Proteomic profiling of urine: implications for 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.

Identification of pattern recognition receptor genes in peripheral blood mononuclear cells and monocytes as biomarkers for the diagnosis of lupus nephritis

BACKGROUND

The study aimed to investigate the diagnostic value of lupus-related pattern recognition receptors (PRRs) genes in peripheral blood mononuclear cells (PBMCs) and monocytes (MONs) for lupus nephritis (LN).

METHODS

PBMCs were isolated from a cohort with 37 LN patients and 39 healthy controls (HCs), and MONs were derived from another cohort with 70 LN patients and 66 HCs. Q-PCR was used to measure the mRNA levels of CGAS, IFNB1, AIM2, IL1Β, NLRC4, NLRP3, NLRP12 and ZBP1 in the PBMCs and MONs. The Mann-Whitney U test was used to compare the data in LN patients and HCs. Eleven GEO datasets of SLE/LN were used to perform differentially expressed genes (DEGs) analysis to these PRR genes. Receiver operating characteristic (ROC) curve analysis was employed to assess the performance of individual genes or the disease prediction model established by combining multiple genes in LN diagnosis. Spearman correlation method was done to analyze the correlation between these PRRs and other clinical characteristics.

RESULTS

The mRNA levels of five genes (AIM2, NLRC4, IL1B, NLRP12 and ZBP1) in PBMCs, and seven genes (CGAS, IFNB1, AIM2, IL1B, NLRP3, NLRP12 and ZBP1) in MONs of LN patients were significantly higher than those of HCs (P < 0.05). DEGs analysis based on the GEO datasets showed that ZBP1, AIM2 and IL1B were significantly increased in several datasets. The ROC curve analysis indicated that the area under curve (AUC) of the LN prediction models derived from PBMCs or MONs were 0.82 or 0.91 respectively. In addition, the expression levels of these PRRs were correlated with other clinical features in LN patients, including Anti-Sm, ESR, serum Cr, and C3.

CONCLUSION

Our study suggests that these lupus-related PRRs might be served as potential biomarkers of LN.

Urinary biomarkers associated with podocyte injury in lupus nephritis

The most prevalent and devastating form of organ damage in systemic lupus erythematosus (SLE) is lupus nephritis (LN). LN is characterized by glomerular injury, inflammation, cell proliferation, and necrosis, leading to podocyte injury and tubular epithelial cell damage. Assays for urine biomarkers have demonstrated significant promise in the early detection of LN, evaluation of disease activity, and tracking of reaction to therapy. This is because they are non-invasive, allow for frequent monitoring and easy self-collection, transport and storage. Podocyte injury is believed to be a essential factor in LN. The extent and type of podocyte injury could be connected to the severity of proteinuria, making podocyte-derived cellular debris and injury-related urinary proteins potential markers for the diagnosis and monitoring of LN. This article focuses on studies examining urinary biomarkers associated with podocyte injury in LN, offering fresh perspectives on the application of biomarkers in the early detection and management of LN.

Urine SERPINC1/ORM1 as biomarkers for early detection of lupus nephritis in MRL-lpr mice

Background

To evaluate the usefulness of urine SERPINC1 and ORM1 as biomarkers for early detection of lupus nephritis (LN).

Methods

Using proteomics, we screened for potential urine biomarkers that differentiate LN from systemic lupus erythematosus (SLE) patients without nephritis. In addition, urine levels of target biomarkers were measured by ELISA in 13- and 23-week-old MRL-lpr (murine model for LN) and MRL/MpJ mice. Histological analysis was also performed on the kidneys of 23-week-old mice.

Results

Urine SERPINC1 and ORM1 were elevated in SLE patients with newly diagnosed LN compared with SLE patients without LN (SERPINC1, AUC=.892, P<.001; ORM1, AUC=.886, P<.001). Levels of urine SERPINC1 and ORM1 were also significantly higher in MRL-lpr mice than in MRL/MpJ mice at 13 and 23 weeks (SERPINC1: p<.01 and p<.001 at 13 and 23 weeks, respectively; ORM1: p<.01 at 13 and 23 weeks). In contrast, a significant difference in urine albumin between the two groups was only observed at 23 weeks (p<.001) not at 13 weeks (p=.83). Regarding the kidney pathology of MPL-lpr mice, urine ORM1 and urine albumin, but not urine SERPINC1, were positively correlated with the activity index (ORM1, rho =.879, p<.001; albumin, rho =.807, p=.003) and chronicity index (ORM1, rho =.947, p<.001; albumin, rho =.869, p<.001).

Conclusion

We propose that urine SERPINC1 and ORM1 are novel biomarkers for early LN.

Elevated serum levels of human epididymis protein 4 in adult patients with proliferative lupus nephritis

Background

This study aimed to access whether serum human epididymis protein 4 (HE4) level could identify lupus nephritis (LN) pathological classes in adults and children.

Methods

The serum HE4 levels of 190 healthy subjects and 182 patients with systemic lupus erythematosus (SLE) (61 adult-onset LN [aLN], 39 childhood-onset LN [cLN], and 82 SLE without LN) were determined using Architect HE4 kits and an Abbott ARCHITECT i2000SR Immunoassay Analyzer.

Results

Serum HE4 level was significantly higher in the aLN patients (median, 85.5 pmol/L) than in the patients with cLN (44 pmol/L, P < 0.001) or SLE without LN (37 pmol/L, P < 0.001), or the healthy controls (30 pmol/L, P < 0.001). Multivariate analysis showed that serum HE4 level was independently associated with aLN. Stratified by LN class, serum HE4 level was significantly higher in the patients with proliferative LN (PLN) than in those with non-PLN, and this difference was found only in aLN (median, 98.3 versus 49.3 pmol/L, P = 0.021) but not in cLN. Stratified by activity (A) and chronicity (C) indices, the aLN patients with class IV (A/C) possessed significantly higher serum HE4 levels than those with class IV (A) (median, 195.5 versus 60.8 pmol/L, P = 0.006), and this difference was not seen in the class III aLN or cLN patients.

Conclusion

Serum HE4 level is elevated in patients with class IV (A/C) aLN. The role of HE4 in the pathogenesis of chronic lesions of class IV aLN needs further investigation.

Triglycerides as Biomarker for Predicting Systemic Lupus Erythematosus Related Kidney Injury of Negative Proteinuria

Fewer biomarkers can be used to predict systemic lupus erythematosus (SLE) related kidney injury. This paper presents an apriori algorithm of association rules to mine the predictive biomarkers for SLE-related kidney injury of negative proteinuria. An apriori algorithm of association rules was employed to identify biomarkers, and logistic regression analysis and spearman correlation analysis were used to evaluate the correlation between triglycerides and SLE-related kidney injury of negative proteinuria. Triglycerides were mined out by the apriori algorithm of association rules. The level of triglycerides was significantly higher, and it was an independent risk factor for SLE-related kidney injury. In the high-triglycerides group, the number of patients with SLE-related kidney injury, SLEDAI-2K, urine P-CAST, the level of blood urea nitrogen, serum creatinine, and proteinuria were increased. Triglycerides level was positively correlated with proteinuria and P-CAST and negatively correlated with albumin and IgG. The area under the ROC curve of triglycerides and triglycerides combined proteinuria was 0.72 and 0.82, respectively. Significantly, 50% of SLE-related kidney injuries of negative proteinuria could be identified by high triglycerides levels. High triglycerides level was found at the time of onset of kidney injury, and it was opposite to glomerular filtration rate. Triglycerides may be a potential marker for predicting SLE-related kidney injury, especially in SLE-related kidney injury of negative proteinuria. Triglycerides combined proteinuria could predict SLE-related kidney injury effectively.

Discovery of NEU1 as a candidatedone. renal biomarker for proliferative lupus nephritis chronicity

OBJECTIVE

Proteomic approach was applied to identify candidate biomarkers of chronicity in patients with proliferative lupus nephritis (LN), and their clinicopathological significance and prognostic values were investigated.

METHODS

This study recruited 10 patients with proliferative LN and 6 normal controls (NCs) with proteomic data to compare protein expression profiles, 58 patients with proliferative LN and 10 NCs to verify proteomic data by immunohistochemistry, and 14 patients with proliferative LN with urine samples to evaluate the urinary expression of the biomarker by western blot assay. The composite endpoints included end-stage renal disease and ≥50% reduction from baseline estimated glomerular filtration rate (eGFR).

RESULTS

Proteomics detected 48 proteins upregulated in the group with chronicity index (CI) ≥1 compared with the CI=0 and NC groups. Further pathway analysis was enriched in 'other glycan degradation'. Neuraminidase 1 (NEU1), the most predominant protein in the pathway of other glycan degradation, was highly expressed in the kidney of patients with proliferative LN and could co-localise with podocyte, mesangial cells, endothelial cells and tubule cells. NEU1 expression in the tubulointerstitium area was significantly higher in the CI ≥1 group compared with the CI=0 and NC groups. Moreover, NEU1 expression was significantly correlated with serum creatinine value, eGFR and CI scores, respectively. Urinary NEU1 excretion in the CI ≥1 group was higher than in the CI=0 group and was also positively correlated with CI scores. Furthermore, the high expression of renal NEU1 was identified as an independent risk factor for renal prognosis by multivariate Cox regression analysis (HR, 6.462 (95% CI 1.025 to 40.732), p=0.047).

CONCLUSIONS

Renal NEU1 expression was associated with pathological CI scores and renal outcomes in patients with proliferative LN.

Psoriasis to Psoriatic Arthritis: The Application of Proteomics Technologies

Psoriatic disease (PsD) is a spectrum of diseases that affect both skin [cutaneous psoriasis (PsC)] and musculoskeletal features [psoriatic arthritis (PsA)]. A considerable number of patients with PsC have asymptomatic synovio-entheseal inflammations, and approximately one-third of those eventually progress to PsA with an enigmatic mechanism. Published studies have shown that early interventions to the very early-stage PsA would effectively prevent substantial bone destructions or deformities, suggesting an unmet goal for exploring early PsA biomarkers. The emergence of proteomics technologies brings a complete view of all involved proteins in PsA transitions, offers a unique chance to map all potential peptides, and allows a direct head-to-head comparison of interaction pathways in PsC and PsA. This review summarized the latest development of proteomics technologies, highlighted its application in PsA biomarker discovery, and discussed the possible clinical detectable PsA risk factors in patients with PsC.

Association Between Hypoalbuminemia, Degree of Proteinuria, and Lupus Nephritis Class: A Single-Center Cross-sectional Biopsy Study

Background: The current study intended to determine whether serum albumin level and urine protein/creatinine rate (uPCR) are appropriate predictors of severe lupus nephritis in childhood-onset SLE. Objectives: Following a cross-sectional single-center design, 85 LN children referred to the National Children Hospital, Ha Noi, Viet Nam, from 6/2019 to 6/2020 were recruited. Renal biopsy was performed for all participants. Methods: Following a cross-sectional single-center design, 85 LN children referred to the National Children Hospital, Ha Noi, Viet Nam, from 6/2019 to 6/2020 were recruited. Renal biopsy was performed for all participants. Results: The mean SLEDAI score of all patients was 14.69. The proportion of patients with high and very high SLEDAI was 61.2 and 17.6%, respectively. The mean concentration of serum albumin was 28.55 g/L, and the proportion of decreased albumin concentration was 55.3%. The median uPCR was 446.6 mg/mmol in which 76.5% of values were ≥ 200 mg/mmol. Pathological morphology of LN class from I to VI was observed in 0%, 17.6%, 37.6 %, 37.6%, 7.1%, and 0%, respectively. Serum albumin level and uPCR presented the predictive value for severe and active LN (class IV and V); (AUC: 0.725 P < 0.001 for both). Conclusions: Serum albumin and uPCR were appropriate predictors for severe and active LN in Vietnamese children.

Urinary proteomics for kidney dysfunction: insights and trends

Introduction: Kidney dysfunction poses a high burden on patients and health care systems. Early detection and accurate prediction of kidney disease progression remains a major challenge. Compared to existing clinical parameters, urinary proteomics has the potential to reveal molecular alterations within the kidney that may alter its function before the onset of clinical symptoms. Thus, urinary proteomics has greater prognostic potential for assessment of kidney dysfunction progression.Areas covered: Advances in urinary proteomics for major causes of kidney dysfunction are discussed. The application of urinary extracellular vesicles for studying kidney dysfunction are discussed. Technological advances in urinary proteomics are discussed. The literature was identified using a database search for titles containing 'proteom*' and 'urin*' and published within the past 5 years. Retrieved literature was manually filtered to retain kidney dysfunctions-related studies.Expert opinion: Despite major advances, diagnosis by urinary proteomics has not been fully applied in any clinical settings. This could be attributed to the complex nature of kidney diseases, in addition to the constraints on study power and feasibility of incorporating mass spectrometry techniques in daily routine analysis. Nevertheless, we are confident that advances in urinary proteomics will soon provide superior insights into kidney disease beyond existing clinical parameters.

Targeting Canonical and Non-Canonical STAT Signaling Pathways in Renal Diseases

Signal transducer and activator of transcription (STAT) plays an essential role in the inflammatory reaction and immune response of numerous renal diseases. STATs can transmit the signals of cytokines, chemokines, and growth factors from the cell membrane to the nucleus. In the canonical STAT signaling pathways, upon binding with their cognate receptors, cytokines lead to a caspase of Janus kinases (JAKs) and STATs tyrosine phosphorylation and activation. Besides receptor-associated tyrosine kinases JAKs, receptors with intrinsic tyrosine kinase activities, G-protein coupled receptors, and non-receptor tyrosine kinases can also activate STATs through tyrosine phosphorylation or, alternatively, other post-translational modifications. Activated STATs translocate into the nucleus and mediate the transcription of specific genes, thus mediating the progression of various renal diseases. Non-canonical STAT pathways consist of preassembled receptor complexes, preformed STAT dimers, unphosphorylated STATs (U-STATs), and non-canonical functions including mitochondria modulation, microtubule regulation and heterochromatin stabilization. Most studies targeting STAT signaling pathways have focused on canonical pathways, but research extending into non-canonical STAT pathways would provide novel strategies for treating renal diseases. In this review, we will introduce both canonical and non-canonical STAT pathways and their roles in a variety of renal diseases.

Hsa_circ_0123190 acts as a competitive endogenous RNA to regulate APLNR expression by sponging hsa-miR-483-3p in lupus nephritis

Background

Lupus nephritis (LN) is one of the most severe complications of systemic lupus erythematosus (SLE). Circular RNAs (circRNAs) can act as competitive endogenous RNAs (ceRNAs) to regulate gene transcription, which is involved in mechanism of many diseases. However, the role of circRNA in lupus nephritis has been rarely reported. In this study, we aim to investigate the clinical value of circRNAs and explore the mechanism of circRNA involvement in the pathogenesis of LN.

Methods

Renal tissues from three untreated LN patients and three normal controls (NCs) were used to identify differently expressed circRNAs by next-generation sequencing (NGS). Validated assays were used by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The interactions between circRNA and miRNA, or miRNA and mRNA were further determined by luciferase reporter assay. The extent of renal fibrosis between the two groups was assessed by Masson-trichome staining and immunohistochemistry (IHC) staining.

Results

159 circRNAs were significantly dysregulated in LN patients compared with NCs. The expression of hsa_circ_0123190 was significantly decreased in the renal tissues of patients with LN (P = 0.014). Bio-informatics analysis and luciferase reporter assay illustrated that hsa_circ_0123190 can act as a sponge for hsa-miR-483-3p, which was also validated to interact with APLNR. APLNR mRNA expression was related with chronicity index (CI) of LN (P = 0.033, R² = 0.452). Moreover, the fibrotic-related protein, transforming growth factor-β1 (TGF-β1), which was regulated by APLNR, was more pronounced in the LN group (P = 0.018).

Conclusion

Hsa_circ_0123190 may function as a ceRNA to regulate APLNR expression by sponging hsa-miR-483-3p in LN.

Identification of Molecular Markers Associated With the Pathophysiology and Treatment of Lupus Nephritis Based on Integrated Transcriptome Analysis

Lupus nephritis (LN) is a well-known complication of systemic lupus erythematosus and is its leading cause of morbidity and mortality. Our study aimed to identify the molecular markers associated with the pathophysiology and treatment of LN. The renal tissue gene expression profiles of LN patients in the GSE32591 dataset were downloaded as a discovery cohort from the Gene Expression Omnibus. Differentially expressed genes (DEGs) were identified; weighted gene co-expression network analysis (WGCNA) was used to identify the co-expression modules of DEGs; and gene function enrichment analysis, molecular crosstalk analysis, and immune cell infiltration analysis were performed to explore the pathophysiological changes in glomeruli and tubulointerstitia of LN patients. The crosstalk genes were validated in another RNA-sequencing cohort. DEGs common in RNA-sequencing dataset and GSE32591 were uploaded to the Connectivity Map (CMap) database to find prospective LN-related drugs. Molecular docking was used to verify the targeting association between candidate small molecular compounds and the potential target. In all, 420 DEGs were identified; five modules and two modules associated with LN were extracted in glomeruli and tubulointerstitia, respectively. Functional enrichment analysis showed that type I interferon (IFN) response was highly active, and some biological processes such as metabolism, detoxification, and ion transport were impaired in LN. Gene transcription in glomeruli and tubulointerstitia might affect each other, and some crosstalk genes, such as IRF7, HLA-DRA, ISG15, PSMB8, and IFITM3, play important roles in this process. Immune cell infiltration analysis revealed that monocytes and macrophages were increased in glomeruli and tubulointerstitia, respectively. CMap analysis identified proscillaridin as a possible drug to treat LN. Molecular docking showed proscillaridin forms four hydrogen bonds with the SH2 domain of signal transducer and activator of transcription 1 (STAT1). The findings of our study may shed light on the pathophysiology of LN and provide potential therapeutic targets for LN.

Systemic lupus erythematosus: The search for the ideal biomarker

During the last decades, there has been an increased interest in the discovery and validation of biomarkers that reliably reflect specific aspects of lupus. Although many biomarkers have been developed, few of them have been validated and used in clinical practice, but with unsatisfactory performances. Thus, there is still a need to rigorously validate many of these novel promising biomarkers in large-scale longitudinal studies and also identify better biomarkers not only for lupus diagnosis but also for monitoring and predicting upcoming flares and response to treatment. Besides serological biomarkers, urinary and cerebrospinal fluid biomarkers have emerged for assessing both renal and central nervous system involvement in systemic lupus erythematosus, respectively. Also, novel omics techniques help us to understand the molecular basis of the disease and also allow the identification of novel biomarkers which may be potentially useful for guiding new therapeutic targets.

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.

Design and application of single-cell RNA sequencing to study kidney immune cells in lupus nephritis

The immune mechanisms that cause tissue injury in lupus nephritis have been challenging to define. The advent of high-dimensional cellular analyses, such as single-cell RNA sequencing, has enabled detailed characterization of the cell populations present in small biopsy samples of kidney tissue. In parallel, the development of methods that cryopreserve kidney biopsy specimens in a manner that preserves intact, viable cells, has enabled the uniform analysis of tissue samples collected at multiple sites and across many geographic areas and demographic cohorts with high-dimensional platforms. The application of these methods to kidney biopsy samples from patients with lupus nephritis has begun to define the phenotypes of both infiltrating and resident immune cells, as well as parenchymal cells, present in nephritic kidneys. The detection of similar immune cell populations in urine suggests that it might be possible to non-invasively monitor immune activation in kidneys. Once applied to large patient cohorts, these high-dimensional studies might enable patient stratification according to patterns of immune cell activation in the kidney or identify disease features that can be used as surrogate measures of efficacy in clinical trials. Applied broadly across multiple inflammatory kidney diseases, these studies promise to enormously expand our understanding of renal inflammation in the next decade.