背景:碳酸氢盐最近被认为是影响肽基精氨酸脱亚胺酶(PAD)活性的关键因素;然而,其在类风湿性关节炎(RA)中的作用机制尚不清楚.Iguratimod(IGU),一种小分子疾病缓解抗风湿药,需要进一步调查。本研究旨在探讨碳酸氢盐影响RA瓜氨酸化和炎症的机制,并确定IGU的新靶点。
方法:我们在研究中招募了20名RA患者。在这些患者的外周血中性粒细胞和外周血单核细胞(PBMC)中检测到碳酸氢钠协同转运蛋白2(NBCe2)。不同浓度的IGU的影响,甲氨蝶呤(MTX),地塞米松(DXM),和S0859(一种NBCe2抑制剂)对NBCe2,PAD2,PAD4和瓜氨酸化组蛋白H3(cit-H3)水平的影响,的迁移能力,检测中性粒细胞和PBMC的细胞因子产生。
结果:我们的研究结果表明,在RA患者中,外周血中性粒细胞而不是PBMC产生瓜氨酸化蛋白,显示更高的NBCe2表达水平,随着碳酸氢盐浓度的增加而增加。此外,肿瘤坏死因子-α(TNF-α)促进RA患者中性粒细胞NBCe2表达。此外,我们揭示了IGU对中性粒细胞NBCe2和cit-H3水平的抑制作用,中性粒细胞和PBMC迁移的抑制程度,和抑制白细胞介素6,TNF-α,中性粒细胞样分化的HL-60细胞分泌的金属蛋白酶-9与MTX没有实质性差异,DXM,和特定剂量的S0859。
结论:碳酸氢盐通过NBCe2促进RA蛋白瓜氨酸化和炎症反应,IGU可下调NBCe2。
BACKGROUND: Bicarbonate has recently been identified as a crucial factor affecting peptidylarginine deiminase (PAD) activity; however, the mechanism underlying its role in rheumatoid arthritis (RA) remains unclear. Iguratimod (IGU), a small-molecule disease-modifying anti-rheumatic drug, requires further investigation. This study aimed to explore the mechanism by which bicarbonate affects citrullination and inflammation in RA and identify new targets for IGU.
METHODS: We enrolled 20 patients with RA in the study. Sodium bicarbonate cotransporter 2 (NBCe2) was detected in the peripheral blood neutrophils and peripheral blood mononuclear cells (PBMCs) of these patients. The effects of varying concentrations of IGU, methotrexate (MTX), dexamethasone (DXM), and S0859 (an NBCe2 inhibitor) on NBCe2, PAD2, PAD4, and citrullinated histone H3 (cit-H3) levels in, migration ability of, and cytokine production from neutrophils and PBMCs were examined.
RESULTS: Our findings showed that in patients with RA, citrullinated protein production by peripheral blood neutrophils instead of PBMCs, which showed higher NBCe2 expression levels, increased with an increase in the bicarbonate concentration. In addition, tumor necrosis factor-alpha (TNF-α) promoted NBCe2 expression in neutrophils from patients with RA. Furthermore, we revealed that the inhibitory effects of IGU on neutrophil NBCe2 and cit-H3 levels, degrees of inhibition of neutrophil and PBMC migration, and suppression of interleukin 6, TNF-α, and metalloproteinase-9 secretion from neutrophil-like differentiated HL-60 cells did not substantially differ from those of MTX, DXM, and S0859 at specific doses.
CONCLUSIONS: Bicarbonate promotes protein citrullination and inflammation in RA via NBCe2, and IGU can downregulate NBCe2.