Impact of N-Acetylcysteine on Neonatal Cardiomyocyte Ischemia-Reperfusion Injury

Abstract

ABSTRACT:Reactive oxygen species (ROS) are hypothesized to play a key role in myocardial ischemia-reperfusion (IR) injury after cardiopulmonary bypass in children. Clinical studies in adults and several animal models suggest that myocardial IR injury involves cardiomyocyte apoptosis and necrosis. This study investigated a potential relationship between IR-induced ROS production and neonatal cardiomyocyte apoptosis using both in vitro and ex vivo techniques. For in vitro experiments, embryonic rat cardiomyocytes (H9c2 cells) exposed to hypoxia-reoxygenation (HR) showed a timedependent increase in gp91 phox (a marker for ROS production by NADPH oxidases), caspase-3 (a key mediator of apoptosis) expression, and a decrease in the glutathione redox ratio. N-acetylcysteine (NAC; 0.25-2 mM), a potent antioxidant, decreased gp91 phox and caspase-3 expression, inhibited apoptosis and restored the glutathione redox ratio. M yocardial ischemia-reperfusion (IR) injury associatedwith cardiopulmonary bypass and cardioplegic arrest contributes to adverse outcomes after cardiac surgery. The pathogenesis of IR injury is complex, but reactive oxygen species (ROS) generated during IR are thought to play a pivotal role leading to membrane lipid peroxidation, protein denaturation, and DNA modification, all of which may result in irreversible myocyte injury and cell death. Oxygen free radicals are cytotoxic molecules generated during reperfusion and/or reoxygenation of a previously hypoxic tissue bed. The cell damage induced by ROS can also initiate a local inflammatory response, which leads to further oxidant stressmediated tissue damage (1).Several studies have suggested that ROS are involved in the pathogenesis of perinatal asphyxia (2). Neonates, especially those born prematurely, are particularly vulnerable to ROSmediated tissue damage due, in part, to their immature native antioxidant system (3,4). Similarly, myocardial IR injury seems to be a more clinically significant problem in infants after cardiac surgery compared with adults (5-7). Several ROS-producing systems have been identified in many cell types. NADPH oxidase is reported to be a primary source of ROS production in cardiac tissue, and gp91 phox is responsible for the catalytic activity of NADPH oxidase (8,9). Increased ROS induce apoptosis in cardiomyocytes. Caspase-3 protein is a member of the cysteine-aspartic acid protease family that has been identified as being a key mediator of apoptosis in mammalian cells (10,11).N-acetylcysteine (NAC) is a thiol-containing molecule that acts as a free radical scavenger. In addition, NAC is a glutathione precursor that increases intracellular antioxidant capacity (12). Clinically, NAC is indicated for the treatment of acetaminophen overdose, for the prevention of radiocontrastinduced nephropathy, and as an adjuvant in respiratory conditions with excessive and/or thick mucus production. However, there are contradictory reports on the effects of NAC in clinical (13,14) and animal studies (15-17) of myocardial IR injury. Furthe...

Respiratory chain signalling is essential for adaptive remodelling following cardiac ischaemia

“…2 Instead, electron flow through the ETC upon reperfusion was described as a source of potentially detrimental reactive oxygen species (ROS), proposed to trigger ischaemia-reperfusion (I/R) injuries. 2 Conversely, the therapeutic use of untargeted antioxidants such as vitamin C for post-ischaemic cardioprotection has given contradictory results, [4][5][6][7][8][9] and itself produced detrimental side effects when therapeutically used. 10 These seemingly contradictory results were thought to be due to biphasic effects of ROS with high ROS concentrations leading to damage and lower concentrations eliciting adaptive responses.…”

Surface-modified particles loaded with CaMKII inhibitor protect cardiac cells against mitochondrial injury

“…This cell line has been used extensively as a model for ischemia/reperfusion injury 22–26 due to its high sensitivity to ischemia/reperfusion injury in terms of cell viability and mitochondrial respiration 24 . Moreover, H9c2 cells have been used in a number of studies involving CaMKII 27–30 .…”

Lysophosphatidic Acid Pretreatment Attenuates Myocardial Ischemia/Reperfusion Injury in the Immature Hearts of Rats

“…Wu et al (2015) reported that cardiomyocyte apoptosis directly resulted in heart dysfunction during IR injury (Peng et al, 2011). Moreover, immature myocardium is more sensitive to oxidative stress (Umansky et al, 1995).…”