Objective
To investigate the effects of Aurantii Fructus Immaturus (Zhishi, ZS) and Atractylodis Macrocephalae Rhizoma (Baizhu, BZ)-containing serum on glutamate-induced autophagy in rat colonic interstitial cells of Cajal (ICCs) and to analyze the underlying mechanism.

Methods
Rat colonic ICCs cultured in vitro were identified by fluorescence and then stimulated with glutamic acid (5 mmol/L) for 24 h to establish a cell model of autophagy. The cells were then treated with different concentrations of ZSBZ-containing serum or rat serum. The viability of the ICCs was detected with cell counting kit-8 assays, and cell apoptosis rates were examined with flow cytometry. The ultrastructure and autophagosomes in the ICCs were observed using transmission electron microscopy. The effects of ZSBZ-containing serum on apoptosis-associated mediators were assessed by Western blotting and real-time quantitative polymerase chain reaction. In addition, microtubule-associated protein light chain 3 (LC3), p-phosphoinositide 3-kinase (p-PI3K), p-Akt and p-mammalian target of rapamycin (p-mTOR) expression was detected via Western blotting analysis.

Results
Compared to those in the model group, ICC viability and apoptosis rates were significantly increased by ZSBZ-containing serum (P < 0.05). In addition, the expression levels of Beclin-1, LC3, p-PI3K, p-Akt and p-mTOR were significantly lower (P < 0.05) and Bcl-2 expression was higher in the ZSBZ-containing serum treatment groups than in the model group (P < 0.05).

Conclusion
Our findings demonstrated that ZSBZ protects glutamic acid-stimulated ICCs, and this beneficial effect may be mediated by a reduction in autophagy via inhibition of the PI3K/Akt/mTOR pathway.

Key words: Herbal medicine, Chinese, Autophagy, Phosphoinositide 3-kinase, Signal pathway