Neurogenic inflammation and the peripheral nervous system in host defense and immunopathology

5 G wireless telecommunications expansion: Public health and environmental implications

The popularity, widespread use and increasing dependency on wireless technologies has spawned a telecommunications industrial revolution with increasing public exposure to broader and higher frequencies of the electromagnetic spectrum to transmit data through a variety of devices and infrastructure. On the horizon, a new generation of even shorter high frequency 5G wavelengths is being proposed to power the Internet of Things (IoT). The IoT promises us convenient and easy lifestyles with a massive 5G interconnected telecommunications network, however, the expansion of broadband with shorter wavelength radiofrequency radiation highlights the concern that health and safety issues remain unknown. Controversy continues with regards to harm from current 2G, 3G and 4G wireless technologies. 5G technologies are far less studied for human or environmental effects. It is argued that the addition of this added high frequency 5G radiation to an already complex mix of lower frequencies, will contribute to a negative public health outcome both from both physical and mental health perspectives. Radiofrequency radiation (RF) is increasingly being recognized as a new form of environmental pollution. Like other common toxic exposures, the effects of radiofrequency electromagnetic radiation (RF EMR) will be problematic if not impossible to sort out epidemiologically as there no longer remains an unexposed control group. This is especially important considering these effects are likely magnified by synergistic toxic exposures and other common health risk behaviors. Effects can also be non-linear. Because this is the first generation to have cradle-to-grave lifespan exposure to this level of man-made microwave (RF EMR) radiofrequencies, it will be years or decades before the true health consequences are known. Precaution in the roll out of this new technology is strongly indicated. This article will review relevant electromagnetic frequencies, exposure standards and current scientific literature on the health implications of 2G, 3G, 4G exposure, including some of the available literature on 5G frequencies. The question of what constitutes a public health issue will be raised, as well as the need for a precautionary approach in advancing new wireless technologies.

Neuroepithelial control of mucosal inflammation in acute cystitis

The nervous system is engaged by infection, indirectly through inflammatory cascades or directly, by bacterial attack on nerve cells. Here we identify a neuro-epithelial activation loop that participates in the control of mucosal inflammation and pain in acute cystitis. We show that infection activates Neurokinin-1 receptor (NK1R) and Substance P (SP) expression in nerve cells and bladder epithelial cells in vitro and in vivo in the urinary bladder mucosa. Specific innate immune response genes regulated this mucosal response, and single gene deletions resulted either in protection (Tlr4^−/− and Il1b^−/− mice) or in accentuated bladder pathology (Asc^−/− and Nlrp3^−/− mice), compared to controls. NK1R/SP expression was lower in Tlr4^−/− and Il1b^−/− mice than in C56BL/6WT controls but in Asc^−/− and Nlrp3^−/− mice, NK1R over-activation accompanied the exaggerated disease phenotype, due, in part to transcriptional de-repression of Tacr1. Pharmacologic NK1R inhibitors attenuated acute cystitis in susceptible mice, supporting a role in disease pathogenesis. Clinical relevance was suggested by elevated urine SP levels in patients with acute cystitis, compared to patients with asymptomatic bacteriuria identifying NK1R/SP as potential therapeutic targets. We propose that NK1R and SP influence the severity of acute cystitis through a neuro-epithelial activation loop that controls pain and mucosal inflammation.

GPR37 regulates macrophage phagocytosis and resolution of inflammatory pain

The mechanisms of pain induction by inflammation have been extensively studied. However, the mechanisms of pain resolution are not fully understood. Here, we report that GPR37, expressed by macrophages (MΦs) but not microglia, contributes to the resolution of inflammatory pain. Neuroprotectin D1 (NPD1) and prosaptide TX14 increase intracellular Ca2+ (iCa2+) levels in GPR37-transfected HEK293 cells. NPD1 and TX14 also bind to GPR37 and cause GPR37-dependent iCa2+ increases in peritoneal MΦs. Activation of GPR37 by NPD1 and TX14 triggers MΦ phagocytosis of zymosan particles via calcium signaling. Hind paw injection of pH-sensitive zymosan particles not only induces inflammatory pain and infiltration of neutrophils and MΦs, but also causes GPR37 upregulation in MΦs, phagocytosis of zymosan particles and neutrophils by MΦs in inflamed paws, and resolution of inflammatory pain in WT mice. Mice lacking Gpr37 display deficits in MΦ phagocytic activity and delayed resolution of inflammatory pain. Gpr37-deficient MΦs also show dysregulations of proinflammatory and antiinflammatory cytokines. MΦ depletion delays the resolution of inflammatory pain. Adoptive transfer of WT but not Gpr37-deficient MΦs promotes the resolution of inflammatory pain. Our findings reveal a previously unrecognized role of GPR37 in regulating MΦ phagocytosis and inflammatory pain resolution.

In Situ Hybridisation Study of Neuronal Neuropeptides Expression in Models of Mandibular Denervation with or without Inflammation: Injury Dependant Neuropeptide Plasticity

Neuronal expression of neuropeptides is altered following peripheral tissue injury associated with inflammation or nerve injury. This results in neuropathic pain with or without neurogenic inflammation which is a major health problem regularly seen in trigeminal neuralgia. Activation of the trigeminal system results in the release of vasoactive neuropeptides substance P and Calcitonin Gene-related Peptide (CGRP) which contribute to nociception, pain and neurogenic inflammation in injured tissues.

Current understanding of meningeal and cerebral vascular function underlying migraine headache

BACKGROUND

The exact mechanisms underlying the onset of a migraine attack are not completely understood. It is, however, now well accepted that the onset of the excruciating throbbing headache of migraine is mediated by the activation and increased mechanosensitivity (i.e. sensitization) of trigeminal nociceptive afferents that innervate the cranial meninges and their related large blood vessels.

OBJECTIVES

To provide a critical summary of current understanding of the role that the cranial meninges, their associated vasculature, and immune cells play in meningeal nociception and the ensuing migraine headache.

METHODS

We discuss the anatomy of the cranial meninges, their associated vasculature, innervation and immune cell population. We then debate the meningeal neurogenic inflammation hypothesis of migraine and its putative contribution to migraine pain. Finally, we provide insights into potential sources of meningeal inflammation and nociception beyond neurogenic inflammation, and their potential contribution to migraine headache.

Potamotrygon motoro stingray venom induces both neurogenic and inflammatory pain behavior in rodents

Freshwater stingray accidents cause an immediate, intense, and unrelieved pain which is followed by edema, erythema and necrosis formation. Treatment for stingray envenomation is based on administration of analgesic, antipyretic and anti-inflammatory drugs. Concerning pain control, it is prescribed to immerse punctured limb on hot water to alleviate pain. There are no studies demonstrating specific targets on which stingray venom acts to promote pain. Therefore, the aim of this work was to investigate some mechanisms of Potamotrygon motoro venom (PmV) that contribute to nociception induction. Evaluating spontaneous pain behavior in mice injected i.pl. with PmV, it was seen that PmV induced both neurogenic and inflammatory pain. PmV also induced hyperalgesia in both mice and rats, evaluated through electronic von Frey and rat paw pressure test, respectively. Partial inhibition of hyperalgesia was observed in mice treated with cromolyn or promethazine, which indicated that mast cell and histamine via H1 receptor participate in the inflammatory pain. To search for some targets involved in PmVinduced hyperalgesia, the participation of TRPV1, calcium channels, neurokinins, CGRP, and norepinephrine, was evaluated in rats. It was seen that PmV-induced hyperalgesia occurs with the participation of neurokinins, mainly via NK1 receptor, CGRP, and calcium influx, through both P/Q and L-type voltage-dependent calcium channels, besides TRPV1 activation. The data presented herein indicate that PmV causes hyperalgesia in rodents which is dependent on the participation of several neuroinflammatory mediators.

Time-dependent changes in paw carrageenan-induced inflammation above and below the level of low thoracic spinal cord injury in rats

STUDY DESIGN

This was an animal study.

OBJECTIVES

Local inflammation is attenuated below high thoracic SCI, where innervation of major lymphoid organs is involved. However, whether inflammatory responses are affected after low thoracic SCI, remains undetermined. The aim of this study was to characterize the influence of low thoracic SCI on carrageenan-induced paw swelling in intact and paralyzed limbs, at acute and subacute stages.

SETTING

University and hospital-based research center, Mexico City, Mexico.

METHODS

Rats received a severe contusive SCI at T9 spinal level or sham injury. Then, 1 and 15 days after lesion, carrageenan or vehicle was subcutaneously injected in forelimb and hindlimb paws. Paw swelling was measured over a 6-h period using a plethysmometer.

RESULTS

Swelling increased progressively reaching the maximum 6 h post-carrageenan injection. Swelling increase in sham-injured rats was approximately 130% and 70% compared with baseline values of forelimbs and hindlimbs, respectively. Paws injected with saline exhibited no measurable swelling. Carrageenan-induced paw swelling 1-day post-SCI was suppressed in both intact and paralyzed limbs. Fifteen days post-injury, the swelling response to carrageenan was completely reestablished in forelimbs, whereas in hindlimbs it remained significantly attenuated compared with sham-injured rats.

CONCLUSIONS

SCI at low spinal level affects the induced swelling response in a different way depending on both, the neurological status of challenged regions and the stage of injury. These findings suggest that neurological compromise of the main immunological organs is not a prerequisite for the local swelling response to be affected after injury.

The neurobiology of acute pain

The mechanisms by which noxious stimuli produce the sensation of pain in animals are complex. Noxious stimuli are transduced at the periphery and transmitted to the CNS, where this information is subject to considerable modulation. Finally, the information is projected to the brain where it is perceived as pain. Additionally, plasticity can develop in the pain pathway and hyperalgesia and allodynia may develop through sensitisation both peripherally and centrally. A large number of different ion channels, receptors, and cell types are involved in pain perception, and it is hoped that through a better understanding of these, new and refined treatments for pain will result.

Impaired CD8 T cell antiviral immunity following acute spinal cord injury

BACKGROUND

Spinal cord injury (SCI) disrupts essential neuroimmune communication, leading to severe immune depression. Previous studies confirmed immune dysfunction in mice with chronic SCI and following high thoracic level injury where sympathetic innervation of the spleen is disrupted. Here, we induced a mid-thoracic injury where integrity of the sympathetic response is maintained and investigated the antiviral T cell response to influenza virus after acute SCI.

METHODS

One week following a contusion SCI at thoracic level T9, mice were infected intranasally with influenza virus. Profiles of immune cell populations were analyzed before infection, and virus-specific CD8 T cell response was analyzed 7 days post-infection.

RESULTS

Following intranasal infection, injured mice had prolonged recovery and significant weight loss. Importantly, expansion and effector functions of virus-specific CD8 T cells were decreased in injured mice. The compromised CD8 T cell response was associated with inflammation and stress responses initiated after injury. Regulatory mechanisms, including increased regulatory T cells (Tregs) and upregulated PD-1/PD-L1, were induced following SCI. Furthermore, we show that increased corticosterone (CORT) levels can inhibit CD8 T cells and that blocking CORT in vivo following SCI enhances CD8 T cell antiviral responses.

CONCLUSIONS

Our results show that mice with mid-thoracic SCI have impaired CD8 T cell function during the acute stage of injury, indicating that impaired antiviral responses occur rapidly following SCI and is not dependent on injury level.

Electroacupuncture therapy in inflammation regulation: current perspectives

Although acupuncture therapy is increasingly used to treat diverse symptoms and disorders in humans, its underlying mechanism is not known well. Only recently have experimental studies begun to provide insights into how acupuncture stimulation generates and relates to pathophysiological responsiveness. Acupuncture intervention is frequently used to control pathologic symptoms in several visceral organs, and a growing number of studies using experimental animal models suggest that acupuncture stimulation may be involved in inducing anti-inflammatory responses. The vagus nerve, a principal parasympathetic nerve connecting neurons in the central nervous system to cardiovascular systems and a majority of visceral organs, is known to modulate neuroimmune communication and anti-inflammatory responses in target organs. Here, we review a broad range of experimental studies demonstrating anti-inflammatory effects of electroacupuncture in pathologic animal models of cardiovascular and visceral organs and also ischemic brains. Then, we provide recent progress on the role of autonomic nerve activity in anti-inflammation mediated by electroacupuncture. We also discuss a perspective on the role of sensory signals generated by acupuncture stimulation, which may induce a neural code unique to acupuncture in the central nervous system.

TRPV1 Agonist, Capsaicin, Induces Axon Outgrowth after Injury via Ca2+/PKA Signaling

Preconditioning nerve injuries activate a pro-regenerative program that enhances axon regeneration for most classes of sensory neurons. However, nociceptive sensory neurons and central nervous system neurons regenerate poorly. In hopes of identifying novel mechanisms that promote regeneration, we screened for drugs that mimicked the preconditioning response and identified a nociceptive ligand that activates a preconditioning-like response to promote axon outgrowth. We show that activating the ion channel TRPV1 with capsaicin induces axon outgrowth of cultured dorsal root ganglion (DRG) sensory neurons, and that this effect is blocked in TRPV1 knockout neurons. Regeneration occurs only in NF200-negative nociceptive neurons, consistent with a cell-autonomous mechanism. Moreover, we identify a signaling pathway in which TRPV1 activation leads to calcium influx and protein kinase A (PKA) activation to induce a preconditioning-like response. Finally, capsaicin administration to the mouse sciatic nerve activates a similar preconditioning-like response and induces enhanced axonal outgrowth, indicating that this pathway can be induced in vivo. These findings highlight the use of local ligands to induce regeneration and suggest that it may be possible to target selective neuronal populations for repair, including cell types that often fail to regenerate.

Skin neurogenic inflammation

The epidermis closely interacts with nerve endings, and both epidermis and nerves produce substances for mutual sustenance. Neuropeptides, like substance P (SP) and calcitonin gene-related protein (CGRP), are produced by sensory nerves in the dermis; they induce mast cells to release vasoactive amines that facilitate infiltration of neutrophils and T cells. Some receptors are more important than others in the generation of itch. The Mas-related G protein-coupled receptors (Mrgpr) family as well as transient receptor potential ankyrin 1 (TRPA1) and protease activated receptor 2(Par2) have important roles in itch and inflammation. The activation of MrgprX1 degranulates mast cells to communicate with sensory nerve and cutaneous cells for developing neurogenic inflammation. Mrgprs and transient receptor potential vanilloid 4 (TRPV4) are crucial for the generation of skin diseases like rosacea, while SP, CGRP, somatostatin, β-endorphin, vasoactive intestinal peptide (VIP), and pituitary adenylate cyclase-activating polypeptide (PACAP) can modulate the immune system during psoriasis development. The increased level of SP, in atopic dermatitis, induces the release of interferon (IFN)-γ, interleukin (IL)-4, tumor necrosis factor (TNF)-α, and IL-10 from the peripheral blood mononuclear leukocytes. We are finally starting to understand the intricate connections between the skin neurons and resident skin cells and how their interaction can be key to controlling inflammation and from there the pathogenesis of diseases like atopic dermatitis, psoriasis, and rosacea.

Interactions of the immune and sensory nervous systems in atopy

A striking feature underlying all atopic disorders, such as asthma, atopic dermatitis, and food allergy, is the presence of pathologic sensory responses, reflexes, and behaviors. These symptoms, exemplified by chronic airway irritation and cough, chronic itch and scratching, as well as gastrointestinal discomfort and dysfunction, are often cited as the most debilitating aspects of atopic disorders. Emerging studies have highlighted how the immune system shapes the scope and intensity of sensory responses by directly modulating the sensory nervous system. Additionally, factors produced by neurons have demonstrated novel functions in propagating atopic inflammation at barrier surfaces. In this review, we highlight new studies that have changed our understanding of atopy through advances in characterizing the reciprocal interactions between the immune and sensory nervous systems.

Association of neuropathic-like pain characteristics with clinical and radiographic features in patients with ankylosing spondylitis

Ankylosing spondylitis (AS) is a chronic, progressive, and inflammatory disorder and causes chronic back pain. It is not unusual for patients with AS to have symptoms similar to neuropathic pain. We aimed to investigate the neuropathic pain (NeP) component in patients with AS using the painDETECT questionnaire (PD-Q) and to assess the relation between NeP and the disease characteristics of AS. A single-center prospective study was performed, including 105 patients. Patients with AS completed three questionnaires: PD-Q, Beck Depression Inventory (BDI), and Euro Quality of Life (EQ-5D) questionnaires. Patients were classified into three groups according to the PD-Q scores: nociceptive pain (NoP) (score ≤ 12), mixed pain (MP) (score 13-18), and NeP pain (score ≥ 19). Fifteen patients (14.2%) were classified into the NeP group, 22 (21.0%) in the MP group, and 68 (64.8%) in the NoP group. The questionnaires and clinical and radiographic findings were analyzed. Patients with NeP and MP scored worse on the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI); BDI; modified Stoke Ankylosing Spondylitis Spine Score; pain-visual analog scale (VAS); and EQ-5L index and showed an increased prevalence of enthesitis and peripheral arthritis. There were no differences in objective inflammatory markers. PD-Q scores were positively correlated with pain-VAS, BASDAI, BDI, and inversely correlated with EQ-5D index. Age, BASDAI, presence of current enthesitis, and BDI score were independently associated with PD-Q scores. The findings showed that NeP component in AS was associated with age, high disease activity, presence of current enthesitis, and depression.

Molecular and Functional Neuroscience in Immunity

The nervous system regulates immunity and inflammation. The molecular detection of pathogen fragments, cytokines, and other immune molecules by sensory neurons generates immunoregulatory responses through efferent autonomic neuron signaling. The functional organization of this neural control is based on principles of reflex regulation. Reflexes involving the vagus nerve and other nerves have been therapeutically explored in models of inflammatory and autoimmune conditions, and recently in clinical settings. The brain integrates neuro-immune communication, and brain function is altered in diseases characterized by peripheral immune dysregulation and inflammation. Here we review the anatomical and molecular basis of the neural interface with immunity, focusing on peripheral neural control of immune functions and the role of the brain in the model of the immunological homunculus. Clinical advances stemming from this knowledge within the framework of bioelectronic medicine are also briefly outlined.

Toll-like receptor expression in pulmonary sensory neurons in the bleomycin-induced fibrosis model

Airway sensory nerves are known to express several receptors and channels that are activated by exogenous and endogenous mediators that cause coughing. Toll-like receptor (TLR) s are expressed in nociceptive neurons and play an important role in neuroinflammation. However, there have been very few studies of TLR expression in lung-derived sensory neurons or their relevance to respiratory symptoms such as cough. We used the bleomycin-induced pulmonary fibrosis model to investigate the change in TLR expression in pulmonary neurons and the association of TLRs with transient receptor potential (TRP) channels in pulmonary neurons. After 2 weeks of bleomycin or saline administration, pulmonary fibrosis changes were confirmed using tissue staining and the SIRCOL collagen assay. TLRs (TLR 1-9) and TRP channel expression was analyzed using single cell reverse transcription polymerase chain reaction (RT-PCR) in isolated sensory neurons from the nodose/jugular ganglion and the dorsal root ganglion (DRG). Pulmonary sensory neurons expressed TLR2 and TLR5. In the bleomycin-induced pulmonary fibrosis model, TLR2 expression was detected in 29.5% (18/61) and 26.9% (21/78) of pulmonary nodose/jugular neurons and DRG neurons, respectively. TLR5 was also detected in 55.7% (34/61) and 42.3% (33/78) of pulmonary nodose/jugular neurons and DRG neurons, respectively, in the bleomycin-induced pulmonary fibrosis model. TLR5 was expressed in 63.4% of TRPV1 positive cells and 43.4% of TRPM8 positive cells. In conclusion, TLR2 and TLR5 expression is enhanced, especially in vagal neurons, in the bleomycin-induced fibrosis model group when compared to the saline treated control group. Co-expression of TLR5 and TRP channels in pulmonary sensory neurons was also observed. This work sheds new light on the role of TLRs in the control and manifestation of clinical symptoms, such as cough. To understand the role of TLRs in pulmonary sensory nerves, further study will be required.

A common pronociceptive pain modulation profile typifying subgroups of chronic pelvic pain syndromes is interrelated with enhanced clinical pain

Provoked vestibulodynia (PVD) and painful bladder syndrome (PBS), subgroups of chronic pelvic pain syndromes (CPPS), are considered to share common biophysiological peripheral mechanisms. In addition, indications of a pronociceptive pain profile coexisting with psychological vulnerability suggest common dysfunctional pain processing and pain modulation in these 2 subgroups of CPPS. We therefore aimed at comparing the pain profile and psychological traits of patients with PVD and PBS to see whether the pain profile contributes to intersubject variability of clinical pain symptoms. Patients with PVD (n = 18) and PBS (n = 21) were compared with healthy controls (n = 20) in their responses to (1) pain psychophysical tests applied to both referred (suprapubis) and remote (hand) body areas and (2) pain-related psychological factors (pain catastrophizing, depression, anxiety, and somatization). We found a similar pronociceptive pain profile in the 2 subgroups of CPPS-enhanced facilitation (ie, hyperalgesia in the referred body area [P < 0.001]) and inefficient inhibition (ie, reduced conditioned pain modulation [P < 0.001] that were associated with both enhanced pain ratings evoked during trigger point examination [P < 0.037]) and higher Brief Pain Inventory ratings (P = 0.002). The latter was also correlated with pain catastrophizing (r = 0.504, P = 0.001) and depression symptoms (r = 0.361, P = 0.024). The findings suggest common mechanisms underlying a dysfunctional nociceptive system in both PVD and PBS. The intersubject variability in the level of dysfunction and its association with disease severity recommends a personalized pain treatment that may alleviate daily pain and dysfunction in patients with CPPS.

Irritable bowel syndrome and endometriosis: New insights for old diseases

Irritable bowel syndrome and endometriosis are two diseases affecting a significant part of the female population, either together or individually, with remarkable consequences in the quality of life. Several studies suggest an epidemiological association between them. Their association may not be just an epidemiological phenomenon, but the manifestation of a pathophysiological correlation, which probably generates a mutual promotion phenomenon. In particular, both clinical entities share the presence of a chronic low-grade inflammatory state at the basis of the disease persistence. Recognizing this association is highly significant due to their prevalence and the common clinical manifestation occurring with a chronic abdominal pain. A further multi disciplinary approach is suggested in these patients' management in order to achieve an adequate diagnostic work up and a targeted therapy. This paper analyses some common pathophysiological mechanisms, such as activation of mast cell line, neuronal inflammation, dysbiosis and impaired intestinal permeability. The aim was to investigate their presence in both IBS and endometriosis, and to show the complexity of their relationship in the generation and maintenance of chronic inflammation.

Panton-Valentine Leukocidin Colocalizes with Retinal Ganglion and Amacrine Cells and Activates Glial Reactions and Microglial Apoptosis

Experimental models have established Panton-Valentine leukocidin (PVL) as a potential critical virulence factor during Staphylococcus aureus endophthalmitis. In the present study, we aimed to identify retinal cell targets for PVL and to analyze early retinal changes during infection. After the intravitreous injection of PVL, adult rabbits were euthanized at different time points (30 min, 1, 2, 4 and 8 h). PVL location in the retina, expression of its binding receptor C5a receptor (C5aR), and changes in Müller and microglial cells were analyzed using immunohistochemistry, Western blotting and RT-qPCR. In this model of PVL eye intoxication, only retinal ganglion cells (RGCs) expressed C5aR, and PVL was identified on the surface of two kinds of retinal neural cells. PVL-linked fluorescence increased in RGCs over time, reaching 98% of all RGCs 2 h after PVL injection. However, displaced amacrine cells (DACs) transiently colocalized with PVL. Müller and microglial cells were increasingly activated after injection over time. IL-6 expression in retina increased and some microglial cells underwent apoptosis 4 h and 8 h after PVL infection, probably because of abnormal nitrotyrosine production in the retina.

As if one pain problem was not enough: prevalence and patterns of coexisting chronic pain conditions and their impact on treatment outcomes

INTRODUCTION

The presence of multiple coexisting chronic pain (CP) conditions (eg, low-back pain and migraines) within patients has received little attention in literature. The goals of this observational longitudinal study were to determine the prevalence of coexisting CP conditions, identify the most frequent ones and patterns of coexistence, investigate the relationships among patients' biopsychosocial characteristics and number of CP conditions, and determine the impact of coexisting CP conditions on treatment response.

PATIENTS AND METHODS

A total of 3,966 patients attending multidisciplinary pain-treatment centers who were enrolled in the Quebec Pain Registry were included. Patients completed self-report and nurse-administered questionnaires before their first visit and 6 months later. Results were analyzed using descriptive statistics, factor and cluster analyses, negative binomials with log-link generalized linear models, and linear mixed-effect models.

RESULTS

A third of patients reported coexisting CP conditions. No specific patterns of comorbidities emerged. The presence of coexisting CP conditions was associated with longer pain duration, older age, being female, and poorer quality of life. The presence of more than one CP condition did not have a clinically significant impact on treatment responses.

DISCUSSION

The novelty of the study results relate to the heterogeneity that was found in the patterns of coexistence of CP conditions and the fact that having multiple CP conditions did not clinically impact treatment response. These results highlight the need for future research that examines causes of coexistence among CP conditions across the spectrum of CP, as opposed to focusing on specific conditions, and to examine whether multiple CP conditions impact on additional domains, such as treatment satisfaction. These results highlight the importance of studying the pathophysiological mechanisms underlying the development of coexisting CP conditions, in order eventually to prevent/minimize their occurrence and/or develop optimal treatment and management approaches.

Nociceptive Roles of TRPM2 Ion Channel in Pathologic Pain

Pain is a protective mechanism that enables us to avoid potentially harmful environments. However, when pathologically persisted and aggravated under severely injured or inflamed conditions, pain often reduces the quality of life and thus is considered as a disease to eliminate. Inflammatory and/or neuropathic mechanisms may exaggerate interactions between damaged tissues and neural pathways for pain mediation. Similar mechanisms also promote the communication among cellular participants in synapses at spinal or higher levels, which may amplify nociceptive firing and subsequent signal transmission, deteriorating the pain sensation. In this pathology, important cellular players are afferent sensory neurons, peripheral immune cells, and spinal glial cells. Arising from damage of injury, overloaded interstitial and intracellular reactive oxygen species (ROS) and intracellular Ca²⁺ are key messengers in the development and maintenance of pathologic pain. Thus, an ROS-sensitive and Ca²⁺-permeable ion channel that is highly expressed in the participant cells might play a critical role in the pathogenesis. Transient receptor potential melastatin subtype 2 (TRPM2) is the unique molecule that satisfies all of the requirements: the sensitivity, permeability, and its expressing cells. Notable progress in delineating the role of TRPM2 in pain has been achieved during the past decade. In the present review, we summarize the important findings in the key cellular components that are involved in pathologic pain. This overview will help to understand TRPM2-mediated pain mechanisms and speculate therapeutic strategies by utilizing this updated information.

Nociceptors: thermal allodynia and thermal pain

The sensation of pain plays a vital protecting role, alerting organisms about potentially damaging stimuli. Tissue injury is detected by nerve endings of specialized peripheral sensory neurons called nociceptors that are equipped with different ion channels activated by thermal, mechanic, and chemical stimuli. Several transient receptor potential channels have been identified as molecular transducers of thermal stimuli in pain-sensing neurons. Skin injury or inflammation leads to increased sensitivity to thermal and mechanic stimuli, clinically defined as allodynia or hyperalgesia. This hypersensitivity is also characteristic of systemic inflammatory disorders and neuropathic pain conditions. Mechanisms of thermal hyperalgesia include peripheral sensitization of nociceptor afferents and maladaptive changes in pain-encoding neurons within the central nervous system. An important aspect of pain management involves attempts to minimize the development of nociceptor hypersensitivity. However, knowledge about the cellular and molecular mechanisms causing thermal hyperalgesia and allodynia in human subjects is still limited, and such knowledge would be an essential step for the development of more effective therapies.

Role of Transient Receptor Potential Vanilloid 1 in Electroacupuncture Analgesia on Chronic Inflammatory Pain in Mice

Chronic inflammatory pain may result from peripheral tissue injury or inflammation, increasing the release of protons, histamines, adenosine triphosphate, and several proinflammatory cytokines and chemokines. Transient receptor potential vanilloid 1 (TRPV1) is known to be involved in acute to subacute neuropathic and inflammatory pain; however, its exact mechanisms in chronic inflammatory pain are not elucidated. Our results showed that EA significantly reduced chronic mechanical and thermal hyperalgesia in the chronic inflammatory pain model. Chronic mechanical and thermal hyperalgesia were also abolished in TRPV1-/- mice. TRPV1 increased in the dorsal root ganglion (DRG) and spinal cord (SC) at 3 weeks after CFA injection. The expression levels of downstream molecules such as pPKA, pPI3K, and pPKC increased, as did those of pERK, pp38, and pJNK. Transcription factors (pCREB and pNFκB) and nociceptive ion channels (Nav1.7 and Nav1.8) were involved in this process. Inflammatory mediators such as GFAP, S100B, and RAGE were also involved. The expression levels of these molecules were reduced in EA and TRPV1-/- mice but not in the sham EA group. Our data provided evidence to support the clinical use of EA for treating chronic inflammatory pain.

Chemical warfare agents. Classes and targets

Synthetic toxic chemicals (toxicants) and biological poisons (toxins) have been developed as chemical warfare agents in the last century. At the time of their initial consideration as chemical weapon, only restricted knowledge existed about their mechanisms of action. There exist two different types of acute toxic action: nonspecific cytotoxic mechanisms with multiple chemo-biological interactions versus specific mechanisms that tend to have just a single or a few target biomolecules. TRPV1- and TRPA-receptors are often involved as chemosensors that induce neurogenic inflammation. The present work briefly surveys classes and toxicologically relevant features of chemical warfare agents and describes mechanisms of toxic action.

Sense and Immunity: Context-Dependent Neuro-Immune Interplay

The sensory nervous and immune systems, historically considered autonomous, actually work in concert to promote host defense and tissue homeostasis. These systems interact with each other through a common language of cell surface G protein-coupled receptors and receptor tyrosine kinases as well as cytokines, growth factors, and neuropeptides. While this bidirectional communication is adaptive in many settings, helping protect from danger, it can also become maladaptive and contribute to disease pathophysiology. The fundamental logic of how, where, and when sensory neurons and immune cells contribute to either health or disease remains, however, unclear. Our lab and others’ have begun to explore how this neuro-immune reciprocal dialog contributes to physiological and pathological immune responses and sensory disorders. The cumulative results collected so far indicate that there is an important role for nociceptors (noxious stimulus detecting sensory neurons) in driving immune responses, but that this is highly context dependent. To illustrate this concept, we present our findings in a model of airway inflammation, in which nociceptors seem to have major involvement in type 2 but not type 1 adaptive immunity.

Targeting neural reflex circuits in immunity to treat kidney disease

Neural pathways regulate immunity and inflammation via the inflammatory reflex and specific molecular targets can be modulated by stimulating neurons. Neuroimmunomodulation by nonpharmacological methods is emerging as a novel therapeutic strategy for inflammatory diseases, including kidney diseases and hypertension. Electrical stimulation of vagus neurons or treatment with pulsed ultrasound activates the cholinergic anti-inflammatory pathway (CAP) and protects mice from acute kidney injury (AKI). Direct innervation of the kidney, by afferent and efferent neurons, might have a role in modulating and responding to inflammation in various diseases, either locally or by providing feedback to regions of the central nervous system that are important in the inflammatory reflex pathway. Increased sympathetic drive to the kidney has a role in the pathogenesis of hypertension, and selective modulation of neuroimmune interactions in the kidney could potentially be more effective for lowering blood pressure and treating inflammatory kidney diseases than renal denervation. Use of optogenetic tools for selective stimulation of specific neurons has enabled the identification of neural circuits in the brain that modulate kidney function via activation of the CAP. In this Review we discuss evidence for a role of neural circuits in the control of renal inflammation as well as the therapeutic potential of targeting these circuits in the settings of AKI, kidney fibrosis and hypertension.

Effects of NSAIDs on the Release of Calcitonin Gene-Related Peptide and Prostaglandin E2 from Rat Trigeminal Ganglia

Nonsteroidal anti-inflammatory drugs (NSAIDs) are frequently used to treat migraine, but the mechanisms of their effects in this pathology are not fully elucidated. The trigeminal ganglia and calcitonin gene-related peptide (CGRP) have been implicated in the pathophysiology of migraine. The release of CGRP and prostaglandin E₂ (PGE₂) from freshly isolated rat trigeminal ganglia was evaluated after oral administration of nimesulide, etoricoxib, and ketoprofen, NSAIDs with different pharmacological features. Thirty minutes after oral administration, nimesulide, 10 mg/Kg, decreased the GCRP release induced by an inflammatory soup, while the other NSAIDs were ineffective at this point in time. Two hours after oral nimesulide (5 and 10 mg/Kg) and ketoprofen (10 mg/Kg), but not of etoricoxib, a significant decrease in the CGRP release was observed. All drugs reduced PGE₂, although with some differences in timing and doses, and the action on CGRP does not seem to be related to PGE₂ inhibition. The reduction of CGRP release from rat trigeminal ganglia after nimesulide and ketoprofen may help to explain the mechanism of action of NSAIDs in migraine. Since at 30 minutes only nimesulide was effective in reducing CGRP release, these results suggest that this NSAID may exert a particularly rapid effect in patients with migraine.

Outdoor Ambient Air Pollution and Neurodegenerative Diseases: the Neuroinflammation Hypothesis

PURPOSE OF REVIEW

Accumulating research indicates that ambient outdoor air pollution impacts the brain and may affect neurodegenerative diseases, yet the potential underlying mechanisms are poorly understood.

RECENT FINDINGS

The neuroinflammation hypothesis holds that elevation of cytokines and reactive oxygen species in the brain mediates the deleterious effects of urban air pollution on the central nervous system (CNS). Studies in human and animal research document that neuroinflammation occurs in response to several inhaled pollutants. Microglia are a prominent source of cytokines and reactive oxygen species in the brain, implicated in the progressive neuron damage in diverse neurodegenerative diseases, and activated by inhaled components of urban air pollution through both direct and indirect pathways. The MAC1-NOX2 pathway has been identified as a mechanism through which microglia respond to different forms of air pollution, suggesting a potential common deleterious pathway. Multiple direct and indirect pathways in response to air pollution exposure likely interact in concert to exert CNS effects.

Increased mast cell degranulation and co-localization of mast cells with the NMDA receptor-1 during healing after Achilles tendon rupture

The role of inflammation and the mechanism of tendon healing after rupture has historically been a matter of controversy. The purpose of the present study is to investigate the role of mast cells and their relation to the NMDA receptor-1 (a glutamate receptor) during healing after Achilles tendon rupture. Eight female Sprague Dawley rats had their right Achilles tendon transected. Three weeks after rupture, histological quantification of mast cell numbers and their state of degranulation was assessed by histochemistry. Co-localization of mast cell tryptase (a mast cell marker) and NMDA receptor-1 was determined by immunofluorescence. The intact left Achilles tendon was used as control. An increased number of mast cells and a higher proportion of degranulated mast cells were found in the healing Achilles tendon compared to the intact. In addition, increased co-localization of mast cell tryptase and NMDA receptor-1 was seen in the areas of myotendinous junction, mid-tendon proper and bone tendon junction of the healing versus the intact tendon. These findings introduce a possible role for mast cells in the healing phase after Achilles tendon rupture.

Modulation of Glycine-Mediated Spinal Neurotransmission for the Treatment of Chronic Pain

Chronic pain constitutes a significant and expanding worldwide health crisis. Currently available analgesics poorly serve individuals suffering from chronic pain, and new therapeutic agents that are more effective, safer, and devoid of abuse liabilities are desperately needed. Among the myriad of cellular and molecular processes contributing to chronic pain, spinal disinhibition of pain signaling to higher cortical centers plays a critical role. Accumulating evidence shows that glycinergic inhibitory neurotransmission in the spinal cord dorsal horn gates nociceptive signaling, is essential in maintaining physiological pain sensitivity, and is diminished in pathological pain states. Thus, it is hypothesized that agents capable of enhancing glycinergic tone within the dorsal horn could obtund nociceptor signaling to the brain and serve as analgesics for persistent pain. This Perspective highlights the potential that pharmacotherapies capable of increasing inhibitory spinal glycinergic neurotransmission hold in providing new and transformative analgesic therapies for the treatment of chronic pain.

Aire-deficient mice provide a model of corneal and lacrimal gland neuropathy in Sjögren's syndrome

Sjögren's syndrome (SS) is a chronic, autoimmune exocrinopathy that leads to severe dryness of the mouth and eyes. Exocrine function is highly regulated by neuronal mechanisms but little is known about the link between chronic inflammation, innervation and altered exocrine function in the diseased eyes and exocrine glands of SS patients. To gain a better understanding of neuronal regulation in the immunopathogenesis of autoimmune exocrinopathy, we profiled a mouse model of spontaneous, autoimmune exocrinopathy that possess key characteristics of peripheral neuropathy experienced by SS patients. Mice deficient in the autoimmune regulator (Aire) gene developed spontaneous, CD4+ T cell-mediated exocrinopathy and aqueous-deficient dry eye that were associated with loss of nerves innervating the cornea and lacrimal gland. Changes in innervation and tear secretion were accompanied by increased proliferation of corneal epithelial basal cells, limbal expansion of KRT19-positive progenitor cells, increased vascularization of the peripheral cornea and reduced nerve function in the lacrimal gland. In addition, we found extensive loss of MIST1+ secretory acinar cells in the Aire -/- lacrimal gland suggesting that acinar cells are a primary target of the disease, Finally, topical application of ophthalmic steroid effectively restored corneal innervation in Aire -/- mice thereby functionally linking nerve loss with local inflammation in the aqueous-deficient dry eye. These data provide important insight regarding the relationship between chronic inflammation and neuropathic changes in autoimmune-mediated dry eye. Peripheral neuropathies characteristic of SS appear to be tightly linked with the underlying immunopathological mechanism and Aire -/- mice provide an excellent tool to explore the interplay between SS-associated immunopathology and peripheral neuropathy.

Effects of Simvastatin Beyond Dyslipidemia: Exploring Its Antinociceptive Action in an Animal Model of Complex Regional Pain Syndrome-Type I

Simvastatin is a lipid-lowering agent that blocks the production of cholesterol through inhibition of 3-hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase. In addition, recent evidence has suggested its anti-inflammatory and antinociceptive actions during inflammatory and pain disorders. Herein, we investigated the effects of simvastatin in an animal model of complex regional pain syndrome-type I, and its underlying mechanisms. Chronic post-ischemia pain (CPIP) was induced by ischemia and reperfusion (IR) injury of the left hind paw. Our findings showed that simvastatin inhibited mechanical hyperalgesia induced by CPIP model in single and repeated treatment schedules, respectively; however simvastatin did not alter inflammatory signs during CPIP model. The mechanisms underlying those actions are related to modulation of transient receptor potential (TRP) channels, especially TRMP8. Moreover, simvastatin oral treatment was able to reduce the nociception induced by acidified saline [an acid-sensing ion channels (ASICs) activator] and bradykinin (BK) stimulus, but not by TRPA1, TRPV1 or prostaglandin-E2 (PGE2). Relevantly, the antinociceptive effects of simvastatin did not seem to be associated with modulation of the descending pain circuits, especially noradrenergic, serotoninergic and dopaminergic systems. These results indicate that simvastatin consistently inhibits mechanical hyperalgesia during neuropathic and inflammatory disorders, possibly by modulating the ascending pain signaling (TRPM8/ASIC/BK pathways expressed in the primary sensory neuron). Thus, simvastatin open-up new standpoint in the development of innovative analgesic drugs for treatment of persistent pain, including CRPS-I.

Age Differences in the Time Course and Magnitude of Changes in Circulating Neuropeptides After Pain Evocation in Humans

This study tested the hypothesis that older adults would have a stronger response for substance P (facilitatory) but weaker response to β-endorphin (inhibitory), in magnitude as well as time course. Eight younger and 9 older adults underwent 3 experimental sessions using well validated laboratory pain models: cold pressor task, contact heat pain, and a nonpainful control. Blood was collected through an indwelling catheter at baseline and 3, 15, 30, 45, and 60 minutes after stimuli administration. Older adults had higher baseline levels of both neuropeptides suggesting increased peripheral activity compared with younger adults. After the cold pressor task, older adults demonstrated a quick and strong release of substance P with dramatic recovery, whereas young adults maintained a constant low-grade response. Unlike substance P, β-endorphin increased between 3 and 15 minutes for both groups with the upsurge substantially higher for older adults. After heat pain, younger adults had an immediate surge in circulating substance P and β-endorphin that was more pronounced than among older adults. However, levels of substance P for younger adults slowly tapered whereas they continued to climb for the older adults through 30 minutes. β-endorphin peaked at 30 minutes for both groups and returned to baseline. No changes were observed during the nonpainful control session.

PERSPECTIVE

Older adults had higher baseline levels of substance P and β-endorphin suggesting increased peripheral activity compared with younger adults. After pain evocation, older adults demonstrated a more intense early response for both neuropeptides suggesting peripheral mechanisms involved in the response to pain may change with age.

Muscle paralysis induces bone marrow inflammation and predisposition to formation of giant osteoclasts

Transient muscle paralysis engendered by a single injection of botulinum toxin A (BTxA) rapidly induces profound focal bone resorption within the medullary cavity of adjacent bones. While initially conceived as a model of mechanical disuse, osteoclastic resorption in this model is disproportionately severe compared with the modest gait defect that is created. Preliminary studies of bone marrow following muscle paralysis suggested acute upregulation of inflammatory cytokines, including TNF-α and IL-1. We therefore hypothesized that BTxA-induced muscle paralysis would rapidly alter the inflammatory microenvironment and the osteoclastic potential of bone marrow. We tested this hypothesis by defining the time course of inflammatory cell infiltration, osteoinflammatory cytokine expression, and alteration in osteoclastogenic potential in the tibia bone marrow following transient muscle paralysis of the calf muscles. Our findings identified inflammatory cell infiltration within 24 h of muscle paralysis. By 72 h, osteoclast fusion and pro-osteoclastic inflammatory gene expression were upregulated in tibia bone marrow. These alterations coincided with bone marrow becoming permissive to the formation of osteoclasts of greater size and greater nuclei numbers. Taken together, our data are consistent with the thesis that transient calf muscle paralysis induces acute inflammation within the marrow of the adjacent tibia and that these alterations are temporally consistent with a role in mediating muscle paralysis-induced bone resorption.

TRPA1 channels: molecular sentinels of cellular stress and tissue damage

TRPA1 is a non-selective cation channel expressed in mammalian peripheral pain receptors, with a major role in chemonociception. TRPA1 has also been implicated in noxious cold and mechanical pain sensation. TRPA1 has an ancient origin and plays important functions in lower organisms, including thermotaxis, mechanotransduction and modulation of lifespan. Here we highlight the role of TRPA1 as a multipurpose sensor of harmful signals, including toxic bacterial products and UV light, and as a sensor of stress and tissue damage. Sensing roles span beyond the peripheral nervous system to include major barrier tissues: gut, skin and lung. Tissue injury, environmental irritants and microbial pathogens are danger signals that can threaten the health of organisms. These signals lead to the coordinated activation of the nociceptive and the innate immune system to provide a homeostatic response trying to re-establish physiological conditions including tissue repair. Activation of TRPA1 participates in protective neuroimmune interactions at multiple levels, sensing ROS and bacterial products and triggering the release of neuropeptides. However, an exaggerated response to danger signals is maladaptive and can lead to the development of chronic inflammatory conditions.

Modulation of CD4+ T Helper Cell Memory Responses in the Human Skin

Immunological memory is defined as the capacity to mount faster and more effective immune responses against antigenic challenges that have been previously encountered by the host. CD4+ T helper (Th) cells play central roles in the establishment of immunological memory as they assist the functions of other leukocytes. Th cells express polarized cytokine profiles and distinct migratory and seeding capacities, but also retain a certain functional plasticity that allows them to modulate their proliferation, activity, and homing behaviour upon need. Thus, in healthy individuals, T cell immunomodulation fulfils the task of eliciting protective immune responses where they are needed. At times, however, Th plasticity can lead to collateral tissue damage and progression to autoimmune diseases or, conversely, incapacity to reject malignant tissues and clear chronic infections. Furthermore, common immune players and molecular pathways of diseases can lead to different outcomes in different individuals. A mechanistic understanding of those pathways is therefore crucial for developing precise and curative medical interventions. Here, I focus on the skin microenvironment and comprehensively describe some of the cellular and molecular determinants of CD4+ T cell memory responses in homeostatic and pathological conditions. In discussing the cellular network orchestrating cutaneous immunity, I comprehensively describe the bidirectional interaction of skin antigen-presenting cells and mononuclear phagocytes with Th17 lymphocytes, and examine how the outcome of this interaction is influenced by endogenous skin molecules, including sodium salts and neuropeptides.

TFOS DEWS II pain and sensation report

Pain associated with mechanical, chemical, and thermal heat stimulation of the ocular surface is mediated by trigeminal ganglion neurons, while cold thermoreceptors detect wetness and reflexly maintain basal tear production and blinking rate. These neurons project into two regions of the trigeminal brain stem nuclear complex: ViVc, activated by changes in the moisture of the ocular surface and VcC1, mediating sensory-discriminative aspects of ocular pain and reflex blinking. ViVc ocular neurons project to brain regions that control lacrimation and spontaneous blinking and to the sensory thalamus. Secretion of the main lacrimal gland is regulated dominantly by autonomic parasympathetic nerves, reflexly activated by eye surface sensory nerves. These also evoke goblet cell secretion through unidentified efferent fibers. Neural pathways involved in the regulation of meibomian gland secretion or mucin release have not been identified. In dry eye disease, reduced tear secretion leads to inflammation and peripheral nerve damage. Inflammation causes sensitization of polymodal and mechano-nociceptor nerve endings and an abnormal increase in cold thermoreceptor activity, altogether evoking dryness sensations and pain. Long-term inflammation and nerve injury alter gene expression of ion channels and receptors at terminals and cell bodies of trigeminal ganglion and brainstem neurons, changing their excitability, connectivity and impulse firing. Perpetuation of molecular, structural and functional disturbances in ocular sensory pathways ultimately leads to dysestesias and neuropathic pain referred to the eye surface. Pain can be assessed with a variety of questionaires while the status of corneal nerves is evaluated with esthesiometry and with in vivo confocal microscopy.

N-Arachidonoyl Dopamine Modulates Acute Systemic Inflammation via Nonhematopoietic TRPV1

N-Arachidonoyl dopamine (NADA) is an endogenous lipid that potently activates the transient receptor potential vanilloid 1 (TRPV1), which mediates pain and thermosensation. NADA is also an agonist of cannabinoid receptors 1 and 2. We have reported that NADA reduces the activation of cultured human endothelial cells by LPS and TNF-α. Thus far, in vivo studies using NADA have focused on its neurologic and behavioral roles. In this article, we show that NADA potently decreases in vivo systemic inflammatory responses and levels of the coagulation intermediary plasminogen activator inhibitor 1 in three mouse models of inflammation: LPS, bacterial lipopeptide, and polymicrobial intra-abdominal sepsis. We also found that the administration of NADA increases survival in endotoxemic mice. Additionally, NADA reduces blood levels of the neuropeptide calcitonin gene-related peptide but increases the neuropeptide substance P in LPS-treated mice. We demonstrate that the anti-inflammatory effects of NADA are mediated by TRPV1 expressed by nonhematopoietic cells and provide data suggesting that neuronal TRPV1 may mediate NADA's anti-inflammatory effects. These results indicate that NADA has novel TRPV1-dependent anti-inflammatory properties and suggest that the endovanilloid system might be targeted therapeutically in acute inflammation.

TRPA1 Mechanoreceptors Mediate the IL-6 Response to a Single PD Dwell in the Rat

BACKGROUND

The development of modern, biocompatible peritoneal dialysis (PD) fluids has not entirely eliminated the local pro-inflammatory effects of PD fluid administration. The present study was performed in order to establish the importance of known signaling pathways connected to mechano-, osmo- and chemo-sensors of the transient receptor potential (TRP) family for the acute inflammatory response to PD.

METHODS

Rats were exposed to a single 4-hour dwell of lactate-buffered, 2.5% glucose, filter-sterilized PD fluid through an implanted PD catheter. In some groups, the PD dwell was preceded by intravenous administration of blockers of TRPV1 (BCTC), TRPA1 (HC030031), or neurokinin 1 (NK1) (Spantide II) receptors. Cytokine messenger ribonucleic acid (mRNA) expressions were quantified in tissue biopsies (real-time polymerase chain reaction [qPCR]), and cytokine concentrations were quantified in dialysate samples by enzyme-linked immunosorbent assay (ELISA). Tissue expressions of TRPV1, TRPA1, and NK1 were evaluated immuno-histochemically.

RESULTS

The PD dwell induced peritoneal synthesis of Il1b, Tnf, and Il6 and a secretion of interleukin-6 (IL-6) into the dialysate. The catheter implantation already induced the transcription of Il1b and Tnf but did not significantly affect Il6 transcription. The Il6 response to the PD dwell could be virtually eliminated by blocking TRPA1 but was not affected by TRPV1 blockade. Blocking the substance P receptor, NK1, produced an insignificant trend towards Il6 inhibition. TRPA1 and NK1 showed a stronger immuno-reactivity than TRPV1 on cells of the peritoneal tissue.

CONCLUSION

The results show that IL-6 synthesis and secretion were connected to acute PD fluid exposure, and this response was triggered by TRPA1 receptors, possibly located to non-neuronal cells.

N-Arachidonoyl Dopamine: A Novel Endocannabinoid and Endovanilloid with Widespread Physiological and Pharmacological Activities

N-arachidonoyl dopamine (NADA) is a member of the family of endocannabinoids to which several other N-acyldopamines belong as well. Their activity is mediated through various targets that include cannabinoid receptors or transient receptor potential vanilloid (TRPV)1. Synthesis and degradation of NADA are not yet fully understood. Nonetheless, there is evidence that NADA plays an important role in nociception and inflammation in the central and peripheral nervous system. The TRPV1 receptor, for which NADA is a potent agonist, was shown to be an endogenous transducer of noxious heat. Moreover, it has been demonstrated that NADA exerts protective and antioxidative properties in microglial cell cultures, cortical neurons, and organotypical hippocampal slice cultures. NADA is present in very low concentrations in the brain and is seemingly not involved in activation of the classical pathways. We believe that treatment with exogenous NADA during and after injury might be beneficial. This review summarizes the recent findings on biochemical properties of NADA and other N-acyldopamines and their role in physiological and pathological processes. These findings provide strong evidence that NADA is an effective agent to manage neuroinflammatory diseases or pain and can be useful in designing novel therapeutic strategies.

Mechanisms and Therapeutic Relevance of Neuro-immune Communication

Active research at the frontiers of immunology and neuroscience has identified multiple points of interaction and communication between the immune system and the nervous system. Immune cell activation stimulates neuronal circuits that regulate innate and adaptive immunity. Molecular mechanistic insights into the inflammatory reflex and other neuro-immune interactions have greatly advanced our understanding of immunity and identified new therapeutic possibilities in inflammatory and autoimmune diseases. Recent successful clinical trials using bioelectronic devices that modulate the inflammatory reflex to significantly ameliorate rheumatoid arthritis and inflammatory bowel disease provide a path for using electrons as a therapeutic modality for targeting molecular mechanisms of immunity. Here, we review mechanisms of peripheral sensory neuronal function in response to immune challenges, the neural regulation of immunity and inflammation, and the therapeutic implications of those mechanistic insights.

Neuroinflammation and Infection: Molecular Mechanisms Associated with Dysfunction of Neurovascular Unit

Neuroinflammation is a complex inflammatory process in the central nervous system, which is sought to play an important defensive role against various pathogens, toxins or factors that induce neurodegeneration. The onset of neurodegenerative diseases and various microbial infections are counted as stimuli that can challenge the host immune system and trigger the development of neuroinflammation. The homeostatic nature of neuroinflammation is essential to maintain the neuroplasticity. Neuroinflammation is regulated by the activity of neuronal, glial, and endothelial cells within the neurovascular unit, which serves as a “platform” for the coordinated action of pro- and anti-inflammatory mechanisms. Production of inflammatory mediators (cytokines, chemokines, reactive oxygen species) by brain resident cells or cells migrating from the peripheral blood, results in the impairment of blood-brain barrier integrity, thereby further affecting the course of local inflammation. In this review, we analyzed the most recent data on the central nervous system inflammation and focused on major mechanisms of neurovascular unit dysfunction caused by neuroinflammation and infections.