Opposite effects of uracil and adenine nucleotides on the survival of murine cardiomyocytes

Abstract

We previously showed that the human heart expresses all known P2X and P2Y receptors activated by extra-cellular adenine or uracil nucleotides. Despite evidence that, both in humans and rodents, plasma levels of ATP and UTP markedly increase during myocardial infarction, the differential effects mediated by the various adenine- and uracil-preferring myocardial P2 receptors are still largely unknown. Here, we studied the effects of adenine and uracil nucleotides on murine HL-1 cardiomyocytes. RT-PCR analysis showed that HL-1 cardiomyocytes express all known P2X receptors (except for P2X2), as well as the P2Y2,4,6,14 subtypes. Exposure of cardiomyocytes to adenine nucleotides (ATP, ADP or BzATP) induced apoptosis and necrosis, as determined by flow-cytometry. Cell death was exacerbated by tumour necrosis factor (TNF)-α, a cytokine implicated in chronic heart failure progression. Conversely, uracil nucleotides (UTP, UDP and UDPglucose) had no effect ‘per se’, but fully counteracted the deleterious effects induced by adenine nucleotides and TNF-α, even if added to cardiomyocytes after beginning exposure to these cell death-inducing agents. Thus, exposure of cardiomyocytes to elevated concentrations of ATP or ADP in the presence of TNF-α contributes to cell death, an effect which is counteracted by uracil-preferring P2 receptors. Cardiomyocytes do not need to be ‘primed’ by uracil nucleotides to become insensitive to adenine nucleotides-induced death, suggesting the existence of a possible ‘therapeutic’ window for uracil nucleotides-mediated protection. Thus, release of UTP during cardiac ischaemia and in chronic heart failure may protect against myocardial damage, setting the basis for developing novel cardioprotective agents that specifically target uracil-preferring P2Y receptors.

Cardiomyocyte death induced by ischaemic/hypoxic stress is differentially affected by distinct purinergic P2 receptors

“…Our previous data are in support of a role of the P2X receptors in the induction of apoptosis mediated by ATP in HL-1 cardiomyocytes [ 18 ]. Indeed, a 24 hr-exposure of HL-1 cardiomyocytes to the selective P2χ 7 agonist BzATP resulted in a dramatic reduction of the number of cells adhering to the culture substrate [ 18 ].…”

Involvement of UTP in protection of cardiomyocytes from hypoxic stressThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 2 of a 2-part Special Issue).

“…UTP therefore may be used in preference to ATP as a P2Y 2 and P2Y 4 receptor agonist because it does not form cardiovascular active metabolites such as adenosine. Mazzola et al (2008) confirmed this assumption by demonstrating different effects of these nucleotides on cardiomyocyte viability. Whereas exposure of the HL-1 cardiomyocytes to ATP induced apoptosis and necrosis, UTP counteracted the deleterious effects of ATP (Mazzola et al 2008).…”

“…Mazzola et al (2008) confirmed this assumption by demonstrating different effects of these nucleotides on cardiomyocyte viability. Whereas exposure of the HL-1 cardiomyocytes to ATP induced apoptosis and necrosis, UTP counteracted the deleterious effects of ATP (Mazzola et al 2008). Arthur et al (2006) have shown that ATP causes a robust activation of phospholipase C via activation of G q in newborn rat cardiomyocytes, and it would be expected to cause hypertrophic responses like other factors that active G q -coupled receptors, such as α-adrenergic agonists, endothelin, and angiotensin II during long-term exposure (Pham et al 2003).…”

Cardiac purinergic signalling in health and disease

“…UTP, released during cardiac ischaemia, was claimed to act via P2Y2R and/or P2Y4R to play a substantial role in mediating cardioprotection from hypoxic damage [325,326,596,597]. In isolated ischaemic rat hearts, ATP-loaded liposomes and ATP-loaded immunoliposomes effectively protected the myocardium from ischaemia-reperfusion damage as determined by systolic and diastolic function [598].…”