Ameliorative effects of Kir4.1 channel inhibitors on lipopolysaccharide-induced cognitive impairment via BDNF/TrkB signaling pathway

Inwardly rectifying potassium 4.1 (Kir4.1) channels are predominantly expressed in astrocytes and considered to be involved in the pathogenesis of brain diseases, including depression and epilepsy. In the present study, we evaluated the effects of Kir4.1 channel inhibitors, VU0134992 and quinacrine, on lipopolysaccharide (LPS)-induced cognitive impairment to clarify the role of Kir4.1 channels in controlling cognitive functions. Male BALB/c mice were treated with LPS, with or without Kir4.1 channel inhibitors, for 7 days. Animals were then subjected to novel object recognition (NOR) and rota-rod tests. Immunohistochemical analyses of glia fibrillary acid protein (GFAP) and neuronal nuclei (NeuN) were also performed. Treatment of LPS clearly showed cognitive impairment in the NOR test, which accompanied elevated GFAP- and reduced NeuN-immunoreactivity in hippocampal CA1 and CA3 regions. VU0134992 and quinacrine significantly ameliorated LPS-induced cognitive impairment without affecting rota-rod performance. In addition, both Kir4.1 channel inhibitors suppressed LPS-induced astrocyte activation and attenuated neuronal damage in CA1 and CA3 regions. Furthermore, combined treatments of ANA-12, a TrkB receptor antagonist, with VU0134992 suppressed the ameliorative effects of VU0134992 on cognitive impairment and hippocampal neuronal damage. These results suggest that blockade of astrocytic Kir4.1 channels ameliorates neuroinflammatory cognitive impairment via BDNF/TrkB signaling pathway.