Department of Gastroenterology, Zhongshan Hospital affiliated to Fudan University, Shanghai, China.
J Control Release. 2012 Apr 30;159(2):261-70. doi: 10.1016/j.jconrel.2011.12.023. Epub 2011 Dec 28.
No drugs have been approved clinically for the therapy of hepatic fibrosis. Though interferon-γ (IFN-γ) is a highly effective anti-fibrotic agent in vitro and in some animal models in vivo, its anti-fibrotic potential in clinical trials has been disappointing, due to unwanted off-target effects and a short half-life period which results in poor efficacy. The aims of this study are to develop a new targeted drug delivery system to selectively deliver IFN-γ to hepatic stellate cells (HSCs) and to investigate whether it will improve the anti-fibrotic effect of IFN-γ and reduce its side effects in fibrotic livers. Sterically stable liposomes (SSLs) were modified by cyclic peptides (pPB) with a specific affinity for platelet-derived growth factor receptor-β (PDGFR-β), and then IFN-γ was encapsulated in the targeted liposomes (pPB-SSL-IFN-γ). In vitro, pPB-SSL was found to be taken up and internalized by cultured activated HSCs. The binding of FITC-labeled pPB-SSL to activated HSCs was in a time-dependent and concentration-dependent manner, which could be inhibited by excess unlabelled pPB-SSL, PDGF-BB, suramin or monensin. The inhibitory effect of pPB-SSL-IFN-γ on the proliferation of activated HSCs was respectively 7.24-fold and 2.95-fold higher than that of free IFN-γ and IFN-γ encapsulated in untargeted SSLs. In healthy rats, the tissue distribution, living-body tracing image analyses and pharmacokinetics study showed that pPB-SSL-IFN-γ accumulated mainly in the livers and had a longer half-life than free IFN-γ (3.98±0.52h vs. 0.21±0.03h). Furthermore, in rats with hepatic fibrosis induced by thioacetamide injection, FITC-labeled pPB-SSL was found to predominantly localize in activated HSCs by immunofluorescent double staining for FITC and albumin or α-smooth muscle actin (α-SMA). The enhanced anti-fibrotic effect of pPB-SSL-IFN-γ treatnment was indicated by significant decreases in the histologic Ishak stage, collagen I-staining positive areas, and α-SMA expression levels in fibrotic livers. In addition, pPB-SSL-IFN-γ treatment improved the leukopenia caused by low- and high-dosage free IFN-γ treatments. In conclusion, IFN-γ encapsulated in pPB-SSL had an extended circulation half-life and was selectively delivered to activated HSCs, which enhanced the anti-fibrotic effect of IFN-γ and reduced its side-effects in rats with hepatic fibrosis. Thus, pPB-SSL-IFN-γ may be an effective agent for the therapy of hepatic fibrosis.
目前临床上尚无药物可用于肝纤维化的治疗。虽然干扰素-γ（IFN-γ）在体外和某些体内动物模型中是一种非常有效的抗纤维化药物，但由于存在非靶向作用和半衰期短等不良反应，其在临床试验中的抗纤维化效果并不理想。本研究旨在开发一种新的靶向药物传递系统，以选择性地将 IFN-γ递送至肝星状细胞（HSCs），并探讨其是否能提高 IFN-γ的抗纤维化效果，同时降低其在肝纤维化中的副作用。采用具有血小板衍生生长因子受体-β（PDGFR-β）特异性亲和力的环肽（pPB）对刚性稳定脂质体（SSL）进行修饰，然后将 IFN-γ包裹在靶向脂质体（pPB-SSL-IFN-γ）中。体外研究发现 pPB-SSL 可被培养的活化 HSCs 摄取和内化。FITC 标记的 pPB-SSL 与活化 HSCs 的结合呈时间和浓度依赖性，且可被过量未标记的 pPB-SSL、PDGF-BB、苏拉明或莫能菌素所抑制。与游离 IFN-γ和未靶向 SSL 包封的 IFN-γ相比，pPB-SSL-IFN-γ对活化 HSCs 的增殖抑制作用分别提高了 7.24 倍和 2.95 倍。在健康大鼠中，组织分布、活体示踪图像分析和药代动力学研究表明，pPB-SSL-IFN-γ主要在肝脏中蓄积，且半衰期长于游离 IFN-γ（3.98±0.52h 比 0.21±0.03h）。此外，在硫代乙酰胺注射诱导的肝纤维化大鼠中，通过 FITC 与白蛋白或α-平滑肌肌动蛋白（α-SMA）的免疫荧光双重染色发现，FITC 标记的 pPB-SSL 主要定位于活化的 HSCs。pPB-SSL-IFN-γ 治疗可显著降低肝纤维化大鼠的组织学 Ishak 分期、胶原 I 染色阳性面积和 α-SMA 表达水平，表明其抗纤维化效果增强。此外，pPB-SSL-IFN-γ 治疗可改善低剂量和高剂量游离 IFN-γ治疗引起的白细胞减少症。综上所述，包封于 pPB-SSL 中的 IFN-γ具有延长的循环半衰期，并能选择性递送至活化的 HSCs，从而增强了 IFN-γ的抗纤维化效果，并降低了其在肝纤维化大鼠中的副作用。因此，pPB-SSL-IFN-γ 可能是治疗肝纤维化的有效药物。
