Effect of gal/GalNAc regioisomerism in galactosylated liposomes on asialoglycoprotein receptor-mediated hepatocyte-selective targeting in vivo

Abstract

In this study, we describe a novel synthesis of galactosylated lipids by lipase catalysis. Lactitol (Lac), galactose (Gal), or N-acetyl galactosamine (GalNAc) was coupled with cholesterol (CHS) as target head groups by enzyme-catalyzed regioselective esterification to produce three kinds of lipids: CHS-1-Gal, CHS-6-Gal, or CHS-6-GalNAc¹. The biological effects of galactosylated lipids carrying different constitutional isomers of the pendent sugar species were investigated. LP-1-Gal (liposomes containing 5.0 molar% of CHS-1-Gal) showed strong binding to tetrameric lectins of Ricinus communis agglutinin (RCA120) in vitro, while LP-6-Gal (liposomes containing 5.0 molar% of CHS-6-Gal) and LP-6-GalNAc (liposomes containing 5.0 molar% of CHS-6-GalNAc) did not. After intravenous injection, LP-6-GalNAc, LP-1-Gal and LP-6-Gal rapidly disappeared from the blood and accumulated rapidly in liver (up to 74.88 ± 4.11%, 58.67 ± 5.75%, and 47.66 ± 4.56% of injected dose/g organ within 4 h, respectively). This is significantly higher than the uptake of unmodified liposomes (Unmod-LP) (18.67 ± 6.07%). Pre-injection of asialofetuin significantly inhibits liver uptake of Gal-liposomes (P < 0.01), with the degree of inhibition appearing in the following order: LP-6-GalNAc (73.29%) > LP-1-Gal (67.06%) > LP-6-Gal (53.61%). More importantly, LP-6-GalNAc was preferentially taken up by hepatocytes and the uptake ratio by parenchymal cells (PC) and nonparenchymal cells (NPC) (PC/NPC ratio) was 11.03 higher than LP-1-Gal (7.32), LP-6-Gal (5.83) and Unmod-LP (2.39). We suggest that liposomes containing the novel galactosylated lipid CHS-6-GalNAc have potential as drug delivery carriers for hepatocyte-selective targeting.

Keywords:

• Cholesterol derivative
• liver targeting
• asialoglycoprotein receptor
• enzyme catalysis
• parenchymal cells
• pharmacokinetics
• N-acetylgalactosamine
• liposomes

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 1 and 6 denote the glycosidic linkage from the 1 position and 6 position of the terminal sugar unit.

Additional information

Funding

This work was financially supported by National Natural Science Foundation of China [No. 81703662], the National Natural Science Foundation of Guangdong, China [No. 2016A030310365 and No. 2017A030307025], Administration of Traditional Chinese Medicine of Guangdong Province, China [No. 20171268], and Guangdong Provincial Development Project of Strengthening Subjects (Agricultural Resources and Environment).