Modulation of Calcium Movements by Urocortin II in Endothelial Cells

Abstract

Background: In endothelial cells urocortin II has recently been found to activate nitric oxide synthase through cAMP-dependent and Ca²⁺-related pathway. Aim: The present study was therefore planned to determine the mechanisms of urocortin II effect on Ca²⁺ movements. Methods. In Fura-2 loaded porcine aortic endothelial cells (PAE), the effects of urocortin II on [Ca²⁺]c were analyzed and compared with those of various K⁺ channels agonists/antagonists. Results: In Fura-2 loaded PAE, urocortin II promoted a transient increase of [Ca²⁺]c mainly originating from an intracellular pool sensitive to thapsigargin and slightly from the extracellular space. In addition, urocortin II caused the hyperpolarization of plasma membrane through the opening of K⁺ channels, which contributed to the increased [Ca²⁺]c. These effects were abolished by the corticotropin releasing factor receptors (CRFR2) blocker, the adenylyl cyclase and Ca²⁺-calmodulin-kinase (CaMKII) inhibitors and by blockers of K⁺ channels. In addition, in PAE cultured in Na⁺-free medium or loaded with the plasma-membrane Ca²⁺ pump inhibitor the urocortin II-evoked Ca²⁺ transient was slower. Conclusion: The results obtained show that urocortin II affects intracellular Ca²⁺ homeostasis in PAE by both promoting a discharge of intracellular pool and by interfering with the operation of store-dependent channels through CRFR2-cAMP-CaMKII related signalling and K⁺ channels opening.

Urocortin 2 in cardiovascular health and disease

“…The activation of these proteins leads ultimately to increased Ca 2+ influx, sarcoplasmic reticulum (SR) Ca 2+ content and accelerated [Ca 2+ ] i transients [27,28]. Ucn-2 also interferes with the opening of K + channels, leading to a hyperpolarized state that increases the driving force for Ca 2+ entry in the cell [29]. cells leads to an increase in expression of inducible NO synthase (iNOS) [30].…”

Asenapine modulates nitric oxide release and calcium movements in cardiomyoblasts

“…Quantification of (Ca 2+ ) c was conventionally obtained by measuring the Fura-2/AM fluorescence in Ca 2+ -free (0.1 M EGTA) and Ca 2+ -saturated conditions by the equation (Ca 2+ ) c = K d ([ R − R min ]/[ R max − R ]). [ 14 15 16 ] The fluorescence intensities obtained were corrected for cell autofluorescence at the wavelengths employed. [ 16 ]…”

Calcium handling in porcine coronary endothelial cells by gastrin-17

“…Transient fluctuations in [Ca 2C ] c may occur following inhibition of Ca 2C ATPases located in the plasma membrane or in the membrane of non-mitochondrial stores and activation of the release from intracellular stores may occur whether or not it is dependent on inositol-1,4,5-triphosphate-phosphate (IP3) generation. Also, the release of intracellular Ca 2C coupled to subsequent Ca 2C entry (Putney 1990), known as 'capacitative Ca 2C entry', is a mechanism widely reported to affect Ca 2C homeostasis in response to both receptor-mediated stimuli (Putney 1990, Schilling et al 1992, Fasolato & Nilius 1998 and receptor-independent emptying of intracellular stores by agents such as thapsigargin, cyclovirobuxine D and urocortin II (Putney 1990, Schilling et al 1992, Fasolato & Nilius 1998, Grossini et al 2005, 2010. In addition, the restoration of basal intracellular Ca 2C levels would play an important role by the activation of the plasma membrane Ca 2C -ATPase (PMCA) pump and of Na C /Ca 2C exchanger (NCX; Moccia et al 2002, Wang et al 2002.…”

“…] c was obtained conventionally, as previously reported (Grynkiewicz et al 1985, Grossini et al 2010) using the following equation:…”