Showing papers in "Basic Research in Cardiology in 2012"
TL;DR: Administration of Nec-1 at the onset of reperfusion inhibits RIP1-dependent necrosis in vivo, leading to infarct size reduction and preservation of cardiac function, thereby opening a new direction for therapy in patients with myocardial infarction.
Abstract: Accumulating evidence indicatesthat programmed necrosis plays a critical role in cell death during ischemia–reperfusion. Necrostatin-1 (Nec-1), a small molecule capable of inhibiting a key regulator of programmed necrosis (RIP1), was shown to prevent necrotic cell death in experimental models including cardiac ischemia. However, no functional follow-up was performed and the action of Nec-1 remains unclear. Here, we studied whether Nec-1 inhibits RIP1-dependent necrosis and leads to long-term improvements after ischemia–reperfusion in vivo. Mice underwent 30 min of ischemia and received, 5 min before reperfusion, 3.3 mg/kg Nec-1 or vehicle treatment, followed by reperfusion. Nec-1 administration reduced infarct size to 26.3 ± 1.3 % (P = 0.001) compared to 38.6 ± 1.7 % in vehicle-treated animals. Furthermore, Nec-1 inhibited RIP1/RIP3 phosphorylation in vivo and significantly reduced necrotic cell death, while apoptotic cell death remained constant. By using MRI, cardiac dimensions and function were assessed before and 28 days after surgery. Nec-1-treated mice displayed less adverse remodeling (end-diastolic volume 63.5 ± 2.8 vs. 74.9 ± 2.8 μl, P = 0.031) and preserved cardiac performance (ejection fraction 45.81 ± 2.05 vs. 36.03 ± 2.37 %, P = 0.016). Nec-1 treatment significantly reduced inflammatory influx, tumor necrosis factor-α mRNA levels and oxidative stress levels. Interestingly, this was accompanied by significant changes in the expression signature of oxidative stress genes. Administration of Nec-1 at the onset of reperfusion inhibits RIP1-dependent necrosis in vivo, leading to infarct size reduction and preservation of cardiac function. The cardioprotective effect of Nec-1 highlights the importance of necrotic cell death in the ischemic heart, thereby opening a new direction for therapy in patients with myocardial infarction.
270 citations
TL;DR: Data demonstrate that Treg cells serve to protect against adverse ventricular remodeling and contribute to improve cardiac function after myocardial infarction via inhibition of inflammation and direct protection of cardiomyocytes.
Abstract: Persistent inflammatory responses participate in the pathogenesis of adverse ventricular remodeling after myocardial infarction (MI). We hypothesized that regulatory T (Treg) cells modulate inflammatory responses, attenuate ventricular remodeling and subsequently improve cardiac function after MI. Acute MI was induced by ligation of the left anterior descending coronary artery in rats. Infiltration of Foxp3(+) Treg cells was detected in the infarcted heart. Expansion of Treg cells in vivo by means of adoptive transfer as well as a CD28 superagonistic antibody (JJ316) resulted in an increased number of Foxp3(+) Treg cells in the infarcted heart. Subsequently, rats with MI showed improved cardiac function following Treg cells transfer or JJ316 injection. Interstitial fibrosis, myocardial matrix metalloproteinase-2 activity and cardiac apoptosis were attenuated in the rats that received Treg cells transfer. Infiltration of neutrophils, macrophages and lymphocytes as well as expression of tumor necrosis factor (TNF)-α and interleukin (IL)-1β were also significantly decreased, and the CD8(+) cardiac-specific cytotoxic T lymphocyte response was inhibited. Expression of interleukin (IL)-10 in the heart, however, was increased. Additional studies in vitro indicated that Treg cells directly protect neonatal rat cardiomyocytes against LPS-induced apoptosis, and this protection depends on the cell-cell contact and IL-10 expression. Furthermore, Treg cells inhibited proinflammatory cytokines production by cardiomyocytes. These data demonstrate that Treg cells serve to protect against adverse ventricular remodeling and contribute to improve cardiac function after myocardial infarction via inhibition of inflammation and direct protection of cardiomyocytes.
245 citations
TL;DR: Direct inhibition of miR-21 by antagomir-21 prevented fibrosis of the atrial myocardium post-myocardial infarction and signalling in vivo were prevented by long-term treatment of the mice with statins.
Abstract: Atrial fibrosis is important for the pathogenesis of atrial fibrillation (AF) but the underlying signal transduction is incompletely understood. We therefore studied the role of microRNA-21 (miR-21) and its downstream target Sprouty 1 (Spry1) during atrial fibrillation. Left atria (LA) from patients with AF showed a 2.5-fold increased expression of miR-21 compared to matched LA of patients in sinus rhythm. Increased miR-21 expression correlated positively with atrial collagen content and was associated with a reduced protein expression of Spry1 and increased expression of connective tissue growth factor (CTGF), lysyl oxidase and Rac1-GTPase. Neonatal cardiac fibroblasts treated with angiotensin II (AngII) or CTGF showed an increased miR-21 and decreased Spry1 expression. Pretreatment with an inhibitor of Rac1 GTPase, NSC23766, reduced the AngII-induced upregulation of miR-21. A small molecule inhibitor of lysyl oxidase, BAPN, prevented the AngII as well as the CTGF-induced miR-21 expression. Transgenic mice with cardiac overexpression of Rac1, which develop spontaneous AF and atrial fibrosis with increasing age, showed upregulation of miR-21 expression associated with reduced Spry1 expression. miR-21 expression and signalling in vivo were prevented by long-term treatment of the mice with statins. Direct inhibition of miR-21 by antagomir-21 prevented fibrosis of the atrial myocardium post-myocardial infarction. Left atria of patients with atrial fibrillation are characterized by upregulation of miR-21 und reduced expression of Spry1. Activation of Rac1 by angiotensin II leads to a CTGF- and lysyl oxidase-mediated increase of miR-21 expression contributing to structural remodelling of the atrial myocardium.
215 citations
TL;DR: The data suggest that the loss of DPP4 activity affects the anti-thrombogenic nature of the endothelium in human myocardial infarction as well as in vitro in HUVECs.
Abstract: Pro-coagulant and pro-inflammatory intramyocardial (micro)vasculature plays an important role in acute myocardial infarction (AMI). Currently, inhibition of serine protease dipeptidyl peptidase 4 (DPP4) receives a lot of interest as an anti-hyperglycemic therapy in type 2 diabetes patients. However, DPP4 also possesses anti-thrombotic properties and may behave as an immobilized anti-coagulant on endothelial cells. Here, we studied the expression and activity of endothelial DPP4 in human myocardial infarction in relation to a prothrombogenic endothelial phenotype. Using (immuno)histochemistry, DPP4 expression and activity were found on the endothelium of intramyocardial blood vessels in autopsied control hearts (n = 9). Within the infarction area of AMI patients (n = 73), this DPP4 expression and activity were significantly decreased, coinciding with an increase in Tissue Factor expression. In primary human umbilical vein endothelial cells (HUVECs), Western blot analysis and digital imaging fluorescence microscopy revealed that DPP4 expression was strongly decreased after metabolic inhibition, also coinciding with Tissue Factor upregulation. Interestingly, inhibition of DPP4 activity with diprotin A also enhanced the amount of Tissue Factor encountered and induced the adherence of platelets under flow conditions. Ischemia induces loss of coronary microvascular endothelial DPP4 expression and increased Tissue Factor expression in AMI as well as in vitro in HUVECs. Our data suggest that the loss of DPP4 activity affects the anti-thrombogenic nature of the endothelium.
177 citations
TL;DR: Results indicate that under pathological conditions, when [Ca2+]i is elevated, Cx43 HC opening is promoted in cardiomyocytes and CxMPs counteract this effect.
Abstract: Connexin mimetic peptides (CxMPs), such as Gap26 and Gap27, are known as inhibitors of gap junction channels but evidence is accruing that these peptides also inhibit unapposed/non-junctional hemichannels (HCs) residing in the plasma membrane. We used voltage clamp studies to investigate the effect of Gap26/27 at the single channel level. Such an approach allows unequivocal identification of HC currents by their single channel conductance that is typically ~220 pS for Cx43. In HeLa cells stably transfected with Cx43 (HeLa-Cx43), Gap26/27 peptides inhibited Cx43 HC unitary currents over minutes and increased the voltage threshold for HC opening. By contrast, an elevation of intracellular calcium ([Ca2+]i) to 200–500 nM potentiated the unitary HC current activity and lowered the voltage threshold for HC opening. Interestingly, Gap26/27 inhibited the Ca2+-potentiated HC currents and prevented lowering of the voltage threshold for HC opening. Experiments on isolated pig ventricular cardiomyocytes, which display strong endogenous Cx43 expression, demonstrated voltage-activated unitary currents with biophysical properties of Cx43 HCs that were inhibited by small interfering RNA targeting Cx43. As observed in HeLa-Cx43 cells, HC current activity in ventricular cardiomyocytes was potentiated by [Ca2+]i elevation to 500 nM and was inhibited by Gap26/27. Our results indicate that under pathological conditions, when [Ca2+]i is elevated, Cx43 HC opening is promoted in cardiomyocytes and CxMPs counteract this effect.
139 citations
TL;DR: Sustained afterload enhancement of EHTs alone is sufficient to induce pathological cardiac remodeling with reduced contractile function and increased glucose consumption, and the model will be useful to investigate novel therapeutic approaches in a simple and fast manner.
Abstract: Increased afterload results in ‘pathological’ cardiac hypertrophy, the most important risk factor for the development of heart failure. Current in vitro models fall short in deciphering the mechanisms of hypertrophy induced by afterload enhancement. The aim of this study was to develop an experimental model that allows investigating the impact of afterload enhancement (AE) on work-performing heart muscles in vitro. Fibrin-based engineered heart tissue (EHT) was cast between two hollow elastic silicone posts in a 24-well cell culture format. After 2 weeks, the posts were reinforced with metal braces, which markedly increased afterload of the spontaneously beating EHTs. Serum-free, triiodothyronine-, and hydrocortisone-supplemented medium conditions were established to prevent undefined serum effects. Control EHTs were handled identically without reinforcement. Endothelin-1 (ET-1)- or phenylephrine (PE)-stimulated EHTs served as positive control for hypertrophy. Cardiomyocytes in EHTs enlarged by 28.4 % under AE and to a similar extent by ET-1- or PE-stimulation (40.6 or 23.6 %), as determined by dystrophin staining. Cardiomyocyte hypertrophy was accompanied by activation of the fetal gene program, increased glucose consumption, and increased mRNA levels and extracellular deposition of collagen-1. Importantly, afterload-enhanced EHTs exhibited reduced contractile force and impaired diastolic relaxation directly after release of the metal braces. These deleterious effects of afterload enhancement were preventable by endothelin-A, but not endothelin-B receptor blockade. Sustained afterload enhancement of EHTs alone is sufficient to induce pathological cardiac remodeling with reduced contractile function and increased glucose consumption. The model will be useful to investigate novel therapeutic approaches in a simple and fast manner.
137 citations
TL;DR: Findings indicate that the release mechanism involves neural pathways in type 2 diabetes mellitus patients and that the cardioprotective effect was attenuated in the subgroup of diabetic patients with neuropathy.
Abstract: Efficacy of ischemic preconditioning is decreased in animal models of type 2 diabetes mellitus while the responses in humans with diabetes are contradictory. It is unknown whether attenuation is related to decreased release of a mediating humoral cardioprotective factor or reduced ability to respond in the target tissue. The aim of the present study was to investigate the release and effect of a circulating cardioprotective factor in type 2 diabetes mellitus patients. Blood samples were drawn from nine non-diabetic subjects, eight diabetic patients without peripheral neuropathy, and eight diabetic patients with peripheral neuropathy before (control) and after a remote ischemic preconditioning (rIPC) stimulus. Blood samples were dialyzed against Krebs–Henseleit buffer and the cardioprotective effects of the dialysates were tested in rabbit hearts mounted on a Langendorff model and subjected to 30-min global ischemia and 120-min reperfusion. rIPC dialysate from non-diabetic and diabetic subjects without peripheral neuropathy reduced infarct size and improved hemodynamic recovery compared to control dialysate from non-diabetic and diabetic subjects. However, in the subgroup of diabetic patients with neuropathy the cardioprotective effect was attenuated. These findings indicate that the release mechanism involves neural pathways.
133 citations
TL;DR: Current knowledge of sirtuin functions in the heart is summarized and its translation into therapy for heart failure is discussed.
Abstract: Sirtuins are a highly conserved family of histone/protein deacetylases whose activity can prolong the lifespan of model organisms such as yeast, worms and flies. In mammalian cells, seven sirtuins (SIRT1–7) modulate distinct metabolic and stress-response pathways, SIRT1 and SIRT3 having been most extensively investigated in the cardiovascular system. SIRT1 and SIRT3 are mainly located in the nuclei and mitochondria, respectively. They participate in biological functions related to development of heart failure, including regulation of energy production, oxidative stress, intracellular signaling, angiogenesis, autophagy and cell death/survival. Emerging evidence indicates that the two sirtuins play protective roles in failing hearts. Here, we summarize current knowledge of sirtuin functions in the heart and discuss its translation into therapy for heart failure.
131 citations
TL;DR: The results suggest that RIPC induces late protection against myocardial IR injury by increasing expression of IL-10 in the remote muscle, followed by release ofIL-10 into the circulation, and activation of protective signaling pathways in the heart.
Abstract: Remote ischemic preconditioning (RIPC) induces a prolonged late phase of multi-organ protection against ischemia-reperfusion (IR) injury. In the present study, we tested the hypothesis that RIPC confers late protection against myocardial IR injury by upregulating expression of interleukin (IL)-10. Mice were exposed to lower limb RIPC or sham ischemia. After 24 h, mice with RIPC demonstrated decreased myocardial infarct size and improved cardiac contractility following 30-min ischemia and 120-min reperfusion (I-30/R-120). These effects of RIPC were completely blocked by anti-IL-10 receptor antibodies. In IL-10 knockout mice, RIPC cardioprotection was lost, but it was mimicked by exogenous IL-10. Administration of IL-10 to isolated perfused hearts increased phosphorylation of the protein kinase Akt and limited infarct size after I-30/R-120. In wild-type mice, RIPC increased plasma and cardiac IL-10 protein levels and caused activation of Akt and endothelial nitric oxide synthase in the heart at 24 h, which was also blocked by anti-IL-10 receptor antibodies. In the gastrocnemius muscle, RIPC resulted in immediate inactivation of the phosphatase PTEN and activation of Stat3, with increased IL-10 expression 24 h later. Myocyte-specific PTEN inactivation led to increased Stat3 phosphorylation and IL-10 protein expression in the gastrocnemius muscle. Taken together, these results suggest that RIPC induces late protection against myocardial IR injury by increasing expression of IL-10 in the remote muscle, followed by release of IL-10 into the circulation, and activation of protective signaling pathways in the heart. This study provides a scientific basis for the use of RIPC to confer systemic protection against IR injury.
122 citations
TL;DR: The results suggest that Cur post-treatment can attenuate IR injury through the activation of the JAK2/STAT3 signaling pathway, which transmits a survival signal to the myocardium.
Abstract: In this study, we evaluated the effect of curcumin (Cur) post-treatment on isolated perfused rat hearts that had been subjected to a protocol of ischemia and reperfusion injury. We also examined whether the Janus kinase 2 and signal transducer and activator 3 of transcription (JAK2/STAT3) signaling pathway plays a role in the cardioprotective effects of Cur post-treatment. Isolated perfused rat hearts were subjected to 60 min of ischemia, followed by 60 min of reperfusion. The hearts were exposed to 1-μM Cur during the first 10 min of reperfusion in the absence or presence of the JAK kinase-specific inhibitor AG490 (AG, 1 μM). The Cur treatment conferred a cardioprotective effect, and the treated hearts demonstrated an improved post-ischemic cardiac functional recovery, a decreased myocardial infarct size and decreased lactate dehydrogenase release in the coronary flow, a reduced number of apoptotic cardiomyocytes, up-regulation of the anti-apoptotic protein Bcl2 and down-regulation of the pro-apoptotic protein Caspase3. AG blocked the Cur-mediated cardioprotection by inhibiting the JAK2/STAT3 signaling pathway, as reflected by the abrogation of the Cur-induced up-regulation of Bcl2 and down-regulation of Caspase3. The results suggest that Cur post-treatment can attenuate IR injury through the activation of the JAK2/STAT3 signaling pathway, which transmits a survival signal to the myocardium.
120 citations
TL;DR: Recent work pertaining to epigenetic changes in a cardiovascular disease setting is outlined and it is suggested that these epigenetic modifications also impact on the development of cardiovascular disease.
Abstract: Epigenetics represents a phenomenon of altered heritable phenotypic expression of genetic information occurring without changes in DNA sequence. Epigenetic modifications control embryonic development, differentiation and stem cell (re)programming. These modifications can be affected by exogenous stimuli (e.g., diabetic milieu, smoking) and oftentimes culminate in disease initiation. DNA methylation has been studied extensively and represents a well-understood epigenetic mechanism. During this process cytosine residues preceding a guanosine in the DNA sequence are methylated. CpG-islands are short-interspersed DNA sequences with clusters of CG sequences. The abnormal methylation of CpG islands in the promoter region of genes leads to a silencing of genetic information and finally to alteration of biological function. Emerging data suggest that these epigenetic modifications also impact on the development of cardiovascular disease. Histone modifications lead to the modulation of the expression of genetic information through modification of DNA accessibility. In addition, RNA-based mechanisms (e.g., microRNAs and long non-coding RNAs) influence the development of disease. We here outline the recent work pertaining to epigenetic changes in a cardiovascular disease setting.
TL;DR: Oxidative stress and inflammation are predicted to be among the first alterations which may trigger other downstream mediators in diabetes associated with endothelial dysfunction and provide insights into potential therapeutic targets that can delay or reverse diabetic vasculopathy.
Abstract: Despite abundant clinical evidence linking metabolic abnormalities to diabetic vasculopathy, the molecular basis of individual susceptibility to diabetic vascular complications is still largely undetermined. Endothelial dysfunction in diabetes-associated vascular complications is considered an early stage of vasculopathy and has attracted considerable research interests. Type 2 diabetes is characterized by metabolic abnormalities, such as hyperglycemia, excess liberation of free fatty acids (FFA), insulin resistance and hyperinsulinemia. These abnormalities exert pathological impact on endothelial function by attenuating endothelium-mediated vasomotor function, enhancing endothelial apoptosis, stimulating endothelium activation/endothelium-monocyte adhesion, promoting an atherogenic response and suppressing barrier function. There are multiple signaling pathways contrib- uting to the adverse effects of glucotoxicity on endothelial function. Insulin maintains the normal balance for release of several factors with vasoactive properties. Abnormal insulin signaling in the endothelium does not affect the whole-body glucose metabolism, but impairs endothelial response to insulin and accelerates atherosclerosis. Excessive level of FFA is implicated in the pathogenesis of insulin resistance. FFA induces endothelial oxidative stress, apoptosis and inflammatory response, and inhibits insulin signaling. Although hyperglycemia, insulin resis- tance, hyperinsulinemia and dyslipidemia independently contribute to endothelial dysfunction via various distinct mechanisms, the mutual interactions may synergistically accelerate their adverse effects. Oxidative stress and inflammation are predicted to be among the first alterations which may trigger other downstream mediators in diabetes associated with endothelial dysfunction. These mecha- nisms may provide insights into potential therapeutic tar- gets that can delay or reverse diabetic vasculopathy.
TL;DR: Epicardial adipocyte-incubated LA myocytes had larger late sodium currents, L-type calcium currents, and transient outward potassium currents, but smaller delayed rectifiers potassium and inward rectifier potassium currents than control myocytes.
Abstract: Obesity is an important risk factor for atrial fibrillation (AF). Increased epicardial adipose tissue in obesity can enhance inflammation and plays an important role in the pathophysiology of AF. However, it is not clear whether epicardial adipocytes directly modulate the electrophysiological characteristics of atrial myocytes. Whole-cell patch clamp was used to record the action potentials (APs) and ionic currents in isolated rabbit left atrium (LA) myocytes incubated with and without (control) isolated adipocytes from epicardial, retrosternal, or abdominal adipose tissues, or adipocytes-conditioned supernatant for 2-4 h. Compared to control LA myocytes (n = 22), LA myocytes incubated with epicardial (n = 17), retrosternal (n = 18), or abdominal adipocytes (n = 22) had longer (80 ± 3, 109 ± 6, 109 ± 6, and 110 ± 7 ms, p 0.05) in comparison to control myocytes. Epicardial adipocyte-incubated LA myocytes had larger late sodium currents, L-type calcium currents, and transient outward potassium currents, but smaller delayed rectifier potassium and inward rectifier potassium currents than control LA myocytes. Moreover, isoproterenol (10 nM) induced a higher incidence (67 vs. 22 %, p < 0.05) of triggered beats in adipocytes-incubated LA myocytes (n = 12) than in control LA myocytes (n = 9). In conclusion, adipocytes can directly modulate the electrophysiological properties and ion currents, causing higher arrhythmogenesis in LA myocytes.
TL;DR: RIPC does not reduce plasma high-sensitivity troponin T levels, AKI, or ICU-support requirements in high-risk cardiac surgery, and RIPC increased post-operative duration of noradrenaline duration.
Abstract: The efficacy of remote ischemic preconditioning (RIPC) in high-risk cardiac surgery is uncertain. In this study, 96 adults undergoing high-risk cardiac surgery were randomised to RIPC (3 cycles of 5 min of upper-limb ischemia induced by inflating a blood pressure cuff to 200 mmHg with 5 min of reperfusion) or control. Main endpoints were plasma high-sensitivity troponin T (hsTNT) levels at 6 and 12 h, worst post-operative acute kidney injury (AKI) based on RIFLE criteria, and noradrenaline duration. hsTNT levels were log-normally distributed and higher with RIPC than control at 6-h post cross-clamp removal [810 ng/ml (IQR 527–1,724) vs. 634 ng/ml (429–1,012); ratio of means 1.41 (99.17% CI 0.92–2.17); P=0.04] and 12 h [742 ng/ml (IQR 427–1,700) vs. 514 ng/ml (IQR 356–833); ratio of means 1.56 (99.17% CI 0.97–2.53); P=0.01]. After adjustment for baseline confounders, the ratio of means of hsTNT at 6 h was 1.23 (99.17% CI 0.88–1.72; P=0.10) and at 12 h was 1.30 (99.17% CI 0.92–1.84; P=0.05). In the RIPC group, 35/48 (72.9%) had no AKI, 5/48 (10.4%) had AKI risk, and 8/48 (16.7%) had either renal injury or failure compared to the control group where 34/48 (70.8%) had no AKI, 7/48 (14.6%) had AKI risk, and 7/48 (14.6%) had renal injury or failure (Chi-squared 0.41; two degrees of freedom; P = 0.82). RIPC increased post-operative duration of noradrenaline support [21 h (IQR 7–45) vs. 9 h (IQR 3–19); ratio of means 1.70 (99.17% CI 0.86–3.34); P=0.04]. RIPC does not reduce hsTNT, AKI, or ICU-support requirements in high-risk cardiac surgery.
TL;DR: Direct electrical or peripheral neural stimulation evoked the release of cardioprotective substances into the bloodstream, with comparable effects to that of rIPC induced by limb ischemia, confirm the central role of peripheral nerves in the local signal transduction of remote cardioprotsection.
Abstract: We have previously shown that remote ischemic preconditioning by limb ischemia (rIPC) or intra-arterial adenosine releases a dialyzable cardioprotective circulating factor(s), the release of which requires an intact neural connection to the limb and is blocked by pretreatment with S-nitroso-N-acetylpenicillamine (SNAP). Remote cardioprotection can be induced by other forms of peripheral stimulation including topical capsaicin, but the mechanisms of their signal transduction are incompletely understood. Rabbits were anesthetized by intravenous pentobarbital, intubated and ventilated, then randomized (4–7 animals in each group) to receive sham procedure, rIPC (4 cycles of 5 min lower limb ischemia, 5 min reperfusion), direct femoral nerve stimulation, topical capsaicin, pretreatment with intra-arterial SNAP + capsaicin, pretreatment with topical DMSO (a sensory nerve blocker) + topical capsaicin, or pretreatment with intra-arterial SNAP + femoral nerve stimulation, topical DMSO alone, or intra-arterial SNAP alone. Blood was then rapidly drawn from the carotid artery to produce the plasma dialysate which was used to perfuse a naive heart from an untreated donor rabbit. The infarct size and recovery of LV-developed pressure and end-diastolic pressure were measured after 30 min of global ischemia and 120 min of reperfusion. Compared to sham, dialysate from rIPC, femoral nerve stimulation, and topical capsaicin groups all produced significant cardioprotection with significantly reduced infarct size, and improved the post-ischemic cardiac performance. Cardioprotection was not seen in the topical DMSO-capsaicin, SNAP + capsaicin, and SNAP + FNS groups. These results confirm the central role of peripheral nerves in the local signal transduction of remote cardioprotection. Direct electrical or peripheral neural stimulation evokes the release of cardioprotective substances into the bloodstream, with comparable effects to that of rIPC induced by limb ischemia.
TL;DR: In vivo administration of antagomiR-92a significantly enhanced re-endothelialization in injured carotid arteries and reduced neointimal formation after balloon injury or arterial stenting, providing the first evidence that inhibition of miR- 92a may represent a novel strategy to improve endothelial regeneration and reduce restenosis after vascular injury.
Abstract: The role of miR-92a on vascular remodelling after injury is currently unknown. Thus, the aim of the present study was to evaluate the role of miR-92a on rat endothelial and vascular smooth muscle cells proliferation and migration in vitro as well as after balloon injury or arterial stenting in vivo. MiR-92a was highly expressed in RAO-ECs and vascular endothelium, but not in RAO-SMCs or medial smooth muscle as assessed by real-time RT-PCR. Importantly, BrdU incorporation and wound healing assay provide evidence that functional inhibition of miR-92a resulted in an increased RAO-ECs proliferation and migration, but had no effect on RAO-SMCs proliferation or migration in vitro. Immunoblotting analysis revealed an increased phosphorylation of ERK1/2, JNK/SAPK as well as eNOS and phospho-eNOS increased expression level in RAO-ECs as a consequence of miR-92a inhibition. Using gain and loss of function experiments, we showed that miR-92a modulates regulation of KLF4 and MKK4 expression level in endothelial cells. Finally, in vivo administration of antagomiR-92a significantly enhanced re-endothelialization in injured carotid arteries and reduced neointimal formation after balloon injury or arterial stenting. These data provide the first evidence that inhibition of miR-92a may represent a novel strategy to improve endothelial regeneration and reduce restenosis after vascular injury.
TL;DR: High-intensity exercise preconditioning elicits cardioprotection through a humorally mediated dependent on opioid receptor activation, similar to rIPC.
Abstract: Exercise protects against myocardial ischemia-reperfusion (I-R) injury but the mechanism remains unclear. Protection can be transferred from a remotely preconditioned human donor to an isolated perfused rabbit heart using a dialysate of plasma. We hypothesized that physical exercise preconditioning also confers cardioprotection through a humorally mediated effector dependent on opioid receptor activation. Thirteen male volunteers performed vigorous exercise (four 2-minute bouts of high-intensity exercise) and 1 week later they underwent remote ischemic preconditioning (four cycles of 5 min upper limb ischemia and reperfusion). Dialysates were prepared from blood collected before (control) and after the two interventions. Isolated rabbit hearts were perfused with the dialysates without and with co-administration of naloxone (opioid receptor antagonist) prior to 40 min regional ischemia and 2 h reperfusion. Exercise and remote ischemic preconditioning (rIPC) reduced infarct size from 60 ± 5 to 35 ± 5 % and from 57 ± 7 to 27 ± 3 % of the area at risk, respectively (p < 0.05 and < 0.01). Furthermore, post-ischemic left ventricular developed pressure was improved compared with controls (p = 0.08 for exercise and p = 0.04 for rIPC). Co-perfusion with naloxone abrogated the protective effects of exercise and remote ischemic preconditioned dialysates. In conclusion, high-intensity exercise preconditioning elicits cardioprotection through a humorally mediated dependent on opioid receptor activation, similar to rIPC.
TL;DR: This study provides evidence that sustained activation of S100A8/A9 critically contributes to the development of post-ischemic HF driving the progressive course of HF through activation of RAGE.
Abstract: The extracellular heterodimeric protein S100A8/A9 activates the innate immune system through activation of the receptor of advanced glycation end products (RAGE) and Toll-like receptors As activation of RAGE has recently been associated with sustained myocardial inflammation and heart failure (HF) we studied the role of S100A8/A9 in the development of post-ischemic HF Hypoxia led to sustained induction of S100A8/A9 accompanied by increased nuclear factor (NF-)κB binding activity and increased expression of pro-inflammatory cytokines in cardiac fibroblasts and macrophages Knockdown of either S100A8/A9 or RAGE rescued the induction of pro-inflammatory cytokines and NF-κB activation after hypoxia In a murine model of post-ischemic HF both cardiac RNA and protein levels of S100A8/A9 were elevated as soon as 30 min after hypoxia with sustained activation up to 28 days after ischemic injury Treatment with recombinant S100A8/A9 resulted in reduced cardiac performance following ischemia/reperfusion Chimera experiments after bone marrow transplantation demonstrated the importance of RAGE expression on immune cells for their recruitment to the injured myocardium aggravating post-ischemic heart failure Signaling studies in isolated ventricles indicated that MAP kinases JNK, ERK1/2 as well as NF-κB mediate signals downstream of S100A8/A9-RAGE in post-ischemic heart failure Interestingly, cardiac performance was not affected by administration of S100A8/A9 in RAGE−/−-mice, which demonstrated significantly improved cardiac recovery compared to WT-mice Our study provides evidence that sustained activation of S100A8/A9 critically contributes to the development of post-ischemic HF driving the progressive course of HF through activation of RAGE
TL;DR: Efficient reprogramming of multipotent bone marrow (BM) mesenchymal stem cells (MSC) to pluripotent status and the resultant MSC derived iPS cells (MiPS) and their derived progenitors effectively repaired the infarcted heart.
Abstract: The strategy to reprogram somatic stem cells to pluripotency status has provided an alternative source of surrogate ES cells (ESC). We report efficient reprogramming of multipotent bone marrow (BM) mesenchymal stem cells (MSC) to pluripotent status and the resultant MSC derived iPS cells (MiPS) and their derived progenitors effectively repaired the infarcted heart. MSC from young, male, Oct4-GFP transgenic mice were reprogrammed by retroviral transduction with Oct4, Sox2, Klf4, and c-Myc stemness factors. MiPS thus generated displayed characteristics of mouse ESC including morphology, surface antigens, gene and miR expression profiles. MiPS also formed spontaneously beating cardiac progenitors which expressed cardiac specific transcription factors and protein markers including Gata4, Mef2c, Nkx2.5, myosin heavy chain, troponin-I, and troponin-T, and showed ultra structural characteristics typical of cardiomyocytes. Intramyocardial delivery of MiPS (group-2) and their derivative cardiac-like cells (MiPS-CP; group-3) in a mouse model of acute myocardial infarction showed extensive survival and engraftment at 4 weeks with resultant attenuation of infarct size (p < 0.001 vs. DMEM injected control; n = 4). Engraftment of MiPS-CP was without cardiac tumorigenesis as compared to 21 % in MiPS transplanted animals. Furthermore, angiogenesis was improved in groups-2 and 3 (p < 0.001 vs. control). Transthoracic echocardiography revealed significantly preserved indices of cardiac contractility (ejection fraction p < 0.001 and fractional shortening p < 0.001 vs. control; n = 7). MSC were successfully reprogrammed into MiPS that displayed ESC-like characteristics and differentiated into spontaneously beating cardiomyocytes. Cardiac progenitors derived from MiPS repopulated the infarcted heart without tumorigenesis and improved global cardiac function.
TL;DR: Cardiac mitochondrial respiration was decreased following chronic hypoxia, associated with downregulation of different pathways in the two mitochondrial populations, determined by their subcellular location.
Abstract: Chronic hypoxia decreases cardiomyocyte respiration, yet the mitochondrial mechanisms remain largely unknown. We investigated the mitochondrial metabolic pathways and enzymes that were decreased following in vivo hypoxia, and questioned whether hypoxic adaptation was protective for the mitochondria. Wistar rats were housed in hypoxia (7 days acclimatisation and 14 days at 11% oxygen), while control rats were housed in normoxia. Chronic exposure to physiological hypoxia increased haematocrit and cardiac vascular endothelial growth factor, in the absence of weight loss and changes in cardiac mass. In both subsarcolemmal (SSM) and interfibrillar (IFM) mitochondria isolated from hypoxic hearts, state 3 respiration rates with fatty acid were decreased by 17-18%, and with pyruvate were decreased by 29-15%, respectively. State 3 respiration rates with electron transport chain (ETC) substrates were decreased only in hypoxic SSM, not in hypoxic IFM. SSM from hypoxic hearts had decreased activities of ETC complexes I, II and IV, which were associated with decreased reactive oxygen species generation and protection against mitochondrial permeability transition pore (MPTP) opening. In contrast, IFM from hypoxic hearts had decreased activity of the Krebs cycle enzyme, aconitase, which did not modify ROS production or MPTP opening. In conclusion, cardiac mitochondrial respiration was decreased following chronic hypoxia, associated with downregulation of different pathways in the two mitochondrial populations, determined by their subcellular location. Hypoxic adaptation was not deleterious for the mitochondria, in fact, SSM acquired increased protection against oxidative damage under the oxygen-limited conditions.
TL;DR: The data suggest UPS activation in early postnatal development of cardiachypertrophy, specific UPS impairment in old KI mice carrying a HCM mutation, and defective ALP as a common mechanism in genetically engineered mice with cardiac hypertrophy.
Abstract: Several lines of evidence suggest that alterations of the ubiquitin-proteasome system (UPS) and autophagy-lysosome pathway (ALP) may be involved in cardiac diseases. Little is known, however, in hypertrophic cardiomyopathy (HCM). This study studied these pathways in two mouse models of HCM that mainly differ by the presence or absence of truncated mutant proteins. Analyses were performed in homozygous Mybpc3-targeted knock-in (KI) mice, carrying a HCM mutation and exhibiting low levels of mutant cardiac myosin-binding protein C (cMyBP-C), and in Mybpc3-targeted knock-out (KO) mice expressing no cMyBP-C, thus serving as a model of pure cMyBP-C insufficiency. In the early postnatal development of cardiac hypertrophy, both models showed higher levels of ubiquitinated proteins and greater proteasomal activities. To specifically monitor the degradation capacity of the UPS with age, mice were crossed with transgenic mice that overexpress UbG76V-GFP. UbG76V-GFP protein levels were fourfold higher in 1-year-old KI, but not KO mice, suggesting a specific UPS impairment in mice expressing truncated cMyBP-C. Whereas protein levels of key ALP markers were higher, suggesting ALP activation in both mutant mice, their mRNA levels did not differ between the groups, underlying rather defective ALP-mediated degradation. Analysis of key proteins regulated in heart failure did not reveal specific alterations in KI and KO mice. Our data suggest (1) UPS activation in early postnatal development of cardiac hypertrophy, (2) specific UPS impairment in old KI mice carrying a HCM mutation, and (3) defective ALP as a common mechanism in genetically engineered mice with cardiac hypertrophy.
TL;DR: A retrospective analysis supports the proposal that clopidogrel attenuates lethal reperfusion injury and suggests that ischemic post-conditioning and clopIDogrel administration were the only two therapeutic independent predictors of the final infarct size as determined by cardiac enzymes release.
Abstract: Antiplatelet agents have been extensively used in acute coronary syndromes and improve clinical outcome in STEMI patients. Previous experimental studies of the impact of antiplatelet agents on infarct size have been equivoqual. We questioned whether clopidogrel might reduce infarct size in STEMI patients, independently of any antithrombotic effect, by activating a post-conditioning-like myocardial protection. We retrospectively analyzed three recent controlled, randomized, proof of concept clinical trials aimed at determining whether PCI post-conditioning might attenuated infarct size in STEMI. We addressed whether clopidogrel (300–600 mg before angioplasty) might have influenced infarct size using a multivariable linear regression analysis with infarct size as the continuous outcome variable and age, clopidogrel and GP IIb/IIIa inhibitors, post-conditioning, area at risk, ischemia time, coronary thrombectomy and final TIMI flow, as covariates. In this population of 88 STEMI patients, ischemic post-conditioning and clopidogrel administration were the only two therapeutic independent predictors of the final infarct size as determined by cardiac enzymes release (p = 0.005 and p < 0.0001, respectively) This retrospective analysis supports the proposal that clopidogrel attenuates lethal reperfusion injury.
TL;DR: A novel pathway of NOx2/VPO1 in myocardium, where VPO1 coordinates with NOX2 and amplifies the role of NOX-derived ROS in oxidative injury following IR is demonstrated.
Abstract: Vascular peroxidase 1 (VPO1) can utilize reactive oxygen species (ROS) generated from NADPH oxidase (NOX) to catalyze peroxidative reactions. This study was performed to identify a novel pathway of NOX/VPO1 in mediating the oxidative injury following myocardial ischemia reperfusion (IR). In a rat model of myocardial IR, the infarct size, serum creatine kinase (CK) activity, apoptosis, NOX activity, NOX2 and VPO1 expression were measured. In a cell (rat heart-derived H9c2 cells) model of hypoxia/reoxygenation (HR), the apoptosis, NOX activity, NOX2 and VPO1 expression, and H(2)O(2) and HOCl levels were examined. In vivo, IR caused 54.8 ± 1.7 % infarct size in myocardium accompanied by elevated activities of CK, caspase-3 and NOX, up-regulated VPO1 expression and high numbers of myocardial apoptotic cells; these effects were attenuated by pretreatment with the inhibitor of NOX. In vitro, inhibition of NOX or silencing of NOX2 or VPO1 expression significantly suppressed HR-induced cellular apoptosis concomitantly with decreased HOCl production. Inhibition of NOX or silencing of NOX2 led to a decrease in H(2)O(2) production accompanied by a decrease in VPO1 expression and HOCl production. However, silencing of VPO1 expression did not affect NOX2 expression and H(2)O(2) production. H(2)O(2)-induced VPO1 expression was partially reversed by JNK or p38 MAPK inhibitor. Our results demonstrate a novel pathway of NOX2/VPO1 in myocardium, where VPO1 coordinates with NOX2 and amplifies the role of NOX-derived ROS in oxidative injury following IR.
TL;DR: PDE5A inhibition with sildenafil may provide a new treatment strategy for cardiac hypertrophy and adverse remodeling in the hypertensive heart.
Abstract: Sildenafil inhibits cyclic GMP-specific phosphodiesterase type-5A (PDE5A) and can prevent cardiac hypertrophy and left ventricular (LV) dysfunction in mice subjected to severe pressure-overload. The pathophysiological role of sildenafil in adverse remodeling in the hypertensive heart after chronic renin–angiotensin aldosterone system stimulation is unknown. Therefore, we studied the efficacy of the PDE5A inhibitor sildenafil for treating advanced cardiac hypertrophy and LV remodeling due to angiotensin (Ang)II-induced heart failure (HF) in vivo. C57BL6/J mice were subjected to AngII-induced cardiac hypertrophy for 3 weeks and cardiac dysfunction, cardiac inflammatory stress response, adverse remodeling as well as apoptosis were documented. Mice were subsequently treated with sildenafil (100 mg/kg/day) or placebo with delay of 5 days for treating AngII infusion-induced adverse events. Compared to controls, AngII infusion resulted in impaired systolic (dP/dt
max −46 %, SV −16 %, SW −43 %, E
a +51 %, EF −37 %, CO −36 %; p < 0.05) and diastolic (dP/dt
min −36 %, LV end diastolic pressure +73 %, Tau +21 %, stiffness constant β +74 %; p < 0.05) LV function. This was associated with a significant increase in cardiac hypertrophy and fibrosis. Increased inflammatory response was also indicated by an increase in immune cell infiltration and apoptosis. Treatment with sildenafil led to a significant improvement in systolic and diastolic LV performance. This effect was associated with less LV hypertrophy, remodeling, cardiac inflammation and apoptosis. PDE5A inhibition with sildenafil may provide a new treatment strategy for cardiac hypertrophy and adverse remodeling in the hypertensive heart.
TL;DR: HDAC inhibition decreases Nox4 transcription in human endothelial cells by preventing the binding of transcription factor and polymerase to the Nox 4 promoter, most likely because of a hyperacetylation-mediated steric inhibition.
Abstract: Nox4 is a member of the NADPH oxidase family, which represents a major source of reactive oxygen species (ROS) in the vascular wall. Nox4-mediated ROS production mainly depends on the expression levels of the enzyme. The present study was aimed to investigate the mechanisms of Nox4 transcription regulation by histone deacetylases (HDAC). In human umbilical vein endothelial cells (HUVEC) and HUVEC-derived EA.hy 926 cells, treatment with the pan-HDAC inhibitor scriptaid led to a marked decrease in Nox4 mRNA expression. A similar down-regulation of Nox4 mRNA expression was observed by siRNA-mediated knockdown of HDAC3. HDAC inhibition in endothelial cells was associated with enhanced histone acetylation, increased chromatin accessibility in the human Nox4 promoter region, with no significant changes in DNA methylation. In addition, we provided evidence that c-Jun played an important role in controlling Nox4 transcription. Knockdown of c-Jun with siRNA led to a down-regulation of Nox4 mRNA expression. In response to scriptaid treatment, the binding of c-Jun to the Nox4 promoter region was reduced despite the open chromatin structure. In parallel, the binding of RNA polymerase IIa to the Nox4 promoter was significantly inhibited as well, which may explain the reduction in Nox4 transcription. In conclusion, HDAC inhibition decreases Nox4 transcription in human endothelial cells by preventing the binding of transcription factor(s) and polymerase(s) to the Nox4 promoter, most likely because of a hyperacetylation-mediated steric inhibition.
TL;DR: Data identify STAT3 as a key molecule for the proliferative response of SMC and neointima formation and inhibition of STAT3 by the potent and specific compound WP1066 might represent a novel and attractive approach for the local treatment of vascular proliferative diseases.
Abstract: Dedifferentiation, migration, and proliferation of resident vascular smooth muscle cells (SMCs) are key components of neointima formation after vascular injury. Activation of signal transducer and activator of transcription-3 (STAT3) is suggested to be critically involved in this process, but the complex regulation of STAT3-dependent genes and the functional significance of inhibiting this pathway during the development of vascular proliferative diseases remain elusive. In this study, we demonstrate that STAT3 was activated in neointimal lesions following wire-induced injury in mice. Phosphorylation of STAT3 induced trans-activation of cyclin D1 and survivin in SMCs in vitro and in neointimal cells in vivo, thus promoting proliferation and migration of SMCs as well as reducing apoptotic cell death. WP1066, a highly potent inhibitor of STAT3 signaling, abrogated phosphorylation of STAT3 and dose-dependently inhibited the functional effects of activated STAT3 in stimulated SMCs. The local application of WP1066 via a thermosensitive pluronic F-127 gel around the dilated arteries significantly inhibited proliferation of neointimal cells and decreased the neointimal lesion size at 3 weeks after injury. Even though WP1066 application attenuated the injury-induced up-regulation of the chemokine RANTES at 6 h after injury, there was no significant effect on the accumulation of circulating cells at 1 week after injury. In conclusion, these data identify STAT3 as a key molecule for the proliferative response of SMC and neointima formation. Moreover, inhibition of STAT3 by the potent and specific compound WP1066 might represent a novel and attractive approach for the local treatment of vascular proliferative diseases.
TL;DR: Evidence is provided that RAGE activation-induced inflammation promotes AV calcification in hypercholesterolemic rabbits, which can be attenuated by pioglitazone treatment, and this beneficial effect is associated with remarkable down-regulation of RAGE expression.
Abstract: Receptor for advanced glycation end products (RAGE) is associated with inflammation and the progression of cardiovascular diseases. The current study tested the hypothesis that RAGE is involved in the pathogenesis of aortic valve (AV) calcification. Pioglitazone attenuated AV calcification in experimental hypercholesterolemic rabbits via down-regulation of RAGE. Male New Zealand rabbits weighing 2.5–3.0 kg were randomly divided into three groups: control group, high cholesterol + vitamin D2 (HC + vitD2) group and HC + vitD2 supplemented with pioglitazone group. Compared with HC + vitD2 group, pioglitazone significantly inhibited the progression of AV calcification assessed by echocardiography. HC + vitD2 diet markedly increased RAGE expression, oxidative stress, inflammatory cells infiltration and osteopontin expression. These changes were also significantly attenuated by administration of pioglitazone. Cultured porcine aortic valve interstitial cells (VICs) were used as in vitro model. We found that advanced glycation end products of bovine serum albumin markedly increased the expression of RAGE, induced high levels of production of pro-inflammatory cytokines and promoted osteoblastic differentiation of VICs. However, these effects were found to be remarkably suppressed by siRNA silencing of RAGE and pioglitazone as well. Our data provide evidence that RAGE activation-induced inflammation promotes AV calcification in hypercholesterolemic rabbits, which can be attenuated by pioglitazone treatment. This beneficial effect is associated with remarkable down-regulation of RAGE expression.
TL;DR: Imiquimod induces macrophage autophagy in atherosclerotic plaques, but stimulates plaque progression through cytokine release and enhanced infiltration of inflammatory cells.
Abstract: Atherosclerotic plaques tend to rupture as a consequence of a weakened fibrous cap, particularly in the shoulder regions where most macrophages reside. Macrophages express Toll-like receptors to recognize pathogens and eliminate intracellular pathogens by inducing autophagy. Because Toll-like receptor 7 (TLR7) is thought to be expressed in macrophages but not in smooth muscle cells (SMCs), we investigated whether induction of macrophage autophagic death by TLR7 ligand imiquimod can affect the composition of atherosclerotic plaques in favor of their stability. Immunohistochemical staining of human carotid plaques as well as Western blotting of cultured macrophages and SMCs confirmed that TLR7 was expressed in macrophages, but not in SMCs. In vitro experiments showed that only TLR7 expressing cells underwent imiquimod-induced cell death, which was characterized by autophagosome formation. Imiquimod-treated macrophages activated nuclear factor-κB (NF-κB) and released pro-inflammatory cytokines and chemokines. This effect was inhibited by the glucocorticoid dexamethasone. Imiquimod-induced cytokine release was significantly decreased in autophagy-deficient macrophages because these cells died by necrosis at an accelerated pace. Local in vivo administration of imiquimod to established atherosclerotic lesions in rabbit carotid arteries induced macrophage autophagy without induction of cell death, and triggered cytokine production, upregulation of vascular adhesion molecule-1, infiltration of T-lymphocytes, accumulation of macrophages and enlargement of plaque area. Treatment with dexamethasone suppressed these pro-inflammatory effects in vivo. SMCs and endothelial cells in imiquimod-treated plaques were not affected. In conclusion, imiquimod induces macrophage autophagy in atherosclerotic plaques, but stimulates plaque progression through cytokine release and enhanced infiltration of inflammatory cells.
TL;DR: It is demonstrated for the first time that functional TRPM7 channels are present in human atrial myocytes, and the channel expression is upregulated in the atria with atrial fibrillation.
Abstract: Transient receptor potential melastatin-7 (TRPM7) channels have been recently reported in human atrial fibroblasts and are believed to mediate fibrogenesis in human atrial fibrillation. The present study investigates whether TRPM7 channels are expressed in human atrial myocytes using whole-cell patch voltage-clamp, RT-PCR and Western blotting analysis. It was found that a gradually activated TRPM7-like current was recorded with a K+- and Mg2+-free pipette solution in human atrial myocytes. The current was enhanced by removing extracellular Ca2+ and Mg2+, and the current increase could be inhibited by Ni2+ or Ba2+. The TRPM7-like current was potentiated by acidic pH and inhibited by La3+ and 2-aminoethoxydiphenyl borate. In addition, Ca2+-activated TRPM4-like current was recorded in human atrial myocytes with the addition of the Ca2+ ionophore A23187 in bath solution. RT-PCR and Western immunoblot analysis revealed that in addition to TRPM4, TRPM7 channel current, mRNA and protein expression were evident in human atrial myocytes. Interestingly, TRPM7 channel protein, but not TRPM4 channel protein, was significantly increased in human atrial specimens from the patients with atrial fibrillation. Our results demonstrate for the first time that functional TRPM7 channels are present in human atrial myocytes, and the channel expression is upregulated in the atria with atrial fibrillation.
TL;DR: HMGB1 mediates the myocardial injury induced by DOX and ONOO−/JNK is a key regulatory pathway of myocardian HMGB1 expression induced byDOX.
Abstract: Doxorubicin (DOX) is a widely used anti-tumor agent. The clinical application of the medication is limited by its side effect which can elicit myocardial apoptosis and cardiac dysfunction. However, the underlying mechanism by which DOX causes cardiomyocyte apoptosis is not clear. The aim of present study is to investigate the role of high-mobility group box 1 (HMGB1) in DOX-induced myocardial injury, and signal pathway involved in regulation of HMGB1 expression in cardiomyocytes with DOX. We found treatment of isolated cardiomyocytes and naive mice with the DOX resulted in an increased HMGB1 expression which was associated with increased myocardial cell apoptosis. Pharmacological (A-box) or genetic blockade (TLR4 deficiency, TLR4−/−) of HMGB1 attenuated the DOX-induced myocardial apoptosis and cardiac dysfunction. In addition, our study showed that DOX resulted in an increment in the generation of peroxynitrite (ONOO−) and an elevation in phosphorylation of c-Jun N terminal kinase (JNK). Pretreatment of myocytes with FeTPPS, a peroxynitrite decomposition catalyst, prevented DOX-induced JNK phosphorylation, HMGB1 expression, myocardial apoptosis and cardiac dysfunction. Genetic (JNK−/−) or pharmacological (SP600125) inhibition of JNK ameliorated the DOX-induced HMGB1 expression and diminished myocardial apoptosis and cardiac dysfunction. Taken together, our results indicate that HMGB1 mediates the myocardial injury induced by DOX and ONOO−/JNK is a key regulatory pathway of myocardial HMGB1 expression induced by DOX.