Exogenous Pituitary Adenylate Cyclase-activating Polypeptide Research Articles

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

We explored the role of pituitary adenylate cyclase-activating polypeptide (PACAP) neurons in the hypothalamic ventromedial nucleus (VMN) in regulating hedonic feeding. We hypothesized that VMN PACAP neurons would inhibit reward-encoding mesolimbic (A10) dopamine neurons 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 optogenetic stimulation of VMN PACAP neurons inhibited postsynaptic targets in the ventral tegmental area (VTA), an effect replicated by bath application of exogenous PACAP during recordings from preidentified A10 dopamine neurons. These inhibitory actions were abrogated by the PAC1/VPAC2 receptor antagonist PACAP6-38, the KATP channel blocker tolbutamide, and by 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. These effects are negated by PACAP6-38, PAC1 receptor knockdown in A10 dopamine neurons, and apoptotic ablation of VMN PACAP neurons. These findings demonstrate that VMN PACAP neurons blunt impulsive, binge feeding behavior by activating PAC1 receptors and KATP channels to inhibit A10 dopamine neurons. As such, they impart impactful insight into potential treatment strategies for conditions such as obesity and food addiction. Work funded by PHS grant DA024314. Work funded by PHS grant DA024314. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Identification of PACAP-Expressing Neurons in the Hypothalamic Origins of Sympathetic Outflow Tracts Terminating in Brown Adipose Tissue of Mice

Abstract Adaptive thermogenesis in brown adipose tissue is stimulated by the sympathetic nervous system (SNS) in response to cold stress. Using retrograde viral transneuronal tract tracers, previous studies have identified that the paraventricular nucleus (PVN), ventromedial hypothalamus (VMH), and median preoptic nucleus (MnPO) contain neurons that are part of sympathetic outflow tracts to brown adipose tissue, presumptively involved in SNS stimulation of interscapular brown adipose tissue (iBAT). Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is a peptide hormone known to regulate energy homeostasis, acting in both the central (CNS) and peripheral nervous system (PNS). Mice lacking PACAP have impaired adrenergic-induced thermogenesis and a cold-sensitive phenotype. In the CNS, PACAP is highly expressed in the VMH, MnPO, and PVN of the hypothalamus. Injection of PACAP into the VMN increased core body temperature and sympathetic nerve activity to brown adipose tissue. While these studies show exogenous PACAP can activate sympathetic outflow tracts to brown adipose tissue, they do not confirm that endogenously expressed PACAP induces sympathetic nerve activity as an adaptive mechanism to cold stress, or if sympathetic outflow tracts originating in the hypothalamus express PACAP. We hypothesize that PACAP is expressed in neurons of sympathetic outflow tracts originating in the hypothalamus. To test this hypothesis, PACAP-eGFP transgenic mice were injected with the retrograde neural tracer, pseudorabies virus tagged with β-galactosidase (β-gal, PRV-BaBlu), in iBAT where postganglionic nerves innervate the tissue. Five-days post-infection, animals were culled, brains removed and cryosectioned. Neurons positive for green fluorescent protein (eGFP) and/or β-gal immunoreactivity (ir) were identified by immunohistochemistry in serial coronal and sagittal brain cryo-sections. Co-occurrence of eGFP-ir and β-gal-ir, inferred PACAP expressing neurons present in sympathetic outflow tracts (ImageJ). Co-occurrence was identified in several structures in the hypothalamus and thalamus. In conclusion, this study presents neuroanatomical evidence for populations of PACAPinergic neurons in the hypothalamus that are part of sympathetic outflow tracts to brown adipose tissue, providing further evidence of a central role for PACAP in regulating energy homeostasis.

Pituitary Adenylate Cyclase-Activating Polypeptide Alleviates Intestinal, Extra-Intestinal and Systemic Inflammatory Responses during Acute Campylobacter jejuni-induced Enterocolitis in Mice.

Human Campylobacter jejuni infections are emerging, and constitute a significant health burden worldwide. The ubiquitously expressed pituitary adenylate cyclase-activating polypeptide (PACAP) is well-known for its cell-protective and immunomodulatory effects. In our actual intervention study, we used an acute campylobacteriosis model and assessed the potential disease-alleviating effects of exogenous PACAP. Therefore, secondary abiotic IL-10−/− mice were perorally infected with C. jejuni and treated with synthetic PACAP38 intraperitoneally from day 2 until day 5 post-infection. Whereas PACAP did not interfere with the gastrointestinal colonization of the pathogen, mice from the PACAP group exhibited less severe clinical signs of C. jejuni-induced disease, as compared to mock controls, which were paralleled by alleviated apoptotic, but enhanced cell proliferative responses in colonic epithelia on day 6 post-infection. Furthermore, PACAP dampened the accumulation of macrophages and monocytes, but enhanced regulatory T cell responses in the colon, which were accompanied by less IFN-γ secretion in intestinal compartments in PACAP versus mock-treated mice. Remarkably, the inflammation-dampening properties of PACAP could also be observed in extra-intestinal organs, and strikingly, even the systemic circulation on day 6 post-infection. For the first time, we provide evidence that synthetic PACAP might be a promising candidate to combat acute campylobacteriosis and post-infectious sequelae.

Pituitary Adenylate Cyclase-Activating Polypeptide Attenuates Brain Edema by Protecting Blood-Brain Barrier and Glymphatic System After Subarachnoid Hemorrhage in Rats.

Brain edema is a vital contributor to early brain injury after subarachnoid hemorrhage (SAH), which is responsible for prolonged hospitalization and poor outcomes. Pharmacological therapeutic targets on edema formation have been the focus of research for decades. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to participate in neural development and brain injury. Here, we used PACAP knockout CRISPR to demonstrate that endogenous PACAP plays an endogenous neuroprotective role against brain edema formation after SAH in rats. The exogenous PACAP treatment provided both short- and long-term neurological benefits by preserving the function of the blood-brain barrier and glymphatic system after SAH. Pretreatment of inhibitors of PACAP receptors showed that the PACAP-involved anti-edema effect and neuroprotection after SAH was facilitated by the selective PACAP receptor (PAC1). Further administration of adenylyl cyclase (AC) inhibitor and sulfonylurea receptor 1 (SUR1) CRISPR activator suggested that the AC-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) axis participated in PACAP signaling after SAH, which inhibited the expression of edema-related proteins, SUR1 and aquaporin-4 (AQP4), through SUR1 phosphorylation. Thus, PACAP may serve as a potential clinical treatment to alleviate brain edema in patients with SAH.

The Neuroprotective and Biomarker Potential of PACAP in Human Traumatic Brain Injury.

Traumatic brain injury remains a growing public health concern and represents the greatest contributor to death and disability globally among all trauma-related injuries. There are limited clinical data regarding biomarkers in the diagnosis and outcome prediction of TBI. The lack of real effective treatment for recovery calls for research of TBI to be shifted into the area of prevention, treatment of secondary brain injury and neurorehabilitation. The neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) has been reported to act as a hormone, a neuromodulator, a neurotransmitter and a trophic factor, and has been implicated in a variety of developmental and regenerative processes. The importance of PACAP in neuronal regeneration lies in the upregulation of endogenous PACAP and its receptors and the protective effect of exogenous PACAP after different central nervous system injury. The aim of this minireview is to summarize both the therapeutic and biomarker potential of the neuropeptide PACAP, as a novel possible target molecule presently being investigated in several human conditions including TBI, and with encouraging results in animal models of TBI.

Immunomodulatory Effects of the Neuropeptide Pituitary Adenylate Cyclase-Activating Polypeptide in Acute Toxoplasmosis

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is an endogenous neuropeptide with distinct functions including the regulation of inflammatory processes. PACAP is able to modify the immune response by directly regulating macrophages and monocytes inhibiting the production of inflammatory cytokines, chemokines and free radicals. Here, we analyzed the effect of exogenous PACAP on peripheral immune cell subsets upon acute infection with the parasite Toxoplasma gondii (T. gondii). PACAP administration was followed by diminished innate immune cell recruitment to the peritoneal cavity of T. gondii-infected mice. PACAP did not directly interfere with parasite replication, instead, indirectly reduced parasite burden in mononuclear cell populations by enhancing their phagocytic capacity. Although proinflammatory cytokine levels were attenuated in the periphery upon PACAP treatment, interleukin (IL)-10 and Transforming growth factor beta (TGF-β) remained stable. While PACAP modulated VPAC1 and VPAC2 receptors in immune cells upon binding, it also increased their expression of brain-derived neurotrophic factor (BDNF). In addition, the expression of p75 neurotrophin receptor (p75NTR) on Ly6Chi inflammatory monocytes was diminished upon PACAP administration. Our findings highlight the immunomodulatory effect of PACAP on peripheral immune cell subsets during acute Toxoplasmosis, providing new insights about host-pathogen interaction and the effects of neuropeptides during inflammation.

Pituitary Adenylate Cyclase-Activating Polypeptide Modulates Dendritic Spine Maturation and Morphogenesis via MicroRNA-132 Upregulation.

Alterations in pituitary adenylate cyclase-activating polypeptide (PACAP), a multifunctional neuropeptide, and its receptors have been identified as risk factors for certain psychiatric disorders, including schizophrenia. Increasing evidence from human genetic and animal model studies suggest an association between various psychiatric disorders and altered dendritic spine morphology. In the present study, we investigated the role of exogenous and endogenous PACAP in spine formation and maturation. PACAP modified the density and morphology of PSD-95-positive spines in primary cultured hippocampal neurons. Notably, PACAP increased the levels of microRNA (miR)-132 and decreased expression of corresponding miR-132 target genes and protein expression of p250GAP, a miR-132 effector known to be involved in spine morphology regulation. In corroboration, PSD-95-positive spines were reduced in PACAP-deficient (PACAP-/-) mice versus WT mice. Golgi staining of hippocampal CA1 neurons revealed a reduced spine densities and atypical morphologies in the male PACAP-/- mice. Furthermore, viral miR-132 overexpression reversed the reduction in hippocampal spinal density in the male PACAP-/- mice. These results indicate that PACAP signaling plays a critical role in spine morphogenesis possibly via miR-132. We suggest that dysfunction of PACAP signaling may contribute to the pathogenesis of neuropsychiatric disorders, at least partly through its effects on spine formation.SIGNIFICANCE STATEMENT Pituitary adenylate cyclase-activating polypeptide (PACAP) signaling dysfunction and dendritic spine morphology alterations have recently been suggested as important pathophysiological mechanisms underlying several psychiatric and neurological disorders. In this study, we investigated whether PACAP regulates dendritic spine morphogenesis. In a combination of pharmacological and viral gain- and loss-of-function approaches in vitro and in vivo experiments, we found PACAP to increase the size and density of dendritic spines via miR-132 upregulation. Together, our data suggest that a dysfunction of PACAP signaling may contribute to the pathogenesis of neuropsychiatric disorders, at least partly through abnormal spine formation.

Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) Reduces Oxidative and Mechanical Stress-Evoked Matrix Degradation in Chondrifying Cell Cultures.

Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide also secreted by non-neural cells, including chondrocytes. PACAP signaling is involved in the regulation of chondrogenesis, but little is known about its connection to matrix turnover during cartilage formation and under cellular stress in developing cartilage. We found that the expression and activity of hyaluronidases (Hyals), matrix metalloproteinases (MMP), and aggrecanase were permanent during the course of chondrogenesis in primary chicken micromass cell cultures, although protein levels changed daily, along with moderate and relatively constant enzymatic activity. Next, we investigated whether PACAP influences matrix destructing enzyme activity during oxidative and mechanical stress in chondrogenic cells. Exogenous PACAP lowered Hyals and aggrecanase expression and activity during cellular stress. Expression and activation of the majority of cartilage matrix specific MMPs such as MMP1, MMP7, MMP8, and MMP13, were also decreased by PACAP addition upon oxidative and mechanical stress, while the activity of MMP9 seemed not to be influenced by the neuropeptide. These results suggest that application of PACAP can help to preserve the integrity of the newly synthetized cartilage matrix via signaling mechanisms, which ultimately inhibit the activity of matrix destroying enzymes under cellular stress. It implies the prospect that application of PACAP can ameliorate articular cartilage destruction in joint diseases.

Effects of Pituitary Adenylate Cyclase Activating Polypeptide in Human Proximal Tubule Cells Against Gentamicin Toxicity

Nephrotoxicity by aminoglycoside antibiotics is a common cause of drug-induced nephropathy. Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide first isolated from hypothalamus, but later shown in widespread distribution. It exerts general cytoprotective effects in different cell types. Renoprotective effects of PACAP have been shown in various in vivo and in vitro experiments, but it is still not known whether it protects human proximal tubular cells against gentamicin toxicity. The aim of the present study was to investigate whether PACAP could influence the survival rate of human proximal tubular epithelial cells exposed to gentamicin treatment. For investigating its effect on cell survival after gentamicin treatment, cell viability was evaluated using MTT assay. Obtaining further insight into the background mechanism of gentamicin exposure and PACAP’s effect, expression of numerous kidney-related proteins was investigated using kidney biomarker array. Our results show that PACAP had protective effects against gentamicin-induced decreased cell viability, while it did not influence the proliferation activity of HK-2 cells. PACAP could counteract the expression-decreasing effect of gentamicin on dipeptidyl peptidase IV and vascular endothelial growth factor as assessed by kidney biomarker array. In summary, our present study could prove the protective effect of exogenous PACAP in gentamicin-induced nephrotoxicity.

PACAP and PAC1R are differentially expressed in motor cortex of amyotrophic lateral sclerosis patients and support survival of iPSC-derived motor neurons.

Amyotrophic lateral sclerosis (ALS) is a fatal and disabling neurodegenerative disease characterized by upper and lower motor neurons depletion. In our previous work, comprehensive genomic profiling of 41 motor cortex samples enabled to discriminate controls from sporadic ALS patients, and segregated these latter into two distinct subgroups (SALS1 and SALS2), each associated with different deregulated genes. In the present study, we focused our attention on two of them, Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) and its type 1 receptor (PAC1R), and validated the results of the transcriptome experiments by quantitative reverse transcription-polymerase chain reaction (qRT-PCR), immunohistochemistry and Western blot analysis. To assess the functional role of PACAP and PAC1R in ALS, we developed an in vitro model of human induced pluripotent stem cells (iPSC)-derived motor neurons and examined the trophic effects of exogenous PACAP following neurodegenerative stimuli. Treatment with 100 nm PACAP was able to effectively rescue iPSC-derived motor neurons from apoptosis, as shown by cell viability assay and protein dosage of the apoptotic marker (BAX). All together, these data suggest that perturbations in the PACAP-PAC1R pathway may be involved in ALS pathology and represent a potential drug target to enhance motor neuron viability.

Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates the expression of PACAP in cultured tilapia astrocytes.

Neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic hormone that is involved in numerous physiologic functions. The present study examines the presence and the functional significance of PACAP and its receptor in the brain and astrocytes of tilapia (Oreochromis mossambicus). This is the first demonstration of the full-length nucleotide sequence of tPACAP gene in tilapia pituitary, brain, and cultured astrocytes. Two cDNA variants of the growth hormone-releasing hormone (GHRH)-PACAP gene were identified in tilapia pituitary, brain, and cultured astrocytes as a result of exon skipping with a long form (271 bp) encoding both tPACAP(38) and tGHRH and a short form (166 bp) encoding only tPACAP(38). The short form was found to be more abundant in astrocytes. Addition of ovine PACAP(38) (1 nM) to cultured astrocytes significantly stimulated the expression of tPACAP(38) at 4 hrs, but the effect dropped after 8 hrs of treatment. By contrast, the expression of PACAP type I receptor (PAC(1)-R) mRNA in the astrocytes was not responsive to PACAP(38) treatment. The tPACAP(38) expression also was activated by the cAMP analog, dibutyryl-cAMP, in a dose-dependent manner. Adding high salinity (170 mM NaCl, 500 mOsm/kg osmolarity) to cultured medium substantially increased astroglial tPACAP(38) expression over 4 hrs to a level that was maintained for 16 hrs. This observation was not found when mannitol (270 mM) was supplemented as an osmolarity-enhancing agent (500 mOsm/ kg). Taken together, tPACAP expression in tilapia astrocytes was well regulated by exogenous PACAP, cAMP, and salinity and might be involved in the adaptation to high salinity when the fish is in a seawater environment.

Differently polarized macrophages affect the viability and growth of NSPCs by regulating the expression of PACAP

ObjectiveTo explore the influence of differently polarized macrophages, M1 or M2, to viability and growth of NSPCs and its possible mechanism, especially the role of pituitary adenylate cyclase-activating polypeptide (PACAP) in it. MethodSpinal cord-derived NSPCs were co-cultured with M1 or M2 through a transwell system. Growth of NSPCs in both groups was observed through an inverted microscope within 3days. NSPCs viability of each group, represented as intracellular ATP levels, was measured using the Cellular ATP Kit HTS following co-culture for 24h. PACAP levels in the co-cultured NSPCs was alleviated with immunofluorescence and Western blot analysis. ResultsMorphologically NSPCs demonstrated a long spindle shape with short sprout on 3rd day when cultured together with M2. NSPCs cultured with M1 showed a small circle or oval shape with no obvious sprout. Expression of PACAP was observed in NSPCs co-cultured with M2 through immunofluorescence. In contrast, NSPCs did not demonstrate PACAP staining in the presence of M1 or cultured alone. PACAP in the NSPCs co-cultured with M2 was upregulated significantly compared with that co-cultured with M1 according to Western blot method. The relative ATP level of NSPCs co-cultured with M1 was markedly decreased while that with M2 was elevated significantly. That trend could be relieved by exogenous PACAP or PACAP 6–38. Viability change of NSPCs by M1/M2 correlated with apoptosis. ConclusionDifferently polarized macrophages could affect the growth and viability of NSPCs by regulating the expression of PACAP.

Backup Mechanisms Maintain PACAP/VIP-Induced Arterial Relaxations in Pituitary Adenylate Cyclase-Activating Polypeptide-Deficient Mice

Background: Pituitary adenylate cyclase-activating polypeptide (PACAP) is a multifunctional neuropeptide in the VIP/secretin/glucagon peptide superfamily. Two active forms, PACAP1-38 and PACAP1-27, act through G protein-coupled receptors, the PAC1 and VPAC1/2 receptors. Effects of PACAP include potent vasomotor activity. Vasomotor activity and organ-specific vasomotor effects of PACAP-deficient mice have not yet been investigated; thus, the assessment of its physiological importance in vasomotor functions is still missing. We hypothesized that backup mechanisms exist to maintain PACAP pathway activity in PACAP knockout (KO) mice. Thus, we investigated the vasomotor effects of exogenous vasoactive intestinal peptide (VIP) and PACAP polypeptides in PACAP wild-type (WT) and PACAP-deficient (KO) male mice. Methods: Carotid and femoral arteries were isolated from 8- to 12-week-old male WT and PACAP-KO mice. Vasomotor responses were measured with isometric myography. Results: In the arteries of WT mice the peptides induced relaxations, which were significantly greater to PACAP1-38 than to PACAP1-27 and VIP. In KO mice, PACAP1-38 did not elicit relaxation, whereas PACAP1-27 and VIP elicited significantly greater relaxation in KO mice than in WT mice. The specific PAC1R and VPAC1R antagonist completely blocked the PACAP-induced relaxations. Conclusion: Our data suggest that in PACAP deficiency, backup mechanisms maintain arterial relaxations to polypeptides, indicating an important physiological role for the PACAP pathway in the regulation of vascular tone.

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Is Involved in Adult Mouse Hippocampal Neurogenesis After Stroke.

In the subgranular zone (SGZ) of the hippocampus, neurogenesis persists throughout life and is upregulated following ischemia. Accumulating evidence suggests that enhanced neurogenesis stimulated by ischemic injury contributes to recovery after stroke. However, the mechanisms underlying the upregulation of neurogenesis are unclear. We have demonstrated that a neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), exerts a wide range of effects on neural stem cells (NSCs) during neural development. Here, we examined the effects of endogenous and exogenous PACAP in adult NSCs of the SGZ. Immunostaining showed expression of the PACAP receptor PAC1R in nestin-positive NSCs of adult naive mice. PACAP injection into the lateral ventricle increased bromodeoxyuridine (BrdU)-positive proliferative cells in the SGZ. These data suggest that PACAP promoted the proliferation of NSCs. In global ischemia model mice, the number of BrdU-positive cells was increased in wild-type mice but not in PACAP heterozygous knockout mice. The BrdU-positive cells that increased in number after ischemia were immunopositive for SOX2, a marker of NSCs, and differentiated into NeuN-positive mature neurons at 4weeks after ischemia. These findings suggest that PACAP contributes to the proliferation of NSCs and may be associated with recovery after brain injury.

Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) Pathway Is Induced by Mechanical Load and Reduces the Activity of Hedgehog Signaling in Chondrogenic Micromass Cell Cultures.

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neurohormone exerting protective function during various stress conditions either in mature or developing tissues. Previously we proved the presence of PACAP signaling elements in chicken limb bud-derived chondrogenic cells in micromass cell cultures. Since no data can be found if PACAP signaling is playing any role during mechanical stress in any tissues, we aimed to investigate its contribution in mechanotransduction during chondrogenesis. Expressions of the mRNAs of PACAP and its major receptor, PAC1 increased, while that of other receptors, VPAC1, VPAC2 decreased upon mechanical stimulus. Mechanical load enhanced the expression of collagen type X, a marker of hypertrophic differentiation of chondrocytes and PACAP addition attenuated this elevation. Moreover, exogenous PACAP also prevented the mechanical load evoked activation of hedgehog signaling: protein levels of Sonic and Indian Hedgehogs and Gli1 transcription factor were lowered while expressions of Gli2 and Gli3 were elevated by PACAP application during mechanical load. Our results suggest that mechanical load activates PACAP signaling and exogenous PACAP acts against the hypertrophy inducing effect of mechanical load.

Pituitary Adenylate Cyclase–Activating Polypeptide Disrupts Motivation, Social Interaction, and Attention in Male Sprague Dawley Rats

BackgroundSevere or prolonged stress can trigger psychiatric illnesses including mood and anxiety disorders. Recent work indicates that pituitary adenylate cyclase–activating polypeptide (PACAP) plays an important role in regulating stress effects. In rodents, exogenous PACAP administration can produce persistent elevations in the acoustic startle response, which may reflect anxiety-like signs including hypervigilance. We investigated whether PACAP causes acute or persistent alterations in behaviors that reflect other core features of mood and anxiety disorders (motivation, social interaction, and attention). MethodsUsing male Sprague Dawley rats, we examined if PACAP (.25–1.0 µg, intracerebroventricular infusion) affects motivation as measured in the intracranial self-stimulation test. We also examined if PACAP alters interactions with a conspecific in the social interaction test. Finally, we examined if PACAP affects performance in the 5-choice serial reaction time task, which quantifies attention and error processing. ResultsDose-dependent disruptions in motivation, social interaction, and attention were produced by PACAP, as reflected by increases in reward thresholds, decreases in social behaviors, and decreases in correct responses and alterations in posterror accuracy. Behavior normalized quickly in the intracranial self-stimulation and 5-choice serial reaction time task tests but remained dysregulated in the social interaction test. Effects on attention were attenuated by the corticotropin-releasing factor receptor-1 antagonist antalarmin but not the κ opioid receptor antagonist JDTic. ConclusionsOur findings suggest that PACAP affects numerous domains often dysregulated in mood and anxiety disorders, but that individual signs depend on brain substrates that are at least partially independent. This work may help to devise therapeutics that mitigate specific signs of these disorders.

Advent and Recent Advances in Research on the Role of Pituitary Adenylate Cyclase-activating Polypeptide (PACAP) in the Regulation of Gonadotropic Hormone Secretion of Female Rats

PACAP (ADCYAP1) was isolated from ovine hypothalami. PACAP activates three distinct receptor types: G-protein coupled PAC1, VPAC1, and VPAC2 with seven transmembrane domains. Eight splice variants of PAC1 receptor are described. A part of the hypothalamic PACAP is released into the hypophyseal portal circulation. Both hypothalamic and pituitary PACAP are involved in the dynamic control of gonadotropic hormone secretion. In female rats, PACAP in the paraventricular nucleus is upregulated in the morning and pituitary PACAP is upregulated in the late evening of the proestrus stage of the reproductive cycle. PACAP mRNA peak in the hypothalamic PVN precedes the LHRH release into the portal circulation. It is supposed that PACAP peak is evoked by the elevated estrogen on proestrous morning. At the beginning of the so-called critical period of the same day, PACAP level starts to decline allowing LHRH release into the portal circulation, resulting in the LH surge that evokes ovulation. Just before the critical period, icv-administered exogenous PACAP blocks the LH surge and ovulation. The blocking effect of PACAP is mediated through CRF and endogenous opioids. The effect of the pituitary-born PACAP depends on the intracellular cross-talk between PACAP and LHRH.

Pituitary Adenylate Cyclase Activating Polypeptide (PACAP) Signalling Exerts Chondrogenesis Promoting and Protecting Effects: Implication of Calcineurin as a Downstream Target

Pituitary adenylate cyclase activating polypeptide (PACAP) is an important neurotrophic factor influencing differentiation of neuronal elements and exerting protecting role during traumatic injuries or inflammatory processes of the central nervous system. Although increasing evidence is available on its presence and protecting function in various peripheral tissues, little is known about the role of PACAP in formation of skeletal components. To this end, we aimed to map elements of PACAP signalling in developing cartilage under physiological conditions and during oxidative stress. mRNAs of PACAP and its receptors (PAC1,VPAC1, VPAC2) were detectable during differentiation of chicken limb bud-derived chondrogenic cells in micromass cell cultures. Expression of PAC1 protein showed a peak on days of final commitment of chondrogenic cells. Administration of either the PAC1 receptor agonist PACAP 1-38, or PACAP 6-38 that is generally used as a PAC1 antagonist, augmented cartilage formation, stimulated cell proliferation and enhanced PAC1 and Sox9 protein expression. Both variants of PACAP elevated the protein expression and activity of the Ca-calmodulin dependent Ser/Thr protein phosphatase calcineurin. Application of PACAPs failed to rescue cartilage formation when the activity of calcineurin was pharmacologically inhibited with cyclosporine A. Moreover, exogenous PACAPs prevented diminishing of cartilage formation and decrease of calcineurin activity during oxidative stress. As an unexpected phenomenon, PACAP 6-38 elicited similar effects to those of PACAP 1-38, although to a different extent. On the basis of the above results, we propose calcineurin as a downstream target of PACAP signalling in differentiating chondrocytes either in normal or pathophysiological conditions. Our observations imply the therapeutical perspective that PACAP can be applied as a natural agent that may have protecting effect during joint inflammation and/or may promote cartilage regeneration during degenerative diseases of articular cartilage.

Effect of PACAP in central and peripheral nerve injuries.

Pituitary adenylate cyclase activating polypeptide (PACAP) is a bioactive peptide with diverse effects in the nervous system. In addition to its more classic role as a neuromodulator, PACAP functions as a neurotrophic factor. Several neurotrophic factors have been shown to play an important role in the endogenous response following both cerebral ischemia and traumatic brain injury and to be effective when given exogenously. A number of studies have shown the neuroprotective effect of PACAP in different models of ischemia, neurodegenerative diseases and retinal degeneration. The aim of this review is to summarize the findings on the neuroprotective potential of PACAP in models of different traumatic nerve injuries. Expression of endogenous PACAP and its specific PAC1 receptor is elevated in different parts of the central and peripheral nervous system after traumatic injuries. Some experiments demonstrate the protective effect of exogenous PACAP treatment in different traumatic brain injury models, in facial nerve and optic nerve trauma. The upregulation of endogenous PACAP and its receptors and the protective effect of exogenous PACAP after different central and peripheral nerve injuries show the important function of PACAP in neuronal regeneration indicating that PACAP may also be a promising therapeutic agent in injuries of the nervous system.

Exogenous Administration of PACAP Alleviates Traumatic Brain Injury in Rats through a Mechanism Involving the TLR4/MyD88/NF-κB Pathway

Pituitary adenylate cyclase-activating polypeptide (PACAP) is effective in reducing axonal damage associated with traumatic brain injury (TBI), and has immunomodulatory properties. Toll-like receptor 4 (TLR4) is an important mediator of the innate immune response. It significantly contributes to neuroinflammation induced by brain injury. However, it remains unknown whether exogenous PACAP can modulate TBI through the TLR4/adapter protein myeloid differentiation factor 88 (MyD88)/nuclear factor-κB (NF-κB) signaling pathway. In this study, we investigated the potential neuroprotective mechanisms of PACAP pretreatment in a weight-drop model of TBI. PACAP38 was microinjected intracerebroventricularly before TBI. Brain samples were extracted from the pericontusional area in the cortex and hippocampus. We found that TBI induced significant upregulation of TLR4, with peak expression occurring 24 h post-trauma, and that pretreatment with PACAP significantly improved motor and cognitive dysfunction, attenuated neuronal apoptosis, and decreased brain edema. Pretreatment with PACAP inhibited upregulation of TLR4 and its downstream signaling molecules MyD88, p-IκB, and NF-κB, and suppressed increases in the levels of the downstream inflammatory agents interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), in the brain tissue around the injured cortex and in the hippocampus. Administration of PACAP both in vitro and in vivo attenuated the ability of the TLR4 agonist lipopolysaccharide (LPS) to increase TLR4 protein levels. Therefore, PACAP exerts a neuroprotective effect in this rat model of TBI, by inhibiting a secondary inflammatory response mediated by the TLR4/MyD88/NF-κB signaling pathway in microglia and neurons, thereby reducing neuronal death and improving the outcome following TBI.