Lower Temperatures Exacerbate NLRP3 Inflammasome Activation by Promoting Monosodium Urate Crystallization, Causing Gout

Abstract

Gout is a recurrent and chronic form of arthritis caused by the deposition of monosodium urate (MSU) crystals in the joints. Macrophages intake MSU crystals, the trigger for NLRP3 inflammasome activation, which leads to the release of interleukin (IL)-1β and results in the flaring of gout. The effects of temperature, an environmental factor for MSU crystallization, on IL-1β secretion have not been well studied. This study examined the effects of temperature on inflammasome activation. Specific triggers activated canonical inflammasomes (NLRP3, NLRC4, and AIM2) in murine macrophages at various temperatures (25, 33, 37, 39, and 42 °C). The maturation of IL-1β and caspase-1 was measured as an indicator for inflammasome activation. As expected, the optimal temperature of inflammasome activation was 37 °C. The MSU crystal-mediated activation of inflammasome increased at temperatures lower than 37 °C and decreased at higher temperatures. MSU crystals at lower temperatures enhanced IL-1β secretion via the NLRP3 inflammasome pathway. A lower temperature promoted the formation of MSU crystals without changing phagocytosis. Overall, lower temperatures form more MSU crystals and enhance NLRP3 inflammasome activation. In light of these findings, it is possible that hyperthermia therapy may reduce gout flaring.

Lipoxin A4 attenuates MSU-crystal-induced NLRP3 inflammasome activation through suppressing Nrf2 thereby increasing TXNRD2

“…Besides promoting IL-1β secretion, the activation of NLRP3 inflammasome can cause inflammatory death to cells, especially NLRP3-mediated pyroptosis ( 7 , 10 , 11 , 30 , 31 ). Immunoblotting results showed that the MSU crystal enhances the GSDMD-N in the cell supernatant of macrophages, the execution protein for pyroptosis ( 32 ), while LXA4 attenuates the elevated GSDMD-N ( Figures 2E, F ).…”

“…The PMA-differentiated THP-1 macrophages were transfected with TXNRD2 siRNA before being primed with LPS and then pretreated with LXA4 (150 nM) for 1 h; subsequently, 100 mg/ml of MSU crystals were added for 24 h. Abnormal ROS production is a critical upstream event for triggering NLRP3 inflammasome assembly (12). It has been widely confirmed that superior ROS are the pivotal regulator for the NLRP3 inflammasome activation induced by the MSU crystal (5, 10,11,30). Recent studies have found that ROS inhibition reversibly affects MSU-crystal-induced inflammatory responses (14,16).…”

Maltol, a Natural Flavor Enhancer, Inhibits NLRP3 and Non-Canonical Inflammasome Activation

“…The LPS-primed cells were replaced with RPMI 1640 media (350 μL per well) containing an inflammasome trigger with maltol (ESFOOD, #186785643, Gunpo-si, Gyeonggi-do, Korea). The inflammasome triggers are as follows: ATP (5 mM, InvivoGen, San Diego, CA, USA) for 1 h, nigericin (NG, 40 μM, Tocris Bioscience, Bristol, UK) for 1 h, monosodium urate crystals (MSU, 400 μg/mL, Sigma-Aldrich Co., Burlington, MA, USA) for 3 h, flagellin (500 ng/mL; Invivogen, San Diego, CA, USA) with Lipofectamine 2000 (10 μL/mL, Invitrogen, Carlsbad, CA, USA) for 3 h, dsDNA (1 μg/mL) with jetPRIME TM (2 μL/mL, Polyplus-transfection Inc., Illkirch, France) for 1 h, LPS (2 μg/mL, Sigma-Aldrich Co., Burlington, MA, USA) with FuGENE ® HD (2.5 μL/mL, Roche, Penzberg, Germany) for 6 h, and rotenone (160 μM, Santa Cruz Biotechnology, Dallas, TX, USA) for 6 h [ 24 , 25 ].…”

“…The cell lysate (Lys) was prepared with a lysis buffer containing 0.01% Triton X-100, NaCl (150 mM), Tris-base (50 mM, pH 8.0), and protease inhibitors (HaltTM cocktail, ThermoFisher Scientific, Waltham, MA, USA), and then harvested by centrifugation. The Sup and Lys were electrophoresed by 10 or 16% SDS-PAGE and transferred to PVDF membranes (GE Healthcare Bio-Science, Pittsburgh, PA, USA) [ 25 , 27 ]. The membranes were incubated with the following 1st antibodies: anti-Casp1 (p20) antibody (AG-20B-0042-C100, AdipoGen Co., San Diego, CA, USA), anti-NLRP3 antibody (AG-20B-0014-C100, AdipoGen ® Co., San Diego, CA, USA), anti-mouse IL-1β antibody (AF-401-NA, R&D Systems, Minneapolis, MN, USA), or anti-Actin antibody (sc-1615, Santa Cruz Biotechnology, Dallas, TX, USA).…”

Inflammatory Response to Regulated Cell Death in Gout and Its Functional Implications

“…Greater NLRP3 activation was observed at lower temperatures, indicating that low temperatures contribute to the MSU-induced activation of the NLRP3 inflammasome. Therefore, thermotherapy may be an effective form of physiotherapy for gout ( 103 ).…”