Regulation of neurotrophic peptide expression in sympathetic neurons: quantitative analysis using radioimmunoassay and real-time quantitative polymerase chain reaction

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

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

Pituitary Adenylate Cyclase-Activating Peptide in the Bed Nucleus of the Stria Terminalis Mediates Stress-Induced Reinstatement of Cocaine Seeking in Rats

Stressors often contribute to difficulties in maintaining behavior change following a period of abstinence, and may play a significant role in drug relapse. The activation of pituitary adenylate cyclase-activating peptide (PACAP) systems in the bed nucleus of the stria terminalis (BNST) mediates many consequences of chronic stressor exposure. Here we ask whether PACAP is also involved in producing reinstatement in a model of stress-induced relapse to drug taking. Rats self-administered cocaine for 1 h daily over 10 days that was followed by 20 days of extinction training in which lever pressing no longer produced cocaine. In experiment 1, quantitative PCR (qPCR) was performed at several stages to determine transcript levels of PACAP and corresponding receptors. Reinstatement of cocaine seeking was then tested after footshock exposure in different groups of rats that were pretreated with vehicle solution, a PAC1 receptor antagonist (experiment 2), or a PACAP agonist (experiment 3) without footshock. In experiment 1, cocaine self-administration increased BNST PACAP transcript levels similar to what we have previously reported with chronic stress. In experiment 2, intra-BNST infusions of the PAC1/VPAC2 antagonist, PACAP 6-38, prevented footshock-induced reinstatement of extinguished cocaine seeking. In experiment 3, intra-BNST PACAP infusion reinstated previously extinguished cocaine-seeking behavior in the absence of footshock. Cocaine self-administration elevated BNST PACAP, and BNST PACAP receptor activation was necessary and sufficient for stress-induced reinstatement of cocaine seeking. These data suggest that BNST PACAP systems may be viable targets for relapse prevention.

Balance between cAMP and Ca(2+) signals regulates expression levels of pituitary adenylate cyclase-activating polypeptide gene in neurons

Mice lacking the gene encoding pituitary adenylate cyclase-activating polypeptide (PACAP) or its specific receptor, PAC1, show abnormal behaviors related to schizophrenia. However, the regulation of PACAP expression in neurons remains unclear. Here, we report that Pacap mRNA levels are regulated transcriptionally and post-transcriptionally by cAMP and Ca(2+) signals in cultured rat cortical cells. Pacap mRNA levels decreased proportionately with the intensity of cAMP signaling, and this decrease was accelerated by N-methyl-D-aspartate (NMDA) receptor blockade, suggesting that cAMP signaling enhances the degradation of Pacap mRNA, whereas NMDA receptor-mediated signals inhibit its degradation. However, depolarization (which produced a robust increase in Ca(2+) signals) together with cAMP signaling resulted in a synergistic induction of Pacap mRNA through calcineurin and its substrate, cAMP-response element-binding protein (CREB)-regulated transcription coactivator 1. These results strongly support the concept that while cAMP signaling can accelerate the degradation of Pacap mRNA, it can also synergistically enhance Ca(2+) signaling-induced transcriptional activation of Pacap. Taken together, our findings suggest that a balance between Ca(2+) and cAMP signals regulates PACAP levels in neurons and that a perturbation of this balance may result in psychiatric disorders, such as schizophrenia.

Intravesical PAC1 Receptor Antagonist, PACAP(6-38), Reduces Urinary Bladder Frequency and Pelvic Sensitivity in NGF-OE Mice

Chronic NGF overexpression (OE) in the urothelium, achieved through the use of a highly urothelium-specific uroplakin II promoter, stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency and non-voiding contractions, and referred somatic sensitivity. Additional NGF-mediated pleiotropic changes might contribute to increased voiding frequency and pelvic hypersensitivity in NGF-OE mice such as neuropeptide/receptor systems including PACAP(Adcyap1) and PAC1 receptor (Adcyap1r1). Given the presence of PAC1-immunoreactive fibers and the expression of PAC1 receptor expression in bladder tissues, and PACAP-facilitated detrusor contraction, whether PACAP/receptor signaling contributes to increased voiding frequency and somatic sensitivity was evaluated in NGF-OE mice. Intravesical administration of the PAC1 receptor antagonist, PACAP(6-38) (300 nM), significantly (p ≤ 0.01) increased intercontraction interval (2.0-fold) and void volume (2.5-fold) in NGF-OE mice. Intravesical instillation of PACAP(6-38) also decreased baseline bladder pressure in NGF-OE mice. PACAP(6-38) had no effects on bladder function in WT mice. Intravesical administration of PACAP(6-38) (300 nM) significantly (p ≤ 0.01) reduced pelvic sensitivity in NGF-OE mice but was without effect in WT mice. PACAP/receptor signaling contributes to the increased voiding frequency and pelvic sensitivity observed in NGF-OE mice.

Social stress in mice induces urinary bladder overactivity and increases TRPV1 channel-dependent afferent nerve activity

Social stress has been implicated as a cause of urinary bladder hypertrophy and dysfunction in humans. Using a murine model of social stress, we and others have shown that social stress leads to bladder overactivity. Here, we show that social stress leads to bladder overactivity, increased bladder compliance, and increased afferent nerve activity. In the social stress paradigm, 6-wk-old male C57BL/6 mice were exposed for a total of 2 wk, via barrier cage, to a C57BL/6 retired breeder aggressor mouse. We performed conscious cystometry with and without intravesical infusion of the TRPV1 inhibitor capsazepine, and measured pressure-volume relationships and afferent nerve activity during bladder filling using an ex vivo bladder model. Stress leads to a decrease in intermicturition interval and void volume in vivo, which was restored by capsazepine. Ex vivo studies demonstrated that at low pressures, bladder compliance and afferent activity were elevated in stressed bladders compared with unstressed bladders. Capsazepine did not significantly change afferent activity in unstressed mice, but significantly decreased afferent activity at all pressures in stressed bladders. Immunohistochemistry revealed that TRPV1 colocalizes with CGRP to stain nerve fibers in unstressed bladders. Colocalization significantly increased along the same nerve fibers in the stressed bladders. Our results support the concept that social stress induces TRPV1-dependent afferent nerve activity, ultimately leading to the development of overactive bladder symptoms.

Regulation of bed nucleus of the stria terminalis PACAP expression by stress and corticosterone

Single-nucleotide polymorphisms (SNPs) in the genes for pituitary adenylyl cyclase-activating peptide (PACAP) and the PAC1 receptor have been associated with stress-related psychiatric disorders. Although, from recent work, we have argued that stress-induced PACAP expression in the bed nucleus of the stria terminalis (BNST) may mediate stress-related psychopathology, it is unclear whether stress-induced increases in BNST PACAP expression require acute or repeated stressor exposure and whether increased BNST PACAP expression is related to stress-induced increases in circulating glucocorticoids. In the current work, we have used real-time quantitative polymerase chain reaction (qPCR) to assess transcript expression in brain punches from rats after stressor exposure paradigms or corticosterone injection. BNST PACAP and PAC1 receptor transcript expression was increased only after 7 days of repeated stressor exposure; no changes in transcript levels were observed 2 or 24 hours after a single-restraint session. Moreover, repeated corticosterone treatment for 7 days was not sufficient to reliably increase BNST PACAP transcript levels, suggesting that stress-induced elevations in corticosterone may not be the primary drivers of BNST PACAP expression. These results may help clarify the mechanisms and temporal processes that underlie BNST PACAP induction for intervention in stress-related anxiety disorders.

Calcium influx, but not intracellular calcium release, supports PACAP-mediated ERK activation in HEK PAC1 receptor cells

In HEK cells expressing GFP-tagged PAC1Hop1 receptors, PACAP augments ERK phosphorylation through two parallel pathways: one through PACAP/PAC1 receptor internalization/endosome MEK/ERK signaling and the other through PLC/DAG/PKC activation. We examined whether elevation of intracellular calcium ([Ca(2+)]i) was required for either of the PACAP/PAC1 receptor-mediated ERK activation mechanisms. The PACAP (25 nM)-induced elevation of [Ca(2+)]i was greater with cells maintained in Ca(2+)-containing than in Ca(2+)-deficient solution, suggesting that both calcium release from internal stores and calcium influx contributed to the rise in [Ca(2+)]i. A thapsigargin-induced increase in [Ca(2+)]i also was greater with calcium in the external solution. OAG, the cell permeable analogue of DAG, increased [Ca(2+)]i, but only in Ca(2+)-containing solution. Decreasing external calcium or depleting internal calcium stores did not block PACAP-induced PAC1 receptor internalization. Omission of calcium from the external solution, but not thapsigargin pretreatment, significantly blunted PACAP-stimulated ERK phosphorylation. The PKC inhibitor BimI decreased PACAP-mediated ERK activation in both Ca(2+)-containing or Ca(2+)-deficient solutions. In contrast, following Pitstop 2 pretreatment to block endocytic mechanisms, PACAP activated ERK only when calcium was present in the external solution. We conclude that the endosome signaling pathway is largely calcium-independent whereas calcium influx appears necessary for the PLC/DAG/PKC component of PACAP-induced ERK activation.

Parabrachial nucleus (PBn) pituitary adenylate cyclase activating polypeptide (PACAP) signaling in the amygdala: implication for the sensory and behavioral effects of pain

The intricate relationships that associate pain, stress responses and emotional behavior have been well established. Acute stressful situations can decrease nociceptive sensations and conversely, chronic pain can enhance other pain experiences and heighten the emotional and behavioral consequences of stress. Accordingly, chronic pain is comorbid with a number of behavioral disorders including depression, anxiety abnormalities and associated stress-related disorders including post traumatic stress disorder (PTSD). The central nucleus of the amygdala (CeA) represents a convergence of pathways for pain, stress and emotion, and we have identified pituitary adenylate cyclase activating polypeptide (PACAP) immunoreactivity in fiber elements in the lateral capsular division of the CeA (CeLC). The PACAP staining patterns colocalized in part with those for calcitonin gene related peptide (CGRP); anterograde fiber tracing and excitotoxic lesion studies demonstrated that the CeLC PACAP/CGRP immunoreactivities represented sensory fiber projections from the lateral parabrachial nucleus (LPBn) along the spino-parabrachioamygdaloid tract. The same PBn PACAP/CGRP fiber system also projected to the BNST. As in the BNST, CeA PACAP signaling increased anxiety-like behaviors accompanied by weight loss and decreased feeding. But in addition to heightened anxiety-like responses, CeA PACAP signaling also altered nociception as reflected by decreased latency and threshold responses in thermal and mechanical sensitivity tests, respectively. From PACAP expression in major pain pathways, the current observations are novel and suggest that CeA PACAP nociceptive signaling and resulting neuroplasticity via the spino-parabrachioamygdaloid tract may represent mechanisms that associate chronic pain with sensory hypersensitivity, fear memory consolidation and severe behavioral disorders.

Intravesical TRPV4 blockade reduces repeated variate stress-induced bladder dysfunction by increasing bladder capacity and decreasing voiding frequency in male rats

Individuals with functional lower urinary tract disorders including interstitial cystitis (IC)/bladder pain syndrome (BPS) and overactive bladder (OAB) often report symptom (e.g., urinary frequency) worsening due to stress. One member of the transient receptor potential ion channel vanilloid family, TRPV4, has recently been implicated in urinary bladder dysfunction disorders including OAB and IC/BPS. These studies address the role of TRPV4 in stress-induced bladder dysfunction using an animal model of stress in male rats. To induce stress, rats were exposed to 7 days of repeated variate stress (RVS). Quantitative PCR data demonstrated significant (P ≤ 0.01) increases in TRPV4 transcript levels in urothelium but not detrusor smooth muscle. Western blot analyses of split urinary bladders (i.e., urothelium and detrusor) showed significant (P ≤ 0.01) increases in TRPV4 protein expression levels in urothelial tissues but not detrusor smooth muscle. We previously showed that RVS produces bladder dysfunction characterized by decreased bladder capacity and increased voiding frequency. The functional role of TRPV4 in RVS-induced bladder dysfunction was evaluated using continuous, open outlet intravesical infusion of saline in conjunction with administration of a TRPV4 agonist, GSK1016790A (3 μM), a TRPV4 antagonist, HC067047 (1 μM), or vehicle (0.1% DMSO in saline) in control and RVS-treated rats. Bladder capacity, void volume, and intercontraction interval significantly decreased following intravesical instillation of GSK1016790A in control rats and significantly (P ≤ 0.01) increased following administration of HC067047 in RVS-treated rats. These results demonstrate increased TRPV4 expression in the urothelium following RVS and that TRPV4 blockade ameliorates RVS-induced bladder dysfunction consistent with the role of TRPV4 as a promising target for bladder function disorders.

Expression and function of transforming growth factor-β isoforms and cognate receptors in the rat urinary bladder following cyclophosphamide-induced cystitis

Numerous proinflammatory cytokines have been implicated in the reorganization of lower urinary tract function following cyclophosphamide (CYP)-induced cystitis. The present study investigated the functional profile of three pleiotropic transforming growth factor-β (TGF-β) isoforms and receptor (TβR) variants in the normal and inflamed (CYP-induced cystitis) rat urinary bladder. Our findings indicate that TGF-β (1, 2, and 3) and TβR (1, 2, and 3) transcript and protein expression were regulated to varying degrees in the urothelium or detrusor smooth muscle following intermediate (48 h; 150 mg/kg ip) or chronic (75 mg/kg ip; once every 3 days for 10 days), but not acute (4 h; 150 mg/kg ip), CYP-induced cystitis. Conscious, open-outlet cystometry was performed to determine whether aberrant TGF-β signaling contributes to urinary bladder dysfunction following intermediate (48 h) CYP-induced cystitis. TβR-1 inhibition with SB505124 (5 μM) significantly (p ≤ 0.001) decreased voiding frequency and increased bladder capacity (2.5-fold), void volume (2.6-fold), and intercontraction intervals (2.5-fold) in CYP-treated (48 h) rats. Taken together, these results provide evidence for 1) the involvement of TGF-β in lower urinary tract neuroplasticity following urinary bladder inflammation, 2) a functional role of TGF-β signaling in the afferent limb of the micturition reflex, and 3) urinary bladder TβR-1 as a viable target to reduce voiding frequency with cystitis.

Increased TRPV4 expression in urinary bladder and lumbosacral dorsal root ganglia in mice with chronic overexpression of NGF in urothelium

Transient receptor potential vanilloid (TRPV) family member 4 (TRPV4) expression has been demonstrated in urothelial cells and dorsal root ganglion (DRG) neurons, and roles in normal micturition reflexes as well as micturition dysfunction have been suggested. TRP channel expression and function is dependent upon target tissue expression of growth factors. These studies expand upon the target tissue dependence of TRPV4 expression in the urinary bladder and lumbosacral DRG using a recently characterized transgenic mouse model with chronic overexpression of nerve growth factor (NGF-OE) in the urothelium. Immunohistochemistry with image analyses, real-time quantitative polymerase chain reaction, and Western blotting were used to determine TRPV4 protein and transcript expression in the urinary bladder (urothelium + suburothelium, detrusor) and lumbosacral DRG from littermate wild-type (WT) and NGF-OE mice. Antibody specificity controls were performed in TRPV4(-/-) mice. TRPV4 transcript and protein expression was significantly (p ≤ 0.001) increased in the urothelium + suburothelium and suburothelial nerve plexus of the urinary bladder and in small- and medium-sized lumbosacral (L1, L2, L6-S1) DRG cells from NGF-OE mice compared to littermate WT mice. NGF-OE mice exhibit significant (p ≤ 0.001) increases in NGF transcript and protein in the urothelium + suburothelium and lumbosacral DRG. These studies demonstrate regulation of TRPV4 expression by NGF in lower urinary tract tissues. Ongoing studies are characterizing the functional roles of TRPV4 expression in the sensory limb (DRG, urothelium) of the micturition reflex.

Pituitary adenylate cyclase 1 receptor internalization and endosomal signaling mediate the pituitary adenylate cyclase activating polypeptide-induced increase in guinea pig cardiac neuron excitability

After G-protein-coupled receptor activation and signaling at the plasma membrane, the receptor complex is often rapidly internalized via endocytic vesicles for trafficking into various intracellular compartments and pathways. The formation of signaling endosomes is recognized as a mechanism that produces sustained intracellular signals that may be distinct from those generated at the cell surface for cellular responses including growth, differentiation, and survival. Pituitary adenylate cyclase activating polypeptide (PACAP; Adcyap1) is a potent neurotransmitter/neurotrophic peptide and mediates its diverse cellular functions in part through internalization of its cognate G-protein-coupled PAC1 receptor (PAC1R; Adcyap1r1). In the present study, we examined whether PAC1R endocytosis participates in the regulation of neuronal excitability. Although PACAP increased excitability in 90% of guinea pig cardiac neurons, pretreatment with Pitstop 2 or dynasore to inhibit clathrin and dynamin I/II, respectively, suppressed the PACAP effect. Subsequent addition of inhibitor after the PACAP-induced increase in excitability developed gradually attenuated excitability with no changes in action potential properties. Likewise, the PACAP-induced increase in excitability was markedly decreased at ambient temperature. Receptor trafficking studies with GFP-PAC1 cell lines demonstrated the efficacy of Pitstop 2, dynasore, and low temperatures at suppressing PAC1R endocytosis. In contrast, brefeldin A pretreatments to disrupt Golgi vesicle trafficking did not blunt the PACAP effect, and PACAP/PAC1R signaling still increased neuronal cAMP production even with endocytic blockade. Our results demonstrate that PACAP/PAC1R complex endocytosis is a key step for the PACAP modulation of cardiac neuron excitability.

Transcriptional and translational plasticity in rodent urinary bladder TRP channels with urinary bladder inflammation, bladder dysfunction, or postnatal maturation

These studies examined the transcriptional and translational plasticity of three transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) with established neuronal and non-neuronal expression and functional roles in the lower urinary tract. Mechanosensor and nociceptor roles in either physiological or pathological lower urinary tract states have been suggested for TRPA1, TRPV1, and TRPV4. We have previously demonstrated the neurochemical, organizational, and functional plasticity in micturition reflex pathways following induction of urinary bladder inflammation using the antineoplastic agent, cyclophosphamide. More recently, we have characterized similar plasticity in micturition reflex pathways in a transgenic mouse model with chronic urothelial overexpression (OE) of nerve growth factor (NGF) and in a transgenic mouse model with deletion of vasoactive intestinal polypeptide (VIP). In addition, the micturition reflex undergoes postnatal maturation that may also reflect plasticity in urinary bladder TRP channel expression. Thus, we examined plasticity in urinary bladder TRP channel expression in diverse contexts using a combination of quantitative, real-time PCR and western blotting approaches. We demonstrate transcriptional and translational plasticity of urinary bladder TRPA1, TRPV1, and TRVP4 expression. Although the functional significance of urinary bladder TRP channel plasticity awaits further investigation, these studies demonstrate context- (inflammation, postnatal development, NGF-OE, VIP deletion) and tissue-dependent (urothelium + suburothelium, detrusor) plasticity.

Autonomic dysfunction and plasticity in micturition reflexes in human α-synuclein mice

Although often overshadowed by the motor dysfunction associated with Parkinson's disease (PD), autonomic dysfunction including urinary bladder and bowel dysfunctions are often associated with PD and may precede motoric changes; such autonomic dysfunction may permit early detection and intervention. Lower urinary tract symptoms are common in PD patients and result in significant morbidity. This studies focus on nonmotor symptoms in PD using a transgenic mouse model with overexpression of human α-synuclein (hSNCA), the peptide found in high concentrations in Lewy body neuronal inclusions, the histopathologic hallmark of PD. We examined changes in the physiological, molecular, chemical, and electrical properties of neuronal pathways controlling urinary bladder function in transgenic mice. The results of these studies reveal that autonomic dysfunction (i.e., urinary bladder) can precede motor dysfunction. In addition, mice with hSNCA overexpression in relevant neuronal populations is associated with alterations in expression of neurotransmitter/neuromodulatory molecules (PACAP, VIP, substance P, and neuronal NOS) within neuronal pathways regulating bladder function as well as with increased NGF expression in the urinary bladder. Changes in the electrical and synaptic properties of neurons in the major pelvic ganglia that provide postganglionic innervation to urogenital tissues were not changed as determined with intracellular recording. The urinary bladder dysfunction observed in transgenic mice likely reflects changes in peripheral (i.e., afferent) and/or central micturition pathways or changes in the urinary bladder. SYN-OE mice provide an opportunity to examine early events underlying the molecular and cellular plasticity of autonomic nervous system pathways underlying synucleinopathies.

Is PACAP the major neurotransmitter for stress transduction at the adrenomedullary synapse?

It has been known for more than a decade that the neuropeptide PACAP (pituitary adenylate cyclase-activating polypeptide) is co-stored with acetylcholine in the splanchnic nerve terminals innervating the adrenal medulla. Both transmitters are robust secretagogues for catecholamine release from chromaffin cells. Here, we review the unique contribution of PACAP to the functioning of the splanchnic-adrenal synapse in stress. While acetylcholine is released across a wide range of firing frequencies, PACAP is released only at high frequencies of stimulation, and its role in the regulation of epinephrine secretion and biosynthesis is highly specialized. PACAP is responsible for long-term catecholamine secretion using secretory mechanisms different from the rapidly desensitizing depolarization evoked by acetylcholine through nicotinic receptor activation. PACAP signaling also maintains catecholamine synthesis required for sustained secretion during prolonged stress via induction of the enzymes TH and PNMT, and enhances transcription of additional secreted molecules found in chromaffin cells that alter further secretion through both autocrine and paracrine mechanisms. PACAP thus mediates chromaffin cell plasticity via functional encoding of cellular experience. These features of PACAP action at the splanchnic-adrenal synapse may be paradigmatic for the general actions of neuropeptides as effectors of stimulus-secretion-synthesis coupling in stress.

The function and mechanisms of Nurr1 action in midbrain dopaminergic neurons, from development and maintenance to survival

Nurr1 is critical for the development and maintenance of midbrain dopaminergic (DA) neurons in mouse. Loss of Nurr1 function early during development in mice leads to the absence of midbrain DA neurons. Reduction of Nurr1 function in adulthood leads to a slowly progressive loss of striatal DA and markers for DAergic neurons, supporting its selective roles in the maintenance of DAergic neuronal survival and function. To understand the molecular mechanisms of Nurr1 action, our group has identified VIP as a potential target gene of Nurr1. Nurr1 regulates VIP mRNA and protein levels, and transactivates the VIP promoter through Nurr1-responsive cis elements. Nurr1 loss of function leads to the decrease of VIP mRNA level in developing midbrain, suggesting that Nurr1 is involved in the in vivo regulation of VIP expression in midbrain. Our group has also cloned a novel protein interactor for Nurr1. We identified a family of gene products that interact and regulate the activity of Nurr1 by screening yeast two-hybrid library and termed the longest splicing form, NuIP. In vivo NuIP protein is largely colocalized with Nurr1 in adult midbrain dopaminergic neurons. NuIP interacts and positively regulates the activity of Nurr1 protein and could also possibly mediate cross talk between Nurr1 and GTPase mediated signaling pathways. Other recently identified potential target genes and interacting proteins of Nurr1 are also summarized and discussed in this review.

The adaptation of the blood-brain barrier to vascular endothelial growth factor and placental growth factor during pregnancy

Vascular endothelial growth factor (VEGF) and placental growth factor (PLGF) are increased in the maternal circulation during pregnancy. These factors may increase blood-brain barrier (BBB) permeability, yet brain edema does not normally occur during pregnancy. We therefore hypothesized that in pregnancy, the BBB adapts to high levels of these permeability factors. We investigated the influence of pregnancy-related circulating factors on VEGF-induced BBB permeability by perfusing cerebral veins with plasma from nonpregnant (NP) or late-pregnant (LP) rats (n=6/group) and measuring permeability in response to VEGF. The effect of VEGF, PLGF, and VEGF-receptor (VEGFR) activation on BBB permeability was also determined. Results showed that VEGF significantly increased permeability (×10(7) μm(3)/min) from 9.7 ± 3.5 to 21.0 ± 1.5 (P<0.05) in NP veins exposed to NP plasma, that was prevented when LP veins were exposed to LP plasma; (9.7±3.8; P>0.05). Both LP plasma and soluble FMS-like tyrosine-kinase 1 (sFlt1) in NP plasma abolished VEGF-induced BBB permeability in NP veins (9.5±2.9 and 12±2.6; P>0.05). PLGF significantly increased BBB permeability in NP plasma (18±1.4; P<0.05), and required only VEGFR1 activation, whereas VEGF-induced BBB permeability required both VEGFR1 and VEGFR2. Our findings suggest that VEGF and PLGF enhance BBB permeability through different VEGFR pathways and that circulating sFlt1 prevents VEGF- and PLGF-induced BBB permeability during pregnancy.

PACAP: a master regulator of neuroendocrine stress circuits and the cellular stress response

The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is released from stress-transducing neurons. It exerts postsynaptic effects required to complete the hypothalamo-pituitary-adrenocortical (HPA) and hypothalamo-sympatho-adrenal (HSA) circuits activated by psychogenic and metabolic stressors. Upon activation of these circuits, PACAP-responsive (in cell culture models) and PACAP-dependent (in vivo) transcriptomic responses in the adrenal gland, hypothalamus, and pituitary have been identified. Gene products produced in response circuits during stress include additional neuropeptides, neurotransmitter biosynthetic enzymes, and neuroprotective factors. Major portions of HPA and HSA stress responses are abolished in PACAP-deficient mice. This deficit occurs at the level of both the hypothalamus (HPA axis) and the adrenal medulla (HSA axis). PACAP-dependent transcriptional stress responses are conveyed through noncanonical cyclic AMP- and calcium-initiated signaling pathways within the HSA circuit. PACAP transcriptional regulation of the HPA axis, in the hypothalamus, is likely to be mediated via canonical cyclic AMP signaling through protein kinase A.

Increased expression of interleukin-6 family members and receptors in urinary bladder with cyclophosphamide-induced bladder inflammation in female rats

Recent studies suggest that janus-activated kinases-signal transducer and activator of transcription signaling pathways contribute to increased voiding frequency and referred pain of cyclophosphamide (CYP)-induced cystitis in rats. Potential upstream chemical mediator(s) that may be activated by CYP-induced cystitis to stimulate JAK/STAT signaling are not known in detail. In these studies, members of the interleukin (IL)-6 family of cytokines including, leukemia inhibitory factor (LIF), IL-6, and ciliary neurotrophic factor (CNTF) and associated receptors, IL-6 receptor (R) α, LIFR, and gp130 were examined in the urinary bladder in control and CYP-treated rats. Cytokine and receptor transcript and protein expression and distribution were determined in urinary bladder after CYP-induced cystitis using quantitative, real-time polymerase chain reaction (Q-PCR), western blotting, and immunohistochemistry. Acute (4 h; 150 mg/kg; i.p.), intermediate (48 h; 150 mg/kg; i.p.), or chronic (75 mg/kg; i.p., once every 3 days for 10 days) cystitis was induced in adult, female Wistar rats with CYP treatment. Q-PCR analyses revealed significant (p ≤ 0.01) CYP duration- and tissue- (e.g., urothelium, detrusor) dependent increases in LIF, IL-6, IL-6Rα, LIFR, and gp130 mRNA expression. Western blotting demonstrated significant (p ≤ 0.01) increases in IL-6, LIF, and gp130 protein expression in whole urinary bladder with CYP treatment. CYP-induced cystitis significantly (p ≤ 0.01) increased LIF-immunoreactivity (IR) in urothelium, detrusor, and suburothelial plexus whereas increased gp130-IR was only observed in urothelium and detrusor. These studies suggest that IL-6 and LIF may be potential upstream chemical mediators that activate JAK/STAT signaling in urinary bladder pathways.

The Krüppel-like factor 4 controls biosynthesis of thyrotropin-releasing hormone during hypothalamus development

Embryonic neurogenesis is controlled by the activation of specific genetic programs. In the hypothalamus, neuronal thyrotropin-releasing hormone (TRH) populations control important physiological process, including energy homeostasis and autonomic function; however, the genetic program leading to the TRH expression is poorly understood. Here, we show that the Klf4 gene, encoding the transcription factor Krüppel-like factor 4 (Klf4), was expressed in the rat hypothalamus during development and regulated Trh expression. In rat fetal hypothalamic cells Klf4 regulated Trh promoter activity through CACCC and GC motifs present on the Trh gene promoter. Accordingly, hypothalamic Trh expression was down-regulated at embryonic day 15 in the Klf4(-/-) mice resulting in diminished bioactive peptide levels. Although at the neonatal stage the Trh transcript levels of the Klf4(-/-) mice were normal, the reduction in peptide levels persisted. Thus, our data indicate that Klf4 plays a key role in the maturation of TRH expression in hypothalamic neurons.

Cardiac ischemia-reperfusion regulates sympathetic neuropeptide expression through gp130-dependent and independent mechanisms

Cardiac function is regulated by a balance of sympathetic and parasympathetic transmission. Neuropeptide Y (NPY) and galanin (GAL) released from cardiac sympathetic neurons inhibits parasympathetic transmission in the heart. Sympathetic peptides may contribute to autonomic imbalance, which is characterized by increased sympathetic and decreased parasympathetic transmission and contributes to life threatening cardiovascular pathologies. Several gp130 cytokines are increased in the heart after myocardial infarction (MI), and these cytokines stimulate neuropeptide expression in sympathetic neurons. We used mice whose sympathetic neurons lack the gp130 receptor (gp130(DBH-Cre/lox) mice) to ask if cytokine activation of gp130 regulated neuropeptide expression in cardiac sympathetic nerves after MI. Myocardial infarction decreased NPY mRNA through a gp130 independent mechanism and increased VIP and PACAP mRNA via gp130, while GAL mRNA was unchanged. Immunohistochemistry revealed a gp130-dependent increase in PACAP38 in cells of the stellate ganglion after MI, and PACAP was detected in pre-ganglionic fibers of all genotypes and surgical groups. VIP was identified in a few sympathetic nerve fibers in all genotypes and surgical groups. GAL and PACAP38 were not detected in sham hearts, but peptide immunoreactivity was high in the infarct three days after MI. Surprisingly, peptides were abundant in cells that co-labeled with macrophage markers F4/80 and MAC2, but were not detected in sympathetic axons. PACAP protects cardiac myocytes from apoptosis, and GAL stimulates axon regeneration in addition to inhibiting parasympathetic transmission. Thus, these peptides may play an important role in cardiac and neuronal remodeling after ischemia-reperfusion.

Neurotrophin/receptor expression in urinary bladder of mice with overexpression of NGF in urothelium

Urothelium-specific overexpression of nerve growth factor (NGF) in the urinary bladder of transgenic mice stimulates neuronal sprouting in the urinary bladder, produces increased voiding frequency, and results in increased referred somatic hypersensitivity. Additional NGF-mediated pleiotropic changes might contribute to the increased voiding frequency and pelvic hypersensitivity observed in these transgenic mice, such as modulation of other growth factor/receptor systems. Chronic overexpression of NGF in the urothelium was achieved through the use of a highly urothelium-specific uroplakin II promoter. In the present study, we examined NGF, brain-derived neurotrophic factor (BDNF), and associated receptor [p75(NTR), tyrosine kinase (Trk)A, TrkB] transcript and protein expression in urothelium and detrusor smooth muscle of NGF-overexpressing (OE) and littermate wild-type mice, using real-time quantitative reverse transcription-polymerase chain reaction, ELISAs, and semiquantitation of immunohistochemistry. We focused on these growth factor/receptors given the established roles of NGF/TrkA, NGF/p75(NTR), and BDNF/TrkB systems in bladder function. Increased voiding frequency in NGF-OE mice was confirmed by examining urination patterns. BDNF, TrkA, and TrkB protein expression was significantly (P ≤ 0.01) reduced and p75(NTR) protein expression was significantly (P ≤ 0.01) increased in urinary bladder of NGF-OE mice. The NGF-OE-induced changes in neurotrophic factor/receptor expression in urinary bladder may represent compensatory changes to reduce voiding frequency in the NGF-OE mouse.

PACAP/VIP and receptor characterization in micturition pathways in mice with overexpression of NGF in urothelium

Urothelium-specific overexpression of nerve growth factor (NGF) in the urinary bladder of transgenic mice stimulates neuronal sprouting or proliferation in the urinary bladder, produces urinary bladder hyperreflexia, and results in increased referred somatic hypersensitivity. Additional NGF-mediated changes might contribute to the urinary bladder hyperreflexia and pelvic hypersensitivity observed in these transgenic mice such as upregulation of neuropeptide/receptor systems. Chronic overexpression of NGF in the urothelium was achieved through the use of a highly urothelium-specific, uroplakin II promoter. In the present study, we examined pituitary adenylate cyclase activating polypeptide (PACAP), vasoactive intestinal polypeptide (VIP), and associated receptor (PAC1, VPAC1, VPAC2) transcripts or protein expression in urothelium and detrusor smooth muscle and lumbosacral dorsal root ganglia in NGF-overexpressing and littermate wildtype mice using real-time quantitative reverse transcription-polymerase chain reaction and immunohistochemical approaches. Results demonstrate upregulation of PAC1 receptor transcript and PAC1-immunoreactivity in urothelium of NGF-OE mice whereas PACAP transcript and PACAP-immunoreactivity were decreased in urothelium of NGF-OE mice. In contrast, VPAC1 receptor transcript was decreased in both urothelium and detrusor smooth muscle of NGF-OE mice. VIP transcript expression and immunostaining was not altered in urinary bladder of NGF-OE mice. Changes in PACAP, VIP, and associated receptor transcripts and protein expression in micturition pathways resemble some, but not all, changes observed after induction of urinary bladder inflammation known to involve NGF production.

PACAP expression in explant cultured mouse major pelvic ganglia

The major pelvic ganglia (MPG) contain both parasympathetic and sympathetic postganglionic neurons and provide much of the autonomic innervation to urogenital organs and components of the lower bowel. Whereas many parasympathetic neurons were found to express vasoactive intestinal polypeptide (VIP), no MPG neurons exhibited immunoreactivity for pituitary adenylate cyclase-activating polypeptide (PACAP). However, in 3-day cultured MPGs, numerous PACAP-IR cells and nerve fibers were present, and transcript levels for PACAP increased significantly. In 3-day cultured MPGs, PACAP immunoreactivity was seen in cells that were also immunoreactive for VIP or neuronal nitric oxide synthase, but not tyrosine hydroxylase, indicating that PACAP expression occurred preferentially in MPG parasympathetic postganglionic neurons. Transcript levels for the VPAC2, but not VPAC1 or PAC1 receptor, also increased significantly following 3 days in culture. Transcript levels of activating transcription factor 3 (ATF-3), a marker of cellular injury, were increased 64-fold in 3-day explants, and ATF-3-IR nuclei were evident in both TH-IR and nNOS-IR neurons as well as in non-neuronal cells. In sum, these results demonstrate that, although only the parasympathetic neurons in explant cultured MPGs increase expression of PACAP, both sympathetic and parasympathetic postganglionic neurons in the cultured MPG whole-mount increase expression of ATF-3.

Expression and response of acid-sensing ion channels in urinary bladder to cyclophosphamide-induced cystitis

The expression of acid-sensing ion channel (ASIC) isoforms, ASIC1, ASIC2a, and ASIC3, was examined in the urinary bladder after cyclophosphamide (CYP)-induced cystitis of varying duration (4 h, 48 h, and chronic). Immunohistochemical, Western blot, and quantitative PCR approaches were used to evaluate channel expression and effects of CYP-induced cystitis in whole urinary bladder and split-bladder preparations from control (no inflammation) and CYP-treated rats. Quantitative PCR demonstrated significant (P ≤ 0.01) increases in ASIC2a and ASIC3 transcripts with CYP-induced cystitis (48 h and chronic) in the urothelium but no changes (e.g., ASIC3) or modest changes (e.g., ASIC2a) in detrusor smooth muscle. ASIC1 mRNA expression in the urothelium or detrusor was not affected by CYP-induced cystitis. Immunohistochemistry for ASIC2a and ASIC3 protein expression revealed significant (P ≤ 0.01) increases in ASIC immunoreactivity in the urothelium and suburothelial plexus with CYP-induced cystitis at all time points examined. Western blotting for ASIC2a and ASIC3 protein expression was complementary and revealed significant (P ≤ 0.01) increases in ASIC immunoreactivity. For the first time, these studies demonstrate that CYP-induced cystitis alters ASIC2a and ASIC3 expression in the urinary bladder; ASIC1 transcript expression is not altered by CYP-induced cystitis. Future studies are necessary to determine ASIC isoform contributions to micturition reflexes in control and inflamed urinary bladder.

Expression and function of CXCL12/CXCR4 in rat urinary bladder with cyclophosphamide-induced cystitis

Chemokines, otherwise known as chemotactic cytokines, are proinflammatory mediators of the immune response and have been implicated in altered sensory processing, hyperalgesia, and central sensitization following tissue injury or inflammation. To address the role of CXCL12/CXCR4 signaling in normal micturition and inflammation-induced bladder hyperreflexia, bladder inflammation in adult female Wistar rats (175-250 g) was induced by injecting cyclophosphamide (CYP) intraperitoneally at acute (150 mg/kg; 4 h), intermediate (150 mg/kg; 48 h), and chronic (75 mg/kg; every 3rd day for 10 days) time points. CXCL12, and its receptor, CXCR4, were examined in the whole urinary bladder of control and CYP-treated rats using enzyme-linked immunosorbent assays (ELISAs), quantitative PCR (qRT-PCR), and immunostaining techniques. ELISAs, qRT-PCR, and immunostaining experiments revealed a significant (P < or = 0.01) increase in CXCL12 and CXCR4 expression in the whole urinary bladder, and particularly in the urothelium, with CYP treatment. The functional role of CXCL12/CXCR4 signaling in micturition was evaluated using conscious cystometry with continuous instillation of saline and CXCR4 receptor antagonist (AMD-3100; 5 microM) administration in control and CYP (48 h)-treated rats. Receptor blockade of CXCR4 using AMD-3100 increased bladder capacity in control (no CYP) rats and reduced CYP-induced bladder hyperexcitability as demonstrated by significant (P < or = 0.01) increases in intercontraction interval, bladder capacity, and void volume. These results suggest a role for CXCL12/CXCR4 signaling in both normal micturition and with bladder hyperreflexia following bladder inflammation.

Signaling pathways in PACAP regulation of VIP gene expression in human neuroblastoma cells

Ganglia expressing the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) innervate vasoactive intestinal peptide (VIP) containing neurons suggesting a role of PACAP in regulating VIP expression. Human NB-1 neuroblastoma cells were applied to study PACAP regulated VIP gene expression aiming to identify the receptor and the signaling proteins involved. The PACAP receptor subtype PAC1 induced VIP gene expression as (i) PACAP and the PAC1 receptor agonist maxadilan were equally efficient and approximately 200-fold more potent than VIP, and (ii) PACAP6-38 and PG99-465, antagonists of PAC1 and VPAC2 receptors, respectively, abolished and did not affect the PACAP-induced VIP mRNA expression, respectively. A pivotal role of PKA was implicated in addition to partial involvement of PKC and ERK1/2 in PACAP-induced VIP gene expression as H-89, Bisindolylmaleimide I (BIS), Gö6976 and U0126 attenuated the VIP mRNA expression by 93%, 58%, 58% and 40%, respectively. PACAP modulated the phosphorylation of ERK1/2 (pERK1/2) and CREB/ATF-1 (pCREB/ATF-1) concomitant with a translocation of PKA to the nucleus. Inhibition of conventional PKC isoforms and MEK1/2 completely abolished pERK1/2 without affecting PACAP induced pCREB/ATF-1. In contrast, inhibiting PKA attenuated PACAP induced pCREB/ATF-1. PACAP also enhanced the FOS gene expression and individual presence of H-89, BIS, Gö6976 and U0126 partially attenuated the PACAP induced FOS mRNA expression. Combining the kinase inhibitors completely suppressed the PACAP induced FOS mRNA expression. Immunoblotting confirmed expression of FOS protein upon addition of PACAP, which was diminished by impairment of PKC, ERK1/2 and PKA activities. The resemblance of the signaling pathways involving concomitant activities of PKC, ERK1/2 and PKA in PACAP regulation of the FOS and VIP gene expressions suggest for the first time a role of FOS in PACAP-induced VIP gene expression in human NB-1 neuroblastoma cells.

Chronic stress increases pituitary adenylate cyclase-activating peptide (PACAP) and brain-derived neurotrophic factor (BDNF) mRNA expression in the bed nucleus of the stria terminalis (BNST): roles for PACAP in anxiety-like behavior

Exposure to chronic stress has been argued to produce maladaptive anxiety-like behavioral states, and many of the brain regions associated with stressor responding also mediate anxiety-like behavior. Pituitary adenylate cyclase activating polypeptide (PACAP) and its specific G protein-coupled PAC(1) receptor have been associated with many of these stress- and anxiety-associated brain regions, and signaling via this peptidergic system may facilitate the neuroplasticity associated with pathological affective states. Here we investigated whether chronic stress increased transcript expression for PACAP, PAC(1) receptor, brain-derived neurotrophic factor (BDNF), and tyrosine receptor kinase B (TrkB) in several nuclei. In rats exposed to a 7 days chronic variate stress paradigm, chronic stress enhanced baseline startle responding induced by handling and exposure to bright lights. Following chronic stress, quantitative transcript assessments of brain regions demonstrated dramatic increases in PACAP and PAC(1) receptor, BDNF, and TrkB receptor mRNA expression selectively in the dorsal aspect of the anterolateral bed nucleus of the stria terminalis (dBNST). Related vasoactive intestinal peptide (VIP) and VPAC receptor, and other stress peptide transcript levels were not altered compared to controls. Moreover, acute PACAP38 infusion into the dBNST resulted in a robust dose-dependent anxiogenic response on baseline startle responding that persisted for 7 days. PACAP/PAC(1) receptor signaling has established trophic functions and its coordinate effects with chronic stress-induced dBNST BDNF and TrkB transcript expression may underlie the maladaptive BNST remodeling and plasticity associated with anxiety-like behavior.

Upregulation of vascular endothelial growth factor isoform VEGF-164 and receptors (VEGFR-2, Npn-1, and Npn-2) in rats with cyclophosphamide-induced cystitis

Regulation of the VEGF-VEGF receptor system was examined in the urinary bladder after acute (2-48 h) and chronic (10 days) cyclophosphamide (CYP)-induced cystitis. ELISAs demonstrated significant (P < or = 0.01) upregulation of VEGF in whole urinary bladder with acute and chronic CYP-induced cystitis; however, the magnitude of increase was greater after acute (2-4 h) cystitis. Immunohistochemistry for VEGF immunoreactivity revealed a significant (P < or = 0.05) increase in VEGF immunoreactivity in the urothelium, suburothelial vasculature, and detrusor smooth muscle with acute (4 and 48 h) CYP treatment. RT-PCR identified the isoform VEGF-164, the VEGF receptor VEGFR-2, and the VEGF co-receptors neuropilin (Npn)-1 and Npn-2 in the urinary bladder. Quantitative PCR demonstrated upregulation of VEGF-164 transcript with acute and chronic CYP-induced cystitis, but VEGFR-2, Npn-1, and Npn-2 transcripts were upregulated (P < or = 0.01) in whole bladder only with chronic CYP-induced cystitis. Additional studies demonstrated regulation of VEGF transcript expression in the urinary bladder by nerve growth factor (NGF) in a novel line of NGF-overexpressing mice. These studies demonstrated that urinary bladder inflammation and NGF regulate the VEGF-VEGF receptor system in the urinary bladder. Functional role(s) for the VEGF-VEGF receptor system in urinary bladder inflammation remain to be determined.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) regulate murine neural progenitor cell survival, proliferation, and differentiation

Neural stem/progenitor cells (NPC) have gained wide interest over the last decade from their therapeutic potential, either through transplantation or endogenous replacement, after central nervous system (CNS) disease and damage. Whereas several growth factors and cytokines have been shown to promote NPC survival, proliferation, or differentiation, the identification of other regulators will provide much needed options for NPC self-renewal or lineage development. Although previous studies have shown that pituitary adenylate cyclase-activating polypeptide (PACAP)/vasoactive intestinal peptide (VIP) can regulate stem/progenitor cells, the responses appeared variable. To examine the direct roles of these peptides in NPCs, postnatal mouse NPC cultures were withdrawn from epidermal growth factor (EGF) and fibroblastic growth factor (FGF) and maintained under serum-free conditions in the presence or absence of PACAP27, PACAP38, or VIP. The NPCs expressed the PAC1(short)null receptor isoform, and the activation of these receptors decreased progenitor cell apoptosis more than 80% from TUNEL assays and facilitated proliferation more than fivefold from bromodeoxyuridine (BrdU) analyses. To evaluate cellular differentiation, replicate control and peptide-treated cultures were examined for cell fate marker protein and transcript expression. In contrast with previous work, PACAP peptides downregulated NPC differentiation, which appeared consistent with the proliferation status of the treated cells. Accordingly, these results demonstrate that PACAP signaling is trophic and can maintain NPCs in a multipotent state. With these attributes, PACAP may be able to promote endogenous NPC self-renewal in the adult CNS, which may be important for endogenous self-repair in disease and ageing processes.

Postnatal expression of corticotropin releasing factor (CRF) in rat urinary bladder

Corticotropin releasing factor (CRF) is a neuropeptide expressed in micturition reflex circuitry and different roles in these reflexes have been suggested. These studies examined the expression of CRF/CRF receptors in the urinary bladder during postnatal development in the rat. Urinary bladder was harvested from rats (postnatal (P) day 0-adult) euthanized by isoflurane (4%) and thoracotomy. CRF protein expression significantly (p<or=0.01) decreased in the urothelium with increasing postnatal age. In contrast, CRF-immunoreactivity (IR) was increased in nerve fibers in the suburothelial plexus during the second-third postnatal week. Total CRF protein from urinary bladder significantly increased during the second-third postnatal weeks as determined with ELISAs. CRF receptor 2 (CRFR(2)) transcript was expressed in urinary bladder of all postnatal ages examined whereas no CRFR(1) transcript was expressed at any postnatal age examined. We also demonstrated changes in urinary bladder mRNA expression for the neuropeptides, galanin, substance P, vasoactive intestinal polypeptide and pituitary adenylate cyclase activating polypeptide during postnatal development. These studies demonstrate changes in the CRF expression in urinary bladder, specifically in the urothelium and nerve fibers of the suburothelial plexus during postnatal development. Changes in CRF expression and neuropeptide expression in general in the urinary bladder may contribute to the emergence of mature voiding reflexes.

PACAP-mediated ATP release from rat urothelium and regulation of PACAP/VIP and receptor mRNA in micturition pathways after cyclophosphamide (CYP)-induced cystitis

Pituitary adenylate cyclase-activating peptide (PACAP) peptides are expressed in micturition pathways, and PACAP expression is regulated by urinary bladder inflammation. Previous physiological studies have demonstrated roles for PACAP27 and PACAP38 in detrusor smooth muscle (DSM) contraction and a PAC1 receptor antagonist reduced cyclophosphamide (CYP)-induced bladder hyperreflexia. To gain insight into PACAP signaling in micturition and regulation with cystitis, receptor characterization by real-time quantitative polymerase chain reaction and physiological assays were performed. PACAP receptors were identified in tissues of rat micturition pathway, including DSM, urothelium (U), and dorsal root ganglia (DRG) after acute (4 h), intermediate (48 h) or chronic (8 days) CYP-induced cystitis. PAC1 messenger RNA expression significantly (p < or = 0.05) increased in U and DSM after 48 h and chronic CYP-induced cystitis after an initial decrease at 4 h. VPAC1 and VPAC2 transcripts increased in U and DSM after acute and intermediate CYP-induced cystitis followed by a decrease in VPAC2 expression with chronic cystitis. Application of PACAP27 (100 nM) to cultured urothelial cells evoked adenosine triphosphate (ATP) release that was blocked by the PAC1 specific antagonist, M65 (1 microM). PACAP38 (100 nM) also evoked ATP release from cultured urothelial cells, but ATP release was less than that observed with PACAP27. PACAP transcripts were increased in the U with intermediate and chronic cystitis, whereas vasoactive intestinal polypeptide (VIP) expression in both tissues was very low and showed no regulation with cystitis. Regulation of PACAP, galanin, and substance P transcripts expression was observed in lumbosacral DRG, but no regulation for VIP was observed. The current data demonstrate PACAP and PAC1 regulation in micturition pathways with inflammation and PACAP-mediated ATP release from urothelium.

Post-infarct cardiac sympathetic hyperactivity regulates galanin expression

The neuropeptide galanin is elevated in the cardiac sympathetic innervation after myocardial infarction (MI). Galanin inhibits vagal transmission and may support the regeneration of sympathetic nerves, thereby contributing to the development of arrhythmia and sudden cardiac death after MI. The reason for increased galanin production in sympathetic neurons after myocardial infarction is not known. Cardiac sympathetic neurons are activated chronically after cardiac ischemia-reperfusion, and activation of sympathetic neurons in culture stimulates galanin expression. Therefore, we tested the hypothesis that increased sympathetic nerve activity stimulates galanin expression in cardiac sympathetic neurons after myocardial infarction. To test this hypothesis we used TGR(ASrAOGEN) transgenic rats, which lack brain angiotensinogen and do not exhibit post-infarct sympathetic hyperactivity. Hearts and stellate ganglia were collected 1 week after ischemia-reperfusion. Galanin mRNA was quantified by real-time PCR and peptide content was assayed by enzyme-linked immunosorbent assay. Galanin mRNA increased approximately 3-fold after MI in cardiac sympathetic neurons of both genotypes compared to unoperated and sham controls. Left ventricular galanin content, however, increased after MI only in Sprague-Dawley rats and not in AOGEN rats. These data suggest that post-infarct cardiac sympathetic hyperactivity stimulates galanin peptide production but is not required for increased galanin mRNA expression.

Role of PACAP in the physiology and pathology of the sympathoadrenal system

Sympathetic neurons and chromaffin cells derive from common sympathoadrenal precursors which arise from the neural crest. Cells from this lineage migrate to their final destination and differentiate by acquiring a catecholaminergic phenotype in response to different environmental factors. It has been shown that the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its PAC1 receptor are expressed at early stages of sympathetic development, and participate to the control of neuroblast proliferation and differentiation. PACAP also acts as a neurotransmitter to stimulate catecholamine and neuropeptide biosynthesis and release from sympathetic neurons and chromaffin cells, during development and in adulthood. In addition, PACAP and its receptors have been described in neuroblastoma and pheochromocytoma, and the neuropeptide regulates the differentiation and activity of sympathoadrenal-derived tumoral cell lines, suggestive of an important role in the pathophysiology of the sympathoadrenal lineage. Transcriptome studies uncovered genes and pathways of known and unknown roles that underlie the effects of PACAP in the sympathoadrenal system.

Expression of Pcp4 gene during osteogenic differentiation of bone marrow mesenchymal stem cells in vitro

In this study, we established an in vitro model of osteogenic-inductive differentiation of rat bone marrow mesenchymal stem cells (BMSCs) to determine the mechanisms and relative gene function underlying BMSCs osteogenesis. Osteoplastic differentiation of the third generation BMSCs was induced with the alpha-minimal essential medium containing beta-glyceraldehyde-3-phosphate, L: -ascorbic acid, dexamethasone and 1,25-2(OH)2 vitamin D3 prior to applying gene chip technology (also called microarray technology) for global gene expression screening. Real-time quantitative PCR (Real-time PCR) was used to determine the temporal profile of mRNA expression of regulated genes during osteogenic differentiation of BMSCs. A bioinformatic analysis was utilized to determine the functional significance of the identified osteogenic-related genes. Purkinje cell protein 4 (Pcp4) mRNA expression was identified by the gene chip screening as being up-regulated during osteoplastic differentiation of BMSCs. Real-time PCR analysis confirmed the increased expression of Pcp4 mRNA expression during osteoplastic differentiation of BMSCs with an upward trend that peaked at day 14. The bioinformatic analysis identified Pcp4 as a gene involved in the deposition of calcium and the modulation of CaM-dependent protein kinase. Thus, we hypothesize that Pcp4 osteoplastic differentiation of BMSCs is mediated in part via Pcp4-induced calcium deposition to form mineral nodules and modulation of certain signal transduction pathways of BMPs.

Microarray analyses of pituitary adenylate cyclase activating polypeptide (PACAP)-regulated gene targets in sympathetic neurons

The high and preferential expression of the PAC(1)(short)HOP1 receptor in postganglionic sympathetic neurons facilitates microarray studies for mechanisms underlying PACAP-mediate neurotrophic signaling in a physiological context. Replicate primary sympathetic neuronal cultures were treated with 100 nM PACAP27 either acutely (9 h) or chronically (96 h) before RNA extraction and preparation for Affymetrix microarray analysis. Compared to untreated control cultures, acute PACAP treatment modulated significantly the expression of 147 transcripts of diverse functional groups, including peptides, growth factors/cytokines, transcriptional factors, receptors/signaling effectors and cell cycle regulators, that collectively appeared to facilitate neuronal plasticity, differentiation and/or regeneration processes. Some regulated transcripts, for example, were related to BDNF/TrkB, IL-6/Jak2/Socs2 and TGF/follistatin signaling; many transcripts affected bioactive peptide and polyamine biosynthesis. Although chronic PACAP treatments altered the expression of 109 sympathetic transcripts, only 43 transcripts were shared between the acute and chronic treatment data sets. The PACAP-mediated changes in transcript expression were corroborated independently by quantitative PCR measurement. The PACAP-regulated transcripts in sympathetic neurons did not bear strong resemblance to those in PACAP-treated pheochromocytoma cells. However, many PACAP-targeted sympathetic transcripts, especially those related to peptide plasticity and nerve regeneration processes, coincided significantly with genes altered after peripheral nerve injury. The ability for sympathetic PAC(1)(short)HOP1 receptors to engage multiple downstream signaling cascades appeared to be reflected in the number and diversity of genes targeted in a multifaceted strategy for comprehensive neurotrophic responses.

Regulation of neuronal pituitary adenylate cyclase-activating polypeptide expression during culture of guinea-pig cardiac ganglia

The trophic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) increases in many different neuron types following injury; a response postulated to support cell survival and regeneration. In acutely isolated cardiac ganglia, approximately 1% of the cardiac neurons exhibited PACAP immunoreactivity whereas after 72 h in culture, approximately 25% of the neurons were PACAP immunoreactive. In contrast, there was no increase in vasoactive intestinal polypeptide (VIP)-immunoreactive (IR) cells. Using a combination of immunocytochemical and molecular techniques, we have quantified PACAP expression, during explant culture of guinea-pig cardiac ganglia. Using real time polymerase chain reaction, PACAP transcript levels increased progressively up to 48 h in culture with no further increase after 72 h. PACAP transcript levels were reduced by neurturin at 48 h in culture but not after 24 or 72 h in culture. In addition, neurturin partially suppressed the percentage of PACAP-IR neurons after 72 h in culture, an effect mediated by activation of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase signaling pathways. The addition of different known regulatory molecules, including ciliary neurotrophic factor (CNTF), interleukin-1 beta (Il-1beta), tumor necrosis factor-alpha (TNFalpha), fibroblast growth factor basic (bFGF), transforming growth factor-beta (TGF-beta) and nerve growth factor (NGF) did not increase the percentage of PACAP-IR neurons after 24 h in culture; a result indicating that the generation and secretion of these factors did not stimulate PACAP expression. The presence of 20 nM PACAP or 10 muM forskolin increased the percentage of PACAP-IR cardiac neurons in 24 h cultures, but not in 72 h cultures. Neither treatment enhanced the number of VIP-IR neurons. The addition of the PACAP selective receptor (PAC(1)) receptor antagonist, M65 (100 nM) suppressed the 20 nM PACAP-induced increase in percentage of PACAP-IR cells in 24 h cultures indicating the effect of PACAP was mediated through the PAC(1) receptor. However, 100 nM M65 had no effect on the percentage of PACAP-IR cells in either 24 or 48 h cultures not treated with exogenous PACAP, suggesting that endogenous release of PACAP likely did not contribute to the enhanced peptide expression. We postulate that the enhanced PACAP expression, which occurs in response to injury is facilitated in the explant cultured cardiac ganglia by the loss of a target-derived inhibitory factor, very likely neurturin. In intact tissues the presence of neurturin would normally suppress PACAP expression. Lastly, our results indicate that many common trophic factors do not enhance PACAP expression in the cultured cardiac neurons. However, the stimulatory role of an, as yet, unidentified factor cannot be excluded.

Bone morphogenetic protein down-regulation of neuronal pituitary adenylate cyclase-activating polypeptide and reciprocal effects on vasoactive intestinal peptide expression

Among bone morphogenetic proteins (BMPs), the decapentaplegic (Dpp; BMP2, BMP4) and glass bottom boat (Gbb/60A; BMP5, BMP6, BMP7) subgroups have well-described functions guiding autonomic and sensory neuronal development, fiber formation and neurophenotypic identities. Evaluation of rat superior cervical ganglia (SCG) post-ganglionic sympathetic neuron developmental regulators identified that selected BMPs of the transforming growth factor beta superfamily have reciprocal effects on neuronal pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) expression. Dpp and Gbb/60A BMPs rapidly down-regulated PACAP expression, while up-regulating other sympathetic neuropeptides, including PACAP-related VIP. The suppressive effects of BMP on PACAP mRNA and peptide expression were potent, efficacious and phosphorylated mothers against decapentaplegic homolog (Smad) signaling-dependent. Axotomy of SCG dramatically increases PACAP expression, and the possibility that abrogation of inhibitory retrograde target tissue BMP signaling may contribute to this up-regulation of sympathetic neuron PACAP was investigated. Replacement of BMP6 to SCG explant preparations significantly blunted the injury-induced elevated PACAP expression, with a concomitant decrease in sympathetic PACAP-immunoreactive neuron numbers. These studies suggested that BMPs modulate neuropeptide identity and diversity by stimulating or restricting the expression of specific peptidergic systems. Furthermore, the liberation of SCG neurons from target-derived BMP inhibition following axotomy may be one participating mechanism associated with injury-induced neuropeptidergic plasticity.

Noncompensation in peptide/receptor gene expression and distinct behavioral phenotypes in VIP- and PACAP-deficient mice

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are closely related neurotrophic peptides of the secretin/glucagon family. The two peptides are derived from a common ancestral gene and share many functional attributes in neuronal development/regeneration which occur not only from overlapping receptor subtype signaling but also through common mechanisms regulating their expression. Although PACAP or VIP null mice have been generated for study, it is unclear whether the expression of the complementary peptide or their receptor systems are altered in a compensatory manner during nervous system development. By radioimmunoassay and quantitative PCR measurements, we first show that PACAP and VIP have very different temporal patterns of expression in developing postnatal mouse brain. In wild-type animals, PACAP transcript and peptide levels increased rapidly 2- and 5-fold, respectively, within 1 week of age. These levels at 1 week of age were maintained through adulthood. VIP transcript and peptide levels, by contrast, increased 25- and 50-fold, respectively, over a later time course. In parallel studies of development, there were no apparent compensatory increases in brain VIP expression in the PACAP knockout animals, PACAP expression in the VIP-deficient animals, or receptor mRNA levels in either genotype. To the contrary, there was evidence for developmental delays in the expression of peptide and receptor transcripts in the knockout animals. A series of behavioral and neurological tests demonstrated differences between the knockout genotypes, revealing some functional distinctions between the two genes. These results suggest that the PACAP and VIP have evolved to possess distinct biological activities and intimate that the respective knockout phenotypes represent deficits unmitigated by the actions of the complementary related peptide.

VIP is a transcriptional target of Nurr1 in dopaminergic cells

The orphan nuclear receptor Nurr1 is required for the development of the ventral mesencephalic dopaminergic neurons. These are the same neurons that are invariantly lost in patients with Parkinson's disease. Nurr1 mRNA expression is not confined to the developing midbrain, and yet Nurr1 appears to be essential for either the maturation of progenitors into fully post-mitotic dopaminergic neurons and/or once formed, their survival. The function of Nurr1 in the transactivation of gene(s) important for neuronal development and/or maintenance is uncharacterized. To characterize potential downstream target genes of Nurr1, we sought to identify mRNAs that are differentially affected by Nurr1 expression. Using a dopaminergic cell line in which Nurr1 content was tightly regulated, differential display analysis identified transcripts altered by Nurr1 expression, including the mRNA encoding vasoactive intestinal peptide (VIP). Herein, we demonstrate that Nurr1 regulates VIP mRNA and protein levels, and transactivates the VIP promoter through Nurr1-responsive cis elements. In addition, dopaminergic cells release and utilize VIP to mediate survival when challenged with paraquat. Nurr1 regulation of VIP is also demonstrated in vivo as loss of Nurr1 function results in diminished VIP mRNA levels within the developing midbrain.

Role for pituitary adenylate cyclase activating polypeptide in cystitis-induced plasticity of micturition reflexes

Pituitary adenylate cyclase activating polypeptide (PACAP) peptides are expressed and regulated in sensory afferents of the micturition pathway. Although these studies have implicated PACAP in bladder control, the physiological significance of these observations has not been firmly established. To clarify these issues, the roles of PACAP and PACAP signaling in micturition and cystitis were examined in receptor characterization and physiological assays. PACAP receptors were identified in various tissues of the micturition pathway, including bladder detrusor smooth muscle and urothelium. Bladder smooth muscle expressed heterogeneously PAC(1)null, PAC(1)HOP1, and VPAC(2) receptors; the urothelium was more restricted in expressing preferentially the PAC(1) receptor subtype only. Immunocytochemical studies for PAC(1) receptors were consistent with these tissue distributions. Furthermore, the addition of 50-100 nM PACAP27 or PACAP38 to isolated bladder strips elicited transient contractions and sustained increases in the amplitude of spontaneous phasic contractions. Treatment of the bladder strips with tetrodotoxin (1 muM) did not alter the spontaneous phasic contractions suggesting direct PACAP effects on bladder smooth muscle. PACAP also increased the amplitude of nerve-evoked contractions. By contrast, vasoactive intestinal polypeptide had no direct effects on bladder smooth muscle. In a rat cyclophosphamide (CYP)-induced cystitis paradigm, intrathecal or intravesical administration of PAC(1) receptor antagonist, PACAP6-38, reduced cystitis-induced bladder overactivity. In summary, these studies support roles for PACAP in micturition and suggest that inflammation-induced plasticity in PACAP expression in peripheral and central micturition pathways contribute to bladder dysfunction with cystitis.

Trophic factor modulation of cocaine- and amphetamine-regulated transcript peptide expression in explant cultured guinea-pig cardiac neurons

The present study investigated the influence of trophic factors on the expression of cocaine- and amphetamine-regulated transcript peptide (CARTp) in guinea-pig cardiac ganglia maintained in explant culture. In acutely isolated cardiac ganglia preparations, <1% of the cholinergic cardiac neurons exhibited CARTp immunoreactivity. In contrast, this number increased to >25% of the cardiac neurons after 72 h in explant culture. This increase in the number of CARTp neurons in cultured cardiac ganglia explants was accompanied by an increase in CARTp transcript levels as assessed by real time polymerase chain reaction. Treatment of cardiac ganglia cultures with neurturin or glial-derived trophic factor (both at 10 ng/ml) for 72 h prevented the increase in neurons that exhibited CARTp immunoreactivity. In contrast, treatment with ciliary neurotrophic factor (50 ng/ml) for 72 h produced a small significant increase in the percentage of CARTp-immunoreactive cardiac neurons and treatment with nerve growth factor (100 ng/ml) had no effect. Neurturin treatment also decreased cardiac neuron CARTp levels after 72 h in explant culture. Cardiac neurons exhibited immunoreactivity to the neurturin receptor GFRalpha2 whereas non-neural cells preferentially exhibited immunoreactivity to the glial-derived neurotrophic factor receptor GFRalpha1 and neurturin transcripts were detected in cardiac tissue extracts. We hypothesize that a target-derived inhibitory factor, very likely neurturin, is a critical factor suppressing the expression of CARTp in guinea-pig cardiac neurons. These observations contrast with those reported in sympathetic neurons that suggest up-regulation of trophic factors after axotomy or during explant culture is a key factor contributing to the up-regulation of many neuropeptides.

Myocardial infarction stimulates galanin expression in cardiac sympathetic neurons

Cardiac ischemia-reperfusion alters sympathetic neurotransmission in the heart, but little is known about its effect on neuropeptide expression in sympathetic neurons. Ischemia followed by reperfusion induces the production of inflammatory cytokines in the heart, including interleukin-6 and cardiotrophin-1. These cytokines and related molecules inhibit the expression of neuropeptide Y (NPY), and stimulate the expression of vasoactive intestinal peptide (VIP), substance P (SubP), and galanin (GAL) in cultured sympathetic neurons. Therefore, we quantified NPY, VIP, SubP, and GAL mRNA in neurons of the stellate ganglia 1 week after ischemia-reperfusion to determine if neuropeptide expression was altered in cardiac sympathetic neurons. NPY, VIP, and SubP mRNAs were unchanged compared to unoperated control animals, but GAL mRNA was increased significantly. The increased GAL mRNA was not accompanied by elevated GAL peptide content in the stellate ganglia. Galanin content was increased significantly in the heart, however, indicating that elevated GAL mRNA led to increased peptide production. GAL content was increased in the left ventricle below the coronary artery ligation, but was not increased significantly in the atria or the base of the heart above the ligation. The buildup of GAL specifically in the damaged left ventricle is consistent with previous reports that GAL is transported to regenerating nerve endings after axon damage.

Pituitary adenylate cyclase activating polypeptide and PAC1 receptor signaling increase Homer 1a expression in central and peripheral neurons

Pituitary adenylate cyclase activating polypeptides (PACAP) and PAC1 receptor signaling have diverse roles in central and peripheral nervous system development and function. In recent microarray analyses for PACAP and PAC1 receptor modulation of neuronal transcripts, the mRNA of Homer 1a (H1a), which encodes the noncrosslinking and immediate early gene product isoform of Homer, was identified to be strongly upregulated in superior cervical ganglion (SCG) sympathetic neurons. Given the prominent roles of Homer in synaptogenesis, synaptic protein complex assembly and receptor/channel signaling, we have examined the ability for PACAP to induce H1a expression in sympathetic, cortical and hippocampal neurons to evaluate more comprehensively the roles of PACAP in synaptic function. In both central and peripheral neuronal cultures, PACAP peptides increased transiently H1a transcript levels approximately 3.5- to 6-fold. From real-time quantitative PCR measurements, the temporal patterns of PACAP-mediated H1a mRNA induction among the different neuronal cultures appeared similar although the onset of sympathetic H1a transcript expression appeared protracted. The increase in H1a transcripts was accompanied by increases in H1a protein levels. Comparative studies with VIP and PACAP(6-38) antagonist demonstrated that the PACAP effects reflected PAC1 receptor activation and signaling. The PAC1 receptor isoforms expressed in central and peripheral neurons can engage diverse intracellular second messenger systems, and studies using selective signaling pathway inhibitors demonstrated that the cyclic AMP/PKA and MEK/ERK cascades are principal mediators of the PACAP-mediated H1a induction response. In modulating H1a transcript and protein expression, these studies may implicate broad roles for PACAP and PAC1 receptor signaling in synaptic development and plasticity.

Neurotransmitters co-existing with VIP or PACAP

It is now recognized that a neuron can produce, store and release more than one transmitter substance, and a number of examples of co-existing transmitters, particularly a neuropeptide together with a classical transmitter, have been reported. The present paper deals with transmitter substances, peptides or classical transmitters, co-existing with the two structurally related peptides VIP and PACAP and the possible functional implications of this co-existence.

Pituitary adenylate cyclase activating polypeptide (PACAP) decreases neuronal somatostatin immunoreactivity in cultured guinea-pig parasympathetic cardiac ganglia

Postganglionic parasympathetic neurons in guinea-pig cardiac ganglia exhibit choline acetyltransferase (ChAT)-immunoreactivity, and a large fraction (60%) of the ChAT-positive cardiac neurons co-express somatostatin-immunoreactivity. This co-expression remained when the cardiac ganglia explants were maintained in culture for 72 h (40% somatostatin-immunoreactive). The guinea-pig cardiac ganglia neurons express the high affinity pituitary adenylate cyclase activating polypeptide (PACAP)-selective PAC1 receptor, and treatment of the ganglia explants with 20 nM PACAP27 for 72 h to evaluate PACAP regulation of somatostatin expression revealed a dramatic 85% decrease in the number of somatostatin-IR neurons (6% somatostatin-IR neurons) compared with untreated control explant preparations. The decrease in percentage of somatostatin-IR neurons by PACAP27 was time- and concentration-dependent, and selective for PACAP27; PACAP38 and vasoactive intestinal polypeptide were less effective. PACAP6-38, a PACAP antagonist, eliminated the PACAP27-induced change in somatostatin positive neurons. The PACAP-mediated decrease in somatostatin-IR neurons was eliminated in calcium-deficient solutions and by the addition of nifedipine, indicating a requirement for calcium influx through L-type calcium channels. The addition of either the calmodulin inhibitor N-(4-aminobutyl)-1-naphthalenesulfonamide or the MEK inhibitor PD98059, also eliminated the PACAP27-induced decrease in somatostatin-IR cells. The PACAP27-mediated effect on somatostatin expression was not affected by inhibitors of protein kinase A or phospholipase C, but was reduced by the adenylyl cyclase inhibitor SQ22356, suggesting cAMP involvement. Semiquantitative and quantitative reverse transcription PCR prosomatostatin transcript measurements showed that cardiac ganglia prosomatostatin mRNA levels were not diminished by chronic PACAP27 exposure despite the dramatic decrement in somatostatin-expressing neurons. Neuronal peptide-IR content represents a balance between production and secretion. These results suggested that one of the primary effects of PACAP exposure may be enhanced levels of neuropeptide release that exceeded production levels, resulting in somatostatin depletion and a decrement in the number of identifiable somatostatin-expressing cardiac neurons.