Neochamaejasmin A inhibits KV1.4 channel activity via direct binding to the pore.

Stellera chamaejasme L. (Thymelaeaceae) is a toxic perennial herb and widespread in Mongolia and the northern parts of China. Previous studies have revealed that Neochamaejasmin A (NCA), one of the main active ingredients in the plant roots, has many bioactivities such as inhibiting the P-gp-mediated efflux. But whether NCA affects ion channels is unknown. Here the whole cell patch clamp technique was used to investigate whether NCA affects ion channels, especially how it inhibits KV1.4. Mutagenesis and structure-based molecular simulation were used for analysis of inhibition mechanism and identification of binding site. Among all the channels assayed, KV1.4 stood out as the one on which NCA showed strongest inhibition activity with IC50 of 7.55 µM. Compared with NCA's isomerides, neochamaejasmin B (NCB) and chamaechromone (CMC), NCA also exhibited superior inhibition ability on KV1.4. Three mutations, V549A, A553V and V560A, occurred inside the pore, were found to significantly alleviate the NCA blocking effects, suggesting that they are the important binding sites of NCA. Structure-based modelling showed that the phenolic hydroxyl group of NCA can form hydrogen bonds with main chains of Val549 and Ala553 in IS6 and IVS6 segment respectively, which support our in vitro results. In conclusion, data suggest that NCA might inhibit KV1.4 channels via direct binding to the pore domain.

Peimine, a main active ingredient of Fritillaria, exhibits anti-inflammatory and pain suppression properties at the cellular level.

Fritillaria is one of the most important herbs in Chinese traditional medicine and represents an annual ï¿¥700 million industry. It is often used as an anti-inflammatory, pain relieving and antitussive medicine. However, the mechanisms of these effects are still unclear. Peimine is one of active ingredients of Fritillaria. Using the patch-clamp technique, we profiled the action of Peimine against selected ion channels stably expressed in HEK 293 cell lines. Our data indicated that Peimine was not only able to block the Nav1.7 ion channel but also preferably inhibited the Kv1.3 ion channel. Thus, the study suggested potential mechanisms of Fritillaria as a pain relieving and anti-inflammatory herb.