Serum neutrophil gelatinase-associated lipocalin and proinflammatory cytokines in pigs with septic versus non-septic acute kidney injury

[The role of neutrophils in the mechanisms of sepsis]

The international consensus Sepsis-3 in 2016 defined sepsis as life-threatening organ dysfunction caused by a disruption of the host response to infection. One of the main mechanisms leading to the death of patients with sepsis is an imbalance of the immune response to pathogens. Activation of immune cells, in particular neutrophils, plays a key role in the mechanisms of sepsis. During sepsis, the number of immature neutrophils in the blood increases, PD-L1 neutrophils appear, which have an immunosuppressive function, and the number of Neu1 subtype of neutrophils, characterized by high expression of the NF-kB inhibitor, the chemokine CXCL8, olfactomedine, which regulates the production of cytokines, and myeloperoxidase, increases. When the inflammatory response generalizes, the phagocytic and bactericidal functions of neutrophils are disrupted. An important role in the mechanisms of sepsis is played by the formation of neutrophil extracellular traps, extracellular DNA, and the nuclear non-histone protein HMGB1, which are DAMPs and have proinflammatory activity. The development of approaches to predicting the development and course of sepsis in injuries and infectious and inflammatory diseases based on assessing the functional activity of neutrophils and their phenotype is a promising area of research, in particular approaches to regulating the functioning of neutrophils using miRNA.

Loss of ZBED6 Protects Against Sepsis-Induced Muscle Atrophy by Upregulating DOCK3-Mediated RAC1/PI3K/AKT Signaling Pathway in Pigs

Sepsis-induced muscle atrophy often increases morbidity and mortality in intensive care unit (ICU) patients, yet neither therapeutic target nor optimal animal model is available for this disease. Here, by modifying the surgical strategy of cecal ligation and puncture (CLP), a novel sepsis pig model is created that for the first time recapitulates the whole course of sepsis in humans. With this model and sepsis patients, increased levels of the transcription factor zinc finger BED-type containing 6 (ZBED6) in skeletal muscle are shown. Protection against sepsis-induced muscle wasting in ZBED6-deficient pigs is further demonstrated. Mechanistically, integrated analysis of RNA-seq and ChIP-seq reveals dedicator of cytokinesis 3 (DOCK3) as the direct target of ZBED6. In septic ZBED6-deficient pigs, DOCK3 expression is increased in skeletal muscle and myocytes, activating the RAC1/PI3K/AKT pathway and protecting against sepsis-induced muscle wasting. Conversely, opposite gene expression patterns and exacerbated muscle wasting are observed in septic ZBED6-overexpressing myotubes. Notably, sepsis patients show increased ZBED6 expression along with reduced DOCK3 and downregulated RAC1/PI3K/AKT pathway. These findings suggest that ZBED6 is a potential therapeutic target for sepsis-induced muscle atrophy, and the established sepsis pig model is a valuable tool for understanding sepsis pathogenesis and developing its therapeutics.

Neutrophils and the Systemic Inflammatory Response Syndrome (SIRS)

We are not entirely able to understand, assess, and modulate the functioning of the immune system in clinical situations that lead to a systemic inflammatory response. In the search for diagnostic and treatment strategies (which are still far from perfect), it became very important to study the pathogenesis and participation of endogenous inflammation mediators. This study attempts to more precisely establish the role of neutrophils in individual phenomena occurring during an inflammatory and anti-inflammatory reaction, taking into account their cidal, immunoregulatory, and reparative abilities. Pro- and anticoagulatory properties of endothelium in systemic inflammatory response syndrome (SIRS) are emphasised, along with the resulting clinical implications (the application of immunotherapy using mesenchymal stem/stromal cells (MSCs) or IL-6 antagonists in sepsis and COVID-19 treatment, among others). Special attention is paid to reactive oxygen species (ROS), produced by neutrophils activated during "respiratory burst" in the course of SIRS; the protective and pathogenic role of these endogenous mediators is highlighted. Moreover, clinically useful biomarkers of SIRS (neutrophil extracellular traps, cell-free DNA, DAMP, TREMs, NGAL, miRNA, selected cytokines, ROS, and recognised markers of endothelial damage from the group of adhesins by means of immunohistochemical techniques) related to the neutrophils are presented, and their role in the diagnosing and forecasting of sepsis, burn disease, and COVID-19 is emphasised. Finally, examples of immunomodulation of sepsis and antioxidative thermal injury therapy are presented.

Porcine models of acute kidney injury

Pigs represent a potentially attractive model for medical research. Similar body size and physiological patterns of kidney injury that more closely mimic those described in humans make larger animals attractive for experimentation. Using larger animals, including pigs, to investigate the pathogenesis of acute kidney injury (AKI) also serves as an experimental bridge, narrowing the gap between clinical disease and preclinical discoveries. This article compares the advantages and disadvantages of large versus small AKI animal models and provides a comprehensive overview of the development and application of porcine models of AKI induced by clinically relevant insults, including ischemia-reperfusion, sepsis, and nephrotoxin exposure. The primary focus of this review is to evaluate the use of pigs for AKI studies by current investigators, including areas where more information is needed.

Differences in acute kidney injury ascertainment for clinical and preclinical studies

Background

Acute kidney injury (AKI) is a common clinical condition directly associated with adverse outcomes. Several AKI biomarkers have been discovered, but their use in clinical and preclinical studies has not been well examined. This study aims to investigate the differences between clinical and preclinical studies on AKI biomarkers.

Methods

We performed a systematic review of clinical and preclinical interventional studies that considered AKI biomarkers in enrollment criteria and/or outcome assessment and described the main differences according to their setting, the inclusion of biomarkers in the definition of AKI and the use of biomarkers as primary or secondary end points.

Results

In the 151 included studies (76 clinical, 75 preclinical), clinical studies have prevalently focused on cardiac surgery (38.1%) and contrast-associated AKI (17.1%), while the majority of preclinical studies have focused on ether ischemia-reperfusion injury or drug-induced AKI (42.6% each). A total of 57.8% of clinical studies defined AKI using the standard criteria and only 19.7% of these studies used AKI biomarkers in the definition of renal injury. Conversely, the majority of preclinical studies defined AKI according to the increase in serum creatinine and blood urea nitrogen, and 32% included biomarkers in that definition. The percentage of both clinical and preclinical studies with biomarkers as a primary end point has not significantly increased in the last 10 years; however, preclinical studies are more likely to use AKI biomarkers as a primary end point compared with clinical studies [odds ratio 2.31 (95% confidence interval 1.17-4.59); P  =  0.016].

Conclusion

Differences between clinical and preclinical studies are evident and may affect the translation of preclinical findings in the clinical setting.

The impact of hydrocortisone treatment on neutrophil gelatinase-associated lipocalin release in porcine endotoxemic shock

Background

A key feature of sepsis is systemic inflammatory activation that could be counteracted by steroids. In this experimental model of systemic inflammation, we sought to investigate whether septic neutrophil activation, evaluated by the plasma levels of neutrophil gelatinase-associated protein (NGAL), is modulated by the timing of hydrocortisone treatment.

Methods

Sixteen anesthetized pigs were allocated to one of four equally sized groups. Three of these groups received endotoxin at 2 μg × kg⁻¹ × h⁻¹ for 6 h so as to induce endotoxemic shock. Hydrocortisone (5 mg × kg⁻¹) was administered intravenously before endotoxemic challenge, or at the onset of endotoxemic shock. Endotoxemic pigs not receiving hydrocortisone and non-endotoxemic pigs served as control groups. Physiologic variables, hematology, and biochemistry, including plasma NGAL, were measured repeatedly.

Results

Hydrocortisone treatment prior to endotoxemia attenuated some inflammatory, hematological, circulatory, and metabolic manifestations of shock (i.e., higher white blood cell count, higher mean arterial pressure, lower heart rate and mean pulmonary arterial pressure, higher left ventricular stroke work index, higher base excess). Endotoxemic shock increased plasma NGAL (p < 0.001). In pigs given hydrocortisone before the endotoxin infusion, plasma NGAL was lower as compared to those given hydrocortisone at endotoxemic shock (p < 0.05). Plasma NGAL levels correlated inversely to neutrophil granulocyte counts (rho = −0.65) but not to urine output (rho = −0.10) at the end of the experiment.

Conclusions

The increase in plasma NGAL is counteracted by hydrocortisone administration prior to endotoxemia; concomitantly, this treatment was associated with less expressed circulatory derangement. Urine NGAL did not differ between the groups, suggesting that the NGAL response was not primarily related to kidney injury.