IL-4 and IFN-gamma up-regulate substance P receptor expression in murine peritoneal macrophages

Substance P - a regulatory peptide with defense and repair functions. Results and perspectives for the fight against COVID-19

Severe acute respiratory syndrome corona virus 2 (SARS CoV-2) is the cause of Corona virus disease 2019 (COVID-19), which turned into a pandemic in late 2019 and early 2020. SARS CoV-2 causes endothelial cell destruction and swelling, microthrombosis, constriction of capillaries, and malfunction of pericytes, all of which are detrimental to capillary integrity, angiogenesis, and healing processes. Cytokine storming has been connected to COVID-19 disease. Hypoxemia and tissue hypoxia may arise from impaired oxygen diffusion exchange in the lungs due to capillary damage and congestion. This personal view will look at how inflammation and capillary damage affect blood and tissue oxygenation, cognitive function, and the duration and intensity of COVID-19 disease. The general effects of microvascular injury, hypoxia, and capillary damage caused by COVID-19 in key organs are also covered in this point of view. Once initiated, this vicious cycle leads to diminished capillary function, which exacerbates inflammation and tissue damage, and increased inflammation due to hypoxia. Brain damage may result from low oxygen levels and high cytokines in brain tissue. In this paper we give a summary in this direction with focus on the role of the neuropeptide Substance P. On the basis of this, we discuss selected approaches to the question: "How Substance P is involved in the etiology of the COVID-19 and how results of our research could improve the prevention or therapy of corona? Thereby pointing out the role of Substance P in the post-corona syndrome and providing novel concepts for therapy and prevention.

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

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

Post COVID-19 complications and follow up biomarkers

Millions of people were infected by the coronavirus disease (COVID-19) epidemic, which left a huge burden on the care of post COVID-19 survivors around the globe. The self-reported COVID-19 symptoms were experienced by an estimated 1.3 million people in the United Kingdom (2% of the population), and these symptoms persisted for about 4 weeks from the beginning of the infection. The symptoms most frequently reported were exhaustion, shortness of breath, muscular discomfort, joint pain, headache, cough, chest pain, cognitive impairment, memory loss, anxiety, sleep difficulties, diarrhea, and a decreased sense of smell and taste in post-COVID-19 affected people. The post COVID-19 complications were frequently related to the respiratory, cardiac, nervous, psychological and musculoskeletal systems. The lungs, liver, kidneys, heart, brain and other organs had been impaired by hypoxia and inflammation in post COVID-19 individuals. The upregulation of substance "P" (SP) and various cytokines such as tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), interleukin 10 (IL-10), interleukin 1 beta (IL-1β), angiotensin-converting enzyme 2 (ACE2) and chemokine C-C motif ligand 3 (CCL3) has muddled respiratory, cardiac, neuropsychiatric, dermatological, endocrine, musculoskeletal, gastrointestinal, renal and genitourinary complications in post COVID-19 people. To prevent these complications from worsening, it was therefore important to study how these biomarkers were upregulated and block their receptors.

Tachykinins and the potential causal factors for post-COVID-19 condition

The most prevalent symptoms of post-COVID-19 condition are pulmonary dysfunction, fatigue and muscle weakness, anxiety, anosmia, dysgeusia, headaches, difficulty in concentrating, sexual dysfunction, and digestive disturbances. Hence, neurological dysfunction and autonomic impairments predominate in post-COVID-19 condition. Tachykinins including the most studied substance P are neuropeptides expressed throughout the nervous and immune systems, and contribute to many physiopathological processes in the nervous, immune, gastrointestinal, respiratory, urogenital, and dermal systems and participate in inflammation, nociception, and cell proliferation. Substance P is a key molecule in neuroimmune crosstalk; immune cells near the peripheral nerve endings can send signals to the brain with cytokines, which highlights the important role of tachykinins in neuroimmune communication. We reviewed the evidence that relates the symptoms of post-COVID-19 condition to the functions of tachykinins and propose a putative pathogenic mechanism. The antagonism of tachykinins receptors can be a potential treatment target.

Nociceptor-Macrophage Interactions in Apical Periodontitis: How Biomolecules Link Inflammation with Pain

Periradicular tissues have a rich supply of peripheral afferent neurons, also known as nociceptive neurons, originating from the trigeminal nerve. While their primary function is to relay pain signals to the brain, these are known to be involved in modulating innate and adaptive immunity by initiating neurogenic inflammation (NI). Studies have investigated neuroanatomy and measured the levels of biomolecules such as cytokines and neuropeptides in human saliva, gingival crevicular fluid, or blood/serum samples in apical periodontitis (AP) to validate the possible role of trigeminal nociceptors in inflammation and tissue regeneration. However, the contributions of nociceptors and the mechanisms involved in the neuro-immune interactions in AP are not fully understood. This narrative review addresses the complex biomolecular interactions of trigeminal nociceptors with macrophages, the effector cells of the innate immune system, in the clinical manifestations of AP.

Substance P Exacerbates the Inflammatory and Pro-osteoclastogenic Responses of Murine Osteoclasts and Osteoblasts to Staphylococcus aureus

Staphylococcus aureus infections of bone tissue are associated with inflammatory bone loss. Resident bone cells, including osteoblasts and osteoclasts, can perceive S. aureus and produce an array of inflammatory and pro-osteoclastogenic mediators, thereby contributing to such damage. The neuropeptide substance P (SP) has been shown to exacerbate microbially induced inflammation at sites such as the gut and the brain and has previously been shown to affect bone cell differentiation and activity. Here we demonstrate that the interaction of SP with its high affinity receptor, neurokinin-1 receptor (NK-1R), expressed on murine osteoblasts and osteoclasts, augments the inflammatory responses of these cells to S. aureus challenge. Additionally, SP alters the production of pro- and anti-osteoclastogenic factors by bacterially challenged bone cells and their proteolytic functions in a manner that would be anticipated to exacerbate inflammatory bone loss at sites of infection. Furthermore, we have demonstrated that the clinically approved NK-1R antagonist, aprepitant, attenuates local inflammatory and pro-osteoclastogenic mediator expression in an in vivo mouse model of post-traumatic staphylococcal osteomyelitis. Taken together, these results indicate that SP/NK-1R interactions could play a significant role in the initiation and/or progression of damaging inflammation in S. aureus bone infections and suggest that the repurposing of currently approved NK-1R antagonists might represent a promising new adjunct therapy for such conditions.

Therapeutic efficacy of topical blockade of substance P in experimental allergic red eye

PURPOSE

Allergic conjunctivitis is the most common cause leading to ocular redness (OR). Herein, using an animal model of allergic OR, we evaluated the therapeutic efficacy of topical blockade of substance P (SP) in treating red eye.

METHODS

Allergic OR was induced in guinea pigs with topical histamine. Ocular SP was blocked using a specific SP receptor (neurokinin-1 receptor, NK1R) antagonist, L-703,606, via topical application 10 min before or 10 min after histamine instillation. Animal eyes were examined and a series of images were taken for up to 60 min post-OR induction. The severity of redness was analyzed using the quantitative ocular redness index (ORI). At the end of clinical examination, conjunctival tissues were collected for histological examination of conjunctival blood vessels and infiltrating eosinophils and neutrophils. In addition, SP concentration was quantified in the tear fluid and expression levels of inflammatory cytokines were assessed in the conjunctival tissues.

RESULTS

Topical histamine application successfully induced red eye, evidenced by the significantly increased ORI during the observation period, with peak values at 10 min, along with significantly increased levels of SP in the tears. Topical treatment with L-703,606, either before histamine application or at the time of peak ORI, effectively reduced ORI and suppressed conjunctival blood vessel dilation, along with decreased eosinophil and neutrophil infiltration, and inflammatory cytokine expression in the conjunctiva, as well as reduced SP levels in the tears.

CONCLUSIONS

Topical blockade of SP effectively prevents and treats allergy-related ocular redness by suppressing blood vessel dilation and allergic inflammation.

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.

Modulating the tachykinin: Role of substance P and neurokinin receptor expression in ocular surface disorders

Substance P (SP) is a tachykinin expressed by various cells in the nervous and immune systems. SP is predominantly released by neurons and exerts its biological and immunological effects through the neurokinin receptors, primarily the neurokinin-1 receptor (NK1R). SP is essential for maintaining ocular surface homeostasis, and its reduced levels in disorders like diabetic neuropathy disrupt the corneal tissue. It also plays an essential role in promoting corneal wound healing by promoting the migration of keratocytes. In this review, we briefly discuss the structure, expression, and function of SP and its principal receptor NK1R. In addition, SP induces pro-inflammatory effects through autocrine or paracrine action on the immune cells in various ocular surface pathologies, including dry eye disease, herpes simplex virus keratitis, and Pseudomonas keratitis. We provide an in-depth review of the pathogenic role of SP in various ocular surface diseases and several new approaches developed to counter the immune-mediated effects of SP either through modulating its production or blocking its target receptor.

Regulation of Carcinogenesis by Sensory Neurons and Neuromediators

Simple Summary

Sensory nerve fibers extensively innervate the entire body. They are the first to sense danger signals, including the ones coming from newly formed cancer cells. Various studies have demonstrated that the inactivation of sensory nerve fibers as well as the vagus nerve enhances tumor growth and spread in models including breast, pancreatic, and gastric cancer. On the other hand, there are also contradictory findings that show the opposite, namely that the inactivation of nerve fibers inhibits tumor growth. These discrepancies are likely caused by the stage and the level of aggressiveness of the tumor model used. Hence, further studies are required to determine the factors involved in neuro-immunological mechanisms of tumor growth and spread.

Abstract

Interactions between the immune system and the nervous system are crucial in maintaining homeostasis, and disturbances of these neuro-immune interactions may participate in carcinogenesis and metastasis. Nerve endings have been identified within solid tumors in humans and experimental animals. Although the involvement of the efferent sympathetic and parasympathetic innervation in carcinogenesis has been extensively investigated, the role of the afferent sensory neurons and the neuropeptides in tumor development, growth, and progression is recently appreciated. Similarly, current findings point to the significant role of Schwann cells as part of neuro-immune interactions. Hence, in this review, we mainly focus on local and systemic effects of sensory nerve activity as well as Schwann cells in carcinogenesis and metastasis. Specific denervation of vagal sensory nerve fibers, or vagotomy, in animal models, has been reported to markedly increase lung metastases of breast carcinoma as well as pancreatic and gastric tumor growth, with the formation of liver metastases demonstrating the protective role of vagal sensory fibers against cancer. Clinical studies have revealed that patients with gastric ulcers who have undergone a vagotomy have a greater risk of stomach, colorectal, biliary tract, and lung cancers. Protective effects of vagal activity have also been documented by epidemiological studies demonstrating that high vagal activity predicts longer survival rates in patients with colon, non-small cell lung, prostate, and breast cancers. However, several studies have reported that inhibition of sensory neuronal activity reduces the development of solid tumors, including prostate, gastric, pancreatic, head and neck, cervical, ovarian, and skin cancers. These contradictory findings are likely to be due to the post-nerve injury-induced activation of systemic sensory fibers, the level of aggressiveness of the tumor model used, and the local heterogeneity of sensory fibers. As the aggressiveness of the tumor model and the level of the inflammatory response increase, the protective role of sensory nerve fibers is apparent and might be mostly due to systemic alterations in the neuro-immune response. Hence, more insights into inductive and permissive mechanisms, such as systemic, cellular neuro-immunological mechanisms of carcinogenesis and metastasis formation, are needed to understand the role of sensory neurons in tumor growth and spread.

Roles of gastrointestinal polypeptides in intestinal barrier regulation

The intestinal barrier is a dynamic entity that is organized as a multilayer system and includes various intracellular and extracellular elements. The gut barrier functions in a coordinated manner to impede the passage of antigens, toxins, and microbiome components and simultaneously preserves the balanced development of the epithelial barrier and the immune system and the acquisition of tolerance to dietary antigens and intestinal pathogens.Numerous scientific studies have shown a significant association between gut barrier damage and gastrointestinal and extraintestinal diseases such as inflammatory bowel disease, celiac disease and hepatic fibrosis. Various internal and external factors regulate the intestinal barrier. Gastrointestinal peptides originate from enteroendocrine cells in the luminal digestive tract and are critical gut barrier regulators. Recent studies have demonstrated that gastrointestinal peptides have a therapeutic effect on digestive tract diseases, enhancing epithelial barrier activity and restoring the gut barrier. This review demonstrates the roles and mechanisms of gastrointestinal polypeptides, especially somatostatin (SST) and vasoactive intestinal peptide (VIP), in intestinal barrier regulation.

Bioinformatic Analysis and Cellular Assays Identify Substance P Influencing Th17/Treg Differentiation via the MyD88 Pathway as a Potential Contributor to the Progression of Asthma and Allergic Rhinitis

Objective

This study is aimed at investigating the role of substance P (SP) in the development of asthma.

Methods

The Gene Expression Omnibus (GEO) database was used to characterize SP expression in allergic rhinitis (AR) and asthma. Peripheral blood was collected from patients with asthma or AR. The expression of relevant cytokines and neuropeptides was measured. Enzyme-linked immunosorbent assay (ELISA) was also performed. The mast cell line LAD2 and the lung bronchial epithelial cell line BEAS-2B were treated with different concentrations of SP concentration. Then, the qRT-PCR method was used to determine the mRNA expression. Furthermore, p38 and p65 and their associated phosphorylated proteins (p-p38 and p-p65) were further validated by western blotting.

Result

Clinical and GSE75011 data analysis suggested that MyD88 expression was upregulated in AR and asthma. Through the gene set variation analysis (GSVA), MyD88-related pathways were noticed and further investigated. ELISA results suggested that the SP expression was significantly increased in AR and asthma and IL-10 expression was decreased, whereas the expression of IL-6, IL-17A, IL-23, and TGF-β expressions increased. The mast cell line LAD2 was treated with different SP concentrations, and ELISA results showed that the expression of IL-6, IL-17A, IL-23, and TGF-β in the cell supernatant gradually increased with increasing SP concentrations, whereas that of IL-10 decreased. The lung bronchial epithelial cell line BEAS-2B was treated with different SP concentrations, and the expression of myeloid differentiation factor 88 (MyD88) and its related proteins was elevated. The expression of p38 and p-p38 proteins was elevated after SP treatment, and their expression levels elevated as SP concentrations increased. Finally, MyD88 expression at the single-cell level was also demonstrated.

Conclusion

SP may affect the cytokine expression through the MyD88 pathway, thereby influencing Th17/Treg differentiation and eventually participating in the pathological process of asthma and AR. There are many pathological similarities between allergic rhinitis (AR) and bronchial asthma. In the present study, SP was found to possibly activate downstream inflammatory signaling pathways via MyD88, thereby affecting Th17/Treg differentiation and ultimately participating in the pathological process of asthma and AR.

Neurokinin-1 Receptor as a potential drug target for COVID-19 treatment

Novel Coronavirus infection (COVID-19) has become a pandemic in these days. It is an acute respiratory and infectious disease with no known etiology and treatment. It is continuously causing losses of precious lives and economy at a global scale on daily basis. It is the need of the hour to find more treatment strategies by either developing a drug or to boost the immune system. This opinion article aims to provide Substance P (SP) as a possible cause of the initiation of cytokine storm developed in COVID-19 infection and to suggest Neurokinin-1 Receptor (NK-1R) antagonist, Aprepitant, as a drug to be used for its treatment. This perspective will provide directions to the Biomedical scientists to explore SP and NK-1R and prepare a drug to alleviate the symptoms and cure the disease. It is very important to work on this perspective at earliest to reach to some conclusion regarding the therapeutic intervention. Clinical studies may also be conducted if proven successful. SP is a neurotransmitter and neuromodulator, released from the trigeminal nerve of brainstem as a result of nociception. It is directly related to the respiratory illness as in COVID-19 infection. It is responsible for the increased inflammation and the signature symptoms associated with this disease. It is the main switch that needs to be switched off by administering Aprepitant along with glucocorticosteroid, dexamethasone.

Recent developments in the pathogenesis of pruritus in bullous pemphigoid

Bullous pemphigoid (BP) is a common autoimmune bullous disease which mainly affects the elderly. The incidence of BP is gradually increasing and associated with high mortality. This disease is clinically characterized by intensely pruritic and widespread bullous lesions. Alternative therapy options for pruritus in patients with BP are limited primarily because pathophysiological mechanisms of itching in BP are still unclear. This review aims to explain crucial concepts of the pathogenesis of pruritus in BP. Vital findings in recent years will be summarized, and cofactors of the pathogenesis of pruritus will be discussed in detail. We will summarize knowledge on pathogenic factors in the immunologic level conducing to skin pruritus in BP.

Sensory denervation increases potential of bisphosphonates to induce osteonecrosis via disproportionate expression of calcitonin gene-related peptide and substance P

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a serious side effect of systematic administration of bisphosphonates (BPs). Sensory innervation is crucial for bone healing. We established inferior alveolar nerve injury (IANI) and inferior alveolar nerve transection (IANT) models characterized by disorganized periosteum, increased osteoclasts, and unbalanced neuropeptide expression. Zoledronate injection disrupted neuropeptide expression in the IANI and IANT models by decreasing calcitonin gene-related peptide (CGRP) and increasing substance P (SP); associated with this, BRONJ prevalence was significantly higher in the IANT model, followed by the IANI model and the sham control. CGRP treatment significantly reduced BRONJ occurrence, whereas SP administration had the opposite effect. In vitro, RAW 264.7 cells were treated with BPs and then CGRP and/or SP to study changes in zoledronate toxicity; combined application of CGRP and SP decreased zoledronate toxicity, whereas CGRP or SP applied alone showed no effects. These results demonstrate that sensory denervation facilitates the occurrence of BRONJ and that CGRP used therapeutically may prevent BRONJ progression, provided that SP is also present. Further studies are necessary to determine the optimal ratio of CGRP to SP for promoting bone healing and to uncover the mechanism by which CGRP and SP cooperate.

Restoration of Regulatory T-Cell Function in Dry Eye Disease by Antagonizing Substance P/Neurokinin-1 Receptor

Substance P (SP) is a tachykinin neuropeptide, implicated in the pathogenesis of various inflammatory conditions and a critical mediator in pain transmission. Recently, the role of SP was described in the pathogenesis of dry eye disease (DED) through its role in the maturation of antigen-presenting cells at the ocular surface after exposure to desiccating stress. However, the effect of SP on regulatory T cells (Tregs), which are functionally impaired in DED, remains unclear. This study examined the phenotypic and functional changes in Tregs in response to SP in DED. The in vitro cultures of normal Tregs in the presence of SP led to a significant reduction in both Treg frequencies and their suppressive function, which was prevented by the addition of an SP receptor (neurokinin-1 receptor) antagonist. Furthermore, in vivo treatment with the neurokinin-1 receptor antagonist in DED mice effectively restored Treg function, suppressed pathogenic T helper 17 response, and significantly ameliorated the disease. Our results show that a significant increase in SP levels promotes Treg dysfunction in DED, and blockade of SP effectively restores Treg function and suppresses DED severity.

Pathophysiologic mechanisms of itch in bullous pemphigoid

BACKGROUND

One of the hallmarks of bullous pemphigoid (BP) is moderate to severe chronic itch. Managing this is difficult because little is known about the mechanisms of itch in BP.

OBJECTIVE

We sought to elucidate the pathophysiologic mechanisms of itch in BP.

METHODS

The expression of itch mediators in lesions of 24 patients with BP and 6 healthy individuals were examined through immunofluorescence staining. Furthermore, the expression of itch mediators and itch severity was correlated.

RESULTS

Itch severity was correlated with eosinophils, substance P, neurokinin 1R, interleukin (IL) 31 receptor A, oncostatin M receptor-β, IL-13, periostin, and basophils. There was also a trend between itch severity and IL-31 expression. Most of the cells expressing IL-31 or neurokinin 1R were identified as eosinophils. Intraepidermal nerve fiber density was decreased. Other itch mediators, including mast cells, IL-4, thymic stromal lymphopoietin, transient receptor potential vanilloid 1 and ankyrin 1, and protease activated receptor 2 were not significantly correlated with itch severity.

LIMITATIONS

The relatively small sample size, the examination of protein expression exclusively through immunofluorescent analysis, and lack of functional assays in patients are the limitations.

CONCLUSIONS

Multiple factors are involved in BP-associated itch, including eosinophils, substance P, neurokinin 1R, IL-31, IL-31 receptor A, oncostatin M receptor-β, IL-13, periostin, and basophils. They could be useful therapeutic targets.

The Neurokinin-1 Receptor Contributes to the Early Phase of Lipopolysaccharide-Induced Fever via Stimulation of Peripheral Cyclooxygenase-2 Protein Expression in Mice

Neurokinin (NK) signaling is involved in various inflammatory processes. A common manifestation of systemic inflammation is fever, which is usually induced in animal models with the administration of bacterial lipopolysaccharide (LPS). A role for the NK1 receptor was shown in LPS-induced fever, but the underlying mechanisms of how the NK1 receptor contributes to febrile response, especially in the early phase, have remained unknown. We administered LPS (120 µg/kg, intraperitoneally) to mice with the Tacr1 gene, i.e., the gene encoding the NK1 receptor, either present (Tacr1^+/+ ) or absent (Tacr1^-/- ) and measured their thermoregulatory responses, serum cytokine levels, tissue cyclooxygenase-2 (COX-2) expression, and prostaglandin (PG) E₂ concentration. We found that the LPS-induced febrile response was attenuated in Tacr1^-/- compared to their Tacr1^+/+ littermates starting from 40 min postinfusion. The febrigenic effect of intracerebroventricularly administered PGE₂ was not suppressed in the Tacr1^-/- mice. Serum concentration of pyrogenic cytokines did not differ between Tacr1^-/- and Tacr1^+/+ at 40 min post-LPS infusion. Administration of LPS resulted in amplification of COX-2 mRNA expression in the lungs, liver, and brain of the mice, which was statistically indistinguishable between the genotypes. In contrast, the LPS-induced augmentation of COX-2 protein expression was attenuated in the lungs and tended to be suppressed in the liver of Tacr1^-/- mice compared with Tacr1^+/+ mice. The Tacr1^+/+ mice responded to LPS with a significant surge of PGE₂ production in the lungs, whereas Tacr1^-/- mice did not. In conclusion, the NK1 receptor is necessary for normal fever genesis. Our results suggest that the NK1 receptor contributes to the early phase of LPS-induced fever by enhancing COX-2 protein expression in the periphery. These findings advance the understanding of the crosstalk between NK signaling and the "cytokine-COX-2-prostaglandin E₂" axis in systemic inflammation, thereby open up the possibilities for new therapeutic approaches.

Human microglia and astrocytes constitutively express the neurokinin-1 receptor and functionally respond to substance P

Background

The tachykinin substance P (SP) is recognized to exacerbate inflammation at peripheral sites via its target receptor, neurokinin 1 receptor (NK-1R), expressed by leukocytes. More recently, SP/NK-1R interactions have been associated with severe neuroinflammation and neuronal damage. We have previously demonstrated that NK-1R antagonists can limit neuroinflammatory damage in a mouse model of bacterial meningitis. Furthermore, we have since shown that these agents can attenuate bacteria-induced neuronal and glial inflammatory mediator production in nonhuman primate (NHP) brain explants and isolated neuronal cells, and following in vivo infection.

Methods

In the present study, we have assessed the ability of NHP brain explants, primary human microglia and astrocytes, and immortalized human glial cell lines to express NK-1R isoforms. We have utilized RT-PCR, immunoblot analysis, immunofluorescent microscopy, and/or flow cytometric analysis, to quantify NK-1R expression in each, at rest, or following bacterial challenge. Furthermore, we have assessed the ability of human microglia to respond to SP by immunoblot analysis of NF-kB nuclear translocation and determined the ability of this neuropeptide to augment inflammatory cytokine release and neurotoxic mediator production by human astrocytes using an ELISA and a neuronal cell toxicity assay, respectively.

Results

We demonstrate that human microglial and astrocytic cells as well as NHP brain tissue constitutively express robust levels of the full-length NK-1R isoform. In addition, we demonstrate that the expression of NK-1R by human astrocytes can be further elevated following exposure to disparate bacterial pathogens or their components. Importantly, we have demonstrated that NK-1R is functional in both human microglia and astrocytes and show that SP can augment the inflammatory and/or neurotoxic immune responses of glial cells to disparate and clinically relevant bacterial pathogens.

Conclusions

The robust constitutive and functional expression of the full-length NK-1R isoform by human microglia and astrocytes, and the ability of SP to augment inflammatory signaling pathways and mediator production by these cells, support the contention that SP/NK-1R interactions play a significant role in the damaging neuroinflammation associated with conditions such as bacterial meningitis.

Role of Substance P Neuropeptide in Inflammation, Wound Healing, and Tissue Homeostasis

Substance P (SP) is an undecapeptide present in the CNS and the peripheral nervous system. SP released from the peripheral nerves exerts its biological and immunological activity via high-affinity neurokinin 1 receptor (NK1R). SP is also produced by immune cells and acts as an autocrine or paracrine fashion to regulate the function of immune cells. In addition to its proinflammatory role, SP and its metabolites in combination with insulin-like growth factor-1 are shown to promote the corneal epithelial wound healing. Recently, we showed an altered ocular surface homeostasis in unmanipulated NK1R^-/- mice, suggesting the role of SP-NK1R signaling in ocular surface homeostasis under steady-state. This review summarizes the immunobiology of SP and its effect on immune cells and immunity to microbial infection. In addition, the effect of SP in inflammation, wound healing, and corneal epithelial homeostasis in the eye is discussed.

Aprepitant limits in vivo neuroinflammatory responses in a rhesus model of Lyme neuroborreliosis

BACKGROUND

Substance P (SP) is produced at high levels in the central nervous system (CNS), and its target receptor, neurokinin 1 receptor (NK-1R), is expressed by glia and leukocytes. This tachykinin functions to exacerbate inflammatory responses at peripheral sites. Moreover, SP/NK-1R interactions have recently been associated with severe neuroinflammation and neuronal damage. We have previously demonstrated that NK-1R antagonists can limit neuroinflammatory damage in a mouse model of bacterial meningitis. Furthermore, we have since shown that these agents can attenuate Borrelia burgdorferi-induced neuronal and glial inflammatory mediator production in non-human primate brain explants and isolated neuronal cells.

METHODS

In the present study, we have assessed the role played by endogenous SP/NK-1R interactions in damaging CNS inflammation in an established rhesus macaque model that faithfully reproduces the key clinical features of Lyme neuroborreliosis, using the specific NK-1R antagonist, aprepitant. We have utilized multiplex ELISA to quantify immune mediator levels in cerebrospinal fluid, and RT-PCR and immunoblot analyses to quantify cytokine and NK-1R expression, respectively, in brain cortex, dorsal root ganglia, and spinal cord tissues. In addition, we have assessed astrocyte number/activation status in brain cortical tissue by immunofluorescence staining and confocal microscopy.

RESULTS

We demonstrate that aprepitant treatment attenuates B. burgdorferi-induced elevations in CCL2, CXCL13, IL-17A, and IL-6 gene expression in dorsal root ganglia, spinal cord, and/or cerebrospinal fluid of rhesus macaques at 2 to 4 weeks following intrathecal infection. In addition, we demonstrate that this selective NK-1R antagonist also prevents increases in total cortical brain NK-1R expression and decreases in the expression of the astrocyte marker, glial fibrillary acidic protein, associated with B. burgdorferi infection.

CONCLUSIONS

The ability of a centrally acting NK-1R inhibitor to attenuate B. burgdorferi-associated neuroinflammatory responses and sequelae raises the intriguing possibility that such FDA-approved agents could be repurposed for use as an adjunctive therapy for the treatment of bacterial CNS infections.

The Therapeutic Potential of Targeting Substance P/NK-1R Interactions in Inflammatory CNS Disorders

The inflammatory responses of resident central nervous system (CNS) cells are now known to play a critical role in the initiation and progression of an array of infectious and sterile neuroinflammatory disorders such as meningitis, encephalitis, Parkinson's disease, Alzheimer's disease and multiple sclerosis (MS). Regulating glial inflammatory responses in a timely manner is therefore critical in preserving normal CNS functions. The neuropeptide substance P is produced at high levels within the CNS and its selective receptor, the neurokinin 1 receptor (NK-1R), is abundantly expressed by neurons and is present on glial cell types including microglia and astrocytes. In addition to its functions as a neurotransmitter in the perception of pain and its essential role in gut motility, this tachykinin is widely recognized to exacerbate inflammation at peripheral sites including the skin, gastrointestinal tract and the lungs. Recently, a number of studies have identified a role for substance P and NK-1R interactions in neuroinflammation and described the ability of this neuropeptide to alter the immune functions of activated microglia and astrocytes. In this review article, we describe the expression of substance P and its receptor by resident CNS cells, and we discuss the ability of this neuropeptide to exacerbate the inflammatory responses of glia and immune cells that are recruited to the brain during neurodegenerative diseases. In addition, we discuss the available data indicating that the NK-1R-mediated augmentation of such responses appears to be detrimental during microbial infection and some sterile neurodegenerative disorders, and propose the repurposed use of NK-1R antagonists, of a type that are currently approved as anti-emetic and anti-anxiolytic agents, as an adjunct therapy to ameliorate the inflammatory CNS damage in these conditions.

Neuropeptide substance P and the immune response

Substance P is a peptide mainly secreted by neurons and is involved in many biological processes, including nociception and inflammation. Animal models have provided insights into the biology of this peptide and offered compelling evidence for the importance of substance P in cell-to-cell communication by either paracrine or endocrine signaling. Substance P mediates interactions between neurons and immune cells, with nerve-derived substance P modulating immune cell proliferation rates and cytokine production. Intriguingly, some immune cells have also been found to secrete substance P, which hints at an integral role of substance P in the immune response. These communications play important functional roles in immunity including mobilization, proliferation and modulation of the activity of immune cells. This review summarizes current knowledge of substance P and its receptors, as well as its physiological and pathological roles. We focus on recent developments in the immunobiology of substance P and discuss the clinical implications of its ability to modulate the immune response.

Cellular and Molecular Mechanisms Underpinning Macrophage Activation during Remyelination

Remyelination is an example of central nervous system (CNS) regeneration, whereby myelin is restored around demyelinated axons, re-establishing saltatory conduction and trophic/metabolic support. In progressive multiple sclerosis, remyelination is limited or fails altogether which is considered to contribute to axonal damage/loss and consequent disability. Macrophages have critical roles in both CNS damage and regeneration, such as remyelination. This diverse range in functions reflects the ability of macrophages to acquire tissue microenvironment-specific activation states. This activation is dynamically regulated during efficient regeneration, with a switch from pro-inflammatory to inflammation-resolution/pro-regenerative phenotypes. Although, some molecules and pathways have been implicated in the dynamic activation of macrophages, such as NFκB, the cellular and molecular mechanisms underpinning plasticity of macrophage activation are unclear. Identifying mechanisms regulating macrophage activation to pro-regenerative phenotypes may lead to novel therapeutic strategies to promote remyelination in multiple sclerosis.

Substance P and the regulation of inflammation in infections and inflammatory bowel disease

Substance P (SP) and its natural analogue hemokinin-1 (HK1) are produced by lymphocytes and macrophages, and at times B cells. These peptides are an important component of the immune response during several infections and in inflammatory bowel disease (IBD). The synthesis of SP and HK1 in leucocytes is subject to immune regulation. IL12 and IL23 stimulate T cells and macrophages to make SP respectively. The cytokines driving HK1 production are not presently defined. These peptides act through a shared receptor called neurokinin-1. T cells, macrophages and probably other immune cell types can express this receptor. Several cytokines IL12, IL18 and TNFα as well as T-cell antigen receptor activation induce neurokinin-1 receptor expression on T cells, while IL10 blocks receptor display. TGFβ delays internalization of the SP/neurokine-1R complex on T cells resulting in stronger receptor signalling. One of the functions of SP and neurokinin-1 receptor is to enhance T cell IFNγ and IL17 production, amplifying the proinflammatory response. Thus, SP and HK1 have overlapping functions and are part of a sophisticated immune regulatory circuit aimed at amplifying inflammation at mucosal surfaces and in other regions of the body as shown in animal models of infection and IBD.

A novel adjuvant, the mixture of alum and naltrexone, augments vaccine-induced immunity against Plasmodium berghei

We previously showed that the mixture of naltrexone (NLT), a general opioid antagonist, and alum, acts as an effective adjuvant in enhancing vaccine-induced T helper 1 (TH1) humoral immune responses against Toxoplasma gondii. Here, we tested the efficacy of the mixture of NLT and alum in the induction of immunity in response to blood stages of Plasmodium berghei (BSPb) as a model vaccine. BALB/c mice were divided into five vaccination groups. Mice in the experimental groups received the BSPb vaccine alone or in combination with the adjuvant alum, NLT or the alum-NLT mixture. Mice in the control group received PBS. All mice were immunized on days 0, 7 and 14. Two weeks after the last immunization, immune responses to Plasmodium berghei were assessed. Our results indicated that including the alum-NLT mixture as an adjuvant during vaccination increased the ability of the BSPb vaccine to enhance lymphocyte proliferation, shifted the immune response towards a TH1 profile and increased Plasmodium berghei-specific IgG2a. This resulted in improved protective immunity against Plasmodium berghei. In conclusion, administering alum-NLT mixture in combination with the BSPb vaccine enhanced the vaccine-induced immunity, and shifted the immune response toward TH1 pattern.

IL-10 function, regulation, and in bacterial keratitis

The immune system protects the host from pathogenic microbes, but tight regulation of the evoked response is requisite to limit bystander damage. The interleukin (IL)-10 family of cytokines, composed of 9 members: IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, and 3 distantly related members, IL-28A, IL-28B, and IL-29, plays a central role in this regulation. IL-10 family cytokines emerged before the adaptive immune response and elicit diverse host defense mechanisms, especially from epithelial cells during an infection. IL-10 family cytokines are also essential for maintenance and integrity of tissue epithelial layers. These cytokines promote innate immune responses from tissue epithelia that limit the damage caused by both viral and bacterial infections. They also facilitate tissue healing after infection/inflammation. In this regard, IL-10 suppresses pro-inflammatory responses, limiting tissue disruption resulting from an inflammatory response. Thus, a central functional theme of IL-10 family cytokines is their role in tissue protection. This review focuses on IL-10, the founding member of this family of cytokines, and integrates recent data on the function and regulation of IL-10 during bacterial infections. Emphasis is placed on the role of IL-10 in Pseudomonas aeruginosa keratitis and the subsequent infectious/inflammatory processes evoked.

Substance P in heart failure: the good and the bad

The tachykinin, substance P, is found primarily in sensory nerves. In the heart, substance P-containing nerve fibers are often found surrounding coronary vessels, making them ideally situated to sense changes in the myocardial environment. Recent studies in rodents have identified substance P as having dual roles in the heart, depending on disease etiology and/or timing. Thus far, these studies indicate that substance P may be protective acutely following ischemia-reperfusion, but damaging long-term in non-ischemic induced remodeling and heart failure. Sensory nerves may be at the apex of the cascade of events leading to heart failure, therefore, they make a promising potential therapeutic target that warrants increased investigation.

Neurotransmitter substance P mediates pancreatic cancer perineural invasion via NK-1R in cancer cells

Pancreatic cancer significantly affects the quality of life due to the severe abdominal pain. However, the underlying mechanism is not clear. This study aimed to determine the relationship between Substance P (SP) and pancreatic cancer perineural invasion (PNI) as well as the mechanism of SP mediating pancreatic cancer PNI, which causes pain in patients with pancreatic cancer. Human pancreatic cancer cells and newborn dorsal root ganglions (DRG) were used to determine the expression of SP or NK-1R in pancreatic cancer cells and DRGs cells by QT-PCR and Western blotting. The effects of SP on pancreatic cancer cell proliferation and invasion were analyzed using MTT assay and Transwell Matrigel invasion assay, respectively. Alterations in the neurotropism of pancreatic cancer cells were assessed by coculture system, which mimics the interaction of tumor/neuron in vivo. SP is not only widely distributed in the neurite outgrowth from newborn DRGs but also expressed in MIA PaCa-2 and BxPC-3 cells. NK-1R is found to be overexpressed in the pancreatic cancer cell lines examined. SP induces cancer cell proliferation and invasion as well as the expression of matrix metalloproteinase (MMP)-2 in pancreatic cancer cells, and NK-1R antagonists inhibit these effects. Furthermore, SP promotes neurite outgrowth and the migration of pancreatic cancer cell cluster to the DRGs, which is blocked by NK-1R antagonists in the coculture model. Our results suggest that SP plays an important role in the development of pancreatic cancer metastasis and PNI, and blocking the SP/NK-1R signaling system is a novel strategy for the treatment of pancreatic cancer.

Analog of somatostatin vapreotide exhibits biological effects in vitro via interaction with neurokinin-1 receptor

OBJECTIVES

Vapreotide, a synthetic analog of somatostatin, has analgesic activity most likely mediated through the blockade of neurokinin-1 receptor (NK1R), the substance P (SP)-preferring receptor. The ability of vapreotide to interfere with other biological effects of SP has yet to be investigated.

METHODS

We studied the ability of vapreotide to antagonize NK1R in three different cell types: immortalized U373MG human astrocytoma cells, human monocyte-derived macrophages (MDM) and a human embryonic kidney cell line, HEK293. Both U373MG and MDM express endogenous NK1R while HEK293 cells, which normally do not express NK1R, are stably transformed to express human NK1R (HEK293-NK1R).

RESULTS

Vapreotide attenuates SP-triggered intracellular calcium increases and nuclear factor-κB activation in a dose-dependent manner. Vapreotide also inhibits SP-induced interleukin-8 and monocyte chemotactic protein-1 production in HEK293-NK1R and U373MG cell lines. Vapreotide inhibits HIV-1 infection of human MDM in vitro, an effect that is reversible by SP pretreatment.

CONCLUSIONS

Our findings indicate that vapreotide has NK1R antagonist activity and may have a potential application as a therapeutic intervention in HIV-1 infection.

A novel adjuvant, a mixture of alum and the general opioid antagonist naloxone, elicits both humoral and cellular immune responses for heat-killed Salmonella typhimurium vaccine

In the current study, we tested the efficacy of the mixture of naloxone, an opioid receptor antagonist, and alum, as a new adjuvant, in the induction of humoral and cellular immunity in response to heat-killed Salmonella typhimurium (HKST) as a model vaccine. BALB/c mice were divided into five groups. Mice in the experimental groups received either the HKST vaccine alone or in combination with the adjuvant alum, naloxone or the alum-naloxone mixture. Mice in the negative control group received phosphate-buffered saline. All mice were immunized two times on days 0 and 14. Two weeks after the last immunization, immune responses to S. typhimurium were assessed. Our results indicated that the administration of the alum-naloxone mixture as an adjuvant increased the ability of the HKST vaccine to enhance lymphocyte proliferation, shifted the immune response towards a T-helper 1 (Th1) pattern and increased S. typhimurium-specific immunoglobulin G (IgG), IgG2a, IgG1 and the ratio of IgG2a to IgG1. This resulted in improved protective immunity against S. typhimurium. In conclusion, the administration of the alum-naloxone mixture as an adjuvant, in combination with the HKST vaccine, can enhance both humoral and cellular immunity and shift the immune responses to a Th1 pattern.

Naloxone and alum synergistically augment adjuvant activities of each other in a mouse vaccine model of Salmonella typhimurium infection

Alum is the most commonly used adjuvant for human vaccination but is a poor inducer of cell mediated immunity and T helper 1 (Th1) responses. We have previously shown that naloxone (NLX), which is a general opioid antagonist, acts as an effective adjuvant in enhancing vaccine-induced cellular immunity and Th1 immune responses. Here, we tested the efficacy of an alum-NLX mixture, as a new adjuvant, in the induction of humoral and cellular immunity in response to endotoxin-removed lysate (ERL) of Salmonella typhimurium (S. typhimurium) as a model vaccine. BALB/c mice were divided into five vaccination groups. Mice in the experimental groups received either the ERL vaccine alone or in combination with the adjuvant alum, NLX or the alum-NLX mixture. Mice in the negative control group received phosphate-buffered saline. All mice were immunized on days 0 and 7. Two weeks after the last immunization, immune responses to S. typhimurium were assessed. Our results indicate that including the alum-NLX mixture as an adjuvant during vaccination increased the ability of the ERL vaccine to enhance lymphocyte proliferation, shifted the immune response toward a Th1 profile and increased S. typhimurium-specific IgG, IgG2a and the ratio of IgG2a to IgG1. This resulted in improved protective immunity against S. typhimurium. In conclusion, administering an alum-NLX mixture adjuvant in combination with the ERL vaccine enhances both humoral and cellular immunity, and shifts the immune response to a Th1 pattern.

Substance P enhances Th17 phenotype in individuals with generalized anxiety disorder: an event resistant to glucocorticoid inhibition

Our objective was to evaluate the effect of stress-related dose of substance P (SP) on the in vitro proliferation and cytokine production in polyclonally activated T cells from healthy individuals or individuals with generalized anxiety disorder (GAD). Our results demonstrated that cell cultures from GAD group proliferated less following T cell activation, as compared with control group. The addition of SP enhanced, while the glucocorticoid (GC) reduced, the proliferative response in activated cell cultures from healthy but not from GAD individuals. The cytokine profile in GAD individuals revealed Th1 and Th2 deficiencies were associated with dominate Th17 phenotype which was enhanced by SP. Differently from control, the production of Th17 cytokines in GAD individuals was not affected by GC. In conclusion, our results show that complex T cell functional dysregulation in GAD individuals is significantly amplified by SP. These immune abnormalities can have impact in increasing the susceptibility to infectious diseases and inflammatory/autoimmune disorders in anxious individuals.

Role of neurogenic substance P in overexpression of alveolar macrophages' neurokinin 1 receptor in mice exposed to cigarette smoke

Neurokinin 1 receptors (NK1Rs) in alveolar macrophages (AMs) are overexpressed by cigarette smoke (CS) in vivo and substance P (SP) in vitro. Because CS could stimulate pulmonary C-fibers (PCFs) to release SP, we asked whether this neurogenic SP was responsible for AMs' NK1R overexpression during CS. We compared pulmonary SP and AMs' NK1R gene and protein levels in intact and PCF-degenerated mice exposed to filtered air (FA) and CS. Pulmonary SP was increased by CS but almost eliminated by PCF degeneration, which closely correlated to the changes in AMs' NK1R expression. Moreover, SP was higher in the PCF-degenerated mice exposed to CS than FA. To evaluate the direct effects of CS and SP on the NK1R expression and the involvement of nuclear factor (NF)-kappaB, macrophages were exposed to CS condensate (CSC) and/or SP without or with blocking NK1R or inhibiting NF-kappaB activation in vitro. CSC itself induced a moderate secretion of SP from macrophages, and amplified NK1R responses to SP that were completely eliminated by blocking NK1R, and substantially reduced after inhibiting NF-kappaB. Our results suggest that CS produces AMs' NK1R overexpression primarily by both promoting neurogenic SP release and synergizing NK1R response to neurogenic SP largely via activating NF-kappaB pathway.

Estrogens augment cell surface TLR4 expression on murine macrophages and regulate sepsis susceptibility in vivo

Gender-based differences exist in infectious disease susceptibility. In general, females generate more robust and potentially protective humoral and cell-mediated immune responses after antigenic challenge than their male counterparts. Furthermore, evidence is accumulating that sex may also influence the early perception of microbial challenges and the generation of inflammatory immune responses such as sepsis. These differences have previously been attributed to the actions of reproductive hormones. Whereas androgens have been shown to suppress acute host immune responses to bacterial endotoxin challenge, estrogens have been found to promote increased resistance to bacterial infections. However, the mechanisms by which estrogens exert immunoprotective effects have not been established. In this study, we investigated the in vivo effects of 17beta-estradiol on endotoxin susceptibility in mice. Importantly, we have examined the actions of this female reproductive hormone on the expression of pattern recognition receptors that recognize bacterial endotoxin by key innate immune sentinel cells. We show that removal of endogenous estrogens decreases both pro- and antiinflammatory cytokine production, with a concomitant reduction in circulating levels of lipopolysaccharide-binding protein and cell surface expression of Toll-like receptor 4 on murine macrophages. Exogenous in vivo replacement of 17beta-estradiol, but not progesterone, significantly elevates sera lipopolysaccharide-binding protein levels and cell surface expression of Toll-like receptor 4 and CD14 on macrophages. Furthermore, this effect corresponds with significantly higher inflammatory cytokine levels after in vivo lipopolysaccharide challenge and a marked increase in endotoxin-associated morbidity. Taken together, these data provide a potential mechanism underlying the immunoenhancing effects of estrogens.

A role for the substance P/NK-1 receptor complex in cell proliferation and apoptosis in oral lichen planus

OBJECTIVES

To determine whether substance P (SP) and NK-1 receptor (NK-1R) are expressed in oral lichen planus (OLP) and are related to cell proliferation and apoptosis in this disease.

MATERIAL AND METHODS

Tissue samples from 50 OLP patients and 26 healthy controls were studied. Immunohistochemistry was performed with anti-SP, anti-NK-1R, anti-ki-67 and anti-caspase-3 monoclonal antibodies and the clinical and pathological data of the OLP patients were evaluated.

RESULTS

With the exception of NK-1R expression in epithelial cell membrane and cytoplasm, all markers were more frequently present in OLP patients than in controls (P < 0.05). Higher cytoplasmatic expression of NK-1R was associated with higher epithelial expression of caspase-3 (P < 0.05). Higher epithelial expression of NK-1R and SP was associated with higher suprabasal and basal epithelial expression of ki-67 (P < 0.05 and P < 0.005, respectively).

CONCLUSIONS

Actions of the SP/NK-1R complex may contribute to the immune disorder underlying OLP and trigger stimuli to induce cell proliferation. These results indicate that this complex might play a role in the malignant transformation of OLP.

Interleukin-12 (IL-12) and IL-23 induction of substance p synthesis in murine T cells and macrophages is subject to IL-10 and transforming growth factor beta regulation

Substance P is a tachykinin that enhances pathways of inflammation. Leukocytes at sites of intestinal inflammation make substance P. This study explored the role of interleukin-12 (IL-12), IL-23, and the regulatory cytokines IL-10 and transforming growth factor beta (TGF-beta) in controlling leukocyte substance P production. In murine schistosomiasis, it was found that IL-12 and IL-23 drive substance P gene expression and peptide synthesis in murine splenic T cells and macrophages, respectively. Cytokine induction of substance P synthesis both in T cells and in macrophages depends on intracellular NF-kappaB activation and is Stat4 independent. IL-10 inhibits T-cell substance P production, while TGF-beta blocks macrophage substance P expression. Intestinal macrophages also produce substance P, subject mostly to IL-23 and TGF-beta regulation. Hemokinin is another tachykinin with homology to substance P. Macrophages and T cells make hemokinin, but hemokinin production is not subject to IL-12 or IL-23 regulation.

Chemical sympathectomy increases susceptibility to ocular herpes simplex virus type 1 infection

The cornea is one of the most highly innervated tissues in the mammalian host. We hypothesized changes to cornea innervation through chemical sympathectomy would significantly alter the host response to the neurotropic viral pathogen, herpes simplex virus type 1 (HSV-1) following ocular infection. Mice treated with 6-hydroxydopamine hydrobromide displayed reduced tyrosine hydroxylase-positive fibers residing in the cornea. Sympathectomized mice were also found to show a transient rise in virus recovered in infected tissues and succumbed to infection in greater numbers. Whereas there were no differences in infiltrating leukocyte populations including HSV-1-specific cytotoxic T lymphocytes in the infected tissue, an increase in substance P and a decrease in IFN-gamma levels in the trigeminal ganglion but not brain stem of sympathectomized mice were noted. Sympathectomized mice treated with the neurokinin-1 receptor antagonist L703,606 had delayed mortality implicating the involvement of substance P in HSV-1-mediated death.

Substance P enhances NF-kappaB transactivation and chemokine response in murine macrophages via ERK1/2 and p38 MAPK signaling pathways

The neuropeptide substance P (SP), as a major mediator of neuroimmunomodulatory activity, modulates diverse functions of immune cells, including macrophages. In the current study, we focused on the yet uncertain role of SP in enhancing the inducible/inflammatory chemokine response of macrophages and the signaling mechanism involved. We studied the effect on the murine monocyte/macrophage cell line RAW 264.7 as well as isolated primary macrophages. Our data show that SP, at nanomolar concentrations, elicited selective chemokine production from murine macrophages. Among the chemokines examined, macrophage inflammatory protein-2 and monocyte chemoattractant protein-1 are two major chemokines that were synthesized by macrophages in response to SP. Furthermore, SP treatment strongly induced the classic pathway of IkappaB-dependent NF-kappaB activation and enhanced DNA binding as well as transactivation activity of the transcription factor. SP-evoked transcriptional induction of chemokines was specific, since it was blocked by treatment with selective neurokinin-1 receptor antagonists. Moreover, SP stimulation of macrophages activated the ERK1/2 and p38 MAPK but not JNKs. Blockade of these two MAPK pathways with specific inhibitors abolished SP-elicited nuclear translocation of phosphorylated NF-kappaB p65 and NF-kappaB-driven chemokine production, suggesting that the two MAPKs lie in the signaling pathways leading to the chemokine response. Collectively, our data demonstrate that SP enhances selective inflammatory chemokine production by murine macrophages via ERK/p38 MAPK-mediated NF-kappaB activation.

A novel activity for substance P: stimulation of peroxisome proliferator-activated receptor-gamma protein expression in human monocytes and macrophages

BACKGROUND AND PURPOSE

Substance P (SP) and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) play important roles in different inflammatory conditions and are both expressed in human monocytes and macrophages. However, it is not known whether or not they interact. This study was undertaken to evaluate the effects of SP on PPAR-gamma protein expression in monocytes and macrophages (MDMs: monocyte-derived macrophages) from healthy smokers and non-smokers.

EXPERIMENTAL APPROACH

PPAR-gamma protein was detected by western blot and quantified by calculating the ratio between PPAR-gamma and beta-actin protein expression. Constitutive tachykinin NK(1) receptor expression in monocytes and MDMs from healthy smokers and non-smokers was evaluated by western blot. Cytokine release was evaluated by ELISA.

KEY RESULTS

In the concentration range 10(-10)-10(-6) M, SP stimulated PPAR-gamma protein expression in monocytes and MDMs, being more effective in cells from healthy smokers. Moreover, in these cells there was a constitutively increased expression of NK(1) receptors. SP-induced expression of the PPAR-gamma protein was receptor-mediated, as it was reproduced by the NK(1) selective agonist [Sar(9)Met(O(2))(11)]SP and reversed by the competitive NK(1) antagonist GR71251. SP-induced maximal effects were similar to those evoked by 15-deoxy-Delta(12,14)-prostaglandin J(2); an endogenous PPAR-gamma agonist, and were significantly reduced by a PPAR-gamma antagonist. NK(1) and PPAR-gamma agonists exerted opposite effects on TNF-alpha release from monocytes and MDMs.

CONCLUSIONS AND IMPLICATIONS

Enhancement of PPAR-gamma protein expression represents a novel activity for SP, which could contribute to a range of chronic inflammatory disorders.

Functional analysis of neuropeptides in avian thymocyte development

The function of lymphoid organs and immune cells is often modulated by peptides and hormones produced by the neuroendocrine and immune systems. We have previously reported the intrathymic expression of neuropeptides in the thymus of different species and that neuropeptides can influence murine thymocyte development in vitro. To further explore the evolutionary nature of neuroendocrine interactions in the thymus, we identified the expression of calcitonin-gene-related peptide, neuropeptide Y, somatostatin (SOM), substance P and vasointestinal polypeptide, as well as their receptors on chicken thymic epithelial cells (TEC) and thymocytes by immunofluorescence and reverse transcription polymerase chain reaction (RT-PCR). All the studied neuropeptides and their receptors were found to be expressed in both TEC and thymocytes, suggesting that intrathymic neuroendocrine interactions may take place within the avian thymus. In order to elucidate whether such interactions play a role in avian thymocyte development, neuropeptides and their antagonists were added to embryonic thymus organ cultures and found to influence chicken thymopoiesis. In particular, an antagonist of SOM increased the proportion of double-positive thymocytes, while SOM itself appeared to inhibit the early stages of thymocyte development. Taken together, these data provide further evidence to suggest that neuropeptides play a conserved role in vertebrate thymocyte development.

Testosterone reduces macrophage expression in the mouse of toll-like receptor 4, a trigger for inflammation and innate immunity

Though gender-based differences in the development of protective or pathological adaptive host responses have been widely noted, it is becoming apparent that sex may also influence the early perception of microbial challenges and the generation of inflammatory immune responses. These differences may be due to the actions of reproductive hormones, and such a hypothesis is supported by the presence of receptors for these hormones in a variety of immune cell types. Androgens such as testosterone have been shown to decrease immune functions, including cytokine production. However, the mechanisms by which testosterone limits such responses remain undefined. In this study, we have investigated the acute effects of testosterone on the level of expression of a key trigger for inflammation and innate immunity, Toll-like receptor 4 (TLR4), on isolated mouse macrophages. We show that in vitro testosterone treatment of macrophages, generated in the absence of androgen, elicits a modest but significant decrease in TLR4 expression and sensitivity to a TLR4-specific ligand. In addition, we have studied the effect of in vivo removal of endogenous testosterone on TLR4 expression and endotoxin susceptibility. We report that orchidectomized mice were significantly more susceptible to endotoxic shock and show that macrophages isolated from these animals have significantly higher TLR4 cell surface expression than those derived from sham gonadectomized mice. Importantly, these effects were not apparent in orchidectomized animals that received exogenous testosterone treatment. As such, these data may represent an important mechanism underlying the immunosuppressive effects of testosterone.

Immunomodulatory properties of substance P: the gastrointestinal system as a model

Communication between nerves and immune and inflammatory cells of the small and large intestine plays a major role in the modulation of several intestinal functions, including intestinal motility, ion transport, and mucosal permeability. Neuroimmune interactions at intestinal sites have been associated with the pathophysiology of infectious and enterotoxin-mediated diarrhea and intestinal inflammation, including inflammatory bowel disease (IBD). During the past 20 years the neuropeptide substance P (SP) has been identified as an important mediator in the development and progress of intestinal inflammation by binding to its high-affinity neurokinin-1 receptor (NK-1R). This peptide, released from enteric nerves, sensory neurons, and inflammatory cells of the lamina propria during intestinal inflammation, participates in gut inflammation by interacting, directly or indirectly, with NK-1R expressed on nerves, epithelial cells, and immune and inflammatory cells, such as mast cells, macrophages, and T cells. SP-dependent activation of these cells leads to the release of cytokines and chemokines as well as other neuropeptides that modulate diarrhea, inflammation, and motility associated with the pathophysiology of several intestinal disease states. The recent development of specific nonpeptide NK-1R antagonists and NK-1R-deficient mice helped us understand the functional importance of the SP-NK-1R system in mediating intestinal neuroimmune interactions and to identify the particular cells and signaling pathways involved in this response. This review summarizes our understanding on the immunomodulatory properties of SP and its receptor in the intestinal tract with particular focus on their involvement in intestinal physiology as well as in the pathophysiology of several intestinal disease states at the in vivo and cell signaling level.

Substance P receptor mediated maintenance of chronic inflammation in EAE

Substance P (SP) is a modulatory, pro-inflammatory neuropeptide. We investigated the role of the SP receptor, neurokinin-1 (NK-1), in EAE. Our data show that in the chronic phase, mice lacking NK-1 have improved mobility and decreased numbers of LFA-1 high CD4+ T cells and MOG-specific, IFN-gamma producing CD4+ T cells. SR140333, an NK-1 antagonist, administered alone during the chronic phase of EAE was not sufficient to ameliorate symptoms. These results indicate that SP, through NK-1, contributes to maintenance of CNS inflammation, and combining NK-1 antagonists with conventional anti-inflammatory treatments may enhance the success of treatments for diseases like multiple sclerosis.

The effect of co-administration of DNA carrying chicken interferon-γ gene on protection of chickens against infectious bursal disease by DNA-mediated vaccination

The purpose of the present study was to determine whether DNA vaccination by co-administration of DNA coding for chicken interferon-gamma (IFN-gamma) gene and DNA encoding for the VP243 gene of IBDV could enhance immune response and protection efficacy of chickens against challenge by IBDV. Plasmids carrying VP243 gene of IBDV strain variant E (VE) (P/VP243/E) and chicken IFN-gamma gene (P/cIFN-gamma) were constructed, respectively. One-day-old chickens were intramuscularly injected with P/VP243/E, or P/cIFN-gamma, or both once, twice, or three times into the thigh muscle of one leg or the thigh muscles of two separate legs at weekly intervals. Chickens were orally challenged with IBDV strain VE at 3 weeks of age and observed for 10 days. Chickens receiving two plasmids in the same site two times had significantly higher (P<0.05) bursal lesion scores and significantly lower (P<0.05) bursa weight/body weight ratios than those that only received P/VP243/E two or three times. Chickens inoculated with two plasmids separately in the thigh muscles of different legs or P/VP243/E two times had 33-50% protection and those receiving two plasmids in the same sites did not have any protection against IBD. The enzyme-linked immunosorbent assay (ELISA) and virus neutralization (VN) titers to IBDV of chickens in the groups with three doses of P/VP243/E were significantly higher (P<0.05) than those in groups receiving two doses of P/VP243/E or P/VP243/E and P/cIFN-gamma. Chickens protected by DNA vaccination did not have detectable IBDV antigen in the bursae as determined by immunofluorescent antibody assay (IFA). The results indicated that co-administration of plasmid encoding chicken IFN-gamma gene with plasmid encoding a large segment gene of the IBDV did not enhance immune response and protection against challenge by IBDV.

Sexual dimorphism in expression of receptors for bacterial lipopolysaccharides in murine macrophages: A possible mechanism for gender-based differences in endotoxic shock susceptibility

Gender-based differences in the incidence and severity of bacterial sepsis render males more susceptible to septic shock than females. However, the mechanisms that underlie this sexual dimorphism remain unclear. In the present study we confirm that males produce significantly higher levels of the inflammatory cytokine IL-6 and the acute phase protein LPS-binding protein (LBP) than females following in vivo lipopolysaccharide (LPS) exposure. It has also been verified that LPS-challenged male-derived macrophages produce higher levels of IL-1beta and lower levels of PGE(2) than similarly treated female-derived cells. Importantly, we demonstrated that male-derived macrophages produce significantly higher levels of the inflammatory chemokine IP-10 following LPS challenge than their female counterparts. It has been demonstrated further that, although resting macrophage levels of mRNA encoding Toll-like receptor 4 (TLR4) and its co-receptor CD14, are not significantly different between genders, male-derived macrophages constitutively express higher levels of these proteins on their cell surface. Elevated circulating levels of LBP and constitutively higher cell surface expression of TLR4 and CD14 on macrophages in males could result in the observed sexual dimorphism in LPS-induced inflammatory mediator production and the greater susceptibility of males to bacterial sepsis.

Full-length and truncated neurokinin-1 receptor expression and function during monocyte/macrophage differentiation

The substance P (SP)-preferring receptor neurokinin-1 receptor (NK-1R) has two forms: a full-length receptor consisting of 407 aa and a truncated receptor consisting of 311 aa. These two receptors differ in the length of the C terminus of NK-1R. We studied the undifferentiated and phorbol myristate acetate (PMA)-differentiated human monocyte/macrophage cell line THP-1 to investigate the expression and function of NK-1R. The expression of full-length and truncated NK-1R in this cell line was determined by using real-time PCR and immunofluorescence staining. Undifferentiated THP-1 cells expressed only truncated NK-1R. The differentiation of THP-1 cells with PMA to a macrophage-like phenotype resulted in the expression of full-length NK-1R, which was functionally accompanied by an SP (10(-6) M)-induced Ca2+ increase. In contrast, the addition of SP (10(-6) M) did not trigger Ca2+ response in undifferentiated THP-1 cells; however, SP did enhance the CCR5-preferring ligand RANTES (CCL5)-mediated Ca2+ increase. When a plasmid containing the full-length NK-1R was introduced into undifferentiated THP-1 cells, exposure to SP triggered Ca2+ increase, demonstrating that the full-length NK-1R is required for SP-induced Ca2+ increase. The NK-1R antagonist aprepitant (Emend, Merck) inhibited both the SP-induced Ca2+ increase in PMA-differentiated THP-1 cells and the SP priming effect on the CCL5-mediated Ca2+ increase, indicating that these effects are mediated through the full-length and truncated NK-1R, respectively. Taken together, these observations demonstrate that there are unique characteristics of NK-1R expression and NK-1R-mediated signaling between undifferentiated THP-1 cells and THP-1 cells differentiated to the macrophage phenotype.

The neuropeptide pituitary adenylate cyclase activating protein is a physiological activator of human monocytes

Pituitary adenylate cyclase activating protein (PACAP) and its structurally related vasointestinal peptide (VIP) bind to three G-protein-coupled receptors named VPAC1 and VPAC2 for VIP/PACAP receptors and PAC1 for PACAP preferred receptors. We report that in freshly isolated human monocytes PACAP acts as a pro-inflammatory molecule. By RT-PCR, VPAC1 mRNA was the only receptor found to be expressed; VPAC1 protein was detected by Western blotting and visualized by immunohistochemistry. Signaling pathways activated by PACAP include the extracellular regulated kinase (ERK), the stress-activated MAPK p38, the focal adhesion kinase, Pyk2 and its associated cytoskeleton protein paxillin and the phosphatidylinositol 3-kinase (PI-3K). PACAP induces a transient peak in cytoplasmic calcium associated with an increase in reactive oxygen species production and upregulation in membrane expression of the integrin CD11b as well as the complement receptor 1. Control of the different pathways and functions stimulated by PACAP were evaluated using Phospholipase C (PLC), PI-3K, ERK and p38 MAPK inhibitors and led to the conclusion that PLC and to a lesser degree PI-3K activation are upstream events occurring in VPAC1 mediated PACAP stimulation of monocytes and are in contrast to ERK and p38 mandatory for the initiation of other cellular events associated with monocytes activation.

Expression of functional NK1 receptors in human alveolar macrophages: superoxide anion production, cytokine release and involvement of NF-kappaB pathway

1 Substance P (SP) is deeply involved in lung pathophysiology and plays a key role in the modulation of inflammatory-immune processes. We previously demonstrated that SP activates guinea-pig alveolar macrophages (AMs) and human monocytes, but a careful examination of its effects on human AMs is still scarce. 2 This study was undertaken to establish the role of SP in human AM isolated from healthy smokers and non-smokers, by evaluating the presence of tachykinin NK(1) receptors (NK-1R) and SP's ability to induce superoxide anion (O(2)(-)) production and cytokine release, as well as activation of the nuclear factor-kappaB (NF-kappaB) pathway. 3 By Western blot analysis and immunofluorescence, we demonstrate that authentic NK-1R are present on human AMs, a three-fold enhanced expression being observed in healthy smokers. These NK-1R are functional, as SP and NK(1) agonists dose-dependently induce O(2)(-) production and cytokine release. In AMs from healthy smokers, SP evokes an enhanced respiratory burst and a significantly increased release of tumor necrosis factor-alpha as compared to healthy non-smokers, but has inconsistent effects on IL-10 release. The NK(1) selective antagonist CP 96,345 ((2S,3S)-cis-2-diphenylmethyl-N[(2-methoxyphenyl)-methyl]-1-azabicyclo-octan-3-amine)) competitively antagonized SP-induced effects. 4 SP activates the transcription factor NF-kappaB, a three-fold increased nuclear translocation being observed in AMs from healthy smokers. This effect is receptor-mediated, as it is reproduced by the NK(1) selective agonist [Sar(9)Met(O(2))(11)]SP and reverted by CP 96,345. 5 These results clearly indicate that human AMs possess functional NK-1R on their surface, which are upregulated in healthy smokers, providing new insights on the mechanisms involved in tobacco smoke toxicity.