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Modulation of CXCR4 expression and SDF-1alpha functional activity during differentiation of human monocytes and
S K Gupta1, K Pillarisetti, P G Lysko
1Department of Cardiovascular Pharmacology, SmithKline Beecham Pharmaceuticals, King of Prussia, Pennsylvania 19406, USA. Shalley_K_Gupta@sbphrd.com
Insights
Monocyte chemoattraction via stromal cell-derived factor-1alpha (SDF-1alpha) and CXCR4 is key in vascular diseases. Oxidized LDL induces CXCR4 re-expression in foam cells, suggesting a role in atherosclerosis progression.
Area of Science:
- Immunology
- Vascular Biology
- Molecular Biology
Background:
- The CXC chemokine stromal cell-derived factor-1alpha (SDF-1alpha) and its receptor CXCR4 mediate monocyte chemoattraction, potentially contributing to vascular diseases like atherosclerosis.
- Understanding the regulation of CXCR4 in monocytes during differentiation is crucial for elucidating its role in disease pathogenesis.
Purpose of the Study:
- To investigate the regulation of CXCR4 transcription and SDF-1-induced functional responses in human monocytes during differentiation.
- To examine the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF), oxidized low-density lipoprotein (Ox-LDL), and unmodified LDL on CXCR4 expression and function.
Main Methods:
- Studied human monocyte differentiation in the presence of GM-CSF, Ox-LDL, and LDL.
- Utilized HL-60 cells induced with phorbol myristate acetate (PMA) to model CXCR4 expression dynamics.
- Assessed CXCR4 mRNA levels and SDF-1-mediated calcium influx ([Ca2+]i).
- Employed flow cytometry to analyze surface CXCR4 expression.
Main Results:
- SDF-1-mediated calcium influx in monocytes initially declines post-isolation but gradually recovers with concomitant re-expression of CXCR4 mRNA.
- Oxidized LDL significantly induces CXCR4 mRNA (3-4 fold) in macrophage-derived foam cells.
- PMA-induced HL-60 cells show rapid CXCR4 mRNA stimulation followed by decline and eventual restoration, mirroring monocyte patterns.
- Surface CXCR4 expression is maintained on PMA-treated HL-60 cells; GM-CSF does not affect CXCR4 mRNA in HL-60 cells or human macrophages.
Conclusions:
- CXCR4 expression and function in monocytes are dynamically regulated during differentiation and influenced by factors like Ox-LDL.
- Oxidized LDL-induced CXCR4 re-expression in foam cells may promote their involvement in atherosclerotic plaque development.
- The findings provide insights into the molecular mechanisms underlying monocyte behavior in vascular disease contexts.
Abstract:
Chemoattraction of monocytes by the CXC chemokine stromal cell-derived factor-1alpha (SDF-1alpha) and its receptor CXCR4 may be involved in vascular diseases like atherosclerosis. We studied the regulation of CXCR4 transcription and SDF-1-induced functional responses in human monocytes during their differentiation in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF), oxidized low-density lipoprotein (Ox-LDL), and unmodified LDL. Our results reveal that the rapid decline of SDF-1-mediated [Ca2+]i influx after monocyte isolation is followed by a gradual functional restoration and a concomitant reexpression of CXCR4 mRNA over time. A further three- to fourfold induction of CXCR4 mRNA occurred in macrophage-derived foam cells on treatment with Ox-LDL. HL-60 cells induced with phorbol myristate acetate (PMA) showed a rapid fourfold stimulation of CXCR4 mRNA within 1 h, declining to barely detectable levels at 3 h, with eventual restoration over time, mirroring the expression pattern in monocytes. Surface expression of CXCR4 is maintained in HL-60 cells during PMA-induced differentiation, as demonstrated by flow cytometry. GM-CSF had no effect on CXCR4 mRNA in HL-60 cells and does not cause its down-regulation in human macrophages.