Urocortin 2 in cardiovascular health and disease

Corticotropin-releasing hormone and obesity: From fetal life to adulthood

Obesity is among the most common chronic disorders, worldwide. It is a complex disease that reflects the interactions between environmental influences, multiple genetic allelic variants, and behavioral factors. Recent developments have also shown that biological conditions in utero play an important role in the programming of energy homeostasis systems and might have an impact on obesity and metabolic disease risk. The corticotropin-releasing hormone (CRH) family of neuropeptides, as a central element of energy homeostasis, has been evaluated for its role in the pathophysiology of obesity. This review aims to summarize the relevance and effects of the CRH family of peptides in the pathophysiology of obesity spanning from fetal life to adulthood.

Urocortins as biomarkers in cardiovascular disease

The urocortins (Ucns) belong to the corticotropin-releasing factor (CRF) family of peptides and have multiple effects within the central nervous and the cardiovascular systems. With growing evidence indicating significant cardioprotective properties and cardiovascular actions of these peptides, the question arises as to whether the plasma profiles of the Ucns are altered in pathologic settings. While reports have shown conflicting results and findings have not been corroborated in multiple independent cohorts, it seems likely that plasma Ucn concentrations are elevated in multiple cardiovascular conditions. The degree of increase and accurate determination of circulating values of the Ucns requires further validation.

Urocortin-2 in Acute Heart Failure: Role as a Marker of Volume Overload and Pulmonary Hypertension

Urocortin (Ucn)-2 has shown promising therapeutic effects on heart failure (HF). However, there are still significant knowledge gaps regarding the role and modulation of the endogenous Ucn-2 axis in the cardiovascular system and, specifically, in acute HF. We evaluated Ucn-2 levels in admission serum samples of 80 acute HF patients and assessed their association with clinical, analytical and echocardiographic parameters. Median age was 76.5 years, and 37 patients (46%) were male. Median serum Ucn-2 was 2.3ng/mL. Ucn-2 levels were positively associated with peripheral edemas (P = 0.022), hepatomegaly (P = 0.007) and sodium retention score (ρ = 0.37, P = 0.001) and inversely correlated with inferior vena cava collapse at inspiration (ρ = -0.37, P = 0.001). Additionally, patients with higher Ucn-2 levels had a higher prevalence of right atrial dilation (P = 0.027), right ventricle dilation (P = 0.008), and higher systolic pulmonary artery pressure (ρ = 0.34, P = 0.002). Regarding analytical parameters, Ucn-2 correlated positively with log BNP (r = 0.22, P = 0.055) and inversely with uric acid (r = 0.24, P = 0.029) and total (r = -0.30, P = 0.007) and low-density lipoprotein cholesterol (r = -0.23, P = 0.038). No associations were found between Ucn-2 and age, sex or left heart structure or function. In conclusion, Circulating Ucn-2 was associated with clinical and echocardiographic markers of volume overload and pulmonary hypertension in acute HF patients.

Changes in Musculoskeletal System and Metabolism in Osteoporotic Rats Treated With Urocortin

Objective: In aging population, postmenopausal osteoporosis and decline of musculoskeletal function, referred to as "frailty syndrome" lead to loss of bone and muscle, causing falls, and fall-related injuries. To limit the impact of this portentous duo, simultaneous treatment of both is needed. Urocortin (UCN) has been reported to improve osteoporotic bone properties while its effect on muscle has not been addressed yet. Design and Methods: We aimed to investigate the effect of urocortin in vivo on skeletal muscle structure in osteopenic rats. Sixty Sprague-Dawley rats were divided into five groups: four were ovariectomized (OVX) and one underwent sham operation (SHAM). One ovariectomized group was left untreated (OVX), while one was treated with urocortin s.c. in 3 μg/kg body weight (bw) (OVX+UCN low), one with 30 μg/kg (OVX+UCN high), while one group was treated with estradiol orally (OVX+E: 0.2 mg/kg bw), each for 35 days. Mm. gastrocnemius, longissimus, and soleus were isolated and capillary density as well as diameters of type I and II fibers were measured. In addition, we examined the effect of UCN on tibia using biomechanical, micro-CT and ashing analysis and investigated the blood serum. Results: We demonstrated a positive effect of UCN on M. soleus, in which fiber diameter was positively influenced. The biomechanical and structural parameters of bone were not changed in UCN treated rats. The higher cholesterol, glucose and triglyceride levels in the "UCN high" group raise concern about this treatment. Conclusions: Our results portray urocortin as a substance that can be assessed for future therapeutic treatments of estrogen deficiency. New and Noteworthy: Urocortin has a positive effect on M. soleus (diameter). Urocortin raises serum cholesterol and triglyceride levels. Bone tissue was not affected by UCN.

Corticotropin-Releasing Hormone Family and Their Receptors in the Cardiovascular System

The identification of corticotropin-releasing hormone (CRH) has led to the discovery of a growing family of ligands and receptors. CRH receptor 1 (CRHR1) and CRHR2 are mammalian G-protein coupled receptors (GPCRs) with high affinity for CRH and the CRH family of peptides. CRHR1 is predominantly expressed in the brain and plays a vital role in the hypothalamic-pituitary-adrenal (HPA) axis stress responses by secreting adrenal corticotropic hormone (ACTH). CRHR2 is predominantly expressed in the heart, and a CRHR2-specific ligand, urocortin 2 (UCN2), shows positive cardiac chronotropic and inotropic effects through 3´,5´-cyclic adenosine monophosphate (cAMP) signaling in response to CRHR2-mediated Gαs activation in mice and humans. Central administration of the CRH family of peptides increases mean arterial pressure through CRHR1 activation, whereas peripheral administration of the peptides decreases mean arterial pressure through CRHR2 activation. These observations have led to further investigations of CRHR2 as an important and unique GPCR in the physiological and pathological functioning of the cardiovascular (CV) system. Moreover, recent clinical trials demonstrate CRHR2 as a potentially therapeutic target in the treatment of heart failure. We present recent reviews of the role of CRHRs in basic CV physiology and in the pathophysiology of CV diseases.

Brain and Gut CRF Signaling: Biological Actions and Role in the Gastrointestinal Tract

BACKGROUND

Corticotropin-releasing factor (CRF) pathways coordinate behavioral, endocrine, autonomic and visceral responses to stress. Convergent anatomical, molecular, pharmacological and functional experimental evidence supports a key role of brain CRF receptor (CRF-R) signaling in stress-related alterations of gastrointestinal functions. These include the inhibition of gastric acid secretion and gastric-small intestinal transit, stimulation of colonic enteric nervous system and secretorymotor function, increase intestinal permeability, and visceral hypersensitivity. Brain sites of CRF actions to alter gut motility encompass the paraventricular nucleus of the hypothalamus, locus coeruleus complex and the dorsal motor nucleus while those modulating visceral pain are localized in the hippocampus and central amygdala. Brain CRF actions are mediated through the autonomic nervous system (decreased gastric vagal and increased sacral parasympathetic and sympathetic activities). The activation of brain CRF-R2 subtype inhibits gastric motor function while CRF-R1 stimulates colonic secretomotor function and induces visceral hypersensitivity. CRF signaling is also located within the gut where CRF-R1 activates colonic myenteric neurons, mucosal cells secreting serotonin, mucus, prostaglandin E2, induces mast cell degranulation, enhances mucosal permeability and propulsive motor functions and induces visceral hyperalgesia in animals and humans. CRF-R1 antagonists prevent CRF- and stressrelated gut alterations in rodents while not influencing basal state.

DISCUSSION

These preclinical studies contrast with the limited clinical positive outcome of CRF-R1 antagonists to alleviate stress-sensitive functional bowel diseases such as irritable bowel syndrome.

CONCLUSION

The translational potential of CRF-R1 antagonists in gut diseases will require additional studies directed to novel anti-CRF therapies and the neurobiology of brain-gut interactions under chronic stress.

Modulation of Iris Sphincter and Ciliary Muscles by Urocortin 2

Urocortin 2 (UCN2) is a peptide related to corticotropin-releasing factor, capable of activating CRF-R2. Among its multisystemic effects, it has actions in all 3 muscle subtypes. This study’s aim was to determine its potential role in two of the intrinsic eye muscle kinetics. Strips of iris sphincter (rabbit) and ciliary (bovine) muscles were dissected and mounted in isometric force-transducer systems filled with aerated-solutions. Contraction was elicited using carbachol (10-6 M for iris sphincter, 10-5 M for ciliary muscle), prior adding to all testing substances. UCN2 induced relaxation in iris sphincter muscle, being the effect maximal at 10-7 M concentrations (-12.2 % variation vs. control). This effect was abolished with incubation of indomethacin, antisauvagine-30, chelerytrine and SQ22536, but preserved with L-nitro-L-arginine. In carbachol pre-stimulated ciliary muscle, UCN2 (10-5 M) enhanced contraction (maximal effect of 18.2 % increase vs. control). UCN2 is a new modulator of iris sphincter relaxation, dependent of CRF-R2 activation, synthesis of prostaglandins (COX pathway) and both adenylate cyclase and PKC signaling pathways, but independent of nitric oxide production. Regarding ciliary muscle, UCN2 enhances carbachol-induced contraction, in higher doses.

Epigenetic Programming of Synthesis, Release, and/or Receptor Expression of Common Mediators Participating in the Risk/Resilience for Comorbid Stress-Related Disorders and Coronary Artery Disease

Corticotrophin releasing factor, vasopressin, oxytocin, natriuretic hormones, angiotensin, neuregulins, some purinergic substances, and some cytokines contribute to the long-term modulation and restructuring of cardiovascular regulation networks and, at the same time, have relevance in situations of comorbid abnormal stress responses. The synthesis, release, and receptor expression of these mediators seem to be under epigenetic control since early stages of life, possibly underlying the comorbidity to coronary artery disease (CAD) and stress-related disorders (SRD). The exposure to environmental conditions, such as stress, during critical periods in early life may cause epigenetic programming modifying the development of pathways that lead to stable and long-lasting alterations in the functioning of these mediators during adulthood, determining the risk of or resilience to CAD and SRD. However, in contrast to genetic information, epigenetic marks may be dynamically altered throughout the lifespan. Therefore, epigenetics may be reprogrammed if the individual accepts the challenge to undertake changes in their lifestyle. Alternatively, epigenetics may remain fixed and/or even be inherited in the next generation. In this paper, we analyze some of the common neuroendocrine functions of these mediators in CAD and SRD and summarize the evidence indicating that they are under early programming to put forward the theoretical hypothesis that the comorbidity of these diseases might be epigenetically programmed and modified over the lifespan of the individual.

Glucocorticoid withdrawal affects stress-induced changes of urocortin 2 gene expression in rat adrenal medulla and brain

Corticotropin-releasing factor is well known activator of the hypothalamic-pituitary-adrenocortical axis, that represents crucial system participating on stress response of the organism. Urocortins are members of the corticotropin-releasing factor family of peptides with proposed effects on neuroendocrine and behavioral stress response mechanisms. Urocortin 2, one of three known urocortins, is present in central and peripheral stress response system and its expression can be augmented by glucocorticoids. In the present study we have examined how glucocorticoid withdrawal affects urocortin 2 gene expression after acute immobilization in the adrenal medulla and selected brain areas in rats. We used pharmacological adrenalectomy to block synthesis of corticosterone. Our results show that the immobilization-induced rise in urocortin 2 mRNA levels in rat adrenal medulla was not inhibited by glucocorticoid withdrawal. On the other hand, observed changes in the brain indicate that the effect of stress and pharmacological adrenalectomy on urocortin 2 gene expression is site-specific. While in the paraventricular nucleus and locus coeruleus the immobilization induced rise of urocortin 2 was not inhibited by pharmacological adrenalectomy in the arcuate nucleus and central amygdala it was. Moreover, we have seen a significant depletion of urocortin 2 plasma levels after immobilization. The immobilization induced rise of urocortin 2 gene expression in rat adrenal medulla and brain areas regulating stress response pathways and preservation of its induction after adrenalectomy suggests a role of urocortin 2 in the neuroendocrine stress response of an organism. This article is protected by copyright. All rights reserved.

Urocortin-2 improves right ventricular function and attenuates pulmonary arterial hypertension

Aims

Pulmonary arterial hypertension (PAH) is a devastating disease and treatment options are limited. Urocortin-2 (Ucn-2) has shown promising therapeutic effects in experimental and clinical left ventricular heart failure (HF). Our aim was to analyse the expression of Ucn-2 in human and experimental PAH, and to investigate the effects of human Ucn-2 (hUcn-2) administration in rats with monocrotaline (MCT)-induced pulmonary hypertension (PH).

Methods and results

Tissue samples were collected from patients with and without PAH and from rats with MCT-induced PH. hUcn-2 (5 μg/kg, bi-daily, i.p., for 10 days) or vehicle was administered to male wistar rats subjected to MCT injection or to pulmonary artery banding (PAB) to induce right ventricular (RV) overload without PAH. Expression of Ucn-2 and its receptor was increased in the RV of patients and rats with PAH. hUcn-2 treatment reduced PAH in MCT rats, resulting in decreased morbidity, improved exercise capacity and attenuated pulmonary arterial and RV remodelling and dysfunction. Additionally, RV gene expression of hypertrophy and failure signalling pathways were attenuated. hUcn-2 treatment also attenuated PAB-induced RV hypertrophy.

Conclusions

Ucn-2 levels are altered in human and experimental PAH. hUcn-2 treatment attenuates PAH and RV dysfunction in MCT-induced PH, has direct anti-remodelling effects on the pressure-overloaded RV, and improves pulmonary vascular function.

CRF and urocortin 3 protect the heart from hypoxia/reoxygenation-induced apoptosis in zebrafish

Fish routinely experience environmental hypoxia and have evolved various strategies to tolerate this challenge. Given the key role of the CRF system in coordinating the response to stressors and its cardioprotective actions against ischemia in mammals, we sought to characterize the cardiac CRF system in zebrafish and its role in hypoxia tolerance. We established that all genes of the CRF system, the ligands CRFa, CRFb, urotensin 1 (UTS1), and urocortin 3 (UCN3); the two receptor subtypes (CRFR1 and CRFR2); and the binding protein (CRFBP) are expressed in the heart of zebrafish: crfr1 > crfr2 = crfbp > crfa > ucn3 > crfb > uts1 In vivo, exposure to 5% O2 saturation for 15 min and 90 min of recovery resulted in four- to five-fold increases in whole heart crfb and ucn3 mRNA levels but did not affect the gene expression of other CRF system components. In vitro, as assessed by monitoring caspase 3 activity and the number of terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive cells, pretreatment of excised whole hearts with CRF or UCN3 for 30 min prevented the increase in apoptosis associated with exposure to 1% O2 saturation for 30 min with a 24-h recovery. Lastly, the addition of the nonselective CRF receptor antagonist αh-CRF(9-41) prevented the cytoprotective effects of CRF. We show that the CRF system is expressed in fish heart, is upregulated by hypoxia, and is cytoprotective. These findings identify a novel role for the CRF system in fish and a new strategy to tolerate hypoxia.

Corticotropin releasing hormone receptor 2 exacerbates chronic cardiac dysfunction

Prognosis of patients with chronic heart failure remains poor, emphasizing the need to identify additional pathophysiological factors. Tsuda et al. show that Crhr2 activation causes cardiac dysfunction and suggest Crhr2 blockade is a promising therapeutic strategy for chronic heart failure.

Heart failure occurs when the heart is unable to effectively pump blood and maintain tissue perfusion. Despite numerous therapeutic advancements over previous decades, the prognosis of patients with chronic heart failure remains poor, emphasizing the need to identify additional pathophysiological factors. Here, we show that corticotropin releasing hormone receptor 2 (Crhr2) is a G protein–coupled receptor highly expressed in cardiomyocytes and continuous infusion of the Crhr2 agonist, urocortin 2 (Ucn2), reduced left ventricular ejection fraction in mice. Moreover, plasma Ucn2 levels were 7.5-fold higher in patients with heart failure compared to those in healthy controls. Additionally, cardiomyocyte-specific deletion of Crhr2 protected mice from pressure overload-induced cardiac dysfunction. Mice treated with a Crhr2 antagonist lost maladaptive 3′-5′-cyclic adenosine monophosphate (cAMP)–dependent signaling and did not develop heart failure in response to overload. Collectively, our results indicate that constitutive Crhr2 activation causes cardiac dysfunction and suggests that Crhr2 blockade is a promising therapeutic strategy for patients with chronic heart failure.

Urocortin Treatment Improves Acute Hemodynamic Instability and Reduces Myocardial Damage in Post-Cardiac Arrest Myocardial Dysfunction

Aims

Hemodynamic instability occurs following cardiac arrest and is associated with high mortality during the post-cardiac period. Urocortin is a novel peptide and a member of the corticotrophin-releasing factor family. Urocortin has the potential to improve acute cardiac dysfunction, as well as to reduce the myocardial damage sustained after ischemia reperfusion injury. The effects of urocortin in post-cardiac arrest myocardial dysfunction remain unclear.

Methods and Results

We developed a preclinical cardiac arrest model and investigated the effects of urocortin. After cardiac arrest induced by 6.5 min asphyxia, male Wistar rats were resuscitated and randomized to either the urocortin treatment group or the control group. Urocortin (10 μg/kg) was administrated intravenously upon onset of resuscitation in the experimental group. The rate of return of spontaneous circulation (ROSC) was similar between the urocortin group (76%) and the control group (72%) after resuscitation. The left ventricular systolic (dP/dt₄₀) and diastolic (maximal negative dP/dt) functions, and cardiac output, were ameliorated within 4 h after ROSC in the urocortin-treated group compared to the control group (P<0.01). The neurological function of surviving animals was better at 6 h after ROSC in the urocortin-treated group (p = 0.023). The 72-h survival rate was greater in the urocortin-treated group compared to the control group (p = 0.044 by log-rank test). Cardiomyocyte apoptosis was lower in the urocortin-treated group (39.9±8.6 vs. 17.5±4.6% of TUNEL positive nuclei, P<0.05) with significantly increased Akt, ERK and STAT-3 activation and phosphorylation in the myocardium (P<0.05).

Conclusions

Urocortin treatment can improve acute hemodynamic instability as well as reducing myocardial damage in post-cardiac arrest myocardial dysfunction.

Urocortin-1 Mediated Cardioprotection Involves XIAP and CD40-Ligand Recovery: Role of EPAC2 and ERK1/2

Aims

Urocortin-1 (Ucn-1) is an endogenous peptide that protects heart from ischemia and reperfusion (I/R) injuries. Ucn-1 is known to prevent cardiac cell death, but its role in the transcription of specific genes related to survival signaling pathway has not been fully defined. The aim of this study was to investigate the molecular signaling implicated in the improvement of cardiac myocytes survival induced by Ucn-1.

Methods and Results

Ucn-1 administration before ischemia and at the onset of reperfusion, in rat hearts perfused in Langendorff system, fully recovered heart contractility and other hemodynamic parameters. Ucn-1 enhanced cell viability and decreased lactate dehydrogenase (LDH) release in adult cardiac myocytes subjected to simulated I/R. Annexin V-FITC/PI staining indicated that Ucn-1 promoted cell survival and decreased cell necrosis through Epac2 (exchange protein directly activated by cAMP) and ERK1/2 (extracellular signal–regulated kinases 1/2) activation. We determined that Ucn-1 shifted cell death from necrosis to apoptosis and activated caspases 9 and 3/7. Furthermore, mini-array, RT-qPCR and protein analyses of apoptotic genes showed that Ucn-1 upregulated the expression of CD40lg, Xiap and BAD in cells undergoing I/R, involving Epac2 and ERK1/2 activation.

Conclusions

Our data indicate that Ucn-1 efficiently protected hearts from I/R damage by increasing the cell survival and stimulated apoptotic genes, CD40lg, Xiap and BAD, overexpression through the activation of Epac2 and ERK1/2.

Chronic heart failure alters orexin and melanin concentrating hormone but not corticotrophin releasing hormone-related gene expression in the brain of male Lewis rats

OBJECTIVE

The aim of this study was to investigate the effect of chronic heart failure (HF; 16 weeks post left coronary artery ligation) on the brain's orexin (ORX) and related neuropeptide systems.

METHODS

Indicators of cardiac function, including the percent fractional shortening (%FS) left ventricular posterior wall shortening velocity (LVPWSV) were assessed via echocardiography at 16 weeks post myocardial infarction or sham treatment in male Lewis rats (n=5/group). Changes in gene expression in HF versus control (CON) groups were quantified by real-time PCR in the hypothalamus, amygdala and dorsal pons.

RESULTS

HF significantly reduced both the %FS and LVPWSV when compared to CON animals (P<0.02). In the hypothalamus ORX gene expression was significantly reduced in HF and correlated with changes in cardiac function when compared to CON (P<0.02). No significant changes in hypothalamic ORX receptor (type 1 or type 2) gene expression were identified. Alternatively hypothalamic melanin concentrating hormone (MCH) gene expression was significantly upregulated in HF animals and negatively correlated with LVPWSV (P<0.006). In both the amygdala and dorsal pons ORX type 2 receptor expression was significantly down-regulated in HF compared to CON. ORX receptor type 1, CRH and CRH type 1 and type 2 receptor expressions were unchanged by HF in all brain regions analyzed.

CONCLUSION

These observations support previous work demonstrating that cardiovascular disease modulates the ORX system and identify that in the case of chronic HF the ORX system is altered in parallel with changes in MCH expression but independent of any significant changes in the central CRH system. This raises the new possibility that ORX and MCH systems may play an important role in the pathophysiology of HF.