Pure and mixed monolayers of mono- and dihexoside cerebrosides with cholesterol have been characterized at the air/water interface. Cholesterol oxidase was used as a reporter enzyme for the cholesterol-cerebroside interaction in the mixed monolayers. The cerebrosides either were derived from bovine brain extracts or were synthetic. The dihexoside cerebrosides were synthesized by coupling of the hepta-O-acetyl-alpha-lactosyl- or maltosylphosphoramidates with D-erythro-N-acylceramides in dichloromethane, in the presence of trimethylsilyl triflate and molecular sieves, followed by hydrolysis of the acetate-protecting groups. All of the bovine-brain-derived cerebrosides [galactosyl cerebroside (GalCer, types I and II), glucosyl cerebroside (GlcCer), and lactosyl cerebroside (LacCer)] had very condensed force-area isotherms (compressibility values of 3-5 x 10(-3) m/mN at 20 mN/m), as did the synthetic N-stearoylmaltosylceramide (N-18:0 MaltCer). Shorter-chain synthetic cerebrosides (N-8:0 LacCer and N-8:0 MaltCer) had more expanded isotherms, with compressibility values of 15-17 x 10(-3) m/mN. When cholesterol was included in mixed monolayers of monohexoside cerebroside, it did not induce significant condensation of packing (indicating that cholesterol did not increase the order of the acyl chains). However, with dihexoside cerebrosides, a cholesterol-induced condensing effect was observed, which amounted to a 11-19% reduction in the observed mean molecular area. When cholesterol oxidase was used to titrate the stoichiometry of cholesterol/cerebroside in mixed monolayers, at which pure cholesterol clusters appeared, it was observed that in monohexoside cerebroside monolayers cholesterol clusters were present even below a 1:1 molar stoichiometry.(ABSTRACT TRUNCATED AT 250 WORDS)

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We have synthesized two ether lipids: 2'-(trimethylammonio)ethyl 4-(hexadecyloxy)-3(S)-methoxybutanephosphonate (compound 1) with antineoplastic activity and a maltosyl derivative (compound 2) without antineoplastic activity. We have compared the antineoplastic activity of these two compounds against WEHI-3B cells with their ability to disrupt the membranes of erythrocytes or neutrophils. Since ether lipids are highly hydrophobic molecules, it is possible that they may exert their cytotoxic action by inducing the nonspecific perturbation of cellular membranes, causing lysis and cell death. Membrane disruption was monitored by the lysis of cells or the change in erythrocyte membrane microviscocity and compared with the effect of detergents (known nonspecific lytic agents). Both compounds 1 and 2 caused the lysis of erythrocytes and neutrophils. The rate of lysis of erythrocytes was comparable to the rate of change of erythrocyte membrane microviscosity caused by both compounds 1 and 2. Both compounds caused the lysis of erythrocytes via a noncolloid osmotic mechanism that displayed features of the lysis caused by detergents at high concentrations.