VIP and PACAP: neuropeptide modulators of CNS inflammation, injury, and repair

PACAP/VIP in the prefrontal cortex mediates the rapid antidepressant effects of zhizichi decoction

ETHNOPHARMACOLOGICAL RELEVANCE

Zhizichi decoction (ZZCD) is a traditional Chinese medicine formula that consists of Gardenia jasminoides J.Ellis (GJ) and Semen Sojae Praeparatum. It is used to treat insomnia and emotion-related disorders, such as irritability. Previous studies have found that GJ has a rapid antidepressant effect. The study found that ZZCD is safer than GJ at the same dosage. Consequently, ZZCD is a superior drug with quicker antidepressant effects than GJ. The rapid antidepressant effects of ZZCD were examined in this study, along with the components that make up this effect. It was determined that the activation of prefrontal Pituitary Adenylate Cyclase Activating Polypeptide (PACAP)/Vasoactive Intestinal Polypeptide (VIP) is essential for ZZCD's rapid antidepressant effects.

AIM

This study identified and discussed the rapid antidepressant effects and biological mechanisms of ZZCD.

MATERIALS AND METHODS

The tail suspension test (TST) and the forced swimming test (FST) were used to screen the effective dosage of ZZCD (0.67 g/kg, 1 g/kg, 4 g/kg). The effective dosage of ZZCD (1 g/kg) was tested in the TST conducted on Institute of Cancer Research (ICR) mice that were treated with lipopolysaccharide (LPS) at a concentration of 0.1 mg/mL. To confirm the expression of c-Fos, PACAP, and VIP in the prefrontal cortex (PFC), immunohistochemistry tests were conducted on mice following intragastric injection of ZZCD. Chemical characterization analysis and HPLC quality control analysis were conducted using UHPLC-Q-Obitrap-HRMS and chromatographic analysis.

RESULTS

The results showed that an acute administration of ZZCD (1 g/kg) decreased the immobility time of Kunming (KM) mice in TST and FST. Depressive behaviors in TST-induced ICR mice treated with LPS (0.1 mg/mL) were reversed by ZZCD (1 g/kg). The results of immunohistochemical experiments showed that ZZCD (1 g/kg) activated neurons in the PFC and PACAP/VIP in the PFC. In this study, 22 substances in ZZCD were identified. Five primary distinctive fingerprint peaks-geniposide, genistin, genipin-1-β-D-gentiobioside, glycitin, and daidzin-were found among the ten common peaks.

CONCLUSION

ZZCD (1 g/kg) had significant rapid antidepressant effects. PACAP/VIP in the PFC was found to mediate the rapid antidepressant effects of ZZCD.

Myeloid-derived β-hexosaminidase is essential for neuronal health and lysosome function: implications for Sandhoff disease

Lysosomal storage disorders (LSDs) are a large disease class involving lysosomal dysfunction, often resulting in neurodegeneration. Sandhoff disease (SD) is an LSD caused by a deficiency in the β subunit of the β-hexosaminidase enzyme ( Hexb ). Although Hexb expression in the brain is specific to microglia, SD primarily affects neurons. To understand how a microglial gene is involved in maintaining neuronal homeostasis, we demonstrated that β-hexosaminidase is secreted by microglia and integrated into the neuronal lysosomal compartment. To assess therapeutic relevance, we treated SD mice with bone marrow transplant and colony stimulating factor 1 receptor inhibition, which broadly replaced Hexb -/- microglia with Hexb -sufficient cells. This intervention reversed apoptotic gene signatures, improved behavior, restored enzymatic activity and Hexb expression, ameliorated substrate accumulation, and normalized neuronal lysosomal phenotypes. These results underscore the critical role of myeloid-derived β- hexosaminidase in neuronal lysosomal function and establish microglial replacement as a potential LSD therapy.

Effects of PACAP Deficiency on Immune Dysfunction and Peyer's Patch Integrity in Adult Mice

PACAP (pituitary adenylate cyclase activating polypeptide) is a widespread neuropeptide with cytoprotective and anti-inflammatory effects. It plays a role in innate and adaptive immunity, but data are limited about gut-associated lymphoid tissue. We aimed to reveal differences in Peyer's patches between wild-type (WT) and PACAP-deficient (KO) mice. Peyer's patch morphology from young (3-months-old) and aging (12-15-months-old) mice was examined, along with flow cytometry to assess immune cell populations, expression of checkpoint molecules (PD-1, PD-L1, TIM-3, Gal-9) and functional markers (CD69, granzyme B, perforin) in CD3+, CD4+, and CD8+ T cells. We found slight differences between aging, but not in young, WT, and KO mice. In WT mice, aging reduced CD8+ T cell numbers frequency and altered checkpoint molecule expression (higher TIM-3, granzyme B; lower Gal-9, CD69). CD4+ T cell frequency was higher with similar checkpoint alterations, indicating a regulatory shift. In PACAP KO mice, aging did not change cell population frequencies but led to higher TIM-3, granzyme B and lower PD-1, PD-L1, Gal-9, and CD69 expression in CD4+ and CD8+ T cells, with reduced overall T cell activity. Thus, PACAP deficiency impacts immune dysfunction by altering checkpoint molecules and T cell functionality, particularly in CD8+ T cells, suggesting complex immune responses by PACAP, highlighting its role in intestinal homeostasis and potential implications for inflammatory bowel diseases.

Research Progress on the Effects of Different Exercise Modes on the Secretion of Exerkines After Spinal Cord Injury

Exercise training is a conventional treatment strategy throughout the entire treatment process for patients with spinal cord injury (SCI). Currently, exercise modalities for SCI patients primarily include aerobic exercise, endurance training, strength training, high-intensity interval training, and mind-body exercises. These exercises play a positive role in enhancing skeletal muscle function, inducing neuroprotection and regeneration, thereby influencing neural plasticity, reducing limb spasticity, and improving motor function and daily living abilities in SCI patients. However, the mechanism by which exercise training promotes functional recovery after SCI is still unclear, and there is no consensus on a unified and standardized exercise treatment plan. Different exercise methods may bring different benefits. After SCI, patients' physical activity levels decrease significantly due to factors such as motor dysfunction, which may be a key factor affecting changes in exerkines. The changes in exerkines of SCI patients caused by exercise training are an important and highly relevant and visual evaluation index, which may provide a new research direction for revealing the intrinsic mechanism by which exercise promotes functional recovery after SCI. Therefore, this article summarizes the changes in the expression of common exerkines (neurotrophic factors, inflammatory factors, myokines, bioactive peptides) after SCI, and intends to analyze the impact and role of different exercise methods on functional recovery after SCI from the perspective of exerkines mechanism. We hope to provide theoretical basis and data support for scientific exercise treatment programs after SCI.

Giant pyramidal neurons of the primary motor cortex express vasoactive intestinal polypeptide (VIP), a known marker of cortical interneurons

Vasoactive intestinal polypeptide (VIP) is known to be present in a subclass of cortical interneurons. Here, using three different antibodies, we demonstrate that VIP is also present in the giant layer 5 pyramidal (Betz) neurons which are characteristic of the limb and axial representations of the marmoset primary motor cortex (cytoarchitectural area 4ab). No VIP staining was observed in smaller layer 5 pyramidal cells present in the primary motor facial representation (cytoarchitectural area 4c), or in the premotor cortex (e.g. the caudal subdivision of the dorsal premotor cortex, A6DC), indicating the selective expression of VIP in Betz cells. VIP in Betz cells was colocalized with neuronal specific marker (NeuN) and a calcium-binding protein parvalbumin (PV). PV also intensely labelled axon terminals surrounding Betz cell somata. VIP-positive interneurons were more abundant in the superficial cortical layers and constituted about 5-7% of total cortical neurons, with the highest density observed in area 4c. Our results demonstrate the expression of VIP in the largest excitatory neurons of the primate cortex, which may offer new functional insights into the role of VIP in the brain, and provide opportunities for genetic manipulation of Betz cells.

Targeting the PAC1 receptor mitigates degradation of myelin and synaptic markers and diminishes locomotor deficits in the cuprizone demyelination model

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system with a strong neuroinflammatory component. Current treatments principally target the immune system but fail to preserve long-term myelin health and do not prevent neurological decline. Studies over the past two decades have shown that the structurally related neuropeptides VIP and PACAP (vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide, respectively) exhibit pronounced anti-inflammatory activities and reduce clinical symptoms in MS disease models, largely via actions on their bivalent VIP receptor type 1 and 2. Here, using the cuprizone demyelination model, we demonstrate that PACAP and VIP, and strikingly the PACAP-selective receptor PAC1 agonist maxadilan, prevented locomotor deficits in the horizontal ladder and open field tests. Moreover, only PACAP and maxadilan were able to prevent myelin deterioration, as assessed by a reduction in the expression of the myelin markers proteolipid protein 1, oligodendrocyte transcription factor 2, quaking-7 (APC) and Luxol Fast Blue staining. Furthermore, PACAP and maxadilan (but not VIP), prevented striatal synaptic loss and diminished astrocyte and microglial activation in the corpus callosum of cuprizone-fed mice. In vitro, PACAP or maxadilan prevented lipopolysaccharide (LPS)-induced polarisation of primary astrocytes at 12-24 h, an effect that was not seen with maxadilan in LPS-stimulated microglia. Taken together, our data demonstrates for the first time that PAC1 agonists provide distinctive protective effects against white matter deterioration, neuroinflammation and consequent locomotor dysfunctions in the cuprizone model. The results indicate that targeting the PAC1 receptor may provide a path to treat myelin-related diseases in humans.

Increased Expression of the Neuropeptides PACAP/VIP in the Brain of Mice with CNS Targeted Production of IL-6 Is Mediated in Part by Trans-Signalling

Inflammation with expression of interleukin 6 (IL-6) in the central nervous system (CNS) occurs in several neurodegenerative/neuroinflammatory conditions and may cause neurochemical changes to endogenous neuroprotective systems. Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are two neuropeptides with well-established protective and anti-inflammatory properties. Yet, whether PACAP and VIP levels are altered in mice with CNS-restricted, astrocyte-targeted production of IL-6 (GFAP-IL6) remains unknown. In this study, PACAP/VIP levels were assessed in the brain of GFAP-IL6 mice. In addition, we utilised bi-genic GFAP-IL6 mice carrying the human sgp130-Fc transgene (termed GFAP-IL6/sgp130Fc mice) to determine whether trans-signalling inhibition rescued PACAP/VIP changes in the CNS. Transcripts and protein levels of PACAP and VIP, as well as their receptors PAC1, VPAC1 and VPAC2, were significantly increased in the cerebrum and cerebellum of GFAP-IL6 mice vs. wild type (WT) littermates. These results were paralleled by a robust activation of the JAK/STAT3, NF-κB and ERK1/2MAPK pathways in GFAP-IL6 mice. In contrast, co-expression of sgp130Fc in GFAP-IL6/sgp130Fc mice reduced VIP expression and activation of STAT3 and NF-κB pathways, but it failed to rescue PACAP, PACAP/VIP receptors and Erk1/2MAPK phosphorylation. We conclude that forced expression of IL-6 in astrocytes induces the activation of the PACAP/VIP neuropeptide system in the brain, which is only partly modulated upon IL-6 trans-signalling inhibition. Increased expression of PACAP/VIP neuropeptides and receptors may represent a homeostatic response of the CNS to an uncontrolled IL-6 synthesis and its neuroinflammatory consequences.

Differential Expression of PACAP/VIP Receptors in the Post-Mortem CNS White Matter of Multiple Sclerosis Donors

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two neuroprotective and anti-inflammatory molecules of the central nervous system (CNS). Both bind to three G protein-coupled receptors, namely PAC1, VPAC1 and VPAC2, to elicit their beneficial effects in various CNS diseases, including multiple sclerosis (MS). In this study, we assessed the expression and distribution of PACAP/VIP receptors in the normal-appearing white matter (NAWM) of MS donors with a clinical history of either relapsing-remitting MS (RRMS), primary MS (PPMS), secondary progressive MS (SPMS) or in aged-matched non-MS controls. Gene expression studies revealed MS-subtype specific changes in PACAP and VIP and in the receptors' levels in the NAWM, which were partly corroborated by immunohistochemical analyses. Most PAC1 immunoreactivity was restricted to myelin-producing cells, whereas VPAC1 reactivity was diffused within the neuropil and in axonal bundles, and VPAC2 in small vessel walls. Within and around lesioned areas, glial cells were the predominant populations showing reactivity for the different PACAP/VIP receptors, with distinctive patterns across MS subtypes. Together, these data identify the differential expression patterns of PACAP/VIP receptors among the different MS clinical entities. These results may offer opportunities for the development of personalized therapeutic approaches to treating MS and/or other demyelinating disorders.

Pleural mesothelioma from fluoro-edenite exposure: PACAP and PAC1 receptor. A preliminary report

Pleural mesothelioma is a devastating malignancy primarily associated with asbestos exposure. However, emerging evidence suggests that exposure to fluoro-edenite fibers, a naturally occurring mineral fiber, can also lead to the development of pleural mesothelioma. In this study, based on the hypothesis that pituitary adenylate cyclase-activating polypeptide (PACAP) and PACAP-preferring receptor (PAC1R) expressions could be dysregulated in pleural mesothelioma samples and that they could potentially act as diagnostic or prognostic biomarkers, we aimed to investigate the immunohistochemical expression of PACAP and PAC1R in pleural biopsies from patients with pleural mesothelioma exposed to fluoro-edenite fibers. A total of 12 patients were included in this study, and their biopsies were processed for immunohistochemical analysis to evaluate the expression of PACAP and its receptor. The study revealed a correlation between the overexpression of PACAP and PAC1R and shorter overall survival in patients with malignant mesothelioma. These findings suggest that PACAP and PAC1R expression levels could serve as potential prognostic biomarkers for malignant mesothelioma. Furthermore, the immunohistochemical analysis of PACAP and PAC1R may provide valuable information for clinicians to guide therapeutic decisions and identify patients with poorer prognosis.

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.

α-Synuclein oligomers potentiate neuroinflammatory NF-κB activity and induce Cav3.2 calcium signaling in astrocytes

BACKGROUND

It is now realized that Parkinson's disease (PD) pathology extends beyond the substantia nigra, affecting both central and peripheral nervous systems, and exhibits a variety of non-motor symptoms often preceding motor features. Neuroinflammation induced by activated microglia and astrocytes is thought to underlie these manifestations. α-Synuclein aggregation has been linked with sustained neuroinflammation in PD, aggravating neuronal degeneration; however, there is still a lack of critical information about the structural identity of the α-synuclein conformers that activate microglia and/or astrocytes and the molecular pathways involved.

METHODS

To investigate the role of α-synuclein conformers in the development and maintenance of neuroinflammation, we used primary quiescent microglia and astrocytes, post-mortem brain tissues from PD patients and A53T α-synuclein transgenic mice that recapitulate key features of PD-related inflammatory responses in the absence of cell death, i.e., increased levels of pro-inflammatory cytokines and complement proteins. Biochemical and -omics techniques including RNAseq and secretomic analyses, combined with 3D reconstruction of individual astrocytes and live calcium imaging, were used to uncover the molecular mechanisms underlying glial responses in the presence of α-synuclein oligomers in vivo and in vitro.

RESULTS

We found that the presence of SDS-resistant hyper-phosphorylated α-synuclein oligomers, but not monomers, was correlated with sustained inflammatory responses, such as elevated levels of endogenous antibodies and cytokines and microglial activation. Similar oligomeric α-synuclein species were found in post-mortem human brain samples of PD patients but not control individuals. Detailed analysis revealed a decrease in Iba1Low/CD68Low microglia and robust alterations in astrocyte number and morphology including process retraction. Our data indicated an activation of the p38/ATF2 signaling pathway mostly in microglia and a sustained induction of the NF-κB pathway in astrocytes of A53T mice. The sustained NF-κB activity triggered the upregulation of astrocytic T-type Cav3.2 Ca2+ channels, altering the astrocytic secretome and promoting the secretion of IGFBPL1, an IGF-1 binding protein with anti-inflammatory and neuroprotective potential.

CONCLUSIONS

Our work supports a causative link between the neuron-produced α-synuclein oligomers and sustained neuroinflammation in vivo and maps the signaling pathways that are stimulated in microglia and astrocytes. It also highlights the recruitment of astrocytic Cav3.2 channels as a potential neuroprotective mediator against the α-synuclein-induced neuroinflammation.

Nesfatin-1: A Biomarker and Potential Therapeutic Target in Neurological Disorders

Nesfatin-1 is a novel adipocytokine consisting of 82 amino acids with anorexic and anti-hyperglycemic properties. Further studies of nesfatin-1 have shown it to be closely associated with neurological disorders. Changes in nesfatin-1 levels are closely linked to the onset, progression and severity of neurological disorders. Nesfatin-1 may affect the development of neurological disorders and can indicate disease evolution and prognosis, thus informing the choice of treatment options. In addition, regulation of the expression or level of nesfatin-1 can improve the level of neuroinflammation, apoptosis, oxidative damage and other indicators. It is demonstrated that nesfatin-1 is involved in neuroprotection and may be a therapeutic target for neurological disorders. In this paper, we will also discuss the role of nesfatin-1 as a biomarker in neurological diseases and its potential mechanism of action in neurological diseases, providing new ideas for the diagnosis and treatment of neurological diseases.

The effect of PACAP administration on LPS-induced cytokine expression in the Atlantic salmon SHK-1 cell line

Recent work has identified pituitary adenylate cyclase activating polypeptide (PACAP) as a potential antimicrobial and immune stimulating agent which may be suitable for use in aquaculture. However, its effects on teleost immunity are not well studied and may be significantly different than what has been observed in mammals. In this study we examined the effects of PACAP on the Atlantic salmon macrophage cell line SHK-1. PACAP was able to increase the expression of LPS-induced il-1β in at concentrations of 1 uM when administered 24h prior to LPS stimulation. Furthermore, concentrations as low as 40nM had an effect when administered both 24h prior and in tandem with LPS. PACAP was also capable of increasing the expression of il-1β and tnf-α in SHK-1 cells challenged with a low dose of heat-killed Flavobacterium columnare. We attempted to get a better understanding of the mechanism underlying this enhancement of il-1β expression by manipulating downstream signaling of PACAP with inhibitors of phosphodiesterase and phospholipase C activity. We found that inducing cAMP accumulation with phosphodiesterase inhibitors failed to recapitulate the effect of PACAP administration on LPS-mediated il-1β expression by PACAP, while use of a phospholipase C inhibitor caused a PACAP-like enhancement in LPS-mediated il-1β expression. Interestingly, the VPAC1 receptor inhibitor PG97-269, but not the PAC1 inhibitor max.d.4, also was capable of causing a PACAP-like enhancement in LPS-mediated il-1β expression. This suggests that fish do not utilize the PACAP receptors in the same manner as mammals, but that it still exerts an immunostimulatory effect that make it a good immunostimulant for use in aquaculture.

Trigeminal nerve stimulation: a current state-of-the-art review

Nearly 5 decades ago, the effect of trigeminal nerve stimulation (TNS) on cerebral blood flow was observed for the first time. This implication directly led to further investigations and TNS' success as a therapeutic intervention. Possessing unique connections with key brain and brainstem regions, TNS has been observed to modulate cerebral vasodilation, brain metabolism, cerebral autoregulation, cerebral and systemic inflammation, and the autonomic nervous system. The unique range of effects make it a prime therapeutic modality and have led to its clinical usage in chronic conditions such as migraine, prolonged disorders of consciousness, and depression. This review aims to present a comprehensive overview of TNS research and its broader therapeutic potentialities. For the purpose of this review, PubMed and Google Scholar were searched from inception to August 28, 2023 to identify a total of 89 relevant studies, both clinical and pre-clinical. TNS harnesses the release of vasoactive neuropeptides, modulation of neurotransmission, and direct action upon the autonomic nervous system to generate a suite of powerful multitarget therapeutic effects. While TNS has been applied clinically to chronic pathological conditions, these powerful effects have recently shown great potential in a number of acute/traumatic pathologies. However, there are still key mechanistic and methodologic knowledge gaps to be solved to make TNS a viable therapeutic option in wider clinical settings. These include bimodal or paradoxical effects and mechanisms, questions regarding its safety in acute/traumatic conditions, the development of more selective stimulation methods to avoid potential maladaptive effects, and its connection to the diving reflex, a trigeminally-mediated protective endogenous reflex. The address of these questions could overcome the current limitations and allow TNS to be applied therapeutically to an innumerable number of pathologies, such that it now stands at the precipice of becoming a ground-breaking therapeutic modality.

Immunomodulatory role of vasoactive intestinal peptide and ghrelin in Oncorhynchus mykiss

Neuropeptides are a group of peptides derived from precursor proteins synthesized in neuronal and nonneuronal cells. The classical functions of neuropeptides have been extensively studied in mammals, including neuromodulation in the central nervous system, molecular signaling in the peripheral nervous system, and immunomodulation associated mainly with anti-inflammatory activity. In contrast, in teleosts, studies of the immunomodulatory function of these neuropeptides are limited. In Oncorhynchus mykiss, vasoactive intestinal peptide (VIP) mRNA sequences have not been cloned, and the role of VIP in modulating the immune system has not been studied. Furthermore, in relation to other neuropeptides with possible immunomodulatory function, such as ghrelin, there are also few studies. Therefore, in this work, we performed molecular cloning, identification, and phylogenetic analysis of three VIP precursor sequences (prepro-VIP1, VIP2 and VIP3) in rainbow trout. In addition, the immunomodulatory function of both neuropeptides was evaluated in an in vitro model using the VIP1 sequence identified in this work and a ghrelin sequence already studied in O. mykiss. The results suggest that the prepro-VIP2 sequence has the lowest percentage of identity with respect to the other homologous sequences and is more closely related to mammalian orthologous sequences. VIP1 induces significant expression of both pro-inflammatory (IFN-γ, IL-1β) and anti-inflammatory (IL-10 and TGF-β) cytokines, whereas ghrelin only induces significant expression of proinflammatory cytokines such as IL-6 and TNF-α.

From CGRP to PACAP, VIP, and Beyond: Unraveling the Next Chapters in Migraine Treatment

Migraine is a neurovascular disorder that can be debilitating for individuals and society. Current research focuses on finding effective analgesics and management strategies for migraines by targeting specific receptors and neuropeptides. Nonetheless, newly approved calcitonin gene-related peptide (CGRP) monoclonal antibodies (mAbs) have a 50% responder rate ranging from 27 to 71.0%, whereas CGRP receptor inhibitors have a 50% responder rate ranging from 56 to 71%. To address the need for novel therapeutic targets, researchers are exploring the potential of another secretin family peptide, pituitary adenylate cyclase-activating polypeptide (PACAP), as a ground-breaking treatment avenue for migraine. Preclinical models have revealed how PACAP affects the trigeminal system, which is implicated in headache disorders. Clinical studies have demonstrated the significance of PACAP in migraine pathophysiology; however, a few clinical trials remain inconclusive: the pituitary adenylate cyclase-activating peptide 1 receptor mAb, AMG 301 showed no benefit for migraine prevention, while the PACAP ligand mAb, Lu AG09222 significantly reduced the number of monthly migraine days over placebo in a phase 2 clinical trial. Meanwhile, another secretin family peptide vasoactive intestinal peptide (VIP) is gaining interest as a potential new target. In light of recent advances in PACAP research, we emphasize the potential of PACAP as a promising target for migraine treatment, highlighting the significance of exploring PACAP as a member of the antimigraine armamentarium, especially for patients who do not respond to or contraindicated to anti-CGRP therapies. By updating our knowledge of PACAP and its unique contribution to migraine pathophysiology, we can pave the way for reinforcing PACAP and other secretin peptides, including VIP, as a novel treatment option for migraines.

Potential Crosstalk between the PACAP/VIP Neuropeptide System and Endoplasmic Reticulum Stress-Relevance to Multiple Sclerosis Pathophysiology

Multiple sclerosis (MS) is an immune-mediated disorder characterized by focal demyelination and chronic inflammation of the central nervous system (CNS). Although the exact etiology is unclear, mounting evidence indicates that endoplasmic reticulum (ER) stress represents a key event in disease pathogenesis. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related neuropeptides that are abundant in the CNS and are known to exert neuroprotective and immune modulatory roles. Activation of this endogenous neuropeptide system may interfere with ER stress processes to promote glial cell survival and myelin self-repair. However, the potential crosstalk between the PACAP/VIP system and ER stress remains elusive. In this review, we aim to discuss how these peptides ameliorate ER stress in the CNS, with a focus on MS pathology. Our goal is to emphasize the importance of this potential interaction to aid in the identification of novel therapeutic targets for the treatment of MS and other demyelinating disorders.

The Eph/ephrin system symphony of gut inflammation

The extent of gut inflammation depends largely on the gut barrier's integrity and enteric neuroimmune interactions. However, the factors and molecular mechanisms that regulate inflammation-related changes in the enteric nervous system (ENS) remain largely unexplored. Eph/ephrin signaling is critical for inflammatory response, neuronal activation, and synaptic plasticity in the brain, but its presence and function in the ENS have been largely unknown to date. This review discusses the critical role of Eph/ephrin in regulating gut homeostasis, inflammation, neuroimmune interactions, and pain pathways. Targeting the Eph/ephrin system offers innovative treatments for gut inflammation disorders, offering hope for enhanced patient prognosis, pain management, and overall quality of life.

Early Alterations of PACAP and VIP Expression in the Female Rat Brain Following Spinal Cord Injury

Previous evidence shows that rapid changes occur in the brain following spinal cord injury (SCI). Here, we interrogated the expression of the neuropeptides pituitary adenylyl cyclase-activating peptide (PACAP), vasoactive intestinal peptides (VIP), and their binding receptors in the rat brain 24 h following SCI. Female Sprague-Dawley rats underwent thoracic laminectomy; half of the rats received a mild contusion injury at the level of the T10 vertebrate (SCI group); the other half underwent sham surgery (sham group). Twenty-four hours post-surgery, the hypothalamus, thalamus, amygdala, hippocampus (dorsal and ventral), prefrontal cortex, and periaqueductal gray were collected. PACAP, VIP, PAC1, VPAC1, and VPAC2 mRNA and protein levels were measured by real-time quantitative polymerase chain reaction and Western blot. In SCI rats, PACAP expression was increased in the hypothalamus (104-141% vs sham) and amygdala (138-350%), but downregulated in the thalamus (35-95%) and periaqueductal gray (58-68%). VIP expression was increased only in the thalamus (175-385%), with a reduction in the amygdala (51-68%), hippocampus (40-75%), and periaqueductal gray (74-76%). The expression of the PAC1 receptor was the least disturbed by SCI, with decrease expression in the ventral hippocampus (63-68%) only. The expression levels of VPAC1 and VPAC2 receptors were globally reduced, with more prominent reductions of VPAC1 vs VPAC2 in the amygdala (21-70%) and ventral hippocampus (72-75%). In addition, VPAC1 downregulation also extended to the dorsal hippocampus (69-70%). These findings demonstrate that as early as 24 h post-SCI, there are region-specific disruptions of PACAP, VIP, and related receptor transcript and protein levels in supraspinal regions controlling higher cognitive functions.

The discovery of the new mechanism: Celastrol improves spinal cord injury by increasing cAMP through VIP-ADCYAP1R1-GNAS pathway

Spinal cord injury (SCI) is a debilitating condition that results in significant impairment of motor function and sensation. Despite the ongoing efforts to develop effective treatments, there are currently very limited options available for patients with SCI. Celastrol, a natural anti-inflammatory compound extracted from Tripterygium wilfordii, has been shown to exhibit anti-inflammatory and anti-apoptotic properties. In this study, we aimed to explore the therapeutic potential of celastrol for SCI and elucidate the underlying molecular mechanisms involved. We found that local tissue often experiences a significant decrease in cAMP content and occurrs apoptosis after SCI. However, the treatment of celastrol could promote the production of cAMP by up-regulating the VIP-ADCYAP1R1-GNAS pathway. This could effectively inhibit the phosphorylation of JNK and prevent apoptosis, ultimately improving the exercise ability after SCI. Together, our results reveal celastrol may be a promising therapeutic agent for the treatment of SCI.

PACAP and VIP Neuropeptides' and Receptors' Effects on Appetite, Satiety and Metabolism

The overwhelming increase in the prevalence of obesity and related disorders in recent years is one of the greatest threats to the global healthcare system since it generates immense healthcare costs. As the prevalence of obesity approaches epidemic proportions, the importance of elucidating the mechanisms regulating appetite, satiety, body metabolism, energy balance and adiposity has garnered significant attention. Currently, gastrointestinal (GI) bariatric surgery remains the only approach capable of achieving successful weight loss. Appetite, satiety, feeding behavior, energy intake and expenditure are regulated by central and peripheral neurohormonal mechanisms that have not been fully elucidated yet. Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and Vasoactive Intestinal Polypeptide (VIP) are members of a family of regulatory peptides that are widely distributed in parallel with their specific receptors, VPAC1R, VPAC2R and PAC1R, in the central nervous system (CNS) and in the periphery, such as in the gastrointestinal tract and its associated organs and immune cells. PACAP and VIP have been reported to play an important role in the regulation of body phenotype, metabolism and homeostatic functions. The purpose of this review is to present recent data on the effects of PACAP, VIP, VPAC1R, VPAC2R and PAC1R on the modulation of appetite, satiety, metabolism, calorie intake and fat accumulation, to evaluate their potential use as therapeutic targets for the treatment of obesity and metabolic syndrome.

Retinal vessels as a window on amyotrophic lateral sclerosis pathophysiology: A systematic review

Amyotrophic lateral sclerosis (ALS) is a rare fatal motor neuron disease. Although many potential mechanisms have been proposed, the pathophysiology of the disease remains unknown. Currently available treatments can only delay the progression of the disease and prolong life expectancy by a few months. There is still no definitive cure for ALS, and the development of new treatments is limited by a lack of understanding of the underlying biological processes that trigger and promote neurodegeneration. Several scientific results suggest a neurovascular impairment in ALS providing perspectives for the development of new biomarkers and treatments. In this article, we performed a systematic review using PRISMA guidelines including PubMed, EmBase, GoogleScholar, and Web of Science Core Collection to analyze the scientific literature published between 2000 and 2021 discussing the neurocardiovascular involvement and ophthalmologic abnormalities in ALS. In total, 122 articles were included to establish this systematic review. Indeed, microvascular pathology seems to be involved in ALS, affecting all the neurovascular unit components. Retinal changes have also been recently highlighted without significant alteration of the visual pathways. Despite the peripheral location of the retina, it is considered as an extension of the central nervous system (CNS) as it displays similarities to the brain, the inner blood-retinal barrier, and the blood-brain barrier. This suggests that the eye could be considered as a 'window' into the brain in many CNS disorders. Thus, studying ocular manifestations of brain pathologies seems very promising in understanding neurodegenerative disorders, mainly ALS. Optical coherence tomography angiography (OCT-A) could therefore be a powerful approach for exploration of retinal microvascularization allowing to obtain new diagnostic and prognostic biomarkers of ALS.

Central Facial Nervous System Biomolecules Involved in Peripheral Facial Nerve Injury Responses and Potential Therapeutic Strategies

Peripheral facial nerve injury leads to changes in the expression of various neuroactive substances that affect nerve cell damage, survival, growth, and regeneration. In the case of peripheral facial nerve damage, the injury directly affects the peripheral nerves and induces changes in the central nervous system (CNS) through various factors, but the substances involved in these changes in the CNS are not well understood. The objective of this review is to investigate the biomolecules involved in peripheral facial nerve damage so as to gain insight into the mechanisms and limitations of targeting the CNS after such damage and identify potential facial nerve treatment strategies. To this end, we searched PubMed using keywords and exclusion criteria and selected 29 eligible experimental studies. Our analysis summarizes basic experimental studies on changes in the CNS following peripheral facial nerve damage, focusing on biomolecules that increase or decrease in the CNS and/or those involved in the damage, and reviews various approaches for treating facial nerve injury. By establishing the biomolecules in the CNS that change after peripheral nerve damage, we can expect to identify factors that play an important role in functional recovery from facial nerve damage. Accordingly, this review could represent a significant step toward developing treatment strategies for peripheral facial palsy.

Control of myeloid cell functions by nociceptors

The immune system has evolved to protect the host from infectious agents, parasites, and tumor growth, and to ensure the maintenance of homeostasis. Similarly, the primary function of the somatosensory branch of the peripheral nervous system is to collect and interpret sensory information about the environment, allowing the organism to react to or avoid situations that could otherwise have deleterious effects. Consequently, a teleological argument can be made that it is of advantage for the two systems to cooperate and form an “integrated defense system” that benefits from the unique strengths of both subsystems. Indeed, nociceptors, sensory neurons that detect noxious stimuli and elicit the sensation of pain or itch, exhibit potent immunomodulatory capabilities. Depending on the context and the cellular identity of their communication partners, nociceptors can play both pro- or anti-inflammatory roles, promote tissue repair or aggravate inflammatory damage, improve resistance to pathogens or impair their clearance. In light of such variability, it is not surprising that the full extent of interactions between nociceptors and the immune system remains to be established. Nonetheless, the field of peripheral neuroimmunology is advancing at a rapid pace, and general rules that appear to govern the outcomes of such neuroimmune interactions are beginning to emerge. Thus, in this review, we summarize our current understanding of the interaction between nociceptors and, specifically, the myeloid cells of the innate immune system, while pointing out some of the outstanding questions and unresolved controversies in the field. We focus on such interactions within the densely innervated barrier tissues, which can serve as points of entry for infectious agents and, where known, highlight the molecular mechanisms underlying these interactions.

Vasoactive intestinal peptide deficiency promotes ovarian dysfunction associated to a proinflammatory microenvironment reminiscent of premature aging

Complex immune regulation during pregnancy is required to ensure a successful pregnancy outcome. Vasoactive intestinal peptide (VIP) has local immunoregulatory effects on the ovary, uterus and maternal-fetal interface that favor a tolerogenic maternal microenvironment. Since the VIP Knockout (KO) mice are subfertile, we investigated the mechanisms underlying the effects of VIP deficiency on ovarian physiology and immune homeostasis. Therefore, we studied VIP KO, deficient (HT) and wild type (WT) female mice in estrus at 3 or 8 months of age. Young KO mice showed abnormal cycle timing and regularity associated with dysfunctional ovaries. Ovaries presented higher number of atretic follicles and reduced number of corpora lutea leading to a lower ovulation rates. Part of the VIP KO mice (25 %) failed to ovulate or ovulated oocytes incompetent to be fertilized (50 %). In particular, ovaries of young KO mice exhibited features of premature aging accompanied by a pro-inflammatory milieu with increased levels of IL-1β. A unique macrophage subpopulation identified as "foamy macrophages" was found. On the other hand, aged VIP KO females did not gain body weight probably due to the sustained production of E2. Finally, the adoptive transfer of FOXP3+ cells to infertile VIP KO females resulted in their selective recruitment to the ovary. It increased FOXP3/RORγt and TGFβ/IL-6 ratio improving ovarian microenvironment and pregnancy rate. The present results suggest that VIP contributes to ovarian homeostatic mechanisms required for a successful pregnancy.

VPAC1 and VPAC2 receptor deficiencies negatively influence pregnancy outcome through distinct and overlapping modulations of immune, trophoblast and vascular functions

Pregnancy outcome relies on the maintenance of immune and metabolic homeostasis at the maternal fetal interface. Maternal and perinatal morbidity and mortality is associated with impaired placental development. Multiple regulatory effects of the endogenous-produced vasoactive intestinal peptide (VIP) on vascular, metabolic and immune functions at the maternal-fetal interface have been reported. Here we studied the involvement of the two primary high affinity receptors for VIP (VPAC1 and VPAC2) on maternal immune response, placental homeostasis and pregnancy outcome. Targeted disruption of each receptor gene led to altered placental structure, vascular and trophoblast functional markers and shaped the functional profiles of macrophages and neutrophils towards a proinflammatory state. Several changes in pregnant mice were receptor specific: ROS production elicited by VIP on neutrophils was selectively dependent on the presence of VPAC1 whereas apoptosis rate was associated with the VPAC2 deletion. In peritoneal macrophages from pregnant mice, levels of MHC-II, TLR2, and IL-10 were selectively altered in VPAC2 receptor-deficient mice, whereas IL-6 gene expression was reduced only in mice lacking VPAC1 receptors. Additionally, MMP9 mRNA in isolated TGCs was reduced in VPAC2 receptor deleted mice, while the percentage of IL-12 cells in post-phagocytosis macrophage cultures was selectively reduced in VPAC2 receptor deficient mice. The results indicate that manipulation of VPAC1 and VPAC2 receptor affects immune, vascular and metabolic environment at the maternal fetal interface. These mouse models offer new approaches to study pregnancy complications adding new perspectives to the development of VPAC receptor-selective drugs.

Tunable Surface Charge Enables the Electrostatic Adsorption-Controlled Release of Neuroprotective Peptides from a Hydrogel-Nanoparticle Drug Delivery System

We exploit the electrostatic interactions between the positively charged neuroprotective peptide, pituitary adenylate cyclase-activating polypeptide (PACAP), and negatively charged poly(lactic-co-glycolic acid) (PLGA) nanoparticles to control PACAP release from the surface of nanoparticles dispersed in a hyaluronan-methylcellulose (HAMC) hydrogel composite. PACAP is a promising therapeutic for the treatment of neurological disorders, yet it has been difficult to deliver in vivo. Herein, the PACAP release rate was tuned by manipulating peptide adsorption onto the surface of blank nanoparticles by modifying either nanoparticle loading in the hydrogel or nanoparticle surface charge. This peptide-nanoparticle interaction was controlled by the pH-responsive carboxylic acid end terminal groups of PLGA. We further validated this system with the controlled release of a novel stabilized PACAP analog: Ac-[Ala¹⁵, Ala²⁰]PACAP-propylamide, which masks its recognition to peptidases in circulation. Both wild-type and stabilized PACAP released from the vehicle increased the production of neuroprotective Interleukin-6 from cultured primary astrocytes. Using computational fluid dynamics methods, PACAP release from the composite was predicted based on experimentally derived adsorption isotherms, which exhibited similar release profiles to experimental data. This versatile adsorption-based system was used to deliver PACAP locally to the brains of stroke-injured mice over a 10 day period in vivo, highlighting its effectiveness for the controlled release of PACAP to the central nervous system.

The neuropeptide PACAP alleviates T. gondii infection-induced neuroinflammation and neuronal impairment

Background

Cerebral infection with the protozoan Toxoplasma gondii (T. gondii) is responsible for inflammation of the central nervous system (CNS) contributing to subtle neuronal alterations. Albeit essential for brain parasite control, continuous microglia activation and recruitment of peripheral immune cells entail distinct neuronal impairment upon infection-induced neuroinflammation. PACAP is an endogenous neuropeptide known to inhibit inflammation and promote neuronal survival. Since PACAP is actively transported into the CNS, we aimed to assess the impact of PACAP on the T. gondii-induced neuroinflammation and subsequent effects on neuronal homeostasis.

Methods

Exogenous PACAP was administered intraperitoneally in the chronic stage of T. gondii infection, and brains were isolated for histopathological analysis and determination of pathogen levels. Immune cells from the brain, blood, and spleen were analyzed by flow cytometry, and the further production of inflammatory mediators was investigated by intracellular protein staining as well as expression levels by RT-qPCR. Neuronal and synaptic alterations were assessed on the transcriptional and protein level, focusing on neurotrophins, neurotrophin-receptors and signature synaptic markers.

Results

Here, we reveal that PACAP administration reduced the inflammatory foci and the number of apoptotic cells in the brain parenchyma and restrained the activation of microglia and recruitment of monocytes. The neuropeptide reduced the expression of inflammatory mediators such as IFN-γ, IL-6, iNOS, and IL-1β. Moreover, PACAP diminished IFN-γ production by recruited CD4⁺ T cells in the CNS. Importantly, PACAP promoted neuronal health via increased expression of the neurotrophin BDNF and reduction of p75^NTR, a receptor related to neuronal cell death. In addition, PACAP administration was associated with increased expression of transporters involved in glutamatergic and GABAergic signaling that are particularly affected during cerebral toxoplasmosis.

Conclusions

Together, our findings unravel the beneficial effects of exogenous PACAP treatment upon infection-induced neuroinflammation, highlighting the potential implication of neuropeptides to promote neuronal survival and minimize synaptic prejudice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02639-z.

PACAP and VIP Mitigate Rotenone-Induced Inflammation in BV-2 Microglial Cells

Rotenone is a commercial pesticide commonly used to model Parkinson's disease (PD) due to its ability to induce dopaminergic degeneration. Studies have confirmed that rotenone causes microglial activation, which seems to contribute to the toxic effects seen in rodent models. Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related neuropeptides that have robust neuroprotective and anti-inflammatory properties. However, their ability to regulate microglial activity in response to rotenone is not fully understood. Using rotenone as an inflammatory stimulus, we tested whether PACAP or VIP could mitigate microglial activation in BV2 microglial cells. Rotenone dose-dependently reduced cell viability and the percentage of apoptotic cells. It also increased the release of nitric oxide (NO) in culture media and the expression of microglial activation markers and pro-inflammatory markers, including CD11b, MMP-9 and IL-6, and heightened the endogenous levels of PACAP and its preferring receptor PAC1. Co-treatment with PACAP or VIP prevented rotenone-induced increase of NO, CD11b, MMP-9 and IL-6. These results indicate that both PACAP and VIP are able to prevent the pro-inflammatory effects of rotenone in BV2 cells, supporting the idea that these molecules can have therapeutic value in slowing down PD progression.

Symptomatic and asymptomatic domoic acid exposure in zebrafish (Danio rerio) revealed distinct non-overlapping gene expression patterns in the brain

Domoic acid (DA) is a naturally produced neurotoxin synthesized by marine diatoms in the genus Pseudo-nitzschia. DA accumulates in filter-feeders such as shellfish, and can cause severe neurotoxicity when contaminated seafood is ingested, resulting in Amnesic Shellfish Poisoning (ASP) in humans. Overt clinical signs of neurotoxicity include seizures and disorientation. ASP is a significant public health concern, and though seafood regulations have effectively minimized the human risk of severe acute DA poisoning, the effects of exposure at asymptomatic levels are poorly understood. The objective of this study was to determine the effects of exposure to symptomatic and asymptomatic doses of DA on gene expression patterns in the zebrafish brain. We exposed adult zebrafish to either a symptomatic (1.1 ± 0.2 μg DA/g fish) or an asymptomatic (0.31 ± 0.03 µg DA/g fish) dose of DA by intracelomic injection and sampled at 24, 48 and 168 h post-injection. Transcriptional profiling was done using Agilent and Affymetrix microarrays. Our analysis revealed distinct, non-overlapping changes in gene expression between the two doses. We found that the majority of transcriptional changes were observed at 24 h post-injection with both doses. Interestingly, asymptomatic exposure produced more persistent transcriptional effects - in response to symptomatic dose exposure, we observed only one differentially expressed gene one week after exposure, compared to 26 in the asymptomatic dose at the same time (FDR <0.05). GO term analysis revealed that symptomatic DA exposure affected genes associated with peptidyl proline modification and retinoic acid metabolism. Asymptomatic exposure caused differential expression of genes that were associated with GO terms including circadian rhythms and visual system, and also the neuroactive ligand-receptor signaling KEGG pathway. Overall, these results suggest that transcriptional responses are specific to the DA dose and that asymptomatic exposure can cause long-term changes. Further studies are needed to characterize the potential downstream neurobehavioral impacts of DA exposure.

Neuroprotective Effects of gH625-lipoPACAP in an In Vitro Fluid Dynamic Model of Parkinson’s Disease

Parkinson’s disease (PD) is an aggressive and devastating age-related disorder. Although the causes are still unclear, several factors, including genetic and environmental, are involved. Except for symptomatic drugs, there are not, to date, any real cures for PD. For this purpose, it is necessary develop a model to better study this disease. Neuroblastoma cell line, SH-SY5Y, differentiated with retinoic acid represents a good in vitro model to explore PD, since it maintains growth cells to differentiated neurons. In the present study, SH-SY5Y cells were treated with 1-methyl-4-phenylpyridinium (MPP⁺), a neurotoxin that induces Parkinsonism, and the neuroprotective effects of pituitary adenylate cyclase-activating polypeptide (PACAP), delivered by functionalized liposomes in a blood–brain barrier fluid dynamic model, were evaluated. We demonstrated PACAP neuroprotective effects when delivered by gH625-liposome on MPP⁺-damaged SH-SY5Y spheroids.

Vasoactive intestinal peptide–VIPR2 signaling regulates tumor cell migration

Phosphoinositide metabolism is critically involved in human cancer cell migration and metastatic growth. The formation of lamellipodia at the leading edge of migrating cells is regulated by metabolism of the inositol phospholipid PI(4,5)P₂ into PI(3,4,5)P₃. The synthesized PI(3,4,5)P₃ promotes the translocation of WASP family verprolin homologous protein 2 (WAVE2) to the plasma membrane and regulates guanine nucleotide exchange factor Rac-mediated actin filament remodeling. Here, we investigated if VIPR2, a receptor for vasoactive intestinal peptide (VIP), has a potential role in regulating cell migration via this pathway. We found that silencing of VIPR2 in MDA-MB-231 and MCF-7 human breast cancer cells inhibited VIP-induced cell migration. In contrast, stable expression of exogenous VIPR2 promoted VIP-induced tumor cell migration, an effect that was inhibited by the addition of a PI3-kinase (PI3K)γ inhibitor or a VIPR2-selective antagonist. VIPR2 stably-expressing cells exhibited increased PI3K activity. Membrane localization of PI(3,4,5)P₃ was significantly attenuated by VIPR2-silencing. VIPR2-silencing in MDA-MB-231 cells suppressed lamellipodium extension; in VIPR2-overexpressing cells, VIPR2 accumulated in the cell membrane on lamellipodia and co-localized with WAVE2. Conversely, VIPR2-silencing reduced WAVE2 level on the cell membrane and inhibited the interaction between WAVE2, actin-related protein 3, and actin. These findings suggest that VIP–VIPR2 signaling controls cancer migration by regulating WAVE2-mediated actin nucleation and elongation for lamellipodium formation through the synthesis of PI(3,4,5)P₃.

Neuropeptides in Cancer: Friend and Foe?

Neuropeptides are small regulatory molecules found throughout the body, most notably in the nervous, cardiovascular, and gastrointestinal systems. They serve as neurotransmitters or hormones in the regulation of diverse physiological processes. Cancer cells escape normal growth control mechanisms by altering their expression of growth factors, receptors, or intracellular signals, and neuropeptides have recently been recognized as mitogens in cancer growth and development. Many neuropeptides and their receptors exist in multiple subtypes, coupling with different downstream signaling pathways and playing distinct roles in cancer progression. The consideration of neuropeptide/receptor systems as anticancer targets is already leading to new biological and diagnostic knowledge that has the potential to enhance the understanding and treatment of cancer. In this review, recent discoveries regarding neuropeptides in a wide range of cancers, emphasizing their mechanisms of action, signaling cascades, regulation, and therapeutic potential, are discussed. Current technologies used to manipulate and analyze neuropeptides/receptors are described. Applications of neuropeptide analogs and their receptor inhibitors in translational studies and radio-oncology are rapidly increasing, and the possibility for their integration into therapeutic trials and clinical treatment appears promising.

Identification of diagnostic signatures associated with immune infiltration in Alzheimer’s disease by integrating bioinformatic analysis and machine-learning strategies

Objective

As a chronic neurodegenerative disorder, Alzheimer’s disease (AD) is the most common form of progressive dementia. The purpose of this study was to identify diagnostic signatures of AD and the effect of immune cell infiltration in this pathology.

Methods

The expression profiles of GSE109887, GSE122063, GSE28146, and GSE1297 were downloaded from the Gene Expression Omnibus (GEO) database to obtain differentially expressed genes (DEGs) between AD and control brain samples. Functional enrichment analysis was performed to reveal AD-associated biological functions and key pathways. Besides, we applied the Least Absolute Shrinkage Selection Operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE) analysis to screen potential diagnostic feature genes in AD, which were further tested in AD brains of the validation cohort (GSE5281). The discriminatory ability was then assessed by the area under the receiver operating characteristic curves (AUC). Finally, the CIBERSORT algorithm and immune cell infiltration analysis were employed to assess the inflammatory state of AD.

Results

A total of 49 DEGs were identified. The functional enrichment analysis revealed that leukocyte transendothelial migration, cytokine receptor interaction, and JAK-STAT signaling pathway were enriched in the AD group. MAF basic leucine zipper transcription factor F (MAFF), ADCYAP1, and ZFP36L1 were identified as the diagnostic biomarkers of AD with high discriminatory ability (AUC = 0.850) and validated in AD brains (AUC = 0.935). As indicated from the immune cell infiltration analysis, naive B cells, plasma cells, activated/resting NK cells, M0 macrophages, M1 macrophages, resting CD4⁺ T memory cells, resting mast cells, memory B cells, and resting/activated dendritic cells may participate in the development of AD. Additionally, all diagnostic signatures presented different degrees of correlation with different infiltrating immune cells.

Conclusion

MAFF, ADCYAP1, and ZFP36L1 may become new candidate biomarkers of AD, which were closely related to the pathogenesis of AD. Moreover, the immune cells mentioned above may play crucial roles in disease occurrence and progression.

Exploring the Pro-Phagocytic and Anti-Inflammatory Functions of PACAP and VIP in Microglia: Implications for Multiple Sclerosis

Multiple sclerosis (MS) is a chronic neuroinflammatory and demyelinating disease of the central nervous system (CNS), characterised by the infiltration of peripheral immune cells, multifocal white-matter lesions, and neurodegeneration. In recent years, microglia have emerged as key contributors to MS pathology, acting as scavengers of toxic myelin/cell debris and modulating the inflammatory microenvironment to promote myelin repair. In this review, we explore the role of two neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP), as important regulators of microglial functioning during demyelination, myelin phagocytosis, and remyelination, emphasising the potential of these neuropeptides as therapeutic targets for the treatment of MS.

The Multifaceted Role of GPCRs in Amyotrophic Lateral Sclerosis: A New Therapeutic Perspective?

Amyotrophic lateral sclerosis (ALS) is a degenerating disease involving the motor neurons, which causes a progressive loss of movement ability, usually leading to death within 2 to 5 years from the diagnosis. Much effort has been put into research for an effective therapy for its eradication, but still, no cure is available. The only two drugs approved for this pathology, Riluzole and Edaravone, are onlyable to slow down the inevitable disease progression. As assessed in the literature, drug targets such as protein kinases have already been extensively examined as potential drug targets for ALS, with some molecules already in clinical trials. Here, we focus on the involvement of another very important and studied class of biological entities, G protein-coupled receptors (GPCRs), in the onset and progression of ALS. This workaimsto give an overview of what has been already discovered on the topic, providing useful information and insights that can be used by scientists all around the world who are putting efforts into the fight against this very important neurodegenerating disease.

Pituitary Adenylate Cyclase-Activating Polypeptide Protects Corneal Epithelial Cells against UV-B-Induced Apoptosis via ROS/JNK Pathway Inhibition

PACAP is widely expressed throughout the body. It exerts a beneficial role in the eye, including the cornea. The corneal epithelium is regularly exposed to diverse types of insults, including ultraviolet B (UV-B) radiation. Previously, we showed the protective role played by PACAP in counteracting UV-B ray insults in human corneal endothelial cells; however, its involvement in corneal epithelium protection against ROS induced by UV-B radiation, and the underlying mechanisms, remain to be determined. Here, we demonstrated that the peptide treatment reduced UV-B-induced ROS generation by playing an anti-apoptotic role via JNK-signaling pathway inhibition. Overall, our results can provide guidance in the therapeutic use of PACAP for the treatment of epithelial corneal damage.

The anxiolytic Drug Buspirone Prevents Rotenone-Induced Toxicity in a Mouse Model of Parkinson’s Disease

A pharmacological and genetic blockade of the dopamine D3 receptor (D3R) has shown to be neuroprotective in models of Parkinson’s disease (PD). The anxiolytic drug buspirone, a serotonin receptor 1A agonist, also functions as a potent D3R antagonist. To test if buspirone elicited neuroprotective activities, C57BL/6 mice were subjected to rotenone treatment (10mg/kg i.p for 21 days) to induce PD-like pathology and were co-treated with increasing dosages of buspirone (1, 3, or 10 mg/kg i.p.) to determine if the drug could prevent rotenone-induced damage to the central nervous system (CNS). We found that high dosages of buspirone prevented the behavioural deficits caused by rotenone in the open field test. Molecular and histological analyses confirmed that 10 mg/kg of buspirone prevented the degeneration of TH-positive neurons. Buspirone attenuated the induction of interleukin-1β and interleukin-6 expression by rotenone, and this was paralleled by the upregulation of arginase-1, brain-derived neurotrophic factor (BDNF), and activity-dependent neuroprotective protein (ADNP) in the midbrain, striatum, prefrontal cortex, amygdala, and hippocampus. Buspirone treatment also improved mitochondrial function and antioxidant activities. Lastly, the drug prevented the disruptions in the expression of two neuroprotective peptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP). These results pinpoint the neuroprotective efficacy of buspirone against rotenone toxicity, suggesting its potential use as a therapeutic agent in neurodegenerative and neuroinflammatory diseases, such as PD.

A Broad Overview on Pituitary Adenylate Cyclase-Activating Polypeptide Role in the Eye: Focus on Its Repairing Effect in Cornea

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is a neuropeptide with widespread distribution throughout the central and peripheral nervous system as well as in many other peripheral organs. It plays cytoprotective effects mediated mainly through the activation of specific receptors. PACAP is known to play pleiotropic effects on the eye, including the cornea, protecting it against different types of insult. This review firstly provides an overview of the anatomy of the cornea and summarizes data present in literature about PACAP’s role in the eye and, in particular, in the cornea, either in physiological or pathological conditions.

Activity-Dependent Neuroprotective Protein (ADNP)-Derived Peptide (NAP) Counteracts UV-B Radiation-Induced ROS Formation in Corneal Epithelium

The corneal epithelium, the outermost layer of the cornea, acts as a dynamic barrier preventing access to harmful agents into the intraocular space. It is subjected daily to different insults, and ultraviolet B (UV-B) irradiation represents one of the main causes of injury. In our previous study, we demonstrated the beneficial effects of pituitary adenylate cyclase-activating polypeptide (PACAP) against UV-B radiation damage in the human corneal endothelium. Some of its effects are mediated through the activation of the intracellular factor, known as the activity-dependent protein (ADNP). In the present paper, we have investigated the role of ADNP and the small peptide derived from ADNP, known as NAP, in the corneal epithelium. Here, we have demonstrated, for the first time, ADNP expression in human and rabbit corneal epithelium as well as its protective effect by treating the corneal epithelial cells exposed to UV-B radiations with NAP. Our results showed that NAP treatment prevents ROS formation by reducing UV-B-irradiation-induced apoptotic cell death and JNK signalling pathway activation. Further investigations are needed to deeply investigate the possible therapeutic use of NAP to counteract corneal UV-B damage.

Metformin Treatment Attenuates Brain Inflammation and Rescues PACAP/VIP Neuropeptide Alterations in Mice Fed a High-Fat Diet

High-fat diet (HFD)-induced comorbid cognitive and behavioural impairments are thought to be the result of persistent low-grade neuroinflammation. Metformin, a first-line medication for the treatment of type-2 diabetes, seems to ameliorate these comorbidities, but the underlying mechanism(s) are not clear. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) are neuroprotective peptides endowed with anti-inflammatory properties. Alterations to the PACAP/VIP system could be pivotal during the development of HFD-induced neuroinflammation. To unveil the pathogenic mechanisms underlying HFD-induced neuroinflammation and assess metformin’s therapeutic activities, (1) we determined if HFD-induced proinflammatory activity was present in vulnerable brain regions associated with the development of comorbid behaviors, (2) investigated if the PACAP/VIP system is altered by HFD, and (3) assessed if metformin rescues such diet-induced neurochemical alterations. C57BL/6J male mice were divided into two groups to receive either standard chow (SC) or HFD for 16 weeks. A further HFD group received metformin (HFD + M) (300 mg/kg BW daily for 5 weeks) via oral gavage. Body weight, fasting glucose, and insulin levels were measured. After 16 weeks, the proinflammatory profile, glial activation markers, and changes within the PI3K/AKT intracellular pathway and the PACAP/VIP system were evaluated by real-time qPCR and/or Western blot in the hypothalamus, hippocampus, prefrontal cortex, and amygdala. Our data showed that HFD causes widespread low-grade neuroinflammation and gliosis, with regional-specific differences across brain regions. HFD also diminished phospho-AKT^(Ser473) expression and caused significant disruptions to the PACAP/VIP system. Treatment with metformin attenuated these neuroinflammatory signatures and reversed PI3K/AKT and PACAP/VIP alterations caused by HFD. Altogether, our findings demonstrate that metformin treatment rescues HFD-induced neuroinflammation in vulnerable brain regions, most likely by a mechanism involving the reinstatement of PACAP/VIP system homeostasis. Data also suggests that the PI3K/AKT pathway, at least in part, mediates some of metformin’s beneficial effects.

Modulatory role of PACAP and VIP on HIFs expression in lung adenocarcinoma

Lung adenocarcinoma is the most frequent form of non-small cell lung cancer. Inside the tumor mass, uncontrolled cell proliferation generates hypoxic areas leading to activation of hypoxia-inducible factors (HIFs) responsible for neovascularization and tumor metastasis. Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two neuropeptides widely distributed in respiratory organs. Previous studies have demonstrated that these peptides interfere with hypoxic pathways in various diseases, including tumors. However, their modulatory role in HIFs expression in lung adenocarcinomas has not yet been evaluated. In the present paper, we detected the expression profile of PACAP, VIP and related receptors in healthy and adenocarcinoma human lung tissue. To characterize peptides' modulatory effects on HIFs expression, we also exposed A549 lung adenocarcinoma cells and human normal bronchial epithelial BEAS-2B cells to microenvironmental hypoxia by treating them with deferoxamine (DFX). The results showed that PACAP and VIP significantly reduced HIF-1α and HIF-2α levels in both cell lines following hypoxic stress. The HIF-3α expression profile was related to cellular phenotype as it was lower in BEAS-2B and higher in A549 cells under low oxygen tension. In lung adenocarcinoma cells, peptide treatment restored HIF-3 α expression to control levels. These results suggest that endogenous PACAP and VIP exert controversial roles in cellular hypoxic microenvironments depending on the pathophysiological conditions of the lung tissue.

Generation of KS-133 as a Novel Bicyclic Peptide with a Potent and Selective VIPR2 Antagonist Activity that Counteracts Cognitive Decline in a Mouse Model of Psychiatric Disorders

Worldwide, more than 20 million people suffer from schizophrenia, but effective and definitive new therapeutic drugs/treatments have not been established. Vasoactive intestinal peptide receptor 2 (VIPR2) might be an attractive drug target for the treatment of schizophrenia because both preclinical and clinical studies have demonstrated a strong link between high expression/overactivation of VIPR2 and schizophrenia. Nevertheless, VIPR2-targeting drugs are not yet available. VIPR2 is a class-B G protein-coupled receptor that possesses high structural homology to its subtypes, vasoactive intestinal peptide receptor 1 (VIPR1) and pituitary adenylate cyclase-activating polypeptide type-1 receptor (PAC1). These biological and structural properties have made it difficult to discover small molecule drugs against VIPR2. In 2018, cyclic peptide VIpep-3, a VIPR2-selective antagonist, was reported. The aim of this study was to generate a VIpep-3 derivative for in vivo experiments. After amino acid substitution and structure optimization, we successfully generated KS-133 with 1) a VIPR2-selective and potent antagonistic activity, 2) at least 24 h of stability in plasma, and 3) in vivo pharmacological efficacies in a mouse model of psychiatric disorders through early postnatal activation of VIPR2. To the best of our knowledge, this is the first report of a VIPR2-selective antagonistic peptide that counteracts cognitive decline, a central feature of schizophrenia. KS-133 may contribute to studies and development of novel schizophrenia therapeutic drugs that target VIPR2.

Significance of serum VIP and PACAP in multiple sclerosis: an exploratory case-control study

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease of the central nervous system. Vasoactive and intestinal peptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are neuropeptides that play roles in anti-inflammation and neuroprotection in MS. In this study, we aimed to determine the serum levels of VIP and PACAP in MS patients versus healthy controls and to correlate them with demographics and clinical characteristics.

METHODS

Serum samples were collected from MS patients (n = 145) and healthy controls (n = 73) to measure serum levels VIP and PACAP.

RESULTS

VIP serum levels were lower in MS patients than healthy controls (p < 0.001). Serum PACAP levels were the same among the two groups. Gender-based analysis showed that VIP levels were lower in healthy females (1238.840 pg/ml) than healthy males (3300.105 pg/ml; p < 0.001), and PACAP serum levels were significantly lower in male MS patients (48,516.214 fg/ml) than female MS patients (62,466.400 fg/ml; p = 0.029). ROC curve suggested that serum VIP level can discriminate patients with MS from healthy controls. Relapsing-remitting MS, progressive-MS, and clinically isolated syndrome groups were different in age, MS disease duration, EDSS score, and VIP levels (p < 0.05). MS disease type and history of previous relapses in the preceding 24 months predicted serum VIP levels, while gender predicted PACAP levels.

CONCLUSION

VIP serum levels are decreased in MS patients and can be used to differentiate between MS patients and healthy controls. Further studies with larger sample sizes are required to investigate VIP as a marker to reflect MS disease progression.

PACAP and VIP Modulate LPS-Induced Microglial Activation and Trigger Distinct Phenotypic Changes in Murine BV2 Microglial Cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related immunosuppressive peptides. However, the underlying mechanisms through which these peptides regulate microglial activity are not fully understood. Using lipopolysaccharide (LPS) to induce an inflammatory challenge, we tested whether PACAP or VIP differentially affected microglial activation, morphology and cell migration. We found that both peptides attenuated LPS-induced expression of the microglial activation markers Iba1 and iNOS (### p < 0.001), as well as the pro-inflammatory mediators IL-1β, IL-6, Itgam and CD68 (### p < 0.001). In contrast, treatment with PACAP or VIP exerted distinct effects on microglial morphology and migration. PACAP reversed LPS-induced soma enlargement and increased the percentage of small-sized, rounded cells (54.09% vs. 12.05% in LPS-treated cells), whereas VIP promoted a phenotypic shift towards cell subpopulations with mid-sized, spindle-shaped somata (48.41% vs. 31.36% in LPS-treated cells). Additionally, PACAP was more efficient than VIP in restoring LPS-induced impairment of cell migration and the expression of urokinase plasminogen activator (uPA) in BV2 cells compared with VIP. These results suggest that whilst both PACAP and VIP exert similar immunosuppressive effects in activated BV2 microglia, each peptide triggers distinctive shifts towards phenotypes of differing morphologies and with differing migration capacities.

Pituitary Adenylate Cyclase Activating Polypeptide Has Inhibitory Effects on Melanoma Cell Proliferation and Migration In Vitro

Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide which is distributed throughout the body. PACAP influences development of various tissues and exerts protective function during cellular stress and in some tumour formation. No evidence is available on its role in neural crest derived melanocytes and its malignant transformation into melanoma. Expression of PACAP receptors was examined in human skin samples, melanoma lesions and in a primary melanocyte cell culture. A2058 and WM35 melanoma cell lines, representing two different stages of melanoma progression, were used to investigate the effects of PACAP. PAC1 receptor was identified in melanocytes in vivo and in vitro and in melanoma cell lines as well as in melanoma lesions. PACAP administration did not alter viability but decreased proliferation of melanoma cells. With live imaging random motility, average speed, vectorial distance and maximum distance of migration of cells were reduced upon PACAP treatment. PACAP administration did not alter viability but decreased proliferation capacity of melanoma cells. On the other hand, PACAP administration decreased the migration of melanoma cell lines towards fibronectin chemoattractant in the Boyden chamber. Furthermore, the presence of the neuropeptide inhibited the invasion capability of melanoma cell lines in Matrigel chambers. In summary, we provide evidence that PACAP receptors are expressed in melanocytes and in melanoma cells. Our results also prove that various aspects of the cellular motility were inhibited by this neuropeptide. On the basis of these results, we propose PACAP signalling as a possible target in melanoma progression.

Endocrine regulation of cancer stem cell compartments in breast tumors

Cancer cells within breast tumors exist within a hierarchy in which only a small and rare subset of cells is able to regenerate growths with the heterogeneity of the original tumor. These highly malignant cancer cells, which behave like stem cells for new cancers and are called "cancer stem cells" or CSCs, have also been shown to possess increased resistance to therapeutics, and represent the root cause underlying therapy failures, persistence of residual disease, and relapse. As >90% of cancer deaths are due to refractory tumors, identification of critical molecular drivers of the CSC-state would reveal vulnerabilities that can be leveraged in designing therapeutics that eradicate advanced disease and improve patient survival outcomes. An expanding and complex body of work has now described the exquisite susceptibility of CSC pools to the regulatory influences of local and systemic hormones. Indeed, breast CSCs express a plethora of hormonal receptors, which funnel hormonal influences over every aspect of breast neoplasia - be it tumor onset, growth, survival, invasion, metastasis, or therapy resistance - via directly impacting CSC behavior. This article is intended to shed light on this active area of investigation by attempting to provide a systematic and comprehensive overview of the available evidence directly linking hormones to breast CSC biology.

Effect of PACAP on Hypoxia-Induced Angiogenesis and Epithelial-Mesenchymal Transition in Glioblastoma

Pituitary adenylate cyclase-activating polypeptide (PACAP) exerts different effects in various human cancer. In glioblastoma (GBM), PACAP has been shown to interfere with the hypoxic micro-environment through the modulation of hypoxia-inducible factors via PI3K/AKT and MAPK/ERK pathways inhibition. Considering that hypoxic tumor micro-environment is strictly linked to angiogenesis and Epithelial–Mesenchymal transition (EMT), in the present study, we have investigated the ability of PACAP to regulate these events. Results have demonstrated that PACAP and its related receptor, PAC1R, are expressed in hypoxic area of human GBM colocalizing either in epithelial or mesenchymal cells. By using an in vitro model of GBM cells, we have observed that PACAP interferes with hypoxic/angiogenic pathway by reducing vascular-endothelial growth factor (VEGF) release and inhibiting formation of vessel-like structures in H5V endothelial cells cultured with GBM-conditioned medium. Moreover, PACAP treatment decreased the expression of mesenchymal markers such as vimentin, matrix metalloproteinase 2 (MMP-2) and matrix metalloproteinase 9 (MMP-9) as well as CD44 in GBM cells by affecting their invasiveness. In conclusion, our study provides new insights regarding the multimodal role of PACAP in GBM malignancy.