Catestatin in rat RVLM is sympathoexcitatory, increases barosensitivity, and attenuates chemosensitivity and the somatosympathetic reflex

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.

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.

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.

Sympathetic nervous system activation and heart failure: Current state of evidence and the pathophysiology in the light of novel biomarkers

Heart failure (HF) is a complex clinical syndrome characterized by the activation of at least several neurohumoral pathways that have a common role in maintaining cardiac output and adequate perfusion pressure of target organs and tissues. The sympathetic nervous system (SNS) is upregulated in HF as evident in dysfunctional baroreceptor and chemoreceptor reflexes, circulating and neuronal catecholamine spillover, attenuated parasympathetic response, and augmented sympathetic outflow to the heart, kidneys and skeletal muscles. When these sympathoexcitatory effects on the cardiovascular system are sustained chronically they initiate the vicious circle of HF progression and become associated with cardiomyocyte apoptosis, maladaptive ventricular and vascular remodeling, arrhythmogenesis, and poor prognosis in patients with HF. These detrimental effects of SNS activity on outcomes in HF warrant adequate diagnostic and treatment modalities. Therefore, this review summarizes basic physiological concepts about the interaction of SNS with the cardiovascular system and highlights key pathophysiological mechanisms of SNS derangement in HF. Finally, special emphasis in this review is placed on the integrative and up-to-date overview of diagnostic modalities such as SNS imaging methods and novel laboratory biomarkers that could aid in the assessment of the degree of SNS activation and provide reliable prognostic information among patients with HF.

Angiotensin-Converting Enzyme 2 in the Rostral Ventrolateral Medulla Regulates Cholinergic Signaling and Cardiovascular and Sympathetic Responses in Hypertensive Rats

The rostral ventrolateral medulla (RVLM) is a key region in cardiovascular regulation. It has been demonstrated that cholinergic synaptic transmission in the RVLM is enhanced in hypertensive rats. Angiotensin-converting enzyme 2 (ACE2) in the brain plays beneficial roles in cardiovascular function in hypertension. The purpose of this study was to determine the effect of ACE2 overexpression in the RVLM on cholinergic synaptic transmission in spontaneously hypertensive rats (SHRs). Four weeks after injecting lentiviral particles containing enhanced green fluorescent protein and ACE2 bilaterally into the RVLM, the blood pressure and heart rate were notably decreased. ACE2 overexpression significantly reduced the concentration of acetylcholine in microdialysis fluid from the RVLM and blunted the decrease in blood pressure evoked by bilateral injection of atropine into the RVLM in SHRs. In conclusion, we suggest that ACE2 overexpression in the RVLM attenuates the enhanced cholinergic synaptic transmission in SHRs.

Catestatin serum levels are increased in male patients with obstructive sleep apnea

PURPOSE

Obstructive sleep apnea (OSA) is a complex sleep disorder associated with autonomic and sympathetic dysregulation. To the contrary, catestatin, an endogenous pleiotropic peptide cleaved from chromogranin A, is known for its inhibitory effects on catecholamine release and sympathetic activity. The aims of the study were to determine catestatin serum levels among male OSA patients compared to healthy control subjects and to explore associations of catestatin with anthropometric, polysomnographic, and lipid profile parameters.

METHODS

Seventy-eight male OSA patients aged 50.3 ± 8.8 years and 51 age/sex/BMI-matched control subjects aged 50.4 ± 7.8 years were enrolled in the study. Catestatin serum levels were determined by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

Catestatin serum levels were significantly higher among OSA patients compared to control subjects (2.9 ± 1.2 vs. 1.5 ± 1.1 ng/mL, p < 0.001). Serum catestatin levels significantly correlated with apnea-hypopnea index (AHI) among non-obese OSA subjects (r = 0.466, p = 0.016; β = 0.448, p = 0.026), while in whole OSA population, catestatin levels significantly correlated with neck circumference (r = 0.318, p < 0.001; β = 0.384, p < 0.001) and high-density lipoprotein (HDL) cholesterol (r = - 0.320, p < 0.001; β = - 0.344, p < 0.001). In multivariate-adjusted regression model, serum catestatin was significant and independent predictor of OSA status (OR 4.98, 95% CI 2.17-11.47, p < 0.001).

CONCLUSIONS

Catestatin serum levels are significantly increased in male OSA population and positively correlate with disease severity in non-obese patients. OSA status is independently predicted by catestatin levels; however, this finding is restricted to patients with moderate-to-severe disease. Further studies are necessary to elucidate the mechanistic role of catestatin in the complex pathophysiology of OSA.

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.

The predictive value of plasma catestatin for all-cause and cardiac deaths in chronic heart failure patients

Catestatin (CST) is a proteolytic fragment of Chromogranin A with a broad spectrum of activities in the cardiovascular system. The level of plasma CST increases in chronic heart failure patients, but its potential relationship to patient prognosis is unknown. In this study, we measured plasma CST levels in 202 chronic heart failure patients and followed them for a median of 52.5 months. The plasma CST level was higher in patients with all-cause death and cardiac death than in survivors. According to univariate COX regression, higher plasma CST levels predicted increased risk of all-cause and cardiac death. After adjustment for other confounding factors, plasma CST was an independent risk factor for both outcomes, and the hazard ratios (HRs) were 1.84 (95% CI: 1.02-3.32, p=0.042) and 2.41 (95% CI: 1.26-4.62, p=0.008) for all-cause death and cardiac death, respectively. The new risk-predictive model considering CST was superior to the previous model for both outcomes by ANOVA and likelihood ratio tests (p=0.040 and p=0.008, respectively). Concurrent increases in plasma BNP (B-type natriuretic peptide) and CST levels predicted the highest risk for both all-cause and cardiac deaths [HR=5.18 (95% CI: 1.94-13.87, p=0.001) and HR=9.19 (95% CI: 2.75-30.78, p<0.001), respectively]. Large-scale studies are needed to further assess the value of plasma CST in predicting heart failure prognosis.

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.

Potential applications of catestatin in cardiovascular diseases

Catestatin (CST) was first named in 1997 for its catecholamine-inhibitory activity. It was discovered as a potent inhibitor of catecholamine secretion and as a regulator of histamine release. Accumulating evidence shows that CST is involved with cardiovascular diseases; however, whether CST is a protective factor for these conditions and the mechanisms by which such actions may be mediated are not well understood. In this article, we review recent basic research and clinical trials in the study of CST and summarize the association of CST with cardiovascular diseases. We review data obtained from MedLine via PubMed and from our own investigations.

Catestatin Gly364Ser Variant Alters Systemic Blood Pressure and the Risk for Hypertension in Human Populations via Endothelial Nitric Oxide Pathway

Catestatin (CST), an endogenous antihypertensive/antiadrenergic peptide, is a novel regulator of cardiovascular physiology. Here, we report case-control studies in 2 geographically/ethnically distinct Indian populations (n≈4000) that showed association of the naturally-occurring human CST-Gly364Ser variant with increased risk for hypertension (age-adjusted odds ratios: 1.483; P=0.009 and 2.951; P=0.005). Consistently, 364Ser allele carriers displayed elevated systolic (up to ≈8 mm Hg; P=0.004) and diastolic (up to ≈6 mm Hg; P=0.001) blood pressure. The variant allele was also found to be in linkage disequilibrium with other functional single-nucleotide polymorphisms in the CHGA promoter and nearby coding region. Functional characterization of the Gly364Ser variant was performed using cellular/molecular biological experiments (viz peptide-receptor binding assays, nitric oxide [NO], phosphorylated extracellular regulated kinase, and phosphorylated endothelial NO synthase estimations) and computational approaches (molecular dynamics simulations for structural analysis of wild-type [CST-WT] and variant [CST-364Ser] peptides and docking of peptide/ligand with β-adrenergic receptors [ADRB1/2]). CST-WT and CST-364Ser peptides differed profoundly in their secondary structures and showed differential interactions with ADRB2; although CST-WT displaced the ligand bound to ADRB2, CST-364Ser failed to do the same. Furthermore, CST-WT significantly inhibited ADRB2-stimulated extracellular regulated kinase activation, suggesting an antagonistic role towards ADRB2 unlike CST-364Ser. Consequently, CST-WT was more potent in NO production in human umbilical vein endothelial cells as compared with CST-364Ser. This NO-producing ability of CST-WT was abrogated by ADRB2 antagonist ICI 118551. In conclusion, CST-364Ser allele enhanced the risk for hypertension in human populations, possibly via diminished endothelial NO production because of altered interactions of CST-364Ser peptide with ADRB2 as compared with CST-WT.

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.

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

The chromogranin A-derived peptide catestatin (CST) exerts sympathoexcitatory and hypertensive effects when microinjected into the rostral ventrolateral medulla (RVLM: excitatory output); it exhibits sympathoinhibitory and antihypertensive effects when microinjected into the caudal ventrolateral medulla (CVLM: inhibitory output) of vagotomized normotensive rats. Here, continuous infusion of CST into the central amygdalar nucleus (CeA) of spontaneously hypertensive rats (SHRs) for 15 days resulted in a marked decrease of blood pressure (BP) in 6-month- (by 37 mm Hg) and 9-month- (by 65 mm Hg)old rats. Whole-cell patch-clamp recordings on pyramidal CeA neurons revealed that CST increased both spontaneous inhibitory postsynaptic current (sIPSC) amplitude plus frequency, along with reductions of sIPSC rise time and decay time. Inhibition of GABAA receptors (GABAARs) by bicuculline completely abolished CST-induced sIPSC, corroborating that CST signals occur through this major neuroreceptor complex. Hypertension is a major risk factor for cerebrovascular diseases, leading to vascular dementia and neurodegeneration. We found a marked neurodegeneration in the amygdala and brainstem of 9-month-old SHRs, while CST and the GABAAR agonist Muscimol provided significant neuroprotection. Enhanced phosphorylation of Akt and ERK accounted for these neuroprotective effects through anti-inflammatory and anti-apoptotic activities. Overall our results point to CST exerting potent antihypertensive and neuroprotective effects plausibly via a GABAergic output, which constitute a novel therapeutic measure to correct defects in blood flow control in disorders such as stroke and Alzheimer's disease.

Catestatin-like immunoreactivity in the rat eye

The aim of the study was to investigate the presence and distribution of the chromogranin A-derived peptide catestatin in the rat eye and trigeminal ganglion by immunofluorescence using an antibody which recognizes not only free catestatin but also larger fragments containing the sequence of catestatin. Western blots were performed in an attempt to characterize the immunoreactivities detected by the catestatin antiserum. Sparse immunoreactive nerve fibers were visualized in the corneal stroma, in the chamber angle, in the sphincter muscle but also in association with the dilator muscle, in the stroma of the ciliary body and processes, but dense in the irideal stroma, around blood vessels at the limbus and in the choroid and in cells of the innermost retina representing amacrine cells as identified by colocalization with substance P. Furthermore, catestatin-immunoreactivity was detected in the trigeminal ganglion in small to medium-sized cells and there were abundant catestatin-positive nerve fibers stained throughout the stroma of the ganglion. Double immunofluorescence of catestatin with substance P revealed colocalization both in cells of the trigeminal ganglion as well as in nerve fibers in the choroid. The immunoreactivities are present obviously as free catestatin and/or small-sized catestatin-containing fragments in the retina and ocular nerves but as large processed fragments as well, weak in the retina and more prominent in remaining ocular tissues, possibly in endothelial cells. This indicates that this peptide is a constituent of sensory neurons innervating the rat eye and the presence in amacrine cells in the retina is typical for neuropeptides. Catestatin is biologically highly active and might be of significance in the pathophysiology of the eye.

MicroRNA-22 and promoter motif polymorphisms at the Chga locus in genetic hypertension: functional and therapeutic implications for gene expression and the pathogenesis of hypertension

Hypertension is a common hereditary syndrome with unclear pathogenesis. Chromogranin A (Chga), which catalyzes formation and cargo storage of regulated secretory granules in neuroendocrine cells, contributes to blood pressure homeostasis centrally and peripherally. Elevated Chga occurs in spontaneously hypertensive rat (SHR) adrenal glands and plasma, but central expression is unexplored. In this report, we measured SHR and Wistar-Kyoto rat (control) Chga expression in central and peripheral nervous systems, and found Chga protein to be decreased in the SHR brainstem, yet increased in the adrenal and the plasma. By re-sequencing, we systematically identified five promoter, two coding and one 3'-untranslated region (3'-UTR) polymorphism at the SHR (versus WKY or BN) Chga locus. Using HXB/BXH recombinant inbred (RI) strain linkage and correlations, we demonstrated genetic determination of Chga expression in SHR, including a cis-quantitative trait loci (QTLs) (i.e. at the Chga locus), and such expression influenced biochemical determinants of blood pressure, including a cascade of catecholamine biosynthetic enzymes, catecholamines themselves and steroids. Luciferase reporter assays demonstrated that the 3'-UTR polymorphism (which disrupts a microRNA miR-22 motif) and promoter polymorphisms altered gene expression consistent with the decline in SHR central Chga expression. Coding region polymorphisms did not account for changes in Chga expression or function. Thus, we hypothesized that the 3'-UTR and promoter mutations lead to dysregulation (diminution) of Chga in brainstem cardiovascular control nuclei, ultimately contributing to the pathogenesis of hypertension in SHR. Accordingly, we demonstrated that in vivo administration of miR-22 antagomir to SHR causes substantial (∼18 mmHg) reductions in blood pressure, opening a novel therapeutic avenue for hypertension.

PACAP causes PAC1/VPAC2 receptor mediated hypertension and sympathoexcitation in normal and hypertensive rats

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an excitatory neuropeptide that plays an important role in hypertension and stress responses. PACAP acts at three G protein-coupled receptors [PACAP type 1 receptor (PAC(1)) and vasoactive intestinal peptide receptor types 1 and 2 (VPAC(1) and VPAC(2))] and is localized to sites involved in cardiovascular control, most significantly the rostral ventrolateral medulla (RVLM). The RVLM is crucial for the tonic and reflex control of efferent sympathetic activity. Increases in sympathetic activity are observed in most types of hypertension and heart failure. PACAP delivered intrathecally also causes massive sympathoexcitation. We aimed to determine the presence and abundance of the three PACAP receptors in the RVLM, the role, in vivo, of PACAP in the RVLM on tonic and reflex cardiovascular control, and the contribution of PACAP to hypertension in the spontaneously hypertensive rat (SHR). Data were obtained using quantitative PCR and microinjection of PACAP and its antagonist, PACAP(6-38), into the RVLM of anesthetized artificially ventilated normotensive rats or SHRs. All three receptors were present in the RVLM. PACAP microinjection into the RVLM caused sustained sympathoexcitation and tachycardia with a transient hypertension but did not affect homeostatic reflexes. The responses were partially mediated through PAC(1)/VPAC(2) receptors since the effect of PACAP was attenuated (∼50%) by PACAP(6-38). PACAP was not tonically active in the RVLM in this preparation because PACAP(6-38) on its own had no inhibitory effect. PACAP has long-lasting cardiovascular effects, but altered PACAP signaling within the RVLM is not a cause of hypertension in the SHR.

Catestatin has an unexpected effect on the intrathecal actions of PACAP dramatically reducing blood pressure

This study focuses on presympathetic neurons of the rostral ventrolateral medulla (RVLM) that regulate sympathetic vasomotor tone. Many neurotransmitters are colocalized in RVLM neurons and are released under specific conditions to modulate efferent homeostatic responses. Of particular interest here are two peptides colocalized in catecholaminergic RVLM neurons: catestatin and pituitary adenylate cyclase-activating polypeptide (PACAP). Chromogranin A-derived catestatin is a potent endogenous noncompetitive nicotinic and adrenoreceptor antagonist. Catestatin impairs adenylate cyclase and phospholipase C action: mechanisms engaged by PACAP. Although PACAP and catestatin are likely coreleased, the possible effects of this are unknown. We aimed to determine whether catestatin affects the normal sympathoexcitatory but isotensive responses to intrathecal PACAP. Urethane-anesthetized, vagotomized, ventilated Sprague-Dawley rats (n = 22) were given an intrathecal injection of catestatin at different times prior to intrathecal administration of PACAP-38. Arterial pressure, splanchnic sympathetic nerve activity, heart rate, and reflex responses to baroreceptor and chemoreceptor activation were recorded. The key findings of this study are that pretreatment with catestatin time dependently enhances the PACAP-38 effect on mean arterial pressure and enhances sympathetic barosensitivity and chemosensitivity. The time-scale of the effect of catestatin on the response to PACAP-38 strongly suggests that catestatin is either causing changes in gene expression to exert its effects, or modifying intracellular mechanisms normally engaged by PAC(1) receptors. The ability of catestatin pretreatment to enhance barosensitivity and chemosensitivity after PACAP-38 injection supports the hypothesis that catestatin manipulates the intracellular environment within sympathetic neurons in a way that increases responses to PACAP.

Noxious somatic stimuli diminish respiratory-sympathetic coupling by selective resetting of the respiratory rhythm in anaesthetized rats

Noxious somatic stimulation evokes respiratory and autonomic responses. The mechanisms underlying the responses and the manner in which they are co-ordinated are still unclear. The effects of activation of somatic nociceptive fibres on lumbar sympathetic nerve activity at slow (2-10 Hz) and fast frequency bands (100-1000 Hz) and the effects on respiratory-sympathetic coupling are unknown. In anaesthetized, artificially ventilated Sprague-Dawley rats under neuromuscular blockade, ensemble averaging of sympathetic activity following high-intensity single-pulse stimulation of the sciatic nerve revealed two peaks (~140 and ~250 ms) that were present at similar latencies whether or not slow or fast band filtering was used. Additionally, in the slow band of both lumbar and splanchnic sympathetic nerve activity, a third peak with a very slow latency (~650 ms) was apparent. In the respiratory system, activation of the sciatic nerve decreased the expiratory period when the stimulus occurred during the first half of expiration, but increased the expiratory period if the stimulus was delivered in the second half of the expiratory phase. The phase shifting of the respiratory cycle also impaired the respiratory-sympathetic coupling in both splanchnic and lumbar sympathetic nerve activity in the subsequent respiratory cycle. The findings suggest that noxious somatosympathetic responses reduce the co-ordination between respiration and perfusion by resetting the respiratory pattern generator.

Catestatin (chromogranin A(352-372)) and novel effects on mobilization of fat from adipose tissue through regulation of adrenergic and leptin signaling

Chromogranin A knock-out (Chga-KO) mice display increased adiposity despite high levels of circulating catecholamines and leptin. Consistent with diet-induced obese mice, desensitization of leptin receptors caused by hyperleptinemia is believed to contribute to the obese phenotype of these KO mice. In contrast, obesity in ob/ob mice is caused by leptin deficiency. To characterize the metabolic phenotype, Chga-KO mice were treated with the CHGA-derived peptide catestatin (CST) that is deficient in these mice. CST treatment reduced fat depot size and increased lipolysis and fatty acid oxidation. In liver, CST enhanced oxidation of fatty acids as well as their assimilation into lipids, effects that are attributable to the up-regulation of genes promoting fatty acid oxidation (Cpt1α, Pparα, Acox, and Ucp2) and incorporation into lipids (Gpat and CD36). CST did not affect basal or isoproterenol-stimulated cAMP production in adipocytes but inhibited phospholipase C activation by the α-adrenergic receptor (AR) agonist phenylephrine, suggesting inhibition of α-AR signaling by CST. Indeed, CST mimicked the lipolytic effect of the α-AR blocker phentolamine on adipocytes. Moreover, CST reversed the hyperleptinemia of Chga-KO mice and improved leptin signaling as determined by phosphorylation of AMPK and Stat3. CST also improved peripheral leptin sensitivity in diet-induced obese mice. In ob/ob mice, CST enhanced leptin-induced signaling in adipose tissue. In conclusion, our results implicate CST in a novel pathway that promotes lipolysis and fatty acid oxidation by blocking α-AR signaling as well as by enhancing leptin receptor signaling.

Chromogranin A and derived peptides in health and disease

Chromogranin A (CgA) is a member of the granins, a family of acidic proteins found in abundance in (neuro)endocrine cells (e.g., in chromaffin cells) and in some tumors. Like other granins, CgA has a granulogenic role in secretory granule biogenesis and is stored in these organelles. CgA is partially processed differentially in various cell types to yield biologically active peptides, such as vasostatin, pancreastatin, catestatin, and serpinins. In this review, we describe the roles of CgA and several of its derived peptides. CgA, which is elevated in the blood of cancer patients, inhibits angiogenesis and exerts protective effects on the endothelial barrier function in tumors, thus affecting response to chemotherapy. Recent studies indicate that the serpinins promote cell survival and myocardial contractility and relaxation. Other peptides such as pancreastatin were found to have significant effects on inhibition of glucose-stimulated insulin secretion and glucose up-take, induction of glycogenolysis in hepatocytes, and inhibition of lipogenesis. In contrast, catestatin has opposite effects to that of pancreastatin in glucose metabolism and lipogenesis. Catestatin appears to also play a significant role in cardiac function, blood pressure regulation, and mutations in the catestatin domain of the CgA gene are associated with hypertension in humans.

Catestatin, a chromogranin A-derived peptide, is sympathoinhibitory and attenuates sympathetic barosensitivity and the chemoreflex in rat CVLM

Hypertension is a major cause of morbidity. The neuropeptide catestatin [human chromogranin A-(352-372)] is a peptide product of the vesicular protein chromogranin A. Studies in the periphery and in vitro studies show that catestatin blocks nicotine-stimulated catecholamine release and interacts with β-adrenoceptors and histamine receptors. Catestatin immunoreactivity is present in the rostral ventrolateral medulla (RVLM), a key site for blood pressure control in the brain stem. Recently, we reported that microinjection of catestatin into the RVLM is sympathoexcitatory and increases barosensitivity. Here, we report the effects of microinjection of catestatin (1 mM, 50 nl) into the caudal ventrolateral medulla (CVLM) in urethane-anesthetized, bilaterally vagotomized, artificially ventilated Sprague-Dawley rats (n = 8). We recorded resting arterial pressure, splanchnic sympathetic nerve activity, phrenic nerve activity, heart rate, and measured cardiovascular homeostatic reflexes. Homeostatic reflexes were evaluated by measuring cardiovascular responses to carotid baroreceptor and peripheral chemoreceptor activation. Catestatin decreased basal levels of arterial pressure (-23 ± 4 mmHg), sympathetic nerve activity (-26.6 ± 5.7%), heart rate (-19 ± 5 bpm), and phrenic nerve amplitude (-16.8 ± 3.3%). Catestatin caused a 15% decrease in phrenic inspiratory period (T(i)) and a 16% increase in phrenic expiratory period (T(e)) but had no net effect on the phrenic interburst interval (T(tot)). Catestatin decreased sympathetic barosensitivity by 63.6% and attenuated the peripheral chemoreflex (sympathetic nerve response to brief hypoxia; range decreased 39.9%; slope decreased 30.1%). The results suggest that catestatin plays an important role in central cardiorespiratory control.

Phosphodiesterase type-2 and NO-dependent S-nitrosylation mediate the cardioinhibition of the antihypertensive catestatin

The chromogranin A (CHGA)-derived peptide catestatin (CST: hCHGA(352-372)) is a noncompetitive catecholamine-release inhibitor that exerts vasodilator, antihypertensive, and cardiosuppressive actions. We have shown that CST directly influences the basal performance of the vertebrate heart where CST dose dependently induced a nitric oxide-cGMP-dependent cardiosuppression and counteracted the effects of adrenergic stimulation through a noncompetitive antagonism. Here, we sought to determine the specific intracardiac signaling activated by CST in the rat heart. Physiological analyses performed on isolated, Langendorff-perfused cardiac preparations revealed that CST-induced negative inotropism and lusitropism involve β(2)/β(3)-adrenergic receptors (β(2)/β(3)-AR), showing a higher affinity for β(2)-AR. Interaction with β(2)-AR activated phosphatidylinositol 3-kinase/endothelial nitric oxide synthase (eNOS), increased cGMP levels, and induced activation of phosphodiesterases type 2 (PDE2), which was found to be involved in the antiadrenergic action of CST as evidenced by the decreased cAMP levels. CST-dependent negative cardiomodulation was abolished by functional denudation of the endothelium with Triton. CST also increased the eNOS expression in cardiac tissue and human umbilical vein endothelial cells. cells, confirming the involvement of the vascular endothelium. In ventricular extracts, CST increased S-nitrosylation of both phospholamban and β-arrestin, suggesting an additional mechanism for intracellular calcium modulation and β-adrenergic responsiveness. We conclude that PDE2 and S-nitrosylation play crucial roles in the CST regulation of cardiac function. Our results are of importance in relation to the putative application of CST as a cardioprotective agent against stress, including excessive sympathochromaffin overactivation.

Catestatin is useful in detecting patients with stage B heart failure

Screening patients with stage B heart failure(HF) may be one strategy for reducing human morbidity. To describe catestatin levels in different stages of HF and evaluate the diagnostic utility of catestatin for detecting stage B HF, we included 300 patients. Catestatin, BNP testing and echocardiogram were performed. Our studies showed catestatin decreased gradually from stage A to C. There was significant difference between stage A and B. Cutoff value for detecting stage B HF was 19.73 ng/ml for catestatin with 90% sensitivity and 50.9% specificity. These results may have implications in the new method to detect patients with stage B HF.