Stimulation of macrophage by polyanions and its conjugated proteins and effect on cell membrane

Lipophilic anionic copolymer (styrene-maleic acid; SMA) conjugates of albumin and antitumor protein neocarzinostatin (NCS) (smancs) were found to stimulate the release of H2O2 and O-2 from the peritoneal macrophages obtained from mice which had been pretreated with the heat-killed preparation of Streptococcus pyogenes (OK-432) in vivo. Some alkyl esters of SMA exhibited effects similar to protein-polymer conjugates. Among them, butyl-SMA was the most effective followed by ethyl-SMA, whereas hydrolyzed SMA showed no effect. This activity was dose-dependent but exhibited a bell-shape profile. These results suggest that the aliphatic ester residue in SMA as well as the main chain of the copolymer may be important for the activation of macrophages. A strong antitumor effect of smancs reported elsewhere may be attributed partly to the activation of macrophages in addition to the direct damage to the cellular DNA by the NCS component. A preliminary investigation of the subcellular mechanism of macrophage activation was carried out in view of membrane fluidity by the fluorescence polarization method. The results showed that the apparent decrease in the cell membrane fluidity and the degree of macrophage activation paralleled the same dose range and at similar time courses. This indicated the interaction of SMA component and macrophage cell membrane.