Mashiningan extract disturbs water absorption by decreasing aquaporin-3 expression in the colon.

Chronic constipation decreases quality of life; therefore, appropriate treatment measures are crucial. However, current treatments are insufficient to adequately control defecation, necessitating the identification of new strategies that are more effective and safer. We investigated the laxative action mechanism of the Kampo medicine Mashiningan (MNG) and discussed its usefulness in constipation. Rats were orally administered extracts of MNG or its herbal constituents, and defecation was analyzed. Expression levels of aquaporin-3 (AQP3) and inflammation-related genes in the colon were detected. The effects of the herbal medicines on inflammation were analyzed using macrophage-like RAW264.7 cells. Fecal water content significantly increased in rats treated with MNG. Expression of AQP3 protein in the colon of the MNG-treated group reduced to ∼20 % of that in the control group. Examining the effect of compound herbal medicines, only administration of Daio extract increased defecation and reduced colonic expression of AQP3. Treatment with MNG significantly increased the expression of interleukin (IL)-1β and IL-6 in the colon, although this increase was less than that in the group treated with Daio alone. Mashinin, Kyonin, and Kijitsu could significantly suppress the lipopolysaccharide (LPS)-induced increase in IL-1β and IL-6 in RAW264.7 cells. MNG exerted a laxative effect by decreasing AQP3 expression and disturbing water absorption in the colon. This effect was attributed to the herbal compound Daio. Furthermore, MNG contains Mashinin, Kyonin, and Kijitsu, which exert anti-inflammatory effects. Accordingly, MNG is a laxative with fewer side effects, such as abdominal pain.