Identification of Immune-Related Genes as Biomarkers for Uremia

Purpose

Uremia, which is characterized by immunodeficiency, is associated with the deterioration of kidney function. Immune-related genes (IRGs) are crucial for uremia progression.

Methods

The co-expression network was constructed to identify key modular genes associated with uremia. IRGs were intersected with differentially expressed genes (DEGs) between uremia and control groups and key modular genes to obtain differentially expressed IRGs (DEIRGs). DEIRGs were subjected to functional enrichment analysis. The protein-protein interaction (PPI) network was constructed. The candidate genes were identified using the cytoHubba tool. The biomarkers were identified using various machine learning algorithms. The diagnostic value of the biomarkers was evaluated using receiver operating characteristic (ROC) analysis. The immune infiltration analysis was implemented. The biological pathways of biomarkers were identified using gene set enrichment analysis and ingenuity pathway analysis. The mRNA expression of biomarkers was validated using blood samples of patients with uremia and healthy subjects with quantitative real-time polymerase chain reaction (qRT-PCR).

Results

In total, four biomarkers (PDCD1, NGF, PDGFRB, and ZAP70) were identified by machine learning methods. ROC analysis demonstrated that the area under the curve values of individual biomarkers were > 0.9, indicating good diagnostic power. The nomogram model of biomarkers exhibited good predictive power. The proportions of six immune cells significantly varied between the uremia and control groups. ZAP70 expression was positively correlated with the proportions of resting natural killer (NK) cells, naïve B cells, and regulatory T cells. Functional enrichment analysis revealed that the biomarkers were mainly associated with translational function and neuroactive ligand-receptor interaction. ZAP70 regulated NK cell signaling. The PDCD1 and NGF expression levels determined using qRT-PCR were consistent with those determined using bioinformatics analysis.

Conclusion

PDCD1, NGF, PDGFRB, and ZAP70 were identified as biomarkers for uremia, providing a theoretical foundation for uremia diagnosis.

The role of neuroimmune and inflammation in pediatric uremia-induced neuropathy

Uremic neuropathy in children encompasses a wide range of central nervous system (CNS), peripheral nervous system (PNS), autonomic nervous system (ANS), and psychological abnormalities, which is associated with progressive renal dysfunction. Clinically, the diagnosis of uremic neuropathy in children is often made retrospectively when symptoms improve after dialysis or transplantation, due to there is no defining signs or laboratory and imaging findings. These neurological disorders consequently result in increased morbidity and mortality among children population, making uremia an urgent public health problem worldwide. In this review, we discuss the epidemiology, potential mechanisms, possible treatments, and the shortcomings of current research of uremic neuropathy in children. Mechanistically, the uremic neuropathy may be caused by retention of uremic solutes, increased oxidative stress, neurotransmitter imbalance, and disturbance of the blood-brain barrier (BBB). Neuroimmune, including the change of inflammatory factors and immune cells, may also play a crucial role in the progression of uremic neuropathy. Different from the invasive treatment of dialysis and kidney transplantation, intervention in neuroimmune and targeted anti-inflammatory therapy may provide a new insight for the treatment of uremia.

MHC class II in renal tubules plays an essential role in renal fibrosis

Immunomodulation is considered a potential therapeutic approach for chronic kidney disease (CKD). Although it has been previously reported that CD4⁺ T cells contribute to the development of renal fibrosis, the role of MHC class II (MHCII) in the development of renal fibrosis remains largely unknown. The present study reports that the expression of MHCII molecules in renal cortical tubules is upregulated in mouse renal fibrosis models generated by unilateral ureter obstruction (UUO) and folic acid (FA). Proximal tubule epithelial cells (PTECs) are functional antigen-presenting cells that promote the proliferation of CD4⁺ T cells in an MHCII-dependent manner. PTECs from mice with renal fibrosis had a stronger ability to induce T cell proliferation and cytokine production than control cells. Global or renal tubule-specific ablation of H2-Ab1 significantly alleviated renal fibrosis following UUO or FA treatment. Renal expression of profibrotic genes showed a consistent reduction in H2-Ab1 gene-deficient mouse lines. Moreover, there was a marked increase in renal tissue CD4⁺ T cells after UUO or FA treatment and a significant decrease following renal tubule-specific ablation of H2-Ab1. Furthermore, renal tubule-specific H2-Ab1 gene knockout mice exhibited higher proportions of regulatory T cells (Tregs) and lower proportions of Th2 cells in the UUO- or FA-treated kidneys. Finally, Immunohistochemistry (IHC) studies showed increased renal expression of MHCII and the profibrotic gene α smooth muscle actin (α-SMA) in CKD patients. Together, our human and mouse data demonstrate that renal tubular MHCII plays an important role in the pathogenesis of renal fibrosis.

Regulation and function of CX3CR1 and its ligand CX3CL1 in kidney disease

Attraction, retention, and differentiation of leukocytes to and within the kidney are governed by chemokines. The chemokine CX3CL1 (fractalkine) and its receptor CX3CR1 are exemplary in this regard as they are highly expressed and further upregulated in a range of kidney diseases. CX3CL1 is chiefly produced by renal endothelium and tubular epithelium, where it promotes leukocyte attraction. Recent data suggest that in addition to established soluble mediators, cellular interactions may enhance CX3CL1 expression. The receptor CX3CR1 is essential in myeloid phagocyte homing to the kidney at homeostasis, after acute cell depletion and in inflammation. CX3CR1 and its ligand are highly regulated in human kidney diseases such as IgA nephritis, systemic lupus erythematosus, and inflammatory conditions such as transplant rejection. A mechanistic role of CX3CR1 has been established in experimental models of nephrotoxic nephritis and renal candidiasis. It is debated in fibrosis. Recent publications demonstrate a role for CX3CR1⁺ myeloid cells in radio-contrast-agent and sepsis-induced kidney damage. Systemically, circulating CX3CR1⁺ monocytes reversibly increase in individuals with renal impairment and correlate with their cardiovascular risk. In this review, we discuss role and regulatory mechanisms of the CX3CL1-CX3CR1 axis in both localized and systemic effects of renal inflammation.

PD-1 immunobiology in glomerulonephritis and renal cell carcinoma

BACKGROUND

Programmed cell death protein (PD)-1 receptors and ligands on immune cells and kidney parenchymal cells help maintain immunological homeostasis in the kidney. Dysregulated PD-1:PD-L1 binding interactions occur during the pathogenesis of glomerulopathies and renal cell carcinoma (RCC). The regulation of these molecules in the kidney is important to PD-1/PD-L1 immunotherapies that treat RCC and may induce glomerulopathies as an adverse event.

METHODS

The expression and function of PD-1 molecules on immune and kidney parenchymal cells were reviewed in the healthy kidney, PD-1 immunotherapy-induced nephrotoxicity, glomerulopathies and RCC.

RESULTS

PD-1 and/or its ligands are expressed on kidney macrophages, dendritic cells, lymphocytes, and renal proximal tubule epithelial cells. Vitamin D3, glutathione and AMP-activated protein kinase (AMPK) regulate hypoxic cell signals involved in the expression and function of PD-1 molecules. These pathways are altered in kidney disease and are linked to the production of vascular endothelial growth factor, erythropoietin, adiponectin, interleukin (IL)-18, IL-23, and chemokines that bind CXCR3, CXCR4, and/or CXCR7. These factors are differentially produced in glomerulonephritis and RCC and may be important biomarkers in patients that receive PD-1 therapies and/or develop glomerulonephritis as an adverse event CONCLUSION: By comparing the functions of the PD-1 axis in glomerulopathies and RCC, we identified similar chemokines involved in the recruitment of immune cells and distinct mediators in T cell differentiation. The expression and function of PD-1 and PD-1 ligands in diseased tissue and particularly on double-negative T cells and parenchymal kidney cells needs continued exploration. The possible regulation of the PD-1 axis by vitamin D3, glutathione and/or AMPK cell signals may be important to kidney disease and the PD-1 immunotherapeutic response.

Increased expression of CX3CL1 and CX3CR1 in papillary thyroid carcinoma

CX3CL1 and its receptor CX3CR1 axis are involved in the development, progression and metastasis of many types of cancers. It has been reported that CX3CL1 and CX3CR1 expression was upregulated in some solid tumors. However, their roles in thyroid cancer remain unknown. In the present study, we investigated the expression of CX3CL1 and CX3CR1 in human papillary thyroid carcinoma (PTC) and their clinical significance. In this study, using immunohistochemistry, we examined the expression of CX3CL1 and CX3CR1 in the tissues of 26 human PTC (including 17 classical or conventional (CPTC) and 9 follicular (FVPTC) variants of PTC; 15 cases without and 11 cases with lymph node metastasis) and 10 cases of nodular goiter (NG). Compared to NG, a significant increase in the expression of CX3CL1 and CX3CR1 was found in PTC overall, as well as in CPTC and FVPTC separately. Higher CX3CL1 expression was found in CPTC than in FVPTC, but there was no significant difference in CX3CR1 expression between these subtypes of PTC. When analyzing their expressions in PTC without and with lymph node metastasis, an increased expression of CX3CL1 and CX3CR1 was observed when compared to NG respectively. There was however no significant difference in CX3CL1 and CX3CR1 expressions in PTC without lymph node metastasis when compared to PTC with lymph node metastasis. Furthermore, when compared to NG, an increased expression of CX3CL1 was correlated with an increased expression of CX3CR1 in PTC. Our data indicate that CX3CL1 and CX3CR1 can be used as tumor markers for PTC and may be potential novel targets for cancer prevention and treatment.

AKI: an increasingly recognized risk factor for CKD development and progression

Acute kidney injury (AKI) is an increasing health burden with high morbidity and mortality rates worldwide. AKI is a risk factor for chronic kidney disease (CKD) development and progression to end stage renal disease (ESRD). Rapid action is required to find treatment options for AKI, plus to anticipate the development of CKD and other complications. Therefore, it is essential to understand the pathophysiology of AKI to CKD transition. Over the last several years, research has revealed maladaptive repair to be an interplay of cell death, endothelial dysfunction, tubular epithelial cell senescence, inflammatory processes and more-terminating in fibrosis. Various pathological mechanisms have been discovered and reveal targets for potential interventions. Furthermore, there have been clinical efforts measures for AKI prevention and progression including the development of novel biomarkers and prediction models. In this review, we provide an overview of pathophysiological mechanisms involved in kidney fibrosis. Furthermore, we discuss research gaps and promising therapeutic approaches for AKI to CKD progression.

Immune Dysfunction in Uremia 2020

Cardiovascular disease and infections are major causes for the high incidence of morbidity and mortality of patients with chronic kidney disease. Both complications are directly or indirectly associated with disturbed functions or altered apoptotic rates of polymorphonuclear leukocytes, monocytes, lymphocytes, and dendritic cells. Normal responses of immune cells can be reduced, leading to infectious diseases or pre-activated/primed, giving rise to inflammation and subsequently to cardiovascular disease. This review summarizes the impact of kidney dysfunction on the immune system. Renal failure results in disturbed renal metabolic activities with reduced renin, erythropoietin, and vitamin D production, which adversely affects the immune system. Decreased kidney function also leads to reduced glomerular filtration and the retention of uremic toxins. A large number of uremic toxins with detrimental effects on immune cells have been identified. Besides small water-soluble and protein-bound compounds originating from the intestinal microbiome, several molecules in the middle molecular range, e.g., immunoglobulin light chains, retinol-binding protein, the neuropeptides Met-enkephalin and neuropeptide Y, endothelin-1, and the adipokines leptin and resistin, adversely affect immune cells. Posttranslational modifications such as carbamoylation, advanced glycation products, and oxidative modifications contribute to uremic toxicity. Furthermore, high-density lipoprotein from uremic patients has an altered protein profile and thereby loses its anti-inflammatory properties.

High renal DC-SIGN+ cell density is associated with severe renal lesions and poor prognosis in patients with immunoglobulin A nephropathy

BACKGROUND AND AIMS

In this observational cohort study, we assessed the prognostic value of DC-SIGN⁺ cells in the pathogenesis and progression of IgA nephropathy (IgAN).

METHODS AND RESULTS

A total of 139 adult IgAN patients were enrolled into this study from June 2009 to June 2010. We characterised DC-SIGN⁺ cells by immunohistochemistry or immunofluorescence in renal biopsy tissue. Correlations between the DC-SIGN, intercellular adhesion molecule 3 (ICAM-3), CD4 and CD8 were evaluated. Patients were classified into the DC-SIGN^high and DC-SIGN^low groups. Depending on an average of 100-month follow-up, the predictive value of DC-SIGN⁺ cells in IgAN progression was analysed. DC-SIGN⁺ cells were found frequently in IgAN kidneys while rarely observed in normal kidneys, and almost all DC-SIGN⁺ cells expressed MHC-II. We also found that DC-SIGN⁺ cells were adjacent to ICAM-3-positive CD4⁺ and CD8⁺ lymphocytes. The density of DC-SIGN⁺ cells was positively and linearly correlated with the density of ICAM-3⁺ cells, CD4⁺ cells and CD8⁺ cells in renal biopsy tissues. In the DC-SIGN^high group, the degree of renal lesion and inflammatory cell infiltration was more severe compared to the DC-SIGN^low group. Patients in the DC-SIGN^high group also had increased incidences of deteriorating renal function during the follow up compared to patients in the DC-SIGN^low group.

CONCLUSIONS

DC-SIGN⁺ cells probably served as a potential contributor to exacerbate local inflammatory response. The density of DC-SIGN⁺ cells was associated with the severity of renal lesions of the patients. High renal DC-SIGN⁺ cell density might be used as a predictor of poor prognosis in patients with IgAN.

How Acute Kidney Injury Contributes to Renal Fibrosis

Acute kidney injury (AKI) is a widespread clinical syndrome directly associated with patient short-term and long-term morbidity and mortality. During the last decade, the incidence rate of AKI has been increasing, the repeated and severe episodes of AKI have been recognized as a major risk factor chronic kidney diseases (CKD) and end-stage kidney disease (ESRD) leading to global disease burden. Proposed pathological processes and risk factors that add to the transition of AKI to CKD and ESRD include severity and frequency of kidney injury, older age, gender, genetics and chronic health conditions like diabetes, hypertension, and obesity. Therefore, there is a great interest in learning about the mechanism of AKI leading to renal fibrosis, the ultimate renal lesions of CKD. Over the last several years, a significant attention has been given to the field of renal fibrosis with impressive progression in knowing the mechanism of renal fibrosis to detailed cellular characterization and molecular pathways implicated in tubulointerstitial fibrosis. Research and clinical trial are underway for emerging biomarkers detecting early kidney injury, predicting kidney disease progression and developing strategies to efficiently treat AKI and to minimize AKI progression to CKD and ESRD. Specific interventions to prevent renal fibrosis are still experimental. Potential therapeutic advances based on those molecular mechanisms will hopefully offer promising insights into the development of new therapeutic interventions for patients in the near future.

Hypoxia and Renal Tubulointerstitial Fibrosis

Hypoxia, one of the most common causes of kidney injury, is a key pathological condition in various kidney diseases. Renal fibrosis is the terminal pathway involved in the continuous progression of chronic kidney disease (CKD), characterized by glomerulosclerosis and tubulointerstitial fibrosis (TIF). Recent studies have shown that hypoxia is a key factor promoting the progression of TIF. Loss of microvasculature, reduced oxygen dispersion, and metabolic abnormality of cells in the kidney are the main causes of the hypoxic state. Hypoxia can, in turn, profoundly affect the tubular epithelial cells, endothelial cells, pericytes, fibroblasts, inflammatory cells, and progenitor cells. In this chapter, we reviewed the critical roles of hypoxia in the pathophysiology of TIF and discussed the potential of anti-hypoxia as its promising therapeutic target.

Renal fibrosis: Primacy of the proximal tubule

Tubulointerstitial fibrosis (TIF) is the hallmark of chronic kidney disease and best predictor of renal survival. Many different cell types contribute to TIF progression including tubular epithelial cells, myofibroblasts, endothelia, and inflammatory cells. Previously, most of the attention has centered on myofibroblasts given their central importance in extracellular matrix production. However, emerging data focuses on how the response of the proximal tubule, a specialized epithelial segment vulnerable to injury, plays a central role in TIF progression. Several proximal tubular responses such as de-differentiation, cell cycle changes, autophagy, and metabolic changes may be adaptive initially, but can lead to maladaptive responses that promote TIF both through autocrine and paracrine effects. This review discusses the current paradigm of TIF progression and the increasingly important role of the proximal tubule in promoting TIF both in tubulointerstitial and glomerular injuries. A better understanding and appreciation of the role of the proximal tubule in TIF has important implications for therapeutic strategies to halt chronic kidney disease progression.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

Macrophage density in early surveillance biopsies predicts future renal transplant function

Inflammation impairs renal allograft survival but is difficult to quantify by eye at low densities. Here we measured leukocyte abundance in early surveillance biopsies by digital image analysis to test for a role of chemokine receptor genotypes and analyze the predictive value of leukocyte subsets to allograft function. In six-week surveillance biopsies, T-cell (CD3), B-cell (CD20), macrophage (CD68), and dendritic cell (CD209) densities were assessed in whole slide scans. Renal cortical CD3, CD20, and CD68 were significantly higher in histologic rejection. The CCR2 V64I genotype was associated with lower CD3 and CD209 densities. Above-median CD68 density was significantly associated with lower combined patient and graft survival with a hazard ratio of 3.5 (95% confidence interval 1.1-11.0). Both CD20 and CD68 densities inversely correlated with estimated glomerular filtration rate (eGFR) four years after transplantation. Additionally, CD68 correlated with eGFR loss. Among histological measurements including a complete Banff classification, only CD68 density was a significant predictor of an eGFR under 30ml/min after four years (odds ratio 7.4, 1.8-31.0) and part of the best eGFR prediction set in a multivariable linear regression analysis of multiple clinical and pathologic parameters. In a second independent cohort, the original CD68 median maintained its discriminative power for survival and eGFR. Thus, digital high-resolution assessment of CD68⁺ leukocyte infiltration significantly improves prognostic value of early renal transplant biopsies.

Advanced Oxidation Protein Products-Modified Albumin Induces Differentiation of RAW264.7 Macrophages into Dendritic-Like Cells Which Is Modulated by Cell Surface Thiols

Local accumulation of Advanced Oxidation Protein Products (AOPP) induces pro-inflammatory and pro-fibrotic processes in kidneys and is an independent predictor of renal fibrosis and of rapid decline of eGFR in patients with chronic kidney disease (CKD). In addition to kidney damage, circulating AOPP may be regarded as mediators of systemic oxidative stress and, in this capacity, they might play a role in the progression of atherosclerotic damage of arterial walls. Atherosclerosis is a chronic inflammatory disease that involves activation of innate and adaptive immunity. Dendritic cells (DCs) are key cells in this process, due to their role in antigen presentation, inflammation resolution and T cell activation. AOPP consist in oxidative modifications of proteins (such as albumin and fibrinogen) that mainly occur through myeloperoxidase (MPO)-derived hypochlorite (HOCl). HOCl modified proteins have been found in atherosclerotic lesions. The oxidizing environment and the shifts in cellular redox equilibrium trigger inflammation, activate immune cells and induce immune responses. Thus, surface thiol groups contribute to the regulation of immune functions. The aims of this work are: (1) to evaluate whether AOPP-proteins induce activation and differentiation of mature macrophages into dendritic cells in vitro; and (2) to define the role of cell surface thiol groups and of free radicals in this process. AOPP-proteins were prepared by in vitro incubation of human serum albumin (HSA) with HOCl. Mouse macrophage-like RAW264.7 were treated with various concentrations of AOPP-HSA with or without the antioxidant N-acetyl cysteine (NAC). Following 48 h of HSA-AOPP treatment, RAW264.7 morphological changes were evaluated by microscopic observation, while markers of dendritic lineage and activation (CD40, CD86, and MHC class II) and allogeneic T cell proliferation were evaluated by flow cytometry. Cell surface thiols were measured by AlexaFluor-maleimide binding, and ROS production was assessed as DCF fluorescence by flow cytometry. HSA-AOPP induced the differentiation of RAW264.7 cells into a dendritic-like phenotype, as shown by morphological changes, by increased CD40, CD86 and MHC class II surface expression and by induction of T cell proliferation. The cell surface thiols dose dependently decreased following HSA-AOPP treatment, while ROS production increased. NAC pre-treatment enhanced the amount of cell surface thiols and prevented their reduction due to treatment with AOPP. Both ROS production and RAW264.7 differentiation into DC-like cells induced by HSA-AOPP were reduced by NAC. Our results highlight that oxidized plasma proteins modulate specific immune responses of macrophages through a process involving changes in the thiol redox equilibrium. We suggest that this mechanism may play a role in determining the rapid progression of the atherosclerotic process observed in CKD patients.

CX3CL1/CX3CR1 Axis, as the Therapeutic Potential in Renal Diseases: Friend or Foe?

The fractalkine receptor chemokine (C-X3-C motif) receptor 1 (CX3CR1) and its highly selective ligand CX3CL1 mediate chemotaxis and adhesion of immune cells, which are involved in the pathogenesis and progression of numerous inflammatory disorders and malignancies. The CX3CL1/CX3CR1 axis has recently drawn attention as a potential therapeutic target because it is involved in the ontogeny, homeostatic migration, or colonization of renal phagocytes. We performed a Medline/PubMed search to detect recently published studies that explored the relationship between the CX3CL1/CX3CR1 axis and renal diseases and disorders, including diabetic nephropathy, renal allograft rejection, infectious renal diseases, IgA nephropathy, fibrotic kidney disease, lupus nephritis and glomerulonephritis, acute kidney injury and renal carcinoma. Most studies demonstrated its role in promoting renal pathopoiesis; however, several recent studies showed that the CX3CL1/CX3CR1 axis could also reduce renal pathopoiesis. Thus, the CX3CL1/CX3CR1 axis is now considered to be a double-edged sword that could provide novel perspectives into the pathogenesis and treatment of renal diseases and disorders.

Progression of chronic kidney disease: too much cellular talk causes damage

Tubulointerstitial fibrosis, tubular atrophy, and peritubular capillary rarefaction are major hallmarks of chronic kidney disease. The tubulointerstitium consists of multiple cell components including tubular epithelial, mesenchymal (fibroblasts and pericytes), endothelial, and inflammatory cells. Crosstalk among these cell components is a key component in the pathogenesis of this complex disease. After severe or recurrent injury, the renal tubular epithelial cells undergo changes in structure and cell cycle that are accompanied by altered expression and production of cytokines. These cytokines contribute to the initiation of the fibrotic response by favoring activation of fibroblasts, recruitment of inflammatory cells, and loss of endothelial cells. This review focuses on how augmented growth factor and cytokine production induces epithelial crosstalk with cells in the interstitium to promote progressive tubulointerstitial fibrosis after renal injury.

The Players: Cells Involved in Glomerular Disease

Glomerular diseases are common and important. They can arise from systemic inflammatory or metabolic diseases that affect the kidney. Alternately, they are caused primarily by local glomerular abnormalities, including genetic diseases. Both intrinsic glomerular cells and leukocytes are critical to the healthy glomerulus and to glomerular dysregulation in disease. Mesangial cells, endothelial cells, podocytes, and parietal epithelial cells within the glomerulus all play unique and specialized roles. Although a specific disease often primarily affects a particular cell type, the close proximity, and interdependent functions and interactions between cells mean that even diseases affecting one cell type usually indirectly influence others. In addition to those cells intrinsic to the glomerulus, leukocytes patrol the glomerulus in health and mediate injury in disease. Distinct leukocyte types and subsets are present, with some being involved in different ways in an individual glomerular disease. Cells of the innate and adaptive immune systems are important, directing systemic immune and inflammatory responses, locally mediating injury, and potentially dampening inflammation and facilitating repair. The advent of new genetic and molecular techniques, and new disease models means that we better understand both the basic biology of the glomerulus and the pathogenesis of glomerular disease. This understanding should lead to better diagnostic techniques, biomarkers, and predictors of prognosis, disease severity, and relapse. With this knowledge comes the promise of better therapies in the future, directed toward halting pathways of injury and fibrosis, or interrupting the underlying pathophysiology of the individual diseases that lead to significant and progressive glomerular disease.

Summary of ISN Forefronts Symposium 2015: ‘Immunomodulation of Cardio-Renal Function’

The International Society of Nephrology Forefronts Symposium Immunomodulation of Cardio-Renal Function took place October 22 to 25, 2015, in Shenzhen, China. The program covered basic and clinical aspects of cardio-renal pathophysiology and immunity. Leading scientists from different and related disciplines of clinical and basic research described and reviewed recent discoveries, and discussed emerging topics under the headings “Immunity and Renal Pathophysiology”; “Autoimmunity and the Inflammasome”; “Immunity and the Gut Microbiome”; “Immuno-Metabolism”; “Immunogenetics, Transcriptomics and Epigenetics; “Immunity and Hypertension”; and “Immunity, Fibrosis, and Kidney Disease.”

CD40 Generation 2.5 Antisense Oligonucleotide Treatment Attenuates Doxorubicin-induced Nephropathy and Kidney Inflammation

Preclinical and clinical data suggest CD40 activation contributes to renal inflammation and injury. We sought to test whether upregulation of CD40 in the kidney is a causative factor of renal pathology and if reduction of renal CD40 expression, using antisense oligonucleotides (ASOs) targeting CD40, would be beneficial in mouse models of glomerular injury and unilateral ureter obstruction. Administration of a Generation 2.5 CD40 ASO reduced CD40 mRNA and protein levels 75–90% in the kidney. CD40 ASO treatment mitigated functional, transcriptional, and pathological endpoints of doxorubicin-induced nephropathy. Experiments using an activating CD40 antibody revealed CD40 is primed in kidneys following doxorubicin injury or unilateral ureter obstruction and CD40 ASO treatment blunted CD40-dependent renal inflammation. Suborgan fractionation and imaging studies demonstrated CD40 in glomeruli before and after doxorubicin administration that becomes highly enriched within interstitial and glomerular foci following CD40 activation. Such foci were also sites of ASO distribution and activity and may be predominately comprised from myeloid cells as bone marrow CD40 deficiency sharply attenuated CD40 antibody responses. These studies suggest an important role of interstitial renal and/or glomerular CD40 to augment kidney injury and inflammation and demonstrate that ASO treatment could be an effective therapy in such disorders.

Renal participation of myeloperoxidase in antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis

Myeloperoxidase (MPO) is an important neutrophil lysosomal enzyme, a major autoantigen, and a potential mediator of tissue injury in MPO-ANCA-associated vasculitis (MPO-AAV) and glomerulonephritis. Here we examined MPO deposition in kidney biopsies from 47 patients with MPO-AAV. Leukocyte accumulation and fibrin deposition consistent with cell-mediated immunity was a major feature. Tubulointerstitial macrophage, CD4+ and CD8+ T-cell, and neutrophil numbers correlated with low presenting eGFR. MPO was not detected in kidneys from patients with minimal change or thin basement membrane disease, but was prominent in glomerular, periglomerular, and tubulointerstitial regions in MPO-AAV. Extracellular MPO released from leukocytes was pronounced in all MPO-AAV patients. Similar numbers of neutrophils and macrophages expressed MPO in the kidneys, but colocalization studies identified neutrophils as the major source of extracellular MPO. Extraleukocyte MPO was prominent in neutrophil extracellular traps in the majority of patients; most of which had traps in half or more glomeruli. These traps were associated with more neutrophils and more MPO within glomeruli. Glomerular MPO-containing macrophages generated extracellular trap-like structures. MPO also localized to endothelial cells and podocytes. The presence of the most active glomerular lesions (both segmental necrosis and cellular crescents) correlated with intraglomerular CD4+ cells and MPO+ macrophages. Thus, cellular and extracellular MPO may cause glomerular and interstitial injury.