Abstract
Objective
Deposition of monosodium urate monohydrate (MSU) crystals in the joints promotes an intense inflammatory response and joint dysfunction. This study evaluated the role of the NLRP3 ...inflammasome and 5‐lipoxygenase (5‐LOX)–derived leukotriene B
4
(LTB
4
) in driving tissue inflammation and hypernociception in a murine model of gout.
Methods
Gout was induced by injecting MSU crystals into the joints of mice. Wild‐type mice and mice deficient in NLRP3, ASC, caspase 1, interleukin‐1β (IL‐1β), IL‐1 receptor type I (IL‐1RI), IL‐18R, myeloid differentiation factor 88 (MyD88), or 5‐LOX were used. Evaluations were performed to assess neutrophil influx, LTB
4
activity, cytokine (IL‐1β, CXCL1) production (by enzyme‐linked immunosorbent assay), synovial microvasculature cell adhesion (by intravital microscopy), and hypernociception. Cleaved caspase 1 and production of reactive oxygen species (ROS) were analyzed in macrophages by Western blotting and fluorometric assay, respectively.
Results
Injection of MSU crystals into the knee joints of mice induced neutrophil influx and neutrophil‐dependent hypernociception. MSU crystal–induced neutrophil influx was CXCR2‐dependent and relied on the induction of CXCL1 in an NLRP3/ASC/caspase 1/IL‐1β/MyD88–dependent manner. LTB
4
was produced rapidly after injection of MSU crystals, and this was necessary for caspase 1–dependent IL‐1β production and consequent release of CXCR2‐acting chemokines in vivo. In vitro, macrophages produced LTB
4
after MSU crystal injection, and LTB
4
was relevant in the MSU crystal–induced maturation of IL‐1β. Mechanistically, LTB
4
drove MSU crystal–induced production of ROS and ROS‐dependent activation of the NLRP3 inflammasome.
Conclusion
These results reveal the role of the NLRP3 inflammasome in mediating MSU crystal–induced inflammation and dysfunction of the joints, and highlight a previously unrecognized role of LTB
4
in driving NLRP3 inflammasome activation in response to MSU crystals, both in vitro and in vivo.
Deposition of monosodium urate monohydrate (MSU) crystals in the joints promotes an intense inflammatory response and joint dysfunction. This study evaluated the role of the NLRP3 inflammasome and ...5-lipoxygenase (5-LOX)-derived leukotriene B(4) (LTB(4) ) in driving tissue inflammation and hypernociception in a murine model of gout.
Gout was induced by injecting MSU crystals into the joints of mice. Wild-type mice and mice deficient in NLRP3, ASC, caspase 1, interleukin-1β (IL-1β), IL-1 receptor type I (IL-1RI), IL-18R, myeloid differentiation factor 88 (MyD88), or 5-LOX were used. Evaluations were performed to assess neutrophil influx, LTB(4) activity, cytokine (IL-1β, CXCL1) production (by enzyme-linked immunosorbent assay), synovial microvasculature cell adhesion (by intravital microscopy), and hypernociception. Cleaved caspase 1 and production of reactive oxygen species (ROS) were analyzed in macrophages by Western blotting and fluorometric assay, respectively.
Injection of MSU crystals into the knee joints of mice induced neutrophil influx and neutrophil-dependent hypernociception. MSU crystal-induced neutrophil influx was CXCR2-dependent and relied on the induction of CXCL1 in an NLRP3/ASC/caspase 1/IL-1β/MyD88-dependent manner. LTB(4) was produced rapidly after injection of MSU crystals, and this was necessary for caspase 1-dependent IL-1β production and consequent release of CXCR2-acting chemokines in vivo. In vitro, macrophages produced LTB(4) after MSU crystal injection, and LTB(4) was relevant in the MSU crystal-induced maturation of IL-1β. Mechanistically, LTB(4) drove MSU crystal-induced production of ROS and ROS-dependent activation of the NLRP3 inflammasome.
These results reveal the role of the NLRP3 inflammasome in mediating MSU crystal-induced inflammation and dysfunction of the joints, and highlight a previously unrecognized role of LTB(4) in driving NLRP3 inflammasome activation in response to MSU crystals, both in vitro and in vivo.
An impaired lipid metabolism is often found in patients with chronic liver diseases. Unfortunately, few studies are available concerning serum lipid and lipoprotein levels in patients with liver ...cirrhosis and chronic active hepatitis (CAH).
To evaluate low-density lipoprotein (LDL), high-density lipoprotein (HDL), very low-density lipoprotein (VLDL), and total cholesterol serum levels in patients with cirrhosis and CAH and control patients and to relate the findings to the severity of the cirrhosis (Child classification).
We measured the serum lipid pattern in 34 consecutive patients with liver cirrhosis (15 men and 19 women; mean +/-SD age, 55 +/- 14 years; Child classes: 14 in A, 9 in B, 11 in C; patients with biliary cirrhosis were excluded), 34 patients with CAH, and 34 control patients. The 3 groups were matched for sex and age. Total serum, HDL cholesterol, and triglyceride levels were measured by enzymatic methods; serum LDL and VLDL levels were calculated.
In patients with cirrhosis, there was a significant decrease in LDL, HDL, and total cholesterol serum levels compared with both the patients with CAH and the control patients, while the VLDL cholesterol level in patients with cirrhosis was significantly lower compared with the control patients alone. A significant decrease in total cholesterol levels was also observed in the CAH group when compared with the control patients. In patients with cirrhosis, levels of LDL, HDL, and total serum cholesterol were progressively lower when comparing patients in Child class A with patients in class C.
In this study, the striking decrease in the level of serum LDL cholesterol in patients with liver disease was related to the increasing severity of the disease. Accordingly, the assessment of the serum LDL cholesterol level is important for an effective treatment and prognostic evaluation of patients with chronic liver disease.
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