title: alpha(1)-Acid glycoprotein modulates apoptosis in bovine monocytes.
abstract: alpha(1)-Acid glycoprotein (AGP, orosomucoid) is a normal constituent of bovine blood. AGP is an immunocalin, a binding protein that can also exert several immunomodulatory functions. In this paper we investigated the effect of bovine alpha(1)-acid glycoprotein (boAGP) on spontaneous and staurosporine-induced apoptosis of blood derived monocytes purified using magnetic cell sorting techniques. Bovine AGP was purified from blood following a chromatographic protocol. The homogeneous protein was used to stimulate the cells as well to raise a polyclonal antibody, that was used throughout all the experiments. When monocytes were incubated with high concentrations of boAGP (0.9 mg/ml), similar to those found in bovine plasma during systemic reaction to inflammation, their spontaneous apoptosis rate was suppressed, as determined by caspase-3/7 enzymatic activity assay. Similar results were obtained when apoptosis was induced by adding staurosporine, a potent protein kinase inhibitor. The apoptosis-modulating activity of boAGP was dependent on its concentration, since physiological concentrations of boAGP (0.3 mg/ml) did not exhibit a statistically significative anti-apoptotic activity. We also investigated whether this apoptosis-modulating activity was dependent on the terminal sialic acid residues exposed on the surface of the protein. Enzymatic treatment with neuraminidase, that cleaves terminal sialic acid residues, completely abolished boAGP's anti-apoptotic activity. These results suggest that the protective effect of AGP is likely mediated by its sialic acid terminal groups.
authors.affiliation: Dipartimento di Patologia Animale, Igiene e Sanità Pubblica Veterinaria, Università degli Studi di Milano, Via Celoria 10, 20133 Milano, Italy. fabrizio.ceciliani@unimi.it
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Ceciliani
authors.forename: Vanessa
authors.initials: V
authors.lastname: Pocacqua
authors.forename: Alba
authors.initials: A
authors.lastname: Miranda-Ribera
authors.forename: Valerio
authors.initials: V
authors.lastname: Bronzo
authors.forename: Cristina
authors.initials: C
authors.lastname: Lecchi
authors.forename: Paola
authors.initials: P
authors.lastname: Sartorelli
mesh_terms: D000818:Animals; D000906:Antibodies; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002417:Cattle; D005260:Female; D066298:In Vitro Techniques; D009000:Monocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D019158:N-Acetylneuraminic Acid / Q000737:chemistry; D009961:Orosomucoid / Q000037:antagonists & inhibitors / Q000276:immunology / Q000494:pharmacology* / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology
chemical_list: D000906:Antibodies; D009961:Orosomucoid; D019158:N-Acetylneuraminic Acid; D019311:Staurosporine