The activation of matrix metalloproteinases by a whole-cell extract from Prevotella nigrescens

Periradicular lesions are primarily evoked as a response to a bacterial challenge emanating from an infected root canal. Many bacteria such as those of the genera Porphyromonas, Prevotella, and others have been isolated from infected root canals. The cause of periradicular lesions is related to the destruction of the extracellular matrix (ECM). Matrix metalloproteinases (MMPs) such as interstitial collagenase (MMP-1), gelatinase A (MMP-2), gelatinase B (MMP-9), and so on are products of inflammatory cells and, once activated, are intimately involved in the degradation of the ECM. However, there are no reports regarding the destruction of the ECM by bacterial extracts from Prevotella nigrescens (P. nigrescens). The present study was conducted to evaluate the activating effect of a whole-cell extract (WCE) of P. nigrescens on proMMP-2 and proMMP-9. P. nigrescens WCE was mixed with proMMP-2 or proMMP-9 under many conditions, and the activation of these MMPs was determined by gelatin zymography. A band indicating a lower molecular weight of 66 kd or 84 kd, which migrated faster than the band of proMMP-2 (72 kd) or proMMP-9 (92 kd) respectively, was detected, which could be the active form of either MMP. The present study suggests that P. nigrescens might be able to activate proMMP-2 and proMMP-9 in vivo and that this activation might be related to the destruction of periapical tissues.