Pathogenesis of lupus nephritis: the contribution of immune and kidney resident cells

Determining IFI44 as a key lupus nephritis's biomarker through bioinformatics and immunohistochemistry

BACKGROUND

Lupus nephritis (LN) emerges as a severe complication of systemic lupus erythematosus (SLE), significantly affecting patient survival. Despite improvements in treatment reducing LN's morbidity and mortality, existing therapies remain suboptimal, emphasizing the necessity for early detection to improve patient outcomes.

METHODS

This study employs bioinformatics and machine learning to identify and validate potential LN biomarkers using immunohistochemistry (IHC). It explores the relationship between these biomarkers and the clinical and pathological characteristics of LN, assessing their prognostic significance. The research provides deeper mechanistic insights by employing Gene Set Enrichment Analysis (GSEA), Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Additionally, the study characterizes the immune profiles of LN patients through the CIBERSORT algorithm, focusing on the role of interferon-inducible protein 44 (IFI44) as a key biomarker.

RESULTS

IFI44 shows elevated expression in LN-affected kidneys, compared to healthy controls. The levels of IFI44 positively correlate with serum creatinine and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and inversely with serum complement C3 and initial estimated glomerular filtration rate (eGFR).

CONCLUSION

IFI44 is identified as a promising biomarker for LN, offering potential to refine the assessment of disease progression and predict clinical outcomes. This facilitates the development of more personalized treatment strategies for LN patients.

HALP Score for Predicting Renal Relapse in Lupus Nephritis: A Nested Case-Control Study

OBJECTIVE

To evaluate the HALP (hemoglobin-albumin-lymphocyte-platelet) score at lupus nephritis (LN) diagnosis in predicting renal relapse (RR).

METHODS

Nested case-control study, including patients aged ≥18 years with diagnosis of LN between 2010 and 2022. Two patient sets were included: training and validation. Each set had 2 groups of patients: RR and non-RR. Data were obtained from clinical records. The optimal cutoff value of the HALP score at LN diagnosis was established to predict RR. Cox regression analysis was used to associate HALP score at diagnosis with RR.

RESULTS

We included 53 LN patients in the training set and 74 LN patients in the validation set. The optimal cutoff value for HALP score at diagnosis was 23.5, with an area under the curve of 0.896, sensitivity of 91.9%, and specificity of 97.3% in the validation set. The median age of patients in this set was 31.0 years, mostly female (93%). In the validation set, LN patients with HALP score at diagnosis ≤23.5 compared with higher HALP score subjects showed a significantly higher baseline SLEDAI-2K (18 [interquartile range {IQR}, 14-20] vs. 14 [IQR, 11-17], p < 0.001), Systemic Lupus Collaborating Clinics/American College of Rheumatology Damage Index at the end of the follow-up (1 [IQR, 0-4] vs. 0 [IQR, 0-1], p = 0.002), chronicity index in renal biopsy (2 [IQR, 1-4] vs. 1 [IQR, 1-2], p = 0.030), and significantly reduced time to RR (4.2 vs. 12.9 years, p < 0.001). A HALP score at diagnosis ≤23.5 was associated with RR (hazard ratio, 18.2; 95% confidence interval, 5.3-30.1; p < 0.001).

CONCLUSION

A HALP score ≤23.5 at LN diagnosis was an independent risk factor for RR.

The imbalance of follicular helper T cells and follicular regulatory T cells is involved in renal injury in active lupus nephritis

OBJECTIVE

This study is to research the role of follicular helper T (TFH) cells and follicular regulatory T (TFR) cells in the progression of lupus nephritis (LN).

METHODS

A total of 33 active LN patients, 30 stable LN patients, and 30 healthy controls (HC) were included in this study. The frequencies of TFH, TFR, T cell Ig and ITIM domain (TIGIT) + TFR, and CD226 + TFR cells in peripheral blood were measured using flow cytometry. The distribution and proportion of TFH and TFR cells in renal tissue were assessed using a multiplex immunohistochemical.

RESULTS

Active LN had a significantly lower TFR and TFR/TFH ratio in peripheral blood than HC and stable LN. TIGIT + TFR was lower in active LN, while CD226 + TFR was higher. In LN, TFR and TFR/TFH ratio showed a negative correlation with creatinine (CREA), but a positive correlation with endogenous creatinine clearance (Ccr). TFH and TFR mainly infiltrated the renal interstitium or surrounding renal tubules and participated in the formation of ectopic lymphoid-like structures in active LN. In active LN, TFH cells in renal tissue were higher than in control renal tissue. The tissue TFH showed a positive correlation with the activity index, CREA, but a negative correlation with Ccr. The tissue TFR/TFH ratio showed a negative correlation with the activity index, CREA, but a positive correlation with Ccr.

CONCLUSION

In active LN, the proportions of TFR cells in peripheral blood are reduced and function is impaired. In active LN, TFH and TFR imbalances have been observed and are associated with renal injury.

Clinical presentation, outcomes and risk of relapses of lupus podocytopathy in a multicentre Italian cohort

BACKGROUND

In an Italian cohort of lupus podocytopathy patients, we aimed to characterize the presenting features, therapy, and outcomes, and explore differences between relapsing and non-relapsing patients.

METHODS

We identified 29 patients with lupus podocytopathy from 1994 to 2023 in 11 Italian Nephrology/Rheumatology Units, and divided them into two groups: relapsing and non-relapsing. Given the limited sample size, a p-value ≤ 0.2 was considered as significant.

RESULTS

The median age of the patients was 43 (25-52) years, 89.7% were females, 89.6% presented with nephrotic syndrome, 34.4% with acute kidney dysfunction, and 44% with arterial hypertension. After corticosteroids and/or immunosuppressive therapy, complete (25 patients) or partial remission (4 patients) occurred within a median of 4 (1-9) months. Nine patients (31%) relapsed. After a further course of therapy, remission was achieved within 5 (2-11) months. Relapsing patients had higher serum creatinine (0.94 [0.73-2.65] vs 0.8 [0.6-1.1] mg/dl; p = 0.12), lower estimated glomerular filtration rate (76 [32.5-107.5] vs 93 [59.3-109.7] ml/min/1.73m2; p = 0.23) and higher proteinuria (7.7 [5.9-11.7] vs 6.5 g/day [3.2-10.1]; p = 0.14) at lupus podocytopathy diagnosis than non-relapsing subjects. Activity indexes at biopsy were higher [(1 (0-2) vs 0 (0-1); p = 0.08] and cutaneous systemic lupus erythematosus manifestations were more prevalent (44.4% vs 10.5%; p = 0.06) in relapsing patients. After an observation of 49 (18-23) months, 86.2% of patients were in complete remission while 13.8% remained in partial remission. One patient developed mild chronic kidney function impairment.

CONCLUSIONS

Lupus podocytopathy typically presents with nephrotic syndrome and kidney dysfunction, it responds favourably to treatment, and generally results in a favourable renal outcome. We observed that more active renal and extrarenal lupus manifestations at the onset of lupus podocytopathy were indicative of higher susceptiblity to disease recurrence.

Interleukin-32 positive immune and resident cells in kidney samples from lupus patients: a pilot study

Introduction

Lupus nephritis (LN), caused by immune complexes produced in situ or deposited from the bloodstream, is one of the most severe features of Systemic Lupus Erythematosus (SLE) leading to an increased morbidity and mortality. Toll like receptors (TLRs), such as TLR3, TLR7 and TLR9, may play a key role in its pathogenesis. Interleukin-32 (IL-32), a cytokine involved in both innate and adaptive immune responses, has been widely considered in autoimmune-inflammatory rheumatic diseases. This study aims to evaluate the IL-32 role in LN, also investigating the effect of LN patients IgG (LN-IgG) on IL-32 production via TLR3.

Methods

In LN patients, IL-32 was detected in sera samples by ELISA KIT and in kidney tissue by immunohistochemistry. HEK293/T3 cells were incubated with LN-IgG and analyzed for TBK1, phospho-p65 NF-κB and IL-32 by Western blot.

Results

We demonstrated IL-32 presence in LN patients compared to SLE patients without renal involvement, observing a direct correlation between IL-32 serum levels and disease duration (p=0.02; r 0.2978). Moreover, IL-32 was strongly expressed in renal samples of LN patients. Phosphorylation of TBK1 resulting in NF-κB activation and IL-32 increase was observed in HEK293/T3 cells following LN-IgG treatment, TLR3 inhibitor using induced a significant reduction in the expression of these molecules.

Discussion

These results showed that IL-32 is up-regulated in the kidney of LN patients suggesting that in renal tissue IL-32 expression could be induced through TLR3 activation by the LN patients' antibodies. This study may indicate a possible role for IL-32 in the pathogenesis of LN.

Single-cell transcriptomics reveal potent extrafollicular B cell response linked with granzyme K+ CD8 T cell activation in lupus kidney

OBJECTIVES

B and T cells constitute the majority of infiltrating lymphocytes in the kidney and represent the local perpetrators in lupus nephritis (LN), but the underlying pathogenic mechanisms are not well elucidated. The aim of this study is to explore the kidney-specific adaptive immune landscape in patients with active LN at the single-cell level.

METHODS

We performed single-cell RNA/B cell receptor (BCR)/T cell receptor (TCR) sequencing analysis on sorting-purified B and T cells from the kidney and paired peripheral blood of patients with active LN, and the periphery of matched controls. Flow cytometry, Assay for Transposase Accessible-sequencing, multiplexed immunohistochemistry and functional studies were performed to validate the transcriptomic results.

RESULTS

High infiltrations of intrarenal atypical B cells (ABCs) and antibody-secreting cells (ASCs) were identified in the B cell compartment. The single-cell BCR repertoire analysis revealed strong clonal expansion of intrarenal ASCs dominated by IGHG1 and IGHG3 isotypes, accompanied by lower frequencies of heavy-chain and light-chain somatic mutations, compared with the peripheral ASCs. Notably, a unique expansion of IGHG4-59 and clonal overlap between ABCs and ASCs was found in kidney-specific clonotypes. In the T cell compartment, we identified granzyme K (GZMK)+ CD8 T cells as the dominant kidney-associated T cells which shared inflammation- and stress-related gene pathways with ABCs. Intrarenal GZMK+ CD8 T cells highly expressed IFNG and displayed strong communication with ABCs via the type II interferon (IFN) pathway. Intrarenal GZMK+ CD8 T cells and ABCs were largely co-localised within the tertiary lymphoid structure, and GZMK+ CD8 T cells potentially contributed to the differentiation of ABCs via IFN-γ and interleukin-21.

CONCLUSIONS

Our study revealed a potent extrafollicular B cell response linked with overactivation of GZMK+ CD8 T cells in the kidney of patients with LN, which may lead to innovative treatments for LN.

Occurrence and role of Tph cells in various renal diseases

A new population of peripheral helper T (Tph) cells has been identified and contributed to various autoimmune diseases. Tph cells can secrete interleukin-21 (IL-21), interferon (IFN) and C-X-C motif chemokine ligand 13 (CXCL13) to moderate renal disease. Moreover, Tph cells can congregate in huge numbers and immerse within inflamed tissue. Compared to Tfh cells, Tph cells express high programmed cell death protein 1 (PD-1), major histocompatibility complex II (MHC-II), C-C chemokine receptor 2 (CCR2) and C-C chemokine receptor 5 (CCR5) but often lack expression of the chemokine receptor C-X-C chemokine receptor 5 (CXCR5). They display features distinct from other T cells, which are uniquely poised to promote responses and antibody production of B cells within pathologically inflamed non-lymphoid tissues and a key feature of Tph cells. In this review, we summarize recent findings on the role of Tph cells in chronic kidney disease, acute kidney injury, kidney transplantation and various renal diseases.

Lupus Nephritis: Immune Cells and the Kidney Microenvironment

Lupus nephritis (LN) is the most common major organ manifestation of the autoimmune disease SLE (lupus), with 10% of those afflicted progressing to ESKD. The kidney in LN is characterized by a significant immune infiltrate and proinflammatory cytokine milieu that affects intrinsic renal cells and is, in part, responsible for the tissue damage observed in LN. It is now increasingly appreciated that LN is not due to unidirectional immune cell activation with subsequent kidney damage. Rather, the kidney microenvironment influences the recruitment, survival, differentiation, and activation of immune cells, which, in turn, modify kidney cell function. This review covers how the biochemical environment of the kidney ( i.e ., low oxygen tension and hypertonicity) and unique kidney cell types affect the intrarenal immune cells in LN. The pathways used by intrinsic renal cells to interact with immune cells, such as antigen presentation and cytokine production, are discussed in detail. An understanding of these mechanisms can lead to the design of more kidney-targeted treatments and the avoidance of systemic immunosuppressive effects and may represent the next frontier of LN therapies.

How Stem and Progenitor Cells Can Affect Renal Diseases

Stem and progenitor cells have been observed to contribute to regenerative processes in acute renal failure and chronic kidney disease. Recent research has delved into the intricate mechanisms by which stem and progenitor cells exert their influence on kidney diseases. Understanding how these cells integrate with the existing renal architecture and their response to injury could pave the way for innovative treatment strategies aimed at promoting kidney repair and regeneration. Overall, the role of stem and progenitor cells in kidney diseases is multifaceted, with their ability to contribute to tissue regeneration, immune modulation, and the maintenance of renal homeostasis. Here, we review the studies that we have available today about the involvement of stem and progenitor cells both in regenerative therapies and in the causes of renal diseases, as well as in natural healing mechanisms, taking into account the main kidney disorders, such as IgA nephropathy, lupus nephritis, diabetic nephropathy, C3 glomerulopathy, focal segmental glomerulosclerosis, idiopathic membranous nephropathy, anti-glomerular basement membrane glomerulonephritis, and ANCA-associated crescentic glomerulonephritis. Moreover, based on the comprehensive data available in the framework of the specific kidney diseases on stem cells and renal progenitors, we hypothesize a possible role of adult renal progenitors in exacerbating or recovering the illness.

Lupus Nephritis from Pathogenesis to New Therapies: An Update

Lupus Nephritis (LN) still represents one of the most severe complications of Systemic Lupus Erythematosus (SLE) and a major risk factor for morbidity and mortality. However, over the last few years, several studies have paved the way for a deeper understanding of its pathogenetic mechanisms and more targeted treatments. This review aims to provide a comprehensive update on progress on several key aspects in this setting: pathogenetic mechanisms of LN, including new insight into the role of autoantibodies, complement, vitamin D deficiency, and interaction between infiltrating immune cells and kidney resident ones; the evolving role of renal biopsy and biomarkers, which may integrate information from renal histology; newly approved drugs such as voclosporin (VOC) and belimumab (BEL), allowing a more articulate strategy for induction therapy, and other promising phase III-immunosuppressive (IS) agents in the pipeline. Several adjunctive treatments aimed at reducing cardiovascular risk and progression of chronic renal damage, such as antiproteinuric agents, represent an important complement to IS therapy. Furthermore, non-pharmacological measures concerning general lifestyle and diet should also be adopted when managing LN. Integrating these therapeutic areas requires an effort towards a holistic and multidisciplinary approach. At the same time, the availability of an increasingly wider armamentarium may translate into improvements in patient's renal outcomes over the next decades.

C5a-C5aR1 axis controls mitochondrial fission to promote podocyte injury in lupus nephritis

Podocytes are essential to maintaining the integrity of the glomerular filtration barrier, but they are frequently affected in lupus nephritis (LN). Here, we show that the significant upregulation of Drp1S616 phosphorylation in podocytes promotes mitochondrial fission, leading to mitochondrial dysfunction and podocyte injury in LN. Inhibition or knockdown of Drp1 promotes mitochondrial fusion and protects podocytes from injury induced by LN serum. In vivo, pharmacological inhibition of Drp1 reduces the phosphorylation of Drp1S616 in podocytes in lupus-prone mice. Podocyte injury is reversed when Drp1 is inhibited, resulting in the alleviation of proteinuria. Mechanistically, complement component C5a (C5a) upregulates the phosphorylation of Drp1S616 and promotes mitochondrial fission in podocytes. Moreover, the expression of C5a receptor 1 (C5aR1) is notably upregulated in podocytes in LN. C5a-C5aR1 axis-controlled phosphorylation of Drp1S616 and mitochondrial fission are substantially suppressed when C5aR1 is knocked down by siRNA. Moreover, lupus-prone mice treated with C5aR inhibitor show reduced phosphorylation of Drp1S616 in podocytes, resulting in significantly less podocyte damage. Together, this study uncovers a novel mechanism by which the C5a-C5aR1 axis promotes podocyte injury by enhancing Drp1-mediated mitochondrial fission, which could have significant implications for the treatment of LN.

The immunoregulatory roles of non-haematopoietic cells in the kidney

The deposition of immune complexes, activation of complement and infiltration of the kidney by cells of the adaptive and innate immune systems have long been considered responsible for the induction of kidney damage in autoimmune, alloimmune and other inflammatory kidney diseases. However, emerging findings have highlighted the contribution of resident immune cells and of immune molecules expressed by kidney-resident parenchymal cells to disease processes. Several types of kidney parenchymal cells seem to express a variety of immune molecules with a distinct topographic distribution, which may reflect the exposure of these cells to different pathogenic threats or microenvironments. A growing body of literature suggests that these cells can stimulate the infiltration of immune cells that provide protection against infections or contribute to inflammation - a process that is also regulated by draining kidney lymph nodes. Moreover, components of the immune system, such as autoantibodies, cytokines and immune cells, can influence the metabolic profile of kidney parenchymal cells in the kidney, highlighting the importance of crosstalk in pathogenic processes. The development of targeted nanomedicine approaches that modulate the immune response or control inflammation and damage directly within the kidney has the potential to eliminate the need for systemically acting drugs.

Blood immunophenotyping identifies distinct kidney histopathology and outcomes in patients with lupus nephritis

Lupus nephritis (LN) is a frequent manifestation of systemic lupus erythematosus, and fewer than half of patients achieve complete renal response with standard immunosuppressants. Identifying non-invasive, blood-based pathologic immune alterations associated with renal injury could aid therapeutic decisions. Here, we used mass cytometry immunophenotyping of peripheral blood mononuclear cells in 145 patients with biopsy-proven LN and 40 healthy controls to evaluate the heterogeneity of immune activation in patients with LN and to identify correlates of renal parameters and treatment response. Unbiased analysis identified 3 immunologically distinct groups of patients with LN that were associated with different patterns of histopathology, renal cell infiltrates, urine proteomic profiles, and treatment response at one year. Patients with enriched circulating granzyme B+ T cells at baseline showed more severe disease and increased numbers of activated CD8 T cells in the kidney, yet they had the highest likelihood of treatment response. A second group characterized primarily by a high type I interferon signature had a lower likelihood of response to therapy, while a third group appeared immunologically inactive by immunophenotyping at enrollment but with chronic renal injuries. Main immune profiles could be distilled down to 5 simple cytometric parameters that recapitulate several of the associations, highlighting the potential for blood immune profiling to translate to clinically useful non-invasive metrics to assess immune-mediated disease in LN.

LATS2 degradation promoted fibrosis damage and rescued by vitamin K3 in lupus nephritis

BACKGROUND

Lupus nephritis (LN) is the most common complication of systemic lupus erythematosus (SLE). The limited treatment options for LN increase the economic burdens on patients. Because fibrotic progression leads to irreversible renal damage in LN patients and further progresses to chronic kidney disease (CKD) and the end stage of renal disease (ESRD), developing new targets to prevent LN fibrotic progression could lead to a feasible treatment strategy for LN patients.

METHODS

In this study, we examined YAP activation and LATS2 downregulation in LN kidney biopsy samples (LN: n = 8, normal: n = 2) and lupus-prone MRL/lpr mice (n = 8 for each disease stage). The function of LATS2 was further investigated by in situ injection of Ad-LATS2 into mice with LN (n = 6 mice per group). We examined the role of SIAH2-LATS2 regulation by IP-MS and co-IP, and the protective effect of the SIAH2 inhibitor was investigated in mice with LN.

RESULTS

Restoring LATS2 by an adenovirus in vivo alleviated renal fibrotic damage in mice with LN. Moreover, we found that LATS2 was degraded by a K48 ubiquitination-proteasome pathway mediated by SIAH2 and promoted YAP activation to worsen fibrosis progression in LN. The H150 region of the substrate binding domain (SBD) is an important site for SIAH2-LATS2 binding. The SIAH2-specific inhibitor vitamin K3 protected against LN-associated fibrotic damage in vivo.

CONCLUSION

In summary, we identified the SIAH2-LATS2 axis as an attractive intervention target in LN to alter the resistance to fibrosis.

Changes in macrophage infiltration and podocyte injury in lupus nephritis patients with repeated renal biopsy: Report of three cases

BACKGROUND

In this study, we retrospectively analysed macrophage infiltration and podocyte injury in three patients with diffuse proliferative lupus nephritis (LN) who underwent repeated renal biopsy.

CASE SUMMARY

Clinical data of three diffuse proliferative LN patients with different pathological characteristics (case 1 was LN IV-G (A), case 2 was LN IV-G (A) + V, and case 3 was LN IV-G (A) + thrombotic microangiopathy) were reviewed. All patients underwent repeated renal biopsies 6 mo later, and renal biopsy specimens were studied. Macrophage infiltration was assessed by CD68 expression detected by immunohistochemical staining, and an immunofluorescence assay was used to detect podocin expression to assess podocyte damage. After treatment, Case 1 changed to LN III-(A), Case 2 remained as type V LN lesions, and Case 3, which changed to LN IV-S (A), had the worst prognosis. We observed reduced macrophage infiltration after therapy. However, two of the patients with active lesions after treatment still showed macrophage infiltration in the renal interstitium. Before treatment, the three patients showed discontinuous expression of podocin. Notably, the integrity of podocin was restored after treatment in Case 1.

CONCLUSION

It may be possible to reverse podocyte damage and decrease the infiltrating macrophages in LN patients through effective treatment.

Identification of driver genes in lupus nephritis based on comprehensive bioinformatics and machine learning

Background

Lupus nephritis (LN) is a common and severe glomerulonephritis that often occurs as an organ manifestation of systemic lupus erythematosus (SLE). However, the complex pathological mechanisms associated with LN have hindered the progress of targeted therapies.

Methods

We analyzed glomerular tissues from 133 patients with LN and 51 normal controls using data obtained from the GEO database. Differentially expressed genes (DEGs) were identified and subjected to enrichment analysis. Weighted gene co-expression network analysis (WGCNA) was utilized to identify key gene modules. The least absolute shrinkage and selection operator (LASSO) and random forest were used to identify hub genes. We also analyzed immune cell infiltration using CIBERSORT. Additionally, we investigated the relationships between hub genes and clinicopathological features, as well as examined the distribution and expression of hub genes in the kidney.

Results

A total of 270 DEGs were identified in LN. Using weighted gene co-expression network analysis (WGCNA), we clustered these DEGs into 14 modules. Among them, the turquoise module displayed a significant correlation with LN (cor=0.88, p<0.0001). Machine learning techniques identified four hub genes, namely CD53 (AUC=0.995), TGFBI (AUC=0.997), MS4A6A (AUC=0.994), and HERC6 (AUC=0.999), which are involved in inflammation response and immune activation. CIBERSORT analysis suggested that these hub genes may contribute to immune cell infiltration. Furthermore, these hub genes exhibited strong correlations with the classification, renal function, and proteinuria of LN. Interestingly, the highest hub gene expression score was observed in macrophages.

Conclusion

CD53, TGFBI, MS4A6A, and HERC6 have emerged as promising candidate driver genes for LN. These hub genes hold the potential to offer valuable insights into the molecular diagnosis and treatment of LN.

Activation of BZW1 by CEBPB in macrophages promotes eIF2α phosphorylation-mediated metabolic reprogramming and endoplasmic reticulum stress in MRL/lpr lupus-prone mice

BACKGROUND

Lupus nephritis (LN) is associated with significant mortality and morbidity, while effective therapeutics and biomarkers are limited since the pathogenesis is complex. This study investigated the roles of the CEBPB/BZW1/eIF2α axis in metabolic reprogramming and endoplasmic reticulum stress in LN.

METHOD

The differentially expressed genes in LN were screened using bioinformatics tools. The expression of CEBPB in the renal tissue of patients with LN and its correlation with the levels of creatinine and urinary protein were analyzed. We used adenoviral vectors to construct LN mice with knockdown CEBPB using MRL/lpr lupus-prone mice and analyzed the physiological and autoimmune indices in mice. Chromatin immunoprecipitation quantitative polymerase chain reaction (ChIP-qPCR) and dual-luciferase reporter assays were conducted to explore the regulation of BZW1 by CEBPB, followed by glycolytic flux analysis, glucose uptake, and enzyme-linked immunosorbent assay (ELISA). Finally, the role of eIF2α phosphorylation by BZW1 in bone marrow-derived macrophages (BMDM) was explored using eIF2α phosphorylation and endoplasmic reticulum stress inhibitors.

RESULTS

CEBPB was significantly increased in renal tissues of patients with LN and positively correlated with creatinine and urine protein levels in patients. Downregulation of CEBPB alleviated the autoimmune response and the development of nephritis in LN mice. Transcriptional activation of BZW1 by CEBPB-mediated glucose metabolic reprogramming in macrophages, and upregulation of BZW1 reversed the mitigating effect of CEBPB knockdown on LN. Regulation of eIF2α phosphorylation levels by BZW1 promoted endoplasmic reticulum stress-amplified inflammatory responses in BMDM.

CONCLUSION

Transcriptional activation of BZW1 by CEBPB promoted phosphorylation of eIF2α to promote macrophage glycolysis and endoplasmic reticulum stress in the development of LN.

Association between immunoglobulin G N-glycosylation and lupus nephritis in female patients with systemic lupus erythematosus: a case-control study

Background

Lupus nephritis (LN) is a crucial complication of systemic lupus erythematosus (SLE) and has important clinical implications in guiding treatment. N-glycosylation of immunoglobulin G (IgG) plays a key role in the development of SLE by affecting the balance of anti-inflammatory and proinflammatory responses. This study aimed to evaluate the performance of IgG N-glycosylation for diagnosing LN in a sample of female SLE patients.

Methods

This case-control study recruited 188 women with SLE, including 94 patients with LN and 94 age-matched patients without LN. The profiles of plasma IgG N-glycans were detected by hydrophilic interaction chromatography with ultra-performance liquid chromatography (HILIC-UPLC). A multivariate logistic regression model was used to explore the associations between IgG N-glycans and LN. A diagnostic model was developed using the significant glycans as well as demographic factors. The performance of IgG N-glycans in the diagnosis of LN was evaluated by receiver operating characteristic (ROC) curve analysis, and the area under the curve (AUC) and its 95% confidence interval (CI) were calculated.

Results

There were significant differences in 9 initial glycans (GP2, GP4, GP6, GP8, GP10, GP14, GP16, GP18 and GP23) between women with SLE with and without LN (P < 0.05). The levels of sialylated, galactosylated and fucosylated glycans were significantly lower in the LN patients than in the control group, while bisected N-acetylglucosamine (GlcNAc) glycans were increased in LN patients (P < 0.05). GP8, GP10, GP18, and anemia were included in our diagnostic model, which performed well in differentiating female SLE patients with LN from those without LN (AUC = 0.792, 95% CI: 0.727 to 0.858).

Conclusion

Our findings indicate that decreased sialylation, galactosylation, and core fucosylation and increased bisecting GlcNAc might play a role in the development of LN by upregulating the proinflammatory response of IgG. IgG N-glycans can serve as potential biomarkers to differentiate individuals with LN among SLE patients.

Role of the transcription factor Fli-1 on the CXCL10/CXCR3 Axis

The transcription factor Fli-1, a member of the ETS family of transcription factors, is implicated in the pathogenesis of lupus disease. Reduced Fli-1 expression in lupus mice leads to decreased renal Cxcl10 mRNA levels and renal infiltrating CXCR3+ T cells that parallels reduced renal inflammatory cell infiltration and renal damage. Inflammatory chemokine CXCL10 is critical for attracting inflammatory cells expressing the chemokine receptor CXCR3. The CXCL10/CXCR3 axis plays a role in the pathogenesis of various inflammatory diseases including lupus. Our data here demonstrate that renal CXCL10 protein levels are significantly lower in Fli-1 heterozygous MRL/lpr mice compared to wild-type MRL/lpr mice. Knockdown of Fli-1 significantly reduced CXCL10 secretion in mouse and human endothelial cells, and human mesangial cells, upon LPS or TNFα stimulation. The Fli-1 inhibitor, Camptothecin, significantly reduced CXCL10 production in human monocyte cells upon interferon stimulation. Four putative Ets binding sites in the Cxcl10 promoter showed significant enrichment for FLI-1; however, FLI-1 did not directly drive transcription from the human or mouse promoters, suggesting FLI-1 may regulate CXCL10 expression indirectly. Our results also suggest that the DNA binding domain of FLI-1 is necessary for regulation of human hCXCR3 promotor activity in human T cells and interactions with co-activators. Together, these results support a role for FLI-1 in modulating the CXCL10-CXCR3 axis by directly or indirectly regulating the expression of both genes to impact lupus disease development. Signaling pathways or drugs that reduce FLI-1 expression may offer novel approaches to lupus treatment.

Decipher the Immunopathological Mechanisms and Set Up Potential Therapeutic Strategies for Patients with Lupus Nephritis

Lupus nephritis (LN) is one of the most severe complications in patients with systemic lupus erythematosus (SLE). Traditionally, LN is regarded as an immune complex (IC) deposition disease led by dsDNA-anti-dsDNA-complement interactions in the subendothelial and/or subepithelial basement membrane of glomeruli to cause inflammation. The activated complements in the IC act as chemoattractants to chemically attract both innate and adaptive immune cells to the kidney tissues, causing inflammatory reactions. However, recent investigations have unveiled that not only the infiltrating immune-related cells, but resident kidney cells, including glomerular mesangial cells, podocytes, macrophage-like cells, tubular epithelial cells and endothelial cells, may also actively participate in the inflammatory and immunological reactions in the kidney. Furthermore, the adaptive immune cells that are infiltrated are genetically restricted to autoimmune predilection. The autoantibodies commonly found in SLE, including anti-dsDNA, are cross-reacting with not only a broad spectrum of chromatin substances, but also extracellular matrix components, including α-actinin, annexin II, laminin, collagen III and IV, and heparan sulfate proteoglycan. Besides, the glycosylation on the Fab portion of IgG anti-dsDNA antibodies can also affect the pathogenic properties of the autoantibodies in that α-2,6-sialylation alleviates, whereas fucosylation aggravates their nephritogenic activity. Some of the coexisting autoantibodies, including anti-cardiolipin, anti-C1q, anti-ribosomal P autoantibodies, may also enhance the pathogenic role of anti-dsDNA antibodies. In clinical practice, the identification of useful biomarkers for diagnosing, monitoring, and following up on LN is quite important for its treatments. The development of a more specific therapeutic strategy to target the pathogenic factors of LN is also critical. We will discuss these issues in detail in the present article.

The Inflammatory Profile Orchestrated by Inducible Nitric Oxide Synthase in Systemic Lupus Erythematosus

(1) Background: The pathogenesis of systemic lupus erythematosus (SLE) involves complicated and multifactorial interactions. Inducible nitric oxide synthase overactivation (iNOS or NOS2) could be involved in SLE pathogenesis and progression. This study explored the relationship between NOS2-associated inflammation profiles and SLE phenotypes. (2) Methods: We developed a prospective, case control study that included a group of 86 SLE subjects, a group of 73 subjects with lupus nephritis, and a control group of 60 people. Laboratory determinations included serum C reactive protein (CRP-mg/L), enzymatic activity of NOS2 (U/L), serum levels of inducible factors of hypoxia 1 and 2 (HIF1a-ng/mL, HIF2a-ng/mL), vascular endothelial growth factor VEGF (pg/mL), matrix metalloproteinases 2 and 9 (MMP-2, MMP-9-ng/mL), thrombospondin 1 (TSP-1-ng/mL), and soluble receptor of VEGF (sVEGFR-ng/mL). (3) Results: CRP, NOS2, HIF-1a, HIF-2a, VEGF, MMP-2, and MMP-9 were significantly increased, while TSP-1 and sVEGFR were decreased in the SLE and lupus nephritis groups compared with the control group. The variations in these biomarkers were strongly associated with the decrease in eGFR and increase in albuminuria. (4) Conclusions: The inflammatory phenotype of SLE patients, with or without LN, is defined by NOS2 and hypoxia over-expression, angiogenesis stimulation, and inactivation of factors that induce resolution of inflammation in relation with eGFR decline.

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.

Abnormalities of T cells in systemic lupus erythematosus: new insights in pathogenesis and therapeutic strategies

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by loss of immune tolerance and sustained production of autoantibodies. Multiple and profound T cell abnormalities in SLE are intertwined with disease expression. Both numerical and functional disturbances have been reported in main CD4⁺ T helper cell subsets including Th1, Th2, Th17, regulatory, and follicular helper cells. SLE CD4⁺ T cells are known to provide help to B cells, produce excessive IL-17 but insufficient IL-2, and infiltrate tissues. In the absence of sufficient amounts of IL-2, regulatory T cells, do not function properly to constrain inflammation. A complicated series of early signaling defects and aberrant activation of kinases and phosphatases result in complex cell phenotypes by altering the metabolic profile and the epigenetic landscape. All main metabolic pathways including glycolysis, glutaminolysis and oxidative phosphorylation are altered in T cells from lupus prone mice and patients with SLE. SLE CD8⁺ cytotoxic T cells display reduced cytolytic activity which accounts for higher rates of infection and the sustenance of autoimmunity. Further, CD8⁺ T cells in the context of rheumatic diseases lose the expression of CD8, acquire IL-17⁺CD4^-CD8^- double negative T (DNT) cell phenotype and infiltrate tissues. Herein we present an update on these T cell abnormalities along with underlying mechanisms and discuss how these advances can be exploited therapeutically. Novel strategies to correct these aberrations in T cells show promise for SLE treatment.