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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

TNFα and MCP-1–induced cell spreading and actin polymerization in THP-1 cells.SIRPα– or mock–transfected THP-1 cells were stimulated with TNFα or MCP-1 for 30 minutes, fixed, and labeled with rhodamine-conjugated phalloidin to visualize actin filaments. As a negative control, mock–transfected THP-1 cells were pretreated with cytochalasin D (Mock+Cyt. D). Bar = 20 µm.
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pone-0003291-g005: TNFα and MCP-1–induced cell spreading and actin polymerization in THP-1 cells.SIRPα– or mock–transfected THP-1 cells were stimulated with TNFα or MCP-1 for 30 minutes, fixed, and labeled with rhodamine-conjugated phalloidin to visualize actin filaments. As a negative control, mock–transfected THP-1 cells were pretreated with cytochalasin D (Mock+Cyt. D). Bar = 20 µm.

Mentions: Leukocyte β2 integrin–mediated cell firm adhesion initiates cell shape changes and spreading of monocytes, events that must occur for subsequent cellular locomotion and transmigration. Next we investigated the effect of SIRPα overexpression on TNFα– and MCP-1–stimulated actin polymerization and cell spreading in THP-1 cells. SIRPα– or mock– transfected THP-1 cells were stimulated with TNFα or MCP-1 for 30 minutes, then fixed, and labeled with rhodamine-conjugated phalloidin to visualize actin filaments. As a control, mock–transfected THP-1 cells were pretreated with cytochalasin D to inhibit actin polymerization [39]. Labeled monocytes were mounted on coverslips and images were obtained using confocal microscopy. As shown in Figure 5, confocal microscope images showed that mock– transfected THP-1 cells exposed to TNFα or MCP-1 underwent morphological changes resulting in multiple pseudopods (arrowheads) with abundant actin filaments, and that this process was inhibited by cytochalasin D. In contrast, significantly less TNFα– or MCP-1–stimulated actin polymerization and cell spreading had occurred in THP-1 cells with SIRPα overexpression (Fig. 5).


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)

TNFα and MCP-1–induced cell spreading and actin polymerization in THP-1 cells.SIRPα– or mock–transfected THP-1 cells were stimulated with TNFα or MCP-1 for 30 minutes, fixed, and labeled with rhodamine-conjugated phalloidin to visualize actin filaments. As a negative control, mock–transfected THP-1 cells were pretreated with cytochalasin D (Mock+Cyt. D). Bar = 20 µm.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0003291-g005: TNFα and MCP-1–induced cell spreading and actin polymerization in THP-1 cells.SIRPα– or mock–transfected THP-1 cells were stimulated with TNFα or MCP-1 for 30 minutes, fixed, and labeled with rhodamine-conjugated phalloidin to visualize actin filaments. As a negative control, mock–transfected THP-1 cells were pretreated with cytochalasin D (Mock+Cyt. D). Bar = 20 µm.
Mentions: Leukocyte β2 integrin–mediated cell firm adhesion initiates cell shape changes and spreading of monocytes, events that must occur for subsequent cellular locomotion and transmigration. Next we investigated the effect of SIRPα overexpression on TNFα– and MCP-1–stimulated actin polymerization and cell spreading in THP-1 cells. SIRPα– or mock– transfected THP-1 cells were stimulated with TNFα or MCP-1 for 30 minutes, then fixed, and labeled with rhodamine-conjugated phalloidin to visualize actin filaments. As a control, mock–transfected THP-1 cells were pretreated with cytochalasin D to inhibit actin polymerization [39]. Labeled monocytes were mounted on coverslips and images were obtained using confocal microscopy. As shown in Figure 5, confocal microscope images showed that mock– transfected THP-1 cells exposed to TNFα or MCP-1 underwent morphological changes resulting in multiple pseudopods (arrowheads) with abundant actin filaments, and that this process was inhibited by cytochalasin D. In contrast, significantly less TNFα– or MCP-1–stimulated actin polymerization and cell spreading had occurred in THP-1 cells with SIRPα overexpression (Fig. 5).

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