n-caproylsphingosine and Leukemia

Construction of a novel PEGylated bioactive lipids-based micelle system for co-delivery of doxorubicin (DOX) and short chain ceramide (C6-ceramide) to overcome multidrug resistance in leukemia.. The PEGylated bioactive lipids-based micelle system was constructed via electrostatic and hydrophobic interactions among DOX, bioactive lipids PazPC and C6-ceramide. The micellar formulation was characterized in terms of size, zeta potential, stability and release behavior, etc., and in vitro cytotoxicity, in vivo antitumor efficacy and the underlying mechanism were further evaluated.. This novel micellar system showed small size (~15 nm), high drug encapsulation efficiency (>90%), good stability and endosomal acid-triggered release of DOX. Synergistic cytotoxic effects between DOX and bioactive lipid C6-ceramide in P-gp overexpressing drug resistant leukemia P388/ADR cells were observed. The mechanistic studies demonstrated that modulation of drug efflux system and induction of apoptotic effects by lipids were responsible for the synergistic effects between DOX and C6-ceramide in drug resistant leukemia P388/ADR cells. Using an in-vivo P388/ADR leukemia mouse model, the median survival time of the DOX-loaded PEGylated micelles with PazPC and C6-ceramide as major components was significantly greater than that of free DOX and control group.. We developed a novel pH sensitive bioactive lipids-based micellar formulation which could potentially be useful in delivering chemotherapeutic drug DOX and provide a novel strategy to increase the therapeutic index for drug resistant leukemia treatment.

Topics: Animals; Antibiotics, Antineoplastic; Cell Line, Tumor; Ceramides; Delayed-Action Preparations; Doxorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Hydrogen-Ion Concentration; Leukemia; Lipids; Male; Mice; Micelles

Ceramide acts as an intracellular second messenger in cellular signal transduction. We examined the effects of two cell-permeable ceramides, C2-ceramide and C6-ceramide, on human monocyte functions. After monocytes were primed with lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma) for 18 hr in suspension culture, they produced a high amount of superoxide (O2-) when triggered by phorbol myristate acetate. C2- or C6-ceramide inhibited O2- release from monocytes primed with LPS (1 ng/ml) or IFN-gamma (100 U/ml), but did not affect unprimed monocytes. An analogue, C2-dihydroceramide, was inactive. C2-ceramide was most effective at 6 microM, and C6-ceramide at 60 microM. C2- or C6-ceramide at these concentrations was not toxic for monocytes, as assessed by trypan blue exclusion and by the 3-[4, 5-dimethylthiazol-2-y1]-2,5 diphenyl tetrazolium bromide (MTT) assay which measures the ability of live cells to produce formazan. C2-ceramide (20 microM) had no effect on the killing of leukaemic cells (HL-60 and K562 cells) by monocytes treated with IFN-gamma, LPS, or both for 18 hr, with killing assessed by an 111 Indium-releasing assay. C2-ceramide (20 microM) induced secretion of low amounts of tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) from the monocytes. But C2-ceramide did not alter the higher secretion of TNF-alpha or IL-1 beta from monocytes treated with IFN-gamma or LPS. Thus the cell-permeable ceramides acted like antagonists of LPS, rather than analogues of LPS, as has been proposed. The results here showed that the signal transduction pathway for O2- release by monocytes differed from that for the cytolysis of leukaemic cells, and confirmed that oxygen radicals are not involved in cytolysis.

Topics: Ceramides; Cytotoxicity, Immunologic; Humans; Interferon-gamma; Interleukin-1; Leukemia; Lipopolysaccharides; Monocytes; Sphingosine; Superoxides; Tumor Cells, Cultured; Tumor Necrosis Factor-alpha