Requirement for neuropeptide Y in the development of type 2 responses and allergen-induced airway hyperresponsiveness and inflammation

Novel Immunopharmacological Drugs for the Treatment of Allergic Diseases

The exponential rise in the prevalence of allergic diseases since the mid-twentieth century has led to a genuine public health emergency and has also fostered major progress in research on the underlying mechanisms and potential treatments. The management of allergic diseases benefits from the biological revolution, with an array of novel immunomodulatory therapeutic and investigational tools targeting players of allergic inflammation at distinct pathophysiological steps. Prominent examples include therapeutic monoclonal antibodies against cytokines, alarmins, and their receptors, as well as small-molecule modifiers of signal transduction mainly mediated by Janus kinases and Bruton's tyrosine kinases. However, the first-line therapeutic options have yet to switch from symptomatic to disease-modifying interventions. Here we present an overview of available drugs in the context of our current understanding of allergy pathophysiology, identify potential therapeutic targets, and conclude by providing a selection of candidate immunopharmacological molecules under investigation for potential future use in allergic diseases.

Pruritogenic Mediators and New Antipruritic Drugs in Atopic Dermatitis

Atopic dermatitis (AD) is a common highly pruritic chronic inflammatory skin disorder affecting 5-20% of children worldwide, while the prevalence in adults varies from 7 to 10%. Patients with AD experience intense pruritus that could lead to sleep disturbance and impaired quality of life. Here, we analyze the pathophysiology of itchiness in AD. We extensively review the histamine-dependent and histamine-independent pruritogens. Several receptors, substance P, secreted molecules, chemokines, and cytokines are involved as mediators in chronic itch. We also, summarize the new emerging antipruritic drugs in atopic dermatitis.

Neuropeptide Y Antagonizes Development of Pulmonary Fibrosis through IL-1β Inhibition

Neuropeptide Y (NPY), a 36 amino acid residue polypeptide distributed throughout the nervous system, acts on various immune cells in many organs, including the respiratory system. However, little is known about its role in the pathogenesis of pulmonary fibrosis. This study was performed to determine the effects of NPY on pulmonary fibrosis. NPY-deficient and wild-type mice were intratracheally administered bleomycin. Inflammatory cells, cytokine concentrations, and morphological morphometry of the lungs were analyzed. Serum NPY concentrations were also measured in patients with idiopathic pulmonary fibrosis and healthy control subjects. NPY-deficient mice exhibited significantly enhanced pulmonary fibrosis and higher IL-1β concentrations in the lungs compared with wild-type mice. Exogenous NPY treatment suppressed the development of bleomycin-induced lung fibrosis and decreased IL-1β concentrations in the lungs. Moreover, IL-1β neutralization in NPY-deficient mice attenuated the fibrotic changes. NPY decreased IL-1β release, and Y1 receptor antagonists inhibited IL-1β release and induced epithelial-mesenchymal transition in human alveolar epithelial cells. Patients with idiopathic pulmonary fibrosis had lower NPY and greater IL-1β concentrations in the serums compared with healthy control subjects. NPY expression was mainly observed around bronchial epithelial cells in human idiopathic pulmonary fibrosis lungs. These data suggest that NPY plays a protective role against pulmonary fibrosis by suppressing IL-1β release, and manipulating the NPY-Y1 receptor axis could be a potential therapeutic strategy for delaying disease progression.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

"Every cell is an immune cell; contributions of non-hematopoietic cells to anti-helminth immunity"

Helminths are remarkably successful parasites that can invade various mammalian hosts and establish chronic infections that can go unnoticed for years despite causing severe tissue damage. To complete their life cycles, helminths migrate through multiple barrier sites that are densely populated by a complex array of hematopoietic and non-hematopoietic cells. While it is clear that type 2 cytokine responses elicited by immune cells promote worm clearance and tissue healing, the actions of non-hematopoietic cells are increasingly recognized as initiators, effectors and regulators of anti-helminth immunity. This review will highlight the collective actions of specialized epithelial cells, stromal niches, stem, muscle and neuroendocrine cells as well as peripheral neurons in the detection and elimination of helminths at mucosal sites. Studies dissecting the interactions between immune and non-hematopoietic cells will truly provide a better understanding of the mechanisms that ensure homeostasis in the context of helminth infections.

Protective effects of neuropeptide Y against elastase-induced pulmonary emphysema

Neuropeptide Y (NPY) is a neuropeptide widely expressed in not only the central nervous system but also immune cells and the respiratory epithelium. Patients with chronic obstructive pulmonary disease (COPD) reportedly exhibit decreased NPY expression in the airway epithelium, but the involvement of NPY in the pathophysiology of COPD has not been defined. We investigated the role of NPY in elastase-induced emphysema. NPY-deficient (NPY^-/-) mice and wild-type (NPY^+/+) mice received intratracheal instillation of porcine pancreas elastase (PPE). The numbers of inflammatory cells and the levels of cytokines and chemokines in the bronchoalveolar lavage (BAL) fluid and lung homogenates were determined along with quantitative morphometry of lung sections. Intratracheal instillation of PPE induced emphysematous changes and increased NPY levels in the lungs. Compared with NPY^+/+ mice, NPY^-/- mice had significantly enhanced PPE-induced emphysematous changes and alveolar enlargement. Neutrophilia seen in BAL flu12id of NPY^+/+ mice on day 4 after PPE instillation was also enhanced in NPY^-/- mice, and the enhancement was associated with increased levels of neutrophil-related and macrophage-related chemokines and IL-17A as well as increased numbers of type 3 innate lymphoid cells in the airways. Treatment with NPY significantly reduced PPE-induced emphysematous changes. Conversely, treatment with a NPY receptor antagonist exacerbated PPE-induced emphysematous changes. These observations indicate that NPY has protective effects against elastase-induced emphysema, and suggest that targeting NPY in emphysema has potential as a therapeutic strategy for delaying disease progression.

Current Insights Into the Role of Neuropeptide Y in Skin Physiology and Pathology

Neuropeptide Y is widely distributed within the body and has long been implicated as a contributor to skin disease based on the correlative clinical data. However, until recently, there have been few empirical investigations to determine whether NPY has a pathophysiological role in the skin. Due to appearance-altering phenotypes of atopic dermatitis, psoriasis, and vitiligo, those suffering from these diseases often face multiple forms of negative social attention. This often results in psychological stress, which has been shown to exacerbate inflammatory skin diseases - creating a vicious cycle that perpetuates disease. This has been shown to drive severe depression, which has resulted in suicidal ideation being a comorbidity of these diseases. Herein, we review what is currently known about the associations of NPY with skin diseases and stress. We also review and provide educated guessing what the effects NPY can have in the skin. Inflammatory skin diseases can affect physical appearance to have significant, negative impacts on quality of life. No cure exists for these conditions, highlighting the need for identification of novel proteins/neuropetides, like NPY, that can be targeted therapeutically. This review sets the stage for future investigations into the role of NPY in skin biology and pathology to stimulate research on therapeutic targeting NPY signaling in order to combat inflammatory skin diseases.

Regulatory Peptides in Asthma

Numerous regulatory peptides play a critical role in the pathogenesis of airway inflammation, airflow obstruction and hyperresponsiveness, which are hallmarks of asthma. Some of them exacerbate asthma symptoms, such as neuropeptide Y and tachykinins, while others have ameliorating properties, such as nociception, neurotensin or β-defensin 2. Interacting with peptide receptors located in the lungs or on immune cells opens up new therapeutic possibilities for the treatment of asthma, especially when it is resistant to available therapies. This article provides a concise review of the most important and current findings regarding the involvement of regulatory peptides in asthma pathology.

Essential role of IL-23 in the development of acute exacerbation of pulmonary fibrosis

Acute exacerbation of idiopathic pulmonary fibrosis has a poor prognosis associated with neutrophilic inflammation. Interleukin-23 is a proinflammatory cytokine involved in neutrophilic inflammation. However, little is known about its role in acute exacerbation of pulmonary fibrosis. This study was performed to determine the role of interleukin-23 in acute exacerbation of pulmonary fibrosis. For assessment of acute exacerbation of pulmonary fibrosis, mice were intratracheally administered bleomycin followed by lipopolysaccharide. Inflammatory cells, cytokine levels, and morphological morphometry of the lungs were analyzed. Cytokine levels were measured in the bronchoalveolar lavage fluid of idiopathic pulmonary fibrosis patients with or without acute exacerbation. Interleukin-23, -17A, and -22 levels were increased in the airway of mice with acute exacerbation of pulmonary fibrosis. Interleukin-23p19-deficient mice with acute exacerbation of pulmonary fibrosis had markedly reduced airway inflammation and fibrosis associated with decreased levels of interleukin-17A and -22 compared with wild-type mice. Treatment with an anti-interleukin-23 antibody attenuated airway inflammation and fibrosis and reduced interleukin-17A and -22 levels in mice with acute exacerbation of pulmonary fibrosis. T-helper type 17 cells were the predominant source of interleukin-17A in mice with acute exacerbation of pulmonary fibrosis. Interleukin-23 levels in bronchoalveolar lavage fluid tended to be higher in idiopathic pulmonary fibrosis patients with than without acute exacerbation. The data presented here suggest that interleukin-23 is essential for the development of acute exacerbation of pulmonary fibrosis and that blockade of interleukin-23 may be a new therapeutic strategy for acute exacerbation of pulmonary fibrosis.

Neuropeptides Involved in Facial Nerve Regeneration

Neuropeptides and neurotransmitters act as intermediaries to transmit impulses from one neuron to another via a synapse. These neuropeptides are also related to nerve degeneration and regeneration during nerve damage. Although there are various neuropeptides, three are associated with neural regeneration in facial nerve damage: calcitonin gene-related peptide (CGRP), galanin, and pituitary adenylyl cyclase-activating peptide (PACAP). Alpha CGRP in facial motoneurons is a signaling factor involved in neuroglial and neuromuscular interactions during regeneration. Thus, it may be a marker for facial nerve regeneration. Galanin is a marker of injured axons rather than nerve regeneration. PACAP has various effects on nerve regeneration by regulating the surrounding cells and providing neurotrophic factors. Thus, it may also be used as a marker for facial nerve regeneration. However, the precise roles of these substances in nerve generation are not yet fully understood. Animal studies have demonstrated that they may act as neuromodulators to promote neurotrophic factors involved in nerve regeneration as they appear early, before changes in the injured cells and their environment. Therefore, they may be markers of nerve regeneration.

Neuropeptide Y Reduces Nasal Epithelial T2R Bitter Taste Receptor-Stimulated Nitric Oxide Production

Bitter taste receptors (T2Rs) are G-protein-coupled receptors (GPCRs) expressed on the tongue but also in various locations throughout the body, including on motile cilia within the upper and lower airways. Within the nasal airway, T2Rs detect secreted bacterial ligands and initiate bactericidal nitric oxide (NO) responses, which also increase ciliary beat frequency (CBF) and mucociliary clearance of pathogens. Various neuropeptides, including neuropeptide tyrosine (neuropeptide Y or NPY), control physiological processes in the airway including cytokine release, fluid secretion, and ciliary beating. NPY levels and/or density of NPYergic neurons may be increased in some sinonasal diseases. We hypothesized that NPY modulates cilia-localized T2R responses in nasal epithelia. Using primary sinonasal epithelial cells cultured at air–liquid interface (ALI), we demonstrate that NPY reduces CBF through NPY2R activation of protein kinase C (PKC) and attenuates responses to T2R14 agonist apigenin. We find that NPY does not alter T2R-induced calcium elevation but does reduce T2R-stimulated NO production via a PKC-dependent process. This study extends our understanding of how T2R responses are modulated within the inflammatory environment of sinonasal diseases, which may improve our ability to effectively treat these disorders.

The Implications of Pruritogens in the Pathogenesis of Atopic Dermatitis

Atopic dermatitis (AD) is a prototypic inflammatory disease that presents with intense itching. The pathophysiology of AD is multifactorial, involving environmental factors, genetic susceptibility, skin barrier function, and immune responses. A recent understanding of pruritus transmission provides more information about the role of pruritogens in the pathogenesis of AD. There is evidence that pruritogens are not only responsible for eliciting pruritus, but also interact with immune cells and act as inflammatory mediators, which exacerbate the severity of AD. In this review, we discuss the interaction between pruritogens and inflammatory molecules and summarize the targeted therapies for AD.

A decision tree model for neuroimmune guidance of allergic immunity

The immune system defends the body from infectious and non-infectious threats. Distinct recognition strategies have evolved to generate antigen-specific immunity against pathogens or toxins versus antigen-independent tissue repair. Structural recognition, or the sensing of conserved motifs, guides the immune response to viruses, bacteria, fungi, and unicellular parasites. Functional recognition, which is sensing that is based on the activities of an input, guides antigen-independent tissue healing and antigen-specific Type 2 immunity to toxins, allergens, and helminth parasites. Damage-associated molecular patterns (DAMPs), released from damaged and dying cells, permit functional recognition by immune cells. However, the DAMP paradigm alone does not explain how functional recognition can lead to such disparate immune responses, namely wound healing and Type 2 immunity. Recent work established that sensory neurons release neuropeptides in response to a variety of toxins and allergens. These neuropeptides act on local innate immune cells, stimulating or inhibiting their activities. By integrating our knowledge on DAMP function with new information on the role of neuropeptides in innate immune activation in Type 2 immunity, we describe a decision tree model of functional recognition. In this model, neuropeptides complement or antagonize DAMPs to guide the development of antigen-specific Type 2 immunity through the activation of innate immune cells. We discuss why this decision tree system evolved and its implications to allergic diseases.

Loss of IL-33 enhances elastase-induced and cigarette smoke extract-induced emphysema in mice

BACKGROUND

IL-33, which is known to induce type 2 immune responses via group 2 innate lymphoid cells, has been reported to contribute to neutrophilic airway inflammation in chronic obstructive pulmonary disease. However, its role in the pathogenesis of emphysema remains unclear.

METHODS

We determined the role of interleukin (IL)-33 in the development of emphysema using porcine pancreas elastase (PPE) and cigarette smoke extract (CSE) in mice. First, IL-33-/- mice and wild-type (WT) mice were given PPE intratracheally. The numbers of inflammatory cells, and the levels of cytokines and chemokines in the bronchoalveolar lavage (BAL) fluid and lung homogenates, were analyzed; quantitative morphometry of lung sections was also performed. Second, mice received CSE by intratracheal instillation. Quantitative morphometry of lung sections was then performed again.

RESULTS

Intratracheal instillation of PPE induced emphysematous changes and increased IL-33 levels in the lungs. Compared to WT mice, IL-33-/- mice showed significantly greater PPE-induced emphysematous changes. No differences were observed between IL-33-/- and WT mice in the numbers of macrophages or neutrophils in BAL fluid. The levels of hepatocyte growth factor were lower in the BAL fluid of PPE-treated IL-33-/- mice than WT mice. IL-33-/- mice also showed significantly greater emphysematous changes in the lungs, compared to WT mice, following intratracheal instillation of CSE.

CONCLUSION

These observations suggest that loss of IL-33 promotes the development of emphysema and may be potentially harmful to patients with COPD.

Neuroimmune Pathophysiology in Asthma

Asthma is a chronic inflammation of lower airway disease, characterized by bronchial hyperresponsiveness. Type I hypersensitivity underlies all atopic diseases including allergic asthma. However, the role of neurotransmitters (NT) and neuropeptides (NP) in this disease has been less explored in comparison with inflammatory mechanisms. Indeed, the airway epithelium contains pulmonary neuroendocrine cells filled with neurotransmitters (serotonin and GABA) and neuropeptides (substance P[SP], neurokinin A [NKA], vasoactive intestinal peptide [VIP], Calcitonin-gene related peptide [CGRP], and orphanins-[N/OFQ]), which are released after allergen exposure. Likewise, the autonomic airway fibers produce acetylcholine (ACh) and the neuropeptide Y(NPY). These NT/NP differ in their effects; SP, NKA, and serotonin exert pro-inflammatory effects, whereas VIP, N/OFQ, and GABA show anti-inflammatory activity. However, CGPR and ACh have dual effects. For example, the ACh-M3 axis induces goblet cell metaplasia, extracellular matrix deposition, and bronchoconstriction; the CGRP-RAMP1 axis enhances Th2 and Th9 responses; and the SP-NK1R axis promotes the synthesis of chemokines in eosinophils, mast cells, and neutrophils. In contrast, the ACh-α7nAChR axis in ILC2 diminishes the synthesis of TNF-α, IL-1, and IL-6, attenuating lung inflammation whereas, VIP-VPAC1, N/OFQ-NOP axes cause bronchodilation and anti-inflammatory effects. Some NT/NP as 5-HT and NKA could be used as biomarkers to monitor asthma patients. In fact, the asthma treatment based on inhaled corticosteroids and anticholinergics blocks M3 and TRPV1 receptors. Moreover, the administration of experimental agents such as NK1R/NK2R antagonists and exogenous VIP decrease inflammatory mediators, suggesting that regulating the effects of NT/NP represents a potential novel approach for the treatment of asthma.

Updated Role of Neuropeptide Y in Nicotine-Induced Endothelial Dysfunction and Atherosclerosis

Cardiovascular disease is the leading cause of death worldwide. Endothelial dysfunction of the arterial vasculature plays a pivotal role in cardiovascular pathogenesis. Nicotine-induced endothelial dysfunction substantially contributes to the development of arteriosclerotic cardiovascular disease. Nicotine promotes oxidative inflammation, thrombosis, pathological angiogenesis, and vasoconstriction, and induces insulin resistance. However, the exact mechanism through which nicotine induces endothelial dysfunction remains unclear. Neuropeptide Y (NPY) is widely distributed in the central nervous system and peripheral tissues, and it participates in the pathogenesis of atherosclerosis by regulating vasoconstriction, energy metabolism, local plaque inflammatory response, activation and aggregation of platelets, and stress and anxiety-related emotion. Nicotine can increase the expression of NPY, suggesting that NPY is involved in nicotine-induced endothelial dysfunction. Herein, we present an updated review of the possible mechanisms of nicotine-induced atherosclerosis, with a focus on endothelial cell dysfunction associated with nicotine and NPY.

[The role of neuropeptide Y for the development of allergic airway responses]

Neuropeptide Y (NPY) is a neurotransmitter that is widely expressed in the brain and peripheral nervous system. Various immune cells express the receptor for NPY, Y1 receptor. NPY modulates these cells via its Y1 receptor, and involvement of NPY in the pathophysiology of bronchial asthma, has been reported. Increased plasma levels of NPY in asthmatic patients have been reported. NPY polymorphisms are associated with an increased risk for asthma in overweight subjects and young adults. We and other researchers have reported that using murine models of allergic airway responses, NPY and Y1 receptor play critical roles for the development of allergic airway inflammation and airway hyperresponsiveness. Therefore, manipulating NPY-Y1 pathway represents a novel therapeutic target to control allergic airway responses, and might be beneficial for treatment of bronchial asthma.

Neuropeptide Y Is an Immunomodulatory Factor: Direct and Indirect

Neuropeptide Y (NPY), which is widely distributed in the nervous system, is involved in regulating a variety of biological processes, including food intake, energy metabolism, and emotional expression. However, emerging evidence points to NPY also as a critical transmitter between the nervous system and immune system, as well as a mediator produced and released by immune cells. In vivo and in vitro studies based on gene-editing techniques and specific NPY receptor agonists and antagonists have demonstrated that NPY is responsible for multifarious direct modulations on immune cells by acting on NPY receptors. Moreover, via the central or peripheral nervous system, NPY is closely connected to body temperature regulation, obesity development, glucose metabolism, and emotional expression, which are all immunomodulatory factors for the immune system. In this review, we focus on the direct role of NPY in immune cells and particularly discuss its indirect impact on the immune response.