Crystal-induced membrane damage: hydroxyapatite crystal-induced hemolysis of erythrocytes.

Microcrystals of hydroxyapatite cause severe membrane damage in human erythrocytes, as is evident from the strong hemolysis that is caused by these crystals. Hemolysis by hydroxyapatite crystals is time and concentration dependent, and is preceded by aggregation of erythrocytes. Polyvinylpyridine-N-oxide, a strong hydrogen acceptor, has no inhibiting effect on hydroxyapatite-induced hemolysis. This suggest that the mechanism of action of these crystals is different from that of urate crystals and silica particles, where hydrogen bonding interaction is supposed to be important. Negatively charged macromolecules, such as dextran sulfate, heparin, and polyglutamic acid, inhibit hydroxyapatite crystal-induced hemolysis, suggesting that positive charges, probably located on the crystals, play an important role in the membrane-damaging effect of these crystals. The structures with which these positive charges interact remain to be determined because removal of negative charges from the erythrocytes by treatment with neuraminidase does not affect crystal-induced hemolysis.