(2) The treatment with L. reuteri NK33 can activate microglial cell infiltration into the hippocampus and induce hippocampal brain-derived neurotrophic factor (BDNF) expression and cAMP-response element binding protein (CREB) phosphorylation in IS-exposed mice as well as LPS-stimulated SH-SY5Y cells by suppressing the activation of the NF-κB pathway and HPA axis, thus suggesting that NK33 alleviated the suppression of NF-κB-mediated BDNF expression in the hippocampus, with the regulation of LPS infiltration into the brain, leading to the attenuation of anxiety and depression. Here, NFKB1 is linked to depressive symptom measurement.