从细胞生物学到生物(化学)工程的实验方法，在四个不同的生物医学研究实验室之间合作研究肺部蛋白质/多肽药物的吸收，这些项目的结果将为推进肺部药物输送的生物工程方法提供新的信息，包括开发通过肺泡上皮屏障提高生物利用度的新方法。

Biotechnological advances are leading to new peptide/protein drugs of great promise for human health. Unfortunately, oral administration usually is ineffective in delivering such drugs, which must be taken parenterally. Recently, transpulmonary drug delivery has shown considerable potential as an alternative route of systemic delivery. Therefore, in this proposal, our long term goals are to elucidate the mechanisms for absorption of peptide and protein drugs across the alveolar epithelium, the surface across which drug absorption from lung airspaces must occur. Although pulmonary delivery of protein/peptide drugs has been shown in animal studies to lead to promising bioavailabilities, absorption mechanisms and pathways are virtually unknown. Bioengineering related issues pertaining to pulmonary drug delivery include formulation modalities, delivery approaches and transepithelial transport. Of these, we chose to delineate specific mechanisms that may prevail in absorption of peptide / protein drugs across alveolar epithelium. We will utilize primary cultured rat alveolar epithelial cell monolayers as an in vitro model and use di-/tri-peptides, granulocyte-colony stimulating factor and human growth hormone as model drugs. We propose to i) delineate the mechanisms and pathways (i.e., paracellular diffusion, fluid-phase transcytosis, receptor-mediated and/or adsorptive transcytosis) for absorption of model protein drugs across the alveolar epithelial barrier, ii) investigate the mechanisms underlying stimulation of protein drug absorption via transcytosis across the alveolar epithelial barrier, iii) investigate how peptide drugs are absorbed across the alveolar epithelium, and iv) determine the stimulatory effect of physicochemical variables on alveolar epithelial absorption of protein/peptide drugs. Through the collaborative investigation of pulmonary protein/peptide drug absorption among four different biomedical research laboratories utilizing experimental approaches spanning cell biology to bio(chemical)engineering, results from these projects will provide new information for advancing bioengineering approaches to pulmonary drug delivery, including development of new methodologies to improve bioavailability via the alveolar epithelial barrier.