Early prediction of IgA nephropathy progression: Proteinuria and AOPP are strong prognostic markers

Post-translational modifications in kidney diseases and associated cardiovascular risk

Patients with chronic kidney disease (CKD) are at an increased cardiovascular risk compared with the general population, which is driven, at least in part, by mechanisms that are uniquely associated with kidney disease. In CKD, increased levels of oxidative stress and uraemic retention solutes, including urea and advanced glycation end products, enhance non-enzymatic post-translational modification events, such as protein oxidation, glycation, carbamylation and guanidinylation. Alterations in enzymatic post-translational modifications such as glycosylation, ubiquitination, acetylation and methylation are also detected in CKD. Post-translational modifications can alter the structure and function of proteins and lipoprotein particles, thereby affecting cellular processes. In CKD, evidence suggests that post-translationally modified proteins can contribute to inflammation, oxidative stress and fibrosis, and induce vascular damage or prothrombotic effects, which might contribute to CKD progression and/or increase cardiovascular risk in patients with CKD. Consequently, post-translational protein modifications prevalent in CKD might be useful as diagnostic biomarkers and indicators of disease activity that could be used to guide and evaluate therapeutic interventions, in addition to providing potential novel therapeutic targets.

Differences in management approaches for lupus nephritis within the UK

Objectives

Outcomes of therapy for LN are often suboptimal. Guidelines offer varied options for treatment of LN and treatment strategies may differ between clinicians and regions. We aimed to assess variations in the usual practice of UK physicians who treat LN.

Methods

We conducted an online survey of simulated LN cases for UK rheumatologists and nephrologists to identify treatment preferences for class IV and class V LN.

Results

Of 77 respondents, 48 (62.3%) were rheumatologists and 29 (37.7%) were nephrologists. A total of 37 (48.0%) reported having a joint clinic between nephrologists and rheumatologists, 54 (70.0%) reported having a multidisciplinary team meeting for LN and 26 (33.7%) reported having a specialized lupus nurse. Of the respondents, 58 (75%) reported arranging a renal biopsy before starting the treatment. A total of 20 (69%) of the nephrologists, but only 13 (27%) rheumatologists, reported having a formal departmental protocol for treating patients with LN (P < 0.001). The first-choice treatment of class IV LN in pre-menopausal patients was MMF [41 (53.2%)], followed by CYC [15 (19.6%)], rituximab [RTX; 12 (12.5%)] or a combination of immunosuppressive drugs [9 (11.7%)] with differences between nephrologists' and rheumatologists' choices (P = 0.026). For class V LN, MMF was the preferred initial treatment, irrespective of whether proteinuria was in the nephrotic range or not. RTX was the preferred second-line therapy for non-responders.

Conclusion

There was variation in the use of protocols, specialist clinic service provision, biopsies and primary and secondary treatment choices for LN reported by nephrologists and rheumatologists in the UK.

IgA Nephropathy - Beyond the Renal Cortex

Immunoglobulin A (IgA) nephropathy is the most common glomerular disease worldwide. It usually presents as a nephritic syndrome with macroscopic hematuria, oliguria, and proteinuria with or without azotemia. Rapidly progressive glomerulonephritis with crescents is being described in about 30% of cases and is mostly associated with nephrotic-range proteinuria, accelerated hypertension, and accelerated decline toward end-stage renal disease. Medullary angiitis is a rare finding in renal biopsy and is usually associated with pauci-immune glomerulonephritis. We describe a rare association of medullary angiitis in IgA nephropathy, probably the first reported case in the country.

The level of serum albumin is associated with renal prognosis and renal function decline in patients with chronic kidney disease

OBJECTIVE

The study's purpose is to explore the link of serum albumin on renal progression in patients with chronic kidney disease (CKD).

METHODS

This study was a secondary analysis of a prospective cohort study in which a total of 954 participants were non-selectively and consecutively collected from the research of CKD-ROUTE in Japan between November 2010 and December 2011. We evaluated the association between baseline ALB and renal prognosis (initiation of dialysis or 50% decline in eGFR from baseline) and renal function decline (annual eGFR decline) using the Cox proportional-hazards and linear regression models, respectively. We performed a number of sensitivity analyses to ensure the validity of the results. In addition, we performed subgroup analyses.

RESULTS

The included patients had a mean age of (66.86 ± 13.41) years, and 522 (69.23%) were male. The mean baseline ALB and eGFR were (3.89 ± 0.59) g/dL and (33.43 ± 17.97) ml/min/1.73 m². The annual decline in eGFR was 2.65 mL/min/1.73 m²/year. 218 (28.9%) individuals experienced renal prognosis during a median follow-up period of 36.0 months. The baseline ALB was inversely linked with renal prognosis (HR = 0.61, 95%CI: 0.45, 0.81) and renal function decline (β = -1.41, 95%CI: -2.11, -0.72) after controlling for covariates. The renal prognosis and ALB had a non-linear connection, with ALB's inflection point occurring at 4.3 g/dL. Effect sizes (HR) were 0.42 (0.32, 0.56) and 6.11 (0.98, 38.22) on the left and right sides of the inflection point, respectively. There was also a non-linear relationship between ALB and renal function decline, and the inflection point of ALB was 4.1 g/dL. The effect sizes(β) on the left and right sides of the inflection point were -2.79(-3.62, -1.96) and 0.02 (-1.97, 1.84), respectively.

CONCLUSION

This study shows a negative and non-linear association between ALB and renal function decline as well as renal prognosis in Japanese CKD patients. When ALB is lower than 4.1 g/dL, ALB decline was closely related to poor renal prognosis and renal function decline. From a therapeutic point of view, reducing the decline in ALB makes sense for delaying CKD progression.

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.

Oxidized Proteins Differentially Affect Maturation and Activation of Human Monocyte-Derived Cells

In cancer, antigen-presenting cells (APC), including dendritic cells (DCs), take up and process proteins to mount adaptive antitumor immune responses. This often happens in the context of inflamed cancer, where reactive oxygen species (ROS) are ubiquitous to modify proteins. However, the inflammatory consequences of oxidized protein uptake in DCs are understudied. To this end, we investigated human monocyte-derived cell surface marker expression and cytokine release profiles when exposed to oxidized and native proteins. Seventeen proteins were analyzed, including viral proteins (e.g., CMV and HBV), inflammation-related proteins (e.g., HO1 and HMGB1), matrix proteins (e.g., Vim and Coll), and vastly in the laboratory used proteins (e.g., BSA and Ova). The multifaceted nature of inflammation-associated ROS was mimicked using gas plasma technology, generating reactive species cocktails for protein oxidation. Fourteen oxidized proteins led to elevated surface marker expression levels of CD25, CD40, CD80, CD86, and MHC-II as well as strongly modified release of IL6, IL8, IL10, IL12, IL23, MCP-1, and TNFα compared to their native counterparts. Especially IL8, heme oxygenase 2, and vimentin oxidation gave pronounced effects. Furthermore, protein kinase phospho-array studies in monocyte-derived cells pulsed with native vs. oxidized IL8 and insulin showed enhanced AKT and RSK2 phosphorylation. In summary, our data provide for the first time an overview of the functional consequences of oxidized protein uptake by human monocyte-derived cells and could therefore be a starting point for exploiting such principle in anticancer therapy in the future.

Association between hemoglobin and chronic kidney disease progression: a secondary analysis of a prospective cohort study in Japanese patients

OBJECTIVE

Anemia has been reported as a risk factor for chronic kidney disease (CKD) progression. However, there are still few studies examining the relationship between specific hemoglobin (Hb) levels and renal prognosis and renal function decline simultaneously. Meanwhile, the possible non-linear relationship between Hb and CKD progression also deserves further exploration. On that account, our primary goal is to explore the link of Hb on renal prognosis and renal function decline in patients with CKD.

METHODS

This study was a secondary analysis of a prospective cohort study, which consecutively and non-selectively collected 962 participants from the research of CKD-ROUTE in Japan from November 2010 to December 2011. We used the Cox proportional-hazards and linear regression models to evaluate the independent association between baseline Hb and renal prognosis (renal composite endpoint, initiation of dialysis during follow-up or 50% decline in eGFR from baseline) and renal function decline(annual eGFR decline), respectively. A multivariate Cox proportional hazards regression analysis with cubic spline functions model and smooth curve fitting (penalized spline method) were conducted to address Hb and CKD prognosis's non-linearity. At the same time, a generalized additive model (GAM) and smooth curve fitting (penalized spline method) was conducted to explore the exact shape of the curve between Hb and renal function decline. Additionally, we did a series of sensitivity analyses to ensure the robustness of the results. Moreover, we conducted subgroup analyses.

RESULTS

The mean age of the included patients was 67.35 ± 13.56 years old, and 69.65% were male. The mean baseline Hb and estimated glomerular filtration rate (eGFR) was 12.06 ± 2.21 g/dL and 33.04 ± 18.01 ml/min per 1.73 m². The annual decline in eGFR was 2.09 mL/min/1.73 m²/year. During a median follow-up time of 33.5 months, 252(26.2%) people experienced renal composite endpoint. After adjusting covariates, the results showed that Hb was negatively associated with renal composite endpoint (HR = 0.836, 95%CI: 0.770, 0.907) and renal function decline (β = -0.436, 95%CI: -0.778, -0.093). There was also a non-linear relationship between Hb and renal composite endpoint, and the inflection point of Hb was 8.6 g/dL. The effect sizes(HR) on the left and right sides of the inflection point were 1.257 (0.841, 1.878) and 0.789 (0.715, 0.870), respectively. And the sensitive analysis demonstrated the robustness of the results. Subgroup analysis showed that Hb was more strongly associated with the renal composite endpoint in non-hypertensive, SBP < 140 mmHg, urine protein-to-creatinine ratio (UPCR) < 0.5 g/gCr, and diuretic use patients. In contrast, the weaker association was probed in hypertensive and non-diuretic use patients and the patients with SBP ≥ 140 mmHg, and UPCR ≥ 0.5 g/gCr.

CONCLUSION

This study demonstrates a negative and non-linear relationship between Hb and renal prognosis and renal function decline in Japanese CKD patients. Hb is strongly related to renal prognosis when Hb is above 8.6 g/dL.

Association of redox and inflammation-related biomarkers with prognosis in IgA nephropathy: A prospective observational study

BACKGROUND

IgA nephropathy (IGAN) has a variable prognosis. Risk stratification tools are usually based on clinical parameters combined with histologic Oxford-MEST-C score. Circulating redox- and inflammation-related biomarkers may be related to histological changes in IGAN. Therefore, we studied the performance of these biomarkers in predicting the rate of GFR-loss in IGAN.

METHODS

This was an observational prospective study. Fifty-seven stable patients with IGAN were examined at baseline and after a mean observational time of 5.9 ± 1.1 years. The main outcome measure was eGFR-loss per year with predefined groups, stable (<1.5 ml/min/1,73 m²/year, intermediate (between 1.5 and 2.5), and progressive (>2.5).

RESULTS

Fifteen patients were in the progressive, 11 in the intermediate, and 31 in the stable groups. Positive relationships were detected between eGFR-loss per year and baseline nitrate, oxidized free cysteine, parathyroid hormone, APRIL, TNFR1, CD30, chitinase 3, and LIF-5. The progressive group had elevated concentrations of these markers plus AOPP and osteopontin. Through ROC analysis, it was observed that AOPP, oxidized free cysteine, TNFR1, osteopontin, and LIF-5 had the best ability to identify progressive vs. non-progressive diseases. The combination of urinary albumin/creatinine ratio with AOPP and TNFR1 significantly improved the ability to identify progressive eGFR decline with ROC AUC 95% (adjusted 85%).

CONCLUSIONS

We found prognostic biomarkers related to the rate of eGFR-loss in IGAN. These biomarkers may help identify patients at risk of progressive disease. AOPP, oxidized free cysteine, TNFR1, and osteopontin are promising prognostic biomarkers in IGAN, however, further validation studies are needed.

Association Between Urinary Protein-to-Creatinine Ratio and Chronic Kidney Disease Progression: A Secondary Analysis of a Prospective Cohort Study

Objective

Studies on the association between urinary protein-to-creatinine ratio (UPCR) and chronic kidney disease (CKD) progression are limited. This study aimed to investigate the relationship between UPCR and CKD progression in a Japanese population.

Methods

The present research was a secondary analysis of a prospective cohort study. Eight hundred and ninety-six subjects from the research of CKD-ROUTE in Japan were included. All the patients were new visitors or first referred to the participating centers of nephrology between October 2010 and December 2011. The target-independent variable was UPCR measured at baseline. The dependent variable was CKD progression and the estimated glomerular filtration rate (eGFR) changes during follow-up. We used Cox proportional hazards regression to investigate the association between UPCR and CKD progression risk. To address UPCR and CKD progression's non-linearity, a multivariate Cox proportional hazards regression analysis with cubic spline functions model and smooth curve fitting (penalized spline method) were conducted. We further used a generalized linear mixed model to explore the relationship between UPCR and the changes of eGFR.

Result

The mean age of the included patients was 67.2 ± 13.4 years old. Two hundred and thirty-four people occurred CKD progression during follow-up. The present study showed that UPCR was independently associated with CKD progression in the multivariate analysis [HR = 1.164, 95% CI (1.116, 1.215)]. The non-linear relationship between UPCR and CKD progression was explored in a dose-dependent manner, with an obvious inflection point of 1.699. Furthermore, our findings indicated that the tendency of the effect sizes on both the left and right sides of the inflection point was not consistent [left HR: 4.377, 95% CI (2.956, 6.483); right HR: 1.100, 95% CI (1.049–1.153)]. Using the linear mixed-effects regression model, we found that UPCR was an independent predictor of the longitudinal changes in eGFR (p < 0.001 for the interaction term with time).

Conclusion

This study demonstrates a nonlinear positive relationship between UPCR and CKD progression in the Japanese population. UPCR is also an independent predictor of the longitudinal changes in eGFR.

Oxidative stress and macrophage infiltration in IgA nephropathy

BACKGROUND

The aim of this study was to evaluate the interactions among serum levels of galactose-deficient IgA1 (Gd-IgA1), oxidative stress and macrophage infiltration and their clinical correlates in patients with IgA Nephropathy (IgAN).

METHODS

A total of 47 patients with biopsy-proven primary IgAN, aged between 16 and 79 years, with a follow-up period ≥ 1 year or who showed progression to end stage kidney disease (ESKD) regardless the duration of follow-up were included. Study endpoint was the progression to ESKD. Serum Gd-IgA1 and advanced oxidation protein product (AOPP) levels were measured using ELISA assays. Kidney biopsies were evaluated according to the Oxford MEST-C scoring, with C4d and CD68 staining.

RESULTS

Seventeen patients (36%) experienced ESKD during a median follow-up time of 6 years (IQR 3.7-7.5). Serum AOPP levels were correlated with the intensity of glomerular C3 deposition (r = 0.325, p = 0.026), glomerular (r = 0.423, p = 0.003) and interstitial CD68 + cell count (r = 0.298, p = 0.042) and Gd-IgA1 levels (r = 0.289, p = 0.049). Serum Gd-IgA1 levels were correlated with the intensity of C3 deposition (r = 0.447, p = 0.002). eGFR at biopsy (adjusted HR (aHR) 0.979 p = 0.011), and E score (aHR, 8.305, p = 0.001) were associated with progression to ESKD in multivariate analysis. 5-year ESKD-free survival rate was significantly lower in patients with higher E score compared to patients with E score 0 [p = 0.021].

CONCLUSIONS

An increased number of macrophages in the glomerular and tubulointerstitial area may play a role in oxidative stress and complement system activation. Endocapillary hypercellularity is a predictive factor for poor prognosis in IgAN.

Immunomodulatory Effects of Heme Oxygenase-1 in Kidney Disease

Kidney disease is a general term for heterogeneous damage that affects the function and the structure of the kidneys. The rising incidence of kidney diseases represents a considerable burden on the healthcare system, so the development of new drugs and the identification of novel therapeutic targets are urgently needed. The pathophysiology of kidney diseases is complex and involves multiple processes, including inflammation, autophagy, cell-cycle progression, and oxidative stress. Heme oxygenase-1 (HO-1), an enzyme involved in the process of heme degradation, has attracted widespread attention in recent years due to its cytoprotective properties. As an enzyme with known anti-oxidative functions, HO-1 plays an indispensable role in the regulation of oxidative stress and is involved in the pathogenesis of several kidney diseases. Moreover, current studies have revealed that HO-1 can affect cell proliferation, cell maturation, and other metabolic processes, thereby altering the function of immune cells. Many strategies, such as the administration of HO-1-overexpressing macrophages, use of phytochemicals, and carbon monoxide-based therapies, have been developed to target HO-1 in a variety of nephropathological animal models, indicating that HO-1 is a promising protein for the treatment of kidney diseases. Here, we briefly review the effects of HO-1 induction on specific immune cell populations with the aim of exploring the potential therapeutic roles of HO-1 and designing HO-1-based therapeutic strategies for the treatment of kidney diseases.

Serum Bilirubin Is Correlated With the Progression of IgA Vasculitis With Nephritis

Background: Bilirubin has been identified as an endogenous antioxidant and cellular protectant. The present study was performed to clarify the potential influence of serum bilirubin on IgA vasculitis with nephritis (IgAV-N). Methods: One hundred and eighty-nine IgAV-N patients over 14 years old were enrolled. The patients were divided into two groups by the optimum cut-off value calculated by ROC curve. The composite endpoints were defined as a 60% decline in estimate glomerular filtration rate (e-GFR), end-stage renal disease (ESRD) and/or death. Kaplan-Meier (K-M) analysis and multivariate Cox analysis were carried out to determine the predictors for renal outcomes. In order to eliminate the influence of different baseline data, a 1:2 propensity score (PS) match was performed to make the results comparable and convictive. Results: The baseline data suggested that patients in low serum bilirubin group had significantly higher levels of systolic blood pressure, proteinuria, serum creatinine and crescent formation ratio and lower levels of serum albumin and hemoglobin. Renal survival analysis indicated that lower serum bilirubin levels were significantly correlated with a poorer prognosis. Multivariate Cox analysis demonstrated that the higher level of serum bilirubin was an independent protective factor for renal survival (HR, 0.172; 95% CI, 0.030-0.991; P = 0.049). After PS matching, the baseline characters of two groups had no statistical differences. Similar outcomes were demonstrated in K-M curve and the multivariate Cox analysis. Conclusion: Elevated bilirubin levels might be related to the favorable renal outcomes.

Clinicopathological features, risk factors, and outcomes of immunoglobulin A nephropathy associated with hepatitis B virus infection

BACKGROUND

Hepatitis B virus (HBV) infections are associated with an increased risk of kidney diseases. However, the effects of HBV infection on the prognosis of immunoglobulin A nephropathy (IgAN) are unclear.

METHODS

A total of 838 patients with biopsy-confirmed IgAN were enrolled in this retrospective cohort study. The patients were categorized into either affected by IgAN and HBV infection (HBsAg-IgAN) or by primary IgAN with no sign of HBV infection (P-IgAN). A 1:1 propensity-score matching was performed between the two groups, followed by a Kaplan-Meier survival analysis, to compare the prognoses, and a Cox regression analysis, to identify factors influencing the HBsAg-IgAN outcomes.

RESULTS

A total of 176 pairs of patients were successfully matched. A significant difference in the systolic blood pressure and urea, serum creatinine, uric acid, and 24-h urine protein levels was observed between the groups. A renal pathological analysis also revealed a significant difference in the mesangial hypercellularity between the groups. During a median follow-up period of 2.4 years, Kaplan-Meier analysis also revealed a significant difference in the renal survival between the groups. Furthermore, multivariate Cox analysis confirmed that HBV infection is an independent risk factor for IgAN progression (hazard ratio [HR] 2.096; 95% confidence interval [CI] 1.091-4.026). Finally, the HBsAg-IgAN patients who received treatment with renin-angiotensin-aldosterone system inhibitors had a better overall prognosis than those who received immunosuppressive therapy and antiviral treatment.

CONCLUSION

Our results indicate that the clinicopathological features and outcomes of patients with IgAN differ significantly between those with and without HBV infection, and that HBV is an independent risk factor for IgAN progression.

Safety, Tolerability and Efficacy of Narsoplimab, a Novel MASP-2 Inhibitor for the Treatment of IgA Nephropathy

Introduction

Narsoplimab is a human monoclonal antibody against mannan-associated lectin-binding serine protease−2 (MASP-2). Now in a phase 3 study, narsoplimab was evaluated in a staged phase 2 study assessing safety and effectiveness in high-risk patients with IgA nephropathy (IgAN).

Methods

Substudy 1 was a single-arm open-label study of 12 weekly infusions and tapered corticosteroids, with 6 weeks of follow-up. In substudy 2, patients were randomized 1:1 to receive a course of treatment consisting of once-weekly narsoplimab or vehicle infusions for 12 weeks. After 6 weeks of follow-up, both substudy 2 groups could continue in an open-label extension, receiving 1 or more narsoplimab courses at the investigator’s discretion.

Results

The most commonly reported adverse events (AEs) included headache, upper respiratory infection, and fatigue. Most AEs were mild or moderate and transient. No treatment-related serious AEs were reported. All 4 patients who were enrolled in substudy 1 had reductions in 24-hour urine protein excretion (UPE) at week 18, ranging from 54% to 95% compared with baseline. In substudy 2, the vehicle and narsoplimab groups had similar proteinuria reductions at week 18. Eight patients (3 vehicle, 5 narsoplimab) continued in the dosing extension; all received narsoplimab. Median reduction in 24-hour UPE in these 8 patients was 61.4% at 31 to 54 weeks postbaseline. Estimated glomerular filtration rates (eGFR) remained stable in both substudies.

Conclusion

This interim analysis suggests that narsoplimab treatment is safe, is well tolerated, and may result in clinically meaningful reductions in proteinuria and stability of eGFR in high-risk patients with advanced IgAN.

Circulating inflammation-related factors are correlated with systemic redox status in IgA nephropathy; a case-control study

BACKGROUND

IgA nephropathy (IGAN) is characterized by oxidative stress and inflammation. In the present study, we explored the relationship of redox status vs. that of circulating inflammation-related factors with other biomarkers in patients with IGAN.

METHODS

This is a case-control study comparing patients with IGAN (Stage 1-4) to healthy controls. Forty patients and 40 controls were matched for age and sex. Two circulating dynamic redox parameters were analysed: oxidized free cysteine (Cys) and nitrate. Thirty-seven inflammation-related factors were measured in serum.

RESULTS

The patients had elevated levels of oxidized free Cys and nitrate, indicating the presence of oxidative stress. Nine circulating inflammation-related factors were higher in the serum of patients than in that of controls. The most important factors were APRIL, MMP-3, osteopontin, TNFR1 and TWEAK. Inflammation-related factors were positively correlated with oxidized free Cys, nitrate, creatinine and parathyroid hormone (PTH) in the patients. The correlation coefficients of Latent Inflammatory Factor vs. oxidized free Cys and nitrate were r = 0.43 (p = 0.007) and r = 0.51 (p = 0.001), respectively. This finding persisted after adjusting for the glomerular filtration rate.

CONCLUSIONS

Patients with IGAN had disturbed redox status. Several circulating inflammation-related factors were elevated, suggesting activation of the non-canonical NF-kB pathway. There was a positive relationship between systemic redox status and the level of inflammation-related factors, partially independent of GFR. The present findings raise the question of whether circulating oxidized free Cys and/or nitrate may be employed as prognostic biomarkers for IGAN in the future.

Changes in Glycation and Oxidation Markers in Patients Starting Peritoneal Dialysis: A Pilot Study

Background

The high incidence of cardiovascular disease in uremic patients makes it a major cause of morbidity and mortality in those patients. Uremia is associated with carbonyl and oxidative stress, which result in the enhanced formation of glycation and oxidation products respectively. In the present study, the blood levels of advanced glycation end products (AGEs) and advanced oxidation protein products (AOPPs) were investigated in uremic patients prior to and after initiation of peritoneal dialysis (PD).

Methods

22 patients [11 nondiabetic (G1) and 11 diabetic (G2) subjects] were enrolled in a single-center prospective study. Prior to starting PD (T0) and 6 and 12 months later, changes in AGE and AOPP levels were analyzed in the total study population and in each group (Friedman test, intragroup). At each time point, a comparison was made between the levels of the above-mentioned products in G1 and G2 (Mann–Whitney test, intergroup). Correlations between AGE or AOPP levels and residual renal function, peritoneal creatinine clearance, glucose peritoneal equilibration test, or daily dextrose exposure were analyzed using the Pearson test.

Results

At T0, no significant difference was found between the two groups for AGE or AOPP levels. Initiation of PD was followed by an increase in AGE levels in all patients ( p < 0.01 at 6 and 12 months). AGE levels were higher in G2 than in G1 at 12 months after the start of PD ( p < 0.05). In contrast to G2 results, initiation of PD in G1 led to reduced AOPP levels (at 6 and 12 months, p = 0.01 and p < 0.05 respectively). However, no correlation between AGE or AOPP levels and residual renal function, peritoneal creatinine clearance, glucose peritoneal equilibration test, or daily dextrose exposure could be established.

Conclusion

This study demonstrates that PD is associated with an increase in levels of blood glycation end products, particularly in diabetic patients, but also with a decrease in oxidative products such as AOPPs, especially in nondiabetic subjects.

Oxidative Stress in the Pathogenesis and Evolution of Chronic Kidney Disease: Untangling Ariadne's Thread

Amplification of oxidative stress is present since the early stages of chronic kidney disease (CKD), holding a key position in the pathogenesis of renal failure. Induction of renal pro-oxidant enzymes with excess generation of reactive oxygen species (ROS) and accumulation of dityrosine-containing protein products produced during oxidative stress (advanced oxidation protein products—AOPPs) have been directly linked to podocyte damage, proteinuria, and the development of focal segmental glomerulosclerosis (FSGS) as well as tubulointerstitial fibrosis. Vascular oxidative stress is considered to play a critical role in CKD progression, and ROS are potential mediators of the impaired myogenic responses of afferent renal arterioles in CKD and impaired renal autoregulation. Both oxidative stress and inflammation are CKD hallmarks. Oxidative stress promotes inflammation via formation of proinflammatory oxidized lipids or AOPPs, whereas activation of nuclear factor κB transcription factor in the pro-oxidant milieu promotes the expression of proinflammatory cytokines and recruitment of proinflammatory cells. Accumulating evidence implicates oxidative stress in various clinical models of CKD, including diabetic nephropathy, IgA nephropathy, polycystic kidney disease as well as the cardiorenal syndrome. The scope of this review is to tackle the issue of oxidative stress in CKD in a holistic manner so as to provide a future framework for potential interventions.

Looking beyond the skin: Cutaneous and systemic oxidative stress in UVB-induced squamous cell carcinoma in hairless mice

Cumulative ultraviolet (UV) exposure is associated with squamous skin cell carcinoma. UV radiation induces oxidative modifications in biomolecules of the skin leading to photocarcinogenesis. Indeed, the cyclobutene pyrimidine dimers and other dimers formed by photoaddition between carbon-carbon bonds also have an important role in the initiation process. However, information on the systemic redox status during these processes is scarce. Thus, we investigated the systemic redox profile in UVB-induced squamous cell carcinoma in mice. Female hairless mice were exposed to UVB radiation (cumulative dose = 17.1 J/cm²). The dorsal skin of these mice developed actinic keratosis (AK) and squamous cell carcinoma (SCC) and presented increased levels of oxidative and nitrosative stress biomarkers (4-hydroxy-2-nonenal and 3-nitrotyrosine), and decreased antioxidant defenses. Systemically, we observed the consumption of plasmatic antioxidant defenses and increased levels of advanced oxidized protein products (AOPP), an oxidative stress product derived from systemic inflammatory response. Taken together, our results indicate that UVB chronic irradiation leads not only to adjacent and tumoral oxidative stress in the skin, but it systemically is reflected through the blood. These new findings clarify some aspects of the pathogenesis of SCC and should assist in formulating better chemoprevention strategies, while avoiding additional primary SCC development and metastasis.

Blood urea nitrogen is independently associated with renal outcomes in Japanese patients with stage 3-5 chronic kidney disease: a prospective observational study

Background

Blood urea nitrogen (BUN) is one of the substances that affects the calculated serum osmolality (cSosm). A previous study demonstrated that BUN and cSosm were independently associated with the development of chronic kidney disease (CKD) in patients with preserved kidney function. In advanced CKD stages, there is a concomitant increase in cSosm and BUN levels. However, it remains unclear whether BUN or cSosm levels are related to renal outcomes in patients with moderate to severe kidney dysfunction. The aim of this study was to clarify whether the BUN or cSosm level is associated with kidney disease progression in patients with advanced CKD.

Methods

In this prospective study, we enrolled 459 patients with CKD (stages 3–5). The composite renal endpoint was end-stage renal disease (ESRD) or death, and ESRD alone was added as an alternative outcome. A Cox proportional hazards model was utilized to determine the risk factors for a poor renal outcome. We adjusted for covariates including estimated glomerular filtration rate (eGFR). The cSosm (mOsm/kg) was calculated using the following formula: (2 × sodium) + (BUN/2.8) + (glucose/18).

Results

During a median follow-up of 25.8 months, the renal endpoint was observed in 210 patients. Multivariable Cox analysis determined the hazard ratio (HR) [95% confidence interval (CI)] for the composite renal outcome in the second, third, and fourth BUN quartiles were 1.36 (0.72–2.58), 1.87 (0.95–3.66), and 2.66 (1.23–5.76) (P for trend < 0.01), respectively compared with the first BUN quartile. Conversely, by multivariable Cox analysis, the HRs (95% CIs) for poor outcomes in the second, third, and fourth cSosm quartiles, compared with the first cSosm quartile, were 1.13 (0.69–1.87), 0.95 (0.58–1.55), and 1.26 (0.78–2.03), respectively (P for trend = 0.39). In addition, with regard to the renal outcome of ESRD alone, higher BUN quartiles had a significantly increased risk for the outcome, but cSosm levels were not associated with the outcome.

Conclusions

Higher BUN levels, but not cSosm levels, were associated with adverse renal outcomes independent of the eGFR, suggesting that BUN may be a useful marker for predicting kidney disease progression.

Electronic supplementary material

The online version of this article (10.1186/s12882-019-1306-1) contains supplementary material, which is available to authorized users.

Oxidative Stress in Animal Models of Acute and Chronic Renal Failure

Introduction

Kidney disease is a worldwide health and economic burden, with rising prevalence. The search for biomarkers for earlier and more effective disease screening and monitoring is needed. Oxidative stress has been linked to both, acute kidney injury (AKI) and chronic kidney disease (CKD). The aim of our study was to investigate whether the concentrations of systemic markers of oxidative stress and antioxidant status are affected by AKI and CKD, and to identify potential biomarkers.

Methods

In adult male Wistar rats, AKI was induced by bilateral nephrectomy, and CKD was induced by 5/6 nephrectomy. Blood was collected 48 hours after surgery in AKI and 6 months after surgery in CKD. Advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), advanced glycation end products (AGEs), fructosamine, total antioxidant capacity (TAC), and ferric reducing antioxidant power (FRAP) were measured.

Results

Impaired renal function was confirmed by high concentrations of plasma creatinine and urea in AKI and CKD animals. AOPP and fructosamine were higher by 100% and 54% in AKI, respectively, and by 100% and 199% in CKD, respectively, when compared to corresponding control groups. Similarly, there was approximately a twofold increase in AGEs (by 92%) and TAC (by 102%) during AKI. In CKD, concentrations of FRAP, as an antioxidative status marker, were doubled (by 107%) when compared to the control group, but concentration of TAC, another marker of antioxidative status, did not differ between the groups.

Conclusions

AKI and CKD led to increased systemic oxidative stress. AOPP and fructosamine could be considered potential biomarkers for both, acute and chronic kidney damage. On the other hand, AGEs, TAC, and FRAP seem to be disease specific, which could help to differentiate between acute and chronic kidney injuries. However, this needs further validation in clinical studies.

HDL in CKD-The Devil Is in the Detail

The picture of HDL cholesterol (HDL-C) as the "good" cholesterol has eroded. This is even more surprising because there exists strong evidence that HDL-C is associated with cardiovascular disease (CVD) in the general population as well as in patients with impairment of kidney function and/or progression of CKD. However, drugs that dramatically increase HDL-C have mostly failed to decrease CVD events. Furthermore, genetic studies took the same line, as genetic variants that have a pronounced influence on HDL-C concentrations did not show an association with cardiovascular risk. For many, this was not surprising, given that an HDL particle is highly complex and carries >80 proteins and several hundred lipid species. Simply measuring cholesterol might not reflect the variety of biologic effects of heterogeneous HDL particles. Therefore, functional studies and the involvement of HDL components in the reverse cholesterol transport, including the cholesterol efflux capacity, have become a further focus of study during recent years. As also observed for other aspects, CKD populations behave differently compared with non-CKD populations. Although clear disturbances have been observed for the "functionality" of HDL particles in patients with CKD, this did not necessarily translate into clear-cut associations with outcomes.

Development and validation of a prognostic nomogram for IgA nephropathy

IgA nephropathy (IgAN) shows strong heterogeneity between individuals. IgAN prognosis is associated with pathological lesions and clinical indicators. However, simple tools for evaluating the clinical prognosis remain inadequate. Our objective was to develop an intuitive estimation tool for predicting the IgAN prognosis. 349 patients with IgAN at The Chinese People’s Liberation Army General Hospital were retrospectively analyzed from data between 2000 and 2006. A nomogram was developed using COX regression coefficients to predict decline of estimate Glomerular filtration rate (eGFR) ≥ 50% and end-stage renal disease (ESRD). The discriminative ability and predictive accuracy of the nomogram was determined via concordance index (C-index) and calibration curve. The results were verified in an independent validation cohort. In the derivation cohort, the nomogram was developed using mesangial hypercellularity, tubular atrophy/interstitial fibrosis, average proteinuria (A-P), and average mean arterial pressure (A-MAP) during hospitalization. The C-index of the nomogram was 0.88 (95% CI, 0.80 to 0.96). The calibration curve showed good agreement between prediction and actual observation. Furthermore, the nomogram demonstrated good discrimination (C-index = 0.87, 95% CI 0.78 to 0.95) and calibration in the validation cohort. The nomogram could predict the prognosis of IgAN effectively and intuitively.

Huang Gan Formula Eliminates the Oxidative Stress Effects of Advanced Oxidation Protein Products on the Divergent Regulation of the Expression of AGEs Receptors via the JAK2/STAT3 Pathway

Chronic kidney disease (CKD) has a high prevalence and low cure rate and represents a significant health issue. Oxidative stress is common in CKD due to metabolic disorders, inflammation, and impaired renal function changing normal proteins into advanced oxidation protein products (AOPPs). Huang Gan formula (HGF) is a new type of traditional Chinese herbal medicine. Although we previously investigated the protective effects of HGF against oxidative stress, the mechanism of HGF in CKD is still not fully understood. In this study, we used western blotting, quantitative polymerase chain reaction, and biochemical assays to show that HGF significantly decreased AOPP-induced oxidative stress damage. Moreover, the protective effects of HGF might be associated with upregulation of the advanced glycation end product receptor 1 (AGE-R1) and downregulation of the receptor for advance glycation end products (RAGE). Treatment with HGF and the Janus kinase 2 (JAK2) inhibitor, AG4-90, significantly attenuated AOPP-induced JAK2/STAT3 protein levels. These findings indicate that HGF inhibits AOPP-mediated biological responses by inactivating the JAK2/STAT3 pathway. In conclusion, HGF eliminated AOPP-induced effects in human mesangial cells (HMCs) by interrupting JAK2/STAT3 signaling, which altered RAGE/AGE-R1 expression and reduced oxidative stress in CKD.

A J-shaped association between serum uric acid levels and poor renal survival in female patients with IgA nephropathy

Recently, low serum uric acid (SUA) levels and high SUA levels, have emerged as risk factors for cardiovascular disease, as well as for the incidence of acute kidney injury and chronic kidney disease (CKD). However, the effect of low SUA on the progression of CKD remains unclear. To evaluate the association between SUA and renal prognosis in patients with immunoglobulin A nephropathy (IgAN), one of the most common causes of CKD, we retrospectively followed 1218 patients who were diagnosed with primary IgAN by kidney biopsy between October 1979 and December 2010. Patients were divided into three groups on the basis of SUA level tertiles: low (L group), middle (M group) and high (H group) tertiles (<6.1, 6.1-7.0, and >7.0 mg dl^-1, respectively, for men and <4.4, 4.4-5.3, and >5.3 mg dl^-1, respectively, for women). The risk factors for developing end-stage renal disease (ESRD) were estimated using a Cox proportional hazards model. After a median follow-up of 5.1 years, 142 patients (11.7%) developed ESRD. The hazard ratio (95% confidence interval) showed a J-shaped trend with the tertiles in both men (1.18 (0.55-2.54), 1.00 (reference), and 1.80 (1.01-3.10) in L, M and H groups, respectively) and women (2.73 (1.10-6.76), 1.00 (reference) and 2.49 (1.16-5.34) in L, M and H groups, respectively). Notably, low SUA was significantly associated with incident ESRD in women. This finding suggests that SUA has a J-shaped association with ESRD in patients with IgAN, especially women.

Advanced oxidation protein products induce endothelial-to-mesenchymal transition in human renal glomerular endothelial cells through induction of endoplasmic reticulum stress

Endothelial-to-mesenchymal transition (EndMT) in renal glomerular endothelial cells plays a critical role in the pathogenesis of diabetic nephropathy (DN). Furthermore, advanced oxidation protein products (AOPPs) have been shown to contribute to the progression of DN. However, whether AOPPs induce EndMT in renal glomerular endothelial cells remains unclear. Thus, we investigated the effect of AOPPs on human renal glomerular endothelial cells (HRGECs) and the mechanisms underlying the effects. Our results showed that AOPP treatment lowered the expression of vascular endothelial cadherin, CD31, and claudin 5 and induced the overexpression of α-smooth muscle actin, vimentin, and fibroblast-specific protein 1, which indicated that AOPPs induced EndMT in HRGECs. Furthermore, AOPP stimulation increased the expression of glucose-regulated protein 78 and CCAAT/enhancer-binding protein-homologous protein, which suggested that AOPPs triggered endoplasmic reticulum (ER) stress in HRGECs. Notably, the aforementioned AOPP effects were reversed following the treatment of cells with salubrinal, an inhibitor of ER stress, whereas the effects were reproduced after exposure to thapsigargin, an inducer of ER stress. Collectively, our results indicate that AOPPs trigger EndMT in HRGECs through the induction of ER stress. These findings suggest novel therapeutic strategies for inhibiting renal fibrosis by targeting ER stress.

Correlation of TGF-β1 and oxidative stress in the blood of patients with melanoma: a clue to understanding melanoma progression?

TGF-β1 and oxidative stress are involved in cancer progression, but in melanoma, their role is still controversial. Our aim was to correlate plasma TGF-β1 levels and systemic oxidative stress biomarkers in patients with melanoma, with or without disease metastasis, to understand their participation in melanoma progression. Thirty patients were recruited for melanoma surveillance, together with 30 healthy volunteers. Patients were divided into two groups: Non-metastasis, comprising patients with tumor removal and no metastatic episode for 3 years; and Metastasis, comprising patients with a metastatic episode. The plasmatic cytokines TGF-β1, IL-1 β, and TNF-α were analyzed by ELISA. For oxidative stress, the following assays were performed: malondialdehyde (MDA), advanced oxidation protein products (AOPP) levels, total radical-trapping antioxidant parameter (TRAP) and thiol in plasma, and lipid peroxidation, SOD and catalase activity and GSH in erythrocytes. Patients with a metastatic episode had less circulating TGF-β1 and increased TRAP, thiol, AOPP and lipid peroxidation levels. MDA was increased in both melanoma groups, while catalase, GSH, and IL-1β was decreased in Non-metastasis patients. Significant negative correlations were observed between TGF-β1 levels and systemic MDA, and TGF-β1 levels and systemic AOPP, while a positive correlation was observed between TGF-β1 levels and erythrocyte GSH. Lower levels of TGF-β1 were related to increased oxidative stress in Metastasis patients, reinforcing new evidence that in melanoma TGF-β1 acts as a tumor suppressor, inhibiting tumor relapse. These findings provide new knowledge concerning this cancer pathophysiology, extending the possibilities of investigating new therapies based on this evidence.

Plasma levels of oxidative stress in children with steroid-sensitive nephrotic syndrome and their predictive value for relapse frequency

BACKGROUND

Oxidative stress has been reported to play an important role in children with primary nephrotic syndrome (PNS). However, the results of previous studies are controversial.

METHODS

Forty children with steroid-sensitive nephrotic syndrome (SSNS) and 20 age- and sex-matched healthy controls were enrolled. Patients were followed-up for 12-18 months and divided into three subgroups: frequent relapse (n = 10), non-frequent relapse (n = 12), and non-relapse (n = 18). The plasma levels of advanced oxidation protein products (AOPP), malondialdehyde (MDA), and superoxide dismutase (SOD) were tested in controls and patient group at first presentation and after 4 weeks of steroid treatment.

RESULTS

Patients had higher AOPP and MDA levels but lower SOD compared with controls. AOPP levels were significantly higher in the frequent relapse subgroup compared with the non-frequent relapse and non-relapse subgroups, respectively. No significant differences were found in the plasma levels of MDA and SOD among the three subgroups. AOPP >87.55 μmol/l before steroid treatment and AOPP >78.5 μmol/l after 4-week steroid treatment were positively correlated with the relapse frequency in patients with SSNS.

CONCLUSIONS

Children with SSNS have oxidative stress. The plasma levels of AOPP before and after 4-week steroid treatment may predict whether patients with SSNS will relapse frequently.

Association of serum total bilirubin with renal outcome in Japanese patients with stages 3-5 chronic kidney disease

OBJECTIVE

Serum bilirubin has been reported to be associated with the progression of kidney disease in patients with diabetic nephropathy. Less is known, however, about the relationship between bilirubin and chronic kidney disease (CKD) of other etiologies. This study was designed to clarify whether serum total bilirubin concentration is associated with kidney disease progression in patients with CKD independent of etiology.

MATERIALS AND METHODS

This prospective observational study enrolled 279 consecutive patients with stages 3-5 CKD. The renal endpoint was the composite of the doubling of serum creatinine or end-stage renal disease requiring dialysis. Patients were divided into three groups by their serum total bilirubin concentrations: ≤0.3 (lowest), 0.4-0.5 (middle), and ≥0.6 (highest) mg/dL. A Cox proportional hazards model was applied to determine the risk factors for poor renal outcome.

RESULTS

The median follow-up period was 21months. One-hundred and three patients reached renal end points. After multivariable adjustment, a 0.1mg/dL increase in serum bilirubin was associated negatively with poor renal outcome (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.60-0.87). In addition, after adjustment for confounding factors, including traditional and nontraditional cardiovascular risk factors, the middle (HR 3.14, 95% CI 1.36-8.57) and lowest (HR 4.22, 95% CI 1.81-11.59) bilirubin groups had significantly higher HRs for renal outcome than the highest bilirubin group.

CONCLUSIONS

Lower serum bilirubin concentration was independently associated with adverse renal outcomes, suggesting that the measurement of serum bilirubin is useful for predicting kidney disease progression in patients with moderate to severe CKD.

Intermedin ameliorates IgA nephropathy by inhibition of oxidative stress and inflammation

IgA nephropathy (IgAN) is the most frequent form of glomerulonephritis worldwide. The role of oxidative stress and inflammation in the pathogenesis of IgAN has been reported. Intermedin (IMD) is a newly discovered peptide that is closely related to adrenomedullin. We have recently reported that IMD can significantly reduce renal ischemia/reperfusion injury by diminishing oxidative stress and suppressing inflammation. The present study was designed to explore whether IMD ameliorates IgAN via oxidative stress- and inflammation-dependent mechanisms. Our results showed that IMD administration resulted in the prevention of albuminuria and ameliorated renal pathomorphological changes. These findings were associated with (1) decreased renal TGF-β1 and collagen IV expression, (2) an increased SOD level and reduced MDA level, (3) the inhibition of the renal activation of NF-κB p65 and (4) the downregulation of the expression of inflammatory factors (TNF-α, MCP-1 and MMP-9) in the kidney. These results indicate that IMD in the kidney protects against IgAN by reducing oxidative stress and suppressing inflammation.

Association between advanced oxidation protein products and 5-year mortality risk among amazon riparian elderly population

Proteins are important targets of several modifications caused by oxidative stress, leading to structural changes and consequently partial or total loss of their functions. The oxidized proteins include advanced oxidation protein products (AOPP) derived from oxidation-modified albumin, as well as fibrinogen and lipoproteins. An increase in AOPP levels indicates an oxidative stress state and the presence of coexisting inflammation. Several investigations have also suggested an association between high AOPP levels and aging-related diseases. However, the link between elevated AOPP levels and elderly mortality risk has not yet been investigated. Here, we report on a 5-year longitudinal study that investigated the potential association between AOPP levels and mortality using a population-based representative sample of riparian elders living in Brazilian Amazon region (Maués-AM). Age, sex, socioeconomic and cultural conditions, chronic morbidities, polypharmacy, and previous morbidities were also tested as potential confounders. The AOPP levels were measured in 540 (84.78%) individuals, all of whom were followed over a 5-year period in order to establish the mortality rate. Within this study period, 74 (13.7%) elders died and 466 (86.3%) survived. The AOPP levels were higher among the elders who died within the 5-year period (46.27 ± 40.6 mmol/L) compared with those who survived (36.79 ± 20.84 mmol/L) (p = 0.002). The analysis confirmed the link between high AOPP levels and mortality risk, independent of other intervenient factors. These results suggest that elevated AOPP levels could be used to predict mortality risk in elderly patients.

AOPPs and the progression of kidney disease

Advanced oxidation protein products (AOPPs) are the dityrosine-containing and crosslinking protein products formed during oxidative stress by reaction of plasma protein with chlorinated oxidants, and often carried by albumin in vivo. Accumulation of plasma and renal AOPPs is a common pathologic finding in chronic kidney disease (CKD) patients. Moreover, AOPP accumulation is an independent risk factor for cardiovascular events (CVDs) in CKD. Clinical and experimental studies indicate that AOPPs are involved in the structural changes of progressive nephropathies such as glomerulosclerosis, interstitial fibrosis, and tubular atrophy via the redox-dependent pathway. Mounting evidence supports the role of AOPPs as a new class of renal pathogenic mediators in the progression of CKD. This mini review describes the formation of AOPPs, the involvement of AOPPs in CKD pathogenesis, and the underlying mechanisms.

Renal expression of advanced oxidative protein products predicts progression of renal fibrosis in patients with IgA nephropathy

Predicting the risk of disease progression in IgA nephropathy (IgAN) remains a challenge. This study was conducted to test the hypothesis that renal accumulation of advanced oxidized protein products (AOPPs) is an early predictor for renal progression in IgAN. This was a single-center prospective cohort study. One hundred IgAN patients with eGFR>80 ml/min/1.73 m(2) were enrolled. Seventy-seven patients were followed for a mean of 4.2 years, and 30 patients received repeat renal biopsy at a mean of 42 months after diagnosis. The outcomes were the progression of renal fibrosis and rapid progression of CKD (>5 ml/min/1.73 m(2)/year) during follow-up. Immunoreactivity of AOPPs was detected predominantly in tubular epithelial cells and co-localized with expression of TGF-β1 and angiotensin II. Renal staining score of AOPPs at diagnosis was associated with the level of tissue cellular inflammation. Accumulation of AOPPs, particularly in interstitial-infiltrating cells, was negatively correlated with changes of eGFR during follow-up; those with expression scores greater than the median at diagnosis had significantly higher incidences of rapid decline of eGFR compared with those with the score less than or equal to the median. For patients who received repeat renal biopsy, renal AOPP levels greater than the median at diagnosis were associated with increase in renal fibrosis index at repeat biopsy. After multivariate adjustment, renal AOPP expression was an independent predictor for progression of renal fibrosis and rapid decline of eGFR. Taken together, these results demonstrate that renal AOPPs might be a predictor, detectable at the time of diagnosis, for renal progression in patients with early stage IgAN.

Can tonsillectomy modify the innate and adaptive immunity pathways involved in IgA nephropathy?

The benefits of tonsillectomy in IgA nephropathy (IgAN) are still debated. Tonsillectomy may remove pathogen sources and reduce the mucosal associated lymphoid tissue (MALT), limiting degalactosylated IgA1 (deGal-IgA1) production, which is considered to be the initiating pathogenetic event leading to IgA glomerular deposition. In the European network VALIGA, 62/1147 IgAN patients underwent tonsillectomy (TxIgAN). In a cross-sectional study 15 of these patients were tested and compared to 45 non-tonsillectomized IgAN (no-TxIgAN) and healthy controls (HC) regarding levels of deGal-IgA1, and markers of innate immunity and oxidative stress, including toll-like receptors (TLR)2, 3, 4 and 9 mRNAs, proteasome (PS) and immunoproteasome (iPS) mRNAs in peripheral blood mononuclear cells (PBMC), and advanced oxidation protein products (AOPP). Levels of deGal-IgA1 were lower in TxIgAN than in no-TxIgAN (p = 0.015), but higher than in HC (p = 0.003). TLR mRNAs were more expressed in TxIgAN than in HC (TLR4, p = 0.021; TLR9, p = 0.027), and higher in TxIgAN than in no-TxIgAN (p ≤ 0.001 for TLR2, 4, 9). A switch from PS to iPS was detected in PBMC of TxIgAN in comparison to HC and it was higher than in no-TxIgAN [large multifunctional peptidase (LMP)2/β1, p = 0.039; LPM7/β5, p < 0.0001]. The levels of AOPP were significantly higher in TxIgAN than HC (p < 0.001) and no-TxIgAN (p = 0.033). In conclusion, the activation of innate immunity via TLRs and ubiquitin-proteasome pathways and the pro-oxidative milieu were not affected by tonsillectomy, even though the levels of aberrantly galactosylated IgA1 were lower in patients with IgAN who had tonsillectomy. The residual hyperactivation of innate immunity in tonsillectomized patients may result from extra-tonsillar MALT.

Protection of rhein on IgA nephropathy mediated by inhibition of fibronectin expression in rats

Objective:

To investigate the protective effects of rhein on IgA nephropathy (IgAN) in the rat model.

Materials and Methods:

Twenty-eight female sprague dawley rats were divided randomly into four groups, namely control, IgAN, rhein-prevented and rhein-treated. The pathologic changes on renal tissue were observed by the H and E, staining and the amount of urinary red blood cells and 24-h urinary protein excretion were measured. The glomerular deposition of immune globulin A (IgA) was measured by immunofluorescence staining. Fibronectin (FN) and α-smooth muscle actin (α-SMA) expression on renal tissue were measured via immunohistochemistry.

Results:

The model of IgAN was established according to Bovine serum albumin-Lipopolysaccharide-Carbon tetrachloride protocol, which was evidenced by histological structural lesions of glomeruli, IgA deposition and urinary measurement. Histological examination of kidney sections from both rhein-prevented group and rhein-treated group showed that glomerular hypertrophy, mesangial expansion, excessive extracellular matrix, and renal capsule dilation were markedly ameliorated compared with IgAN group. Moreover, rhein treatment significantly reduced IgA deposition in glomerulus, the volume of urinary red blood cells and 24-h urinary protein excretion. More importantly, increased FN expression in IgAN was back to normal level in rhein-prevented and rhein-treated group, which was along with the reduction of α-SMA expression in renal tissues.

Conclusions:

These findings indicate that rhein prevents the development of glomerulosclerosis and halts the progression of IgAN via inhibition of FN and α-SMA expression.

Antroquinonol mitigates an accelerated and progressive IgA nephropathy model in mice by activating the Nrf2 pathway and inhibiting T cells and NLRP3 inflammasome

High levels of reactive oxygen species (ROS), systemic T cell activation, and macrophage infiltration in the kidney are implicated in the acceleration and progression of IgA nephropathy (IgAN), the most frequent type of primary glomerulonephritis. However, the pathogenic mechanism of IgAN is still little understood, and it remains a challenge to establish a specific therapeutic strategy for this type of glomerular disorder. Recently, we showed that antroquinonol (Antroq), a pure active compound from Antrodia camphorata mycelium, inhibits renal inflammation and reduces oxidative stress in a mouse model of renal fibrosis. But the anti-inflammatory and immune-regulatory effects of Antroq on the acceleration and progression of primary glomerular disorders have not been determined. In this study, we show that Antroq administration substantially impeded the development of severe renal lesions, such as intense glomerular proliferation, crescents, sclerosis, and periglomerular interstitial inflammation, in mice with induced accelerated and progressive IgAN (AcP-IgAN). Further mechanistic analysis in AcP-IgAN mice showed that, early in the developmental stage of the AcP-IgAN model, Antroq promoted the Nrf2 antioxidant pathway and inhibited the activation of T cells and NLRP3 inflammasome. Significantly improved proteinuria/renal function and histopathology in AcP-IgAN mice of an established stage supported potential therapeutic effects of Antroq on the disease. In addition, Antroq was shown to inhibit activation of NLRP3 inflammasome in vitro by an IgA immune complex (IC) partly involving a reduced ROS production in IgA-IC-primed macrophages, and this finding may be helpful in the understanding of the mode of action of Antroq in the treated AcP-IgAN mice.

Serum immunoglobulin A/C3 ratio predicts progression of immunoglobulin A nephropathy

AIM

The serum immunoglobulin A (IgA)/C3 ratio has been shown to be a good predictor of histological lesions and prognosis for patients with IgA nephropathy (IgAN) in Japanese. But its validity in the Chinese population is unclear. We sought to explore the long-term outcomes of IgAN, its clinical and histopathological predictors in Chinese patients. In particular, the role of serum IgA/C3 ratio in the course of IgAN was addressed.

METHODS

A total of 217 biopsy-diagnosed IgAN patients were recruited into this prospective cohort with a mean follow-up of 36 months (25-75th percentile, 27-48). Sociodemographics, serum IgA/C3 level, other clinical examinations and Lee's histological grade were measured. The patients with a decline of estimated glomerular filtration rate (eGFR) > 50% or developing end-stage renal disease (ESRD) were defined as progression.

RESULTS

A total of 21 patients was found to progress (9.7%). In multivariate analysis, renal end point of IgAN was significantly predicted by proteinuria ≥1 g/day (relative risk (RR) = 2.65, 95% confidence interval (CI) 1.01-7.68), hypertension (RR = 3.15, 95% CI 1.07-9.29), higher Lee's histological grade (RR = 4.67, 95% CI 1.43-15.25) and serum IgA/C3 ratio ≥ 3.32 (RR = 4.31, 95% CI 1.33-13.96).

CONCLUSION

A proportion of patients with IgAN developed end stage renal disease in a Chinese group. In addition to some traditional risk factors, we also confirmed that IgA/C3 ratio is a useful predictor of poor outcomes of IgAN in Chinese patients.

Redox properties of serum albumin

BACKGROUND

Oxidative damage results in protein modification, and is observed in numerous diseases. Human serum albumin (HSA), the most abundant circulating protein in the plasma, exerts important antioxidant activities against oxidative damage.

SCOPE OF REVIEW

The present review focuses on the characterization of chemical changes in HSA that are induced by oxidative damage, their relevance to human pathology and the most recent advances in clinical applications.

MAJOR CONCLUSIONS

The antioxidant properties of HSA are largely dependent on Cys34 and its contribution to the maintenance of intravascular homeostasis, including protecting the vascular endothelium under disease conditions related to oxidative stress. Recent studies also evaluated the susceptibility of other important amino acid residues to free radicals. The findings suggest that a redox change in HSA is related to the oxidation of several amino acid residues by different oxidants. Further, Cys34 adducts, such as S-nitrosylated and S-guanylated forms also play an important role in clinical applications. On the other hand, the ratio of the oxidized form to the normal form of albumin (HMA/HNA), which is a function of the redox states of Cys34, could serve as a useful marker for evaluating systemic redox states, which would be useful for the evaluation of disease progression and therapeutic efficacy.

GENERAL SIGNIFICANCE

This review provides new insights into our current understanding of the mechanism of HSA oxidation, based on in vitro and in vivo studies. This article is part of a Special Issue entitled Serum Albumin.

Oxidized albumin. The long way of a protein of uncertain function

BACKGROUND

Proteins are extremely reactive to oxidants and should represent a potential target of instable reactive oxygen. This may represent a problem for plasma proteins since they may be directly modified in vivo in a compartment where antioxidant enzymatic systems are scarcely represented. On the other hand, it is possible that some plasma components have evolved over time to guarantee protection, in which case they can be considered as anti-oxidants.

SCOPE OF REVIEW

To present and discuss main studies which addressed the role of albumin in plasma antioxidant activity mainly utilizing in vitro models of oxidation. To present some advances on structural features of oxidized albumin deriving from studies carried out on in vitro models as well as albumin purified in vivo from patients affected by clinical conditions characterized by oxidative stress.

MAJOR CONCLUSIONS

There are different interaction with HOCl and chloramines. In the former case, HOCl produces an extensive alteration of (238)Trp and (162)Tyr, (425)Tyr, (47)Tyr, while thiol groups are only partially involved. Chloramines are extremely reactive with the unique free SH group of albumin ((34)Cys) with the formation of sulfenic and sulfinic acid as intermediates and sulfonic acid as end-product. Oxidized albumin has a modified electrical charge for the addition of an acidic residue and presents α-helix and random coil reorganization with subtle changes in domain orientation.

GENERAL SIGNIFICANCE

Albumin, is the major antioxidants in plasma with a concentration (0.8mM) higher than other antioxidants by an exponential factor. Functional and protective roles in the presence of oxidative stress must be defined. This article is part of a Special Issue entitled Serum Albumin.

Advanced oxidation protein products activate intrarenal renin-angiotensin system via a CD36-mediated, redox-dependent pathway

AIMS

Activation of intrarenal renin-angiotensin system (RAS) has a detrimental effect on the progression of chronic kidney diseases (CKDs), although the regulation of intrarenal RAS remains unclear. The aim of the present study was to evaluate the role of advanced oxidation protein products (AOPPs) in intrarenal RAS activation.

RESULTS

AOPPs upregulated the expression of almost all components of RAS and increased activity of angiotensin-converting enzyme in cultured proximal tubular epithelial cells. The triggering effect of AOPP-albumin was 100-times stronger than that of unmodified albumin. The effect of AOPP-albumin was mainly mediated by a CD36-dependent, redox-sensitive signaling involving activation of protein kinase Cα, NADPH oxidase, and nuclear factor-κB/activation protein-1. Chronic AOPP-albumin loading in unilateral nephrectomy rats resulted in deposition of AOPPs in renal tubular cells accompanied with local RAS activation and functional perturbations such as increase in urinary albumin excretion. Accumulation of AOPPs was also detected in human renal tubular cells and correlated with expression of angiotensin II in renal biopsies from 19 patients with IgA nephropathy.

INNOVATION AND CONCLUSION

This study demonstrated for the first time that AOPPs modified albumin functions as a strong trigger of intrarenal RAS via a CD36-mediated, redox-dependent pathway. Given the fact that accumulation of AOPPs is prevalent in diabetes and CKD, targeting AOPPs could be a strategy for the therapeutic intervention of CKD. Antioxid. Redox Signal. 18, 19-35.

Non transferrin bound iron: nature, manifestations and analytical approaches for estimation

Iron is an essential trace element and plays a number of vital roles in biological system. It also leads the chains of pathological actions if present in excess and/or present in free form. Major portion of iron in circulation is associated with transferrin, a classical iron transporter, which prevent the existence of free iron. The fraction of iron which is free of transferrin is known as "non transferrin bound iron". Along with the incidence in iron over loaded patient non transferrin bound iron has been indicated in patients without iron overload. It has been suggested as cause as well as consequence in a number of pathological conditions. The major organs influenced by iron toxicity are heart, pancreas, kidney, organs involved in hematopoiesis etc. The most commonly suggested way for iron mediated pathogenesis is through increased oxidative stress and their secondary effects. Generation of free oxygen radicals by iron has been well documented in Fenton chemistry and Haber-Weiss reaction. Non transferrin bound iron has obvious chance to generate the free reactive radicals as it is not been shielded by the protective carrier protein apo transferrin. The nature of non transferrin bound iron is not clear at present time but it is definitely a group of heterogenous iron forms free from transferrin and ferritin. A variety of analytical approaches like colorimetry, chromatography, fluorimetry etc. have been experimented in different research laboratories for estimation of non transferrin bound iron. However the universally accepted gold standard method which can be operated in pathological laboratories is still to be developed.

Relationship of advanced oxidative protein products in human saliva and plasma: age- and gender-related changes and stability during storage

The blood levels of advanced oxidative protein products (AOPP) elevate in aging and age-related diseases. However, saliva AOPP in healthy humans have been unexplored. Thus, we investigated 143 Chinese healthy adults to assay age- and gender-related changes in saliva and plasma AOPP levels and the stability of saliva AOPP stored both at - 20°C and - 80°C. We found the mean AOPP levels in saliva and plasma of 119 subjects were 7.51 ± 3.20 and 28.31 ± 5.53 μmol/L (μM). An age-dependent increase was observed in both saliva and plasma AOPP levels. This increase was particularly significant in the elderly subjects compared with that in the young and middle-aged ones. A significant positive correlation among age, saliva and plasma AOPP levels was observed. No gender-dependent difference was observed in either saliva or plasma AOPP levels during the aging process. Furthermore, AOPP levels in the 24 saliva samples showed no significant change at every successive determination during 4 weeks at - 80°C, whereas those levels significantly increased after 7 days of storage at - 20°C. These results indicate the feasibility to screen aging biochemical indicators using saliva AOPP as an alternative to blood AOPP. Saliva AOPP samples are suitable to be stored at - 80°C.

The receptor of advanced glycation end products plays a central role in advanced oxidation protein products-induced podocyte apoptosis

The accumulation of plasma advanced oxidation protein products (AOPPs) is prevalent in chronic kidney disease. We previously showed that accumulation of AOPPs resulted in podocyte apoptosis and their deletion by a cascade of signaling events coupled with intracellular oxidative stress. The transmembrane receptor that specifically transmits the AOPPs' signals to elicit cellular activity, however, remains unknown. Using co-immunoprecipitation and immunofluorescence, we found that AOPPs colocalized and interacted with the receptor of advanced glycation end products (RAGE) on podocytes. Blocking RAGE by anti-RAGE immunoglobulin G or its silencing by siRNA significantly protected podocytes from AOPPs-induced apoptosis both in vitro and in vivo and ameliorated albuminuria in AOPPs-challenged mice. AOPPs-induced activation of nicotinamide adenine dinucleotide phosphate oxidase and the excessive generation of intracellular superoxide were largely inhibited by anti-RAGE immunoglobulin G or RAGE siRNA. Moreover, blockade of RAGE decreased the activation of the p53/Bax/caspase-dependent proapoptotic pathway induced by AOPPs. Thus, AOPPs interact with RAGE to induce podocyte apoptosis and this, in part, may contribute to the progression of chronic kidney disease.