A novel function of nuclear nonmuscle myosin regulatory light chain in promotion of xanthine oxidase transcription after myocardial ischemia/reperfusion

Substrate stiffness induces nuclear localization of myosin regulatory light chain to suppress apoptosis

Stiffness of the extracellular matrix regulates various biological responses, but the response mechanisms are poorly understood. Here, we found that the nuclear diphosphorylated myosin regulatory light chain (2P-MRLC) is a critical mechanomediator that suppresses apoptosis in response to substrate stiffness. Stiff substrates promoted the nuclear localization of 2P-MRLC. Zipper-interacting protein kinase [ZIPK; also known as death-associated protein kinase 3 (DAPK3)], a kinase for MRLC, was localized in the nucleus in response to stiff substrates and promoted the nuclear localization of 2P-MRLC. Moreover, actin fiber formation induced by substrate stiffness promoted the nuclear localization of 2P-MRLC via ZIPK. 2P-MRLC in response to substrate stiffness suppressed the expression of MAF bZIP transcription factor B (MafB) and repressed apoptosis. These findings reveal a newly identified role of MRLC in mechanotransduction.

Allopurinol attenuates oxidative injury in rat hearts suffered ischemia/reperfusion via suppressing the xanthine oxidase/vascular peroxidase 1 pathway

Allopurinol, a xanthine oxidase (XO) inhibitor, is reported to alleviate myocardial ischemia/reperfusion (I/R) injury by reducing the production of reactive oxygen species (ROS). As an XO-derived product, H2O2 can act as a substrate of vascular peroxidase 1 (VPO1) to induce the generation of hypochlorous acid (HOCl), a potent oxidant. This study aims to explore whether the XO/VPO1 pathway is involved in the anti-oxidative effects of allopurinol on the myocardial I/R injury. In a rat heart model of I/R, allopurinol alleviated I/R oxidative injury accompanied by decreased XO activity, XO-derived products (H2O2 and uric acid), and VPO1 expression (mRNA and protein). In a cardiac cell model of hypoxia/reoxygenation (H/R), allopurinol or XO siRNA reduced H/R injury concomitant with decreased XO activity, VPO1 expression as well as the XO and VPO1-derived products (H2O2, uric acid, and HOCl). Although knockdown of VPO1 could also exert a beneficial effect on H/R injury, it did not affect XO activity, XO expression, and XO-derived products. Based on these observations, we conclude that the novel pathway of XO/VPO1 is responsible for, at least partly, myocardial I/R-induced oxidative injury, and allopurinol exerted the cardioprotective effects on myocardial I/R injury via inhibiting the XO/VPO1 pathway.

Therapeutic hypothermia reduces inflammation and oxidative stress in the liver after asphyxial cardiac arrest in rats

BACKGROUND

Few studies have evaluated the effects of hypothermia on cardiac arrest (CA)-induced liver damage. This study aimed to investigate the effects of hypothermic therapy on the liver in a rat model of asphyxial cardiac arrest (ACA).

METHODS

Rats were subjected to 5-minute ACA followed by return of spontaneous circulation (RoSC). Body temperature was controlled at 33°C±0.5°C or 37°C±0.5°C for 4 hours after RoSC in the hypothermia group and normothermia group, respectively. Liver tissues in each group were collected at 6 hours, 12 hours, 1 day, and 2 days after RoSC. To examine hepatic inflammation, mast cells were stained with toluidine blue. Superoxide anion radical production was evaluated using dihydroethidium fluorescence straining and expression of endogenous antioxidants (superoxide dismutase 1 [SOD1] and SOD2) was examined using immunohistochemistry.

RESULTS

There were significantly more mast cells in the livers of the normothermia group with ACA than in the hypothermia group with ACA. Gradual increase in superoxide anion radical production was found with time in the normothermia group with ACA, but production was significantly suppressed in the hypothermia group with ACA relative to the normothermia group with ACA. SOD1 and SOD2 levels were higher in the hypothermia group with ACA than in the normothermia group with ACA.

CONCLUSIONS

Experimental hypothermic treatment after ACA significantly inhibited inflammation and superoxide anion radical production in the rat liver, indicating that this treatment enhanced or maintained expression of antioxidants. Our findings suggest that hypothermic therapy after CA can reduce mast cell-mediated inflammation through regulation of oxidative stress and the expression of antioxidants in the liver.

Aging Attenuates Cardiac Contractility and Affects Therapeutic Consequences for Myocardial Infarction

Cardiac function of the human heart changes with age. The age-related change of systolic function is subtle under normal conditions, but abrupt under stress or in a pathogenesis state. Aging decreases the cardiac tolerance to stress and increases susceptibility to ischemia, which caused by aging-induced Ca2+ transient impairment and metabolic dysfunction. The changes of contractility proteins and the relative molecules are in a non-linear fashion. Specifically, the expression and activation of cMLCK increase first then fall during ischemia and reperfusion (I/R). This change is responsible for the nonmonotonic contractility alteration in I/R which the underlying mechanism is still unclear. Contractility recovery in I/R is also attenuated by age. The age-related change in cardiac contractility influences the therapeutic effect and intervention timepoint. For most cardiac ischemia therapies, the therapeutic result in the elderly is not identical to the young. Anti-aging treatment has the potential to prevent the development of ischemic injury and improves cardiac function. In this review we discuss the mechanism underlying the contractility changes in the aged heart and age-induced ischemic injury. The potential mechanism underlying the increased susceptibility to ischemic injury in advanced age is highlighted. Furthermore, we discuss the effect of age and the administration time for intervention in cardiac ischemia therapies.

Ischemia/Reperfusion Injury Revisited: An Overview of the Latest Pharmacological Strategies

Ischemia/reperfusion injury (IRI) permeates a variety of diseases and is a ubiquitous concern in every transplantation proceeding, from whole organs to modest grafts. Given its significance, efforts to evade the damaging effects of both ischemia and reperfusion are abundant in the literature and they consist of several strategies, such as applying pre-ischemic conditioning protocols, improving protection from preservation solutions, thus providing extended cold ischemia time and so on. In this review, we describe many of the latest pharmacological approaches that have been proven effective against IRI, while also revisiting well-established concepts and presenting recent pathophysiological findings in this ever-expanding field. A plethora of promising protocols has emerged in the last few years. They have been showing exciting results regarding protection against IRI by employing drugs that engage several strategies, such as modulating cell-surviving pathways, evading oxidative damage, physically protecting cell membrane integrity, and enhancing cell energetics.

N-terminal acetylation and methylation differentially affect the function of MYL9

Deciphering the histone code has illustrated that acetylation or methylation on the same residue can have analogous or opposing roles. However, little is known about the interplay between these post-translational modifications (PTMs) on the same nonhistone residues. We have recently discovered that N-terminal acetyltransferases (NATs) and N-terminal methyltransferases (NRMTs) can have overlapping substrates and identified myosin regulatory light chain 9 (MYL9) as the first confirmed protein to occur in either α-amino-methylated (Nα-methyl) or α-amino-acetylated (Nα-acetyl) states in vivo Here we aim to determine if these PTMs function similarly or create different MYL9 proteoforms with distinct roles. We use enzymatic assays to directly verify MYL9 is a substrate of both NRMT1 and NatA and generate mutants of MYL9 that are exclusive for Nα-acetylation or Nα-methylation. We then employ eukaryotic cell models to probe the regulatory functions of these Nα-PTMs on MYL9. Our results show that, contrary to prevailing dogma, neither of these modifications regulate the stability of MYL9. Rather, exclusive Nα-acetylation promotes cytoplasmic roles of MYL9, while exclusive Nα-methylation promotes the nuclear role of MYL9 as a transcription factor. The increased cytoplasmic activity of Nα-acetylated MYL9 corresponds with increased phosphorylation at serine 19, a key MYL9 activating PTM. Increased nuclear activity of Nα-methylated MYL9 corresponds with increased DNA binding. Nα-methylation also results in a decrease of interactions between the N-terminus of MYL9 and a host of cytoskeletal proteins. These results confirm that Nα-acetylation and Nα-methylation differentially affect MYL9 function by creating distinct proteoforms with different internal PTM patterns and binding properties.

Mild Therapeutic Hypothermia Increases Glutathione Levels in Postcardiac Arrest Patients

Ischemia-reperfusion (I/R)-induced oxidative stress is one of the main mechanisms of tissue injury after cardiac arrest (CA). A decrease in antioxidant defenses may contribute to I/R injury. The present study aims to investigate the influence of mild therapeutic hypothermia (MTH) on levels of nonenzymatic antioxidants after CA. We investigated antioxidant levels at 6, 12, 36, and 72 hours after CA in central venous blood samples of patients admitted to intensive care. The sample consisted of 31 patients under controlled normothermia (36°C) and 11 patients treated with 24 hours of MTH (33°C). Erythrocyte glutathione (GSH) levels were elevated by MTH, increasing at 6, 12, 36, and 72 hours after CA in hypothermic patients (mean GSH levels in normothermic patients: 6 hours = 73.89, 12 hours = 56.45, 36 hours = 56.46, 72 hours = 61.80 vs. hypothermic patients: 6 hours = 176.89, 12 hours = 198.78, 36 hours = 186.96, and 72 hours = 173.68 μmol/g of protein). Vitamin C levels decreased significantly at 6 and 12 hours after CA in hypothermic patients (median vitamin C levels in normothermic patients: 6 hours = 7.53, 12 hours = 9.40, 36 hours = 8.56, and 72 hours = 8.51 vs. hypothermic patients: 6 hours = 5.46, 12 hours = 5.44, 36 hours = 6.10, and 72 hours = 5.89 mmol/L), coinciding with the period of therapeutic hypothermia. Vitamin E and nitric oxide levels were not altered by hypothermic treatment. These findings suggest that MTH alters nonenzymatic antioxidants differently, decreasing circulating vitamin C levels during treatment; however, MTH elevates GSH levels, possibly protecting tissues from I/R injury after CA.

Myosins as fundamental components during tumorigenesis: diverse and indispensable

Myosin is a kind of actin-based motor protein. As the crucial functions of myosin during tumorigenesis have become increasingly apparent, the profile of myosin in the field of cancer research has also been growing. Eighteen distinct classes of myosins have been discovered in the past twenty years and constitute a diverse superfamily. Various myosins share similar structures. They all convert energy from ATP hydrolysis to exert mechanical stress upon interactions with microfilaments. Ongoing research is increasingly suggesting that at least seven kinds of myosins participate in the formation and development of cancer. Myosins play essential roles in cytokinesis failure, chromosomal and centrosomal amplification, multipolar spindle formation and DNA microsatellite instability. These are all prerequisites of tumor formation. Subsequently, myosins activate various processes of tumor invasion and metastasis development including cell migration, adhesion, protrusion formation, loss of cell polarity and suppression of apoptosis. In this review, we summarize the current understanding of the roles of myosins during tumorigenesis and discuss the factors and mechanisms which may regulate myosins in tumor progression. Furthermore, we put forward a completely new concept of “chromomyosin” to demonstrate the pivotal functions of myosins during karyokinesis and how this acts to optimize the functions of the members of the myosin superfamily.

Inactivated Lactobacillus promotes protection against myocardial ischemia-reperfusion injury through NF-κB pathway

Although restoration of blood flow to an ischemic organ is essential to prevent irreversible cellular injury, reperfusion may augment tissue injury in excess of that produced by ischemia alone. So this experiment was designed to study the protective effects and mechanism of inactivated Lactobacillus (Lac) on myocardial ischemia–reperfusion (I–R) injury (MIRI). MIRI rat models were established by ligation of left anterior descending coronary artery for ~30 min and then, reperfusion for 120 min and divided into control group, model group, and Lac (10⁶, 10⁷, and 10⁸ cfu/kg) groups. At the end of the test, the creatine kinase (CK) activity, lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were assayed by corresponding kits. The heart was obtained from rats and the myocardial infarction area was determined by TTC staining and myocardial endothelial cell apoptosis rate was determined by Tunel kit. Besides, A20, IκB, nuclear factor (NF)-κB, and nitric oxide (NO) synthase (NOS) were also assayed by Western blot. When compared with model group, Lac obviously reduces MIRI in the rat by reducing myocardial infarction area and the apoptosis rate of endothelial cells; reduce the serum CK, LDH, and MDA content; increase the serum SOD activity; and suppress NF-κB signaling and NOS expression in the myocardial tissues. Lac pretreatment can inhibit lipid peroxidation and effectively improve MIRI caused by oxygen free radical through inhibiting NF-κB signaling.

Febuxostat Modulates MAPK/NF-κBp65/TNF-α Signaling in Cardiac Ischemia-Reperfusion Injury

Xanthine oxidase and xanthine dehydrogenase have been implicated in producing myocardial damage following reperfusion of an occluded coronary artery. We investigated and compared the effect of febuxostat and allopurinol in an experimental model of ischemia-reperfusion (IR) injury with a focus on the signaling pathways involved. Male Wistar rats were orally administered vehicle (CMC) once daily (sham and IR + control), febuxostat (10 mg/kg/day; FEB10 + IR), or allopurinol (100 mg/kg/day; ALL100 + IR) for 14 days. On the 15th day, the IR-control and treatment groups were subjected to one-stage left anterior descending (LAD) coronary artery ligation for 45 minutes followed by a 60-minute reperfusion. Febuxostat and allopurinol pretreatment significantly improved cardiac function and maintained morphological alterations. They also attenuated oxidative stress and apoptosis by suppressing the expression of proapoptotic proteins (Bax and caspase-3), reducing TUNEL-positive cells, and increasing the level of antiapoptotic proteins (Bcl-2). The MAPK-based molecular mechanism revealed suppression of active JNK and p38 proteins concomitant with the rise in ERK1/ERK2, a prosurvival kinase. Additionally, a reduction in the level of inflammatory markers (TNF-α, IL-6, and NF-κB) was also observed. The changes observed with febuxostat were remarkable in comparison with those observed with allopurinol. Febuxostat protects relatively better against IR injury than allopurinol by suppressing inflammation and apoptosis mediating the MAPK/NF-κBp65/TNF-α pathway.

Cardioprotective effect of the xanthones from Gentianella acuta against myocardial ischemia/reperfusion injury in isolated rat heart

Gentianella acuta (Michx.) Hulten is widely used for the treatment of arrhythmia and coronary heart disease in Ewenki Folk Medicinal Plants and Mongolian Medicine, popularly known as "Wenxincao" in China. To investigate the potential protective role of the xanthones from G. acuta against myocardial I/R injury in isolated rat heart and its possible related mechanism. The protective role of xanthones on myocardial I/R injury was studied on Langendorff apparatus. The hemodynamic parameters including the left ventricular developed pressure (LVDP), the maximum rate of up/down left intraventricular pressure (±dp/dt_max), coronary flow (CF) and heart rate (HR) were recorded during the perfusion. The results demonstrated that the xanthones from G. acuta treatment significantly improved myocardial function (LVDP, ±dp/dt_max and CF), increased the levels of superoxide dismutase (SOD) and catalase (CAT), succinate dehydrogenase (SDH), malate dehydrogenase (MDH), ATP and the ratio of glutathione and glutathione disulfide (GSH/GSSG), whereas suppressed the levels of Lactate dehydrogenase (LDH), creatine kinase (CK) and malondialdehyde (MDA). Furthermore, the xanthones upregulate the level of Bcl-2 protein and downregulate the level of Bax protein. These results indicated that xanthones from G. acuta exhibited cardioprotective effects on myocardial I/R injury through its activities of anti-oxidative effect and anti-apoptosis effect.

Therapeutic Hypothermia Reduces Oxidative Damage and Alters Antioxidant Defenses after Cardiac Arrest

After cardiac arrest, organ damage consequent to ischemia-reperfusion has been attributed to oxidative stress. Mild therapeutic hypothermia has been applied to reduce this damage, and it may reduce oxidative damage as well. This study aimed to compare oxidative damage and antioxidant defenses in patients treated with controlled normothermia versus mild therapeutic hypothermia during postcardiac arrest syndrome. The sample consisted of 31 patients under controlled normothermia (36°C) and 11 patients treated with 24 h mild therapeutic hypothermia (33°C), victims of in- or out-of-hospital cardiac arrest. Parameters were assessed at 6, 12, 36, and 72 h after cardiac arrest in the central venous blood samples. Hypothermic and normothermic patients had similar S100B levels, a biomarker of brain injury. Xanthine oxidase activity is similar between hypothermic and normothermic patients; however, it decreases posthypothermia treatment. Xanthine oxidase activity is positively correlated with lactate and S100B and inversely correlated with pH, calcium, and sodium levels. Hypothermia reduces malondialdehyde and protein carbonyl levels, markers of oxidative damage. Concomitantly, hypothermia increases the activity of erythrocyte antioxidant enzymes superoxide dismutase, glutathione peroxidase, and glutathione S-transferase while decreasing the activity of serum paraoxonase-1. These findings suggest that mild therapeutic hypothermia reduces oxidative damage and alters antioxidant defenses in postcardiac arrest patients.

Resveratrol attenuates myocardial ischemia/reperfusion injury through up-regulation of vascular endothelial growth factor B

The objective was to examine the protective effect of resveratrol (RSV) on myocardial ischemia/reperfusion (IR) injury and whether the mechanism was related to vascular endothelial growth factor B (VEGF-B) signaling pathway. Rat hearts were isolated for Langendorff perfusion test and H9c2 cells were used for in vitro assessments. RSV treatment significantly improved left ventricular function, inhibited CK-MB release, and reduced infarct size in comparison with IR group ex vivo. RSV treatment markedly decreased cell death and apoptosis of H9c2 cells during IR. We found that RSV was responsible for the up-regulation of VEGF-B mRNA and protein level, which caused the activation of Akt and the inhibition of GSK3β. Additionally, RSV prevented the generation of reactive oxygen species (ROS) by up-regulating the expression of MnSOD either in vitro or ex vivo. We also found that the inhibition of VEGF-B abolished the cardioprotective effect of RSV, increased apoptosis, and led to the down-regulation of phosphorylated Akt, GSK3β, and MnSOD in H9c2 cells. These results demonstrated that RSV was able to attenuate myocardial IR injury via promotion of VEGF-B/antioxidant signaling pathway. Therefore, the up-regulation of VEGF-B can be a promising modality for clinical myocardial IR injury therapy.

Phosphorylation of Nonmuscle Myosin Light Chain Promotes Endothelial Injury in Hyperlipidemic Rats Through a Mechanism Involving Downregulation of Dimethylarginine Dimethylaminohydrolase 2

Suppression of dimethylarginine dimethylaminohydrolase (DDAH) activation is related to endothelial dysfunction in hyperlipidemia, and nonmuscle myosin regulatory light chain (nmMLC₂₀) has been show to exert transcriptional function in regulation of gene expression. This study aims to explore whether the suppression of DDAH activation promotes endothelial injury under the condition of hyperlipidemia and whether nmMLC₂₀ can regulate DDAH expression in a phosphorylation-dependent manner. The rats were fed with high-fat diet for 8 weeks to establish a hyperlipidemic model, which showed an increase in plasma lipids and endothelial injury, accompanied by an elevation in myosin light chain kinase (MLCK) activity, phosphorylated nmMLC₂₀ (p-nmMLC₂₀) level, and asymmetric dimethylarginine (ADMA) content as well as a reduction in DDAH2 expression, DDAH activity, and nitric oxide (NO) content. Next, human umbilical vein endothelial cells (HUVECs) were incubated with oxidized low-density lipoprotein (ox-LDL; 100 μg/mL) for 24 hours to establish a cellular injury model in vitro. Consistent with the finding in vivo, ox-LDL induced HUVECs injury (apoptosis and necrosis) concomitant with an increase in MLCK activity, p-nmMLC₂₀ level (in total or nuclear proteins), and ADMA content as well as a reduction in DDAH2 expression, DDAH activity, and NO content; these phenomena were attenuated by MLCK inhibitor. Either in hyperlipidemic rats or in ox-LDL-treated HUVECs, there was not significant change in DDAH1 expression. Based on these observations, we conclude that the suppression of DDAH2 expression might account for, at least partially, the vascular endothelial dysfunction in hyperlipidemia, and nmMLC₂₀ plays a role in suppression of DDAH2 expression in a phosphorylation-dependent manner.

Non-muscle myosin light chain promotes endothelial progenitor cells senescence and dysfunction in pulmonary hypertensive rats through up-regulation of NADPH oxidase

Non-muscle myosin regulatory light chain (nmMLC20) is reported to exert transcriptional function in regulation of gene expression, and NADPH oxidase (NOX)-derived reactive oxygen species contribute to vascular remodeling of pulmonary artery hypertension (PAH). This study aims to determine if nmMLC20 can promote endothelial progenitor cells (EPCs) senescence and dysfunction through up-regulation of NOX in PAH rats. The rats were exposed to10% hypoxia for 3 weeks to establish a PAH model, which showed an increase in right ventricle systolic pressure, right ventricular and pulmonary vascular remodeling, and the accelerated senescence and impaired functions in EPCs, accompanied by an increase in Rho-kinase (ROCK) and NOX activities, p-nmMLC20 level, NOX expression and H2O2 content; these phenomena were reversed by fasudil, a selective inhibitor of ROCK. Next, normal EPCs were cultured under hypoxia to induce senescence in vitro. Consistent with the in vivo findings, hypoxia increased the senescence and dysfunction of EPCs concomitant with an increase in ROCK and NOX activities, p-nmMLC20 level, NOX expression and H2O2 content; these phenomena were reversed by fasudil. Knockdown of nmMLC20 showed similar results to that of fasudil except no effect on ROCK activity. Based on these observations, we conclude that nmMLC20 could promote the senescence and dysfunctions of EPCs in PAH through up-regulation of NOX in a phosphorylation-dependent manner.

Involvement of NADPH oxidases and non-muscle myosin light chain in senescence of endothelial progenitor cells in hyperlipidemia

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) is involved in endothelial dysfunction of hyperlipidemia, and non-muscle myosin regulatory light chain (nmMLC20) is reported to have a transcriptional function in regulation of gene expression. The purposes of this study are to determine whether NOX-derived ROS can promote endothelial progenitor cell (EPC) senescence and whether nmMLC20 can regulate NOX expression through a phosphorylation-dependent manner. The rats were subjected to 8 weeks of high-fat diet feeding to establish a hyperlipidemic model, which showed an increase in plasma lipids and the accelerated senescence and reduced number of circulating EPCs, accompanied by an increase in myosin light chain kinase (MLCK) and NOX activities, p-nmMLC20 level, NOX (NOX2, NOX4) expression, and H2O2 content. Next, EPCs isolated from normal rats were incubated with ox-LDL (100 μg/mL) for 24 h to establish a senescent model in vitro. Consistent with our in vivo findings, ox-LDL treatment increased the senescence of EPCs concomitant with an increase in MLCK and NOX activities, p-nmMLC20 level (in total or nuclear proteins), NOX expression, and H2O2 content; these phenomena were reversed by MLCK inhibitor. NOX inhibitor achieved similar results to that of MLCK inhibitor except that there is no effect on MLCK activity and p-nmMLC20 level. Furthermore, knockdown of nmMLC20, NOX2, or NOX4 led to a down-regulation in NOX and a reduction in ox-LDL-induced EPC senescence. These results suggest that NOX-derived ROS promotes the senescence of circulating EPCs in hyperlipidemia and nmMLC20 may play a transcriptional role in the upregulation of NOX through a phosphorylation-dependent manner.

Proteomic analysis of physiological versus pathological cardiac remodeling in animal models expressing mutations in myosin essential light chains

In this study we aimed to provide an in-depth proteomic analysis of differentially expressed proteins in the hearts of transgenic mouse models of pathological and physiological cardiac hypertrophy using tandem mass tag labeling and liquid chromatography tandem mass spectrometry. The Δ43 mouse model, expressing the 43-amino-acid N-terminally truncated myosin essential light chain (ELC) served as a tool to study the mechanisms of physiological cardiac remodeling, while the pathological hypertrophy was investigated in A57G (Alanine 57 → Glycine) ELC mice. The results showed that 30 proteins were differentially expressed in Δ43 versus A57G hearts as determined by multiple pair comparisons of the mutant versus wild-type (WT) samples with P < 0.05. The A57G hearts showed differential expression of nine mitochondrial proteins involved in metabolic processes compared to four proteins for ∆43 hearts when both mutants were compared to WT hearts. Comparisons between ∆43 and A57G hearts showed an upregulation of three metabolically important mitochondrial proteins but downregulation of nine proteins in ∆43 hearts. The physiological model of cardiac hypertrophy (∆43) showed no changes in the levels of Ca(2+)-binding proteins relative to WT, while the pathologic model (A57G) showed the upregulation of three Ca(2+)-binding proteins, including sarcalumenin. Unique differences in chaperone and fatty acid metabolism proteins were also observed in Δ43 versus A57G hearts. The proteomics data support the results from functional studies performed previously on both animal models of cardiac hypertrophy and suggest that the A57G- and not ∆43- mediated alterations in fatty acid metabolism and Ca(2+) homeostasis may contribute to pathological cardiac remodeling in A57G hearts.

Molecular Characterization of Reactive Oxygen Species in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion (I/R) injury is experienced by individuals suffering from cardiovascular diseases such as coronary heart diseases and subsequently undergoing reperfusion treatments in order to manage the conditions. The occlusion of blood flow to the tissue, termed ischemia, can be especially detrimental to the heart due to its high energy demand. Several cellular alterations have been observed upon the onset of ischemia. The danger created by cardiac ischemia is somewhat paradoxical in that a return of blood to the tissue can result in further damage. Reactive oxygen species (ROS) have been studied intensively to reveal their role in myocardial I/R injury. Under normal conditions, ROS function as a mediator in many cell signaling pathways. However, stressful environments significantly induce the generation of ROS which causes the level to exceed body's antioxidant defense system. Such altered redox homeostasis is implicated in myocardial I/R injury. Despite the detrimental effects from ROS, low levels of ROS have been shown to exert a protective effect in the ischemic preconditioning. In this review, we will summarize the detrimental role of ROS in myocardial I/R injury, the protective mechanism induced by ROS, and potential treatments for ROS-related myocardial injury.

Dispelling dogma and misconceptions regarding the most pharmacologically targetable source of reactive species in inflammatory disease, xanthine oxidoreductase

Xanthine oxidoreductase (XOR), the molybdoflavin enzyme responsible for the terminal steps of purine degradation in humans, is also recognized as a significant source of reactive species contributory to inflammatory disease. In animal models and clinical studies, inhibition of XOR has resulted in diminution of symptoms and enhancement of function in a number of pathologies including heart failure, diabetes, sickle cell anemia, hypertension and ischemia-reperfusion injury. For decades, XOR involvement in pathologic processes has been established by salutary outcomes attained from treatment with the XOR inhibitor allopurinol. This has served to frame a working dogma that elevation of XOR-specific activity is associated with enhanced rates of reactive species generation that mediate negative outcomes. While adherence to this narrowly focused practice of designating elevated XOR activity to be "bad" has produced some benefit, it has also led to significant underdevelopment of the processes mediating XOR regulation, identification of alternative reactants and products as well as micro-environmental factors that alter enzymatic activity. This is exemplified by recent reports: (1) identifying XOR as a nitrite reductase and thus a source of beneficial nitric oxide ((•)NO) under in vivo conditions similar to those where XOR inhibition has been assumed an optimal treatment choice, (2) describing XOR-derived uric acid (UA) as a critical pro-inflammatory mediator in vascular and metabolic disease and (3) ascribing an antioxidant/protective role for XOR-derived UA. When taken together, these proposed and countervailing functions of XOR affirm the need for a more comprehensive evaluation of product formation as well as the factors that govern product identity. As such, this review will critically evaluate XOR-catalyzed oxidant, (•)NO and UA formation as well as identify factors that mediate their production, inhibition and the resultant impact on inflammatory disease.