Paeoniflorin Alleviates Lipopolysaccharide-Induced Neuroinflammation and Depression Through the Keap1/Nrf2/HO-1 Signaling Pathway.

Depression is associated with bidirectional interactions between inflammatory responses and behavioral dysfunction. Paeoniflorin (PF), a monoterpene glycoside derived from Paeonia lactiflora, exhibits potent anti-inflammatory properties. This study investigates the therapeutic effects of PF on lipopolysaccharide (LPS)-induced depression-like behaviors in mice and neuroinflammation in BV2 microglial cells. Mice were co-administered PF (20, 40, or 80 mg/kg/day) and LPS (2 mg/kg) for 7 days. Behavioral tests; Nissl staining; and Golgi, Iba1, DLG4, and cytokine assays were conducted. Additionally, hippocampal NF-κB, Nrf2, and BDNF signaling pathways were analyzed using Western blots. In BV2 cells, oxidative stress and the Nrf2/HO-1 pathway were assessed using CCK-8, flow cytometry, and Western blotting after 24 h of LPS and PF treatment. PF significantly alleviated LPS-induced depression-like behaviors, increased hippocampal neuron and dendritic spine density, and upregulated synaptic proteins (PSD95, SNAP25, and BDNF). Mechanistically, PF suppressed NLRP3 inflammasome activation via the Akt/GSK3β pathway, reduced pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), and enhanced the Nrf2/HO-1 antioxidant axis. In BV2 cells, PF restored mitochondrial membrane potential, inhibited apoptosis, and decreased cytokine levels (TNF-α, IL-1β, and IL-6) by inhibiting TLR4/NF-κB signaling. In conclusion, PF significantly improved LPS-induced depression-like behaviors and attenuated neuroinflammation in BV2 microglial cells, highlighting its potential as a therapeutic agent for inflammation-associated depression.