Superoxide induces protein oxidation in plasma and TNF-α elevation in macrophage culture: Insights into mechanisms of neurotoxicity following doxorubicin chemotherapy

Chemotherapy-induced cognitive impairment (CICI) is a quality of life-altering consequence of chemotherapy experienced by a large percentage of cancer survivors. Approximately half of FDA-approved anti-cancer drugs are known to produce ROS. Doxorubicin (Dox), a prototypical ROS-generating chemotherapeutic agent, generates superoxide (O₂^-) via redox cycling. Our group previously demonstrated that Dox, which does not cross the BBB, induced oxidative damage to plasma proteins leading to TNF-α elevation in the periphery and, subsequently, in brain following cancer chemotherapy. We hypothesize that such processes play a central role in CICI. The current study tested the notion that O₂^- is involved and likely responsible for Dox-induced plasma protein oxidation and TNF-α release. Addition of O₂^- as the potassium salt (KO₂) to plasma resulted in significantly increased oxidative damage to proteins, indexed by protein carbonyl (PC) and protein-bound HNE levels. We then adapted this protocol for use in cell culture. Incubation of J774A.1 macrophage culture using this KO₂-18crown6 protocol with 1 and 10 M KO₂ resulted in dramatically increased levels of TNF-α produced. These findings, together with our prior results, provide strong evidence that O₂^- and its resulting reactive species are critically involved in Dox-induced plasma protein oxidation and TNF-α release.