Identification of the Acid-Sensitive Site Critical for Chloral Hydrate (CH) Activation of the Proton-Activated Chloride Channel.

The transmembrane protein TMEM206 was recently identified as the molecular basis of the extracellular proton-activated Cl- channel (PAC), which plays an essential role in neuronal death in ischemia-reperfusion. The PAC channel is activated by extracellular acid, but the proton-sensitive mechanism remains unclear, although different acid-sensitive pockets have been suggested based on the cryo-EM structure of the human PAC (hPAC) channel. In the present study, we firstly identified two acidic amino acid residues that removed the pH-dependent activation of the hPAC channel by neutralization all the conservative negative charged residues located in the extracellular domain of the hPAC channel and some positively charged residues at the hotspot combined with two-electrode voltage-clamp (TEVC) recording in the Xenopus oocytes system. Double-mutant cycle analysis and double cysteine mutant of these two residues proved that these two residues cooperatively form a proton-sensitive site. In addition, we found that chloral hydrate activates the hPAC channel depending on the normal pH sensitivity of the hPAC channel. Furthermore, the PAC channel knock-out (KO) male mice (C57BL/6J) resist chloral hydrate-induced sedation and hypnosis. Our study provides a molecular basis for understanding the proton-dependent activation mechanism of the hPAC channel and a novel drug target of chloral hydrate.SIGNIFICANCE STATEMENT Proton-activated Cl- channel (PAC) channels are widely distributed in the nervous system and play a vital pathophysiological role in ischemia and endosomal acidification. The main discovery of this paper is that we identified the proton activation mechanism of the human proton-activated chloride channel (hPAC). Intriguingly, we also found that anesthetic chloral hydrate can activate the hPAC channel in a pH-dependent manner. We found that the chloral hydrate activates the hPAC channel and needs the integrity of the pH-sensitive site. In addition, the PAC channel knock-out (KO) mice are resistant to chloral hydrate-induced anesthesia. The study on PAC channels' pH activation mechanism enables us to better understand PAC's biophysical mechanism and provides a novel target of chloral hydrate.

The effect of obstructive jaundice on the sensitivity of intravenous anesthetic of remimazolam: study protocol for a controlled multicenter trial.

BACKGROUND: It is well known that obstructive jaundice could affect the pharmacodynamics of some anesthetics, and the sensitivity of some anesthetics would increase among icteric patients. Remimazolam is a new ultra-short-acting intravenous benzodiazepine sedative/anesthetic, which is a high-selective and affinity ligand for the benzodiazepine site on the GABAA receptor. However, no study has reported the pharmacodynamics of remimazolam in patients with obstructive jaundice. We hypothesize that obstructive jaundice affects the pharmacodynamics of remimazolam, and the sensitivity of remimazolam increases among icteric patients. METHODS/DESIGN: The study will be performed as a prospective, controlled, multicenter trial. The study design is a comparison of remimazolam requirements to reach a bispectral index of 50 in patients with obstructive jaundice versus non-jaundiced patients with chronic cholecystitisor intrahepatic bile duct stones. Remimazolam was infused at 6 mg/kg/h until this endpoint was reached. DISCUSSION: Remimazolam could be suitable for anesthesia of patients with obstructive jaundice, because remimazolam is not biotransformed in the liver. Hyperbilirubinemia has been well-described to have toxic effects on the brain, which causes the increasing of sensitivity to some anesthetics, such as desflurane, isoflurane, and etomidate. Furthermore, remimazolam and etomidate have the same mechanism of action when exerting an anesthetic effect. We aim to demonstrate that obstructive jaundice affects the pharmacodynamics of remimazolam, and the dose of remimazolam when administered to patients with obstructive jaundice should be modified. TRIAL REGISTRATION: Chinese Clinical Trial Registry ChiCTR2100043585 . Registered on 23 February 2021.

C/EBPα Regulates FOXC1 to Modulate Tumor Growth by Interacting with PPARγ in Hepatocellular Carcinoma.

BACKGROUND: Forkhead box C1 (FOXC1) is an important cancer-associated gene in tumor. PPAR-γ and C/EBPα are both transcriptional regulators involved in tumor development. OBJECTIVE: We aimed to clarify the function of PPAR-γ, C/EBPα in hepatocellular carcinoma (HCC) and the relationship of PPAR-γ, C/EBPα and FOXC1 in HCC. METHODS: Western blotting, immunofluorescent staining, and immunohistochemistry were used to evaluate protein expression. qRT-PCR was used to assess mRNA expression. Co-IP was performed to detect the protein interaction. And ChIP and fluorescent reporter detection were used to determine the binding between protein and FOXC1 promoter. RESULTS: C/EBPα could bind to FOXC1 promoter and PPAR-γ could strengthen C/EBPα's function. Expressions of C/EBPα and PPAR-γ were both negatively related to FOXC1 in human HCC tissue. Confocal displayed that C/EBPα was co-located with FOXC1 in HepG2 cells. C/EBPα could bind to FOXC1 promoter by ChIP. Luciferase activity detection exhibited that C/EBPα could inhibit FOXC1 promoter activity, especially FOXC1 promoter from -600 to -300 was the critical binding site. Only PPAR-γ could not influence luciferase activity but strengthen inhibited effect of C/EBPα. Further, the Co-IP displayed that PPAR-γ could bind to C/EBPα. When C/EBPα and PPAR-γ were both high expressed, cell proliferation, migration, invasion, and colony information were inhibited enormously. C/EBPα plasmid combined with or without PPAR-γ agonist MDG548 treatment exhibited a strong tumor inhibition and FOXC1 suppression in mice. CONCLUSION: Our data establish C/EBPα targeting FOXC1 as a potential determinant in the HCC, which supplies a new pathway to treat HCC. However, PPAR-γ has no effect on FOXC1 expression.

[Changes of brain oxidative stress induced by nano-alumina in ICR mice].

OBJECTIVE: To investigate the brain oxidative stress injury induced by nano-alumina particles in ICR mice. METHODS: Sixty male ICR mice were randomly divided into 6 groups: control group, solvent control group, 100 mg/kg micro-alumina particles group, 3 groups exposed to nano-alumina particles at the doses of 50, 100 and 200 mg/kg. The mice were exposed by nasal drip for 30 days. Then levels of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-PX) in brain tissues of mice were detected. RESULTS: There was no difference of SOD activity in mouse brain between control group [(17.32 +/- 6.23)U/gHb] and 50 mg/kg nano-alumina particles group [(17.89 +/- 1.82) U/gHb]. The SOD activity [(4.93 +/- 2.30)U/gHb] in 200 mg/kg nano-alumina particles group was significantly lower than that in control group (P < 0.05). The MDA levels in 3 nano-alumina particles groups were (0.76 +/- 0.13), (1.00 +/- 0.30) and (1.16 +/- 0.39)nmol/ml, respectively, which were significantly higher than that [( 0.24 +/- 0.09)nmol/ml] in control group (P < 0.05). The GSH levels in 3 nano-alumina particles groups were (0.72 +/- 0.08), (0.55 +/- 0.19) and (0.61 +/- 0.20)mg/gpro, respectively, which were significantly lower than that [(1.55 +/- 0.34)mg/gpro]] in control group (P < 0.05). The CAT activity in 50 and 100 mg/kg nano-alumina particles groups were (10.40 +/- 3.84) and (10.40 +/- 2.00)U/mgpro, respectively, which were significantly higher than that [(5.79 +/- 0.96) U/mgpro] in control group (P < 0.05). The CAT activity [(3.25 +/- 1.04)U/mgpro] in 200 mg/kg nano-alumina particles group was significantly lower than that in control group (P < 0.05 ). CONCLUSION: Nano-alumina particles can induce the oxidative stress damage in brain tissues of mice.