Retinoic Acid-Differentiated Neuroblastoma SH-SY5Y Is an Accessible In Vitro Model to Study Native Human Acid-Sensing Ion Channels 1a (ASIC1a)

Physical TRPV1-PKR2 interaction modulates PKR2 localization, activation and β-arrestin-2 recruitment

Transient Receptor Potential Vanilloid 1 (TRPV1) plays a central role in nociception and inflammation-induced hyperalgesia. Prokineticin receptors (PKR1 and PKR2) are G protein-coupled receptors (GPCRs) that are expressed both centrally and peripherally and induce various signalling pathways through the binding of their endogenous ligands, the prokineticins. The activation of PKRs is modulated by interaction with accessory proteins such as snapin and β-arrestin-2. The prokineticin system is involved in the mechanisms of pain perception by triggering a strong hyperalgesia that lowers the thresholds for thermal and mechanical stimuli. PKR1 and PKR2 are both expressed in dorsal root ganglia (DRG) neurons where they colocalise with TRPV1. In this work, we have identified the regions that mediate the physical interaction between TRPV1 and PKR2. We demonstrated that in the presence of the accessory protein snapin, the strength of binding between TRPV1 and PKR2 is increased. TRPV1 proves to be a physiological regulator of PKR2, modulating its activation, localisation and β-arrestin binding as well as PK2-induced mechanical allodynia. The results obtained show for the first time that TRPV1 regulates PKR2 signalling, suggesting a bidirectional interaction between the two systems.

Two Amino Acid Substitutions Improve the Pharmacological Profile of the Snake Venom Peptide Mambalgin

Mambalgins are peptide inhibitors of acid-sensing ion channels type 1 (ASIC1) with potent analgesic effects in models of inflammatory and neuropathic pain. To optimize recombinant peptide production and enhance pharmacological properties, we developed a mutant analog of mambalgin-1 (Mamb) through molecular modeling and site-directed mutagenesis. The resulting peptide, Mamb-AL, features methionine-to-alanine and methionine-to-leucine substitutions, allowing for a more efficient recombinant production protocol in E. coli. Electrophysiological experiments demonstrated that Mamb-AL exhibits three-fold and five-fold greater inhibition of homomeric ASIC1a and ASIC1b channels, respectively, and a two-fold increase in inhibition of heteromeric ASIC1a/3 channels compared with Mamb. In a mouse model of acetic acid-induced writhing pain, Mamb-AL showed a trend toward stronger analgesic efficacy than the wild-type peptide. These improvements in both production efficiency and pharmacological properties make Mamb-AL a valuable tool for studying ASIC channels and a promising candidate for analgesic drug development.

Sea anemone Cys-ladder peptide Ms13-1 induces a pain response as a positive modulator of acid-sensing ion channel 1a

Acid-sensing ion channel 1a (ASIC1a) is involved in processes associated with fear, learning, and neurodegeneration within the central nervous system. However, ASIC1a is also abundant in the peripheral nervous system, where its role is still poorly understood, largely due to the lack of selective ligands. In this study, we present the discovery of the first selective positive allosteric modulator for ASIC1a, isolated from the sea anemone Metridium senile. The active compound, a peptide named Ms13-1, features a novel type of fold named 'Cys-ladder'. Ms13-1 exhibits high affinity and selectivity for ASIC1a, enhancing channel activation in response to a broad range of acidic stimuli (pH 6.9-5.5) without altering the proton affinity for the channel. Moreover, injection of Ms13-1 into the hind paw of mice provokes robust and long-lasting pain-related behavior, which is significantly attenuated by a selective ASIC1 antagonist. The discovery of this novel selective positive allosteric modulator opens up new perspectives to investigate the role of ASIC1a in various physiological processes.

Robust In Vitro Models for Studying Parkinson's Disease? LUHMES Cells and SH-SH5Y Cells

As our population ages, there is an increased unmet clinical need surrounding neurodegenerative diseases such as Parkinson's disease (PD). To tackle this ever-increasing problem, we must ensure that the cell models that we use to develop therapeutics in vitro are robust, reliable, and replicable. In this study, we compared SH-SY5Y cells with LUHMES cells in response to 6-Hydroxydopamine (6OHDA) and 1-Methyl-4-phenylpyridinium (MPP+), two common Parkinson's insults used in in vitro analysis. Both these cell types have apparent dopaminergic phenotypes, which could aid us in understanding their potential in this race to novel therapies. The LUHMES cells showed consistent dopaminergic (DA) expression through tyrosine hydroxylase (TH) positivity, alongside depleted ATP levels and elevated reactive oxygen species (ROS) production, whereas the SH-SH5Y cells displayed resilience to both chemical insults, raising questions about their utility in accurately modelling PD pathology. Further electrophysiological analysis revealed comparable firing rates and ion channel signalling between both cell types; however, LUHMES cells demonstrated stronger calcium signalling responses, further supporting their use as a more robust PD model. While SH-SY5Y cells showed some adaptability in vitro, their inconsistent DA phenotype and limited response to chemical insults limit their suitability for advanced research, suggesting that LUHMES cells should and must take their place as a hallmark in Parkinson's disease research.

Short-term starvation activates AMPK and restores mitochondrial inorganic polyphosphate, but fails to reverse associated neuronal senescence

Neuronal senescence is a major risk factor for the development of many neurodegenerative disorders. The mechanisms that drive neurons to senescence remain largely elusive; however, dysregulated mitochondrial physiology seems to play a pivotal role in this process. Consequently, strategies aimed to preserve mitochondrial function may hold promise in mitigating neuronal senescence. For example, dietary restriction has shown to reduce senescence, via a mechanism that still remains far from being totally understood, but that could be at least partially mediated by mitochondria. Here, we address the role of mitochondrial inorganic polyphosphate (polyP) in the intersection between neuronal senescence and dietary restriction. PolyP is highly present in mammalian mitochondria; and its regulatory role in mammalian bioenergetics has already been described by us and others. Our data demonstrate that depletion of mitochondrial polyP exacerbates neuronal senescence, independently of whether dietary restriction is present. However, dietary restriction in polyP-depleted cells activates AMPK, and it restores some components of mitochondrial physiology, even if this is not sufficient to revert increased senescence. The effects of dietary restriction on polyP levels and AMPK activation are conserved in differentiated SH-SY5Y cells and brain tissue of male mice. Our results identify polyP as an important component in mitochondrial physiology at the intersection of dietary restriction and senescence, and they highlight the importance of the organelle in this intersection.

High OXPHOS efficiency in RA-FUdr-differentiated SH-SY5Y cells: involvement of cAMP signalling and respiratory supercomplexes

Neurons are highly dependent on mitochondria to meet their bioenergetic needs and understanding the metabolic changes during the differentiation process is crucial in the neurodegeneration context. Several in vitro approaches have been developed to study neuronal differentiation and bioenergetic changes. The human SH-SY5Y cell line is a widely used cellular model and several differentiation protocols have been developed to induce a neuron-like phenotype including retinoic acid (RA) treatment. In this work we obtained a homogeneous functional population of neuron-like cells by a two-step differentiation protocol in which SH-SY5Y cells were treated with RA plus the mitotic inhibitor 2-deoxy-5-fluorouridine (FUdr). RA-FUdr treatment induced a neuronal phenotype characterized by increased expression of neuronal markers and electrical properties specific to excitable cells. In addition, the RA-FUdr differentiated cells showed an enrichment of long chain and unsaturated fatty acids (FA) in the acyl chain composition of cardiolipin (CL) and the bioenergetic analysis evidences a high coupled and maximal respiration associated with high mitochondrial ATP levels. Our results suggest that the observed high oxidative phosphorylation (OXPHOS) capacity may be related to the activation of the cyclic adenosine monophosphate (cAMP) pathway and the assembly of respiratory supercomplexes (SCs), highlighting the change in mitochondrial phenotype during neuronal differentiation.

Effect of Acrylamide and Mycotoxins in SH-SY5Y Cells: A Review

Thermal processes induce the formation of undesired toxic components, such as acrylamide (AA), which has been shown to induce brain toxicity in humans and classified as Group 2A by the International Agency of Research in Cancer (IARC), as well as some mycotoxins. AA and mycotoxins' toxicity is studied in several in vitro models, including the neuroblastoma cell line model SH-SY5Y cells. Both AA and mycotoxins occur together in the same food matrix cereal base (bread, pasta, potatoes, coffee roasting, etc.). Therefore, the goal of this review is to deepen the knowledge about the neurological effects that AA and mycotoxins can induce on the in vitro model SH-SY5Y and its mechanism of action (MoA) focusing on the experimental assays reported in publications of the last 10 years. The analysis of the latest publications shows that most of them are focused on cytotoxicity, apoptosis, and alteration in protein expression, while others are interested in oxidative stress, axonopathy, and the disruption of neurite outgrowth. While both AA and mycotoxins have been studied in SH-SY5Y cells separately, the mixture of them is starting to draw the interest of the scientific community. This highlights a new and interesting field to explore due to the findings reported in several publications that can be compared and the implications in human health that both could cause. In relation to the assays used, the most employed were the MTT, axonopathy, and qPCR assays. The concentration dose range studied was 0.1-10 mM for AA and 2 fM to 200 µM depending on the toxicity and time of exposure for mycotoxins. A healthy and varied diet allows the incorporation of a large family of bioactive compounds that can mitigate the toxic effects associated with contaminants present in food. Although this has been reported in some publications for mycotoxins, there is still a big gap for AA which evidences that more investigations are needed to better explore the risks for human health when exposed to AA and mycotoxins.

Modulation of TRPV1 and TRPA1 Channels Function by Sea Anemones' Peptides Enhances the Viability of SH-SY5Y Cell Model of Parkinson's Disease

Cellular dysfunction during Parkinson's disease leads to neuroinflammation in various brain regions, inducing neuronal death and contributing to the progression of the disease. Different ion channels may influence the process of neurodegeneration. The peptides Ms 9a-1 and APHC3 can modulate the function of TRPA1 and TRPV1 channels, and we evaluated their cytoprotective effects in differentiated to dopaminergic neuron-like SH-SY5Y cells. We used the stable neuroblastoma cell lines SH-SY5Y, producing wild-type alpha-synuclein and its mutant A53T, which are prone to accumulation of thioflavin-S-positive aggregates. We analyzed the viability of cells, as well as the mRNA expression levels of TRPA1, TRPV1, ASIC1a channels, alpha-synuclein, and tyrosine hydroxylase after differentiation of these cell lines using RT-PCR. Overexpression of alpha-synuclein showed a neuroprotective effect and was accompanied by a reduction of tyrosine hydroxylase expression. A mutant alpha-synuclein A53T significantly increased the expression of the pro-apoptotic protein BAX and made cells more susceptible to apoptosis. Generally, overexpression of alpha-synuclein could be a model for the early stages of PD, while expression of mutant alpha-synuclein A53T mimics a genetic variant of PD. The peptides Ms 9a-1 and APHC3 significantly reduced the susceptibility to apoptosis of all cell lines but differentially influenced the expression of the genes of interest. Therefore, these modulators of TRPA1 and TRPV1 have the potential for the development of new therapeutic agents for neurodegenerative disease treatment.

Ion channels regulate energy homeostasis and the progression of metabolic disorders: Novel mechanisms and pharmacology of their modulators

The progression of metabolic diseases, featured by dysregulated metabolic signaling pathways, is orchestrated by numerous signaling networks. Among the regulators, ion channels transport ions across the membranes and trigger downstream signaling transduction. They critically regulate energy homeostasis and pathogenesis of metabolic diseases and are potential therapeutic targets for treating metabolic disorders. Ion channel blockers have been used to treat diabetes for decades by stimulating insulin secretion, yet with hypoglycemia and other adverse effects. It calls for deeper understanding of the largely elusive regulatory mechanisms, which facilitates the identification of new therapeutic targets and safe drugs against ion channels. In the article, we critically assess the two principal regulatory mechanisms, protein-channel interaction and post-translational modification on the activities of ion channels to modulate energy homeostasis and metabolic disorders through multiple novel mechanisms. Moreover, we discuss the multidisciplinary methods that provide the tools for elucidation of the regulatory mechanisms mediating metabolic disorders by ion channels. In terms of translational perspective, the mechanistic analysis of recently validated ion channels that regulate insulin resistance, body weight control, and adverse effects of current ion channel antagonists are discussed in details. Their small molecule modulators serve as promising new drug candidates to combat metabolic disorders.

Dual Modulator of ASIC Channels and GABAA Receptors from Thyme Alters Fear-Related Hippocampal Activity

Acid-sensing ion channels (ASICs) are proton-gated ion channels that mediate nociception in the peripheral nervous system and contribute to fear and learning in the central nervous system. Sevanol was reported previously as a naturally-occurring ASIC inhibitor from thyme with favorable analgesic and anti-inflammatory activity. Using electrophysiological methods, we found that in the high micromolar range, the compound effectively inhibited homomeric ASIC1a and, in sub- and low-micromolar ranges, positively modulated the currents of α1β2γ2 GABAA receptors. Next, we tested the compound in anxiety-related behavior models using a targeted delivery into the hippocampus with parallel electroencephalographic measurements. In the open field, 6 µM sevanol reduced both locomotor and θ-rhythmic activity similar to GABA, suggesting a primary action on the GABAergic system. At 300 μM, sevanol markedly suppressed passive avoidance behavior, implying alterations in conditioned fear memory. The observed effects could be linked to distinct mechanisms involving GABAAR and ASIC1a. These results elaborate the preclinical profile of sevanol as a candidate for drug development and support the role of ASIC channels in fear-related functions of the hippocampus.

Δ8-THC Induces Up-Regulation of Glutamatergic Pathway Genes in Differentiated SH-SY5Y: A Transcriptomic Study

Cannabinoids, natural or synthetic, have antidepressant, anxiolytic, anticonvulsant, and anti-psychotic properties. Cannabidiol (CBD) and delta-9-tetrahydrocannabinol (Δ⁹-THC) are the most studied cannabinoids, but recently, attention has turned towards minor cannabinoids. Delta-8-tetrahydrocannabinol (Δ⁸-THC), an isomer of Δ⁹-THC, is a compound for which, to date, there is no evidence of its role in the modulation of synaptic pathways. The aim of our work was to evaluate the effects of Δ⁸-THC on differentiated SH-SY5Y human neuroblastoma cells. Using next generation sequencing (NGS), we investigated whether Δ⁸-THC could modify the transcriptomic profile of genes involved in synapse functions. Our results showed that Δ⁸-THC upregulates the expression of genes involved in the glutamatergic pathway and inhibits gene expression at cholinergic synapses. Conversely, Δ⁸-THC did not modify the transcriptomic profile of genes involved in the GABAergic and dopaminergic pathways.

Investigation of 2-Hydroxypropyl-β-Cyclodextrin Treatment in a Neuronal-Like Cell Model of Niemann-Pick Type C Using Quantitative Proteomics

Niemann-Pick, type C (NPC) is a fatal, neurovisceral lysosomal storage disorder with progressive neurodegeneration and no FDA-approved therapy. Significant efforts have been focused on the development of therapeutic options, and 2-hydroxypropyl-β-cyclodextrin (HP-b-CD) has emerged as a promising candidate. In cell culture, HP-b-CD ameliorates cholesterol storage in endo/lysosomes, a hallmark of the disorder. Furthermore, in animal studies, treatment with HP-b-CD delays neurodegeneration and extends lifespan. While HP-b-CD has been promising in vitro and in vivo, a clear understanding of the mechanism(s) of action is lacking. Utilizing a neuron-like cell culture model of SH-SY5Y differentiated cells and U18666A to induce the NPC phenotype, we report here a large-scale mass-spectrometry-based proteomic study to evaluate proteome changes upon treatment with these small molecules. In this study, we show that differentiated SH-SY5Y cells display morphological changes representative of neuronal-like cells along with increased levels of proliferation markers. Inhibition of the NPC cholesterol transporter 1 protein by U18666A resulted in increased levels of known NPC markers including SCARB2/LIMP2 and LAMP2. Finally, investigation of HP-b-CD treatment was performed where we observe that, although HP-b-CD reduces cholesterol storage, levels of NPC1 and NPC2 are not normalized to control levels. This finding further supports the need for a proteostasis strategy for NPC drug development. Moreover, proteins that were dysregulated in the U18666A model of NPC and normalized to control levels suggest that HP-b-CD promotes exocytosis in this neuron-like model. Utilizing state of the art mass spectrometry analysis, these data demonstrate newly reported changes with pharmacological perturbations related to NPC disease and provide insight into the mechanisms of HP-b-CD as a potential therapeutic.

Mechanisms of Action of the Peptide Toxins Targeting Human and Rodent Acid-Sensing Ion Channels and Relevance to Their In Vivo Analgesic Effects

Acid-sensing ion channels (ASICs) are voltage-independent H⁺-gated cation channels largely expressed in the nervous system of rodents and humans. At least six isoforms (ASIC1a, 1b, 2a, 2b, 3 and 4) associate into homotrimers or heterotrimers to form functional channels with highly pH-dependent gating properties. This review provides an update on the pharmacological profiles of animal peptide toxins targeting ASICs, including PcTx1 from tarantula and related spider toxins, APETx2 and APETx-like peptides from sea anemone, and mambalgin from snake, as well as the dimeric protein snake toxin MitTx that have all been instrumental to understanding the structure and the pH-dependent gating of rodent and human cloned ASICs and to study the physiological and pathological roles of native ASICs in vitro and in vivo. ASICs are expressed all along the pain pathways and the pharmacological data clearly support a role for these channels in pain. ASIC-targeting peptide toxins interfere with ASIC gating by complex and pH-dependent mechanisms sometimes leading to opposite effects. However, these dual pH-dependent effects of ASIC-inhibiting toxins (PcTx1, mambalgin and APETx2) are fully compatible with, and even support, their analgesic effects in vivo, both in the central and the peripheral nervous system, as well as potential effects in humans.

Lignans as Pharmacological Agents in Disorders Related to Oxidative Stress and Inflammation: Chemical Synthesis Approaches and Biological Activities

Plant lignans exhibit a wide range of biological activities, which makes them the research objects of potential use as therapeutic agents. They provide diverse naturally-occurring pharmacophores and are available for production by chemical synthesis. A large amount of accumulated data indicates that lignans of different structural groups are apt to demonstrate both anti-inflammatory and antioxidant effects, in many cases, simultaneously. In this review, we summarize the comprehensive knowledge about lignan use as a bioactive agent in disorders associated with oxidative stress and inflammation, pharmacological effects in vitro and in vivo, molecular mechanisms underlying these effects, and chemical synthesis approaches. This article provides an up-to-date overview of the current data in this area, available in PubMed, Scopus, and Web of Science databases, screened from 2000 to 2022.

Hypoxia Induces DPSC Differentiation versus a Neurogenic Phenotype by the Paracrine Mechanism

As previously described by several authors, dental pulp stem cells (DPSCs), when adequately stimulated, may acquire a neuronal-like phenotype acting as a favorable source of stem cells in the generation of nerves. Besides, it is known that hypoxia conditioning is capable of stimulating cell differentiation as well as survival and self-renewal, and that multiple growth factors, including Epidermal Growth factor (EGF) and basic fibroblast growth factor (bFGF), are often involved in the induction of the neuronal differentiation of progenitor cells. In this work, we investigated the role of hypoxia in the commitment of DPSCs into a neuronal phenotype. These cells were conditioned with hypoxia (O₂ 1%) for 5 and 16 days; subsequently, we analyzed the proliferation rate and morphology, and tested the cells for neural and stem markers. Moreover, we verified the possible autocrine/paracrine role of DPSCs in the induction of neural differentiation by comparing the secretome profile of the hypoxic and normoxic conditioned media (CM). Our results showed that the hypoxia-mediated DPSC differentiation was time dependent. Moreover, conditioned media (CM derived from DPSCs stimulated by hypoxia were able, in turn, to induce the neural differentiation of SH-SY5Y neuroblastoma cells and undifferentiated DPSCs. In conclusion, under the herein-mentioned conditions, hypoxia seems to favor the differentiation of DPSCs into neuron-like cells. In this way, we confirm the potential clinical utility of differentiated neuronal DPSCs, and we also suggest the even greater potential of CM-derived-hypoxic DPSCs that could more readily be used in regenerative therapies.