Modulation of Brain Kynurenic Acid by N-Acetylcysteine Prevents Cognitive Impairment and Muscular Weakness Induced by...

Cisplatin (CIS) is a potent chemotherapeutic agent primarily used to treat hematologic malignancies and solid tumors, including lymphomas, sarcomas, and some carcinomas. Patients receiving this treatment for tumors outside the nervous system develop cognitive impairment. Alterations in the kynurenine pathway (KP) following CIS treatment suggest that certain KP metabolites may cross the blood-brain barrier, leading to increased production of the neuromodulator kynurenic acid (KYNA), which is associated with cognitive impairment. This study aimed to evaluate the effects of modulating brain KYNA levels by the administration of N-acetylcysteine (NAC), an inhibitor of kynurenine aminotransferase II (KATII), an enzyme responsible for KYNA biosynthesis on the cognitive and neuromuscular deficits induced by CIS. Female Wistar rats were divided into four groups: control, NAC (300 mg/day/8 days), CIS (3 mg/kg i.p/5 days), and NAC + CIS (both treatments co-administered in parallel). Seven days after the last CIS administration, cognitive performance, muscle strength, brain KYNA levels, KATII activity, and brain tissue redox profile (lipid peroxidation and oxidized/reduced glutathione (GSH/GSSG) ratio) were assessed. CIS did not affect short-term memory but induced long-term memory deficits and reduced muscle strength, effects which were prevented by NAC co-administration. CIS decreased the GSH/GSSG ratio and the number of cells in the brain cortex while it increased lipid peroxidation, KYNA levels, and marginal KATII activity. All these effects were attenuated by the co-administration of NAC. These findings suggest that NAC mitigates the side effects of CIS, such as chemo-brain and muscle weakness, by improving the redox imbalance and modulating KYNA levels by limiting its non-enzymatic production by reactive oxygen species (ROS).