Vasoactive Intestinal Peptide Receptor Research Articles

Chemical Modifications to Enhance the Drug Properties of a VIP Receptor Antagonist (ANT) Peptide.

Antagonist peptides (ANTs) of vasoactive intestinal polypeptide receptors (VIP-Rs) are shown to enhance T cell activation and proliferation in vitro, as well as improving T cell-dependent anti-tumor response in acute myeloid leukemia (AML) murine models. However, peptide therapeutics often suffer from poor metabolic stability and exhibit a short half-life/fast elimination in vivo. In this study, we describe efforts to enhance the drug properties of ANTs via chemical modifications. The lead antagonist (ANT308) is derivatized with the following modifications: N-terminus acetylation, peptide stapling, and PEGylation. Acetylated ANT308 exhibits diminished T cell activation in vitro, indicating that N-terminus conservation is critical for antagonist activity. The replacement of residues 13 and 17 with cysteine to accommodate a chemical staple results in diminished survival using the modified peptide to treat mice with AML. However, the incorporation of the constraint increases survival and reduces tumor burden relative to its unstapled counterpart. Notably, PEGylation has a significant positive effect, with fewer doses of PEGylated ANT308 needed to achieve comparable overall survival and tumor burden in leukemic mice dosed with the parenteral ANT308 peptide, suggesting that polyethylene glycol (PEG) incorporation enhances longevity, and thus the antagonist activity of ANT308.

18Beta-Glycyrrhetinic Acid Attenuates H2O2-Induced Oxidative Damage and Apoptosis in Intestinal Epithelial Cells via Activating the PI3K/Akt Signaling Pathway.

Oxidative stress causes gut dysfunction and is a contributing factor in several intestinal disorders. Intestinal epithelial cell survival is essential for maintaining human and animal health under oxidative stress. 18beta-Glycyrrhetinic acid (GA) is known to have multiple beneficial effects, including antioxidant activity; however, the underlying molecular mechanisms have not been well established. Thus, the present study evaluated the therapeutic effects of GA on H2O2-induced oxidative stress in intestinal porcine epithelial cells. The results showed that pretreatment with GA (100 nM for 16 h) significantly increased the levels of several antioxidant enzymes and reduced corresponding intracellular levels of reactive oxidative species and malondialdehyde. GA inhibited cell apoptosis via activating the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) signaling pathway, as confirmed by RNA sequencing. Further analyses demonstrated that GA upregulated the phosphorylation levels of PI3K and Akt and the protein level of B cell lymphoma 2, whereas it downregulated Cytochrome c and tumor suppressor protein p53 levels. Moreover, molecular docking analysis predicted the binding of GA to Vasoactive intestinal peptide receptor 1, a primary membrane receptor, to activate the PI3K/Akt signaling pathway. Collectively, these results revealed that GA protected against H2O2-induced oxidative damage and cell apoptosis via activating the PI3K/Akt signaling pathway, suggesting the potential therapeutic use of GA to alleviate oxidative stress in humans/animals.

Pharmacology of PACAP and VIP receptors in the spinal cord highlights the importance of the PAC1 receptor.

The spinal cord is a key structure involved in the transmission and modulation of pain. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP), are expressed in the spinal cord. These peptides activate G protein-coupled receptors (PAC1, VPAC1 and VPAC2) that could provide targets for the development of novel pain treatments. However, it is not clear which of these receptors are expressed within the spinal cord and how these receptors signal. Dissociated rat spinal cord cultures were used to examine agonist and antagonist receptor pharmacology. Signalling profiles were determined for five signalling pathways. The expression of different PACAP and VIP receptors was then investigated in mouse, rat and human spinal cords using immunoblotting and immunofluorescence. PACAP, but not VIP, potently stimulated cAMP, IP1 accumulation and ERK and cAMP response element-binding protein (CREB) but not Akt phosphorylation in spinal cord cultures. Signalling was antagonised by M65 and PACAP6-38. PACAP-27 was more effectively antagonised than either PACAP-38 or VIP. The patterns of PAC1 and VPAC2 receptor-like immunoreactivity appeared to be distinct in the spinal cord. The pharmacological profile in the spinal cord suggested that a PAC1 receptor is the major functional receptor subtype present and thus likely mediates the nociceptive effects of the PACAP family of peptides in the spinal cord. However, the potential expression of both PAC1 and VPAC2 receptors in the spinal cord highlights that these receptors may play differential roles and are both possible therapeutic targets.

Vasoactive intestinal peptide excites GnRH neurons via KCa3.1, a potential player in the slow afterhyperpolarization current.

Vasoactive intestinal peptide (VIP) is an important component of the suprachiasmatic nucleus (SCN) which relays circadian information to neuronal populations, including GnRH neurons. Human and animal studies have shown an impact of disrupted daily rhythms (chronic shift work, temporal food restriction, clock gene disruption) on both male and female reproduction and fertility. To date, how VIP modulates GnRH neurons remains unknown. Calcium imaging and electrophysiology on primary GnRH neurons in explants and adult mouse brain slice, respectively, were used to address this question. We found VIP excites GnRH neurons via the VIP receptor, VPAC2. The downstream signaling pathway uses both Gs protein/adenylyl cyclase/protein kinase A (PKA) and phospholipase C/phosphatidylinositol 4,5-bisphosphate (PIP2) depletion. Furthermore, we identified a UCL2077-sensitive target, likely contributing to the slow afterhyperpolarization current (IAHP), as the PKA and PIP2 depletion target, and the KCa3.1 channel as a specific target. Thus, VIP/VPAC2 provides an example of Gs protein-coupled receptor-triggered excitation in GnRH neurons, modulating GnRH neurons likely via the slow IAHP. The possible identification of KCa3.1 in the GnRH neuron slow IAHP may provide a new therapeutical target for fertility treatments.

Mismatch novelty exploration training shifts VPAC1 receptor-mediated modulation of hippocampal synaptic plasticity by endogenous VIP in male rats.

Novelty influences hippocampal-dependent memory through metaplasticity. Mismatch novelty detection activates the human hippocampal CA1 area and enhances rat hippocampal-dependent learning and exploration. Remarkably, mismatch novelty training (NT) also enhances rodent hippocampal synaptic plasticity while inhibition of VIP interneurons promotes rodent exploration. Since VIP, acting on VPAC1 receptors (Rs), restrains hippocampal LTP and depotentiation by modulating disinhibition, we now investigated the impact of NT on VPAC1 modulation of hippocampal synaptic plasticity in male Wistar rats. NT enhanced both CA1 hippocampal LTP and depotentiation unlike exploring an empty holeboard (HT) or a fixed configuration of objects (FT). Blocking VIP VPAC1Rs with PG 97269 (100 nM) enhanced both LTP and depotentiation in naïve animals, but this effect was less effective in NT rats. Altered endogenous VIP modulation of LTP was absent in animals exposed to the empty environment (HT). HT and FT animals showed mildly enhanced synaptic VPAC1R levels, but neither VIP nor VPAC1R levels were altered in NT animals. Conversely, NT enhanced the GluA1/GluA2 AMPAR ratio and gephyrin synaptic content but not PSD-95 excitatory synaptic marker. In conclusion, NT influences hippocampal synaptic plasticity by reshaping brain circuits modulating disinhibition and its control by VIP-expressing hippocampal interneurons while upregulation of VIP VPAC1Rs is associated with the maintenance of VIP control of LTP in FT and HT animals. This suggests VIP receptor ligands may be relevant to co-adjuvate cognitive recovery therapies in aging or epilepsy, where LTP/LTD imbalance occurs.

Estrogen-mediated coupling via gap junctions in the suprachiasmatic nucleus.

The circadian clock orchestrates many physiological and behavioural rhythms in mammals with 24-h periodicity, through a hierarchical organisation, with the central clock located in the suprachiasmatic nucleus (SCN) in the hypothalamus. The circuits of the SCN generate circadian rhythms with precision, relying on intrinsic coupling mechanisms, for example, neurotransmitters like arginine vasopressin (AVP), vasoactive intestinal peptide (VIP), neuronal gamma-aminobutyric acid (GABA) signalling and astrocytes connected by gap junctions composed of connexins (Cx). In female rodents, the presence of estrogen receptors (ERs) in the dorsal SCN suggests an influence of estrogen (E2) on the circuit timekeeping that could regulate circadian rhythm and coupling. To investigate this, we used SCN explants together with hypothalamic neurons and astrocytes. First, we showed that E2 stabilised the circadian amplitude in the SCN when rAVPs (receptor-associated vasopressin peptides) were inhibited. However, the phase delay induced by VIPAC2 (VIP receptors) inhibition remained unaffected by E2. We then showed that E2 exerted its effects in the SCN via ERβ (estrogen receptor beta), resulting in increased expression of Cx36 and Cx43. Notably, specific inhibition of both connexins resulted in a significant reduction in circadian amplitude within the SCN. Remarkably, E2 restored the period with inhibited Cx36 but not with Cx43 inhibition. This implies that the network between astrocytes and neurons, responsible for coupling in the SCN, can be reinforced through E2. In conclusion, these findings provide new insights into how E2 regulates circadian rhythms ex vivo in an ERβ-dependent manner, underscoring its crucial role in fortifying the SCN's rhythm.

Vasoactive Intestinal Peptide Receptor, CRTH2, Antagonist Treatment Improves Eosinophil and Mast Cell-Mediated Esophageal Remodeling and Motility Dysfunction in Eosinophilic Esophagitis.

Ultrasonography has shown that eosinophils accumulate in each segment of the esophageal mucosa in human EoE, ultimately promoting esophageal motility dysfunction; however, no mechanistic evidence explains how or why this accumulation occurs. Quantitative PCR, ELISA, flow cytometry, immunostaining, and immunofluorescence analyses were performed using antibodies specific to the related antigens and receptors. In deep esophageal biopsies of EoE patients, eosinophils and mast cells accumulate adjacent to nerve cell-derived VIP in each esophageal segment. qRT-PCR analysis revealed five- to sixfold increases in expression levels of VIP, CRTH2, and VAPC2 receptors and proteins in human blood- and tissue-accumulated eosinophils and mast cells. We also observed a significant correlation between mRNA CRTH2 levels and eosinophil- and nerve cell-derived VIPs in human EoE (p < 0.05). We provide evidence that eosinophil and mast cell deficiency following CRTH2 antagonist treatment improves motility dysfunction in a chronic DOX-inducible CC10-IL-13 murine model of experimental EoE. CRTH2 antagonist treatment is a novel therapeutic strategy for inflammatory cell-induced esophageal motility dysfunction in IL-13-induced chronic experimental EoE.

Blockade of vasoactive intestinal peptide receptor 2 (VIPR2) signaling suppresses cyclin D1-dependent cell-cycle progression in MCF-7 cells

Vasoactive intestinal peptide (VIP) receptor 2 (VIPR2) is a G protein-coupled receptor that binds to Gαs, Gαi, and Gαq proteins to regulate various downstream signaling molecules, such as protein kinase A (PKA), phosphatidylinositol 3-kinase (PI3K), and phospholipase C. In this study, we examined the role of VIPR2 in cell cycle progression. KS-133, a newly developed VIPR2-selective antagonist peptide, attenuated VIP-induced cell proliferation in MCF-7 cells. The percentage of cells in the S-M phase was decreased in MCF-7 cells treated with KS-133. KS-133 in the presence of VIP decreased the phosphorylation of extracellular signal-regulated kinase (ERK), AKT, and glycogen synthase kinase-3β (GSK3β), resulting in a decrease in cyclin D1 levels. In MCF-7 cells stably-expressing VIPR2, KS-133 decreased PI3K activity and cAMP levels. Treatment with the ERK-specific kinase (MEK) inhibitor U0126 and the class I PI3K inhibitor ZSTK474 decreased the percentage of cells in the S phase. KS-133 reduced the percentage of cells in the S phase more than treatment with U0126 or ZSTK474 alone and did not affect the effect of the mixture of these inhibitors. Our findings suggest that VIPR2 signaling regulates cyclin D1 levels through the cAMP/PKA/ERK and PI3K/AKT/GSK3β pathways, and mediates the G1/S transition to control cell proliferation.

Sympathetic Neurotransmitter, VIP, Delays Intervertebral Disc Degeneration via FGF18/FGFR2-Mediated Activation of Akt Signaling Pathway.

Neuromodulation-related intervertebral disc degeneration (IVDD) is a novel IVDD pattern and are proposed recently. However, the mechanistic basis of neuromodulation and intervertebral disc (IVD) homeostasis remains unclear. Here, this study aimed to investigate the expression of postganglionic sympathetic nerve fiber-derived vasoactive intestinal peptide (VIP) system in human IVD tissue, and to assess the role of VIP-related neuromodulation in IVDD. Patient samples and in vitro cell experiments showed that the expression of receptors for VIP is negatively correlated with the severity of IVDD, and the administration of exogenous VIP can ameliorate interleukin 1β-induced nucleus pulposus (NP) cell apoptosis and inflammation. Further mRNA-seq analysis revealed that fibroblast growth factor 18- (FGF18)-mediated activation of V-akt murine thymoma viral oncogene homolog signaling pathway is involved in the protective effects of VIP on inflammation-induced NP cell degeneration. Further analysis identified VIP via its receptor vasoactive intestinal peptide receptor 2 can directly result in decreased expression of miR-15a-5p, which targeted FGF18. Finally, in vivo mice lumbar IVDD model confirmed that focally exogenous administration of VIP can effectively ameliorated the progression of IVDD, as shown by the radiological and histological analysis. In conclusion, these results indicated that sympathetic neurotransmitter, VIP, delayed IVDD via FGF18/FGFR2-mediated activation of V-akt murine thymoma viral oncogene homolog signaling pathway, which will broaden the horizon concerning how the neuromodulation correlates with IVDD and shed new light on novel therapeutical alternatives to IVDD.

Donor T Cell Infusions Limit Novel Immune Checkpoint Therapy in Pancreatic Cancer: Implications for Adoptive T Cell Therapy

Background: We have previously published that pancreatic cancers over-express an immunosuppressive peptide, vasoactive intestinal polypeptide (VIP), and that a novel combination of antin-PD1 antibodies and small molecule antagonists to the VIP receptor can induce complete remission of pancreatic ductal adenocarcinoma (PDAC) in multiple mouse models (Ravibndranathan, Nat. Comm. 2022). To enhance the efficacy of this novel immunotherapy approach, we hypothesized that infusions of additional donor T cells to PDAC-bearing mice receiving the combination of anti-PD1/VIP receptor antagonists would lead to more intra-tumoral effector T cells and increased tumor regression rates. To investigate the potential impact of adoptive splenocyte infusion on checkpoint immunotherapy, we established sub-cutaneous KPC PDAC tumors in C57Bl/6 mice. As previously described, we treated them with a combination of ANT308 (VIP-receptor antagonists) and anti-PD1. We tested whether adding splenocyte infusions from donor mice that were immunologically naïve or donor mice previously engrafted with PDAC with regressed (positive control) or progressed tumors (negative control) would enhance the efficacy of the immune checkpoint blockade therapy. Methods: C57BL/6 B6 CD45.1 recipient mice were inoculated subcutaneously with 1 x 10 6 KPC-luc PDAC cell line cells on day -5. Recipient mice received anti-PD1 (200mg) every three days (totaling four doses) and 21 daily s.c. injections of 20 ug ANT308. Splenocytes from three groups of CD45.2+ C57BL/6 donor mice were injected into tumor-bearing recipients: naive mice, mice with a history of KPC regression post-ANT308/anti-PD1 treatment, and mice with progressed KPC tumors without any treatment. Anti-PD1 and ANT308 treatments were initiated simultaneously with adoptive splenocyte infusion (25 x 10 6 cells) on day 0. Tumor size was measured biweekly, and IVIS imaging was performed weekly. Blood was drawn weekly from recipient mice for flow cytometric analysis of immune cell subsets. A fraction of tumor-bearing recipient mice was euthanized ten days after donor splenocyte infusion and initiation of immune checkpoint therapy or at IAUCAC-defined endpoints. When tumor-bearing mice were euthanized, the spleen, lymph nodes, and tumors were harvested for further flow cytometric analysis. The remaining mice were monitored for tumor growth and survival kinetics. Results: Contrary to our original hypothesis, we observed substantially lower survival rates and faster tumor growth in the group that received splenocytes from immunologically naive donor mice versus the group treated with splenocytes from tumor-bearing mice (Figures 1A and 1B). Splenocytes from immunologically naive donors contained fewer Treg cells, whereas myeloid-derived suppressor cells (CD11b+Ly-6G+ Gr-1+) were increased in donor splenocytes from tumor-bearing mice. We next repeated the experiment utilizing the adoptive transfer of splenocytes from immunologically naïve donors separated into 8 x 10 6 MACS-purified T cell or 17 x 10 6 non-T cell fractions. Remarkably, the transfer of 8 x 10 6 immunologically naïve T cells abrogated the efficacy of immune checkpoint therapy leading to rapid tumor growth compared to tumor regression in mice treated with immune checkpoint therapy without added donor splenocytes or mice that received immune checkpoint therapy with 17 x 10 6 T-cell-depleted donor splenocytes. Flow cytometric and gene expression analyses of splenocytes from the recipient mice, and those not receiving donor T cell infusions, revealed that the tetramer population in the infusion group was significantly higher than in the group treated only with immune checkpoint inhibitors. Conclusion: Our findings indicated that natural suppressor/ Treg in immunologically naïve splenocytes could exert a profound negative regulatory effect on immune checkpoint therapy's efficacy in a murine PDAC model. Despite having fewer Treg than splenocytes from tumor-bearing donors, immunologically naïve natural Treg had increased potency in suppressing anti-cancer immunity. These findings suggest the importance of the depletion of natural Treg in adoptive cell therapy strategies to treat solid tumor malignancies. This research underscores the critical role of immune contexture in shaping therapeutic outcomes and proposes a novel biomarker for patient stratification in PDAC immunotherapy.

Antagonizing Vasoactive Intestinal Peptide (VIP) Receptors on CAR T Cells Improves Efficacy and Persistence

Vasoactive intestinal peptide (VIP) is an emerging checkpoint pathway for T cell function 1. VIP is expressed by both T cells 2,3 and tumor cells 1 and is upregulated during TCR activation 1,4,5. Augmentation of the VIP/VIPR axis during expansion of primary human T cells enhances less differentiated T cell phenotypes, anti-tumor cytotoxicity, and in vivo persistence 6. In this work, we elucidate the mechanisms by which the VIP/VIPR axis is a critical and targetable immune checkpoint pathway for chimeric antigen receptor (CAR) T cell therapy. By engineering CAR T cells to secrete novel and potent VIPR antagonistic peptides, these cells can overcome the immunosuppression of VIP-rich tumor microenvironments. First, we demonstrated that VIP suppresses CAR T cell function as evident by reduced expansion with exogenous VIP supplementation, which can be rescued by the addition of VIPRa peptides. The VIP/VIPR axis is relevant to CAR T cell signaling as these cells produce VIP after antigen stimulation and upregulate VIPR expression. In fact, polyfunctionality and cytotoxic killing is enhanced by VIPR knockout of CAR T cells. Together, these results demonstrate the critical role of the VIP/VIPR axis in CAR T cell function. To harness this axis, CAR T cells were engineered to secrete VIPRa peptides (VIPRa CAR T) to provide continuous and localized delivery of VIPRa peptides. Continuously delivered VIPR antagonism increases the viability and proportions of less-differentiated and less-exhaustive phenotypes of CAR T cells at baseline. Functionally, VIPRa CAR T cells have a proliferative advantage and enhanced activation compared to parental CAR T cells. RNA sequencing was performed on VIPRa CAR T cells before and after antigen-stimulation to illuminate in-depth phenotypic and functional differences compared parental CAR T cells. Finally, these novel CAR T cells were tested in xenograft and syngeneic mouse models. VIPRa CAR T cells show improved tumor control and persistence as evidence long-lived circulating cells in the peripheral blood. To validate the clinical relevance of this target for CAR T therapy, patient-derived xenograft (PDX) pancreatic tumors were assayed to show robust expression of VIP. VIPRa CAR T cells significantly reduced tumor burden and improved survival in PDX tumor-bearing mice. Collectively, this data demonstrates that targeting VIP is a novel and successful approach to improving CAR T cell anti-tumor efficacy. VIPR antagonism enhances initial CAR T cell phenotypes and function, which has the potential to improve CAR T cell therapy for a variety of tumor types. The mechanisms by which CAR T cell-mediated delivery of VIPRa peptides can modulate tumor microenvironments in a syngeneic model are currently being evaluated. VIPRa CAR T cells are a uniquely improved cellular therapy capable of enhanced anti-tumor function against clinically relevant tumors.

Gene deletion of the PACAP/VIP receptor, VPAC2R, alters glycemic responses during metabolic and psychogenic stress in adult female mice.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and the homologous peptide, vasoactive intestinal peptide (VIP), participate in glucose homeostasis using insulinotropic and counterregulatory processes. The role of VIP receptor 2 (VPAC2R) in these opposing actions needs further characterization. In this study, we examined the participation of VPAC2R on basal glycemia, fasted levels of glucoregulatory hormones and on glycemia responses during metabolic and psychogenic stress using gene-deleted (Vipr2-/- ) female mice. The mean basal glycemia was significantly greater in Vipr2-/- in the fed state and after an 8-h overnight fast as compared to wild-type (WT) mice. Insulin tolerance testing following a 5-h fast (morning fast, 0.38 U/kg insulin) indicated no effect of genotype. However, during a more intense metabolic challenge (8 h, ON fast, 0.25 U/kg insulin), Vipr2-/- females displayed significantly impaired insulin hypoglycemia. During immobilization stress, the hyperglycemic response and plasma epinephrine levels were significantly elevated above basal in Vipr2-/- , but not WT mice, in spite of similar stress levels of plasma corticosterone. Together, these results implicate participation of VPAC2R in upregulated counterregulatory processes influenced by enhanced sympathoexcitation. Moreover, the suppression of plasma GLP-1 levels in Vipr2-/- mice may have removed the inhibition on hepatic glucose production and the promotion of glucose disposal by GLP-1. qPCR analysis indicated deregulation of central gene markers of PACAP/VIP signaling in Vipr2-/- , upregulated medulla tyrosine hydroxylase (Th) and downregulated hypothalamic Vip transcripts. These results demonstrate a physiological role for VPAC2R in glucose metabolism, especially during insulin challenge and psychogenic stress, likely involving the participation of sympathoadrenal activity and/or metabolic hormones.

Development of a New Enzyme-Linked Immunosorbent Assay (ELISA) for Measuring the Content of PACAP in Mammalian Tissue and Plasma.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a naturally occurring neuropeptide found in both the central and peripheral nervous systems of vertebrates. Recent studies have revealed the presence of PACAP and its corresponding receptors, namely, the pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1R), vasoactive intestinal peptide receptor 1 (VIPR1), and vasoactive intestinal peptide receptor 2 (VIPR2), in various structures implicated in migraine pathophysiology, including sensory trigeminal neurons. Human studies have demonstrated that when infused, PACAP can cause dilation of cranial vessels and result in delayed migraine-like attacks. In light of this, we present a novel ELISA assay that has been validated for quantifying PACAP in tissue extracts and human plasma. Using two well characterized antibodies specifically targeting PACAP, we successfully developed a sandwich ELISA assay, capable of detecting and accurately quantifying PACAP without any cross-reactivity to closely related peptides. The quantification range was between 5.2 pmol/L and 400 pmol/L. The recovery in plasma ranged from 98.2% to 100%. The increasing evidence pointing to the crucial role of PACAP in migraine pathophysiology necessitates the availability of tools capable of detecting changes in the circulatory levels of PACAP and its potential application as a reliable biomarker.

β-Arrestin-independent endosomal cAMP signaling by a polypeptide hormone GPCR

Many G protein-coupled receptors (GPCRs) initiate a second phase of stimulatory heterotrimeric G protein (Gs)-coupled cAMP signaling after endocytosis. The prevailing current view is that the endosomal signal is inherently β-arrestin-dependent because β-arrestin is necessary for receptor internalization and, for some GPCRs, to prolong the endosomal signal. Here we revise this view by showing that the vasoactive intestinal peptide receptor 1 (VIPR1), a secretin-family polypeptide hormone receptor, does not require β-arrestin to internalize or to generate an endosomal signal. β-Arrestin instead resolves the plasma membrane and endosomal signaling phases into sequential cAMP peaks by desensitizing the plasma membrane phase without affecting the endosomal phase. This appears to occur through the formation of functionally distinct VIPR1–β-arrestin complexes at each location that differ in their phosphorylation dependence. We conclude that endosomal GPCR signaling can occur in the absence of β-arrestin and that β-arrestin sculpts the spatiotemporal profile of cellular GPCR–G protein signaling through location-specific remodeling of GPCR–β-arrestin complexes.

Neural targets of the enteric dopaminergic system in regulating motility of rat proximal colon.

In isolated segments of the rat proximal colon, the dopamine reuptake inhibitor GBR 12909 (GBR) causes a dilatation, while the D1-like receptor antagonist SCH 23390 (SCH) induces a tonic constriction, suggesting that neurally released dopamine tonically stimulates enteric inhibitory efferent neurons. Here, the targets of the enteric dopaminergic neurons were investigated. Cannulated segments of rat proximal colon were bathed in physiological salt solution and luminally perfused with 0.9% saline, while all drugs were applied to the bath. Spatio-temporal maps of colonic motility were constructed from video recordings of peristaltic contractions, and the maximum diameter was measured as an index of colonic contractility. GBR (1μM)-induced dilatations of colonic segments were prevented by SCH (5μM), L-nitro arginine (L-NA; 100μM), a nitric oxide synthase inhibitor, or tetrodotoxin (0.6μM). In contrast, constrictions induced by a higher concentration of SCH (20μM) were unaffected by either L-NA or tetrodotoxin. The vasoactive intestinal peptide (VIP) receptor antagonist VIP10-28 (3μM) or P2Y1 receptor antagonist MRS 2500 (1μM) had no effect on either the GBR-induced dilatation or the SCH-induced constriction. In colonic segments that had been pretreated with 6-hydroxydopamine (100μM, 3h) to deplete enteric dopamine, GBR failed to increase the colonic diameter, while SCH was still capable of constricting colonic segments. Enteric dopaminergic neurons appear to project to nitrergic neurons to dilate the proximal colon by activating neuronal D1-like receptors. In addition, constitutively activated D1-like receptors expressed in cells yet to be determined may provide a tonic inhibition on colonic constrictions.

Association of vasoactive intestinal peptide receptor 1 gene polymorphism with layer economic traits in Rhode Island Red chicken

The research work was conducted to determine allelic polymorphism of vasoactive intestinal peptide receptor-1 (VIPR-1) gene and its association with layer traits in Rhode Island Red (RIR) chicken. Blood samples were collected from pullets (n=111) belonging to five hatches. Data on body weight at 20 weeks of age (BW20) and layer economic traits, viz. age at sexual maturity (ASM), egg weight at 28 (EW28) and 40 weeks (EW40) of age, and egg production up to 40 weeks of age (EP40)) were recorded. Genomic DNA was isolated by phenol chloroform extraction method. Samples were amplified for product sizes of 364, 434 and 486 bp of VIPR-1 gene. Amplified regions were digested by TaiI, HhaI and TaqI restriction enzymes. Digested fragments of TaiI and HhaI revealed monomorphism, whereas TaqI showed polymorphism. Allelic frequencies for polymorphic locus were 0.98 (A) and 0.02 (B) and genotypic frequencies for AA and AB were 0.96 and 0.04, respectively. The BW20 and layer traits (ASM, EW28, EW40 and EP40) were analysed by least-squares analysis of variance taking sire as random and hatch as fixed effect. Average ASM and egg production up to 40 weeks of age were 135.19±1.15 days and 124.55±1.94 eggs, respectively. Least-square analysis of variance had revealed significant effect of hatch on ASM, EW28 and EP40. However, effect of TaqI-RFLP genotypes was non-significant on layer traits. Further investigations on a larger sample basis are suggested to confirm effect of this mutation on layer traits as molecular marker in RIR chicken.

The VIPR2-selective antagonist KS-133 changes macrophage polarization and exerts potent anti-tumor effects as a single agent and in combination with an anti-PD-1 antibody.

We have previously demonstrated that KS-133 is a specific and potent antagonist of vasoactive intestinal peptide receptor 2 (VIPR2). We have also shown that vasoactive intestinal peptide-VIPR2 signaling affects the polarity and activation of tumor-associated macrophages, which is another strategy for cancer immunotherapy apart from the activation of effector T cells. In this study, we aimed to examine whether the selective blockade of VIPR2 by KS-133 changes the polarization of macrophages and induces anti-tumor effects. In the presence of KS-133, genetic markers indicative of tumor-aggressive M1-type macrophages were upregulated, and conversely, those of tumor-supportive M2-type macrophages were downregulated. Daily subcutaneous administration of KS-133 tended to suppress the growth of CT26 tumors (murine colorectal cancer-derived cells) implanted subcutaneously in Balb/c mice. To improve the pharmacological efficacy and reduce the number of doses, we examined a nanoformulation of KS-133 using the US Food and Drug Administration-approved pharmaceutical additive surfactant Cremophor® EL. KS-133 nanoparticles (NPs) were approximately 15 nm in size and stable at 4°C after preparation. Meanwhile, KS-133 was gradually released from the NPs as the temperature was increased. Subcutaneous administration of KS-133 NPs once every 3 days had stronger anti-tumor effects than daily subcutaneous administration of KS-133. Furthermore, KS-133 NPs significantly enhanced the pharmacological efficacy of an immune checkpoint-inhibiting anti-PD-1 antibody. A pharmacokinetic study suggested that the enhancement of anti-tumor activity was associated with improvement of the pharmacokinetic profile of KS-133 upon nanoformulation. Our data have revealed that specific blockade of VIPR2 by KS-133 has therapeutic potential for cancer both alone and in combination with immune checkpoint inhibitors.

Functional Expression of IP, 5-HT4, D1, A2A, and VIP Receptors in Human Odontoblast Cell Line.

Odontoblasts are involved in sensory generation as sensory receptor cells and in dentin formation. We previously reported that an increase in intracellular cAMP levels by cannabinoid 1 receptor activation induces Ca2+ influx via transient receptor potential vanilloid subfamily member 1 channels in odontoblasts, indicating that intracellular cAMP/Ca2+ signal coupling is involved in dentinal pain generation and reactionary dentin formation. Here, intracellular cAMP dynamics in cultured human odontoblasts were investigated to understand the detailed expression patterns of the intracellular cAMP signaling pathway activated by the Gs protein-coupled receptor and to clarify its role in cellular functions. The presence of plasma membrane Gαs as well as prostaglandin I2 (IP), 5-hydroxytryptamine 5-HT4 (5-HT4), dopamine D1 (D1), adenosine A2A (A2A), and vasoactive intestinal polypeptide (VIP) receptor immunoreactivity was observed in human odontoblasts. In the presence of extracellular Ca2+, the application of agonists for the IP (beraprost), 5-HT4 (BIMU8), D1 (SKF83959), A2A (PSB0777), and VIP (VIP) receptors increased intracellular cAMP levels. This increase in cAMP levels was inhibited by the application of the adenylyl cyclase (AC) inhibitor SQ22536 and each receptor antagonist, dose-dependently. These results suggested that odontoblasts express Gs protein-coupled IP, 5-HT4, D1, A2A, and VIP receptors. In addition, activation of these receptors increased intracellular cAMP levels by activating AC in odontoblasts.

PACAP key interactions with PAC1, VPAC1, and VPAC2 identified by molecular dynamics simulations

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) belongs to the glucagon/secretin family. PACAP interacts with the pituitary adenylate cyclase-activating polypeptide receptor type 1 (PAC1) and vasoactive intestinal peptide receptors 1 and 2 (VPAC1 and VPAC2), exhibiting functions in the immune, endocrine, and nervous systems. This peptide is upregulated in numerous instances of brain injury, acting as a neuroprotective agent. It can also suppress HIV-1 and SARS-CoV-2 viral replication in vitro. This work aimed to identify, in each peptide-receptor system, the most relevant residues for complex stability and interaction energy communication via Molecular Dynamics (MD), Free Energy calculations, and Protein-energy networks, thus revealing in detail the underlying mechanisms of activation of these receptors. Hydrogen bond formation, interaction energies, and computational alanine scanning between PACAP and its receptors showed that His1, Asp3, Arg12, Arg14, and Lys15 are crucial to the peptide’s stability. Furthermore, several PACAP interactions with structurally conserved positions deemed necessary in GPCR B1 activation, including Arg2.60, Lys2.67, and Glu7.42, were significant for the peptide’s stability within the receptors. According to the protein-energy network, the connection between Asp3 of PACAP and the receptors’ conserved Arg2.60 represents a critical energy communication hub in all complexes. Additionally, the ECDs of the receptors were also found to function as energy communication hubs for PACAP. Although the overall binding mode of PACAP in the three receptors was found to be highly conserved, Arg12 and Tyr13 of PACAP were more prominent in complex with PAC1, while Ser2 of PACAP was with VPAC2. The detailed analyses performed in this work pave the way for using PACAP and its receptors as therapeutic targets. Communicated by Ramaswamy H. Sarma

Ion transport basis of norovirus diarrhea in a neonatal mouse model

Background: Human Norovirus (HuNoV) is the leading cause of infectious gastroenteritis and food-borne outbreaks, responsible for over 220K deaths annually. Given difficulties studying HuNoV, Murine Norovirus (MNV) has been used as a model for norovirus (NoV) pathophysiology. A major barrier to understand how NoV causes diarrhea is the absence of diarrhea in adult wild-type (WT) mice, which have asymptomatic MNV infections. While several KO mouse strains (e.g., STAT1) have been employed to recapitulate disease, these mice often have exaggerated, systemic, and lethal disease courses that imperfectly match human disease. Very recently, a new model of MNV that appears to recapitulate symptomatic HuNoV infection has been established. This model involves the oral gavage of three- or four-day-old (d.o.) WT BALB/c mice with high-concentrations of MNV resulting in a diarrheal phenotype. Current studies were undertaken to understand the ion transport basis of MNV diarrhea using this novel model. Methods: Three to four d.o. BALB/c pups were gavaged with either 1x10 8 plaque-forming units (PFU) of MNV-1 (CW3) or PBS alone followed by sacrifice at 48 hours-post-gavage (hpg). Small and large intestines were harvested for RNA and immunofluorescence (IF) analysis of multiple ion transporters that have been linked to diarrhea in other disease models. Results: MNV-gavaged pups had loose, orange stools, consistent with a diarrheal phenotype observed previously with this model. MNV RNA was detectable in small and large intestinal tissue for CW3-gavaged vs mock-gavaged pups (p-values &lt;0.05) demonstrating successful infection with MNV. MNV infection had no significant effect on transcript levels of various electrolyte and nutrient transporters including DRA, NHE3, PAT-1, Na-K-ATPase, or SGLT-1. However, we found significant increases in CFTR and Vasoactive intestinal peptide receptor 1 (VPAC1) transcripts (p &lt;0.05 and 0.01, respectively) and a significant increase in CFTR IF staining in frozen sections of the SI over mock (p&lt;0.01). We did not find a significant increase in VIP transcript, VPAC1 protein expression or immunofluorescent staining, nor nuclear localization of pCREB in SI frozen sections. Conclusion: Using this novel neonatal WT BALB/c MNV mouse model to evaluate the effect of infection on gene transcription, and protein expression and localization of ion transporters commonly implicated in diarrhea, we observed significant increases in CFTR and VPAC1 SI gene expression in CW3-gavaged pups with negligible changes in transcription of all other transporters examined in this study. In addition, apical and total CFTR staining increased significantly without changes in VPAC1 or pCREB nuclear localization in frozen SI sections of CW3-gavaged pups compared to mock, suggesting that MNV causes a CFTR-mediated secretory diarrhea in the absence of changes in VPAC1 protein expression, localization, or activation. These studies were supported by the Department of Veterans Affairs, Veterans Heath Administration, Office of Research and Development, Biomedical Laboratory Research and Development: Merit Review Award: BX002011 (PKD), and VA Senior Research Career Scientist Award:1IK6BX005242 (PKD). The studies were also supported by NIH/NIDDK grants, R01 DK54016 and DK92441 (PKD). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.