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5 pages, 207 KiB

Open AccessEditorial

Cellular and Molecular Mechanisms Underlying Pain Chronicity

by Manuela Simonetti and Daniela Mauceri

Cells 2023, 12(8), 1126; https://doi.org/10.3390/cells12081126 - 11 Apr 2023

Viewed by 1426

Abstract

Chronic pain affects a significant amount of the population and is responsible for vast worldwide socio-economic costs [...] Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

Research

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19 pages, 13047 KiB

Open AccessArticle

Quanty-cFOS, a Novel ImageJ/Fiji Algorithm for Automated Counting of Immunoreactive Cells in Tissue Sections

by Carlo Antonio Beretta, Sheng Liu, Alina Stegemann, Zheng Gan, Lirong Wang, Linette Liqi Tan and Rohini Kuner

Cells 2023, 12(5), 704; https://doi.org/10.3390/cells12050704 - 23 Feb 2023

Cited by 2 | Viewed by 4718

Abstract

Analysis of neural encoding and plasticity processes frequently relies on studying spatial patterns of activity-induced immediate early genes’ expression, such as c-fos. Quantitatively analyzing the numbers of cells expressing the Fos protein or c-fos mRNA is a major challenge owing to large [...] Read more.

Analysis of neural encoding and plasticity processes frequently relies on studying spatial patterns of activity-induced immediate early genes’ expression, such as c-fos. Quantitatively analyzing the numbers of cells expressing the Fos protein or c-fos mRNA is a major challenge owing to large human bias, subjectivity and variability in baseline and activity-induced expression. Here, we describe a novel open-source ImageJ/Fiji tool, called ‘Quanty-cFOS’, with an easy-to-use, streamlined pipeline for the automated or semi-automated counting of cells positive for the Fos protein and/or c-fos mRNA on images derived from tissue sections. The algorithms compute the intensity cutoff for positive cells on a user-specified number of images and apply this on all the images to process. This allows for the overcoming of variations in the data and the deriving of cell counts registered to specific brain areas in a highly time-efficient and reliable manner. We validated the tool using data from brain sections in response to somatosensory stimuli in a user-interactive manner. Here, we demonstrate the application of the tool in a step-by-step manner, with video tutorials, making it easy for novice users to implement. Quanty-cFOS facilitates a rapid, accurate and unbiased spatial mapping of neural activity and can also be easily extended to count other types of labelled cells. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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28 pages, 9483 KiB

Open AccessArticle

Activation of β2-Adrenergic Receptors in Microglia Alleviates Neuropathic Hypersensitivity in Mice

by Elisa Damo, Amit Agarwal and Manuela Simonetti

Cells 2023, 12(2), 284; https://doi.org/10.3390/cells12020284 - 11 Jan 2023

Cited by 6 | Viewed by 2617

Abstract

Drugs enhancing the availability of noradrenaline are gaining prominence in the therapy of chronic neuropathic pain. However, underlying mechanisms are not well understood, and research has thus far focused on α2-adrenergic receptors and neuronal excitability. Adrenergic receptors are also expressed on glial cells, [...] Read more.

Drugs enhancing the availability of noradrenaline are gaining prominence in the therapy of chronic neuropathic pain. However, underlying mechanisms are not well understood, and research has thus far focused on α2-adrenergic receptors and neuronal excitability. Adrenergic receptors are also expressed on glial cells, but their roles toward antinociception are not well deciphered. This study addresses the contribution of β2-adrenergic receptors (β2-ARs) to the therapeutic modulation of neuropathic pain in mice. We report that selective activation of β2-ARs with Formoterol inhibits pro-inflammatory signaling in microglia ex vivo and nerve injury-induced structural remodeling and functional activation of microglia in vivo. Systemic delivery of Formoterol inhibits behaviors related to neuropathic pain, such as mechanical hypersensitivity, cold allodynia as well as the aversive component of pain, and reverses chronically established neuropathic pain. Using conditional gene targeting for microglia-specific deletion of β2-ARs, we demonstrate that the anti-allodynic effects of Formoterol are primarily mediated by microglia. Although Formoterol also reduces astrogliosis at late stages of neuropathic pain, these functions are unrelated to β2-AR signaling in microglia. Our results underline the value of developing microglial β2-AR agonists for relief from neuropathic pain and clarify mechanistic underpinnings. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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18 pages, 17969 KiB

Open AccessFeature PaperArticle

Prolonged Suppression of Neuropathic Hypersensitivity upon Neurostimulation of the Posterior Insula in Mice

by Han Li, Zheng Gan, Lirong Wang, Manfred Josef Oswald and Rohini Kuner

Cells 2022, 11(20), 3303; https://doi.org/10.3390/cells11203303 - 20 Oct 2022

Cited by 3 | Viewed by 1695

Abstract

Neurostimulation-based therapeutic approaches are emerging as alternatives to pharmacological drugs, but need further development to optimize efficacy and reduce variability. Despite its key relevance to pain, the insular cortex has not been explored in cortical neurostimulation approaches. Here, we developed an approach to [...] Read more.

Neurostimulation-based therapeutic approaches are emerging as alternatives to pharmacological drugs, but need further development to optimize efficacy and reduce variability. Despite its key relevance to pain, the insular cortex has not been explored in cortical neurostimulation approaches. Here, we developed an approach to perform repetitive transcranial direct current stimulation of the posterior insula (PI tDCS) and studied its impact on sensory and aversive components of neuropathic pain and pain-related anxiety and the underlying neural circuitry in mice using behavioral methods, pharmacological interventions and the expression of the activity-induced gene product, Fos. We observed that repetitive PI tDCS strongly attenuates the development of neuropathic mechanical allodynia and also reverses chronically established mechanical and cold allodynia for several weeks post-treatment by employing descending opioidergic antinociceptive pathways. Pain-related anxiety, but not pain-related aversion, were inhibited by PI tDCS. These effects were associated with a long-term suppression in the activity of key areas involved in pain modulation, such as the cingulate, prefrontal and motor cortices. These data uncover the significant potential of targeting the insular cortex with the objective of pain relief and open the way for more detailed mechanistic analyses that will contribute to improving cortical neurostimulation therapies for use in the clinical management of pain. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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27 pages, 3490 KiB

Open AccessArticle

Human Stem Cell-Derived TRPV1-Positive Sensory Neurons: A New Tool to Study Mechanisms of Sensitization

by Katrin Schrenk-Siemens, Jörg Pohle, Charlotte Rostock, Muad Abd El Hay, Ruby M. Lam, Marcin Szczot, Shiying Lu, Alexander T. Chesler and Jan Siemens

Cells 2022, 11(18), 2905; https://doi.org/10.3390/cells11182905 - 17 Sep 2022

Cited by 5 | Viewed by 3039

Abstract

Somatosensation, the detection and transduction of external and internal stimuli such as temperature or mechanical force, is vital to sustaining our bodily integrity. But still, some of the mechanisms of distinct stimuli detection and transduction are not entirely understood, especially when noxious perception [...] Read more.

Somatosensation, the detection and transduction of external and internal stimuli such as temperature or mechanical force, is vital to sustaining our bodily integrity. But still, some of the mechanisms of distinct stimuli detection and transduction are not entirely understood, especially when noxious perception turns into chronic pain. Over the past decade major progress has increased our understanding in areas such as mechanotransduction or sensory neuron classification. However, it is in particular the access to human pluripotent stem cells and the possibility of generating and studying human sensory neurons that has enriched the somatosensory research field. Based on our previous work, we describe here the generation of human stem cell-derived nociceptor-like cells. We show that by varying the differentiation strategy, we can produce different nociceptive subpopulations with different responsiveness to nociceptive stimuli such as capsaicin. Functional as well as deep sequencing analysis demonstrated that one protocol in particular allowed the generation of a mechano-nociceptive sensory neuron population, homogeneously expressing TRPV1. Accordingly, we find the cells to homogenously respond to capsaicin, to become sensitized upon inflammatory stimuli, and to respond to temperature stimulation. The efficient and homogenous generation of these neurons make them an ideal translational tool to study mechanisms of sensitization, also in the context of chronic pain. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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17 pages, 4040 KiB

Open AccessFeature PaperArticle

Genetic Mouse Models to Study Pancreatic Cancer-Induced Pain and Reduction in Well-Being

by Michael Hirth, Yong Xie, Christiane Höper, Amandine Prats, Thilo Hackert, Matthias P. Ebert and Rohini Kuner

Cells 2022, 11(17), 2634; https://doi.org/10.3390/cells11172634 - 24 Aug 2022

Cited by 4 | Viewed by 3058

Abstract

In addition to the poor prognosis, excruciating abdominal pain is a major challenge in pancreatic cancer. Neurotropism appears to be the underlying mechanism leading to neuronal invasion. However, there is a lack of animal models suitable for translationally bridging in vitro findings with [...] Read more.

In addition to the poor prognosis, excruciating abdominal pain is a major challenge in pancreatic cancer. Neurotropism appears to be the underlying mechanism leading to neuronal invasion. However, there is a lack of animal models suitable for translationally bridging in vitro findings with clinical trials. We characterized KPC (Kras^G12D/+; Trp53^R172H/+; P48-Cre) and KPPC (Kras^G12D/+; Trp53^R172H/R172H; P48-Cre) mice with genetically determined pancreatic ductal adenocarcinoma (PDAC) and compared them with an orthotopic pancreatic cancer mouse model, healthy littermates and human tissue. We analyzed behavioral correlates of cancer-associated pain and well-being, and studied neuronal remodeling and cytokine expression. Histologically, we found similarities between KPC and KPPC tissue with human samples. Compared to healthy littermates, we detect nerve fiber hypertrophy, which was not restricted to a certain fiber type. Interestingly, while KPPC mice showed significantly reduced well-being, KPC mice emerged to be better suited for studying long-lasting cancer pain that emerges over a slow course of tumor progression. To address the neuroinflammatory correlate of loss of well-being, we studied cytokine levels in KPPC mice and observed a significant upregulation of CXCL16, TNFRSF5, CCL24, CXCL1, CCL22, CLL20 and CX2CL1. In summary, we demonstrate that the KPC mouse model is best suited to studying cancer pain, whereas the KPPC model can be employed to study cancer-associated reduction in well-being. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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26 pages, 4207 KiB

Open AccessArticle

Pre-Synaptic GABA_A in NaV1.8⁺ Primary Afferents Is Required for the Development of Punctate but Not Dynamic Mechanical Allodynia following CFA Inflammation

by Sheng Liu, Veronica Bonalume, Qi Gao, Jeremy Tsung-Chieh Chen, Karl Rohr, Jing Hu and Richard Carr

Cells 2022, 11(15), 2390; https://doi.org/10.3390/cells11152390 - 03 Aug 2022

Cited by 1 | Viewed by 2517

Abstract

Hypersensitivity to mechanical stimuli is a cardinal symptom of neuropathic and inflammatory pain. A reduction in spinal inhibition is generally considered a causal factor in the development of mechanical hypersensitivity after injury. However, the extent to which presynaptic inhibition contributes to altered spinal [...] Read more.

Hypersensitivity to mechanical stimuli is a cardinal symptom of neuropathic and inflammatory pain. A reduction in spinal inhibition is generally considered a causal factor in the development of mechanical hypersensitivity after injury. However, the extent to which presynaptic inhibition contributes to altered spinal inhibition is less well established. Here, we used conditional deletion of GABA_A in NaV1.8-positive sensory neurons (Scn10a^Cre;Gabrb3^fl/fl) to manipulate selectively presynaptic GABAergic inhibition. Behavioral testing showed that the development of inflammatory punctate allodynia was mitigated in mice lacking pre-synaptic GABA_A. Dorsal horn cellular circuits were visualized in single slices using stimulus-tractable dual-labelling of c-fos mRNA for punctate and the cognate c-Fos protein for dynamic mechanical stimulation. This revealed a substantial reduction in the number of cells activated by punctate stimulation in mice lacking presynaptic GABA_A and an approximate 50% overlap of the punctate with the dynamic circuit, the relative percentage of which did not change following inflammation. The reduction in dorsal horn cells activated by punctate stimuli was equally prevalent in parvalbumin- and calretinin-positive cells and across all laminae I–V, indicating a generalized reduction in spinal input. In peripheral DRG neurons, inflammation following complete Freund’s adjuvant (CFA) led to an increase in axonal excitability responses to GABA, suggesting that presynaptic GABA effects in NaV1.8⁺ afferents switch from inhibition to excitation after CFA. In the days after inflammation, presynaptic GABA_A in NaV1.8⁺ nociceptors constitutes an “open gate” pathway allowing mechanoreceptors responding to punctate mechanical stimulation access to nociceptive dorsal horn circuits. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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21 pages, 6236 KiB

Open AccessArticle

Dysregulation of Immune Response Mediators and Pain-Related Ion Channels Is Associated with Pain-like Behavior in the GLA KO Mouse Model of Fabry Disease

by Marlene Spitzel, Elise Wagner, Maximilian Breyer, Dorothea Henniger, Mehtap Bayin, Lukas Hofmann, Daniela Mauceri, Claudia Sommer and Nurcan Üçeyler

Cells 2022, 11(11), 1730; https://doi.org/10.3390/cells11111730 - 24 May 2022

Cited by 8 | Viewed by 2840

Abstract

Fabry disease (FD) is a rare life-threatening disorder caused by deficiency of the alpha-galactosidase A (GLA) enzyme with a characteristic pain phenotype. Impaired GLA production or function leads to the accumulation of the cell membrane compound globotriaosylceramide (Gb3) in the neurons of the [...] Read more.

Fabry disease (FD) is a rare life-threatening disorder caused by deficiency of the alpha-galactosidase A (GLA) enzyme with a characteristic pain phenotype. Impaired GLA production or function leads to the accumulation of the cell membrane compound globotriaosylceramide (Gb3) in the neurons of the dorsal root ganglia (DRG) of FD patients. Applying immunohistochemistry (IHC) and quantitative real-time polymerase chain reaction (qRT PCR) analysis on DRG tissue of the GLA knockout (KO) mouse model of FD, we address the question of how Gb3 accumulation may contribute to FD pain and focus on the immune system and pain-associated ion channel gene expression. We show a higher Gb3 load in the DRG of young (<6 months) (p < 0.01) and old (≥12 months) (p < 0.001) GLA KO mice compared to old wildtype (WT) littermates, and an overall suppressed immune response in the DRG of old GLA KO mice, represented by a reduced number of CD206⁺ macrophages (p < 0.01) and lower gene expression levels of the inflammation-associated targets interleukin(IL)1b (p < 0.05), IL10 (p < 0.001), glial fibrillary acidic protein (GFAP) (p < 0.05), and leucine rich alpha-2-glycoprotein 1 (LRG1) (p < 0.01) in the DRG of old GLA KO mice compared to old WT. Dysregulation of immune-related genes may be linked to lower gene expression levels of the pain-associated ion channels calcium-activated potassium channel 3.1 (KCa3.1) and transient receptor potential ankyrin 1 channel (TRPA1). Ion channel expression might further be disturbed by impaired sphingolipid recruitment mediated via the lipid raft marker flotillin-1 (FLOT1). This impairment is represented by an increased number of FLOT1⁺ DRG neurons with a membranous expression pattern in old GLA KO mice compared to young GLA KO, young WT, and old WT mice (p < 0.001 each). Further, we provide evidence for aberrant behavior of GLA KO mice, which might be linked to dysregulated ion channel gene expression levels and disturbed FLOT1 distribution patterns. Behavioral testing revealed mechanical hypersensitivity in young (p < 0.01) and old (p < 0.001) GLA KO mice compared to WT, heat hypersensitivity in young GLA KO mice (p < 0.001) compared to WT, age-dependent heat hyposensitivity in old GLA KO mice (p < 0.001) compared to young GLA KO mice, and cold hyposensitivity in young (p < 0.001) and old (p < 0.001) GLA KO mice compared to WT, which well reflects the clinical phenotype observed in FD patients. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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Review

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22 pages, 2712 KiB

Open AccessReview

Role of SUMOylation in Neurodegenerative Diseases

by Nicolas Mandel and Nitin Agarwal

Cells 2022, 11(21), 3395; https://doi.org/10.3390/cells11213395 - 27 Oct 2022

Cited by 10 | Viewed by 3697

Abstract

Neurodegenerative diseases (NDDs) are irreversible, progressive diseases with no effective treatment. The hallmark of NDDs is the aggregation of misfolded, modified proteins, which impair neuronal vulnerability and cause brain damage. The loss of synaptic connection and the progressive loss of neurons result in [...] Read more.

Neurodegenerative diseases (NDDs) are irreversible, progressive diseases with no effective treatment. The hallmark of NDDs is the aggregation of misfolded, modified proteins, which impair neuronal vulnerability and cause brain damage. The loss of synaptic connection and the progressive loss of neurons result in cognitive defects. Several dysregulated proteins and overlapping molecular mechanisms contribute to the pathophysiology of NDDs. Post-translational modifications (PTMs) are essential regulators of protein function, trafficking, and maintaining neuronal hemostasis. The conjugation of a small ubiquitin-like modifier (SUMO) is a reversible, dynamic PTM required for synaptic and cognitive function. The onset and progression of neurodegenerative diseases are associated with aberrant SUMOylation. In this review, we have summarized the role of SUMOylation in regulating critical proteins involved in the onset and progression of several NDDs. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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30 pages, 1700 KiB

Open AccessReview

Axon Guidance Molecules and Pain

by Elisa Damo and Manuela Simonetti

Cells 2022, 11(19), 3143; https://doi.org/10.3390/cells11193143 - 06 Oct 2022

Cited by 10 | Viewed by 3005

Abstract

Chronic pain is a debilitating condition that influences the social, economic, and psychological aspects of patients’ lives. Hence, the need for better treatment is drawing extensive interest from the research community. Developmental molecules such as Wnt, ephrins, and semaphorins are acknowledged as central [...] Read more.

Chronic pain is a debilitating condition that influences the social, economic, and psychological aspects of patients’ lives. Hence, the need for better treatment is drawing extensive interest from the research community. Developmental molecules such as Wnt, ephrins, and semaphorins are acknowledged as central players in the proper growth of a biological system. Their receptors and ligands are expressed in a wide variety in both neurons and glial cells, which are implicated in pain development, maintenance, and resolution. Thereby, it is not surprising that the impairment of those pathways affects the activities and functions of the entire cell. Evidence indicates aberrant activation of their pathways in the nervous system in rodent models of chronic pain. In those conditions, Wnt, ephrin, and semaphorin signaling participate in enhancing neuronal excitability, peripheral sensitization, synaptic plasticity, and the production and release of inflammatory cytokines. This review summarizes the current knowledge on three main developmental pathways and their mechanisms linked with the pathogenesis and progression of pain, considering their impacts on neuronal and glial cells in experimental animal models. Elucidations of the downstream pathways may provide a new mechanism for the involvement of Wnt, ephrin, and semaphorin pathways in pain chronicity. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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30 pages, 5202 KiB

Open AccessFeature PaperReview

The Impact of Activity-Based Interventions on Neuropathic Pain in Experimental Spinal Cord Injury

by Jing Chen, Norbert Weidner and Radhika Puttagunta

Cells 2022, 11(19), 3087; https://doi.org/10.3390/cells11193087 - 30 Sep 2022

Cited by 7 | Viewed by 2097

Abstract

Physical activity-based rehabilitative interventions represent the main treatment concept for people suffering from spinal cord injury (SCI). The role such interventions play in the relief of neuropathic pain (NP) states is emerging, along with underlying mechanisms resulting in SCI-induced NP (SCI-NP). Animal models [...] Read more.

Physical activity-based rehabilitative interventions represent the main treatment concept for people suffering from spinal cord injury (SCI). The role such interventions play in the relief of neuropathic pain (NP) states is emerging, along with underlying mechanisms resulting in SCI-induced NP (SCI-NP). Animal models have been used to investigate the benefits of activity-based interventions (ABI), such as treadmill training, wheel running, walking, swimming, and bipedal standing. These activity-based paradigms have been shown to modulate inflammatory-related alterations as well as induce functional and structural changes in the spinal cord gray matter circuitry correlated with pain behaviors. Thus far, the research available provides an incomplete picture of the cellular and molecular pathways involved in this beneficial effect. Continued research is essential for understanding how such interventions benefit SCI patients suffering from NP and allow the development of individualized rehabilitative therapies. This article reviews preclinical studies on this specific topic, goes over mechanisms involved in SCI-NP in relation to ABI, and then discusses the effectiveness of different activity-based paradigms as they relate to different forms, intensity, initiation times, and duration of ABI. This article also summarizes the mechanisms of respective interventions to ameliorate NP after SCI and provides suggestions for future research directions. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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16 pages, 1570 KiB

Open AccessReview

Role of Epigenetic Mechanisms in Chronic Pain

by Daniela Mauceri

Cells 2022, 11(16), 2613; https://doi.org/10.3390/cells11162613 - 22 Aug 2022

Cited by 13 | Viewed by 3446

Abstract

Pain is an unpleasant but essential-to-life sensation, usually resulting from tissue damage. When pain persists long after the injury has resolved, it becomes pathological. The precise molecular and cellular mechanisms causing the transition from acute to chronic pain are not fully understood. A [...] Read more.

Pain is an unpleasant but essential-to-life sensation, usually resulting from tissue damage. When pain persists long after the injury has resolved, it becomes pathological. The precise molecular and cellular mechanisms causing the transition from acute to chronic pain are not fully understood. A key aspect of pain chronicity is that several plasticity events happen along the neural pathways involved in pain. These long-lasting adaptive changes are enabled by alteration in the expression of relevant genes. Among the different modulators of gene transcription in adaptive processes in the nervous system, epigenetic mechanisms play a pivotal role. In this review, I will first outline the main classes of epigenetic mediators and then discuss their implications in chronic pain. Full article

(This article belongs to the Special Issue Cellular and Molecular Mechanisms Underlying Pain Chronicity)

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