Qadri Marwa, ElSayed Sandy, Elsaid Khaled A
Department of Pharmacology, College of Pharmacy, Jazan University, Jazan, Kingdom of Saudi Arabia (M.Q.) and Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Rinker Health Sciences Campus, Irvine, California (S.E., K.A.E.).
Department of Pharmacology, College of Pharmacy, Jazan University, Jazan, Kingdom of Saudi Arabia (M.Q.) and Department of Biomedical and Pharmaceutical Sciences, Chapman University School of Pharmacy, Rinker Health Sciences Campus, Irvine, California (S.E., K.A.E.)
J Pharmacol Exp Ther. 2021 Feb;376(2):222-230. doi: 10.1124/jpet.120.000321. Epub 2020 Nov 25.
Gout is a chronic inflammatory arthritis caused by monosodium urate monohydrate (MSU) crystal deposits in joints of lower limbs. Phagocytic uptake of MSU crystals by joint-resident macrophages and recruited circulating monocytes results in IL-1 expression and production. Current acute gout treatments have serious toxicities and suffer suboptimal clinical outcomes. Protein phosphatase 2A (PP2A) plays an important role in regulating signaling pathways relevant to inflammation. We hypothesized that innate immune danger signals, e.g., lipopolysaccharide (LPS) and soluble uric acid (sUA), prime human monocytes toward MSU crystal phagocytosis and that increased IL-1 production mediated by a reduction in PP2A activity and restoring PP2A activity exerts an anti-inflammatory effect in this setting. Priming monocytes with LPS + sUA increased cytosolic pro-IL-1 and mature IL-1 and enhanced MSU crystal phagocytosis and its downstream IL-1 expression ( < 0.001). A combination of LPS + sUA priming and MSU crystals reduced PP2A activity in monocytes by 60% ( = 0.013). PP2A catalytic subunit gene knockdown reduced PP2A activity and exacerbated MSU crystal-induced IL-1 expression and secretion ( < 0.0001). Fingolimod (FTY720) and its active metabolite, fingolimod phosphate (FTY720-P), were evaluated for their ability to activate PP2A in human monocytes over 24 hours. FTY720 and FTY720-P activated PP2A to a similar extent, and maximal enzyme activity occurred at 24 hours for FTY720 and at 6 hours for FTY720-P. FTY720-P (2.5 μM) reduced pro-IL-1 production and IL-1 secretion in primed and MSU crystal-stimulated monocytes ( < 0.0001) without changing the magnitude of crystal phagocytosis. We conclude that PP2A is a promising new target in acute gout. SIGNIFICANCE STATEMENT: The activity of protein phosphatase 2A (PP2A) is implicated in the enhanced expression and production of IL-1 by human monocytes in response to priming with soluble uric acid and lipopolysaccharide and phagocytosis of monosodium urate monohydrate (MSU) crystals. Fingolimod phosphate activates PP2A in human monocytes and reduces cytosolic pro-IL-1 content and its conversion to biologically active IL-1 in human monocytes exposed to MSU crystals.
痛风是一种慢性炎症性关节炎，由单水尿酸钠（MSU）晶体沉积于下肢关节所致。关节驻留巨噬细胞和募集的循环单核细胞对MSU晶体的吞噬摄取会导致白细胞介素-1（IL-1）的表达和产生。目前的急性痛风治疗方法存在严重毒性，临床疗效欠佳。蛋白磷酸酶2A（PP2A）在调节与炎症相关的信号通路中起重要作用。我们推测，先天性免疫危险信号，如脂多糖（LPS）和可溶性尿酸（sUA），会使人类单核细胞对MSU晶体吞噬作用产生预刺激，并且PP2A活性降低介导的IL-1产生增加，而恢复PP2A活性在这种情况下会发挥抗炎作用。用LPS + sUA预刺激单核细胞会增加细胞溶质前体IL-1和成熟IL-1的水平，并增强MSU晶体吞噬作用及其下游IL-1表达（P < 0.001）。LPS + sUA预刺激与MSU晶体联合作用可使单核细胞中的PP2A活性降低60%（P = 0.013）。PP2A催化亚基基因敲低会降低PP2A活性，并加剧MSU晶体诱导的IL-1表达和分泌（P < 0.0001）。对芬戈莫德（FTY720）及其活性代谢产物磷酸芬戈莫德（FTY720-P）在24小时内激活人类单核细胞中PP2A的能力进行了评估。FTY720和FTY720-P激活PP2A的程度相似，FTY720的最大酶活性出现在24小时，FTY720-P的最大酶活性出现在6小时。FTY720-P（2.5 μM）可降低预刺激且经MSU晶体刺激的单核细胞中前体IL-1的产生和IL-1的分泌（P < 0.0001），而不改变晶体吞噬的程度。我们得出结论，PP2A是急性痛风中一个有前景的新靶点。意义声明：蛋白磷酸酶2A（PP2A）的活性与人类单核细胞在可溶性尿酸和脂多糖预刺激以及单水尿酸钠（MSU）晶体吞噬作用下IL-1表达和产生的增强有关。磷酸芬戈莫德可激活人类单核细胞中的PP2A，并降低暴露于MSU晶体的人类单核细胞中细胞溶质前体IL-1的含量及其向生物活性IL-1的转化。
