Neuro-Immunity and Gut Dysbiosis Drive Parkinson's Disease-Induced Pain

Language errors in pain medicine: An umbrella review

Errors in language are common in pain medicine, but the extent of such errors has not been systematically measured. This pre-registered umbrella review explored Embase, PubMed, Medline and CINAHL and seeks to quantify the prevalence of errors in language in review articles since the last IASP definition revision. To be eligible, studies must have met the following criteria: 1) Primary aim was stated as to provide neurophysiological explanations of nociception and/or pain in humans in context of a pathology/condition; 2) Any type of review article; 3) Written in English; 4) Published in a peer-reviewed journal. Studies were excluded if they met any of the following criteria: 5) Published prior to the last revision of the IASP definition; 6) Published after May 2023; 7) Published in a predatory journal. Out of 5470 articles screened, 48 review articles met the inclusion criteria. All articles contained at least one error in language, there were no differences in the proportions of errors in language in review articles between years of publication, and various predictors were mostly not associated with a higher or lower number of errors in language counts in articles. Our findings reveal the need for heightened awareness among researchers, clinicians, journals and editorial boards regarding the prevalence and impact of these errors. Given our findings and their limitations, further research should focus on examining the contextual influence of misnomer usage and replication of these results. PERSPECTIVE: This umbrella review explored the main biomedical databases to see how many review articles contained language errors. Our findings underscore the imperative for prompt action in regulating pain medicine terminology. PRE-REGISTRATION: This umbrella review was pre-registered on OSF registries (https://doi.org/10.17605/osf.io/kau8m). ONLINE MATERIAL: https://osf.io/kdweg/.

Progress in the mechanisms of pain associated with neurodegenerative diseases

Neurodegenerative diseases (NDDs) represent a class of neurological disorders characterized by the progressive degeneration or loss of neurons, impacting millions of individuals globally. In addition to the typical manifestations, pain is a prevalent symptom associated with NDDs, seriously impacting the quality of life for patients. The pathogenesis of pain associated with NDDs is intricate and multifaceted. Currently, the clinical management of NDDs-related pain symptoms predominantly relies on conventional pharmacological agents or physical therapy. However, these approaches often fail to produce satisfactory outcomes. This article summarizes the underlying mechanisms of major NDDs-associated pain: Neuroinflammation, Brain and spinal cord dysfunctions, Mitochondrial dysfunction, Risk gene and pathological protein, as well as Receptor, channel, and neurotransmitter. While numerous studies have investigated the downstream pathological processes associated with these mechanisms, there remains a significant gap in identifying the key initiating factors. Specifically, there is insufficient evidence for the upstream elements that activate microglia and astrocytes in neuroinflammation leading to pain in NDDs. Likewise, there is an absence of upstream factors elucidating how dysfunctions in the brain and spinal cord, as well as mitochondrial impairments, contribute to the development of pain. Furthermore, the specific mechanisms through which hallmark pathological proteins related to NDDs contribute to these pathological processes remain inadequately understood. The objective of this article is to synthesize the existing mechanisms underlying pain associated with NDDs, including Alzheimer's disease, Parkinson's disease, Huntington's disease, Schizophrenia, Amyotrophic lateral sclerosis, and Multiple sclerosis, while also identifying gaps and deficiencies in these mechanisms. This paper offers insights for future research trajectories. Given the intricate pathogenesis of NDDs-related pain, it emphasizes that a promising short-term strategy is combination therapy-intervening concurrently in multiple pathological processes-akin to the cocktail approach utilized in treating acquired immunodeficiency syndrome (AIDS). For long-term advancements, achieving breakthroughs in the treatment of the NDDs themselves will remain essential for alleviating accompanying pain symptoms.

NOCICEPTOR NEURONS CONTROL POLLUTION-MEDIATED NEUTROPHILIC ASTHMA

The immune and sensory nervous systems, having evolved together, use a shared language of receptors and transmitters to maintain homeostasis by responding to external and internal disruptions. Although beneficial in many cases, neurons can exacerbate inflammation during allergic reactions, such as asthma. Our research modeled asthma aggravated by pollution, exposing mice to ambient PM2.5 particles and ovalbumin. This exposure significantly increased bronchoalveolar lavage fluid neutrophils and γδ T cells compared to exposure to ovalbumin alone. We normalized airway inflammation and lung neutrophil levels by silencing nociceptor neurons at inflammation's peak using intranasal QX-314 or ablating TRPV1-expressing neurons. Additionally, we observed heightened sensitivity in chemical-sensing TRPA1 channels in neurons from pollution-exacerbated asthmatic mice. Elevated levels of artemin were detected in the bronchoalveolar lavage fluid from pollution-exposed mice, with artemin levels normalizing in mice with ablated nociceptor neurons. Upon exposure PM2.5 particles, alveolar macrophages expressing pollution-sensing aryl hydrocarbon receptors, were identified as the source of artemin. This molecule enhanced TRPA1 responsiveness and increased neutrophil influx, providing a novel mechanism by which lung-innervating neurons respond to air pollution and suggesting a potential therapeutic target for controlling neutrophilic airway inflammation in asthma, a clinically intractable condition.

Pain in Parkinson's disease: a neuroanatomy-based approach

Parkinson's disease is a progressive neurodegenerative disorder characterized by the deposition of misfolded alpha-synuclein in different regions of the central and peripheral nervous system. Motor impairment represents the signature clinical expression of Parkinson's disease. Nevertheless, non-motor symptoms are invariably present at different stages of the disease and constitute an important therapeutic challenge with a high impact for the patients' quality of life. Among non-motor symptoms, pain is frequently experienced by patients, being present in a range of 24-85% of Parkinson's disease population. Moreover, in more than 5% of patients, pain represents the first clinical manifestation, preceding by decades the exordium of motor symptoms. Pain implies a complex biopsychosocial experience with a downstream complex anatomical network involved in pain perception, modulation, and processing. Interestingly, all the anatomical areas involved in pain network can be affected by a-synuclein pathology, suggesting that pathophysiology of pain in Parkinson's disease encompasses a 'pain spectrum', involving different anatomical and neurochemical substrates. Here the various anatomical sites recruited in pain perception, modulation and processing are discussed, highlighting the consequences of their possible degeneration in course of Parkinson's disease. Starting from peripheral small fibres neuropathy and pathological alterations at the level of the posterior laminae of the spinal cord, we then describe the multifaceted role of noradrenaline and dopamine loss in driving dysregulated pain perception. Finally, we focus on the possible role of the intertwined circuits between amygdala, nucleus accumbens and habenula in determining the psycho-emotional, autonomic and cognitive experience of pain in Parkinson's disease. This narrative review provides the first anatomically driven comprehension of pain in Parkinson's disease, aiming at fostering new insights for personalized clinical diagnosis and therapeutic interventions.

The Effect of Gua Sha Therapy on Pain in Parkinson's Disease: a Randomized Controlled Trial

Purpose

Pain is a common yet undertreated symptom of Parkinson's disease (PD). This study investigated the effect of Gua Sha therapy on pain in patients with PD.

Patients and Methods

A total of 56 PD patients with pain were randomized into either the experimental group (n=28), receiving 12 sessions of Gua Sha therapy, or the control group (n=28) without additional treatment. Participants underwent assessment at baseline, after the twelfth invention, and at the 2-month follow-up timepoints. The primary outcome was KPPS and VAS. Secondary outcomes included UPDRS I-III, PDSS-2, HADS, PDQ-39, and blood biomarkers (5-HT, IL-8, IL-10).

Results

The experimental group reported a significant improvement in pain severity, motor functions, affective disorder, and sleep quality (P < 0.05). Furthermore, increasing trends in both 5-HT and IL-10, as well as decreasing trends in IL-8 were observed. No serious adverse events occurred.

Conclusion

The preliminary findings suggest that Gua Sha therapy may be effective and safe for alleviating pain and improving other disease-related symptoms in PD patients.

Application of sensory nerve quantitative tests to analyze the subtypes of motor disorders in Parkinson's disease

This study investigated the sensory nerve function in people with different subtypes of Parkinson's disease (PD), which included the tremor-dominant (TD) group (n = 30), postural instability and gait disorder (PIGD) group (n = 33), and healthy-controls (HC) group (n = 33). Sural nerve's current perception threshold (CPT) and pain tolerance threshold (PTT) in both feet were measured at different frequencies. Results were evaluated using the mini-mental state examination (MMSE), Hoehn Yahr scale (H-Y) , and 3-meter timed-up-and-go-test (TUGT). The MMSE scores of the TD and HC groups were higher than those of the PIGD group (TD < HC). The 3-meter TUGT scores of the PIGD group were higher than theTD and HC groups (TD > HC). The PIGD patients experienced a significantly shorter disease duration and higher H-Y score than the TD patients ( P  < 0.05). The values of 2 KHz CPT of left-side (CPTL), 2KHz CPT of right-side (CPTR), and 5 Hz CPTR in the PIGD group were significantly higher compared to the TD and HC groups ( P  < 0.05, Bonferroni correction). Additionally, the values of 250 Hz CPTL, 5 Hz CPTL, 250 Hz CPTR, 2 kHz PTT of left-side (PTTL), 250 Hz PTTL, and 5 Hz PTTL in the PIGD group were significantly elevated relative to the TD group ( P  < 0.05, Bonferroni correction). Distinctive current threshold perception and PTT of the sural nerve can be observed in patients with varying PD subtypes, and sensory nerve conduction threshold electrical diagnostic testing can detect these discrepancies in sensory nerve function.

Cellular and Molecular Roles of Immune Cells in the Gut-Brain Axis in Migraine

Migraine is a complex and multi-system dysfunction. The realization of its pathophysiology and diagnosis is developing rapidly. Migraine has been linked to gastrointestinal disorders such as irritable bowel syndrome and celiac disease. There is also direct and indirect evidence for a relationship between migraine and the gut-brain axis, but the exact mechanism is not yet explained. Studies have shown that this interaction appears to be influenced by a variety of factors, such as inflammatory mediators, gut microbiota, neuropeptides, and serotonin pathways. Recent studies suggest that immune cells can be the potential tertiary structure between migraine and gut-brain axis. As the hot interdisciplinary subject, the relationship between immunology and gastrointestinal tract is now gradually clear. Inflammatory signals are involved in cellular and molecular responses that link central and peripheral systems. The gastrointestinal symptoms associated with migraine and experiments associated with antibiotics have shown that the intestinal microbiota is abnormal during the attacks. In this review, we focus on the mechanism of migraine and gut-brain axis, and summarize the tertiary structure between immune cells, neural network, and gastrointestinal tract.

Human metabolism and body composition: prospects for novel studies

CONTEXT

Most articles on gut microbiota argue the importance of body composition assessment in patients; however, body composition assessments are fragile (ie, with methodological limitations) in the most recent studies.

OBJECTIVE

To present two suggestions for further research using the human body composition assessment.

METHODS

The methods used in this study are based on a Pinto et al article published in Nutrition Reviews.

DATA EXTRACTION

On the basis of data.

obtained from the PubMed, SCOPUS, LILACS, and Web of Science databases, Pinto et al provided a current survey of intermittent fasting protocols and an understanding of the outcomes to date in terms of the profile of the intestinal microbiota in obese organisms.

DATA ANALYSIS

Of the 82 original articles identified from the databases, 35 were eliminated because of duplication and 32 were excluded for not meeting the inclusion criteria. Two additional articles found in a new search were added, yielding a total of 17 studies to be included in this review. Among the protocols, alternate-day fasting and time-restricted feeding were the most common, and they were shown to have different mechanisms of metabolic signaling. Time-restricted feeding influences body mass control and biochemical parameters by regulating the circadian system and improving satiety control systems by acting on leptin secretion. In contrast, alternate-day fasting leads to a reduction of ±75% of all energy consumption regardless of dietary composition, in addition to promoting hormonal adjustments that promote body mass control. Furthermore, both protocols could remodel the intestinal microbiota by changing the Firmicutes to Bacteroidetes ratio and increasing the abundance of strains such as Lactobacillus spp. and Akkermansia that have a protective effect on metabolism against the effects of body mass gain.

CONCLUSION

Changes in adipose tissue (eg, body mass loss, control, gain) should be interpreted via the sum of skinfolds in absolute values, waist perimeter, and patients' body proportionality, because fat is just a fraction of the adipocyte (lipid).

Enteric glia as a player of gut-brain interactions during Parkinson's disease

The enteric glia has been shown as a potential component of neuroimmune interactions that signal in the gut-brain axis during Parkinson's disease (PD). Enteric glia are a peripheral glial type found in the enteric nervous system (ENS) that, associated with enteric neurons, command various gastrointestinal (GI) functions. They are a unique cell type, with distinct phenotypes and distribution in the gut layers, which establish relevant neuroimmune modulation and regulate neuronal function. Comprehension of enteric glial roles during prodromal and symptomatic phases of PD should be a priority in neurogastroenterology research, as the reactive enteric glial profile, gastrointestinal dysfunction, and colonic inflammation have been verified during the prodromal phase of PD-a moment that may be interesting for interventions. In this review, we explore the mechanisms that should govern enteric glial signaling through the gut-brain axis to understand pathological events and verify the possible windows and pathways for therapeutic intervention. Enteric glia directly modulate several functional aspects of the intestine, such as motility, visceral sensory signaling, and immune polarization, key GI processes found deregulated in patients with PD. The search for glial biomarkers, the investigation of temporal-spatial events involving glial reactivity/signaling, and the proposal of enteric glia-based therapies are clearly demanded for innovative and intestine-related management of PD.

CENTRAL AND PERIPHERAL EFFECT OF MPTP VIA DOSE-DEPENDENT MAGNESIUM MODULATION

Background

Recent studies suggested that MPTP could cause gastrointestinal motility deficits additionally to its nonconclusive and controverted effects on the CNS (behavior and brain oxidative stress) in rats. A possible interaction between MPTP typical impairments and magnesium modulatory potential was previously suggested, as magnesium role was described in neuroprotection, gastrointestinal function, and oxidative stress.

Aim

To investigate the possible modulatory effect of several magnesium intake formulations (via drinking water) in MPTP neurotoxicity and functional gastrointestinal impairment induction.

Materials and Methods

Adult male Wistar rats were subjected to 3-week magnesium intake-controlled diets (magnesium depleted food and magnesium enriched drinking water) previously to acute subcutaneous MPTP treatment (30 mg/ kg body weight). Gastrointestinal motility (one hour stool collection test), and behavioral patterns (Y maze task, elevated plus maze test, open field test, forced swim test) were evaluated. Followingly, brain and bowel samples were collected, and oxidative stress was evaluated (glutathione peroxidase activity, malondial-dehyde concentrations).

Results

MPTP could lead to magnesium intake-dependent constipation-like gastrointestinal motility impairments, anxiety- and depressive-like affective behavior changes, and mild pain tolerance defects. Also, we found similar brain and intestinal patterns in magnesium-dependent oxidative stress.

Conclusion

While the MPTP effects in normal magnesium intake could be regarded as not fully relevant in rat models and limited to the current experimental conditions, the abnormalities observed in the affective behavior, gastrointestinal status, pain tolerance, peripheric and central oxidative status could be indicative of the extent of the systemic effects of MPTP that are not restricted to the CNS level, but also to gastro-intestinal system.

[Characteristics and treatment of pain in Parkinson's disease]

Pain is a representative non-motor symptom in patients with Parkinson's disease (PD). Pain is one of the most common symptoms that plague patients with PD regardless of the stage of the disease, also it can exacerbate other symptoms, such as depression, anxiety or sleep disturbance, and lead to impaired quality of life. However, pain is often not adequately evaluated and treated. PD patients complain of a wide variety of pain, including both PD-related pain which caused by PD-specific symptoms, for example, rigidity, bradykinesia or motor fluctuation, and PD-unrelated pain, and it can be divided into central and peripheral depending on the site of the disorder. In the medical care of the pain, it is important to evaluate the type and severity of the pain using PD-specific assessment scales such as King's PD pain scale and to consider the evidence-based treatment methods according to the pathophysiology of the pain.

Hydrogen Sulfide Increases the Analgesic Effects of µ- and δ-Opioid Receptors during Neuropathic Pain: Pathways Implicated

Recent studies have revealed that hydrogen sulfide (H₂S) increases the analgesic actions of the δ-opioid receptor (DOR) in inflammatory pain. However, the possible improvement of the analgesia of μ-opioid receptor (MOR) and DOR agonists during neuropathic pain, through pretreatment with two slow-releasing H₂S donors—DADS (diallyl disulfide) and GYY4137 (morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate dichloromethane complex)—is still unknown. In male C57BL/6J mice with neuropathic pain incited by chronic constriction of the sciatic nerve (CCI), we evaluated: (1) the influence of DADS (3.5 mg/kg) and GYY4137 (0.7 mg/kg) on the inhibition of the allodynia and hyperalgesia produced by the systemic or local administration of morphine (3 mg/kg or 65 µg) and UFP-512 (1 mg/kg or 12.5 µg); (2) the reversion of the antinociceptive actions of high doses of DADS (30 mg/kg) and GYY4137 (24 mg/kg) with MOR and DOR antagonists; and (3) the effects of H₂S donors on oxidative stress, apoptotic responses, and MOR and DOR expression in the medial septum (MS) and dorsal root ganglia (DRG). The results revealed that both DADS and GYY4137 improved the antiallodynic effects of morphine and UFP-512, possibly by up-regulating MOR and DOR expression in DRG. The administration of MOR and DOR antagonists blocked the analgesic properties of DADS and GYY4137, revealing the feasible participation of the endogenous opioid system in H₂S analgesic effects. Moreover, both H₂S donors inhibited oxidative stress and apoptosis generated by CCI in the MS and/or DRG. This study suggests the co-treatment of H₂S donors with MOR or DOR agonists as a potential therapy for neuropathic pain.