Lipopolysaccharide Binding Protein and Bactericidal/Permeability-Increasing Protein as Biomarkers for Invasive Pulmonary Aspergillosis

Evaluation of interleukin-8 levels in the diagnosis of invasive pulmonary aspergillosis in patients with haematological malignancies

This study aimed to determine the level of interleukin (IL)-8 in diagnosing of invasive pulmonary aspergillosis (IPA). We conducted this study with 50 controls and 25 IPA patients with haematological malignancies. Demographic data, haematological diagnoses, chemotherapy regimen, galactomannan level, fungal culture, and computed tomography findings of the patients were evaluated prospectively. IL-8 levels were studied with the ELISA method. The mean age of patients in the case group was 60.84 ± 15.38 years, while that of the controls was 58.38 ± 16.64 years. Of the patients, 2/25 were classified as having 'proven', 13/25 as 'probable', and 10/25 as 'possible' invasive aspergillosis (IA). Serum IL-8 levels were found to be significantly higher in the case group compared to the controls. There was a negative correlation between serum IL-8 levels and neutrophil counts and a positive correlation with the duration of neutropenia. A significant cutoff value for serum IL-8 parameter in detecting IPA disease was obtained as ≥274 ng/l; sensitivity was 72%; specificity was 64%; PPV was 50%; and NPV was 82%. In the subgroup analysis, there was no significant difference in serum IL-8 levels between the case group and the patients in the neutropenic control group, while a significant difference was found in with the patients in the non-neutropenic control group. Serum IL-8 levels in neutropenic patients who develop IPA are not adequate in terms of both the diagnosis of the disease and predicting mortality. New, easily applicable methods with high sensitivity and specificity in diagnosing IPA are still needed.

High Na+ Environments Impair Phagocyte Oxidase-Dependent Antibacterial Activity of Neutrophils

Infection and inflammation can augment local Na⁺ abundance. These increases in local Na⁺ levels boost proinflammatory and antimicrobial macrophage activity and can favor polarization of T cells towards a proinflammatory Th17 phenotype. Although neutrophils play an important role in fighting intruding invaders, the impact of increased Na⁺ on the antimicrobial activity of neutrophils remains elusive. Here we show that, in neutrophils, increases in Na⁺ (high salt, HS) impair the ability of human and murine neutrophils to eliminate Escherichia coli and Staphylococcus aureus. High salt caused reduced spontaneous movement, degranulation and impaired production of reactive oxygen species (ROS) while leaving neutrophil viability unchanged. High salt enhanced the activity of the p38 mitogen-activated protein kinase (p38/MAPK) and increased the interleukin (IL)-8 release in a p38/MAPK-dependent manner. Whereas inhibition of p38/MAPK did not result in improved neutrophil defense, pharmacological blockade of the phagocyte oxidase (PHOX) or its genetic ablation mimicked the impaired antimicrobial activity detected under high salt conditions. Stimulation of neutrophils with phorbol-12-myristate-13-acetate (PMA) overcame high salt-induced impairment in ROS production and restored antimicrobial activity of neutrophils. Hence, we conclude that high salt-impaired PHOX activity results in diminished antimicrobial activity. Our findings suggest that increases in local Na⁺ represent an ionic checkpoint that prevents excessive ROS production of neutrophils, which decreases their antimicrobial potential and could potentially curtail ROS-mediated tissue damage.