Hippocampal Galectin-3 knockdown alleviates lipopolysaccharide-induced neurotoxicity and cognitive deficits by inhibiting TLR4/NF-кB signaling in aged mice

Abstract

Neuroinflammation is thought to contribute to the onset and progression of Alzheimer's disease (AD). Galectin-3 (Gal-3), the only member of the galectin chimeric subfamily, is a key regulator of neuroinflammation and microglial activation. However, the effects of Gal-3 inhibition in AD-related neuroinflammation are unclear. Here, we investigated whether hippocampal Gal-3 knockdown alleviated lipopolysaccharide (LPS)-induced neurotoxicity and cognitive deficits, as well as the underlying mechanisms. First, we bilaterally injected aged mice (23 months old) with anti-Gal-3 short hairpin RNA into the hippocampus dentate gyrus, followed by systemic LPS administration. To determine the effects of hippocampal Gal-3 knockdown on neuroinflammatory response and neuronal apoptosis, we assessed the effects of Gal-3 silencing on the levels of pro-inflammatory cytokines, microglial activation, and apoptosis in the hippocampus of LPS-exposed aged mice. Behavioral tests were used to access the cognitive function of the mice. To explore the potential signaling, protein extracts from the brains of mice were subjected to analyze the expression levels of key molecules (including Toll-like receptor 4 (TLR4), myeloid differentiation factor 88, and nuclear transcription factor-κB (NF-κB) p65) of the TLR4/NF-кB pathway, and BV2 cells were pretreated with TLR4 inhibitor or NF-κB inhibitor before Gal-3 stimulation. These analyses showed that hippocampal Gal-3 knockdown attenuated neuroinflammation and neuronal apoptosis in the hippocampus of LPS-challenged aged mice, and this was associated with improved cognitive function. Hippocampal Gal-3 knockdown may protect against LPS-induced neurotoxicity by inhibiting the TLR4/NF-кB pathway. Our findings highlight Gal-3 as a potential therapeutic target against AD-associated neuroinflammation.