The Pivotal Role of a Novel Biomarker of Reactive Oxygen Species in Chronic Kidney Disease

Safety Landscape of Therapeutic Nanozymes and Future Research Directions

Oxidative stress and inflammation are at the root of a multitude of diseases. Treatment of these conditions is often necessary but current standard therapies to fight excessive reactive oxygen species (ROS) and inflammation are often ineffective or complicated by substantial safety concerns. Nanozymes are emerging nanomaterials with intrinsic enzyme-like properties that hold great promise for effective cancer treatment, bacterial elimination, and anti-inflammatory/anti-oxidant therapy. While there is rapid progress in tailoring their catalytic activities as evidenced by the recent integration of single-atom catalysts (SACs) to create next-generation nanozymes with superior activity, selectivity, and stability, a better understanding and tuning of their safety profile is imperative for successful clinical translation. This review outlines the current applied safety assessment approaches and provides a comprehensive summary of the safety knowledge of therapeutic nanozymes. Overall, nanozymes so far show good in vitro and in vivo biocompatibility despite considerable differences in their composition and enzymatic activities. However, current safety investigations mostly cover a limited set of basic toxicological endpoints, which do not allow for a thorough and deep assessment. Ultimately, remaining research gaps that should be carefully addressed in future studies are highlighted, to optimize the safety profile of therapeutic nanozymes early in their pre-clinical development.

Myeloperoxidase, carnitine, and derivatives of reactive oxidative metabolites in heart failure with preserved versus reduced ejection fraction: A meta-analysis

BACKGROUND

Understanding the pathophysiology of heart failure (HF) with preserved ejection fraction (HFpEF) continues to be challenging. Several inflammatory and metabolic biomarkers have recently been suggested to be involved in HFpEF.

OBJECTIVES

The purpose of this review was to synthesize the evidence on non-traditional biomarkers from metabolomic studies that may distinguish HFpEF from heart failure with reduced ejection fraction (HFrEF) and controls without HF.

METHODS

A systematic search was conducted using Medline and PubMed with search terms such as "HFpEF" and "metabolomics", and a meta-analysis was conducted.

RESULTS

Myeloperoxidase (MPO) levels were significantly (p < 0.001) higher in HFpEF than controls without HF, but comparable (p = 0.838) between HFpEF and HFrEF. Carnitine levels were significantly (p < 0.0001) higher in HFrEF than HFpEF, but comparable (p = 0.443) between HFpEF and controls without HF. Derivatives of reactive oxidative metabolites (DROMs) were not significantly (p = 0.575) higher in HFpEF than controls without HF.

CONCLUSION

These data suggest that MPO is operative in HFpEF and HFrEF and may be a biomarker for HF. Furthermore, circulating carnitine levels may distinguish HFrEF from HFpEF.

Development of a Microminipig Model of Atherosclerosis for the Evaluation of a HMGCR Inhibitor

BACKGROUND/AIM

Atherosclerosis is known as a major risk factor for cardiovascular disease, and development of an animal model of atherosclerosis is required to investigate its clinical pathogenesis. We studied the optimal amount of cholesterol in the diet and the optimal experimental period for development of a Microminipig model of atherosclerosis for the evaluation of a hydroxymethylglutaryl-CoA reductase (HMGCR) inhibitor (atorvastatin).

MATERIALS AND METHODS

Eighteen male animals (3-4 months old) were divided into 3 groups. Group 1 consisted of control animals receiving a normal chow diet, Group 2 animals received a high fat (12% w/w) and low cholesterol (0.1% w/w) diet (HFLCD), and Group 3 animals received HFLCD+statin for 12 weeks. Animals received statin at 3 mg/kg body weight per day. HFLCD did not down-regulate the hepatic expression of HMGCR mRNA.

RESULTS

HFLCD increased body, omentum, and mesenteric adipose tissue weight, and induced hypercholesterolemia and atherosclerotic lesions in the abdominal aorta. HFLCD+statin inhibited hypercholesterolemia and atherosclerotic lesions, but not obesity.

CONCLUSION

A microminipig atherosclerosis model induced by HFLCD can be used in the evaluation of HMGCR inhibitors for the treatment of hypercholesterolemia and atherosclerosis.

Acupuncture Treatment Improves Transport Stress in Microminipigs Through the Acupoint in Ears

BACKGROUND/AIM

This study aimed to investigate the effects of acupuncture treatment through the ear acupoints on transport stress in experimental microminipigs.

MATERIALS AND METHODS

Experiment 1: Six animals were equally divided into two groups (Control and Treatment). In the treatment group, before transportation (6 h; vehicle and plane), short, ultrathin circular transdermal needles were applied to locations corresponding to the acupoints on the apical area of both ears. Peripheral blood samples were collected from the cranial vena cava 2 days before and immediately after transportation. Blood stress markers, biochemistry indicators, and oxidative stress levels were examined. Experiment 2 (follow-up study: diarrhea incidence after transportation): Diarrhea incidence after transportation in the control and treatment groups was investigated.

RESULTS

Experiment 1: Transport stress induced an increase in blood cortisol, serum amyloid A (SAA), glucose, non-esterified fatty acid, and derivatives of reactive oxygen metabolites (d-ROMs) and decreased the biological antioxidant potential (BAP)/d-ROMs ratio yet did not affect BAP. Acupuncture suppressed the increases in SAA and d-ROMs values and the decrease in BAP/d-ROMs ratio. Experiment 2: The total diarrhea incidence was 25% in the control group, whereas diarrhea was not observed in the treatment group.

CONCLUSION

Acupuncture treatment suppresses hypothalamic-pituitary-adrenal function and, as a result, reduces transport stress without affecting the suppression of the central catecholaminergic system. Acupuncture treatment for transport stress can improve animal welfare.

The Prognostic Value of Derivatives-Reactive Oxygen Metabolites (d-ROMs) for Cardiovascular Disease Events and Mortality: A Review

Oxidative stress participates in the development and exacerbation of cardiovascular diseases (CVD). The ability to promptly quantify an imbalance in an individual reductive-oxidative (RedOx) state could improve cardiovascular risk assessment and management. Derivatives-reactive oxygen metabolites (d-ROMs) are an emerging biomarker of oxidative stress quantifiable in minutes through standard biochemical analysers or by a bedside point-of-care test. The current review evaluates available data on the prognostic value of d-ROMs for CVD events and mortality in individuals with known and unknown CVD. Outcome studies involving small and large cohorts were analysed and hazard ratio, risk ratio, odds ratio, and mean differences were used as measures of effect. High d-ROM plasma levels were found to be an independent predictor of CVD events and mortality. Risk begins increasing at d-ROM levels higher than 340 UCARR and rises considerably above 400 UCARR. Conversely, low d-ROM plasma levels are a good negative predictor for CVD events in patients with coronary artery disease and heart failure. Moreover, combining d-ROMs with other relevant biomarkers routinely used in clinical practice might support a more precise cardiovascular risk assessment. We conclude that d-ROMs represent an emerging oxidative-stress-related biomarker with the potential for better risk stratification both in primary and secondary cardiovascular prevention.

Potential biomarkers for chronic seasonal heat stress in Kagoshima Berkshire pigs reared in the subtropical region

Introduction

Potential biomarkers for chronic seasonal heat stress in Kagoshima Berkshire pigs reared in the subtropical region were investigated by comparing the biomarker changes in the summer (a period of chronic heat stress) and winter (a thermoneutral period) seasons.

Material and Methods

Pigs were allocated to summer- and winter-finishing cohorts, 12 each. The evaluations included assessment of carcass traits and internal organs’ normality carried out at the time of slaughter, and measurement of biomarkers in whole blood: derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential as markers of oxidative stress, and serum amyloid A and albumin/globulin (A/G) ratio as markers of acute and chronic inflammation, respectively.

Results

The summer-finished pigs reared under subtropical field conditions showed lower carcass quality than the winter-finished pigs, indicating a potential adverse effect of summer temperatures on the swine industry. Marginal changes were observed in d-ROMs and the A/G ratio between the summer- and winter-finishing cohorts.

Conclusions

The results demonstrate that d-ROMs and the A/G ratio could be used as sensitive markers for heat stress under field conditions.

Oxidative Stress and Abnormal Tendon Sonographic Features in Elite Soccer Players (A Pilot Study)

Objective  Sound experimental data suggest that oxidative stress plays an important role in the pathogenesis of tendinopathies. However, this hypothesis in humans remains speculative given that clinical data are lacking to confirm it. Recently, a new methodology has allowed to quantify the oxidative stress in vivo by measuring the concentration of hydroperoxides of organic compounds, which have been utilized as an oxidative stress-related marker in several pathologic and physiologic conditions. Given the reliability of this test and the lack of information in subjects with tendinopathies, the aim of the present study was to assess the oxidative stress status in elite professional soccer players with and without ultrasonographic features of tendon damage.

Methods  In 73 elite players, blood metabolic parameters were evaluated and oxidative stress was measured by means of a specific test (expressed as U-Carr units). Therefore, an ultrasonographic evaluation of the Achilles and patellar tendons was performed.

Results  No significant relationships were observed between metabolic parameters and oxidative stress biomarkers. The Achilles and patellar tendons showed a normal echographic pattern in 58 athletes, and sonographic abnormalities in 15. The athletes with ultrasonographic alterations, compared to those with normal US picture, showed significantly higher U-Carr levels ( p  = 0.000), body mass index (BMI) values ( p  = 0.03) and were older ( p  = 0.005). The difference in U-Carr values among the subjects remained significant also after adjustment for age and BMI.

Conclusion  The results of the present study support the hypothesis that oxidative substances, also increased at systemic and not only at local level, may favor tendon damage.

Level of Evidence  IV (pilot study).

Protective Effect of Autologous Arteriovenous Fistulae Against Oxidative Stress in Hemodialyzed Patients

Introduction: Oxidative stress (OS) is ubiquitous in chronic kidney disease (CKD) and is exacerbated by hemodialysis (HD). OS is also associated with anemia, malnutrition, and cardiovascular (CV) disease and is an independent predictor of mortality and morbidity in patients undergoing HD. HD vascular access (VA) types are strongly correlated with CKD patient outcomes. Prolonged use of central venous catheters (CVC) for HD and arteriovenous grafts (AVG) promotes inflammation and OS. However, the effects of the VA type on OS have been poorly studied in HD patients. This study investigated OS prevalence in an HD population to determine the relationship between the VA type and HD.

Methods: The oxidative stress index (OSI) was used to assess the HD patients’ OS status. OSI summarizes information derived from the reactive oxygen metabolites (d-ROMs) fast test and the plasma antioxidant test (PAT) in a single value, using the hydrogen peroxide concentration (for d-ROMs) and ascorbic acid (for PAT) as reference standards. The OSI was created to indicate how far the OS status deviates from normal (i.e., fully compensated oxidative balance). An index increase may be from an increase or decrease in peroxide or antioxidant concentrations. Patients undergoing chronic HD were evaluated by dividing the cases according to the OSI status: normal (N-OSI), borderline (BL-OSI), high (H-OSI), and very high (VH-OSI). Patients with clinical evidence of active infections were excluded.

Results: In total, 129 patients were included; 86.8% used high-flux dialyzers, 13.2% used hemodiafiltration (HDF), and 24.5% were diabetic. An altered OSI was observed in 86 of 129 patients (66.7%). An increased OSI correlated with a significant increase in d-ROMs (r = 0.420) and PAT (r = 0.710). There were no differences between sex, diabetes status, age, dialysis vintage, or dialysis modalities. d-ROMs were inversely correlated with hemoglobin levels (r = −0.209). The iron dose by month correlated with the OSI (r = 0.189) and was significantly lower in the N-OSI group. N- and BL-OSI patients had a significantly higher rate of autologous arteriovenous fistula (AVF) compared to the other groups, and VH-OSI patients had a higher rate of permanent tunneled CVC.

Conclusion: Most HD patients had more OS, indicated by the OSI scores. In chronic HD patients, AVF had a protective effect against imbalanced peroxidation-antioxidation.

Establishment of a Nanopatterned Renal Disease Model by Mimicking the Physical and Chemical Cues of a Diseased Mesangial Cell Microenvironment

Modulation of mesangial cell (MC) response by in vitro disease models offers therapeutic strategies for the treatment of several glomerular diseases. However, traditional cell culture models lack the nanostructured extracellular matrix (ECM), which has unique physical and chemical properties, so they poorly reflect the complexities of the native microenvironment. Therefore, a cell disease model with ECM nanostructures is required to better mimic the in vivo diseased nanoenvironment. To establish a renal disease model, we used a titanium dioxide-based disease-mimic nanopattern as the physical cues and transforming growth factor-beta 1 (TGF-β1) as a chemical cue. The effects of this renal disease model on proliferation and mesangial matrix (MM) component changes in the SV40MES13 (MES13) mouse mesangial cell line were evaluated. Our results showed that both the presence of the disease-mimic nanopattern and TGF-β1 intensified proliferation and resulted in increased type I collagen and fibronectin and decreased type IV collagen expressions in MES13 cells. These effects could be involved in increased TGF-β type I receptor expression in MES13 cells. The intracellular reactive oxygen species (ROS) level as a biomarker of this renal disease model indicated that the cells were in a diseased state. A small molecule A83-01 and known drug dexamethasone markedly attenuated the intracellular ROS production in MES13 that was induced by the disease-mimic nanopattern and TGF-β1. These results highlight the significant effects of physical and chemical cues in facilitating disease-like behavior in MES13 cells, providing an important theoretical basis for developing a drug screening platform for glomerular diseases.

Salvianolic acid A alleviates the renal damage in rats with chronic renal failure1

Purpose

To investigate the protective effects of salvianolic acid A (SAA) on renal damage in rats with chronic renal failure (CRF).

Methods

The five-sixth nephrectomy model of CRF was successfully established in group CRF (10 rats) and group CRF+SAA (10 rats). Ten rats were selected as sham-operated group (group S), in which only the capsules of both kidneys were removed. The rats in group CRF+SAA were intragastrically administrated with 10 mg/kg SAA for 8 weeks. The blood urine nitrogen (BUN), urine creatinine (Ucr), creatinine clearance rate (Ccr), and serum uperoxide dismutase (SOD) and malondialdehyde (MDA) were tested. The expressions of transforming growth factor-β1 (TGF-β1), bone morphogenetic protein 7 (BMP-7) and Smad6 protein in renal tissue were determined.

Results

After treatment, compared with group CRF, in group CRF+SAA the BUN, Scr, serum MDA and kidney/body weight ratio were decreased, the Ccr and serum SOD were increased, the TGF-β1 protein expression level in renal tissue was decreased, and the BMP-7 and Smad6 protein levels were increased (all P < 0.05).

Conclusion

SAA can alleviate the renal damage in CRF rats through anti-oxidant stress, down-regulation of TGF-β1 signaling pathway and up-regulation of BMP-7/Smad6 signaling pathway.

Association of serum markers of oxidative stress with myocardial infarction and stroke: pooled results from four large European cohort studies

Oxidative stress contributes to endothelial dysfunction and is involved in the pathogenesis of myocardial infarction (MI) and stroke. However, associations of biomarkers of oxidative stress with MI and stroke have not yet been addressed in large cohort studies. A nested case-control design was applied in four population-based cohort studies from Germany, Czech Republic, Poland and Lithuania. Derivatives of reactive oxygen metabolites (d-ROMs) levels, as a proxy for the reactive oxygen species burden, and total thiol levels (TTL), as a proxy for the reductive capacity, were measured in baseline serum samples of 476 incident MI cases and 454 incident stroke cases as well as five controls per case individually matched by study center, age and sex. Statistical analyses were conducted with multi-variable adjusted conditional logistic regression models. d-ROMs levels were associated with both MI (odds ratio (OR), 1.21 [95% confidence interval (CI) 1.05-1.40] for 100 Carr units increase) and stroke (OR, 1.17 [95% CI 1.01-1.35] for 100 Carr units increase). TTL were only associated with stroke incidence (OR, 0.79 [95% CI 0.63-0.99] for quartiles 2-4 vs. quartile 1). The observed relationships were stronger with fatal than with non-fatal endpoints; association of TTL with fatal MI was statistically significant (OR, 0.69 [95% CI 0.51-0.93] for 100 μmol/L-increase). This pooled analysis of four large population-based cohorts suggests an important contribution of an imbalanced redox system to the etiology of mainly fatal MI and stroke events.

Molecular hydrogen ameliorates several characteristics of preeclampsia in the Reduced Uterine Perfusion Pressure (RUPP) rat model

Oxidative stress plays an important role in the pathogenesis of preeclampsia. Recently, molecular hydrogen (H₂) has been shown to have therapeutic potential in various oxidative stress-related diseases. The aim of this study is to investigate the effect of H₂ on preeclampsia. We used the reduced utero-placental perfusion pressure (RUPP) rat model, which has been widely used as a model of preeclampsia. H₂ water (HW) was administered orally ad libitum in RUPP rats from gestational day (GD) 12-19, starting 2 days before RUPP procedure. On GD19, mean arterial pressure (MAP) was measured, and samples were collected. Maternal administration of HW significantly decreased MAP, and increased fetal and placental weight in RUPP rats. The increased levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and diacron reactive oxygen metabolites as a biomarker of reactive oxygen species in maternal blood were decreased by HW administration. However, vascular endothelial growth factor level in maternal blood was increased by HW administration. Proteinuria, and histological findings in kidney were improved by HW administration. In addition, the effects of H₂ on placental villi were examined by using a trophoblast cell line (BeWo) and villous explants from the placental tissue of women with or without preeclampsia. H₂ significantly attenuated hydrogen peroxide-induced sFlt-1 expression, but could not reduce the expression induced by hypoxia in BeWo cells. H₂ significantly attenuated sFlt-1 expression in villous explants from women with preeclampsia, but not affected them from normotensive pregnancy. The prophylactic administration of H₂ attenuated placental ischemia-induced hypertension, angiogenic imbalance, and oxidative stress. These results support the theory that H₂ has a potential benefit in the prevention of preeclampsia.

Usefulness of the d-ROMs test for prediction of cardiovascular events

BACKGROUND

d-ROMs test developed to determine the degree of individual oxidative stress may predict cardiovascular events.

METHODS AND RESULTS

265 patients (204 men, 61 women; age, 65±13years) who had been treated for cardiovascular disease were divided evenly by quartile of baseline d-ROMs levels, and were followed up. During the observation periods of 2.66±1.47years, there were 14 (5%) deaths, 8 (3%) cardiovascular deaths, 13 (5%) major adverse cardiovascular events (MACEs), and 51 (19%) all cardiovascular events including heart failure, cardiovascular surgery, and revascularization. Log-rank tests demonstrated that the patients in the 4th quartile (d-ROMs≧395.00U.CARR) had a higher incidence rate of cardiovascular death than those in the 2nd quartile (d-ROMs 286.00-335.00, p=0.022). In multivariate Cox regression analysis, even after adjustment for age, sex, coronary risk factors, C-reactive protein, and renal function, high d-ROMs was a risk factor for all-cause death [adjusted HR of 4th vs. 1st quartile, 10.791 (95% confidence interval 1.032-112.805), p=0.047], and all cardiovascular events [HR of 4th vs. 1st quartile, 2.651 (95% confidence interval 1.138-6.177), p=0.024].

CONCLUSIONS

Our results suggest that d-ROMs is a useful oxidative stress marker to assess prognosis and risk of further cardiovascular events.

Association of Circulating Follistatin-Like 1 Levels with Inflammatory and Oxidative Stress Markers in Healthy Men

Objectives

Follistatin-like 1 (Fstl1) is a circulating glycoprotein that plays a crucial role in cardiovascular diseases and inflammation-related disorders. We have shown that Fstl1 acts as an anti-inflammatory factor that protects against ischemic heart disease and chronic kidney disease. Here we examined whether plasma level of Fstl1 associates with markers of inflammation and oxidative stress in apparently healthy Japanese men.

Methods and Results

Plasma Fstl1 levels were measured by enzyme-linked immunosorbent assay. Circulating Fstl1 concentrations positively correlated with levels of fasting immune-reactive insulin (FIRI), high-sensitive CRP (hsCRP) and derivatives of reactive oxidative metabolites (dROMs), an indicator of oxidative stress. The levels of hsCRP positively associated with Fstl1, body mass index (BMI), triglyceride, FIRI and dROMs levels. dROMs levels positively associated with Fstl1, Hemoglobin A1c and hsCRP levels. Multiple regression analysis with confounding factors revealed that Fstl1 levels, together with BMI and FIRI, correlated with hsCRP and that Fstl1 levels correlated with dROMs.

Conclusion

Our observations indicate that measurement of plasma Fstl1 levels can be valuable for assessment of pro-inflammatory and oxidative stress conditions.

N-acetylcysteine alleviates angiotensin II-mediated renal fibrosis in mouse obstructed kidneys

AIM

To investigate the effects of ROS scavenger N-acetylcysteine (NAC) on angiotensin II (Ang II)-mediated renal fibrosis in vivo and in vitro.

METHODS

Mice were subjected to unilateral ureteral obstruction (UUO), and then treated with vehicle or NAC (250 mg/kg, ip) for 7 days. Histological changes of the obstructed kidneys were observed with Masson's trichrome staining. ROS levels were detected with DHE staining. The expression of relevant proteins in the obstructed kidneys was assessed using Western blotting assays. Cultured rat renal fibroblast NRK-49F cells were used for in vitro experiments.

RESULTS

In the obstructed kidneys, Ang II levels were significantly elevated, and collagen I was accumulated in the interstitial spaces. Furthermore, ROS production and the expression of p47 (a key subunit of NADPH oxidase complexes) were increased in a time-dependent manner; the expression of fibronectin, α-SMA and TGF-β were upregulated. Administration of NAC significantly alleviated the fibrotic responses in the obstructed kidneys. In cultured NRK-49F cells, treatment with Ang II (0.001-10 μmol/L) increased the expression of fibronectin, collagen I, α-SMA and TGF-β in dose-dependent and time-dependent manners. Ang II also increased ROS production and the phosphorylation of Smad3. Pretreatment with NAC (5 μmol/L) blocked Ang II-induced oxidative stress and ECM production in the cells.

CONCLUSION

In mouse obstructed kidneys, the fibrotic responses result from Ang II upregulation can be alleviated by the ROS scavenger N-acetylcysteine.