Figure 1.

Monosodium urate (MSU) crystals trigger intracellular reactive oxygen species (ROS) production in neutrophils. MSU crystals (300 μg/mL, solid line) triggered significant (p < 0.0001 compared to buffer treated cells, n = 16), intracellular ROS (icROS) production in neutrophils, as measured by luminol-amplified chemiluminiscense (CL) (A), representative kinetic curves are shown), and a clear dose-dependency could be noted when different concentrations of MSU crystals were used. Shown in (B) are mean peak CL values +/− SD of five independent experiments. (C) A representative kinetic extracellular ROS (ecROS) response, as measured by isoluminol-enhanced CL, of neutrophils stimulated with MSU crystals (500 µg/mL, solid line), PMA (50 nM, dotted line) or buffer (broken line). A close-up of the MSU crystal and buffer traces are also shown in the inset. (D) MSU crystals (300 µg/mL) did not trigger extracellular H₂O₂ release above buffer-levels, as measured after 20 min incubation with the H₂O₂ specific probe Amplex Red. Shown are a mean +/− SD of seven independent experiments. Statistical significance was calculated by the use of the Wilcoxon matched-pairs signed rank test.