Antihypertensive and neuroprotective effects of catestatin in spontaneously hypertensive rats: interaction with GABAergic transmission in amygdala and brainstem

Plasma catestatin levels are related to metabolic parameters in patients with essential hypertension and type 2 diabetes mellitus

Catestatin (CST) is a pleiotropic peptide with cardioprotective and metabolic effects. CST is involved in the pathogenesis of both arterial hypertension (AH) and type 2 diabetes mellitus (T2DM), which are the risk factors of cardiovascular diseases. In this study, we aimed to investigate the plasma CST levels in hypertensive patients, especially with T2DM, as well as compare those with healthy volunteers, and explore the relationship between CST levels and clinical, anthropometric and laboratory parameters. 106 Hypertensive patients, 55 of which had comorbidity T2DM, and 30 healthy volunteers were enrolled in the study. All subjects underwent clinical examination, including vital signs and anthropometric data assessment, medical history interview, and blood sample collection. Plasma CST levels were measured by an enzyme-linked immunosorbent assay (ELISA), using a commercial diagnostic kit. The plasma CST levels were significantly lower in hypertensive patients (N = 106) compared with healthy subjects (N = 30) (5.02 ± 1.09 vs. 6.64 ± 0.72; p < 0.001). Furthermore, hypertensive patients with T2DM (N = 55) have significantly reduced CST levels in comparison with those without T2DM (N = 51) (4.47 ± 1.16 vs. 5.61 ± 0.61; p < 0.001). CST significantly correlated with anthropometric characteristics, in particular, weight (r =  - 0.344; p < 0.001), BMI (r =  - 0.42; p < 0.001), neck (r =  - 0.358; p < 0.001), waist (r =  - 0.487; p < 0.001), hip (r =  - 0.312; p < 0.001), wrist circumferences (r =  - 0.264; p = 0.002), and waist-to-hip ratio (r =  - 0.395; p < 0.001). Due to its antihypertensive effect, CST has significant associations with systolic BP (r =  - 0.475; p < 0.001) and duration of AH (r =  - 0.26; p = 0.007). CST also has an inverse relationship with insulin (r =  - 0.382; p < 0.001), glucose (r =  - 0.45; p < 0.001), index HOMA-IR (r =  - 0.481; p < 0.001) and HbA1c (r =  - 0.525; p < 0.001), that indicate its involvement in T2DM development. Besides, CST has significant correlations with uric acid levels (r =  - 0.412; p < 0.001) as well as lipid parameters, especially HDL-C (r = 0.480; p < 0.001), VLDL-C (r =  - 0.238; p = 0.005), TG (r =  - 0.4; p < 0.001), non-HDL-C/HDL-C (r =  - 0.499; p < 0.001). Multiple linear regression analysis indicated BMI (β =  - 0.22; p = 0.007), AH duration (β =  - 0.25; p = 0.008), HbA1c (β =  - 0.43; p = 0.019) and HDL-C levels (β = 0.27; p = 0.001) as independent predictors of CST levels. The hypertensive patients have significantly decreased CST levels that are even more reduced in the presence of comorbid T2DM. The established correlations with anthropometric and laboratory parameters indicate not only antihypertensive but also metabolic effects of CST. Our results suggest the probable role of CST in the pathophysiology of cardiometabolic diseases and the development of cardiovascular complications.

Mitochondrial-derived peptides: Antidiabetic functions and evolutionary perspectives

Mitochondrial-derived peptides (MDPs) are a novel class of bioactive microproteins encoded by short open-reading frames (sORF) in mitochondrial DNA (mtDNA). Currently, three types of MDPs have been identified: Humanin (HN), MOTS-c (Mitochondrial ORF within Twelve S rRNA type-c), and SHLP1-6 (small Humanin-like peptide, 1 to 6). The 12 S ribosomal RNA (MT-RNR1) gene harbors the sequence for MOTS-c, whereas HN and SHLP1-6 are encoded by the 16 S ribosomal RNA (MT-RNR2) gene. Special genetic codes are used in mtDNA as compared to nuclear DNA: (i) ATA and ATT are used as start codons in addition to the standard start codon ATG; (ii) AGA and AGG are used as stop codons instead of coding for arginine; (iii) the standard stop codon UGA is used to code for tryptophan. While HN, SHLP6, and MOTS-c are encoded by the H (heavy owing to high guanine + thymine base composition)-strand of the mtDNA, SHLP1-5 are encoded by the L (light owing to less guanine + thymine base composition)-strand. MDPs attenuate disease pathology including Type 1 diabetes (T1D), Type 2 diabetes (T2D), gestational diabetes, Alzheimer's disease (AD), cardiovascular diseases, prostate cancer, and macular degeneration. The current review will focus on the MDP regulation of T2D, T1D, and gestational diabetes along with an emphasis on the evolutionary pressures for conservation of the amino acid sequences of MDPs.

Catestanin – a promising biological marker for heart failure: A review

The epidemic of heart failure (HF) is one of the problems that the global health system has been facing for decades. HF is a multicomponent clinical syndrome caused by dysfunction of the heart and its pathological remodeling. In addition to the well-known natriuretic peptides, a number of cardiovascular biological markers have now been identified that provide clinicians with additional opportunities in diagnosing, classifying, predicting, and monitoring the effectiveness of treating patients with HF. From the position of establishing the sympathetic load in patients with HF, it seems very promising to assess the concentrations of catestatin. The presented data of our literature review suggest that catestatin is probably a reliable biological marker of the activity of the sympathetic division of the autonomic nervous system, and its elevated concentrations in patients with HF reflect the severity of the pathological process. However, despite the reliable results of studies, the clinical significance of assessing the values of this marker both separately and in the framework of a multimarker model requires further study in larger prospective clinical studies.

Role of Catestatin in the Cardiovascular System and Metabolic Disorders

Catestatin is a multifunctional peptide that is involved in the regulation of the cardiovascular and immune systems as well as metabolic homeostatis. It mitigates detrimental, excessive activity of the sympathetic nervous system by inhibiting catecholamine secretion. Based on in vitro and in vivo studies, catestatin was shown to reduce adipose tissue, inhibit inflammatory response, prevent macrophage-driven atherosclerosis, and regulate cytokine production and release. Clinical studies indicate that catestatin may influence the processes leading to hypertension, affect the course of coronary artery diseases and heart failure. This review presents up-to-date research on catestatin with a particular emphasis on cardiovascular diseases based on a literature search.

Gut microbial DNA and immune checkpoint gene Vsig4/CRIg are key antagonistic players in healthy aging and age-associated development of hypertension and diabetes

AIMS

Aging is associated with the development of insulin resistance and hypertension which may stem from inflammation induced by accumulation of toxic bacterial DNA crossing the gut barrier. The aim of this study was to identify factors counter-regulating these processes. Taking advantage of the Chromogranin A (CgA) knockout (CgA-KO) mouse as a model for healthy aging, we have identified Vsig4 (V-set and immunoglobulin domain containing 4) as the critical checkpoint gene in offsetting age-associated hypertension and diabetes.

METHODS AND RESULTS

The CgA-KO mice display two opposite aging phenotypes: hypertension but heightened insulin sensitivity at young age, whereas the blood pressure normalizes at older age and insulin sensitivity further improves. In comparison, aging WT mice gradually lost glucose tolerance and insulin sensitivity and developed hypertension. The gut barrier, compromised in aging WT mice, was preserved in CgA KO mice leading to major 35-fold protection against bacterial DNA-induced inflammation. Similarly, RNA sequencing showed increased expression of the Vsig4 gene (which removes bacterial DNA) in the liver of 2-yr-old CgA-KO mice, which may account for the very low accumulation of microbial DNA in the heart. The reversal of hypertension in aging CgA-KO mice likely stems from (i) low accumulation of microbial DNA, (ii) decreased spillover of norepinephrine in the heart and kidneys, and (iii) reduced inflammation.

CONCLUSION

We conclude that healthy aging relies on protection from bacterial DNA and the consequent low inflammation afforded by CgA-KO. Vsig4 also plays a crucial role in "healthy aging" by counteracting age-associated insulin resistance and hypertension.

Catestatin as a Biomarker of Cardiovascular Diseases: A Clinical Perspective

Accounting for almost one-third of the global mortality, cardiovascular diseases (CVDs) represent a major global health issue. Emerging data suggest that most of the well-established mechanistic explanations regarding the cardiovascular pathophysiology are flawed, and cannot fully explain the progression and long-term effects of these diseases. On the other hand, dysregulation of the sympathetic nervous system (SNS) has emerged as an important player in the pathophysiology of CVDs. Even though upregulated SNS activity is an essential compensatory response to various stress conditions, in the long term, it becomes a major contributor to both cardiac dysfunction and vascular damage. Despite the fact that the importance of SNS hyperactivity in the setting of CVDs has been well-appreciated, its exact quantification and clinical application in either diagnostics or therapy of CVDs is still out of reach. Nevertheless, in recent years a number of novel laboratory biomarkers implicated in the pathophysiology of SNS activation have been explored. Specifically, in this review, we aimed to discuss the role of catestatin, a potent physiological inhibitor of catecholamine spillover that offers cardioprotective effects. Limited data indicate that catestatin could also be a reliable indirect marker of SNS activity and it is likely that high CST levels reflect advanced CV disease burden. Consequently, large-scale studies are required to validate these observations in the upcoming future.

New insights into methoxetamine mechanisms of action: Focus on serotonergic 5-HT2 receptors in pharmacological and behavioral effects in the rat

Methoxetamine (MXE) is a dissociative substance of the arylcyclohexylamine class that has been present on the designer drug market as a ketamine-substitute since 2010. We have previously shown that MXE (i) possesses ketamine-like discriminative and positive rewarding effects in rats, (ii) affects brain processing involved in cognition and emotional responses, (iii) causes long-lasting behavioral abnormalities and neurotoxicity in rats and (iv) induces neurological, sensorimotor and cardiorespiratory alterations in mice. To shed light on the mechanisms through which MXE exerts its effects, we conducted a multidisciplinary study to evaluate the various neurotransmitter systems presumably involved in its actions on the brain. In vivo microdialysis study first showed that a single administration of MXE (0.25 and 0.5 mg/kg, i.v.) is able to significantly alter serotonin levels in the rat medial prefrontal cortex (mPFC) and nucleus accumbens. Then, we observed that blockade of the serotonin 5-HT₂ receptors through two selective antagonists, ketanserin (0.1 mg/kg, i.p.) and MDL 100907 (0.03 mg/kg, i.p.), at doses not affecting animals behavior per se, attenuated the facilitatory motor effect and the inhibition on visual sensory responses induced by MXE (3 mg/kg, i.p.) and ketamine (3 mg/kg, i.p.), and prevented MXE-induced reduction of the prepulse inhibition in rats, pointing to the 5-HT₂ receptors as a key target for the recently described MXE-induced sensorimotor effects. Finally, in-vitro electrophysiological studies revealed that the GABAergic and glutamatergic systems are also likely involved in the mechanisms through which MXE exerts its central effects since MXE inhibits, in a concentration-dependent manner, NMDA-mediated field postsynaptic potentials and GABA-mediated spontaneous currents. Conversely, MXE failed to alter both the AMPA component of field potentials and presynaptic glutamate release, and seems not to interfere with the endocannabinoid-mediated effects on mPFC GABAergic synapses. Altogether, our results support the notion of MXE as a NMDA receptor antagonist and shed further lights into the central mechanisms of action of this ketamine-substitute by pointing to serotonin 5-HT₂ receptors as crucial players in the expression of its sensorimotor altering effects and to the NMDA and GABA receptors as potential further important targets of action.

Immunosuppression of Macrophages Underlies the Cardioprotective Effects of CST (Catestatin)

[Figure: see text].

Plasma Catestatin Levels and Advanced Glycation End Products in Patients on Hemodialysis

Catestatin (CST) is a pleiotropic peptide involved in cardiovascular protection with its antihypertensive and angiogenic effects. Considering that patients with end-stage renal disease (ESRD) who are undergoing hemodialysis (HD) are associated with higher cardiovascular risk, the aim of this study was to investigate plasma CST levels in HD patients, compare them to healthy controls and evaluate possible CST associations with advanced glycation end products (AGEs) and laboratory, anthropometric and clinical parameters. The study included 91 patients on HD and 70 healthy controls. Plasma CST levels were determined by an enzyme-linked immunosorbent assay in a commercially available diagnostic kit, while AGEs were determined using skin autofluorescence. Plasma CST levels were significantly higher in the HD group compared to the controls (32.85 ± 20.18 vs. 5.39 ± 1.24 ng/mL, p < 0.001) and there was a significant positive correlation between CST and AGEs (r = 0.492, p < 0.001). Furthermore, there was a significant positive correlation between plasma CST levels with both the Dialysis Malnutrition Score (r = 0.295, p = 0.004) and Malnutrition-Inflammation Score (r = 0.290, p = 0.005). These results suggest that CST could be playing a role in the complex pathophysiology of ESRD/HD and that it could affect the higher cardiovascular risk of patients on HD.

Catestatin prevents endothelial inflammation and promotes thrombus resolution in acute pulmonary embolism in mice

Catestatin (CTS), a catecholamine-release inhibitory peptide, exerts pleiotropic cardiac protective effects. Pulmonary embolism caused by deep vein thrombosis involving vascular dysfunction. The present study aims to investigate the effects of CTS on thrombus formation that may inhibit the development of pulmonary embolism and its potential pathway. Acute pulmonary embolism (APE) model was developed as an in vivo model. The effects of CTS on mice with APE were examined. Human pulmonary artery endothelial cells (HPAECs) were pretreated with CTS before thrombin stimulation, and endothelial inflammation and underlying mechanisms were evaluated in vitro. That plasma CTS level was decreased in APE mice, while the number of platelets was significantly increased. The decreased circulating CTS level negatively associated with the number of platelets. CTS administration increased the survival rate of APE mice and protected against microvascular thrombosis in lung. APE-induced the increase in platelets number and plasma von Willebrand factor (VWF) were inhibited by CTS. Platelets from CTS-treated APE mice showed impaired agonist-induced platelets aggregation and spreading. CTS also ameliorated APE-induced the systemic inflammatory response. In in vivo study, thrombin-induced the increase in inflammation, TLR-4 expression and p38 phosphorylation were abrogated by CTS in HPAECs. Furthermore, TLR-4 overexpression inhibited the effect of CTS on VWF release and inflammation in HPAECs. Collectively, CTS increases thrombus resolution by attenuating endothelial inflammation at partially via inhibiting TLR-4-p38 pathway. The present study may provide a novel approach for anti-thrombosis.

Gamma-Aminobutyric Acid Increases Erythropoietin by Activation of Citrate Cycle and Stimulation of Hypoxia-Inducible Factors Expression in Rats

Erythropoietin (EPO) is the primary regulator of erythropoiesis in the mammalian fetus and adult. Deficiency of EPO induces anemia. In this study, we investigated the effect of gamma-aminobutyric acid (GABA) on serum EPO levels and erythropoiesis in rats. Expression levels of Epo-related genes were measured by quantitative real-time PCR (qPCR) and expression of Epo and Epo receptor (Epor) proteins were measured by immunohistochemistry. The gene and protein expression profiles of kidney tissue in GABA-treated rats were evaluated by ribonucleic acid (RNA) sequencing and two-dimensional electrophoresis (2-DE), respectively. GABA significantly increased serum EPO levels and expression levels of Epo and Epor. GABA increased expression levels of hypoxia-inducible factor (Hif)-1 and Hif-2. Seven proteins with expression levels showing >2-fold change were identified by 2-DE followed by MALDI-TOF MS in GABA-treated rat kidney. The top KEGG pathway from the identified proteins was the tricarboxylic acid cycle, and nicotinamide adenine dinucleotide (NADH) dehydrogenase, succinate dehydrogenase, and isocitrate dehydrogenase were identified as key proteins. GABA treatment significantly increased ATP levels and NADH dehydrogenase activity in a dose-dependent manner. In conclusion, GABA shows a new physiological role in EPO production, and it can thus can contribute to the prevention of anemia when used alone or in combination with other anemia treating drugs.

Chromogranin A and its fragments in cardiovascular, immunometabolic, and cancer regulation

Chromogranin A (CgA)-the index member of the chromogranin/secretogranin secretory protein family-is ubiquitously distributed in endocrine, neuroendocrine, and immune cells. Elevated levels of CgA-related polypeptides, consisting of full-length molecules and fragments, are detected in the blood of patients suffering from neuroendocrine tumors, heart failure, renal failure, hypertension, rheumatoid arthritis, and inflammatory bowel disease. Full-length CgA and various CgA-derived peptides, including vasostatin-1, pancreastatin, catestatin, and serpinin, are expressed at different relative levels in normal and pathological conditions and exert diverse, and sometime opposite, biological functions. For example, CgA is overexpressed in genetic hypertension, whereas catestatin is diminished. In rodents, the administration of catestatin decreases hypertension, cardiac contractility, obesity, atherosclerosis, and inflammation, and it improves insulin sensitivity. By contrast, pancreastatin is elevated in diabetic patients, and the administration of this peptide to obese mice decreases insulin sensitivity and increases inflammation. CgA and the N-terminal fragment of vasostatin-1 can enhance the endothelial barrier function, exert antiangiogenic effects, and inhibit tumor growth in animal models, whereas CgA fragments lacking the CgA C-terminal region promote angiogenesis and tumor growth. Overall, the CgA system, consisting of full-length CgA and its fragments, is emerging as an important and complex player in cardiovascular, immunometabolic, and cancer regulation.

Modulation of the coronary tone in the expanding scenario of Chromogranin-A and its derived peptides

The cardiac function critically depends on an adequate myocardial oxygenation and on a correct coronary blood flow. Endothelial, hormonal and extravascular factors work together generating a fine balance between oxygen supply and oxygen utilization through the coronary circulation. Among the regulatory factors that contribute to the coronary tone, increasing attention is paid to the cardiac endocrines, such as chromogranin A, a prohormone for many biologically active peptides, including vasostatin and catestatin. In this review, we will summarize the available evidences about the coronary effects of these molecules, and their putative mechanism of action. Laboratory and clinical data on chromogranin A and its derived fragments will be analyzed in relation to the scenario of the endocrine heart, and of its putative clinical perspectives.

Catestatin as a Target for Treatment of Inflammatory Diseases

It is increasingly clear that inflammatory diseases and cancers are influenced by cleavage products of the pro-hormone chromogranin A (CgA), such as the 21-amino acids long catestatin (CST). The goal of this review is to provide an overview of the anti-inflammatory effects of CST and its mechanism of action. We discuss evidence proving that CST and its precursor CgA are crucial for maintaining metabolic and immune homeostasis. CST could reduce inflammation in various mouse models for diabetes, colitis and atherosclerosis. In these mouse models, CST treatment resulted in less infiltration of immune cells in affected tissues, although in vitro monocyte migration was increased by CST. Both in vivo and in vitro, CST can shift macrophage differentiation from a pro- to an anti-inflammatory phenotype. Thus, the concept is emerging that CST plays a role in tissue homeostasis by regulating immune cell infiltration and macrophage differentiation. These findings warrant studying the effects of CST in humans and make it an interesting therapeutic target for treatment and/or diagnosis of various metabolic and immune diseases.

Acute sleep deprivation preconditions the heart against ischemia/ reperfusion injury: the role of central GABA-A receptors

OBJECTIVES

Central γ-aminobutyric acid (GABA) neurotransmission modulates cardiovascular functions and sleep. Acute sleep deprivation (ASD) affects functions of various body organs via different mechanisms. Here, we evaluated the effect of ASD on cardiac ischemia/reperfusion injury (IRI), and studied the role of GABA-A receptor inhibition in central nucleus of amygdala (CeA) by assessing nitric oxide (NO) and oxidative stress.

MATERIALS AND METHODS

The CeA in sixty male Wistar rats was cannulated for saline or bicuculline (GABA-A receptor antagonist) administration. All animals underwent 30 min of coronary occlusion (ischemia), followed by 2 hr reperfusion (IR). The five experimental groups (n=12) included are as follows: IR: received saline; BIC+IR: received Bicuculline; MLP+IR: received saline, followed by the placement of animals in an aquarium with multiple large platforms; ASD+IR: underwent ASD in an aquarium with multiple small platforms; and BIC+ASD+IR: received bicuculline prior to ASD.

RESULTS

Bicuculline administration increased the malondialdehyde levels and infarct size, and decreased the NO metabolites levels and endothelial nitric oxide synthase (eNOS) gene expression in infarcted and non-infarcted areas in comparison to IR group. ASD reduced malondialdehyde levels and infarct size and increased NO metabolites, corticosterone levels and eNOS expression in infarcted and non-infarcted areas as compared to the IR group. Levels of malondialdehyde were increased while levels of NO metabolites, corticosterone and eNOS expression in infarcted and non-infarcted areas were reduced in the BIC+ASD+IR as compared to the ASD+IR group.

CONCLUSION

Blockade of GABA-A receptors in the CeA abolishes ASD-induced cardioprotection by suppressing oxidative stress and NO production.

Granin-derived peptides

The granin family comprises altogether 7 different proteins originating from the diffuse neuroendocrine system and elements of the central and peripheral nervous systems. The family is dominated by three uniquely acidic members, namely chromogranin A (CgA), chromogranin B (CgB) and secretogranin II (SgII). Since the late 1980s it has become evident that these proteins are proteolytically processed, intragranularly and/or extracellularly into a range of biologically active peptides; a number of them with regulatory properties of physiological and/or pathophysiological significance. The aim of this comprehensive overview is to provide an up-to-date insight into the distribution and properties of the well established granin-derived peptides and their putative roles in homeostatic regulations. Hence, focus is directed to peptides derived from the three main granins, e.g. to the chromogranin A derived vasostatins, betagranins, pancreastatin and catestatins, the chromogranin B-derived secretolytin and the secretogranin II-derived secretoneurin (SN). In addition, the distribution and properties of the chromogranin A-derived peptides prochromacin, chromofungin, WE14, parastatin, GE-25 and serpinins, the CgB-peptide PE-11 and the SgII-peptides EM66 and manserin will also be commented on. Finally, the opposing effects of the CgA-derived vasostatin-I and catestatin and the SgII-derived peptide SN on the integrity of the vasculature, myocardial contractility, angiogenesis in wound healing, inflammatory conditions and tumors will be discussed.

Application of the Co-culture Membrane System Pointed to a Protective Role of Catestatin on Hippocampal Plus Hypothalamic Neurons Exposed to Oxygen and Glucose Deprivation

Depletion of oxygen and glucose even for brief periods is sufficient to cause cerebral ischemia, which is a predominant worldwide cause of motor deficits with the reduction of life quality and subsequently death. Hence, more insights regarding protective measures against ischemic events are becoming a major research goal. Among the many neuronal factors, N-methyl-D-aspartate receptors (NMDAR), orexinergic neuroreceptors (ORXR), and sympatho-inhibitory neuropeptide catestatin (CST) are widely involved with ischemic episodes. In this study, it was possible to induce in vitro ischemic conditions of the hamster (Mesocricetus auratus) hippocampal and hypothalamic neuronal cultures, grown on a newly compartmentalized membrane system, via oxygen and glucose deprivation (OGD). These cultures displayed notably differentiated NMDARergic and ORXergic receptor expression activities along with evident brain-derived neurotrophic factor (BDNF) plus orexin A (ORX-A) secretion, especially under co-cultured conditions. Interestingly, addition of CST in OGD-insulted hippocampal cells accounted for upregulated GluN1 and ORX1R transcripts that in the case of the latter neuroreceptor was very strongly (p < 0.001) increased when co-cultured with hypothalamic cells. Similarly, hypothalamic neurons supplied very evident upregulations of GluN1, ORX1R, and above all of GluN2A transcripts along with increased BDNF and ORX-A secretion in the presence of hippocampal cells. Overall, the preferential CST effects on BDNF plus ORX-A production together with altered NMDAR and ORXR levels, especially in co-cultured hypothalamic cells pointed to ORX-containing neurons as major protective constituents against ischemic damages thus opening new scenarios on the cross-talking roles of CST during ischemic disorders.

Characterization of brevetoxin (PbTx-3) exposure in neurons of the anoxia-tolerant freshwater turtle (Trachemys scripta)

Harmful algal blooms are increasing in frequency and extent worldwide and occur nearly annually off the west coast of Florida where they affect both humans and wildlife. The dinoflagellate Karenia brevis is a key organism in Florida red tides that produces a suite of potent neurotoxins collectively referred to as the brevetoxins (PbTx). Brevetoxins bind to and open voltage gated sodium channels (VGSC), increasing cell permeability in excitable cells and depolarizing nerve and muscle tissue. Exposed animals may thus show muscular and neurological symptoms including head bobbing, muscle twitching, paralysis, and coma; large HABs can result in significant morbidity and mortality of marine life, including fish, birds, marine mammals, and sea turtles. Brevetoxicosis however is difficult to treat in endangered sea turtles as the physiological impacts have not been investigated and the magnitude and duration of brevetoxin exposure are generally unknown. In this study we used the freshwater turtle Trachemys scripta as a model organism to investigate the effects of the specific brevetoxin PbTx-3 in the turtle brain. Primary turtle neuronal cell cultures were exposed to a range of PbTx-3 concentrations to determine excitotoxicity. Agonists and antagonists of voltage-gated sodium channels and downstream targets were utilized to confirm the toxin's mode of action. We found that turtle neurons are highly resistant to PbTx-3; while cell viability decreased in a dose dependent manner across PbTx-3 concentrations of 100-2000nM, the EC₅₀ was significantly higher than has been reported in mammalian neurons. PbTx-3 exposure resulted in significant Ca²⁺ influx, which could be fully abrogated by the VGSC antagonist tetrodotoxin, NMDA receptor blocker MK-801, and tetanus toxin, indicating that the mode of action in turtle neurons is the same as in mammalian cells. As both turtle and mammalian VGSCs have a high affinity for PbTx-3, we suggest that the high resistance of the turtle neuron to PbTx-3 may be related to its ability to withstand anoxic depolarization. The ultimate goal of this work is to design treatment protocols for sea turtles exposed to red tides worldwide.

Chronic Administration of Catestatin Improves Autonomic Function and Exerts Cardioprotective Effects in Myocardial Infarction Rats

Catestatin (CST), which is emerging as a novel cardiac modulator, can protect the heart against excessive sympathetic drive in hypertensive cardiomyopathy. The aim of this study is to investigate whether exogenous CST decreases excessive cardiac sympathetic drive and improves autonomic function and exerts cardioprotective effects in myocardial infarction (MI) rats. Rats were divided into a sham group, MI group, and MI plus CST (MI + CST) group. Four weeks later, the autonomic function of the animals was assessed by analyzing heart rate variability (HRV) and measuring plasma catecholamine. Cardiac function was evaluated via echocardiography. Electrophysiological characteristics were assessed in Langendorff-perfused hearts. Compared to the MI group, the chronic administration of CST significantly increased the standard deviation of normal–normal intervals ( P < .01) and low-frequency (LF) and high-frequency (HF) HRV and decreased the ratio of LF–HF HRV ( P < .01 for all). Additionally, the level of plasma catecholamine was reduced in the MI + CST group compared to the MI group ( P < .01). Treatment with CST significantly increased ejection fraction (EF) and fraction shorting (FS) and significantly decreased the left ventricular end-systolic diameter and left ventricular end-diastolic diameter at 28 days postmyocardial infraction ( P < .05 for all). After MI, the ventricular repolarization duration, such as QTc intervals and action potential duration (APD) at 90% repolarization, was prolonged, and this prolongation could be decreased by CST ( P < .05 for all). The CST also increased the threshold of ADP alternans ( P < .01). Moreover, ventricular arrhythmias were induced in 83% of the MI group but only 33% of the MI + CST group ( P < .05). These results suggested that the chronic administration of CST plays a role in cardioprotection in MI rats, which may function by decreasing the cardiac sympathetic drive and improving autonomic function.

Plasma Catestatin: A Useful Biomarker for Coronary Collateral Development with Chronic Myocardial Ischemia

Backgrounds

Catestatin is an endogenous multifunctional neuroendocrinepeptide. Recently, catestatin was discovered as a novel angiogenic cytokine. The study was to investigate the associations between endogenous catestatin and coronary collateral development among the patients with chronic myocardial ischemia.

Methods

Thirty-eight patients with coronary artery chronic total occlusions (CTO) (CTO group) and 38 patients with normal coronary arteries (normal group) were enrolled in the series. Among the patients with CTO, coronary collateral development was graded according to the Rentrop score method. Rentrop score 0–1 collateral development was regarded as poor collateral group and 2–3 collateral development was regarded as good collateral group. Plasma catestatin level and vascular endothelial growth factor (VEGF) were measured by ELISA kits.

Results

The plasma catestatin levels in CTO group were significantly higher than that in normal group (1.97±1.01 vs 1.36±0.97ng/ml, p = 0.009). In the CTO group, the patients with good collateral development had significantly higher catestatin and VEGF levels than those with poor collateral development (2.36±0.73 vs 1.61±1.12 ng/ml, p = 0.018; 425.23±140.10 vs 238.48±101.00pg/mL, p<0.001). There is a positive correlation between plasma catestatin levels and Rentrop scores (r = 0.40, p = 0.013) among the patients with CTO. However, there is no correlations between plasma catestatin levels and VEGF (r = -0.06, p = 0.744). In the multiple linear regression models, plasma catestatin level was one of the independent factors of coronary collateral development after adjustment for confounders.

Conclusions

Plasma catestatin was associated with coronary collateral developments. It may be a useful biomarker for coronary collateral development and potential target for therapeutic angiogenesis in patients with CTO.

Catestatin and GABA(A)R related feeding habits rely on dopamine, ghrelin plus leptin neuroreceptor expression variations

Catestatin (CST), an endogenously small sympathoinhibitory peptide is capable of interfering with the major cerebral neuroreceptor-blocking site, i.e. γ-aminobutyric acidA receptor (GABAAR) system especially in limbic brain areas that are involved with feeding behaviors. The GABAARergic-related effects seem to derive from its interaction with other molecular neuroreceptors such as dopaminergic, ghrelin and leptinergic. In this context, the present study aimed to investigate probable feeding responses (eating and drinking) induced by treatment with CST and the GABAAR antagonist bicucullin (BIC) alone or simultaneously (CST+BIC) in the Syrian hibernating hamster (Mesocricetus auratus) model. Hamsters that received these compounds via intracerebroventricular infusions displayed notable variations of feeding and drinking bouts. In particular, an anorexigenic response was evident following treatment with CST while BIC evoked a significant increase of eating and drinking behaviors. Surprisingly when both agents were given simultaneously, a predominating anorexigenic response was detected as shown by evident CST-dependent reduction of feeding bouts. Contextually such behaviors, especially those following the combined treatment were tightly correlated with the significantly increased cerebral dopamine receptor 1 (D1) plus reduced ghrelin receptor (GhsR) and leptin receptor (LepR) transcript levels. Overall, the anorexigenic effect of CST deriving from its tight interaction with GABAARs activity plus D1 and GhsR transcripts tends to propose these neuronal elements as pivotal factors responsible for feeding disorders.

"Unclassical" Combination of Smell Dysfunction, Altered Abdominal Nociception and Human Hypertension Associated "Classical" Adrenal-Augmentation

We report a 33-year-old female patient, who arrived to the emergency ward with an abdominal pain that suddenly started 10 days before admission. Simultaneously, the patient developed sudden arterial hypertension and smell disturbances. Conventional medical treatment for pain and arterial hypertension was effortless. Laboratory tests ruled out pancreatitis. Metanephrines in her urine were also normal. A dual-phase intravenous contrast computed tomography of the abdomen showed a large mass within left adrenal gland. Adrenocortical adenoma was diagnosed. The mass was not hypervascularized but positive for synaptophysin and chromogranin A. Importantly, these proteins are heavily involved with acetylcholine metabolism. The triad of olfactory disorders, pain and arterial hypertension normalized after surgically extracting the adrenal mass. To our knowledge, this medical case is the first reported patient exhibiting immediate recovery of such unclassical triad of local and remote findings. The function and dysfunction of key nanocholinergic pathways involved with smell, blood pressure and nociception would explain the pathophysiology of this unique medical case.

Catestatin and orexin-A influence hamster thermic states during hibernation

Decreased body temperature during hibernation evokes a neuroprotective effect against the frequent neurodegenerative events of ischemic/reperfusion injuries. This neuroprotection appears to stem from a direct involvement of orexin-A plus the sympathoinhibitory neuroactive peptide catestatin on orexin 2 receptor-dependent feeding and motor behaviors of the facultative hibernating hamster.