Gout is a chronic arthritis caused by the deposition of poorly soluble monosodium urate monohydrate (MSU) crystals in peripheral joints. Resident macrophages initiate inflammation in response to MSU mediated by NF-κB nuclear translocation and NLRP3 inflammasome activation. We investigated the role of CD44, a transmembrane receptor, in mediating MSU phagocytosis by macrophages. We used an antibody that sheds the extracellular domain (ECD) of CD44 to study the role of the receptor and its associated protein phosphatase 2A (PP2A) in macrophage activation. We also studied the significance of CD44 in mediating MSU inflammation in-vivo. Cd44^−/− BMDMs showed reduced MSU phagocytosis, LDH release, IL-1β expression and production compared to Cd44^+/+ BMDMs. Elevated CD44 staining was detected intracellularly and CD44 colocalized with α-tubulin as a result of MSU exposure and ECD-shedding reduced MSU phagocytosis in murine and human macrophages. Anti-CD44 antibody treatment reduced NF-κB p65 subunit nuclear levels, IL-1β expression, pro-IL-1β and IL-8 production in MSU stimulated THP-1 macrophages (p < 0.01). The effect of the antibody was mediated by an enhancement in PP2A activity. CD44 ECD-shedding reduced the conversion of procaspase-1 to active caspase-1, caspase-1 activity and resultant generation of mature IL-1β in macrophages. Neutrophil and monocyte influx and upregulated production of IL-1β was evident in wildtype mice. MSU failed to trigger neutrophil and monocyte recruitment in Cd44^−/− mice and lower IL-1β levels were detected in peritoneal lavages from Cd44^−/− mice (p < 0.01). Anti-CD44 antibody treatment reduced neutrophil and monocyte recruitment and resulted in reduced lavage IL-1β levels in the same model. CD44 plays a biologically significant role in mediating phagocytosis of MSU and downstream inflammation and is a novel target in gout treatment.

痛风是一种慢性关节炎，由难溶性尿酸一钠一水合物（MSU）晶体在周围关节中沉积引起。居民巨噬细胞响应由NF-κB核易位和NLRP3炎性小体激活介导的MSU引发炎症。我们调查了跨膜受体CD44在巨噬细胞介导MSU吞噬作用中的作用。我们使用了脱落CD44的胞外域（ECD）的抗体来研究受体及其相关蛋白磷酸酶2A（PP2A）在巨噬细胞激活中的作用。我们还研究了CD44在介导MSU体内炎症中的意义。与Cd44 ^{+ / +}相比，Cd44 ^-/- BMDMs降低MSU吞噬作用，LDH释放，IL-1β表达和产生BMDM。由于MSU暴露和ECD脱落减少了鼠和人巨噬细胞中MSU的吞噬作用，因此在细胞内检测到CD44染色升高，并且CD44与α-微管蛋白共定位。抗CD44抗体治疗可降低MSU刺激的THP-1巨噬细胞中NF-κBp65亚基的核水平，IL-1β表达，IL-1β的表达和IL-8的产生（p  <  0.01）。PP2A活性的增强介导了抗体的作用。CD44 ECD脱落可减少procaspase-1向活性caspase-1的转化，caspase-1活性以及巨噬细胞中成熟IL-1β的产生。在野生型小鼠中，嗜中性粒细胞和单核细胞大量涌入，IL-1β产生上调。MSU未能触发Cd44中的中性粒细胞和单核细胞募集^-/-在Cd44 ^-/-小鼠的腹腔灌洗液中检测到小鼠和较低的IL-1β水平（p  <  0.01）。在同一模型中，抗CD44抗体治疗可减少中性粒细胞和单核细胞募集，并减少灌洗液IL-1β的水平。CD44在介导MSU的吞噬作用和下游炎症中起着生物学上的重要作用，并且是痛风治疗的新靶标。