Mast cell tissue inhibitor of metalloproteinase-1 is cleaved and inactivated extracellularly by alpha-chymase.

We previously reported that mast cell alpha-chymase cleaves and activates progelatinase B (progel B). Outside of cells, progel B is complexed with tissue inhibitor of metalloproteinase (TIMP)-1, which hinders zymogen activation and inhibits activity of mature forms. The current work demonstrates that dog BR mastocytoma cells, HMC-1 cells, and murine bone marrow-derived mast cells secrete TIMP-1 whose electrophoretic profile in supernatants suggests degranulation-dependent proteolysis. Alpha-chymase cleaves uncomplexed TIMP-1, reducing its ability to inhibit gel B, whereas tryptase has no effect. Sequencing of TIMP-1's alpha-chymase-mediated cleavage products reveals hydrolysis at Phe(12)-Cys(13) and Phe(23)-Val(24) in loop 1 and Phe(101)-Val(102) and Trp(105)-Asn(106) in loop 3 of the NH(2)-terminal domain. TIMP-1 in a ternary complex with progel B and neutrophil gelatinase-associated lipocalin is also susceptible to alpha-chymase cleavage, yielding products like those resulting from processing of free TIMP-1. Thus, alpha-chymase cleaves free and gel B-bound TIMP-1. Incubation of the progel B-TIMP-1-neutrophil gelatinase-associated lipocalin complex with alpha-chymase increases gel B activity 2- to 5-fold, suggesting that alpha-chymase activates progel B whether it exists as free monomer or as a complex with TIMP-1. Furthermore, inhibition of alpha-chymase blocks degranulation-induced TIMP-1 processing (absent in alpha-chymase-deficient HMC-1 cells). Purified alpha-chymase processes TIMP-1 in BR supernatants, generating products like those induced by degranulation. In summary, these results suggest that controlled exocytosis of mast cell alpha-chymase activates progel B even in the presence of TIMP-1. This is the first identification of a protease that overcomes inhibition by bound TIMP-1 to activate progel B without involvement of other proteases.

Endodontic status in older U.S. adults. Report of a survey.

BACKGROUND: Aging people experience a number of changes in the root canal systems of teeth that, while they are normal, have the potential to compromise the pulp's response to injury. METHODS: To better understand the dental perspective on these changes, the authors mailed a questionnaire to diplomates of the American Board of Endodontics. The questions dealt with the respondents' experiences, ages of their patient population and their perception of root canal changes in aging patients. The authors analyzed the data in terms of number of diplomates providing a response and stratified them on the basis of the respondents' number of years in practice. RESULTS: Respondents indicated that the number of patients aged 65 years and older in their practices is increasing. Virtually all of the diplomates agreed that the root canal gets smaller with age, but that this diminution does not contribute to the failure of treatment of affected teeth. Most respondents indicated that aging patients' teeth are in poorer condition than those of younger patients. CONCLUSIONS: As the U.S. population ages, clinicians need to have a better understanding of the physiological changes occurring in older patients' teeth that may influence the treatment required to help patients retain their natural dentition. Further studies are needed to determine the impact of aging on dental disease and treatment modalities. CLINICAL IMPLICATIONS: Recognition of changes in the dentition of aging patients will lead to more successful treatment, retention of functional natural dentition and better maintenance of general health.