Protective effects of pituitary adenylate cyclase activating polypeptide in endothelial cells against oxidative stress-induced apoptosis

Effects of Pituitary Adenylate Cyclase Activating Polypeptide on Cell Death

Pituitary adenylate cyclase activating polypeptide (PACAP) was first isolated as a hypothalamic peptide based on its efficacy to increase adenylate cyclase (AC) activity. It has a widespread distribution throughout the body including the nervous system and peripheral organs, where PACAP exerts protective effects both in vivo and in vitro through its anti-apoptotic, anti-inflammatory, and antioxidant functions. The aim of the present paper was to review the currently available literature regarding the effects of PACAP on cell death in vitro in neural and non-neural cells. Among others, its effect on apoptosis can be detected in cerebellar granule cells against different toxic stimuli. Different neural cell types from the cerebral cortex are also prevented from cell death. PACAP also shows effects on cell death in cells belonging to the peripheral nervous system and protects both neural and non-neural cells of sensory organs. In addition, cell survival-promoting effect can be observed in different peripheral organ systems including cardiovascular, immune, respiratory, gastrointestinal, urinary, and reproductive systems. The studies summarized here indicate its noteworthy effect on cell death in different in vitro models, suggesting PACAP’s potential therapeutic usage in several pathological conditions.

Effects of pituitary adenylate cyclase activating polypeptide (PACAP) in corneal epithelial regeneration and signal transduction in rats

Corneal epithelium responds to insults with a rapid wound healing, which is essential for maintaining vision. The proper balance of apoptotic and proliferation-stimulating pathways is critical for normal regeneration. Pituitary adenylate cyclase activating polypeptide (PACAP) is an important growth factor during the development of the nervous system and exerts cytoprotective effects in injuries. The aim of the present study was to investigate the effects of PACAP on corneal epithelial wound healing in rats and on two important protective signaling molecules, Akt and ERK1/2, both of which have been reported to play important roles during cell survival and regeneration, including corneal wound healing. Wistar rats received PACAP treatment in form of eyedrops, containing 1, 5 and 10 µg PACAP27, immediately and every two hours after corneal abrasion. Corneas were stained with fluorescein dye and further processed for histological staining or Western blot analysis for Akt and ERK1/2 expression. Our results showed that topical PACAP application enhanced corneal wound healing, as the area of injury was significantly less in PACAP-treated groups. Furthermore, both ERK1/2 and Akt signaling was induced upon PACAP administration in both injured and intact corneas. In summary, the present results show that PACAP enhances corneal wound healing in a rat model of corneal abrasion.

PACAP-38 and PAC1 Receptor Alterations in Plasma and Cardiac Tissue Samples of Heart Failure Patients

Pituitary adenylate cyclase activating polypeptide-38 (PACAP-38) is a multifunctional neuropeptide, which may play a role in cardioprotection. However, little is known about the presence of PACAP-38 in heart failure (HF) patients. The aim of our study was to measure the alterations of PACAP-38 like immunoreactivity (LI) in acute (n = 13) and chronic HF (n = 33) and to examine potential correlations between PACAP-38 and HF predictors (cytokines, NT-proBNP). Tissue PACAP-38 LI and PAC1 receptor levels were also investigated in heart tissue samples of patients with HF. Significantly higher plasma PACAP-38 LI was detected in patients with acute HF, while in chronic HF patients, a lower level of immunoreactivity was observed compared to healthy controls (n = 13). Strong negative correlation was identified between plasma PACAP-38 and NT-proBNP levels in chronic HF, as opposed to the positive connection seen in the acute HF group. Plasma IL-1 β, IL-2 and IL-4 levels were significantly lower in chronic HF, and IL-10 was significantly higher in patients with acute HF. PACAP-38 levels of myocardial tissues were lower in all end-stage HF patients and lower PAC1 receptor levels were detected in the primary dilated cardiomyopathy group compared to the controls. We conclude that PACAP-38 and PAC1 expression correlates with some biomarkers of acute and chronic HF; therefore, further studies are necessary to explore whether PACAP could be a suitable prognostic biomarker in HF patients.

Protective Effects of PACAP in a Rat Model of Diabetic Neuropathy

Pituitary adenylate cyclase-activating peptide (PACAP) is a neuropeptide with a widespread occurrence and diverse effects. PACAP has well-documented neuro- and cytoprotective effects, proven in numerous studies. Among others, PACAP is protective in models of diabetes-associated diseases, such as diabetic nephropathy and retinopathy. As the neuropeptide has strong neurotrophic and neuroprotective actions, we aimed at investigating the effects of PACAP in a rat model of streptozotocin-induced diabetic neuropathy, another common complication of diabetes. Rats were treated with PACAP1-38 every second day for 8 weeks starting simultaneously with the streptozotocin injection. Nerve fiber morphology was examined with electron microscopy, chronic neuronal activation in pain processing centers was studied with FosB immunohistochemistry, and functionality was assessed by determining the mechanical nociceptive threshold. PACAP treatment did not alter body weight or blood glucose levels during the 8-week observation period. However, PACAP attenuated the mechanical hyperalgesia, compared to vehicle-treated diabetic animals, and it markedly reduced the morphological signs characteristic for neuropathy: axon–myelin separation, mitochondrial fission, unmyelinated fiber atrophy, and basement membrane thickening of endoneurial vessels. Furthermore, PACAP attenuated the increase in FosB immunoreactivity in the dorsal spinal horn and periaqueductal grey matter. Our results show that PACAP is a promising therapeutic agent in diabetes-associated complications, including diabetic neuropathy.

Pituitary adenylate cyclase-activating polypeptide attenuates mitochondria-mediated oxidative stress and neuronal apoptosis after subarachnoid hemorrhage in rats

Mitochondria-mediated oxidative stress and neuronal apoptosis play an important role in early brain injury following subarachnoid hemorrhage (SAH). Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to reduce oxidative stress and cellular apoptosis by maintaining mitochondrial function under stress. The objective of this study is to investigate the effects of PACAP on mitochondria dysfunction - induced oxidative stress and neuronal apoptosis in both vivo and vitro models of SAH. PACAP Knockout CRISPR and exogenous PACAP38 were used to verify the neuroprotective effects of PACAP in rats after endovascular perforation - induced SAH as well as in primary neuron culture after hemoglobin stimulation. The results showed that endogenous PACAP knockout aggravated mitochondria dysfunction - mediated ATP reduction, reactive oxygen species accumulation and neuronal apoptosis in ipsilateral hemisphere at 24 h after SAH in rats. The exogenous PACAP38 treatment provided both short- and long-term neurological benefits by attenuating mitochondria - mediated oxidative stress and neuronal apoptosis after SAH in rats. Consistently, the exogenous PACAP38 treatment presented similar neuroprotection in the primary neuron culture after hemoglobin stimulation. Pharmacological inhibition of adenylyl cyclase (AC) or extracellular signal-regulated kinase (ERK) partly abolished the anti-oxidative stress and anti-apoptotic effects provided by PACAP38 treatment after the experimental SAH both in vivo and in vitro, suggesting the involvement of the AC-cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) and ERK pathway. Collectively, PACAP38 may serve as a promising treatment strategy for alleviating early brain injury after SAH.

Neurotransmitters, neuropeptides and their receptors interact with immune response in healthy and psoriatic skin

Psoriasis is a chronic inflammatory disease with a multifactorial origin that affects the skin. It is characterized by keratinocyte hyperproliferation, which results in erythemato-squamous plaques. Just as the immune system plays a fundamental role in psoriasis physiopathology, the nervous system maintains the inflammatory process through the neuropeptides and neurotransmitters synthesis, as histamine, serotonin, calcitonin gene-related peptide, nerve growth factor, vasoactive intestinal peptide, substance P, adenosine, glucagon-like peptide, somatostatin and pituitary adenylate cyclase polypeptide. In patients with psoriasis, the systemic or in situ expression of these chemical mediators and their receptors are altered, which affects the clinical activity of patients due to its link to the immune system, provoking neurogenic inflammation. It is important to establish the role of the nervous system since it could represent a therapeutic alternative for psoriasis patients. The aim of this review is to offer a detailed review of the current literature about the neuropeptides and neurotransmitters involved in the physiopathology of psoriasis.

Protective Effects of PACAP in Peripheral Organs

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide widely distributed in the nervous system, where it exerts strong neuroprotective effects. PACAP is also expressed in peripheral organs but its peripheral protective effects have not been summarized so far. Therefore, the aim of the present paper is to review the existing literature regarding the cytoprotective effects of PACAP in non-neuronal cell types, peripheral tissues, and organs. Among others, PACAP has widespread expression in the digestive system, where it shows protective effects in various intestinal pathologies, such as duodenal ulcer, small bowel ischemia, and intestinal inflammation. PACAP is present in both the exocrine and endocrine pancreas as well as liver where it reduces inflammation and steatosis by interfering with hepatic pathology related to obesity. It is found in several exocrine glands and also in urinary organs, where, with its protective effects being mainly published regarding renal pathologies, PACAP is protective in numerous conditions. PACAP displays anti-inflammatory effects in upper and lower airways of the respiratory system. In the skin, it is involved in the development of inflammatory pathology such as psoriasis and also has anti-allergic effects in a model of contact dermatitis. In the non-neuronal part of the visual system, PACAP showed protective effects in pathological conditions of the cornea and retinal pigment epithelial cells. The positive role of PACAP has been demonstrated on the formation and healing processes of cartilage and bone where it also prevents osteoarthritis and rheumatoid arthritis development. The protective role of PACAP was also demonstrated in the cardiovascular system in different pathological processes including hyperglycaemia-induced endothelial dysfunction and age-related vascular changes. In the heart, PACAP protects against ischemia, oxidative stress, and cardiomyopathies. PACAP is also involved in the protection against the development of pre-senile systemic amyloidosis, which is presented in various peripheral organs in PACAP-deficient mice. The studies summarized here provide strong evidence for the cytoprotective effects of the peptide. The survival-promoting effects of PACAP depend on a number of factors which are also shortly discussed in the present review.

The Neuropeptide Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is Protective in Inflammation and Oxidative Stress-Induced Damage in the Kidney

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide with a widespread distribution throughout the entire body including the urinary system. PACAP exerts protective actions in different injury models related to several organ systems. Its protective effect is mainly based on its antiapoptotic, anti-inflammatory and antioxidant effects. The present review aims to summarize the effects of PACAP in pathologies associated with inflammation and oxidative stress-induced damage in the kidney. Both in vitro and in vivo data are available proving its protective actions against oxidative stress, hypoxia, renal ischemia/reperfusion, diabetic nephropathy, myeloma kidney injury, amyloidosis and different types of drug-induced nephropathies. Data showing the nephroprotection by PACAP emphasize the potential of PACAP’s therapeutic use in various renal pathologies.

PACAP deficiency as a model of aging

Dysregulation of neuropeptides may play an important role in aging-induced impairments. In the long list of neuropeptides, pituitary adenylate cyclase-activating polypeptide (PACAP) represents a highly effective cytoprotective peptide that provides an endogenous control against a variety of tissue-damaging stimuli. PACAP has neuro- and general cytoprotective effects due to anti-apoptotic, anti-inflammatory, and antioxidant actions. As PACAP is also a part of the endogenous protective machinery, it can be hypothesized that the decreased protective effects in lack of endogenous PACAP would accelerate age-related degeneration and PACAP knockout mice would display age-related degenerative signs earlier. Recent results support this hypothesis showing that PACAP deficiency mimics aspects of age-related pathophysiological changes including increased neuronal vulnerability and systemic degeneration accompanied by increased apoptosis, oxidative stress, and inflammation. Decrease in PACAP expression has been shown in different species from invertebrates to humans. PACAP-deficient mice display numerous pathological alterations mimicking early aging, such as retinal changes, corneal keratinization and blurring, and systemic amyloidosis. In the present review, we summarize these findings and propose that PACAP deficiency could be a good model of premature aging.

Comparison of the effects of PACAP-38 and its analog, acetyl-[Ala15, Ala20] PACAP-38-propylamide, on spatial memory, post-learning BDNF expression and oxidative stress in rat

We compared the effects of single intraveinous injection of pituitary adenylate cyclase-activating polypeptide-38 (P38) to those of its analog, acetyl-[Ala¹⁵, Ala²⁰]PACAP-38-propylamide (P38-alg) on spatial memory in the Morris water maze (MWM) using a weak massed-learning procedure, post-training brain derived neurotrophic factor (BDNF) and post-training oxidative stress biomarker assays in male Wistar rats. Acquisition of the MWM task following P38 (30 μg/kg) and P38-alg (30 μg/kg) treatments was similar to control group (Saline: 0.9% NaCl) and there was no interaction between treatments and performance. However, in the probe test, P38-treated group showed a specific interest for the target quadrant whereas the two other groups exhibited less focused place searching behavior. Moreover, P38 had an anxiogenic effect as measured by the distribution of swimming at the periphery of the pool. The swimming test resulted in a decrease in BDNF contents in the hippocampus. P38 but not P38-alg treatment restored BDNF expression. In terms of oxidative stress, both P38 and P38-alg treatments had antioxidative effects. The activity of antioxidative enzymes in the neocortex was increased. However only P38 reduced the levels of carbonylated proteins (CP). These data show that P38 and P38-alg have different behavioral and neurobiological effects. Thus, P38-alg and other analogs with specific functional profiles, inducing beneficial central effects (e.g. neuroprotection) while minimizing undesired peripheral effects may be useful for potential therapeutical use.

Pituitary adenylate cyclase-activating polypeptide ameliorates vascular dysfunction induced by hyperglycaemia

BACKGROUND

Short-lasting hyperglycaemia occurs frequently in prediabetes and poorly controlled diabetes mellitus leading to vascular damage. Pituitary adenylate cyclase-activating polypeptide (PACAP) has been shown to play a protective role in vascular complications of diabetes; moreover, antioxidant effects of PACAP were also described. Therefore, we hypothesized that PACAP exerts protective effects in short-term hyperglycaemia-induced vascular dysfunctions.

METHODS

After short-term hyperglycaemia, acetylcholine-induced and sodium nitroprusside-induced vascular relaxation of mouse carotid arteries were tested with a myograph with or without the presence of PACAP or superoxide dismutase. Potential direct antioxidant superoxide-scavenging action of pituitary adenylate cyclase-activating peptide was tested with pyrogallol autoxidation assay; furthermore, the effect of pituitary adenylate cyclase-activating peptide or superoxide dismutase was investigated on hyperglycaemia-associated vascular markers.

RESULTS

PACAP administration resulted in reduced endothelial dysfunction after a 1-h hyperglycaemic episode. PACAP was able to restore acetylcholine-induced relaxation of the vessels and improved sodium nitroprusside-induced relaxation. This effect was comparable to the protective effect of superoxide dismutase, but PACAP was unable to directly scavenge superoxide produced by autoxidation of pyrogallol. Endothelial dysfunction was associated with elevated levels of fibroblast growth factor basic, matrix metalloproteinase 9 and nephroblastoma overexpressed gene proteins. Their release was reduced by PACAP administration.

CONCLUSION

These results suggest a strong protective role of PACAP in the vascular complications of diabetes.

Examination of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) as a Potential Biomarker in Heart Failure Patients

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide having neurotrophic, neuroprotective, and general cytoprotective actions in a variety of tissues based on its anti-apoptotic, anti-inflammatory, and antioxidant effects. Several studies have demonstrated its cardioprotective effects in vitro and in various animal models. However, few data are available on the presence of PACAP in human cardiac tissues and its role in the pathomechanism and progression of different cardiac disorders, particularly heart failure. Earlier, our research group has shown PAC1 receptor immunoreactivity in human heart tissue samples and we have found significantly elevated PACAP27- and PACAP38-like immunoreactivity in ischemic cardiac samples compared to valvular abnormalities with radioimmunoassay. In the last few years, numerous studies examined the presence and the changes of PACAP levels in different human tissue samples and biological fluids to show alterations in different physiological and pathological conditions. Therefore, the aim of the present study was to measure the alterations of blood PACAP levels in chronic heart failure caused by primary dilated cardiomyopathy or ischemic cardiomyopathy and to examine the possible relationship between serum levels of PACAP, N-terminal prohormone of brain natriuretic peptide (NT-proBNP), and systolic left ventricular function, the most reliable biomarkers of heart failure. In the group of mild heart failure patients, a significant strong negative correlation was detected. Furthermore, in moderate heart failure, we found a significant moderate negative correlation between PACAP and NT-proBNP levels only in ischemic subgroup. Positive correlation was found between serum PACAP level and ejection fraction only in patients with heart failure due to ischemic cardiomyopathy but not in patients with primary dilated cardiomyopathy. In summary, remarkable differences were observed between the ischemic and non-ischemic heart failure suggesting that PACAP might play an important role in the pathomechanism and progression of ischemic heart failure and it might be a potential biomarker of cardiac diseases in the future.

Disturbed spermatogenic signaling in pituitary adenylate cyclase activating polypeptide-deficient mice

PACAP is a neuropeptide with diverse functions in various organs, including reproductive system. It is present in the testis in high concentrations, and in addition to the stage-specific expression within the seminiferous tubules, PACAP affects spermatogenesis and the functions of Leydig and Sertoli cells. Mice lacking endogenous PACAP show reduced fertility, but the possibility of abnormalities in spermatogenic signaling has not yet been investigated. Therefore, we performed a detailed morphological analysis of spermatozoa, sperm motility and investigated signaling pathways that play a role during spermatogenesis in knockout mice. No significant alterations were found in testicular morphology or motility of sperm in homozygous and heterozygous PACAP-deficient mice in spite of the moderately increased number of severely damaged sperms. However, we found robust changes in mRNA and/or protein expression of several factors that play an important role in spermatogenesis. Protein kinase A expression was markedly reduced, while downstream phospho-ERK and p38 were elevated in knockout animals. Expression of major transcription factors, such as Sox9 and phospho-Sox9, was decreased, while that of Sox10, as a redundant factor, was increased in PACAP-deficient mice. The reduced phospho-Sox9 expression was partly due to increased expression and activity of phosphatase PP2A in knockout mice. Targets of Sox transcription factors, such as collagen type IV, were reduced in knockout mice. In summary, our results show that lack of PACAP leads to disturbed signaling in spermatogenesis, which could be a factor responsible for reduced fertility in PACAP knockout mice, and further support the role of PACAP in reproduction.

Effects of pituitary adenylate cyclase activating polypeptide on small intestinal INT 407 cells

Pituitary adenylate cyclase activating polypeptide (PACAP) is an endogenous neuropeptide having a widespread distribution both in the nervous system and peripheral organs including the gastrointestinal tract. It has been shown to exert actions on intestinal functions, mainly affecting glandular secretion and motility. PACAP has several different effects on cell survival depending on the cell type and the applied stimulus. Its influences on small intestinal epithelial cells are not yet elucidated, therefore the aim of the present study was to investigate the effects of PACAP on intestinal epithelial cells having high turnover (INT 407) against different harmful stimuli, such as oxidative stress, in vitro hypoxia and gamma radiation. We tested the effect of PACAP on proliferation and cell survival using MTT assay. Moreover, various cancer-related factors were evaluated by oncology array. PACAP did not influence the proliferation rate of INT 407 cells. Its cell survival-enhancing effect could be detected against oxidative stress, but not against in vitro hypoxia or gamma irradiation. Clonogenic survival assay was performed to analyze the effect of PACAP on clonogenic potential of cells exposed to gamma radiation. Surprisingly, PACAP enhanced the clone-forming ability decrease induced by irradiation. Western blot analysis of ERK1/2 phosphorylation was performed in order to obtain further information on the molecular background. Our data showed phospho-ERK1/2 suppression of PACAP in irradiated cells. Furthermore, the role of endogenous PACAP against oxidative stress was also investigated performing ADCYAP1 small interfering RNA transfection. We found significant difference in the cell vulnerability between cells undergoing silencing and cells without transfection suggesting the protective role of the endogenously present PACAP against oxidative stress in INT 407 cells. In summary, PACAP seems to be able to exert contradictory effects in INT 407 cells depending on the applied stressor, suggesting its regulatory role in the cellular household.

Protective Effects of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) Against Oxidative Stress in Zebrafish Hair Cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic neuropeptide, with known antiapoptotic functions. Our previous in vitro study has demonstrated the ameliorative role of PACAP-38 in chicken hair cells under oxidative stress conditions, but its effects on living hair cells is now yet known. Therefore, the aim of the present study was to investigate in vivo the protective role of PACAP-38 in hair cells found in zebrafish (Danio rerio) sense organs-neuromasts. To induce oxidative stress the 5-day postfertilization (dpf) zebrafish larvae were exposed to 1.5 mM H₂O₂ for 15 min or 1 h. This resulted in an increase in caspase-3 and p-38 MAPK level in the hair cells as well as in an impairment of the larvae basic behavior. To investigate the ameliorative role of PACAP-38, the larvae were incubated with a mixture of 1.5 mM H₂O₂ and 100 nM PACAP-38 following 1 h preincubation with 100 nM PACAP-38 only. PACAP-38 abilities to prevent hair cells from apoptosis were investigated. Whole-mount immunohistochemistry and confocal microscopy analyses revealed that PACAP-38 treatment decreased the cleaved caspase-3 level in the hair cells, but had no influence on p-38 MAPK. The analyses of basic locomotor activity supported the protective role of PACAP-38 by demonstrating the improvement of the fish behavior after PACAP-38 treatment. In summary, our in vivo findings demonstrate that PACAP-38 protects zebrafish hair cells from oxidative stress by attenuating oxidative stress-induced apoptosis.

Pleiotropic and retinoprotective functions of PACAP

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 27- or 38-amino acid neuropeptide, which belongs to the vasoactive intestinal polypeptide/glucagon/secretin family. PACAP and its three receptor subtypes are expressed in neural tissues of the eye, including the retina, cornea and lacrimal gland, and PACAP is known to exert pleiotropic effects throughout the central nervous system. This review provides an overview of current knowledge regarding the cell protective effects, mechanisms of action and therapeutic potential of PACAP in response to several types of eye injury.

PAC1R agonist maxadilan enhances hADSC viability and neural differentiation potential

Pituitary adenylate cyclase‐activating polypeptide (PACAP) is a structurally endogenous peptide with many biological roles. However, little is known about its presence or effects in human adipose‐derived stem cells (hADSCs). In this study, the expression of PACAP type I receptor (PAC1R) was first confirmed in hADSCs. Maxadilan, a specific agonist of PAC1R, could increase hADSC proliferation as determined by Cell Counting Kit‐8 and cell cycle analysis and promote migration as shown in wound‐healing assays. Maxadilan also showed anti‐apoptotic activity in hADSCs against serum withdrawal‐induced apoptosis based on Annexin V/propidium iodide analysis and mitochondrial membrane potential assays. The anti‐apoptotic effects of maxadilan correlated with the down‐regulation of Cleaved Caspase 3 and Caspase 9 as well as up‐regulation of Bcl‐2. The chemical neural differentiation potential could be enhanced by maxadilan as indicated through quantitative PCR, Western blot and cell morphology analysis. Moreover, cytokine neural redifferentiation of hADSCs treated with maxadilan acquired stronger neuron‐like functions with higher voltage‐dependent tetrodotoxin‐sensitive sodium currents, higher outward potassium currents and partial electrical impulses as determined using whole‐cell patch clamp recordings. Maxadilan up‐regulated the Wnt/β‐catenin signalling pathway associated with dimer‐dependent activity of PAC1R, promoting cell viability that was inhibited by XAV939, and it also activated the protein kinase A (PKA) signalling pathway associated with ligand‐dependent activity of PAC1R, enhancing cell viability and neural differentiation potential that was inhibited by H‐89. In summary, these results demonstrated that PAC1R is present in hADSCs, and maxadilan could enhance hADSC viability and neural differentiation potential in neural differentiation medium.

Pituitary Adenylate Cyclase-Activating Polypeptide Is Upregulated in Murine Skin Inflammation and Mediates Transient Receptor Potential Vanilloid-1-Induced Neurogenic Edema

Although pituitary adenylate cyclase-activating polypeptide (PACAP) was described as a key vasoregulator in human skin, little is known about its expression in mouse skin. As it is important to investigate PACAP signaling in translational mouse dermatitis models, we determined its presence, regulation, and role in neurogenic and non-neurogenic cutaneous inflammatory mechanisms. The mRNA of PACAP and its specific receptor PAC1 was detected with real-time PCR in several skin regions at comparable levels. PACAP-38-immunoreactivity measured with radioimmunoassay was similar in plantar and dorsal paw skin and the ear but significantly smaller in the back skin. PACAP and PAC1 mRNA, as well as PACAP-38 and PAC1 protein expression, significantly increased in the plantar skin after intraplantar administration of capsaicin (50 μl, 100 μg ml(-1)), an agonist of the transient receptor potential vanilloid 1 (TRPV1) receptor, evoking chiefly neurogenic inflammation without inflammatory cell accumulation. Intraplantar complete Freund's adjuvant (CFA; 50 μl, 1 mg ml(-1)) also increased PACAP/PAC1 mRNA but not the PACAP peptide. Capsaicin-induced neurogenic paw edema, but not CFA-evoked non-neurogenic swelling, was significantly smaller in PACAP-deficient mice throughout a 24-hour period. To our knowledge, we provide previously unreported evidence for PACAP and PAC1 expression upregulation during skin inflammation of different mechanisms and for its pro-inflammatory function in neurogenic edema formation.

Emerging Role of PACAP as a New Potential Therapeutic Target in Major Diabetes Complications

Enduring diabetes increases the probability of developing secondary damage to numerous systems, and these complications represent a cause of morbidity and mortality. Establishing the causes of diabetes remains the key step to eradicate the disease, but prevention as well as finding therapies to ameliorate some of the major diabetic complications is an equally important step to increase life expectancy and quality for the millions of individuals already affected by the disease or who are likely to develop it before cures become routinely available. In this review, we will firstly summarize some of the major complications of diabetes, including endothelial and pancreatic islets dysfunction, retinopathy, and nephropathy, and then discuss the emerging roles exerted by the neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) to counteract these ranges of pathologies that are precipitated by the prolonged hyperglycemic state. Finally, we will describe the main signalling routes activated by the peptide and propose possible future directions to focus on developing more effective peptide-based therapies to treat the major complications associated with longstanding diabetes.

Age-related decline of autocrine pituitary adenylate cyclase-activating polypeptide impairs angiogenic capacity of rat cerebromicrovascular endothelial cells

Aging impairs angiogenic capacity of cerebromicrovascular endothelial cells (CMVECs) promoting microvascular rarefaction, but the underlying mechanisms remain elusive. PACAP is an evolutionarily conserved neuropeptide secreted by endothelial cells and neurons, which confers important antiaging effects. To test the hypothesis that age-related changes in autocrine PACAP signaling contributes to dysregulation of endothelial angiogenic capacity, primary CMVECs were isolated from 3-month-old (young) and 24-month-old (aged) Fischer 344 x Brown Norway rats. In aged CMVECs, expression of PACAP was decreased, which was associated with impaired capacity to form capillary-like structures, impaired adhesiveness to collagen (assessed using electric cell-substrate impedance sensing [ECIS] technology), and increased apoptosis (caspase3 activity) when compared with young cells. Overexpression of PACAP in aged CMVECs resulted in increased formation of capillary-like structures, whereas it did not affect cell adhesion. Treatment with recombinant PACAP also significantly increased endothelial tube formation and inhibited apoptosis in aged CMVECs. In young CMVECs shRNA knockdown of autocrine PACAP expression significantly impaired tube formation capacity, mimicking the aging phenotype. Cellular and mitochondrial reactive oxygen species production (dihydroethidium and MitoSox fluorescence, respectively) were increased in aged CMVECs and were unaffected by PACAP. Collectively, PACAP exerts proangiogenic effects and age-related dysregulation of autocrine PACAP signaling may contribute to impaired angiogenic capacity of CMVECs in aging.

PACAP38 suppresses cortical damage in mice with traumatic brain injury by enhancing antioxidant activity

The production of reactive oxygen species (ROS) and the resulting oxidative stress in mice in response to a controlled cortical impact (CCI) are typical exacerbating factors associated with traumatic brain injury (TBI). Pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) is a multifunctional peptide that has been shown to exhibit neuroprotective effects in response to a diverse range of injuries to neuronal cells. We recently reported that PACAP38 might regulate oxidative stress in mice. The aim of the present study was to determine whether PACAP38 exerts neuroprotective effects by regulating oxidative stress in mice with TBI. Reactive oxidative metabolites (ROMs) and biological antioxidant potential (BAP) were measured in male C57Bl/6 mice before and 3, 4, and 24 h after CCI. PACAP38 was administered intravenously immediately following CCI, and immunostaining for the oxidative stress indicator nitrotyrosine (NT), and for neuronal death as an indicator of the area affected by TBI, was measured 24 h later. Western blot experiments to determine antioxidant activity [as indicated by superoxide dismutase-2 (SOD-2) and glutathione peroxidase 1 (GPx-1)] in the neocortical region were also performed 3 h post-CCI. Results showed that plasma BAP and ROM levels were dramatically increased 3 h after CCI. PACAP38 suppressed the extent of TBI and NT-positive regions 24 h after CCI, and increased SOD-2 and GPx-1 levels in both hemispheres. Taken together, these results suggest that increasing antioxidant might be involving in the neuroprotective effect of PACAP38 in mice subjected to a CCI.

Pituitary adenylate cyclase activating polypeptide (PACAP) signalling exerts chondrogenesis promoting and protecting effects: implication of calcineurin as a downstream target

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

PACAP enhances barrier properties of cerebral microvessels

Cerebral microvascular endothelial cells-coming in contact with pericytes and astrocytes-constitute the structural basis of the blood-brain barrier (BBB). The continuous belt of interendothelial tight junctions (TJs) and the presence of specific transport systems, enzymes, and receptors in the brain endothelium regulate the molecular and cellular traffic into the central nervous system. Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide having several cellular protective effects. However, little is known about the effects of PACAP on the cerebral endothelium and BBB functions. Here, we show that PACAP has no significant pro-survival role in cerebral microvascular endothelial cells; however, it improves the barrier properties of the brain endothelium. PACAP induces an increase in the transendothelial electrical resistance, which is the most important marker of the tightness of the TJs. Moreover, PACAP has a protective role against glucose deprivation- and oxidative stress-induced junctional damage in microvascular brain endothelial cells.

Pituitary adenylate cyclase-activating polypeptide prevents contrast-induced nephropathy in a novel mouse model

We determined whether pituitary adenylate cyclase-activating polypeptide 38 (PACAP38) prevents contrast-induced nephropathy using human renal proximal tubule epithelial (HK-2) cells and homozygous endothelial nitric oxide synthase-deficient (eNOS(-/-)) mice as a novel in vivo model. Cultured HK-2 cells were pretreated with 10(-9)-10(-6) mol/L PACAP or vasoactive intestinal peptide (VIP) for 1 h, and then exposed to ionic (Urografin) or nonionic (iohexol) contrast media at 50 mg iodine/mL for 24 h. Male eNOS(-/-) mice received Urografin (1.85 g iodine/kg) intravenously after water deprivation for 24 h, and PACAP38 (10 μg) intraperitoneally 1 h before and 12 h after Urografin injection. Urografin and iohexol increased lactate dehydrogenase and kidney injury molecule 1 in the culture medium, induced apoptosis, and inhibited cell proliferation in HK-2 cell cultures. PACAP38 and VIP reduced these changes in a dose-dependent manner. PACAP38 was more potent than VIP. In eNOS(-/-) mice, Urografin raised serum creatinine and cystatin C levels, caused renal tubule damage, induced apoptosis, and promoted neutrophil influx. Urografin also increased kidney protein levels of proinflammatory cytokines, and kidney mRNA levels of proinflammatory cytokines, kidney injury biomarkers, and enzymes responsible for reactive oxygen and nitrogen species. PACAP38 significantly reduced these Urografin-induced changes in eNOS(-/-) mice. This study shows that both Urografin and iohexol are toxic to HK-2 cells, but Urografin is more toxic than iohexol. Urografin causes acute kidney injury in eNOS(-/-) mice. PACAP38 protects HK-2 cells and mouse kidneys from contrast media and is a potential therapeutic agent for contrast-induced nephropathy.

Examination of calcium-binding protein expression in the inner ear of wild-type, heterozygous and homozygous pituitary adenylate cyclase-activating polypeptide (PACAP)-knockout mice in kanamycin-induced ototoxicity

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide with diverse biological effects. It also occurs and exerts protective effects in sensory organs; however, little is known about its effects in the auditory system. Recently, we have shown that PACAP protects cochlear cells against oxidative-stress-induced apoptosis and homozygous PACAP-deficient animals show stronger expression of Ca(2+)-binding proteins in the hair cells of the inner ear, but there are no data about the consequences of the lack of endogenous PACAP in different ototoxic insults such as aminoglycoside-induced toxicity. In this study, we examined the effect of kanamycin treatment on Ca(2+)-binding protein expression in hair cells of wild-type, heterozygous and homozygous PACAP-deficient mice. We treated 5-day-old mice with kanamycin, and 2 days later, we examined the Ca(2+)-binding protein expression of the hair cells with immunohistochemistry. We found stronger expression of Ca(2+)-binding proteins in the hair cells of control heterozygous and homozygous PACAP-deficient mice compared with wild-type animals. Kanamycin induced a significant increase in Ca(2+)-binding protein expression in wild-type and heterozygous PACAP-deficient mice, but the baseline higher expression in homozygous PACAP-deficient mice did not show further changes after the treatment. Elevated endolymphatic Ca(2+) is deleterious for the cochlear function, against which the high concentration of Ca(2+)-buffers in hair cells may protect. Meanwhile, the increased immunoreactivity of Ca(2+)-binding proteins in the absence of PACAP provide further evidence for the important protective role of PACAP in ototoxicity, but further investigations are necessary to examine the exact role of endogenous PACAP in ototoxic insults.

Effect of PACAP in central and peripheral nerve injuries

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

PACAP immunoreactivity in human malignant tumor samples and cardiac diseases

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide having important roles in various physiological processes. Recent trends in PACAP research point to the clinical introduction of PACAP or its analogs/fragments possibly in the near future. Recently, we have shown the presence of PACAP in human plasma, milk, placenta, and follicular fluid samples. However, relatively few data are available on PACAP in human tissues from patients with different disorders. The aim of the present study was to determine, by radioimmunoassay, the tissue level of PACAP38-like immunoreactivity (LI) and PACAP27-LI in different primary non-small cell lung cancer, colon tumor samples, and in cardiac muscle samples from patients suffering from ischemic heart disease and valvular disorders. We also labeled the PAC1 receptors in human cardiac cells. All samples showed significantly higher PACAP38-LI compared with PACAP27-LI. We found significantly lower levels of PACAP38-LI and PACAP27-LI in tumoral and peripheral samples compared with normal healthy tissue in both lung and colon cancers. Further investigations are necessary to describe the exact function of PACAP in oncogenesis. We showed that PACAP38-LI and PACAP27-LI are significantly higher in ischemic heart diseases compared with valvular abnormalities, suggesting that PACAP might play a role in ischemic heart disorders.

Effects of pituitary adenylate cyclase activating polypeptide in the urinary system, with special emphasis on its protective effects in the kidney

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widespread neuropeptide with diverse effects in the nervous system and peripheral organs. One of the most well-studied effects of PACAP is its cytoprotective action, against different harmful stimuli in a wide variety of cells and tissues. PACAP occurs in the urinary system, from the kidney to the lower urinary tract. The present review focuses on the nephroprotective effects of PACAP and summarizes data obtained regarding the protective effects of PACAP in different models of kidney pathologies. In vitro data show that PACAP protects tubular cells against oxidative stress, myeloma light chain, cisplatin, cyclosporine-A and hypoxia. In vivo data provide evidence for its protective effects in ischemia/reperfusion, cisplatin, cyclosporine-A, myeloma kidney injury, diabetic nephropathy and gentamicin-induced kidney damage. Results accumulated on the renoprotective effects of PACAP suggest that PACAP is an emerging candidate for treatment of human kidney pathologies.

Role of PACAP in Female Fertility and Reproduction at Gonadal Level - Recent Advances

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic neuropeptide, first isolated from hypothalamic extracts, but later shown in peripheral organs, such as endocrine glands, gastrointestinal system, cardiovascular system, and reproductive organs. PACAP plays a role in fertility and reproduction. Numerous studies report on the gonadal regulatory effects of PACAP at hypothalamo-hypophyseal levels. However, the local effects of PACAP at gonadal levels are also important. The present review summarizes the effects of PACAP in the ovary. PACAP and its receptors are present in the ovary, and PACAP plays a role in germ cell migration, meiotic division, follicular development, and atresia. The autocrine-paracrine hormonal effects seem to play a regulatory role in ovulation, luteinization, and follicular atrophy. Altogether, PACAP belongs to the ovarian regulatory peptides.

Mice deficient in pituitary adenylate cyclase activating polypeptide (PACAP) show increased susceptibility to in vivo renal ischemia/reperfusion injury

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with well-known cytoprotective effects. We have reported earlier that PACAP decreases mortality and the degree of tubular atrophy in a rat model of renal ischemia/reperfusion injury. Recently, we have shown that kidney cultures isolated from PACAP deficient mice show increased susceptibility to renal oxidative stress. Based on these previous studies, we raised the question whether PACAP deficient mice display increased sensitivity to in vivo kidney ischemia/reperfusion. PACAP⁻/⁻ mice underwent 45 or 60 min of renal ischemia followed by 2 weeks reperfusion. Kidneys were processed for histological analysis. Sections stained with PAS-haematoxylin were graded for the following parameters: degree of tubular dilation, Bowmann's capsule dilation, lymphocyte and macrophage infiltration, thyroidization and the disappearance of the PAS-positive glycocalyx from under the brush border. In other sets of experiments, tissue cytokine expression and the level of the endogenous antioxidant superoxide dismutase (SOD) were also determined after 60 min ischemia/reperfusion. Our results show that while intact kidneys were not different between wild-type and PACAP deficient mice, marked differences were observed in the histological structures in groups that underwent ischemia/reperfusion. PACAP deficient mice had a worse histological outcome, with significantly higher histological scores for all tested parameters. Cytokine expression was also markedly different between wild-type and PACAP deficient mice. In addition, the level of SOD was significantly lower in PACAP⁻/⁻ animals after ischemia/reperfusion. In conclusion, the lack of endogenous PACAP leads to higher susceptibility to in vivo renal ischemia/reperfusion, suggesting that PACAP has an endogenous renoprotective effect.

Effects of PACAP on oxidative stress-induced cell death in rat kidney and human hepatocyte cells

Oxidative stress plays an important role in various renal and hepatic pathologies, and reduction of oxidative stress-induced processes is an important protective strategy in tissues of diverse origins against harmful stimuli. Pituitary adenylate cyclase activating polypeptide (PACAP) is a well-known cytotrophic and cytoprotective peptide. PACAP promotes cell survival in numerous cells and tissues exposed to various stimuli. Protective effects of PACAP have been shown in the kidney, but it is not known whether PACAP is protective against oxidative stress in renal cells. Little is known about the effects of PACAP in the liver. The aim of the present study was to investigate whether PACAP is protective against oxidative stress in primary rat kidney cell culture and whether PACAP has any effect on cell survival in human WRL-68 hepatocytes and HEP-G2 hepatocellular carcinoma cells subjected to oxidative stress. Cells were exposed to various concentrations of H(2)O(2) with or without PACAP co-treatment and cell viability was evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test (MTT). We found that oxidative stress induced a significant decrease in cell viability in both cell lines. PACAP could dose-dependently increase the percentage of living cells in kidney cells, but it failed to do so in hepatocytes. Given the survival-promoting effects of PACAP against oxidative stress in rat kidney, we conducted a further experiment to determine whether PACAP influences the markers of oxidative stress in vivo. We have proven earlier that PACAP was effective in kidney ischemia/reperfusion injury in vivo. In the present study, we determined the levels of the oxidative stress marker malondialdehyde and the activity of the scavenger molecules glutathione (GSH) and superoxide dismutase (SOD) following kidney ischemia/reperfusion in rats. We found that PACAP significantly increased the level of GSH and counteracted the marked reduction of SOD activity after ischemia/reperfusion in vivo. In summary, the present study showed that while PACAP was able to significantly increase the cell survival in primary kidney cell cultures exposed to oxidative stress, possibly involving interaction with the endogenous scavenger system, it failed to influence the viability of normal or cancerous hepatocytes.

Changes in the expression of pituitary adenylate cyclase-activating polypeptide in the human placenta during pregnancy and its effects on the survival of JAR choriocarcinoma cells

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with survival-promoting actions, has been observed in endocrine organs and is thought to play a role in reproductive functions, including pregnancy. PACAP occurs in two forms, 27 and 38 amino acid residues, with PACAP38 being the predominant form in human tissues. In the present study, we determined the concentrations of PACAP38 and PACAP27 in first-trimester and full-term human placentas using radioimmunoassay. We found high levels of PACAP38 and lower levels of PACAP27 in different parts of the full-term human placenta. PACAP38 content increased in the placenta during pregnancy, both on the maternal side and on the fetal side. The effects of PACAP on the survival of JAR human choriocarcinoma cells were investigated using flow cytometry and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) cell viability assay in cells exposed to the widely used chemotherapeutic agent methotrexate (MTX). It was found that PACAP neither influenced the survival of JAR cytotrophoblast cells nor affected cellular response to the death-inducing effect of the chemotherapeutic agent MTX. The present observations further support the significance of PACAP in the human placenta. The observation that PACAP did not influence the effects of MTX may have future clinical importance, showing that PACAP does not decrease the effects of certain chemotherapeutic agents.

Comparison of intestinal warm ischemic injury in PACAP knockout and wild-type mice

Pituitary adenylate cyclase-activating polypeptide (PACAP) is present in the gastrointestinal tract and plays a central role in the intestinal physiology, mainly in the secretion and motility. The aim of our study was to compare the ischemic injury in wild-type and PACAP-38 knockout mice following warm mesenteric small bowel ischemia. Warm ischemia groups were designed with occlusion of superior mesenteric artery for 1, 3, and 6 h in wild-type (n = 10 in each group) and PACAP-38 knockout (n = 10 in each group) mice. Small bowel biopsies were collected after laparotomy (control) and at the end of the ischemia periods. To determine oxidative stress parameters, malondialdehyde (MDA), reduced glutathione (GSH), and superoxide dismutase (SOD) were measured. Tissue damage was analyzed by qualitative and quantitative methods on hematoxylin/eosin-stained sections. In PACAP-38 knockout animals, tissue MDA increased significantly after 3 and 6 h ischemia (133.97 ± 6,2; 141.86 ± 5,8) compared to sham-operated (100.92 ± 3,6) and compared to wild-type results (112.8 ± 2,1; 118.4 ± 1.03 μmol/g, p < 0.05). Meanwhile, tissue concentration of GSH and activity of SOD decreased significantly in knockout mice compared to wild-type form (GSH, 795.97 ± 10.4; 665.1 ± 8,8 vs. 893.23 ± μmol/g; SOD, 94.4 ± 1.4; 81.2 ± 3.9 vs. 208.09 ± 3,7 IU/g). Qualitative and quantitative histological results showed destruction of the mucous, submucous layers, and crypts in knockout mice compared to wild-type tissues. These processes correlated with the warm ischemia periods. Our present results propose an important protective effect of endogenous PACAP-38 against intestinal warm ischemia, which provides basis for further investigation to elucidate the mechanism of this protective effect.

Effects of PACAP on mitochondrial apoptotic pathways and cytokine expression in rats subjected to renal ischemia/reperfusion

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with highly efficient cytoprotective actions. Its neuroprotective effects are well-known, but PACAP is able to exert similar actions in non-neuronal cells. Recently, we have shown that PACAP prolongs renal ischemic time, decreases mortality, and attenuates tubular degeneration in a rat model of renal ischemia/reperfusion, but the mechanism of renoprotection is not yet known. Therefore, the aim of the present study was to obtain further insight into the renoprotective effects of PACAP by examining its direct effects of PACAP on mitochondrial permeability transition in vitro and on the expression of the anti-apoptotic Bcl-2 and cytokines/chemokines in kidney tissues following 45 and 60 min renal ischemia and reperfusion in vivo. We found that PACAP did not have any direct effect on mitochondrial permeability transition. Cytokine array revealed that the expression of a few cytokines/chemokines was strongly increased after ischemia/reperfusion, which was ameliorated by PACAP treatment. Furthermore, in rats subjected to renal ischemia, PACAP treatment counteracted the ischemia/reperfusion-induced decrease of the anti-apoptotic Bcl-2, both after 45 and 60 min ischemia, as analyzed by Western blot. In summary, we showed that PACAP could attenuate tissue injury involving both anti-inflammatory and anti-apoptotic effects, but not directly acting on mitochondrial permeability transition.

PACAP and VIP affect NF1 expression in rat malignant peripheral nerve sheath tumor (MPNST) cells

In our previous study we have identified PACAP, VIP and their receptors in rat malignant peripheral nerve sheath tumor (MPNST) cells, thus showing anti-apoptotic roles. Recently it has been shown that the tumor suppressor neurofibromin, encoded by the Neurofibromatosis type I (NF1) gene, promotes MPNST cells sensitivity to apoptosis after serum withdrawal. In the present study we investigated whether PACAP or VIP negatively regulate NF1 expression under normal or serum-dependent pro-apoptotic culture conditions. Results indicated that serum itself significantly influenced gene and protein levels. In fact, the low NF1 levels of cells cultured in normal serum-containing medium were remarkably increased in cells switched to low- or no-serum after 24h and 48 h. Treatment with 100 nM PACAP or VIP did not affect NF1 expression when using normal amounts of serum, whereas it significantly inhibited transcript and protein levels both in low- or no-serum cultured cells. In particular, PACAP reduced NF1 levels already after 24h in low-serum cultured cells, while VIP showed a similar effect only after serum deprivation. However, both PACAP and VIP downregulated gene and protein levels within 48 h either in low-dose and serum-starved cells. Results were confirmed by fluorescence microscopy, showing that 100 nM PACAP or VIP attenuated neurofibromin cytoplasmic localization only in low- or no-serum cultured cells. The present study provides a comprehensive analysis of both neuropeptides effect on NF1 expression in normal, low- or serum-starved MPNST cells, ameliorating the hypothesis that resistance to apoptosis in serum-deprived cells might be correlated to PACAP-/VIP-induced NF1 inhibition.

PACAP stimulation of maturational gonadotropin secretion in goldfish involves extracellular signal-regulated kinase, but not nitric oxide or guanylate cyclase, signaling

In goldfish, nitric oxide synthase (NOS) immunoreactivity is present in gonadotropes and extracellular signal-regulated protein kinase (ERK) mediates GnRH stimulation of gonadotropin release and synthesis. In this study, we tested the possible involvement of nitric oxide (NO) and ERK in mediating PACAP-stimulated maturational gonadotropin (GTH-II) release from primary cultures of dispersed goldfish pituitary cells. In static incubation experiments, PACAP-induced GTH-II release was unaffected by two inhibitors of NOS synthase, AGH and 1400W; whereas addition of a NO donor, SNAP, elevated GTH-II secretion. In perifusion experiments, neither NOS inhibitors (AGH, 1400W and 7-Ni) nor NO scavengers (PTIO and rutin hydrate) attenuated the GTH-II response to pulse applications of PACAP. In addition, the GTH-II responses to PACAP and the NO donor SNP were additive while PTIO blocked SNP action. Although dibutyryl cGMP increased GTH-II secretion in static incubation, inhibition of guanylate cyclase (GC), a known down-stream target for NO signaling, did not reduce the GTH-II response to pulse application of PACAP. On the other hand, GTH-II responses to PACAP in perifusion were attenuated in the presence of two inhibitors of ERK kinase (MEK), U 0126 and PD 98059. These results suggest that although increased availability of NO and cGMP can lead to increased GTH-II secretion, MEK/ERK signaling, rather than NOS/NO/GC activation, mediates PACAP action on GTH-II release in goldfish.

PACAP ameliorates oxidative stress in the chicken inner ear: an in vitro study

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide. Numerous studies prove that PACAP has neuroprotective effects in diverse neuronal systems in vitro and in vivo. The involvement of PACAP in visual and olfactory sensory processing has also been documented, but little is known about its effects in the auditory system. The presence of PACAP and its receptor, the specific PAC1 receptor, has been shown in the cochlea and in brain structures involved in auditory pathways. The aim of the present study was to investigate whether PACAP is protective in cochlear oxidative stress-induced cell death, which is known to play a role in several ototoxic insults. Chicken cochlear cells were exposed to 1mM H(2)O(2), which resulted in a marked reduction of cell viability and a parallel increase of apoptotic and necrotic cells assessed by MTT test, annexin V/propidium iodide flow cytometry and JC-1 apoptosis assay. Co-incubation with 100nM PACAP increased cell viability and reduced the percentage of apoptotic cells. Furthermore, oxidative stress increased the activation of caspase-3, while simultaneous PACAP treatment reduced it. In summary, our present results demonstrate that PACAP effectively protects cochlear cells against oxidative stress-induced apoptotic cell death.

Mice deficient in pituitary adenylate cyclase activating polypeptide display increased sensitivity to renal oxidative stress in vitro

Pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide, showing widespread occurrence in the nervous system and also in peripheral organs. The neuroprotective effects of PACAP are well-established in different neuronal systems against noxious stimuli in vitro and in vivo. Recently, its general cytoprotective actions have been recognized, including renoprotective effects. However, the effect of endogenous PACAP in the kidneys is not known. The main aim of the present study was to investigate whether the lack of this endogenous neuropeptide influences survival of kidney cells against oxidative stress. First, we determined the presence of endogenous PACAP from mouse kidney homogenates by mass spectrometry and PACAP-like immunoreactivity by radioimmunoassay. Second, primary cultures were isolated from wild type and PACAP deficient mice and cell viability was assessed following oxidative stress induced by 0.5, 1.5 and 3mM H(2)O(2). Our mass spectrometry and radioimmunoassay results show that PACAP is endogenously present in the kidney. The main part of our study revealed that the sensitivity of cells from PACAP deficient mice was increased to oxidative stress: both after 2 or 4h of exposure, cell viability was significantly reduced compared to that from control wild type mice. This increased sensitivity of kidneys from PACAP deficient mice could be counteracted by exogenously given PACAP38. These results show, for the first time, that endogenous PACAP protects against oxidative stress in the kidney, and that PACAP may act as a stress sensor in renal cells. These findings further support the general cytoprotective nature of this neuropeptide.