Caspases are a family of cysteine proteases that predominantly cleave their substrates after aspartic acid residues. Much of what we know of caspases emerged from investigation a highly conserved form of programmed cell death called apoptosis. This form of cell death is regulated by several caspases, including caspase-2, caspase-3, caspase-7, caspase-8 and caspase-9. However, these “killer” apoptotic caspases have emerged as versatile enzymes that play key roles in a wide range of non-apoptotic processes. Much of what we understand about these non-apoptotic roles is built on work investigating how “killer” caspases control a range of neuronal cell behaviors. This review will attempt to provide an up to date synopsis of these roles.

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Non-Canonical Roles of Apoptotic Caspases in the Nervous System

Significance The gene CACNA1C encodes for a calcium channel that has been linked to various psychiatric conditions, including schizophrenia and bipolar disorder, through hitherto unknown cellular mechanisms. Here, we report that deletion of Cacna1c in neurons of the developing brain disrupts spontaneous calcium activity and causes abnormal brain development and anxiety. Our results indicate that marginally alterations in the expression level of Cacna1c have major effects on the intrinsic spontaneous calcium activity of neural progenitors that play a crucial role in brain development. Thus, Cacna1c acts as a molecular switch that can increase susceptibility to psychiatric disease. The L-type voltage-gated Ca2+ channel gene CACNA1C is a risk gene for various psychiatric conditions, including schizophrenia and bipolar disorder. However, the cellular mechanism by which CACNA1C contributes to psychiatric disorders has not been elucidated. Here, we report that the embryonic deletion of Cacna1c in neurons destined for the cerebral cortex using an Emx1-Cre strategy disturbs spontaneous Ca2+ activity and causes abnormal brain development and anxiety. By combining computational modeling with electrophysiological membrane potential manipulation, we found that neural network activity was driven by intrinsic spontaneous Ca2+ activity in distinct progenitor cells expressing marginally increased levels of voltage-gated Ca2+ channels. MRI examination of the Cacna1c knockout mouse brains revealed volumetric differences in the neocortex, hippocampus, and periaqueductal gray. These results suggest that Cacna1c acts as a molecular switch and that its disruption during embryogenesis can perturb Ca2+ handling and neural development, which may increase susceptibility to psychiatric disease.

Disrupted Cacna1c gene expression perturbs spontaneous Ca2+ activity causing abnormal brain development and increased anxiety

Glyphosate‐based herbicides (GBH) are among the most sold pesticides in the world. There are several formulations based on the active ingredient glyphosate (GLY) used along with other chemicals to improve the absorption and penetration in plants. The final composition of commercial GBH may modify GLY toxicological profile, potentially enhancing its neurotoxic properties. The developing nervous system is particularly susceptible to insults occurring during the early phases of development, and exposure to chemicals in this period may lead to persistent impairments on neurogenesis and differentiation. The aim of this study was to evaluate the long‐lasting effects of a sub‐cytotoxic concentration, 2.5 parts per million of GBH and GLY, on the differentiation of human neuroepithelial stem cells (NES) derived from induced pluripotent stem cells (iPSC). We treated NES cells with each compound and evaluated the effects on key cellular processes, such as proliferation and differentiation in daughter cells never directly exposed to the toxicants. We found that GBH induced a more immature neuronal profile associated to increased PAX6, NESTIN and DCX expression, and a shift in the differentiation process toward glial cell fate at the expense of mature neurons, as shown by an increase in the glial markers GFAP, GLT1, GLAST and a decrease in MAP2. Such alterations were associated to dysregulation of key genes critically involved in neurogenesis, including PAX6, HES1, HES5, and DDK1. Altogether, the data indicate that subtoxic concentrations of GBH, but not of GLY, induce long‐lasting impairments on the differentiation potential of NES cells.

Glyphosate‐based herbicide induces long‐lasting impairment in neuronal and glial differentiation

Background Propofol is an anesthetic used in clinical surgery. Many studies have shown that propofol has the potential to kill cancer cells; however, the mechanism by which it kills hepatocellular carcinoma (HCC) cells remains unclear. Methods To examine this issue, the apoptosis change of HepG2 and Huh-7 cell lines treated with propofol were observed. Additionally, a quantitative reverse-transcriptase polymerase chain reaction was used to measure the expression level of hsa-miR-134 (miR-134), and a Cell Counting Kit-8 assay and flow cytometry assay were used to observe cell apoptosis. A dual-luciferase assay was used to confirm the binding effect of miR-134 and BCL-2 (B cell lymphoma-2), and a western blot assay was used to detect expression level changes of BCL-2 and cleaved caspase-3. Results The results showed that propofol significantly promoted HepG2 and Huh-7 cell apoptosis, and that miR-134 expression level is related to the concentration of propofol. The dual-luciferase assay showed that miR-134 significantly reduced the luciferase activity of BCL-2-wt, but had no notable effect on BCL-2-mut. In rescue experiments, miR-134 deficiency resulted in a high apoptosis rate, a low BCL-2 expression level, and a high cleaved caspase-3 expression level induced by propofol in HepG2. Conclusions In summary, propofol appears to upregulate the expression level of miR-134, decrease the BCL-2 level, and induce HCC cell apoptosis by promoting the cleaved caspase-3 expression level. Trial registration Chinese Clinical Trial Registry ChiCTR18000199

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Propofol induces apoptosis of hepatocellular carcinoma cells by upregulating miR-134 expression

The embryonic developing cerebral cortex is characterized by the presence of distinctive cell types such as progenitor pools, immature projection neurons and interneurons. Each of these cell types is diverse on itself, but they all take part of the developmental process responding to intrinsic and extrinsic cues that can affect their calcium oscillations. Importantly, calcium activity is crucial for controlling cellular events linked to cell cycle progression, cell fate determination, specification, cell positioning, morphological development and maturation. Therefore, in this work we measured calcium activity in control conditions and in response to neurotransmitter inhibition. Different data analysis methods were applied over the experimental measurements including statistical methods entropy and fractal calculations, and spectral and principal component analyses. We found that developing projection neurons are differentially affected by classic inhibitory neurotransmission as a cell type and at different places compared to migrating interneurons, which are also heterogeneous in their response to neurotransmitter inhibition. This reveals important insights into the developmental role of neurotransmitters and calcium oscillations in the forming brain cortex. Moreover, we present an improved analysis proposing a Gini coefficient-based inequality distribution and principal component analysis as mathematical tools for understanding the earliest patterns of brain activity.

https://www.mdpi.com/1422-0067/21/21/8013/pdf

Glycine Receptor Inhibition Differentially Affect Selected Neuronal Populations of the Developing Embryonic Cortex, as Evidenced by the Analysis of Spontaneous Calcium Oscillations

The T-type Ca2+ Channel Cav3.2 Regulates Differentiation of Neural Progenitor Cells during Cortical Development via Caspase-3.

Cell-cell communication plays a central role in the guidance of migrating neurons during the development of the cerebral cortex. Neuregulins (NRGs) are essential mediators for migration and maintenance of the radial glial scaffold. We show, in this study that soluble NRG reduces neuronal motility, causes transition of bipolar cells to multipolar ones, and induces neuronal mitosis. Blocking the NRG receptor, ErbB4, results in reduction of neuron-neuron and neuron-radial glial contacts and causes an increase in neuronal motility. Blocking the radial glial metabotropic glutamate receptor 5 (mGluR5), the nonselective cation channel transient receptor potential 3 (TRPC3), or matrix metalloproteinases (MMPs) results in similar effects as ErbB4 blockade. Soluble NRG counteract the changes in motility pattern. Stimulation of other radial glial G-protein-coupled receptors (GPCRs), such as muscarinic acetylcholine receptors or endothelin receptors counteract all the effect of mGluR5 blockade, but not that of ErbB4, TRPC3, and MMP blockade. The results indicate that neurotransmitters and endothelins acting on radial glial GPCRs are, through proteolytic NRG/ErbB4 activation, able to modify the migratory behavior of neurons.

Neurotransmitters and Endothelins Acting on Radial Glial G-Protein-Coupled Receptors Are, Through Proteolytic NRG/ErbB4 Activation, Able to Modify the Migratory Behavior of Neocortical Cells and Mediate Bipolar-to-Multipolar Transition.

Ibrahim Al Rayyes

Papers

The T-type Ca2+ Channel Cav3.2 Regulates Differentiation of Neural Progenitor Cells during Cortical Development via Caspase-3.

Glyphosate‐based herbicide induces long‐lasting impairment in neuronal and glial differentiation

Neurotransmitters and Endothelins Acting on Radial Glial G-Protein-Coupled Receptors Are, Through Proteolytic NRG/ErbB4 Activation, Able to Modify the Migratory Behavior of Neocortical Cells and Mediate Bipolar-to-Multipolar Transition.