AB4 ameliorates DSS-induced colitis symptoms
In order to seek the Pulsatilla saponins with anti-inflammatory
activities in vitro, we screened a series of saponins AB4,
Anemoside A3 (AA3), and 23-hydroxy botulinic acid (23-HA) (Fig. 1A) and
tested their inhibitory activity against IL-1β in
LPS-challenged
differentiated THP-1 cells. Interestingly, AB4 showed the highest
inhibitory activity against IL-1β (Fig. 1B and C). In parallel, the cell
viability assay showed that AB4 was not cytotoxic at concentrations
below 200μM (Supporting Information Fig. S1A-C). Therefore, we
hypothesized that AB4 might be the main component of BTWT against
colitis.
DSS-induced colitis is known to be a widely accepted model with clinical
symptoms similar to human UC, including diarrhea, rectal bleeding and
weight loss (Chassaing, Aitken, Malleshappa, & Vijay-Kumar, 2014;
Clapper, Cooper, & Chang, 2007). To evaluate the effect of AB4 on
colitis in mice, C57BL/6 (wild-type; WT) mice were challenged with 3.0%
DSS for 7 days and then administered with AB4 (5 mg/kg) daily for 7 days
or 14 days, as well as the 5-ASA (200 mg/kg) being the positive control
(Supporting
Information Fig. S2A). AB4 markedly decreased the disease activity
indices characterized by diarrhea, bleeding, and weight loss compared to
the DSS group (Fig.
S2B
and S2C). Decreased disease severity was also accompanied by a reduction
of colon shortening, which was
ameliorated
by both AB4 treatment and pretreatment. There was no significant
difference between AB4 (5mg/kg) alone group and the normal group (Fig.
S2D). Notably, we found that the AB4 pretreatment group was more
effective than the AB4 treatment
group
and the 5-ASA group (Fig. S2B-D). Therefore, we continued to investigate
the effect of AB4 pretreatment on DSS-induced colitis in mice. We found
AB4 (5, 10, and 15 mg/kg) markedly decreased the disease activity
indices characterized by body weight loss, diarrhea, and bleeding in a
dose-dependent manner compared with the DSS group
(Fig.
1D and E).
Colonic
shortening (Fig. 1F), and
splenomegaly
(Fig. 1G) caused by the DSS challenge were also improved at the given
doses. There was no significant difference between AB4 (15mg/kg) alone
group and the normal group. At the same time, the survival experiment
showed that AB4 improved the survival rate of mice compared with the DSS
group (Fig. 1H). These data suggested that AB4 successfully ameliorated
DSS-induced colitis in mice.