Guma Monica, Ronacher Lisa, Liu-Bryan Ru, Takai Shinji, Karin Michael, Corr Maripat
University of California at San Diego, La Jolla.
Arthritis Rheum. 2009 Dec;60(12):3642-50. doi: 10.1002/art.24959.
Interleukin-1beta (IL-1beta) is a key cytokine linked to the pathogenesis of acute arthritis. Caspase 1, neutrophil elastase, and chymase all process proIL-1beta to its biologically active form. This study was undertaken to examine the potential contributions of each of these proteases in experimental models of inflammatory arthritis.
Caspase 1-deficient (Casp1-/-) and wild-type (WT) mice were tested for their response to arthritogenic K/BxN serum transfer for induction of arthritis or injection of monosodium urate monohydrate (MSU) crystals for induction of peritonitis. All mice were prophylactically treated with inhibitors of neutrophil elastase or chymase. Arthritic paws were tested for the presence of IL-1beta protein by enzyme-linked immunosorbent assay and Western blotting. Neutrophils and mast cells from WT and mutant mice were tested for their ability to secrete IL-1beta after in vitro stimulation, in the presence of protease inhibitors.
Casp1-/- and WT mice developed paw swelling to the same extent in the K/BxN serum transfer-induced arthritis model. MSU crystal injection into Casp1-/- mice also resulted in neutrophil influx and production of measurable peritoneal IL-1beta protein. Both of these responses were attenuated with neutrophil elastase inhibitors. K/BxN serum transfer-induced arthritis was also reduced by treatment with a chymase inhibitor. Casp1-/- neutrophils and mast cells, when exposed to MSU crystals, secreted similar amounts of IL-1beta protein upon in vitro stimulation with lipopolysaccharide, albeit at lower levels than that secreted by WT cells. Elastase and chymase inhibitors reduced the amount of IL-1beta released by these cells.
The production of IL-1beta by neutrophils and mast cells is not exclusively dependent on caspase 1, and other proteases can compensate for the loss of caspase 1 in vivo. These pathways might therefore compromise the caspase 1-targeted therapies in neutrophil-predominant arthritis.
白细胞介素-1β（IL-1β）是一种与急性关节炎发病机制相关的关键细胞因子。半胱天冬酶1、中性粒细胞弹性蛋白酶和糜酶均可将前体IL-1β加工成其生物活性形式。本研究旨在探讨这些蛋白酶在炎症性关节炎实验模型中的潜在作用。
对缺乏半胱天冬酶1（Casp1-/-）的小鼠和野生型（WT）小鼠进行测试，观察它们对致关节炎的K/BxN血清转移诱导关节炎或注射一水合尿酸钠（MSU）晶体诱导腹膜炎的反应。所有小鼠均预防性给予中性粒细胞弹性蛋白酶或糜酶抑制剂。通过酶联免疫吸附测定和蛋白质印迹法检测关节炎爪子中IL-1β蛋白的存在情况。在蛋白酶抑制剂存在的情况下，检测WT和突变小鼠的中性粒细胞和肥大细胞在体外刺激后分泌IL-1β的能力。
在K/BxN血清转移诱导的关节炎模型中，Casp1-/-小鼠和WT小鼠爪子肿胀程度相同。向Casp1-/-小鼠注射MSU晶体也导致中性粒细胞流入并产生可测量的腹膜IL-1β蛋白。这两种反应均被中性粒细胞弹性蛋白酶抑制剂减弱。用糜酶抑制剂治疗也可减轻K/BxN血清转移诱导的关节炎。当暴露于MSU晶体时，Casp1-/-中性粒细胞和肥大细胞在体外受到脂多糖刺激后分泌的IL-1β蛋白量相似，尽管低于WT细胞分泌的水平。弹性蛋白酶和糜酶抑制剂减少了这些细胞释放的IL-1β量。
中性粒细胞和肥大细胞产生IL-1β并不完全依赖于半胱天冬酶1，其他蛋白酶可以在体内补偿半胱天冬酶1的缺失。因此，这些途径可能会影响以中性粒细胞为主的关节炎中针对半胱天冬酶1的治疗效果。
