Sodium and potassium urate crystals differ in their inflammatory potential

Uric acid (UA) is identified as a danger signal released from dying cells. It precipitates in sodium-rich extracellular fluid and in potassium-rich intracellular fluid as monosodium urate (MSU) and monopotassium urate (MPU), respectively. Here, we examined the structural and functional features of these crystals. In contrast to MPU MSU crystals induced reactive oxygen species production and release of pro-inflammatory cytokines in whole blood ex vivo assays. These results show that the cation of urate crystals determines the response of innate immune cells, indicating that the micromilieu at the site of crystal formation is important for their inflammatory potential.