Pituitary adenylate cyclase-activating polypeptide and its receptors: 20 years after the discovery

PACAP induces increased excitability in D1- and D2-expressing nucleus accumbens medium spiny neurons

One of the main eating disorders associated with overweight and obesity is binge eating disorder. Binge eating is characterized by excessive consumption of high-calorie foods over a short period of time, approximately 2 hours. The nucleus accumbens (NAc) plays a key role in modulating the hedonic value of high-calorie foods, commonly referred to as palatable foods. Specific subregions of the shell portion of the NAc (NAcSh), known as hedonic hot spots, may play an important role in the motivational aspect of food consumption. Previous work has shown that the pituitary adenylate cyclase-activating polypeptide (PACAP) injected into the NAc reduces palatable food intake, suggesting that this peptide could be a potential tool for treating binge eating. However, the mechanisms of action of PACAP on the NAc are poorly understood. Here, we used whole-cell recording and calcium imaging techniques in NAcSh brain slices from D1-Cre and A2A-Cre mice to investigate PACAP modulation of medium spiny neuron (MSN) activity. We found that PACAP administration increased the firing rate of D1- and D2-expressing MSNs. In addition, in a binge-eating mouse model, nasal PACAP reduced binge-eating behavior.

Targeting PACAP: Beyond Migraine to Cluster, Menstrual, and Post-traumatic Headaches

The pituitary adenylate cyclase-activating peptide (PACAP) pathway is a critical focus in the pathophysiology of several headache disorders. PACAP influences headache pathophysiology through interactions with distinct receptors (PAC1, VPAC1, and VPAC2) and pathways linked to neurovascular and hormonal regulation. Evidence supports its role in the modulation of trigeminal and parasympathetic systems, implicated in cluster headaches and menstrual migraine, and its involvement in sensitizing pain pathways post trauma in post-traumatic headaches. Early clinical trials targeting PACAP signaling show promise, with one study demonstrating efficacy in migraine prophylaxis. This narrative review synthesizes current evidence while addressing gaps in understanding PACAP's precise mechanisms. Future research should prioritize expanding the scope of PACAP-focused investigations across diverse headache types, aiming to establish it as a therapeutic target for several headache disorders. Success in ongoing and future trials could redefine headache management for millions of underserved patients worldwide.

Neuropeptide Signaling in Glioblastoma: A Comprehensive Review of the Current State and Future Direction

Glioblastoma multiforme (GBM) is a highly aggressive brain tumor characterized by complex pathophysiology and significant clinical challenges. Emerging research emphasizes the crucial role of neuropeptides in GBM and its influence on tumor progression, immune modulation, and therapy resistance. This review highlighted the importance of neuropeptides and their receptors in maintaining brain homeostasis and the glioblastoma tumor microenvironment. We discussed new therapeutic frontiers, including neuropeptide receptors as therapeutic targets, renin-angiotensin system, peptide receptor modulation, targeted cytotoxic analogs (such as Bombesin and Somatostatin), and advances in targeted radiotherapy. The review highlighted the potential of neuropeptide-based targeted therapies to improve GBM patient outcomes and suggests future research directions. This underscores the importance of targeting neuropeptide-related pathways for innovative therapeutic strategies in GBM, aiming to enhance patient prognosis and effective treatment.

Dimerisation of the VIP receptor VIPR2 is essential to its binding VIP and Gαi proteins, and to its functions in breast cancer cells

BACKGROUND AND PURPOSE

Several G protein-coupled receptors (GPCRs) are known to homodimerise. Dimeric GPCRs may have different properties from their monomers, but the molecular basis and functional significance of GPCR dimerisation remain largely unknown. We recently found that signalling by the vasoactive intestinal peptide receptor, VIPR2, regulates breast cancer cell migration and proliferation. However, it is unclear whether VIPR2 monomers directly interact with each other and what function the dimeric receptor has. Here, we showed that VIPR2 dimerises and investigated their role in breast cancer progression.

EXPERIMENTAL APPROACH

Dimerisation of VIPR2 was assessed by fluorescence resonance energy transfer (FRET) analysis and a pull-down assay. Breast cancer progression was analysed by orthotopic growth and metastasis of human breast cancers into proper axillary and subiliac lymph-nodes in mice.

KEY RESULTS

VIPR2 monomers directly interacted with each other through transmembrane domains (TM)3-4. FRET analysis revealed that VIPR2 moved further apart in cells expressing TM3-4-peptides, suggesting that TM3-4 prevents VIPR2 dimerisation. Breast cancer cells stably expressing TM3-4 region exhibited suppressed tumour growth and lymph-node metastasis. Furthermore, ligand-receptor binding assays revealed that VIP-FITC bound to cells dose-dependently, and VIPR2 de-dimerisation by TM3-4 expression decreased VIP's affinity to cells. Additionally, TM3-4 expression decreased Gαi-VIPR2 interactions.

CONCLUSION AND IMPLICATIONS

Dimeric VIPR2 forms the minimal functional unit that effectively promotes growth and metastasis of breast cancer. Therefore, dimeric VIPR2 is a potential therapeutic target for breast cancer, and TM3-4-peptides are potential anti-cancer drug candidates to suppress cancer progression.

Deconvolution Analysis of G and F-Actin Unfolding: Insights into the Thermal Stability and Structural Modifications Induced by PACAP

Actin, a key component of the cytoskeleton, undergoes significant structural and thermal changes in response to various regulatory factors, including the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP). In this study, we applied deconvolution analysis to previously obtained differential scanning calorimetry (DSC) data to resolve overlapping thermal transitions in G- and F-actin unfolding. Our findings reveal that PACAP38 and PACAP6-38 significantly alter actin stability, increasing structural cooperativity in G-actin while reducing monomer-monomer interactions in F-actin. These thermodynamic changes suggest a potential role for PACAP in modulating actin polymerization and depolymerization dynamics, contributing to cytoskeletal remodeling.

Sex shapes phenotype-linked metabolic signatures of stress exposure in the mouse hypothalamus and pituitary

In chronic stress-induced anxiodepression, sex differences in the dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis are well-documented, yet the underlying molecular mechanisms remain largely unexplored. This study investigated sex-specific metabolic signatures associated with stress exposure in the hypothalamus and pituitary, given the potential significance of brain metabolism in sex-related mechanisms underlying anxiodepression. Utilizing a chronic restraint stress (CRS) model, we conducted a comparative analysis of the metabolic profiles in female and male mice to identify distinct phenotypic expressions related to sex differences. Our findings revealed that metabolite alterations in the pituitary were more pronounced than those in the hypothalamus, indicating significant sex-based variations. These differences facilitated phenotypic differentiation and underscored the relevance of sex-specific metabolic changes and their functional associations to behavioral phenotypes. Moreover, diverging and converging pathways were identified to elucidate the molecular and physiological bases of stress susceptibility in both sexes. Key metabolic and immune-related pathways in the hypothalamus and pituitary, such as histidine, tryptophan, lipid, glycerophospholipid, amino acid, and carbohydrate metabolism, showed specific associations with sex and phenotype. Additionally, correlation analysis uncovered several differential metabolites that were significantly linked to mouse behaviors, with marked sex differences. Collectively, our results demonstrate a pronounced sexual dimorphism at the metabolic level in the hypothalamus and pituitary in response to chronic stress. This study provides a valuable molecular resource for further exploration of the interplay between sex and behavioral phenotypes within the dysregulation of the HPA axis that contributes to stress susceptibility and immune response, emphasizing the critical role of sex-specific metabolic mechanisms in anxiodepressive disorder.

Distribution and Neurochemical Characterization of Dorsal Root Ganglia (DRG) Neurons Containing Phoenixin (PNX) and Supplying the Porcine Urinary Bladder

The present study was designed to establish the distribution pattern and immunohistochemical characteristics of phoenixin-immunoreactive (PNX-IR) urinary bladder afferent neurons (UB-ANs) of dorsal root ganglia (DRG) in female pigs. The sensory neurons investigated were visualized with a retrograde tracing method using Fast Blue (FB), while their chemical profile(s) were identified using double-labelling immunohistochemistry with antibodies against PNX, calcitonin gene-related peptide (CGRP), calretinin (CRT), galanin (GAL), neuronal nitric oxide synthase (nNOS), pituitary adenylate cyclase-activating polypeptide (PACAP), somatostatin (SOM) and substance P (SP). Nearly half of UB-ANs contained PNX (45%), and the majority of such encoded sensory neurons were small in size (66%). The most numerous subpopulation of FB/PNX-positive neurons were those containing SP (71%). CGRP, GAL or PACAP were observed in a smaller number of PNX-containing UB-ANs (50%, 30% or 25%, respectively), while PNX-positive sensory neurons simultaneously immunostained with nNOS, CRT or SOM constituted a small fraction of all retrogradely-traced DRG neurons (DRGs; 15%, 6.5% or 1.6%, respectively). Furthermore, the numerical analysis of neurons expressing individual antigens, performed on 10 μm-thick consecutive sections, allows us to state that studied sensory neurons can be classified as neurons "coded" either by the simultaneous presence of SP/CGRP/PACAP/GAL, SP/CGRP/PACAP/NOS, SP/CGRP/PACAP/NOS/CRT and/or SP/CGRP/GAL/PACAP, or, as a separate population, those capable of SOM synthesis (SP/CGRP/SOM/PACAP/GAL-positive neurons). The present study reveals the extensive expression of PNX in the DRGs supplying to the urinary bladder, indicating an important regulatory role of this neuropeptide in the control of physiological function(s) of this organ.

VIP and PACAP enhance hippocampal neuronal cell proliferation especially GFAP-positive astrocytes, while PACAP inhibits neurite outgrowth

Despite their known roles in regulating food intake, appetite, satiety, and social behavior, the roles of vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) in hippocampal neuronal cell development remain unclear. Therefore, the aim was to evaluate the effect of VIP and PACAP on 1) the proliferation of a hippocampal cell line, 2) the number of neurons and astrocytes in primary hippocampal cell culture, and 3) the morphology of primary hippocampal neurons. It was found that both VIP (100 nM) and PACAP (100 nM) stimulated the proliferation of E2 hippocampal cells over a 72-hour period. A significant increase in the number of NeuN-positive primary hippocampal neurons was observed following VIP incubation on day in vitro (DIV) 9. An increase in GFAP-positive cells following PACAP incubation was observed from DIV3 compared to DIV5, DIV7, and DIV9. PACAP significantly inhibited the growth of short neurites in primary hippocampal neurons. In conclusion, this study demonstrates that both neuropeptides VIP and PACAP influence the proliferation and growth of hippocampal neuronal cells, with PACAP having a more pronounced effect on astrocyte numbers and reducing neurite branching. These findings emphasize the role of VIP and PACAP in the hippocampus during early brain development.

PACAP Signaling Network in the Nucleus Accumbens Core Regulates Reinstatement Behavior in Rat

Cocaine use disorder (CUD) lacks FDA-approved treatments, partly due to the difficulty of creating therapeutics that target behavior-related neural circuits without disrupting signaling throughout the brain. Recent evidence highlights the therapeutic potential of targeting gut-brain axis components, such as GLP-1 receptors, to modulate neural circuits with minimal central nervous system disruption. Like GLP-1, pituitary adenylate cyclase polypeptide (PACAP) is a component of the gut-brain axis that regulates behavior through a network spanning the gut and brain. Here, we investigated the potential existence and function of an endogenous PACAP signaling network within the nucleus accumbens core (NAcc), which is a structure that integrates emotional, cognitive, and reward processes underlying behavior. We found that PACAP and its receptor, PAC1R, are endogenously expressed in the rat NAcc and that PACAP mRNA is present in medial prefrontal cortical projections to the NAcc. Behaviorally, intra-NAcc infusions of PACAP (100 pm) did not induce seeking behavior but blocked cocaine-primed reinstatement (10 mg/kg, IP). Intra-NAcc PACAP also inhibited reinstatement driven by co-infusion of the D1 receptor agonist (SKF 81297, 3 µg) but not the D2 receptor agonist (sumanirole, 10 ng). These findings are significant since D1 and D2 receptor activities in the NAcc govern distinct behavioral mechanisms indicating precise actions of PACAP even within the NAcc. Future research should examine whether NAcc PACAP signaling can be selectively engaged by peripheral gut-brain axis mechanisms, potentially unveiling novel therapeutic approaches for CUD and related disorders.

Revolutionizing the treatment of intervertebral disc degeneration: an approach based on molecular typing

BACKGROUND

Intervertebral disc degeneration (IVDD) is a significant cause of global disability, reducing labor productivity, increasing the burden on public health, and affecting socio-economic well-being. Currently, there is a lack of recognized clinical approaches for molecular classification and precision therapy.

METHODS

Chondrocyte differentiation and prognosis-related genes were extracted from single-cell RNA sequencing and multi-omics data in the Gene Expression Omnibus (GEO) database through chondrocyte trajectory analysis and non-parametric tests. Subsequently, a precise IVDD risk stratification system was developed using ConsensusClusterPlus analysis. The clinical significance of molecular typing was demonstrated through case-control trials involving IVDD patients. Specific inhibitors of molecular typing were predicted using the pRRophetic package in R language and then validated in vitro.

RESULTS

A stratified model for IVDD, considering chondrocyte differentiation and demonstrating high clinical relevance, was developed using a set of 44 chondrocyte fate genes. Extensive analyses of multi-omics data confirmed the clinical relevance of this model, indicating that cases in the High Chondrocyte Scoring Classification (HCSC) group had the most favorable prognosis, whereas those in the Low Chondrocyte Scoring Classification (LCSC) group had the worst prognosis. Additionally, clinical case-control studies provided evidence of the utility of IVDD molecular typing in translational medicine. A gene expression-based molecular typing approach was used to create a matrix identifying potential inhibitors specific to each IVDD subtype. In vitro experiments revealed that gefitinib, a drug designed for LCSC, not only had protective effects on chondrocytes but also could induce the conversion of LCSC into the HCSC subgroup. Therefore, IVDD molecular typing played a critical role in assisting clinicians with risk stratification and enabling personalized treatment decisions.

CONCLUSION

The results of the study have provided a comprehensive and clinically relevant molecular typing for IVDD, involving a precise stratification system that offers a new opportunity for customizing personalized treatments for IVDD.

Pituitary adenylate cyclase-activating polypeptide plays a role in neuropsychiatric and substance use disorders: sex-specific perspective

The neuropeptide pituitary adenylate cyclase-activating peptide (PACAP) plays a pivotal role in regulating stress, fear, and anxiety responses. Genetic and molecular studies investigating PACAP demonstrate sex-dimorphic characteristics, with females exhibiting increased reactivity of PACAP signaling in neuropsychiatric disorders. Studies expand the role of PACAP to substance use disorders (SUD) by demonstrating modulation of PACAP can lead to neurobiological changes induced by nicotine, ethanol, stimulants and opioids. Given that females with SUD exhibit distinct drug use, relapse, and withdrawal sensitivity relative to males, we hypothesize that the PACAP system contributes to these sex-specific differences. Therefore, we review the role of PACAP in SUD by characterizing the role of PACAP at the molecular, brain regional, and behavioral levels relevant to the addiction cycle. We present literature linking PACAP to neuropsychiatric disorders, which demonstrate the intricate role of PACAP within neuronal signaling and pathways modulating addiction. We hypothesize that females are more particularly susceptible to PACAP-related changes during the intoxication and withdrawal phases of the addiction cycle. Altogether understanding the sex-specific differences in the PACAP system offers a foundation for future studies aimed at developing tailored interventions for addressing SUD.

PACAP regulates neuroendocrine and behavioral stress responses via CRF-containing neurons of the rat hypothalamic paraventricular nucleus

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide widely distributed in the brain including the hypothalamic paraventricular nucleus (PVN) implying a regulatory role in stress function. Recent evidence indicates that one of the main targets of PACAP within the PVN are corticotropin-releasing factor (CRF) neurons, which are key regulators of the hypothalamic-pituitary-adrenal (HPA) axis. However, the neural correlates that mediate PACAP effects on stress function are not fully understood. In the present study, we characterized the neuronal mechanism by which PACAP regulates neuroendocrine and behavioral stress responses in rats. We found that intracerebroventricular administration of PACAP increased the swim stress-induced c-Fos expression in distinct brain areas of the stress and anxiety circuitry including the parvocellular part of the PVN and changed behavioral stress coping during forced swimming to a more passive coping style (i.e., indicated by increased floating and reduced struggling behavior). Subsequently, PACAP administration directly into the PVN mimicked these behavioral effects and potentiated the plasma ACTH response to forced swim stress suggesting an excitatory role of PACAP on HPA stress axis reactivity. In addition, immunohistochemical analysis revealed a considerable portion of stress-activated CRF neurons in the medial parvocellular part of the PVN that co-localized PAC1 receptors suggesting that PACAP-induced effects on stress function are likely mediated directly by activation of CRF neurons in the PVN. Thus, these findings suggest that the PVN may represent one of the key areas where PACAP regulates the neuroendocrine and behavioral stress response.

Spinal pituitary adenylate cyclase-activating polypeptide and PAC1 receptor signaling system is involved in the oxaliplatin-induced acute cold allodynia in mice

Chemotherapy-induced peripheral neuropathy (CIPN) is a type of peripheral neuropathy that develops in patients treated with certain anticancer drugs. Oxaliplatin (OXA) causes CIPN in approximately 80-90 % of patients; thus, it is necessary to elucidate its underlying mechanism and develop effective treatments and prevention methods. The purpose of this study was to determine whether the pituitary adenylate cyclase-activating polypeptide (PACAP)/PAC1 receptor system in the spinal dorsal horn is involved in OXA-induced acute cold allodynia and examine the effect of a PAC1 receptor antagonist. Administration of OXA induced acute cold allodynia in wild-type mice, but not in PACAP-/- mice. In the dorsal root ganglia, OXA upregulated PACAP expression, particularly in small-sized neurons. OXA-induced cold allodynia was ameliorated by intrathecal (i.t.) injection of PACAP6-38 (peptide antagonist for PACAP receptor) and PA-8 (small-molecule antagonist specific for PAC1 receptor). I.t. PACAP, but not vasoactive intestinal polypeptide, resulted in cold allodynia, which was blocked by PA-8. OXA induced the activation of spinal astrocytes in a PAC1 receptor-dependent manner. The results suggest that spinal PACAP/PAC1 receptor systems are involved in OXA-induced acute cold allodynia through astrocyte activation. Furthermore, we demonstrated that the systemic administration of PA-8 resulted in therapeutic and preventative effects on OXA-induced acute cold allodynia. Because PA-8 did not affect the anticancer effects of OXA, we propose PAC1 receptor inhibition as a new strategy for the treatment and prevention of CIPN. PERSPECTIVE: Cold allodynia is a hallmark of OXA-induced peripheral neuropathy. This study demonstrated the involvement of spinal PACAP/PAC1 receptors in OXA-induced acute cold allodynia. We propose PAC1 receptor inhibition as a new strategy for the treatment and prevention of OXA-induced acute cold allodynia.

Stress-induced changes in the molecular processes underlying fear memories: implications for PTSD and relevant animal models

Most of the fear literature on humans and animals tests healthy individuals. However, fear memories can differ between healthy individuals and those previously exposed to traumatic stress, such as a car accident, sexual abuse, military combat and personal assault. Traumatic stress can lead to post-traumatic stress disorder (PTSD) which presents alterations in fear memories, such as an impairment of fear extinction and extinction recall. PTSD-like animal models are exposed to a single highly stressful experience in the laboratory, such as stress immobilization or single-prolonged stress. Some days later, animals exposed to a PTSD-like model can be tested in fear procedures that help uncover molecular mechanisms of fear memories. In this review, there are discussed the molecular mechanisms in stress-induced fear memories of patients with PTSD and PTSD-like animal models. The focus is on the effects of estradiol and cortisol/corticosterone hormones and of different genes, such as FKBP prolyl isomerase 5 gene (FKBP5) - FK506 binding protein 51 (FKBP51), pituitary adenylate cyclase-activating peptide (PACAP) - pituitary adenylate cyclase-activating polypeptide type I receptor (PAC1R), endocannabinoid (eCB) system and the tropomyosin receptor kinase B (TrkB) - brain-derived neurotrophic factor (BDNF). The conclusion is that greater emphasis should be placed on investigating the molecular mechanisms of fear memories in PTSD, through direct testing of patients with PTSD or the use of relevant PTSD-like models.

A Procedural Overview of the Involvement of Small Molecules in the Nervous System in the Regulation of Bone Healing

Clinically, a multitude of factors can contribute to the development of bone defects. In the process of bone healing, the nervous system plays a vital role in bone regeneration. Small molecules from the nervous system, such as neurotrophic factors and neuropeptides, have been found to stimulate osteoblast proliferation and differentiation by activating signaling pathways associated with bone calcification and angiogenesis. These small molecules play a crucial regulatory role at various stages of bone healing. The systematic release mechanism of small molecules within the nervous system through diverse bone tissue engineering materials holds significant clinical implications for the controlled regulation of the bone healing process. This review provides an overview of the involvement of various nervous system small molecules at different stages of bone healing and discusses their regulatory mechanisms, aiming to establish a theoretical foundation for programmed regulation in bone regeneration and design of replacement materials in bone tissue engineering.

CamKIIα and VPAC1 Expressions in the Caudal Trigeminal Nucleus of Rats After Systemic Nitroglycerin Treatment: Interaction with Anandamide

Migraines are a frequently occurring neurological condition that affects up to 16% of the global population. The precise pathomechanism of the disease remains unknown, but from animal and human observations, it appears that calcium/calmodulin-dependent protein kinase II alpha (CamKIIα), pituitary adenylate cyclase-activating polypeptide (PACAP), and vasoactive intestinal polypeptide (VIP) are involved in its pathogenesis. One of the animal models of migraines uses the systemic administration of nitroglycerin (NTG), which, as a nitric oxide (NO) donor, initiates a self-amplifying process in the trigeminal system, leading to central sensitization. Endocannabinoids, such as anandamide (AEA), are thought to play a modulatory role in trigeminal activation and sensitization phenomena. In the present experiment, we aimed to investigate the effect of NTG and AEA on CamKIIα, PACAP/VIP, and vasoactive intestinal polypeptide type 1 receptor (VPAC1) expression levels in the upper cervical spinal cord (C1-C2) of rats, where trigeminal nociceptive afferents are clustered. Four groups of animals were formed: in the first group, the rats received only the vehicle; in the second group, they were treated with an intraperitoneal injection of NTG (10 mg/kg); animals in the third and fourth groups received AEA (2 × 5 mg/kg) half an hour before and one hour after the placebo or treatment with NTG. Four hours after the placebo/NTG injection, the animals were transcardially perfused, and the cervical spinal cords were removed for Western blot. Our results show that both NTG and AEA alone can increase the expression of CamKIIα and VPAC1 in the C1-C2 segments. Interestingly, the combination of NTG and AEA had no such effect on these markers, possibly due to various negative feedback mechanisms.

Estrogens impair hypophagia and hypothalamic cell activation induced by vasoactive intestinal peptide, but not by pituitary adenylate cyclase-activating polypeptide

The neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) act in arcuate (ARC) and paraventricular (PVN) hypothalamic nuclei, reducing food intake and changing plasma parameters. Estrogens (E) also regulate energy homeostasis, and loss of ovarian function leads to hyperphagia and body weight gain. This study aimed to evaluate the effects of estradiol (E) in a postmenopausal rat model, ovariectomy (OVX), on PAC1 and VPAC2 receptors in the PVN and ARC, as well as on food intake, plasma parameters, and PVN and ARC cell activation in response to intracerebroventricular microinjection of VIP and PACAP. For this, the rats underwent intracerebroventricular and OVX surgeries, being treated daily with subcutaneous injections of 0.2 mL of corn oil or 10 μg/0.2 mL of estradiol cypionate, comprising the OVX+O and OVX+E groups, respectively. OVX+E showed reduced VPAC2 mRNA expression in the PVN. PACAP reduced food intake in both groups, and VIP-induced hypophagia was not observed in OVX+E. VIP increased plasma glucose in both groups, and PACAP increased plasma glucose only in OVX+O. VIP decreased free fatty acids in OVX+E. Furthermore, PACAP increased ARC cell activation in both groups, and in the PVN only in OVX+O. Cell activation induced by VIP in ARC and PVN was blocked by estradiol. Therefore, estrogens disrupted the hypophagia induced by VIP, but not by PACAP, and these differences seem to be, at least in part, due to an impairment of the activation of the ARC-PVN pathway.

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.

Anxiety and the brain: Neuropeptides as emerging factors

Anxiety disorders are characterized by intense feelings of worry and fear, which can significantly interfere with daily functioning. Current treatment options primarily include selective serotonin reuptake inhibitors, benzodiazepines, non-benzodiazepine anxiolytics, gabapentinoids, and beta-blockers. Neuropeptides have shown an important role in the regulation of complex behaviours, such as psychopathology and anxiety-related reactions. Neuropeptides have a great deal of promise to advance our understanding of and ability to help people with anxiety disorders. This review focuses on the expanding role of neuropeptides in anxiety management, particularly examining the impact of substance P, neuropeptide Y, corticotropin-releasing hormone, arginine-vasopressin, pituitary adenylate cyclase-activating polypeptide, and cholecystokinin. Furthermore, the paper discusses the neuropeptides that are becoming more and more recognized for their impact on anxiety-related reactions and their potential as therapeutic targets.

Vasoactive Intestinal Peptide (VIP) and its Receptors in Adipose Tissue: Implications for Cold Stress Adaptation

Adipose tissue represents an organ that is highly dynamic and contributes toward vital survival events such as immune responses, lactation, metabolism fuel, and thermogenesis. Data emerging from recent studies support the notion of adipose tissue being organized into a complex system characterized by a discrete anatomy, elevated physiological plasticity, and specific vascular and nerve supplies. Vasoactive intestinal peptide (VIP), along with its receptors, type 1 (VPAC1) and type 2 (VPAC2), has been implicated in various physiological and pathophysiological processes. However, studies on VIP and its receptors in adipose tissue are limited. To explore VIP's presence and activity, as well as its adipose tissue-based receptors, we conducted a study on isolated adipocytes and adipose tissue from inguinal white adipose tissue (WAT) and interscapular brown adipose tissue (BAT) in normal and cold-stressed rats. Our findings indicate the presence of the gene expression VIP and VPAC1 in both WAT and BAT under normal conditions, while VPAC2 was absent. In both WAT and BAT, cold exposure upregulated VIP gene expression. However, the response of VIP receptors to cold exposure is controversial. VPAC2 gene expression was induced in both WAT and BAT, while VPAC1 gene expression presented no change of significance in BAT and a slight reduction in WAT. Additionally, VIP, VPAC1, and VPAC2 proteins were identified from Western blot studies on white and brown adipocytes. After exposure to cold there was an increase of significance in the VIP, VPAC1, and VPAC2 protein levels. This study provides novel insights into how VIP and its receptors alter gene expression and protein levels in adipose tissue and adipocytes during cold stress, indicating their potential involvement in adipose tissue regulation. The findings propose VIP's potentially crucial role in adipose tissue's adaptation to cold stress by affecting the metabolic and biochemical functions of subcutaneous and interscapular adipocytes, with potentially significant implications in the context of developing therapies targeting metabolic disorders.

Same same, but different: exploring the enigmatic role of the pituitary adenylate cyclase-activating polypeptide (PACAP) in invertebrate physiology

Evidence has been accumulating that elements of the vertebrate pituitary adenylate cyclase-activating polypeptide (PACAP) system are missing in non-chordate genomes, which is at odds with the partial sequence-, immunohistochemical-, and physiological data in the literature. Multilevel experiments were performed on the great pond snail (Lymnaea stagnalis) to explore the role of PACAP in invertebrates. Screening of neuronal transcriptome and genome data did not reveal homologs to the elements of vertebrate PACAP system. Despite this, immunohistochemical investigations with an anti-human PAC1 receptor antibody yielded a positive signal in the neuronal elements in the heart. Although Western blotting of proteins extracted from the nervous system found a relevant band for PACAP-38, immunoprecipitation and mass spectrometric analyses revealed no corresponding peptide fragments. Similarly to the effects reported in vertebrates, PACAP-38 significantly increased cAMP synthesis in the heart and had a positive ionotropic effect on heart preparations. Moreover, it significantly modulated the effects of serotonin and acetylcholine. Homologs to members of Cluster B receptors, which have shared common evolutionary origin with the vertebrate PACAP receptors, PTHRs, and GCGRs, were identified and shown not to be expressed in the heart, which does not support a potential role in the mediation of PACAP-induced effects. Our findings support the notion that the PACAP system emerged after the protostome-deuterostome divergence. Using antibodies against vertebrate proteins is again highlighted to have little/no value in invertebrate studies. The physiological effects of vertebrate PACAP peptides in protostomes, no matter how similar they are to those in vertebrates, should be considered non-specific.

The pivotal role of PACAP/PAC1R signaling from the anterior insular cortex to the locus coeruleus on anxiety-related behaviors of mice

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its specific receptor (PAC1R) are widely present in the central nervous system (CNS), and PACAP/PAC1R signaling has been implicated in anxiety-related behaviors. The locus coeruleus (LC), with its extensive noradrenergic (NA) projections throughout the CNS, is also implicated in anxiety. Although the LC exhibits a high expression of PAC1R, the precise role of PACAP/PAC1R signaling in the LC's involvement in anxiety remains unclear. Histochemical analysis confirmed high levels of PAC1R mRNA in the LC and showed that PAC1R gene transcripts were highly localized to NA neurons. Targeted deletion of PAC1R from these cells led to a hyperactive/low anxiety phenotype in the open field and elevated-plus maze tests. Retrograde neurocircuit tracing indicated PACAP neurons from the anterior insular cortex (aIC) and a few other regions projected axons to the LC. The selective activation of PACAP neurons in the aIC led to significantly increased anxiety behavior without a change in overall locomotor activity. Moreover, shRNA PACAP knockdown in the aIC in wild-type mice led to a selective decrease in anxiety. The present results identify an aIC to LC neurocircuit controlling anxiety that critically requires PACAP/PAC1R signaling.

Pituitary adenylate cyclase-activating polypeptide signalling as a therapeutic target in migraine

Migraine is a disabling neurological disorder that affects more than one billion people worldwide. The clinical presentation is characterized by recurrent headache attacks, which are often accompanied by photophobia, phonophobia, nausea and vomiting. Although the pathogenesis of migraine remains incompletely understood, mounting evidence suggests that specific signalling molecules are involved in the initiation and modulation of migraine attacks. These signalling molecules include pituitary adenylate cyclase-activating polypeptide (PACAP), a vasoactive peptide that is known to induce migraine attacks when administered by intravenous infusion to people with migraine. Discoveries linking PACAP to migraine pathogenesis have led to the development of drugs that target PACAP signalling, and a phase II trial has provided evidence that a monoclonal antibody against PACAP is effective for migraine prevention. In this Review, we explore the molecular and cellular mechanisms of PACAP signalling, shedding light on its role in the trigeminovascular system and migraine pathogenesis. We then discuss emerging therapeutic strategies that target PACAP signalling for the treatment of migraine and consider the research needed to translate the current knowledge into a treatment for migraine in the clinic.

Hallmarks of primary headache: part 1 - migraine

BACKGROUND AND AIM

Migraine is a common disabling conditions which, globally, affects 15.2% of the population. It is the second cause of health loss in terms of years lived with disability, the first among women. Despite being so common, it is poorly recognised and too often undertreated. Specialty centres and neurologists with specific expertise on headache disorders have the knowledge to provide specific care: however, those who do not regularly treat patients with migraine will benefit from a synopsis on the most relevant and updated information about this condition. This paper presents a comprehensive view on the hallmarks of migraine, from genetics and diagnostic markers, up to treatments and societal impact, and reports the elements that identify migraine specific features.

MAIN RESULTS

The most relevant hallmark of migraine is that it has common and individual features together. Besides the known clinical manifestations, migraine presentation is heterogeneous with regard to frequency of attacks, presence of aura, response to therapy, associated comorbidities or other symptoms, which likely reflect migraine heterogeneous genetic and molecular basis. The amount of therapies for acute and for prophylactic treatment is really wide, and one of the difficulties is with finding the best treatment for the single patient. In addition to this, patients carry out different daily life activities, and might show lifestyle habits which are not entirely adequate to manage migraine day by day. Education will be more and more important as a strategy of brain health promotion, because this will enable reducing the amount of subjects needing specialty care, thus leaving it to those who require it in reason of refractory condition or presence of comorbidities.

CONCLUSIONS

Recognizing the hallmarks of migraine and the features of single patients enables prescribing specific pharmacological and non-pharmacological treatments. Medical research on headaches today particularly suffers from the syndrome of single-disease approach, but it is important to have a cross-sectional and joint vision with other close specialties, in order to treat our patients with a comprehensive approach that a heterogeneous condition like migraine requires.

Investigating the potential role of the pituitary adenylate cyclase-activating polypeptide (PACAP) in regulating the ubiquitin signaling pathway in poultry

The physiological processes in animal production are regulated through biologically active molecules like peptides, proteins, and hormones identified through the development of the fundamental sciences and their application. One of the main polypeptides that plays an essential role in regulating physiological responses is the pituitary adenylate cyclase-activating polypeptide (PACAP). PACAP belongs to the glucagon/growth hormone-releasing hormone (GHRH)/vasoactive intestinal proteins (VIP) family and regulates feed intake, stress, and immune response in birds. Most of these regulations occur after PACAP stimulates the cAMP signaling pathway, which can regulate the expression of genes like MuRF1, FOXO1, Atrogin 1, and other ligases that are essential members of the ubiquitin system. On the other hand, PACAP stimulates the secretion of CRH in response to stress, activating the ubiquitin signaling pathway that plays a vital role in protein degradation and regulates oxidative stress and immune responses. Many studies conducted on rodents, mammals, and other models confirm the regulatory effects of PACAP, cAMP, and the ubiquitin pathway; however, there are no studies testing whether PACAP-induced cAMP signaling in poultry regulates the ubiquitin pathway. Besides, it would be interesting to investigate if PACAP can regulate ubiquitin signaling during stress response via CRH altered by HPA axis stimulation. Therefore, this review highlights a summary of research studies that indicate the potential interaction of the PACAP and ubiquitin signaling pathways on different molecular and physiological parameters in poultry species through the cAMP and stress signaling pathways.

A Monoclonal Antibody to PACAP for Migraine Prevention

BACKGROUND

Targeting pituitary adenylate cyclase-activating polypeptide (PACAP) is a new avenue for treating migraine. The efficacy and safety of intravenous Lu AG09222, a humanized monoclonal antibody directed against the PACAP ligand, for migraine prevention are unclear.

METHODS

In a phase 2, double-blind, randomized, placebo-controlled trial, we enrolled adult participants (18 to 65 years of age) with migraine for whom two to four previous preventive treatments had failed to provide a benefit. The trial included a 4-week treatment period and an 8-week follow-up period. Participants were randomly assigned in a 2:1:2 ratio to receive a single-dose baseline infusion of 750 mg of Lu AG09222, 100 mg of Lu AG09222, or placebo. The primary end point was the mean change from baseline in the number of migraine days per month, during weeks 1 through 4, in the Lu AG09222 750-mg group as compared with the placebo group.

RESULTS

Of 237 participants enrolled, 97 received 750 mg of Lu AG09222, 46 received 100 mg of Lu AG09222, and 94 received placebo. The mean number of baseline migraine days per month was 16.7 in the overall population, and the mean change from baseline over weeks 1 through 4 was -6.2 days in the Lu AG09222 750-mg group, as compared with -4.2 days in the placebo group (difference, -2.0 days; 95% confidence interval, -3.8 to -0.3; P = 0.02). Adverse events with a higher incidence in the Lu AG09222 750-mg group than in the placebo group during the 12-week observation period included coronavirus disease 2019 (7% vs. 3%), nasopharyngitis (7% vs. 4%), and fatigue (5% vs. 1%).

CONCLUSIONS

In a phase 2 trial, a single intravenous infusion of 750 mg of Lu AG09222 showed superiority over placebo in reducing migraine frequency over the subsequent 4 weeks. (Funded by H. Lundbeck; HOPE ClinicalTrials.gov number, NCT05133323.).

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.

The role of pituitary adenylate cyclase-activating polypeptide neurons in the hypothalamic ventromedial nucleus and the cognate PAC1 receptor in the regulation of hedonic feeding

Obesity is a health malady that affects mental, physical, and social health. Pathology includes chronic imbalance between energy intake and expenditure, likely facilitated by dysregulation of the mesolimbic dopamine (DA) pathway. We explored the role of pituitary adenylate cyclase-activating polypeptide (PACAP) neurons in the hypothalamic ventromedial nucleus (VMN) and the PACAP-selective (PAC1) receptor in regulating hedonic feeding. We hypothesized that VMN PACAP neurons would inhibit reward-encoding mesolimbic (A10) dopamine neurons via PAC1 receptor activation and thereby suppress impulsive consumption brought on by intermittent exposure to highly palatable food. Visualized whole-cell patch clamp recordings coupled with in vivo behavioral experiments were utilized in wildtype, PACAP-cre, TH-cre, and TH-cre/PAC1 receptor-floxed mice. We found that bath application of PACAP directly inhibited preidentified A10 dopamine neurons in the ventral tegmental area (VTA) from TH-cre mice. This inhibitory action was abrogated by the selective knockdown of the PAC1 receptor in A10 dopamine neurons. PACAP delivered directly into the VTA decreases binge feeding accompanied by reduced meal size and duration in TH-cre mice. These effects are negated by PAC1 receptor knockdown in A10 dopamine neurons. Additionally, apoptotic ablation of VMN PACAP neurons increased binge consumption in both lean and obese, male and female PACAP-cre mice relative to wildtype controls. These findings demonstrate that VMN PACAP neurons blunt impulsive, binge feeding behavior by activating PAC1 receptors to inhibit A10 dopamine neurons. As such, they impart impactful insight into potential treatment strategies for conditions such as obesity and food addiction.

Dipeptidyl Peptidase (DPP)-4 Inhibitors and Pituitary Adenylate Cyclase-Activating Polypeptide, a DPP-4 Substrate, Extend Neurite Outgrowth of Mouse Dorsal Root Ganglia Neurons: A Promising Approach in Diabetic Polyneuropathy Treatment

Individuals suffering from diabetic polyneuropathy (DPN) experience debilitating symptoms such as pain, paranesthesia, and sensory disturbances, prompting a quest for effective treatments. Dipeptidyl-peptidase (DPP)-4 inhibitors, recognized for their potential in ameliorating DPN, have sparked interest, yet the precise mechanism underlying their neurotrophic impact on the peripheral nerve system (PNS) remains elusive. Our study delves into the neurotrophic effects of DPP-4 inhibitors, including Diprotin A, linagliptin, and sitagliptin, alongside pituitary adenylate cyclase-activating polypeptide (PACAP), Neuropeptide Y (NPY), and Stromal cell-derived factor (SDF)-1a-known DPP-4 substrates with neurotrophic properties. Utilizing primary culture dorsal root ganglia (DRG) neurons, we meticulously evaluated neurite outgrowth in response to these agents. Remarkably, all DPP-4 inhibitors and PACAP demonstrated a significant elongation of neurite length in DRG neurons (PACAP 0.1 μM: 2221 ± 466 μm, control: 1379 ± 420, p < 0.0001), underscoring their potential in nerve regeneration. Conversely, NPY and SDF-1a failed to induce neurite elongation, accentuating the unique neurotrophic properties of DPP-4 inhibition and PACAP. Our findings suggest that the upregulation of PACAP, facilitated by DPP-4 inhibition, plays a pivotal role in promoting neurite elongation within the PNS, presenting a promising avenue for the development of novel DPN therapies with enhanced neurodegenerative capabilities.

VPAC1 and VPAC2 receptors mediate tactile hindpaw hypersensitivity and carotid artery dilatation induced by PACAP38 in a migraine relevant mouse model

BACKGROUND

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide pivotal in migraine pathophysiology and is considered a promising new migraine drug target. Although intravenous PACAP triggers migraine attacks and a recent phase II trial with a PACAP-inhibiting antibody showed efficacy in migraine prevention, targeting the PACAP receptor PAC1 alone has been unsuccessful. The present study investigated the role of three PACAP receptors (PAC1, VPAC1 and VPAC2) in inducing migraine-relevant hypersensitivity in mice.

METHODS

Hindpaw hypersensitivity was induced by repeated PACAP38 injections. Tactile sensitivity responses were quantified using von Frey filaments in three knockout (KO) mouse strains, each lacking one of the PACAP-receptors (Ntotal = 160). Additionally, ex vivo wire myography was used to assess vasoactivity of the carotid artery, and gene expression of PACAP receptors was examined by qPCR.

RESULTS

PACAP38 induced hypersensitivity in WT controls (p < 0.01) that was diminished in VPAC1 and VPAC2 KO mice (p < 0.05). In contrast, PAC1 KO mice showed similar responses to WT controls (p > 0.05). Myograph experiments supported these findings showing diminished vasoactivity in VPAC1 and VPAC2 KO mice. We found no upregulation of the non-modified PACAP receptors in KO mice.

CONCLUSIONS

This study assessed all three PACAP receptors in a migraine mouse model and suggests a significant role of VPAC receptors in migraine pathophysiology. The lack of hypersensitivity reduction in PAC1 KO mice suggests the involvement of other PACAP receptors or compensatory mechanisms. The results indicate that targeting only individual PACAP receptors may not be an effective migraine treatment.

Hippocampal PACAP signaling activation triggers a rapid antidepressant response

BACKGROUND

The development of ketamine-like rapid antidepressants holds promise for enhancing the therapeutic efficacy of depression, but the underlying cellular and molecular mechanisms remain unclear. Implicated in depression regulation, the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is investigated here to examine its role in mediating the rapid antidepressant response.

METHODS

The onset of antidepressant response was assessed through depression-related behavioral paradigms. The signaling mechanism of PACAP in the hippocampal dentate gyrus (DG) was evaluated by utilizing site-directed gene knockdown, pharmacological interventions, or optogenetic manipulations. Overall, 446 mice were used for behavioral and molecular signaling testing. Mice were divided into control or experimental groups randomly in each experiment, and the experimental manipulations included: chronic paroxetine treatments (4, 9, 14 d) or a single treatment of ketamine; social defeat or lipopolysaccharides-injection induced depression models; different doses of PACAP (0.4, 2, 4 ng/site; microinjected into the hippocampal DG); pharmacological intra-DG interventions (CALM and PACAP6-38); intra-DG viral-mediated PACAP RNAi; and opotogenetics using channelrhodopsins 2 (ChR2) or endoplasmic natronomonas halorhodopsine 3.0 (eNpHR3.0). Behavioral paradigms included novelty suppressed feeding test, tail suspension test, forced swimming test, and sucrose preference test. Western blotting, ELISA, or quantitative real-time PCR (RT-PCR) analysis were used to detect the expressions of proteins/peptides or genes in the hippocampus.

RESULTS

Chronic administration of the slow-onset antidepressant paroxetine resulted in an increase in hippocampal PACAP expression, and intra-DG blockade of PACAP attenuated the onset of the antidepressant response. The levels of hippocampal PACAP expression were reduced in both two distinct depression animal models and intra-DG knockdown of PACAP induced depression-like behaviors. Conversely, a single infusion of PACAP into the DG region produced a rapid and sustained antidepressant response in both normal and chronically stressed mice. Optogenetic intra-DG excitation of PACAP-expressing neurons instantly elicited antidepressant responses, while optogenetic inhibition induced depression-like behaviors. The longer optogenetic excitation/inhibition elicited the more sustained antidepressant/depression-like responses. Intra-DG PACAP infusion immediately facilitated the signaling for rapid antidepressant response by inhibiting calcium/calmodulin-dependent protein kinase II (CaMKII)-eukaryotic elongation factor 2 (eEF2) and activating the mammalian target of rapamycin (mTOR). Pre-activation of CaMKII signaling within the DG blunted PACAP-induced rapid antidepressant response as well as eEF2-mTOR-brain-derived neurotrophic factor (BDNF) signaling. Finally, acute ketamine treatment upregulated hippocampal PACAP expression, whereas intra-DG blockade of PACAP signaling attenuated ketamine's rapid antidepressant response.

CONCLUSIONS

Activation of hippocampal PACAP signaling induces a rapid antidepressant response through the regulation of CaMKII inhibition-governed eEF2-mTOR-BDNF signaling.

Pituitary cyclase-activating polypeptide targeted treatments for the treatment of primary headache disorders

OBJECTIVE

Migraine is a complex and disabling neurological disorder. Recent years have witnessed the development and emergence of novel treatments for the condition, namely those targeting calcitonin gene-related peptide (CGRP). However, there remains a substantial need for further treatments for those unresponsive to current therapies. Targeting pituitary adenylate cyclase-activating polypeptide (PACAP) as a possible therapeutic strategy in the primary headache disorders has gained interest over recent years.

METHODS

This review will summarize what we know about PACAP to date: its expression, receptors, roles in migraine and cluster headache biology, insights gained from preclinical and clinical models of migraine, and therapeutic scope.

RESULTS

PACAP shares homology with vasoactive intestinal polypeptide (VIP) and is one of several vasoactive neuropeptides along with CGRP and VIP, which has been implicated in migraine neurobiology. PACAP is widely expressed in areas of interest in migraine pathophysiology, such as the thalamus, trigeminal nucleus caudalis, and sphenopalatine ganglion. Preclinical evidence suggests a role for PACAP in trigeminovascular sensitization, while clinical evidence shows ictal release of PACAP in migraine and intravenous infusion of PACAP triggering attacks in susceptible individuals. PACAP leads to dural vasodilatation and secondary central phenomena via its binding to different G-protein-coupled receptors, and intracellular downstream effects through cyclic adenosine monophosphate (cAMP) and phosphokinase C (PKC). Targeting PACAP as a therapeutic strategy in headache has been explored using monoclonal antibodies developed against PACAP and against the PAC1 receptor, with initial positive results.

INTERPRETATION

Future clinical trials hold considerable promise for a new therapeutic approach using PACAP-targeted therapies in both migraine and cluster headache.

Intervening in the Premonitory Phase to Prevent Migraine: Prospects for Pharmacotherapy

Migraine is a common brain condition characterised by disabling attacks of headache with sensory sensitivities. Despite increasing understanding of migraine neurobiology and the impacts of this on therapeutic developments, there remains a need for treatment options for patients underserved by currently available therapies. The first specific drugs developed to treat migraine acutely, the serotonin-5-hydroxytryptamine [5-HT1B/1D] receptor agonists (triptans), seem to require headache onset in order to have an effect, while early treatment during mild pain before headache escalation improves short-term and long-term outcomes. Some patients find treating in the early window once headache has started but not escalated difficult, and migraine can arise from sleep or in the early hours of the morning, making prompt treatment after pain onset challenging. Triptans may be deemed unsuitable for use in patients with vascular disease and in those of older age and may not be effective in a proportion of patients. Headache is also increasingly recognised as being just one of the many facets of the migraine attack, and for some patients it is not the most disabling symptom. In many patients, painless symptoms can start prior to headache onset and can reliably warn of impending headache. There is, therefore, a need to identify therapeutic targets and agents that may be used as early as possible in the course of the attack, to prevent headache onset before it starts, and to reduce both headache and non-headache related attack burden. Early small studies using domperidone, naratriptan and dihydroergotamine have suggested that this approach could be useful; these studies were methodologically less rigorous than modern day treatment studies, of small sample size, and have not since been replicated. The emergence of novel targeted migraine treatments more recently, specifically calcitonin gene-related peptide (CGRP) receptor antagonists (gepants), has reignited interest in this strategy, with encouraging results. This review summarises historical and emerging data in this area, supporting use of the premonitory phase as an opportunity to intervene as early as possible in migraine to prevent attack-related morbidity.

The olfactory bulb: A neuroendocrine spotlight on feeding and metabolism

Olfaction is the most ancient sense and is needed for food-seeking, danger protection, mating and survival. It is often the first sensory modality to perceive changes in the external environment, before sight, taste or sound. Odour molecules activate olfactory sensory neurons that reside on the olfactory epithelium in the nasal cavity, which transmits this odour-specific information to the olfactory bulb (OB), where it is relayed to higher brain regions involved in olfactory perception and behaviour. Besides odour processing, recent studies suggest that the OB extends its function into the regulation of food intake and energy balance. Furthermore, numerous hormone receptors associated with appetite and metabolism are expressed within the OB, suggesting a neuroendocrine role outside the hypothalamus. Olfactory cues are important to promote food preparatory behaviours and consumption, such as enhancing appetite and salivation. In addition, altered metabolism or energy state (fasting, satiety and overnutrition) can change olfactory processing and perception. Similarly, various animal models and human pathologies indicate a strong link between olfactory impairment and metabolic dysfunction. Therefore, understanding the nature of this reciprocal relationship is critical to understand how olfactory or metabolic disorders arise. This present review elaborates on the connection between olfaction, feeding behaviour and metabolism and will shed light on the neuroendocrine role of the OB as an interface between the external and internal environments. Elucidating the specific mechanisms by which olfactory signals are integrated and translated into metabolic responses holds promise for the development of targeted therapeutic strategies and interventions aimed at modulating appetite and promoting metabolic health.

Affinity-Driven Aryl Diazonium Labeling of Peptide Receptors on Living Cells

Peptide-receptor interactions play critical roles in a wide variety of physiological processes. Methods to link bioactive peptides covalently to unmodified receptors on the surfaces of living cells are valuable for studying receptor signaling, dynamics, and trafficking and for identifying novel peptide-receptor interactions. Here, we utilize peptide analogues bearing deactivated aryl diazonium groups for the affinity-driven labeling of unmodified receptors. We demonstrate that aryl diazonium-bearing peptide analogues can covalently label receptors on the surface of living cells using both the neurotensin and the glucagon-like peptide 1 receptor systems. Receptor labeling occurs in the complex environment of the cell surface in a sequence-specific manner. We further demonstrate the utility of this covalent labeling approach for the visualization of peptide receptors by confocal fluorescence microscopy and for the enrichment and identification of labeled receptors by mass spectrometry-based proteomics. Aryl diazonium-based affinity-driven receptor labeling is attractive due to the high abundance of tyrosine and histidine residues susceptible to azo coupling in the peptide binding sites of receptors, the ease of incorporation of aryl diazonium groups into peptides, and the relatively small size of the aryl diazonium group. This approach should prove to be a powerful and relatively general method to study peptide-receptor interactions in cellular contexts.

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.

Association between social dominance hierarchy and PACAP expression in the extended amygdala, corticosterone, and behavior in C57BL/6 male mice

The natural alignment of animals into social dominance hierarchies produces adaptive, and potentially maladaptive, changes in the brain that influence health and behavior. Aggressive and submissive behaviors assumed by animals through dominance interactions engage stress-dependent neural and hormonal systems that have been shown to correspond with social rank. Here, we examined the association between social dominance hierarchy status established within cages of group-housed mice and the expression of the stress peptide PACAP in the bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA). We also examined the relationship between social dominance rank and blood corticosterone (CORT) levels, body weight, motor coordination (rotorod) and acoustic startle. Male C57BL/6 mice were ranked as either Dominant, Submissive, or Intermediate based on counts of aggressive/submissive encounters assessed at 12 weeks-old following a change in homecage conditions. PACAP expression was significantly higher in the BNST, but not the CeA, of Submissive mice compared to the other groups. CORT levels were lowest in Submissive mice and appeared to reflect a blunted response following events where dominance status is recapitulated. Together, these data reveal changes in specific neural/neuroendocrine systems that are predominant in animals of lowest social dominance rank, and implicate PACAP in brain adaptations that occur through the development of social dominance hierarchies.

Hypersensitivity to PACAP-38 in post-traumatic headache: a randomized clinical trial

Pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38), known for its role in migraine pathogenesis, has been identified as a novel drug target. Given the clinical parallels between post-traumatic headache (PTH) and migraine, we explored the possible role of PACAP-38 in the pathogenesis of PTH. To this end, we conducted a randomized, double-blind, placebo-controlled, two-way crossover trial involving adult participants diagnosed with persistent PTH resulting from mild traumatic brain injury. Participants were randomly assigned to receive a 20-min continuous intravenous infusion of either PACAP-38 (10 pmol/kg/min) or placebo (isotonic saline) on two separate experimental days, with a 1-week washout period in between. The primary outcome was the difference in incidence of migraine-like headache between PACAP-38 and placebo during a 12-h observational period post-infusion. The secondary outcome was the difference in the area under the curve (AUC) for baseline-corrected median headache intensity scores during the same 12-h observational period. Of 49 individuals assessed for eligibility, 21 were enrolled and completed the trial. The participants had a mean age of 35.2 years, and 16 (76%) were female. Most [19 of 21 (90%)] had a migraine-like phenotype. During the 12-h observational period, 20 of 21 (95%) participants developed migraine-like headache after intravenous infusion of PACAP-38, compared with two (10%) participants after placebo (P < 0.001). Furthermore, the baseline-corrected AUC values for median headache intensity scores during the 12-h observational period was higher after PACAP-38 than placebo (P < 0.001). These compelling results demonstrate that PACAP-38 is potent inducer of migraine-like headache in people with persistent PTH. Thus, targeting PACAP-38 signalling might be a promising avenue for the treatment of PTH.

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.

Retinal VIP-amacrine cells: their development, structure, and function

Amacrine cells (ACs) are the most structurally and functionally diverse neuron type in the retina. Different ACs have distinct functions, such as neuropeptide secretion and inhibitory connection. Vasoactive intestinal peptide (VIP) -ergic -ACs are retina gamma-aminobutyric acid (GABA) -ergic -ACs that were discovered long ago. They secrete VIP and form connections with bipolar cells (BCs), other ACs, and retinal ganglion cells (RGCs). They have a specific structure, density, distribution, and function. They play an important role in myopia, light stimulated responses, retinal vascular disease and other ocular diseases. Their significance in the study of refractive development and disease is increasing daily. However, a systematic review of the structure and function of retinal VIP-ACs is lacking. We discussed the detailed characteristics of VIP-ACs from every aspect across species and providing systematic knowledge base for future studies. Our review led to the main conclusion that retinal VIP-ACs develop early, and although their morphology and distribution across species are not the same, they have similar functions in a wide range of ocular diseases based on their function of secreting neuropeptides and forming inhibitory connections with other cells.

Integrated Transcriptomic and Proteomic Study of the Mechanism of Action of the Novel Small-Molecule Positive Allosteric Modulator 1 in Targeting PAC1-R for the Treatment of D-Gal-Induced Aging Mice

Small-molecule positive allosteric modulator 1 (SPAM1), which targets pituitary adenylate cyclase-activating polypeptide receptor 1 (PAC1-R), has been found to have a neuroprotective effect, and the underlying mechanism was explored in this study. First, using a D-galactose (D-gal)-induced aging mouse model, we confirmed that SPAM1 improves the structure of the hippocampal dentate gyrus and restores the number of neurons. Compared with D-gal model mice, SPAM1-treated mice showed up-regulated expression of Sirtuin 6 (SIRT6) and Lamin B1 and down-regulated expression of YinYang 1 (YY1) and p16. A similar tendency was observed in senescent RGC-5 cells induced by long-term culture, indicating that SPAM1 exhibits significant in vitro and in vivo anti-senescence activity in neurons. Then, using whole-transcriptome sequencing and proteomic analysis, we further explored the mechanism behind SPAM1's neuroprotective effects and found that SPAM is involved in the longevity-regulating pathway. Finally, the up-regulation of neurofilament light and medium polypeptides indicated by the proteomics results was further confirmed by Western blotting. These results help to lay a pharmacological network foundation for the use of SPAM1 as a potent anti-aging therapeutic drug to combat neurodegeneration with anti-senescence, neuroprotective, and nerve regeneration activity.

Targeting the PACAP-38 pathway is an emerging therapeutic strategy for migraine prevention

INTRODUCTION

The pituitary adenylate cyclase-activating polypeptide-38 (PACAP-38) has emerged as a key mediator of migraine pathogenesis. PACAP-38 and its receptors are predominantly distributed in arteries, sensory and parasympathetic neurons of the trigeminovascular system. Phase 2 trials have tested human monoclonal antibodies designed to bind and inhibit PACAP-38 and the pituitary adenylate cyclase-activating polypeptide type I (PAC1) receptor for migraine prevention.

AREAS COVERED

This review focuses on the significance of the PACAP-38 pathway as a target in migraine prevention. English peer-reviewed articles were searched in PubMed, Scopus and ClinicalTrials.gov electronic databases.

EXPERT OPINION

A PAC1 receptor monoclonal antibody was not effective for preventing migraine in a proof-of-concept trial, paving the way for alternative strategies to be considered. Lu AG09222 is a humanized monoclonal antibody targeting PACAP-38 that was effective in preventing physiological responses of PACAP38 and reducing monthly migraine days in individuals with migraine. Further studies are necessary to elucidate the clinical utility, long-term safety and cost-effectiveness of therapies targeting the PACAP pathway.

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.

Investigation of PACAP38 and PAC1 Receptor Expression in Human Retinoblastoma and the Effect of PACAP38 Administration on Human Y-79 Retinoblastoma Cells

Retinoblastoma represents the most prevalent malignant neoplasm affecting the eyes in childhood. The clear-cut origin of retinoblastoma has not yet been determined; however, based on experiments, it has been suggested that RB1 loss in cone photoreceptors causes retinoblastoma. Pituitary adenylate-cyclase activating polypeptide (PACAP) is a pleiotropic neuropeptide which has been shown to be affected in certain tumorous transformations, such as breast, lung, kidney, pancreatic, colon, and endocrine cancers. This study aimed to investigate potential changes in both PACAP38 and PAC1 receptor (PAC1R) expression in human retinoblastoma and the effect of PACAP38 administration on the survival of a human retinoblastoma cell line (Y-79). We analyzed human enucleation specimens removed because of retinoblastoma for PACAP38 and PAC1R immunostaining and the effect of PACAP38 on the survival of the Y-79 cell line. We described for the first time that human retinoblastoma cells from patients showed only perinuclear, dot-like immunopositivity for both PACAP38 and PAC1R, irrespective of laterality, genetic background, or histopathological features. Nanomolar (100 nM and 500 nM) PACAP38 concentrations had no effect on the viability of Y-79 cells, while micromolar (2 µM and 6 µM) PACAP38 significantly decreased tumor cell viability. These findings, along with general observations from animal studies showing that PACAP38 has strong anti-apoptotic, anti-inflammatory, and antioxidant effects on ocular tissues, together suggest that PACAP38 and its analogs are promising candidates in retinoblastoma therapy.

Novel Targets and Drug Delivery System in the Treatment of Postoperative Pain: Recent Studies and Clinical Advancement

Pain is generated by a small number of peripheral targets. These can be made more sensitive by inflammatory mediators. The number of opioids prescribed to the patients can be reduced dramatically with better pain management. Any therapy that safely and reliably provides extended analgesia and is flexible enough to facilitate a diverse array of release profiles would be useful for improving patient comfort, quality of care, and compliance after surgical procedures. Comparisons are made between new and traditional methods, and the current state of development has been discussed; taking into account the availability of molecular and cellular level data, preclinical and clinical data, and early post-market data. There are a number of benefits associated with the use of nanotechnology in the delivery of analgesics to specific areas of the body. Nanoparticles are able to transport drugs to inaccessible bodily areas because of their small molecular size. This review focuses on targets that act specifically or primarily on sensory neurons, as well as inflammatory mediators that have been shown to have an analgesic effect as a side effect of their anti- inflammatory properties. New, regulated post-operative pain management devices that use existing polymeric systems were presented in this article, along with the areas for potential development. Analgesic treatments, both pharmacological and non-pharmacological, have also been discussed.

Neuroprotective effect of the PACAP-ADNP axis on SOD1G93A mutant motor neuron death induced by trophic factors deprivation

Amyotrophic lateral Sclerosis (ALS) is a neurodegenerative disease characterized by progressive degeneration of motor neurons in the central nervous system. Mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1) account for approximately in 20% of familial ALS cases. The pathological mechanisms underlying the toxicity induced by mutated SOD1 are still unknown. However, it has been hypothesized that oxidative stress (OS) has a crucial role in motor neuron degeneration in ALS patients. Moreover, it has been described that SOD1 mutation interferes expression of nuclear factor erythroid 2-related factor 2 (Nrf2), a protective key modulator against OS and reactive oxygen species (ROS) formation. The protective effect of pituitary adenylate cyclase-activating peptide (PACAP) has been demonstrated in various neurological disorders, including ALS. Some of its effects are mediated by the stimulation of an intracellular factor known as activity-dependent protein (ADNP). The role of PACAP-ADNP axis on mutated SOD1 motor neuron degeneration has not been explored, yet. The present study aimed to investigate whether PACAP prevented apoptotic cell death induced by growth factor deprivation through ADNP activation and whether the peptidergic axis can counteract the OS insult. By using an in vitro model of ALS, we demonstrated that PACAP by binding to PAC1 receptor (PAC1R) prevented motor neuron death induced by serum deprivation through induction of the ADNP expression via PKC stimulation. Furthermore, we have also demonstrated that the PACAP/ADNP axis counteracted ROS formation by inducing translocation of the Nfr2 from the cytoplasm to the nucleus. In conclusion, our study provides new insights regarding the protective role of PACAP-ADNP in ALS.

Impact Assessment of Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) and Hemostatic Sponge on Vascular Anastomosis Regeneration in Rats

The proper regeneration of vessel anastomoses in microvascular surgery is crucial for surgical safety. Pituitary adenylate cyclase-activating polypeptide (PACAP) can aid healing by decreasing inflammation, apoptosis and oxidative stress. In addition to hematological and hemorheological tests, we examined the biomechanical and histological features of vascular anastomoses with or without PACAP addition and/or using a hemostatic sponge (HS). End-to-end anastomoses were established on the right femoral arteries of rats. On the 21st postoperative day, femoral arteries were surgically removed for evaluation of tensile strength and for histological and molecular biological examination. Effects of PACAP were also investigated in tissue culture in vitro to avoid the effects of PACAP degrading enzymes. Surgical trauma and PACAP absorption altered laboratory parameters; most notably, the erythrocyte deformability decreased. Arterial wall thickness showed a reduction in the presence of HS, which was compensated by PACAP in both the tunica media and adventitia in vivo. The administration of PACAP elevated these parameters in vitro. In conclusion, the application of the neuropeptide augmented elastin expression while HS reduced it, but no significant alterations were detected in collagen type I expression. Elasticity and tensile strength increased in the PACAP group, while it decreased in the HS decreased. Their combined use was beneficial for vascular regeneration.

PAC1 deficiency reduces chondrogenesis in atherosclerotic lesions of hypercholesterolemic ApoE-deficient mice

BACKGROUND

Induction of chondrogenesis is associated with progressive atherosclerosis. Deficiency of the ADCYAP1 gene encoding pituitary adenylate cyclase-activating peptide (PACAP) aggravates atherosclerosis in ApoE deficient (ApoE-/-) mice. PACAP signaling regulates chondrogenesis and osteogenesis during cartilage and bone development. Therefore, this study aimed to decipher whether PACAP signaling is related to atherogenesis-related chondrogenesis in the ApoE-/- mouse model of atherosclerosis and under the influence of a high-fat diet.

METHODS

For this purpose, PACAP-/-/ApoE-/-, PAC1-/-/ApoE-/-, and ApoE-/- mice, as well as wildtype (WT) mice, were studied under standard chow (SC) or cholesterol-enriched diet (CED) for 20 weeks. The amount of cartilage matrix in atherosclerotic lesions of the brachiocephalic trunk (BT) with maximal lumen stenosis was monitored by alcian blue and collagen II staining on deparaffinized cross sections. The chondrogenic RUNX family transcription factor 2 (RUNX2), macrophages [(MΦ), Iba1+], and smooth muscle cells (SMC, sm-α-actin) were immunohistochemically analyzed and quantified.

RESULTS

ApoE-/- mice fed either SC or CED revealed an increase of alcian blue-positive areas within the media compared to WT mice. PAC1-/-/ApoE-/- mice under CED showed a reduction in the alcian blue-positive plaque area in the BT compared to ApoE-/- mice. In contrast, PACAP deficiency in ApoE-/- mice did not affect the chondrogenic signature under either diet.

CONCLUSIONS

Our data show that PAC1 deficiency reduces chondrogenesis in atherosclerotic plaques exclusively under conditions of CED-induced hypercholesterolemia. We conclude that CED-related chondrogenesis occurs in atherosclerotic plaques via transdifferentiation of SMCs and MΦ, partly depending on PACAP signaling through PAC1. Thus, PAC1 antagonists or PACAP agonists may offer therapeutic potential against pathological chondrogenesis in atherosclerotic lesions generated under hypercholesterolemic conditions, especially in familial hypercholesterolemia. This discovery opens therapeutic perspectives to be used in the treatment against the progression of atherosclerosis.

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.

Pituitary adenylate cyclase-activating polypeptide deficient mice show length abnormalities of the axon initial segment

We previously found that pituitary adenylate cyclase-activating polypeptide (PACAP)-deficient (PACAP-/-) mice exhibit dendritic spine morphology impairment and neurodevelopmental disorder (NDD)-like behaviors such as hyperactivity, increased novelty-seeking behavior, and deficient pre-pulse inhibition. Recent studies have indicated that rodent models of NDDs (e.g., attention-deficit hyperactivity disorder (ADHD) and autism spectrum disorder) show abnormalities in the axon initial segment (AIS). Here, we revealed that PACAP-/- mice exhibited a longer AIS length in layer 2/3 pyramidal neurons of the primary somatosensory barrel field compared with wild-type control mice. Further, we previously showed that a single injection of atomoxetine, an ADHD drug, improved hyperactivity in PACAP-/- mice. In this study, we found that repeated treatments of atomoxetine significantly improved AIS abnormality along with hyperactivity in PACAP-/- mice. These results suggest that AIS abnormalities are associated with NDDs-like behaviors in PACAP-/- mice. Thus, improvement in AIS abnormalities will be a novel drug therapy for NDDs.