Soluble urate-induced effects on cytokine production in vitro - Assessment of methodologies and cell types

Hyperuricemia has been shown to be an inducer of pro-inflammatory mediators by human primary monocytes. To study the deleterious effects of hyperuricemia, a reliable and stable in vitro model using soluble urate is needed. One recent report showed different urate-dissolving methods resulted in either pro-inflammatory or anti-inflammatory properties. The aim of this study was to compare the effect of two methods of dissolving urate on both primary human peripheral blood mononuclear cells (PBMCs) and THP-1 cells. The two methods tested were 'pre-warming' and 'dissolving with NaOH'.

Primary human PBMCs and THP-1 cells were exposed to urate solutions, prepared using the two methodologies: pre-warming and dissolving with NaOH. Afterwards, cells were stimulated with various stimuli, followed by the measurement of the inflammatory mediators IL-1β, IL-6, IL-1Ra, TNF, IL-8, and MCP-1.

In PBMCs, we observed an overall pro-inflammatory effect of urate, both in the pre-warming and the NaOH dissolving method. A similar pro-inflammatory effect was seen in THP-1 cells for both dissolving methods after restimulation. However, THP-1 cells exhibited pro-inflammatory profile with exposure to urate alone without restimulation. We did not find MSU crystals in our cellular assays.

Overall, the urate dissolving methods do not have critical impact on its inflammatory properties. Soluble urate prepared using either of the two methods showed mostly pro-inflammatory effects on human primary PBMCs and monocytic cell line THP-1. However, human primary PBMCs and the THP-1 differ in their response to soluble urate without restimulation.