van Meurs J B, van Lent P L, van de Loo A A, Holthuysen A E, Bayne E K, Singer I I, van den Berg W B
Department of Rheumatology, University Hospital Nijmegen, Geert Grooteplein Zuid 8, 6525GA Nijmegen, the Netherlands.
Ann Rheum Dis. 1999 Jun;58(6):350-6. doi: 10.1136/ard.58.6.350.
Murine antigen induced arthritis (AIA) is a chronic, smouldering inflammation. Flares of arthritis can be induced by antigen rechallenge or exposure to inflammatory mediators like interleukin 1 (IL1). These flares are characterised by a fast and marked proteoglycan (PG) depletion if compared with the initial arthritis. This study investigated the involvement of metalloproteinases in both the initial and the flare phase of arthritis.
Murine AIA was induced and a flare up of arthritis was induced by injection of 10 ng of IL1beta. Messenger RNA levels of MMP-1 and -3 were studied by RT-PCR. MMP activity in cartilage, during both primary AIA as well as the flare up of arthritis, was studied by immunodetection of MMP specific neoepitopes in aggrecan (VDIPEN). Cartilage just before flare induction was analysed for presence of MMPs at the mRNA level as well as at the protein level by zymography.
At the onset of AIA, a fast upregulation of mRNA for stromelysin and collagenase was noted. However, no VDIPEN epitopes were detected during this early phase of arthritis. They appeared when PG depletion was severe at day 7 of arthritis and disappeared when cartilage was repaired. IL1 injection into a knee joint at week 4 of AIA caused a flare up of arthritis, coinciding with a fast and marked PG degradation. This degradation was characterised by accelerated expression of VDIPEN epitopes if compared with the expression in primary AIA. Analysis of cartilage at week 4 of AIA showed still increased mRNA levels of MMP-1 and -3. Moreover, increased levels of latent MMPs were present as well, as APMA activation induced profound VDIPEN epitope. In vitro exposure to IL1 did show increased PG breakdown but no VDIPEN expression, suggesting that factors in addition to IL1 are needed to cause the in vivo VDIPEN expression.
The fast and marked PG depletion seen in a flare up of AIA coincides with accelarated expression of MMP induced neoepitopes compared with expression during primary AIA. This accelerated expression is probably linked to increased levels of latent enzyme, which were found to be present in the cartilage before induction of a flare up.
小鼠抗原诱导性关节炎（AIA）是一种慢性隐匿性炎症。关节炎的发作可由抗原再次激发或暴露于白细胞介素1（IL1）等炎症介质诱发。与初始关节炎相比，这些发作的特征是蛋白聚糖（PG）迅速且显著减少。本研究调查了金属蛋白酶在关节炎初始阶段和发作阶段的作用。
诱导小鼠AIA，并通过注射10 ng IL1β诱发关节炎发作。通过逆转录聚合酶链反应（RT-PCR）研究MMP-1和-3的信使核糖核酸（mRNA）水平。在原发性AIA以及关节炎发作期间，通过免疫检测聚集蛋白聚糖中MMP特异性新表位（VDIPEN）来研究软骨中的MMP活性。在发作诱导前，通过酶谱法分析软骨中MMP在mRNA水平和蛋白质水平的存在情况。
在AIA发作时，观察到基质溶解素和胶原酶的mRNA迅速上调。然而，在关节炎的这个早期阶段未检测到VDIPEN表位。它们在关节炎第7天PG严重耗竭时出现，并在软骨修复时消失。在AIA第4周向膝关节注射IL1导致关节炎发作，同时伴有快速且显著的PG降解。与原发性AIA中的表达相比，这种降解的特征是VDIPEN表位的表达加速。对AIA第4周的软骨分析显示，MMP-1和-3的mRNA水平仍然升高。此外，潜伏性MMP的水平也升高，因为阿朴吗啡激活诱导了显著的VDIPEN表位。体外暴露于IL1确实显示PG分解增加，但没有VDIPEN表达，这表明除IL1外还需要其他因素来导致体内VDIPEN表达。
与原发性AIA期间的表达相比，AIA发作时快速且显著的PG耗竭与MMP诱导的新表位的加速表达一致。这种加速表达可能与潜伏酶水平的增加有关，在发作诱导前发现潜伏酶存在于软骨中。
