Search Results (201)

CXCL12 and CXCR4 proteins and mRNAs were monitored in the dorsal root ganglia (DRGs) of lumbar (L4–L5) and cervical (C7–C8) spinal segments of naïve rats, rats subjected to sham operation, and those undergoing unilateral complete sciatic nerve transection (CSNT) on post-operation day 7 (POD7). Immunohistochemical, Western blot, and RT-PCR analyses revealed bilaterally increased levels of CXCR4 protein and mRNA in both lumbar and cervical DRG neurons after CSNT. Similarly, CXCL12 protein levels increased, and CXCL12 mRNA was upregulated primarily in lumbar DRGs ipsilateral to the nerve lesion. Intrathecal application of the CXCR4 inhibitor AMD3100 following CSNT reduced CXCL12 and CXCR4 protein levels in cervical DRG neurons, as well as the length of afferent axons regenerated distal to the ulnar nerve crush. Furthermore, treatment with the CXCR4 inhibitor decreased levels of activated Signal Transducer and Activator of Transcription 3 (STAT3), a critical transforming factor in the neuronal regeneration program. Administration of IL-6 increased CXCR4 levels, whereas the JAK2-dependent STAT3 phosphorylation inhibitor (AG490) conversely decreased CXCR4 levels. This indicates a link between the CXCL12/CXCR4 signaling axis and IL-6-induced activation of STAT3 in the sciatic nerve injury-induced pro-regenerative state of cervical DRG neurons. The role of CXCR4 signaling in the axon-promoting state of DRG neurons was confirmed through in vitro cultivation of primary sensory neurons in a medium supplemented with CXCL12, with or without AMD3100. The potential involvement of conditioned cervical DRG neurons in the induction of neuropathic pain is discussed. Full article

Acupuncturing the ST36 acupoint can evoke a responding activity in the spinal dorsal root ganglia and generate spikes. In order to identify the responding mechanism of different acupuncture manipulations, in this paper the spike history of neurons is taken as the starting point and the coupling generalized linear model is adopted to encode the neuronal spiking activity evoked by different acupuncture manipulations. Then, maximum likelihood estimation is used to fit the model parameters and estimate the coupling parameters of stimulus, the self-coupling parameters of the neuron’s own spike history and the cross-coupling parameters of other neurons’ spike history. We use simulation data to test the estimation algorithm’s effectiveness and analyze the main factors that evoke neuronal responding activity. Finally, we use the coupling generalized linear model to encode neuronal spiking activity evoked by two acupuncture manipulations, and estimate the coupling parameters of stimulus, the self-coupling parameters and the cross-coupling parameters. The results show that in acupuncture experiments, acupuncture stimulus is the inducing factor of neuronal spiking activity, and the cross-coupling of other neurons’ spike history is the main factor of neuronal spiking activity. Additionally, the higher the amplitude of the neuronal spiking waveform, the greater the cross-coupling parameter. This lays a theoretical foundation for the scientific application of acupuncture therapy. Full article

Background: The biologics derived from human amniotic membranes (AMs) demonstrate potential pain-inhibitory effects in clinical settings. However, the molecular basis underlying this therapeutic effect remains elusive. HC-HA/PTX3 is a unique water-soluble regenerative matrix that is purified from human AMs. We examined whether HC-HA/PTX3 can modulate the gene networks and transcriptional signatures in the dorsal root ganglia (DRG) neurons transmitting peripheral sensory inputs to the spinal cord. Methods: We conducted bulk RNA-sequencing (RNA-seq) of mouse DRG neurons after treating them with HC-HA/PTX3 (15 µg/mL) for 10 min and 24 h in culture. Differential gene expression analysis was performed using the limma package, and Gene Ontology (GO) and protein–protein interaction (PPI) analyses were conducted to identify the networks of pain-related genes. Western blotting and in vitro calcium imaging were used to examine the protein levels and signaling of pro-opiomelanocortin (POMC) in DRG neurons. Results: Compared to the vehicle-treated group, 24 h treatment with HC-HA/PTX3 induced 2047 differentially expressed genes (DEGs), which were centered on the ATPase activity, receptor–ligand activity, and extracellular matrix pathways. Importantly, PPI analysis revealed that over 50 of these DEGs are closely related to pain and analgesia. Notably, HC-HA/PTX3 increased the expression and signaling pathway of POMC, which may affect opioid analgesia. Conclusions: HC-HA/PTX3 induced profound changes in the gene expression in DRG neurons, centered around various neurochemical mechanisms associated with pain modulation. Our findings suggest that HC-HA/PTX3 may be an important biological active component in human AMs that partly underlies its pain inhibitory effect, presenting a new strategy for pain treatment. Full article

Memory impairment is caused by the absence of the 4E-BP2 protein in the brain. This protein undergoes deamidation spontaneously in the neurons. 4E-BP2 deamidation significantly alters protein synthesis in the neurons and affects the balance of protein production required for a healthy nervous system. Any imbalance in protein production in the nervous system causes neurodegenerative diseases. Discovering what causes 4E-BP2 deamidation will make it possible to control this balance of protein production and develop effective treatments against neurodegenerative diseases such as Alzheimer’s and Parkinson’s. The purpose of this work is to discover the neurobiological mechanism that causes the deamidation reaction in the 4E-BP2 protein by performing immunoblotting in the retinal ganglia, the optic nerve, the dorsal root ganglia, the sciatic nerve, and the whole brain, extracted via dissection from 2-month-old, Wild-type male mice. The results show that axons and their unique properties cause neuron-specific 4E-BP2 deamidation in the nervous system, confirming conclusively that axons are the critical factors behind the fundamental neurobiological mechanism of 4E-BP2 protein deamidation. Full article

Parkinson’s disease (PD) is the second-most common neurodegenerative disease worldwide. Patients are diagnosed based upon movement disorders, including bradykinesia, tremor and stiffness of movement. However, non-motor signs, including constipation, rapid eye movement sleep behavior disorder, smell deficits and pain are well recognized. Peripheral neuropathy is also increasingly recognized, as the vast majority of patients show reduced intraepidermal nerve fibers, and sensory nerve conduction and sensory function is also impaired. Many case studies in the literature show that high-dose levodopa may induce or exacerbate neuropathy in PD, which is thought to involve levodopa’s metabolism to homocysteine. Here, we treated primary cultures of dorsal root ganglia and a sensory neuronal cell line with levodopa to examine effects on cell morphology, mitochondrial content and physiology, and lysosomal function. High-dose levodopa reduced mitochondrial membrane potential. At concentrations observed in the patient, levodopa enhanced immunoreactivity to beta III tubulin. Critically, levodopa reduced lysosomal content and also reduced the proportion of lysosomes that were acidic, thereby impairing their function, whereas homocysteine tended to increase lysosome content. Levodopa is a critically important drug for the treatment of PD. However, our data suggest that at concentrations observed in the patient, it has deleterious effects on sensory neurons that are not related to homocysteine. Full article

Neuropathic pain is a prevalent and debilitating chronic syndrome that is often resistant to treatment. It frequently arises as a consequence of damage to first-order nociceptive neurons in the lumbar dorsal root ganglia (DRG), with chromatolysis being the primary neuropathological response following sciatic nerve injury (SNI). Nevertheless, the function of miRNAs in modulating this chromatolytic response in the context of neuropathic pain remains unexplored. Our previous research demonstrated that the intracisternal administration of a miR-30c mimic accelerates the development of neuropathic pain, whereas the inhibition of miR-30c prevents pain onset and reverses established allodynia. In the present study, we sought to elucidate the role of miR-30c-5p in the pathogenesis of neuropathic pain, with a particular focus on its impact on DRG neurons following SNI. The organisation and ultrastructural changes in DRG neurons, particularly in the protein synthesis machinery, nucleolus, and Cajal bodies (CBs), were analysed. The results demonstrated that the administration of a miR-30c-5p mimic exacerbates chromatolytic damage and nucleolar stress and induces CB depletion in DRG neurons following SNI, whereas the administration of a miR-30c-5p inhibitor alleviates these effects. We proposed that three essential cellular responses—nucleolar stress, CB depletion, and chromatolysis—are the pathological mechanisms in stressed DRG neurons underlying neuropathic pain. Moreover, miR-30c-5p inhibition has a neuroprotective effect by reducing the stress response in DRG neurons, which supports its potential as a therapeutic target for neuropathic pain management. This study emphasises the importance of miR-30c-5p in neuropathic pain pathogenesis and supports further exploration of miRNA-based treatments. Full article

Within the phylum Cnidaria, sea anemones (class Anthozoa) express a rich diversity of ion-channel peptide modulators with biomedical applications, but corollary discoveries from jellyfish (subphylum Medusozoa) are lacking. To bridge this gap, bioactivities of previously unexplored proteinaceous and small molecular weight (~15 kDa to 5 kDa) venom components were assessed in a mouse dorsal root ganglia (DRG) high-content calcium-imaging assay, known as constellation pharmacology. While the addition of crude venom led to nonspecific cell death and Fura-2 signal leakage due to pore-forming activity, purified small molecular weight fractions of venom demonstrated three main, concentration-dependent and reversible effects on defined heterogeneous cell types found in the primary cultures of mouse DRG. These three phenotypic responses are herein referred to as phenotype A, B and C: excitatory amplification (A) or inhibition (B) of KCl-induced calcium signals, and test compound-induced disturbances to baseline calcium levels (C). Most notably, certain Alatina alata venom fractions showed phenotype A effects in all DRG neurons; Physalia physalis and Chironex fleckeri fractions predominantly showed phenotype B effects in small- and medium-diameter neurons. Finally, specific Physalia physalis and Alatina alata venom components induced direct excitatory responses (phenotype C) in glial cells. These findings demonstrate a diversity of neuroactive compounds in jellyfish venom potentially targeting a constellation of ion channels and ligand-gated receptors with broad physiological implications. Full article

Background/Objectives: Cisplatin, a common chemotherapy agent, is well known to cause severe side effects in the gastrointestinal and nervous systems due to its toxic and pro-inflammatory effects. Although pharmacological manipulation of the endocannabinoid system (ECS) can alleviate these side effects, how chemotherapy affects the ECS components in these systems remains poorly understood. Our aim was to evaluate these changes. Methods: Male Wistar rats received cisplatin (5 mg/kg, i.p.) or saline on day 0 (D0). Immediately after, serial X-rays were taken for 24 h (D0). Body weight was recorded (D0, D1, D2 and D7) and behavioural tests were performed on D4. On D7, animals were euthanized, and gastrointestinal tissue, dorsal root ganglia (DRGs) and brain areas were collected. Expression of genes related to the ECS was assessed via Rt-PCR, while LC-MS/MS was used to analyse endocannabinoid and related N-acylethanolamine levels in tissue and plasma. Results: Animals treated with cisplatin showed a reduction in body weight. Cisplatin reduced gastric emptying during D0 and decreased MAGL gene expression in the antrum at D7. Despite cisplatin not causing mechanical or heat sensitivity, we observed ECS alterations in the prefrontal cortex (PFC) and DRGs similar to those seen in other chronic pain conditions, including an increased CB₁ gene expression in L4/L5 DRGs and a decreased MAGL expression in PFC. Conclusions: A single dose of cisplatin (5 mg/kg, i.p.), subnoxious, but capable of inducing acute gastrointestinal effects, caused ECS changes in both gastrointestinal and nervous systems. Modulating the ECS could alleviate or potentially prevent chemotherapy-induced toxicity. Full article

Traumatic spinal cord injury (tSCI) has complex pathophysiological events that begin after the initial trauma. One such event is fibroglial scar formation by fibroblasts and reactive astrocytes. A strong inhibition of axonal growth is caused by the activated astroglial cells as a component of fibroglial scarring through the production of inhibitory molecules, such as chondroitin sulfate proteoglycans or myelin-associated proteins. Here, we used neural precursor cells (aldynoglia) as promoters of axonal growth and a fibrin hydrogel gelled under alkaline conditions to support and guide neuronal cell growth, respectively. We added Tol-51 sulfoglycolipid as a synthetic inhibitor of astrocyte and microglia in order to test its effect on the axonal growth-promoting function of aldynoglia precursor cells. We obtained an increase in GFAP expression corresponding to the expected glial phenotype for aldynoglia cells cultured in alkaline fibrin. In co-cultures of dorsal root ganglia (DRG) and aldynoglia, the axonal growth promotion of DRG neurons by aldynoglia was not affected. We observed that the neural precursor cells first clustered together and then formed niches from which aldynoglia cells grew and connected to groups of adjacent cells. We conclude that the combination of alkaline fibrin with synthetic sulfoglycolipid Tol-51 increased cell adhesion, cell migration, fasciculation, and axonal growth capacity, promoted by aldynoglia cells. There was no negative effect on the behavior of aldynoglia cells after the addition of sulfoglycolipid Tol-51, suggesting that a combination of aldynoglia plus alkaline fibrin and Tol-51 compound could be useful as a therapeutic strategy for tSCI repair. Full article

Individuals suffering from diabetic polyneuropathy (DPN) experience debilitating symptoms such as pain, paranesthesia, and sensory disturbances, prompting a quest for effective treatments. Dipeptidyl-peptidase (DPP)-4 inhibitors, recognized for their potential in ameliorating DPN, have sparked interest, yet the precise mechanism underlying their neurotrophic impact on the peripheral nerve system (PNS) remains elusive. Our study delves into the neurotrophic effects of DPP-4 inhibitors, including Diprotin A, linagliptin, and sitagliptin, alongside pituitary adenylate cyclase-activating polypeptide (PACAP), Neuropeptide Y (NPY), and Stromal cell-derived factor (SDF)-1a—known DPP-4 substrates with neurotrophic properties. Utilizing primary culture dorsal root ganglia (DRG) neurons, we meticulously evaluated neurite outgrowth in response to these agents. Remarkably, all DPP-4 inhibitors and PACAP demonstrated a significant elongation of neurite length in DRG neurons (PACAP 0.1 μM: 2221 ± 466 μm, control: 1379 ± 420, p < 0.0001), underscoring their potential in nerve regeneration. Conversely, NPY and SDF-1a failed to induce neurite elongation, accentuating the unique neurotrophic properties of DPP-4 inhibition and PACAP. Our findings suggest that the upregulation of PACAP, facilitated by DPP-4 inhibition, plays a pivotal role in promoting neurite elongation within the PNS, presenting a promising avenue for the development of novel DPN therapies with enhanced neurodegenerative capabilities. Full article

Neurological symptoms associated with COVID-19, acute and long term, suggest SARS-CoV-2 affects both the peripheral and central nervous systems (PNS/CNS). Although studies have shown olfactory and hematogenous invasion into the CNS, coinciding with neuroinflammation, little attention has been paid to susceptibility of the PNS to infection or to its contribution to CNS invasion. Here we show that sensory and autonomic neurons in the PNS are susceptible to productive infection with SARS-CoV-2 and outline physiological and molecular mechanisms mediating neuroinvasion. Our infection of K18-hACE2 mice, wild-type mice, and golden Syrian hamsters, as well as primary peripheral sensory and autonomic neuronal cultures, show viral RNA, proteins, and infectious virus in PNS neurons, satellite glial cells, and functionally connected CNS tissues. Additionally, we demonstrate, in vitro, that neuropilin-1 facilitates SARS-CoV-2 neuronal entry. SARS-CoV-2 rapidly invades the PNS prior to viremia, establishes a productive infection in peripheral neurons, and results in sensory symptoms often reported by COVID-19 patients. Full article

Lysophosphatidic acids (LPAs) evoke nociception and itch in mice and humans. In this study, we assessed the signaling paths. Hydroxychloroquine was injected intradermally to evoke itch in mice, which evoked an increase of LPAs in the skin and in the thalamus, suggesting that peripheral and central LPA receptors (LPARs) were involved in HCQ-evoked pruriception. To unravel the signaling paths, we assessed the localization of candidate genes and itching behavior in knockout models addressing LPAR5, LPAR2, autotaxin/ENPP2 and the lysophospholipid phosphatases, as well as the plasticity-related genes Prg1/LPPR4 and Prg2/LPPR3. LacZ reporter studies and RNAscope revealed LPAR5 in neurons of the dorsal root ganglia (DRGs) and in skin keratinocytes, LPAR2 in cortical and thalamic neurons, and Prg1 in neuronal structures of the dorsal horn, thalamus and SSC. HCQ-evoked scratching behavior was reduced in sensory neuron-specific Advillin-LPAR5^−/− mice (peripheral) but increased in LPAR2^−/− and Prg1^−/− mice (central), and it was not affected by deficiency of glial autotaxin (GFAP-ENPP2^−/−) or Prg2 (PRG2^−/−). Heat and mechanical nociception were not affected by any of the genotypes. The behavior suggested that HCQ-mediated itch involves the activation of peripheral LPAR5, which was supported by reduced itch upon treatment with an LPAR5 antagonist and autotaxin inhibitor. Further, HCQ-evoked calcium fluxes were reduced in primary sensory neurons of Advillin-LPAR5^−/− mice. The results suggest that LPA-mediated itch is primarily mediated via peripheral LPAR5, suggesting that a topical LPAR5 blocker might suppress “non-histaminergic” itch. Full article

Sexual dimorphism among mammals includes variations in the pain threshold. These differences are influenced by hormonal fluctuations in females during the estrous and menstrual cycles of rodents and humans, respectively. These physiological conditions display various phases, including proestrus and diestrus in rodents and follicular and luteal phases in humans, distinctly characterized by varying estrogen levels. In this study, we evaluated the capsaicin responses in male and female mice at different estrous cycle phases, using two murine acute pain models. Our findings indicate that the capsaicin-induced pain threshold was lower in the proestrus phase than in the other three phases in both pain assays. We also found that male mice exhibited a higher pain threshold than females in the proestrus phase, although it was similar to females in the other cycle phases. We also assessed the mRNA and protein levels of TRPV1 in the dorsal root and trigeminal ganglia of mice. Our results showed higher TRPV1 protein levels during proestrus compared to diestrus and male mice. Unexpectedly, we observed that the diestrus phase was associated with higher TRPV1 mRNA levels than those in both proestrus and male mice. These results underscore the hormonal influence on TRPV1 expression regulation and highlight the role of sex steroids in capsaicin-induced pain. Full article

Chemotherapy-provoked peripheral neuropathy and its associated affective disorders are important adverse effects in cancer patients, and its treatment is not completely resolved. A recent study reveals a positive interaction between molecular hydrogen (H₂) and a heme oxygenase (HO-1) enzyme inducer, cobalt protoporphyrin IX (CoPP), in the inhibition of neuropathic pain provoked by nerve injury. Nevertheless, the efficacy of CoPP co-administered with hydrogen-rich water (HRW) on the allodynia and emotional disorders related to paclitaxel (PTX) administration has not yet been assessed. Using male C57BL/6 mice injected with PTX, we examined the effects of the co-administration of low doses of CoPP and HRW on mechanical and thermal allodynia and anxiodepressive-like behaviors triggered by PTX. Moreover, the impact of this combined treatment on the oxidative stress and inflammation caused by PTX in the amygdala (AMG) and dorsal root ganglia (DRG) were studied. Our results indicated that the antiallodynic actions of the co-administration of CoPP plus HRW are more rapid and higher than those given by each of them when independently administered. This combination inhibited anxiodepressive-like behaviors, the up-regulation of the inflammasome NLRP3 and 4-hydroxynonenal, as well as the high mRNA levels of some inflammatory mediators. This combination also increased the expression of NRF2, HO-1, superoxide dismutase 1, glutathione S-transferase mu 1, and/or the glutamate-cysteine ligase modifier subunit and decreased the protein levels of BACH1 in the DRG and/or AMG. Thus, it shows a positive interaction among HO-1 and H₂ systems in controlling PTX-induced neuropathy by modulating inflammation and activating the antioxidant system. This study recommends the co-administration of CoPP plus HRW as an effective treatment for PTX-provoked neuropathy and its linked emotive deficits. Full article

GRT-X, which targets both the mitochondrial translocator protein (TSPO) and the Kv7.2/3 (KCNQ2/3) potassium channels, has been shown to efficiently promote recovery from cervical spine injury. In the present work, we investigate the role of GRT-X and its two targets in the axonal growth of dorsal root ganglion (DRG) neurons. Neurite outgrowth was quantified in DRG explant cultures prepared from wild-type C57BL6/J and TSPO-KO mice. TSPO was pharmacologically targeted with the agonist XBD173 and the Kv7 channels with the activator ICA-27243 and the inhibitor XE991. GRT-X efficiently stimulated DRG axonal growth at 4 and 8 days after its single administration. XBD173 also promoted axonal elongation, but only after 8 days and its repeated administration. In contrast, both ICA27243 and XE991 tended to decrease axonal elongation. In dissociated DRG neuron/Schwann cell co-cultures, GRT-X upregulated the expression of genes associated with axonal growth and myelination. In the TSPO-KO DRG cultures, the stimulatory effect of GRT-X on axonal growth was completely lost. However, GRT-X and XBD173 activated neuronal and Schwann cell gene expression after TSPO knockout, indicating the presence of additional targets warranting further investigation. These findings uncover a key role of the dual mode of action of GRT-X in the axonal elongation of DRG neurons. Full article