Carvacrol Modulates the Hippocampal Prostaglandin-Cytokine Axis in LPS-Induced Neuroinflammation

Objective: Neuroinflammation contributes to cognitive impairment across neurodegenerative disorders. Prostaglandins (e.g., PGE₂, PGD₂, PGF₂α) and pro-inflammatory cytokines (TNF-α, IL-1β) are key mediators of lipopolysaccharide (LPS)-induced hippocampal dysfunction. Carvacrol (CRV), a monoterpenic phenol with anti-inflammatory and antioxidant properties, may mitigate these effects, but its impact on hippocampal prostaglandin profiles is not well-defined. Methods: BALB/c mice were randomly assigned to Control (PBS; n = 7), LPS (1 mg/kg, i.p.; n = 10), or LPS + CRV (50 mg/kg, p.o.; n = 7). Body weight was tracked daily for 7 days; rectal temperature was measured once before behavioral testing and euthanasia. Locomotion/anxiety were assessed by the open-field test (OFT; average speed, total distance, freezing, mobility rate) using ToxTrac. Spatial recognition memory was evaluated in the Y-maze novel-arm task (novel-arm entries, duration, total entries, discrimination index [DI]). Hippocampal PGE₂, PGD₂, PGF₂α, TNF-α, and IL-1β were quantified by ELISA. Data were analyzed by one-way ANOVA with Sidak's post hoc test. Results: OFT measures did not differ among groups (p > 0.05), indicating no confounding locomotor deficits. In the Y-maze, LPS reduced novel-arm entries versus the Control (p = 0.0029), while LPS + CRV showed a nonsignificant increase versus LPS (p = 0.2406). Novel-arm duration differed among groups (p = 0.0033); LPS + CRV spent less time than LPS (p = 0.0128). Critically, DI showed a robust treatment effect (p < 0.0001): LPS markedly impaired DI versus the Control (p < 0.0001), and CRV significantly improved DI versus LPS (p < 0.0001). Biochemically, LPS elevated hippocampal PGE₂ (p < 0.0001) and PGF₂α (p = 0.0040); CRV normalized PGE₂ (p < 0.0001) but not PGF₂α (p = 0.2656). PGD₂ was unchanged. LPS increased TNF-α and IL-1β (both p < 0.0001), and CRV significantly reduced both versus LPS (both p < 0.0001). Conclusions: Acute LPS provokes prostaglandin- and cytokine-driven hippocampal inflammation with associated recognition memory deficits. Carvacrol attenuates cognitive impairment and suppresses hippocampal PGE₂, TNF-α, and IL-1β, supporting a mechanism involving modulation of the prostaglandin-cytokine axis. These findings highlight CRV as a candidate adjunct for inflammation-associated cognitive dysfunction.