Roles of inflammation, neurogenic inflammation, and neuroinflammation in pain

Tear neuropeptides are associated with clinical symptoms and signs of dry eye patients

PURPOSE

To evaluate levels of 3 tear-soluble neuropeptides in dry eye patients and to identify the correlations with clinical signs and symptoms.

METHODS

A total of 16 dry eye patients and 12 healthy volunteers were enrolled. Dry eye disease (DED) diagnosis was based on the 2017 Report of the Tear Film & Ocular Surface Society International Dry Eye Workshop (TFOS DEWS II). First time of noninvasive breakup time (NIBUT-1st), mean time of noninvasive breakup time (NIBUT-avg), tear meniscus height (TMH), Schirmer test, corneal fluorescein staining (CFS) score and ocular surface disease index (OSDI) were recorded. Tear fluid samples were collected and enzyme-linked immunoassay (ELISA was performed to analyze levels of calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and substance P (SP), as well as the association among the 3 neuropeptides and clinical findings.

RESULTS

Compared to normal controls, levels of tear CGRP (p=.003) and SP (p=.002) were significantly decreased in dry eye patients yet not NPY concentrations. Levels of tear CGRP and SP showed an inverse correlation with CFS and OSDI, which positively correlated with NIBUT-1st, NIBUT-avg and Schirmer test values. Multiple linear regression analysis showed that Schirmer test values were related to tear CGRP concentration. Subgroup analysis showed lower tear CGRP concentration in DED patients with severe symptoms (OSDI ≥ 46).

CONCLUSIONS

Levels of tear CGRP and SP decreased in DED patients and showed meaningful correlations with clinical symptoms and signs, implying a potential relationship between tear neuropeptides and ocular neurosensory function.

Bidirectional regulation of the brain-gut-microbiota axis following traumatic brain injury

JOURNAL/nrgr/04.03/01300535-202508000-00002/figure1/v/2024-09-30T120553Z/r/image-tiff Traumatic brain injury is a prevalent disorder of the central nervous system. In addition to primary brain parenchymal damage, the enduring biological consequences of traumatic brain injury pose long-term risks for patients with traumatic brain injury; however, the underlying pathogenesis remains unclear, and effective intervention methods are lacking. Intestinal dysfunction is a significant consequence of traumatic brain injury. Being the most densely innervated peripheral tissue in the body, the gut possesses multiple pathways for the establishment of a bidirectional "brain-gut axis" with the central nervous system. The gut harbors a vast microbial community, and alterations of the gut niche contribute to the progression of traumatic brain injury and its unfavorable prognosis through neuronal, hormonal, and immune pathways. A comprehensive understanding of microbiota-mediated peripheral neuroimmunomodulation mechanisms is needed to enhance treatment strategies for traumatic brain injury and its associated complications. We comprehensively reviewed alterations in the gut microecological environment following traumatic brain injury, with a specific focus on the complex biological processes of peripheral nerves, immunity, and microbes triggered by traumatic brain injury, encompassing autonomic dysfunction, neuroendocrine disturbances, peripheral immunosuppression, increased intestinal barrier permeability, compromised responses of sensory nerves to microorganisms, and potential effector nuclei in the central nervous system influenced by gut microbiota. Additionally, we reviewed the mechanisms underlying secondary biological injury and the dynamic pathological responses that occur following injury to enhance our current understanding of how peripheral pathways impact the outcome of patients with traumatic brain injury. This review aimed to propose a conceptual model for future risk assessment of central nervous system-related diseases while elucidating novel insights into the bidirectional effects of the "brain-gut-microbiota axis."

Distinct functional cerebral hypersensitivity networks during incisional and inflammatory pain in rats

Although the pathophysiology of pain has been investigated tremendously, there are still many open questions with regard to specific pain entities and their pain-related symptoms. To increase the translational impact of (preclinical) animal neuroimaging pain studies, the use of disease-specific pain models, as well as relevant stimulus modalities, are critical. We developed a comprehensive framework for brain network analysis combining functional magnetic resonance imaging (MRI) with graph-theory (GT) and data classification by linear discriminant analysis. This enabled us to expand our knowledge of stimulus modalities processing under incisional (INC) and pathogen-induced inflammatory (CFA) pain entities compared to acute pain conditions. GT-analysis has uncovered specific features in pain modality processing that align well with those previously identified in humans. These include areas such as S1, M1, CPu, HC, piriform, and cingulate cortex. Additionally, we have identified unique Network Signatures of Pain Hypersensitivity (NSPH) for INC and CFA. This leads to a diminished ability to differentiate between stimulus modalities in both pain models compared to control conditions, while also enhancing aversion processing and descending pain modulation. Our findings further show that different pain entities modulate sensory input through distinct NSPHs. These neuroimaging signatures are an important step toward identifying novel cerebral pain biomarkers for certain diseases and relevant outcomes to evaluate target engagement of novel therapeutic and diagnostic options, which ultimately can be translated to the clinic.

Laryngeal Hypersensitivity From the Perspective of Pain Science: An Integrative Review of Empirical Studies on Associated Factors and Processes

OBJECTIVE

Laryngeal hypersensitivity (LHS) is a state of heightened sensorimotor response to stimuli in the upper airway. Although its clinical picture is becoming progressively clearer with recent research progress, specificities about its associated factors and processes remain to be clarified. The aim of this integrative review was to synthesize published empirical data from human studies on LHS, focusing on related factors and pathophysiology.

STUDY DESIGN AND DATA SOURCES

Integrative review of the literature; Pubmed, EMBASE, and Web of Science.

METHODS

Keywords associated with the following three main concepts were used to query databases: (1) manifestations potentially associated with an irritable larynx (dysphonia, inducible laryngeal obstruction (ILO), chronic cough, and globus); (2) hypersensitivity; and (3) pathophysiology. Peer-reviewed studies in English providing empirical original research data on the pathophysiology of LHS were included, with no restriction based on study design.

RESULTS

In total, 54 papers met the inclusion criteria. Factors potentially associated with LHS were identified, namely (1) psychological and lifestyle factors, (2) upper airway inflammation and injuries from exogenous/endogenous irritants, infections, or mucosal atrophy, (3) sex hormones, (4) metabolic abnormalities, and (5) aberrant respiratory behavior. Given the parallels between pain-related mechanisms and suggested LHS mechanisms, processes identified as putatively contributing to LHS were categorized in light of the current pain literature. Findings suggest that LHS may stem from a peripheral tissue insult, a neuropathic insult, and/or maladaptive neuroplasticity. Gaps in the literature were identified, in part driven by an uneven repartition of research across the various alleged manifestations of LHS. In fact, a large majority of studies pertained to chronic cough, with very few addressing muscle tension dysphonia, ILO, and globus.

CONCLUSION

Future research can focus on the potential role of hypersensitivity in manifestations such as muscle tension dysphonia and ILO, and on the development of guidelines to identify the specific underlying factors and mechanisms at play in LHS symptoms.

Inhibition of Macrophage Activation by Minocycline Attenuates CCI-Induced Neuropathic Pain

Neuropathic pain is characterized by a high prevalence and associated with a variety of disorders of the peripheral and central nervous systems. It remains a major challenge for clinical management due to lack effective treatments. Our previous studies have demonstrated that nerve injury-induced neuroinflammation plays a critical role in regulating the development and maintenance of neuropathic pain. In the present study, we found that chronic constriction injury (CCI) led to a significant increase in the number of macrophages at the site of injured nerves. To elucidate the role of macrophage activation in CCI-induced neuropathic pain, we employed chemical agents, including clodronate liposomes, which is known for their ability to deplete macrophages, and minocycline, an inhibitor of macrophage function. Both intravenous injection of liposome-encapsulated clodronate and intrasciatic delivery of minocycline effectively attenuated CCI-induced mechanical and heat hyperalgesia. Furthermore, transfer of polarized M2 macrophages significantly alleviated CCI-induced neuropathic pain, but not under the condition of M1 macrophage transfer. Mechanistically, our findings indicated that pretreatment with minocycline increased the expression level of CD206 but decreased that of IL-1β, while post-polarization treatment markedly decreased the expression level of both. Additionally, an in vitro migration assay revealed that minocycline exerts an inhibitory effect on macrophage migration. In brief, our study elucidates the effect of CCI-induced macrophage activation on neuropathic pain and provides new insights into the potential clinical application of minocycline for managing neuropathic pain.

The gut microbiota promotes pain in fibromyalgia

Fibromyalgia is a prevalent syndrome characterized by widespread pain in the absence of evident tissue injury or pathology, making it one of the most mysterious chronic pain conditions. The composition of the gut microbiota in individuals with fibromyalgia differs from that of healthy controls, but its functional role in the syndrome is unknown. Here, we show that fecal microbiota transplantation from fibromyalgia patients, but not from healthy controls, into germ-free mice induces pain and numerous molecular phenotypes that parallel known changes in fibromyalgia patients, including immune activation and metabolomic profile alterations. Replacing the fibromyalgia microbiota with a healthy microbiota substantially alleviated pain in mice. An open-label trial in women with fibromyalgia (Registry MOH_2021-11-04_010374) showed that transplantation of a healthy microbiota is associated with reduced pain and improved quality of life. We conclude that altered gut microbiota has a role in fibromyalgia pain, highlighting it as a promising target for therapeutic interventions.

Research progress in different physical therapies for treating peripheral nerve injuries

Physical therapy is gaining recognition as an effective therapeutic approach in the realm of peripheral nerve injury (PNI) research. This article seeks to provide a comprehensive review of the latest advancements, applications, and mechanisms of action of four physical therapy modalities-ultrasound, electrical stimulation, photobiomodulation, and aerobic exercise-in the context of PNI. Ultrasound, characterized by its mechanical and thermal effects, is widely regarded as an effective non-invasive or minimally invasive method for neural modulation. Electrical stimulation therapy, a prevalent technique in PNI treatment, entails the application of electric currents to stimulate nerve and muscle tissues, thereby facilitating nerve regeneration and mitigating muscle atrophy. Photobiomodulation, a process that influences cell metabolism through the absorption of photon energy, is closely associated with neural regeneration in the field of rehabilitation medicine. Additionally, aerobic exercise, a popular form of physical activity, serves to enhance blood circulation and improve neuronal function. The article discusses various physical therapy methods for peripheral nerve injuries, including hyperbaric oxygen therapy, magnetic therapy, and biofeedback therapy, in addition to traditional approaches. Despite advancements, challenges in nerve injury treatment persist, such as the need for standardized treatment protocols, consideration of individual variations, and assessment of long-term effectiveness. Future research is needed to address these issues. In summary, this article offers theoretical and empirical evidence supporting the utilization of physical therapy in the management of PNI. This research aims to promote further research and clinical practice in this field, contributing to enhancing patient quality of life and recovery outcomes.

Role of efferocytosis in chronic pain -- From molecular perspective

The complex nature of pain pathophysiology complicates the establishment of objective diagnostic criteria and targeted treatments. The heterogeneous manifestations of pain stemming from various primary diseases contribute to the complexity and diversity of underlying mechanisms, leading to challenges in treatment efficacy and undesirable side effects. Recent evidence suggests the presence of apoptotic cells at injury sites, the distal dorsal root ganglia (DRG), spinal cord, and certain brain regions, indicating a potential link between the ineffective clearance of dead cells and debris and pain persistence. This review highlights recent research findings indicating that efferocytosis plays a significant yet often overlooked role in lesion expansion while also representing a potentially reversible impairment that could be targeted therapeutically to mitigate chronic pain progression. We examine recent advances into how efferocytosis, a process by which phagocytes clear apoptotic cells without triggering inflammation, influences pain initiation and intensity in both human diseases and animal models. This review summarizes that efferocytosis contributes to pain progression from the perspective of defective and inefficient efferocytosis and its subsequent secondary necrocytosis, cascade inflammatory response, and the shift of phenotypic plasticity and metabolism. Additionally, we investigate the roles of newly discovered genetic alterations or modifications in biological signaling pathways in pain development and chronicity, providing insights into innovative treatment strategies that modulate efferocytosis, which are promising candidates and potential avenues for further research in pain management and prevention.

Preparation and structure-function relationships of homogalacturonan-rich and rhamnogalacturonan-I rich pectin: A review

Pectin has multiple functions and is widely used in the food industry. It is an acidic heteropolysaccharide found in most plants, mainly consisting of two regions: homogalacturonan (HG) and rhamnogalacturonan-I (RG-I). HG and RG-I rich pectin have unique structures and functional properties, which can be obtained through specific preparation methods. Some emerging physics assisted preparation strategies are more advantageous for preparing specific structures with higher purity and efficiency than traditional preparation methods. HG and RG-I rich pectin have unique processing and functional properties, but sometimes a proper ratio of HG and RG-I pectin may have better effects than individuals. Therefore, it is speculated that there may be some synergistic effects between the two pectin structures. A comprehensive understanding of the preparation, structure, and functional relationship of HG and RG-I rich pectin is crucial for the efficient preparation of pectin with targeted functions.

Knowledge of the genetics of human pain gained over the last decade from next-generation sequencing

Next-generation sequencing (NGS) technologies have revolutionized pain research by providing comprehensive insights into genetic variation across the genome. Recent studies have expanded the known spectrum of mutations in genes such as SCN9A and NTRK1, which are commonly mutated in hereditary sensory neuropathies. NGS has uncovered critical alternative splicing events and facilitated single-cell transcriptomics, revealing cellular heterogeneity within tissues. An NGS-based classifier predicted extremely high opioid requirements with 80 % accuracy, highlighting the importance of tailoring opioid therapy based on genetic profiles. Key genes such as GDF5, COL11A1, and TRPV1 have been linked to osteoarthritis risk and pain sensitivity, while HLA-DRB1, TNF, and P2X7 play critical roles in inflammation and pain modulation in rheumatoid arthritis. Innovative tools, such as an atlas of the somatosensory system in neuropathic pain, have been developed based on NGS data, focusing on the dorsal root and trigeminal ganglia. This approach allows the analysis of cellular changes during the development of chronic pain. In the study of rare variants, NGS outperforms single nucleotide variant candidate studies and classical genome-wide association approaches. The complex data generated by NGS enables integrated multi-omics approaches, allowing deeper exploration of the molecular and cellular basis of pain perception. In addition, the characterization of non-coding RNAs has opened new therapeutic avenues. NGS-based pain research faces challenges related to complex data analysis and interpretation of rare genetic variants with unknown biological functions. Nevertheless, NGS offers significant potential for improving personalized pain management and highlights the need for interdisciplinary collaboration to translate findings into clinical practice.

Chronic postsurgical pain after cardiac surgery: A narrative review

Chronic postsurgical pain (CPSP) is a prevalent and debilitating sequela of cardiac surgery, exerting a profound impact on patients' quality of life, functional recovery, and healthcare systems. Its pathophysiology includes complex mechanisms, including peripheral and central sensitization, neuroplastic alterations, and inflammatory pathways, influenced by demographic, psychological, and perioperative factors. Inadequate management of acute pain is a critical contributor to its development. This review examines the etiology of CPSP, presents key risk factors, and critically evaluates pharmacological and nonpharmacological interventions. Particular attention is devoted to the role of regional anesthesia techniques and emerging preventive and therapeutic strategies, highlighting the necessity of multidisciplinary, evidence-informed approaches to address this persistent clinical challenge.

The Role of Purinergic Mechanisms in the Excitability of Trigeminal Afferents of Rats with Prenatal Hyperhomocysteinemia

Elevated levels of homocysteine in the blood plasma (hyperhomocysteinemia, HHCY) positively correlate with migraine symptoms in patients. Experimental studies show a higher sensitivity of rats with prenatal HHCY (pHHCY) to migraine symptoms like allodynia, photophobia, anxiety, and a higher excitability of meningeal trigeminal afferents. In the present study, the roles of purinergic mechanisms in the homocysteine-induced hyperexcitability of the trigeminal ganglion (TG) system using electrophysiological recordings from the trigeminal nerve, Ca2+ imaging of cells isolated from TG, and mast cell staining in meninges were investigated. Experiments were performed using rats with pHHCY born from females fed with a high-methionine-containing diet before and during pregnancy. Firstly, we found that lower concentrations of 4-aminopyridine, a K+-channel blocker, were able to induce an increase in the nociceptive activity of trigeminal afferents, supporting the hypothesis of the higher excitability of the trigeminal nerve of rats with pHHCY. Trigeminal afferents of rats with pHHCY were more sensitive to the exogenous application of the nonspecific agonist of purinergic ATP receptors. In neurons and satellite glial cells of TG of rats with pHHCY ATP, ADP (an agonist of metabotropic P2Y receptors) and BzATP (an agonist of ionotropic P2X with especially high potency for the P2X7 receptor) induced larger Ca2+ transients. The incubation of TG neurons in homocysteine for 24 h increased the ratio of neurons responding simultaneously to ATP and capsaicin. Moreover, rats with pHHCY exhibit a higher rate of degranulation of mast cells and increased response to the agonist of the P2X7 receptor BzATP application. In addition, higher levels of calcitonin gene-related peptide (CGRP) were found in rats with pHHCY. Our results suggest that chronic elevated levels of homocysteine induce the upregulation of ionotropic or metabotropic ATP receptors in neurons, satellite glial cells, and mast cells, which further provide inflammatory conditions and the sensitization of peripheral afferents underlying pain.

Association Between Synovial NTN4 Expression and Pain Scores, and Its Effects on Fibroblasts and Sensory Neurons in End-Stage Knee Osteoarthritis

Osteoarthritis (OA) is a chronic joint disease marked by synovial inflammation, cartilage degradation, and persistent pain. Although Netrin-4 (NTN4) has been implicated in pain modulation in rheumatoid arthritis (RA), its role in OA pain remains less understood. Previous research has documented that NTN4 promotes axonal growth in rodent-derived neurons; however, its effects on human sensory neurons are yet to be fully explored. NTN4 also plays a multifactorial role in various non-neuronal cells, such as endothelial cells, tumor cells, and stromal cells. Nevertheless, its specific impact on synovial fibroblasts, which are key components of the synovium and have been linked to OA pain, is still unclear. This study examined the correlation between NTN4 expression levels and pain severity in OA, specifically investigating its effects on human iPSC-derived sensory neurons (iPSC-SNs) and synovial fibroblasts from OA patients. Our findings indicate a positive correlation between synovial NTN4 expression and pain severity. Recombinant human Netrin-4 (rh-NTN4) was also shown to enhance neurite outgrowth in human iPSC-SNs, suggesting a potential role in neuronal sensitization. Additionally, rh-NTN4 stimulated the production of pro-inflammatory cytokines (IL-6, IL-8) and chemokines (CXCL1, CXCL6, CXCL8) in synovium-derived fibroblastic cells, implicating it in synovial inflammation. Collectively, these results suggest that NTN4 may contribute to KOA pathology by promoting synovial inflammation and potentially sensitizing sensory neurons, thereby influencing the mechanisms of underlying pain.

Botulinum toxin effects on biochemical biomarkers related to inflammation-associated head and neck chronic conditions: a systematic review of clinical research

Botulinum toxin type A (BoNT) has emerged as a potential alternative to conventional therapies to many debilitating chronic diseases characterised by inflammatory states. However, the biological rationale remains ambiguous. Our review aimed to systematically assessed which biochemical biomarkers have been reported in clinical research to evaluate BoNT analgesic and mood-lifting effects in head and neck chronic conditions related to inflammation. We searched databases and registries between inception and September 29, 2023. Of the nine included studies, there were concerns about risk of bias for six studies. The leading biomarker with five studies was the calcitonin gene-related peptide (CGRP), followed by serotonin with two studies. Oxidative stress biomarkers were only reported in one study. Several important players in inflammatory processes and different immune cell classes have been evaluated in four studies. There was only one trial measuring changes in beta Tubulin and SNAP-25, and another study evaluating cutaneous neuropeptide substance-P. After BoNT, a significant effect was reported in six studies, including decrease in plasma levels of CGRP in chronic migraine and trigeminal neuralgia; serotonin decrease when collected from human tears in refractory intractable dry eye disease and increase in peripheral blood platelets in painful cervical dystonia associated to depression and anxiety; decrease in plasma concentration of markers of oxidative damage to proteins and increase in biomarkers for antioxidant power; decrease in expression of gene sets involved in inflammatory pathways and immune cells classes in the periosteum and metalloproteinase-9 molecule in the tears. BoNT seems to affect some biomarkers present in chronic inflammatory conditions. However, the certainty evidence found was very low to moderate. This study is registered on PROSPERO (CRD42023432131).

Conditioned Pain Modulation in Patients with Hemophilic Arthropathy: A Cross-Sectional Cohort Study

Background/Objectives: Hemophilic arthropathy causes functional impairment, disability, and chronic pain. Conditioned pain modulation describes the effect of endogenous pathways that potentiate or diminish the effects of noxious afferent stimuli. The objective was to identify conditioned pain modulation in patients with bilateral hemophilic ankle and knee arthropathy, and the best predictive model thereof. Methods: Cross-sectional cohort study. Forty-nine adult patients with hemophilic arthropathy were recruited. The dependent variable was the Conditioned Pain Modulation Index (CPMI). Age was the predictor variable. Secondary variables, estimated as modifying or confounding variables, were kinesiophobia (Tampa Scale for Kinesiophobia), catastrophizing (Pain Catastrophizing Scale), anxiety (State-Trait Anxiety Inventory), and clinical, anthropometric, and sociodemographic variables. Results: Conditioned pain modulation in patients with hemophilic arthropathy presents values close to zero (mean = 0.004: 95%CI: -0.05; 0.06). Anxiety, pain intensity, and pressure pain threshold explained the variability in the conditioned modulation of ankle pain (R2adj = 0.24). Variables explaining 23.05% of variability of conditioned modulation of knee pain were age, inhibitor development, anxiety, and pressure pain threshold (R2adj = 0.23). Conclusions: Patients with hemophilia presented a modulation close to zero, representing a balance between the ability to inhibit and facilitate painful stimuli. The predictive model of conditioned modulation of ankle pain includes anxiety, and pain intensity and threshold. Age, inhibitory development, anxiety, and pain threshold predict knee pain modulation.

Neurogenic inflammation and itch in barrier tissues

Once regarded as distinct systems, the nervous system and the immune system are now recognized for their complex interactions within the barrier tissues. The neuroimmune circuitry comprises a dual-network system that detects external and internal disturbances, providing critical information to tailor a context-specific response to various threats to tissue integrity, such as wounding or exposure to noxious and harmful stimuli like pathogens, toxins, or allergens. Using the skin as an example of a barrier tissue with the polarized sensory neuronal responses of itch and pain, we explore the molecular pathways driving neuronal activation and the effects of this activation on the immune response. We then apply these findings to other barrier tissues, to find common pathways controlling neuroimmune responses in the barriers.

Prevention of motor relapses and associated trigeminal pain in experimental autoimmune encephalomyelitis by reducing neuroinflammation with a purple corn extract enriched in anthocyanins

Multiple sclerosis (MS) is the leading cause of disability in young adults, with about 2.5-3 million cases currently diagnosed. Pain is a common comorbid symptom of MS, and develops independently from motor impairments. Currently utilized drugs bear severe side effects; thus, new therapeutic strategies are needed, and nutraceutical supplements represent innovative and safe opportunities. We have selected a variety of anthocyanin-enriched purple corn, from which a water-soluble extract (Red extract) has been obtained and administered to male rats exposed to experimental autoimmune encephalomyelitis (EAE). Animals developed relapsing-remitting motor symptoms, accompanied by early onset trigeminal allodynia. The preventive administration of Red extract facilitated the remission of motor symptoms, prevented the development of relapses, and delayed and reduced the development of EAE-associated trigeminal pain. An overall inhibition of neuroinflammation, blunted microgliosis and astrogliosis, activation of autophagy and reduced immune cell infiltration in the brainstem, cervical and lumbar spinal cord were observed. Yellow corn extract, lacking anthocyanins, had no behavioral effects, despite a limited anti-inflammatory action. Therapeutic Red extract administration did not affect EAE motor symptoms, only partially reduced the development of trigeminal pain but maintained its ability to reduce neuroinflammation and glial cell activation and to promote autophagy. Overall, our data suggest that a nutraceutical supplement from anthocyanin-enriched purple corn represents an interesting option to limit the development of motor relapses and the chronicization of multiple sclerosis-associated pain, through the mitigation of neuroinflammation, of the infiltration of immune cells and the promotion of autophagy.

Endometriosis in Adolescence: A Narrative Review of the Psychological and Clinical Implications

Endometriosis is a chronic, inflammatory condition where endometrial-like tissue grows outside the uterus, affecting around 10% of women of reproductive age. This condition is associated with debilitating symptoms, including dysmenorrhea, dyspareunia, chronic pelvic pain, fatigue, and infertility. Adolescents with endometriosis face unique challenges, as the disease is often misdiagnosed or undiagnosed for an average of 7-10 years due to its complex and multifactorial nature. Consequently, patients frequently suffer from worsening symptoms and significant psychological distress, including anxiety, depression, and social withdrawal. While there is no definitive cure for endometriosis, treatment approaches typically involve hormonal therapies, lifestyle adjustments (such as diet and exercise), and psychological support. Recent studies emphasize the profound impact of endometriosis on the mental health of adolescents, highlighting the need for a more holistic treatment approach that integrates both medical and psychological care. This narrative review explores the psychological and psychosocial effects of endometriosis in adolescents, examining the biological and psychological mechanisms linking the disease to mental health outcomes. It also discusses current therapeutic strategies, such as cognitive behavioral therapy, mindfulness, and peer support, and underscores the importance of early diagnosis and multidisciplinary care to mitigate both the physical and emotional burdens of the condition. This integrated approach is critical in improving the overall well-being and quality of life for adolescents living with endometriosis.

Substance P receptor signaling contributes to host maladaptive responses during enteric bacterial infection

Immune responses in the intestine are intricately balanced to prevent pathogen entry without inducing immunopathology. The nervous system is well established to interface with the immune system to fine-tune immunity in various organ systems including the gastrointestinal tract. Specialized sensory neurons can detect bacteria, bacterial products, and the resulting inflammation, to coordinate the immune response in the gastrointestinal tract. These sensory neurons release peptide neurotransmitters such as Substance P (SP), to induce both neuronal signaling and localized responses in nonneuronal cells. With this in mind, we assessed the immunoregulatory roles of SP receptor signaling during enteric bacterial infection with the noninvasive pathogen Citrobacter rodentium. Pharmacological antagonism of the SP receptor significantly reduced bacterial burden and prevented colonic crypt hyperplasia. Mice with SP receptor signaling blockade had significantly reduced inflammation and recruitment of T cells in the colon. Reduced colonic T cell recruitment is due to reduced expression of adhesion molecules on colonic endothelial cells in SP receptor antagonist-treated mice. Using SP receptor T cell conditional knockout mice, we further confirmed SP receptor signaling enhanced select aspects of T cell responses. Our data demonstrate that SP receptor signaling can significantly reduce inflammation and prevent host-maladaptive responses without impinging upon host protection.

Human molecular mechanisms of discogenic low back pain: A scoping review

The limited understanding of the mechanisms underlying human discogenic low back pain (DLBP) has hampered the development of effective treatments. While there is much research on disc degeneration, the association between degeneration and pain is weak. Therefore, there is an urgent need to identify pain-inducing molecular mechanism to facilitate the development of mechanism-specific therapeutics. This scoping review aims to determine the current knowledge of molecular mechanisms associated with human DLBP. A systematic search on CENTRAL, CINAHL, Citation searching, ClinicalTrials.gov, Embase, Google Scholar, MEDLINE, PsycINFO, PubMed, Scopus, Web of Science, and World Health Organization was performed. Studies with human DLBP as diagnosed by discography or imaging that analyzed human disc tissues and reported pain-related outcomes were included, and those on predominant radicular pain were excluded. The search returned 6012 studies. Most studies did not collect pain-related outcomes. Those that included pain assessment relied on self-report of pain intensity and disability. Six studies qualified for data extraction and synthesis. The main molecular mechanisms associated with DLBP were the expressions of nociceptive neuropeptides and cytokines, particularly TNF-αdue to its strong association with pain outcomes. Activation of NF-κB signaling pathway, alterations in adrenoceptor expressions, and increase in reactive oxygen species (ROS) were also associated with DLBP through regulation of pro-inflammatory factors and pain-related neuropeptides. Current evidence converges to TNF-α, NF-κB signaling, and ROS-induced pro-inflammation. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes. PERSPECTIVE: This scoping review identified TNF-α, NF-κB signaling, and ROS-induced pro-inflammation as relevant mechanisms of human discogenic low back pain. Major weaknesses in the current literature are the focus on degeneration without pain phenotyping, and lack of association of molecular findings with pain outcomes.

Evolution of Lipid Metabolism in the Injured Mouse Spinal Cord

Following spinal cord injury (SCI), there is a short-lived recovery phase that ultimately plateaus. Understanding changes within the spinal cord over time may facilitate targeted approaches to prevent and/or reverse this plateau and allow for continued recovery. Untargeted metabolomics revealed distinct metabolic profiles within the injured cord during recovery (7 days postinjury [DPI]) and plateau (21 DPI) periods in a mouse model of severe contusion SCI. Alterations in lipid metabolites, particularly those involved in phospholipid (PL) metabolism, largely contributed to overall differences. PLs are hydrolyzed by phospholipases A2 (PLA2s), yielding lysophospholipids (LPLs) and fatty acids (FAs). PL metabolites decreased between 7 and 21 DPI, whereas LPLs increased at 21 DPI, suggesting amplified PL metabolism during the plateau phase. Expression of various PLA2s also differed between the two time points, further supporting dysregulation of PL metabolism during the two phases of injury. FAs, which can promote inflammation, mitochondrial dysfunction, and neuronal damage, were increased regardless of time point. Carnitine can bind with FAs to form acylcarnitines, lessening FA-induced toxicity. In contrast to FAs, carnitine and acylcarnitines were increased at 7 DPI, but decreased at 21 DPI, suggesting a loss of carnitine-mediated mitigation of FA toxicity at the later time point, which may contribute to the cessation of recovery post-SCI. Alterations in oxidative phosphorylation and tricarboxylic acid cycle metabolites were also observed, indicating persistent although dissimilar disruptions in mitochondrial function. These data aid in increasing our understanding of lipid metabolism following SCI and have the potential to lead to new biomarkers and/or therapeutic strategies.

Assessment of phytochemical screening, antibacterial, analgesic, and antipyretic potentials of Litsea glutinosa (L.) leaves extracts in a mice model

BACKGROUND

Litsea glutinosa (LG) leaves have been traditionally used in ethnomedicine for the treatment of various ailments, including pain, fever, and microbial infections. This study aims to scientifically evaluate the therapeutic potential of cold methanol extracts of LG leaves, specifically focusing on their analgesic, antipyretic, and antibacterial activities. In addition, the research includes preliminary phytochemical screening to identify key bioactive compounds and an acute toxicity test to assess the safety profile of the extract.

METHODS

In this study, we conducted an initial investigation of the major phytochemical groups present in L. glutinosa leaves using both modern chromatographic techniques, specifically High-Performance Liquid Chromatography (HPLC), and conventional phytochemical screening methods applied to cold methanol extracts. Both approaches consistently identified phenols and flavonoids as the predominant bioactive compounds. Following this phytochemical characterization, we assessed the analgesic efficacy of the extracts using acetic acid-induced writhing and electrical heat-induced nociceptive pain stimuli, evaluated antipyretic effects through Brewer's yeast-induced pyrexia, and determined antibacterial activity via the disc diffusion method. Additionally, the toxicity of the extracts was evaluated through preclinical testing.

RESULTS

In hot plate method, the highest pain inhibitory activity was found at a dose of 500 mg/kg of crude extract (3.37 ± 0.31 sec) which differed significantly (P < 0.01 and P < 0.001) with that of the standard drug morphine (6.47 ± 0.23 sec). The extract significantly prolonged reaction latency to thermal-induced pain in hotplate model. Analgesic activity at 500 mg/kg, LG extract produced a 70% suppression of writhing in mice, which was statistically significant (p < 0.001) compared to standard morphine's (77.5%) inhibition. In antipyretic activity assay, the crude extract showed notable reduction in body temperature (36.17 ±  0.32 °C) at dose of 300 mg/kg-body weight, when the standard (at dose 100 mg/kg-body weight) exerted (36.32 ±  0.67 °C) after 3 h of administration. In antibacterial studies, results showed that inhibition of bacterial growth at 400 μg dose of each extract clearly inhibited growth of bacteria from 11 to 22 mm. The extractives carbon tetrachloride fraction, chloroform soluble fraction, ethyl acetate fraction demonstrated notably greater inhibitory zone widths (p < 0.05) against tested strains.

CONCLUSION

Overall, the cold methanol extract of LG leaves demonstrates the therapeutic potential in preclinical settings. Future research is warranted to isolate the specific bioactive compounds and elucidate their mechanisms of action to further support the development of new treatments and contributing to modern medicinal practices based on this plant leaves.

Mast Cells at the Crossroads of Hypersensitivity Reactions and Neurogenic Inflammation

Although mast cells have long been known, they are not yet fully understood. They are traditionally recognized for their role in allergic reactions through the IgE/FcεRI axis, but different groups of surface receptors have since been characterized, which appear to be involved in the manifestation of peculiar clinical features. In particular, MRGPRX2 has emerged as a crucial receptor involved in degranulating human skin mast cells. Because of mast cells' close proximity to peripheral nerve endings, it may play a key role in neuroimmune interactions. This paper provides an overview of mast cell contributions to hypersensitivity and so-called "pseudoallergic" reactions, as well as an update on neuroinflammatory implications in the main models of airway and skin allergic diseases. In particular, the main cellular characteristics and the most relevant surface receptors involved in MC pathophysiology have been reappraised in light of recent advancements in MC research. Molecular and clinical aspects related to MC degranulation induced by IgE or MRGPRX2 have been analyzed and compared, along with their possible repercussions and limitations on future therapeutic perspectives.

A Genetic and Environmental Analysis of Inflammatory Factors in Chronic Widespread Pain Using the TwinsUK Cohort

Chronic widespread musculoskeletal pain (CWP), a significant health issue affecting individuals and society, is often diagnosed as part of fibromyalgia but is not generally considered inflammatory. This study investigated the relationship between blood-based inflammatory factors and CWP in 904 individuals from the TwinsUK cohort. Participants, free of major inflammatory conditions, completed questionnaires to assess CWP. Plasma samples were analysed using the Olink panel, alongside assays for C-reactive protein (CRP) and Apolipoproteins A1 and B. No significant associations were observed between CWP and inflammatory factors after adjusting for multiple testing. Twin modelling revealed significant heritability for both CWP and inflammatory factors, with genetic covariance observed between CWP and several inflammatory factors. Additive Bayesian network modelling suggested that any association between CWP and inflammatory factors is mediated by body mass index (BMI). These findings emphasize the complexity of CWP and its potential reliance on factors beyond inflammation, such as BMI, which strongly correlates with CRP and other inflammatory markers. Future research should explore additional molecular, genetic, and environmental contributors to CWP variability and investigate clinical factors or covariates that may obscure relationships with inflammation, providing a more comprehensive understanding of this multifaceted condition.

Neuroinflammation and neurodegeneration in Huntington's disease: genetic hallmarks, role of metals and organophosphates

Huntington's disease (HDs) is a fatal, autosomal dominant, and hereditary neurodegenerative disorder characterized by progressive motor dysfunction, cognitive decline, and psychiatric disturbances. HD is well linked to mutation in the HTT gene, which leads to an abnormal expansion of trinucleotide CAG repeats, resulting in the production of the mHTT protein and responsible for abnormally long poly-Q tract. These abnormal proteins disrupt cellular processes, including neuroinflammation, endoplasmic reticulum (ER) stress, and mitochondrial dysfunction, ultimately leading to selective neuronal loss in the brain. Epidemiological studies reveal significant regional variability in HDs prevalence, with the highest rates observed in North America and the lowest in Africa. In addition to genetic factors, environmental influences such as exposure to metals, and chemicals, and lifestyle factors like alcohol and tobacco use may exacerbate disease progression. This review explores the molecular mechanisms underlying HDs and emphasize the role of neuroinflammatory mediators and environmental factors, in HD research. Understanding these complex interactions is crucial for developing targeted interventions that can slow or halt the progression of this devastating disease.

Facilitation of Ca V 3.2 channel gating in pain pathways reveals a novel mechanism of serum-induced hyperalgesia

The Ca V 3.2 isoform of T-type voltage-gated calcium channels plays a crucial role in regulating the excitability of nociceptive neurons; the endogenous molecules that modulate its activity, however, remain poorly understood. Here, we used serum proteomics and patch-clamp physiology to discover a novel peptide albumin (1-26) that facilitates channel gating by chelating trace metals that tonically inhibit Ca V 3.2 via H191 residue. Importantly, serum also potently modulated T-currents in human and rodent dorsal root ganglion (DRG) neurons. In vivo pain studies revealed that injections of serum and albumin (1-26) peptide resulted in robust mechanical and heat hypersensitivity. This hypersensitivity was abolished with a T-channel inhibitor, in Ca V 3.2 null mice and in Ca V 3.2 H191Q knock-in mice. The discovery of endogenous chelators of trace metals in the serum deepens our understanding of the role of Ca V 3.2 channels in neuronal hyperexcitability and may facilitate the design of novel analgesics with unique mechanisms of action.

A Comprehensive Analysis of Fibromyalgia and the Role of the Endogenous Opioid System

Fibromyalgia represents a chronic pain disorder characterized by musculoskeletal pain, fatigue, and cognitive impairments. The exact mechanisms underlying fibromyalgia remain undefined; as a result, diagnosis and treatment present considerable challenges. On the other hand, the endogenous opioid system is believed to regulate pain intensity and emotional responses; hence, it might be expected to play a key role in the enhanced sensitivity experienced by fibromyalgia patients. One explanation for the emergence of disrupted pain modulation in individuals with fibromyalgia is a significant reduction in opioid receptor activity or an imbalance in the levels of endogenous opioid peptides. Further research is essential to clarify the complex details of the mechanisms underlying this abnormality. This complexity arises from the notion that an improved understanding could contribute to the development of innovative therapeutic strategies aimed at targeting the endogenous opioid system in the context of fibromyalgia. Although progress is being made, a complete understanding of these complexities remains a significant challenge. This paradigm has the potential to revolutionize the complex management of fibromyalgia, although its implementation may experience challenges. The effectiveness of this approach depends on multiple factors, but the implications could be profound. Despite the challenges involved in this transformation, the potential for improving patient care is considerable, as this condition has long been inadequately treated.

Causal effects of circulating inflammatory proteins on oral phenotypes: Deciphering immune-mediated profiles in the host-oral axis

BACKGROUND

Oral manifestations function as precursors to potential systemic pathologies, signaling early indicators of underlying health complications or immunological dysfunctions. Within these dynamics, circulating inflammatory proteins are recognized as critical mediators in immunopharmacology, bridging holistic health, immune response, and oral health.

METHODS

We employed genetic data from genome-wide association studies to perform comprehensive Mendelian randomization (MR) analyses on 91 circulating inflammatory proteins and 17 oral phenotypes. Six MR algorithms and five auxiliary control measures were utilized to estimate the causal effects. Subsequently, the MR-Bayesian model averaging (MR-BMA) approach was conducted to elucidate the priorities in host-oral communication, followed by network analyses to explore the interactions among phenotypes.

RESULTS

After multiple corrections, MR identified five genetically predicted proteins associated with oral phenotypes. Specifically, FGF21 was correlated with Nteeth and DMFS; hGDNF with gingival pain; CCL4 with stomatitis; and S100A12 with denture use. The causal associations remained robust in sensitivity analyses. Nine protein-phenotype clusters were prioritized using MR-BMA. Among these, S100A12, FGF19, FGF21, and CCL4 exhibited extensive correlations with various oral phenotypes.

CONCLUSIONS

Our study offers novel genetic insights into the causal relationships, prioritizations, and connections between circulating inflammatory proteins and oral phenotypes. These findings comprehensively depict immune-mediated proteomic profiles underlying the host-oral axis, providing significant implications for clinical practice, public health, and immunopharmacology.

Early diagnostics of fibromyalgia: an overview of the challenges and opportunities

INTRODUCTION

Fibromyalgia is a common pain disorder with features of widespread musculoskeletal pain, fatigue, disrupted sleep, cognitive dysfunction, autonomic dysfunction, and mood disorders. Despite its high prevalence and significant impact on quality of life, the diagnosis and management of fibromyalgia remain challenging. Advancements in classification and diagnostics in broad areas have improved our understanding and treatment approach for this condition. We culminate with a discussion of future directions for research into early diagnostics in fibromyalgia.

AREAS COVERED

This perspective examines the current landscape of fibromyalgia biomarker discovery, highlighting challenges that must be addressed and opportunities that are presented as the field evolves.

EXPERT OPINION

Advances in fibromyalgia diagnostics provide an opportunity to dramatically reduce the cost burden placed on health resources for fibromyalgia once we have discovered a reliable reproducible biomarker that is widely accepted among practitioners and patients. Promising results in a number of fields may lead to point of care technologies that will be applicable in the office or bedside without the need for transport to specialized centers. Future research should focus on integrating these various diagnostic approaches to develop a comprehensive, multi-modal diagnostic tool for fibromyalgia.

[Post-Intensive Care Syndrome: functional impairments of critical illness survivors]

With a decrease in mortality of critically ill patients in recent years, intensive care medicine research has shifted its focus on functional impairments of intensive care units (ICU) survivors. ICU survivorship is characterized by long-term impairments of cognition, mental health, and physical health. Since 2012, these impairments have been summarized with the umbrella term Post-Intensive Care Syndrome (PICS). Mental health impairments frequently entail new are aggravated symptoms of depression, anxiety, and posttraumatic stress disorder. Beyond impairments in the three PICS domains, critical illness survivors frequently suffer from chronic pain, dysphagia, and nutritional deficiencies. Furthermore, they have a higher risk for osteoporosis, bone fractures, and diabetes mellitus. Taken together, these sequelae reduce their health-related quality of life. Additionally, ICU survivors are challenged by social problems such as isolation, economic problems such as treatment costs and lost earnings, and return to previous employment. Yet, patients and caregivers have described post-ICU care as inadequate and fragmented. ICU follow-up clinics could improve post-ICU care, but there is insufficient evidence for their effectiveness. Thus far, large high-quality trials with multicomponent and interdisciplinary post-ICU interventions have mostly failed to improve patient outcomes. Hence, preventing PICS and minimizing risk factors by optimizing ICU care is crucial, e.g. by implementing the ABCDE bundle. Future studies need to identify effective components of post-ICU recovery interventions and determine which patient populations may benefit most from ICU recovery services.

Nicorandil restores endothelial cell Kir6.2 expression to alleviate neuropathic pain in mice after chronic constriction injury

The clinical management of neuropathic pain (NP) remains a significant challenge, as current pharmacological treatments do not fully meet clinical needs. Nicorandil, a potassium ATP channel agonist widely used in cardiovascular medicine, has recently been shown to have significant potential for analgesia. This study aimed to investigate the effects and mechanisms of nicorandil in a chronic constriction injury (CCI) mouse model. Nicorandil significantly alleviated pain hypersensitivity and reduced neuronal injury in the sciatic nerve (SN) and dorsal root ganglion (DRG) post-CCI. Nicorandil primarily affected endothelial cells and Schwann cells in the sciatic nerve, restoring the expression of the KATP channel subunit Kir6.2. Furthermore, nicorandil attenuated the hypoxia-induced apoptosis program in sciatic nerve endothelial cells, leading to reduced expression of apoptotic proteins, which provided significant endothelial protection, improved blood-nerve barrier leakage, and decreased the release of DRG inflammatory factors and pain neurotransmitter substance P. In vitro, nicorandil attenuated the apoptosis of human umbilical vein endothelial cells (HUVECs) in a hypoxic environment while maintaining cellular functions. In addition, administering the KATP channel inhibitor glibenclamide in vitro further confirmed the crucial role of Kir6.2 in reducing endothelial hypoxic stress, as confirmed by transmission electron microscopy and behavioural experiments. Overall, these findings indicate that nicorandil significantly ameliorates CCI-induced NP in mice by targeting Kir6.2 in sciatic nerve endothelial cells, thus inhibiting pain sensitization.

Longitudinal relationship between adverse childhood experiences and depressive symptoms: the mediating role of physical pain

BACKGROUND

This study explored the relationship between Adverse Childhood Experiences (ACE), physical pain, and depressive symptoms, and examined the mediating role of pain in the correlation between ACE and depressive symptoms among middle-aged and elderly Chinese (over the age of 45).

METHODS

Cox proportional hazards regression models were used to analysis the association between ACE, physical pain, and depressive symptoms. To assess the mediating role of physical pain in the relationship between ACE and depressive symptoms, mediation analysis was conducted. Indirect, direct, and total effects were estimated by combining mediation and outcome models, adjusting for relevant covariates. Bayesian network models were used to visually demonstrate the interrelations between factors influencing depressive symptoms, further verifying the association between ACE, physical pain, and depressive symptoms.

RESULTS

In the fully adjusted model, middle-aged and elderly individuals reporting ACE had a higher risk of developing depressive symptoms (hazard ratios [HR] and 95% confidence intervals [95% CI], 1.379 [1.266-1.503]). Compared to those without physical pain, individuals reporting severe physical pain were at an increased risk of depressive symptoms (HR [95% CI], 1.438 [1.235-1.673]). The risk was even higher for those with both ACE and severe physical pain compared to those with neither (HR [95% CI], 2.020 [1.630-2.505]). The intensity of pain explained 7.48% of the association between ACE and depressive symptoms, while the number of pain sites accounted for 7.86%.

CONCLUSIONS

Physical pain partially mediated the association between ACE and depressive symptoms. The study findings highlighted the importance of early screening and intervention for physical pain in middle-aged and older adults with ACE.

CLINICAL TRIAL NUMBER

Not applicable.

Calmodulin binding is required for calcium mediated TRPA1 desensitization

Calcium (Ca2+) ions affect nearly all aspects of biology. Excessive Ca2+ entry is cytotoxic and Ca2+-mobilizing receptors have evolved diverse mechanisms for tight regulation that often include Calmodulin (CaM). TRPA1, an essential Ca2+-permeable ion channel involved in pain signaling and inflammation, exhibits complex Ca2+ regulation with initial channel potentiation followed by rapid desensitization. The molecular mechanisms of TRPA1 Ca2+ regulation and whether CaM plays a role remain elusive. We find that TRPA1 binds CaM best at basal Ca2+ concentration, that they co-localize in resting cells, and that CaM suppresses TRPA1 activity. Combining biochemical, biophysical, modeling, NMR spectroscopy, and functional approaches, we identify an evolutionarily conserved, high-affinity CaM binding element in the distal TRPA1 C-terminus (DCTCaMBE). Genetic or biochemical perturbation of Ca2+/CaM binding to the TRPA1 DCTCaMBE yields hyperactive channels that exhibit drastic slowing of desensitization with no effect on potentiation. Ca2+/CaM TRPA1 regulation does not require the N-lobe, raising the possibility that CaM is not the Ca2+ sensor, per se. Higher extracellular Ca2+ can partially rescue slowed desensitization suggesting Ca2+/CaM binding to the TRPA1 DCTCaMBE primes an intrinsic TRPA1 Ca2+ binding site that, upon binding Ca2+, triggers rapid desensitization. Collectively, our results identify a critical regulatory element in an unstructured TRPA1 region highlighting the importance of these domains, they reveal Ca2+/CaM is an essential TRPA1 auxiliary subunit required for rapid desensitization that establishes proper channel function with implications for all future TRPA1 work, and they uncover a mechanism for receptor regulation by Ca2+/CaM that expands the scope of CaM biology.

Antinociceptive Potential of Ximenia americana L. Bark Extract and Caffeic Acid: Insights into Pain Modulation Pathways

Background/Objectives: This study evaluated the antinociceptive effect of the Ximenia americana L. bark extract (HEXA) and its primary component, caffeic acid (CA), through in vivo assays. Methods: The antinociceptive properties were assessed using abdominal writhing, hot plate, and Von Frey tests. Additionally, the study investigated the modulation of various pain signaling pathways using a pharmacological approach. Results: The results demonstrated that all doses of the HEXA significantly increased latency in the hot plate test, decreased the number of abdominal contortions, reduced hyperalgesia in the Von Frey test, and reduced both phases of the formalin test. Caffeic acid reduced licking time in the first phase of the formalin test at all doses, with the highest dose showing significant effects in the second phase. The HEXA potentially modulated α2-adrenergic (52.99%), nitric oxide (57.77%), glutamatergic (33.66%), vanilloid (39.84%), cyclic guanosine monophosphate (56.11%), and K+ATP channel-dependent pathways (38.70%). Conversely, CA influenced the opioid, glutamatergic (53.60%), and vanilloid (34.42%) pathways while inhibiting nitric oxide (52.99%) and cyclic guanosine monophosphate (38.98%). Conclusions: HEXA and CA exhibit significant antinociceptive effects due to their potential interference in multiple pain signaling pathways. While the molecular targets remain to be fully investigated, HEXA and CA demonstrate significant potential for the development of new analgesic drugs.

Abietic acid antagonizes the anti-inflammatory effects of celecoxib and ketoprofen: Preclinical assessment and molecular dynamic simulations

The present work is designed to explore the anti-inflammatory properties of AA and its modulatory effects on celecoxib (CEL) and ketoprofen (KET) through in vitro, ex vivo, in vivo, and in silico approaches. Different concentrations of AA were utilized to evaluate the membrane-stabilizing potential via egg albumin and the Human Red Blood Cell (HRBC) denaturation model. In the animal model, formalin (50 μL) was injected into the right hind paw of young chicks to induce inflammation. AA was administered at 20 and 40 mg/kg (p.o.) to the experimental animals. We used CEL and KET as positive controls. The vehicle was provided as a control group. Two combinations of AA with CEL and KET were also investigated in all tests to assess the modulatory activity of AA. In addition, in silico investigation was used for predictions about drug-likeness, pharmacokinetics, and toxicity of the selected chemical compounds, and the study also evaluated the binding affinity, visualization, and stability of ligand-receptor interactions through molecular dynamic (MD) simulation. Results manifested that AA concentration-dependently significantly inhibited the egg albumin denaturation (IC50: 27.53 ± 0.88 μg/ml) and breakdown of HRBC (IC50: 15.69 ± 0.75 μg/ml), indicating the membrane stabilizing potential compared to the control group. AA also significantly (p < 0.05) lessened the frequency of licking and alleviated the paw edema in a dose-dependent manner in an in vivo test. However, AA reduced the activity of CEL and KET in combination treatment. AA showed good pharmacokinetic characteristics to be considered as a therapeutic candidate. Additionally, the in silico study displayed that AA demonstrated a relatively higher docking score of -9.1 kcal/mol with the cyclooxygenase-2 (COX-2) enzyme and stable binding in MD simulation. Whereas the standard ligand (CEL) expressed the highest binding value of -9.2 kcal/mol to the COX-2.

Exploring molecular mechanisms of postoperative delirium through multi-omics strategies in plasma exosomes

Currently, the diagnosis of delirium is solely based on clinical observation, lacking objective diagnostic tools, and the regulatory networks and pathological mechanisms behind it are not yet fully understood. Exosomes have garnered considerable interest as potential biomarkers for a variety of illnesses. This research aimed to delineate both the proteomic and metabolomic landscapes inherent to exosomes, assessing their diagnostic utility in postoperative delirium (POD) and understanding the underlying pathophysiological frameworks. Integrated analyses of proteomics and metabolomics were conducted on exosomes derived from plasma of individuals from both the non-postoperative delirium (NPOD) control group and the POD group. Subsequently, the study utilized the Connectivity Map (CMap) methodology for the identification of promising small-molecule drugs and carried out molecular docking assessments to explore the binding affinities with the enzyme MMP9 of these identified molecules. We identified significant differences in exosomal metabolites and proteins between the POD and control groups, highlighting pathways related to neuroinflammation and blood-brain barrier (BBB) integrity. Our CMap analysis identified potential small-molecule therapeutics, and molecular docking studies revealed two compounds with high affinity to MMP9, suggesting a new therapeutic avenue for POD. This study highlights MMP9, TLR2, ICAM1, S100B, and glutamate as key biomarkers in the pathophysiology of POD, emphasizing the roles of neuroinflammation and BBB integrity. Notably, molecular docking suggests mirin and orantinib as potential inhibitors targeting MMP9, providing new therapeutic avenues. The findings broaden our understanding of POD mechanisms and suggest targeted strategies for its management, reinforcing the importance of multidimensional biomarker analysis and molecular targeting in POD intervention.

Pathophysiology of Pain and Mechanisms of Neuromodulation: A Narrative Review (A Neuron Project)

Pain serves as a vital innate defense mechanism that can significantly impact an individual's quality of life. Understanding the physiological effects of pain well plays an important role in developing novel pain treatments. Nociceptor neurons play a key role in pain and inflammation. Interactions between nociceptors and the immune system occur both at the site of injury and within the central nervous system. Modulating chemical mediators and nociceptor activity offers promising new approaches to pain management. Essentially, the sensory nervous system is essential for modulating the body's protective response, making it critical to understand these interactions to discover new pain treatment strategies. New innovations in neuromodulation have led to alternatives to opioids individuals with chronic pain with consequent improvement in disease-based treatment and nerve targeting. New neural targets from cellular and structural perspectives have revolutionized the field of neuromodulation. This narrative review aims to elucidate the mechanisms of pain transmission and processing, examine the characteristics and properties of nociceptors, and explore how the immune system influences pain perception. It further provides an updated overview of the physiology of pain and neuromodulatory mechanisms essential for managing acute and chronic pain. We assess the current understanding of different pain types, focusing on key molecules involved in each type and their physiological effects. Additionally, we compare painful and painless neuropathies and discuss the neuroimmune interactions involved in pain manifestation.

Novel analgesic peptide derived from Cinobufacini injection suppressing inflammation and pain via ERK1/2/COX-2 pathway

Inflammatory pain is a chronic pain caused by peripheral tissue inflammation, seriously impacting the patient's life quality. Cinobufacini injection, as a traditional Chinese medicine injection preparation, shows excellent efficacy in anti-inflammatory and analgesic treatment in patients with advanced tumors. In this study, a novel analgesic peptide CI5 with anti-inflammatory and analgesic bio-functions that naturally presents in Cinobufacini injection and its regulatory mechanism are reported. Our results showed that the administration of CI5 significantly relieved the pain of mice in the acetic acid twisting analgesic model and formalin inflammatory pain model. Furthermore, CI5 effectively reduced the inflammatory cytokines (IL-6, TNF-α and IL-1β) and inflammatory mediator (PGE2) expressions, and prevented the carrageenan-induced paw edema in mice. Further LC-MS/MS results showed the anti-inflammatory and analgesic bio-functions of CI5 depended on its interaction with the Rac-2 protein upstream of ERK1/2 and the inflammatory signaling pathway (ERK1/2/COX-2 axis). In summary, CI5, as a novel natural candidate identified from Cinobufacini injection, showed substantial clinical promise for inflammatory pain treatments.

About Distress in Chronic Pain Conditions: A Pre-Post Study on the Effectiveness of a Mindfulness-Based Intervention for Fibromyalgia and Low Back Pain Patients

Chronic pain (CP) affects about 30% of the global population and poses significant challenges to individuals and healthcare systems worldwide. The interactions between physiological, psychological, and social factors are crucial in the onset and development of CP conditions. This study aimed to evaluate the effectiveness of mindfulness-based intervention, examining its impact on perceived stress (PSS), depression and anxiety (BDI-II, PGWBI/DEP, SAS, STAI Y), sleep quality (PSQI), and mindfulness abilities (MAAS) in individuals with CP. Participants (N = 89, 84.3% female) underwent one of two diagnoses [fibromyalgia (FM) or low back pain (LBP)] and took part in an MBSR intervention. The mindfulness program proved effective in reducing PSQI scores (F = 11.97; p < 0.01) over time, independently of the type of diagnosis. There was also a marginal increase in trait mindfulness as measured by MAAS (F = 3.25; p = 0.07) in both groups. A significant difference between the two groups was found for the effect on PSS: F (1,87) = 6.46; p < 0.05. Mindfulness practice also reduced anxiety in FM and depressive symptoms in LBP, indicating a reduction in psychological distress among participants. Our findings suggest that mindfulness-based interventions may offer promising avenues for personalized pain management in clinical settings.

Synthesis and Anti-Inflammatory and Analgesic Potentials of Ethyl 2-(2,5-Dioxo-1-Phenylpyrrolidin-3-yl)-2-Methylpropanoate

Background/Objectives: Inflammation and analgesia are two prominent symptoms and often lead to chronic medical conditions. To control inflammation and analgesia, many marketed drugs are in practice but the majority of them have severe side effects. Methods: This study involved the synthesis of a pivalate-based Michael product and evaluated it for in vitro COX-1, COX-2, and 5-LOX inhibitory potentials using specific assays. Molecular docking studies were also assessed. Based on the in vitro results, the compound was also subjected to in vivo anti-inflammatory and antinociceptive studies. Results: The pivalate-based Michael product (MAK01) was synthesized by an organocatalytic asymmetric Michael addition of ethyl isobutyrate to N-phenylmaleimide with an isolated yield of 96%. The structure of the compound was confirmed through 1H and 13C NMR analyses. The observed IC50 values for COX-1, COX-2, and 5-LOX were 314, 130, and 105 μg/mL, respectively. The molecular docking studies on the synthesized compound showed binding interactions with the minimized pockets of the respective enzymes. In a carrageenan model, a percent reduction in edema when administered at 10 mg/kg (a reduction of 33.3 ± 0.77% at the second hour), 20 mg/kg (a reduction of 34.7 ± 0.74% at the second hour), and 30 mg/kg (a reduction of 40.58% ± 0.84% after the fifth hour) was observed. The compound showed a significant response at concentrations of 50, 100, and 150 mg/kg with latency times of 10.32 ± 0.82, 12.16 ± 0.51, and 12.93 ± 0.45 s, respectively. Conclusion: In this study, we synthesized a pivalate-based Michael product for the first time. Moreover, based on its rationality and potency, it was found to be an effective future medicine for the management of analgesia and inflammation.

Activated microglia secretome and proinflammatory cytokines increase neuronal mu-opioid receptor signalling and expression

Due to its potential role in processes which rely on mu-opioid receptor function, investigating the relationship between Mu-Opioid receptors (MORs), neuroinflammation, and glial cells has gained momentum. Traditionally, MOR activation has been associated with immunosuppression, but recent findings suggest a more nuanced, bidirectional relationship with the immune system. To further investigate this relationship, herein, we investigated the role of the activated microglia secretome and proinflammatory cytokines in neuronal MOR expression and signalling. Our results show that both microglial secretome and specific cytokines increase neuronal MOR expression and enhance the [D-Ala2, N-MePhe4, Gly-ol]-enkephalin (DAMGO)-induced MOR activation. We also show that DAMGO-induced neuroinflammation increases neuronal MOR expression, activation, and regulation. Our findings suggest a feedback loop between microglial activation, cytokine release, and neuronal MOR dynamics. Future research should delve into the temporal dynamics and functional implications of this relationship, particularly concerning clinically relevant opioids like morphine and fentanyl and pain management.

Up-regulation of IL-1β and sPLA2-III in the medial prefrontal cortex contributes to orofacial and somatic hyperalgesia induced by malocclusion via glial-neuron crosstalk

The medial prefrontal cortex (mPFC) has been identified as a key brain region involved in the modulation of chronic pain. Our recent study demonstrated that unilateral anterior crossbite (UAC) developed the comorbidity model of temporomandibular disorders (TMD) and fibromyalgia syndrome (FMS), which was characterized by both orofacial and somatic hyperalgesia. In the present study, UAC rats exhibited significant changes in gene expression in the mPFC. Enrichment analysis revealed that the significantly involved pathways were cytokines-cytokine receptor interaction and immune response. The expression of group III secretory phospholipase A2 (sPLA2-III) was significantly increased in the mPFC of UAC rats. Silencing sPLA2-III expression in the mPFC blocked the orofacial and somatic hyperalgesia. Immunofluorescence showed that sPLA2-III was mainly localized in neurons. The expression of interleukin-1β (IL-1β) in the mPFC significantly increased after UAC. Injection of IL-1β antibody into the mPFC blocked orofacial and somatic hyperalgesia. IL-1β was mainly localized in microglia cells. Furthermore, injection of IL-1β antibody significantly reduced the expression of sPLA2-III. These results indicate that neuroinflammatory cascade responses induced by glial-neuron crosstalk in the mPFC may contribute to the development of TMD and FMS comorbidity, and IL-1β and sPLA2-III are identified as novel potential therapeutic targets for the treatment of chronic pain in the comorbidity of TMD and FMS.

Pain research in a petri dish? Advantages and limitations of neuro-glial primary cell cultures from structures of the nociceptive system

How can we learn more about pain without causing pain in humans or animals? This short review focuses on neuro-glial primary cell cultures as models to study neuro-immune interactions in the context of pain and discusses their advantages and limitations. The field of basic pain research places scientists in an ethical dilemma. We aim to understand underlying mechanisms of pain for an improved pain therapy for humans and animals. At the same time, this regularly includes the induction of pain in model animals. Within the field of psychoneuroimmunology, the examination of the complexity of neuro-immune interactions in health and disease as well as the bi-directional communication between the brain and the periphery make animal experiments an inevitable part of pain research. To address ethical and legal considerations as well as the growing societal awareness for animal welfare, scientists push for the identification and characterization of complementary methods to implement the 3R principle of Russel and Burch. As such, methods to replace animal studies, reduce the number of animals used, and refine experiments are tested. Neuro-glial primary cell cultures of structures of the nociceptive system, such as dorsal root ganglia (DRG) or the spinal dorsal horn (SDH) represent useful in vitro tools, when research comes to a cellular and molecular level. They allow for studying mechanisms of neuronal sensitization, glial cell activation, or the role of specific inflammatory mediators and intracellular signaling cascades involved in the development of inflammatory and neuropathic pain. Moreover, DRG/SDH-cultures provide the opportunity to test novel strategies for interventions, such as pharmaceuticals or cell-based therapies targeting neuroinflammatory processes. Thereby, in vitro models contribute to a better understanding of neuron-glia-immune communication in the context of pain and in the advancement of pain therapies. However, this can only be one piece in a large puzzle. Our knowledge about the complexity of pain will depend on studies in humans and animals applied in vitro and in vivo and will benefit from clear and open-minded interdisciplinary communication and transparency in public outreach.

Beneficial Effects of Ginger Root Extract on Pain Behaviors, Inflammation, and Mitochondrial Function in the Colon and Different Brain Regions of Male and Female Neuropathic Rats: A Gut-Brain Axis Study

BACKGROUND

Neuroinflammation and mitochondrial dysfunction have been implicated in the progression of neuropathic pain (NP) but can be mitigated by supplementation with gingerol-enriched ginger (GEG). However, the exact benefits of GEG for each sex in treating neuroinflammation and mitochondrial homeostasis in different brain regions and the colon remain to be determined.

OBJECTIVE

Evaluate the effects of GEG on emotional/affective pain and spontaneous pain behaviors, neuroinflammation, as well as mitochondria homeostasis in the amygdala, frontal cortex, hippocampus, and colon of male and female rats in the spinal nerve ligation (SNL) NP model.

METHODS

One hundred rats (fifty males and fifty females) were randomly assigned to five groups: sham + vehicle, SNL + vehicle, and SNL with three different GEG doses (200, 400, and 600 mg/kg BW) for 5 weeks. A rat grimace scale and vocalizations were used to assess spontaneous and emotional/affective pain behaviors, respectively. mRNA gene and protein expression levels for tight junction protein, neuroinflammation, mitochondria homeostasis, and oxidative stress were measured in the amygdala, frontal cortex, hippocampus, and colon using qRT-PCR and Western blot (colon).

RESULTS

GEG supplementation mitigated spontaneous pain in both male and female rats with NP while decreasing emotional/affective responses only in male NP rats. GEG supplementation increased intestinal integrity (claudin 3) and suppressed neuroinflammation [glial activation (GFAP, CD11b, IBA1) and inflammation (TNFα, NFκB, IL1β)] in the selected brain regions and colon of male and female NP rats. GEG supplementation improved mitochondrial homeostasis [increased biogenesis (TFAM, PGC1α), increased fission (FIS, DRP1), decreased fusion (MFN2, MFN1) and mitophagy (PINK1), and increased Complex III] in the selected brain regions and colon in both sexes. Some GEG dose-response effects in gene expression were observed in NP rats of both sexes.

CONCLUSIONS

GEG supplementation decreased emotional/affective pain behaviors of males and females via improving gut integrity, suppressing neuroinflammation, and improving mitochondrial homeostasis in the amygdala, frontal cortex, hippocampus, and colon in both male and female SNL rats in an NP model, implicating the gut-brain axis in NP. Sex differences observed in the vocalizations assay may suggest different mechanisms of evoked NP responses in females.

Proteomic Analysis of Signaling Pathways Modulated by Fatty Acid Binding Protein 5 (FABP5) in Macrophages

Although acute inflammation serves essential functions in maintaining tissue homeostasis, chronic inflammation is causally linked to many diseases. Macrophages are a major cell type that orchestrates inflammatory processes. During inflammation, macrophages undergo polarization and activation, thereby mobilizing pro-inflammatory and anti-inflammatory transcriptional programs that regulate ensuing macrophage functions. Fatty acid binding protein 5 (FABP5) is a lipid chaperone highly expressed in macrophages. FABP5 deletion is implicated in driving macrophages toward an anti-inflammatory phenotype, yet signaling pathways regulated by macrophage-FABP5 have not been systematically profiled. We leveraged proteomic and phosphoproteomic approaches to characterize pathways modulated by FABP5 in M1 and M2 polarized bone marrow-derived macrophages (BMDMs). Stable isotope labeling by amino acids-based analysis of M1 and M2 polarized wild-type and FABP5 knockout BMDMs revealed numerous differentially regulated proteins and phosphoproteins. FABP5 deletion impacted downstream pathways associated with inflammation, cytokine production, oxidative stress, and kinase activity. Toll-like receptor 2 (TLR2) emerged as a novel target of FABP5 and pharmacological FABP5 inhibition blunted TLR2-mediated activation of downstream pathways, ascribing a novel role for FABP5 in TLR2 signaling. This study represents a comprehensive characterization of the impact of FABP5 deletion on the proteomic and phosphoproteomic landscape of M1 and M2 polarized BMDMs. Loss of FABP5 altered pathways implicated in inflammatory responses, macrophage function, and TLR2 signaling. This work provides a foundation for future studies seeking to investigate the therapeutic potential of FABP5 inhibition in pathophysiological states resulting from dysregulated inflammatory signaling. SIGNIFICANCE STATEMENT: This research offers a comprehensive analysis of fatty acid binding protein 5 (FABP5) in macrophages during inflammatory response. The authors employed quantitative proteomic and phosphoproteomic approaches to investigate this utilizing bone marrow-derived macrophages that were M1 and M2 polarized using lipopolysaccharide with interferon γ and interleukin-4, respectively. This revealed multiple pathways related to inflammation that were differentially regulated due to the absence of FABP5. These findings underscore the potential therapeutic significance of macrophage-FABP5 as a candidate for addressing inflammatory-related diseases.

Interplay between cannabinoids and the neuroimmune system in migraine

Migraine is a common and complex neurological disorder that has a high impact on quality of life. Recent advances with drugs that target the neuropeptide calcitonin gene-related peptide (CGRP) have helped, but treatment options remain insufficient. CGRP is released from trigeminal sensory fibers and contributes to peripheral sensitization, perhaps in part due to actions on immune cells in the trigeminovascular system. In this review, we will discuss the potential of cannabinoid targeting of immune cells as an innovative therapeutic target for migraine treatment. We will cover endogenous endocannabinoids, plant-derived phytocannabinoids and synthetically derived cannabinoids. The focus will be on six types of immune cells known to express multiple cannabinoid receptors: macrophages, monocytes, mast cells, dendritic cells, B cells, and T cells. These cells also contain receptors for CGRP and as such, cannabinoids might potentially modulate the efficacy of current CGRP-targeting drugs. Unfortunately, to date most studies on cannabinoids and immune cells have relied on cell cultures and only a single preclinical study has tested cannabinoid actions on immune cells in a migraine model. Encouragingly, in that study a synthetically created stable chiral analog of an endocannabinoid reduced meningeal mast cell degranulation. Likewise, clinical trials evaluating the safety and efficacy of cannabinoid-based therapies for migraine patients have been limited but are encouraging. Thus, the field is at its infancy and there are significant gaps in our understanding of the impact of cannabinoids on immune cells in migraine. Future research exploring the interactions between cannabinoids and immune cells could lead to more targeted and effective migraine treatments.

Neuroinflammation in osteoarthritis: From pain to mood disorders

Osteoarthritis (OA) is the most common form of musculoskeletal disease, and its prevalence is increasing due to the aging of the population. Chronic pain is the most burdensome symptom of OA that significantly lowers patients' quality of life, also due to its frequent association with emotional comorbidities, such as anxiety and depression. In recent years, both chronic pain and mood alterations have been linked to the development of neuroinflammation in the peripheral nervous system, spinal cord and supraspinal brain areas. Thus, mechanisms at the basis of the development of the neuroinflammatory process may indicate promising targets for novel treatment for pain and affective comorbidities that accompany OA. In order to assess the key role of neuroinflammation in the maintenance of chronic pain and its potential involvement in development of psychiatric components, the monoiodoacetate (MIA) model of OA in rodents has been used and validated. In the present commentary article, we aim to summarize up-to-date results achieved in this experimental model of OA, focusing on glia activation and cytokine production in the sciatic nerve, dorsal root ganglia (DRGs), spinal cord and brain areas. The association of a neuroinflammatory state with the development of pain and anxiety- and depression-like behaviors are discussed. Results suggest that cells and molecules involved in neuroinflammation may represent novel targets for innovative pharmacological treatments of OA pain and mood comorbidities.

Transcriptomic Profiling of Primary Microglia: Effects of miR-19a-3p and miR-19b-3p on Microglia Activation

Neuropathic pain resulting from spinal cord injury (SCI) is a significant secondary health issue affecting around 60% of individuals with SCI. After SCI, activation of microglia, the immune cells within the central nervous system, leads to neuroinflammation by producing pro-inflammatory cytokines and affects neuropathic pain. This interplay between inflammation and pain contributes to the persistent and intense pain experienced by many individuals with SCI. MicroRNAs (miRs) have been critical regulators of neuroinflammation. Previous research in our laboratory has revealed upregulation levels of circulating miR-19a and miR-19b in individuals with SCI with neuropathic pain compared to those without pain. In this study, we treated primary microglial cultures from mice with miR-19a and miR-19b for 24 h and conducted RNA sequencing analysis. Our results showed that miR-19a and miR-19b up- and downregulate different genes according to the volcano plots and the heatmaps. miR-19a and miR-19b regulate inflammation through distinct signaling pathways. The results showed that miR-19a promotes inflammation via toll-like receptor signaling, TNF signaling, and cytokine-cytokine receptor interactions, while miR-19b increases inflammatory responses through the PI3K-Akt signaling pathway, focal adhesion, and extracellular matrix receptor interactions. The protein-protein interaction (PPI) networks used the STRING database to identify transcription factors associated with genes up- or downregulated by miR-19a and miR-19b. Key transcription factors, such as STAT1, STAT2, and KLF4 for miR-19a, and Nr4a1, Nr4a2, and Nr4a3 for miR-19b, were identified and revealed their roles in regulating neuroinflammation. This study demonstrates that miR-19a and miR-19b modulate diverse patterns of gene expression, regulate inflammation, and induce inflammatory responses in microglia.

Recent developments and challenges in positron emission tomography imaging of gliosis in chronic neuropathic pain

ABSTRACT

Understanding the mechanisms that underpin the transition from acute to chronic pain is critical for the development of more effective and targeted treatments. There is growing interest in the contribution of glial cells to this process, with cross-sectional preclinical studies demonstrating specific changes in these cell types capturing targeted timepoints from the acute phase and the chronic phase. In vivo longitudinal assessment of the development and evolution of these changes in experimental animals and humans has presented a significant challenge. Recent technological advances in preclinical and clinical positron emission tomography, including the development of specific radiotracers for gliosis, offer great promise for the field. These advances now permit tracking of glial changes over time and provide the ability to relate these changes to pain-relevant symptomology, comorbid psychiatric conditions, and treatment outcomes at both a group and an individual level. In this article, we summarize evidence for gliosis in the transition from acute to chronic pain and provide an overview of the specific radiotracers available to measure this process, highlighting their potential, particularly when combined with ex vivo / in vitro techniques, to understand the pathophysiology of chronic neuropathic pain. These complementary investigations can be used to bridge the existing gap in the field concerning the contribution of gliosis to neuropathic pain and identify potential targets for interventions.