Heat-Killed Lactococcus Lactis KC24 Ameliorates Scopolamine-Induced Memory Impairment in ICR Mice

Heat-killed Lactococcus lactis KC24 (H-KC24) has been examined for its neuroprotective effects in SH-SY5Y cells. We hypothesized that H-KC24 could alleviate memory impairment through the gut-brain axis. Scopolamine (1 mg/kg/day) was administered to ICR mice to induce memory impairment. Low- and high-dose H-KC24 cells (1 × 10⁹ and 2 × 10⁹ CFU/day, respectively) or donepezil (DO, 2 mg/kg) were administered for 14 days. H-KC24 treatment alleviated the deleterious scopolamine-induced memory effects on the recognition index and object recognition ability in the novel object recognition test and the Y-maze test. Changes in neurotransmitters and synaptic plasticity were confirmed by measuring acetylcholine, acetylcholinesterase, choline acetyltransferase, brain-derived neurotrophic factor, cyclic AMP response element-binding protein, and phosphorylated cyclic AMP response element-binding protein expression in brain tissues. In the H-KC24 and DO groups, β-secretase levels increased, whereas amyloid β levels decreased, demonstrating that H-KC24 can improve memory impairment caused by oxidative stress. This study demonstrated the positive effects of H-KC24 in a scopolamine-induced memory impairment mouse model.