Fig 2: a SCr in rats subjected to LPS at 6 h. The data show SCr of Con and sAKI, with means ± SD values/group obtained by colorimetric assay (µM/L). SCr increased in rats with sAKI. SCr: serum creatinine, LPS: lipopolysaccharide. **p < 0.01, relative to the Con group. b Renal histological injury observed under light microscopy at 6 h after LPS treatment (H&E, 200×). Histopathlogical changes included renal tubular epithelial swelling and inflammatory cell infiltration without glomerular injury. c uNGAL in rats subjected to LPS at 6 h. Data show respective uNGAL of Con and sAKI, with means ± SD values/group obtained by ELISA (ng/mL). uNGAL was significantly increased in rats with sAKI. uNGAL: urine NGAL, LPS: lipopolysaccharide. ***p < 0.001, relative to the con group

Fig 3: a Expression of NGAL mRNA in the LPS-treated HK-2. Data are means ± SD of three separate experiments in duplicate. There was a 2.2-fold increase in NGAL mRNA expression 1 h after LPS treatment, which increased to 3.2-fold at 3 h and then decreased to 1.8-fold at 6 h. NGAL: neutrophil gelatinase-associated lipocalin, LPS: lipopolysaccharide. **p < 0.01, ***p < 0.001, relative to the control group. b Expression of caspase 3 mRNA in the LPS-treated HK-2. Data are means ± SD of three separate experiments in duplicate. There was a 2.02-fold increase in NGAL mRNA expression at 1 h after LPS treatment, and this decreased to 1.3-fold at 3 h. **p < 0.01, ***p < 0.001, relative to controls. NGAL: neutrophil gelatinase-associated lipocalin, LPS: lipopolysaccharide

Fig 4: Expression of NGAL mRNA and caspase 3 mRNA in HK-2 after NGAL siRNA transfection. Data are means ± SD of three separate experiments in duplicate. **p < 0.01, ***p < 0.001, relative to controls. ##p < 0.01, ###p < 0.001, relative to the LPS group. NGAL: neutrophil gelatinase-associated lipocalin

Fig 5: a Renal tubular epithelial cell injury and apoptosis observed under TEM at 6 h after LPS treatment (TEM, 5000×). Arrows indicate disarrayed microvilli, mitochondrial ballooning, and unevenly distributed nuclear chromatin in the outer nuclear layer gathered toward the center. TEM: transmission electron microscopy, LPS: lipopolysaccharide. b Localization of NGAL protein expression in rat kidneys under light microscopy 6 h after LPS treatment. Con: Control group, sAKI-1: renal cortex of sAKI group, sAKI-2: renal medulla of the sAKI group. (original magnification 400×). NGAL: neutrophil gelatinase-associated lipocalin, LPS: lipopolysaccharide. c Localization of caspase 3 protein expression in rat kidneys under light microscopy at 6 h after LPS treatment. Con: Control group, sAKI-1: renal cortex of sAKI group, sAKI-2: renal medulla of the sAKI group. Original magnification 400×. LPS: lipopolysaccharide. d Semi-quantification of immunohistochemical staining for NGAL and caspase 3 in kidneys of Con and sAKI rats. Data are expressed as means ± SD. ***p < 0.001, relative to controls