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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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Related in: MedlinePlus

SIRPα overexpression in THP-1 cells and its effect on cell surface expression of β2 integrins and CCR2.THP-1 cells were transfected with the empty pcDNA3.1 vector (Mock) or the SIRPα-encoding pcDNA3.1 vector (SIRPα). A: SIRPα protein level in SIRPα– or mock– transfected THP-1 cells; B: Cell surface SIRPα expression in Mock– and SIRPα–transfected THP-1 cells; C: THP-1 cell surface expression of CD11a, CD11b, CD11c and CCR2. Note that SIRPα overexpression significantly suppressed MCP-1–induced up-regulation of THP-1 surface expression of CD11b and CD11a but not CCR2, and that SIRPα overexpression did not affect the basal level of β2 integrins. All data are mean±SD of three independent experiments.
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pone-0003291-g002: SIRPα overexpression in THP-1 cells and its effect on cell surface expression of β2 integrins and CCR2.THP-1 cells were transfected with the empty pcDNA3.1 vector (Mock) or the SIRPα-encoding pcDNA3.1 vector (SIRPα). A: SIRPα protein level in SIRPα– or mock– transfected THP-1 cells; B: Cell surface SIRPα expression in Mock– and SIRPα–transfected THP-1 cells; C: THP-1 cell surface expression of CD11a, CD11b, CD11c and CCR2. Note that SIRPα overexpression significantly suppressed MCP-1–induced up-regulation of THP-1 surface expression of CD11b and CD11a but not CCR2, and that SIRPα overexpression did not affect the basal level of β2 integrins. All data are mean±SD of three independent experiments.

Mentions: To define the role of SIRPα in regulating monocyte inflammatory response, we characterized the alteration of β2 integrin expression and β2 integrin-mediated cell adhesion, migration and phagocytosis in THP-1 cells after significantly increase SIRPα expression level. As shown in Figure 2A, immunoblot analysis showed that the delivery of the pcDNA3.1 vector encoding human SIRPα into THP-1 cells profoundly enhanced SIRPα expression. Compared to mock–transfected THP-1 cells, SIRPα–transfected THP-1 cells also showed a significantly enhanced expression of SIRPα on cell surface, as indicated by flow cytometry (Fig. 2B).


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)

SIRPα overexpression in THP-1 cells and its effect on cell surface expression of β2 integrins and CCR2.THP-1 cells were transfected with the empty pcDNA3.1 vector (Mock) or the SIRPα-encoding pcDNA3.1 vector (SIRPα). A: SIRPα protein level in SIRPα– or mock– transfected THP-1 cells; B: Cell surface SIRPα expression in Mock– and SIRPα–transfected THP-1 cells; C: THP-1 cell surface expression of CD11a, CD11b, CD11c and CCR2. Note that SIRPα overexpression significantly suppressed MCP-1–induced up-regulation of THP-1 surface expression of CD11b and CD11a but not CCR2, and that SIRPα overexpression did not affect the basal level of β2 integrins. All data are mean±SD of three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0003291-g002: SIRPα overexpression in THP-1 cells and its effect on cell surface expression of β2 integrins and CCR2.THP-1 cells were transfected with the empty pcDNA3.1 vector (Mock) or the SIRPα-encoding pcDNA3.1 vector (SIRPα). A: SIRPα protein level in SIRPα– or mock– transfected THP-1 cells; B: Cell surface SIRPα expression in Mock– and SIRPα–transfected THP-1 cells; C: THP-1 cell surface expression of CD11a, CD11b, CD11c and CCR2. Note that SIRPα overexpression significantly suppressed MCP-1–induced up-regulation of THP-1 surface expression of CD11b and CD11a but not CCR2, and that SIRPα overexpression did not affect the basal level of β2 integrins. All data are mean±SD of three independent experiments.
Mentions: To define the role of SIRPα in regulating monocyte inflammatory response, we characterized the alteration of β2 integrin expression and β2 integrin-mediated cell adhesion, migration and phagocytosis in THP-1 cells after significantly increase SIRPα expression level. As shown in Figure 2A, immunoblot analysis showed that the delivery of the pcDNA3.1 vector encoding human SIRPα into THP-1 cells profoundly enhanced SIRPα expression. Compared to mock–transfected THP-1 cells, SIRPα–transfected THP-1 cells also showed a significantly enhanced expression of SIRPα on cell surface, as indicated by flow cytometry (Fig. 2B).

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