Protein Kinase N1 Level Predicts Acute Kidney Injury in Patients Undergoing Cardiac Surgery: A Prospective Cohort Study.

INTRODUCTION: The objective of this study was to examine the utility of protein kinase N1 (PKN1) as a biomarker of cardiac surgery-associated AKI (CSA-AKI). METHODS: A prospective cohort study of 110 adults undergoing on-pump cardiac surgery was conducted. The associations between post-operative PKN1 and CSA-AKI, AKI severity, need for renal replacement therapy (RRT), duration of AKI, length of ICU stay, and post-operative hospital stay were evaluated. RESULTS: Patients were categorized into three groups according to PKN1 tertiles. The incidence of CSA-AKI in the third tertile was 3.4-fold higher than that in the first. PKN1 was an independent risk factor for CSA-AKI. The discrimination of PKN1 to CSA-AKI assessed by ROC curve indicated that the AUC was 0.70, and the best cutoff was 5.025 ng/mL. This group (>5.025 ng/mL) was more likely to develop CSA-AKI (p < 0.001). The combined AUC of EuroSCORE, aortic cross-clamp time, and PKN1 was 0.82 (p < 0.001). A higher level of PKN1 was related to increased need for RRT, longer duration of AKI, and length of ICU and post-operative hospital stays. CONCLUSIONS: PKN1 could be a potential biomarker for the prediction of CSA-AKI. The combination of PKN1, EuroSCORE, and aortic cross-clamp time was likely to predict the occurrence of CSA-AKI.

TIMP2 mediates endoplasmic reticulum stress contributing to sepsis-induced acute kidney injury.

Tissue inhibitor of metalloproteinase 2 (TIMP2) has been recognized as an important biomarker for predicting acute kidney injury (AKI) because of its involvement in the process of inflammation and apoptosis in septic AKI. Endoplasmic reticulum (ER) stress, a condition of disrupted ER homeostasis, is implicated in multiple pathophysiological processes, including kidney disease. Herein, we investigated the correlation between ER stress and septic AKI and further explored how TIMP2 regulated ER stress-mediated apoptosis. To assess the role of TIMP2 in sepsis-induced AKI, we used a cecal ligation and puncture (CLP) model in mice with tubule-specific deficiency of TIMP2 (Ksp-Cre/TIMP2flox/flox ) and their wild-type counterparts. Compared to the wild-type mice, TIMP2-deficient mice demonstrated lower serum creatinine levels and decreased ER stress-mediated apoptosis when subjected to CLP. Interestingly, in human kidney (HK-2) cells, overexpression of TIMP2 caused ER stress, whereas TIMP2 knockdown attenuated lipopolysaccharide-induced ER stress and apoptosis. TIMP2 interacted with the binding immunoglobulin protein, an ER chaperone, and facilitates its extracellular secretion, thereby triggering ER stress. This study identified that the deletion of TIMP2 in mouse tubules mitigated sepsis-induced AKI by inhibiting ER stress-mediated apoptosis, which might be a potential therapeutic strategy to alleviate renal injury.

Synergistic effect of elevated glucose levels with SARS-CoV-2 spike protein induced NOX-dependent ROS production in endothelial cells.

BACKGROUND: Diabetic patients infected with coronavirus disease 2019 (COVID-19) often have a higher probability of organ failure and mortality. The potential cellular mechanisms through which blood glucose exacerbates tissue damage due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is still unclear. METHODS AND RESULTS: We cultured endothelial cells within differing glucose mediums with an increasing concentration gradient of SARS-CoV-2 Spike protein (S protein). S protein can cause the reduction of ACE2 and TMPRSS2, and activation of NOX2 and NOX4. A high glucose medium was shown to aggravate the decrease of ACE2 and activation of NOX2 and NOX4 in cultured cells, but had no effect on TMPRSS2. S protein mediated activation of the ACE2-NOX axis induced oxidative stress and apoptosis within endothelial cells, leading to cellular dysfunction via the reduction of NO and tight junction proteins which may collectively be exacerbated by elevated glucose. In addition, the glucose variability model demonstrated activation of the ACE2-NOX axis in a similar manner observed in the high glucose model in vitro. CONCLUSIONS: Our present study provides evidence for a mechanism through which hyperglycemia aggravates endothelial cell injury resulting from S protein mediated activation of the ACE2-NOX axis. Our research thus highlights the importance of strict monitoring and control of blood glucose levels within the context of COVID-19 treatment to potentially improve clinical outcomes.

The role of kidney injury biomarkers in COVID-19.

The coronavirus disease-2019 (COVID-19) outbreak has been declared a global pandemic. COVID-19-associated acute kidney injury (COVID-19 AKI) is related to a high mortality rate and serves as an independent risk factor for hospital death in patients with COVID-19. Early diagnosis would allow for earlier intervention and potentially improve patient outcomes. The goal of early identification of AKI has been the primary impetus for AKI biomarker research, and several kidney injury biomarkers have been demonstrated to be beneficial in predicting COVID-19 AKI as well as disease progression in COVID-19. Furthermore, such data provide valuable insights into the molecular mechanisms underlying this complex and unique disease and serve as a molecular phenotyping tool that could be utilized to direct clinical intervention. This review focuses on a number of kidney injury biomarkers, such as CysC, NAGAL, KIM-1, L-FABP, IL-18, suPAR, and [TIMP-2] • [IGFBP7], which have been widely studied in common clinical settings, such as sepsis, cardiac surgery, and contrast-induced AKI. We explore the role of kidney injury biomarkers in COVID-19 and discuss what remains to be learned.

Pannexin 1 mediates ferroptosis that contributes to renal ischemia/reperfusion injury.

Renal ischemia/reperfusion injury (IRI) is a significant challenge in perioperative medicine and is related to oxidative programmed cell death. However, the role of ferroptosis, a newly discovered form of oxidative cell death, has not been evaluated widely. Pannexin 1 (PANX1), an ATP-releasing pathway family protein, has pro-apoptotic effects during kidney injury. Here, we demonstrate that PANX1 deletion protects against renal IRI by regulating ferroptotic cell death. Panx1 knockout mice subjected to renal IRI had decreased plasma creatinine, malondialdehyde (MDA) levels in kidney tissues, and tubular cell death (visible as decreased TUNEL-positive renal tubular cells) compared with WT mice. In cultured human kidney 2 (HK-2) cells, silenced Panx1 expression significantly attenuated ferroptotic lipid peroxidation and iron accumulation induced by the ferroptosis inducer erastin. Moreover, the Panx1 silencing significantly modulated ferroptosis-related protein expression. Furthermore, Panx1 deletion induced the expression of a cytoprotective chaperone, heme oxygenase-1 (HO-1), and inhibited ferroptinophagy via the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway. In summary, Panx1 deletion protects against renal IRI by attenuating MAPK/ERK activation in a ferroptotic pathway. Our findings provide critical insights into the role of PANX1 in ferroptotic cell death and highlight a potential therapeutic target for the management of acute kidney injury (AKI) during the perioperative period.

Incidence, Risk factors, and Biomarkers Predicting Ischemic or Hemorrhagic Stroke Associated Acute Kidney Injury and Outcome: A Retrospective Study in a General Intensive Care Unit.

OBJECTIVE: We investigated the epidemiology, risk factors, and predictive parameters for ischemic or hemorrhagic stroke-associated acute kidney injury (AKI) and mortality in a general intensive care unit (ICU) in China. METHODS: During 5 years, 479 stroke patients were screened, and 381 were enrolled. AKI was diagnosed within 7 days after ICU admission, based on the Kidney Disease Improving Global Outcomes criteria. Risk factors of AKI were assessed by Logistic regression analyses, and the predictive biomarkers for AKI were determined using receiver operating characteristic (ROC) curves. Also examined were factors influencing 28-day mortality, using Cox regression analyses and Kaplan-Meier curves. -Results: Among all, 115 (30.18%) patients developed AKI. Multivariate regression analyses revealed that the following features at ICU admission significantly increased the risk of developing AKI: an increased National Institutes of Health Stroke Scale score (OR 1.136, p < 0.001) and Acute Physiology and Chronic Health Evaluation II score (OR 1.107, p = 0.042); hypertension (OR 2.346, p = 0.008); use of loop diuretics (OR 1.961, p = 0.032); and higher serum cystatin C (sCysC; OR 8.156, p = 0.001). The area under the ROC curves for predicting AKI using sCysC was 0.772, slightly better than that of other biomarkers. The sCysC ≥0.93 mg/L (hazard ratio 1.844, p = 0.004) significantly predicted 28-day mortality. CONCLUSIONS: Among stroke patients in ICU, we identified significant risk factors of stroke-associated AKI. Serum CysC level at ICU admission was an important biomarker for predicting AKI and 28-day mortality.

Mitochondria ROS and mitophagy in acute kidney injury.

Mitophagy is an essential mitochondrial quality control mechanism that eliminates damaged mitochondria and the production of reactive oxygen species (ROS). The relationship between mitochondria oxidative stress, ROS production and mitophagy are intimately interwoven, and these processes are all involved in various pathological conditions of acute kidney injury (AKI). The elimination of damaged mitochondria through mitophagy in mammals is a complicated process which involves several pathways. Furthermore, the interplay between mitophagy and different types of cell death, such as apoptosis, pyroptosis and ferroptosis in kidney injury is unclear. Here we will review recent advances in our understanding of the relationship between ROS and mitophagy, the different mitophagy pathways, the relationship between mitophagy and cell death, and the relevance of these processes in the pathogenesis of AKI.Abbreviations: AKI: acute kidney injury; AMBRA1: autophagy and beclin 1 regulator 1; ATP: adenosine triphosphate; BAK1: BCL2 antagonist/killer 1; BAX: BCL2 associated X, apoptosis regulator; BCL2: BCL2 apoptosis regulator; BECN1: beclin 1; BH3: BCL2 homology domain 3; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; CASP1: caspase 1; CAT: catalase; CCCP: carbonyl cyanide m-chlorophenylhydrazone; CI-AKI: contrast-induced acute kidney injury; CISD1: CDGSH iron sulfur domain 1; CL: cardiolipin; CNP: 2',3'-cyclic nucleotide 3'-phosphodiesterase; DNM1L/DRP1: dynamin 1 like; E3: enzyme 3; ETC: electron transport chain; FA: folic acid; FUNDC1: FUN14 domain containing 1; G3P: glycerol-3-phosphate; G6PD: glucose-6-phosphate dehydrogenase; GPX: glutathione peroxidase; GSH: glutathione; GSK3B: glycogen synthase kinase 3 beta; GSR: glutathione-disulfide reductase; HIF1A: hypoxia inducible factor 1 subunit alpha; HUWE1: HECT, UBA and WWE domain containing 1; IL1B: interleukin 1 beta; IMM: inner mitochondrial membrane; IPC: ischemic preconditioning; IRI: ischemia-reperfusion injury; LIR: LC3-interacting region; LPS: lipopolysaccharide; MA: malate-aspartate; MPT: mitochondrial permeability transition; MUL1: mitochondrial E3 ubiquitin protein ligase 1; mtROS: mitochondrial ROS; NLR: NOD-like receptor; NLRP3: NLR family pyrin domain containing 3; NOX: NADPH oxidase; OGD-R: oxygen-glucose deprivation-reperfusion; OMM: outer mitochondrial membrane; OPA1: OPA1 mitochondrial dynamin like GTPase; OXPHOS: oxidative phosphorylation; PARL: presenilin associated rhomboid like; PINK1: PTEN induced kinase 1; PLSCR3: phospholipid scramblase 3; PMP: peptidase, mitochondrial processing; PRDX: peroxiredoxin; PRKN: parkin RBR E3 ubiquitin protein ligase; RPTC: rat proximal tubular cells; ROS: reactive oxygen species; SLC7A11/xCT: solute carrier family 7 member 11; SOD: superoxide dismutase; SOR: superoxide reductase; SQSTM1/p62: sequestosome 1; TCA: tricarboxylic acid; TIMM: translocase of inner mitochondrial membrane; TOMM: translocase of outer mitochondrial membrane; TXN: thioredoxin; VDAC: voltage dependent anion channel; VCP: valosin containing protein.

Pannexin 1 targets mitophagy to mediate renal ischemia/reperfusion injury.

Renal ischemia/reperfusion (I/R) injury contributes to the development of acute kidney injury (AKI). Kidney is the second organ rich in mitochondrial content next to the heart. Mitochondrial damage substantially contributes for AKI development. Mitophagy eliminates damaged mitochondria from the cells to maintain a healthy mitochondrial population, which plays an important role in AKI. Pannexin 1 (PANX1) channel transmembrane proteins are known to drive inflammation and release of adenosine triphosphate (ATP) during I/R injury. However, the specific role of PANX1 on mitophagy regulation in renal I/R injury remains elusive. In this study, we find that serum level of PANX1 is elevated in patients who developed AKI after cardiac surgery, and the level of PANX1 is positively correlated with serum creatinine and urea nitrogen levels. Using the mouse model of renal I/R injury in vivo and cell-based hypoxia/reoxygenation (H/R) model in vitro, we prove that genetic deletion of PANX1 mitigate the kidney tubular cell death, oxidative stress and mitochondrial damage after I/R injury through enhanced mitophagy. Mechanistically, PANX1 disrupts mitophagy by influencing ATP-P2Y-mTOR signal pathway. These observations provide evidence that PANX1 could be a potential biomarker for AKI and a therapeutic target to alleviate AKI caused by I/R injury.

Macrophage Migration Inhibitory Factor Provides a Predictive Performance of Septic Acute Kidney Injury.

BACKGROUND: Septic acute kidney injury (AKI) is a common condition in ICU with poor outcomes. Septic AKI patients have a progressively decreased urine output and increased serum creatinine. However, urine volume and serum creatinine showed poor sensitivity to early diagnosis of septic AKI. Searching for potential biomarkers to early detect AKI is crucial in day-to-day clinical practice. Macrophage migration inhibitory factor (MIF), primarily released by renal tubular epithelial cells, vascular endothelial cells, and immune cells, was found to be closely associated with the inflammatory response in sepsis. MIF may be used as a biomarker of septic AKI indicating aggravation of systemic inflammatory response. METHODS: Our study included sepsis patients admitted to the ICU. The KDIGO guideline was used to confirm the diagnosis and staging of septic AKI. Blood samples were collected and tested, as well as clinical data were recorded. Independent risk factors were selected via logistic regression analysis. By drawing the receiver operating characteristic (ROC) curves, the area under the ROC curves (AUC) was computed. The relationship between serum MIF level and mortality of septic AKI was analyzed using Cox regression analysis. RESULTS: With high serum MIF level at ICU admission, the patients were more likely to develop AKI. The AUC of serum MIF (MIFAUC = 0.797) was found to be a good predictor of septic AKI. In addition, higher serum MIF levels corresponded to more severe AKI as well as a higher mortality rate. CONCLUSIONS: Serum MIF might be a biomarker for predicting the occurrence, development, and outcomes of septic AKI. This conclusion will need to be confirmed by more robust investigations in the future.

Downregulation of macrophage migration inhibitory factor attenuates NLRP3 inflammasome mediated pyroptosis in sepsis-induced AKI.

Sepsis-induced AKI (acute kidney injury) is considered an inflammation-related disease with high mortality. LPS-induced (Lipopolysaccharide) TLR4-NFκB pathway activation plays an important role in sepsis-induced AKI. Pyroptosis closely associated with inflammation response includes inflammasome formation, caspase1 activation and GSDMD N-terminal fragment cleavage that leads to cell membrane rupture and cell death, which may be related to the pathogenesis of sepsis-induced AKI. MIF (Macrophage migration inhibitory factor), associated with inflammation response, has been proved as a biomarker of sepsis, and perhaps regulate pyroptosis in sepsis-induced AKI. In this study, we focus on investigating the mechanism of MIF promoting pyroptosis in sepsis-induced AKI. MIF and pyroptosis-related proteins were up-regulated in kidney tissue of mice with CLP (cecum ligation puncture) surgery and in LPS-injured human kidney-2 (HK-2) cells. NLRP3 was down-regulated following the suppression of MIF topoisomerase activity by ISO-1 in kidney tissue of CLP mice. Knockdown of MIF alleviated NLRP3 inflammasome mediated pyroptosis in LPS-injured HK-2 cells. Meanwhile, we noted that phosphorylation of p65 was down-regulated by knockdown of MIF. Up-regulation of NLRP3 in response to LPS stimulation could be reversed by JSH-23, an inhibitor of NFκB pathway, but MIF was not affected. In conclusion, up-regulation of MIF in sepsis-induced AKI shows a renal damaged effect that aggravates NLRP3 inflammasome mediated cell pyroptosis through promoting phosphorylation of p65. This study demonstrated a novel mechanism of MIF regulating NLRP3 inflammasome mediated pyroptosis in sepsis-induced AKI.

Acetate Ringer's solution versus 0.9% saline for septic patients: study protocol for a multi-center parallel controlled trial.

BACKGROUND: Previous study drew different conclusions on significant differences between saline and balanced crystalloid solution infused in critical illness but both showed a statistical difference in the sepsis subgroup. Thus, we will specifically focus on septic patients in this study to compare the effects of saline and balanced solution. We hypothesize that effects of saline on renal outcomes are related to the underline acute kidney injury (AKI) severity and total volumes of infusion. METHODS/DESIGN: The investigators designed a pragmatic, multi-center parallel controlled trial recruiting 312 patients who are diagnosed with sepsis/septic shock in the intensive care unit (ICU) and will be assigned with either acetate Ringer's solution or saline in the corresponding month. Patients with an end-stage renal disease (ESRD) or who need renal replacement therapy (RRT) prior to or at the time of enrolment are excluded. Enrolled patients will be regarded as with mild, moderate, or severe sepsis on the basis of the severity of their illness and will be divided into subgroups according to their initial renal function and various intravenous infusion volumes when being analyzed. The primary outcome is major adverse kidney events within 28 days (MAKE28), including the composite of in-hospital death, receipt of new renal replacement therapy, or persistent renal dysfunction. Secondary outcomes include 28-day mortality, internal environment disturbance, incidence and duration of vasoactive drug treatment, duration of mechanical ventilation, duration of RRT, and ICU and hospital length of stay. RESULTS AND CONCLUSIONS: To our knowledge, this study will be the first to focus on septic patients and provide credible and evident data on the comparison of outcome between acetate Ringer's solution and saline for intravenous infusion in adult septic patients on the basis of baseline renal function and infusion volumes taken into consideration. TRIAL REGISTRATION: ClinicalTrials.gov NCT03685214 . Registered on August 15, 2018.

Association between Thymosin beta-4, acute kidney injury, and mortality in patients with sepsis: An observational cohort study.

BACKGROUND: Sepsis is a systemic inflammatory response syndrome, associated with high risk of acute kidney injury (AKI) and in-hospital mortality. Thymosin beta-4 (Tß4) is an actin-sequestering protein that can prevent inflammation in several tissues. Thus, we studied the role of Tß4 in sepsis. METHODS: The Tß4 concentrations were prospectively measured in 191 patients within 6 h of the intensive care units (ICU) admission with diagnosis of sepsis. The cohort was divided into Tß4 concentration tertiles: 1.19-7.11 ng/ml (n = 64), 7.12-11.01 ng/ml (n = 64), and 11.02-28.10 ng/ml (n = 63). RESULTS: Of 191 patients, 92 patients developed AKI, 24 of whom received continuous renal replacement therapy (CRRT), 29 patients died within 7 days, and 53 patients died within 28 days. Lower Tß4 stages were correlated with poor prognosis, including AKI(odds ratio [OR], 2.102 per stage lower; 95% confidence interval [CI], 1.448 to 3.050; P < 0.001), CRRT(OR, 2.346 per stage lower; 95% CI, 1.287 to 4.276; P = 0.005), 7-day mortality(OR, 1.755 per stage lower; 95% CI, 1.050 to 2.935; P = 0.032), and 28-day mortality(OR, 1.821 per stage lower; 95% CI, 1.209 to 2.743; P = 0.004). Kaplan-Meier analysis also demonstrated that patients with lower Tß4 stages had a high risk of AKI and death. In addition, the area under the curve (AUC) of Tß4 for predicting AKI, CRRT, 7-day mortality, and 28-day mortality were, respectively, 0.702 (95% CI 0.628-0.776), 0.717 (95% CI 0.592-0.842), 0.694 (95% CI 0.579-0.808), and 0.682 (95% CI 0.598-0.767). CONCLUSIONS: Lower Tß4 stages are associated with higher odds of poor prognosis in ICU patients with sepsis.

[Analysis of factors influencing recovery of renal functions in septic shock patients in intensive care unit with acute kidney injury].

OBJECTIVE: To analyze multiple factors that may affect renal function in septic shock patients with acute kidney injury (AKI) in the intensive care unit (ICU), in order to find factors of predictive value for renal function change in those patients. METHODS: Septic patients with AKI admitted to department of critical care medicine of Wuhan University Zhongnan Hospital from January 2017 to June 2019 were enrolled, and the patients were divided into renal function improvement group and renal function non-improvement group according to their renal function change. Baseline, laboratory and clinical indicators of them were collected to conduct retrospective analysis. Comparing the difference of each index between the two groups, the statistically significant indexes in the univariate analysis were selected to perform ridge regression analysis. The receiver operating characteristic (ROC) curve and its 95% confidence interval (95%CI) were used to analyze the predictive value of each influencing factor on the recovery of renal function in patients. RESULTS: A total of 323 patients met the inclusion criteria, and 195 of them were divided into renal function improvement group while the other 128 of them into the renal function non-improvement group. Univariate analysis showed that, there was significantly difference in acute physiology and chronic health evaluation II (APACHE II), sequential organ failure assessment (SOFA), Glasgow coma score (GCS), heart rate (HR), serum creatinine (SCr), blood urea nitrogen (BUN), potassium (K+), white blood cell count (WBC), maximum central venous pressure (CVPmax), maximum-minimum central venous pressure distance (ΔCVP), fluid balance, maximum lactic acid (LACmax), and maximum norepinephrine infusion speed (NEmax) between the renal function improvement group and the renal function non-improvement group. Ridge regression analysis of those indexes found that APACHE II, SOFA, SCr, BUN, HR, WBC, fluid balance, and NEmax were influential factors of non-improvement renal function (t values were 5.507, 3.690, 2.026, 4.815, 2.512, 2.114, 3.532, 3.735, all P < 0.05). ROC analysis found the predictive value combining the APACHE II, SOFA, BUN, NEmax was the highest [the area under ROC curve (AUC) and 95%CI: 0.863 (0.821-0.899)], which had a higher AUC than any of APACHE II, SOFA, BUN, SCr and NEmax [AUC and 95%CI: 0.863 (0.821-0.899) vs. 0.755 (0.705-0.801), 0.722 (0.670-0.770), 0.738 (0.686-0.785), 0.743 (0.692-0.790), 0.748 (0.697-0.794), all P < 0.01], and so did it when compared to APACHE II, SOFA, SCr and NEmax combination [AUC and 95%CI: 0.863 (0.821-0.899) vs. 0.825 (0.799-0.865), P < 0.01]. CONCLUSIONS: APACHE II, SOFA, SCr, BUN, HR, WBC, fluid balance, and NEmax are the positive influencing factors for patients without renal function improvement. The combination of APACHE II, SOFA, BUN, and NEmax had a relatively high predictive value for renal function recovery.

[Clinical characteristics and risk factors of acute kidney injury in coronavirus disease 2019].

OBJECTIVE: To investigate the characteristics and the risk factors of coronavirus disease 2019 (COVID-19) associated acute kidney injury (AKI). METHODS: A retrospective cohort study was performed to examine the basic data, clinical characteristics and prognosis of patients with COVID-19 in Zhongnan Hospital of Wuhan University and Wuhan Fourth Hospital from January 1st to February 1st in 2020. According to the diagnostic criteria of Kidney Disease: Improving Global Outcomes (KDIGO), patients with AKI were included in AKI group and those without AKI were included in non-AKI group. The differences of each index between the two groups were compared. The prognostic value of AKI for COVID-19 was analyzed by Kaplan-Meier survival curve and Cox regression. RESULTS: A total of 394 COVID-19 patients were included, with a total mortality of 5.6%; 37 (9.4%) of them developed AKI. The mortality of patients with COVID-19 associated AKI was 18.9%. There were significant differences in age, gender, smoking history, hypertension history, malignancy history, cardiovascular disease history and cerebrovascular disease history between the two groups. In addition to the difference of serum creatinine (SCr) and blood urea nitrogen (BUN), white blood cell count (WBC), neutrophil count (NEU), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), D-dimer, procalcitonin (PCT) and C-reaction protein (CRP) in AKI group were significantly higher than those in non-AKI group [WBC (×109/L): 5.75 (4.13, 7.83) vs. 4.52 (3.35, 5.90), NEU (×109/L): 4.55 (2.81, 6.11) vs. 3.06 (2.03, 4.50), AST (U/L): 40.0 (24.5, 69.5) vs. 30.0 (23.0, 42.5), LDH (µmol×s-1×L-1): 5.21 (3.68, 7.57) vs. 4.24 (3.05, 5.53), D-dimer (µg/L): 456 (266, 2 172) vs. 290 (152, 610), PCT (µg/L): 0.33 (0.03, 1.52) vs. 0.01 (0.01, 0.11), CRP (mg/L): 53.80 (26.00, 100.90) vs. 23.60 (9.25, 51.10), all P < 0.05], while lymphocyte count (LYM) and platelet count (PLT) were decreased [LYM (×109/L): 0.68 (0.47, 1.05) vs. 0.91 (0.63, 1.25), PLT (×109/L): 142.0 (118.0, 190.0) vs. 171.0 (130.0, 2 190.0), both P < 0.05]. The mortality of AKI group was significantly higher than that of non-AKI group [18.9% (7/37) vs. 4.2% (15/357), P < 0.01]. Kaplan-Meier survival curve showed that the 30-day cumulative survival of AKI group was lower than that of non-AKI group (log-rank: P = 0.003). Cox analysis also showed that AKI increased the odds of patients with COVID-19 mortality by 3.2-fold [hazard ratio (HR) = 3.208, 95% confidence interval (95%CI) was 1.076-9.566, P = 0.037]. CONCLUSIONS: The risk of AKI is higher in patients with COVID-19. Early intervention to prevent AKI in patients with COVID-19 is of great significance to improve the prognosis of patients.

Downregulation of TIMP2 attenuates sepsis-induced AKI through the NF-κb pathway.

Acute kidney injury (AKI) is a frequent complication of sepsis and contributes to increased morbidity and mortality. Urinary tissue inhibitor of metalloproteinases-2 (TIMP2) has been recently recognized as an early biomarker to predict AKI in critically ill patients. However, the biological functions of TIMP2 remain largely unknown. In this study, we investigated the role of TIMP2 in mediating inflammation and tubular cell apoptosis in AKI. In kidney tissue taken from mice exposed to cecal ligation and puncture (CLP) and in human kidney 2 (HK-2) cells exposed to lipopolysaccharide (LPS) in culture, TIMP2 expression was significantly upregulated. The expression of TIMP2 in the kidney tissue correlated with the severity of AKI in vivo. In cultured HK-2 cells, LPS challenge markedly induced cytokine release, and recombinant cytokines promoted TIMP2 expression and apoptosis. However, TIMP2 silencing ameliorated LPS-induced cytokine release, apoptosis, and cell injury. We further found that the effects of downregulation of TIMP2 on a suppression of release of inflammatory cytokines were mediated by p-P65. Stable, kidney-specific TIMP2 knockdown mice were transduced by injecting the TIMP2 knockdown lentiviral vector into kidney parenchyma. TIMP2 silencing ameliorated CLP-induced proinflammatory cytokines, kidney dysfunction as measured by serum creatinine level, and histopathological changes. Downregulation of TIMP2 showed renoprotective effects on endotoxin-induced AKI, which was associated with the anti-inflammatory activity through inhibition of the nuclear factor (NF)-κB pathway. Collectively, our results indicate that TIMP2 plays an important role in mediating sepsis-induced AKI through regulation of NF-κB. These findings reveal the pathogenic role of TIMP2 in AKI and suggest a novel target for the treatment of AKI.

Reactive Oxygen Species-Induced Lipid Peroxidation in Apoptosis, Autophagy, and Ferroptosis.

Reactive oxygen species- (ROS-) induced lipid peroxidation plays a critical role in cell death including apoptosis, autophagy, and ferroptosis. This fundamental and conserved mechanism is based on an excess of ROS which attacks biomembranes, propagates lipid peroxidation chain reactions, and subsequently induces different types of cell death. A highly evolved sophisticated antioxidant system exists that acts to protect the cells from oxidative damage. In this review, we discussed how ROS propagate lipid peroxidation chain reactions and how the products of lipid peroxidation initiate apoptosis and autophagy in current models. We also discussed the mechanism of lipid peroxidation during ferroptosis, and we summarized lipid peroxidation in pathological conditions of critical illness. We aim to bring a more global and integrative sight to know how different ROS-induced lipid peroxidation occurs among apoptosis, autophagy, and ferroptosis.