Neonatal Asphyxia Induces the Nitration of Cardiac Myosin Light Chain 2 That is Associated with Cardiac Systolic Dysfunction

Abstract

Background Hypoxia followed by reoxygenation (H-R) observed during perinatal asphyxia is a serious complication with a high mortality and morbidity rate which may cause adverse cardiovascular effects in neonates. Our aim was to determine if oxidative stress related to H-R induces peroxynitrite-dependent modifications of the cardiac contractile protein, myosin regulatory light chain 2 (MLC2) and whether this is associated with development of cardiac systolic dysfunction. Methods and Results Twelve newborn piglets were acutely instrumented for hemodynamic monitoring and randomized to a control group ventilated with only atmospheric air or to the H-R study group, exposed to alveolar normocapnic hypoxia followed by reoxygenation. Afterwards, animals were euthanized and the hearts harvested for biochemical analyses. Systolic function as well as cardiac MLC2 levels decreased in H-R animals, whereas nitrates and nitrotyrosine levels increased. Negative correlations between nitrates, nitrotyrosine and MLC2 levels were observed. Moreover, H-R induced nitration of two tyrosine residues within the MLC2 protein. Similarly, in vitro exposure of MLC2 to peroxynitrite resulted in the nitration of tyrosine, which increased the susceptibility of MLC2 to subsequent degradation by matrix metalloproteinase-2 (MMP-2). Substitution of this tyrosine with phenylalanine prevented the MMP-2 dependent degradation of MLC2. In addition, a large decrease in MLC2 phosphorylation due to H-R was observed. Conclusions 1. Oxidative stress related to asphyxia induces nitration of cardiac MLC2 protein and thus increases its degradation. This and a large decrease in MLC2 phosphorylation contribute to the development of systolic dysfunction. 2. Inhibition of MLC2 nitration and/or direct inhibition of its degradation by MMP-2 could be potential therapeutic targets aiming at reduction of myocardial damage during resuscitation of asphyxiated newborns.

Tackling proteome changes in the longissimus thoracis bovine muscle in response to pre-slaughter stress

“…This is not a 493 surprising result when the myosin is a major structural protein of the muscle sarcomere 494 in association with actin and other contractile proteins. The MYL3, MYL6B and MYL2 495 proteins play important structural and functional roles by supporting the structure of the 496 22 myosin neck region and fine-tuning the kinetics of the actin-myosin interaction [53]. 497 We also found that levels of MYL3, MYL6B and MYL2 were lower in DFD than in 498 normal meat, probably because of a more intensive enzymatic degradation of myofibril 499 structure, which can contribute to explain its tenderness differential.…”

“…It is well-recognized that MYL2 is highly 522 phosphorylated and that this phosphorylation is crucial for the regulation of MYL2 [56]. 523 Levels of MYL2 phosphorylation around 30-40% have been reported in humans and pig 524 [53]. Interestingly, the N-terminal domain in the human orthologue MYL2 contains a 525…”

A change of heart: oxidative stress in governing muscle function?

“…Both the MLC1 and MLC2 isoforms are subject to tyrosine nitration and cysteine S-nitrosylation in cardiac models of oxidative stress: MLC1 is S-nitrosylated at . These changes promoted degradation of both isoforms by MMP-2 (Doroszko et al 2009(Doroszko et al , 2010Polewicz et al 2011). It has been consistently demonstrated that inhibition of MMP-2 and nitration/nitrosylation of MLC1 attenuates ischemia/ reperfusion injury and prevents MLC1 degradation in isolated rat hearts.…”

“…Increased peroxynitrite production also induces MLC1 nitration/nitrosylation, leading to its increased degradation by the proteolytic enzyme MMP-2. This in turn suppresses cardiomyocyte contractility during either reoxygenation or reperfusion (Doroszko et al 2010;Polewicz et al 2011). Both the MLC1 and MLC2 isoforms are subject to tyrosine nitration and cysteine S-nitrosylation in cardiac models of oxidative stress: MLC1 is S-nitrosylated at .…”

Propofol administration to the fetal–maternal unit reduces cardiac oxidative stress in preterm lambs subjected to prenatal asphyxia and cardiac arrest

“…But under hypoxic conditions, MLC2 is assaulted by reactive oxygen species (ROS), especially in the presence of nitric oxide (NO), by the aggressive fusion product peroxynitrite. This results in MLC2 degradation and subsequent systolic dysfunction (9). However, previous research has indicated that propofol might interfere with this cascade (10).…”