Albumin Protects Against Cyclophosphamide-Induced Hemorrhagic Cystitis by Scavenging Acrolein and Reactive Oxygen Species.

Cyclophosphamide (CYP) is an effective chemotherapeutic, but its use is limited by hemorrhagic cystitis caused by its toxic metabolite acrolein. Acrolein, when concentrated in the urine, triggers oxidative stress, leading to urothelial inflammation and cell death. Given that albumin is the most abundant plasma protein that contains free thiol groups capable of neutralizing electrophiles and oxidants, we, therefore, hypothesized that albumin could mitigate CYP-induced bladder injury. Here, we tested this hypothesis. In CYP-induced mouse cystitis, albumin administration markedly reduced bladder enlargement, edema, and hemorrhage, effectively normalizing the bladder weight. Albumin also reduced bladder oxidative injury and preserved the expression of anti-ferroptotic proteins, including the cystine/glutamate antiporter xCT and glutathione peroxidase 4 (GPX4). In addition, albumin-treated mice showed less leakage of inflammatory protein into bladder tissue. In vitro, albumin protected urothelial cells from acrolein-induced cell death. It also significantly prevented H2O2-induced cytotoxicity. Mechanistically, albumin acted as an extracellular scavenger that preferentially reacted with acrolein and H2O2, thereby sparing cellular components from oxidative damage. Notably, oral albumin supplementation similarly attenuated CYP-induced cystitis. Furthermore, albumin administration improved survival in a high-dose CYP toxicity model. These findings establish albumin as a potent protector against CYP-induced toxicity by sequestering acrolein and scavenging reactive oxygen species. Albumin supplementation could be a practical strategy to mitigate chemotherapy-associated bladder and systemic injury.