Social motility (SoMo) is the ability of Trypanosoma brucei procyclic forms to generate and respond to pH gradients.The differential responses of early and late procyclic forms to pH results in the ...self-organisation of communities on semi-solid surfaces.pH gradients occur in the tsetse fly host and might be used by the parasite to guide migration.pH sensing requires specific adenylate cyclases and a cAMP response protein, CARP3.T. brucei encodes a large number of adenylate cyclases that are likely to sense other environmental signals, enabling parasites to home into specific tissues in both hosts.
Recent studies showed that the formation of elegant geometric patterns by communities of Trypanosoma brucei on semi-solid surfaces, dubbed social motility (SoMo) by its discoverers, is a manifestation of pH taxis. This is caused by procyclic forms generating and responding to pH gradients through glucose metabolism and cAMP signalling. These findings established that trypanosomes can sense and manipulate gradients, potentially helping them to navigate through host tissues. At the same time, the host itself and bystanders such as endosymbionts have the potential to shape the environment and influence the chances of successful transmission. We postulate that the ability to sense and contribute to the gradient landscape may also underlie the tissue tropism and migration of other parasites in their hosts.
Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide originally purified from ovine hypothalamus for its potent activity to stimulate cAMP production. However, its presence ...and action have also been demonstrated in various peripheral tissues including the ovary. In the zebrafish, two forms of PACAP (PACAP(38)-1, adcyap1a; and PACAP(38)-2, adcyap1b) and three PACAP receptors (PAC(1)-R, adcyap1r1; VPAC(1)-R, vipr1; and VPAC(2)-R, vipr2) were all expressed in the ovary. Interestingly, although both follicle cells and oocytes express adcyap1b, the expression of adcyap1a was restricted to the oocytes only. Among the three receptors, adcyap1r1 and vipr2 were expressed in the oocytes, whereas the expression of vipr1 was exclusively located in the follicle cells. Temporal expression analysis of PACAP ligands and receptors during folliculogenesis suggested that PACAP might play differential roles in regulating follicle growth and maturation through different receptors. The two receptors that are expressed in the oocyte (adcyap1r1 and vipr2) showed a significant increase in expression at the transition from the primary growth (PG) stage to previtellogenic (PV) stage and their levels maintained high during follicle growth. However, when the follicle development approached full-grown (FG) stage, these two receptors both decreased significantly in expression. In contrast, vipr1, the receptor expressed in the follicle cells, showed little change in expression at the PG-PV transition and afterwards during follicle growth; however, its expression surged dramatically at the FG stage prior to oocyte maturation. Based on these results, we hypothesized that PACAP might play dual roles in regulating follicle growth and maturation through different receptors located in different compartments. PACAP may stimulate oocyte growth but block its maturation in early follicles by acting directly on the oocyte via PAC1-R and VPAC2-R, whose expression is dominant in growth phase; however, PACAP may promote oocyte maturation in the maturation phase via VPAC1-R on the follicle cells, whose expression surges in FG follicles prior to maturation and is consistently high in the follicles undergoing final maturation. This hypothesis was further supported by the observation that PACAP promoted maturation of follicle-enclosed oocytes but suppressed spontaneous maturation of denuded oocytes in vitro. This study provides strong evidence for a PACAP-mediated signaling network in the zebrafish ovarian follicle, which may play roles in orchestrating follicle growth and maturation via different types of receptors located in different compartments of the follicle.
Ginsenoside, the active principles in
Panax ginseng root, has been demonstrated to show neurotrophic and neuroprotective actions for prevention of neuron degeneration. Deposition of β-amyloid peptide ...(Aβ) causes neurotoxicity through the formation of plaques in brains with Alzheimer's disease. Pituitary adenylate cyclase-activating polypeptide (PACAP) is introduced as a neurotrophic factor to promote cell survival. However, effect of Rh2, one of ginsenosides, on PACAP expression induced by Aβ remains unclear. In the present study, we found that Rh2 stimulates PACAP gene expression and cell proliferation in type I rat brain astrocytes (RBA1) cells and both effects were not modified by the estrogen antagonists (MPP or ICI 182780). Also, Rh2 ameliorates the RBA1 growth inhibition of Aβ. Moreover, blockade of PACAP receptor PAC1 using PACAP (6-38) inhibits all the actions of Rh2. These results suggest that Rh2 can induce an increase of PACAP to activate PAC1, but not estrogen receptor, and thereby leads to attenuate Aβ-induced toxicity. Thus, ginseng seems useful in the prevention of dementia.
•PACAP increased activity-regulated cytoskeleton associated protein after fear conditioning.•Significant increases were seen in the extended amygdala but not the hippocampus.•Expression was ...co-localized with PKCdelta in the extended amygdala.•Freezing behavior was significantly reduced in PACAP treated rats one day after fear conditioning.
The stress-related neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is implicated in neuromodulation of learning and memory. PACAP can alter synaptic plasticity and has direct actions on neurons in the amygdala and hippocampus that could contribute to its acute and persistent effects on the consolidation and expression of conditioned fear. We recently demonstrated that intracerebroventricular (ICV) infusion of PACAP prior to fear conditioning (FC) results in initial amnestic-like effects followed by hyper-expression of conditioned freezing with repeated testing, and analyses of immediate-early gene c-Fos expression suggested that the central nucleus of the amygdala (CeA), but not the lateral/basolateral amygdala (LA/BLA) or hippocampus, are involved in these PACAP effects. Here, we extend that work by examining the expression of the synaptic plasticity marker activity-regulated cytoskeleton-associated protein (Arc/Arg 3.1) after PACAP administration and FC. Male Sprague-Dawley rats were implanted with cannula for ICV infusion of PACAP-38 (1.5 µg) or vehicle followed by FC and tests for conditioned freezing. One hour after FC, Arc protein expression was significantly elevated in the CeA and bed nucleus of the stria terminalis (BNST), interconnected structures that are key elements of the extended amygdala, in rats that received the combination of PACAP + FC. In contrast, Arc expression within the subdivisions of the hippocampus, or the LA/BLA, were unchanged. A subpopulation of Arc-positive cells in both the CeA and BNST also express PKCdelta, an intracellular marker that has been used to identify microcircuits that gate conditioned fear in the CeA. Consistent with our previous findings, on the following day conditioned freezing behavior was reduced in rats that had been given the combination of PACAP + FC—an amnestic-like effect—and Arc expression levels had returned to baseline. Given the established role of Arc in modifying synaptic plasticity and memory formation, our findings suggest that PACAP-induced overexpression of Arc following fear conditioning may disrupt neuroplastic changes within populations of CeA and BNST neurons normally responsible for encoding fear-related cues that, in this case, results in altered fear memory consolidation. Hence, PACAP systems may represent an axis on which stress and experience-driven neurotransmission converge to alter emotional memory, and mediate pathologies that are characteristic of psychiatric illnesses such as post-traumatic stress disorder.
The oxygen-induced retinopathy (OIR) is a well-established rodent model of retinopathy of prematurity (ROP), which is one of the most common causes of childhood visual impairment affecting preterm ...babies. Pituitary adenylate cyclase-activating polypeptide (PACAP) is known to have neuroprotective effects. Several studies have revealed the presence of PACAP and its receptors in the retina and reported its protective effects in ischemic and diabetic retinopathy. In this study, we investigated whether PACAP administration can influence the vascular changes in the rat OIR model. OIR was generated by placing the animals in daily alternating 10/50 oxygen concentrations from postnatal day (PD) 0 to PD14 then returned them to room air. Meanwhile, animals received PACAP or saline intraperitoneally or intravitreally from PD1 to PD8 or on PD11, PD14, and PD17, respectively. On PD19 ± 1, the retinas were isolated and the vessels were visualized by isolectin staining. The percentage of avascular to whole retinal areas and the number of branching points were measured. Change in cytokine expression was also determined. Intravitreal treatment with PACAP remarkably reduced the extent of avascular area compared to the non- and saline-treated OIR groups. Intraperitoneal PACAP injection did not influence the vascular extent. Retinal images of room-air controls did not show vascular alterations. No changes in the number of vessel branching were observed after treatments. Alterations in cytokine profile after local PACAP injection further supported the protective role of the peptide. This is the first study to examine the effects of PACAP in ROP. Although the exact mechanism is still not revealed, the present results show that PACAP treatment can ameliorate the vascular changes in the animal model of ROP.
Summary The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) regulates activation of the hypothalamic-pituitary-adrenal (HPA) axis and the adrenal gland in response to various ...stressors. We previously found that in response to acute psychological stress (restraint), elevated corticotrophin-releasing hormone (CRH) mRNA levels in the hypothalamic paraventricular nucleus (PVN) as well as elevated plasma corticosterone (CORT) were profoundly attenuated in PACAP-deficient mice. To determine whether HPA axis responses and stress-induced depressive-like behaviors in a chronic stress paradigm are affected by PACAP deficiency, we subjected mice to 14 days of social defeat stress. Defeat-exposed PACAP−/− mice showed a marked attenuation of stress-induced increases in serum CORT levels, cellular PVN ΔFosB immunostaining, and depressive-like behaviors (social interaction and forced swim tests) compared to wild-type control mice. The PACAP−/− mice showed reduced PVN FosB-positive cell numbers, but relatively elevated cell counts in several forebrain areas including the medial prefrontal cortex, after social stress. PACAP appears to be specific for mediating HPA activation only in psychological stress because marked elevations in plasma CORT after a systemic stressor (lipopolysaccharide administration) occurred regardless of genotype. We conclude that chronically elevated CORT is a key component of depressive effects of social defeat, and that attenuation of the CORT response at the level of the PVN, as well as extrahypothalamic forebrain regions, in PACAP-deficient mice protects from development of depressive behavior.
•In vivo PACAP is a C-terminally α-amidated neuropeptide of 27 or 38 residues.•PACAP does not require α-amidation to activate the rat or human PAC1 receptor.•Amidation of PACAP is also dispensable ...for neuroendocrine cell differentiation.
PACAP-27 and PACAP-38 are the exclusive physiological ligands for the mammalian PAC1 receptor. The role of C-terminal amidation of these ligands at that receptor was examined in neuroendocrine cells expressing the PAC1 receptor endogenously and in non-neuroendocrine cells in which the human and rat PAC1 receptors were expressed from stable single-copy genes driven by the CMV promoter, providing stoichiometrically appropriate levels of this Gs-coupled GPCR in order to examine the potency and intrinsic activity of PACAP ligands and their des-amidated congeners. We found that replacement of the C-terminal glycine residues of PACAP-27 and -38 with a free acid; or extension of either peptide with the two to three amino acids normally found at these positions in PACAP processing intermediates in vivo following endoproteolytic cleavage and after exoproteolytic trimming and glycine-directed amidated, were equivalent in potency to the fully processed peptides in a variety of cell-based assays. These included real-time monitoring of cyclic AMP generation in both NS-1 neuroendocrine cells and non-neuroendocrine HEK293 cells; PKA-dependent gene activation in HEK293 cells; and neuritogenesis and cell growth arrest in NS-1 cells. The specific implications for the role of amidation in arming of secretin-related neuropeptides for biological function, and the general implications for neuropeptide-based delivery in the context of gene therapy, are discussed.
The signal transduction mechanisms of pituitary adenylate cyclase activating polypeptide (PACAP) were investigated in lung cancer cells. Previously, PACAP-27 addition to NCI-H838 cells increased ...phosphatidylinositol turnover and intracellular cAMP leading to proliferation of lung cancer cells. Also, PACAP receptors (PAC1) regulated the tyrosine phosphorylation of ERK, focal adhesion kinase, and paxillin. In this communication, the effects of PACAP on cytosolic Ca
2+
and PYK-2 tyrosine phosphorylation were investigated. PACAP-27 increased cytosolic Ca
2+
within seconds after addition to FURA-2 AM loaded NCI-H838 cells. The increase in cytosolic Ca
2+
caused by PACAP was inhibited by PACAP(6–38) (PAC1 antagonist), U73122 (phospholipase C inhibitor), or BAPTA (calcium chelator), but not H89 (PKA inhibitor). PACAP-38, but not vasoactive intestinal peptide (VIP), addition to NCI-H838 or H1299 cells significantly increased the tyrosine phosphorylation of PYK-2 after 2 min. The increase in PYK-2 tyrosine phosphorylation caused by PACAP was inhibited by PACAP(6–38), U73122, or BAPTA, but not H89. The results suggest that PAC1 regulates PYK-2 tyrosine phosphorylation in a calcium-dependent manner.
We recently identified novel small-molecule antagonists of the PACAP type I (PAC1) receptor using docking-based in silico screening followed by in vitro/vivo pharmacological assays. In the present ...study, we synthesized 18 novel derivatives based on the structure of PA-9, a recently developed antagonist of the PAC1 receptor, with a view to obtain a panel of compounds with more potent antagonistic and analgesic activities. Among them, compound 3d showed improved antagonistic activities. Intrathecal injection of 3d inhibited both pituitary adenylate cyclase-activating polypeptide (PACAP) and spinal nerve ligation-induced mechanical allodynia. The effects were more potent than PA-9. Compound 3d also showed anti-allodynic effects following oral administration. Hence, our results suggest that 3d may become an orally available analgesic in the treatment of the neuropathic pain.
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•A novel and potent small-molecule antagonist of PAC1 receptor was synthesized.•We identified compound 3d as a novel and potent PAC1 receptor antagonist.•Intrathecal injection of 3d inhibited PACAP- and nerve injury-induced allodynia.•Compound 3d also showed anti-allodynic effects following oral administration.
Obesity develops, in part, due to frequent overconsumption. Therefore, it is important to identify the regulatory mechanisms that promote eating beyond satiety. Previously, we have demonstrated that ...an acute microinjection of the neuropeptide PACAP into the nucleus accumbens (NAcc) attenuates palatable food consumption in satiated rats. To better understand the mechanism by which intra-NAcc PACAP selectively blocks palatable food intake, the current work employed a rodent taste reactivity paradigm to assess the impact of PACAP on the hedonic processing of a 1% sucrose solution. Our results revealed that bilateral intra-NAcc PACAP infusions significantly reduced appetitive orofacial responses to sucrose. Interestingly, the effect of PACAP on the expression of aversive responses to sucrose was dependent on the rostral-caudal placement of the microinjection. In a separate group of rats, PACAP was microinjected into the hypothalamus (a region of the brain in which PACAP does not attenuate palatable feeding). Here we found that PACAP had no effect on the hedonic perception of the sucrose solution. Taken together, this dataset indicates that PACAP acts in specific subregions of the NAcc to attenuate palatability-induced feeding by reducing the perceived hedonic value of palatable food.
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