Neutrophil attractant protein-1 interleukin 8 and its autoantibodies in IgA nephropathy

Identifying functional subtypes of IgA nephropathy based on three machine learning algorithms and WGCNA

BACKGROUND

IgA nephropathy (IgAN) is one of the most common primary glomerulonephritis, which is a significant cause of renal failure. At present, the classification of IgAN is often limited to pathology, and its molecular mechanism has not been established. Therefore we aim to identify subtypes of IgAN at the molecular level and explore the heterogeneity of subtypes in terms of immune cell infiltration, functional level.

METHODS

Two microarray datasets (GSE116626 and GSE115857) were downloaded from GEO. Differential expression genes (DEGs) for IgAN were screened with limma. Three unsupervised clustering algorithms (hclust, PAM, and ConsensusClusterPlus) were combined to develop a single-sample subtype random forest classifier (SSRC). Functional subtypes of IgAN were defined based on functional analysis and current IgAN findings. Then the correlation between IgAN subtypes and clinical features such as eGFR and proteinuria was evaluated by using Pearson method. Subsequently, subtype heterogeneity was verified by subtype-specific modules identification based on weighted gene co-expression network analysis(WGCNA) and immune cell infiltration analysis based on CIBERSORT algorithm.

RESULTS

We identified 102 DEGs as marker genes for IgAN and three functional subtypes namely: viral-hormonal, bacterial-immune and mixed type. We screened seventeen genes specific to viral hormonal type (ATF3, JUN and FOS etc.), and seven genes specific to bacterial immune type (LIF, C19orf51 and SLPI etc.). The subtype-specific genes showed significantly high correlation with proteinuria and eGFR. The WGCNA modules were in keeping with functions of the IgAN subtypes where the MEcyan module was specific to the viral-hormonal type and the MElightgreen module was specific to the bacterial-immune type. The results of immune cell infiltration revealed subtype-specific cell heterogeneity which included significant differences in T follicular helper cells, resting NK cells between viral-hormone type and control group; significant differences in eosinophils, monocytes, macrophages, mast cells and other cells between bacterial-immune type and control.

CONCLUSION

In this study, we identified three functional subtypes of IgAN for the first time and specific expressed genes for each subtype. Then we constructed a subtype classifier and classify IgAN patients into specific subtypes, which may be benefit for the precise treatment of IgAN patients in future.

High Neutrophil-To-Lymphocyte Ratio Is an Independent Risk Factor for End Stage Renal Diseases in IgA Nephropathy

Background

Complex factors are involved in the development and progression of immunoglobulin A nephropathy (IgAN), a common primary glomerulonephritis worldwide. Autoimmunity and inflammation have been considered to be the basic mechanisms; however, the exact pathogenesis remains unclear. As a novel marker of inflammation, the neutrophil-to-lymphocyte ratio (NLR) has been studied in various diseases. Whether the NLR can predict the renal outcome of patients with IgAN remains unclear. We evaluated the relationships between the NLR and renal function, pathologic lesions, renal progression, and prognosis in patients with IgAN.

Methods

This retrospective study involved 966 patients with biopsy-proven IgAN. They were divided into two groups based on the cut-off value of the NLR: the high group (NLR ≥ 2.67, n = 384) and the low group (NLR < 2.67, n = 582). The endpoint was end-stage renal disease [estimated glomerular filtration rate (eGFR) of <15 mL/min/1.73 m² or performance of renal replacement therapy]. A correlation test was conducted to explore the relationship between the NLR and other important parameters (eGFR, serum creatinine, proteinuria, hypertension and renal pathologic lesions). The predictive value was determined by the area under the receiver operating characteristics curve (AUROC). Kaplan–Meier and Cox proportional hazards analyses were performed to evaluate renal progression and prognosis.

Results

The NLR had the highest AUROC, which was 0.633 (p < 0.001). The correlation test revealed that the NLR was positively correlated with serum creatinine (r = 0.127, p < 0.001) and 24-hour urine protein (r = 0.18, p < 0.001) and negatively correlated with eGFR (r = 0.14, p < 0.001). Patients with IgAN who had a high NLR were more likely to have hypertension (p = 0.003). Multivariate Cox regression analysis indicated that a high NLR was an independent risk factor for IgAN even after adjustment for important clinical and pathological parameters (p = 0.043, HR = 1.74, 95%CI: 1.02-2.97). Kaplan–Meier analysis showed that a high NLR was significantly associated with the renal prognosis of patients with IgAN (p < 0.001), especially patients with stage 3 to 4 chronic kidney disease (p = 0.028) or 24-hour urine protein of >1 g/day (p < 0.001).

Conclusion

An elevated NLR affects the renal progression and prognosis in patients with IgAN and could be a marker for evaluation of renal function and pathologic lesions.

LCC18, a benzamide-linked small molecule, ameliorates IgA nephropathy in mice

IgA nephropathy (IgAN), an immune complex-mediated process and the most common primary glomerulonephritis, can progress to end-stage renal disease in up to 40% of patients. Accordingly, a therapeutic strategy targeting a specific molecular pathway is urgently warranted. Aided by structure characterisation and target identification, we predicted that a novel ring-fused 6-(2,4-difluorophenyl)-3-(3-(trifluoromethyl)phenyl)-2H-benzo[e][1,3]oxazine-2,4(3H)-dione (LCC18) targets the NLRP3 inflammasome, which participates in IgAN pathogenesis. We further developed biomarkers for the disease. We used two complementary IgAN models in C57BL/6 mice, involving TEPC-15 hybridoma-derived IgA, and in gddY mice. Moreover, we created specific cell models to validate therapeutic effects of LCC18 on IgAN and to explain its underlying mechanisms. IgAN mice benefited significantly from treatment with LCC18, showing dramatically improved renal function, including greatly reduced proteinuria and renal pathology. Mechanistic studies showed that the mode of action specifically involved: (1) blocking of the MAPKs/COX-2 axis-mediated priming of the NLRP3 inflammasome; (2) inhibition of ASC oligomerisation and NLRP3 inflammasome assembly by inhibiting NLRP3 binding to PKR, NEK7 and ASC; and (3) activation of autophagy. LCC18 exerts therapeutic effects on murine IgAN by differentially regulating NLRP3 inflammasome activation and autophagy induction, suggesting this new compound as a promising drug candidate to treat IgAN. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Serologic and Histologic Predictors of Long-Term Renal Outcome in Biopsy-Confirmed IgA Nephropathy (Haas Classification): An Observational Study

Background and objective: The Haas classification of IgA nephropathy should be validated for Asian populations. More detailed and newer predictions regarding renal outcome of IgA nephropathy remains mandatory. Materials: We conducted a retrospective cohort study between January 2003 and December 2013. Clinical, Pathological, and laboratory data were all collected via available medical records. A Mann–Whitney U test was used for continuous variables and the Chi-square test was implemented for categorical variables. A Kaplan–Meier curve was put in place in order to determine patient survival and renal survival. The Youden index and Cox proportional hazard regression were used to investigate the possible factors for renal survival and predictive power. Results: All 272 renal biopsy-confirmed IgAN patients were enrolled for further studies. The univariate analysis showed that risk factors for poor renal outcome included stage 4–5 of Haas classification (HR = 3.67, p < 0.001), a poor baseline renal function (HR = 1.02 and p < 0.001 for higher BUN; HR = 1.14 and p < 0.001 for higher serum creatinine; HR = 0.95, p < 0.001 for higher eGFR), IgG ≤ 907 (HR = 2.29, p = 0.003), C3 ≤ 79.7 (HR = 2.76, p = 0.002), a higher C4 (HR = 1.02, p = 0.026), neutrophil-to-lymphocyte ratio > 2.75 (HR = 2.92, p < 0.001), and a platelet-to-lymphocyte ratio ≥ 16.06 (HR = 2.02, p = 0.012). A routine-checked markers, such as neutrophil-to-lymphocyte ratio and platelet-to-lymphocyte ratio, in order to predict the renal outcome, is recommended. Conclusions: This is the first study to demonstrate that Haas classification is also useful for establishing predictive values in Asian groups. A lower serum IgG (≤907 mg/dL) and serum C3 (≤79.7 mg/dL) were both risk factors for poor renal outcome. Additionally, this is the first study to reveal that serum C4 levels, an NLR > 2.75 and a PLR > 16.06, S could suggest poor renal outcome.

Polymorphisms of CXCL8 and its receptor CXCR2 contribute to the development and progression of childhood IgA nephropathy

Many studies have suggested that CXCL8 and CXCR2 play an important role in the pathogenesis of several types of renal diseases. However, there is no prior study on the association between polymorphisms of these genes and IgA nephropathy (IgAN), especially in children. The genotyping data from 192 patients with childhood IgAN and 397 controls showed significant differences in the frequencies of the CXCL8 gene with rs2227306 (dominant, P = 0.019; overdominant, P = 0.009), rs2227543 (dominant, P = 0.01; overdominant, P = 0.0057), and rs4073 (codominant, P = 0.034; dominant, P = 0.011; overdominant, P = 0.022). In addition, 2 single-nucleotide polymorphism frequencies of the CXCR2 gene (rs4674257 and rs4674259) significantly differed between the patients with pathologically mild and patients with advanced disease. Further, 5 single-nucleotide polymorphisms of the CXCL8 and CXCR2 genes significantly differed in the patients with infiltration of inflammatory cells on the renal biopsy samples. The results of this study suggest that polymorphisms of CXCL8 are associated with increased susceptibility to IgAN, and polymorphisms of CXCR2 with the pathological progression of childhood IgAN. These genetic variations might provide insight into novel individualized antichemokine regimens for treatment.

Circulating IL-8 and anti-IL-8 autoantibody in patients with ovarian cancer

OBJECTIVES

In an ongoing effort to identify diagnostic ovarian cancer biomarkers, SEREX (serological analysis of recombinant cDNA expression libraries) technique was employed resulting in detection of 20 known genes, nine ESTs and one novel sequence. Interleukin-8 (IL-8) was one of ovarian cancer-associated antigens identified by SEREX screening. The objective of this study was, therefore, to evaluate the potential importance of circulating anti-IL-8 antibody as ovarian cancer biomarker.

METHODS

We developed and optimized a new immunofluorescent bead-based assay for detection of anti-IL-8 antibody in blood serum. Circulating IL-8 and anti-IL-8 IgG concentrations were measured in blood sera from 44 patients with early stage (I-II) ovarian cancer, 50 patients with late stage (III-IV) ovarian cancer, 37 patients with benign pelvic masses, and 80 healthy women using the bead-based assay.

RESULTS

Our data indicate that serum contains IL-8 cytokine, anti-IL-8 antibody, and IL-8:anti-IL-8 complexes. We found that concentrations of IL-8 and anti-IL-8 antibody were elevated in sera of patients with ovarian cancer as compared with healthy controls. Logistic regression analysis of circulating concentrations of anti-IL-8 IgG in patients with stages I-II ovarian cancer versus healthy controls allowed for prediction of early ovarian cancer with 98% specificity, 65.5% sensitivity, 80.3% of patients correctly classified. Combining IL-8 and anti-IL-8 IgG with CA 125 resulted in increased classification power as compared to individual markers analyzed separately.

CONCLUSION

Thus, IL-8 and anti-IL-8 autoantibody might potentially serve as additional biomarkers for ovarian cancer.

Up-regulation of macrophage inflammatory protein-2 and complement 3A receptor by the trichothecenes deoxynivalenol and satratoxin G

The trichothecenes are a group of mycotoxins that target leukocytes and have a wide range of immunomodulatory effects. Differential display analysis was applied to assess the effects of the trichothecenes deoxynivalenol (vomitoxin, DON) and satratoxin G (SG), on mRNA in the RAW 264.7 macrophage cell line. Cells were incubated with DON (1 microg/ml) or SG (5 ng/ml) for 2 h and total RNA then subjected to RT-PCR with a set of oligo(dT) primers. Resultant cDNA was amplified using an oligo (dT) downstream primer and an arbitrary decanucleotide upstream primer to make 35S-labeled PCR products. After separation of the products in denaturing polyacrylamide gel, 23 differentially expressed cDNA fragments were isolated and sequenced. Two of these were identified as known genes, namely, macrophage inflammatory protein-2 (MIP-2), a potent neutrophil chemoattractant involved in tissue injury and inflammation, and complement 3a receptor (C3aR), a proinflammatory mediator. Both MIP-2 and C3aR mRNAs were up-regulated by DON while only MIP-2 mRNA was induced by SG. Using commercially available antibodies, MIP-2 protein was also found to be induced by both DON and SG in RAW 264.7 cell cultures. When mice were treated with DON (12.5 mg/kg), splenic MIP-2 mRNA and serum MIP-2 levels were increased. MIP-2 mRNA and serum MIP-2 levels were synergistically increased when mice were co-treated with DON and LPS. Up-regulation of MIP-2 and C3aR are consistent with previous reports of trichothecene-induced inflammatory gene up-regulation and suggest that the specific genes affected may depend on trichothecene structures.

Future directions in the treatment of IgA nephropathy

IgA nephropathy (IgAN) is the most common primary glomerulonephritis yet its etiology remains uncertain. Recent data suggest a structural aberration of the IgA molecule in IgAN that may exert pathophysiologic effects on target cells, reduce clearance of IgA-immune complexes (IC), or favor mesangial IC trapping. Mesangial reactivity to immune complexes triggers off the release of cytokines and the alteration of prostaglandin and thromboxane A(2) production promoting mesangial cell proliferation. Angiotensin II-induced mesangial cells contraction with efferent arteriolar vasodilatation initiates glomerular injury and eventually lead to glomerulosclerosis following increased local production of transforming growth factor-beta (TGF-beta) and platelet-derived growth factor (PDGF). This paper highlights the potential therapeutic strategies in the future. These strategies include: (i) decreasing the synthesis of IgA-IC; (ii) limiting the mesangial uptake of IgA-IC; (iii) antagonizing the effect of PDGF and TGF-beta to reduce mesangial proliferation and glomerulosclerosis; and (iv) reducing the noxious glomerular injury due to infiltrating neutrophils. The effective treatment of IgAN requires a better clarification of the pathogenesis of the nephropathy. Future therapeutic attempts to slow down the renal deterioration should target at prevention of mesangial IgA deposition and the amelioration of inflammatory injury induced by infiltrating neutrophils and the released cytokines.

Characteristics of polymeric lambda-IgA binding to leukocytes in IgA nephropathy

IgA nephropathy (IgAN) is characterized by predominant mesangial polymeric IgA1 (pIgA1) deposits, with increased plasma IgA1 levels. Plasma IgA levels are determined by the rate of IgA production, uptake by leukocytes, and removal by hepatocytes. Fc(alpha) receptor 1 (Fc(alpha)R1) is a candidate molecule for the regulation of IgA levels, but reports of its expression in leukocytes in IgAN are conflicting. Increased binding of endogenous IgA to circulating granulocytes and monocytes in IgAN was demonstrated in this study. Fc(alpha)R1 expression on leukocytes was increased, independently of plasma IgA levels. Fc(alpha)R1 was not saturated in leukocytes, because of internalization of IgA after uptake. Further binding of exogenous IgA isolated from individual subjects was observed with leukocytes from the same subjects. Compared with cells from control subjects, granulocytes but not monocytes from patients with IgAN exhibited a greater binding capacity for exogenous IgA, predominantly pIgA. To circumvent the possibility that endogenous IgA might alter Fc(alpha)R1 expression, granulocytes or monocytes derived from the HL-60 or U937 cell lines were used to explore the nature of IgA binding. A higher affinity for pIgA was demonstrated. Inhibition studies using unlabeled IgA, other serum proteins, or a specific Fc(alpha)R1-blocking antibody suggested binding mechanisms other than Fc(alpha)R1 for pIgA uptake by leukocytes. This study also suggested the migration and/or sequestration of "activated" leukocytes with predominant lambda-IgA in the mononuclear phagocytic system or inflammatory tissues, after the initial binding of lambda-pIgA. These immunologic abnormalities might contribute to the glomerulointerstitial injury in IgAN, in the presence of leukocytic infiltration.

Urinary levels of interleukin-8 (IL-8) and disease activity in patients with IgA nephropathy

Using quantitative sandwich ELISA, we studied 27 patients with IgA nephropathy to determine whether the levels of urinary IL-8 might reflect the disease activity. The levels of urinary IL-8 in patients with advanced stage IgA nephropathy were significantly higher than those in the patients with the mild stage of this disease, or in the healthy controls. The results showed a positive significant correlation between the levels of IL-8 and disease activity, i.e., between levels of urinary protein and urinary casts. A significant correlation between levels of urinary IL-8 and tubular function damage was also found. It was thus suggested that measurement of urinary IL-8 might be useful in evaluating the degree of renal injuries and/or prognosis in patients with IgA nephropathy.

Chemokines, renal disease, and HIV infection

Renal disease is characterized by the influx of leukocytes into the injured tissue. Before leukocytes can exert their effects on renal damage or repair, they have to reach the site of injury. To recruit specific populations of leukocytes during inflammation is the role of a family of cytokines called chemokines. The characterization of this family has emerged within the past years, yet chemokines have already been the subject of thousands of scientific reports and promise to have many clinical applications. There is good evidence that chemokines contribute to leukocyte infiltration in glomeruli and interstitium and that they play a pivotal role in various renal diseases. The fact that there exist so many chemokines suggests the biological need for redundancy to effect recruitment of immune cells. Although they were originally defined as host defense proteins, chemokines clearly have other functions that extend well beyond the regulation of leukocyte migration. The recent suggestion that chemokines may contribute to a slow progression of the human immunodeficiency virus (HIV) infection and the very recent identification of chemokine receptors as docking molecules for HIV infection add another aspect to chemokine research. The speed at which researchers are exploring the HIV-chemokine connection is evident in the large number of publications on this topic as well as the rapid translation of publications into possible therapeutic applications. Delineating a precise role for chemokines in mediating pathologic changes is an area of fruitful investigation.