5-MTP: 5-methoxytryptophan; AKI: acute kidney injury; CKD: chronic kidney disease; GFR: glomerular filtration rate; H2O2: hydrogen peroxide; IL: interleukin; KIM-1: kidney injury molecule-1; NGAL: neutrophil gelatinase-associated lipocalin; NO: nitric oxide; O2•-: superoxide anions; OH•-: hydroxyl radical; RNS: reactive nitrogen species; ROS: reactive oxygen species; SCr: serum creatinine; UO: urine output. Here, LCN2 is linked to acute kidney injury.