Serum alpha 1-antitrypsin predicts severe acute kidney injury after cardiac surgery

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.

The nephrotoxic potential of polystyrene microplastics at realistic environmental concentrations

As microplastics (MPs) dispersed into the environment, people might be exposed to MPs. Most pollutants either pass through or concentrate in the kidney. Therefore, nephrotoxicity tests are needed to verify the toxic potential of MPs. Here we used human embryonic kidney 293 (HEK293) cells to determine the association between nephrotoxicity and round-shape polystyrene MPs (PSMPs) (3.54 ± 0.39 μm) under realistic environmental exposure concentrations. Results revealed that PSMPs can adhere to the cell membrane and get entirely engulfed by HEK293 cells. PSMPs can induce cytotoxicity by oxidative stress via inhibition of the antioxidant haem oxygenase-1. Depolarisation of the mitochondrial membrane potential and formation of autophagosomes confirmed that apoptosis and autophagy can be simultaneously induced by PSMPs. The inflammatory factor was only activated (33 cytokines) by noncytotoxic concentration of PSMPs (3 ng/mL); however, the cytotoxic concentration (300 ng/mL) of PSMPs induced autophagy, which might further reduce NLRP3 expression, thus contributing to dampening inflammation (35 cytokines) in HEK293 cells. PSMPs (300 ng/mL) can impair kidney barrier integrity and increase the probability of developing acute kidney injury through the depletion of the zonula occludens-2 proteins and α1-antitrypsin. Altogether, our results demonstrated that environmental exposure to PSMPs may lead to an increased risk of renal disease.

Plasma Metabolites-Based Prediction in Cardiac Surgery-Associated Acute Kidney Injury

Background

Cardiac surgery–associated acute kidney injury (CSA‐AKI) is a common postoperative complication following cardiac surgery. Currently, there are no reliable methods for the early prediction of CSA‐AKI in hospitalized patients. This study developed and evaluated the diagnostic use of metabolomics‐based biomarkers in patients with CSA‐AKI.

Methods and Results

A total of 214 individuals (122 patients with acute kidney injury [AKI], 92 patients without AKI as controls) were enrolled in this study. Plasma samples were analyzed by liquid chromatography tandem mass spectrometry using untargeted and targeted metabolomic approaches. Time‐dependent effects of selected metabolites were investigated in an AKI swine model. Multiple machine learning algorithms were used to identify plasma metabolites positively associated with CSA‐AKI. Metabolomic analyses from plasma samples taken within 24 hours following cardiac surgery were useful for distinguishing patients with AKI from controls without AKI. Gluconic acid, fumaric acid, and pseudouridine were significantly upregulated in patients with AKI. A random forest model constructed with selected clinical parameters and metabolites exhibited excellent discriminative ability (area under curve, 0.939; 95% CI, 0.879–0.998). In the AKI swine model, plasma levels of the 3 discriminating metabolites increased in a time‐dependent manner (R², 0.480–0.945). Use of this AKI predictive model was then confirmed in the validation cohort (area under curve, 0.972; 95% CI, 0.947–0.996). The predictive model remained robust when tested in a subset of patients with early‐stage AKI in the validation cohort (area under curve, 0.943; 95% CI, 0.883–1.000).

Conclusions

High‐resolution metabolomics is sufficiently powerful for developing novel biomarkers. Plasma levels of 3 metabolites were useful for the early identification of CSA‐AKI.

ATF3: a novel biomarker for the diagnosis of acute kidney injury after cardiac surgery

Background

To investigate the expression of ATF3 in the blood and urine of adult patients undergoing cardiopulmonary bypass (CPB) surgery and to identify the changes during the perioperative period of CPB, and to determine whether ATF3 can be used as a biological marker for the early diagnosis of acute kidney injury (AKI).

Methods

We prospectively studied 83 patients who underwent elective CPB (ECB). Relevant clinical information was collected. Blood and urine samples were collected preoperatively (T0) and at 2 h (T1), 6 h (T2), 12 h (T3), 24 h (T4), and 48 h (T5) after surgery, and grouped according to the occurrence of AKI. The changes in ATF3 levels were observed, and the accuracy of the diagnosis of AKI was compared through receiver operating characteristic (ROC) curve analysis. Factors influencing the expression of ATF3 at baseline were also analyzed.

Results

A total of 83 adult patients undergoing cardiac surgery with CPB were included, and 42 of them developed AKI. The levels of serum ATF3 (sATF3) in the AKI group were significantly higher than those in the non-AKI group 24 h after surgery, and the difference was statistically significant (662.62±204.72 vs. 586.93±175.87; P=0.0345). Urinary ATF3 (uATF3) increased significantly 6 h after surgery, and the area under the ROC curve (AUC) for diagnosing AKI 12 h after surgery was 0.691 (95% CI: 0.576–0.807). When uATF3 was higher than 1,216 pg/mL, the sensitivity and specificity for the diagnosis of AKI were 0.43 and 0.85, respectively. On the other hand, the preoperative expression of ATF3 was negatively correlated with the preoperative creatinine level, but not affected by the patient’s age, weight, gender, preoperative cardiac function, preoperative blood routine examination and liver function.

Conclusions

ATF3 can be expressed early in the blood and urine of patients after CPB and can be used as a diagnostic marker for AKI after CPB in adult patients.

Copeptin concentration following cardiac surgery as a prognostic marker of postoperative acute kidney injury: a prospective cohort study

Background

Copeptin, the C-terminal portion of the arginine vasopressin precursor, is a novel candidate biomarker. This study investigated the prognostic value of copeptin levels following cardiac surgery for the occurrence of postoperative acute kidney injury.

Methods

We studied 23 patients who underwent cardiac surgery between January 2018 and December 2019. The primary endpoint was postoperative acute kidney injury onset. Copeptin levels were measured before, right after, and daily for 7 days. The patients were divided into two groups according to the copeptin levels: low (values <43.7 pmol/L) and high (values ≥43.7 pmol/L). Correlations between copeptin levels and variables, such as central venous pressure, were assessed by bivariate analysis.

Results

The high copeptin group exhibited significantly higher levels of arginine vasopressin and cortisol following surgery, compared to those of the low copeptin group. The copeptin concentration following surgery was correlated to central venous pressure (P=0.03) and norepinephrine administered dose (P=0.008). Also, the copeptin levels right after surgery robustly predicted the onset of postoperative acute kidney injury (area under the receiver operating characteristic curve of 0.83, P=0.004).

Conclusions

Elevated copeptin levels in patients following cardiac surgery predicted postoperative acute kidney injury development. Therefore, the copeptin concentration after surgery could represent a promising clinical biomarker of the postoperative cardiac outcome.