Urocortin Protects against Ischemic and Reperfusion Injury via a MAPK-dependent Pathway

Abstract

Urocortin (UCN) is a peptide related to hypothalamic corticotrophin-releasing hormone and binds with high affinity to corticotrophin-releasing hormone receptor-2␤, which is expressed in the heart. In this study, we report that UCN prevented cell death when administered to primary cardiac myocyte cultures both prior to simulated hypoxia/ischemia and at the point of reoxygenation after simulated hypoxia/ischemia. UCN-mediated cell survival was measured by trypan blue exclusion, 3-OH end labeling of DNA (TUNEL), annexin V, and fluorescence-activated cell sorting. To explore the mechanisms that could be responsible for this effect, we investigated the involvement of MAPK-dependent pathways. UCN caused rapid phosphorylation of ERK1/2-p42/ 44, and PD98059, which blocks the MEK1-ERK1/2-p42/44 cascade, also inhibited the survival-promoting effect of UCN. Most important, UCN reduced damage in isolated rat hearts ex vivo subjected to regional ischemia/reperfusion, with the protective effect being observed when UCN was given either prior to ischemia or at the time of reperfusion after ischemia. This suggests a novel function of UCN as a cardioprotective agent that could act when given after ischemia, at reperfusion. Urocortin (UCN)1 is a peptide related to the hypothalamic hormone corticotrophin-releasing factor (CRF), the central mediator of the hypothalamic-pituitary-adrenal axis and stress response in mammals (1-3). UCN and CRF share 45% homology at the amino acid level, and both are synthesized as precursors, which are subsequently processed to the mature biologically active peptides (in the case of UCN, a 40-amino acid molecule) (4, 5). Although UCN was originally identified in restricted areas of the brain, it has also been found in the placenta, lymphocytes, and heart (6 -9).The CRF family of peptides bind two types of CRF receptors, CRF-R1 and CRF-R2. CRF-R2 exists in three alternative splice variant forms, CRF-R2␣, CRF-R2␤, and CRF-R2␥ (10 -12); and CRF-R2 binds UCN with a higher affinity than CRF both in ligand binding studies (4) and as shown by the effects of ligand on intracellular cAMP (13). In contrast, the R1 receptors show little ligand selectivity for UCN versus CRF. R2 receptors are the only type of CRF receptor found in the heart: the ␣ form in man (14) and the ␤ form in the rat (15). The CRF family of peptides have been shown to stimulate adenylate cyclase activity in cardiac myocytes (16), and changes in CRF-R2 expression have been reported in the hearts of spontaneously hypertensive rats (17).The coincident expression of CRF-R2 receptors with their preferred UCN ligand in the heart suggests that UCN may have physiological cardiac properties. Indeed UCN, but not CRF, induces a dose-dependent increase in heart rate, cardiac output, and coronary blood flow (18). Moreover, cardiac CRF-R2␤ expression is modulated by endotoxin, a potent inducer of cardiovascular dysregulation, further suggesting a possible link between UCN and the cardiovascular response to stress (19). Indeed, in previous studies, we have...

Urocortin 2 autocrine/paracrine and pharmacologic effects to activate AMP-activated protein kinase in the heart

“…We observed more necrosis in the AMPK KD mice, but Ucn2 treatment had the residual effect of diminishing injury in their hearts (Fig. S3), consistent with the additional known cardioprotective effects of Ucn2 (8,(23)(24)(25)(26).…”

The C-terminal activation domain of the STAT-1 transcription factor is necessary and sufficient for stress-induced apoptosis

“…We have previously used this method to successfully quantify the effect of specific transfected plasmids on apoptosis in a variety of cell types. 10,11,13,14 In these experiments ( In the next series of experiments, we tested whether this effect of STAT-1 could be reproduced with the related protein STAT-3 or with mutant or truncated derivatives of STAT-1. In our previous experiments, these factors have been shown to be expressed at similar levels in the transfected cells, 10,11 and this was confirmed in our current experiments (see for example, Figure 4).…”

The cardiovascular physiologic actions of urocortin II: Acute effects in murine heart failure

“…UcnII activation of CRFR2 leads to increased cAMPdependent PKA activity, phosphorylation of phospholamban, and reduced inhibition of sarcoendoplasmic reticulum calcium-ATPase (13,37). UcnII is also known to activate the phosphatidylinositol-3 kinase͞PKB (Akt) pathway (38).…”