Neutrophil gelatinase-associated lipocalin/lipocalin2, derived from gut crypt cells, exerts intestinal antimicrobial effect via bacterial stimulation of Toll-like receptor 4 and 9

Neutrophil gelatinase-associated lipocalin (NGAL)/ lipocalin2, known as a sensitive biomarker of acute kidney injury, prevents bacterial iron uptake, resulting in the inhibition of its overgrowth [1]. We previously demonstrated that this protein was discharged into gut lumen from crypt cells in septic conditions, and inhibited the growth of Escherichia coli [2]. However, it remains unclear which pathway is associated with the upregulation of NGAL. We therefore designed the present study to reveal whether the pattern-recognition receptor of bacteria, the Toll-like receptor (TLR) family, plays a pivotal role for NGAL secretion from gut crypt cells.