Biomedical subjects

Norihito Shintani

Publications and source records attributed to Norihito Shintani.

At least 19 recordsLinked to original sources

PubMed2006

Expression of prokineticin receptors in mouse cultured astrocytes and involvement in cell proliferation.

Effects of prokineticins (PKs), a novel family of bioactive peptides with a mitogenic action to endothelial cells of the endocrine gland and testis, on astrocytic functions were examined. Mouse cultured astrocytes expressed PK-R1 type PK receptors, while there was little expression of the PK-R2 type. PKs caused increases in astrocytic cytosolic Ca2+ levels and BrdU incorporation. Increases in Ca2+ levels by PK-2 were diminished by U73122 (a phospholipase C inhibitor). PK-induced BrdU incorporation was inhibited by U73122, GF109203 (a protein kinase C inhibitor) and PD98059 (a MEK/ERK inhibitor). These results indicate that PK receptors are expressed in astrocytes and regulate astrocytic proliferation.

Animals↗

PubMed2006

Psychostimulant-induced attenuation of hyperactivity and prepulse inhibition deficits in Adcyap1-deficient mice.

Psychostimulants, including amphetamine, act as antihyperkinetic agents in humans with hyperkinetic disorder such as attention-deficit hyperactivity disorder and are known to be effective in enhancing attention-related processes; however, the underlying mechanisms have not been adequately addressed. Mice lacking the Adcyap1 gene encoding the neuropeptide pituitary adenylate cyclase-activating polypeptide (Adcyap1(-/-)) display psychomotor abnormalities, including increased novelty-seeking behavior and hyperactivity. In this study, Adcyap1(-/-) mice showed sensory-motor gating deficits, measured as deficits in prepulse inhibition (PPI), and showed normal PPI in response to amphetamine. Amphetamine also significantly decreased hyperlocomotion in Adcyap1(-/-) mice, and this paradoxical antihyperkinetic effect depended on serotonin 1A (5-HT(1A)) receptor signaling. c-Fos-positive neurons were increased in the prefrontal cortex in amphetamine-treated Adcyap1(-/-) mice, suggesting increased inhibitory control by prefrontal neurons. Additionally, amphetamine produced an antihyperkinetic effect in wild-type mice that received the 5-HT(1A) agonist 8-hydroxy-2-(di-n-propylamino)tetralin. These results indicate that Adcyap1(-/-) mice act as a model of hyperlocomotion and PPI deficits and suggest that 5-HT(1A)-mediated pathways are important determinants of the psychostimulant-elicited, rate-dependent effects that are in a negative function of the baseline rate of activity.

Acoustic Stimulation↗

PubMed2006

Pituitary adenylate cyclase-activating polypeptide (PACAP) decreases ischemic neuronal cell death in association with IL-6.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has been reported to decrease ischemic neuronal damage and increase IL-6 secretion in rats. However, the mechanisms underlying neuroprotection are still to be fully elucidated. The present study was designed to investigate the role played by PACAP and IL-6 in mediating neuroprotection after ischemia in a null mouse. Infarct volume, neurological deficits, and cytochrome c in cytoplasm were higher in PACAP(+/-) and PACAP(-/-) mice than in PACAP(+/+) animals after focal ischemia, although the severity of response was ameliorated by the injection of PACAP38. A decrease in mitochondrial bcl-2 was also accentuated in PACAP(+/-) and PACAP(-/-) mice, but the decrease could be prevented by PACAP38 injection. PACAP receptor 1 (PAC1R) immunoreactivity was colocalized with IL-6 immunoreactivity in neurons, although the intensity of IL-6 immunoreactivity in PACAP(+/-) mice was less than that in PACAP(+/+) animals. IL-6 levels increased in response to PACAP38 injection, an effect that was canceled by cotreatment with the PAC1R antagonist. However, unlike in wild-type controls, PACAP38 treatment did not reduce the infarction in IL-6 null mice. To clarify the signaling pathway associated with the activity of PACAP and IL-6, phosphorylated STAT (signal transducer and activator of transcription) 3, ERK (extracellular signal-regulated kinase), and AKT levels were examined in PACAP(+/-) and IL-6 null mice after ischemia. Lower levels of pSTAT3 and pERK were observed in the PACAP(+/-) mice, whereas a reduction in pSTAT3 was recorded in the IL-6 null mice. These results suggest that PACAP prevents neuronal cell death after ischemia via a signaling mechanism involving IL-6.

Animals↗

PubMed2006

New insights into the central PACAPergic system from the phenotypes in PACAP- and PACAP receptor-knockout mice.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a structurally highly conserved neuropeptide and displays pleiotropic activity, including functioning as a neurotransmitter, neuromodulator, and neurotrophic factor. A series of recent experiments, including genetic manipulation of PACAP and its receptors, has led to better understanding of both normal and pathological processes in which PACAP has been proposed to play a role, and sheds light on previously uncharacterized functions of endogenous PACAP. The aim of this article is to briefly review the recent advances in understanding the role of PACAP in the central nervous system from PACAP- and PACAP receptor-deficient mice, particularly with respect to behavioral and neurological features, including psychomotor behavior, feeding, stress responses, memory performance, ethanol sensitivity, chronic pain, and circadian rhythms. This article also discusses their potential involvement in human diseases.

Animals↗

PubMed2006

Inhibition of self-renewal and induction of neural differentiation by PACAP in neural progenitor cells.

Several lines of evidence have suggested roles for pituitary adenylate cyclase-activating polypeptide (PACAP) in the developing nervous system. Previously, we showed that mRNA for PACAP, vasoactive intestinal peptide (VIP), and their three receptor subtypes, is differentially expressed in embryonic stem (ES) cells, ES cell-derived, neural stem cell-enriched cultures, and differentiated neurons, by using the five steps of the in vitro neuronal culture model of ES cell differentiation. Here, we examined the effects of PACAP on self-renewal and cell lineage determination of neural progenitor/stem cells. PACAP inhibited the basic fibroblast growth factor-induced proliferation (self-renewal), as assessed by neurosphere formation. PACAP increased microtubule-associated protein 2-positive neurons without affecting the number of cells positive for the neural stem cell marker nestin, astrocyte marker glial fibrillary acidic protein, and oligodendrocyte marker CNPase. These results suggest that PACAP inhibits self-renewal but, instead, induces early neuronal differentiation of neural progenitor cells.

Animals↗

PubMed2006

Lack of trimethyltin (TMT)-induced elevation of plasma corticosterone in PACAP-deficient mice.

Accumulating evidence implicates pituitary adenylate cyclase-activating polypeptide (PACAP) in a number of stress responses. By using PACAP-deficient mice, PACAP has been shown to have an in vivo role in the regulation of the sympathoadrenal axis, but a role in regulating the hypothalamo-pituitary-adrenal (HPA) axis has not been fully addressed. To elucidate the role of endogenous PACAP in HPA axis regulation during pathological conditions, mice lacking the Adcyap1 gene encoding the neuropeptide PACAP (Adcyap1-/-) were injected with trimethyltin (TMT), a neurotoxin known to induce neuronal damage and several systemic responses including elevated plasma corticosterone levels. In wild-type controls, TMT induced transient decreases in water and food intake, with a concomitant decrease in body weight; however, no significant changes were observed in Adcyap1-/- mice. Basal corticosterone levels were not significantly different between the mutant and wild-type mice. TMT induced a marked elevation of plasma corticosterone above basal levels in wild-type mice but no significant increase was seen in Adcyap1-/- mice. The present article suggests that PACAP is involved in the corticosterone release in some pathological conditions but not in the basal state.

Animals↗

PubMed2006

Serotonergic inhibition of intense jumping behavior in mice lacking PACAP (Adcyap1-/-).

Genetic manipulation of pituitary adenylate cyclase-activating polypeptide (PACAP) in mice has uncovered its involvement in psychomotor function. We previously observed that mice lacking the Adcyap1 gene encoding the neuropeptide PACAP (Adcyap1-/-) displayed intense jumping behavior when placed in a novel environment such as an open field. Here, we show that Adcyap1-/- mice manifest jumping behavior as early as at least 6 weeks of age when compared with wild-type mice and that the selective serotonin (5-HT) reuptake inhibitor, fluoxetine, as well as the serotonin precursor, 5-hydroxytryptophan, suppress jumping behavior. Our previous study showed a slight decrease in 5-HT metabolite, 5-hydroxyindoleacetic acid (5-HIAA) in Adcyap1-/- mouse brain. Taken together, these results suggest that there is a developmental aspect to the jumping behavior seen in Adcyap1-/- mice, and that jumping behaviour may involve the serotonergic system.

5-Hydroxytryptophan↗

PubMed2005

Roles of PACAP and PHI as inhibitory neurotransmitters in the circular muscle of mouse antrum.

Mediators of neurogenic responses of the gastric antrum were studied in wild-type and pituitary adenylate cyclase-activating polypeptide (PACAP) -knockout (KO) mice. Electrical field stimulation (EFS) to the circular muscle strips of the wild-type mouse antrum induced a triphasic response; rapid transient relaxation and contraction, and sustained relaxation that was prolonged for an extended period after the end of EFS. The transient relaxation and contraction were completely inhibited by L-nitroarginine and atropine, respectively. The sustained relaxation was significantly inhibited by a PACAP receptor antagonist, PACAP(6-38). The antral strips prepared from PACAP-KO mice unexpectedly exhibited a tri-phasic response. However, the sustained relaxation was decreased to about one-half of that observed in wild-type mice. PACAP(6-38) inhibited EFS-induced sustained relaxation (33.5% of control) in PACAP-KO mice. Anti-peptide histidine isoleucine (PHI) serum partially (the 30% inhibition) or significantly (the 60% inhibition) inhibited the sustained relaxations in the wild-type and PACAP-KO mice, respectively. The immunoreactivities to the anti-PACAP and anti-PHI serums were found in myenteric ganglia of the mouse antrum. These results suggest that nitric oxide and acetylcholine mediate the transient relaxation and contraction, respectively, and that PACAP and PHI separately mediate the sustained relaxation in the antrum of the mouse stomach.

Animals↗

PubMed2005

PACAP- and PHI-mediated sustained relaxation in circular muscle of gastric fundus: findings obtained in PACAP knockout mice.

Mediators of neurogenic responses of the gastric fundus were studied in wild type and pituitary adenylate cyclase activating peptide (PACAP) knockout mice. Electrical field stimulation (EFS) to the circular muscle strips of the wild type mouse fundus induced a tri-phasic response, rapid transient contraction and relaxation, and sustained relaxation that was prolonged for an extended period after the end of EFS. The transient relaxation and contraction were completely inhibited by N(G)-nitro-L-arginine and atropine, respectively. The sustained relaxation was completely inhibited by a PACAP receptors antagonist, PACAP(6-38). The strips prepared from PACAP knockout mice exhibited a large contraction without rapid relaxation and unexpectedly, a sustained relaxation. However, the sustained relaxation was decreased to about a half of that observed in wild type mice. Anti-peptide histidine isoleucine (PHI) serum abolished the sustained relaxation in the knockout mice. The serum partially inhibited the sustained relaxation in wild type mice and PACAP(6-38) abolished the relaxation that remained after the antiserum-treatment. PHI relaxed the strips prepared from wild type mice. The relaxation was completely inhibited by PACAP(6-38). It was concluded that PACAP and PHI separately mediate the sustained relaxation in the mouse gastric fundus, and that nitric oxide and ACh mediate transient relaxation and contraction, respectively.

Animals↗

PubMed2005

Neuroprotective action of endogenous PACAP in cultured rat cortical neurons.

Pituitary adenylate cyclase-activating polypeptide (PACAP) exerts neurotrophic effects both in vitro and in vivo. Here we demonstrate the upregulation of PACAP mRNA expression in cultured rat cortical neurons after excitotoxic glutamate exposure, and the exacerbating effect of the PACAP receptor antagonist, PACAP(6-38), on neuronal viability. PACAP mRNA levels were increased up to 3.5-fold 8 h after glutamate exposure. PACAP(6-38) decreased the viability of cortical neurons, irrespective of whether the cells were exposed to glutamate or not. PACAP(6-38) also inhibited glutamate-induced expression of PACAP mRNA, suggesting that PACAP acts via an autocrine or paracrine mechanism to enhance PACAP expression itself. Glutamate exposure is known to increase brain-derived neurotrophic factor (BDNF) mRNA expression. This increased expression was markedly suppressed by PACAP(6-38). Our previous study has shown that PACAP stimulates the PACAP gene transcription in PC12 cells. Taken together, these data may suggest that endogenous PACAP regulates the expression of PACAP itself and BDNF. Although it may also be possible that PACAP(6-38)-induced death of PACAP and BDNF mRNA-expressing cells, per se, results in reduced levels of these mRNAs, the present results support the idea that endogenous PACAP has a neuroprotective action.

Animals↗

PubMed2005

Differential expression of mRNAs for PACAP and its receptors during neural differentiation of embryonic stem cells.

The expressions of mRNAs for pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP), and their receptors (PAC1, VPAC1 and VPAC2) were examined in the five steps of the in vitro neuronal culture model of embryonic stem (ES) cell differentiation. mRNAs for PACAP, VIP, PAC1 receptor, and VPAC2 receptor were moderately expressed in neural stem cell-enriched cultures, while VPAC1 receptor mRNA was most prominently expressed in embryoid bodies (EBs). The expression of PAC1 receptor mRNA was further upregulated after terminal differentiation into neurons. In contrast, the expressions of PAC1 receptor and PACAP mRNAs were markedly decreased after glial differentiation. These results suggest that this in vitro neuronal culture system will be a useful model for future studies on the functional role of the PACAPergic system during different stages of neuronal development.

Animals↗

PubMed2004

Overexpression of PACAP in the pancreas failed to rescue early postnatal mortality in PACAP-null mice.

PACAP exerts multiple activities as a hormone and neurotransmitter, and has been proposed to play vital roles in a variety of neuronal functions. PACAP is also involved in insulin secretion from pancreatic beta-cells. Recently, we and other groups demonstrated that PACAP-deficient mice (PACAP(-/-)) are viable, but suffer from increased postnatal mortality. To ascertain whether this high mortality is rescued by overexpression of PACAP in peripheral tissue (such as pancreas), we performed a genetic cross between PACAP(-/-) and our recently developed transgenic mice overexpressing PACAP in pancreatic beta-cells; and then examined the survival rate of their F2 progeny. PACAP(-/-) mice were segregated into two groups based on mortality as well as body weight gain: PACAP(-/-) that survived >20 days of age with normal weight gain and PACAP(-/-) that died before 20 days with a marked weight loss. Kaplan-Meier survival analysis demonstrated that PACAP(-/-) mice and those carrying the PACAP transgene have similarly lower survival probability compared with their heterozygous littermates that served as positive controls. Further study using additional tissue-specific transgenic or knockout mouse models will be required to determine the causative defects underlying the high mortality of PACAP(-/-) mice.

Animals↗

PubMed2004

Reduced hypothermic and hypnotic responses to ethanol in PACAP-deficient mice.

Using pituitary adenylate cyclase-activating polypeptide (PACAP)-deficient mice, we investigated whether PACAP is involved in the intoxicating effects of ethanol. The structure of PACAP is highly conserved during evolution, and in Drosophila, loss-of-function mutations in a PACAP-like neuropeptide gene, amnesiac, result in impairment of memory retention and increased sensitivity to ethanol. In mice, PACAP deficiency is associated with impaired memory performance and hippocampal long-term potentiation (LTP), however, sensitivity to ethanol has not been well investigated. Here, we addressed this issue in our recently developed PACAP-deficient mice. Sleep time (duration of the loss of righting reflex) was markedly shortened in PACAP-deficient mice compared with wild-type, although latency to the loss of righting reflex was not different between the two groups. Ethanol-induced hypothermia in wild-type control mice was significantly reduced in PACAP-deficient mice. Blood ethanol levels were not different between the two groups, excluding the possibility of increased ethanol metabolism. Thus, in contrast to that in Drosophila, PACAP deficiency in mammals caused a reduced sensitivity to ethanol. However, in both cases, PACAP or amnesiac products are likely to play significant roles in modifying the intoxicating effects of ethanol.

Animals↗

PubMed2004

Apelin is a novel angiogenic factor in retinal endothelial cells.

There has been much focus recently on the possible functions of apelin, an endogenous ligand for the orphan G-protein-coupled receptor APJ, in cardiovascular and central nervous systems. We report a new function of apelin as a novel angiogenic factor in retinal endothelial cells. The retinal endothelial cell line RF/6A highly expressed both apelin and APJ transcripts, while human umbilical venous endothelial cells (HUVECs) only expressed apelin mRNA. In accordance with these observations, apelin at concentrations of 1 pM-1 microM significantly enhanced migration, proliferation, and capillary-like tube formation of RF/6A cells, but not those of HUVECs, whereas VEGF stimulates those parameters of both cell types. In vivo Matrigel plug assay for angiogenesis, the inclusion of 1 nM apelin in the Matrigel resulted in clear capillary-like formations with an increase of hemoglobin content in the plug. This is the first report showing that apelin is an angiogenic factor in retinal endothelial cells.

Adipokines↗

PubMed2004

PACAP deficient mice display reduced carbohydrate intake and PACAP activates NPY-containing neurons in the rat hypothalamic arcuate nucleus.

Pituitary adenylate cyclase-activating polypeptide (PACAP) potentiates both insulin release from islets and insulin action in adipocytes. Therefore, this peptide is considered a regulator of glucose homeostasis. PACAP and its receptors are localized not only in the peripheral tissues but in the central nervous system. The present study examined whether PACAP regulates the feeding behavior and the activity of neurons in the hypothalamic arcuate nucleus (ARC), a feeding center. Food intake was measured in the PACAP knock-out mice. Cytosolic Ca2+ concentration ([Ca2+]i) in single neurons isolated from the ARC of rats was measured by fura-2 microfluorometry, followed by immunocytochemical staining with anti-NPY antiserum. PACAP knock-out mice showed a decrease in the intake of high carbohydrate, but not high fat, food. PACAP increased [Ca2+]i in NPY neurons of the ARC that are implicated in the feeding, particularly the carbohydrate ingestion. Agonists of PACAP receptors, PAC1-R and VPAC2-R, also increased [Ca2+]i. The present study, by demonstrating that PACAP directly reacts with the ARC NPY neurons to increase [Ca2+]i and that ingestion of the carbohydrate-rich food is reduced in PACAP-deficiency, suggests a facilitative role for PACAP in the carbohydrate intake.

Animals↗

PubMed2004

Pituitary adenylate cyclase-activating polypeptide is required for the development of spinal sensitization and induction of neuropathic pain.

The prolonged sensitization of pain transmission after nerve injury by increasing excitability of spinal neurons and thereby promoting repair is an adaptive response of the body. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is widely distributed in the nervous system and implicated in neurotransmission, neural plasticity, and neurotrophic actions. Although PACAP is distributed in the spinal cord and dorsal root ganglia, a role of PACAP in pain responses remains essentially unknown. Here we show that mice lacking the PACAP gene (PACAP-/-) did not exhibit inflammatory pain induced by intraplantar injection of carrageenan or neuropathic pain induced by L5 spinal nerve transection, whereas they did retain normal nociceptive responses. Intrathecal administration of NMDA induced mechanical allodynia in wild-type mice, but not in PACAP-/- mice. The NMDA-induced allodynia in PACAP-/- mice was reproduced by simultaneous intrathecal injection of PACAP with NMDA. Concomitant with the increase in PACAP immunoreactivity after nerve injury, NADPH-dependent nitric oxide synthase (NOS) activity visualized by NADPH diaphorase histochemistry markedly increased in the superficial layer of the spinal cord of wild-type mice, which was not observed in PACAP-/- mice. Simultaneous addition of PACAP and NMDA caused translocation of neuronal NOS from the cytosol to the membrane and stimulated NO production in vitro. These results demonstrate that PACAP might promote the functional coupling of neuronal NOS to NMDA receptors for both inflammatory and neuropathic pain to occur.

Animals↗

PubMed2004

PACAP activates Rac1 and synergizes with NGF to activate ERK1/2, thereby inducing neurite outgrowth in PC12 cells.

The mechanisms linked to the neuritogenic effect of PACAP acting in synergy with NGF were analyzed in PC12 cells. Recently, we have shown that PACAP synergizes with NGF to stimulate PACAP gene transcription and neurite outgrowth, differentially dependent on both the ERK1/2 and p38 MAP kinase pathways in PC12 cells. This suggests that PACAP modulates mitogen signaling pathways governing cell differentiation, in part through MAP kinase activation and an autocrine mechanism. Here, we studied the mechanism of the underlying neuritogenic actions of PACAP. PACAP induced transient activation of Rac1, a small GTPase involved in neurite outgrowth, in a PI3-kinase-independent manner, and stimulated accumulation of active Rac1 at filamentous actin-rich protrusions on the cell surface to induce subsequent neurite formation. PACAP had no additional effect on the activity of Rac1 beyond the effect of NGF and failed to activate Ras or Cdc42. By contrast, simultaneous treatment with PACAP and NGF acts in synergy to induce prolonged activation of ERK1/2. These results indicate for the first time that PACAP induces activation of Rac1 associated with neurite outgrowth and suggest that the synergistic effect of PACAP and NGF on neurite extension is due to enhanced activation of ERK1/2.

Actin Cytoskeleton↗

PubMed2004

Overexpression of pituitary adenylate cyclase-activating polypeptide in islets inhibits hyperinsulinemia and islet hyperplasia in agouti yellow mice.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an intraislet neuropeptide and shares insulinotropic and insulin-sensitizing properties with glucagon-like peptide-1 (GLP-1); however, the pathophysiological significance of PACAP in diabetes remains largely unknown. To assess this, we crossed our recently developed transgenic mice overexpressing PACAP in pancreatic beta-cells (Tg/+), with lethal yellow agouti (KKA(y)) mice (A(y)/+), a genetic model for obesity-diabetes, and examined the metabolic and morphological phenotypes of F(1) animals. Tg/+ mice with the A(y) allele (Tg/+:A(y)/+) developed maturity-onset obesity and diabetes associated with hyperglycemia, hyperlipidemia, and hyperphagia, similar to those of A(y)/+ mice, but hyperinsulinemia was significantly ameliorated in Tg/+:A(y)/+ mice. Although A(y)/+ mice exhibited a marked increase in islet mass resulting from hyperplasia and hypertrophy, this increase was significantly attenuated in Tg/+:A(y)/+ mice. Size frequency distribution analysis revealed that the very large islets comprising one-fourth of islets of A(y)/+ mice were selectively reduced in Tg/+:A(y)/+ mice. Because functional defects have been demonstrated in the large islets of obese animal models, together these findings suggest that PACAP regulates hyperinsulinemia and the abnormal increase in islet mass that occurs during the diabetic process.

Animals↗