Myeloid-related protein 8 expression on macrophages is a useful prognostic marker for renal dysfunction in children with MPGN type 1

The predictive role of serum calprotectin on mortality in hemodialysis patients with high phosphoremia

Background

The inflammatory mediator calprotectin (CPT, myeloid-related protein 8/14) is known as an endogenous ligand contributing to pathophysiology in inflammatory diseases. Serum CPT reportedly became a potential biomarker in these conditions, though there is no report predicting the prognosis in hemodialysis patients. The aim of this study is to investigate the predictive role of serum CPT on mortality in hemodialysis patients.

Methods

We conducted a multicenter, observational cohort study of 388 Japanese subjects undergoing hemodialysis. Serum CPT were measured using an ELISA. The potential associations between serum CPT and clinical variables were cross-sectionally examined. Multivariate Cox regression was used to estimate the association between serum CPT, high-sensitivity C reactive protein (hs-CRP), white blood cell (WBC) count and mortality. Median follow-up was 6.6 years.

Results

The median CPT level was 6108 ng/ml (median in healthy subjects, 2800) at baseline. Serum CPT positively correlated with WBC count (ρ = 0.54, P < 0.001) and hs-CRP values (ρ = 0.35, P < 0.001). In multivariate analysis, hs-CRP was an independent predictor of all-cause mortality after adjusting confounding factors (middle vs. low: hazard ratio [HR] 2.09, 95% confidence interval [CI] 1.23–3.66; high vs. low: 2.47, 1.40–4.47). In the analysis by stratum of phosphate levels, elevated CPT levels were significantly associated with all-cause mortality in the highest tertile (18.1; 3.15–345.9) among the high-phosphate group, but not among the low-phosphate group.

Conclusions

Serum CPT would become a potential predictive marker on mortality in hemodialysis patients with high-phosphate levels.

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

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.

Serum myeloid-related protein 8/14 in minimal change- and glomerulonephritis-related nephrotic syndrome

BACKGROUND

Myeloid-related protein 8/14 (MRP8/14) forms stable heterodimers and is the major calcium-binding protein secreted by activated granulocytes and monocytes. We evaluated whether serum MRP8/14 level is a useful indicator for a differential diagnosis of glomerulonephritis (GN)- and minimal change disease (MC)- related nephrotic syndrome (NS).

METHODS

Serum MRP8/14 complex was evaluated in 37 NS patients with MC or GN. These patients were divided into two groups. Group 1 consisted of 13 NS patients with MC, and group 2 consisted of 24 NS patients with GN. Group 2 was further divided into four subgroups: IgA nephropathy (IgAN; n = 5), Henoch-Schönlein purpura nephritis (HSPN; n = 6), focal segmental glomerulosclerosis (FSGS; n = 12), and acute GN Poststreptococcal acute glomeruloNephritis (PSAGN; n = 1).

RESULTS

The clinical manifestations, laboratory findings, serum MRP8/14 level, and renal accumulation of MRP8 were investigated for each group. No significant inter-group differences were observed for serum total protein, serum albumin, or blood urea nitrogen and urinary protein excretions. Mean serum MRP8/14 in the IgAN, HSPN, FSGS, and PSAGN groups was higher than in group 1. Further, the mean glomerular and interstitial MRP8 staining scores in the IgAN, HSPN, and PSAGN groups were higher than in group 1.

CONCLUSIONS

Serum MRP8/14 level may be a useful indicator for differential diagnosis between GN- and MC- related NS.

Predictive significance of kidney myeloid-related protein 8 expression in patients with obesity- or type 2 diabetes-associated kidney diseases

BACKGROUND AND OBJECTIVE

We have reported that toll-like receptor 4 (TLR4) and one of its endogenous ligands, myeloid-related protein 8 (MRP8 or S100A8), play an important role in the progression of diabetic nephropathy in mice. The aim of this study was to evaluate significance of kidney MRP8 expression in patients with obesity- or type 2 diabetes-associated kidney diseases.

METHODS

In diabetic, obese or control subjects, MRP8 mRNA and protein expression levels in renal biopsy samples were determined by real-time RT-PCR and immunohistochemistry (n = 28 and 65, respectively), and their associations with baseline and prognostic parameters were analyzed. Effects of MRP8 upon pro-inflammatory gene expressions were examined using macrophages.

RESULTS

Kidney MRP8 gene and protein expression levels were elevated in obese or diabetic groups compared to control group. Among all subjects, by univariate linear regression analysis, glomerular MRP8-positive cell count and tubulointerstitial MRP8-positive area at baseline were both, respectively, correlated not only with various known risk factors for diabetic nephropathy (such as systolic blood pressure, proteinuria and serum creatinine) but also with extent of glomerulosclerosis and tubulointerstitial fibrosis. Independent factors predicting urinary protein levels a year later were examined by multivariate analysis, and they included glomerular MRP8-positive cell count (β = 0.59, P<0.001), proteinuria (β = 0.37, P = 0.002) and systolic blood pressure (β = 0.21, P = 0.04) at baseline, after adjustment for known risk factors. MRP8 protein expression was observed in CD68-positive macrophages and atrophic tubules. In cultured mouse macrophages, MRP8 protein induced proinflammatory cytokine expressions and also triggered auto-induction of MRP8 in a TLR4-dependent manner.

CONCLUSIONS

Glomerular MRP8 expression appears to be associated with progression of proteinuria in obese or type 2 diabetic patients, possibly by inducing inflammatory changes in macrophages through TLR4 signaling.

The role of calprotectin in pediatric disease

Calprotectin (CP) is a calcium- and zinc-binding protein of the S100 family expressed mainly by neutrophils with important extracellular activity. The aim of the current review is to summarize the latest findings concerning the role of CP in a diverse range of inflammatory and noninflammatory conditions among children. Increasing evidence suggests the implication of CP in the diagnosis, followup, assessment of relapses, and response to treatment in pediatric pathological conditions, such as inflammatory bowel disease, necrotizing enterocolitis, celiac disease, intestinal cystic fibrosis, acute appendicitis, juvenile idiopathic arthritis, Kawasaki disease, polymyositis-dermatomyositis, glomerulonephritis, IgA nephropathy, malaria, HIV infection, hyperzincemia and hypercalprotectinemia, and cancer. Further studies are required to provide insights into the actual role of CP in these pathological processes in pediatrics.

The role of serum myeloid-related protein 8/14 complex in Henoch-Schönlein purpura nephritis

Myeloid-related protein (MRP) 8/14 complex is a marker of monocyte and neutrophil activation. We evaluated whether serum MRP8/14 complex is associated with clinical manifestations and pathological findings of Henoch-Schönlein purpura nephritis (HSPN). Patients were divided into two groups based on serum MRP8/14 complex levels at renal biopsy. Group 1 consisted of 18 HSPN patients with less than median (670 ng/ml) MRP8/14 complex levels, and Group 2 of 12 HSPN patients with greater than median levels. Clinical manifestations, laboratory findings and serum E-selectin levels, as a marker of vascular endothelial cell dysfunction, as well as histological and immunohistochemical findings were investigated for both groups. We also measured MRP8/14 complex levels in disease control and healthy control children. Urinary protein excretions, serum MRP8/14 complex levels, and serum E-selectin levels were all higher in Group 2 than in Group 1 patients. Serum MRP8/14 complex levels were higher in HSPN patients than in controls. Serum MRP8/14 complex levels were strongly associated with serum E-selectin levels. Pathological findings revealed that the proportions of patients with ISKDC grades III, IV and V in Group 2 were higher than in Group 1. Our findings suggest that serum MRP8/14 complex levels might be associated with the severity of renal injury and endothelial cell dysfunction in HSPN patients.

Accumulation of macrophages expressing myeloid-related protein 8 associated with the progression of sclerotic changes in children with IgA nephropathy

Myeloid-related protein (MRP) 8 is a calcium-binding protein of the S100 family. The renal accumulation of macrophages expressing MRP8 is associated with the inflammatory activity of glomerulonephritis. We evaluated the renal accumulation of macrophages expressing MRP8 in children with IgA nephropathy (IgAN). We collected data on 25 IgAN children who had been treated with prednisolone and divided these patients into two groups: Favorable group, consisting of 11 patients with normal urine and 6 with minor urinary abnormalities at 4.3 +/- 1.3 years after initial treatment; and Unfavorable group, consisting of 8 patients with persistent nephropathy. The pathological renal findings were compared between both groups. The second biopsy was performed at two years after first biopsy at 5.5 +/- 4.9 months from onset. In Favorable group, the glomerular accumulation of macrophages expressing MRP8, and mesangial cells expressing alpha-smooth muscle actin (alpha-SMA) were lower in the second biopsy specimens than those of the first biopsy specimens. In Unfavorable group, the glomerular accumulation of macrophages expressing MRP8 detected in the second biopsy specimens was similar to that of the first biopsy, while the number of mesangial cells expressing alpha-SMA and the index of renal sclerosis were higher in the second biopsy than in the first biopsy. The indexes of renal sclerosis were higher in children with more macrophages expressing MRP8 than in children with less macrophages expressing MRP8. Our results suggest that renal macrophages expressing MRP8 may be involved in the progression of sclerotic changes in children with IgAN.