Tjäderhane L, Larjava H, Sorsa T, Uitto V J, Larmas M, Salo T
Faculty of Dentistry, University of British Columbia, Vancouver, Canada.
J Dent Res. 1998 Aug;77(8):1622-9. doi: 10.1177/00220345980770081001.
Matrix metalloproteinases (MMPs) are a family of enzymes which, in concert, are capable of degrading collagen. We investigated whether human MMPs could participate in the degradation of dentin organic matrix after demineralization. We performed Western blot analyses using MMP-specific antibodies to identify MMPs in human dental caries lesions. Enzymography and functional activity assays, with 125I-labeled gelatin as substrate or quantitating the degradation of type I collagen, were used to determine the activity of purified and salivary gelatinolytic (MMP-2 and MMP-9) and collagenolytic (MMP-8) enzymes with and without acid-activation in pHs relevant to caries. Respective analyses were done with caries-related bacteria. We performed electron microscope analyses to assess the degradative activity of sterilized salivary host MMPs on demineralized human dentin. Human MMP-2, MMP-8, and MMP-9 were identified in demineralized dentinal lesions. The latent purified forms of these enzymes were activated at low pH (4.5), followed by neutralization, mimicking the conditions during caries progression. Incubation of human saliva at low pH followed by neutralization resulted in a four-fold increase in the gelatinolytic activity. No gelatinolytic or collagenolytic activity was observed in bacterial samples. The activated enzymes in saliva degraded demineralized dentin organic matrix in vitro. These results demonstrate the pH-dependent activation mechanism of MMPs, which may have a distinct role in different physiological and pathological conditions. They further demonstrate that host MMPs, activated by bacterial acids, have a crucial role in the destruction of dentin by caries.
基质金属蛋白酶（MMPs）是一类酶，它们协同作用能够降解胶原蛋白。我们研究了人类MMPs在脱矿后是否能参与牙本质有机基质的降解。我们使用MMP特异性抗体进行蛋白质印迹分析，以鉴定人类龋齿病变中的MMPs。酶谱分析和功能活性测定，以125I标记的明胶为底物或定量I型胶原蛋白的降解，用于测定纯化的和唾液中的明胶溶解酶（MMP-2和MMP-9）以及胶原蛋白溶解酶（MMP-8）在与龋齿相关的pH值下有无酸激活时的活性。对与龋齿相关的细菌进行了相应分析。我们进行了电子显微镜分析，以评估无菌唾液中宿主MMPs对脱矿人类牙本质的降解活性。在脱矿的牙本质病变中检测到了人类MMP-2、MMP-8和MMP-9。这些酶的潜在纯化形式在低pH（4.5）下被激活，随后中和，模拟龋齿进展过程中的条件。在低pH下孵育人类唾液然后中和，导致明胶溶解活性增加了四倍。在细菌样本中未观察到明胶溶解或胶原蛋白溶解活性。唾液中的激活酶在体外降解了脱矿的牙本质有机基质。这些结果证明了MMPs的pH依赖性激活机制，这可能在不同的生理和病理条件下具有独特作用。它们进一步证明，被细菌酸激活的宿主MMPs在龋齿破坏牙本质过程中起关键作用。
