The activation of GABAergic neurons in the hypothalamic tuberomammillary nucleus attenuates sevoflurane and propofol-induced anesthesia in mice

Background: The histaminergic neurons in the hypothalamic tuberomammillary nucleus (TMN) have been suggested to play a vital role in maintaining a rising state. But the neuronal types of the TMN are in debate and the role of GABAergic neurons remains unclear. Methods: In the present study, we examined the role of TMN GABAergic neurons in general anesthesia using chemogenetics and optogenetics strategies to regulate the activity of TMN GABAergic neurons. Results: The results indicated that either chemogenetic or optogenetic activation of TMN GABAergic neurons in mice decreased the effect of sevoflurane and propofol anesthesia. In contrast, inhibition of the TMN GABAergic neurons facilitates the sevoflurane anesthesia effect. Conclusion: Our results suggest that the activity of TMN GABAergic neurons produces an anti-anesthesia effect in loss of consciousness and analgesia.

Identification of Sodium- and Chloride-Sensitive Sites in the Slack Channel

The Slack channel (KCNT1, Slo2.2) is a sodium-activated and chloride-activated potassium channel that regulates heart rate and maintains the normal excitability of the nervous system. Despite intense interest in the sodium gating mechanism, a comprehensive investigation to identify the sodium-sensitive and chloride-sensitive sites has been missing. In the present study, we identified two potential sodium-binding sites in the C-terminal domain of the rat Slack channel by conducting electrophysical recordings and systematic mutagenesis of cytosolic acidic residues in the rat Slack channel C terminus. In particular, by taking advantage of the M335A mutant, which results in the opening of the Slack channel in the absence of cytosolic sodium, we found that among the 92 screened negatively charged amino acids, E373 mutants could completely remove sodium sensitivity of the Slack channel. In contrast, several other mutants showed dramatic decreases in sodium sensitivity but did not abolish it altogether. Furthermore, molecular dynamics (MD) simulations performed at the hundreds of nanoseconds timescale revealed one or two sodium ions at the E373 position or an acidic pocket composed of several negatively charged residues. Moreover, the MD simulations predicted possible chloride interaction sites. By screening predicted positively charged residues, we identified R379 as a chloride interaction site. Thus, we conclude that the E373 site and the D863/E865 pocket are two potential sodium-sensitive sites, while R379 is a chloride interaction site in the Slack channel.SIGNIFICANCE STATEMENT The research presented here identified two distinct sodium and one chloride interaction sites located in the intracellular C-terminal domain of the Slack (Slo2.2, KCNT1) channel. Identification of the sites responsible for the sodium and chloride activation of the Slack channel sets its gating property apart from other potassium channels in the BK channel family. This finding sets the stage for future functional and pharmacological studies of this channel.

Two types of peptides derived from the neurotoxin GsMTx4 inhibit a mechanosensitive potassium channel by modifying the mechano-gate

Atrial fibrillation is the most common sustained cardiac arrhythmia in humans. Current atrial fibrillation antiarrhythmic drugs have limited efficacy and carry the risk of ventricular proarrhythmia. GsMTx4, a mechanosensitive channel–selective inhibitor, has been shown to suppress arrhythmias through the inhibition of stretch-activated channels (SACs) in the heart. The cost of synthesizing this peptide is a major obstacle to clinical use. Here, we studied two types of short peptides derived from GsMTx4 for their effects on a stretch-activated big potassium channel (SAKcaC) from the heart. Type I, a 17-residue peptide (referred to as Pept 01), showed comparable efficacy, whereas type II (i.e., Pept 02), a 10-residue peptide, exerted even more potent inhibitory efficacy on SAKcaC compared with GsMTx4. We identified through mutagenesis important sequences required for peptide functions. In addition, molecular dynamics simulations revealed common structural features with a hydrophobic head followed by a positively charged protrusion that may be involved in peptide channel–lipid interactions. Furthermore, we suggest that these short peptides may inhibit SAKcaC through a specific modification to the mechanogate, as the inhibitory effects for both types of peptides were mostly abolished when tested with a mechano-insensitive channel variant (STREX-del) and a nonmechanosensitive big potassium (mouse Slo1) channel. These findings may offer an opportunity for the development of a new class of drugs in the treatment of cardiac arrhythmia generated by excitatory SACs in the heart.

The Slack Channel Deletion Causes Mechanical Pain Hypersensitivity in Mice

The role of the Slack (also known as Slo2.2, KNa1.1, or KCNT1) channel in pain-sensing is still in debate on which kind of pain it regulates. In the present study, we found that the Slack–/– mice exhibited decreased mechanical pain threshold but normal heat and cold pain sensitivity. Subsequently, X-gal staining, in situ hybridization, and immunofluorescence staining revealed high expression of the Slack channel in Isolectin B4 positive (IB4+) neurons in the dorsal root ganglion (DRG) and somatostatin-positive (SOM+) neurons in the spinal cord. Patch-clamp recordings indicated the firing frequency was increased in both small neurons in DRG and spinal SOM+ neurons in the Slack–/– mice whereas no obvious slow afterhyperpolarization was observed in both WT mice and Slack–/– mice. Furthermore, we found Kcnt1 gene expression in spinal SOM+ neurons in Slack–/– mice partially relieved the mechanical pain hypersensitivity of Slack–/– mice and decreased AP firing rates of the spinal SOM+ neurons. Finally, deletion of the Slack channel in spinal SOM+ neurons is sufficient to result in mechanical pain hypersensitivity in mice. In summary, our results suggest the important role of the Slack channel in the regulation of mechanical pain-sensing both in small neurons in DRG and SOM+ neurons in the spinal dorsal horn.

[Cell heterogeneity of laryngeal carcinoma and evolution trajectory of epithelial cells]

Objective: To analyze the classification and functions of cell subsets in laryngeal carcinoma and metastatic lymph nodes, and to explore the evolution trajectory of epithelial cells to tumor cells. Methods: Single-cell RNA sequencing was performed on 5 cases of laryngeal cancer, matched metastatic lymph nodes and 3 normal tissues. Patients were admitted to Ningbo Medical Center Lihuili Hospital from October 22, 2019 to December 16, all patients were male, aged 53-70 years old. Cell subsets of the above-mentioned tissues were analyzed by the Seurat, and the biological functions of cell subpopulation were investigated by functional enrichment analysis. Malignant epithelial cells were identified using copy number variation (CNV). The evolutionary trajectory of epithelial cells to cancer cells was analyzed by cell trajectory analysis, and cancerous transitional cells were identified. The highly expressed genes in transitional cells were analyzed by the FindAllMarker of the Seurat and verified by immunohistochemistry. Results: A total of 66 969 high-quality cells were obtained in 9 major clusters: epithelial cells, T cells, B cells, fibroblasts, endothelial cells, myeloid cells, mast cells, plasmacytoid dendritic cells and nerve cells. The first 5 cell clusters were divided into 8, 6, 4, 3 and 2 subgroups, respectively. Four epithelial cell subsets (C0, C1, C2 and C5) were derived from tumor tissues and metastatic lymph nodes, and had high levels of CNV and tumor cell content. Cell trajectory analysis showed that the evolution trajectory of epithelial cells was from normal epithelial subpopulation C4 to early cancerous cell population C0, which differentiated into three major malignant cell subsets C1, C3, and C5. Epithelial cell C0 may represent the transitional cell population of carcinogenesis, and were enriched in biological processes such as epithelial-mesenchymal transformation and angiogenesis. C0 highly expressed sulforaphane (SFN) which may be related to the occurrence and development of cancer. Immunohistochemistry confirmed that SFN was highly expressed in tumor tissues and metastatic lymph nodes compared with paracancerous tissues. Conclusion: Single-cell sequencing may be used to elucidate the diversity of cells and functions in laryngeal carcinoma tissues and metastatic lymph nodes, and cell population C0 plays a key role in the evolution of cells.

The neuropeptide GsMTx4 inhibits a mechanosensitive BK channel through the voltage-dependent modification specific to mechano-gating

The cardiac mechanosensitive BK (Slo1) channels are gated by Ca²⁺, voltage, and membrane stretch. The neuropeptide GsMTx4 is a selective inhibitor of mechanosensitive (MS) channels. It has been reported to suppress stretch-induced cardiac fibrillation in the heart, but the mechanism underlying the specificity and even the targeting channel(s) in the heart remain elusive. Here, we report that GsMTx4 inhibits a stretch-activated BK channel (SAKcaC) in the heart through a modulation specific to mechano-gating. We show that membrane stretching increases while GsMTx4 decreases the open probability (P _o) of SAKcaC. These effects were mostly abolished by the deletion of the STREX axis-regulated (STREX) exon located between RCK1 and RCK2 domains in BK channels. Single-channel kinetics analysis revealed that membrane stretch activates SAKcaC by prolonging the open-time duration (τ_O) and shortening the closed-time constant (τ_C). In contrast, GsMTx4 reversed the effects of membrane stretch, suggesting that GsMTx4 inhibits SAKcaC activity by interfering with mechano-gating of the channel. Moreover, GsMTx4 exerted stronger efficacy on SAKcaC under membrane-hyperpolarized/resting conditions. Molecular dynamics simulation study revealed that GsMTx4 appeared to have the ability to penetrate deeply within the bilayer, thus generating strong membrane deformation under the hyperpolarizing/resting conditions. Immunostaining results indicate that BK variants containing STREX are also expressed in mouse ventricular cardiomyocytes. Our results provide common mechanisms of peptide actions on MS channels and may give clues to therapeutic suppression of cardiac arrhythmias caused by excitatory currents through MS channels under hyper-mechanical stress in the heart.

Up-regulation of antioxidative proteins TRX1, TXNL1 and TXNRD1 in the cortex of PTZ kindling seizure model mice

Oxidative stress has been considered as one of pathogenesis of brain damage led by epilepsy. Reducing oxidative stress can ameliorate brain damage during seizures. However, expression levels of important antioxidative enzymes such as thioredoxin-1 (TRX1), thioredoxin-like 1 protein (TXNL1) and thioredoxin reductase 1 (TXNRD1) during seizures have not been investigated. In this study, we examined protein and mRNA expression levels of TRX1, TXNL1 and TXNRD1 in different brain regions in PTZ induced seizure model mice. We found that protein expression levels of TRX1, TXNL1 and TXNRD1 are simultaneously up-regulated by 2- or 3-fold in the cortex of both acute and chronic seizure model mice. But there is no unified expression pattern change of these enzymes in the hippocampus, cerebellum and diencephalon in the seizure model mice. Less extent up-regulation of mRNA expression of these enzymes were also observed in the cortex of seizure mice. These data suggest that antioxidative enzymes may provide a protective effect against oxidative stress in the cortex during seizures.

[Severe side effects of the treatment of acute promyelocytic leukemia with all-trans retinoic acid]

Sixty-three cases with acute promyelocytic leukemia (APL) were treated with all-trans retinoic acid (ATRA). The rates of hyperleukocytosis, intracranial hypertension, retinoic acid syndrome were 57.1%, 9.5%, and 3.2% respectively. Mortality of the treatment was 11.1%. Under ATRA treatment, hyperleukocytosis leading to leukostasis was the cause of death in patients with APL. We therefore suggest that the patients with such leukocyte levels (that is, 5.0 x 10(9).L-1 on the 6th day, 10.0 x 10(9).L-1 on the 10th day, 15.0 x 10(9).L-1 on the 15th day) can be used as guidelines for starting chemotherapy(homoharringtonine); before ATRA treatment, while leukocyte counts are > 10 x 10(9).L-1, the patients only receive homoharringtonine; when leukocyte counts are < or = 5.0 x 10(9).L-1, the patients receive a combination of homoharringtonine and ATRA. Retinoic acid syndrome is a distinctive complication of ATRA therapy in the patients with APL. While the syndrome occurs, the treatment of ATRA must be stopped and corticosteroids must be used.

Effect of homoharringtonine on proliferation and differentiation of human leukemic cells in vitro

Homoharringtonine (HHT) is a cephalotaxine ester derived from an evergreen tree of southern China. We studied the effect of HHT on the clonal proliferation and differentiation of human leukemic cells from cell lines and patients. Dose-response studies found that HHT inhibited colony formation of myeloid cell lines (50% inhibitory dose range, 7 to 12 ng/ml), lymphocytic cell lines (50% inhibitory dose range, 4 to 7 ng/ml), and fresh leukemic cells (50% inhibitory dose range, 2 to 25 ng/ml). Pulse-exposure studies showed that colony formation of HL-60 cells was inhibited 50% by HHT (10 to 20 ng/ml) at 45 h and completely inhibited at 72 h. Radioactive precursor studies using HL-60 cells showed that HHT predominantly inhibited protein synthesis as compared with RNA and DNA synthesis. Taking advantage of this, we have found that the combination of HHT with 1-beta-D-arabinofuranosylcytosine (inhibitor of DNA synthesis) was synergistic in the inhibition of HL-60 clonal growth. HHT (2 to 20 ng/ml) also was found to induce up to 28% of HL-60 cells to differentiate toward macrophage-like cells.