Overcoming Multidrug Resistance By Doxorubicin And Schisandrin B Co-delivery Liposomes

BACKGROUND:Drug resistance is a major problem that limits the effectiveness of chemotherapies used to treat cancer.Drug carrier is a novel approach to overcoming multidrug resistance(MDR)in cancer nowadays.OBJECTIVE:To investigate the synergetic effect of Schisandrin B and liposomes on overcoming MDR.METHODS:(1)Preparation and charaeterization of Doxorubicin-Schisandrin B co-liposomes(DSCL);(2)Evaluation of overcoming MDR effect of DSCL with the resistanct cancer cells K562/DOX;(3)Investigation of the mechanism of overoming MDR with K562/DOX;(4)Study of pharmacodynamics of DSCL in K562/DOX bearing mice.RESULTS:Our previous studies have proved that Liposomes could partially overcome multidrug resistance.In this thesis,we developed a novel formulation that Doxorubcin(DOX)and Schisandrin B(Sch B)were simultaneously loaded into liposomes by a ammonium sulfate gradient-driven method,where Sch B plays the role of a chemical sensitizer which could inhibit the express of P-gp and induce apoptotis.We want to investigate the synergetic effect of Schisandrin B and liposomes on overcoming multidrug resistance(MDR).Firstly,DSCL were prepared and various manufacture factors were investigated in order to optimize the DOX and Sch B liposomes(DSCL)with the high encapsulation efficiencies(EE%)greater than 85%(DOX EE%:93.96±3.30%,Sch B EE%:87.81士1.97%),And the size of DSCL is 163±102nm and Zeta potential distribution is-23±4ev.The DSCL was suitable for follow-up study.Furthermore,the MTT test were measured and it shows that the resistance factor(RF)of Group DSCL were 1.68,14.52 and 1.42 times of Group Schisandrin and doxorubicin mixture(Sch B+DOX),Doxorubicin liposomes(DOX-L)and Group Doxorubicin liposomes and Schisandrin B mixture(DOX-L+Sch B)respectively.The amount of doxorubicin in the K562/DOX cells at different time were determined by HPLC,and the Uptake test shows that amount of doxorubicin to K562/DOX cells in Group DSCL was 1.30 and 1.21 times of Group DOX-L and Group Sch B+DOX,and the Efflux test shows DSCL could delay the efflux effect.Thirdly,the uptake of DSCL was energy-dependent and was influenced by temperature.Endocytosis inhibitors(sodium azide,mannitol and chloroquine)decreased significantly accumulation of DOX.The result revealed that DSCL was uptaken through the endocytosis of energy-dependent.In addition,from the results of flow cytometry,the expression of P-gp of K562/DOX cells was significantly inhibited after treatment with DSCL,and it shows DSCL induces a regulated apoptotis cell death in K562/DOX cells.Therefore,we proposed that DSCL simultaneously loaded with the anticancer drug DOX and the chemosensitizer Sch B might be a suitable strategy for cancer therapy by the reversal of P-gp and apoptotis-mediated multidrug resistance.Finally,the pharmacodynamics of DSCL was eatablished using K562/DOX bearing mice.The size and weight of tumor shows the anticancer effect of DSCL,and the tumor inhibiton rate of DSCL is 84.14%.CONCLUSION:The co-delivery of chemotherapeutics and P-gp inhibitors by liposome was a promising approach to overcome MDR.And there is a synergistic effect between liposome and Sch B to overcome MDR.