Abstract P4-21-08: A phase I/II of S-222611, a reversible EGFR and HER2 inhibitor, combined with trastuzumab +/- chemotherapy in patients with HER2-positive metastatic breast cancer

Background: S-222611, an oral, reversible EGFR and HER2 inhibitor, has been shown to be well-tolerated as monotherapy at a dose of 800mg daily with good anti-tumor activity in patients previously treated with other anti-HER2-based regimens. This study evaluated the tolerability and safety of daily oral administration of S-222611 (S) in combination with trastuzumab (T), trastuzumab + vinorelbine (T+V) and trastzumab + capecitabine (T+C) in HER2-positive (HER2+) metastatic breast cancer (MBC) with or without brain metastases.

Methods: This study was performed as a 3+3 dose escalation followed by expansion to examine the tolerability and safety of S in combination with T, T+V and T+C in Arms A, B and C, respectively. S was administered orally once daily, starting at a dose of 400mg in Arm A, and 200mg in Arms B and C. The dosing of T was 8mg/kg loading followed by 6mg/kg or fixed dose of 600mg subcutaneously every 21 days as recommended. V was administered at 60mg/m2 orally on Day 1 and 8 of a 21-day cycle, and C 1000mg/m2 orally daily for 14 days followed by a 7-day rest period. All patients had HER2+ MBC and were required to have progressed following at least one prior line of anti-HER2 therapy. Prior treatments with V and C were permitted. Anti-diarrhea prophylaxis with loperamide was not required.

Results: A total of 45 patients were enrolled. All patients had received prior anti-tumor regimens including T (n=45), T-DM1 (n=26), pertuzumab (n=9) and lapatinib (n=12). The clinically recommended doses of S at which most adverse events were manageable,were determined as:600mg in Arm A, 200mg in Arm B and 400mg in Arm C. Dose limiting toxicities included Grade 3 diarrhea for Arm A; and Grade 4 neutropenia, Grade 3 Hypokalemia and Hypophosphatemia for Arm B. As of 13 May 2016, treatment is ongoing in 2 patients. No other Grade 4 AEs related to S-222611 have been observed. Grade 3 bilirubin elevation was observed in 5/45 patients, probably due to transporter (UGT1A1) inhibition, while no G3/4 liver dysfunction was reported. RECIST partial responses (PR) were observed in 6 of 9 patients in Arm A and 5 of 9 patients in Arm C, at respective clinically recommended doses. Nine of 45 patients had brain metastases; 4 of these patients showed RECIST PR including an intracranial tumor response in one patient (400mg in Arm C) who had prior treatments with paclitaxel, T+C, T-DM1 and V after diagnosis of BM.

Conclusions: The clinically recommended doses of S-222611 combined with T, T +V and T+C were determined for further clinical studies. Clinical benefit (PR and SD >6 month) was seen with each combination even in heavily pre-treated HER2+ MBC patients.

Summary of the safety and efficacy of S-222611 (S) combination. Dose (mg)nDLT (1st cycle)G3 Diarrhea during study (N of patients)RECIST tumor response, PR n/ SD ≥6M nORR n (%)CBR n (%)Arm A: S + T4005010/10/5 (0%)1/5 (20%)Arm A: S + T6009036/06/9 (67%)6/9 (67%)Arm A: S + T8007141/11/7 (14%)2/7 (29%)Arm B: S + T + V2005020/40/5 (0%)4/5 (80%)Arm B: S + T + V4002211/01/2 (50%)1/2 (50%)Arm C: S + T + C2004010/10/4 (0%)1/4 (25%)Arm C: S + T + C4009025/05/9 (56%)5/9 (56%)Arm C: S + T + C6004022/12/4 (50%)3/4 (75%)

Citation Format: Rafii S, Macpherson I, Baird R, Saggese M, Spiliopoulou P, Kumar S, Italiano A, Bonneterre J, Campone M, Cresti N, Posner J, Takeda Y, Arimura A, Spicer J. A phase I/II of S-222611, a reversible EGFR and HER2 inhibitor, combined with trastuzumab +/- chemotherapy in patients with HER2-positive metastatic breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-08.

Abstract P4-14-26: Phase I expansion of S-222611, a reversible inhibitor of EGFR and HER2, in advanced solid tumors, including HER2-positive breast cancer patients with brain metastases

BACKGROUND

S-222611 is an oral, reversible ErbB tyrosine kinase inhibitor of EGFR and HER2 with potent pre-clinical activity. MTD was not reached during the dose-escalation phase, (maximum dose 1600 mg QD). PK and efficacy data supported a daily dose of 800 mg. An expansion cohort of patients has been treated to further explore safety and efficacy.

METHODS

Subjects with advanced solid tumors expressing EGFR and/or overexpressing HER2 were enrolled. S-222611 800 mg daily was administered until disease progression or unacceptable toxicity.

RESULTS

76 patients were included in this phase 1 expansion cohort with a variety of tumor types. Dose reduction was required because of adverse events in 15 patients; the most frequent of which being diarrhea and elevated bilirubin. Two patients discontinued treatment due to drug- related adverse events. Of the 25 patients with HER2-positive metastatic breast cancer (MBC), 4 partial responses were observed, and prolonged stable disease (≥ 6 months) was observed in 3 additional patients. These 25 patients had received prior HER2-directed therapy as shown in Table 1.

Table 1. Prior therapies received by patients with HER2-positive MBCPrior therapyn (%)Trastuzumab22 (88)T-DM13 (12)Lapatinib16 (64)Chemotherapy23 (92)

Six of these patients had brain metastases, in whom 1 intracranial response and 2 prolonged stable disease (≥ 6 months) were observed (Table 2).

Table 2. HER2-positive MBC patients with brain metastases - best overall response to S-222611Pts #HER2 IHCBrain metastasesBest overall response (RECIST 1.1)Patient 13+Target lesionPRPatient 23+Target lesionSD (≥12 M)Patient 33+Target lesionSD (6.0 M)Patient 43+Non-target lesionSD (4.7 M)Patient 53+Non-target lesionSD (3.3 M)Patient 63+Non-target lesionNE

The patient showing intracranial response was previously treated with lapatinib and capecitabine after diagnosis of BM.

CONCLUSIONS

S-222611 was well tolerated at a dose of 800 mg once daily. Anti-tumour activity, including shrinkage of brain metastases, was evident in a heavily pre-treated population of patients with HER2-positive breast cancer.

Citation Format: Baird RD, Arkenau H-T, Deva S, Cresti N, Garcia-Corbacho J, Hogarth L, Frenkel E, Kawaguchi K, Arimura A, Donaldson K, Posner J, Sarker D, Jodrell D, Plummer R, Spicer J, Italiano A. Phase I expansion of S-222611, a reversible inhibitor of EGFR and HER2, in advanced solid tumors, including HER2-positive breast cancer patients with brain metastases. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-14-26.

Increased sensitivity of glioblastoma cells to interleukin 1 after long-term incubation with dexamethasone

Cytokines may act as chemical messengers in the central nervous system and affect trophic, immune, and neuroendocrine functions. However, little is known about the regulation of cytokine production in nervous system tissue, although it has been demonstrated recently that glucocorticoids augment interleukin 1 (IL 1) receptor expression in the glioblastoma cell line, U87MG. Here, the effects of glucocorticoids on IL 1-induced interleukin 6 (IL 6) production are determined in the same cell line. During short-term incubations of U87MG cells (6 h) in the presence of IL 1beta and dexamethasone (DEX), DEX inhibited IL 1beta-stimulated IL 6 production over the entire range of the dose-response curve. However, when cells were preincubated in the presence of DEX for 15 h and then challenged with IL 1beta or IL 1beta and DEX, there was a left-shift in the IL 1,B dose-response curve, suggesting an increased sensitivity of the cells to respond to IL 1 and produce IL 6. In fact, the ED(50) for IL 1beta-stimulated IL 6 production was about 1.3 pM in cells not preincubated with DEX, but was reduced to 0.25 pM in cells that were preincubated with DEX. However, maximum IL 6 production at high doses of IL 1beta was inhibited in cells cultured in the presence of DEX during the IL 1 challenge. Thus, the results suggest the possibility that when glucocorticoids are elevated for extended periods, and concentrations of IL 1 are low because of steroid suppression of IL 1 production, actions of IL 1 may be maintained or even augmented due to up-regulated IL 1 receptor expression in particular cell types. This would allow for glucocorticoid-targeted actions of IL-1 to be maintained in particular cell types that up-regulate IL 1 receptors in response to glucocorticoid, whereas in those cell types that do not up-regulate IL 1 receptor number, IL 1 actions are suppressed.

A prostaglandin D2 receptor antagonist modifies experimental asthma in sheep

BACKGROUND

Prostaglandin (PG) D(2) is the major cylooxygenase metabolite released by mast cells upon allergen stimulation, and elicits responses through either the prostanoid DP1 receptor and/or the chemoattractant receptor homologous molecule expressed on T-helper type 2 (Th2) cells (CRTH2/DP2). Experimental evidence suggests that stimulation of one or both these receptors contributes to asthma pathophysiology.

OBJECTIVE

The aim of this study was to test the hypothesis that the prostanoid DP1 receptor contributes to asthma pathophysiology by determining the efficacy of an orally active antagonist for this receptor, S-5751, on allergen-induced bronchoconstriction, airway hyperresponsiveness (AHR) and cellular inflammation in the sheep model of asthma.

METHODS

PGD(2)-induced cyclic adenosine monophosphate (cAMP) production in platelet-rich plasma was used to establish the in vitro efficacy of S-5751. In vivo, sheep naturally allergic to Ascaris suum were challenged with an aerosolized antigen with and without S-5751 treatment (given 4 days before and for 6 days after the challenge).

RESULTS

S-5751 inhibited PGD(2)-induced cAMP production in platelet-rich plasma with an IC(50) value of 0.12 microm. S-5751 at 30 mg/kg, but not at 3 mg/kg, reduced the early bronchoconstriction and inhibited the late bronchoconstriction. AHR and inflammatory cell infiltration in bronchoalveolar lavage fluid at days 1 and 7 were also inhibited with the 30 mg/kg dose. The responses observed with S-5751 at 30 mg/kg were comparable with those with montelukast treatment (0.15 mg/kg, twice a day, intravenous); however, S-5751 did not block inhaled leukotrieneD(4)-induced broncoconstriction.

CONCLUSION

Prostanoid DP1 receptor inhibition may represent an alternative target for asthma therapy.

Association of T-cell receptor Vbeta haplotypes with dry skin in DS-Nh mice

BACKGROUND

Although dry skin and T cell-dependent disease exacerbation are characteristic features of atopic dermatitis (AD), the involvement of T cells in the development of dry skin remains unclear.

AIMS

We aimed to elucidate the role of T cells in the development of dry skin in DS-Nh mice as a model for AD, and to evaluate this skin condition pharmacologically.

METHODS

We prepared DS-Nh mice harbouring a T-cell receptor (TCR)Vbeta(a) haplotype with a central deletion in the TCRBV gene segments, and mice harbouring a TCRVbeta(b) haplotype without any deletion. We analysed the TCRVbeta chain usage and cytokine response to antimouse CD3 monoclonal antibodies in the splenocytes from the two mouse substrains. Transepidermal water loss (TEWL) was measured, and histochemical examination of these mice was carried out. Finally, a pharmacological analysis using loratadine was also performed to evaluate the features of spontaneous dry skin in DS-Nh mice as a model of AD.

RESULTS

Although the deletion of TCRBV gene segments in the TCRVbeta(a) haplotype yielded different representations of each TCRVbeta mRNA, this deletion did not evoke distinct cytokine profiles in the splenocytes compared with those of mice with the TCRVbeta(b) haplotype. Furthermore, our results indicated that the onset of dry skin occurred earlier in mice with TCRVbeta(b) than in those with TCRVbeta(a). Pharmacologically, AD-like dry skin in DS-Nh with TCRVbeta(b) mice is susceptible to an H1 blocker.

CONCLUSIONS

A specific lymphocyte subpopulation bearing T-cell receptors may be responsible for loratadine-responsive dermatitis in DS-Nh mice.

Pituitary adenylate cyclase-activating polypeptide-induced differentiation of embryonic neural stem cells into astrocytes is mediated via the beta isoform of protein kinase C

We have found previously that pituitary adenylate cyclase-activating polypeptide (PACAP) increases the number of astrocytes generated from cultured mouse neural stem cells (NSCs) via a mechanism that is independent of the cyclic AMP/protein kinase A pathway (Ohno et al., 2005). In the present study, the signaling pathway involved in the differentiation process was further investigated. PACAP-induced differentiation was inhibited by the phospholipase C inhibitor, U73122, the protein kinase C (PKC) inhibitor, chelerythrine, and the intracellular calcium chelator, BAPTA-AM, and was mimicked by phorbol 12-myristate 13-acetate (PMA), but not by 4alpha-PMA. These results suggest that the PACAP-generated signal was mediated via the PACAP receptor, PAC1 stimulated heterotrimeric G-protein, resulting in activation of phospholipase C, followed by calcium- and phospholipid-dependent protein kinase C (cPKC). To elucidate the involvement of the different isoforms of cPKC, their gene and protein expression were examined. Embryonic NSCs expressed alpha and betaII PKC, but lacked PKCgamma. When NSCs were exposed to 2 nM PACAP, protein expression levels of the betaII isoform transiently increased two-fold before differentiation, returning to basal levels by Day 4, whereas the level of PKCalpha increased linearly up to Day 6. Overexpression of PKCbetaII with adenovirus vector synergistically enhanced differentiation in the presence of 1 nM PACAP, whereas expression of the dominant-negative mutant of PKCbetaII proved inhibitory. These results indicate that the beta isoform of PKC plays a crucial role in the PACAP-induced differentiation of mouse embryonic NSCs into astrocytes.

Comparative anatomy of PACAP-immunoreactive structures in the ventral nerve cord ganglia of lumbricid oligochaetes

By means of a whole mount immunocytochemical approach, the distribution patterns of pituitary adenylate cyclase-activating polypeptide (PACAP)-27 and PACAP-38 were identified in the ventral nerve cord (VNC) ganglia of the earthworms Eisenia fetida and Lumbricus terrestris. Each PACAP form appears to occur in a distinct neuron population. Positions of these populations, as well as numbers and sizes of the constituting neurons do not essentially differ between the two species. The data suggest that in Lumbricid Oligochaetes, PACAP-27 and PACAP-38 neuron populations may mediate distinct physiological processes.

Pituitary Adenylate Cyclase-Activating Polypeptide Is a Potent Inhibitor of the Growth of Light Chain-Secreting Human Multiple Myeloma Cells

Multiple myeloma represents a malignant proliferation of plasma cells in the bone marrow, which often overproduces immunoglobulin light chains. We have shown previously that pituitary adenylate cyclase-activating polypeptide (PACAP) markedly suppresses the release of proinflammatory cytokines from light chain-stimulated human renal proximal tubule epithelial cells and prevents the resulting tubule cell injury. In this study, we have shown that PACAP suppresses the proliferation of human kappa and lambda light chain-secreting multiple myeloma-derived cells. The addition of PACAP suppressed light chain-producing myeloma cell-stimulated interleukin 6 (IL-6) secretion by the bone marrow stromal cells (BMSCs). A specific antagonist to either the human PACAP-specific receptor or the vasoactive intestinal peptide receptor attenuated the suppressive effect of PACAP on IL-6 production in the adhesion of human multiple myeloma cells to BMSCs. The secretion of IL-6 by BMSCs was completely inhibited by 10(-9) mol/L PACAP, which also attenuated the phosphorylation of both p42/44 and p38 mitogen-activated protein kinases (MAPK) as well as nuclear factor-kappaB (NF-kappaB) activation in response to the adhesion of multiple myeloma cells to BMSCs, whereas the inhibition of p42/44 MAPK signaling attenuated PACAP action. The signaling cascades involved in the inhibitory effect of PACAP on IL-6-mediated paracrine stimulation of light chain-secreting myeloma cell growth was mediated through the suppression of p38 MAPK as well as modulation of activation of transcription factor NF-kappaB. These findings suggest that PACAP may be a new antitumor agent that directly suppresses light chain-secreting myeloma cell growth and indirectly affects tumor cell growth by modifying the bone marrow milieu of the multiple myeloma.

Spontaneous scratching behaviour in DS-Nh mice as a possible model for pruritus in atopic dermatitis

Itching is one of the major clinical symptoms in atopic dermatitis (AD) and complicates the management of this pathological condition. An animal model of AD-like pruritus would contribute to a better understanding of AD and could lead to the development of safe and effective antipruritic agents. DS non-hair (DS-Nh) mice raised under conventional conditions spontaneously develop pruritus, which is associated with a dermatitis similar to human AD. There is a significant positive correlation between disease severity and the period of scratching behaviour in DS-Nh mice. In the present study, we found that levels of histamine and nerve growth factor (NGF) in serum and/or skin tissue were higher in DS-Nh mice with AD-like dermatitis than in age-matched mice without dermatitis. The histopathological data indicated that nerve fibres extend into and mast cells infiltrate the surrounding area of the skin lesion. NGF production by XB-2 cells, which was derived from mouse keratinocytes, was enhanced by histamine via the H1 receptor. We also found that prolonged treatment with an H1-antagonist was effective against pruritus through depression of the production of NGF, which is thought to be generated by keratinocytes. We conclude that DS-Nh mice can serve as a suitable model for gaining a better understanding of pruritus in AD, and that prolonged treatment with an H1-antagonist may be beneficial in patients with AD-associated pruritus.

Presence of PACAP and VIP in Embryonic Chicken Brain

The aim of the present article was to investigate the occurrence and temporary changes of pituitary adenylate cyclase-activating polypeptide (PACAP)-38 and vasoactive intestinal peptide (VIP) in various brain areas of chicken embryos by means of radioimmunoassay. The highest concentrations of PACAP-38 were measured in the brain stem followed by the hypothalamus, cerebellum, and telencephalon. PACAP-38 levels were significantly higher than those of VIP in all examined brain areas. The levels of both PACAP-38 and VIP showed a tendency to decrease until hatching during embryonic development of the chicken.

Short-Term Fasting Differentially Alters PACAP and VIP Levels in the Brains of Rat and Chicken

The present article investigated the levels of pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) in the brains of rats and chickens 12, 36, and 84 h after starvation. PACAP levels increased in both species, 12 h after food deprivation in rats, and with a 24-h delay in chickens. VIP levels showed a more complex pattern: a gradual increase in the hypothalamus and telencephalon, and a significant decrease in the brain stem of rats. In chickens, a decrease was observed in every brain area after 36 h of starvation. These data show that PACAP and VIP are differentially regulated and are involved in the regulatory processes under a food-restricted regimen, and are differentially altered in nocturnal and diurnal species.

Changes in PACAP Levels in the Central Nervous System after Ovariectomy and Castration

The aim of the present article was to investigate the influence of gonadectomy on pituitary adenylate cyclase-activating polypeptide (PACAP) levels in different brain areas. In males, there seems to be an inverse relationship between gonadotropins and PACAP in the brain in the acute phase of castration: PACAP levels decreased in almost all brain areas examined within the first week after castration. In females, such pattern was observed in the hypothalamus, brain stem, and temporal cortex. In the pituitary, levels decreased only on the first day after ovariectomy, and later, as in the thalamus, increases were observed. Although the pattern of change showed gender differences, our results provide further evidence that levels of gonadotropins and possibly gonadotropin-releasing hormone influence PACAP levels and that PACAP is involved in the regulation of gonadal functions.

Signaling involved in pituitary adenylate cyclase-activating polypeptide-stimulated ADNP expression

Activity-dependent neurotrophic protein (ADNP) was discovered as a novel response gene for VIP and has neuroprotective potential. When the VIP paralog, PACAP38 was added to mouse neuron-glia co-cultures, it induced ADNP mRNA expression in a bimodal fashion at subpico- and nanomolar concentrations with greater response at subpicomolar level. The response was attenuated by a PAC1-R antagonist at both concentrations and by a VPAC1-R antagonist at nanomolar concentration only. An IP3/PLC inhibitor attenuated the response at both concentrations of PACAP38, but a MAPK inhibitor had no effect. A PKA inhibitor suppressed the response at nanomolar concentration only. These findings suggest that ADNP expression is mediated through multiple receptors and signaling pathways that are regulated by different concentrations of PACAP.

Treatment of Renal Failure Associated with Multiple Myeloma and Other Diseases by PACAP-38

Myeloma kidney injury is caused by the large amount of light chain (LC) of immunoglobulins produced by cancerous plasma cells through stimulation of proinflamatory cytokines like TNF-alpha and IL-6. PACAP-38 suppressed LC-stimulated cytokine production by tubular epithelial cells in vitro and in vivo, and prevented injury of these epithelial cells. The suppressive effect is comparable or greater than dexamethasone (dex). Although dex produces adverse side effects when it is given for a long time period, PACAP-38 is a natural and safe neuropeptide and no adverse effect has been reported when administered to produce significant biological effects. Furthermore, PACAP-38 suppressed growth of myeloma cells in culture and also suppressed production of their growth factor, IL-6, production from the bone marrow stromal cells that was stimulated by adhesion of myeloma cells. These findings render PACAP-38 worth evaluation as a safe and potent renoprotectant in myeloma kidney as well as a new antitumor agent for myeloma cells.

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.

Potential protective action of pituitary adenylate cyclase-activating polypeptide (PACAP38) on in vitro and in vivo models of myeloma kidney injury

The most common type of renal injury in multiple myeloma is chronic tubulointerstitial nephropathy associated with casts in tubule lumens, an entity referred to as “myeloma kidney” that often progresses to end-stage kidney diseases. Myeloma kidney is associated with a significant increase in all-cause mortality, yet no effective intervention, except a limited use of steroid, is available. Here, we report that pituitary adenylate cyclase-activating polypeptide with 38 residues (PACAP38) dramatically prevents injury of cultured renal proximal tubule cells caused by myeloma light chains through suppression of proinflammatory cytokines production, by inhibiting p38 MAPK and translocation of NFκB via both PAC1 and VPAC1 receptors. The suppressive effects of PACAP was as effective as dexamethasone in all of their cytokine assays and demonstrated both in vitro and in vivo. Furthermore, PACAP38 inhibits myeloma cell growth directly and may also indirectly by suppressing production of the growth factor, IL-6, from bone marrow stromal cells, that is stimulated by adhesion of myeloma cells. These findings render PACAP38 worth evaluation as a promising candidate for an effective and safe renoprotectant in myeloma kidney, and possibly other nephropathy, and also as a new antitumor agent in multiple myeloma.

Signaling Cascades Involved in Neuroprotection by Subpicomolar Pituitary Adenylate Cyclase-Activating Polypeptide 38

In neuronal/glial cocultures, pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) prevented neuronal death induced by gp120, lipopolysaccharide (LPS), or other toxic agents, but the dose response of the neuroprotective effect is bimodal, with a peak at a subpicomolar concentration and another peak at a subnanomolar to nanomolar concentration. Although the signaling cascade involved in neuroprotection by nanomolar concentration of the peptide has been shown to be mediated by activation of cAMP-dependent protein kinase and subsequent activation of mitogen-activated protein kinase (MAPK), the mechanism for neuroprotection by a subpicomolar level of PACAP38 remains elusive. In the present study, the signaling involved in neuroprotection by subpicomolar PACAP38 was studied in rat neuronal/glial cocultures. Addition of PACAP38 stimulated expression and activation of extracellular signal-related kinase-type MAPK with a peak response at 10-13 M; greater concentrations of the peptide induced lesser response. cAMP production also increased at subpicomolar levels of PACAP38, but the level remained unchanged at a level four to five times higher than the base level at concentrations below 10-11 M. cAMP then started increasing again dose-dependently in a range >10-11 M PACAP38. Lipopolysaccharide (LPS)-induced neuronal death, indicated by increased release of neuron-specific enolase, was suppressed by PACAP38 in a bimodal fashion. Neuroprotection by 10-12 M PACAP38 was completely abolished by a MAPK kinase-1 inhibitor, PD98059, and also partially suppressed by Rp-cAMP, a cAMP-dependent protein kinase inhibitor. Moreover, neuroprotection by a nanomolar level of PACAP38 was completely suppressed by Rp-cAMP but not affected by PD98059. We conclude that neuroprotection by subpicomolar PACAP38 is mainly mediated by the signaling pathway involving MAPK activation and partially regulated by cAMP-dependent protein kinase activation. Furthermore, PACAP38 stimulated expression of activity- dependent neuroprotective protein (ADNP), with a peak at 10-13 M. Greater doses of the peptide induced lesser response. However, 10-13 M PACAP38-stimulated expression of ADNP was not affected by PD98059. This suggests that neuroprotection by subpicomolar PACAP38 might be mediated partially by expression of ADNP, but the major events for neuroprotection by subpicomolar PACAP38 remain to be identified.

Effect of PACAP on LH release studied by cell immunoblot assay depends on the gender, on the time of day and in female rats on the day of the estrous cycle

We have previously demonstrated that pituitary adenylate cyclase activating polypeptide (PACAP) can be released from cultured rat anterior pituitary cells and when added to the medium in physiological concentration it releases LH from individual gonadotropes. In the present work, we studied whether the release of PACAP and the responsiveness of LH cells to PACAP depend on the gender, on the time of day when the animals were sacrificed, and in females on the stage of the estrous cycle. Anterior pituitary cells were cultured on nitrocellulose membrane. We found that the number of PACAP releasing cells was higher in proestrous than in diestrous female or in male rats and their number was always higher in the evening than at the other times. The effect of PACAP on LH cells was stimulatory in the morning of proestrus and diestrus. In proestrous rats, PACAP did not influence LH release in the afternoon or the evening, but in diestrous rats it decreased it in the afternoon and the evening. In males, there was a decrease of LH due to PACAP treatment at 10 and 20 h; however, PACAP did not influence LH at 16 h. It was concluded that in vivo PACAP might be involved in the circadian and episodic release of LH at pituitary level.

Deficits in reproduction and pro-gonadotropin-releasing hormone processing in male Cpefat mice

Cpe(fat/fat) mice are obese, diabetic, and infertile. These animals have a point mutation in carboxypeptidase E (CPE), an exopeptidase that removes C-terminal basic amino acids from peptide intermediates. The mutation renders the enzyme unstable, and it is rapidly degraded. Although the infertility of Cpe(fat/fat) mice has not been systematically investigated, it is thought to be due to a deficit in GnRH processing. We have evaluated this hypothesis and found hypothalamic GnRH levels to be reduced by 65-78% and concentrations of pro-GnRH and C-terminal-extended intermediates to be high. Basal serum gonadotropin contents are similar among wild-type, heterozygous, and homozygous mice. Testis morphology and function are abnormal in older obese Cpe(fat/fat) mice. Matings between homozygous mutants yield a 5% pregnancy rate. By comparison, when 50-d-old Cpe(fat/fat) males are paired with heterozygous females, rates increase to 43%, and they rapidly decrease to negligible levels by 120 d. As fertility declines without accompanying changes in the hypothalamic-pituitary-gonadal axis and before obesity is evident, reproduction is more complex than originally thought. This suspicion is confirmed in 90-d-old Cpe(fat/fat) males, who readily interact with females, but rarely mount and fail to show intromission or ejaculation behaviors. Together, these findings show that CPE is a key enzyme for pro-GnRH processing in vivo; however, the reproductive deficits in Cpe(fat/fat) males appear to be due primarily to abnormal sexual behavior.

Pituitary adenylate cyclase activating polypeptide-mediated intracrine signaling in the testicular germ cells

Pituitary adenylate cyclase activating polypeptide (PACAP) is found not only in the brain, but is also abundantly expressed in the testicular germ cells. However, the physiological role of testicular PACAP remains unknown. Autoradiographic studies showed a considerable number of PACAP-specific binding sites in the seminiferous tubules. Immunohistochemistry demonstrated PAC1-receptor (R)-like immunoreactivity (li) in the cytoplasm of round spermatids, aggregated in the acrosome and coexpressed with PACAP-li. Spermatid-enriched fractions were examined for the subcellular localization of PACAP binding sites and PAC1-R-li. The highest levels of PACAP binding sites and PAC1-R-li were found in the cytosolic, followed by the nuclear, and the lowest levels in the membrane fraction. The testicular cytosolic PAC1-R-like protein showed a specific competitive inhibition in the radio-receptor assay for PACAP38 and 27, with a Ki of 0.069 nM and 0.179 nM, respectively. The addition of PACAP to the cytosol of spermatids only slightly activated adenylate cyclase, while it markedly stimulated the expression and activation of ERK-type mitogen-activated protein kinase (MAPK). In the PAC1-R-like protein-depleted cytosol, a PAC1-R-specific agonist, maxadilan, did not activate MAPK, but PACAP and VIP still did. Because VPAC2-R, which binds both PACAP and VIP, is expressed in the testis, the findings suggest that cytosolic VPAC2-R-like proteins are also present and coupled to MAPK. The MAPK activation does not seem to require a heterotrimeric G-protein. Because PACAP and its receptors are coexpressed in the cytoplasm of spermatids, endogenous PACAP may directly interact with the cytosolic PAC1-R-like protein without the ligand being released into the extracellular space. This possibility is supported by the observation that cytosolic endogenous PACAP in spermatids was co-immunoprecipitated with the cytosolic PAC1-R. This mechanism may be called "intracrine," and its physiological significance is discussed.

The effect of PACAP on rhythmic melatonin release of avian pineals

Pituitary adenylate cyclase activating polypeptide (PACAP) is a ubiquitous member of the VIP/secretin/glucagon bioactive peptide family. The distribution, concentration of PACAP, and its role in the control of rhythmic melatonin (MT) secretion from chicken pineal gland were studied. In the chicken pineal gland (ChPG), 40ng PACAP/g tissue was measured with radioimmunoassay. No midday-midnight differences in the PACAP content of the ChPG could be detected. Immunohistochemical studies of ChPG showed PACAP immunoreactive nerve fibers in the perivascular space and around the pinealocytes. Neither PACAP-labeled perikarya nor PACAP immunopositivity in the pinealocytes could be detected. In five day perifusion experiments, carried out under darkness, both MT and cAMP showed circadian rhythmic release pattern from explanted ChPG. One hour exposure of ChPG to PACAP induced transient (3-4h) elevation of MT and cAMP release. The responses were dose-dependent in the range from 1 to 100nM PACAP concentrations. The magnitude of the response was independent on the phase of the daily cycle in which PACAP was applied. cAMP levels during normal daily cycle and also PACAP-induced cAMP responses always preceded similar changes of MT by about an hour suggesting that cAMP is an intracellular intermediate in controlling MT release from the ChPG. At the same time PACAP, similarly to VIP, did not shift the phase of the in vitro circadian MT rhythm of the pineals. Our data reveal, that PACAP is present in nerve fibers in the chicken pineals and pineal cells contain functioning PACAP-sensitive receptors. PACAP apparently exerts a modulatory effect of the rhythmic MT release from the chicken pineal but does not modify the intrinsic biological clock in the avian pineal gland. Thus, cAMP-mediated intracellular mechanisms in ChPG are not components of the pineal circadian clock, but intermediaries between the clock-mechanism and MT release and may also be components of clock-independent MT release modifiers.

Neuropeptides of the pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide/growth hormone-releasing hormone/secretin family in testis

Mammalian testicular development and the maintenance of spermatogenesis are hormone-dependent processes that are controlled by the pituitary gonadotropins and testosterone. Recent studies have demonstrated the presence of many neuropeptides and their receptors in the testis, suggesting that these peptides operate as local regulators of testicular germ cell development and function. Among these testicular neuropeptides, the peptides that belong to the pituitary adenylate cyclase-activating polypeptide (PACAP) family, particularly growth hormone-releasing hormone and secretin, appear to show some unique common features in terms of intratesticular localization and the time of expression during the spermatogenic cycle. However, their precise physiologic roles and mechanisms of action remain unknown. This review analyzes the available information on the functional interactions among the testicular cells that appear to be mediated by locally produced neuropeptides, with a special emphasis on the peptides of the PACAP family.

Pituitary adenylate cyclase-activating polypeptide does not colocalize with vasoactive intestinal polypeptide in the hypothalamic magnocellular nuclei and posterior pituitary of cats and rats

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) immunoreactive cells were demonstrated in the hypothalamic magnocellular nuclei in cats and rats. In cats these immunoreactive cells were stained without any treatment or intervention; however, in rats we had to use the pituitary stalk section to enhance the amount of PACAP and VIP for successful immunostaining. In both species the regions occupied by PACAP and VIP immunoreactive cells partially overlap each other in the paraventricular and supraoptic nuclei. Nevertheless, in either cats or rats PACAP and VIP immunoreactivities do not colocalize in the same cells studied by double labeling immunohistochemistry (IHC) or by the combination of immunohistochemistry and in situ hybridization. As was expected, PACAP and VIP immunoreactive materials were stored in different fibers of the posterior pituitary where the distribution of PACAP and VIP fibers also showed different patterns: PACAP fibers form a dense plexus at the periphery of the posterior lobe, in the vicinity of the intermediate lobe; however, the VIP fibers were evenly distributed mainly in the center of the posterior lobe. In spite of the high sequence homology of PACAP and VIP, the two peptides are synthesized in different subpopulations of hypothalamic neurons. This different distribution correlates well with the different role of the hypothalamic PACAP and VIP in the biologic clock and in the functions of the anterior and posterior pituitary.

Rapidly activated microglial cells in the preoptic area may play a role in the generation of hyperthermia following occlusion of the middle cerebral artery in the rat

Postischemic hyperthermia occurs after the occlusion of the middle cerebral artery (MCAO) with an intraluminal filament in rats. The cause of hyperthermia is presumed to be damage to the preoptic area, which is one of the temperature-regulatory centers of the hypothalamus. In the present study, reactions of microglial cells and astrocytes in the preoptic area were examined during the first 6 h following transient MCAO. Microglial cells and astrocytes were visualized with immunohistochemistry using antibodies against the CR3 complement receptor and the glial fibrillary acidic protein, respectively. One hour after the occlusion, activated microglial cells were observed in both the medial and lateral preoptic areas ipsilaterally, and in the medial preoptic area contralateral to the infarct. Following reperfusion, the activation of microglial cells decreased in the medial preoptic area of both hemispheres, and in the lateral preoptic area there was a loss of immunoreactive microglial cells. Fragmentation of astrocytic processes was detected in the lateral preoptic area, while in the ipsilateral medial preoptic area a moderate swelling was observed. Immunohistochemistry with an antibody against interleukin-1beta (IL-1beta) revealed scattered immunoreactive cells in both the ipsilateral and the contralateral medial preoptic area 2 h after the MCAO. Our results show that microglial activation in the preoptic area coincides with postischemic hyperthermia. However, an exclusive role for IL-1beta in the generation of hyperthermia is unlikely, and other factors are probably also responsible for postischemic hyperthermia.

Gastric atrial natriuretic peptide regulates endocrine secretion in antrum and fundus of human and rat stomach

Atrial natriuretic peptide (ANP) is present in gastric mucosa and preferentially binds to two subtypes of natriuretic peptide receptors (NPR), NPR-A and NPR-C. The present study examines the role of endogenous ANP in regulating endocrine secretion in rat and human stomachs. NPR-A protein expression and transcripts were identified in rat antral and fundic mucosa by Western blot and RT-PCR. In superfused rat and human antral and fundic segments, ANP (0.1 pM to 0.1 microM) caused a concentration-dependent increase in somatostatin secretion. In antrum, this was accompanied by a decrease in gastrin, and in fundus, this was accompanied by a decrease in histamine secretion. Changes in gastrin and histamine secretion reflected changes in somatostatin secretion and were abolished by somatostatin antibody. The NPR-A receptor antagonist anantin 1) inhibited basal somatostatin secretion and 2) abolished the somatostatin, gastrin, and histamine responses to ANP. We conclude that endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion from both antrum and fundus of rat and human stomach. Stimulation of somatostatin secretion is coupled to inhibition of gastrin secretion in the antrum and inhibition of histamine secretion in the fundus.

Neuropeptides of the pituitary adenylate cyclase-activating polypeptide/vasoactive intestinal polypeptide/growth hormone-releasing hormone/secretin family in testis

Mammalian testicular development and the maintenance of spermatogenesis are hormone-dependent processes that are controlled by the pituitary gonadotropins and testosterone. Recent studies have demonstrated the presence of many neuropeptides and their receptors in the testis, suggesting that these peptides operate as local regulators of testicular germ cell development and function. Among these testicular neuropeptides, the peptides that belong to the pituitary adenylate cyclase-activating polypeptide (PACAP) family, particularly growth hormone-releasing hormone and secretin, appear to show some unique common features in terms of intratesticular localization and the time of expression during the spermatogenic cycle. However, their precise physiologic roles and mechanisms of action remain unknown. This review analyzes the available information on the functional interactions among the testicular cells that appear to be mediated by locally produced neuropeptides, with a special emphasis on the peptides of the PACAP family.

The role of PACAP in gonadotropic hormone secretion at hypothalamic and pituitary levels

The presence of pituitary adenylate cyclase-activating polypeptide (PACAP) and its mRNAin the three levels of the hypothalamo-hypophyseal-ovarian axis was previously demonstrated using immunohistochemistry, in situ hybridization, and reverse transcriptase polymerase chain reaction (RT-PCR). In the hypothalamus, PACAP is present in neuroendocrine effector cells and in the median eminence. In the anterior pituitary and ovary, PACAP is transiently present during the proestrous stage of the estrous cycle. In the pituitary, PACAP was observed in gonadotropes. In the ovary, PACAP was demonstrated in the granulosa cells of the preovulatory ovarian follicles. The effect of PACAP on luteinizing hormone (LH) secretion was demonstrated in in vivo and in vitro models. In our work we have studied the role of PACAP in gonadotropic hormone secretion at hypothalamic and pituitary levels. At the hypothalamic level, PACAP, administered intracerebroventricularly to female rats before the critical period of the proestrus stage, can inhibit LH release and ovulation. Its inhibiting effect is mediated through corticotropin-releasing factor (CRF) and endogenous opioids. PACAP administered to neonatal female rats delayed the onset of puberty by influencing the luteinizing hormone-releasing hormone (LHRH) neuronal system. In the pituitary gland, the release of PACAP depended on the stage of the estrous cycle and on the time of day the animals were sacrificed. On the day of proestrus, the number of PACAP-releasing cells showed a diurnal change with two peaks (in the morning and in the evening). The peak was much higher in the evening at the end of the LH surge than in the morning.

DS-Nh as an experimental model of atopic dermatitis induced by Staphylococcus aureus producing staphylococcal enterotoxin C

DS-Nh mice raised under conventional conditions spontaneously develop dermatitis similar to human atopic dermatitis (AD), which is associated with staphylococcal infection. In the present study, we show that Staphylococcus aureus producing staphylococcus exotoxin C (SEC) was recovered from the culture of the skin lesions of DS-Nh mice with AD-like dermatitis and that the serum levels of anti-SEC antibodies from these mice were elevated. We describe here how to promote experimental AD by epicutaneous injection with SEC-producing S. aureus to DS-Nh mice. In order to assess the role of SEC in the pathogenesis of AD, the mitogenic activity, TCRBV repertoire analysis and the production of IL-4 and IFN-gamma from spleen mononuclear cells (MNC) from DS-Nh stimulated by SEC were compared with those due to SEA, SEB and TSST. The weakest was the mitogenic activity of SEC, and higher IL-4 responses and lower IFN-gamma responses to SEC showed correlation with TCRBV8S2-positive T cells, which were selectively stimulated by SEC. We also demonstrate that SEC-producing S. aureus was able to survive in DS-Nh after intradermal injection. These results suggest a possible role for SEC in the pathogenesis of AD through host-S. aureus relationships.

Adrenomedullin stimulates somatostatin and thus inhibits histamine and acid secretion in the fundus of the stomach

Adrenomedullin has recently been localized to enterochromaffin-like (ECL) and chief cells in the gastric fundus. It has been proposed that adrenomedullin may play a role in gastric mucosal defense and repair. In the present study, we have used the isolated, luminally perfused mouse stomach and superfused rat fundic segments to examine the effect of adrenomedullin on exocrine and endocrine secretion in this region of the stomach. Addition of adrenomedullin (1 pM to 1 microM) to the isolated mouse stomach caused a concentration-dependent decrease in acid secretion. The EC(50) value was 1.4 x 10(-9) and maximal inhibition of acid secretion was obtained at a concentration of 1 microM (31+/-4% below basal level, P<0.001). In rat fundic segments, superfusion with adrenomedullin (0.1 pM to 0.1 microM) caused a concentration-dependent increase in somatostatin secretion (EC(50), 1 x 10(-10)) that was accompanied by a reciprocal decrease in histamine secretion (EC(50), 1.2 x 10(-11)). Maximal stimulation of somatostatin secretion (60+/-5% above basal level, P<0.001) and inhibition of histamine secretion (50+/-5% below basal level, P<0.01) was obtained at a concentration of 0.1 microM. Changes in acid and histamine secretion induced by adrenomedullin reflected changes in somatostatin secretion and could be abolished by addition of somatostatin antibody. The axonal blocker, tetrodotoxin, also abolished the somatostatin and, consequently, the acid and histamine responses to adrenomedullin, implying that the effect of adrenomedullin on somatostatin secretion was mediated via activation of intramural neurons. We conclude that adrenomedullin, acting via intramural fundic neurons, stimulates somatostatin and thus inhibits histamine and acid secretion. This represents one mechanism by which adrenomedullin might enhance mucosal defense and repair.

Reciprocal paracrine pathways link atrial natriuretic peptide and somatostatin secretion in the antrum of the stomach

Atrial natriuretic peptide (ANP) as well as its receptor, NPR-A, have been identified in gastric antral mucosa, suggesting that ANP may act in a paracrine fashion to regulate gastric secretion. In the present study, we have superfused antral mucosal segments obtained from rat stomach to examine the paracrine pathways linking ANP and somatostatin secretion in this region.ANP (0.1 pM to 0.1 microM) caused a concentration-dependent increase in somatostatin secretion (EC(50), 0.3 nM). The somatostatin response to ANP was unaffected by the axonal blocker tetrodotoxin but abolished by addition of the selective NPR-A antagonist, anantin. Anantin alone inhibited somatostatin secretion by 18+/-3% (P<0.005), implying that endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion. Somatostatin (1 pM to 1 microM) caused a concentration-dependent decrease in ANP secretion (EC(50), 0.7 nM) that was abolished by addition of the somatostatin subtype 2 receptor (sst2) antagonist, PRL2903. Neutralization of ambient somatostatin with somatostatin antibody (final dilution 1:200) increased basal ANP secretion by 70+/-8% (P<001), implying that endogenous somatostatin inhibits ANP secretion. We conclude that antral ANP and somatostatin secretion are linked by paracrine feedback pathways: endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion, and endogenous somatostatin, acting via the sst2 receptor, inhibits ANP secretion.

Effects of pretreatment with PACAP on the infarct size and functional outcome in rat permanent focal cerebral ischemia

PACAP exerts neuroprotective effects under various neurotoxic conditions in vitro. In vivo, it reduces brain damage after global and transient focal ischemia. The present study investigated whether PACAP has neuroprotective effects when applied before the onset of permanent ischemia. Rats were given bolus injections of PACAP38 intracerebroventricularly, and then underwent permanent middle cerebral artery occlusion. The results show that 2 microg of PACAP significantly reduced the infarct size measured 12 and 24h after the onset of ischemia. No further reduction was obtained by a 7-day pretreatment. PACAP also ameliorated certain sensorimotor deficits. Our present study provides further evidence for the neuroprotective effects of PACAP, and implies that it might be a promising preventive therapeutic agent in ameliorating ischemic brain damage.

Dopamine- and cyclic AMP-regulated phosphoprotein-immunoreactive neurons activated by acute stress are innervated by fiber terminals immunopositive for pituitary adenylate cyclase-activating polypeptide in the extended amygdala in the rat

The bed nuclei of the stria terminalis (BST) and the central nucleus of the amygdala are highly heterogeneous structures, which form one functional unit, the so-called extended amygdala. Several studies described increased c-fos expression following acute stress in this brain area, confirming its central role in the modulation/regulation of stress responses. The oval nucleus of the BST and the central amygdala exhibit a dense network of pituitary adenylate cyclase-activating polypeptide (PACAP)-immunoreactive (ir) fiber terminals. In addition, several dopamine- and cyclic AMP-regulated phosphoprotein (DARPP-32)-immunoreactive neurons were also observed here. Because the extended amygdala plays an important role in the central autonomic regulation during stress and the distribution of PACAP-ir and that of DARPP-32-ir nervous structures overlap, the aims of this study were to investigate the possible activation of DARPP-32-ir neurons following acute systemic stress and to demonstrate synaptic interactions between DARPP-32-ir neurons and fiber terminals immunopositive for PACAP.In summary, this study provided morphological evidence that acute stress resulted in the activation of DARPP-32 neurons, which were innervated by PACAP-ir neuronal structures in the extended amygdala. Furthermore, interaction between neuropeptides/neurotransmitters and phosphoproteins was also demonstrated.

Cell immunoblot assay study demonstrating the release of PACAP from individual anterior pituitary cells of rats and the effect of PACAP on LH release

The presence of pituitary adenylate cyclase activating polypeptide (PACAP) was previously demonstrated in the anterior pituitary by radioimmunoassay, immunohistochemistry, and reverse transcript-polymerase chain reaction (RT-PCR). With the use of cell immunoblot assay (CIBA), when the pituitary cells were cultured on nitrocellulose membrane, the release of PACAP by individual anterior pituitary cells was observed. The released peptide, trapped by the nitrocellulose membrane forming a blot around the cells, was demonstrated by immunocytochemistry. Double labeling revealed that a part of PACAP-immunoreactive cells can release LH as well. With the use of sandwich enzyme immunoassay (S-EIA), it was found that the concentration of PACAP in the anterior pituitaries is 10(-10) M. In cell culture in a similar concentration, PACAP stimulated the LH release from female gonadotropes, but did not influence it from male ones. The stimulated release of LH was indicated by the enhancement in the diameter of LH blots compared to the untreated control cultures. We concluded that PACAP may be released from the anterior pituitary cells in a concentration which would be able to influence LH release not only in vitro but under in vivo conditions as well. The effect of PACAP on LH release was different in female and male pituitary cultures.

Neonatal PACAP administration in rats delays puberty through the influence of the LHRH neuronal system

The onset of puberty is a concerted action of many factors which leads to cyclic LHRH release in rats. It has been demonstrated that; in common with vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase activating polypeptide (PACAP) is also involved in the differentiation of the central nervous system. In our previous work, it was shown that a single PACAP injection into neonatal female rats delayed puberty. In the present work, neonatal administration of PACAP delayed the vaginal opening and decreased the weight of anterior pituitaries, the number of expelled ova at the first ovulation and the intensity of LHRH immunostaining in the septo-preoptico-infundibular system. PACAP antiserum had a reverse effect on LHRH immunoreactivity. The other studied parameters in the latter group remained unchanged compared to control rats. It was concluded that neonatal PACAP administration delayed the onset of puberty through the influence of the LHRH neuronal system.

PACAP inhibits anoxia-induced changes in physiological responses in horizontal cells in the turtle retina

Pituitary adenylate cyclase activating polypeptide (PACAP) has neurotrophic and neuroprotective effects against various cytotoxic agents in vitro, and ischemia in vivo. Anoxia tolerance is most highly developed in some species of turtles. Recently, we have demonstrated high levels of PACAP38 in the turtle brain, exceeding those in corresponding rat and human brain areas by 10- to 100-fold. The aim of the present study was to investigate with electrophysiological methods the protective effects of PACAP in anoxia-induced neuronal damage of turtle retinal horizontal cells. Adult turtles (Pseudemys scripta elegans) were used for the experiments. After decapitation, half of the isolated eyecup slices were placed into a non-oxygenated Ringer solution, the other half into 0.165 microM PACAP solution. Intracellular recordings were obtained from horizontal cells 18, 22, 42 and 46 h after removal of the eyes. The amplitudes of light responses with the exception of the 0-h measurement, were larger at all time-points in PACAP-incubated slices than in control retinal slices. After both 18 and 22 h, the response amplitudes of PACAP-treated cells exceeded those taken from control horizontal cells by 1.2-fold. At later times, this difference became larger than 2-fold. In summary, the present results provide evidence that PACAP has neuroprotective effects on the anoxic retinal cells in the turtle.

Influence of pinealectomy on levels of PACAP and cAMP in the chicken brain

One of the recently found functions of pituitary adenylate cyclase activating polypeptide (PACAP) is the modulation of circadian rhythms. Widespread distribution of PACAP-containing neurons and receptors has been shown in the chicken. Recently, we have demonstrated that PACAP levels oscillate in a circadian manner in the chicken brain. Daily variation in PACAP levels might be influenced by several regulatory mechanisms. Among the structures that may regulate PACAP levels, one candidate is the pineal gland. Therefore, in the present study, we investigated the effect of pinealectomy on the levels of PACAP in the chicken brain. Animals were kept under 12:12-h light-dark schedule. Pinealectomy was performed at 3 weeks of age; sham-operated animals were used as controls. The animals were sacrificed at 15 and 24 h 1 week after pinealectomy. The brainstem and diencephalon were removed, and tissue samples were processed for PACAP and cAMP radioimmunoassay (RIA).PACAP and cAMP levels showed nighttime elevations in both the sham-operated and pinealectomized animals, except for the PACAP content in the diencephalon of pinealectomized chicken. PACAP levels of pinealectomized animals were significantly higher in the diencephalon and brainstem as compared to the control animals at both time-points. Levels of cAMP correlated well with levels of PACAP. The present results provide evidence that the pineal gland has an inhibitory impact on PACAP-neurons in the chicken brainstem and diencephalon.

Distribution of urocortin-like immunoreactivity in the central nervous system of the frog Rana esculenta

Corticotropin-releasing factor (CRF), sauvagine, and urotensin I are all members of the so-called CRF neuropeptide family. Urocortin (Ucn), a 40-amino-acid neuropeptide recently isolated from the rat brain, is the newest member of this family. Until now, the distribution of Ucn in the central nervous system (CNS) has been studied only in placental mammals. We used a polyclonal antiserum against rat Ucn to determine the distribution of Ucn-like immunoreactivity in the CNS of the green frog, Rana esculenta. The great majority of Ucn-immunoreactive perikarya was seen in the anterior preoptic area, ventromedial thalamic nucleus, posterior tuberculum, nucleus of the medial longitudinal fasciculus, and Edinger-Westphal nucleus. Urocortin-immunoreactive nerve cells were also observed in the motor nuclei of the trigeminal and facial nerves and in the hypoglossal nucleus. Immunoreactive fibers were found in the medial and lateral septal nuclei, bed nucleus of the stria terminalis, many of the thalamic and hypothalamic nuclei, mesencephalic tectum, tegmental nuclei, torus semicircularis, and dorsal horn and central field of the spinal cord. Only scattered Ucn-immunoreactive axon terminals were observed in the external zone of the medial eminence. The densest accumulations of Ucn-immunoreactive nerve terminals were seen in the granular layer of the cerebellum and cochlear nuclei. Our results suggest that an ortholog of mammalian Ucn occurs in the CNS of the green frog. The distribution of Ucn-like immunoreactivity in Rana esculenta showed many similarities to the distribution in placental mammals. The distribution of Ucn-like immunoreactivity in the anuran CNS was different from that of CRF and sauvagine, so our results suggest that at least three different lineages of the CRF neuropeptide family occur in the anuran CNS.

A newly developed enzyme-immunoassay for measuring the tissue contents of PACAP in fish

We have developed a novel and easy enzyme-immunoassay (EIA) for pituitary adenylate cyclase-activating polypeptide (PACAP). We used it to determine immunoreactive PACAP levels in the central nervous system (CNS) and peripheral tissues of two fishes, a teleost (the stargazer) and an elasmobranch (a stingray). An antiserum was raised in a white rabbit immunized with a conjugate of synthetic stargazer PACAP27 plus keyhole limpet hemocyanin. The EIA system used an antiserum/biotin-labeled PACAP/avidin/biotin-conjugated enzyme complex, and a double antibody method was used to precipitate the immune complexes. We call the system the avidin-biotin complex detectable EIA (ABCDEIA) for PACAP. ABCDEIA with biotin-labeled PACAP27 detected only PACAP27, recognizing neither the longer forms of PACAP nor any other peptides. PACAPs with 27, 38, and 44 residues cross-reacted in another ABCDEIA with biotin-labeled PACAP38 or PACAP44. Whole brains of both fishes contained much higher levels of PACAP, 6-30 times as high as the levels in the mammalian brain, but unexpectedly, no immunoreactive PACAP27 was found in any CNS or peripheral tissue in either fish. The gastrointestinal tracts of fish also contained lower, but significant amounts of PACAP.

Distribution of urocortin in the rat's gastrointestinal tract and its colocalization with tyrosine hydroxylase

Urocortin (Ucn), a newly identified member of the corticotropin-releasing factor (CRF) family, is not only expressed in the brain, but also abundantly present in the peripheral tissues, especially in the gastrointestinal tract (GI) as determined by radioimmuoassay. In order to determine the precise localization of urocorin in the GI, we mapped the distribution of urocortin-like immunoreactivity (ir) in the GI of the rat using an immunofluorescence histochemical technique. Ucn, both in the brain and the peripheral tissues, is involved in the regulatory control of host-defense mechanism during stress. In order to study the possible involvement of the sympathetic system in the expression of GI urocortin in response to stress, we examined the effect of chemical sympathectomy on urocortin-ir and its colocalization with tyrosine hydroxylase (TH). UCn was expressed in all parietal cells of the stomach, myenteric and submucosal plexuses as well as in cells in Lieberkühn crypts of the small and large intestine. Most of the acid secreting parietal cells contained both Ucn and TH. Chemical sympathectomy did not affect Ucn immunoreactivity of parietal cells.