Huang-Lian-Jie-Du decoction alleviates cognitive impairment in periodontitis rats through restoring microbiota-gut-brain axis and inhibiting neuroinflammation via TLR4/NF-κB pathway

Abstract Background Huang-Lian-Jie-Du decoction (HLJDD), a typical formulation for heat clearance and detoxification, shows therapeutic potential for oral diseases and cognitive impairment. Nevertheless, the mechanism by which HLJDD influences periodontitis-induced cognitive impairment via the microbiota-gut-brain axis remains unknown. Aim of the study We investigated HLJDD’s neuroprotective effects in periodontitis rats, focusing on its modulation of the microbiota-gut-brain axis and underlying molecular mechanisms. Materials and methods Chemical profiling of HLJDD was performed via UHPLC-Q-Exactive Orbitrap HRMS. Periodontitis was induced in SD rats using ligatures and Porphyromonas gingivalis for 2 weeks, followed by 8-week treatments with HLJDD (0.75/1.5/3 g/kg/day), doxycycline (10 mg/kg/day), or vehicle. Alveolar bone loss was assessed via micro-CT, while cognitive function was assessed via the Morris water maze (MWM). Hippocampal and colon pathology was analyzed via H&E, Nissl staining, and immunohistochemistry. The composition of gut microbiota was analyzed by 16S rDNA sequencing. The tight junction proteins in hippocampus and colon were examined by RT- qPCR and immunofluorescence (IF). Inflammatory cytokine levels in intestinal and hippocampus tissue and serum were quantified by ELISA. Network pharmacology predicted potential mechanisms, and Western blotting assessed TLR4/NF-κB pathway proteins. Results HLJDD contained 94 bioactive compounds and significantly attenuated alveolar bone loss, improved cognitive function, and reduced neuronal damage and Aβ deposition. It restored gut microbiota homeostasis, enhanced intestinal and blood–brain barrier integrity, and suppressed neuroinflammation by modulating pro- and anti-inflammatory cytokines. Mechanistically, HLJDD inhibited TLR4/NF-κB signaling, suggesting its therapeutic potential in periodontitis-related cognitive impairment. Conclusion HLJDD ameliorates cognitive impairment in periodontitis by modulating the microbiota-gut-brain axis, reducing neuroinflammation, and inhibiting TLR4/NF-κB activation. These findings support its potential as a novel therapeutic strategy for periodontitis-associated cognitive impairment. Graphical Abstract