Elevated conversion of alpha-2-macroglobulin to the complexed form in gingival crevicular fluid from adult periodontitis patients

Abstract

The broad spectrum protease inhibitor, α₂‐macgrolobulin (α2M), is one of the host's principal regulators of both endogenous and exogenous proteases and is likely to have an important role in the regulation of proteolytic activity at inflammatory sites. We have determined the amount of complexed (comα₂M) and total α₂M (totα₂M) in gingival crevicular fluid (GCF) harvested from shallow and deep sites in adult periodontitis (AP) patients (n=21). An ELISA technique was developed to measure both forms of α₂M in the same sample utilizing a monoclonal antibody (MAb) specific for the complexed form. In addition, protease activity towards human serum albumin (Protl), transferrin (Prot2) and Nα‐benzoyl‐L‐arginine 7‐amido‐4‐methylcoumarin‐hydrochloride (BAAMc; Prot3) were determined in a second GCF sample from the same site. Plasma α₂M concentrations were only positively correlated (p=0.0163) with GCF totα₂M from highly inflamed sites. We observed a significant positive correlation between totα₂M and proteolytic activity in GCF from deep sites but not from shallow sites (Protl: p=0.002; Prot2: p=0.005). A similar correlation between totα₂M and proteolytic activity was found at highly inflamed sites (Protl: p=0.014; Prot2: p=0.002). A very high proportion of the totα₂M in GCF was in the complexed form at both shallow (71.14%±29.13) and deep sites (68.17%±28.5) Comα₂M was positively correlated with proteolytic activity only in deep sites (Protl: p=0.015; Prot2: p=0.031). Our results suggest that the concentration of totα₂M in the gingival crevice is positively associated with the amount of proteolytic activity at the site and that protease activities in GCF may only partly explain the high percentage conversion α₂M to the complexed form. The high level of α₂M inactivation in GCF from AP patients reported here may have significance not only in view of its role as a broad spectrum protease inhibitor but also through the differential effects of native vs complexed α₂M on the regulation of immune responses.