Neuropeptide Substance Research Articles

Spatiotemporal Patterns of Substance P-Bound MRGPRX2 Reveal a Novel Connection Between Macropinosome Resolution and Secretory Granule Regeneration in Mast Cells.

MRGPRX2, the human member of the MAS-related G protein coupled receptors (Mrgprs), serves as the cellular target of human mast cells (MCs) for innate ligands, including neuropeptides and antimicrobial peptides. In addition, MRGPRX2 also functions as the receptor for multiple FDA-approved drugs. As such, MRGPRX2 is a mediator of MC responses in neurogenic inflammation, host defense and pseudoallergy. We analyzed the spatiotemporal patterns of MRGPRX2 following its binding of the neuropeptide substance P (SP). Herein, we show that MRGPRX2 internalizes via both endocytosis and macropinocytosis, followed by its distribution between a perinuclear region and the secretory granules (SGs). Further, we show that MRGPRX2-containing macropinosomes undergo resolution by a mechanism that involves dynamin and LC3, giving rise to the incorporation of both LC3 and MRGPRX2 into the SGs. SP then promotes the acidification of the LC3-associated SGs, presumably by stimulating their fusion with lysosomes. Taken together, our results reveal a unique mode of MRGPRX2 trafficking that complements endocytosis and involves macropinocytosis, autophagic machinery-assisted macropinosome resolution and receptor delivery to the SGs.

Effects of substance P on human cerebral microvascular endothelial cell line hCMEC/D3 are mediated exclusively through a truncated NK-1 receptor and depend on cell confluence

The neuropeptide substance P (SP) mediates pain transmission, immune modulation, vasodilation and neurogenic inflammation. Its role in the peripheral nervous system has been well characterised. However, its actions on the blood-brain barrier (BBB) are less clear and warrant further study. The aim of this study was to characterise the effect of SP on the brain microvascular endothelial cells using the immortalized human brain microvascular endothelial cell line hCMEC/D3. As part of our studies, we have evaluated changes in expression, at mRNA and protein levels, of genes involved in the function of the blood-brain barrier such as occludin, induced by exposure to SP. We show that the effect of SP is dependent on cell confluence status. Thus, at low confluence but not at full confluence, SP treatment reduced occludin expression. The expression of the SP receptor, neurokinin-1 receptor (NK-1R) (the truncated form of the receptor expressed exclusively in this cell line) was also modulated in a similar pattern. SP treatment stimulated extracellular signal-regulated kinase (Erk2) phosphorylation which was not associated to changes in Interleukin-6 (IL-6), Interleukin-8 (IL-8), or Intercellular Adhesion Molecule 1 (ICAM-1) protein expression. In addition, SP treatment effectively recovered nitric oxide production on cells exposed to tumour necrosis factor alpha (TNF-α). SP did not trigger intracellular calcium release in hCMEC/D3 cells. We conclude that hCMEC/D3 cells are partially responsive to SP, that the effects are mediated through the truncated form of the receptor and are dependent on the confluence status of these cells.

Berberine Alleviates Gastroesophageal Reflux-Induced Airway Hyperresponsiveness in a Transient Receptor Potential A1-Dependent Manner.

Background To investigate the beneficial effect of berberine on gastroesophageal reflux-induced airway hyperresponsiveness (GERAHR) and explore the underlying mechanism. Methods Coword cluster analysis and strategic coordinates were used to identify hotspots for GERAHR research, and an online tool (STRING, https://string-db.org/) was used to predict the potential relationships between proteins. Guinea pigs with chemically induced GERAHR received PBS or different berberine-based treatments to evaluate the therapeutic effect of berberine and characterize the underlying mechanism. Airway responsiveness was assessed using a plethysmography system, and protein expression was evaluated by western blotting, immunohistochemical staining, and quantitative PCR analysis. Results Bioinformatics analyses revealed that TRP channels are hotspots of GERAHR research, and TRPA1 is related to the proinflammatory neuropeptide substance P (SP). Berberine, especially at the middle dose tested (MB, 150 mg/kg), significantly improved lung function, suppressed inflammatory cell infiltration, and protected inflammation-driven tissue damage in the lung, trachea, esophagus, and nerve tissues in GERAHR guinea pigs. MB reduced the expression of TRPA1, SP, and tumor necrosis factor-alpha (TNF-α) in evaluated organs and tissues. Meanwhile, the MB-mediated protective effects were attenuated by simultaneous TRPA1 activation. Conclusions Mechanistically, berberine was found to suppress GERAHR-induced upregulation of TRPA1, SP, and TNF-α in many tissues. Our study has highlighted the potential therapeutic value of berberine for the treatment of GERAHR.

Sensory neurons shape allergic Type 2 inflammation in the sinonasal tract

Abstract Whether neuro-immune interactions regulate homeostasis vs. inflammation within the sinonasal tract is entirely unknown. Transient receptor potential vanilloid 1 ion channel (TRPV1+)-expressing sensory neurons of the trigeminal ganglion (TG) innervate the upper airway near sinonasal tuft cells (STC), a rare lineage of epithelial cells that initiate inflammation in the intestine by secreting pro-Type 2 cytokines. Given the vicinity of STC and TG neurons, we hypothesized that STC function(s) may be at least partially controlled by neuronal inputs. A mouse model of sinonasal allergic inflammation was developed using intranasal administration of a fungal allergen mix (FAM) that mimics key aspects of chronic rhinosinusitis pathophysiology, including increased numbers of sneezing bouts, STC, eosinophils, and levels of interleukin (IL)-25 in the sinonasal fluid. Our data show that FAM also evokes the release of neuropeptides substance P and neuromedin U from TG neurons. Also, chemical ablation of TRPV1+ neurons significantly reduces STC expansion and eosinophil accumulation, which collectively suggests that TRPV1+ sensory neurons produce factors that promote STC to release Type 2 cytokines driving allergic disease pathophysiology. Ongoing studies are designed to uncover important insight(s) into how STC/sensory neuron interactions are involved in the pathogenesis of allergic diseases in the sinonasal tract. Supported by grants from NIH (U01 AI163062, R01 AI164715, and R01 AI123173) awarded to DRH.

Probing the Cellular Basis of Spinal Kappa Opioid Receptor Inhibition of Itch

The kappa opioid receptor (KOR, encoded by Oprk1) is an extremely attractive target for the treatment of chronic itch. The KOR agonist nalfurafine is used to treat chronic itch associated with kidney and liver disease in Japan, with additional KOR agonists in development for atopic dermatitis and neuropathic itch. Despite the clinical promise of KOR agonists, the cellular basis of KOR inhibition of itch remains unknown. Previous work from our lab demonstrated that KOR inhibition of itch occurs – at least in part – at the level of the spinal cord, raising the question: how does KOR signaling inhibit itch spinal circuits? We are addressing this fundamental gap in knowledge through a combination of molecular, genetic, behavioral, and physiological approaches in mice. First, we used fluorescent in situ hybridization to determine which spinal neuron populations express Oprk1. We show that Oprk1 is expressed within a heterogenous population of spinal neurons, but primarily those that express the neuropeptide substance P or the neurokinin-1 receptor, which drive itch behavior. Moreover, retrograde viral labeling revealed that Oprk1 is expressed in spinoparabrachial neurons that relay itch input from the spinal cord to the brain. Next, we tested whether Oprk1 spinal neurons contribute to itch behaviors. We selectively expressed excitatory chemogenetic tools in Oprk1-Cre spinal neurons and found that chemogenetic activation of these neurons potentiated itch behaviors. Finally, we used ex vivo two-photon calcium imaging of the spinal cord to visualize the neuron networks activated by spinal itch neuropeptides and investigated how KOR agonists inhibit these networks. Notably, these data are the first in-depth look into the cellular basis of spinal KOR inhibition of itch and provide fundamental mechanistic insights into KOR agonists that are clinically effective in alleviating chronic itch. Supported by NIH grants F32NS110155 (TDS) and R01NS0967905 (SER).

The neuropeptide Substance P facilitates the transition from an inflammatory to proliferation phase-associated responses in dermal fibroblasts.

The wound healing process is a product of three successive and overlapping phases of inflammation, proliferation and remodelling. Considerable efforts have been invested in deconstructing the intercellular crosstalk that orchestrates tissue repair, and we investigated the role of neuropeptides released from peripheral neurons upon injury in mediating these interactions. Amongst the most abundant of these neuropeptides secreted by nerves in the skin, is Substance P (SP). Given the role of dermal fibroblasts in coordinating multiple processes in the wound healing program, the effect of SP on human dermal fibroblasts of different ages was evaluated. The use of a substrate that recapitulates the mechanical properties of the in vivo tissue revealed novel effects of SP on dermal fibroblasts, including a block in inflammatory cytokine expression. Moreover, SP can promote expression of some extracellular matrix components and generates signals that regulate angiogenesis. Interestingly, the response of fibroblasts to SP was reduced concomitant with donor age. Altogether, SP acts to inhibit the inflammatory responses and promote proliferation-associated responses in an age-dependent manner in dermal fibroblasts, suggesting a role as a molecular switch between the inflammatory and proliferative phases of the wound healing response.

Estrogenic impregnation alters pain expression: analysis through functional neuropeptidomics in a surgical rat model of osteoarthritis.

Several observational studies suggest that estrogens could bias pain perception. To evaluate the influence of estrogenic impregnation on pain expression, a prospective, randomized, controlled, blinded study was conducted in a Sprague-Dawley rat model of surgically induced osteoarthritis (OA). Female rats were ovariectomized and pre-emptive 17β-estradiol (0.025mg, 90-day release time) or placebo pellets were installed subcutaneously during the OVX procedures. Thirty-five days after, OA was surgically induced on both 17β-estradiol (OA-E) and placebo (OA-P) groups. Mechanical hypersensitivity was assessed by static weight-bearing (SWB) and paw withdrawal threshold (PWT) tests. Mass spectrometry coupled with high-performance liquid chromatography (HPLC-MS) was performed to quantify the spinal pronociceptive neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), bradykinin (BK), somatostatin (SST), and dynorphin-A (Dyn-A). Compared to control, ovariectomized rats presented higher SP (P = 0.009) and CGRP (P = 0.017) concentrations. OA induction increased the spinal level of SP (+ 33%, P < 0.020) and decreased the release of BK (- 20%, (P < 0.037)). The OA-E rats at functional assessment put more % body weight on the affected hind limb than OA-P rats at D7 (P = 0.027) and D56 (P = 0.033), and showed higher PWT at D56 (P = 0.009), suggesting an analgesic and anti-allodynic effect of 17β-estradiol. Interestingly, the 17β-estradiol treatment counteracted the increase of spinal concentration of Dyn-A (P < 0.016) and CGRP (P < 0.018). These results clearly indicate that 17β-estradiol interfers with the development of central sensitization and confirm that gender dimorphism should be considered when looking at pain evaluation.

MMPs Regulate Neuronal Substance P After a Painful Equibiaxial Stretch in a Co-Culture Collagen Gel Model Simulating Injury of an Innervated Ligament

Chronic joint pain is a major health problem that can result from abnormal loading of the innervated ligamentous capsule that surrounds synovial joints. The matrix metalloproteinases-1 (MMP-1) and MMP-9 are hypothesized pain mediators from stretch-induced injuries since they increase in pathologic joint tissues and are implicated in biomechanical and nociceptive pathways that underlay painful joint injuries. There is also emerging evidence that MMP-1 and MMP-9 have mechanistic interactions with the nociceptive neuropeptide substance P. Yet, how a ligament stretch induces painful responses during sub-failure loading and whether MMP-1 or MMP-9 modulates nociception via substance P are unknown. We used a neuron–fibroblast co-culture collagen gel model of the capsular ligament to test whether a sub-failure equibiaxial stretch above the magnitude for initiating nociceptive responses in neurons also regulates MMP-1 and MMP-9. Pre-stretch treatment with the MMP inhibitor ilomastat also tested whether inhibiting MMPs attenuates the stretch-induced nociceptive responses. Because of the role of MMPs in collagen remodeling, collagen microstructural kinematics were measured in all tests. Co-culture gels were incubated for one week in either normal conditions, with five days of ilomastat treatment, or with five days of a vehicle control solution before a planar equibiaxial stretch that imposed strains at magnitudes that induce pain in vivo and increase nociceptive modulators in vitro. Force, displacement, and strain were measured, and polarized light imaging captured collagen fiber kinematics during loading. At 24 h after stretch, immunolabeling quantified substance P, MMP-1, and MMP-9 protein expression. The same sub-failure equibiaxial stretch was imposed on all co-cultures, inducing a significant re-organization of collagen fibers (p ≤ 0.031) indicative of fiber realignment. Stretch induces a doubling of substance P expression in normal and vehicle-treated co-cultures (p = 0.038) that is prevented with ilomastat treatment (p = 0.114). Although MMP-1 and MMP-9 expression are unaffected by the stretch in all co-culture groups, ilomastat treatment abolishes the correlative relationships between MMP-1 and substance P (p = 0.002; R2 = 0.13) and between MMP-1 and MMP-9 (p = 0.007; R2 = 0.11) that are detected without an inhibitor. Collectively, these findings implicate MMPs in a painful ligamentous injury and contribute to a growing body of work linking MMPs to nociceptive-related signaling pathways and/or pain.

Aloe vera and Fermented Extracts Exhibit an Anti-Inflammatory Effect on Human Glioblastoma/Astrocytoma U373 MG Cells.

The anti-inflammatory effects of Aloe vera (AV), polysaccharide extract from AV, and extracts from the digestion and colonic fermentation of AV were evaluated using an immortal astrocyte cell line (U373 MG) that develops a neuro-inflammatory profile. Cell viability and inflammatory markers were assessed after stimulation with neuropeptide substance P (SP) that activates the pro-inflammatory MAPK (mitogen-activated protein kinase) pathway. Cell viability after SP treatment was over 50% at 10mg/mL AV, polysaccharide extract from AV, extracts from the digestion: non-digestible fraction of AV non-digestible fraction of polysaccharide extract from AV and extracts from the colonic fermentation of AV, at 4 and 24h. Moreover, cells exposed to SP and treated with these extracts showed lower protein-activated ERK1/ERK2 (extracellular signal-regulated kinases 1 and 2), p38 (MAPK protein p38), and NFκB (nuclear factor κB) levels with respect to the SP-stimulated control. Inflammation inhibition by extracts of polysaccharide extract from AV and extracts from the colonic fermentation of AV, at 24h in the study of p38 was not as statistically significant in ERK1/ERK2 and NFκB. Nevertheless, there was a significant decrease (p < 0.05) in pro-inflammatory cytokine IL-6 levels in cells exposed to all samples. Samples with extracts from the colonic fermentation of AV, at 4 or 24h showed the highest inhibitory effect on IL-6 production.

Efficacy of Intense Pulsed Light Combined Blood Extract Eye Drops for Treatment of Nociceptive Pain in Dry Eye Patients.

Purpose: To investigate the efficacy of intense pulsed light (IPL) combined with deproteinized calf blood extract (DCBE) eye drops for dry eye disease (DED) patients with nociceptive ocular pain. Methods: In this prospective, one-center, interventional study, 23 subjects with DED and ocular pain were treated with a combination of IPL and DCBE eye drops for four sessions at a four-week interval. Subjective and objective assessments on nociceptive pain and dry eye were examined and analyzed. Results: The visual analog scale (VAS), ocular surface disease index, ocular pain assessment survey (OPAS), patient health questionnaire-9 items, generalized anxiety disorder (GAD-7), Athens insomnia scale, corneal fluorescein staining score, meibomian gland secretion quality, and expressibility scores were significantly reduced after the treatment. Tear break-up time and Schirmer I test increased significantly. The brand density of corneal nerves and neuropeptide substance P also significantly increased. OPAS, GAD-7, meibomian gland secretion quality, and expressibility scores were essential factors affecting the VAS changes. Conclusions: IPL combined with DCBE drop therapy was effective for DED patients with ocular pain. With such treatment, both DED symptoms and the sensation of ocular pain may be improved.

SP/NK1R system regulates carcinogenesis in prostate cancer: Shedding light on the antitumoral function of aprepitant

AimsProstate cancer continues to be one of the main global health issues in men. Neuropeptide substance P (SP) acting via neurokinin-1receptor (NK1R) promotes tumorigenicity in many human malignant tumors. However, its pro-tumorigenic functions and the therapeutic effects of its inhibition in prostate cancer remain unclear. MethodsMTT assay was employed for measuring cellular proliferation and cytotoxicity. mRNAs and proteins expression levels were evaluated by qRT-PCR and western blot assay, respectively. Gelatinase activity was assessed by zymography. The migration ability was defined using wound-healing assay. Flow cytometry was employed to evaluate the cell cycle distribution. We also performed an in vivo experiment in a mouse model of prostate cancer to confirm the in vitro therapeutic effect of targeting the SP/NK1R system. ResultsWe found a noticeable increase in the expression of the truncated isoform of NK1R as an oncogenic NK1R splice variant in tumor cells. We also demonstrated that SP promotes both proliferative and migrative phenotypes of prostate cancer through modifying cell cycle-related proteins (c-Myc, cyclin D1, cyclin B1, p21), and apoptosis-related genes (Bcl-2 and Bax), promoting cell migration and increasing MMP-2 and MMP-9 expression and activity, while aprepitant administration could remarkably reverse these effects. SP also stimulated tumor growth in vivo, which was correlated with shorter survival times, while aprepitant reversed this effect and led to significantly longer survival time. SignificanceOur findings suggest that SP/NK1R system may serve as a novel therapeutic target in prostate cancer and support the possible candidacy of aprepitant in future prostate cancer therapy.

Trichodynia: An Update on Definition, Etiopathogenesis, Diagnosis, and Treatment

: Trichodynia was elucidated as a distressing, painful sensation of the scalp hair and/or the skin of the scalp that becomes more vigorous when hairs are touched without an underlying cutaneous disease and is frequently associated with hair shedding. It was often more in women than men, directly correlating with hair loss. The etiology of trichodynia is not well-known, but it may be multifactorial. Several possible hypotheses can explain the etiopathogenesis of trichodynia, including enhanced expression of neuropeptide substance P with perifollicular inflammation, psychiatric diseases, and nutritional deficiencies. Currently, there is no specific and effective therapy for trichodynia. Various available treatments included L-cystine-containing oral preparation, topical corticosteroid, low-dose antidepressant, oral propranolol, and botulinum toxin injection. This review article highlights an update of the definition, etiopathogenesis, diagnosis, and treatment of trichodynia.

Skin codelivery of contact sensitizers and neurokinin-1 receptor antagonists integrated in microneedle arrays suppresses allergic contact dermatitis

Allergic contact dermatitis (CD) is a chronic inflammatory skin disease caused by type 1 biased adaptive immunity for which there is an unmet need for antigen (Ag)-specific immunotherapies. Exposure to skin sensitizers stimulates secretion of the proinflammatory neuropeptides substance P and hemokinin 1, which signal via the neurokinin-1 receptor (NK1R) to promote the innate and adaptive immune responses of CD. Accordingly, mice lacking the NK1R develop impaired CD. Nonetheless, the role and therapeutic opportunities of targeting the NK1R in CD remain to be elucidated. We sought to develop an Ag-specific immunosuppressive approach to treat CD by skin codelivery of hapten and NK1R antagonists integrated in dissolvable microneedle arrays (MNA). Invivo mouse models of contact hypersensitivity and exvivo models of human skin were used to delineate the effects and mechanisms of NK1R signaling and the immunosuppressive effects of the contact sensitizer NK1R antagonist MNA in CD. We demonstrated in mice that CD requires NK1R signaling by substance P and hemokinin 1. Specific deletion of the NK1R in keratinocytes and dendritic cells, but not in mast cells, prevented CD. Skin codelivery of hapten or Ag MNA inhibited neuropeptide-mediated skin inflammation in mouse and human skin, promoted deletion of Ag-specific effector T cells, and increased regulatory T cells, which prevented CD onset and relapses locally and systemically in an Ag-specific manner. Immunoregulation by engineering localized skin neuroimmune networks can be used to treat cutaneous diseases that like CD are caused by type 1 immunity.

Modulation of inspiratory burst duration and frequency by bombesin in vitro.

Mammalian respiratory rhythm-generating circuits in the brainstem are subject to neuromodulation by multiple peptidergic afferent inputs controlling circuit behavior and outputs. Although functionally important, actions of neuropeptide modulators have not been fully characterized. We analyzed at cellular and circuit levels two inspiratory patterns intrinsically generated by the preBötzinger complex (preBötC) and their modulation by the neuropeptides bombesin and substance P (SP) in neonatal rat medullary slices in vitro. We found that, in recordings of hypoglossal nerve and preBötC neuron inspiratory activity, some inspiratory bursts occurring spontaneously under basal conditions have a biphasic shape with longer duration than normal inspiratory bursts and occur at a lower frequency. This biphasic burst pattern has been proposed to represent inspiratory activity underling periodic sighs. Bath-applied bombesin or SP decreased the period and increased the duration of both normal inspiratory and biphasic bursts and their underlying synaptic drives. The ratio of the biphasic long-duration burst period to the normal inspiratory burst period and the ratio of their burst durations remained the same before and after peptidergic modulation. Bombesin increased the frequency of the inspiratory rhythm in a Ca2+-independent manner and the frequency of long-duration bursts in a Ca2+-dependent manner. This finding suggests that period and burst duration coupling are due to intrinsic mechanisms controlling simultaneously timing and burst termination within the inspiratory rhythm-generating network. We propose a model in which signaling cascades activated by bombesin and SP modulate mechanisms controlling inspiratory burst frequency and duration to coordinate preBötC circuit behavioral outputs.

Inhibition of Orai Channel Function Regulates Mas-Related G Protein-Coupled Receptor-Mediated Responses in Mast Cells.

Mast cells (MCs) are tissue resident immune cells that play important roles in the pathogenesis of allergic disorders. These responses are mediated via the cross-linking of cell surface high affinity IgE receptor (FcϵRI) by antigen resulting in calcium (Ca2+) mobilization, followed by degranulation and release of proinflammatory mediators. In addition to FcϵRI, cutaneous MCs express Mas-related G protein-coupled receptor X2 (MRGPRX2; mouse ortholog MrgprB2). Activation of MRGPRX2/B2 by the neuropeptide substance P (SP) is implicated in neurogenic inflammation, chronic urticaria, mastocytosis and atopic dermatitis. Although Ca2+ entry is required for MRGPRX2/B2-mediated MC responses, the possibility that calcium release-activated calcium (CRAC/Orai) channels participate in these responses has not been tested. Lentiviral shRNA-mediated silencing of Orai1, Orai2 or Orai3 in a human MC line (LAD2 cells) resulted in partial inhibition of SP-induced Ca2+ mobilization, degranulation and cytokine/chemokine generation (TNF-α, IL-8, and CCL-3). Synta66, which blocks homo and hetero-dimerization of Orai channels, caused a more robust inhibition of SP-induced responses than knockdown of individual Orai channels. Synta66 also blocked SP-induced extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt phosphorylation and abrogated cytokine/chemokine production. It also inhibited SP-induced Ca2+ mobilization and degranulation in primary human skin MCs and mouse peritoneal MCs. Furthermore, Synta66 attenuated both SP-induced cutaneous vascular permeability and leukocyte recruitment in mouse peritoneum. These findings demonstrate that Orai channels contribute to MRGPRX2/B2-mediated MC activation and suggest that their inhibition could provide a novel approach for the modulation of SP-induced MC/MRGPRX2-mediated disorders.

Self-assembling peptide gels promote angiogenesis and functional recovery after spinal cord injury in rats

Spinal cord injury (SCI) leads to disruption of the blood–spinal cord barrier, hemorrhage, and tissue edema, which impair blood circulation and induce ischemia. Angiogenesis after SCI is an important step in the repair of damaged tissues, and the extent of angiogenesis strongly correlates with the neural regeneration. Various biomaterials have been developed to promote angiogenesis signaling pathways, and angiogenic self-assembling peptides are useful for producing diverse supramolecular structures with tunable functionality. RADA16 (Ac-RARADADARARADADA-NH2), which forms nanofiber networks under physiological conditions, is a self-assembling peptide that can provide mechanical support for tissue regeneration and reportedly has diverse roles in wound healing. In this study, we applied an injectable form of RADA16 with or without the neuropeptide substance P to the contused spinal cords of rats and examined angiogenesis within the damaged spinal cord and subsequent functional improvement. Histological and immunohistochemical analyses revealed that the inflammatory cell population in the lesion cavity was decreased, the vessel number and density around the damaged spinal cord were increased, and the levels of neurofilaments within the lesion cavity were increased in SCI rats that received RADA16 and RADA16 with substance P (rats in the RADA16/SP group). Moreover, real-time PCR analysis of damaged spinal cord tissues showed that IL-10 expression was increased and that locomotor function (as assessed by the Basso, Beattie, and Bresnahan (BBB) scale and the horizontal ladder test) was significantly improved in the RADA16/SP group compared to the control group. Our findings indicate that RADA16 modified with substance P effectively stimulates angiogenesis within the damaged spinal cord and is a candidate agent for promoting functional recovery post-SCI.

The prognostic value of peripheral ischemic microvascular reserve in sepsis is not related to calcitonin gene-related peptide or substance P

OBJECTIVE: To evaluate the mechanisms attributed to the prognostic value of peripheral ischemic microvascular reserve in patients with sepsis. METHODS: This observational cohort study enrolled 46 consecutive septic patients in the intensive care unit between November 2020 and October 2021. After fluid resuscitation, the peripheral ischemic microvascular reserve was evaluated using the association of postocclusion reactive hyperemia with the peripheral perfusion index. Additionally, peripheral venous blood samples were used to evaluate the neuropeptide calcitonin gene-related peptide and substance P levels in the upper limb before and immediately after postocclusion reactive hyperemia RESULTS: There was no statistically significant correlation (p > 0.05) between basal values (pg/mL) or variations from neuropeptide levels (%) and the peripheral ischemic microvascular reserve (%). CONCLUSION: Although calcitonin gene-related peptide and substance P may have a prognostic role in sepsis, these neuropeptides do not appear to contribute to peripheral ischemic microvascular reserve.

The two-faced effects of nerves and neuropeptides in corneal diseases.

Corneal nerves are instrumental to maintain cornea integrity through regulation of key physiological functions such as tear secretion, blink reflex, and neuropeptide turnover. Corneal nerve injury/stimulation can follow many insults including mechanical/chemical trauma, infections and surgeries. Nerve disruption initiates a process named neurogenic inflammation which leads to edema, pain, and recruitment and activation of leukocytes. Interestingly, leukocyte influx in the cornea can further damage nerves by releasing inflammatory mediators-including neuropeptides. The clinical outcome of neuroinflammation can be beneficial or detrimental to corneal integrity. On one side, it ensures prompt wound healing and prevents infections. On the other, prolonged and/or deranged neuroinflammation can permanently disrupt corneal integrity and impair vision. The cornea is an ideal site to study peripheral neuroinflammation and neurogenic inflammation since it receives the highest density of sensory nerves of the entire body. We will review the corneal nerve anatomy and neurochemistry, discuss the beneficial and detrimental effects of neurogenic inflammation in corneal wound healing, inflammatory processes, and pain. We will also examine the emerging remote impact of corneal nerve disruption on the trigeminal ganglion and the brain, highlighting the key role of neuropeptide Substance P. Finally, we will discuss the clinical relevance of such neuroinflammatory network in the context of severe and highly prevalent ocular diseases, including potential treatments.

Nociceptor neurons promote IgE class switch in B cells.

Nociceptors, the high-threshold primary sensory neurons that trigger pain, interact with immune cells in the periphery to modulate innate immune responses. Whether they also participate in adaptive and humoral immunity is, however, not known. In this study, we probed if nociceptors have a role in distinct airway and skin models of allergic inflammation. In both models, the genetic ablation and pharmacological silencing of nociceptors substantially reduced inflammatory cell infiltration to the affected tissue. Moreover, we also found a profound and specific deficit in IgE production in these models of allergic inflammation. Mechanistically, we discovered that the nociceptor-released neuropeptide substance P helped trigger the formation of antibody-secreting cells and their release of IgE. Our findings suggest that nociceptors, in addition to their contributions to innate immunity, play a key role in modulating the adaptive immune response, particularly B cell antibody class switching to IgE.

The SP/NK1R System-Mediated ROS Generation in GBM Cells through Inhibiting Glutaredoxin Protein.

Altered redox balance is among the main contributing factors developing glioblastoma multiforme (GBM), a highly aggressive grade IV brain tumor. Neuropeptide substance P (SP) plays a key role in modifying the cellular redox environment by activating the neurokinin-1 receptor (NK1R). In this study, we aimed to investigate the redox-modulating properties of both SP and a commercially available NK1R antagonist, aprepitant in GBM cells. To detect the effect of aprepitant on the viability of U87 glioblastoma cells, resazurin assay was applied. The level of intracellular ROS was assessed using 2′,7′-dichlorodihydrofluorescein diacetate (H2DCFDA) assay. The expression of glutaredoxin, a well-known redox-active protein, was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Concurrently, the activity of glutaredoxin was also analyzed by a commercial kit (ZellBio GmbH). We found that SP increased the intracellular levels of reactive oxygen species (ROS) in U87 GBM cells, and aprepitant remarkably decreased this effect. We also explored the effects of SP/NK1R signaling on the glutaredoxin system as a major cellular redox buffer in GBM cells. SP reduced both expression and enzymatic activity of glutaredoxin, and these effects were significantly decreased by aprepitant. In conclusion, our results suggest a possible involvement of SP/NK1R signaling in GBM pathogenesis through oxidative stress and offering new insight for the application of aprepitant as a redox-modulating strategy in GBM patients.