Advanced oxidation protein products as prognostic biomarkers for recovery from acute kidney injury after coronary artery bypass grafting

Urinary proteome analysis of acute kidney injury in post-cardiac surgery patients using enrichment materials with high-resolution mass spectrometry

Background: Cardiac surgery-associated acute kidney injury (CSA-AKI) may increase the mortality and incidence rates of chronic kidney disease in critically ill patients. This study aimed to investigate the underlying correlations between urinary proteomic changes and CSA-AKI.

Methods: Nontargeted proteomics was performed using nano liquid chromatography coupled with Orbitrap Exploris mass spectrometry (MS) on urinary samples preoperatively and postoperatively collected from patients with CSA-AKI. Gemini C18 silica microspheres were used to separate and enrich trypsin-hydrolysed peptides under basic mobile phase conditions. Differential analysis was conducted to screen out urinary differential expressed proteins (DEPs) among patients with CSA-AKI for bioinformatics. Kyoto Encyclopedia of Genes and Genomes (KEGG) database analysis was adopted to identify the altered signal pathways associated with CSA-AKI.

Results: Approximately 2000 urinary proteins were identified and quantified through data-independent acquisition MS, and 324 DEPs associated with AKI were screened by univariate statistics. According to KEGG enrichment analysis, the signal pathway of protein processing in the endoplasmic reticulum was enriched as the most up-regulated DEPs, and cell adhesion molecules were enriched as the most down-regulated DEPs. In protein–protein interaction analysis, the three hub targets in the up-regulated DEPs were α-1-antitrypsin, β-2-microglobulin and angiotensinogen, and the three key down-regulated DEPs were growth arrest-specific protein 6, matrix metalloproteinase-9 and urokinase-type plasminogen activator.

Conclusion: Urinary protein disorder was observed in CSA-AKI due to ischaemia and reperfusion. The application of Gemini C18 silica microspheres can improve the protein identification rate to obtain highly valuable resources for the urinary DEPs of AKI. This work provides valuable knowledge about urinary proteome biomarkers and essential resources for further research on AKI.

Evaluation of acute kidney injury with oxidative stress biomarkers and Renal Resistive Index after cardiac surgery

BACKGROUND

We investigated whether cardiopulmonary bypass (CPB) related oxidative stress mediated glycocalyx degradation can cause an increase in renal resistive index (RRI) or postoperative AKI. Additionally, to evaluate whether RRI and early postoperative serum cystatin C levels could improve the prediction sensitivity of acute kidney injury (AKI).

METHODS

Forty-two patients undergoing cardiac surgery were included in this prospective observational study. RRI was measured pre-operatively and in the cardiac intensive care unit. Blood samples were collected for analyzing of cellular injury biomarkers at preoperative and postoperative second hours. We determined areas under the receiver operating characteristic curve (AUC) and odds ratios for postoperative biomarkers and RRI to predict AKI.

RESULTS

While postoperative cystatin C level (AUC: 0.902, 95% CI = 0.79-1.00, p < .001) and RRI (AUC: 0.748, 95% CI = 0.56-0.93, p = .023) have diagnostic and predictive value in the prediction of AKI, we could not identify any relation between products of oxidative stress and the glycocalyx degradation and AKI.

CONCLUSION

These data suggest that CPB leads to structural and oxidative changes at the protein level and the integrity of glycocalyx is disturbing, but these changes are not specific to kidney injury. Our data suggest that serum cystatin C level and RRI could be used as an early biomarker for postoperative AKI after cardiac surgery.

The Relationship between Advanced Oxidation Protein Products, Vascular Calcifications and Arterial Stiffness in Predialysis Chronic Kidney Disease Patients

Background and Objectives: Cardiovascular morbidity and mortality are increased in patients with chronic kidney disease (CKD). It is likely that the accumulation of uremic toxins resulting in increased oxidative stress (OS) is a major contributing factor, but no clear link has been identified. The purpose of this research is to establish if advanced oxidation protein product (AOPP) levels in the serum of predialysis patients are a contributing factor to vascular calcification and increased arterial stiffness. Materials and Methods: After obtaining the informed consent, 46 predialysis patients (CKD stages G3-G5) were included in the study. In order to identify vascular calcifications, hand and pelvic radiographs were performed. Valvular calcifications were identified using cardiac ultrasound. AOPP were measured using a commercially available ELISA kit. The relationships between serum AOPP values and biochemical parameters relevant in the evaluation of CKD patients were analyzed. In addition to identifying the differences in AOPP levels between patients with/without vascular or valvular calcifications, the research focused on describing the relationship between OS and arterial stiffness assessed by oscillometric pulse-wave velocity (PWV) measurement. Results: No significant relationship between serum AOPP and vascular or valvular calcifications was highlighted, but significant correlations of AOPP with C-reactive protein (p = 0.025), HDL-cholesterol levels (p = 0.04), HbA1c (p = 0.05) and PWV values (p = 0.02) were identified. Conclusions: The usefulness of (OS) measurement in clinical practice remains debatable; however, the relationship between AOPP and arterial stiffness could be valuable in improving cardiovascular risk assessment of patients with CKD.

Effects of upper limb ischemia-reperfusion on regional oxidative stress during aortic surgery with moderate hypothermia

INTRODUCTION

This study aims to evaluate the effect of acute, iatrogenic right arm ischemia and reperfusion (I/R) due to right axillary cannulation on regional oxidative stress using tissue perfusion markers such as central venous oxygen saturation, lactate, the difference between central venous and arterial CO₂ pressure, near-infrared spectroscopy (NIRS) measurements, and biomarkers like sialic acid, malondialdehyde, advanced oxidative protein products in aortic surgery with moderate hypothermia.

METHODS

Adult patients undergoing ascending aorta repair with antegrade cerebral perfusion via the axillary artery participated. Blood samples were collected from the internal jugular vein, right arm cubital vein, and left arm cubital vein, and analysis was performed at intraoperative time points.

RESULTS

Right-arm venous oxygen saturation levels are significantly lower than left arm and central venous, as expected in iatrogenic ischemia. Right arm lactate levels are significantly higher. Somatic right arm NIRS values are significantly lower than somatic left arm. There are no significant differences for biomarkers throughout the time points.

CONCLUSIONS

We have concluded that well-known markers reflect the results of ischemia-reperfusion more rapidly, and are more valuable than novel biomarkers. NIRS is a promising monitor in terms of providing information about tissue oxygenation. Oxidative stress biomarkers do not change quickly enough to give useful information in a short enough period of time; moreover, their costs are high and laboratory studies take time. Although axillary cannulation is controlled limb ischemia, the local effects of I/R did not completely normalize at the end of the surgery, and this regional I/R did not affect the global body organism.

Comparative Effects of Blood and Crystalloid Cardioplegia on Cellular Injury and Oxidative Stress in Cardiovascular Surgery

Purpose: The purpose of this study was to evaluate the effect of different cardioplegic solutions on endothelial integrity and oxidative stress in cardiovascular surgery.

Methods: In this randomized prospective study, after ethics approval and informed consent, 60 surgical patients were included. Patients undergoing coronary bypass surgery were randomized into two groups as warm blood cardioplegia (n = 30) and cold crystalloid cardioplegia (n = 30) following the cross-clamping. Measurements were performed at three time points: before induction of anesthesia (T1), at admission to intensive care unit (ICU) (T2) and at the 24th postoperative hour (T3). Besides biochemical routine hemodynamic monitoring, patients were assessed for the sialic acid (SA), ischemic-modified albumin (IMA), advanced oxide protein products (AOPPs), total thiol (SH), and free hemoglobin (fHb) level.

Results: Neither crystalloid nor blood cardioplegia led to significant changes in the AOPPs, T-SH, and SA level (p >0.05). Crystalloid cardioplegia, however, increased IMA level compared to both baseline (p <0.01) and blood cardioplegia group (p <0.05). fHb levels were transiently increased in both groups at the second-time point (p <0.001). fHb level was lower in the crystalloid group compared to that in the other group (p <0.05) at T2.

Conclusion: Cardioplegia type creates similar effects on glycocalyx integrity. However, myocardial protection could be provided with warm blood cardioplegia.

Establishment of a model to predict the prognosis of pregnancy-related acute kidney injury

BACKGROUND

Our aim was to investigate the prognostic factors of pregnancy related acute kidney injury (PR-AKI), establish the prognosis prediction model and evaluate predictability with the model.

METHODS

Serum creatinine (SCr), placental growth factor (PLGF), endothelin-1 (ET-1), urinary kidney injury molecule-1 (KIM-1), and β2-microglobulin (β2-MG) levels in 122 patients with PR-AKI were measured at 1 month, 3 months, 6 months, and 1 year after delivery and the logistic backward stepwise regression method was used to screen the factors associated with the prognosis, establish the model to predict the prognosis of patients 1 year after delivery, and evaluate predictability with the model.

RESULTS

1) At 1 month, 3 months, 6 months, and 1 year after delivery, SCr was not significantly different in the poor prognosis group (P˃0.05); ET-1, KIM-1 and β2-MG were decreased significantly, and PLGF was significantly increased (P˂0.05); all testing indicators in the good prognosis group were significantly different and returned to normal within 1 year (P˂0.05). By comparing the two groups, there were no significant differences in SCr, PLGF and β2-MG levels at 1 month after delivery (P˃0.05), while there were significant differences in the remaining testing indicators at each time point (P˂0.05). 2) Logistic backward stepwise regression analysis showed that SCr, KIM-1, ET-1, and time were related to the prognosis of patients with PR-AKI, and the above screening indicators were used to fit the model Logit.

CONCLUSIONS

The logistic regression model fitting-effect was good, its accuracy of predicting renal injury prognosis was high. SCr, KIM-1, and ET-1 can be used for PR-AKI screening and are important for monitoring the disease condition of patients, intervention, and evaluation of prognosis.

Correction of dilutional anemia induces renal dysfunction in diabetic patients undergoing coronary artery bypass grafting: a consequence of microcirculatory alterations?

BACKGROUND

In this study we aimed to evaluate the effects of dilutional anemia resulting from cardiopulmonary bypass (CPB) and its correction with red blood cell (RBC) transfusion on tissue oxygenation and renal function in diabetic patients undergoing coronary artery bypass grafting (CABG).

METHOD

70 diabetic patients who underwent elective CABG and whose hematocrit values had been between 24-28% at any time during CBP were prospectively randomized and equally allocated to two groups: patients who received RBC during CPB (group I, n = 35) vs. did not receive RBC during CPB (group II, n = 35). Besides routine hemodynamic and biochemical parameters, biomarkers of ischemia and renal injury such as ischemia modified albumin (IMA), protein oxidation parameters [advanced oxidative protein products (AOPP), total thiol (T-SH)], neutrophil gelatinase-associated lipocalin (NGAL) and estimated glomerular filtration rate (eGFR) were measured in both groups.

RESULTS

In group I, T-SH, NGAL and urea levels were found to be significantly increased postoperatively compared to preoperative measurements (p < 0.05). Also, postoperatively, NGAL, creatinine, aspartate aminotransferase and AOPP levels were higher in group I than group II (p < 0.05).

CONCLUSION

The correction of anemia with RBC transfusion in diabetic patients undergoing CABG could increase the risk of renal injury. Further studies verifying the effects of blood transfusions at the microcirculatory level are needed to optimize the efficacy of transfusions.

Unilateral Antegrade Cerebral Perfusion and Moderate Hypothermia: Assessing Safety With Novel Biomarkers

BACKGROUND

Antegrade cerebral perfusion in aortic surgery is a well-established brain protection method. Open distal anastomosis during aortic surgery has some well-known advantages. Antegrade cerebral perfusion allows repair to some extent of the aortic arch, even in isolated ascending aortic aneurysm. The present study aims to investigate the adequacy of contralateral perfusion with novel oxidative stress parameters during unilateral antegrade cerebral perfusion.

METHOD

The study included 30 consecutive patients undergoing thoracic aortic surgery with unilateral antegrade cerebral perfusion (uACP) under moderate hypothermia (28° C). Blood samples from right and left jugular vein were obtained at four time intervals during surgery (after the anaesthetic induction - Phase 1, at the beginning of cardiopulmonary bypass - Phase 2, 15^th minute of uACP - Phase 3 and after weaning from cardiopulmonary bypass - Phase 4). Novel oxidative stress parameters (advanced oxidation protein products, sialic acid, thiol reagents and ischaemia-modified serum albumin), blood gas analysis, and serum glucose and lactate levels were measured. In addition, intraoperative and early postoperative follow-up parameters were recorded.

RESULTS

Mean unilateral antegrade cerebral perfusion time was observed to be 16.4±5.9min (9 - 46min). No significant differences between right and left hemispheres were observed in novel oxidative parameters or biochemical values. There was only one temporary neurological deficit (3.3%) in the patient group.

CONCLUSIONS

The present study demonstrated that open distal anastomosis for hemiarch repair can be performed safely with unilateral antegrade cerebral perfusion under moderate hypothermia with both clinical outcome and novel biomarkers.

Plasma level of advanced oxidation protein products as a novel biomarker of acute lung injury following cardiac surgery

This study was designed to test the hypothesis that whether the plasma level of advanced oxidant protein products (AOPPs) would be useful for the clinical diagnosis of acute lung injury (ALI) following cardiac surgery with the technique of cardiopulmonary bypass (CPB). In this prospective study, seventy consecutive adults undergoing open heart surgery with CPB were included and assigned into the ALI (n = 18) and non-ALI (n = 52) groups according to the American-European Consensus Criteria. Plasma concentrations of AOPPs were measured at baseline, postoperative 1 h, 12 h, 24 h, and 48 h. Eighteen patients (25.7 %) developed ALI after surgery. The plasma levels of AOPPs in the ALI group were significantly increased and remained considerably higher at all time points after operation (all P < 0.05). Multivariate logistic regression analysis revealed that the plasma level of AOPPs at 1 h after operation was an independent predictor for the diagnosis of ALI (OR 1.164; 95 % CI 1.068–1.269; P = 0.001). Plasma level of AOPPs could serve as an early biomarker of the incidence of ALI in adult patients who underwent open cardiac surgery with the technique of CPB.

Advanced oxidation protein products in predicting acute kidney injury following cardiac surgery

To test the hypothesis whether serum advanced oxidation protein products (AOPP) are associated with increased acute kidney injury (AKI) after cardiopulmonary bypass (CPB) and could serve as a biomarker in this aspect, we performed a prospective cohort study. Thirty-five (22.3%) patients developed AKI, and 32 age- and gender-matched patients without AKI were selected as control. Serum AOPP 1 h after CPB were significantly higher among AKI patients compared with non-AKI patients (81.8 ± 18.6 versus 67.4 ± 12.5 μmol/L, p < 0.001), with an area under the receiver-operating characteristic (ROC) curve of 0.714. An optimal serum AOPP 1 h after CPB cutoff of 69.9 μmol/L had a sensitivity of 74%, specificity of 63% and a positive predictive value of 68% for predicting AKI. These results demonstrated that serum AOPP might be an early biomarker for AKI after CPB.

Performance of urinary NGAL and L-FABP in predicting acute kidney injury and subsequent renal recovery: a cohort study based on major surgeries

BACKGROUND

Acute kidney injury (AKI) is a frequent complication of major surgery. The current study evaluated the power of two biomarkers [urinary neutrophil gelatinase-associated lipocalin (NGAL) and liver-type fatty acid binding protein (L-FABP)] to detect the occurrence of AKI and to predict the recovery from renal dysfunction in a major surgery cohort.

METHODS

In this prospective study, 199 patients undergoing major surgery were enrolled. Urinary samples collected from participants before surgery, and 0, 4, and 12 h and 1, 2, 7, and 14 days after surgery were tested for NGAL and L-FABP.

RESULTS

Thirty-seven (18.6%) subjects developed AKI. Urinary NGAL and L-FABP were significantly increased from the time surgery was completed (p<0.05). The peak levels of NGAL and L-FABP occurred 12 and 4 h postoperatively (16.4- and 172.0-fold compared to baseline) in AKI group, respectively. The area under the receiver operating characteristic (ROC) curve (AUC) in NGAL (at 12 h), L-FABP (at 4 h), the most predictive model (NGAL at 12 h+L-FABP at 4 h), and the best combination at the same time point (12 h) was 0.83 [95% confidence interval (CI), 0.74-0.91], 0.85 (95% CI 0.77-0.93), 0.94 (95% CI 0.89-0.98), and 0.91 (95% CI 0.85-0.97), respectively. However, the largest AUC of single and combined biomarkers for predicting non-recovery after AKI only reached 0.70.

CONCLUSIONS

Urinary NGAL and L-FABP can be used to detect AKI and combining NGAL and L-FABP may improve the diagnostic performance; however, NGAL and L-FABP may be poor predictors for renal recovery after AKI.

Atorvastatin treatment attenuates renal injury in an experimental model of ischemia-reperfusion in rats

BACKGROUND

Recent studies in animal models have shown that statins can protect against renal failure independent of their lipid-lowering actions, and there is also an association between statin use and improved renal function after suprarenal aortic clamping. We investigated the hypothesis that post-ischemic acute renal failure could be ameliorated with atorvastatin (ATO) treatment and the possible molecular mechanisms in a model of ischemia-reperfusion (IR) in rats.

METHODS

Twenty-four male Sprague-Dawley rats were divided into three groups: sham, IR, and IR + ATO. ATO was given by a single intraperitoneal injection (10 mg/kg) 30 min before reperfusion in the IR + ATO group. The IR group and sham group received saline vehicle via the intraperitoneal route.

RESULTS

After 24 h of IR, serum creatinine levels were increased in the IR group compared with the sham group (p < 0.001). ATO treatment reduced the elevation of serum creatinine level by 18% (p < 0.05) and significantly increased the creatinine clearance rate (p < 0.001). Concentrations of advanced oxidation protein products and malondialdehyde were reduced in the ATO group, approaching levels observed in sham-group rats. ATO treatment alleviated pathological changes in renal tubular cells. Protein and mRNA levels of intercellular adhesion molecule-1 and monocyte chemotactic protein-1 were reduced significantly.

CONCLUSIONS

These data suggest that direct protection of injured kidneys by ATO was possible even though the drug was injected 30 min before reperfusion, and that ATO may reduce IR injury by anti-inflammatory effects and by reducing oxidation stress.

A novel high resolution MS approach for the screening of 4-hydroxy-trans-2-nonenal sequestering agents

An in vitro high resolution mass spectrometry (MS) method was set-up to test the ability of compounds, mixtures and extracts to inhibit protein carbonylation induced by reactive carbonyl species (RCS). The method consists of incubating the protein target (ubiquitin) with 4-hydroxy-trans-2-nonenal (HNE) in the presence and absence of the tested compound. After 24h of incubation, the reaction is stopped and the protein is analyzed by high-resolution MS. The extent of protein carbonylation is determined by measuring the area of the +11 multicharged peak of the HNE adduct in respect to the native form. The method was validated by measuring the effect of well-known RCS sequestering agents, namely aminoguanidine, pyridoxamine, hydralazine and carnosine, yielding a good reproducibility and the possibility to be automatable. All the compounds were found to dose-dependently inhibit the protein carbonylation with the following order of potency carnosine≈hydralazine≫aminoguanidine>pyridoxamine, as determined by calculating the UC50 values, that is the concentration required to inhibit ubiquitin carbonylation by 50%. A good correlation was found with the results obtained by measuring HNE consumption using an HPLC method optimized by a mobile phase set at pH 7.4, in order to stabilize the eluted adducts. The MS approach was then applied to test the effect of two selected natural extracts on protein carbonylation, i.e. green coffee bean extract and procyanidins from Vitis vinifera. In summary, this paper reports a validated and highly reproducible MS method to test the ability of pure compounds as well as natural extracts to act as protein carbonylation inhibitors.