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Monocyte adhesion to mesangial matrix modulates cytokine and metalloproteinase production
Ravinder S Chana1, John Martin, Enam U Rahman
1Department of Nephrology, University Hospital Birmingham NHS Trust, London, United Kingdom.
Background:
Monocytes migrate into the glomerular mesangium during acute inflammatory renal disease, differentiate into macrophages, and may play a key role in the development and progression of glomerular scarring. Treatment strategies that inhibit monocyte infiltration ameliorate glomerular injury in animal models. Mesangial matrix contains several potential monocyte-binding domains that may contribute to monocyte entrapment and modulate cell activation.
Methods:
Adhesion of peripheral blood-derived monocytes to matrix synthesized by human mesangial cells and to individual matrix proteins was assessed by colorimetry of nuclear staining with crystal violet. Monoclonal antibodies were used to identify the cell-surface integrins and matrix ligands involved. Monocyte proliferation was assessed by 3H-thymidine incorporation and cytokine production using enzyme-linked immunosorbent assay (ELISA). Secretion of metalloproteinases and their inhibitors was determined by zymography and ELISA, respectively.
Results:
Monocytes bound to matrix synthesized by mesangial cells. Prestimulation of mesangial cells with tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta) enhanced matrix fibronectin content (P < 0.001) and monocyte binding (P < 0.001). Blocking antibodies to fibronectin, as well as to the integrins very late antigen-4 (VLA-4) and VLA-5, reduced monocyte adhesion to mesangial matrix by approximately 50%. Incubation of monocytes with matrix, fibronectin, laminin and collagen IV enhanced production of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), TNF-alpha and metalloproteinase-9 (MMP-9) when compared to cells incubated in plastic wells. However, there was no apparent difference in proliferation rate and no change in production of metalloproteinase inhibitors.
Conclusion:
Monocyte activation within the glomerulus may be mediated by binding to mesangial matrix components, particularly fibronectin. Matrix-mediated activation enhances production of inflammatory cytokines and matrix-degrading enzymes.
Insights
Monocyte binding to kidney mesangial matrix, especially fibronectin, activates inflammatory responses. This process enhances the production of cytokines and matrix-degrading enzymes, contributing to kidney scarring.
Area of Science:
- Nephrology
- Immunology
- Cell Biology
Background:
- Monocytes infiltrate the glomerulus in renal disease, potentially causing scarring.
- Inhibiting monocyte infiltration can reduce glomerular injury in animal models.
- Mesangial matrix components may trap monocytes and influence their activation.
Purpose of the Study:
- To investigate monocyte adhesion to mesangial matrix components.
- To identify the specific matrix ligands and cell surface receptors involved in monocyte binding.
- To determine the effects of matrix interaction on monocyte activation, including cytokine and metalloproteinase production.
Main Methods:
- Assessed monocyte adhesion to human mesangial cell matrix and individual proteins using crystal violet staining.
- Utilized monoclonal antibodies to identify integrins (VLA-4, VLA-5) and matrix ligands (fibronectin).
- Measured monocyte proliferation (3H-thymidine incorporation), cytokine production (ELISA), and metalloproteinase secretion (zymography).
Main Results:
- Monocytes adhered to mesangial matrix, with binding enhanced by TNF-alpha and TGF-beta stimulation of mesangial cells.
- Blocking antibodies against fibronectin, VLA-4, and VLA-5 reduced monocyte adhesion by approximately 50%.
- Matrix and specific proteins increased production of IL-1beta, IL-6, TNF-alpha, and MMP-9, but did not affect proliferation or inhibitor production.
Conclusions:
- Monocyte activation in the glomerulus is likely mediated by binding to mesangial matrix components, particularly fibronectin.
- This matrix-mediated activation stimulates the release of inflammatory cytokines and matrix-degrading enzymes.
- Targeting these interactions may offer therapeutic strategies for inflammatory renal diseases.