Differential effects of kidney-lung cross-talk during acute kidney injury and bacterial pneumonia. Kidney Int. 2011;80:633-644. [PMID: 21734638 DOI: 10.1038/ki.2011.201]

Dexamethasone inhibited angiotensin II and its receptors to reduce sepsis-induced lung and kidney injury in rats

OBJECTIVES

To investigate the effect of dexamethasone (DXM) on acute lung and kidney injury with sepsis and its possible mechanism.

METHODS

Control (NC), lipopolysaccharide (LPS) and lipopolysaccharide + dexamethasone (LPS+DXM) treated groups were established by random assignment of 72 Wistar rats. The NC rats were injected with physiological saline, while the LPS group was injected with LPS (5 mg/kg) and LPS+DXM group was injected with LPS(5 mg/kg) first and followed by DXM (1 mg/kg). Serum tumor necrosis factor-α (TNF-α) and serum macrophage inflammatory protein 1α (MIP-1α) were measured by ELISA. Lung wet/dry weight ratio, serum creatinine(SCR) and blood urea nitrogen(BUN) were determined at various time points. Hematoxylin Eosin staining (HE) for pathological changes in the lung and kidney. Radioimmunoassay was used to detect the levels of angiotensin II (Ang II) in plasma, lung and kidney tissues. Immunohistochemistry and western blot (WB) were used to detect angiotensin II receptor type 1 (AT1R) protein and angiotensin II receptor type 2 (AT2R) protein in lung and kidney tissues. The level of nitric oxide (NO) in serum, lung and kidney were detected using nitrate reductase method.

RESULTS

Compared with control group, serum TNF-α, MIP-1α, SCR, BUN, lung W/D, Ang II level in plasma, lung and kidney, lung and kidney AT2R protein, NO level in serum, lung and kidney were significantly elevated(P<0.05) and pathological damage of lung and kidney tissues were showed in LPS group rats (P<0.05), whereas DXM down-regulated the above indexes and alleviate pathological damage of lung and kidney tissues. However, the expression of the lung and kidney AT1R protein was opposite to the above results.

CONCLUSIONS

Sepsis can cause acute lung and kidney injury and changes RAAS components in circulating, lung and renal. DXM can improve acute lung and kidney injury in septic rats, and the mechanism may be related to the down-regulation of inflammatory factors, AngII, AT2R, NO and up-regulation of AT1R expression by DXM.

Immune profiling of critically ill patients with acute kidney injury during the first week after various types of injuries: the REALAKI study

BACKGROUND

Acute kidney injury (AKI) is common in hospitalized patients and results in significant morbidity and mortality. The objective of the study was to explore the systemic immune response of intensive care unit patients presenting with AKI, especially the association between immune profiles and persistent AKI during the first week after admission following various types of injuries (sepsis, trauma, surgery, and burns).

METHODS

REALAKI is an ancillary analysis of the REAnimation Low Immune Status Marker (REALISM) cohort study, in which 359 critically ill patients were enrolled in three different intensive care units. Patients with end-stage renal disease were excluded from the REALAKI study. Clinical samples and data were collected three times after admission: at day 1 or 2 (D1-2), day 3 or 4 (D3-4) and day 5, 6 or 7 (D5-7). Immune profiles were compared between patients presenting with or without AKI. Patients with AKI at both D1-2 and D5-7 were defined as persistent AKI. A multivariable logistic regression model was performed to determine the independent association between AKI and patients' immunological parameters.

RESULTS

Three hundred and fifty-nine patients were included in this analysis. Among them, 137 (38%) were trauma patients, 103 (29%) post-surgery patients, 95 (26%) sepsis patients, and 24 (7%) were burn patients. One hundred and thirty-nine (39%) patients presented with AKI at D1-2 and 61 (20%) at D5-7. Overall, 94% presented with persistent AKI at D5-7. Patients with AKI presented with increased pro and anti-inflammatory cytokines and altered innate and adaptive immune responses. The modifications observed in the immune profiles tended to be more pronounced with increasing KDIGO stages. In the logistic regression model, a statistically significant association was observed at D1-2 between AKI and CD10lowCD16low immature neutrophils (OR 3.03 [1.7-5.5]-p < 0.001). At D5-7, increased interleukin-10 (IL-10) levels and reduced ex vivo TNF-α production after LPS stimulation were significantly associated with the presence of AKI (OR 1.38 [1.12-1.71]-p = 0.001 and 0.51 [0.27-0.91]-p = 0.03, respectively). Patients who recovered from AKI between D1-2 and D5-7 compared to patients with persistent AKI at D5-7, tended to correct these alterations.

CONCLUSION

Following various types of severe injuries, early AKI is associated with the initial inflammatory response. Presence of AKI at the end of the first week after injury is associated with injury-induced immunosuppression.

Acute and Chronic Kidney Disease Worsen Outcomes in Experimental Sepsis

Key Points

Acute kidney disease (AKD) and CKD are common conditions associated with high rates of incident infection, and poor outcomes once infection have been established. We successfully modeled AKD and CKD in rodents and then administered a cecal slurry solution to create peritonitis and tracked sepsis severity, end organ injury, and inflammatory changes. Our results indicate that AKD mice are more susceptible to infection than CKD mice, developing an aggravated inflammatory response and suggests that this condition predisposes to disparate infection risk.

Background

Infection is a leading cause of morbidity in individuals with acute kidney disease (AKD) and CKD. However, there is significant difficulty in modeling infection into an animal host with preexisting kidney disease. We report a novel method of peritoneal infection induced via cecal slurry (CS) inoculation deployed into mice with experimental aristolochic acid–induced AKD and CKD.

Methods

AKD, CKD, and paired control mice were injected with sham, low, or higher doses of donor–recipient matched CS solution. Animal survival, sepsis severity, and change in GFR were tracked longitudinally throughout the study. Histology for kidney injury, flow cytometry, plasma cytokines, and evidence of indirect organ injury from sepsis were also assessed.

Results

Infected AKD mice experienced significantly heightened sepsis severity, with 100% mortality by 24 hours after high CS doses versus no mortality in control mice. In addition, AKD mice receiving lower CS doses developed dramatically increased proinflammatory cytokines and persistent cytopenias. Infected CKD mice also had worse outcomes than paired CKD controls, although less severe than in AKD mice. Interestingly, animals with AKD had worse outcomes than mice with CKD after any CS dose or time point after inoculation, despite higher baseline kidney function and less uremic sequela.

Conclusions

These data confirm that acute bacterial infection can be modeled in animals with established kidney disease and suggest that the clinical state of kidney disease (AKD versus CKD) may influence host susceptibility to infection more than the degree of kidney failure alone.

Association between input/weight ratio and acute kidney injury in obese critical ill patients: a propensity analysis of multicenter clinical databases

Rehydration volume may be underestimated in obese critically ill patients, which can lead to acute kidney injury (AKI). This study aimed to investigate the association between input/weight ratio (IWR) and AKI risk in obese critical patients. This retrospective observational study analyzed data from three large open databases. Patients were divided into lean and obese groups and matched 1:1 based on age, sex, APACHE II score, SOFA score, sepsis status, mechanical ventilation status, renal replacement therapy status, and hospital type. The exposure of interest was the mean IWR during the first three ICU admission days. The primary outcome was the incidence of AKI within 28 days after ICU admission. Cox regression analysis was used to evaluate the association between IWR and AKI risk. A total of 82,031 eligible patients were included in the study, with 25,427 obese patients matched with 25,427 lean patients. The IWRs were significantly lower in the obese groups in both the unmatched cohort (35.85 ± 19.05 vs. 46.01 ± 30.43 ml/kg, p < 0.01) and the matched cohort (36.13 ± 19.16 vs. 47.34 ± 31.13 ml/kg, p < 0.01). An increase in IWR was significantly associated with decreased creatinine levels, increased urine output and a lower AKI risk. The interaction terms of IWR and obesity were significantly associated with decreased AKI incidence in both the unmatched cohort (hazard ratio [HR] = 0.97, 95% CI 0.96-0.97, p < 0.01) and the matched cohort (HR = 0.97, 95% CI 0.96-0.97, p < 0.01). Inadequate rehydration of patients with obesity may contribute to an increased risk of AKI in patients with obesity. These results highlight the need for better rehydration management in patients with obesity.

Construction and evaluation of a risk prediction model for pulmonary infection-associated acute kidney injury in intensive care units

Acute kidney injury (AKI) is one of the common complications of pulmonary infections. However, nomograms predicting the risk of early-onset AKI in patients with pulmonary infections have not been comprehensively researched. In this study, 3278 patients with pulmonary infection were extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database. These patients were randomly divided into training and validation cohorts, with the training cohort used for model building and the validation cohort used for validation. Independent risk factors for patients with pulmonary infection were determined using the least absolute shrinkage and selection operator (LASSO) method and forward stepwise logistic regression, which revealed that 11 independent risk factors for AKI in patients with pulmonary infections were congestive heart failure (CHF), hypertension, diabetes, transcutaneous oxygen saturation (SpO2), 24-h urine output, white blood cells (WBC), serum creatinine (Scr), prothrombin time (PT), potential of hydrogen (PH), vasopressor use, and mechanical ventilation (MV) use. The nomogram was then constructed and validated. The area under the receiver operating characteristic curve (AUC) values of the nomogram were 0.770 (95% CI = 0.789-0.807) in the training cohort and 0.724 (95% CI = 0.754-0.784) in the validation cohort. High AUC values indicated the good discriminative ability of the nomogram, while the calibration curves and Hosmer-Lemeshow test results indicated that the nomogram was well-calibrated. Improvements in net reclassification index (NRI) and integrated discrimination improvement (IDI) values indicate that our nomogram was superior to the Simplified Acute Physiology Score (SAPS) II scoring system, and the decision-curve analysis (DCA) curves indicate that the nomogram has good clinical application. We established a risk-prediction model for AKI in patients with pulmonary infection, which has good discriminative power and is superior to the SAPS II scoring system. This model can provide clinical reference information for patients with this type of disease in the intensive care unit.

A predictive model for the risk of sepsis within 30 days of admission in patients with traumatic brain injury in the intensive care unit: a retrospective analysis based on MIMIC-IV database

PURPOSE

Traumatic brain injury (TBI) patients admitted to the intensive care unit (ICU) are at a high risk of infection and sepsis. However, there are few studies on predicting secondary sepsis in TBI patients in the ICU. This study aimed to build a prediction model for the risk of secondary sepsis in TBI patients in the ICU, and provide effective information for clinical diagnosis and treatment.

METHODS

Using the MIMIC IV database version 2.0 (Medical Information Mart for Intensive Care IV), we searched data on TBI patients admitted to ICU and considered them as a study cohort. The extracted data included patient demographic information, laboratory indicators, complications, and other clinical data. The study cohort was divided into a training cohort and a validation cohort. In the training cohort, variables were screened by LASSO (Least absolute shrinkage and selection operator) regression and stepwise Logistic regression to assess the predictive ability of each feature on the incidence of patients. The screened variables were included in the final Logistic regression model. Finally, the decision curve, calibration curve, and receiver operating character (ROC) were used to test the performance of the model.

RESULTS

Finally, a total of 1167 patients were included in the study, and these patients were randomly divided into the training (N = 817) and validation (N = 350) cohorts at a ratio of 7:3. In the training cohort, seven features were identified as key predictors of secondary sepsis in TBI patients in the ICU, including acute kidney injury (AKI), anemia, invasive ventilation, GCS (Glasgow Coma Scale) score, lactic acid, and blood calcium level, which were included in the final model. The areas under the ROC curve in the training cohort and the validation cohort were 0.756 and 0.711, respectively. The calibration curve and ROC curve show that the model has favorable predictive accuracy, while the decision curve shows that the model has favorable clinical benefits with good and robust predictive efficiency.

CONCLUSION

We have developed a nomogram model for predicting secondary sepsis in TBI patients admitted to the ICU, which can provide useful predictive information for clinical decision-making.

Feasibility Assessment of a Biomarker-Guided Kidney-Sparing Sepsis Bundle: The Limiting Acute Kidney Injury Progression In Sepsis Trial

OBJECTIVES

To determine the feasibility, safety, and efficacy of a biomarker-guided implementation of a kidney-sparing sepsis bundle (KSSB) of care in comparison with standard of care (SOC) on clinical outcomes in patients with sepsis.

DESIGN

Adaptive, multicenter, randomized clinical trial.

SETTING

Five University Hospitals in Europe and North America.

PATIENTS

Adult patients, admitted to the ICU with an indwelling urinary catheter and diagnosis of sepsis or septic shock, without acute kidney injury (acute kidney injury) stage 2 or 3 or chronic kidney disease.

INTERVENTIONS

A three-level KSSB based on Kidney Disease: Improving Global Outcomes (KDIGOs) recommendations guided by serial measurements of urinary tissue inhibitor of metalloproteinases-2 and insulin-like growth factor-binding protein 7 used as a combined biomarker [TIMP2]•[IGFBP7].

MEASUREMENTS AND MAIN RESULTS

The trial was stopped for low enrollment related to the COVID-19 pandemic. Nineteen patients enrolled in five sites over 12 months were randomized to the SOC (n = 8, 42.0%) or intervention (n = 11, 58.0%). The primary outcome was feasibility, and key secondary outcomes were safety and efficacy. Adherence to protocol in patients assigned to the first two levels of KSSB was 15 of 19 (81.8%) and 19 of 19 (100%) but was 1 of 4 (25%) for level 3 KSSB. Serious adverse events were more frequent in the intervention arm (4/11, 36.4%) than in the control arm (1/8, 12.5%), but none were related to study interventions. The secondary efficacy outcome was a composite of death, dialysis, or progression of greater than or equal to 2 stages of acute kidney injury within 72 hours after enrollment and was reached by 3 of 8 (37.5%) patients in the control arm, and 0 of 11 (0%) patients in the intervention arm. In the control arm, two patients experienced progression of acute kidney injury, and one patient died.

CONCLUSIONS

Although the COVID-19 pandemic impeded recruitment, the actual implementation of a therapeutic strategy that deploys a KDIGO-based KSSB of care guided by risk stratification using urinary [TIMP2]•[IGFBP7] seems feasible and appears to be safe in patients with sepsis.

Risk and Timing of De Novo Sepsis in Critically Ill Children after Acute Kidney Injury

Key Points

Critically ill children who developed AKI have a 42% increase in the probability of developing subsequent hospital-acquired sepsis when compared with children without AKI. When evaluating risk of sepsis over time, children with stage 3 AKI remain at increased risk for sepsis for at least 2 weeks after AKI onset. Medical providers should monitor for signs of sepsis after AKI and limit exposures that may increase the risk for infection.

Background

AKI is common among critically ill children and is associated with an increased risk for de novo infection; however, little is known about the epidemiology and temporal relationship between AKI and AKI-associated infection in this cohort.

Methods

We conducted a single-center retrospective cohort study of children admitted to the pediatric and cardiac intensive care units (ICUs) at a tertiary pediatric care center. The relationship between nonseptic AKI and the development of hospital-acquired sepsis was assessed using Cox proportional hazards models using AKI as a time-varying covariate.

Results

Among the 5695 children included in this study, AKI occurred in 20.2% from ICU admission through 30 days. Hospital-acquired sepsis occurred twice as often among children with AKI compared with those without AKI (10.1% versus 4.6%) with an adjusted hazard ratio of 1.42 (95% confidence interval, 1.12 to 1.81). Among the 117 children who developed sepsis after AKI, 80.3% developed sepsis within 7 days and 96.6% within 14 days of AKI onset, with a median time from AKI onset to sepsis of 2.6 days (interquartile range, 1.5–4.7). When assessing change in risk over time, the hazard rate for sepsis remained elevated for children with stage 3 AKI compared with children without AKI at 13.5 days after AKI onset, after which the estimation of hazard rates was limited by the number of children remaining in the hospital.

Conclusions

AKI is an independent risk factor for de novo sepsis. Critically ill children with stage 3 AKI remain at increased risk for sepsis at 13.5 days after AKI onset.

Acute Kidney Injury: Advances in Clinical Management

Acute kidney injury (AKI), closely related to increased mortality, involved 15-20% of hospitalized patients with higher incidence, with about 50% in the intensive care unit (ICU) [...].

Organ Crosstalk in Acute Kidney Injury: Evidence and Mechanisms

Acute kidney injury (AKI) is becoming a public health problem worldwide. AKI is usually considered a complication of lung, heart, liver, gut, and brain disease, but recent findings have supported that injured kidney can also cause dysfunction of other organs, suggesting organ crosstalk existence in AKI. However, the organ crosstalk in AKI and the underlying mechanisms have not been broadly reviewed or fully investigated. In this review, we summarize recent clinical and laboratory findings of organ crosstalk in AKI and highlight the related molecular mechanisms. Moreover, their crosstalk involves inflammatory and immune responses, hemodynamic change, fluid homeostasis, hormone secretion, nerve reflex regulation, uremic toxin, and oxidative stress. Our review provides important clues for the intervention for AKI and investigates important therapeutic potential from a new perspective.

Sepsis and Acute Kidney Injury: A Review Focusing on the Bidirectional Interplay

Although sepsis and acute kidney injury (AKI) have a bidirectional interplay, the pathophysiological mechanisms between AKI and sepsis are not clarified and worthy of a comprehensive and updated review. The primary pathophysiology of sepsis-associated AKI (SA-AKI) includes inflammatory cascade, macrovascular and microvascular dysfunction, cell cycle arrest, and apoptosis. The pathophysiology of sepsis following AKI contains fluid overload, hyperinflammatory state, immunosuppression, and infection associated with kidney replacement therapy and catheter cannulation. The preventive strategies for SA-AKI are non-specific, mainly focusing on infection control and preventing further kidney insults. On the other hand, the preventive strategies for sepsis following AKI might focus on decreasing some metabolites, cytokines, or molecules harmful to our immunity, supplementing vitamin D3 for its immunomodulation effect, and avoiding fluid overload and unnecessary catheter cannulation. To date, several limitations persistently prohibit the understanding of the bidirectional pathophysiologies. Conducting studies, such as the Kidney Precision Medicine Project, to investigate human kidney tissue and establishing parameters or scores better to determine the occurrence timing of sepsis and AKI and the definition of SA-AKI might be the prospects to unveil the mystery and improve the prognoses of AKI patients.

Blood and Urine Biomarkers Predicting Worsening Kidney Function in Patients with Type 2 Diabetes Post-Acute Coronary Syndrome: An Analysis from the EXAMINE Trial

INTRODUCTION

Worsening kidney function (WKF) is frequent among patients with type 2 diabetes (T2D) and a recent acute coronary syndrome (ACS) and is associated with a poor prognosis. An accurate prediction of WKF is clinically important.

AIMS

Using data from the Cardiovascular Outcomes Study of Alogliptin in Patients with Type 2 Diabetes and Acute Coronary Syndrome trial including patients with T2D and a recent ACS, and a large biomarker panel incorporating proteins measured both in blood and urine, we aim to determine those with best performance for WKF prediction.

METHODS

WKF was defined as a ≥40% estimated glomerular filtration rate (eGFR) drop from baseline, eGFR <15 mL/min, or dialysis. Mixed-effects and time-updated Cox models were used.

RESULTS

5,131 patients were included from whom 222 (4.3%) developed at least one WKF episode over a median follow-up of 18 months. Patients who developed WKF were more frequently women, had longer diabetes duration, a more frequent heart failure history, higher anemia prevalence, and impaired kidney function. In multivariable models including all variables (clinical and biomarkers) independently associated with WKF with a p value ≤0.0001, blood kidney injury molecule 1 (KIM-1) was (by far) the variable with strongest WKF association, followed by anemia. KIM-1 alone provided good discrimination for WKF prediction (area under the curve = 0.73). Patients in the high KIM-1-derived risk tertile had a 6.7-fold higher risk of any WKF than patients classified as low risk. In time-updated Cox models, the occurrence of WKF was independently associated with a higher risk of death: adjusted hazard ratio = 4.93 (3.06-7.96), p value <0.0001.

CONCLUSION

Blood KIM-1 was the biomarker with the strongest association with WKF. The occurrence of WKF was independently associated with a higher risk of subsequent cardiovascular events and mortality.

A high dose of estrogen can improve renal ischemia-reperfusion-induced pulmonary injury in ovariectomized female rats

Renal ischemia-reperfusion injury (RIRI) as a pathological process induces remote organ injury such as lung complications and it is regulated in a hormone-dependent manner. This study investigates the effect of estrogen on RIR-induced pulmonary injury in ovariectomized (OV) rats. A total of 60 female Wistar rats were divided into six groups: (i) intact sham, (ii) OV sham, (iii) OV sham + estradiol valerate (E), (iv) intact ischemia, (v) OV ischemia, and (vi) OV ischemia + E. Bilateral ischemia was performed for 45 min in all groups except sham. Before the ischemia, OV groups received an intramuscular (i.m.) injection of E. After reperfusion, blood samples were collected for serum analysis and kidney and lung tissue were separated for pathological experiment and malondialdehyde (MDA) and nitrite measurement. The left lung was weighed to measure pulmonary edema. Estrogen deficiency caused a greater increase in blood urea nitrogen and creatinine levels during IRI. Ischemia reduced nitrite of serum and lung tissue. The increased level of MDA during ischemia, returned to normal levels via estrogen injection. The severity of renal and lung damage in ischemic groups increased significantly, and estrogen improved this injury. Estrogen as an antioxidant agent can reduce oxidative stress and may improve renal function and ameliorating lung damage caused by RIR.

Influence of renal impairment on neurologic outcomes following mechanical thrombectomy in acute vertebrobasilar stroke

PURPOSE

Renal impairment (RI) has been regarded as a risk factor for unfavorable neurologic outcomes after mechanical thrombectomy (MT) in acute ischemic stroke. However, most of the previous studies were conducted on patients with anterior circulation stroke. Accordingly, the influence of RI on MT outcomes has not been well elucidated in detail in acute vertebrobasilar stroke.

METHODS

Consecutive stroke patients with MT due to acute vertebrobasilar artery occlusion between March 2015 and December 2020 at four institutions were included. Multivariable logistic regression analysis was conducted to assess the associations between RI and outcomes and mortality at 3 months, and the development of intracerebral hemorrhage (ICH) after the procedure. Additionally, the multivariable Cox proportional hazards model was performed to determine the influence of RI on survival probability after patient discharge.

RESULTS

A total of 110 patients were included in the final analysis. The presence of RI (OR = 0.268, 95% CI: 0.077-0.935), National Institute of Health Stroke Scale scores (OR = 0.849, 95% CI: 0.791-0.910), and puncture-to-recanalization time (OR = 0.981, 95% CI: 0.966-0.997) were related to outcomes. There was no significant association between RI and 3-month mortality or ICH. The cumulative survival probability after adjusting for relevant risk factors demonstrated that RI remained significantly associated with poorer survival after MT compared to patients without RI (HR = 2.111, 95% CI: 0.919-4.847).

CONCLUSION

RI was an independent risk factor for poor 3-month neurologic outcomes and survival probability after MT in patients with acute vertebrobasilar stroke.

Defining Acute Kidney Injury

Acute kidney injury (AKI) is a syndrome of impaired kidney function associated with reduced survival and increased morbidity. International consensus criteria were developed based on changes in serum creatinine and urine output. Based on these definitions, epidemiologic studies have shown strong associations with clinical outcomes including death and dialysis. However, numerous limitations exist for creatinine and urine volume as markers of AKI and novel biomarkers have been developed to detect cellular stress or damage. Persistent AKI and acute kidney disease are relatively new concepts that explore the idea of AKI as a continuum with chronic kidney disease.

Acute kidney injury

Acute kidney injury (AKI) is defined by a sudden loss of excretory kidney function. AKI is part of a range of conditions summarized as acute kidney diseases and disorders (AKD), in which slow deterioration of kidney function or persistent kidney dysfunction is associated with an irreversible loss of kidney cells and nephrons, which can lead to chronic kidney disease (CKD). New biomarkers to identify injury before function loss await clinical implementation. AKI and AKD are a global concern. In low-income and middle-income countries, infections and hypovolaemic shock are the predominant causes of AKI. In high-income countries, AKI mostly occurs in elderly patients who are in hospital, and is related to sepsis, drugs or invasive procedures. Infection and trauma-related AKI and AKD are frequent in all regions. The large spectrum of AKI implies diverse pathophysiological mechanisms. AKI management in critical care settings is challenging, including appropriate volume control, nephrotoxic drug management, and the timing and type of kidney support. Fluid and electrolyte management are essential. As AKI can be lethal, kidney replacement therapy is frequently required. AKI has a poor prognosis in critically ill patients. Long-term consequences of AKI and AKD include CKD and cardiovascular morbidity. Thus, prevention and early detection of AKI are essential.

Role of Damage-Associated Molecular Patterns in Septic Acute Kidney Injury, From Injury to Recovery

Damage-associated molecular patterns (DAMPs) are a group of immunostimulatory molecules, which take part in inflammatory response after tissue injury. Kidney-specific DAMPs include Tamm-Horsfall glycoprotein, crystals, and uromodulin, released by tubular damage for example. Non-kidney-specific DAMPs include intracellular particles such as nucleus [histones, high-mobility group box 1 protein (HMGB1)] and cytosol parts. DAMPs trigger innate immunity by activating the NRLP3 inflammasome, G-protein coupled class receptors or the Toll-like receptor. Tubular necrosis leads to acute kidney injury (AKI) in either septic, ischemic or toxic conditions. Tubular necrosis releases DAMPs such as histones and HMGB1 and increases vascular permeability, which perpetuates shock and hypoperfusion via Toll Like Receptors. In acute tubular necrosis, intracellular abundance of NADPH may explain a chain reaction where necrosis spreads from cell to cell. The nature AKI in intensive care units does not have preclinical models that meet a variation of blood perfusion or a variation of glomerular filtration within hours before catecholamine infusion. However, the dampening of several DAMPs in AKI could provide organ protection. Research should be focused on the numerous pathophysiological pathways to identify the relative contribution to renal dysfunction. The therapeutic perspectives could be strategies to suppress side effect of DAMPs and to promote renal function regeneration.

Angiopoietin-2 outperforms other endothelial biomarkers associated with severe acute kidney injury in patients with severe sepsis and respiratory failure

BACKGROUND

Endothelial dysfunction and injury is a major pathophysiologic feature of sepsis. Sepsis is also the most frequent cause of acute kidney injury (AKI) in critically ill patients. Though most studies of AKI in sepsis have focused on tubular epithelial injury, the role of endothelial dysfunction and injury is less well studied. The goal of this study was first to investigate whether endothelial dysfunction and injury biomarkers were associated with severe AKI in sepsis patients. The second goal was to determine the best performing biomarker for severe AKI and whether this biomarker was associated with severe AKI across different etiologies of sepsis and clinical outcomes.

METHODS

We studied adults with severe sepsis and acute respiratory failure (ARF) enrolled in the prospective observational Validating Acute Lung Injury markers for Diagnosis (VALID) study. Plasma endothelial dysfunction and injury biomarkers, including angiopoietin-2, soluble vascular endothelial cadherin (sVE-cadherin), endocan and syndecan-1, were measured at study enrollment. Primary analysis focused on the association between endothelial biomarker levels with severe AKI (defined as Kidney Disease: Improving Global Outcomes [KDIGO] AKI stage 2 or 3), other organ dysfunctions (defined by Brussels organ failure scores), and comparison of pulmonary versus non-pulmonary sepsis.

RESULTS

Among 228 sepsis patients enrolled, 141 developed severe AKI. Plasma levels of angiopoietin-2, endocan, sVE-cadherin, and syndecan-1 were significantly higher in sepsis patients with severe AKI compared to those without severe AKI. Among four endothelial biomarkers, only angiopoietin-2 was independently associated with severe AKI (odds ratio 6.07 per log increase, 95% CI 2.34-15.78, p < 0.001). Plasma angiopoietin-2 levels by quartile were significantly higher in sepsis patients with hepatic, coagulation, and circulatory failure. Plasma angiopoietin-2 levels were also significantly higher in patients with non-pulmonary sepsis compared to subjects with pulmonary sepsis.

CONCLUSION

Among four biomarkers of endothelial dysfunction and injury, angiopoietin-2 had the most robust independent association with development of severe AKI in patients with severe sepsis and ARF. Plasma angiopoietin-2 levels were also associated with other organ dysfunctions, non-pulmonary sepsis, and death. These findings highlight the importance of early endothelial dysfunction and injury in the pathogenesis of sepsis-induced AKI.

Acute Kidney Injury in Hospitalized Patients Infected with COVID-19 from Wuhan, China: A Retrospective Study

Background

Since the first diagnosed case of infection with the novel coronavirus (SARS-CoV-2), there has been a rapid spread of the disease with an increasing number of cases confirmed every day, as well as a rising death toll. An association has been reported between acute kidney injury (AKI) and mortality in patients infected with SARS-CoV-2. Therefore, our study was conducted to explore possible risk factors of AKI as well as whether AKI was a risk factor for worse outcome, especially mortality among patients with coronavirus disease (COVID-19).

Methods

We included all hospital admissions with confirmed or clinically diagnosed COVID-19 from January 29 to February 25, 2020. We collected demographic and epidemiological information, past medical history, symptoms, laboratory tests, treatments, and outcome data from electronic medical records. A total of 492 patients with diagnosed or clinically diagnosed COVID-19 were included in this study.

Results

The prevalence rate of AKI was 7.32%. Among the factors associated with AKI, males versus females (aOR 2.73), chronic kidney disease (aOR 42.2), hypertension (aOR 2.82), increased leucocytes (aOR 6.08), and diuretic use (aOR 7.89) were identified as independent risk factors for AKI among patients infected by SARS-CoV-2. There was a significant difference in hospital fees and death in patients with and without AKI (p < 0.05). The mortality rate in patients with AKI was 63.9%.

Conclusions

AKI was widespread among patients with COVID-19. The risk factors of AKI in COVID-19 patients included sex, chronic kidney disease, hypertension, infection, and diuretic use. AKI may be associated with a worse outcome, especially mortality in COVID-19 patients.

Association of Acute Kidney Injury With Subsequent Sepsis in Critically Ill Children

OBJECTIVES

Acute kidney injury is a major cause of morbidity and mortality in critically ill children. A growing body of evidence has shown that acute kidney injury affects immune function, yet little is known about the association between acute kidney injury and subsequent infection in pediatric patients. Our objective was to examine the association of non-septic acute kidney injury with the development of subsequent sepsis in critically ill children.

DESIGN

A single-center retrospective cohort study.

SETTING

The pediatric and cardiac ICUs at a tertiary pediatric care center.

PATIENTS

All patients 0-18 years old without a history of chronic kidney disease, who did not have sepsis prior to or within the initial 48 hours of ICU admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We analyzed data for 5,538 children (median age, 5.3 yr; 58.2% male), and identified 255 (4.6%) with stage 2 or 3 acute kidney injury. Suspected sepsis occurred in 46 children (18%) with stage 2 or 3 acute kidney injury compared to 286 children (5.4%) with stage 1 or no acute kidney injury. On adjusted analysis, children with stage 2 or 3 acute kidney injury had 2.05 times greater odds of developing sepsis compared to those with stage 1 or no acute kidney injury (95% CI, 1.39-3.03; p < 0.001). Looking at acute kidney injury severity, children with stage 2 and 3 acute kidney injury had a 1.79-fold (95% CI, 1.15-2.79; p = 0.01) and 3.24-fold (95% CI, 1.55-6.80; p = 0.002) increased odds of developing suspected sepsis, respectively.

CONCLUSIONS

Acute kidney injury is associated with an increased risk for subsequent infection in critically ill children. These results further support the concept of acute kidney injury as a clinically relevant immunocompromised state.

Acute Kidney Injury Induces Innate Immune Response and Neutrophil Activation in the Lung

Complication in acute kidney injury (AKI) is significantly associated with developing acute respiratory failure (ARF), while ARF is one of the most important risks for AKI. These data suggest AKI and ARF may synergistically worsen the outcomes of critically ill patients and these organ injuries may not occur independently. Organ crosstalk between the kidney and the lung has been investigated by using animal models so far. This review will focus on innate immune response and neutrophil activation among the mechanisms that contribute to this organ crosstalk. AKI increased the blood level of an inflammatory mediator in high-mobility group box 1, which induces an innate immune reaction via toll-like receptor 4. The remarkable infiltration of neutrophils to the lung was observed in animal AKI models. IL-6 and IL-8 have been demonstrated to contribute to pulmonary neutrophil activation in AKI. In addition, the formation of a neutrophil extracellular trap was also observed in the lung after the exposure of renal ischemia reperfusion in the animal model. Further investigation is necessary to determine whether targeting innate immune response and neutrophil activation will be useful for developing new therapeutics that could improve multiple organ failure in critically ill patients.

Kidney injury in COVID-19

Coronavirus disease 2019 (COVID-19) continues to affect millions of people around the globe. As data emerge, it is becoming more evident that extrapulmonary organ involvement, particularly the kidneys, highly influence mortality. The incidence of acute kidney injury has been estimated to be 30% in COVID-19 non-survivors. Current evidence suggests four broad mechanisms of renal injury: Hypovolaemia, acute respiratory distress syndrome related, cytokine storm and direct viral invasion as seen on renal autopsy findings. We look to critically assess the epidemiology, pathophysiology and management of kidney injury in COVID-19.

Targeting acute kidney injury in COVID-19

As of 15 August 2020, Coronavirus disease 2019 (COVID-19) has been reported in >21 million people world-wide and is responsible for more than 750,000 deaths. The occurrence of acute kidney injury (AKI) in patients hospitalized with COVID-19 has been reported to be as high as 43%. This is comparable to AKI in other forms of pneumonia requiring hospitalization, as well as in non-infectious conditions like cardiac surgery. The impact of AKI on COVID-19 outcomes is difficult to assess at present but, similar to other forms of sepsis, AKI is strongly associated with hospital mortality. Indeed, mortality is reported to be very low in COVID-19 patients without AKI. Given that AKI contributes to fluid and acid-base imbalances, compromises immune response and may impair resolution of inflammation, it seems likely that AKI contributes to mortality in these patients. The pathophysiologic mechanisms of AKI in COVID-19 are thought to be multifactorial including systemic immune and inflammatory responses induced by viral infection, systemic tissue hypoxia, reduced renal perfusion, endothelial damage and direct epithelial infection with Severe Acute Respiratory Syndrome Coronavirus 2. Mitochondria play a central role in the metabolic deregulation in the adaptive response to the systemic inflammation and are also found to be vital in response to both direct viral damage and tissue reperfusion. These stress conditions are associated with increased glycolysis and reduced fatty acid oxidation. Thus, there is a strong rationale to target AKI for therapy in COVID-19. Furthermore, many approaches that have been developed for other etiologies of AKI such as sepsis, inflammation and ischemia-reperfusion, have relevance in the treatment of COVID-19 AKI and could be rapidly pivoted to this new disease.

Kidney injury induced by elevated histones in community-acquired pneumonia

Previous studies showed that extracellular histones could damage organs, but the role of extracellular histones in pneumonia patients with acute kidney injury (AKI) is unknown. This study aims to investigate the impact of extracellular histones on patients with community-acquired pneumonia (CAP) developed AKI. Blood samples were obtained within 24 h after admission to hospital from patients who were diagnosed with CAP. According to the discharge diagnosis, the patients were divided into 2 groups (Non-AKI and AKI). In vitro, A549 cells were treated with lipopolysaccharides (LPS) and conditioned media were collected. HK2 cells were exposed to the conditioned media or not. Cells proliferation and apoptosis of HK2 were determined. Clinically, Log₂ Histones (OR 3.068; 95% CI 1.544-6.097, P = 0.001) and estimated glomerular filtration rate (eGFR) (OR 0.945; 95% CI 0.914-0.978, P = 0.001) were predictors of AKI in CAP patients. Compared to the lower histones group, patients in the higher histones group were more likely to be admitted to ICU, receive mechanical ventilation, and have a longer length of in-hospital stay. In vitro, A549 cells injured by LPS released extracellular histones, in conditioned media which significantly promoted HK2 cells apoptosis. Extracellular histones was a high risk factor for developing AKI in CAP patients and a predictor of worse short-term outcomes. We also showed that extracellular histones in conditioned media damaged HK2 cells.Trial registration number: KY20181102-03; Date of registration: 20181102.

Lung-kidney interactions in critically ill patients: consensus report of the Acute Disease Quality Initiative (ADQI) 21 Workgroup

BACKGROUND

Multi-organ dysfunction in critical illness is common and frequently involves the lungs and kidneys, often requiring organ support such as invasive mechanical ventilation (IMV), renal replacement therapy (RRT) and/or extracorporeal membrane oxygenation (ECMO).

METHODS

A consensus conference on the spectrum of lung-kidney interactions in critical illness was held under the auspices of the Acute Disease Quality Initiative (ADQI) in Innsbruck, Austria, in June 2018. Through review and critical appraisal of the available evidence, the current state of research, and both clinical and research recommendations were described on the following topics: epidemiology, pathophysiology and strategies to mitigate pulmonary dysfunction among patients with acute kidney injury and/or kidney dysfunction among patients with acute respiratory failure/acute respiratory distress syndrome. Furthermore, emphasis was put on patients receiving organ support (RRT, IMV and/or ECMO) and its impact on lung and kidney function.

CONCLUSION

The ADQI 21 conference found significant knowledge gaps about organ crosstalk between lung and kidney and its relevance for critically ill patients. Lung protective ventilation, conservative fluid management and early recognition and treatment of pulmonary infections were the only clinical recommendations with higher quality of evidence. Recommendations for research were formulated, targeting lung-kidney interactions to improve care processes and outcomes in critical illness.

Intravenous Immunoglobulin Attenuates Cecum Ligation and Puncture-Induced Acute Lung Injury by Inhibiting Apoptosis of Alveolar Epithelial Cells

PURPOSE

Intravenous immunoglobulin (IVIG) therapy has been used to treat sepsis, but its mechanisms of action remain unclear. Sepsis causes multiple organ failure, such as acute lung injury (ALI), which involves apoptosis of alveolar epithelial cells. In this study, we hypothesized that IVIG suppresses apoptosis in alveolar epithelial cells and evaluated mortality, cytokine levels, histological changes in the lung, and alveolar epithelial cell apoptosis after IVIG administration, in mice with experimentally induced sepsis.

METHODS

Mice received an injection of vehicle (saline) or immunoglobulin (100 mg/kg or 400 mg/kg) into the tail vein, after which they underwent cecal ligation and puncture. A sham-operated group was used as the normal control. Survival was assessed in all groups after 72 hours. Plasma levels of TNF-α and IL-6, histopathological changes and wet-to-dry ratio in lung, and alveolar epithelial cell apoptosis were evaluated in all groups at 4 hours after surgery.

RESULTS

In the vehicle group, histopathological injury of the lung was severe, and apoptosis of alveolar epithelial cells was significant. Survival and plasma cytokine levels were better in the IVIG treatment groups than in the vehicle group. IVIG 400 mg/kg suppressed apoptosis of alveolar epithelial cells and reduced ALI.

CONCLUSION

IVIG suppressed inflammatory cytokine levels and improved survival. Lung histopathology and alveolar epithelial cell apoptosis were improved by IVIG treatment, in a dose-dependent manner. Suppressing apoptosis in alveolar epithelial cells appears to be a mechanism by which IVIG improves survival.

Acute kidney injury

Acute kidney injury (AKI) is defined by a rapid increase in serum creatinine, decrease in urine output, or both. AKI occurs in approximately 10-15% of patients admitted to hospital, while its incidence in intensive care has been reported in more than 50% of patients. Kidney dysfunction or damage can occur over a longer period or follow AKI in a continuum with acute and chronic kidney disease. Biomarkers of kidney injury or stress are new tools for risk assessment and could possibly guide therapy. AKI is not a single disease but rather a loose collection of syndromes as diverse as sepsis, cardiorenal syndrome, and urinary tract obstruction. The approach to a patient with AKI depends on the clinical context and can also vary by resource availability. Although the effectiveness of several widely applied treatments is still controversial, evidence for several interventions, especially when used together, has increased over the past decade.

Acute kidney injury as an independent predictor of infection and malignancy: the NARA-AKI cohort study

BACKGROUND

Acute kidney injury (AKI) is associated with higher mortality and cardiovascular events. However, association between AKI and non-cardiac events such as infection or malignancy is largely unknown.

METHODS

This is a retrospective cohort study. Inclusion criteria were adults who underwent non-cardiac surgery from 2007 to 2011 at Nara Medical University Hospital. Exclusion criteria were urological surgery, obstetric surgery, missing creatinine values peri-operatively, and pre-operative dialysis. The end of observation period was at the end of 2015 or loss to follow-up. A predictor was AKI defined by KDIGO criteria within 1-week post-operatively. Outcomes were hospitalization for infection or diagnoses of malignancy. Associations between AKI and outcomes were examined by Cox regression models.

RESULTS

Among 6692 subjects, 445 (6.6%) developed AKI. During median follow-up of 4.0 years, there were 485 hospitalizations for infection and 1138 diagnoses of malignancy (2.0 and 5.1 events/100 patient-years, respectively). After adjustment for potential confounders, AKI was independently associated with hospitalization for infection and diagnoses of malignancy (Hazard ratio [95% confidence interval]: 1.64 [1.23-2.20] and 1.31 [1.06-1.61], respectively). Excluding recurrence of malignancy from outcomes and analyses limited to those who recover renal function by the time of discharge yielded similar results. Absolute lymphocyte counts were significantly lower and neutrophil-to-lymphocyte ratios were significantly higher among those with AKI.

CONCLUSIONS

AKI was significantly associated with hospitalization for infection and development of malignancy during long-term follow-up. Those with AKI might be in persistent immunosuppressed state.

Peak Creatinine, Cardiopulmonary Bypass, and Mortality After Stage 1 Single-Ventricle Reconstruction

BACKGROUND

Serum creatinine is the most commonly used marker to diagnose acute kidney injury. Studies exploring creatinine patterns in the single-ventricle population are scarce. We studied serum creatinine up to 5 postoperative days after the stage 1 operation and assessed its relationship with outcomes.

METHODS

Neonates who underwent a first-stage single-ventricle operation (Norwood or a Damus-Kaye-Stansel) between 2005 and 2017 were retrospectively analyzed. Peak percentage creatinine change (PPCC) was defined as the difference between the baseline (preoperative) and the peak postoperative level (within 5 postoperative days), expressed as a percentage of the baseline level.

RESULTS

Among 187 neonates included, the median PPCC was 38.7% (interquartile range, 14.1%-73.1%), and in-hospital mortality was 17% (31 of 187). A controlled analysis showed that for every 10-minute increase in cardiopulmonary bypass duration (CPB), the PPCC increased by 1.8% (95% confidence interval [CI], 0.7%-2.9%; P = .002). Risk of in-hospital death increased log-linearly with PPCC. The adjusted odds ratios for death in the hospital associated with a 50%, 100%, and 200%, increase in peak percentage creatinine change were 1.85 (95% CI, 1.23-2.78), 3.41 (95% CI, 1.15-7.72), and 11.66 (95% CI, 2.28-59.63), respectively. In-hospital death was also associated with CPB duration (adjusted odds ratio, 1.13 per 10-minute increase; 95% CI, 1.05-1.22; P = .001).

CONCLUSIONS

Increase in CPB duration has a strong linear association with increase in PPCC after stage 1 single-ventricle reconstruction. Increase in PPCC and CPB duration has a strong linear association with hospital mortality. It is important to identify therapies that minimize complications associated with prolonged CPB duration in high-risk populations.

Integrative Physiology of Pneumonia

Pneumonia is a type of acute lower respiratory infection that is common and severe. The outcome of lower respiratory infection is determined by the degrees to which immunity is protective and inflammation is damaging. Intercellular and interorgan signaling networks coordinate these actions to fight infection and protect the tissue. Cells residing in the lung initiate and steer these responses, with additional immunity effectors recruited from the bloodstream. Responses of extrapulmonary tissues, including the liver, bone marrow, and others, are essential to resistance and resilience. Responses in the lung and extrapulmonary organs can also be counterproductive and drive acute and chronic comorbidities after respiratory infection. This review discusses cell-specific and organ-specific roles in the integrated physiological response to acute lung infection, and the mechanisms by which intercellular and interorgan signaling contribute to host defense and healthy respiratory physiology or to acute lung injury, chronic pulmonary disease, and adverse extrapulmonary sequelae. Pneumonia should no longer be perceived as simply an acute infection of the lung. Pneumonia susceptibility reflects ongoing and poorly understood chronic conditions, and pneumonia results in diverse and often persistent deleterious consequences for multiple physiological systems.

Surfactant protein D attenuates acute lung and kidney injuries in pneumonia-induced sepsis through modulating apoptosis, inflammation and NF-κB signaling

Pneumonia and sepsis are major risk factors for acute kidney injury (AKI). Patients with pneumonia and AKI are at increased risk for morbidity and mortality. Surfactant protein D (SP-D) expressed in lung and kidney plays important roles in innate immunity. However, little is known about the role of organ-specific SP-D in the sepsis. The current study uses wild type (WT), SP-D knockout (KO), and humanized SP-D transgenic (hTG, lung-specific SP-D expression) mice to study organ-specific role of SP-D in pneumonia-induced sepsis. Analyses demonstrated differential lung and kidney injury among three-type mice infected with Pseudomonas aeruginosa. After infection, KO mice showed higher injurious scores in both lung and kidney, and decreased renal function than WT and hTG mice. hTG mice exhibited comparable lung injury but more severe kidney injury compared to WT mice. Increased renal tubular apoptosis, NF-κB activation and proinflammatory cytokines in the kidney of KO mice were found when compared with WT and hTG mice. Furthermore, in vitro primary proximal tubular epithelial cells from KO mice showed more apoptosis with higher level of activated caspase-3 than those from WT mice after LPS treatment. Collectively, SP-D attenuates AKI in the sepsis by modulating renal apoptosis, inflammation and NF-κB signaling.

A review of the role of immune cells in acute kidney injury

Acute kidney injury (AKI) is a systemic disease occurring commonly in patients who are critically ill. Etiologies of AKI can be septic or aseptic (nephrotoxic, or ischemia-reperfusion injury). Recent evidence reveals that innate and adaptive immune responses are involved in mediating damage to renal tubular cells and in recovery from AKI. Dendritic cells, monocytes/macrophages, neutrophils, T lymphocytes, and B lymphocytes all contribute to kidney injury. Conversely, M2 macrophages and regulatory T cells are essential in suppressing inflammation, tissue remodeling and repair following kidney injury. AKI itself confers an increased risk for developing infection owing to increased production and decreased clearance of cytokines, in addition to dysfunction of immune cells themselves. Neutrophils are the predominant cell type rendered dysfunctional by AKI. In this review, we describe the bi-directional interplay between the immune system and AKI and summarize recent developments in this field of research.

[Interactions between lung and kidney in the critically ill]

Interactions between lung and kidney can significantly affect the course of acute diseases, a phenomenon that was first observed in the 1950s by describing pulmonary dysfunction in uremic patients. From animal experiments there is ample evidence for remote lung injury following acute kidney injury (AKI), with an increased risk for the development of pulmonary edema and acute respiratory distress syndrome (ARDS). Coincident ARDS and AKI are associated with higher rates of intubation and mechanical ventilation, significantly prolonged weaning from mechanical ventilation and increased mortality. On the other hand, acute lung diseases and mechanical ventilation can promote the development of AKI and are associated with increased mortality when AKI is also present. These bidirectional interactions may include hemodynamic adverse effects during mechanical ventilation or volume overload as well as the release or decreased clearance and metabolism of proinflammatory mediators (e.g., interleukin-6 and tumor necrosis factor-α), which may induce and aggravate distant organ injury. The aim of this work is to examine the interactions between lung and the kidney in critically ill patients, as well as discuss potential preventive approaches.

A zebrafish model of infection-associated acute kidney injury

Sepsis-associated acute kidney injury (S-AKI) independently predicts mortality among critically ill patients. The role of innate immunity in this process is unclear, and there is an unmet need for S-AKI models to delineate the pathophysiological response. Mammals and zebrafish ( Danio rerio) share a conserved nephron structure and homologous innate immune systems, making the latter suitable for S-AKI research. We introduced Edwardsiella tarda to the zebrafish. Systemic E. tarda bacteremia resulted in sustained bacterial infection and dose-dependent mortality. A systemic immune reaction was characterized by increased mRNA expressions of il1b, tnfa, tgfb1a, and cxcl8-l1 ( P < 0.0001, P < 0.001, P < 0.001, and P < 0.01, respectively). Increase of host stress response genes ccnd1 and tp53 was observed at 24 h postinjection ( P < 0.0001 and P < 0.05, respectively). Moderate E. tarda infection induced zebrafish mortality of over 50% in larvae and 20% in adults, accompanied by pericardial edema in larvae and renal dysfunction in both larval and adult zebrafish. Expression of AKI markers insulin-like growth factor-binding protein-7 (IGFBP7), tissue inhibitor of metalloproteinases 2 (TIMP-2), and kidney injury molecule-1 (KIM-1) was found to be significantly increased in the septic animals at the transcription level ( P < 0.01, P < 0.05, and P < 0.05) and in nephric tubules compared with noninfected animals. In conclusion, we established a zebrafish model of S-AKI induced by E. tarda injection, with both larval and adult zebrafish showing nephron injury in the setting of infection.

Glucose-6-phosphate dehydrogenase inhibition attenuates acute lung injury through reduction in NADPH oxidase-derived reactive oxygen species

Acute lung injury (ALI) is a heterogeneous disease with the hallmarks of alveolar capillary membrane injury, increased pulmonary oedema and pulmonary inflammation. The most common direct aetiological factor for ALI is usually parenchymal lung infection or haemorrhage. Reactive oxygen species (ROS) generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX2) are thought to play an important role in the pathophysiology of ALI. Glucose-6-phosphate dehydrogenase (G6PD) plays an important role both in production of ROS as well as their removal through the supply of NADPH. However, how G6PD modulation affects NOX2-mediated ROS in the airway epithelial cells (AECs) during acute lung injury has not been explored previously. Therefore, we investigated the effect of G6PD inhibitor, 6-aminonicotinamide on G6PD activity, NOX2 expression, ROS production and enzymatic anti-oxidants in AECs in a mouse model of ALI induced by lipopolysaccharide (LPS). ALI led to increased G6PD activity in the AECs with concomitant elevation of NOX2, ROS, SOD1 and nitrotyrosine. G6PD inhibitor led to reduction of LPS-induced airway inflammation, bronchoalveolar lavage fluid protein concentration as well as NOX2-derived ROS and subsequent oxidative stress. Conversely, ALI led to decreased glutathione reductase activity in AECs, which was normalized by G6PD inhibitor. These data show that activation of G6PD is associated with enhancement of oxidative inflammation in during ALI. Therefore, inhibition of G6PD might be a beneficial strategy during ALI to limit oxidative damage and ameliorate airway inflammation.

Blood platelets and sepsis pathophysiology: A new therapeutic prospect in critically [corrected] ill patients?

Beyond haemostasis, platelets have emerged as versatile effectors of the immune response. The contribution of platelets in inflammation, tissue integrity and defence against infections has considerably widened the spectrum of their role in health and disease. Here, we propose a narrative review that first describes these new platelet attributes. We then examine their relevance to microcirculatory alterations in multi-organ dysfunction, a major sepsis complication. Rapid progresses that are made on the knowledge of novel platelet functions should improve the understanding of thrombocytopenia, a common condition and a predictor of adverse outcome in sepsis, and may provide potential avenues for management and therapy.

Mechanisms of Organ Dysfunction in Sepsis

Sepsis-associated organ dysfunction involves multiple responses to inflammation, including endothelial and microvascular dysfunction, immune and autonomic dysregulation, and cellular metabolic reprogramming. The effect of targeting these mechanistic pathways on short- and long-term outcomes depends highly on the timing of therapeutic intervention. Furthermore, there is a need to understand the adaptive or maladaptive character of these mechanisms, to discover phase-specific biomarkers to guide therapy, and to conceptualize these mechanisms in terms of resistance and tolerance.

Hemoadsorption corrects hyperresistinemia and restores anti-bacterial neutrophil function

Background

Mounting evidence suggests that sepsis-induced morbidity and mortality are due to both immune activation and immunosuppression. Resistin is an inflammatory cytokine and uremic toxin. Septic hyperresistinemia (plasma resistin >20 ng/ml) has been associated with greater disease severity and worse outcomes, and it is further exacerbated by concomitant acute kidney injury (AKI). Septic hyperresistinemia disturbs actin polymerization in neutrophils leading to impaired neutrophil migration, a crucial first-line mechanism in host defense to bacterial infection. Our experimental objective was to study the effects of hyperresistinemia on other F-actin-dependent neutrophil defense mechanisms, in particular intracellular bacterial clearance and generation of reactive oxygen species (ROS). We also sought to examine the effects of hemoadsorption on hyperresistinemia and neutrophil dysfunction.

Methods

Thirteen patients with septic shock and six control patients were analyzed for serum resistin levels and their effects on neutrophil migration. In vitro, following incubation with resistin-spiked serum samples, Pseudomonasaeruginosa clearance and ROS generation in neutrophils were measured. Phosphorylation of 3-phosphoinositide-dependent protein kinase-1 (PDPK1) was assessed using flow cytometry. In vitro hemoadsorption with both Amberchrome™ columns (AC) and CytoSorb® cartridges (CC) were used to test correction of hyperresistinemia. We further tested AC for their effect on cell migration and ROS generation and CC for their effect on bacterial clearance.

Results

Patients with septic shock had higher serum resistin levels than control ICU patients and showed a strong, negative correlation between hyperresistinemia and neutrophil transwell migration (ρ= − 0.915, p < 0.001). In vitro, neutrophils exposed to hyperresistinemia exhibited twofold lower intracellular bacterial clearance rates compared to controls. Resistin impaired intracellular signaling and ROS production in a dose-dependent manner. Hemoadsorption with AC reduced serum concentrations of resistin and restored neutrophil migration and generation of ROS to normal levels. Hemoadsorption with CC also corrected hyperresistinemia and reconstituted normal intracellular bacterial clearance.

Conclusions

Septic hyperresistinemia strongly correlates with inhibition of neutrophil migration in vitro. Hyperresistinemia itself reversibly impairs neutrophil intracellular bacterial clearance and ROS generation. Hemoadsorption therapy with a clinically approved device corrects hyperresistinemia and neutrophil dysfunction. It may therefore provide a therapeutic option to improve neutrophil function during septic hyperresistinemia and ultimately alleviate immunosuppression in this disease state.

Reversal of Acute Kidney Injury-Induced Neutrophil Dysfunction: A Critical Role for Resistin

OBJECTIVES

To assess the reversibility of acute kidney injury-induced neutrophil dysfunction and to identify involved mechanisms.

DESIGN

Controlled laboratory experiment and prospective observational clinical study.

SETTING

University laboratory and hospital.

SUBJECTS

C57BL/6 wild-type mice.

PATIENTS

Patients with septic shock with or without acute kidney injury.

INTERVENTIONS

Murine acute kidney injury was induced by intraperitoneal injections of folic acid (nephrotoxic acute kidney injury) or by IM injections of glycerol (rhabdomyolysis-induced acute kidney injury). After 24 hours, we incubated isolated neutrophils for 3 hours in normal mouse serum or minimum essential medium buffer. We further studied the effects of plasma samples from 13 patients with septic shock (with or without severe acute kidney injury) on neutrophilic-differentiated NB4 cells.

MEASUREMENTS AND MAIN RESULTS

Experimental acute kidney injury significantly inhibited neutrophil migration and intracellular actin polymerization. Plasma levels of resistin, a proinflammatory cytokine and uremic toxin, were significantly elevated during both forms of acute kidney injury. Incubation in serum or minimum essential medium buffer restored normal neutrophil function. Resistin by itself was able to induce acute kidney injury-like neutrophil dysfunction in vitro. Plasma resistin was significantly higher in patients with septic shock with acute kidney injury compared with patients with septic shock alone. Compared with plasma from patients with septic shock, plasma from patients with septic shock and acute kidney injury inhibited neutrophilic-differentiated NB4 cell migration. Even after 4 days of renal replacement therapy, plasma from patients with septic shock plus acute kidney injury still showed elevated resistin levels and inhibited neutrophilic-differentiated NB4 cell migration. Resistin inhibited neutrophilic-differentiated NB4 cell migration and intracellular actin polymerization at concentrations seen during acute kidney injury, but not at normal physiologic concentrations.

CONCLUSIONS

Acute kidney injury-induced neutrophil dysfunction is reversible in vitro. However, standard renal replacement therapy does not correct this defect in patients with septic shock and acute kidney injury. Resistin is greatly elevated during acute kidney injury, even with ongoing renal replacement therapy, and is sufficient to cause acute kidney injury-like neutrophil dysfunction by itself.

Impact of Acute Kidney Injury in Patients Hospitalized With Pneumonia

OBJECTIVES

Pneumonia is a common cause of hospitalization and can be complicated by the development of acute kidney injury. Acute kidney injury is associated with major adverse kidney events (death, dialysis, and durable loss of renal function [chronic kidney disease]). Because pneumonia and acute kidney injury are in part mediated by inflammation, we hypothesized that when acute kidney injury complicates pneumonia, major adverse kidney events outcomes would be exacerbated. We sought to assess the frequency of major adverse kidney events after a hospitalization for either pneumonia, acute kidney injury, or the combination of both.

DESIGN AND SETTING

We conducted a retrospective database analysis of the national Veterans Affairs database for patients with a admission diagnosis of International Classification of Diseases-9 code 584.xx (acute kidney injury) or 486.xx (pneumonia) between October 1, 1999, and December 31, 2005. Three groups of patients were created, based on the diagnosis of the index admission and serum creatinine values: 1) acute kidney injury, 2) pneumonia, and 3) pneumonia with acute kidney injury. Patients with mean baseline estimated glomerular filtration rate less than 45 mL/min/1.73 m were excluded.

MEASUREMENTS AND MAIN RESULTS

The primary endpoint was major adverse kidney events defined as the composite of death, chronic dialysis, or a permanent loss of renal function after the primary discharge. The observations of 54,894 subjects were analyzed. Mean age was 68.7 ± 12.3 years. The percentage of female was 2.4, 73.3% were Caucasian, and 19.7% were African-American. Differences across the three diagnostic groups were significant for death, 25% decrease in estimated glomerular filtration rate from baseline, major adverse kidney events following admission, and major adverse kidney events during admission (all p < 0.0001). Death alone and major adverse kidney events after discharge were most common in the pneumonia + acute kidney injury group (51% died and 62% reached major adverse kidney events). In both unadjusted and adjusted time to event analyses, patients with pneumonia + acute kidney injury were most likely to die or reach major adverse kidney events.

CONCLUSIONS

When acute kidney injury accompanies pneumonia, postdischarge outcomes are worse than either diagnosis alone. Patients who survive a pneumonia hospitalization and develop acute kidney injury are at high risk for major adverse kidney events including death and should receive careful follow-up.

Short-term Effects of Acute Kidney Injury

Acute kidney injury (AKI) is associated with significant short-term morbidity and mortality, which cannot solely be explained by loss of organ function. Renal replacement therapy allows rapid correction of most acute changes associated with AKI, indicating that additional pathogenetic factors play a major role in AKI. Evidence suggests that reduced renal cytokine clearance as well as increased cytokine production by the acutely injured kidney contribute to a systemic inflammation state, which results in significant effects on other organs. AKI seems to compromise the function of the innate immune system. AKI is an acute systemic disease with serious distant organ effects.

Sepsis-induced acute kidney injury revisited: pathophysiology, prevention and future therapies

PURPOSE OF REVIEW

Acute kidney injury (AKI) is a common complication in critically ill patients and is associated with increased morbidity and mortality. Sepsis is the most common cause of AKI. Considerable evidence now suggests that the pathogenic mechanisms of sepsis-induced AKI are different from those seen in other causes of AKI. This review focuses on the recent advances in this area and discusses possible therapeutic interventions that might derive from these new insights into the pathogenesis of sepsis-induced AKI.

RECENT FINDINGS

The traditional paradigm that sepsis-induced AKI arises from ischemia has been challenged by recent evidence that total renal blood flow in is not universally impaired during sepsis, and AKI can develop in the presence of normal or even increased renal blood flow. Animal and human studies suggest that adaptive responses of tubular epithelial cells to injurious signals are responsible for renal dysfunction. Simultaneously occurring renal inflammation and microcirculatory dysfunction further amplify these mechanisms.

SUMMARY

An understanding of the pathologic mechanisms of sepsis-induced AKI emphasizes the important role of maladaptive responses to the septic insult. Preventive and therapeutic measures should be based on counteracting these maladaptive responses of tubular epithelial cells, inflammation, and microvascular dysfunction.

PARP inhibitor, olaparib ameliorates acute lung and kidney injury upon intratracheal administration of LPS in mice

We have previously shown that PARP-1 inhibition provides protection against lung inflammation in the context of asthma and acute lung injury. Olaparib is a potent new generation PARP inhibitor that has been approved for human testing. The present work was designed to evaluate its beneficial potential against LPS-induced acute lung injury and acute kidney injury upon intratracheal administration of the endotoxin in mice. Administration of olaparib at different doses, 30 min after LPS treatment showed that single intraperitoneal injection of the drug at 5 mg/kg b.wt. reduced the total number of inflammatory cells particularly neutrophils in the lungs. This was associated with reduced pulmonary edema as the total protein content in the bronchoalveolar fluid was found to be decreased substantially. Olaparib provided strong protection against LPS-mediated secondary kidney injury as reflected by restoration of serum levels of urea, creatinine, and uric acid toward normal. The drug restored the LPS-mediated redox imbalance toward normal in lung and kidney tissues as assessed by measuring malondialdehyde and GSH levels. Finally, RT-PCR data revealed that olaparib downregulates the LPS-induced expression of NF-κB-dependent genes namely TNF-α, IL-1β, and VCAM-1 in the lungs without altering the expression of total p65NF-κB. Overall, the data suggest that olaparib has a strong potential to protect against LPS-induced lung injury and associated dysfunctioning of kidney in mice. Given the fact that olaparib is approved by FDA for human testing, our findings can pave the way for testing of the drug on humans inflicted with acute lung injury.

Inhibition of poly (adenosine diphosphate-ribose) polymerase attenuates lung-kidney crosstalk induced by intratracheal lipopolysaccharide instillation in rats

Background

Acute respiratory distress syndrome (ARDS) is a severe form of lung injury that frequently occurs during pneumonia and sepsis. Lung inflammation in ARDS patients may have deleterious effects on remote organs such as the kidney. The nuclear enzyme poly(adenosine diphosphate-ribose) polymerase (PARP) enhances the nuclear factor (NF)-κB-dependent transcription of inflammatory cytokines. This study was conducted to elucidate two questions: first, whether the activation of PARP and NF-κB mediates the renal inflammation secondary to the lipopolysaccharide (LPS)-induced acute lung inflammation; second, whether a PARP inhibitor, 3-aminobenzamide (3-AB), attenuates lung and kidney inflammation by inhibiting NF-κB-dependent proinflammatory cytokines.

Methods

Male Sprague–Dawley rats were anesthetized, ventilated, and divided into three groups; a control group (n = 8); an LPS group (n = 12) intratracheally instilled with LPS (16 mg/kg), and an LPS + 3-AB group (n = 12) given the same dose of LPS by the same method followed by an intravenous injection of 3-AB (20 mg/kg). Hemodynamics, arterial blood gas, and the plasma levels of lactate, creatinine and potassium were measured at 0,1,2,3, and 4 h after treatment. The lung wet/dry ratio was measured at 4 h. The mRNA expression of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in the lung and kidney were measured by TaqMan real-time PCR. PARP and NF-κB in the lung and kidney were histologically examined by immunostaining and assigned expression scores.

Results

LPS induced metabolic acidosis, hypotension, hypoxemia, increased the lung wet/dry ratio, increased the plasma levels of creatinine and potassium, and increased the cytokine mRNA expressions in the lung and kidney. All of these effects were associated with strong expression of PARP and NF-κB. Treatment with 3-AB prevented the LPS-induced metabolic acidosis and hypotension, reduced the plasma levels of lactate, creatinine and potassium, reduced the cytokine mRNA expressions, reduced the expression of PARP and NF-κB, improved pulmonary edema and oxygenation and preserved renal function.

Conclusions

The PARP inhibition attenuated lung-kidney crosstalk induced by intratracheal LPS instillation, partly via an inhibition of NF-κB dependent proinflammatory cytokines.

Acute lung injury and acute kidney injury are established by four hours in experimental sepsis and are improved with pre, but not post, sepsis administration of TNF-α antibodies

INTRODUCTION

Acute kidney injury (AKI) and acute lung injury (ALI) are serious complications of sepsis. AKI is often viewed as a late complication of sepsis. Notably, the onset of AKI relative to ALI is unclear as routine measures of kidney function (BUN and creatinine) are insensitive and increase late. In this study, we hypothesized that AKI and ALI would occur simultaneously due to a shared pathophysiology (i.e., TNF-α mediated systemic inflammatory response syndrome [SIRS]), but that sensitive markers of kidney function would be required to identify AKI.

METHODS

Sepsis was induced in adult male C57B/6 mice with 5 different one time doses of intraperitoneal (IP) endotoxin (LPS) (0.00001, 0.0001, 0.001, 0.01, or 0.25 mg) or cecal ligation and puncture (CLP). SIRS was assessed by serum proinflammatory cytokines (TNF-α, IL-1β, CXCL1, IL-6), ALI was assessed by lung inflammation (lung myeloperoxidase [MPO] activity), and AKI was assessed by serum creatinine, BUN, and glomerular filtration rate (GFR) (by FITC-labeled inulin clearance) at 4 hours. 20 µgs of TNF-α antibody (Ab) or vehicle were injected IP 2 hours before or 2 hours after IP LPS.

RESULTS

Serum cytokines increased with all 5 doses of LPS; AKI and ALI were detected within 4 hours of IP LPS or CLP, using sensitive markers of GFR and lung inflammation, respectively. Notably, creatinine did not increase with any dose; BUN increased with 0.01 and 0.25 mg. Remarkably, GFR was reduced 50% in the 0.001 mg LPS dose, demonstrating that dramatic loss of kidney function can occur in sepsis without a change in BUN or creatinine. Prophylactic TNF-α Ab reduced serum cytokines, lung MPO activity, and BUN; however, post-sepsis administration had no effect.

CONCLUSIONS

ALI and AKI occur together early in the course of sepsis and TNF-α plays a role in the early pathogenesis of both.