Renal Fibrosis in Lupus Nephritis

Urinary Biomarkers for Lupus Nephritis: A Systems Biology Approach

Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disorder. Kidney involvement, termed lupus nephritis (LN), is seen in 40-60% of patients with systemic lupus erythematosus (SLE). After the diagnosis, serial measurement of proteinuria is the most common method of monitoring treatment response and progression. However, present treatments for LN-corticosteroids and immunosuppressants-target inflammation, not proteinuria. Furthermore, subclinical renal inflammation can persist despite improving proteinuria. Serial kidney biopsies-the gold standard for disease monitoring-are also not feasible due to their inherent risk of complications. Biomarkers that reflect the underlying renal inflammatory process and better predict LN progression and treatment response are urgently needed. Urinary biomarkers are particularly relevant as they can be measured non-invasively and may better reflect the compartmentalized renal response in LN, unlike serum studies that are non-specific to the kidney. The past decade has overseen a boom in applying cutting-edge technologies to dissect the pathogenesis of diseases at the molecular and cellular levels. Using these technologies in LN is beginning to reveal novel disease biomarkers and therapeutic targets for LN, potentially improving patient outcomes if successfully translated to clinical practice.

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.

Factors Associated with Worsening Interstitial Fibrosis/Tubular Atrophy in Lupus Nephritis Patients Undergoing Repeat Kidney Biopsy

Background

Lupus nephritis (LN) is one of the most severe manifestations of systemic lupus erythematosus (SLE). Interstitial fibrosis/tubular atrophy (IFTA) on kidney biopsies strongly predicts progression to end-stage renal disease. However, factors associated with progression of IFTA are not known. The objective of this study was to evaluate the demographic, clinical, and histopathological factors at the time of index kidney biopsies that are associated with worsening IFTA on repeat biopsies.

Methods

Patients with LN Class I to V or mixed LN on index biopsies who underwent a clinically indicated repeat biopsy between 2004 and 2020 were identified. None-mild IFTA was defined as < 25% acreage of the interstitium affected by fibrosis and atrophy, and moderate-severe IFTA was defined as ≥ 25% of the interstitium affected. Patients with none-mild IFTA on index biopsies who progressed to moderate-severe IFTA on repeat biopsies were defined as progressors. Patients with none-mild IFTA on both biopsies were defined as non-progressors.

Results

Seventy-two patients who underwent clinically indicated repeat kidney biopsies were included, and 35 (49%) were identified as progressors. Compared to non-progressors, progressors had a higher proportion of proliferative LN (20 [57%] vs. 6 [17%], p = 0.002) and crescents (9 [26%] vs. 3 [8%], p = 0.045) on index biopsies. There was no difference regarding the time to repeat biopsy or the baseline characteristics, including eGFR, presence of hypertension and diabetes, urine protein to creatinine ratio, or the initial treatments.

Conclusions

Proliferative LN and the presence of crescents on index biopsies were associated with subsequent IFTA progression on repeat biopsies. This association indicates that glomerular damage is one of the major drivers of tubulointerstitial scarring in SLE. IFTA progression may, in turn, be the driving factor of poor treatment response and progression to chronic kidney disease.

Association of serum Nrf2 protein levels with disease activity and renal impairment in lupus nephritis

Introduction

We aimed to investigate the relationship between nuclear factor erythroid 2-related factor 2 (Nrf2) protein expression levels, lupus nephritis (LN) disease activity, and the degree of renal injury (based on the estimated glomerular filtration rate [eGFR]) in patients with LN.

Methods

We selected 40 healthy control participants and 102 patients with LN who were treated in the Second Hospital of Jilin University, China, for inclusion in this study. Patients with LN were classified into LN with high-eGFR and LN with low-eGFR groups. Nrf2 protein levels were measured in the serum and renal tissues of the participants in both groups to assess the correlation between Nrf2 protein levels and different LN disease states.

Results

There was a significantly positive correlation between serum Nrf2 protein levels, the degree of renal injury, and systemic lupus erythematosus disease activity index (SLEDAI) scores in patients with LN. Nrf2 protein levels were higher in the LN with high-eGFR group than in the healthy control and LN with low-eGFR groups. In follow-up patients in the LN high eGFR group, Nrf2 protein levels decreased significantly after remission of disease activity.

Conclusion

Nrf2 protein expression has a dual role in patients with LN. Nrf2 protein levels not only correlate with disease activity in patients with LN, but also with the degree of kidney injury. Before implementing targeted therapy for Nrf2, evaluating both Nrf2 protein expression and the disease state in patients with LN is necessary to better identify and place each patient in an appropriate patient group.

Transcription Factors in the Pathogenesis of Lupus Nephritis and Their Targeted Therapy

Systemic lupus erythematosus (SLE) is a prototype inflammatory autoimmune disease, characterized by breakdown of immunotolerance to self-antigens. Renal involvement, known as lupus nephritis (LN), is one of the leading causes of morbidity and a significant contributor to mortality in SLE. Despite current pathophysiological advances, further studies are needed to fully understand complex mechanisms underlying the development and progression of LN. Transcription factors (TFs) are proteins that regulate the expression of genes and play a crucial role in the development and progression of LN. The mechanisms of TF promoting or inhibiting gene expression are complex, and studies have just begun to reveal the pathological roles of TFs in LN. Understanding TFs in the pathogenesis of LN can provide valuable insights into this disease's mechanisms and potentially lead to the development of targeted therapies for its management. This review will focus on recent findings on TFs in the pathogenesis of LN and newly developed TF-targeted therapy in renal inflammation.

Cordyceps cicadae ameliorates inflammatory responses, oxidative stress, and fibrosis by targeting the PI3K/mTOR-mediated autophagy pathway in the renal of MRL/lpr mice

BACKGROUND

The vast majority of systemic lupus erythematosus patients develop lupus nephritis (LN) with severe renal manifestations, such as inflammatory responses, oxidative stress, and fibrosis. The purpose of this research was to investigate Cordyceps cicadae as a potential therapeutic target for treating inflammatory responses, oxidative stress, and fibrosis in LN.

METHODS

The effects of C. cicadae on lupus symptoms in mice with LN were determined. MRL/lpr mice were treated with C. cicadae (4 g/kg/day, i.e., CC group, n = 8) or an equal volume of saline (model group, n = 8), and MRL/MP mice were treated with an equal volume of saline (control group, n = 8). Renal function indices, renal pathology, inflammatory markers, oxidative stress markers, and renal interstitial fibrosis levels were evaluated after C. cicadae treatment. Western blot analysis was performed to investigate the effect of C. cicadae on the expression of fibrosis biomarkers and the phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR)-mediated autophagy pathway in the renal tissues of mice.

RESULTS

C. cicadae ameliorated renal lesions, the inflammatory response, and oxidative stress damage in MRL/lpr mice. C. cicadae treatment inhibited renal fibrosis (16.31 ± 4.16 vs. 31.25 ± 5.61) and downregulated the expression of the fibrosis biomarkers alpha-smooth muscle actin, fibronectin, and collagen I (COL I) in the kidneys of MRL/lpr mice. In addition, further research showed that the PI3K/mTOR-mediated autophagy pathway was involved in C. cicadae-mediated effects on renal fibrosis in MRL/lpr mice. Furthermore, the therapeutic effect of C. cicadae on repairing renal fibrosis and damage in MRL/lpr mice was abolished by the PI3K agonist 740 Y-P.

CONCLUSIONS

The findings of the present research showed that C. cicadae could alleviate inflammatory responses, oxidative stress, and fibrosis in the renal tissues of mice with LN by targeting the PI3K/mTOR-mediated autophagy pathway.

Phosphorylated vimentin at Ser72 is associated with epithelial-mesenchymal transition in lupus nephritis

OBJECTIVES

To measure the expression of vimentin and its phosphorylated forms in lupus nephritis (LN) and explore their potential role in LN development.

METHODS

Lupus renal biopsies from LN patients and normal renal biopsies from kidney transplant donors were collected. The expression of vimentin and its phosphorylated forms (p-vimentin (Ser39, Ser56, Ser72, Ser83, and Tyr117)) were measured by Western blots and immunohistochemistry. To construct stable cell line that overexpress vimentin and its phosphorylated forms, an immortalized proximal tubule epithelial cell line (HK-2 cells) was utilized. The roles of vimentin and its phosphorylated forms on the migration of HK-2 cells were examined by transwell migration assay and wound healing analysis.

RESULTS

We first observed a significant upregulation of vimentin protein in TGFβ1-induced HK-2 cells. This finding was further confirmed in renal tissues obtained from LN patients and animal model. Interestingly, among the five phosphorylated forms of vimentin, only vimentin phosphorylated at Ser72 was upregulated in LN. Through the establishment of stable vimentin and its phosphorylated forms overexpression in HK-2 cells, we found that the overexpression of vimentin and its phosphorylated forms at Ser72 significantly enhances the cell migration.

CONCLUSIONS

Vimentin phosphorylated on Ser72 is important for renal epithelial cell migration, which would enhance the progression of vimentin-induced epithelial-mesenchymal transition during LN development.

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.

Pharmacokinetic-pharmacodynamic modeling of the active components of Shenkang injection in rats with chronic renal failure and its protective effect on damaged renal cells

The study aimed to explore the pharmacokinetic and pharmacodynamic alterations of the active components of Shenkang injection (i.e. hydroxy saffron yellow pigment A [HSYA], tanshinol, rheum emodin, and astragaloside IV) in rats with chronic renal failure (CRF), and establish a pharmacokinetic-pharmacodynamic model (PK-PD model) in order to provide a scientific and theoretical basis for the rational clinical use of Shenkang injection. Sprague-Dawley (SD) rats were randomly divided into a normal group, model group, and Shenkang injection group. A rat model of CRF was induced by adenine gavage and then followed by drug administration via tail vein injection. Orbital blood was collected at different timepoints and the blood concentrations of the four active components were measured by UHPLC-Q-Orbitrap HRMS. Serum levels of creatinine (Scr), urea nitrogen (BUN), and uric acid (UA) were determined using an automatic biochemical analyzer. A PK-PD model was established, and DAS 3.2.6 software was used for model fitting as well as statistical analysis. TGF-β1 was utilized to induce normal rat kidney cells to construct a renal fibrosis model to investigate the protective effect of the pharmacological components on renal fibrosis. The pharmacokinetic analysis of hydroxy saffron yellow pigment A, tanshinol, rheum emodin, and astragaloside IV based on UHPLC-Q-Orbitrap HRMS was stable. The linear regression equations for the four active components were as follows: Y = 0.031X + 0.0091 (R2  = 0.9986) for hydroxy saffron yellow pigment A, Y = 0.0389X + 0.164 (R2  = 0.9979) for tanshinol, Y = 0.0257X + 0.0146 (R2  = 0.9973) for rheum emodin, and Y = 0.0763X + 0.0139 (R2  = 0.9993) for astragaloside IV, which indicated good linear relationships. The methodological investigation was stable, with the interday and intraday precision RSD <10%. Meanwhile, the recoveries ranged between 90% and 120%, in accordance with the requirements for in vivo analysis of drugs. Compared with the model group, the levels of Scr, BUN, and UA were significantly decreased after 20 min in the Shenkang injection group (p < 0.01). The PK-PD model showed that the four active components in the Shenkang injection group could fit well with the three effect measures (i.e. Scr, BUN, and UA), with the measured values similar to the predicted values. The cell model of renal fibrosis showed that the connective tissue growth factor and FN1 protein expression levels were significantly lower in the Shenkang injection group than those in the model group, and the cell fibrosis was improved. The established method for in vivo analysis of Shenkang injection was highly specific, with good separation of the components and simple operation. The total statistical moment could well integrate the pharmacokinetic parameters of the four active components. After treatment with Shenkang injection, all indexes in the administered group improved and showed significant inhibition of renal cell fibrosis in vitro. This study could provide scientific reference ideas for the clinical rational use of traditional Chinese medicine.

Research progress in functional magnetic resonance imaging assessment of lupus nephritis kidney injury

Lupus nephritis is one of the most common and severe complications of systemic lupus erythematosus and is also a major predictor of poor prognosis and mortality. Lupus nephritis has the characteristics of insidious onset, complex pathological types, rapid progression of organ damage, and easy recurrence. Currently, kidney damage in lupus nephritis is usually assessed based on urine analysis, renal biopsy, and glomerular filtration rates. However, they all have certain limitations, making it difficult to diagnose lupus nephritis early and assess its severity and progression. With the rapid development of functional magnetic resonance, multiple functional imaging techniques are expected to provide more useful information for the pathophysiological development, early diagnosis, progression, prognosis, and renal function evaluation of lupus nephritis. This article reviews the principle of multiple functional magnetic resonance imaging and the research status of evaluating renal function in lupus nephritis.

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.

Immune and Non-Immune Inflammatory Cells Involved in Autoimmune Fibrosis: New Discoveries

Fibrosis is an important health problem and its pathogenetic activation is still largely unknown. It can develop either spontaneously or, more frequently, as a consequence of various underlying diseases, such as chronic inflammatory autoimmune diseases. Fibrotic tissue is always characterized by mononuclear immune cells infiltration. The cytokine profile of these cells shows clear proinflammatory and profibrotic characteristics. Furthermore, the production of inflammatory mediators by non-immune cells, in response to several stimuli, can be involved in the fibrotic process. It is now established that defects in the abilities of non-immune cells to mediate immune regulation may be involved in the pathogenicity of a series of inflammatory diseases. The convergence of several, not yet well identified, factors results in the aberrant activation of non-immune cells, such as epithelial cells, endothelial cells, and fibroblasts, that, by producing pro-inflammatory molecules, exacerbate the inflammatory condition leading to the excessive and chaotic secretion of extracellular matrix proteins. However, the precise cellular mechanisms involved in this process have not yet been fully elucidated. In this review, we explore the latest discoveries on the mechanisms that initiate and perpetuate the vicious circle of abnormal communications between immune and non-immune cells, responsible for fibrotic evolution of inflammatory autoimmune diseases.

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.

Towards a Unified Approach in Autoimmune Fibrotic Signalling Pathways

Autoimmunity is a chronic process resulting in inflammation, tissue damage, and subsequent tissue remodelling and organ fibrosis. In contrast to acute inflammatory reactions, pathogenic fibrosis typically results from the chronic inflammatory reactions characterizing autoimmune diseases. Despite having obvious aetiological and clinical outcome distinctions, most chronic autoimmune fibrotic disorders have in common a persistent and sustained production of growth factors, proteolytic enzymes, angiogenic factors, and fibrogenic cytokines, which together stimulate the deposition of connective tissue elements or epithelial to mesenchymal transformation (EMT) that progressively remodels and destroys normal tissue architecture leading to organ failure. Despite its enormous impact on human health, there are currently no approved treatments that directly target the molecular mechanisms of fibrosis. The primary goal of this review is to discuss the most recent identified mechanisms of chronic autoimmune diseases characterized by a fibrotic evolution with the aim to identify possible common and unique mechanisms of fibrogenesis that might be exploited in the development of effective antifibrotic therapies.