Chronic Itch Research Articles

Elevated vesicular Zn2+ in dorsal root ganglion neurons expressing the transporter TMEM163 causes age-associated itchy skin in mice.

The prevalent itching condition associated with aging, historically referred to as senile pruritus, diminishes quality of life. Despite its impact, effective treatments remain elusive, largely due to an incomplete understanding of its pathological cause. In this study, we reveal a subset of dorsal root ganglion neurons enriched with Zn2+ that express the vesicular Zn2+ transporter TMEM163. These neurons form direct synapses with and modulate the activity of spinal NPY+ inhibitory interneurons. In aged mice, both the expression of TMEM163 and the concentration of vesicular Zn2+ within the central terminals of TMEM163+ primary afferents show marked elevation. Importantly, the excessive release of vesicular Zn2+ significantly dampens the activity of NPY+ neurons, triggering the disinhibition of itch-transmitting neural circuits and resulting in chronic itch. Intriguingly, chelating Zn2+ within the spinal dorsal horn effectively relieves itch in aged mice. Our study thus unveils a novel molecular mechanism underlying senile pruritus.

Thyrotropin-Releasing Hormone Analog Taltirelin Inhibits Acute and Chronic Itch in Mice

Thyrotropin-Releasing Hormone Analog Taltirelin Inhibits Acute and Chronic Itch in Mice

Trpv1-lineage neuron-expressing Kcnq4 channel modulates itch sensation in mice.

Voltage-gated potassium channel subfamily q member 4 (Kcnq4) is predominantly expressed by hair cells and auditory neurons and regulates the neuronal excitability in the auditory pathway. Although it is further detected in myelinated large-diameter dorsal root ganglia (DRG) neurons in the periphery, the expression and function of Kcnq4 channel in nociceptors remains unknown. Here we showed that Kcnq4 is substantially expressed by unmyelinated small-diameter DRG neurons in both human and mouse. In spite of a dispensable role in acute pain and chronic skin inflammation, Kcnq4 is specifically involved in the regulation of scratching behavior through controlling action potential firing properties, evidenced by the increased neuronal excitability in small-diameter DRG neurons isolated from Kcnq4 deficient mice. Moreover, genetic ablation of Kcnq4 in Trpv1-positive neurons exacerbates both acute and chronic itch behavior in mice. Taken together, our results uncover a functional role of Trpv1-lineage neuron-expressing Kcnq4 channel in the modulation of itch-specific neuronal excitation in the periphery.

A Narrative Review on Stress and Itch: What We Know and What We Would Like to Know.

Itch is one of the most prevalent symptoms experienced by patients with inflammatory skin conditions, yet it is also one of the most debilitating. Patients suffering from chronic itch have been found to have significantly higher stress levels compared with those not experiencing itch. In fact, recent studies have revealed a bidirectional relationship between stress and itch, where each condition worsens the other. This is thought to be driven by the vicious itch-scratch cycle, which is fueled by underlying inflammation. The precise molecular pathways and mediators involved, however, remain unclear. This narrative review discusses the existing research on the relationship between stress and itch and outlines future research directions that will be necessary to advance our understanding and treatment of these conditions. Given that the effective management of both symptoms often requires a combined treatment approach, further investigation into their shared mechanisms is essential for identifying successful therapies and improving patient outcomes.

Scratching the surface: Unveiling the complex interplay of itch and psoriasis through contemporary research

The long-lasting presence of itch is an unbearable symptom for people with psoriatic disease, having a profound effect on their quality of life. The itch experience in psoriasis is complex and multifaceted. It is underpinned by neuroimmune interactions, skin barrier dysfunction, and central sensitization pathways. While it has recently been realized that there are neuroimmune interactions in the pathophysiology of itch, tackling chronic itch still proves to be a challenge. The aim of this Perspective Article is two-fold: to assess the novel optimal management strategies for psoriasis-associated itch, while considering the mechanisms of itch in psoriasis and future directions for research.

Neuropeptide Y Y2 receptors in acute and chronic pain and itch

Pain and itch are regulated by a diverse array of neuropeptides and their receptors in superficial laminae of the spinal cord dorsal horn (DH). Neuropeptide Y (NPY) is normally expressed on DH neurons but not sensory neurons. By contrast, the Npy2r receptor (Y2) is expressed on the central and peripheral terminals of sensory neurons but not on DH neurons. Neurophysiological slice recordings indicate that Y2-selective agonists inhibits spinal neurotransmitter release from sensory neurons. However, behavioral pharmacology studies indicate that Y2 agonists exert minimal changes in nociception, even after injury. Additional discrepancies in the behavioral actions of the Y2-antagonist BIIE0246 – reports of either pronociception or antinociception – have now been resolved. In the normal state, spinally-directed (intrathecal) administration of BIIE0246 elicits ongoing nociception, hypersensitivity to sensory stimulation, and aversion. Conversely, in the setting of nerve injury and inflammation, intrathecal BIIE024 reduced not only mechanical and thermal hypersensitivity, but also a measure of the affective dimension of pain (conditioned place preference). When administered in chronic pain models of latent sensitization, BIIE0246 produced a profound reinstatement of pain-like behaviors. We propose that tissue or nerve injury induces a G protein switch in the action of NPY-Y2 signaling from antinociception in the naïve state to the inhibition of mechanical and heat hyperalgesia in the injured state, and then a switch back to antinociception to keep LS in a state of remission. This model clarifies the pharmacotherapeutic potential of Y2 research, pointing to the development of a new non-opioid pharmacotherapy for chronic pain using Y2 antagonists in patients who do not develop LS.

Molecular and cellular mechanisms of itch sensation and the anti-itch drug targets.

Itch is an uncomfortable feeling that evokes a desire to scratch. This protective reflex can effectively eliminate parasites that invade the skin. When itchy skin becomes severe or lasts for more than six weeks, it has deleterious effects on both quality of life and productivity. Despite decades of research, the complete molecular and cellular coding of chronic itch remains elusive. This persistent condition often defies treatment, including with antihistamines, and poses a significant societal challenge. Obtaining pathophysiological insights into the generation of chronic itch is essential for understanding its mechanisms and the development of innovative anti-itch medications. In this review we provide a systematic overview of the recent advancement in itch research, alongside the progress made in drug discovery within this field. We have examined the diversity and complexity of the classification and mechanisms underlying the complex sensation of itch. We have also delved into recent advancements in the field of itch mechanism research and how these findings hold potential for the development of new itch treatment medications. But the treatment of clinical itch symptoms still faces significant challenges. Future research needs to continue to delve deeper, not only to discover more itch-related pathways but also to explore how to improve treatment efficacy through multitarget or combination therapy.

Structure-guided discovery of bile acid derivatives for treating liver diseases without causing itch.

Chronic itch is a debilitating symptom profoundly impacting the quality of life in patients with liver diseases like cholestasis. Activation of the human G-protein coupled receptor, MRGPRX4 (hX4), by bile acids (BAs) is implicated in promoting cholestasis itch. However, the detailed underlying mechanisms remain elusive. Here, we identified 3-sulfated BAs that are elevated in cholestatic patients with itch symptoms. We solved the cryo-EM structure of hX4-Gq in a complex with 3-phosphated deoxycholic acid (DCA-3P), a mimic of the endogenous 3-sulfated deoxycholic acid (DCA-3S). This structure revealed an unprecedented ligand-binding pocket in MRGPR family proteins, highlighting the crucial role of the 3-hydroxyl (3-OH) group on BAs in activating hX4. Guided by this structural information, we designed and developed compound 7 (C7), a BA derivative lacking the 3-OH. Notably, C7 effectively alleviates hepatic injury and fibrosis in liver disease models while significantly mitigating the itch side effects.

Chi3l1 Knockout Mitigates Chronic Itch and Cutaneous Inflammation in Mice

Chi3l1 Knockout Mitigates Chronic Itch and Cutaneous Inflammation in Mice

B‐type natriuretic peptide levels are associated with chronic itch: A case–control study

B‐type natriuretic peptide levels are associated with chronic itch: A case–control study

Baicalein ameliorates chronic itch in ACD mice by suppressing the spinal astrocytic STAT3-LCN2 cascade.

Chronic itch is a maladaptive and debilitating symptom in patients with allergic contact dermatitis (ACD), adversely affecting their quality of life. There is a lack of effective treatments for ACD-associated uncontrollable itch. In this study, we explored the antipruritic effects of baicalein (BE), a bioactive flavonoid extracted from the root of Scutellaria baicalensis Georgi, and the underlying mechanisms in alleviating chronic itch triggered by diphenylcyclopropenone (DCP) in a mouse model of ACD. The ACD mice were intraperitoneally injected with BE (5, 30, and 60 mg·kg-1·d-1) for 7 days during the DCP challenge phase. The results showed that DCP-treated mice exhibited severe spontaneous scratching behaviors that wasreduced after BE injections in a dose-dependent manner accompanied by inhibition of spinal astrocyte activation. We observed that the spinal astrocytic STAT3-LCN2 cascade plays a crucial role in controlling the activation of astrocytes in chronic itch. Intrathecal injection of the STAT3 inhibitor AG490 or Lcn2 siRNA significantly reduced scratching behavior and astrocyte activation in ACD mice. Moreover, BE markedly attenuated the increased phosphorylation of STAT3 (p-STAT3) and LCN2 expression in the spinal cords of ACD mice and in lipopolysaccharide-stimulated primary spinal astrocytes. Altogether, BE relieved chronic itch by suppressing the spinal astrocytic STAT3-LCN2 cascade. These findings provide a potential avenue for the management of chronic itch. Schematic summary of the main findings illustrating that BE alleviates chronic itch through suppressing the spinal astrocytic STAT3-LCN2 cascade. Specifically, BE suppresses the expression of p-STAT3 to inhibit the reactive state of astrocytes in spinal dorsal horn, and then decreases the expression of astrocytic LCN2 to alleviate chronic itch in ACD mice.

Pruritus: An Overlooked Symptom of Spinal Tumors

Background Chronic itch is often associated with pain due to its complex nature. Neuropathic pruritus is defined as a debilitating form of chronic itching, about which not much is known to date. This condition may develop as a result of various neurological events and is associated with damage to the somatosensory nervous system, accounting for approximately 10% of chronic itching cases. Syringomyelia, transverse myelitis, radiculopathies, thoracic spine masses, brain tumors, strokes, and abscesses are among the conditions associated with neuropathic itching to date. Case presentation A 65-year-old female patient, with no known diseases and no regular medication usage, presented with a complaint of itching that had been ongoing for the past two years. Itching initially started in approximately five cm areas on the bilateral below-knee flexor surfaces. The patient, whose complaints persisted, was referred to the internal medicine outpatient clinic by dermatology. On physical examination, erythematous excoriated papules were observed in the areas affected by itching. The patient's blood sugar, liver and kidney function tests, complete blood count, erythrocyte sedimentation rate, thyroid function tests, urinalysis, stool parasitology were all normal or negative. The patient reported a sensation of coldness in the same area, was referred to neurosurgery to investigate the etiology of possible neuropathic itching. The patient's spinal imaging, revealed a spinal mass. She underwent surgery performed by a neurosurgeon, during which the spinal mass was completely removed. She reported that her itching had completely disappeared post-operatively. Conclusions The concept of itching as a variant of pain is not very new. Any damage occurring in the central nervous system or peripheral nervous system that affects the neurons responsible for transmitting and processing itch can lead to neuropathic itching. Focusing on spinal cord pathologies, any condition that damages the spinal cord may cause itching, depending on the level of damage. In cases of itching with dermatomal localization, where pain, hot or cold sensations, and paroxysmal itching are present, additional imaging methods or investigations for etiology should be performed.

52406 More Than Just a Rash: The Multifaceted Nature of Chronic Itch Through the Historical Perspective of Napoleon Bonaparte

52406 More Than Just a Rash: The Multifaceted Nature of Chronic Itch Through the Historical Perspective of Napoleon Bonaparte

Mouse Models of Itch

Murine models are vital preclinical and biological tools for studying itch. In this paper, we explore how these models have enhanced our understanding of the mechanisms underlying itch through both acute and chronic itch models. We provide detailed protocols and recommend experimental setups for specific models to guide researchers in conducting itch research. We distinguish between what constitutes a bona fide pruritogen versus a stimulus that causes pruritogen release, an acute itch model versus a chronic itch model, and how murine models can capture aspects of pruritus in human disease. Finally, we highlight how mouse models of itch have transformed our understanding and development of therapeutics for chronic pruritus in patients.

TRPV4-β-catenin axis is a novel therapeutic target for dry skin-induced chronic itch

Dry skin induced chronic pruritus is an increasingly common and debilitating problem, especially in the elderly. Although keratinocytes play important roles in innate and adaptive immunity and keratinocyte proliferation is a key feature of dry skin induced chronic pruritus, the exact contribution of keratinocytes to the pathogenesis of dry skin induced chronic pruritus is poorly understood. In this study, we generated the acetone-ether-water induced dry skin model in mice and found that epidermal hyperplasia induced by this model is partly dependent on the β-catenin signaling pathway. XAV939, an antagonist of β-catenin signaling pathway, inhibited epidermal hyperplasia in dry skin model mice. Importantly, dry skin induced chronic pruritus also dramatically reduced in XAV939 treated mice. Moreover, acetone-ether-water treatment-induced epidermal hyperplasia and chronic itch were decreased in Trpv4−/− mice. In vitro, XAV939 inhibited hypo-osmotic stress induced proliferation of HaCaT cells, and hypo-osmotic stress induced proliferation of in HaCaT cells and primary cultured keratinocytes were also significantly reduced by blocking TRPV4 function. Finally, thymic stromal lymphopoietin release was examined both in vivo and in vitro, which was significantly inhibited by XAV939 treatment and Trpv4 deficiency, and anti-TSLP antibody treatment significantly decreased AEW-induced scratching behavior. Overall, our study revealed a unique ability of TRPV4 expressing keratinocytes in the skin, which critically mediated dry skin induced epidermal hyperplasia and chronic pruritus, thus provided novel insights into the development of therapies for chronic pruritus in the elderly.

Chronic Itch Affects Patients' Ability to Experience Pleasure: Anhedonia in Itchy Disorders.

Anhedonia, the reduced ability to experience pleasure, is a prevalent symptom in various psychiatric disorders, but has not been investigated in dermatological conditions, particularly those characterized by chronic itch. This study aimed to examine the prevalence and clinical correlates of anhedonia in patients with chronic itch. A cross-sectional study was conducted in 137 patients with chronic itch, classified according to the International Forum for the Study of Itch (IFSI) classification. Anhedonia was assessed using the Snaith-Hamilton Pleasure Scale (SHAPS) and Anticipatory and Consummatory Interpersonal Pleasure Scale (ACIPS). Itch severity, quality of life, and psychological distress were assessed using the Visual Analogue Scale (VAS), Verbal Rating Scale (VRS), ItchyQoL, and Hospital Anxiety and Depression Scale (HADS), respectively. The mean SHAPS score was 1.0 ± 1.7 points, and the mean ACIPS total score was 76.9 ± 16.2 points. In the study sample, 13.1% of patients were identified as anhedonic, with a higher prevalence observed in those with severe and very severe itch. Anhedonia was significantly correlated with itch severity (R = 0.2, p=0.02 for 24 h VASmean and SHAPS; R = 0.2, p = 0.01 for 24 h VASmax and SHAPS), anxiety symptoms (R = 0.3, p < 0.001 for SHAPS and HADS-anxiety), depression symptoms (R = 0.4, p < 0.001 for SHAPS and HADS-depression), and impairment in quality of life (R = 0.2, p = 0.014 for SHAPS and ItchyQoL). Anhedonia is a significant and prevalent aspect of psychological distress in patients with chronic itch. Addressing this symptom may not only improve patients' overall mental health but also enhance the effectiveness of treatments for chronic itch. Future research is needed to elucidate further the mechanisms underlying the relationship between anhedonia and chronic itch and to develop targeted interventions for this population.

Investigating the relationship between chronic pruritus and fibromyalgia: an evaluation of 200 patients.

Pruritus is a common complaint in dermatology outpatient clinics. It is defined as chronic pruritus if the symptoms last 6weeks or longer. Fibromyalgia is a chronic, extensive pain syndrome that is well-known for its clinical signs, such as exhaustion, sleeping disorders, and some other pain symptoms. In the present study, it was investigated whether chronic pruritus patients were accompanied by fibromyalgia. The study included 100 patients with chronic pruritus and 100 controls without dermatological disease. All of the individuals were first evaluated in the dermatology clinic, and the patients having any musculoskeletal symptoms were then referred to a physiatrist in terms of accompanying fibromyalgia syndrome. Fibromyalgia was detected in 29 (29%) of 100 chronic pruritus patients and 6 (6%) of 100 patients in the control group. There was a statistically significant difference between the two groups regarding accompanying FM (p < 0.001). In the chronic pruritus group, pruritus severity, according to VAS and the four-item itch questionnaire score, was statistically significantly higher in patients with fibromyalgia than in patients without fibromyalgia (p = 0.027, p = 0.002, respectively). In addition, the number of patients with severe/very severe chronic pruritus was statistically significantly higher in the group accompanied by fibromyalgia (p = 0.023). It may be suggested that fibromyalgia is a frequent disease that can accompany chronic pruritus. Clinicians should keep in mind that there is a possibility of the coexistence of both diseases. This study calls attention to the complex relationship between chronic itch and pain.

Mechanisms and Therapeutic Targets of Staphylococcus Aureus - Induced Itch in Atopic Dermatitis

Atopic dermatitis is a chronic skin disorder marked by inflammation, erythema, and pruritus, often beginning in childhood and characterized by exacerbations and remissions. Its etiology involves genetic, immunological, and environmental factors. Staphylococcus aureus, a common pathogen, exacerbates atopic dermatitis by producing toxins and enzymes such as the serine protease V8, which activates the protease-activated receptor 1 (PAR1) on sensory neurons, inducing itch. This mechanism highlights potential therapeutic targets for alleviating pruritus. Research into the physiological pathways of itch, including the role of PAR1 and other protease-activated receptors, reveals promising strategies for treatment. PAR1 antagonists could be repurposed to treat chronic itch, providing new therapeutic avenues. PAR1 and other protease-activated receptors, is crucial in developing new treatment strategies. Anti-pruritic therapies targeting these pathways, such as PAR1 antagonists, show promise in mitigating itch symptoms. Moreover, existing drugs that inhibit PAR1 could be repurposed for treating chronic itch, providing a new avenue for relief in patients with atopic dermatitis. Additionally, the evolutionary role of itch induced by microorganisms suggests pathogens may exploit neural reflexes to enhance their spread. Advancements in understanding the mechanisms behind S. aureus-induced itch and the physiological pathways involved offer promising new directions for therapeutic intervention. Advancements in understanding the mechanisms of Staphylococcal aureus-induced itch and associated physiological pathways offer promising directions for therapeutic intervention, potentially improving management and treatment outcomes for patients with atopic dermatitis and other pruritic conditions.

The role of ecology in the region of residence of patients with epidermolysis bullosa and during the experiment

BACKGROUND: A person is constantly influenced by the environment, which determines his state of health. Animal testing is used to determine the danger of certain chemical agents of inanimate nature. To extrapolate the experimental result to humans, the body of patients with the dystrophic form of epidermolysis bullosa, which has a low threshold of resistance to aggressive stimuli, is preferable. AIM: To study the impact of anthropogenic physicochemical factors on the skin of white mice, as well as environmental ecology on the population of patients with the dystrophic form of congenital epidermolysis bullosa. MATERIALS AND METHODS: Scientific research is both observational and interventional. The observational part of the study included patients suffering from dystrophic form of epidermolysis bullosa. There are white mice in the interventional part. RESULTS: Seeding with agrochemicals causes skin eczema, periorbital dermatitis, finger mutation and contracture, claw deformity and chronic itching in white mice. The possibility and criteria for extrapolating the results of the experiment to patients suffering from dystrophic form of epidermolysis bullosa have been established. These criteria include: itching of the skin, mutation and pseudosyndactyly of the fingers. The effect on the body of patients with dystrophic form of epidermolysis bullosa with toxic agents was carried out by the living environment. It has been established that in order to achieve the positive effect of complex therapy, in addition to highly qualified medical care, an environmentally safe living environment is necessary. Traveling and living in conditions that do not pose an environmental danger to humans helps to reduce the severity of the disease and improve their quality of life. CONCLUSION: The ecology of the living environment determines the effectiveness of therapy in patients with dystrophic form of epidermolysis bullosa, as well as the timing of manifestation and severity of the disease. A healthy environment contributes to the epithelization of ulcerative elements and the disappearance of itching.

Attentiveness and mental health in adolescents with moderate-to-severe atopic dermatitis without ADHD

Patients with moderate-to-severe atopic dermatitis (AD) experience intense chronic itch and impaired sleep. Reports from parents and teachers suggest that AD patients may also have attention problems. However, attention has not yet been directly assessed in AD patients. We utilized an objective, computer-based continuous performance test (CPT) validated for use in attention-deficit/hyperactivity disorder (ADHD) diagnosis to formally evaluate attention in adolescent AD subjects. This was a single-visit, cross-sectional, non-interventional study of moderate-to-severe (Investigator’s Global Assessment [IGA] ≥ 3) AD subjects aged 12–17 years without clinician-diagnosed ADHD. Attention was evaluated using two performance-based measures: Conners, CPT-3 and the Stroop Color and Word Test. The primary parameter was CPT-3 detectability (d’) measure. Lesional severity measures included Eczema Area and Severity Index (EASI) and body surface area (BSA) involvement. Subjects completed self-report rating scales assessing sensory responsiveness patterns (Adult/Adolescent Sensory Profile [AASP]), itch (Peak Pruritus Numerical Rating Scale [PP-NRS]), skin pain, quality of life, sleep, anxiety, and depressive symptoms. A total of 44 subjects were included in the study (61.4% female; mean age 15.0 [SD 1.78] years; mean EASI 20.4 [SD 7.8]; mean PP-NRS 7.0 [SD 1.8]). Results indicated substantial disease impact on sleep, quality of life, and comorbid anxiety and depressive symptoms. The mean (SD) Conners, CPT-3 dʹ T-score was 48.7 (SD 10.7), similar to the expected mean from a randomly selected age/gender-matched sample of the general population (50 [SD 10], by definition). Overall, 13.6% of subjects exhibited a dʹ T-score ≥ 60 (clinically significant poor performance), which was not greater than the expected general population value (15.9%). Subject-level data review by two psychologists determined that only 2 subjects demonstrated an overall response pattern that clearly indicated attention deficit. Many subjects had atypical sensory responsiveness profiles: sensory hypersensitivity (38.6%), sensory avoidance (50%), and low registration (hypo-sensitivity, 36.4%). Adolescents with moderate-to-severe AD without existing ADHD diagnosis did not demonstrate greater attention problems on performance-based measures than would be expected in age/gender-matched peers.Trial registration NCT05203380.