Plasma Neutrophil Gelatinase-Associated Lipocalin Is Primarily Related to Inflammation during Sepsis: A Translational Approach

Acute kidney injury (AKI) during sepsis is common and underestimated. Plasma neutrophil gelatinase-associated lipocalin (plasma-NGAL) is discussed as new biomarker for AKI diagnosis, but during inflammation its function and diagnostic impact remain unclear. The association between plasma-NGAL and inflammatory markers in septic patients, but also in healthy controls and patients with chronic inflammation before and after either maximum exercise test or treatment with an anti-TNF therapy were investigated. In-vitro blood stimulations with IL-6, lipopolysaccharide, NGAL or its combinations were performed to investigate cause-effect-relationship. Plasma-NGAL levels were stronger associated with inflammation markers including IL-6 (Sepsis: r = 0.785 P < 0.001; chronic inflammation after anti-TNF: r = 0.558 P < 0.001), IL-8 (Sepsis: r = 0.714 P<0.004; healthy controls after exercise r = 0.786 P < 0.028; chronic inflammation before anti-TNF: r = 0.429 P < 0.041) and IL-10 (healthy controls before exercise: r = 0.791 P < 0.028) than with kidney injury or function. Correlation to kidney injury or function was found only in septic patients (for creatinine: r = 0.906 P < 0.001; for eGFR: r = -0.686 P = 0.005) and in patients with rheumatic disease after anti-TNF therapy (for creatinine: r = 0.466 P < 0.025). In stimulation assays with IL-6 and lipopolysaccharide plasma-NGAL was increased. Co-stimulation of lipopolysaccharide with plasma-NGAL decreased cellular injury (P < 0.05) and in trend IL-10 levels (P = 0.057). Septic mice demonstrated a significantly improved survival rate after NGAL treatment (P < 0.01). Plasma-NGAL seams to be strongly involved in inflammation. For clinical relevance, it might not only be useful for AKI detection during severe inflammation - indeed it has to be interpreted carefully within this setting - but additionally might offer therapeutic potential.