Anti-apoptotic actions of vasopressin in H32 neurons involve MAP kinase transactivation and Bad phosphorylation

The role of vasopressin V1A and oxytocin OTR receptors in protective effects of arginine vasopressin against H2O2-induced oxidative stress in H9C2 cells

BACKGROUND

Oxidative stress, has been shown to play an important role in the pathophysiology of cardiac remodelling and heart failure. The aim of study is effect of arginine vasopressin (AVP) on apoptosis of cardiomyocyte via its receptors.

MATERIALS AND METHODS

The cell viability effect of AVP in H9C2 cardiomyocytes was assayed using the MTT method. The transcription and translation level of apoptosis genes (Bax, Bcl-2, caspase-3) were discovered with qRT-PCR and western blotting.

RESULTS

The results showed that vasopressin could reduce apoptosis in cardiomyocytes cell line through downregulation of caspase-3, BAX and upregulation of Bcl-2 (p < .001). Also, there was a decrease in anti-apoptosis effect of vasopressin when V1A and OTR receptors were blocked with their antagonists.

DISCUSSION

These results suggest that activation of V1A and OTR receptors in H9C2 cells mediate protective effect of vasopressin via regulating apoptosis marker that lead to cell survival under conditions of stress oxidative.Key pointAVP may contribute to the improvement of heart ischaemia through its actions on V1A and OTR receptors.

The promiscuity of the oxytocin-vasopressin systems and their involvement in autism spectrum disorder

Oxytocin and vasopressin systems have been studied separately in autism spectrum disorder (ASD). Here, we provide evidence from an evolutionary and neuroscience perspective about the shared mechanisms and the common roles in regulating social behaviors. We first discuss findings on the evolutionary history of oxytocin and vasopressin ligands and receptors that highlight their common origin and clarify the evolutionary background of the crosstalk between them. Second, we conducted a comprehensive review of the increasing evidence for the role of both neuropeptides in regulating social behaviors. Third, we reviewed the growing evidence on the associations between the oxytocin/vasopressin systems and ASD, which includes oxytocin and vasopressin dysfunction in animal models of autism and in human patients, and the impact of treatments targeting the oxytocin or the vasopressin systems in children and in adults. Here, we highlight the potential of targeting the oxytocin/vasopressin systems to improve social deficits observed in ASD and the need for further investigations on how to transfer these research innovations into clinical applications.

Terlipressin protects intestinal epithelial cells against oxygen-glucose deprivation/re-oxygenation injury via the phosphatidylinositol 3-kinase pathway

Intestinal ischemia/reperfusion (I/R) injury is associated with a high morbidity and mortality. Vasopressin is administered to critically ill patients with potential intestinal I/R. However, the impacts of vasopressin on intestinal epithelia under ischemic/anoxic conditions remain unclear. The aim of the present study was to evaluate the effects of terlipressin, a highly selective vasopressin V1 receptor agonist, on oxygen and glucose deprivation/re-oxygenation (OGD/R)-induced damage in intestinal epithelial cells (IEC-6). IEC-6 cells were subjected to OGD for 4 h, followed by 4 h re-oxygenation. Terlipressin was incubated with cells for 4 h following OGD. Following OGD/R, IEC-6 cell viability, proliferation and apoptosis, as well as cell cycle dynamics, were assessed and the levels of tumor necrosis factor (TNF)-α and 15-F2t-isoprostane in the culture medium were measured. In addition, wortmannin, a specific phosphatidylinositol 3-kinase (PI3K) inhibitor, was administrated to investigate the mechanism of terlipressin action. The results demonstrated that IEC-6 cell viability and proliferation decreased, and cell apoptosis increased, following OGD/R. However, IEC-6 cell cycle dynamics did not significantly change 4 h after OGD. Incubation with 25 nM terlipressin significantly improved cell viability, proliferation and apoptosis. Furthermore, terlipressin inhibited the secretion of TNF-α and 15-F2t-isoprostane from IEC-6 cells following OGD/R. The aforementioned effects of terlipressin were completely abolished following the application of 2 µM wortmannin. Therefore, the current study demonstrated that terlipressin administration following OGD attenuates OGD/R-induced cell damage via the PI3K signaling pathway. These results may help physicians to better understand and more effectively use terlipressin in a clinical setting.

An electrocardiographic, molecular and biochemical approach to explore the cardioprotective effect of vasopressin and milrinone against phosphide toxicity in rats

The present study was conducted to identify the protective effect of vasopressin (AVP) and milrinone on cardiovascular function, mitochondrial complex activities, cellular ATP reserve, oxidative stress, and apoptosis in rats poisoned by aluminum phosphide (AlP). Rats were divided into five groups (n = 12) including control, AlP (12.5 mg/kg), AlP + AVP (2.0 Units/kg), AlP + milrinone (0.25 mg/kg) and AlP + AVP + milrinone. After treatment, the animals were connected to an electronic cardiovascular monitoring device to monitor electrocardiographic (ECG) parameter. Finally, oxidative stress biomarkers, mitochondrial complex activities, ADP/ATP ratio and apoptosis were evaluated on the heart tissues. Results indicated that AlP administration induced ECG abnormalities along with a decline in blood pressure and heart rate. AVP and milrinone significantly ameliorated these changes in all treated groups. Considerable protective effects on oxidative stress biomarkers, complex IV activity, ADP/ATP ratio and caspase-3 and -9 activities in treated groups were also found. These findings were supported by flow cytometry assay of cardiomyocytes. In conclusion, administration of AVP and milrinone, not only improve cardiovascular functions in AlP poisoned rats in the short time, but after a long time can also restore mitochondrial function and ATP level and reduce the oxidative damage, which prevent cardiomyocytes from entering the apoptotic phase.

Neonatal maternal separation up-regulates protein signalling for cell survival in rat hypothalamus

We have previously reported that in response to early life stress, such as maternal hyperthyroidism and maternal separation (MS), the rat hypothalamic vasopressinergic system becomes up-regulated, showing enlarged nuclear volume and cell number, with stress hyperresponsivity and high anxiety during adulthood. The detailed signaling pathways involving cell death/survival, modified by adverse experiences in this developmental window remains unknown. Here, we report the effects of MS on cellular density and time-dependent fluctuations of the expression of pro- and anti-apoptotic factors during the development of the hypothalamus. Neonatal male rats were exposed to 3 h-daily MS from postnatal days 2 to 15 (PND 2-15). Cellular density was assessed in the hypothalamus at PND 21 using methylene blue staining, and neuronal nuclear specific protein and glial fibrillary acidic protein immunostaining at PND 36. Expression of factors related to apoptosis and cell survival in the hypothalamus was examined at PND 1, 3, 6, 9, 12, 15, 20 and 43 by Western blot. Rats subjected to MS exhibited greater cell-density and increased neuronal density in all hypothalamic regions assessed. The time course of protein expression in the postnatal brain showed: (1) decreased expression of active caspase 3; (2) increased Bcl-2/Bax ratio; (3) increased activation of ERK1/2, Akt and inactivation of Bad; PND 15 and PND 20 were the most prominent time-points. These data indicate that MS can induce hypothalamic structural reorganization by promoting survival, suppressing cell death pathways, increasing cellular density which may alter the contribution of these modified regions to homeostasis.

Stress responsiveness of the hypothalamic-pituitary-adrenal axis: age-related features of the vasopressinergic regulation

The hypothalamic-pituitary-adrenal (HPA) axis plays a key role in adaptation to environmental stresses. Parvicellular neurons of the hypothalamic paraventricular nucleus secrete corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) into pituitary portal system; CRH and AVP stimulate adrenocorticotropic hormone (ACTH) release through specific G-protein-coupled membrane receptors on pituitary corticotrophs, CRHR1 for CRH and V1b for AVP; the adrenal gland cortex secretes glucocorticoids in response to ACTH. The glucocorticoids activate specific receptors in brain and peripheral tissues thereby triggering the necessary metabolic, immune, neuromodulatory, and behavioral changes to resist stress. While importance of CRH, as a key hypothalamic factor of HPA axis regulation in basal and stress conditions in most species, is generally recognized, role of AVP remains to be clarified. This review focuses on the role of AVP in the regulation of stress responsiveness of the HPA axis with emphasis on the effects of aging on vasopressinergic regulation of HPA axis stress responsiveness. Under most of the known stressors, AVP is necessary for acute ACTH secretion but in a context-specific manner. The current data on the AVP role in regulation of HPA responsiveness to chronic stress in adulthood are rather contradictory. The importance of the vasopressinergic regulation of the HPA stress responsiveness is greatest during fetal development, in neonatal period, and in the lactating adult. Aging associated with increased variability in several parameters of HPA function including basal state, responsiveness to stressors, and special testing. Reports on the possible role of the AVP/V1b receptor system in the increase of HPA axis hyperactivity with aging are contradictory and requires further research. Many contradictory results may be due to age and species differences in the HPA function of rodents and primates.

Vasopressin inhibits apoptosis in renal collecting duct cells

The peptide hormone arginine vasopressin (AVP) plays a critical role in regulating salt and water transport in the mammalian kidney. Recent studies have also demonstrated that AVP can promote cell survival in neuronal cells through V1 receptors. The current study addresses whether AVP can inhibit apoptosis in kidney collecting duct cells via V2 receptors and also explores the downstream signaling pathways regulating this phenomenon. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling analysis and caspase cleavage assays demonstrated that 1-desamino-8-d-arginine vasopressin (dDAVP) inhibited apoptosis induced by various agents (staurosporine, actinomycin D, and cycloheximide) in cultured mouse cortical collecting duct cells (mpkCCD). Incubation with dDAVP also inhibited apoptosis induced by the phosphatidylinositol 3-kinase (PI3K) pathway inhibitor LY294002, suggesting that the antiapoptotic effects of dDAVP are largely independent of PI3K signaling. The V2 receptor antagonist SR121463 completely abolished the antiapoptotic effects of dDAVP. In addition, incubation with 8-cpt-cAMP, a cell-permeable analog of cAMP, reproduced the antiapoptotic effects of dDAVP. Both dDAVP and 8-cpt-cAMP increased phosphorylation of proapoptotic Bcl-2 family members Bad and Bok. Bad phosphorylation at Ser-112 and Ser-155 is known to inhibit its proapoptotic activity. Preincubation with H89 blocked dDAVP-induced phosphorylation of both Bad and Bok, suggesting dependence on protein kinase A (PKA). This study provides evidence that AVP can inhibit apoptosis through the V2 receptor and downstream cAMP-mediated pathways in mammalian kidney. The antiapoptotic action of AVP may be relevant to a number of physiological and pathophysiological conditions including osmotic tolerance in the inner medulla, escape from AVP-induced antidiuresis, and polycystic kidney disease.

Differential contribution of hypothalamic MAPK activity to anxiety-like behaviour in virgin and lactating rats

The c-Raf – MEK1/2 – ERK1/2 mitogen-activated protein kinase (MAPK) intracellular signalling cascade in neurons plays important roles in the control of a variety of behaviours, including social behaviours and anxiety. These roles partially overlap with those described for oxytocin (OXT), and it has been shown that OXT activates the MAPK pathway in the hypothalamus (of male), and hippocampus (of female) rats. Here, by combining behavioural (light/dark box) and biochemical analyses (western blotting), we tested two hypotheses: (i) that OXT is anxiolytic within the hypothalamus of females, and (ii) that this effect, as well as that of lactation-associated anxiolysis, depends on the recruitment of the MAPK pathway. We found that, when injected bilaterally into the hypothalamic paraventricular nucleus (PVN), OXT decreased anxiety-like behaviour in virgins, and that this effect depended on phosphorylation of MEK1/2. MAPK pathway activation in lactation was evident by high phosphorylated (p) MEK1/2 levels, and nuclear translocation of ERK1. The high pMEK1/2 levels were necessary for the anxiolytic phenotype typically observed during lactation. Interestingly, exogenous OXT in lactating rats reduced pMEK1/2 levels without a concomitant effect on anxiety, indicating that OXT receptor activation can lead to recruitment of additional intracellular pathways to modulate MEK activity. Still other pathways could include MEK, but without subsequent activation of ERK, as we did not observe any increase in OXT-induced ERK phosphorylation. Together the results demonstrate that the MAPK pathway, especially MEK1/2, is critically involved in the regulation of anxiety-like behaviour in female rats.

17β-Estradiol is required for the sexually dimorphic effects of repeated binge-pattern alcohol exposure on the HPA axis during adolescence

Alcohol consumption during adolescence has long-term sexually dimorphic effects on anxiety behavior and mood disorders. We have previously shown that repeated binge-pattern alcohol exposure increased the expression of two critical central regulators of stress and anxiety, corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP), in adolescent male rats. By contrast, there was no effect of alcohol on these same genes in adolescent females. Therefore, we tested the hypothesis that 17β-estradiol (E₂), the predominant sex steroid hormone in females, prevents alcohol-induced changes in CRH and AVP gene expression in the paraventricular nucleus (PVN) of the hypothalamus. To test this hypothesis, postnatal day (PND) 26 females were ovariectomized and given E₂ replacement or cholesterol as a control. Next, they were given an alcohol exposure paradigm of 1) saline alone, 2) acute (single dose) or 3) a repeated binge-pattern. Our results showed that acute and repeated binge-pattern alcohol treatment increased plasma ACTH and CORT levels in both E₂- and Ch-treated groups, however habituation to repeated binge-pattern alcohol exposure was evident only in E₂-treated animals. Further, repeated binge-pattern alcohol exposure significantly decreased CRH and AVP mRNA in Ch-, but not E₂-treated animals, which was consistent with our previous observations in gonad intact females. We further tested the effects of E₂ and alcohol treatment on the activity of the wild type CRH promoter in a PVN-derived neuronal cell line. Alcohol increased CRH promoter activity in these cells and concomitant treatment with E₂ completely abolished the effect. Together our data suggest that E₂ regulates the reactivity of the HPA axis to a repeated stressor through modulation of the habituation response and further serves to maintain normal steady state mRNA levels of CRH and AVP in the PVN in response to a repeated alcohol stressor.

Dynamics of the G protein-coupled vasopressin V2 receptor signaling network revealed by quantitative phosphoproteomics

G protein-coupled receptors (GPCRs) regulate diverse physiological processes, and many human diseases are due to defects in GPCR signaling. To identify the dynamic response of a signaling network downstream from a prototypical G(s)-coupled GPCR, the vasopressin V2 receptor, we have carried out multireplicate, quantitative phosphoproteomics with iTRAQ labeling at four time points following vasopressin exposure at a physiological concentration in cells isolated from rat kidney. A total of 12,167 phosphopeptides were identified from 2,783 proteins, with 273 changing significantly in abundance with vasopressin. Two-dimensional clustering of phosphopeptide time courses and Gene Ontology terms revealed that ligand binding to the V2 receptor affects more than simply the canonical cyclic adenosine monophosphate-protein kinase A and arrestin pathways under physiological conditions. The regulated proteins included key components of actin cytoskeleton remodeling, cell-cell adhesion, mitogen-activated protein kinase signaling, Wnt/β-catenin signaling, and apoptosis pathways. These data suggest that vasopressin can regulate an array of cellular functions well beyond its classical role in regulating water and solute transport. These results greatly expand the current view of GPCR signaling in a physiological context and shed new light on potential roles for this signaling network in disorders such as polycystic kidney disease. Finally, we provide an online resource of physiologically regulated phosphorylation sites with dynamic quantitative data (http://helixweb.nih.gov/ESBL/Database/TiPD/index.html).

HPA axis responsiveness to stress: implications for healthy aging

The major neuroendocrine response mediating stress adaptation is activation of the hypothalamic pituitary adrenal axis, with stimulation of corticotropin releasing hormone (CRH) and vasopressin (VP) from parvocellular neurons of the hypothalamic paraventricular nucleus, leading to stimulation of pituitary ACTH secretion and increases in glucocorticoid secretion from the adrenal cortex. Basal production and transient increases during stress of glucocorticoids and its hypothalamic regulators are essential for neuronal plasticity and normal brain function. While activation of the HPA axis is essential for survival during stress, chronic exposure to stress hormones can predispose to psychological, metabolic and immune alterations. Thus, prompt termination of the stress response is essential to prevent negative effects of inappropriate levels of CRH and glucocorticoids. This review addresses the regulation of HPA axis activity with emphasis on the mechanisms of termination of CRH transcription, which is a critical step in this process. In addition, the actions by which glucocorticoids, CRH and VP can affect the aging process will be discussed.

Vasopressin protects hippocampal neurones in culture against nutrient deprivation or glutamate-induced apoptosis

Vasopressin (VP) secreted within the brain modulates neuronal function by acting as a neurotransmitter. Recent studies show that VP prevents serum deprivation-induced apoptosis in the neuronal cell line, H32. To determine whether VP is anti-apoptotic in hippocampal neurones, primary cultures of these neurones were used to examine the effect of VP on neuronal culture supplement (B27) deprivation-, or glutamate-induced apoptosis, and the signalling pathways mediating the effects. Removal of B27 supplement from the culture medium for 24 h or the addition of glutamate (3-10μm) decreased neuronal viability (P<0.05) and increased Tdt-mediated dUTP nick-end labelling (TUNEL) staining and caspase-3 activity (P<0.05), which is consistent with apoptotic cell death. VP (10 nm) reduced B27 deprivation- or glutamate-induced cell death (P<0.05). These anti-apoptotic effects of VP were completely blocked by a V1 but not a V2 receptor antagonist, indicating that they are mediated via V1 VP receptors. The anti-apoptotic effect of VP in neurones involves activation of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and inositol trisphosphate/protein kinase B (Akt) signalling pathways. This was shown by the transient increases in phospho-ERK and phospho-Akt after incubation with VP revealed by western blot analyses, and the ability of specific inhibitors to reduce the inhibitory effect of VP on caspase-3 activity and TUNEL staining by 70% and 35%, respectively (P<0.05). These studies demonstrate that VP has anti-apoptotic actions in hippocampal neurones, an effect that is mediated by the MAPK/ERK and phosphatidylinositol-3 kinase/Akt signalling pathways. The ability of VP to reduce nutrient deprivation or glutamate overstimulation-induced neuronal death suggests that VP acts as a neuroprotective agent within the brain.

ERK-1 MAP kinase prevents TNF-induced apoptosis through bad phosphorylation and inhibition of Bax translocation in HeLa Cells

Extracellular signal-regulated kinase (ERK) 1/2 signaling is involved in tumor cell survival through the regulation of Bcl-2 family members. To explore this further and to demonstrate the central role of the mitochondria in the ERK1/2 pathway we used the HeLa cellular model where apoptosis was induced by tumor necrosis factor (TNF) and cycloheximide (CHX). We show that HeLa cells overexpressing ERK-1 displayed resistance to TNF and CHX. HeLa cells overexpressing a kinase-deficient form of ERK-1 (K71R) were more sensitive to TNF and CHX. In the ERK-1 cells, Bad was phosphorylated during TNF + CHX treatment. In the HeLa wt cells and in the K71R clones TNF and CHX decreased Bad phosphorylation. ERK-1 cells treated with TNF and CHX did not release cytochrome c from the mitochondria. By contrast, HeLa wt and K71R clones released cytochrome c. Bax did not translocate to the mitochondria in ERK-1 cells treated with TNF + CHX. Conversely, HeLa wt and K71R clones accumulated Bax in the mitochondria. In the HeLa wt cells and in both ERK-1 transfectants Bid was cleaved and accumulated in the mitochondria. The caspase-8 inhibitor IETD-FMK and the mitochondrial membrane permeabilization inhibitor bongkrekic acid (BK), partially prevented cell death by TNF + CHX. Anisomycin, a c-Jun N-terminal kinases activator, increased TNF-killing. The ERK-1 cells were resistant to TNF and anisomycin, whereas K71R clones resulted more sensitive. Our study demonstrates that in HeLa cells the ERK-1 kinase prevents TNF + CHX apoptosis by regulating the intrinsic mitochondrial pathway through different mechanisms. Inhibition of the intrinsic pathway is sufficient to almost completely prevent cell death.

Association study between single nucleotide polymorphisms in promoter region of AVPR1A and Korean autism spectrum disorders

To determine the association between arginine vasopressin receptor 1A gene (AVPR1A) and autism spectrum disorders (ASDs), we examined 3 single nucleotide polymorphisms (SNPs), namely, rs7294536, rs3759292, and rs10877969, in the promoter region of AVPR1A by using a family-based association test (FBAT) in 151 Korean trios. Our results demonstrated a statistically significant association between autism and SNPs (additive model: rs7294536, chi(2)=9.328, df=2, P=0.002; rs10877969, chi(2)=11.529, df=2, P<0.001) as well as between autism and haplotype analysis (additive model: chi(2)=14.122, df=3, P=0.003). In addition, we found that ADI-R scores calculated by using a diagnostic algorithm for failure to develop peer relationships (A2) were higher in subjects having the AA genotype than in subjects having the AG and GG genotypes of rs7294536. Thus, our study provides evidence for a possible association between these SNPs and the phenotype of ASDs.

Binge-pattern alcohol exposure during puberty induces sexually dimorphic changes in genes regulating the HPA axis

Maternal alcohol consumption during critical periods of fetal brain development leads to devastating long-term consequences on adult reproductive physiology, cognitive function, and social behaviors. However, very little is known about the long-term consequences of alcohol consumption during puberty, which is perhaps an equally dynamic and critical period of brain development. Alcohol abuse during adulthood has been linked with an increase in clinically diagnosed anxiety disorders, yet the etiology and neurochemical mechanisms of alcohol-induced anxiety behavior is unknown. In this study, we determined the effects of binge ethanol exposure during puberty on two critical central regulators of stress and anxiety behavior: corticotrophin-releasing hormone (CRH) and arginine vasopressin (AVP). Our results showed that ethanol increased plasma corticosterone (CORT) levels in both sexes, yet binge-treated animals had significantly lower CORT levels than animals exposed to a single dose, suggesting that the hypothalamo-pituitary-adrenal (HPA) axis habituated to the repeated stressful stimuli of ethanol. Binge ethanol exposure also significantly increased CRH and AVP gene expression in the paraventricular nucleus of males, but not females. Overall, our results demonstrate that binge ethanol exposure during puberty changes the central expression of stress-related genes in a sex-specific manner, potentially leading to permanent dysregulation of the HPA axis and long-term behavioral consequences.

Antiapoptotic effects of vasopressin in the neuronal cell line H32 involve protein kinase Calpha and beta

Activation of V1 vasopressin (VP) receptors prevents serum deprivation-induced apoptosis in neuronal H32 cells, partially through mitogen-activated protein kinase (MAPK) mediated Bad phosphorylation. In this study, we investigated the role of protein kinases C (PKC) and B (PKB) mediating VP-induced antiapoptosis in H32 cells. Serum deprivation increased PKCdelta but not PKCalpha or PKCbeta activity, while VP increased PKCalpha and PKCbeta without affecting PKCdelta activity. Inhibition of PKCdelta prevented caspase 3 activation, indicating that PKCdelta mediates the pro-apoptotic actions of serum deprivation. Simultaneous inhibition of PKCalpha and beta and MAPK abolished VP-induced Bad phosphorylation, but it only partially prevented caspase 3 inhibition. Complete abolition of the protective effect of VP on serum deprivation-induced caspase 3 activity required additional blockade of phosphoinositide 3 kinase (PI3K)/protein kinase B. The data demonstrate that VP exerts antiapoptosis through multiple pathways; while PKCalpha and beta together with extracellular signal-regulated kinases/MAPK activation mediates Bad phosphorylation (inactivation), the full protective action of VP requires additional activation of PKB (PI3K/protein kinase B) pathway.