Background/Aims: Accumulation of protein-bound uremic toxins (PBUTs) is associated with mortality due to various systemic disorders in patients with chronic kidney disease (CKD), especially in those undergoing dialysis treatment. The clinical outcomes of such patients could be improved by removing sufficient amounts of PBUTs; however, conventional dialysis lacks this ability. We examined the efficacy of activated carbon in adsorbing circulating PBUTs through direct hemoperfusion (DHP) in vitro. Methods: An in vitro blood circulating system was constructed with 8.5 mL blood circulating around a column containing activated carbon (50, 100, or 200 mg). Bovine blood containing a kind of PBUT (at the same concentration as that found in the blood of dialysis patients) and blood from hemodialysis patients (n = 8) were used. After circulation for the designated amount of time, sera were collected and the levels of PBUTs, including indoxyl sulfate (IS), p-cresyl sulfate, indole acetic acid (IAA), phenyl sulfate, and hippuric acid, were analyzed with mass spectrometry. Results: Activated carbon decreased the PBUT level in bovine blood in a dose-dependent manner (e.g., reduction rate of IS: 67.9 ± 3.8, 83.3 ± 1.9, and 94.5 ± 1.1% after 60-min circulation in columns containing 50, 100, and 200 mg activated carbon respectively). IS, PCS, and IAA were dramatically adsorbed by activated carbon from the blood of patients undergoing hemodialysis (pre vs. post 240-min reaction: IS 2.835 ± 0.876 vs. 0.455 ± 0.108 mg/dL [p < 0.01], PCS 3.208 ± 2.876 vs. 0.768 ± 0.632 mg/dL [p < 0.01], IAA 0.082 ± 0.045 vs. 0.016 ± 0.005 mg/dL [p < 0.01]). Conclusion: Activated carbon effectively adsorbed blood PBUTs in vitro. DHP with activated carbon could be a promising strategy for removing circulating PBUTs from the blood of patients with CKD.

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