title: Mechanism of adjuvant activity of cationic liposome: phosphorylation of a MAP kinase, ERK and induction of chemokines.
abstract: Cationic liposome has been effectively used as a delivery system for DNA and protein vaccines. Recently, we discovered that strong anti-tumor immunity could be generated when a peptide antigen (E7) was incorporated into 1,2-dioleoyl-3-trimethylammonium-propane (chloride salt) (DOTAP) cationic liposome. Therefore, DOTAP liposome exhibits not only efficient delivery capacity, but also a potent adjuvant activity. In this report, the molecular mechanism of the adjuvanticity was studied both in vitro and in vivo. Microarray of mRNA analysis demonstrated that several chemokine genes are up-regulated by DOTAP liposome, including CCL2, CCL3 and CCL4, upon treatment of dendritic cells (DC) with DOTAP liposomes. CCL2 induction was mediated through extracellular-signal-regulated kinase (ERK) pathway, demonstrated by specific inhibitors of ERK pathway and siRNA approaches. Furthermore, DOTAP-induced CCL2 expression is negatively regulated by the p38 pathway. Consistently, ERK activation by DOTAP is also negatively regulated by p38. Moreover, PI-3 kinase was shown to be involved in both activation of ERK and induction of CCL2 by DOTAP. DOTAP- induced CCL2 release was also confirmed in the draining lymph nodes. More importantly, inhibition of ERK pathway completely abolishes the CCL2 accumulation in the draining lymph nodes and attenuates anti-tumor activity of DOTAP/E7. In conclusion, DOTAP is an active lipid stimulator for DC resulting in ERK activation and CC chemokine induction. Our data elucidated one important mechanism of adjuvant activity of cationic liposome and could facilitate rational design of synthetic lipid based adjuvants.
authors.affiliation: Division of Molecular Pharmaceutics, School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Weili
authors.initials: W
authors.lastname: Yan
authors.forename: Weihsu
authors.initials: W
authors.lastname: Chen
authors.forename: Leaf
authors.initials: L
authors.lastname: Huang
mesh_terms: D000276:Adjuvants, Immunologic / Q000378:metabolism*; D000818:Animals; D039521:CD11c Antigen / Q000235:genetics; D002460:Cell Line; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D018925:Chemokines / Q000235:genetics*; D003713:Dendritic Cells / Q000187:drug effects / Q000201:enzymology; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005229:Fatty Acids, Monounsaturated / Q000494:pharmacology; D005260:Female; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D008081:Liposomes / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D018448:Models, Immunological; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000276:Adjuvants, Immunologic; D039521:CD11c Antigen; D018932:Chemokine CCL2; D018925:Chemokines; D005229:Fatty Acids, Monounsaturated; D008081:Liposomes; D047428:Protein Kinase Inhibitors; D000644:Quaternary Ammonium Compounds; D034741:RNA, Small Interfering; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; C070046:1,2-dioleoyloxy-3-(trimethylammonium)propane