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Signal regulatory protein alpha negatively regulates beta2 integrin-mediated monocyte adhesion, transendothelial migration and phagocytosis.

Liu DQ, Li LM, Guo YL, Bai R, Wang C, Bian Z, Zhang CY, Zen K - PLoS ONE (2008)

Bottom Line: In contrast, SIRPalpha overexpression in THP-1 cells showed a significant less monocyte chemotactic protein-1 (MCP-1)-triggered cell surface expression of beta(2) integrins, in particular CD11b/CD18.SIRPalpha overexpression also reduced MCP-1-initiated migration of THP-1 cells across TNFalpha-stimulated HMEC-1 monolayers.Furthermore, beta(2) integrin-mediated THP-1 cell spreading and actin polymerization in response to MCP-1, and phagocytosis of bacteria were both inhibited by SIRPalpha overexpression.

View Article: PubMed Central - PubMed

Affiliation: Jiangsu Diabetes Research Center, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China.

ABSTRACT

Background: Signal regulate protein alpha (SIRPalpha) is involved in many functional aspects of monocytes. Here we investigate the role of SIRPalpha in regulating beta(2) integrin-mediated monocyte adhesion, transendothelial migration (TEM) and phagocytosis.

Methodology/principal findings: THP-1 monocytes/macropahges treated with advanced glycation end products (AGEs) resulted in a decrease of SIRPalpha expression but an increase of beta(2) integrin cell surface expression and beta(2) integrin-mediated adhesion to tumor necrosis factor-alpha (TNFalpha)-stimulated human microvascular endothelial cell (HMEC-1) monolayers. In contrast, SIRPalpha overexpression in THP-1 cells showed a significant less monocyte chemotactic protein-1 (MCP-1)-triggered cell surface expression of beta(2) integrins, in particular CD11b/CD18. SIRPalpha overexpression reduced beta(2) integrin-mediated firm adhesion of THP-1 cells to either TNFalpha-stimulated HMEC-1 monolayers or to immobilized intercellular adhesion molecule-1 (ICAM-1). SIRPalpha overexpression also reduced MCP-1-initiated migration of THP-1 cells across TNFalpha-stimulated HMEC-1 monolayers. Furthermore, beta(2) integrin-mediated THP-1 cell spreading and actin polymerization in response to MCP-1, and phagocytosis of bacteria were both inhibited by SIRPalpha overexpression.

Conclusions/significance: SIRPalpha negatively regulates beta(2) integrin-mediated monocyte adhesion, transendothelial migration and phagocytosis, thus may serve as a critical molecule in preventing excessive activation and accumulation of monocytes in the arterial wall during early stage of atherosclerosis.

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Down-regulation of SIRPα in THP-1 cells treated with BSA-AGEs is correlated to enhanced THP-1 cell surface expression of leukocyte β2 integrins and β2 integrins-mediated THP-1 cell inflammatory responses.In these experiments, THP-1 cells were treated with BSA-AGEs (AGEs) or BSA overnight at 37°C. A: SIRPα protein level in THP-1 cells; B: reduction of SIRPα protein level by AGEs in dose-dependent fashion; C: Cell surface expression level of β2 integrins in THP-1 cells; D and E: THP-1 cell adhesion to and migration across TNFα–pre-activated HMEC-1 monolayers, respectively. All data are mean±SD (n = 3) of three independent experiments.
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pone-0003291-g001: Down-regulation of SIRPα in THP-1 cells treated with BSA-AGEs is correlated to enhanced THP-1 cell surface expression of leukocyte β2 integrins and β2 integrins-mediated THP-1 cell inflammatory responses.In these experiments, THP-1 cells were treated with BSA-AGEs (AGEs) or BSA overnight at 37°C. A: SIRPα protein level in THP-1 cells; B: reduction of SIRPα protein level by AGEs in dose-dependent fashion; C: Cell surface expression level of β2 integrins in THP-1 cells; D and E: THP-1 cell adhesion to and migration across TNFα–pre-activated HMEC-1 monolayers, respectively. All data are mean±SD (n = 3) of three independent experiments.

Mentions: It has been reported that advanced glycation end products (AGEs) are involved in tissue damage associated with diabetic complications and aging [34], [35]. Although the mechanism is still not clear, monocytes tend to be activated by AGEs and show an enhanced chemotaxis under such inflammatory conditions. As shown by Western blot analysis in Figure 1A, the expression of SIRPα in THP-1 cells was decreased after AGEs treatment. Served as controls, β-actin level was not altered. The down-regulation of SIRPα in AGEs–treated THP-1 cells is contrast to that of receptor for advanced glycation end products (RAGE) and junctional adhesion molecule-like protein (JAML), which expression levels are both increased after AGEs treatment (Zen et al, unpublished). Fig. 1B showed the quantitative analysis of SIRPα downregulation by AGEs in a dose-dependent fashion. Interestingly, AGEs–treated THP-1 cells showed a significant enhanced cell surface expression of β2 integrins, in particular CD11b/CD18, in response to the stimulation of MCP-1 (Fig. 1C). Also, compared to BSA–treated THP-1 cells, AGEs– treated THP-1 cells had a higher percentage of cell adhesion to TNFα–activated HMEC-1 monolayer (Fig. 1D). In response to MCP-1, AGEs–treated THP-1 cells also showed an increased transmigration across TNFα–activated HMEC-1 monolayers compared to THP-1 cells treated with BSA (Fig. 1E). Together, these results suggest that AGEs treatment can activate THP-1 cells and enhance cell chemotaxis.


Signal regulatory protein alpha negatively regulates beta2 integrin-mediated monocyte adhesion, transendothelial migration and phagocytosis.

Liu DQ, Li LM, Guo YL, Bai R, Wang C, Bian Z, Zhang CY, Zen K - PLoS ONE (2008)

Down-regulation of SIRPα in THP-1 cells treated with BSA-AGEs is correlated to enhanced THP-1 cell surface expression of leukocyte β2 integrins and β2 integrins-mediated THP-1 cell inflammatory responses.In these experiments, THP-1 cells were treated with BSA-AGEs (AGEs) or BSA overnight at 37°C. A: SIRPα protein level in THP-1 cells; B: reduction of SIRPα protein level by AGEs in dose-dependent fashion; C: Cell surface expression level of β2 integrins in THP-1 cells; D and E: THP-1 cell adhesion to and migration across TNFα–pre-activated HMEC-1 monolayers, respectively. All data are mean±SD (n = 3) of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2553263&req=5

pone-0003291-g001: Down-regulation of SIRPα in THP-1 cells treated with BSA-AGEs is correlated to enhanced THP-1 cell surface expression of leukocyte β2 integrins and β2 integrins-mediated THP-1 cell inflammatory responses.In these experiments, THP-1 cells were treated with BSA-AGEs (AGEs) or BSA overnight at 37°C. A: SIRPα protein level in THP-1 cells; B: reduction of SIRPα protein level by AGEs in dose-dependent fashion; C: Cell surface expression level of β2 integrins in THP-1 cells; D and E: THP-1 cell adhesion to and migration across TNFα–pre-activated HMEC-1 monolayers, respectively. All data are mean±SD (n = 3) of three independent experiments.
Mentions: It has been reported that advanced glycation end products (AGEs) are involved in tissue damage associated with diabetic complications and aging [34], [35]. Although the mechanism is still not clear, monocytes tend to be activated by AGEs and show an enhanced chemotaxis under such inflammatory conditions. As shown by Western blot analysis in Figure 1A, the expression of SIRPα in THP-1 cells was decreased after AGEs treatment. Served as controls, β-actin level was not altered. The down-regulation of SIRPα in AGEs–treated THP-1 cells is contrast to that of receptor for advanced glycation end products (RAGE) and junctional adhesion molecule-like protein (JAML), which expression levels are both increased after AGEs treatment (Zen et al, unpublished). Fig. 1B showed the quantitative analysis of SIRPα downregulation by AGEs in a dose-dependent fashion. Interestingly, AGEs–treated THP-1 cells showed a significant enhanced cell surface expression of β2 integrins, in particular CD11b/CD18, in response to the stimulation of MCP-1 (Fig. 1C). Also, compared to BSA–treated THP-1 cells, AGEs– treated THP-1 cells had a higher percentage of cell adhesion to TNFα–activated HMEC-1 monolayer (Fig. 1D). In response to MCP-1, AGEs–treated THP-1 cells also showed an increased transmigration across TNFα–activated HMEC-1 monolayers compared to THP-1 cells treated with BSA (Fig. 1E). Together, these results suggest that AGEs treatment can activate THP-1 cells and enhance cell chemotaxis.

Bottom Line: In contrast, SIRPalpha overexpression in THP-1 cells showed a significant less monocyte chemotactic protein-1 (MCP-1)-triggered cell surface expression of beta(2) integrins, in particular CD11b/CD18.SIRPalpha overexpression also reduced MCP-1-initiated migration of THP-1 cells across TNFalpha-stimulated HMEC-1 monolayers.Furthermore, beta(2) integrin-mediated THP-1 cell spreading and actin polymerization in response to MCP-1, and phagocytosis of bacteria were both inhibited by SIRPalpha overexpression.

View Article: PubMed Central - PubMed

Affiliation: Jiangsu Diabetes Research Center, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing, Jiangsu, China.

ABSTRACT

Background: Signal regulate protein alpha (SIRPalpha) is involved in many functional aspects of monocytes. Here we investigate the role of SIRPalpha in regulating beta(2) integrin-mediated monocyte adhesion, transendothelial migration (TEM) and phagocytosis.

Methodology/principal findings: THP-1 monocytes/macropahges treated with advanced glycation end products (AGEs) resulted in a decrease of SIRPalpha expression but an increase of beta(2) integrin cell surface expression and beta(2) integrin-mediated adhesion to tumor necrosis factor-alpha (TNFalpha)-stimulated human microvascular endothelial cell (HMEC-1) monolayers. In contrast, SIRPalpha overexpression in THP-1 cells showed a significant less monocyte chemotactic protein-1 (MCP-1)-triggered cell surface expression of beta(2) integrins, in particular CD11b/CD18. SIRPalpha overexpression reduced beta(2) integrin-mediated firm adhesion of THP-1 cells to either TNFalpha-stimulated HMEC-1 monolayers or to immobilized intercellular adhesion molecule-1 (ICAM-1). SIRPalpha overexpression also reduced MCP-1-initiated migration of THP-1 cells across TNFalpha-stimulated HMEC-1 monolayers. Furthermore, beta(2) integrin-mediated THP-1 cell spreading and actin polymerization in response to MCP-1, and phagocytosis of bacteria were both inhibited by SIRPalpha overexpression.

Conclusions/significance: SIRPalpha negatively regulates beta(2) integrin-mediated monocyte adhesion, transendothelial migration and phagocytosis, thus may serve as a critical molecule in preventing excessive activation and accumulation of monocytes in the arterial wall during early stage of atherosclerosis.

Show MeSH
Related in: MedlinePlus