Pharmacological Dissection of the Crosstalk between NaV and CaV Channels in GH3b6 Cells

Thanks to the crosstalk between Na+ and Ca2+ channels, Na+ and Ca2+ homeostasis interplay in so-called excitable cells enables the generation of action potential in response to electrical stimulation. Here, we investigated the impact of persistent activation of voltage-gated Na+ (NaV) channels by neurotoxins, such as veratridine (VTD), on intracellular Ca2+ concentration ([Ca2+]i) in a model of excitable cells, the rat pituitary GH3b6 cells, in order to identify the molecular actors involved in Na+-Ca2+ homeostasis crosstalk. By combining RT-qPCR, immunoblotting, immunocytochemistry, and patch-clamp techniques, we showed that GH3b6 cells predominantly express the NaV1.3 channel subtype, which likely endorses their voltage-activated Na+ currents. Notably, these Na+ currents were blocked by ICA-121431 and activated by the β-scorpion toxin Tf2, two selective NaV1.3 channel ligands. Using Fura-2, we showed that VTD induced a [Ca2+]i increase. This effect was suppressed by the selective NaV channel blocker tetrodotoxin, as well by the selective L-type CaV channel (LTCC) blocker nifedipine. We also evidenced that crobenetine, a NaV channel blocker, abolished VTD-induced [Ca2+]i elevation, while it had no effects on LTCC. Altogether, our findings highlight a crosstalk between NaV and LTCC in GH3b6 cells, providing a new insight into the mode of action of neurotoxins.

Raw and wine processed Schisandra chinensis regulate NREM-sleep and alleviate cardiovascular dysfunction associated with insomnia by modulating HPA Axis

Clinical studies have shown that insomnia and anxiety are usually accompanied by cardiovascular dysfunction. In traditional Chinese medicine, Schisandra chinensis (SC) and wine processed Schisandra chinensis (WSC) are mainly used for the treatment of dysphoria, palpitation and insomnia. However, little attention was paid to its mechanism. In this study, we monitored the effect of SC and WSC on the nervous system and cardiovascular system of free-moving rats in the real-time. Our results show that SC and WSC can alleviate cardiovascular dysfunction while promoting sleep, and we further explored their potential mechanisms. HPLC-QTOF-MS was used for the quality control of chemical components in SC and WSC. Data sciences international (DSI) physiological telemetry system was applied to collect the electroencephalogram (EEG), electrocardiogram (ECG) and other parameters of free-moving rats to understand the effects of long-term intake of SC and WSC on rats. The content of Cortisol (CORT), neurotransmitters and amino acids in rat pituitary and hypothalamus were analyzed by UPLC-MS to determine the activity of HPA axis. The expression of melatonin receptor MT1 was analyzed by immunofluorescence technique. Our results suggested that SC and WSC may play the role of promoting sleep by increasing the expression level of melatonin receptor MT1 in hypothalamus, and modulate the activity of HPA axis by regulating the levels of the related neurotransmitters and amino acid, so as to improve the abnormal cardiovascular system of rats. This study may provide theoretical support for explicating the advantages of SC and other phytomedicines in the treatment of insomnia.

Effective Perturbations on the Amplitude and Hysteresis of Erg-Mediated Potassium Current Caused by 1-Octylnonyl 8-[(2-hydroxyethyl)[6-oxo-6(undecyloxy)hexyl]amino]-octanoate (SM-102), a Cationic Lipid

SM-102 (1-octylnonyl 8-[(2-hydroxyethyl)[6-oxo-6-(undecyloxy)hexyl]amino]-octanoate) is an amino cationic lipid that has been tailored for the formation of lipid nanoparticles and it is one of the essential ingredients present in the ModernaTM COVID-19 vaccine. However, to what extent it may modify varying types of plasmalemmal ionic currents remains largely uncertain. In this study, we investigate the effects of SM-102 on ionic currents either in two types of endocrine cells (e.g., rat pituitary tumor (GH3) cells and mouse Leydig tumor (MA-10) cells) or in microglial (BV2) cells. Hyperpolarization-activated K+ currents in these cells bathed in high-K+, Ca2+-free extracellular solution were examined to assess the effects of SM-102 on the amplitude and hysteresis of the erg-mediated K+ current (IK(erg)). The SM-102 addition was effective at blocking IK(erg) in a concentration-dependent fashion with a half-maximal concentration (IC50) of 108 μM, a value which is similar to the KD value (i.e., 134 μM) required for its accentuation of deactivation time constant of the current. The hysteretic strength of IK(erg) in response to the long-lasting isosceles-triangular ramp pulse was effectively decreased in the presence of SM-102. Cell exposure to TurboFectinTM 8.0 (0.1%, v/v), a transfection reagent, was able to inhibit hyperpolarization-activated IK(erg) effectively with an increase in the deactivation time course of the current. Additionally, in GH3 cells dialyzed with spermine (30 μM), the IK(erg) amplitude progressively decreased; moreover, a further bath application of SM-102 (100 μM) or TurboFectin (0.1%) diminished the current magnitude further. In MA-10 Leydig cells, the IK(erg) was also blocked by the presence of SM-102 or TurboFectin. The IC50 value for SM-102-induced inhibition of IK(erg) in MA-10 cells was 98 μM. In BV2 microglial cells, the amplitude of the inwardly rectifying K+ current was inhibited by SM-102. Taken together, the presence of SM-102 concentration-dependently inhibited IK(erg) in endocrine cells (e.g., GH3 or MA-10 cells), and such action may contribute to their functional activities, assuming that similar in vivo findings exist.

Proteomic Response of Rat Pituitary Under Chronic Mild Stress Reveals Insights Into Vulnerability and Resistance to Anxiety or Depression

Chronic stress as one of the most significant risk factor can trigger overactivity of hypothalamic-pituitary-adrenal (HPA) axis in depression as well as anxiety. Yet, the shared and unique neurobiological underpinnings underlying the pituitary abnormality in these two disorders have not been made clear. We previously have established depression-susceptible, anxiety-susceptible and insusceptible groups using a valid chronic mild stress (CMS) model. In this work, the possible protein expression changes in the rat pituitary of these three groups were continuously investigated through the use of the comparative quantitative proteomics and bioinformatics approaches. The pituitary-proteome analysis identified totally 197 differential proteins as a CMS response. These deregulated proteins were involved in diverse biological functions and significant pathways potentially connected with the three different behavioral phenotypes, likely serving as new investigative protein targets. Afterwards, parallel reaction monitoring-based independent analysis found out that expression alterations in Oxct1, Sec24c, Ppp1cb, Dock1, and Coq3; Lama1, Glb1, Gapdh, Sccpdh, and Renbp; Sephs1, Nup188, Spp1, Prodh1, and Srm were specifically linked to depression-susceptible, anxiety-susceptible and insusceptible groups, respectively, suggesting that the same CMS had different impacts on the pituitary protein regulatory system. Collectively, the current proteomics research elucidated an important molecular basis and furnished new valuable insights into neurochemical commonalities and specificities of the pituitary dysfunctional mechanisms in HPA axis underlying vulnerability and resistance to stress-induced anxiety or depression.

Curcumin sensitizes prolactinoma to bromocriptine by activating the ERK/EGR1 and inhibiting AKT/GSK3β signaling pathway

Background Although bromocriptine (BRC) as first-line drugs are recommended for treating patients with prolactinoma, a minority of patients with prolactinoma resistance to BRC. Curcumin (Cur) has been shown to inhibit proliferation of prolactinoma cell lines. The aim of this study is to investigate whether Cur could enhance the growth-inhibitory effect of BRC resistance on prolactinoma cell lines and its possible mechanism. Methods CCK-8 kit was used to test cell growth. Cell-cycle analysis and apoptosis was performed by flow cytometry. Electron microscopy was used to test autophagosome. The mRNA expression profiles were analysed using the Affymetrix Gene-Chip array. Western blotting was used to test protein expression. The SPSS version 17.0 software was applied for statistical analysis. Results Our data showed that Cur enhanced the growth-inhibitory effect of BRC on GH3 and MMQ cell proliferation. BRC and Cur both induced cell apoptosis, and Cur could significantly increase the apoptosis of BRC on pituitary adenoma cells through the ERK/EGR1 signaling pathway. Moreover, Cur could enhance the autophagic cell death (ACD) of BRC on tumor cell by inhibiting the AKT/GSK3β signaling pathway. The same results were confirmed in vivo study. Conclusion Cur sensitizes rat pituitary adenoma cell to BRC by activating the ERK/EGR1 and inhibiting AKT/GSK3β signaling pathway.

CircAgtpbp1 Acts as a Molecular Sponge of miR-543-5p to Regulate the Secretion of GH in Rat Pituitary Cells

CircRNAs have been identified to be expressed differently and stably in numerous species and tissues, but their functions in growth hormone (GH) secretion are still largely unknown. In summary, we have revealed a circRNA-miRNA-mRNA network that may play a biological role in the rat pituitary gland. First, we verified the chromosome location information of circAgtpbp1 according to sequencing analysis. The circAgtpbp1 characteristics were authenticated through PCR, qRT–PCR, treating with RNase and fluorescent in situ hybridization (FISH). Second, we detected the expression pattern of circAgtpbp1 in the rat anterior pituitary by qRT–PCR. We also designed circAgtpbp1 siRNA and constructed overexpression plasmid to evaluate the effect of circAgtpbp1 function on GH secretion by qRT–PCR, ELISA and Western blot. CircAgtpbp1 is a stable, truly circular molecule. We found that circAgtpbp1 interacted with miR-543-5p and can regulate GH secretion in pituitary cells through a circAgtpbp1-miR-543-5p-GH axis. Overall, the evidence generated by our study suggests that circAgtpbp1 can act as a sponge of miR-543-5p to reduce the inhibitory effect of miR-543-5p on Gh1 and further promote GH secretion. These findings expand our existing knowledge on the mechanisms of hormone regulation in the pituitary gland.

Genome-wide screening of circadian and non-circadian impact of Neat1 genetic deletion

The functions of the long non-coding RNA, Nuclear enriched abundant transcript 1 (Neat1), are poorly understood. Neat1 is required for the formation of paraspeckles, but its respective paraspeckle-dependent or independent functions are unknown. Several studies including ours reported that Neat1 is involved in the regulation of circadian rhythms. We characterized the impact of Neat1 genetic deletion in a rat pituitary cell line. The mRNAs whose circadian expression pattern or expression level is regulated by Neat1 were identified after high-throughput RNA sequencing of the circadian transcriptome of wild-type cells compared to cells in which Neat1 was deleted by CRISPR/Cas9. The numerous RNAs affected by Neat1 deletion were found to be circadian or non-circadian, targets or non-targets of paraspeckles, and to be associated with many key biological processes showing that Neat1, interacting or independently of the circadian system, could play crucial roles in key physiological functions through diverse mechanisms.

Calcium dynamics and chromatin remodelling underlie heterogeneity in prolactin transcription

Pituitary cells have been reported to show spontaneous calcium oscillations and dynamic transcription cycles. To study both processes in the same living cell in real time, we used rat pituitary GH3 cells stably expressing human prolactin-luciferase or prolactin-EGFP reporter gene constructs loaded with a fluorescent calcium indicator and measured activity using single-cell time-lapse microscopy. We observed heterogeneity between clonal cells in the calcium activity and prolactin transcription in unstimulated conditions. There was a significant correlation between cells displaying spontaneous calcium spikes and cells showing spontaneous bursts in prolactin expression. Notably, cells showing no basal calcium activity showed low prolactin expression but elicited a significantly greater transcriptional response to BayK8644 compared to cells showing basal calcium activity. This suggested the presence of two subsets of cells within the population at any one time. Fluorescence-activated cell sorting was used to sort cells into two populations based on the expression level of prolactin-EGFP however, the bimodal pattern of expression was restored within 26 h. Chromatin immunoprecipitation showed that these sorted populations were distinct due to the extent of histone acetylation. We suggest that maintenance of a heterogeneous bimodal population is a fundamental characteristic of this cell type and that calcium activation and histone acetylation, at least in part, drive prolactin transcriptional competence.