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.
Cañadas
Olga
O
Department of Biochemistry and Molecular Biology I, Complutense University of Madrid, 28040 Madrid, Spain.
Guerrero
Rosa
R
García-Cañero
Rafael
R
Orellana
Guillermo
G
Menéndez
Margarita
M
Casals
Cristina
C
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