PEO+ induced acute kidney injury and identification of HWM PEO in the microvasculature. (A) Representative kidney sections stained with H&E (top panel) and for fibrinogen by immunohistochemistry (NovaRed, bottom panel) (scale bar, 20 µm). Multidosed (5×) animals demonstrate glomerular capillary swelling (arrow), patchy necrosis of proximal tubule cells with widespread eosinophilic intracellular inclusions (rightmost panel), and hemoglobin laden tubular casts (*). A dose-dependent increase in fibrin deposition within the glomerular capillaries of PEO+ treated animals could be found. (B-D) Quantitation of T_24h plasma creatinine levels, renal cortex mRNA NGAL levels, and urinary albumin after PEO+ administration (n = 4 per group). (E) Kidney sections of control, single (1×) and multidosed (5×) PEO+ animals were immunohistochemically stained for PEO using a monoclonal antibody against the polyethylene backbone with DAB development. Interlobular arteries (top panel) and vasa recta lining the loop of Henle (bottom panel) are shown (scale bar, 20 µm). (F) Western blot for HIF-1α expression in the renal cortex of representative animals. β-actin was probed as a protein loading control. Cell lysates of hypoxic (8 hours at 1% O₂) and normoxic (21% O₂) HEK293 cells served as a reference of the HIF-1α–specific upregulated band. (G) HUVECs were cultured for 24 hours in the presence of various concentrations of PEO+ or activated with 1 µg/mL lipopolysaccharide. The amount of sVCAM released into the cell culture supernatant was quantified by ELISA. *P < .05 (1-way ANOVA).