Search Results (468)

Background: Lower phylogenetic species are known to rebuild cut-off caudal parts with regeneration of the central nervous system (CNS). In contrast, CNS regeneration in higher vertebrates is often attributed to immaturity, although this has never been conclusively demonstrated. The emergence of stem cells and their effective medical applications has intensified research into spinal cord regeneration. However, despite these advances, the impact of clinical trials involving spinal cord-injured (SCI) patients remains disappointingly low. Long-distance regeneration has yet to be proven. Methods: Our study involved a microsurgical dorsal myelotomy in fetal rats. The development of pioneering long primary afferent axons during early gestation was examined long after birth. Results: A single cut triggered the intrinsic ability of the dorsal root ganglion (DRG) neurons to reprogram. Susceptibility to hypoxia caused the axons to stop developing. However, the residual axonal outgrowth sheds light on the intriguing temporal and spatial events that reveal long-distance CNS regeneration. The altered phenotypes displayed axons of varying lengths and different features, which remained visible throughout life. The previously designed developmental blueprint was crucial for interpreting these enigmatic features. Conclusions: This research into immaturity enabled the exploration of the previously impenetrable domain of early life and the identification of a potential missing link in CNS regeneration research. Central axon regeneration appeared to occur much faster than is generally believed. The paradigm provides a challenging approach for exhaustive intrauterine reprogramming. When the results demonstrate pre-clinical effectiveness in CNS regeneration research, the transformational impact may ultimately lead to improved outcomes for patients with spinal cord injuries. Full article

Chronic visceral pain, a significant contributor to morbidity in the United States, affects millions and results in substantial economic costs. Despite its impact, the mechanisms underlying disorders of gut–brain interaction (DGBIs), such as irritable bowel syndrome (IBS), remain poorly understood. Visceral hypersensitivity, a hallmark of chronic visceral pain, involves an enhanced pain response in internal organs to normal stimuli. Various factors like inflammation, intestinal hyperpermeability, and epigenetic modifications influence its presentation. Emerging evidence suggests that persistent colonic stimuli, disrupted gut barriers, and altered non-coding RNA (ncRNA) expression contribute to the pathophysiology of visceral pain. Additionally, cross-sensitization of afferent pathways shared by pelvic organs underpins the overlap of chronic pelvic pain disorders, such as interstitial cystitis and IBS. Central sensitization and viscerosomatic convergence further exacerbate pain, with evidence showing IBS patients exhibit hypersensitivity to both visceral and somatic stimuli. The molecular mechanisms of visceral pain involve critical mediators such as cytokines, prostaglandins, and neuropeptides, alongside ion channels like transient receptor potential vanilloid 1 (TRPV1) and acid-sensing ion channels (ASICs). These molecular insights indicate potential therapeutic targets and highlight the possible use of TRPV1 antagonists and ASIC inhibitors to mitigate visceral pain. This review explores the neurophysiological pathways of visceral pain, focusing on peripheral and central sensitization mechanisms, to advance the development of targeted treatments for chronic pain syndromes, particularly IBS and related disorders. Full article

Background/Objectives: Depression is frequently comorbid with obesity. We previously showed that astrocyte-mediated hyperactive ventral hippocampal glutamatergic afferents to the nucleus accumbens determined the exhibition of depression-like behaviors in obese murine models. However, it remains unclear if the metabolic disorder-induced depressive phenotypes and astrocytic maladaptation in the ventral hippocampus (vHPC) could be reversed following the amelioration of key metabolic impairments such as insulin resistance and dyslipidemia. Method: Male mice were fed a high-fat diet (HFD) for 12 weeks, followed by either continued HFD feeding (HFD/HFD group) or a switch to a standard diet for 4 weeks (HFD/SD group). Results: Results showed that HFD/HFD mice displayed not only glucose/lipid metabolic dysfunction, but also depression-like behaviors. In contrast, HFD/SD mice showed improvements in metabolic disorders and depressive phenotypes. Mechanistically, dietary fat reduction restored astrocyte morphology and glutamate transporter expression (GLT-1, GLAST) in the vHPC and suppressed neuroinflammatory signaling, as evidenced by reduced levels of phospho-IKK, TNF-α, IL-1β, and IL-6 in the vHPC. Conclusions: These findings suggest that dietary fat reduction reverses obesity-induced depressive phenotypes, astrocytic deficits, at least in part via suppression of neuroinflammation through the NF-κB signaling pathway. Full article

Objectives: This research aims to examine the impact of intracystic hemorrhage (ICH) on therapeutic outcomes in children with macro or mixed cystic lymphatic malformation (cLM). Methods: This retrospective study included macro/mixed cLM cases with or without ICH who underwent treatment between January 2019 and June 2024. All patients were diagnosed using preoperative imaging findings and intraoperative indocyanine green (ICG) lymphography. The baseline data of enrolled cases were retrospectively collected. The clinical characteristics were documented, including gender, age, histological typing, location, maximum diameter, and intracystic condition. Patients with or without ICH were divided into two groups. The dependent variables for predicting an excellent outcome were analyzed using multivariable logistic regression models after adjusting for potential factors using a univariable regression model. Postoperative variables, including duration of negative drainage, local infection, scar hyperplasia, and follow-up, were compared between the two groups. Results: A total of 83 cLM patients were included (ICH group: n = 36 and without ICH group: n = 47). A complete absence of afferent lymphatic vessels was demonstrated using intraoperative ICG lymphography, suggesting the isolated nature of ICH cases. ICH (p = 031; OR, 2.560; 95% CI, 1.089–6.020) was identified as the main predictor, and younger patients (p = 035; OR, 0.415; 95% CI, 0.183–0.940) had a lower potential for excellent outcomes. For the postoperative variables, the ICH group exhibited a shorter duration of negative drainage than the without ICH group (p < 0.001), while no significant differences were found regarding local infection (p = 0.693) and scar hypertrophy (p = 0.648). Conclusions: Although characterized by aggressive progression and compressive symptoms, ICH emerges as an independent favorable prognostic predictor in macro/mixed cLM management, potentially attributable to its isolated nature. Full article

For centuries, researchers have been fascinated by the composition of scorpion venom and its local and systemic effects on humans. During a sting, scorpions inject peptides and proteins that can affect immune cells and neurons. While the immune and nervous systems have been studied independently in the context of scorpion stings, here we reveal part of the mechanism by which Tityus serrulatus venom induces hyperalgesia in mice. Through behavioral, immune, imaging assays, and mice genetics, we demonstrate evidence of neuroimmune crosstalk during scorpion stings. Tityus serrulatus venom induced mechanical and thermal hyperalgesia in a dose-dependent manner, as well as overt pain-like behavior. The venom directly activated dorsal root ganglia neurons and increased the recruitment of macrophages and neutrophils, releasing pro-inflammatory cytokines TNF-α and IL-1β. Blocking TRPV1⁺ neurons, TNF-α, IL-1β, and NFκB reduced the mechanical and thermal hyperalgesia, overt pain-like behavior, and the migration of macrophages and neutrophils induced by Tityus serrulatus venom. Collectively, Tityus serrulatus venom targets primary afferent nociceptive TRPV1⁺ neurons to induce hyperalgesia through the recruitment of macrophages and neutrophils and the release of pro-inflammatory cytokines. Full article

The gut-brain axis (GBA) represents an operant acting in a two-direction communication system between the gastrointestinal tract and the central nervous system, mediated by the enteric nervous system (ENS), vagus nerve, immune pathways, and endocrine signaling. In recent years, evidence has highlighted the pivotal role of the gut microbiota in modulating this axis, forming the microbiota-gut-brain axis (MGBA). Our review synthesizes current knowledge on the anatomical and functional substrates of gut-brain communication, focusing on interoceptive signaling, the roles of intrinsic primary afferent neurons (IPANs) and enteroendocrine cells (EECs) and the influence of microbial metabolites, including short-chain fatty acids (SCFAs), bile acids, and indoles. These agents modulate neurotransmission, epithelial barrier function, and neuroimmune interactions. The vagus nerve serves as a primary pathway for afferent sensory signaling from the gut influenced indirectly by the ENS and microbiota. Dysbiosis has been associated with altered gut-brain signaling and implicated in the pathophysiology of disorders ranging from irritable bowel syndrome to mood disorders and neurodegeneration. Microbial modulation of host gene expression via epigenetic mechanisms, including microRNAs, adds another layer of complexity. The gut has a crucial role as an active sensory and signaling organ capable of influencing higher-order brain functions. Understanding the MGBA has significant implications for new therapeutic interventions targeting the microbiome to manage neurogastroenterological and even neuropsychiatric conditions. Full article

Background: Kölliker’s organ (KO), a transient structure in the cochlea, plays a critical role in the auditory maturation of mammals, particularly during embryonic and early postnatal development. This organ is essential for the proper differentiation and function of cochlear cells, acting as a pivotal source of signalling molecules that influence hair cell development and synaptic connectivity. Methods: This study systematically analyses the literature according to the PRISMA statement in order to evaluate the function roles of KO during cochlea development, reporting the molecular mechanisms and signalling pathways involved. Results: From our study, it emerged that KO supporting cells release adenosine triphosphate (ATP) through connexin hemichannels, initiating a cascade of intracellular calcium (Ca²⁺) signalling in adjacent inner hair cells (IHCs). This signalling promotes the release of glutamate, facilitating synaptic excitation of afferent nerve fibres and enhancing auditory neuron maturation prior to the onset of hearing. Additionally, the spontaneous electrical activity generated within KO supports the establishment of essential neural connections in the auditory pathway. The dynamic interplay between ATP release, Ca²⁺ signalling, and morphological changes in KO is crucial for cochlear compartmentalisation and fluid regulation, contributing to the formation of endolymph and perilymph. Furthermore, KO supports cellular plasticity and may provide a reservoir of precursor cells capable of trans-differentiating into hair cells under specific conditions. Conclusions: Dysregulation of KO function or delayed degeneration of its supporting cells has been implicated in auditory disorders, underscoring the importance of this organ in normal cochlear development and auditory function. Despite its identification over a century ago, further investigation is necessary to elucidate the molecular mechanisms underlying KO’s contributions to auditory maturation, particularly in human physiology. Full article

Basic helix–loop–helix (bHLH) transcription factors, such as those in the atonal family, are important in cellular fate determination. The expression of the sponge ortholog of the atonal bHLH gene family, AmqbHLH1, in Xenopus laevis previously resulted in the formation of ectodermal ectopic neurons. However, the extent to which these neurons persist through development and the effects on the inner ear and lateral line, which require a critical level and timing of bHLH genes, remains unexplored. To test these long-term effects, we injected various concentrations of AmqbHLH1 mRNA into X. laevis embryos and assessed neurosensory development at developmental stages coinciding with fully developed neurosensory structures. The expression of AmqbHLH1 mRNA in X. laevis resulted in a dose-dependent reduction in or loss of ears and the lateral line system without eliminating ectopic neurons. At the lowest concentrations examined, we found that inner ear neurosensory development consisted sometimes of only a few scattered hair cells in a single-layer epithelium. Furthermore, low concentrations of AmqbHLH1 mRNA affected inner ear afferent guidance. Our data suggest that the AmqbHLH1 gene has some anti-neurosensory abilities in frogs and that the overexpression of a single gene may not be sufficient for stable long-term transdifferentiation in cells. Full article

The presence of dichotomizing neurons in the dorsal root ganglia (DRG) of cattle, innervating both the reticulum and the withers, may indicate a pre-spinal convergence of visceral and cutaneous sensory information, i.e., that the DRG primary sensory neurons may elaborate the sensory information coming from two different anatomical areas before reaching the secondary sensory neurons within the spinal cord. This anatomical feature could be the underlying basis for the cutaneous allodynia observed in traumatic reticuloperitonitis, also known as the “Kalchschmidt pain test”. The aim of the study was to identify the DRG primary sensory neurons innervating the reticulum and the withers by using two different retrograde fluorescent tracers, Fast Blue (FB, affinity for cytoplasm) and Diamidino Yellow (DY, affinity for nucleus). In two anesthetized calves, FB and DY were injected into the reticulum and skin of the withers, respectively. At the end of the experimental period, the calves were deeply anesthetized and then euthanatized. The thoracic (T1–T8) DRG were collected and processed to obtain cryosections which were examined on a fluorescent microscope. A large number of neurons localized, especially in the T7 DRG, presented nuclei labeled with DY. On the contrary, only a few neurons localized exclusively in T6 and T7 DRG presented the cytoplasm labeled with FB. No neurons displayed FB and DY simultaneously within the cytoplasm and nucleus, respectively. The absence of double-labeled DRG neurons suggests that the convergence of visceral and somatic sensory inputs underlying the Kalchschmidt pain response likely does not occur at the level of individual DRG neurons. Rather, it may involve higher-order integrative centers, possibly including vagal pathways and brainstem nuclei which integrate the afferent information to coordinate respiratory movements of the diaphragm, intercostal muscles, and larynx. Although limited by the sample size, this case study provides a neuroanatomical basis for further investigation into central mechanisms of referred visceral pain in cattle. Full article

Background/Objectives: Aging is one of the greatest risk factors for neurodegenerative diseases such as Alzheimer’s disease (AD). As the disease progresses, neural loss in brain regions, such as the olfactory cortex (OC), i.e., a set of areas including the mediotemporal and orbitofrontal regions, may lead to dysfunction in the sense of smell and affect other brain regions that relate to the olfactory cortex by either afferent or efferent projections. Methods: The objective of this study was to assess sex-related differences in olfactory cortex volume using magnetic resonance imaging in individuals with mild cognitive impairment, probable dementia of the AD type and in healthy older adults, using the Mini-Mental Statement Examination score, years of education, and total intracranial volume as correction factors. Results: Atrophy of the olfactory cortex was observed in patients of both sexes with probable AD dementia. However, at the MCI stage, significant volumetric loss in the OC was detected in females only but not in males. Conclusions: This finding indicates greater pathological effects in this region in females at an earlier disease stage than in males. This study suggests that OC volume loss occurs differently between the sexes in older adults, with volumetric loss being greater in females. Full article

The carotid body (CB) senses arterial PO₂, PCO₂, and pH levels, eliciting reflex responses to maintain cardiorespiratory homeostasis. Chronic intermittent hypoxia (CIH), the hallmark of obstructive sleep apnea, elicits autonomic and cardiorespiratory alterations that are attributed to an enhanced CB chemosensory responsiveness to hypoxia, which in turn activates neurons and glial cells in the nucleus of the tractus solitarius (NTS). Although the CB contribution to the CIH-induced pathological alterations is well-known, the underlying mechanisms are not fully understood. A growing body of new evidence suggests a crucial role for ROS in acute CB oxygen sensing, as well as in the potentiation of chemosensory discharge and the activation of the central chemoreflex pathway in CIH. Indeed, it has been proposed that acute hypoxia disrupts mitochondrial electron transport, increasing ROS and NADH in the chemoreceptor cells, which inhibit voltage-gated K⁺ channels, producing cell depolarization, Ca²⁺ entry, and release of excitatory transmitters. In addition, new evidence supports that the enhanced CB afferent discharge contributes to persistent CIH-induced cardiorespiratory alterations, likely triggering neuroinflammation in the NTS. Thus, in this review, we will examine the experimental evidence that supports the involvement of ROS in the acute O₂ sensing process, and their role in the enhanced CB chemosensory discharges, the glial-related inflammation in the NTS, and the cardiorespiratory alterations induced by CIH. Full article

Background: Histamine intolerance, a disorder due to impaired degradation of dietary histamine, is frequently associated with headaches, but the underlying pathophysiology is largely unknown; the sensitization of meningeal afferents appears likely. We approached this issue by examining histamine concentrations in different tissues and meningeal histamine release in a new mouse model of high-histamine diets. Methods: C57BL/6 mice of both sexes were fed with diets containing 3 or 9 g/kg histamine and compared to control groups. After 10–30 days, the histamine concentration was determined in plasma, samples of homogenized ileum, trigeminal ganglia, spinal medulla, and cerebellum using an ELISA. The histamine release from mast cells in the dura mater stimulated with compound 48/80 was also examined. Results: Animals supplied with high dietary histamine showed normal behavior and no signs of suffering. Compared with the controls, the histamine concentration was significantly higher in plasma and ileum of mice fed with 3 g/kg, highest in animals fed with 9 g/kg histamine. In addition, this group of animals showed also higher histamine concentrations in the trigeminal ganglion. The histamine release from the dura mater in mice supplied with 3 g/kg histamine was not significantly different to control animals, but the relative increase in stimulated release was lower in male animals of the high histamine group. Conclusions: High dietary histamine increases histamine levels in blood plasma and the gut, whereas the histamine content of neural tissues is not significantly influenced. The lowered stimulated release in animals subjected to high dietary histamine may indicate compensatory mechanisms. Full article

The paraventricular nucleus of the hypothalamus (PVN) regulates, among others, the stress response, sexual behavior, and energy metabolism through its magnocellular and parvocellular neurosecretory cells. Within the PVN, ensemble coordination occurs through the many long-range synaptic afferents, whose activity in time relies on retrograde neuromodulation by, e.g., endocannabinoids. However, the nanoarchitecture of endocannabinoid signaling in the PVN, especially during neuronal development, remains undescribed. By using single-cell RNA sequencing, in situ hybridization, and immunohistochemistry during fetal and postnatal development in mice, we present a spatiotemporal map of both the 2-arachidonoylglycerol (2-AG) and anandamide (AEA) signaling cassettes, with a focus on receptors and metabolic enzymes, in both molecularly defined neurons and astrocytes. We find type 1 cannabinoid receptors (Cnr1), but neither Cnr2 nor Gpr55, expressed in neurons of the PVN. Dagla and Daglb, which encode the enzymes synthesizing 2-AG, were found in all neuronal subtypes of the PVN, with a developmental switch from Daglb to Dagla. Mgll, which encodes an enzyme degrading 2-AG, was only found sporadically. Napepld and Faah, encoding enzymes that synthesize and degrade AEA, respectively, were sparsely expressed in neurons throughout development. Notably, astrocytes expressed Mgll and both Dagl isoforms. In contrast, mRNA for any of the three major cannabinoid-receptor subtypes could not be detected. Immunohistochemistry validated mRNA expression and suggested that endocannabinoid signaling is configured to modulate the activity of afferent inputs, rather than local neurocircuits, in the PVN. Full article

Background: Acute respiratory distress syndrome (ARDS) is a high-mortality disease strongly associated with an imbalance in the inflammatory response. The ratio of helper T 17 (Th17) cells to regulatory T (Treg) cells is significantly correlated with prognosis and outcomes in ARDS. Vagus nerve stimulation (VNS) alleviates lung injury in ARDS model rats. The objective of this study was to further investigate whether VNS attenuates lipopolysaccharide-induced ARDS by regulating Th17/Treg homeostasis and to explore the underlying mechanisms. Methods: We assessed the degree of lung injury using hematoxylin and eosin staining, the lung wet-to-dry ratio, and total protein and pro-inflammatory cytokine levels in bronchoalveolar lavage fluid. The expression levels of Th17 and Treg cells were determined using flow cytometry, Western blotting, quantitative real-time PCR, and enzyme-linked immunosorbent assays. Results: We found that VNS reduced lung injury in ARDS model rats. Additionally, VNS regulated Th17/Treg homeostasis and reduced the levels of inflammatory factors in both the lungs and spleens. Notably, the effects of VNS were consistent when the afferent or efferent vagus nerve, or both, were stimulated. Further investigation revealed that VNS upregulated splenic α7 nicotinic acetylcholine receptors (α7nAChRs). The administration of an α7nAChR agonist enhanced VNS-mediated regulation of Th17/Treg homeostasis and attenuated lung injury, while these effects were blocked by α7nAChR antagonists. Conclusions: Our study demonstrated that VNS regulates the Th17/Treg balance through α7nAChR activation in the spleen, thereby mitigating lung injury in ARDS. These findings provide new theoretical support for the use of VNS in attenuating ARDS. Full article

Background/Objectives: Increasing evidence reveals the likely peripheral etiology of Parkinson’s disease; however, the mechanistic insight into α-Synuclein aggregation in the periphery remains unclear. This study aimed to explore the effect of abnormal expression of renalase on dopamine metabolism, toxic DOPAL generation, and subsequently, α-Synuclein aggregation. Methods: Blood pressure (BP) was monitored while changing the body position of rats; the serum level of renalase was detected by ELISA; the mRNA/protein of renalase and α-Synuclein were determined by qRT-PCR/Western blot; DOPAL was measured using HPLC; renalase distribution was explored by immunostaining; cell viability and ultrastructure were examined by TUNEL and electron microscopy, respectively. Results: The results showed that, in PD model rats, the serum level of renalase was increased time-dependently with up-regulated renalase gene/protein expression in the nodose ganglia, nucleus tractus solitarius, and heart; a reduced dopamine content was also detected by the renalase overexpression in PC12 cells. Strikingly, up-regulated renalase and orthostatic BP changes were observed before the behavioral changes in the model rats. Meanwhile, the levels of DOPAL and α-Synuclein were increased time-dependently. Intriguingly, the low molecular weight of α-Synuclein declined coordinately with the increase in the higher molecular weight of α-Synuclein. Clear ultrastructure damage at the cellular level supported the notion of molecular findings. Notably, the α-Synuclein aggregation-induced impairment of the axonal transport function predates neuronal degeneration mediated by renalase overexpression. Conclusions: Our results demonstrate that abnormal peripheral dopamine metabolism mediated by overexpressed renalase promotes the DOPAL-induced α-Synuclein and leads to baroreflex afferent neuronal degeneration and early autonomic failure. Full article