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MSU Crystals induce sterile IL-1β secretion via P2X7 receptor activation and HMGB1 release
Ygor Marinho1, Camila Marques-da-Silva1, Patricia Teixeira Santana1
1Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil.
Backgroud:
The mechanism by which monosodium urate (MSU) crystals induce inflammation is not completely understood. Few studies have shown that MSU is capable of stimulating the release of IL-1β in the absence of LPS treatment. The purinergic P2X7 receptor is involved in the release of IL-1β in inflammatory settings caused by crystals, as is the case in silicosis.
Methods:
We investigated the role of P2X7 receptor in sterile MSU-induced inflammation by evaluating peritonitis and paw edema. In in vitro models, we performed the experiments using peritoneal macrophages and THP-1 cells. We measured inflammatory parameters using ELISA and immunoblotting. We measured cell recruitment using cell phenotypic identification and hemocytometer counts.
Results:
Our in vivo data showed that animals without P2X7 receptors generated less paw edema, less cell recruitment, and lower levels of IL-1β release in a peritonitis model. In the in vitro model, we observed that MSU induced dye uptake by the P2X7 receptor. In the absence of the receptor, or when it was blocked, MSU crystals induced less IL-1β release and this effect corresponded to the concentration of extracellular ATP. Moreover, MSU treatment induced HMGB1 release; pre-treatment with P2X7 antagonist reduced the amount of HMGB1 in cell supernatants.
Conclusions:
IL-1β secretion induced by MSU depends on P2X7 receptor activation and involves HMGB1 release.
General Significance:
We propose that cell activation caused by MSU crystals induces peritoneal macrophages and THP-1 cells to release ATP and HMGB1, causing IL-1β secretion via P2X7 receptor activation.
Insights
Monosodium urate (MSU) crystals trigger inflammation via P2X7 receptor activation, leading to IL-1β and HMGB1 release. Blocking this receptor reduces inflammatory responses in sterile crystal-induced inflammation.
Area of Science:
- Immunology
- Inflammation Research
- Crystal-Induced Arthritis
Background:
- The precise mechanisms of monosodium urate (MSU) crystal-induced inflammation remain unclear.
- MSU can stimulate interleukin-1 beta (IL-1β) release independently of lipopolysaccharide (LPS).
- The purinergic P2X7 receptor is implicated in IL-1β release during crystal-induced inflammation.
Purpose of the Study:
- To elucidate the role of the P2X7 receptor in sterile MSU crystal-induced inflammation.
- To investigate the involvement of P2X7 receptor in peritonitis and paw edema models.
- To analyze IL-1β and HMGB1 release in vitro and in vivo.
Main Methods:
- In vivo studies utilized peritonitis and paw edema models in P2X7 receptor-deficient animals.
- In vitro experiments were conducted using peritoneal macrophages and THP-1 cells.
- Inflammatory markers, cell recruitment, and receptor activation were assessed via ELISA, immunoblotting, and cell counting.
Main Results:
- P2X7 receptor knockout mice exhibited reduced paw edema, cell recruitment, and IL-1β levels.
- MSU crystals induced P2X7 receptor-mediated dye uptake in vitro.
- Inhibition of P2X7 receptor or extracellular ATP reduced MSU-induced IL-1β and HMGB1 release.
Conclusions:
- MSU-induced IL-1β secretion is dependent on P2X7 receptor activation.
- HMGB1 release is a key component in the P2X7-mediated inflammatory pathway.
- MSU crystals activate cells to release ATP and HMGB1, driving IL-1β secretion through P2X7.
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