Ammonium Increases TRPC1 Expression Via Cav-1/PTEN/AKT/GSK3β Pathway

Ketamine modulates neural stem cell differentiation by regulating TRPC3 expression through the GSK3β/β-catenin pathway

Ketamine, a popular anesthetic, is often abused by people for its hallucinogenic effect. Thus, the safety of ketamine in pediatric populations has been called into question for potential neurotoxic effects. However, ketamine also has neuroprotective effects in many brain injury models. The differentiation of neural stem cells (NSCs) was influenced significantly by ketamine, but the molecular mechanism is still unclear. NSCs were extracted from the hippocampi of postnatal day 1 rats and treated with ketamine to induce NSCs differentiation. Our results found that ketamine promoted neuronal differentiation of NSCs dose-dependently in a small dose range (P < 0.001). The main types of neurons from NSCs were cholinergic (51 ± 4 %; 95 % CI: 41-61 %) and glutamatergic neurons (34 ± 3 %; 95 % CI: 27-42 %). Furthermore, we performed RNA sequencing to promise a more comprehensive understanding of the molecules regulated by ketamine. Finally, we combined bioimaging and multiple molecular biology techniques to clarify that ketamine influences NSC differentiation by regulating transient receptor potential canonical 3 (TRPC3) expressions. Ketamine dramatically repressed TRPC3 expression (MD [95 % CI]=0.67 [0.40-0.95], P < 0.001) with a significant increase of phosphorylated glycogen synthase kinase 3β (p-GSK3β; MD [95 % CI]=1.00 [0.74-1.27], P < 0.001) and a decrease of β-catenin protein expression (MD [95 % CI]=0.60 [0.32-0.89], P = 0.001), thereby promoting the differentiation of NSCs into neurons and inhibiting their differentiation into astrocytes. These results suggest that TRPC3 is necessary for ketamine to modulate NSC differentiation, which occurs partly via regulation of the GSK3β/β-catenin pathway.

The Glycogen Synthase Kinase-3 in the Regulation of Ion Channels and Cellular Carriers

Glycogen synthase kinase-3 (GSK-3) is a highly evolutionarily conserved and ubiquitously expressed serine/threonine kinase, an enzyme protein profoundly specific for glycogen synthase (GS). GSK-3 is involved in various cellular functions and physiological processes, including cell proliferation, differentiation, motility, and survival as well as glycogen metabolism, protein synthesis, and apoptosis. There are two isoforms of human GSK-3 (named GSK-3α and GSK-3β) encoded by two distinct genes. Recently, GSK-3β has been reported to function as a powerful regulator of various transport processes across the cell membrane. This kinase, GSK-3β, either directly or indirectly, may stimulate or inhibit many different types of transporter proteins, including ion channel and cellular carriers. More specifically, GSK-3β-sensitive cellular transport regulation involves various calcium, chloride, sodium, and potassium ion channels, as well as a number of Na+-coupled cellular carriers including excitatory amino acid transporters EAAT2, 3 and 4, high-affinity Na+ coupled glucose carriers SGLT1, creatine transporter 1 CreaT1, and the type II sodium/phosphate cotransporter NaPi-IIa. The GSK-3β-dependent cellular transport regulations are a part of the kinase functions in numerous physiological and pathophysiological processes. Clearly, additional studies are required to examine the role of GSK-3β in many other types of cellular transporters as well as further elucidating the underlying mechanisms of GSK-3β-mediated cellular transport regulation.

Transcriptome analysis of response mechanism to ammonia stress in Asian clam (Corbicula fluminea)

Corbicula fluminea is highly sensitive to ammonia, and its response mechanism to ammonia stress is unclear. In this study, C. fluminea was exposed to different levels of ammonia (control group, 10 mg/L, and 25 mg/L) for 24 h and 48 h. A comparative analysis of transcriptome sequencing (RNA-seq) of C. fluminea digestive gland showed that the expression of 6742 genes (11.54%) was significantly affected by ammonia stress. The TLR, NF-κB, FOXO, and apoptotic signaling pathways were involved in the regulation. The differential expression of 14 genes was confirmed by real-time PCR. In summary, the response mechanism of C. fluminea digestive gland under ammonia stress may be different from that of oxidative stress in marine vertebrates. Also, the NMDAR-mediated pathway may not be the main mechanism in the response to ammonia stress in C. fluminea. The present study is a preliminary study for further investigation into ammonia toxicity in shellfish.

Design, Synthesis and in Vitro Tumor Cytotoxicity Evaluation of 3,5-Diamino-N-substituted Benzamide Derivatives as Novel GSK-3β Small Molecule Inhibitors

Glycogen synthase kinase-3 (GSK-3) plays an important regulatory role in various signaling pathways; such as PI3 K/AKT, which is closely related to the occurrence and development of tumors. At present, the most reported active GSK-3 inhibitors have the same structure: lactam ring or amide structure. To find out the GSK-3β small molecule inhibitor with novel, safe, efficient and more uncomplicated synthesis method, we analyzed in-depth reported crystal-binding patterns of GSK-3β small molecule inhibitor with GSK-3β protein, and designed and synthesized 17 non-reported 3,5-diamino-N-substituted benzamide compounds. Their structures were confirmed by ¹ H-NMR, ¹³ C-NMR, and HR-MS. The preliminary screening of tumor cytotoxicity of compounds in vitro was detected by MTT, and their structure-activity relationships were illustrated. The results have shown that 3,5-diamino-N-[3-(trifluoromethyl)phenyl]benzamide (4d) exhibited significant tumor cytotoxicity against human colon cancer cells (HCT-116) with IC₅₀ of 8.3 μm and showed commendable selectivity to GSK-3β. In addition, Compound 4d induced apoptosis to some extent and possessed modest PK properties.

Ammonium induced dysfunction of 5-HT2B receptor in astrocytes

Previously we reported that gene expression of astrocytic 5-HT_2B receptors was decreased in brains of depressed animals exposed to chronic mild stress (CMS) (Li et al., 2012) and of Parkinson's disease (Song et al., 2018). Depression is also one of the psychiatric symptoms in hyperammonemia, and astrocyte is a primary target of ammonium in brain in vivo. In the present study, we have used preparations of the brains of urease-treated mice and ammonium-treated astrocytes in culture to study gene expression and function of 5-HT_2B receptors. The urease-treated mice showed depressive behaviour. Both mRNA and protein of 5-HT_2B receptors were increased in the brains of urease-treated mice and in ammonium-treated cultured astrocytes. Further study revealed that mRNA and protein expression of adenosine deaminase acting on RNA 2 (ADAR2), an enzyme catalyze RNA deamination of adenosine to inosine was increased in the brains of urease-treated mice and in ammonium-treated cultured astrocytes. This increase in ADAR2 induced RNA editing of 5-HT_2B receptors. Cultured astrocytes treated with ammonium lost 5-HT induced Ca²⁺ signalling and ERK_1/2 phosphorylation, indicating dysfunction of 5-HT_2B receptors. This is in agreement with our previous observation that edited 5-HT_2B receptors no longer respond to 5-HT (Hertz et al., 2014). Ammonium effects are inhibited by ADAR2 siRNA in cultured astrocytes, suggesting that increased gene expression and editing and loss of function of 5-HT_2B receptors are results of increased activity of ADAR2. In summary, we have demonstrated that functional malfunction of astrocytic 5-HT_2B receptors occurs in animal models of major depression, Parkinson depression and hepatic encephalopathy albeit via different mechanisms. Understanding the role of astrocytic 5-HT_2B receptors in different pathological contexts may instigate development of novel therapeutic strategies for treating disease-specific depressive behaviour.

MiR-124-3p attenuates hyperphosphorylation of Tau protein-induced apoptosis via caveolin-1-PI3K/Akt/GSK3β pathway in N2a/APP695swe cells

Hyperphosphorylation of Tau forming neurofibrillary tangles has been considered as a crucial event in the pathogenesis of Alzheimer's disease (AD). MiR-124-3p belongs to microRNA (miRNA) family and was markedly decreased in AD, however, the functions of miR-124-3p in the pathogenesis of AD remain unknown. We observed that the expression of miR-124-3p was significantly decreased in N2a/APP695swe cells; and transfection of miR-124-3p mimics not only attenuated cell apoptosis and abnormal hyperphosphorylation of Tau protein without any changes of total Tau protein, but also increased expression levels of Caveolin-1, phosphoinositide 3-kinase (PI3K), phospho-Akt (Akt-Ser473)/Akt, phospho-glycogen synthase kinase-3 beta (GSK-3β-Ser9)/GSK-3β in N2a/APP695swe cells. We further found that miR-12-3p directly targeted Caveolin-1; miR-124-3p inhibited abnormal hyperphosphorylation of Tau by regulating Caveolin-1-PI3K/Akt/GSK3β pathway in AD. This study reveals that miR-124-3p may play a neuroprotective role in AD, which may provide new ideas and therapeutic targets for AD.

Renal carcinoma/kidney progenitor cell chimera organoid as a novel tumorigenesis gene discovery model

Three-dimensional (3D) organoids provide a new way to model various diseases, including cancer. We made use of recently developed kidney-organ-primordia tissue-engineering technologies to create novel renal organoids for cancer gene discovery. We then tested whether our novel assays can be used to examine kidney cancer development. First, we identified the transcriptomic profiles of quiescent embryonic mouse metanephric mesenchyme (MM) and of MM in which the nephrogenesis program had been induced ex vivo. The transcriptome profiles were then compared to the profiles of tumor biopsies from renal cell carcinoma (RCC) patients, and control samples from the same kidneys. Certain signature genes were identified that correlated in the developmentally induced MM and RCC, including components of the caveolar-mediated endocytosis signaling pathway. An efficient siRNA-mediated knockdown (KD) of Bnip3, Gsn, Lgals3, Pax8, Cav1, Egfr or Itgb2 gene expression was achieved in mouse RCC (Renca) cells. The live-cell imaging analysis revealed inhibition of cell migration and cell viability in the gene-KD Renca cells in comparison to Renca controls. Upon siRNA treatment, the transwell invasion capacity of Renca cells was also inhibited. Finally, we mixed E11.5 MM with yellow fluorescent protein (YFP)-expressing Renca cells to establish chimera organoids. Strikingly, we found that the Bnip3-, Cav1- and Gsn-KD Renca-YFP+ cells as a chimera with the MM in 3D organoid rescued, in part, the RCC-mediated inhibition of the nephrogenesis program during epithelial tubules formation. Altogether, our research indicates that comparing renal ontogenesis control genes to the genes involved in kidney cancer may provide new growth-associated gene screens and that 3D RCC-MM chimera organoids can serve as a novel model with which to investigate the behavioral roles of cancer cells within the context of emergent complex tissue structures.

Editor’s Choice: Chimeras between embryonic kidney cells and renal carcinoma cells serve as a novel model to assay the roles of co-regulated genes in kidney development and renal carcinogenesis.

Biphasic Regulation of Caveolin-1 Gene Expression by Fluoxetine in Astrocytes: Opposite Effects of PI3K/AKT and MAPK/ERK Signaling Pathways on c-fos

Previously, we reported that fluoxetine acts on 5-HT_2B receptor and induces epidermal growth factor receptor (EGFR) transactivation in astrocytes. Recently, we have found that chronic treatment with fluoxetine regulates Caveolin-1 (Cav-1)/PTEN/PI3K/AKT/glycogen synthase kinase 3β (GSK-3β) signaling pathway and glycogen content in primary cultures of astrocytes with bi-phasic concentration dependence. At low concentrations fluoxetine down-regulates Cav-1 gene expression, decreases membrane content of PTEN, increases PI3K activity and increases phosphorylation of GSK-3β and increases its activity; at high concentrations fluoxetine acts on PTEN/PI3K/AKT/GSK-3β in an inverse fashion. Here, we present the data indicating that acute treatment with fluoxetine at lower concentrations down-regulates c-Fos gene expression via PI3K/AKT signaling pathway; in contrast at higher concentrations fluoxetine up-regulates c-Fos gene expression via MAPK/extracellular-regulated kinase (ERK) signaling pathway. However, acute treatment with fluoxetine has no effect on Cav-1 protein content. Similarly, chronic effects of fluoxetine on Cav-1 gene expression are suppressed by inhibitor of PI3K at lower concentrations, but by inhibitor of MAPK at higher concentrations, indicating that the mechanism underlying bi-phasic regulation of Cav-1 gene expression by fluoxetine is opposing effects of PI3K/AKT and MAPK/ERK signal pathways on c-Fos gene expression. The effects of fluoxetine on Cav-1 gene expression at both lower and higher concentrations are abolished by AG1478, an inhibitor of EGFR, indicating the involvement of 5-HT_2B receptor induced EGFR transactivation as we reported previously. However, PP1, an inhibitor of Src only abolished the effect by lower concentrations, suggesting the relevance of Src with PI3K/AKT signal pathway during activation of EGFR.

Bi-phasic regulation of glycogen content in astrocytes via Cav-1/PTEN/PI3K/AKT/GSK-3β pathway by fluoxetine

OBJECTIVE

Here, we present the data indicating that chronic treatment with fluoxetine regulates Cav-1/PTEN/PI3K/AKT/GSK-3β signalling pathway and glycogen content in primary cultures of astrocytes with bi-phasic concentration dependence.

RESULTS

At lower concentrations, fluoxetine downregulates gene expression of Cav-1, decreases membrane content of PTEN, increases activity of PI3K/AKT, and elevates GSK-3β phosphorylation thus suppressing its activity. At higher concentrations, fluoxetine acts in an inverse fashion. As expected, fluoxetine at lower concentrations increased while at higher concentrations decreased glycogen content in astrocytes.

CONCLUSIONS

Our findings indicate that bi-phasic regulation of glycogen content via Cav-1/PTEN/PI3K/AKT/GSK-3β pathway by fluoxetine may be responsible for both therapeutic and side effects of the drug.