Soluble monosodium urate, but not its crystal, induces toll like receptor 4-dependent immune activation in renal mesangial cells.

•Immune effects of soluble monosodium urate (MSU) and MSU crystals were compared.•Soluble MSU and MSU crystals both activated TLR4 in renal mesangial cells.•Soluble MSU, but not MSU crystals, increased both NLRP3 and IL-1β production.•Soluble MSU, but not MSU crystals, induced HLA-DR and CD40 over-expression.•The effects of soluble MSU were TLR4-dependent.