Ablation of Myeloid Cell MRP8 Ameliorates Nephrotoxic Serum-induced Glomerulonephritis by Affecting Macrophage Characterization through Intraglomerular Crosstalk

Abstract

Toll-like receptor 4 (TLR4) and one of its endogenous ligands myeloid-related protein 8 (MRP8 or S100A8), especially expressed in macrophages, play an important role in diabetic nephropathy and autoimmune disorders. However, detailed mechanisms and consequence of MRP8 expression remain unknown, partly due to embryonic lethality of MRP8 knockout mice. In this study, Myeloid lineage cell-specific MRP8 knockout mice were generated, and nephrotoxic serum-induced glomerulonephritis was developed. Mice with conditional ablation of MRP8 gene in myeloid cells exhibited less severe histological damage, proteinuria and inflammatory changes compared to control mice. Mechanism of MRP8 upregulation was investigated using cultured cells. Co-culture of macrophages with mesangial cells or mesangial cell-conditioned media, but not with proximal tubules, markedly upregulated MRP8 gene expression and inflammatory M1 phenotype in macrophages, which was attenuated in MRP8-deleted bone marrow-derived macrophages. Effects of MRP8 deletion was further studied in the context of macrophage-inducible C-type lectin (Mincle), which is critically involved in maintenance of M1 phenotype of macrophages. MRP8 ablation in myeloid cells suppressed the induction of Mincle expression on macrophages in glomerulonephritis. Thus, we propose that intraglomerular crosstalk between mesangial cells and macrophages plays a role in inflammatory changes in glomerulonephritis, and MRP8-dependent Mincle expression in macrophage may be involved in the process.

Single Cell RNA Sequencing Identifies a Unique Inflammatory Macrophage Subset as a Druggable Target for Alleviating Acute Kidney Injury

“…In previous studies, genetic modifications of mice with conditional ablation of S100a8 gene in myeloid cells or general knockout of S100a9 gene have exhibited beneficial effects in glomerulonephritis and obstructive nephropathy due to the inhibition of inflammatory response. [ 33 , 34 , 35 ] Yet in a bIRI (bIRI) mouse model, sustained S100a8/a9 deficiency by S100a9 knockout shows detrimental effects leading to renal fibrosis and damage. [ 36 ] However, we observed a recovery of survival rate and improved renal function after small molecule inhibition of S100a8/a9 signaling in bIRI mouse model.…”

Utilizing methylglyoxal and D-lactate in urine to evaluate saikosaponin C treatment in mice with accelerated nephrotoxic serum nephritis

“…It revealed that the level of macrophage infiltration induced by NTS injection is positively correlated with nephritis severity as previous reports noted [ 50 ]. Besides, the depletion of macrophage may improve disease in several animal models of autoimmune related nephritis [ 50 , 51 ]. In addition, it was observed that SSC may partly ameliorate the disease progression and decrease the level of macrophage infiltration, although it did not work in all treatment groups.…”

Suppressed ER‐associated degradation by intraglomerular cross talk between mesangial cells and podocytes causes podocyte injury in diabetic kidney disease

“…The cell suspensions were incubated with secondary antibodies and then, with Annexin V‐FITC and propidium iodide solutions for 15 minutes at room temperature. The samples were washed with PBS, resuspended in PBS, and analyzed using flow cytometry (SH800S Cell Sorter, Sony Biotechnology) 24 …”

“…The samples were washed with PBS, resuspended in PBS, and analyzed using flow cytometry (SH800S Cell Sorter, Sony Biotechnology). 24…”