Activation of human neutrophils by calcium carbonate polymorphs

Gallstone formation is frequently accompanied by inflammation of the gallbladder mucosa. Some gallstone components such as cholesterol, calcium bilirubinate, and calcium hydroxyapatite have been previously shown to activate neutrophils. We investigated the effect on neutrophils of the calcium carbonate polymorphs aragonite, calcite, and vaterite (all found in gallstones). By chemiluminescence, superoxide, and degranulation assay, all three crystals were shown to cause rapid activation of neutrophils. The potency of the crystals was aragonite > vaterite > calcite. In vivo, crystals may be plasma-protein-coated before they encounter neutrophils; therefore some experiments were repeated using crystals that had been preincubated with plasma. For aragonite and vaterite, protein adsorption decreased the chemiluminescence response by approximately 50%. In contrast, protein-coated calcite crystals elicited a greater chemiluminescence response than did uncoated crystals. In summary, the calcium carbonate polymorphs are potent activators of neutrophils and thus have the potential to contribute to gallstone-associated cholecystitis.