Huqi San-Evoked Rat Colonic Anion Secretion through Increasing CFTR Expression

Antitumor Efficacy of Huqizhengxiao (HQZX) Decoction Based on Inhibition of Telomerase Activity in Nude Mice of Hepatocarcinoma Xenograft

Objective: Huqizhengxiao (HQZX) decoction is a mixture of traditional Chinese medicines comprising 10 herbs, with inhibitory effects on hepatocarcinoma. The aim of the study is to observe the antitumor efficacy and mechanism of HQZX decoction in nude mice with hepatocellular carcinoma xenografts. Methods: HepG2-luc subcutaneous hepatocarcinoma was established in nude mice. The mice were divided into 5 groups: control, cinobufagin, HQZXS, HQZXM, and HQZXH with doses 13.52, 27.03, and 54.06 g/kg, respectively. HQZX decoction was prepared for intraperitoneal intragastric administration for 3 weeks. Tumor growth was measured with Vernier calipers and in vivo imaging system. α-Fetoprotein (AFP) was determined by radioimmunoassay. Tumor necrosis factor–α (TNF-α) was measured with enzyme-linked immunosorbent assay (ELISA) assay. Telomerase activity was measured with polymerase chain reaction–ELISA. Nuclear mitosis and necrosis were observed with hematoxylin-eosin stain. Apoptotic proteins of caspase-3, Bcl-2, and Bax were examined by Western blot. Signaling molecules of ERK, mTOR, and STAT3 were measured with Luminex assay. Results: HQZX decoction showed good inhibition of HepG2-luc xenografts. Compared with control group, the relative tumor proliferation rate was less than 60% in the HQZXH and HQZXS. The tumor inhibition rate of HQZXH group reached 52% ± 15%. Relative average optical density values of the HQZXS and HQZXH groups decreased significantly. The mitotic index in HQZXS, HQZXM, and HQZXH groups decreased greatly. Telomerase activity of HQZXS was clearly reduced, and, the caspase-3 expression upregulated in HQZXH group. Bcl-2 expression was downregulated in HQZXS and HQZXH. The ratios of p-ERK/ERK and p-STAT3/STAT3 in HQZXS group were significantly downregulated. Conclusion: HQZX decoction can clearly inhibit the growth of hepatocellular carcinoma and induce tumor apoptosis. Its antitumor mechanism may be related to reducing telomerase activity and regulating the STAT3 and ERK signal pathway.

Mechanistic insight into the heme-independent interplay between iron and carbon monoxide in CFTR and Slo1 BKCa channels

Ion channels have been extensively reported as effectors of carbon monoxide (CO). However, the mechanisms of heme-independent CO action are still not known. Because most ion channels are heterologously expressed on human embryonic kidney cells that are cultured in Fe³⁺-containing media, CO may act as a small and strong iron chelator to disrupt a putative iron bridge in ion channels and thus to tune their activity. In this review CFTR and Slo1 BK_Ca channels are employed to discuss the possible heme-independent interplay between iron and CO. Our recent studies demonstrated a high-affinity Fe³⁺ site at the interface between the regulatory domain and intracellular loop 3 of CFTR. Because the binding of Fe³⁺ to CFTR prevents channel opening, the stimulatory effect of CO on the Cl^- and HCO₃^- currents across the apical membrane of rat distal colon may be due to the release of inhibitive Fe³⁺ by CO. In contrast, CO repeatedly stimulates the human Slo1 BK_Ca channel opening, possibly by binding to an unknown iron site, because cyanide prohibits this heme-independent CO stimulation. Here, in silico research on recent structural data of the slo1 BK_Ca channels indicates two putative binuclear Fe²⁺-binding motifs in the gating ring in which CO may compete with protein residues to bind to either Fe²⁺ bowl to disrupt the Fe²⁺ bridge but not to release Fe²⁺ from the channel. Thus, these two new regulation models of CO, with iron releasing from and retaining in the ion channel, may have significant and extensive implications for other metalloproteins.