Monosodium urate crystals activate the NLRP3 inflammasome in macrophages, resulting in caspase-1-mediated maturation and release of IL-1β, which induces neutrophil recruitment and amplifies joint swelling, pain, and erythema in gouty arthritis.

When urate crystals form in the joint, immune cells called macrophages swallow them, which breaks open their internal trash bags, releasing enzymes that set off a danger signal. This signal, combined with a drop in potassium inside the cell, activates a protein complex that cuts a dormant inflammatory molecule into its active form. The active molecule escapes the cell and draws in white blood cells that cause swelling, heat, and pain in the joint.