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Receptor mediated endocytosis by mesangial cells modulates transmigration of macrophages
P C Singhal1, S Gupta, P Sharma
1Department of Medicine, Long Island Jewish Medical Center, Nev Hyde Park, New York 11040, USA.
Background:
Accumulation of immune complexes in the mesangium is a common finding. Since migration of macrophages (Mphi) in the mesangium has been demonstrated to be an important event in the development of glomerular lesions, we studied the role of immune complexes and mesangial cell (MC) interaction in the transmigration (Tm) of Mphi.
Methods:
To determine the effect of MC and immune complexes (aggregated IgG, IgGAg) on transmigration of Mphi. MC were incubated with or without IgGAg in the lower compartment of a modified Boyden Chamber. To determine the effects of the secretory products (as a result of endocytosis of IgGAg by mesangial cells), MC-IgAg conditioned media was prepared and placed in the lower compartment of the Boyden chamber. We evaluated the effects of MC alone, MC + IgGAg, or MC-IgGAg conditioned media on the transmigration of macrophages across a filter. To determine the effect of free radicals on MC-IgAg endocytosis-induced Mphi migration we evaluated the effect of free radical scavengers such as dimethyl thiourea (DMTU) and tetramethylthiourea (TMTU) in MC-IgAg endocytosis-induced Mphi migration. To determine the role of chemokines in MC-IgAs endocytosis-induced Mphi migration we evaluated the effect of ani-MCP-1 antibodies on MC-IgAg endocytosis-induced Mphi migration, and also studied the effects of IgAg on MC mRNA expression of MCP-1 and RANTES. In addition, we evaluated the role of Fc receptors and actin cytoskeleton of MC in transmigration of Mphi.
Results:
Mesangial cell endocytosis of IgG aggregates (IgGAg) is associated with enhanced (P < 0.001) transmigration of Mphi (control, 11.2 +/- 0.2 vs. MC + IgGAg, 22.1 +/- 0.9 migrated Mphi/field). IgGAg also induced MC mRNA expression for RANTES and MCP-1 on MC. DMTU and TMTU attenuated (P < 0.001) the MC + IgGAg-induced migration of Mphi as well as IgGAg-induced mRNA expression for RANTES and MCP-1. MC and IgGAg interaction products (MC-IgGAg conditioned media) also increased (P < 0.01) transmigration of Mphi (control, 18.3 +/- 1.7 vs. MC-IgGAg conditioned media, 30.7 +/- 0.6 Mphi/field). This effect of MC-IgGAg conditioned media on the migration of macrophages was dose dependent. Anti-MCP-1 antibody partially inhibited MC-IgGAg-induced migration of macrophages. MC and monomeric IgG (MIgG) interaction (MC-MIgG conditioned media) showed a lower (P < 0.05) migration of Mphi, when compared to the MC-IgGAg conditioned media. MC-IgGAg conditioned media prepared from cytochalasin B pretreated MCs also showed a lower (P < 0.001) migration of Mphi when compared with MC-IgGAg conditioned media-induced migration.
Conclusions:
These results indicate that MC-IgGAg conditioned media-induced transmigration of macrophages may be mediated through the generation of RANTES and MCP-1 by MC.
Insights
Immune complexes interacting with mesangial cells (MC) enhance macrophage migration, potentially through RANTES and MCP-1 generation. This finding is crucial for understanding glomerular lesion development.
Area of Science:
- Immunology
- Nephrology
- Cell Biology
Background:
- Immune complex accumulation in the mesangium is a common pathological finding.
- Macrophage (Mphi) migration into the mesangium is critical in glomerular lesion development.
Purpose of the Study:
- To investigate the role of immune complexes and mesangial cell (MC) interactions in macrophage transmigration (Tm).
- To elucidate the mechanisms underlying MC-mediated Mphi migration in response to immune complexes.
Main Methods:
- Utilized a modified Boyden Chamber to assess Mphi transmigration across filters in response to MCs and aggregated IgG (IgGAg).
- Evaluated the impact of MC-IgGAg conditioned media, free radical scavengers (DMTU, TMTU), anti-MCP-1 antibodies, and cytochalasin B on Mphi migration.
- Assessed MC mRNA expression of chemokines (MCP-1, RANTES) and the role of Fc receptors and actin cytoskeleton.
Main Results:
- MC endocytosis of IgGAg significantly enhanced Mphi transmigration (P < 0.001).
- IgGAg induced MC mRNA expression for RANTES and MCP-1, which was attenuated by free radical scavengers.
- MC-IgGAg conditioned media also increased Mphi transmigration in a dose-dependent manner, partially inhibited by anti-MCP-1 antibodies.
Conclusions:
- MC-IgGAg conditioned media-induced macrophage transmigration is likely mediated by the generation of RANTES and MCP-1 by MCs.
- This study highlights the intricate interplay between immune complexes, mesangial cells, and macrophage recruitment in renal pathology.