Subclinical infection combined with surgery induced cognitive dysfunction: a novel adult mouse model for perioperative neurocognitive disorder

Introduction: Perioperative neurocognitive disorder (PND) describes a range of cognitive impairments associated with surgery and anaesthesia, often driven by neuroinflammation. This study explored a novel adult mouse model, in which preoperative subclinical infection, induced by low-dose lipopolysaccharide (LPS) in combination with surgery, led to cognitive dysfunction in adult mice. Methods: Adult male C57BL/6J mice were treated with 0.75 mg/kg LPS two hours before undergoing tibial fracture fixation or appendicectomy. Spontaneous activity and anxiety-like behaviours were tested by open field test. Cognitive outcomes were evaluated using the novel object recognition test and morris water maze. Inflammatory markers and synaptic proteins in the hippocampus were analysed through ELISA, RT-qPCR, and Western blot, while proteomics provided deeper insights into molecular changes. Results: We found that preoperative LPS sensitised the immune system, leading to heightened neuroinflammation and microglial activation after surgery. This was accompanied by memory and learning impairments. Key synaptic proteins, including PSD-95, GAP-43, SYN and mature BDNF, were significantly reduced, indicating disrupted synaptic function. Proteomics revealed changes in pathways related to immune responses, synaptic organisation, and energy metabolism, providing a potential molecular basis for these cognitive deficits. Discussion: This study provided a practical adult mouse model for PND, demonstrating that low-dose LPS followed by surgery induced an inflammatory response, leading to postoperative impairments in learning and memory.