Kamishoyosan and Kamikihito protect against decreased KCC2 expression induced by the P. gingivalis lipopolysaccharide treatment in PC-12 cells and improve behavioral abnormalities in male mice

Kamishoyosan (KSS) and Kamikihito (KKT) have been traditionally prescribed for neuropsychiatric symptoms in Japan. However, the molecular mechanism of its effect is not elucidated enough. On the other hand, it has been reported that lipopolysaccharide derived from Porphyromonas gingivalis (P. g LPS) is involved not only in periodontal disease but also in the systemic diseases such as psychiatric disorders via neuroinflammation. Here, we investigated the molecular mechanism of KSS and KKT treatment by LPS-induced neuropathy using PC-12 cells. When P. g LPS was administrated during the NGF treatment, the KCC2 expression was decreased in PC-12 cells. P. g LPS treatment also decreased the WNK and phospho SPAK (pSPAK) expression and enhanced GSK-3β expression that negatively regulates WNK-SPAK signaling. Moreover, when KSS or KKT was administrated before P. g LPS treatment, the decrease of KCC2, WNK and pSPAK was rescued. KSS and KKT treatment also rescued the enhancement of GSK3β expression by P. g LPS treatment. Furthermore, KSS, KKT and/or oxytocin could rescue behavioral abnormalities caused by P. g LPS treatment by animal experiments. These effects were not shown in the Goreisan treatment, which has been reported to act on the central nervous system. These results indicate that KSS and KKT are candidates for therapeutic agents for neural dysfunction.