MN-08 Attenuates Delirium-Related Cognitive Impairment via Inhibition of Microglial Lipocalin-2

摘要

Objective: Delirium, a common and severe neuropsychiatric syndrome characterized by acute cognitive impairment and attention deficits, significantly impacts patient prognosis and quality of life. Effective pharmacological treatments are lacking, underscoring the need to elucidate its underlying mechanisms. Microglia are implicated in neuroinflammation and cognitive dysfunction, but their specific role in delirium remains unclear. Lipocalin-2(LCN2), a microglial effector molecule, may mediate neuroinflammation and neuronal dysfunction. This study aimed to investigate the role of hippocampal microglial LCN2 in delirium-related cognitive impairment and evaluate how the memantine derivative MN-08 modulates this pathway. Methods:(1) In delirium model of mice intraperitoneal injected with LPS and midazolam(referred to as LM treatment), delirium-related cognitive impairment was assessed using the novel object recognition(NOR) and Y-maze tests.(2) Transcriptomic analysis, immunofluorescence staining, RT-qPCR, and Western blotting were employed to identify LCN2 as a core gene involved in delirium pathogenesis and to elucidate the underlying pathological mechanisms.(3) In the hippocampus, which is closely associated with cognitive function, microglia-specific transduction via AAV armed with Iba1 promoter was injected to achieve microglia-specific overexpression or knockdown of LCN2, allowing evaluation of its regulatory role in delirium.(4) LCN2 overexpression in BV2 cells was achieved via lentiviral transfection to investigate its effects on microglial activation.(5) A BV2–HT22 coculture system was established to further examine the impact of activated microglia on neuronal function.(6) Using the delirium mouse model, the effects of MN-08 on delirium-associated cognitive impairment were evaluated with NOR and Y-maze tests.(7) ChIP-qPCR and luciferase reporter assays were conducted to determine that MN-08 inhibits the binding of the transcription factor NF-κB1 to the LCN2 promoter.(8) Immunofluorescence staining, RT-qPCR, and Western blotting were performed to investigate the regulatory effects of MN-08 on the LCN2–MAPK signaling pathway and microglial activation. Results: Delirium mice exhibited significant cognitive impairment, which was accompanied by hippocampal microglial activation and increased levels of inflammatory mediators. Transcriptomic and functional analyses revealed that LCN2 expression in hippocampal microglia played a key role in regulating delirium-related cognitive function, further influencing neuronal synaptic activity. Overexpression or inhibition of microglial LCN2 confirmed its critical involvement in cognitive dysfunction. Importantly, treatment with MN-08 alleviated cognitive decline in delirium mice, while concurrently suppressing hippocampal microglial activation and reducing LCN2 expression. Mechanistically, MN-08 downregulated Lcn2 by inhibiting NF-κB1 binding to its promoter and modulated delirium-associated cognitive deficits through the LCN2–MAPK signaling pathway. Conclusion: This study reveals a novel pathway in which chronic stress upregulates Sema3A in GABAergic interneurons, promoting PNN formation around PV-INs. This leads to reduced inhibitory input and increased PV-IN excitability, ultimately facilitating depressive-like behaviors. The Sema3A–PNN–PV-IN axis represents a potential therapeutic target for stress-related mood disorders.

关键词

lipocalin-2 (LCN2) / microglia / delirium / MAPK / MN-08 / cognitive dysfunction