Apoptotic human cells inhibit migration of granulocytes via release of lactoferrin
Irini Bournazou, … , Adriano G. Rossi, Christopher D. Gregory
Irini Bournazou, … , Adriano G. Rossi, Christopher D. Gregory
Published December 1, 2008
Citation Information: J Clin Invest. 2009;119(1):20-32. https://doi.org/10.1172/JCI36226.
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Research Article Immunology

Apoptotic human cells inhibit migration of granulocytes via release of lactoferrin

Abstract

Apoptosis is a noninflammatory, programmed form of cell death. One mechanism underlying the non-phlogistic nature of the apoptosis program is the swift phagocytosis of the dying cells. How apoptotic cells attract mononuclear phagocytes and not granulocytes, the professional phagocytes that accumulate at sites of inflammation, has not been determined. Here, we show that apoptotic human cell lines of diverse lineages synthesize and secrete lactoferrin, a pleiotropic glycoprotein with known antiinflammatory properties. We further demonstrated that lactoferrin selectively inhibited migration of granulocytes but not mononuclear phagocytes, both in vitro and in vivo. Finally, we were able to attribute this antiinflammatory function of lactoferrin to its effects on granulocyte signaling pathways that regulate cell adhesion and motility. Together, our results identify lactoferrin as an antiinflammatory component of the apoptosis milieu and define what we believe to be a novel antiinflammatory property of lactoferrin: the ability to function as a negative regulator of granulocyte migration.

Authors

Irini Bournazou, John D. Pound, Rodger Duffin, Stylianos Bournazos, Lynsey A. Melville, Simon B. Brown, Adriano G. Rossi, Christopher D. Gregory

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Figure 8

Induction of apoptosis upregulates lactoferrin expression and release.

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Effect of lactoferrin on neutrophil activation status. The expression of...
(A) RT-PCR analysis in cell lines stimulated to undergo apoptosis (A) and unstimulated controls (V). MCF7 cells transfected with caspase-3 (25.4% apoptosis; 100 μM etoposide, 20 hours), Jurkat (18.4% apoptosis; 1 μM staurosporine, 3 hours), BL2 (12.46% apoptosis), and BL2/Bcl-2 (7.42% apoptosis; 1 μM staurosporine, 1 hour). The lanes were run on the same gel but, where indicated by the vertical lines, were noncontiguous. (B) Lactoferrin expression in A549 cells at defined time points (hours) following stimulation with 100 μM etoposide or 1 μM staurosporine. (C) Addition of pan-caspase inhibitor zVAD-fmk (100 μg/ml) for 12 hours in order to prevent etoposide-induced apoptosis in A549 cells. (D) Immunoblot analysis of cell supernatants from: BL2 and primary lymphocytes in the presence (+) or absence (–) of staurosporine (1 μM) in serum-free conditions for 1 hour. A549 cells were stimulated with (+) or without (–) 100 μM etoposide for 5 hours. All samples were run on the same gel. Noncontiguous samples of A549 cells and lymphocytes (Lymph) are indicated by the vertical lines. (E) A549 cells were induced to become apoptotic (100 μM etoposide; 20 hours) in the presence or absence of brefeldin A (1 μg/ml), a protein release inhibitor. (F) Immunoblot analysis of cell supernatants from control BL2 cells (1 × 106/ml) induced to undergo apoptosis (1 μM staurosporine, 1 hour) or primary necrosis (56°C, 1 hour) in serum-free conditions. St, staurosporine; con; control; Etop, etoposide.