Kushenol E alleviates sepsis-associated cognitive dysfunction via microglial indoleamine 2,3-dioxygenase 1 inhibition

Sepsis-associated encephalopathy (SAE) affects up to 70% of septic patients, but lacks specific therapeutic interventions. Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes tryptophan degradation via the kynurenine pathway, producing neurotoxic metabolites that drive neuroinflammation.

This study investigates whether kushenol E, a prenylated flavonoid from Sophora flavescens, mitigates SAE by inhibiting microglial IDO1.

Sepsis was induced by cecal ligation and puncture (CLP) in male C57BL/6J mice. Cognitive function was assessed by the novel object recognition test and the Morris water maze. Neuronal injury, neuroinflammation, and oxidative stress were evaluated by histology and biochemical assays. IDO1 expression was quantified by quantitative PCR and Western blot, and kynurenine pathway metabolites were profiled by LC-MS/MS. Kushenol E inhibition of murine IDO1 was verified in IFN-γ-stimulated BV-2 microglia. AAV9-mediated F4/80⁺ myeloid-cell-targeted IDO1 overexpression was used as an in vivo rescue strategy.

CLP induced cognitive impairment, neuronal loss, neuroinflammation, and oxidative stress, accompanied by marked microglial IDO1 upregulation. Kushenol E preserved cognitive function, hippocampal integrity, and synaptic architecture; suppressed neuroinflammation; and limited neurotoxic kynurenine accumulation. Mechanistically, kushenol E inhibited IDO1 catalytic activity without altering its transcript or protein levels. In IFN-γ-stimulated BV-2 microglia, kushenol E suppressed kynurenine production in a concentration-dependent manner (IC₅₀ = 7.38 μM), confirming direct inhibition of murine IDO1. F4/80⁺ myeloid-cell-targeted IDO1 overexpression reversed these protective effects, identifying microglial IDO1 as the principal therapeutic target.

Kushenol E mitigates SAE primarily by inhibiting microglial IDO1 catalytic activity, thereby limiting neurotoxic kynurenine production. These findings nominate microglial IDO1 as a therapeutic target for SAE and support kushenol E as a lead compound for the management of cognitive sequelae in sepsis survivors.