Prolactin-releasing peptide (PrRP) is a member of the family of RF-amide peptides. These peptides have typical C-terminal sequence -Arg-Phe-NH2 and similar biological effects. PrRP was discovered as an endogenous ligand of an orphan receptor GPR10 while searching for a factor responsible for a prolactin secretion. This effect was not later confirmed and nowadays, PrRP is mainly considered as an anorexigenic peptide. This is supported by a fact that PrRP and GPR10 deficient mice suffer from hyperphagia and late-onset obesity. Besides GPR10, PrRP is bound to NPFF2 receptor whose endogenous ligand is neuropeptide FF (NPFF). In this study, the PrRP's analogues modified at the N-terminus with fatty acids of different lenghts were tested in vitro on binding and activation MAPK/ERK1/2 signalling pathway. In in vivo experiments on food intake, the central anorexigenic effects of lipidized PrRP-analogues were tested provided their crossing blood brain barrier. Binding studies showed that all analogues bound to rat pituitary RC-4B/C cells with high affinity, analogues containing fatty acid with Ki of one order of magnitude lower than native PrRP. High affinity was also confirmed for binding to cells overexpressing GPR10 receptor and cell membranes with overexpressed NPFF2 receptor. All tested analogues...

Cocaine- and amphetamine-regulated transcript (CART) peptide-immunoreactivity was detected in neurons of the rostral ventrolateral medulla (RVLM), but few in the caudal ventrolateral medulla (CVLM). Double-labeling the medullary sections with sheep polyclonal phenylethanolamine N-methyltransferase-antiserum (PNMT) or monoclonal tyrosine hydroxylase-antibody and rabbit polyclonal CART peptide-antiserum revealed that nearly all adrenergic cells in the C1 area were CART peptide-positive and vice versa; tyrosine hydroxylase-positive cells in the A1 area were not. In the thoracolumbar spinal cord, neurons in the intermediolateral cell column (IML) and other sympathetic autonomic nuclei were CART peptide-positive; some of these were contacted by immunoreactive fibers arising from the lateral funiculus. By immuno-electron microscopy, axon terminals containing closely packed agranular CART peptide-immunoreactive vesicles appeared to make synaptic contacts with immunoreactive dendrites and soma in the IML, albeit the incidence of such contacts was low. Microinjection of the retrograde tracer Fluorogold into the lateral horn area of the T1-T3 spinal segments labeled a population of neurons in the C1 area, many of which were also CART peptide-positive. The results indicate that CART peptide-immunoreactivity is expressed in C1 adrenergic neurons, some of which project to the thoracolumbar spinal cord. The presence of this novel peptide in C1 adrenergic neurons underscores the multiplicity of putative transmitters that may be involved in signaling between putative cardiovascular neurons in the medulla oblongata and sympathetic preganglionic neurons (SPNs) in the spinal cord.

Distribution of prolactin-releasing peptide-like immunoreactivity (PrRP- LI) was investigated in the rat medulla with the use of a rabbit polyclonal antiserum against the human PrRP-31 peptide. PrRP-positive neurons were noted mainly in two areas of the caudal medulla: ventrolateral reticular formation and commissural nucleus of the nucleus of the solitary tract (NTS), corresponding to the A1 and A2 areas. PrRP-LI neurons were absent in the medulla rostral to the area postrema. Double-labeling the sections with PrRP antisera and tyrosine hydroxylase (TH) monoclonal antibodies revealed extensive colocalization of PrRP- and TH-like immunoreactivity (TH-LI) in neurons of the A1 and A2 areas. Our results show that PrRP-LI is expressed in a population of A1 and A2 noradrenergic neurons of the rat caudal medulla.

Abstract The heart adapts to hemodynamic overload with cardiac hypertrophy. Initially the increase in heart mass normalizes wall stress and permits normal cardiac function. In the long term pathological growth is associated with increased heart size, loss of functional myocytes and fibrotic replacement, heart dilatation and cardiac dysfunction, which can ultimately lead to heart failure. Vasoactive peptides participate in the regulation of cardiac contractility in an auto/paracrine way, but the peptidergic signaling pathways are largely unknown. The present study aimed to characterize the signaling mechanisms mediating the positive inotropic effect of endothelin-1 (ET-1) and the effects of prolactin releasing peptide (PrRP) on cardiac contractility in the isolated perfused rat heart preparation. The study demonstrated that mitogen-activated protein kinases (MAPK) have opposing roles in the regulation of cardiac contractility stimulated by ET-1. Extracellular signal-regulated kinase 1/2 (ERK1/2) mediated positive inotropic response to ET-1 was found to be counterbalanced by p38-MAPK. In addition, the effect of ET-1 was partly dependent on enhanced NADPH oxidase reactive oxygen species (ROS) generation, which activated the ERK1/2 pathway. In contrast, β-adrenergic inotropic effect was limited by stimulation of ROS production via negating phospholamban phosphorylation. The positive inotropic effect of ET-1 was counterbalanced by guanylyl cyclase (GC)-cGMP-protein kinase G (PKG) pathway and neuronal nitric oxide synthase (nNOS). PrRP was found to exert a direct positive inotropic effect which was independent of cAMP and was suppressed by concurrent activation of protein kinase Cα (PKCα) and protein phosphatase 1 (PP1), and dephosphorylation of phospholamban. In conclusion, in the present study signaling pathways in the acute regulation of cardiac contractility stimulated by ET-1 were characterized. The results suggest that the positive inotropic effect of ET-1 is mediated by ROS and ERK1/2 while p38-MAPK counterbalances the effect of ET-1. In addition, GC-cGMP-PKG pathway and nNOS modulate the response to ET-1. The study also established the previously unknown cardiac effects of PrRP. The findings provide a better understanding of molecular mechanisms involved in the regulation of cardiac contractility, and may indicate potential targets for novel therapeutic interventions. / Tiivistelmä Sydänlihaksen lisääntynyt mekaaninen kuormitus esimerkiksi verenpainetaudin tai sydäninfarktin yhteydessä voi johtaa sydämen kammion seinämän paksuuntumiseen eli hypertrofiaan. Hypertrofia auttaa sydäntä sopeutumaan lisääntyneeseen työmäärään, mutta se on myös sydän- ja verisuonitautitapahtumien riskitekijä. Pitkään jatkuva kuormitus johtaa usein sydämen pumppausvoiman heikkenemiseen ja sydämen vajaatoimintaan. Sydän tuottaa useita paikallisesti vaikuttavia vasoaktiivisia tekijöitä, jotka osallistuvat sydämen supistuvuuden säätelyyn. Väitöskirjatutkimuksessa tutkittiin signaalinvälitysjärjestelmiä, jotka osallistuvat endoteliini-1:n (ET-1) sydämen supistusvoimaa lisäävän eli positiivisen inotrooppisen vaikutuksen muodostumiseen sekä selvitettiin prolaktiinia vapauttavan peptidin (PrRP) vaikutuksia sydämen supistusvoimaan käyttämällä koemallina eristettyä, perfusoitua rotan sydäntä. Väitöskirjatyön tutkimustulokset osoittivat, että mitogeeni-aktivoituvat proteiinikinaasit (MAPK) ERK1/2 ja p38-MAPK osallistuvat ET-1:n inotrooppisen vaikutuksen säätelyyn. ERK1/2 välitti, ja p38-MAPK rajoitti ET-1:n lisäämää supistusvoiman kasvua. NADPH-oksidaasin tuottamat reaktiiviset happiradikaalit välittivät sydämessä ET-1:n inotrooppista vaikutusta ja ERK1/2 fosforylaatiota. Toisaalta NADPH-oksidaasin tuottamat happiradikaalit rajoittivat β-adrenergisen agonistin inotrooppista vaikutusta. Guanylaattisyklaasi (GC)-cGMP-proteiinikinaasi G (PKG) -järjestelmä ja neuronaalinen typpioksidisyntaasi (nNOS) vaimensivat ET-1:n lisäämää sydämen supistusvoiman kasvua. PrRP lisäsi sydämen inotropiaa syklisestä AMP:stä riippumattomalla tavalla, mutta vasteen säätelyyn havaittiin osallistuvan proteiinikinaasi C ja proteiinifosfataasi 1. Väitöskirjatutkimuksessa saatiin uutta tietoa solunsisäisistä viestinvälitysjärjestelmistä, jotka osallistuvat sydämen supistusvoimaan säätelyyn. Havaintojen perusteella ET-1:n positiivisen inotrooppisen vaikutuksen muodostumista välittävät reaktiiviset happiradikaalit ja ERK1/2, kun taas p38-MAPK rajoittaa vastetta. Lisäksi GC-cGMP-PKG -järjestelmä ja nNOS osallistuvat ET-1:n vaikutusten säätelyyn. Tutkimuksessa havaittiin myös, että PrRP vaikuttaa sydämen supistuvuuteen. Solutason mekanismien yksityiskohtien tunteminen voi mahdollistaa tulevaisuudessa sydän- ja verisuonisairauksien, kuten sydämen hypertrofian ja vajaatoiminnan, hoitomenetelmien tehostumisen ja mahdollisesti uudentyyppisten hoitomenetelmien kehittämisen.

Anorexigenic neuropeptides have the potential to decrease food intake and ameliorate obesity and its complications such as high blood glucose or high blood pressure. However, they are not able to cross the blood-brain barrier after peripheral application. Recently, we have designed and synthesized lipidized analogs of prolactin-releasing peptide (PrRP), which resulted in stabilization of the molecule and allowed us to apply the peptide to the periphery to achieve its central biological effect, as it was demonstrated by increased neuronal activity shown by c-Fos in particular hypothalamus nuclei. The aim of this study was to choose the effective dose in acute food intake experiments and then to characterize the subchronic effect of palmitoylated PrRP analogs in mouse and rat models of obesity and diabetes. Several animal models were used: diet-induced obese (DIO) mice (C57Bl/6J), DIO Sprague-Dawley rats, and two rat models with leptin receptor-deficiency: Zucker diabetic (ZDF) rats and spontaneously hypertensive (SHROB) rats. Consumption of a high-fat diet in DIO mice and rats increased their body weight and blood pressure. Two-week intraperitoneal treatment with palmitoylated PrRP31 lowered the food intake, body weight, and returned the blood pressure to normal levels. This treatment also improved...