Long term Coptidis Rhizoma intake induce gastrointestinal emptying inhibition and colon barrier weaken via bitter taste receptors activation in mice

•Long term Coptidis Rhizoma intake induce gastrointestinal emptying inhibition and colon barrier weaken.•Rhizoma alkaloids are agonists for bitter taste receptors.•Coptidis Rhizoma induce gastrointestinal emptying inhibition via promoting α-gustducin binding to CHRM3 caused by activating bitter taste receptors•Coptidis Rhizoma weaken colon barrier via up-regulating PKCβ/RhoA/ROCK1/MLC-2 caused by bitter taste receptors activation. Coptidis Rhizoma, a classic bitter traditional Chinese medicine, can lead to digestive dysfunction when long-term use according to traditional experience. Bitter taste receptors have been found to regulate gastrointestinal smooth muscle contraction. Coptidis Rhizoma alkaloids are potential agonists for bitter taste receptors, but whether they can induce gastrointestinal dysfunction via bitter taste receptors is not clear. The purpose of this study is to elucidate whether long-term Coptidis Rhizoma decoction/berberine intake can affect gastrointestinal function via bitter taste receptors. Firstly, mice were orally administered Coptidis Rhizoma decoction (or berberine) for 8 weeks, then their appetite, gastrointestinal emptying function, colon barrier function, and gut microbiota homeostasis were evaluated. Subsequently, isolated intestine, molecular docking, calcium release, and immunofluorescence co-localization experiments were applied to explore the mechanism of Coptidis Rhizoma decoction (or berberine) inhibition effects on gastrointestinal motility. Finally, transmembrane resistance, scratch assay, tight junction and cytoskeletal protein immunofluorescence staining were conducted to verify that the bitter taste receptor is the target for Coptidis Rhizoma decoction (or berberine) to damage the colon barrier function. Long-term Coptidis Rhizoma decoction (or berberine) intake can reduce appetite, inhibit gastrointestinal contractions, disrupt bacterial balance and colon barrier function in mice. Further mechanistic studies have shown that the alkaloids of Coptidis Rhizoma are agonists for bitter taste receptors, which can promote α-gustducin binding to CHRM3 by activating bitter taste receptors, finally inhibiting gastrointestinal smooth muscle contraction. In addition, Coptidis Rhizoma decoction (or berberine) can activate bitter taste receptors and its downstream pathways PKCβ/RhoA/ROCK1/MLC-2, reshape skeletal proteins, downregulate tight junction protein expression, and ultimately disrupt colon barrier function. Long term C