CCK receptors-related signaling involved in nitric oxide production caused by gastrin 17 in porcine coronary endothelial cells

Gut Hormones in Heart Failure

Heart failure (HF) is a syndrome affecting all organ systems. While some organ interactions have been studied intensively in HF (such as the cardiorenal interaction), the endocrine gut has to some degree been overlooked. However, there is growing evidence of direct cardiac effects of several hormones secreted from the gastrointestinal tract. For instance, GLP-1 (glucagon-like peptide-1), an incretin hormone secreted from the distal intestine following food intake, has notable effects on the heart, impacting heart rate and contractility. GLP-1 may even possess cardioprotective abilities, such as inhibition of myocardial ischemia and cardiac remodeling. While other gut hormones have been less studied, there is evidence suggesting cardiostimulatory properties of several hormones. Moreover, it has been reported that patients with HF have altered bioavailability of numerous gastrointestinal hormones, which may have prognostic implications. This might indicate an important role of gut hormones in cardiac physiology and pathology, which may be of particular importance in the failing heart. We present an overview of the current knowledge on gut hormones in HF, focusing on HF with reduced ejection fraction, and discuss how these hormones may be regulators of cardiac function and central hemodynamics. Potential therapeutic perspectives are discussed, and knowledge gaps are highlighted herein.

The hyperthermic effect of central cholecystokinin is mediated by the cyclooxygenase-2 pathway

Cholecystokinin (CCK) increases core body temperature via CCK₂ receptors when administered intracerebroventricularly (icv). The mechanisms of CCK-induced hyperthermia are unknown, and it is also unknown whether CCK contributes to the fever response to systemic inflammation. We studied the interaction between central CCK signaling and the cyclooxygenase (COX) pathway. Body temperature was measured in adult male Wistar rats pretreated with intraperitoneal infusion of the nonselective COX enzyme inhibitor metamizol (120 mg/kg) or a selective COX-2 inhibitor, meloxicam, or etoricoxib (10 mg/kg for both) and, 30 min later, treated with intracerebroventricular CCK (1.7 µg/kg). In separate experiments, CCK-induced neuronal activation (with and without COX inhibition) was studied in thermoregulation- and feeding-related nuclei with c-Fos immunohistochemistry. CCK increased body temperature by ∼0.4°C from 10 min postinfusion, which was attenuated by metamizol. CCK reduced the number of c-Fos-positive cells in the median preoptic area (by ∼70%) but increased it in the dorsal hypothalamic area and in the rostral raphe pallidus (by ∼50% in both); all these changes were completely blocked with metamizol. In contrast, CCK-induced satiety and neuronal activation in the ventromedial hypothalamus were not influenced by metamizol. CCK-induced hyperthermia was also completely blocked with both selective COX-2 inhibitors studied. Finally, the CCK₂ receptor antagonist YM022 (10 µg/kg icv) attenuated the late phases of fever induced by bacterial lipopolysaccharide (10 µg/kg; intravenously). We conclude that centrally administered CCK causes hyperthermia through changes in the activity of "classical" thermoeffector pathways and that the activation of COX-2 is required for the development of this response.NEW & NOTEWORTHY An association between central cholecystokinin signaling and the cyclooxygenase-prostaglandin E pathway has been proposed but remained poorly understood. We show that the hyperthermic response to the central administration of cholecystokinin alters the neuronal activity within efferent thermoeffector pathways and that these effects are fully blocked by the inhibition of cyclooxygenase. We also show that the activation of cyclooxygenase-2 is required for the hyperthermic effect of cholecystokinin and that cholecystokinin is a modulator of endotoxin-induced fever.

Spinal CCK contributes to somatic hyperalgesia induced by orofacial inflammation combined with stress in adult female rats

In some chronic primary pain conditions such as temporomandibular disorder (TMD) and fibromyalgia syndrome (FMS), mild or chronic stress enhances pain. TMD and FMS often occur together, but the underlying mechanisms are unclear. The purpose of this study was to investigate the role of cholecystokinin (CCK) in the spinal cord in somatic hyperalgesia induced by orofacial inflammation combined with stress. Somatic hyperalgesia was detected by the thermal withdrawal latency and mechanical withdrawal threshold. The expression of CCK₁ receptors, CCK₂ receptors, ERK1/2 and p-ERK1/2 in the spinal cord was examined by Western blot. After the stimulation of orofacial inflammation combined with 3 day forced swim, the expression of CCK₂ receptors and p-ERK1/2 protein in the L4-L5 spinal dorsal horn increased significantly, while the expression of CCK₁ receptors and ERK1/2 protein remained unchanged. Intrathecal injection of the CCK₂ receptor antagonist YM-022 or mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitor PD98059 blocked somatic hyperalgesia induced by orofacial inflammation combined with stress. Intrathecal administration of the MEK inhibitor blocked somatic sensitization caused by the CCK receptor agonist CCK8. The CCK₂ receptor antagonist YM-022 significantly reduced the expression of p-ERK1/2. These data indicate that upregulation of CCK₂ receptors through the MAPK pathway contributes to somatic hyperalgesia in this comorbid pain model. Thus, CCK₂ receptors and MAPK pathway may be potential targets for the treatment of TMD comorbid with FMS.

Gastrin exerts a protective effect against myocardial infarction via promoting angiogenesis

Background

It is known that increased gastrin concentration is negatively correlated with cardiovascular mortality, and plasma gastrin levels are increased in patients after myocardial infarction (MI). However, whether gastrin can play a protective role in MI remains unknown.

Methods

Adult C57BL/6 mice were subjected to ligation of the left anterior descending coronary artery (LAD) and subcutaneous infusion of gastrin (120 μg/Kg body weight/day, 100 μL in the pump) for 28 days after MI. Plasma gastrin concentrations were measured through an ELISA detection kit. Mice were analyzed by echocardiography after surgery. CD31 and VEGF expression were quantified using immunofluorescence staining or/and western blot to assess the angiogenesis in peri-infarct myocardium. Capillary-like tube formation and cell migration assays were performed to detect gastrin-induced angiogenesis.

Results

We found that gastrin administration significantly ameliorated MI-induced cardiac dysfunction and reduced fibrosis at 28 days in post-MI hearts. Additionally, gastrin treatment significantly decreased cardiomyocyte apoptosis and increased angiogenesis in the infarct border zone without influencing cardiomyocyte proliferation. In vitro results revealed that gastrin up-regulated the PI3K/Akt/vascular endothelial growth factor (VEGF) signaling pathway and promoted migration and tube formation of human coronary artery endothelial cells (HCAECs). Cholecystokinin 2 receptor (CCK₂R) mediated the protective effect of gastrin since the CCK₂R blocker CI988 attenuated the gastrin-mediated angiogenesis and cardiac function protection.

Conclusion

Our data revealed that gastrin promoted angiogenesis and improved cardiac function in post-MI mice, highlighting its potential as a therapeutic target candidate.

Gastrin mediates cardioprotection through angiogenesis after myocardial infarction by activating the HIF-1α/VEGF signalling pathway

Acute myocardial infarction (MI) is one of the leading causes of death in humans. Our previous studies showed that gastrin alleviated acute myocardial ischaemia-reperfusion injury. We hypothesize that gastrin might protect against heart injury after MI by promoting angiogenesis. An MI model was simulated by ligating the anterior descending coronary artery in adult male C57BL/6J mice. Gastrin was administered twice daily by intraperitoneal injection for 2 weeks after MI. We found that gastrin reduced mortality, improved myocardial function with reduced infarct size and promoted angiogenesis. Gastrin increased HIF-1α and VEGF expression. Downregulation of HIF-1α expression by siRNA reduced the proliferation, migration and tube formation of human umbilical vein endothelial cells. These results indicate that gastrin restores cardiac function after MI by promoting angiogenesis via the HIF-1α/VEGF pathway.

The Role of Gasotransmitters in Gut Peptide Actions

Although gasotransmitters nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H₂S) receive a bad connotation; in low concentrations these play a major governing role in local and systemic blood flow, stomach acid release, smooth muscles relaxations, anti-inflammatory behavior, protective effect and more. Many of these physiological processes are upstream regulated by gut peptides, for instance gastrin, cholecystokinin, secretin, motilin, ghrelin, glucagon-like peptide 1 and 2. The relationship between gasotransmitters and gut hormones is poorly understood. In this review, we discuss the role of NO, CO and H₂S on gut peptide release and functioning, and whether manipulation by gasotransmitter substrates or specific blockers leads to physiological alterations.

Monomeric adiponectin modulates nitric oxide release and calcium movements in porcine aortic endothelial cells in normal/high glucose conditions

AIMS

Perivascular adipose tissue can be involved in the process of cardiovascular pathology through the release of adipokines, namely adiponectins. Monomeric adiponectin has been shown to increase coronary blood flow in anesthetized pigs through increased nitric oxide (NO) release and the involvement of adiponectin receptor 1 (AdipoR1). The present study was therefore planned to examine the effects of monomeric adiponectin on NO release and Ca(2+) transients in porcine aortic endothelial cells (PAEs) in normal/high glucose conditions and the related mechanisms.

MAIN METHODS

PAEs were treated with monomeric adiponectin alone or in the presence of intracellular kinases blocker, AdipoR1 and Ca(2+)-ATPase pump inhibitors. The role of Na(+)/Ca(2+) exchanger was examined in experiments performed in zero Na(+) medium. NO release and intracellular Ca(2+) were measured through specific probes.

KEY FINDINGS

In PAE cultured in normal glucose conditions, monomeric adiponectin elevated NO production and [Ca(2+)]c. Similar effects were observed in high glucose conditions, although the response was lower and not transient. The Ca(2+) mobilized by monomeric adiponectin originated from an intracellular pool thapsigargin- and ATP-sensitive and from the extracellular space. Moreover, the effects of monomeric adiponectin were prevented by kinase blockers and AdipoR1 inhibitor. Finally, in normal glucose condition, a role for Na(+)/Ca(2+) exchanger and Ca(2+)-ATPase pump in restoring Ca(2+) was found.

SIGNIFICANCE

Our results add new information about the control of endothelial function elicited by monomeric adiponectin, which would be achieved by modulation of NO release and Ca(2+) transients. A signalling related to Akt, ERK1/2 and p38MAPK downstream AdipoR1 would be involved.

Intracoronary Des-Acyl Ghrelin Acutely Increases Cardiac Perfusion Through a Nitric Oxide-Related Mechanism in Female Anesthetized Pigs

Des-acyl ghrelin (DAG), the most abundant form of ghrelin in humans, has been found to reduce arterial blood pressure and prevent cardiac and endothelial cell apoptosis. Despite this, data regarding its direct effect on cardiac function and coronary blood flow, as well as the related involvement of autonomic nervous system and nitric oxide (NO), are scarce. We therefore examined these issues using both in vivo and in vitro studies. In 20 anesthetized pigs, intracoronary 100 pmol/mL DAG infusion with a constant heart rate and aortic blood pressure, increased coronary blood flow and NO release, whereas reducing coronary vascular resistances (P < .05). Dose responses to DAG were evaluated in five pigs. No effects on cardiac contractility/relaxation or myocardial oxygen consumption were observed. Moreover, whereas the blockade of muscarinic cholinoceptors (n = 5) or α- and β-adrenoceptors (n = 5 each) did not abolish the observed responses, NO synthase inhibition (n = 5) prevented the effects of DAG on coronary blood flow and NO release. In coronary artery endothelial cells, DAG dose dependently increased NO release through cAMP signaling and ERK1/2, Akt, and p38 MAPK involvement as well as the phosphorylation of endothelial NO synthase. In conclusion, in anesthetized pigs, DAG primarily increased cardiac perfusion through the involvement of NO release. Moreover, the phosphorylation of ERK1/2 and Akt appears to play roles in eliciting the observed NO production in coronary artery endothelial cells.

Postsynaptic Depolarization Enhances GABA Drive to Dorsomedial Hypothalamic Neurons through Somatodendritic Cholecystokinin Release

Somatodendritically released peptides alter synaptic function through a variety of mechanisms, including autocrine actions that liberate retrograde transmitters. Cholecystokinin (CCK) is a neuropeptide expressed in neurons in the dorsomedial hypothalamic nucleus (DMH), a region implicated in satiety and stress. There are clear demonstrations that exogenous CCK modulates food intake and neuropeptide expression in the DMH, but there is no information on how endogenous CCK alters synaptic properties. Here, we provide the first report of somatodendritic release of CCK in the brain in male Sprague Dawley rats. CCK is released from DMH neurons in response to repeated postsynaptic depolarizations, and acts in an autocrine fashion on CCK2 receptors to enhance postsynaptic NMDA receptor function and liberate the retrograde transmitter, nitric oxide (NO). NO subsequently acts presynaptically to enhance GABA release through a soluble guanylate cyclase-mediated pathway. These data provide the first demonstration of synaptic actions of somatodendritically released CCK in the hypothalamus and reveal a new form of retrograde plasticity, depolarization-induced potentiation of inhibition. Significance statement: Somatodendritic signaling using endocannabinoids or nitric oxide to alter the efficacy of afferent transmission is well established. Despite early convincing evidence for somatodendritic release of neurohypophysial peptides in the hypothalamus, there is only limited evidence for this mode of release for other peptides. Here, we provide the first evidence for somatodendritic release of the satiety peptide cholecystokinin (CCK) in the brain. We also reveal a new form of synaptic plasticity in which postsynaptic depolarization results in enhancement of inhibition through the somatodendritic release of CCK.

Effects of Artemetin on Nitric Oxide Release and Protection against Peroxidative Injuries in Porcine Coronary Artery Endothelial Cells

Artemetin is one of the main components of Achillea millefolium L. and Artemisia absinthium, which have long been used for the treatment of various diseases. To date, however, available information about protective effects of their extracts on the cardiovascular system is scarce. Therefore, we planned to analyze the effects of artemetin on nitric oxide (NO) release and the protection exerted against oxidation in porcine aortic endothelial (PAE) cells. In PAE, we examined the modulation of NO release caused by artemetin and the involvement of muscarinic receptors, β2-adrenoreceptors, estrogenic receptors (ER), protein-kinase A, phospholipase-C, endothelial-NO-synthase (eNOS), Akt, extracellular-signal-regulated kinases 1/2 (ERK1/2) and p38 mitogen activated protein kinase (p38 MAPK). Moreover, in cells treated with hydrogen peroxide, the effects of artemetin were examined on cell survival, glutathione (GSH) levels, apoptosis, mitochondrial membrane potential and transition pore opening. Artemetin increased eNOS-dependent NO production by the involvement of muscarinic receptors, β2-adrenoreceptors, ER and all the aforementioned kinases. Furthermore, artemetin improved cell viability in PAE that were subjected to peroxidation by counteracting GSH depletion and apoptosis and through the modulation of mitochondrial function. In conclusion, artemetin protected endothelial function by acting as antioxidant and antiapoptotic agent and through the activation of ERK1/2 and Akt. Copyright © 2015 John Wiley & Sons, Ltd.

Levosimendan inhibits peroxidation in hepatocytes by modulating apoptosis/autophagy interplay

Background

Levosimendan protects rat liver against peroxidative injuries through mechanisms related to nitric oxide (NO) production and mitochondrial ATP-dependent K (mitoK_ATP) channels opening. However, whether levosimendan could modulate the cross-talk between apoptosis and autophagy in the liver is still a matter of debate. Thus, the aim of this study was to examine the role of levosimendan as a modulator of the apoptosis/autophagy interplay in liver cells subjected to peroxidation and the related involvement of NO and mitoK_ATP.

Methods and Findings

In primary rat hepatocytes that have been subjected to oxidative stress, Western blot was performed to examine endothelial and inducible NO synthase isoforms (eNOS, iNOS) activation, apoptosis/autophagy and survival signalling detection in response to levosimendan. In addition, NO release, cell viability, mitochondrial membrane potential and mitochondrial permeability transition pore opening (MPTP) were examined through specific dyes. Some of those evaluations were also performed in human hepatic stellate cells (HSC). Pre-treatment of hepatocytes with levosimendan dose-dependently counteracted the injuries caused by oxidative stress and reduced NO release by modulating eNOS/iNOS activation. In hepatocytes, while the autophagic inhibition reduced the effects of levosimendan, after the pan-caspases inhibition, cell survival and autophagy in response to levosimendan were increased. Finally, all protective effects were prevented by both mitoK_ATP channels inhibition and NOS blocking. In HSC, levosimendan was able to modulate the oxidative balance and inhibit autophagy without improving cell viability and apoptosis.

Conclusions

Levosimendan protects hepatocytes against oxidative injuries by autophagic-dependent inhibition of apoptosis and the activation of survival signalling. Such effects would involve mitoK_ATP channels opening and the modulation of NO release by the different NOS isoforms. In HSC, levosimendan would also play a role in cell activation and possible evolution toward fibrosis. These findings highlight the potential of levosimendan as a therapeutic agent for the treatment or prevention of liver ischemia/reperfusion injuries.

Cholecystokinin-8 induces brain-derived neurotrophic factor expression in noradrenergic neuronal cells

The sulfated cholecystokinin octapeptide (CCK-8S) is one of the most abundant CCK fragment in the brain, but the effects of CCK-8S on locus coeruleus (LC) noradrenergic (NA) neuronal cells activity have not been studied. In this study, we investigated the effects of CCK-8S on the expression of brain-derived neurotrophic factor (BDNF) in LC NA neuronal cell line, LC3541. Results showed that CCK-8S (10 nM) elevates BDNF levels time-dependently and by 1.82-fold after 4h of incubation. In addition, pretreatment with CCK-8S reversed H₂O₂ (100 μM)-mediated down-regulation of BDNF expression, and effectively suppressed H₂O₂-induced caspase-3 activation. Furthermore, CCK-8S markedly induced expression of neuronal survival markers, such as extracellular signal-regulated kinase 1/2 (ERK 1/2), Akt/protein kinase B (PKB), Bcl-2, and peroxisome proliferators-activated receptor gamma coactivator-1α (PGC-1α). Pharmacological inhibitors of ERK 1/2, Akt/PKB, and protein kinase A (PKA) reversed CCK-8S-mediated BDNF induction in LC3541 cells. These results suggest the first evidence that CCK-8S can protect noradrenergic neurons and enhance the expression of BDNF via ERK 1/2-Akt/PKB-PKA-dependent pathways.

Calcium handling in porcine coronary endothelial cells by gastrin-17

In porcine coronary artery endothelial cells (PCAEC), gastrin-17 has recently been found to increase nitric oxide (NO) production by the endothelial NO synthase (eNOS) isoform through cholecystokinin 1/2 (CCK1/2) receptors and the involvement of protein kinase A (PKA), PKC and the β2-adrenoreceptor-related pathway. As eNOS is the Ca(2)(+)-dependent isoform of the enzyme, we aimed to examine the effects of gastrin-17 on Ca(2)(+) movements. Thus, experiments were performed in Fura-2-acetoxymethyl-ester-loaded PCAEC, where changes of cytosolic Ca(2)(+) ([Ca(2)(+)]c) caused by gastrin-17 were analysed and compared with those of CCK receptors and β2-adrenoreceptors agonists/antagonists. In addition, some experiments were performed by stimulating cells with gastrin-17 in the presence or absence of cAMP/PKA activator/inhibitor and of phospholipase C (PLC) and Ca(2)(+)-calmodulin dependent protein kinase II (CaMKII) blockers. The results have shown that gastrin-17 can promote a transient increase in [Ca(2)(+)]c mainly originating from an intracellular pool sensitive to thapsigargin and from the extracellular space. In addition, the response of cells to gastrin-17 was increased by the adenylyl cyclase activator and the β2-adrenoreceptor agonists and affected mainly by the CCK2 receptor agonists/antagonists. Moreover, the effects of gastrin-17 were prevented by β2-adrenoreceptors and CaMKII blockers and the adenylyl cyclase/PKA and PLC inhibitors. Finally, in PCAEC cultured in Na(+)-free medium or loaded with the plasma membrane Ca(2)(+) pump inhibitor, the gastrin-17-evoked Ca(2)(+) transient was long lasting. In conclusion, this study shows that gastrin-17 affected intracellular Ca(2)(+) homeostasis in PCAEC by both promoting a discharge of an intracellular pool and by interfering with the operation of store-dependent channels through mainly CCK2 receptors and PKA/PLC- and CaMKII-related signalling downstream of β2-adrenoreceptor stimulation.