Natural killer cell functions mediated by the neuropeptide substance P

Neuro-immune regulation in allergic Diseases: Role of neuropeptides

The role of neuro-immune interaction in allergic diseases, a group of common immune system diseases, has garnered increasing attention. Neuropeptides, as a crucial component of neuro-immune crosstalk with local neuroendocrine and signaling functions, play a significant role that must not be overlooked. Neuropeptides are released by neurons and even some immune cells, and mediate neuro-immune crosstalk by activating relevant specific receptors on immune cells. Recent studies have found that neuropeptides have a certain regulatory effect on allergic diseases, which could be beneficial or detrimental for the development of allergic diseases. Nevertheless, the precise mechanism of neuropeptides in allergic diseases remains unclear, particularly in the context of food allergy where their role is poorly understood. This review summarized the interplay between neuropeptides and different immune cells, as well as their current research progress in several common allergic diseases: atopic dermatitis, allergic asthma, and food allergy. It is evident that neuropeptides such as substance P, calcitonin gene-related peptide, vasoactive intestinal peptide, and neuromedin U, exert important regulatory effects on allergic diseases, yet further investigation is required to fully elucidate their mechanisms of action, which may contribute to better understanding of the onset and progression of allergic diseases and finding better immunomodulatory strategies.

The influence of sex on neuroimmune communication, pain, and physiology

With the National Institutes of Health's mandate to consider sex as a biological variable (SABV), there has been a significant increase of studies utilizing both sexes. Historically, we have known that biological sex and hormones influence immunological processes and now studies focusing on interactions between the immune, endocrine, and nervous systems are revealing sex differences that influence pain behavior and various molecular and biochemical processes. Neuroendocrine-immune interactions represent a key integrative discipline that will reveal critical processes in each field as it pertains to novel mechanisms in sex differences and necessary therapeutics. Here we appraise preclinical and clinical literature to discuss these interactions and key pathways that drive cell- and sex-specific differences in immunity, pain, and physiology.

Meta-analysis of natural killer cell cytotoxicity in myalgic encephalomyelitis/chronic fatigue syndrome

Reduced natural killer (NK) cell cytotoxicity is the most consistent immune finding in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Meta-analysis of the published literature determined the effect size of the decrement in ME/CFS. Databases were screened for papers comparing NK cell cytotoxicity in ME/CFS and healthy controls. A total of 28 papers and 55 effector:target cell ratio (E:T) data points were collected. Cytotoxicity in ME/CFS was significantly reduced to about half of healthy control levels, with an overall Hedges' g of 0.96 (0.75-1.18). Heterogeneity was high but was explained by the range of E:T ratios, different methods, and potential outliers. The outcomes confirm reproducible NK cell dysfunction in ME/CFS and will guide studies using the NK cell model system for pathomechanistic investigations.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024542140.

From pain to tumor immunity: influence of peripheral sensory neurons in cancer

The nervous and immune systems are the primary sensory interfaces of the body, allowing it to recognize, process, and respond to various stimuli from both the external and internal environment. These systems work in concert through various mechanisms of neuro-immune crosstalk to detect threats, provide defense against pathogens, and maintain or restore homeostasis, but can also contribute to the development of diseases. Among peripheral sensory neurons (PSNs), nociceptive PSNs are of particular interest. They possess a remarkable capability to detect noxious stimuli in the periphery and transmit this information to the brain, resulting in the perception of pain and the activation of adaptive responses. Pain is an early symptom of cancer, often leading to its diagnosis, but it is also a major source of distress for patients as the disease progresses. In this review, we aim to provide an overview of the mechanisms within tumors that are likely to induce cancer pain, exploring a range of factors from etiological elements to cellular and molecular mediators. In addition to transmitting sensory information to the central nervous system, PSNs are also capable, when activated, to produce and release neuropeptides (e.g., CGRP and SP) from their peripheral terminals. These neuropeptides have been shown to modulate immunity in cases of inflammation, infection, and cancer. PSNs, often found within solid tumors, are likely to play a significant role in the tumor microenvironment, potentially influencing both tumor growth and anti-tumor immune responses. In this review, we discuss the current state of knowledge about the degree of sensory innervation in tumors. We also seek to understand whether and how PSNs may influence the tumor growth and associated anti-tumor immunity in different mouse models of cancer. Finally, we discuss the extent to which the tumor is able to influence the development and functions of the PSNs that innervate it.

The Role of Substance P Within Traumatic Brain Injury and Implications for Therapy

This review examines the role of the neuropeptide substance P within the neuroinflammation that follows traumatic brain injury. It examines it in reference to its preferential receptor, the neurokinin-1 receptor, and explores the evidence for antagonism of this receptor in traumatic brain injury with therapeutic intent. Expression of substance P increases following traumatic brain injury. Subsequent binding to the neurokinin-1 receptor results in neurogenic inflammation, a cause of deleterious secondary effects that include an increased intracranial pressure and poor clinical outcome. In several animal models of TBI, neurokinin-1 receptor antagonism has been shown to reduce brain edema and the resultant rise in intracranial pressure. A brief overview of the history of substance P is presented, alongside an exploration into the chemistry of the neuropeptide with a relevance to its functions within the central nervous system. This review summarizes the scientific and clinical rationale for substance P antagonism as a promising therapy for human TBI.

The diversity of neuroimmune circuits controlling lung inflammation

It is becoming increasingly appreciated that the nervous and immune systems communicate bidirectionally to regulate immunological outcomes in a variety of organs including the lung. Activation of neuronal signaling can be induced by inflammation, tissue damage, or pathogens to evoke or reduce immune cell activation in what has been termed a neuroimmune reflex. In the periphery, these reflexes include the cholinergic anti-inflammatory pathway, sympathetic reflex, and sensory nociceptor-immune cell pathways. Continual advances in neuroimmunology in peripheral organ systems have fueled small-scale clinical trials that have yielded encouraging results for a range of immunopathologies such as rheumatoid arthritis. Despite these successes, several limitations should give clinical investigators pause in the application of neural stimulation as a therapeutic for lung inflammation, especially if inflammation arises from a novel pathogen. In this review, the general mechanisms of each reflex, the evidence for these circuits in the control of lung inflammation, and the key knowledge gaps in our understanding of these neuroimmune circuits will be discussed. These limitations can be overcome not only through a better understanding of neuroanatomy but also through a systematic evaluation of stimulation parameters using immune activation in lung tissues as primary readouts. Our rapidly evolving understanding of the nervous and immune systems highlights the importance of communication between these cells in health and disease. This integrative approach has tremendous potential in the development of targeted therapeutics if specific challenges can be overcome.

Role of neurotransmitters in immune-mediated inflammatory disorders: a crosstalk between the nervous and immune systems

Immune-mediated inflammatory diseases (IMIDs) are a group of common heterogeneous disorders, characterized by an alteration of cellular homeostasis. Primarily, it has been shown that the release and diffusion of neurotransmitters from nervous tissue could result in signaling through lymphocyte cell-surface receptors and the modulation of immune function. This finding led to the idea that the neurotransmitters could serve as immunomodulators. It is now manifested that neurotransmitters can also be released from leukocytes and act as autocrine or paracrine modulators. Increasing data indicate that there is a crosstalk between inflammation and alterations in neurotransmission. The primary goal of this review is to demonstrate how these two pathways may converge at the level of the neuron and glia to involve in IMID. We review the role of neurotransmitters in IMID. The different effects that these compounds exert on a variety of immune cells are also reviewed. Current and future developments in understanding the cross-talk between the immune and nervous systems will undoubtedly identify new ways for treating immune-mediated diseases utilizing agonists or antagonists of neurotransmitter receptors.

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.

Regulation of Carcinogenesis by Sensory Neurons and Neuromediators

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.

Aging of the Immune System: Focus on Natural Killer Cells Phenotype and Functions

Aging is the greatest risk factor for nearly all major chronic diseases, including cardiovascular diseases, cancer, Alzheimer’s and other neurodegenerative diseases of aging. Age-related impairment of immune function (immunosenescence) is one important cause of age-related morbidity and mortality, which may extend beyond its role in infectious disease. One aspect of immunosenescence that has received less attention is age-related natural killer (NK) cell dysfunction, characterized by reduced cytokine secretion and decreased target cell cytotoxicity, accompanied by and despite an increase in NK cell numbers with age. Moreover, recent studies have revealed that NK cells are the central actors in the immunosurveillance of senescent cells, whose age-related accumulation is itself a probable contributor to the chronic sterile low-grade inflammation developed with aging (“inflammaging”). NK cell dysfunction is therefore implicated in the increasing burden of infection, malignancy, inflammatory disorders, and senescent cells with age. This review will focus on recent advances and open questions in understanding the interplay between systemic inflammation, senescence burden, and NK cell dysfunction in the context of aging. Understanding the factors driving and enforcing NK cell aging may potentially lead to therapies countering age-related diseases and underlying drivers of the biological aging process itself.

Substance P and Neurokinin 1 Receptor in Chronic Inflammation and Cancer of the Head and Neck: A Review of the Literature

Head and neck cancer is a growing worldwide public health problem, accounting for approximately 1,500,000 new cases and 500,000 deaths annually. Substance P (SP) is a peptide of the tachykinin family, which has roles related to a large number of physiological mechanisms in humans. The implications of SP in carcinogenesis have recently been reported through the stimulation of the neurokinin 1 receptor (NK1R), or directly, through the effects derived from the constitutive activation of NK1R. Consequently, SP/NK1R seems to play relevant roles in cancer, upregulating cell proliferation, cell migration and chronic inflammation, among other oncogenic actions. Furthermore, there is growing evidence pointing to a central role for SP in tumour progression, singularly so in laryngeal and oral squamous cell carcinomas. The current narrative review of the literature focuses on the relationship between the SP/NK1R system and chronic inflammation and cancer in the head-and-neck region. We described a role for SP/NK1R in the transition from chronic inflammation of the head and neck mucosa, to preneoplastic and neoplastic transformation and progression.

Substance P accelerates the progression of human esophageal squamous cell carcinoma via MMP-2, MMP-9, VEGF-A, and VEGFR1 overexpression

Tachykinins such as Substance P (SP) are a group of neuropeptides that are involved in cancer development. Neurokinin-1 receptor (NK-1R) is the main tachykinin receptor mediating the effects of SP, which is overexpressed in human esophageal squamous cell carcinoma (ESCC) and other malignant tissues. However, the effects of SP/NK-1R system on the migration of esophageal cancer cells and angiogenesis is not clear yet. This study seeks to obtain data to address these research gaps. In order to assess the effects of the FDA-approved aprepitant drug, a commercially available NK-1R antagonist, on the viability of KYSE-30 ESCC cells, resazurin assay was performed. The influence of SP/NK-1R system on the migration potential of these cells was examined using scratch assay. The effects of this system on the expression levels of metastatic factors were also examined by RT-PCR and western blot analyses. The half-maximal inhibitory concentration (IC50) value for KYSE-30 cells treated with aprepitant found to be 29.88 μM. Treatment with SP significantly promoted KYSE-30 esophageal cancer cell migration, and aprepitant blocked this effect. In addition, SP significantly induced the expression of matrix metalloproteinase-2 (MMP-2), MMP-9, vascular endothelial growth factor-A (VEGF-A), and VEGF receptor1 (VEGFR1) in the cells, whereas aprepitant inhibited the up-regulation effects caused by SP. SP plays important roles in the development of human esophageal squamous cell carcinoma by promoting cancer cell invasion and enhancing the expression of factors involved in cellular migration and angiogenesis, which can be blocked by the NK-1R antagonist, aprepitant.

NK1R antagonist decreases inflammation and metastasis of breast carcinoma cells metastasized to liver but not to brain; phenotype-dependent therapeutic and toxic consequences

Substance P a neuro-immune mediator acts on Neurokinin-1 and -2 receptors (NK1R and NK2R). Inhibitors of NK1R are considered to be safe and effective approaches for cancer treatment since Aprepitant, a non-peptide antagonist of NK1R is widely used for chemotherapy-induced emesis and has cytotoxic and antitumor effects in various models for cancer. On the other hand, our previous findings demonstrated that systemic inhibition of NK1R may decrease cytotoxic anti-tumoral immune response. Hence, actual consequences of inhibition of neurokinin receptors under in vivo conditions in a syngeneic model of carcinoma should be determined. The effects of highly potent and selective non-peptide mouse NK1R and NK2R antagonists RP 67580 and GR 159897, respectively, on metastatic breast carcinoma were evaluated. Specifically, 4T1 breast cancer cells metastasized to brain (denoted as 4TBM) and liver (denoted as 4TLM) were used to induce tumors in Balb-c mice. Changes in tumor growth, metastasis and immune response to cancer cells were determined. We here observed differential effects of NK1R antagonist depended on the subset of metastatic cells. Specifically, inhibition of NK1R markedly increased liver metastasis of tumors formed by 4TBM but not 4TLM cells. On the contrary, NK1R antagonist decreased inflammatory response and liver metastasis in 4TLM-injected mice. 4TLM tumors act more aggressively inducing more inflammatory response compared to 4TBM tumors. Hence, differential effects of NK1R antagonist are at least partly due to extend and type of the inflammatory response evoked by specific subset metastatic cells. These findings demonstrate the necessity for understanding the immunological consequences of tumor-microenvironment interactions.

The immunomodulatory effects of tachykinins and their receptors

Tachykinins (TKs) are a family of neuropeptides mainly expressed by neuronal and non-neuronal cell types, especially immune cells. Expression of TKs receptors on immune cell surfaces, their involvement in immune-related disorders, and therefore, understanding their immunomodulatory roles have become of particular interest to researchers. In fact, the precise understanding of TKs intervention in the immune system would help to design novel therapeutic approaches for patients suffering from immune disorders. The present review summarizes studies on TKs function as modulators of the immune system by reviewing their roles in generation, activation, development, and migration of immune cells. Also, it discusses TKs involvement in three main cellular mechanisms including inflammation, apoptosis, and proliferation.

Immune privilege in corneal transplantation

Corneal transplantation is the most successful solid organ transplantation performed in humans. The extraordinary success of orthotopic corneal allografts, in both humans and experimental animals, is related to the phenomenon of "immune privilege". Inflammation is self-regulated to preserve ocular functions because the eye has immune privilege. At present, three major mechanisms are considered to provide immune privilege in corneal transplantation: 1) anatomical, cellular, and molecular barriers in the cornea; 2) tolerance related to anterior chamber-associated immune deviation and regulatory T cells; and 3) an immunosuppressive intraocular microenvironment. This review describes the mechanisms of immune privilege that have been elucidated from animal models of ocular inflammation, especially those involving corneal transplantation, and its relevance for the clinic. An update on molecular, cellular, and neural interactions in local and systemic immune regulation is provided. Therapeutic strategies for restoring immune privilege are also discussed.

Interaction of neurotransmitters and neurochemicals with lymphocytes

Neurotransmitters and neurochemicals can act on lymphocytes by binding to receptors expressed by lymphocytes. This review describes lymphocyte expression of receptors for a selection of neurotransmitters and neurochemicals, the anatomical locations where lymphocytes can interact with neurotransmitters, and the effects of the neurotransmitters on lymphocyte function. Implications for health and disease are also discussed.

Sensing of physiological regulators by innate lymphoid cells

Maintenance of homeostasis and immune protection rely  on the coordinated action of different physiological systems. Bidirectional communication between the immune system and physiological systems is required to sense and restore any disruption of equilibrium. Recent transcriptomic analyses of innate lymphoid cells (ILCs) from different tissues have revealed that ILCs express a large array of receptors involved in the recognition of neuropeptides, hormones and metabolic signals. ILCs rapidly secrete effector cytokines that are central in the development and activation of early immune responses, but they also constitutively secrete mediators that are important for tissue homeostasis. To achieve these functions effectively, ILCs integrate intrinsic and extrinsic signals that modulate their constitutive and induced activity. Disruption of the regulation of ILCs by physiological regulators leads to altered immune responses with harmful consequences for the organism. An understanding of these complex interactions between the immune system and physiological mediators is crucial to decipher the events leading to the protective versus pathological effects of these cells.

Truncation of neurokinin-1 receptor-Negative regulation of substance P signaling

Substance P (SP) is a tachykinin peptide, which triggers intracellular signaling in the nervous and immune systems, as well as, other local and systemic events. The interaction between SP and its receptor, neurokinin-1 receptor (NK1R), results in major downstream cellular actions, which include changes in calcium fluxes, ERK, and p21-activated kinase phosphorylation and NFκB activation. Two naturally occurring variants of the NK1R, the full-length, 407 aa receptor (NK1R-F) and the truncated, 311 aa isoform (NK1R-T), mediate the actions of SP. Receptor truncation partially disrupts signaling motifs of the carboxyl tail, a critical site for mediating NK1R signaling, resulting in a "less-efficient" receptor. Although NK1R-F is the predominant isoform in the central and peripheral nervous systems, NK1R-T is expressed in several tissues and cells, which include monocytes, NK cells, and T-cells. The SP binding domain is not affected by truncation and this site is identical in both NK1R receptor isoforms. However, while cells expressing NK1R-F respond to nanomolar concentrations of SP, monocyte and macrophage activation, mediated through NK1R-T, requires micromolar concentrations of SP in order to elicit signaling responses. Elevated plasma levels of SP are associated with increased inflammatory responses and NK1R antagonists reduce inflammation and cytokine production in vivo. This mini review presents and discusses the novel hypothesis that the expression of NK1R-T on immune system cells prevents immune activation in a milieu, which usually contains low concentrations of SP and, thus, maintains immune homeostasis. In contrast, in the activated neuronal microenvironment, when SP levels reach the threshold at tissue sites, SP promotes immune activation and modulates monocyte/macrophage polarization.

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.

The neuropeptide galanin modulates natural killer cell function

Natural killer (NK) cells are part of the innate immune system and combat pathogens and tumors by secreting pro-inflammatory cytokines like interferon gamma (IFN-γ) and by their cytotoxic action. Galanin is a neuropeptide also expressed in peripheral tissue where it impacts several physiological functions, including inflammation. The effects of galanin are mediated via three receptors, GAL_1-3. Since other neuropeptides have been shown to regulate NK cell activity, we investigated the potential of galanin to modulate human NK cell function. NK cells were isolated from human peripheral blood mononuclear cells. mRNA expression was analyzed by qRT-PCR. The dynamic mass redistribution of NK cells upon regulatory peptide stimulation was determined by label-free biochip technology. IFN-γ producing NK cells were identified by flow cytometry analysis and IFN-γ secretion was measured by ELISA. NK cell cytotoxicity was analyzed by flow cytometry via CD107a mobilization. NK cells were found to express the receptor GAL₂ but not GAL₁, GAL₃ or galanin. Galanin per se did not affect the dynamic mass redistribution of NK cells, but significantly enhanced the response of NK cells to IL-18. Galanin significantly modulated the IFN-γ production of the CD56^bright NK cell population upon IL-12 and IL-18 stimulation. Furthermore, galanin significantly modulated the IL-12 and IL-18 stimulated IFN-γ secretion. NK cell cytotoxicity was not modulated by galanin treatment. Galanin can be classified as an immunomodulatory peptide as it is able to sensitize NK cells toward specific cytokines.

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.

Human hemokinin-1 promotes migration of melanoma cells and increases MMP-2 and MT1-MMP expression by activating tumor cell NK1 receptors

Receptors and their regulatory peptides are aberrantly expressed in tumors, suggesting a potential tumor therapy target. Human hemokinin-1 (hHK-1) is a tachykinin peptide ligand of the neurokinin-1 (NK1) receptor which is overexpressed in melanoma and other tumor tissues. Here, we investigated the role of hHK-1 and the NK1 receptor in melanoma cell migration. NK1 receptor expression was associated with melanoma metastatic potential. Treatment with hHK-1 significantly enhanced A375 and B16F10 melanoma cell migration and an NK1 receptor antagonist L732138 blocked this effect. MMP-2 and MT1-MMP expression were up-regulated in hHK-1-treated melanoma cells and cell signaling data suggested that hHK-1 induced phosphorylation of ERK1/2, JNK and p38 by way of PKC or PKA. Kinase activation led to increased MMP-2 and MT1-MMP expression and melanoma cell migration induced by hHK-1. Thus, hHK-1 and the NK1 receptor are critical to melanoma cell migration and each may be a promising chemotherapeutic target.

Neurokinin-1 receptor mediated breast cancer cell migration by increased expression of MMP-2 and MMP-14

Breast cancer (BC) is a common reason of cancer-associated death in female. To develop novel strategy of therapeutics, it is crucial to comprehensively understand the receptor status of BC cells on the surface and inner, because chemical messengers can bind the receptors and promote tumorigenesis. Compared with normal and benign samples, BC cell lines and malignant biopsies showed higher expression of neurokinin-1 receptor (NK1). In current work, we examined the role and mechanism of NK1 receptor signaling in BC cell migration. Human hemokinin-1 (hHK-1) was the peripheral agonist of NK1 receptor. Our results showed that by activating NK1 receptor, hHK-1 promoted the migration of BC cells. Gelatin zymography and WB experiment showed that hHK-1 enhanced the levels of MMP-2 and MMP-14; inhibition of these two MMPs blocked hHK-1-induced cell migration. We further explored the underlying mechanism. hHK-1 incuced the phosphorylation of ERK1/2, JNK and Akt through PKC or PKA pathway. The phosphorylation of these kinases further regulated the activation of transcriptional factor AP-1 and NF-κB. Inhibition of AP-1 and NF-κB reduced the up-regulation of MMP-2 and MMP-14 by hHK-1. Taken together, we showed NK1 receptor was an important regulator of human BC cell migration and a potential target for BC treatment.

Neuroimmunomodulation in the Gut: Focus on Inflammatory Bowel Disease

Intestinal immunity is finely regulated by several concomitant and overlapping mechanisms, in order to efficiently sense external stimuli and mount an adequate response of either tolerance or defense. In this context, a complex interplay between immune and nonimmune cells is responsible for the maintenance of normal homeostasis. However, in certain conditions, the disruption of such an intricate network may result in intestinal inflammation, including inflammatory bowel disease (IBD). IBD is believed to result from a combination of genetic and environmental factors acting in concert with an inappropriate immune response, which in turn interacts with nonimmune cells, including nervous system components. Currently, evidence shows that the interaction between the immune and the nervous system is bidirectional and plays a critical role in the regulation of intestinal inflammation. Recently, the maintenance of intestinal homeostasis has been shown to be under the reciprocal control of the microbiota by immune mechanisms, whereas intestinal microorganisms can modulate mucosal immunity. Therefore, in addition to presenting the mechanisms underlying the interaction between immune and nervous systems in the gut, here we discuss the role of the microbiota also in the regulation of neuroimmune crosstalk involved in intestinal homeostasis and inflammation, with potential implications to IBD pathogenesis.

Neurotrophins and neuropeptides as inflammatory mediators in case of chronic dermatosis

This literature review examines the role of neurotrophins and neuropeptides for the development of skin inflammatory reactions in case of chronic inflammatory dermatoses. The article describes inflammatory effects of neurotrophin, a nerve growth factor, neuropeptide substance P and calcitonin gene-related peptide. Factors affecting the condition of skin innervation and development of inflammation - neurotrophin, a nerve growth factor, amphiregulin, an epidermal growth factor, and semaphorin 3A, a nerve repulsion factor - were examined. Searching for and administering antagonists of proinflammatory effects of neuropeptides, neurotrophins and epidermal growth factor can become new approaches to the treatment of chronic inflammatory dermatoses.

Autocrine hemokinin-1 functions as an endogenous adjuvant for IgE-mediated mast cell inflammatory responses

BACKGROUND

Efficient development of atopic diseases requires interactions between allergen and adjuvant to initiate and amplify the underlying inflammatory responses. Substance P (SP) and hemokinin-1 (HK-1) are neuropeptides that signal through the neurokinin-1 receptor (NK1R) to promote inflammation. Mast cells initiate the symptoms and tissue effects of atopic disorders, secreting TNF and IL-6 after FcεRI cross-linking by antigen-IgE complexes (FcεRI-activated mast cells [FcεRI-MCs]). Additionally, MCs express the NK1R, suggesting an adjuvant role for NK1R agonists in FcεRI-MC-mediated pathologies; however, in-depth research addressing this relevant aspect of MC biology is lacking.

OBJECTIVE

We sought to investigate the effect of NK1R signaling and the individual roles of SP and HK-1 as potential adjuvants for FcεRI-MC-mediated allergic disorders.

METHODS

Bone marrow-derived mast cells (BMMCs) from C57BL/6 wild-type (WT) or NK1R(-/-) mice were used to investigate the effects of NK1R signaling on FcεRI-MCs. BMMCs generated from Tac1(-/-) mice or after culture with Tac4 small interfering RNA were used to address the adjuvancy of SP and HK-1. WT, NK1R(-/-), and c-Kit(W-sh/W-sh) mice reconstituted with WT or NK1R(-/-) BMMCs were used to evaluate NK1R signaling on FcεRI-MC-mediated passive local and systemic anaphylaxis and on airway inflammation.

RESULTS

FcεRI-activated MCs upregulated NK1R and HK-1 transcripts and protein synthesis, without modifying SP expression. In a positive signaling loop HK-1 promoted TNF and IL-6 secretion by MC degranulation and protein synthesis, the latter through the phosphoinositide 3-kinase/Akt/nuclear factor κB pathways. In vivo NK1R signaling was necessary for the development of passive local and systemic anaphylaxis and airway inflammation.

CONCLUSIONS

FcεRI stimulation of MCs promotes autocrine secretion of HK-1, which signals through NK1R to provide adjuvancy for efficient development of FcεRI-MC-mediated disorders.

Neuro-endocrine networks controlling immune system in health and disease

The nervous and immune systems have long been considered as compartments that perform separate and different functions. However, recent clinical, epidemiological, and experimental data have suggested that the pathogenesis of several immune-mediated disorders, such as multiple sclerosis (MS), might involve factors, hormones, and neural mediators that link the immune and nervous system. These molecules are members of the same superfamily, which allow the mutual and bi-directional neural-immune interaction. More recently, the discovery of leptin, one of the most abundant adipocyte-derived hormones that control food intake and metabolism, has suggested that nutritional/metabolic status, acting at central level, can control immune self-tolerance, since it promotes experimental autoimmune encephalomyelitis, an animal model of MS. Here, we summarize the most recent advances and the key players linking the central nervous system, immune tolerance, and the metabolic status. Understanding this coordinated interaction may pave the way for novel therapeutic approaches to increase host defense and suppress immune-mediated disorders.

Neuro-endocrine networks controlling immune system in health and disease

The nervous and immune systems have long been considered as compartments that perform separate and different functions. However, recent clinical, epidemiological, and experimental data have suggested that the pathogenesis of several immune-mediated disorders, such as multiple sclerosis (MS), might involve factors, hormones, and neural mediators that link the immune and nervous system. These molecules are members of the same superfamily, which allow the mutual and bi-directional neural-immune interaction. More recently, the discovery of leptin, one of the most abundant adipocyte-derived hormones that control food intake and metabolism, has suggested that nutritional/metabolic status, acting at central level, can control immune self-tolerance, since it promotes experimental autoimmune encephalomyelitis, an animal model of MS. Here, we summarize the most recent advances and the key players linking the central nervous system, immune tolerance, and the metabolic status. Understanding this coordinated interaction may pave the way for novel therapeutic approaches to increase host defense and suppress immune-mediated disorders.

Involvement of substance P and the NK-1 receptor in human pathology

The peptide substance P (SP) shows a widespread distribution in both the central and peripheral nervous systems, but it is also present in cells not belonging to the nervous system (immune cells, liver, lung, placenta, etc.). SP is located in all body fluids, such as blood, cerebrospinal fluid, breast milk, etc. i.e. it is ubiquitous in human body. After binding to the neurokinin-1 (NK-1) receptor, SP regulates many pathophysiological functions in the central nervous system, such as emotional behavior, stress, depression, anxiety, emesis, vomiting, migraine, alcohol addiction, seizures and neurodegeneration. SP has been also implicated in pain, inflammation, hepatitis, hepatotoxicity, cholestasis, pruritus, myocarditis, bronchiolitis, abortus, bacteria and viral infection (e.g., HIV infection) and it plays an important role in cancer (e.g., tumor cell proliferation, antiapoptotic effects in tumor cells, angiogenesis, migration of tumor cells for invasion, infiltration and metastasis). This means that the SP/NK-1 receptor system is involved in the molecular bases of many human pathologies. Thus, knowledge of this system is the key for a better understanding and hence a better management of many human diseases. In this review, we update the involvement of the SP/NK-1 receptor system in the physiopathology of the above-mentioned pathologies and we suggest valuable future therapeutic interventions involving the use of NK-1 receptor antagonists, particularly in the treatment of emesis, depression, cancer, neural degeneration, inflammatory bowel disease, viral infection and pruritus, in which that system is upregulated.

Tachykinins and their receptors: contributions to physiological control and the mechanisms of disease

The tachykinins, exemplified by substance P, are one of the most intensively studied neuropeptide families. They comprise a series of structurally related peptides that derive from alternate processing of three Tac genes and are expressed throughout the nervous and immune systems. Tachykinins interact with three neurokinin G protein-coupled receptors. The signaling, trafficking, and regulation of neurokinin receptors have also been topics of intense study. Tachykinins participate in important physiological processes in the nervous, immune, gastrointestinal, respiratory, urogenital, and dermal systems, including inflammation, nociception, smooth muscle contractility, epithelial secretion, and proliferation. They contribute to multiple diseases processes, including acute and chronic inflammation and pain, fibrosis, affective and addictive disorders, functional disorders of the intestine and urinary bladder, infection, and cancer. Neurokinin receptor antagonists are selective, potent, and show efficacy in models of disease. In clinical trials there is a singular success: neurokinin 1 receptor antagonists to treat nausea and vomiting. New information about the involvement of tachykinins in infection, fibrosis, and pruritus justifies further trials. A deeper understanding of disease mechanisms is required for the development of more predictive experimental models, and for the design and interpretation of clinical trials. Knowledge of neurokinin receptor structure, and the development of targeting strategies to disrupt disease-relevant subcellular signaling of neurokinin receptors, may refine the next generation of neurokinin receptor antagonists.

Direct and indirect antimicrobial activities of neuropeptides and their therapeutic potential

As global resistance to conventional antibiotics rises we need to develop new strategies to develop future novel therapeutics. In our quest to design novel anti-infectives and antimicrobials it is of interest to investigate host-pathogen interactions and learn from the complexity of host defense strategies that have evolved over millennia. A myriad of host defense molecules are now known to play a role in protection against human infection. However, the interaction between host and pathogen is recognized to be a multifaceted one, involving countless host proteins, including several families of peptides. The regulation of infection and inflammation by multiple peptide families may represent an evolutionary failsafe in terms of functional degeneracy and emphasizes the significance of host defense in survival. One such family is the neuropeptides (NPs), which are conventionally defined as peptide neurotransmitters but have recently been shown to be pleiotropic molecules that are integral components of the nervous and immune systems. In this review we address the antimicrobial and anti-infective effects of NPs both in vitro and in vivo and discuss their potential therapeutic usefulness in overcoming infectious diseases. With improved understanding of the efficacy of NPs, these molecules could become an important part of our arsenal of weapons in the treatment of infection and inflammation. It is envisaged that targeted therapy approaches that selectively exploit the anti-infective, antimicrobial and immunomodulatory properties of NPs could become useful adjuncts to our current therapeutic modalities.

Proteomic analysis of NK92-MI cells activated by neuropeptide substance P

Substance P (SP) has been well known by its immunoregulatory properties on the functions of NK cells. However, the changes of molecules involved in the signaling pathways and effects of these molecules of NK92-MI cells activated by SP remain unclear. In this study, we explored the global changes in cellular protein expression of NK92-MI cells activated by SP by 2D-PAGE analysis. Subsequently, we demonstrated that 40 protein spots showed more than 2-fold changes, which displayed marked alterations with statistic significance (p<0.05) between the testing group and control group. Compared with the control we also found that 16 proteins were up-regulated and 24 proteins were down-regulated among the 40 differentially expressed protein spots in the NK92-MI cells activated by SP. In addition 21 differentially expressed proteins were identified by MS/MS, suggesting that those proteins may play important roles in the process of activation of NK92-MI cells by SP. Moreover, the protein Rho GDI-2, Protein DJ-1 and alpha-enolase were reconfirmed by western blotting. Taken together, these findings may provide a new insight into better understanding at the molecular mechanisms of activation of NK92-MI cells by SP.

Substance P decreases fat storage and increases adipocytokine production in 3T3-L1 adipocytes

Obesity, inflammation, and insulin resistance are closely linked. Substance P (SP), via its neurokinin 1 receptor (NK1R), mediates inflammatory and, possibly, neuroendocrine processes. We examined SP effects on lipid storage and cytokine production in 3T3-L1 adipocytes and adipose tissues. 3T3-L1 adipocytes and preadipocytes express NK1R, and 8 days of SP supplementation during differentiation to 3T3-L1 preadipocytes decreased lipid droplet accumulation. SP (10 nM, 24 h) increased lipolysis in primary adipocytes (138 ± 7%, P < 0.05) and reduced fatty acid uptake (-31 ± 7%, P < 0.05) and mRNA expression of the differentiation-related transcription factors peroxisome proliferator-activated receptor-γ type 2 (-64 ± 2%, P < 0.001) and CCAAT enhancer-binding protein (CEBP)-α (-65 ± 2%, P < 0.001) and the lipid storage genes fatty acid-binding protein type 4 (-59 ± 2%, P < 0.001) and diacylglycerol O-acyltransferase-1 (-45 ± 2%, P < 0.01) in 3T3-L1 adipocytes, while CD36, a fatty acid transporter (+82 ± 19%, P < 0.01), was augmented. SP increased secretion of complement C3 (148 ± 15%, P < 0.04), monocyte chemoattractant protein-1 (156 ± 16%, P < 0.03), and keratinocyte-derived chemokine (148 ± 18%, P = 0.045) in 3T3-L1 adipocytes and monocyte chemoattractant protein-1 (496 ± 142%, P < 0.02) and complement C3 (152 ± 25%, P < 0.04) in adipose tissue and primary adipocytes, respectively. These SP effects were accompanied by downregulation of insulin receptor substrate 1 (-82 ± 2%, P < 0.01) and GLUT4 (-76 ± 2%, P < 0.01) mRNA expression, and SP acutely blocked insulin-mediated stimulation of fatty acid uptake and Akt phosphorylation. Although adiponectin secretion was unchanged, mRNA expression was decreased (-86 ± 8%, P < 0.001). In humans, NK1R expression correlates positively with plasma insulin, fatty acid, and complement C3 and negatively with adiponectin, CEBPα, CEBPβ, and peroxisome proliferator-activated receptor-γ mRNA expression in omental, but not subcutaneous, adipose tissue. Our results suggest that, beyond its neuroendocrine and inflammatory effects, SP could also be involved in targeting adipose tissue and influencing insulin resistance.

Altered serum stress neuropeptide levels in critically ill individuals and associations with lymphocyte populations

OBJECTIVE

Potential physiological correlates of stress and the role of stress neuropeptides, other than those of the hypothalamic-pituitary-adrenal axis, in critical illness have not been addressed. We investigated: (a) serum levels of stress neuropeptides (ACTH, substance P (SP), neuropeptide Y (NPY), cortisol, prolactin) in critically ill individuals compared to matched controls, (b) associations with lymphocyte counts, (c) associations among stress neuropeptide levels, and (d) associations with perceived intensity of stress, critical illness severity and survival.

METHODS

Correlational design with repeated measures. Thirty-six critically ill patients were followed up for 14 days compared to 36 healthy matched controls. Stress was assessed by the ICUESS scale. Correlations, cross-sectional comparisons and multiple regression models were pursued.

RESULTS

For the first time, we report lower SP (Difference of means (DM) = 2928-3286 ng/ml, p < 0.001) and NPY (DM = 0.77-0.83 ng/ml, p < 0.0001) levels in critically ill individuals compared to controls. Cortisol levels were higher (DM = 140-173 ng/ml, p<0.0001) and lymphocyte population counts (p < 0.002) were lower in patients throughout the study. NPY levels associated with lymphocyte (r = 0.411-0.664, p < 0.04), T-lymphocyte (r = 0.403-0.781, p< 0.05), T-helper (r = 0.492-0.690, p < 0.03) and T-cytotoxic cell populations (r = 0.39-0.740, p < 0.03). On day 1, cortisol levels exhibited associations with lymphocyte (r = -0.452, p = 0.01), T-cell (r = -0.446, p = 0.02), T-helper (r = -0.428, p = 0.026) and T-cytotoxic cells ( r = -0.426, p = 0.027). ACTH levels associated with NK cell counts (r = 0.326-0.441, p < 0.05). Associations among stress neuropeptides levels were observed throughout (p < 0.05). ACTH levels associated with disease severity (r = 0.340-0.387, p < 0.005). A trend for an association between ACTH levels and intensity of stress was noted (r = 0.340, p = 0.057).

CONCLUSION

The significantly lowered NPY and SP levels and the associations with cortisol, ACTH and lymphocytes suggest that the role of these peptides in critical illness merit further investigation. Future studies need to address associations between these neuropeptides and functional immune cell responses and inflammatory markers in critical illness.

Neurokinin-1 receptor directly mediates glioma cell migration by up-regulation of matrix metalloproteinase-2 (MMP-2) and membrane type 1-matrix metalloproteinase (MT1-MMP)

Neurokinin-1 receptor (NK1R) occurs naturally on human glioblastomas. Its activation mediates glioma cell proliferation. However, it is unknown whether NK1R is directly involved in tumor cell migration. In this study, we found human hemokinin-1 (hHK-1), via NK1R, dose-dependently promoted the migration of U-251 and U-87 cells. In addition, we showed that hHK-1 enhanced the activity of MMP-2 and the expression of MMP-2 and MT1-matrix metalloproteinase (MMP), which were responsible for cell migration, because neutralizing the MMPs with antibodies decreased cell migration. The involved mechanisms were then investigated. In U-251, hHK-1 induced significant calcium efflux; phospholipase C inhibitor U-73122 reduced the calcium mobilization, the up-regulation of MMP-2 and MT1-MMP, and the cell migration induced by hHK-1, which meant the migration effect of NK1R was mainly mediated through the G(q)-PLC pathway. We further demonstrated that hHK-1 boosted rapid phosphorylation of ERK, JNK, and Akt; inhibition of ERK and Akt effectively reduced MMP-2 induction by hHK-1. Meanwhile, inhibition of ERK, JNK, and Akt reduced the MT1-MMP induction. hHK-1 stimulated significant phosphorylation of p65 and c-JUN in U-251. Reporter gene assays indicated hHK-1 enhanced both AP-1 and NF-κB activity; inhibition of ERK, JNK, and Akt dose-dependently suppressed the NF-κB activity; only the inhibition of ERK significantly suppressed the AP-1 activity. Treatment with specific inhibitors for AP-1 or NF-κB strongly blocked the MMP up-regulation by hHK-1. Taken together, our data suggested NK1R was a potential regulator of human glioma cell migration by the up-regulation of MMP-2 and MT1-MMP.

The role of neurokinin-1 receptor in the microenvironment of inflammation and cancer

The recent years have witnessed an exponential increase in cancer research, leading to a considerable investment in the field. However, with few exceptions, this effort has not yet translated into a better overall prognosis for patients with cancer, and the search for new drug targets continues. After binding to the specific neurokinin-1 (NK-1) receptor, the peptide substance P (SP), which is widely distributed in both the central and peripheral nervous systems, triggers a wide variety of functions. Antagonists against the NK-1 receptor are safe clinical drugs that are known to have anti-inflammatory, analgesic, anxiolytic, antidepressant, and antiemetic effects. Recently, it has become apparent that SP can induce tumor cell proliferation, angiogenesis, and migration via the NK-1 receptor, and that the SP/NK-1 receptor complex is an integral part of the microenvironment of inflammation and cancer. Therefore, the use of NK-1 receptor antagonists as a novel and promising approach for treating patients with cancer is currently under intense investigation. In this paper, we evaluate the recent scientific developments regarding this receptor system, its role in the microenvironment of inflammation and cancer, and its potentials and pitfalls for the usage as part of modern anticancer strategies.

Regulation of NK92-MI cell cytotoxicity by substance P

The neuropeptide substance P (SP) can regulate a number of immunological functions in vitro and in vivo and may regulate natural killer (NK) cell activity. Here, we investigated whether SP has a role in regulating NK92-MI cell function in vitro, and how it influences NK cell activity. We found that SP dose dependently increased the cytotoxicity of NK92-MI cells and had a maximal effect at a concentration of 10(-12) and 10(-10) m. Furthermore, the expression of cytotoxic-associated molecules (perforin, granzyme) and activating receptor NKp46 [a member of natural cytotoxicity receptors (NCRs)] was observed to be upregulated by SP at optimal concentration, at which SP enhanced the cytotoxicity of NK92-MI cells. Neurokinin-1 receptor (NK-1R), a functional receptor of SP, was found on NK92-MI cells, and the observed effects of SP on NK92-MI cells could be more partially blocked by an NK-1R antagonist. Our data suggest that SP induces NK92-MI cell cytotoxicity by directly increasing the expression of cytotoxic granules and upregulates NK92-MI cell receptor-mediated functions indirectly. Thus, SP may regulate NK cell function mainly through NK-1R.

Substance P inhibits natural killer cell cytotoxicity through the neurokinin-1 receptor

SP is a potent neuroimmunomodulator that functions through ligating members of the neurokinin receptor family, one of which, NK1R, is widely expressed in immune cells. As in humans, circulating SP levels are increased in pathologic states associated with impairment of NK cell functions, such as depression and HIV infection, we hypothesized that SP has a direct, inhibitory effect upon NK cells. We have studied a clonal human NK cell line (YTS) as well as ex vivo human NK cells and have determined that truncated and full-length NK1R isoforms are expressed in and SP bound by ex vivo NK cells and the YTS NK cell line. Incubation of YTS cells with 10⁻⁶ M SP and ex vivo NK cells with 10⁻⁵ M SP inhibited cytotoxic ability by ∼20% and reduced degranulation. This inhibitory effect upon cytotoxicity was partially prevented by the NK1R antagonist CP96,345. The treatment of YTS or ex vivo NK cells with SP neither down-modulated NCR expression nor affected triggering receptor-induced NF-κB activation. Preincubation of YTS cells with SP, however, did abbreviate the typically prolonged intracellular calcium increase induced by target cell engagement and reduced triggering receptor-induced pERK. Thus, SP has the potential to regulate NK cell functions and acts downstream from neurokinin receptors to modulate NK cell activation signaling. This mechanism may contribute to impairment of NK cell function in certain disease states associated with increased circulating SP. Antagonism of this system may present an opportunity to augment NK cell function therapeutically in selected human diseases.

Common variants of the neuropeptide expressing tachykinin genes and susceptibility to asthma: a case-control study

Since tachykinins appear to be involved in the pathogenesis of allergic asthma, we investigated a possible association between 28 single nucleotide polymorphisms of the tachykinin genes TAC1, TAC3 and TAC4, and asthma susceptibility. A case-control study was conducted on 102 patients and 100 healthy subjects from the Canary Islands (Spain). A significant association with asthma was observed for two SNPs: rs2291855 in the TAC3 gene conferring asthma protection (Odds ratio [OR]: 0.46; 95% Confidence Interval [CI]: 0.22-0.97; P=0.038), and rs4794068 in the TAC4 gene associated with an increased risk for asthma (OR: 1.94; 95% CI: 1.06-3.54; P=0.03). The present study represents a preliminary step in elucidating the association between tachykinin gene polymorphisms and asthma susceptibility.

Sensory neuropeptides are potent chemoattractants for human basophils in vitro

The sensory neuropeptides secretoneurin (SN) and substance P (SP) are involved in "neurogenic" inflammatory processes as they occur in bronchial asthma or allergic rhinitis. A possible interaction with basophils has not been reported to date. Basophils were isolated from healthy donors by magnetic cell sorting technique and migration was explored using Boyden microchemotaxis chambers. SN [10(-8)M] and SP [10(-6) to 10(-8)M] proved to be chemoattractants equally potent to FMLP [10(-8)M] or LPS [10 pg/ml]. Specific anti-SN antibodies and a trypsinization preparation of SN were used to determine the specificity of the SN effect on basophils. The preincubation of basophils with neurokinin-1 (NK-1) or -2 (NK-2) receptor antagonists revealed the SP effect to act via NK-1 receptors in basophils. In addition, we were able to show phosphodiesterases and phosphoinositide-3 kinases to be engaged in the downstream signalling pathway. Our observations reveal for the first time a link between basophils, which are engaged in allergic processes, and the neuropeptides SN and SP. Furthermore, our data might suggest phosphodiesterases or phosphoinositide-3 kinases to be new therapeutic targets for the treatment of allergic diseases such as asthma or allergic rhinitis.

Neurokinin 1 receptor mediates membrane blebbing in HEK293 cells through a Rho/Rho-associated coiled-coil kinase-dependent mechanism

We have investigated the effect of neurokinin 1 receptor (NK1R) agonists on HEK293 cells transfected with the NK1R receptor. The NK1R receptor mediates dramatic shape changes that include contractions of the membrane cortex resulting in membrane bleb formation. We have found that the cell shape changes correlate with changes in electrical impedance measured in cellular monolayers. The shape and impedance changes were prevented after preincubation with NK1R antagonists aprepitant and L-73060. Although bleb formation usually heralds apoptotic cell death, we have found that NK1R-mediated cellular blebbing does not associate with apoptosis. Preincubation with a cell-permeable derivative of C3 transferase that blocks Rho or with the Rho-associated coiled-coil kinase inhibitor Y27632 completely prevented NK1R-induced shape and impedance changes. Blebbing was also completely inhibited by ML-9, a myosin light chain kinase inhibitor. Furthermore, the phospholipase C inhibitor U73,122 did not interfere with the effect of Substance P (SP) on cellular morphology and cellular impedance but completely blocked SP-induced intracellular calcium increase, indicating that the blebbing is a process independent of intracellular calcium elevations. Blebbing is a protein kinase C-independent process, since the nonselective protein kinase C inhibitor GF109203X did not interfere with SP-induced effects. Based on these results, we provide the first evidence that NK1R receptor-ligand interaction can cause apoptosis-independent cellular blebbing and that this process is mediated by the Rho/Rho-associated coiled-coil kinase pathway.

Sensory-nerve-derived neuropeptides: possible therapeutic targets

This review examines our developing understanding of the families and activities of some of the best known sensory-nerve-derived inflammatory neuropeptides, namely substance P, calcitonin gene-related peptide and galanin. Evidence to date shows involvement of these transmitters in a wide range of systems that includes roles as inflammatory modulators. There is an increasing understanding of the mechanisms involved in the release of the peptides from sensory nerves and these are key in understanding the potential of neuropeptides in modulating inflammatory responses and may also provide novel targets for anti-inflammatory therapy. The neuropeptides released act via specific G protein coupled receptors, most of which have now been cloned. There is knowledge of selective agonists and antagonists for many subtypes within these families. The study of neuropeptides in animal models has additionally revealed pathophysiological roles that in turn have led to the development of new drugs, based on selective receptor antagonism.

The impact of substance P signalling on the development of experimental staphylococcal sepsis and arthritis

Substance P (SP), acting on the neurokinin-1 receptor (NK-1R), is a neuropeptide, involved in the inflammatory processes. It promotes vasodilatation and increases vasopermeability, thus ensuing extravasation and accumulation of leucocytes at sites of injury. The aim of this study was to assess the impact of SP signalling on the responses during staphylococcal infection and the accompanying arthritis. Three experiments were performed where NK-1R-/- mice and controls were intravenously infected with different doses of Staphylococcus aureus. Clinical assessment of arthritis was performed as well as histological analysis of bone and cartilage destruction in the joints. In addition, the impact of NK-1R mutation on bacterial load in the kidneys as well as the phagocytic capacity of blood leucocytes were studied. Mice lacking the NK-1R displayed significantly higher bacterial load in the kidneys and significantly more severe synovitis and cartilage/bone destruction than the controls when inoculated with 1.4 x 10(7) staphylococci. Infection with 3.5 x 10(8) CFU/mouse induced sepsis. Thus, 11 days after bacterial inoculation 15 of 19 mice in the NK-1R-/- group had died versus 8 of 15 in the control group. Phagocytosis test revealed that significantly fewer macrophages from NK-1R-/- mice were able to phagocytose S. aureus when compared with macrophages from congenic control mice. Blocking the biological responses to substance P via its receptor NK-1R results in a less efficient clearance of bacteria leading to more severe arthritic lesions in mice.