Characterization of liposomal tacrolimus in lung surfactant-like phospholipids and evaluation of its immunosuppressive activity.
Tacrolimus (FK506) is a hydrophobic immunosuppressive agent that rapidly penetrates the plasmatic membrane and inhibits the signal transduction cascade of T lymphocytes. The objective of this study was the characterization of liposomal FK506 with surfactant-like phospholipids to be administered intratracheally after lung transplantation or in inflammatory lung diseases. We evaluated the optimal incorporation of FK506 in dipalmitoylphosphatidylcholine (DPPC) and DPPC/1-palmitoyl-2-oleoylphosphatidylglycerol (POPG) monolayers and bilayers and the effects of FK506 on the physical properties of DPPC and DPPC/POPG (8:2 w/w) vesicles. In addition, we assessed the immunosuppressive effects of surfactant-like phospholipid vesicles containing different amounts of FK506 on T-cell proliferation and interleukin 2 production. From surface pressure measurements of FK506/DPPC and FK506/DPPC/POPG mixed monolayers, we determined that FK506 was embedded into these monolayers up to an FK506 concentration of about 0.4 mol %. Beyond this concentration, FK506 was not quantitatively incorporated into the monolayer, suggesting possible concentration-dependent aggregation of tacrolimus. The incorporation of FK506 into DPPC monolayers, at concentrations <or= 5 microM, occurred with a partition coefficient of (3.9 +/- 0.3) x 10(3) at the bilayer equivalence pressure. FK506 was incorporated in DPPC bilayers up to an FK506 concentration of about 0.7-1 mol %, which was about double that obtained via the monolayer technique. FK506 hardly affected the transition enthalpy, the T(m), and cooperativity of the phase transition of DPPC and DPPC/POPG vesicles as determined by differential scanning calorimetry and steady-state 1,6-diphenyl-1,3,5-hexatriene anisotropy. Finally, this study provides evidence that liposomal FK506 retains the immunosuppressive efficacy of the drug.
Department of Biochemistry and Molecular Biology I, Complutense University of Madrid, 28040 Madrid, Spain.
Olga
O
Cañadas
Rosa
R
Guerrero
Rafael
R
García-Cañero
Guillermo
G
Orellana
Margarita
M
Menéndez
Cristina
C
Casals
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry / Q000378:metabolism; D002103:Cadaverine / Q000031:analogs & derivatives* / Q000378:metabolism; D002118:Calcium / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D004161:Diphenylhexatriene / Q000378:metabolism; D005454:Fluorescence Polarization; D006131:Growth Inhibitors / Q000494:pharmacology; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D019169:Jurkat Cells; D008081:Liposomes; D008213:Lymphocyte Activation / Q000187:drug effects; D044367:Phase Transition / Q000187:drug effects; D010715:Phosphatidylglycerols / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism; D037662:Pulmonary Surfactant-Associated Protein A / Q000737:chemistry* / Q000378:metabolism; D013499:Surface Properties; D016559:Tacrolimus / Q000737:chemistry* / Q000378:metabolism
D006131:Growth Inhibitors; D007166:Immunosuppressive Agents; D007376:Interleukin-2; D008081:Liposomes; D010715:Phosphatidylglycerols; D010743:Phospholipids; D037662:Pulmonary Surfactant-Associated Protein A; D004161:Diphenylhexatriene; D015060:1,2-Dipalmitoylphosphatidylcholine; C060037:1-palmitoyl-2-oleoylglycero-3-phosphoglycerol; C008542:monodansylcadaverine; D002103:Cadaverine; D002118:Calcium; D016559:Tacrolimus