Paediatric sepsis survivors are resistant to sepsis-induced long-term immune dysfunction

BACKGROUND AND PURPOSE

Sepsis-surviving adult individuals commonly develop immunosuppression and increased susceptibility to secondary infections, an outcome mediated by the axis IL-33/ILC2s/M2 macrophages/Tregs. Nonetheless, the long-term immune consequences of paediatric sepsis are indeterminate. We sought to investigate the role of age in the genesis of immunosuppression following sepsis.

EXPERIMENTAL APPROACH

Here, we compared the frequency of Tregs, the activation of the IL-33/ILC2s axis in M2 macrophages and the DNA methylation of epithelial lung cells from post-septic infant and adult mice. Likewise, sepsis-surviving mice were inoculated intranasally with Pseudomonas aeruginosa or by subcutaneous inoculation of the B16 melanoma cell line. Finally, blood samples from sepsis-surviving patients were collected and the concentration of IL-33 and Tregs frequency were assessed.

KEY RESULTS

In contrast to 6-week-old mice, 2-week-old mice were resistant to secondary infection and did not show impairment in tumour controls upon melanoma challenge. Mechanistically, increased IL-33 levels, Tregs expansion, and activation of ILC2s and M2-macrophages were observed in 6-week-old but not 2-week-old post-septic mice. Moreover, impaired IL-33 production in 2-week-old post-septic mice was associated with increased DNA methylation in lung epithelial cells. Notably, IL-33 treatment boosted the expansion of Tregs and induced immunosuppression in 2-week-old mice. Clinically, adults but not paediatric post-septic patients exhibited higher counts of Tregs and seral IL-33 levels.

CONCLUSION AND IMPLICATIONS

These findings demonstrate a crucial and age-dependent role for IL-33 in post-sepsis immunosuppression. Thus, a better understanding of this process may lead to differential treatments for adult and paediatric sepsis.

Neutrophil extracellular traps (NETs) exacerbate severity of infant sepsis

Background

Neutrophil extracellular traps (NETs) are innate defense mechanisms that are also implicated in the pathogenesis of organ dysfunction. However, the role of NETs in pediatric sepsis is unknown.

Methods

Infant (2 weeks old) and adult (6 weeks old) mice were submitted to sepsis by intraperitoneal (i.p.) injection of bacteria suspension or lipopolysaccharide (LPS). Neutrophil infiltration, bacteremia, organ injury, and concentrations of cytokine, NETs, and DNase in the plasma were measured. Production of reactive oxygen and nitrogen species and release of NETs by neutrophils were also evaluated. To investigate the functional role of NETs, mice undergoing sepsis were treated with antibiotic plus rhDNase and the survival, organ injury, and levels of inflammatory markers and NETs were determined. Blood samples from pediatric and adult sepsis patients were collected and the concentrations of NETs measured.

Results

Infant C57BL/6 mice subjected to sepsis or LPS-induced endotoxemia produced significantly higher levels of NETs than the adult mice. Moreover, compared to that of the adult mice, this outcome was accompanied by increased organ injury and production of inflammatory cytokines. The increased NETs were associated with elevated expression of Padi4 and histone H3 citrullination in the neutrophils. Furthermore, treatment of infant septic mice with rhDNase or a PAD-4 inhibitor markedly attenuated sepsis. Importantly, pediatric septic patients had high levels of NETs, and the severity of pediatric sepsis was positively correlated with the level of NETs.

Conclusion

This study reveals a hitherto unrecognized mechanism of pediatric sepsis susceptibility and suggests that NETs represents a potential target to improve clinical outcomes of sepsis.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2407-8) contains supplementary material, which is available to authorized users.

A method to estimate urinary electrolyte excretion in patients at risk for developing cerebral salt wasting

OBJECT

Two major criteria are necessary to diagnose cerebral salt wasting (CSW): a cerebral lesion and a large urinary excretion of Na+ and Cl- at a time when the extracellular fluid (ECF) volume is contracted. Nevertheless, it is difficult for the physician to confirm from bedside observation that a patient has a contracted ECF volume. Hyponatremia, although frequently present, should not be a criterion for a diagnosis of salt wasting. A contracted ECF volume is unlikely if there are positive balances of Na+ and Cl-. The goal of this study was to assess the accuracy of calculating balances for Na+ plus K+ and of Cl- over 1 to 10 days in an intensive care unit (ICU) setting.

METHODS

A prospective comparison of measured and estimated quantities of Na+ plus K+ and of Cl- excreted over 1 to 10 days in 10 children and 12 adults who had recently received a traumatic brain injury or undergone recent neurosurgery. Plasma concentrations of electrolytes were recorded at the beginning and end of the study period. The total volumes infused and excreted and the concentrations of Na+, K+, and Cl- in the infusate were obtained from each patient's ICU chart. The electrolytes in the patients' urine were measured and calculated. Correlations between measured and calculated values for excretions of Cl- and of Na+ plus K+ were excellent.

CONCLUSIONS

Mass balances for Na+ plus K+ and for Cl- can be accurately estimated. These data provide information to support or refute a clinical diagnosis of CSW. The danger of relying on balances for these electrolytes measured within a single day to diagnose CSW is illustrated.

Tonicity balance, and not electrolyte-free water calculations, more accurately guides therapy for acute changes in natremia

The usual way to decide why hyponatremia or hypernatremia has developed and to plan goals for its therapy is to analyze events in electrolyte-free water (EFW) terms. We shall demonstrate that an EFW balance does not supply this information. Rather, one must calculate mass balances for water and sodium plus potassium separately (a tonicity balance) to understand the basis for the change in natremia and the proper goals for its therapy. These points are illustrated with a clinical example.

[Protein/creatinine ratio in single urine samples for the semiquantitation of proteinuria in children with nephrosis]

OBJECTIVE: To estimate, semiquantitatively, the proteinuria of nephrotic patients by the use of the value of protein/creatinine ratio in single urine samples and determine its correlation with 24-hour proteinuria.METHODS: Analysis of 30 single urine samples and thirty 24-hour urine samples from 20 children with nephrosis followed up at the Division of Pediatric Nephrology of the University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo. Proteinuria in single urine samples and 24-hour urine samples was measured by the turbidimetric method with 3% sulfosalicylic acid. Urinary creatinine concentration was measured by the method of Hare, modified by Haugen and Blegen, adapted to the microtechnique.RESULTS: An excellent correlation was observed between 24-hour proteinuria and the protein/creatinine ratio in single urine samples, by linear regression analysis before (r = 0.82; p < 0.001) and after logarithmic transformation (r = 0.93; p < 0.001). All patients with 24-hour proteinuria at physiological levels (less than 0.1 g/m(2)/day) had a protein/creatinine ratio of less than 0.1 (mg/mg) in single urine samples. All patients with nephrotic 24-hour proteinuria (more than 1.0 g/m(2)/day) had a protein/creatinine ratio of more than 1.0 (mg/mg). The patients with intermediate proteinuria (between 0.1 and 1.0 g/m(2)/day) had a protein/creatinine ratio distributed on the three levels.CONCLUSIONS: The protein/creatinine ratio in a single urine sample is a simple and reliable method for the evaluation of proteinuria and eliminates the errors due to inadequate 24-hour urine collection.