Crystal interactions with isolated human neutrophils : effect of adsorbed proteins

Crystal deposition diseases such as gout and pseudogout are characterized by the deposition of monosodium urate monohydrate (MSUM) and calcium pyrophosphate dihydrate (CPPD) crystals respectively in the joints. Inflammation arises from the interaction of these crystals with the synoviocytes and polymorphonuclear leukocytes or neutrophils. We have studied the neutrophil responses to stimulation by MSUM and CPPD crystals and the effect of various protein coatings on the crystal surface on the neutrophil responses. The neutrophil responses studied were the respiratory burst accompanying phagocytosis leading to production of superoxide anion and generation of chemiluminescence. Degranulation of the neutrophil was also studied by monitoring the release of myeloperoxidase and lysozyme enzymes. Both MSUM and CPPD induced the generation of superoxide anion to the same degree although MSUM induced a faster rate of production of superoxide anion than CPPD. The reduction of ferricytochrome c was superoxide dismutase inhibitable for CPPD/neutrophil incubations but not inhibitable for MSUM/neutrophil incubations, probably due to inactivation of superoxide dismutase by adsorption of the protein onto MSUM crystals. Precoating of MSUM and CPPD crystals with Immunoglobulin G, Bovine serum albumin or plasma proteins did not influence the generation of superoxide significantly. The generation of luminol enhanced neutrophil chemiluminescence induced by MSUM was of a greater magnitude and the maximal response was attained faster than for CPPD crystals. Precoating MSUM or CPPD crystals with immunoglobulin G enhanced the chemiluminescence response while plasma precoating inhibited the chemiluminescence response. Release of myeloperoxidase induced by MSUM crystals could not be measured due to adsorption of myeloperoxidase by MSUM. Precoating MSUM crystals with proteins did not influence the adsorption of myeloperoxidase. Hence degranulation was monitored by measuring the release of lysozyme induced by MSUM and CPPD crystals. Lysozyme was also found to adsorb onto MSUM crystals although less extensively than myeloperoxidase. There was no significant effect of protein coating on MSUM and CPPD induced lysozyme release. The particulate stimulants MSUM and CPPD produced activation of neutrophils with superoxide release, chemiluminescence generation and degranulation. Neutrophil responses, and in particular the chemiluminescence responses, to the crystals could be modulated by the nature of the protein adsorbed to the crystal surface.Pharmaceutical Sciences, Faculty ofGraduat