Dysregulated heme oxygenase-1low M2-like macrophages augment lupus nephritis via Bach1 induced by type I interferons

The shared circulating diagnostic biomarkers and molecular mechanisms of systemic lupus erythematosus and inflammatory bowel disease

Background

Systemic lupus erythematosus (SLE) is a multi-organ chronic autoimmune disease. Inflammatory bowel disease (IBD) is a common chronic inflammatory disease of the gastrointestinal tract. Previous studies have shown that SLE and IBD share common pathogenic pathways and genetic susceptibility, but the specific pathogenic mechanisms remain unclear.

Methods

The datasets of SLE and IBD were downloaded from the Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) were identified using the Limma package. Weighted gene coexpression network analysis (WGCNA) was used to determine co-expression modules related to SLE and IBD. Pathway enrichment was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis for co-driver genes. Using the Least AbsoluteShrinkage and Selection Operator (Lasso) regressionand Support Vector Machine-Recursive Feature Elimination (SVM-RFE), common diagnostic markers for both diseases were further evaluated. Then, we utilizedthe CIBERSORT method to assess the abundance of immune cell infiltration. Finally,we used the single-cell analysis to obtain the location of common diagnostic markers.

Results

71 common driver genes were identified in the SLE and IBD cohorts based on the DEGs and module genes. KEGG and GO enrichment results showed that these genes were closely associated with positive regulation of programmed cell death and inflammatory responses. By using LASSO regression and SVM, five hub genes (KLRF1, GZMK, KLRB1, CD40LG, and IL-7R) were ultimately determined as common diagnostic markers for SLE and IBD. ROC curve analysis also showed good diagnostic performance. The outcomes of immune cell infiltration demonstrated that SLE and IBD shared almost identical immune infiltration patterns. Furthermore, the majority of the hub genes were commonly expressed in NK cells by single-cell analysis.

Conclusion

This study demonstrates that SLE and IBD share common diagnostic markers and pathogenic pathways. In addition, SLE and IBD show similar immune cellinfiltration microenvironments which provides newperspectives for future treatment.

Macrophage subpopulations in pediatric patients with lupus nephritis and other inflammatory diseases affecting the kidney

BACKGROUND

Macrophages play an important role in the pathogenesis of lupus nephritis (LN), but less is known about macrophage subtypes in pediatric LN. Here we compared renal inflammation in LN with other inflammatory pediatric kidney diseases and assessed whether inflammation correlates with clinical parameters.

METHODS

Using immunofluorescence microscopy, we analyzed renal biopsies from 20 pediatric patients with lupus nephritis (ISN/RPS classes II-V) and pediatric controls with other inflammatory kidney diseases for infiltration with M1-like (CD68 + /CD206 - , CD68 + /CD163 -), M2a-like (CD206 + /CD68 +), and M2c-like macrophages (CD163 + /CD68 +) as well as CD3 + T-cells, CD20 + B-cells, and MPO + neutrophilic granulocytes. In addition, the correlation of macrophage infiltration with clinical parameters at the time of renal biopsy, e.g., eGFR and serum urea, was investigated. Macrophage subpopulations were compared with data from a former study of adult LN patients.

RESULTS

The frequency of different macrophage subtypes in biopsies of pediatric LN was dependent on ISN/RPS class and showed the most pronounced M1-like macrophage infiltration in patients with LN class IV, whereas M2c-like macrophages were most abundant in class III and IV. Interestingly, on average, only half as many macrophages were found in renal biopsies of pediatric LN compared to adult patients with LN. The distribution of frequencies of macrophage subpopulations, however, was different for CD68 + CD206 + (M2a-like) but comparable for CD68 + CD163 - (M1-like) CD68 + CD163 + (M2c-like) cells in pediatric and adult patients. Compared to other inflammatory kidney diseases in children, fewer macrophages and other inflammatory cells were found in kidney biopsies of LN. Depending on the disease, the frequency of individual immune cell types varied, but we were unable to confirm disease-specific inflammatory signatures in our study due to the small number of pediatric cases. Worsened renal function, measured as elevated serum urea and decreased eGFR, correlated particularly strongly with the number of CD68 + /CD163 - M1-like macrophages and CD20 + B cells in pediatric inflammatory kidney disease.

CONCLUSION

Although M1-like macrophages play a greater role in pediatric LN patients than in adult LN patients, M2-like macrophages appear to be key players and are more abundant in other pediatric inflammatory kidney diseases compared to LN.

BACH1 promotes tissue necrosis and Mycobacterium tuberculosis susceptibility

Oxidative stress triggers ferroptosis, a form of cellular necrosis characterized by iron-dependent lipid peroxidation, and has been implicated in Mycobacterium tuberculosis (Mtb) pathogenesis. We investigated whether Bach1, a transcription factor that represses multiple antioxidant genes, regulates host resistance to Mtb. We found that BACH1 expression is associated clinically with active pulmonary tuberculosis. Bach1 deletion in Mtb-infected mice increased glutathione levels and Gpx4 expression that inhibit lipid peroxidation. Bach1-/- macrophages exhibited increased resistance to Mtb-induced cell death, while Mtb-infected Bach1-deficient mice displayed reduced bacterial loads, pulmonary necrosis and lipid peroxidation concurrent with increased survival. Single-cell RNA-seq analysis of lungs from Mtb-infected Bach1-/- mice revealed an enrichment of genes associated with ferroptosis suppression. Bach1 depletion in Mtb-infected B6.Sst1S mice that display human-like necrotic lung pathology also markedly reduced necrosis and increased host resistance. These findings identify Bach1 as a key regulator of cellular and tissue necrosis and host resistance in Mtb infection.

BACH1 Loss Exerts Antitumor Effects on Mantle Cell Lymphoma Cells via Inducing a Tumor-Intrinsic Innate Immune Response and Cell-Cycle Arrest

BTB and CNC homology 1 (BACH1) is a transcription repressor that regulates multiple physiological processes, including intracellular heme homeostasis and immune responses. Increasing lines of evidence indicate that BACH1 reshapes metastasis and metabolism of human solid tumors. However, its potential roles in mantle cell lymphoma (MCL) remain largely unknown. Here, we found that silencing BACH1 in MCL cells induced markedly cell-cycle arrest and cell apoptosis, whereas overexpression of BACH1 exhibited the opposite patterns. Increased BACH1 levels not only promoted tumor growth and dispersal in xenografts, but also conferred a long-term poor prognosis in patients with MCL. Interestingly, RNA sequencing analysis revealed noncanonical function of BACH1 in regulation of type I interferon (IFNI) response, DNA replication and repair, and cell cycle. Mechanistically, zinc finger and BTB domain containing 20 (ZBTB20) and HMG-box transcription factor 1 (HBP1) were for the first time identified as two novel downstream targets repressed by BACH1 in MCL cells. Further double-knockdown functional assays confirmed that loss of BACH1 induced ZBTB20-mediated IFNα production and HBP1-mediated cell-cycle arrest, indicating that BACH1-centered regulatory network may be a novel targetable vulnerability in MCL cells.

IMPLICATIONS

BACH1 serves as a pleotropic regulator of tumor-intrinsic innate immune response and cell-cycle progression, disruption of which may offer a promising therapeutic strategy for MCL treatment.

Immunoregulation mechanism of VEGF signaling pathway inhibitors and its efficacy on the kidney

Angiogenesis and immunosuppression are closely related pathophysiologic processes. Widely prescribed in malignant tumor and proliferative retinal lesions, VEGF signaling pathway inhibitors may cause hypertension and renal injury in some patients, presenting with proteinuria, nephrotic syndrome, renal failure and thrombotic microangiopathy. VEGF signaling pathway inhibitors block the action of both VEGF-A and VEGF-C. However, VEGF-A and VEGF-C produced by podocytes are vital to maintain the physiological function of glomerular endothelial cells and podocytes. There is still no effective treatment for kidney disease associated with VEGF signaling pathway inhibitors and some patients have progressive renal failure even after withdrawal of the drug. Recent studies reveal that blocking of VEGF-A and VEGF-C can activate CD4 +and CD8+ T cells, augment antigen-presenting function of dendritic cells, enhance cytotoxicity of macrophages and initiate complement cascade activation. VEGF and VEGFR are expressed in immune cells, which are involved in the immunosuppression and cross-talk among immune cells. This review summarizes the expression and function of VEGF-A and VEGF-C in the kidney. The current immunoregulation mechanisms of VEGF signaling pathway inhibitors are reviewed. Finally, combinate strategies are summarized to highlight the proposal for VEGF signaling pathway inhibitors.

Regulatory Mechanism of M1/M2 Macrophage Polarization in the Development of Autoimmune Diseases

Macrophages are innate immune cells in the organism and can be found in almost tissues and organs. They are highly plastic and heterogeneous cells and can participate in the immune response, thereby playing a crucial role in maintaining the immune homeostasis of the body. It is well known that undifferentiated macrophages can polarize into classically activated macrophages (M1 macrophages) and alternatively activated macrophages (M2 macrophages) under different microenvironmental conditions. The directions of macrophage polarization can be regulated by a series of factors, including interferon, lipopolysaccharide, interleukin, and noncoding RNAs. To elucidate the role of macrophages in various autoimmune diseases, we searched the literature on macrophages with the PubMed database. Search terms are as follows: macrophages, polarization, signaling pathways, noncoding RNA, inflammation, autoimmune diseases, systemic lupus erythematosus, rheumatoid arthritis, lupus nephritis, Sjogren's syndrome, Guillain-Barré syndrome, and multiple sclerosis. In the present study, we summarize the role of macrophage polarization in common autoimmune diseases. In addition, we also summarize the features and recent advances with a particular focus on the immunotherapeutic potential of macrophage polarization in autoimmune diseases and the potentially effective therapeutic targets.

Pathogenic cellular and molecular mediators in lupus nephritis

Kidney involvement in patients with systemic lupus erythematosus - lupus nephritis (LN) - is one of the most important and common clinical manifestations of this disease and occurs in 40-60% of patients. Current treatment regimens achieve a complete kidney response in only a minority of affected individuals, and 10-15% of patients with LN develop kidney failure, with its attendant morbidity and considerable prognostic implications. Moreover, the medications most often used to treat LN - corticosteroids in combination with immunosuppressive or cytotoxic drugs - are associated with substantial side effects. Advances in proteomics, flow cytometry and RNA sequencing have led to important new insights into immune cells, molecules and mechanistic pathways that are instrumental in the pathogenesis of LN. These insights, together with a renewed focus on the study of human LN kidney tissue, suggest new therapeutic targets that are already being tested in lupus animal models and early-phase clinical trials and, as such, are hoped to eventually lead to meaningful improvements in the care of patients with systemic lupus erythematosus-associated kidney disease.

The role of thyroid hormone in the renal immune microenvironment

Thyroid hormones are essential for proper kidney growth and development. The kidney is not only the organ of thyroid hormone metabolism but also the target organ of thyroid hormone. Kidney disease is a common type of kidney damage, mainly including different types of acute kidney injury, chronic kidney disease, diabetic nephropathy, lupus nephritis, and renal cell carcinoma. The kidney is often damaged by an immune response directed against its antigens or a systemic immune response. A variety of immune cells in the innate and adaptive immune systems, including neutrophils, macrophages, dendritic cells, T lymphocytes, and B lymphocytes, is essential for maintaining immune homeostasis and preventing autoimmune kidney disease. Recent studies have found that thyroid hormone plays an indispensable role in the immune microenvironment of various kidney diseases. Thyroid hormones regulate the activity of neutrophils, and dendritic cells express triiodothyronine receptors. Compared to hypothyroidism, hyperthyroidism has a greater effect on neutrophils. Furthermore, in adaptive immune systems, thyroid hormone may activate T lymphocytes through several underlying mechanisms, such as mediating NF-κB, protein kinase C signalling pathways, and β-adrenergic receptors, leading to increased T lymphocyte activation. The present review discusses the effects of thyroid hormone metabolism regulation in the immune microenvironment on the function of various immune cells, especially neutrophils, macrophages, dendritic cells, T lymphocytes, and B lymphocytes. Although there are not enough data at this stage to conclude the clinical relevance of these findings, thyroid hormone metabolism may influence autoimmune kidney disease by regulating the renal immune microenvironment.

Metalloporphyrins as Tools for Deciphering the Role of Heme Oxygenase in Renal Immune Injury

Renal immune injury is a frequent cause of end-stage renal disease, and, despite the progress made in understanding underlying pathogenetic mechanisms, current treatments to preserve renal function continue to be based mainly on systemic immunosuppression. Small molecules, naturally occurring biologic agents, show considerable promise in acting as disease modifiers and may provide novel therapeutic leads. Certain naturally occurring or synthetic Metalloporphyrins (Mps) can act as disease modifiers by increasing heme oxygenase (HO) enzymatic activity and/or synthesis of the inducible HO isoform (HO-1). Depending on the metal moiety of the Mp employed, these effects may occur in tandem or can be discordant (increased HO-1 synthesis but inhibition of enzyme activity). This review discusses effects of Mps, with varying redox-active transitional metals and cyclic porphyrin cores, on mechanisms underlying pathogenesis and outcomes of renal immune injury.

The Role of Heme Oxygenase-1 as an Immunomodulator in Kidney Disease

The protein heme oxygenase (HO)-1 has been implicated in the regulations of multiple immunological processes. It is well known that kidney injury is affected by immune mechanisms and that various kidney-disease forms may be a result of autoimmune disease. The current study describes in detail the role of HO-1 in kidney disease and provides the most recent observations of the effect of HO-1 on immune pathways and responses both in animal models of immune-mediated disease forms and in patient studies.

Macrophages in Lupus Nephritis: Exploring a potential new therapeutic avenue

Lupus nephritis (LN) is a serious complication of systemic lupus erythematosus (SLE) that occurs in about half of patients. LN is characterized by glomerular deposition of immune complexes, leading to subendothelial, mesangial and subepithelial electron dense deposits, triggering immune cell infiltration and glomerular as well as tubulointerstitial injury. Monocytes and macrophages are abundantly present in inflammatory lesions, both in glomeruli and the tubulointerstitium. Here we discuss how monocytes and macrophages are involved in this process and how monocytes and macrophages may represent specific therapeutic targets to control LN.

Renal Fibrosis in Lupus Nephritis

Fibrosis can be defined as a pathological process in which deposition of connective tissue replaces normal parenchyma. The kidney, like any organ or tissue, can be impacted by this maladaptive reaction, resulting in persistent inflammation or long-lasting injury. While glomerular injury has traditionally been regarded as the primary focus for classification and prognosis of lupus nephritis (LN), increasing attention has been placed on interstitial fibrosis and tubular atrophy as markers of injury severity, predictors of therapeutic response, and prognostic factors of renal outcome in recent years. This review will discuss the fibrogenesis in LN and known mechanisms of renal fibrosis. The importance of the chronicity index, which was recently added to the histological categorization of LN, and its role in predicting treatment response and renal prognosis for patients with LN, will be explored. A better understanding of cellular and molecular pathways involved in fibrosis in LN could enable the identification of individuals at higher risk of progression to chronic kidney disease and end-stage renal disease, and the development of new therapeutic strategies for lupus patients.

Harnessing the Therapeutic Potential of the Nrf2/Bach1 Signaling Pathway in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative movement disorder characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Although a complex interplay of multiple environmental and genetic factors has been implicated, the etiology of neuronal death in PD remains unresolved. Various mechanisms of neuronal degeneration in PD have been proposed, including oxidative stress, mitochondrial dysfunction, neuroinflammation, α-synuclein proteostasis, disruption of calcium homeostasis, and other cell death pathways. While many drugs individually targeting these pathways have shown promise in preclinical PD models, this promise has not yet translated into neuroprotective therapies in human PD. This has consequently spurred efforts to identify alternative targets with multipronged therapeutic approaches. A promising therapeutic target that could modulate multiple etiological pathways involves drug-induced activation of a coordinated genetic program regulated by the transcription factor, nuclear factor E2-related factor 2 (Nrf2). Nrf2 regulates the transcription of over 250 genes, creating a multifaceted network that integrates cellular activities by expressing cytoprotective genes, promoting the resolution of inflammation, restoring redox and protein homeostasis, stimulating energy metabolism, and facilitating repair. However, FDA-approved electrophilic Nrf2 activators cause irreversible alkylation of cysteine residues in various cellular proteins resulting in side effects. We propose that the transcriptional repressor of BTB and CNC homology 1 (Bach1), which antagonizes Nrf2, could serve as a promising complementary target for the activation of both Nrf2-dependent and Nrf2-independent neuroprotective pathways. This review presents the current knowledge on the Nrf2/Bach1 signaling pathway, its role in various cellular processes, and the benefits of simultaneously inhibiting Bach1 and stabilizing Nrf2 using non-electrophilic small molecules as a novel therapeutic approach for PD.

CircRTN4 aggravates mesangial cell dysfunction by activating the miR-513a-5p/FN axis in lupus nephritis

Circular RNAs (circRNAs) are regulators of gene expression that can regulate cell proliferation and programmed cell death and serve as biomarkers in renal diseases. However, the specific traits and underlying mechanisms of circRNAs in the progression of lupus nephritis (LN) have not been elucidated. In the present study, we clarified that hsa_circ_0054595 (circRTN4) was upregulated in human renal mesangial cells (HRMCs). In cultured HRMCs, circRTN4 could enhance FN expression by directly interacting with miR-513a-5p. High circRTN4 expression in monocytes disseminated into HRMCs in an exosomal manner, thereby accelerating cell proliferation and extracellular matrix deposition. In addition, knockdown of circRTN4 in the kidney or peripheral blood alleviated renal damage in MRL/lpr and BALB/c mice. Clinically, high levels of circRTN4 were found in peripheral blood mononuclear cells and kidney tissues of LN patients, hence serving as an effective biomarker for LN detection and a novel therapeutic target. Our findings indicated that circRTN4 exacerbates mesangial cell dysfunction by activating the miR-513a-5p/FN axis in lupus nephritis.

Immunomodulatory Activity of Mesenchymal Stem Cells in Lupus Nephritis: Advances and Applications

Lupus nephritis (LN) is a significant cause of various acute and chronic renal diseases, which can eventually lead to end-stage renal disease. The pathogenic mechanisms of LN are characterized by abnormal activation of the immune responses, increased cytokine production, and dysregulation of inflammatory signaling pathways. LN treatment is an important issue in the prevention and treatment of systemic lupus erythematosus. Mesenchymal stem cells (MSCs) have the advantages of immunomodulation, anti-inflammation, and anti-proliferation. These unique properties make MSCs a strong candidate for cell therapy of autoimmune diseases. MSCs can suppress the proliferation of innate and adaptive immune cells, such as natural killer cells (NKs), dendritic cells (DCs), T cells, and B cells. Furthermore, MSCs suppress the functions of various immune cells, such as the cytotoxicity of T cells and NKs, maturation and antibody secretion of B cells, maturation and antigen presentation of DCs, and inhibition of cytokine secretion, such as interleukins (ILs), tumor necrosis factor (TNF), and interferons (IFNs) by a variety of immune cells. MSCs can exert immunomodulatory effects in LN through these immune functions to suppress autoimmunity, improve renal pathology, and restore kidney function in lupus mice and LN patients. Herein, we review the role of immune cells and cytokines in the pathogenesis of LN and the mechanisms involved, as well as the progress of research on the immunomodulatory role of MSCs in LN.

Type I interferon-related kidney disorders

Type I interferon (IFN-I) mediates tissue damage in a wide range of kidney disorders, directly affecting the biology and function of several renal cell types including podocytes, mesangial, endothelial and parietal epithelial cells (PECs).Enhanced IFN-I signalling is observed in the context of viral infections, autoimmunity (e.g., systemic lupus erythematosus, SLE), and the type 1 interferonopathies (T1Is), rare monogenic disorders characterised by constitutive activation of the IFN-I pathway. All of these IFN I-related disorders can cause renal dysfunction, and share pathogenic and histopathological features. Collapsing glomerulopathy, a histopathological lesion characterised by podocyte loss, collapse of the vascular tuft and PEC proliferation, is commonly associated with viral infections, has been described in T1Is such as Aicardi-Goutières syndrome and STING-associated vasculopathy with onset in infancy (SAVI), and can also be induced by recombinant IFN-therapy. In all of these conditions, podocytes and PECs seem to be the primary target of IFN I-mediated damage. Additionally, immune-mediated glomerular injury is common to viral infections, SLE, and T1Is such as COPA syndrome and DNASE1L3 deficiency, diseases in which IFN-I apparently promotes immune-mediated kidney injury. Finally, kidney pathology primarily characterised by vascular lesions (e.g., thrombotic microangiopathy, vasculitis) is a hallmark of the T1I ADA2 deficiency as well as of SLE, viral infections and IFN-therapy.Defining the nosology, pathogenic mechanisms and histopathological patterns of IFN I-related kidney disorders has diagnostic and therapeutic implications, especially considering the likely near-term availability of novel drugs targeting the IFN-I pathway.

Macrophage Polarization and Plasticity in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that attacks almost every organ. The condition mostly happens to adults but is also found in children, and the latter have the most severe manifestations. Among adults, females, especially non-Caucasian, are mostly affected. Even if the etiology of SLE remains unclear, studies show a close relation between this disease and both genetics and environment. Despite the large number of published articles about SLE, we still do not have a clear picture of its pathogenesis, and no specific drug has been found to treat this condition effectively. The implication of macrophages in SLE development is gaining ground, and studying it could answer these gaps. Indeed, both in vivo and in vitro studies increasingly report a strong link between this disease and macrophages. Hence, this review aims to explore the role of macrophages polarization and plasticity in SLE development. Understanding this role is of paramount importance because in-depth knowledge of the connection between macrophages and this systemic disease could clarify its pathogenesis and provide a foundation for macrophage-centered therapeutic approaches.

MicroRNA-98-5p inhibits human mesangial cell proliferation and TNF-α and IL-6 secretion by targeting BTB and CNC homology 1

MicroRNA (miR)-98-5p has been reported to be involved in the development of lupus nephritis (LN); however, its specific role in LN remains unclear. The present study aimed to investigate the effect of miR-98-5p on human mesangial cell proliferation and the secretion of TNF-α and IL-6. Reverse transcription-quantitative PCR (RT-qPCR) and western blotting were used to analyze the level of gene and protein expression, respectively. Cellular proliferation was assessed using a Cell Counting Kit-8 (CCK-8) assay. ELISA was used to detect the secretion of TNF-α and IL-6 by human mesangial cells. RT-qPCR analysis revealed that miR-98-5p expression was downregulated in LN renal tissues compared with control renal tissues. Overexpression of miR-98-5p inhibited human mesangial cell proliferation and the secretion of TNF-α and IL-6, whereas miR-98-5p-knockdown demonstrated the opposite effect. Dual luciferase reporter assays demonstrated that miR-98-5p directly targeted BTB and CNC homology 1 (BACH1). BACH1-overexpression promoted human mesangial cell proliferation and the secretion of TNF-α and IL-6, whereas BACH1-knockdown demonstrated the opposite effect. Notably, co-transfection with miR-98-5p mimic inhibited BACH1-overexpression induced human mesangial cell proliferation and the secretion of TNF-α and IL-6. The results of the present study indicated that miR-98-5p inhibited human mesangial cell proliferation and the secretion of TNF-α and IL-6 by targeting BACH1. Therefore, miR-98-5p and BACH1 may represent potential therapeutic targets for LN.

Role of Macrophages and Related Cytokines in Kidney Disease

Inflammation is a key characteristic of kidney disease, but this immune response is two-faced. In the acute phase of kidney injury, there is an activation of the immune cells to fight against the insult, contributing to kidney repair and regeneration. However, in chronic kidney diseases (CKD), immune cells that infiltrate the kidney play a deleterious role, actively participating in disease progression, and contributing to nephron loss and fibrosis. Importantly, CKD is a chronic inflammatory disease. In early CKD stages, patients present sub-clinical inflammation, activation of immune circulating cells and therefore, anti-inflammatory strategies have been proposed as a common therapeutic target for renal diseases. Recent studies have highlighted the plasticity of immune cells and the complexity of their functions. Among immune cells, monocytes/macrophages play an important role in all steps of kidney injury. However, the phenotype characterization between human and mice immune cells showed different markers; therefore the extrapolation of experimental studies in mice could not reflect human renal diseases. Here we will review the current information about the characteristics of different macrophage phenotypes, mainly focused on macrophage-related cytokines, with special attention to the chemokine CCL18, and its murine functional homolog CCL8, and the macrophage marker CD163, and their role in kidney pathology.

IFN-I Mediates Lupus Nephritis From the Beginning to Renal Fibrosis

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus (SLE) and a major risk factor for morbidity and mortality. The abundant cell-free nucleic (DNA/RNA) in SLE patients, especially dsDNA, is a key substance in the pathogenesis of SLE and LN. The deposition of DNA/RNA-immune complexes (DNA/RNA-ICs) in the glomerulus causes a series of inflammatory reactions that lead to resident renal cell disturbance and eventually renal fibrosis. Cell-free DNA/RNA is the most effective inducer of type I interferons (IFN-I). Resident renal cells (rather than infiltrating immune cells) are the main source of IFN-I in the kidney. IFN-I in turn damages resident renal cells. Not only are resident renal cells victims, but also participants in this immunity war. However, the mechanism for generation of IFN-I in resident renal cells and the pathological mechanism of IFN-I promoting renal fibrosis have not been fully elucidated. This paper reviews the latest epidemiology of LN and its development process, discusses the mechanism for generation of IFN-I in resident renal cells and the role of IFN-I in the pathogenesis of LN, and may open a new perspective for the treatment of LN.

Azithromycin alleviates systemic lupus erythematosus via the promotion of M2 polarisation in lupus mice

Our previous study demonstrated that azithromycin could promote alternatively activated (M2) macrophages under lupus conditions in vitro, which might be beneficial for lupus treatment. Thus, the aim of this study was to further confirm whether azithromycin can drive M2 polarisation in lupus and ultimately alleviate systemic lupus erythematosus (SLE) in vivo. Lymphocyte-derived DNA (ALD-DNA)-induced mice (induced lupus model) and MRL-Fas^lpr mice (spontaneous lupus model) were both used in the experiment. First, we observed symptoms of lupus by assessing the levels of serum anti-dsDNA antibodies and serum creatinine and renal pathology. We found that both murine models showed increased levels of serum anti-dsDNA antibodies and creatinine, enhanced glomerular fibrosis and cell infiltration, basement membrane thickening and elevated IgG deposition. After azithromycin treatment, all these medical indexes were alleviated, and kidney damage was effectively reversed. Next, macrophage polarisation was assessed in the spleen and kidneys. Macrophage infiltration in the spleen was notably decreased after azithromycin treatment in both murine models, with a remarkably elevated proportion of M2 macrophages. In addition, the expression of interleukin (IL)-1, IL-6, tumour necrosis factor (TNF)-α, inducible nitric oxide synthase (iNOS), CD86, toll-like receptor (TLR)2 and TLR4 was extremely downregulated, while the expression of transforming growth factor (TGF)-β, arginase-1 (Arg-1), chitinase-like 3 (Ym-1), found in inflammatory zone (Fizz-1) and mannose receptor (CD206) was significantly upregulated in the kidneys after azithromycin treatment. Taken together, our results indicated for the first time that azithromycin could alleviate lupus by promoting M2 polarisation in vivo. These findings exploited the newly discovered potential of azithromycin, a conventional drug with verified safety, affordability and global availability, which could be a novel treat-to-target strategy for SLE via macrophage modulation.

Heme Oxygenase 1: A Defensive Mediator in Kidney Diseases

The incidence of kidney disease is rising, constituting a significant burden on the healthcare system and making identification of new therapeutic targets increasingly urgent. The heme oxygenase (HO) system performs an important function in the regulation of oxidative stress and inflammation and, via these mechanisms, is thought to play a role in the prevention of non-specific injuries following acute renal failure or resulting from chronic kidney disease. The expression of HO-1 is strongly inducible by a wide range of stimuli in the kidney, consequent to the kidney's filtration role which means HO-1 is exposed to a wide range of endogenous and exogenous molecules, and it has been shown to be protective in a variety of nephropathological animal models. Interestingly, the positive effect of HO-1 occurs in both hemolysis- and rhabdomyolysis-dominated diseases, where the kidney is extensively exposed to heme (a major HO-1 inducer), as well as in non-heme-dependent diseases such as hypertension, diabetic nephropathy or progression to end-stage renal disease. This highlights the complexity of HO-1's functions, which is also illustrated by the fact that, despite the abundance of preclinical data, no drug targeting HO-1 has so far been translated into clinical use. The objective of this review is to assess current knowledge relating HO-1's role in the kidney and its potential interest as a nephroprotection agent. The potential therapeutic openings will be presented, in particular through the identification of clinical trials targeting this enzyme or its products.

Regulating T Cell Population Alleviates SLE by Inhibiting mTORC1/C2 in MRL/lpr Mice

It’s well known that the mammalian target of rapamycin (mTOR) exerts a critical role in the regulator of immune cells and is associated with T cells dysfunction in patients with systemic lupus erythematosus (SLE). Antigen-induced T-cell proliferation via mTORC1 suppressed by Rapamycin has been used to improve SLE primarily. Previously it has showed that INK128, a highly potent, specific orally inhibitor of mTORC1 and mTORC2, significantly attenuates SLE in pristine-induced lupus mice. Herein we compared the cure effects of INK128 and rapamycin on lupus mice. We treated MRL/lpr mice with INK128 or rapamycin at 12 weeks-age. The effect of the two inhibitors on the lupus mice was determined by immunohistochemistry. The effect of the two inhibitors on T cell populations was investigated by flow cytometry. The mTOR signaling was measured by Western Blot. INK128 remarkably alleviated SLE by reducing splenomegaly, renal inflammation and damage, and resuming T-cell dysfunction. The more effective of INK128 on SLE than rapamycin. INK128 effectively suppressed mTORC1 and mTORC2 activity in T cells, but rapamycin just suppressed mTORC1 activity. Thus, our results show that INK128 is can effectively alleviate SLE and be used as one of the potential clinical therapeutic candidates for SLE.

Immune Cell Landscape Identification Associates Intrarenal Mononuclear Phagocytes With Onset and Remission of Lupus Nephritis in NZB/W Mice

Objective

A challenging issue in the clinical management of lupus nephritis (LN) is the resistance to immunosuppressive therapy. We postulated that perturbed intrarenal immune cell landscape affected LN onset and remission induction, and shedding light on the characteristics of intrarenal immune cell infiltration could cultivate more efficient treatment regimens.

Materials and Methods

Genome-wide expression profiles of microarray datasets were downloaded from the Gene Expression Omnibus database. The CIBERSORT algorithm was used to analyze the intrarenal immune cell landscape, followed by Pearson correlation analysis and principal component analysis. The differentially expressed genes were identified and subjected to Gene Ontology (GO) enrichment analyses and protein-protein interaction network establishment, being visualized by Cytoscape and further analyzed by CytoHubba to extract hub genes. Hub genes were also validated in the genomic dataset from kidney biopsy-proven LN patients.

Results

In addition to memory B cells, monocytes and M1 macrophages were identified as two predominantly increased intrarenal immune cell types in LN-prone NZB/W mice upon nephritis onset. Most interestingly, apart from memory B cells, monocytes and M1 macrophages proportions in kidney tissue were significantly lower in early remission mice compared with late remission mice. Furthermore, GO analysis showed that intrarenal mononuclear phagocytes triggered nephritis onset mainly via the initiation of adaptive immune response and inflammatory reaction, but this functional involvement was mitigated upon remission induction. Hub genes related to LN onset in NZB/W mice were validated in the genomic dataset from kidney biopsy-proven LN patients.

Conclusion

LN characterizes aberrant mononuclear phagocytes abundance and signature upon disease onset, of which the reversal is associated with early remission induction in LN-prone NZB/W mice. Mononuclear phagocytes might be an adjunctive histology marker for monitoring disease onset and stratifying LN patients in terms of response to remission induction therapy.

Urinary soluble CD163 is a good biomarker for renal disease activity in lupus nephritis

OBJECTIVES

Activated macrophages expressing CD163 (M2) are the most abundant macrophage subtype in renal biopsies from lupus nephritis (LN) patients. We studied the role of proteolytically cleaved soluble CD163 (sCD163) as a biomarker of LN disease activity.

METHODS

SLE patients were classified as active LN (AN), inactive disease (ID), and active non-renal disease (ANR). Urine and plasma samples were collected at baseline from all patients and at 3 monthly follow-up from AN patients. sCD163 was measured by ELISA. Urine values were normalized to urinary creatinine excretion and expressed as pg/mg. Urine samples from 25 healthy controls (HC) and 20 rheumatoid arthritis patients served as disease controls (DC).

RESULTS

Among the 122 patients studied (114 females, 57 AN, 42 ID, 23 ANR), baseline median urinary sCD163 in the AN group (114.01 pg/mg) was significantly higher (p < 0.001) as compared with ID (10.34 pg/mg), ANR (3.82 pg/mg), HC (0 pg/mg), and DC (7.56 pg/mg) groups and showed modest correlation with renal SLEDAI (r = 0.47; p < 0.001). Urinary sCD163 performed the best on receiver operating characteristics (ROC) analysis (AUC = 0.76) at baseline to differentiate between AN and ANR as compared with plasma sCD163, anti-ds DNA antibodies, and C3 and C4. In follow-up study, urinary sCD163 decreased significantly (p < 0.001) in AN patients at 3 (22.07 pg/mg), 6 (12.7 pg/mg), 9 (11.09 pg/mg), and 12 months (7.2 pg/mg). In 4 patients who had either relapse or developed CKD, urinary sCD163 levels correlated with the changing disease activity.

CONCLUSIONS

Urinary sCD163 is a good biomarker of LN disease activity. Key Points • Urinary sCD163 levels are raised in patients with active lupus nephritis and correlate with renal SLEDAI. • Urinary sCD163 levels fall after treatment and may be helpful in monitoring response to therapy in lupus nephritis.

Lupus nephritis: challenges and progress

PURPOSE OF REVIEW

The management of lupus nephritis remains unsatisfactory due to insufficiently effective treatment regimens and the dearth of reliable predictors of disease onset or progression to guide individualized therapeutic decisions. This review summarizes new findings related to lupus nephritis over the last 18 months and discusses clinical needs that should be considered to advance trials of mechanism-based therapeutic strategies.

RECENT FINDINGS

Collaborative teams are addressing how to improve disease definitions and are developing predictive models for disease onset, disease response and risk of flare in individual patients. More attention is being paid to clinical trial design. Advanced technologic approaches are allowing the analysis of small amounts of human tissue and urine in unprecedented detail so as to discover new pathogenic mechanisms and identify disease biomarkers. Novel therapies continue to be tested in disease models and include new strategies to protect renal tissue from cell damage and fibrosis.

SUMMARY

The collaborative efforts of patients, clinical and translational researchers, the pharmaceutical industry and funding sources are needed to advance therapies for lupus nephritis. Specialized clinical centers can then deliver optimal and more personalized patient care that will improve patient outcomes.

Update on the cellular and molecular aspects of lupus nephritis

Recent progress has highlighted the involvement of a variety of innate and adaptive immune cells in lupus nephritis. These include activated neutrophils producing extracellular chromatin traps that induce type I interferon production and endothelial injury, metabolically-rewired IL-17-producing T-cells causing tissue inflammation, follicular and extra-follicular helper T-cells promoting the maturation of autoantibody-producing B-cells that may also sustain the formation of germinal centers, and alternatively activated monocytes/macrophages participating in tissue repair and remodeling. The role of resident cells such as podocytes and tubular epithelial cells is increasingly recognized in regulating the local immune responses and determining the kidney function and integrity. These findings are corroborated by advanced, high-throughput genomic studies, which have revealed an unprecedented amount of data highlighting the molecular heterogeneity of immune and non-immune cells implicated in lupus kidney disease. Importantly, this research has led to the discovery of putative pathogenic pathways, enabling the rationale design of novel treatments.

Type I Interferons Rule with an Iron Fist

Pathogens rely on nutrient assimilation, particularly essential metal incorporation, to successfully survive in the host. In this issue of Cell Host & Microbe, Riedelberger et al. (2020) convincingly demonstrate that type I interferons (IFNs-I) promote dysregulation of iron homeostasis in macrophages upon infection with Candida glabrata and exacerbate infection.

Type I Interferon Response Dysregulates Host Iron Homeostasis and Enhances Candida glabrata Infection

Type I interferons (IFNs-I) fulfil multiple protective functions during pathogenic infections, but they can also cause detrimental effects and enhance immunopathology. Here, we report that IFNs-I promote the dysregulation of iron homeostasis in macrophages during systemic infections with the intracellular pathogen Candida glabrata, leading to fungal survival and persistence. By engaging JAK1, IFNs-I disturb the balance of the transcriptional activator NRF2 and repressor BACH1 to induce downregulation of the key iron exporter Fpn1 in macrophages. This leads to enhanced iron accumulation in the phagolysosome and failure to restrict fungal access to iron pools. As a result, C. glabrata acquires iron via the Sit1/Ftr1 iron transporter system, facilitating fungal intracellular replication and immune evasion. Thus, IFNs-I are central regulators of iron homeostasis, which can impact infection, and restricting iron bioavailability may offer therapeutic strategies to combat invasive fungal infections.

Heme-Oxygenase-1 Is Decreased in Circulating Monocytes and Is Associated With Impaired Phagocytosis and ROS Production in Lupus Nephritis

Lupus nephritis (LN) is one of the most serious manifestations of systemic lupus erythematosus (SLE). Based on studies showing the potential role of heme oxygenase-1 (HO-1), an enzyme that catalyzes the degradation of heme and has anti-inflammatory properties in SLE development, we decided to explore HO-1 in LN. Accordingly, we evaluated HO-1 levels and function in circulating and infiltrating monocytes and neutrophils of LN patients. HO-1 levels were assessed in peripheral monocytes of LN patients and controls by flow cytometry and immunofluorescence microscopy. Phagocytosis and the production of reactive oxygen species (ROS) were evaluated to determine the effect of HO-1 in monocyte function. In addition, renal biopsies with proliferative LN were used to identify HO-1 in infiltrating cells and renal tissue by immunofluorescence and immunohistochemistry. Biopsies of healthy controls (HC) and patients who underwent nephrectomy were included as controls. Circulating pro-inflammatory monocytes and activated neutrophils were increased in LN patients. HO-1 levels were decreased in all subsets of monocytes and in activated neutrophils. LN monocytes showed increased phagocytosis and higher production of ROS than those of HC. When HO-1 was induced, phagocytosis and ROS levels became similar to those of HC. HO-1 was mostly expressed in renal tubular epithelial cells (RTEC). Renal tissue of LN patients showed lower levels of HO-1 than HC, whereas infiltrating immune cells of LN showed lower levels of HO-1 than biopsies of patients who had renal surgery. HO-1 is decreased in circulating monocytes and activated neutrophils of LN patients. HO-1 levels modulate the phagocytosis of LN monocytes and ROS production. HO-1 expression in RTEC might be an attempt of self-protection from inflammation.

Heme oxygenase-1 as a potential therapeutic target in rheumatic diseases

BACKGROUND

Heme oxygenase-1 (HO-1), a cellular stress protein, serves a vital metabolic function as the rate-limiting enzyme in the degradation of heme to generate carbon monoxide (CO), iron, and biliverdin (BR). HO-1 may function as one of the most momentous factors of cell adaptation to oxidase stress, as well as a regulator of inflammatory signaling programs through the generation of its biologically active end products. Intensive investigation is now focusing on the potential function of HO-1 in inflammatory disorders, among which rheumatic diseases are one of the principal issues.

METHODS

"Heme oxygenase-1", "rheumatic diseases"; "lupus", "rheumatic arthritis", "osteoarthritis" and "oxidative stress" were used as key words for searching in Pubmed and Google scholar database.

RESULTS

Collected information from the related articles revealed the important role of pathogenesis and therapeutic potential of HO-1 in rheumatic diseases. Conclusions and discussions HO-1 has potential as a target for the treatment of rheumatic diseases due to its characteristic anti-inflammatory and anti-oxidative role. However, it is essential to monitor the HO-1 expression during particular stage of the disorders, and levels of HO-1 in different tissues and organs should be further confirmed in order to correlate it with clinical symptoms and other hallmarks of rheumatic diseases.