Alpha 1-antitrypsin and Protease Complexation Is Induced by Lipopolysaccharide, Interleukin-1 β , and Tumor Necrosis Factor- α in Monocytes

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Abstract
Local regulation of alpha1-antitrypsin (alpha1-AT) may have importance in maintenance of the protease-antiprotease balance in the microenvironment of inflammatory cells. We therefore studied whether lipopolysaccharide (LPS), interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNFalpha) affect the pericellular concentration of alpha1-AT in human peripheral blood mononuclear cells (PBMC). PBMC taken from normal healthy volunteers were treated with LPS, IL-1beta, and TNFalpha, and the concentration of human alpha1-AT in conditioned supernatants was measured. When compared with unstimulated control supernatants (147 +/- 19 ng/ml), LPS (439 +/- 66 ng/ml; p < or = 0.001), IL-1beta (263 +/- 37 ng/ml; p < or = 0.01), and TNFalpha (316 +/- 59 ng/ml; p < or = 0.05) induced a 2- to 3-fold increase of alpha1-AT. Up-regulation of alpha1-AT protein correlated with an increase in alpha1-AT mRNA, suggesting a simultaneous increase in alpha1-AT synthesis. Despite the increase in alpha1-AT concentration, functional antiprotease activity could not be detected. Furthermore, protease activity was present in all samples, with the amount of activity being inversely related to the amount of alpha1-AT measured in supernatants. These findings suggest that local inflammatory conditions up-regulate alpha1-AT production by monocytes which complex with a protease derived from the PBMC population.

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