title: Alpha-1-antitrypsin is an endogenous inhibitor of proinflammatory cytokine production in whole blood.
abstract: Several observations suggest endogenous suppressors of inflammatory mediators are present in human blood. alpha-1-Antitrypsin (AAT) is the most abundant serine protease inhibitor in blood, and AAT possesses anti-inflammatory activity in vitro and in vivo. Here, we show that in vitro stimulation of whole blood from persons with a genetic AAT deficiency resulted in enhanced cytokine production compared with blood from healthy subjects. Using whole blood from healthy subjects, dilution of blood with RPMI tissue-culture medium, followed by incubation for 18 h, increased spontaneous production of IL-8, TNF-alpha, IL-1 beta, and IL-1R antagonist (IL-1Ra) significantly, compared with undiluted blood. Dilution-induced cytokine production suggested the presence of one or more circulating inhibitors of cytokine synthesis present in blood. Serially diluting blood with tissue-culture medium in the presence of cytokine stimulation with heat-killed Staphylococcus epidermidis (S. epi) resulted in 1.2- to 55-fold increases in cytokine production compared with S. epi stimulation alone. Diluting blood with autologous plasma did not increase the production of IL-8, TNF-alpha, IL-1 beta, or IL-1Ra, suggesting that the endogenous, inhibitory activity of blood resided in plasma. In whole blood, diluted and stimulated with S. epi, exogenous AAT inhibited IL-8, IL-6, TNF-alpha, and IL-1 beta significantly but did not suppress induction of the anti-inflammatory cytokines IL-1Ra and IL-10. These ex vivo and in vitro observations suggest that endogenous AAT in blood contributes to the suppression of proinflammatory cytokine synthesis.
authors.affiliation: Denver Veterans Affairs Medical Center, Department of Medicine, Division of Infectious Diseases, University of Colorado Denver, 12700 E. 19th Ave., Aurora, CO 80045, USA.
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Pott
authors.forename: Edward D
authors.initials: ED
authors.lastname: Chan
authors.forename: Charles A
authors.initials: CA
authors.lastname: Dinarello
authors.forename: Leland
authors.initials: L
authors.lastname: Shapiro
mesh_terms: D000328:Adult; D000368:Aged; D001773:Blood Cells / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein / Q000096:biosynthesis* / Q000097:blood; D053583:Interleukin-1beta / Q000096:biosynthesis* / Q000097:blood; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000097:blood; D008297:Male; D008875:Middle Aged; D013212:Staphylococcus epidermidis / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000097:blood; D019896:alpha 1-Antitrypsin Deficiency / Q000097:blood / Q000378:metabolism*
chemical_list: C508606:CXCL8 protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D053583:Interleukin-1beta; D016209:Interleukin-8; D014409:Tumor Necrosis Factor-alpha