ROS generated during early reperfusion contribute to intermittent hypobaric hypoxia-afforded cardioprotection against postischemia-induced Ca(2+) overload and contractile dysfunction via the JAK2/STAT3 pathway

Cardioprotection of voluntary exercise against breast cancer-induced cardiac injury via STAT3

Exercise is an effective way to alleviate breast cancer-induced cardiac injury to a certain extent. However, whether voluntary exercise (VE) activates cardiac signal transducer and activator of transcription 3 (STAT3) and the underlying mechanisms remain unclear. This study investigated the role of STAT3-microRNA(miRNA)-targeted protein axis in VE against breast cancer-induced cardiac injury.VE for 4 weeks not only improved cardiac function of transgenic breast cancer female mice [mouse mammary tumor virus-polyomavirus middle T antigen (MMTV-PyMT +)] compared with littermate mice with no cancer (MMTV-PyMT -), but also increased myocardial STAT3 tyrosine 705 phosphorylation. Significantly more obvious cardiac fibrosis, smaller cardiomyocyte size, lower cell viability, and higher serum tumor necrosis factor (TNF)-α were shown in MMTV-PyMT + mice compared with MMTV-PyMT - mice, which were ameliorated by VE. However, VE did not influence the tumor growth. MiRNA sequencing identified that miR-181a-5p was upregulated and miR-130b-3p was downregulated in VE induced-cardioprotection. Myocardial injection of Adeno-associated virus serotype 9 driving STAT3 tyrosine 705 mutations abolished cardioprotective effects above. Myocardial STAT3 was identified as the transcription factor binding the promoters of pri-miR-181a (the precursor of miR-181a-5p) and HOX transcript antisense RNA (HOTAIR, sponged miR-130b-3p) in isolated cardiomyocytes. Furthermore, miR-181a-5p targeting PTEN and miR-130b-3p targeting Zinc finger and BTB domain containing protein 20 (Zbtb20) were proved in AC-16 cells. These findings indicated that VE protects against breast cancer-induced cardiac injury via activating STAT3 to promote miR-181a-5p targeting PTEN and to promote HOTAIR to sponge miR-130b-3p targeting Zbtb20, helping to develop new targets in exercise therapy for breast cancer-induced cardiac injury.

Mitochondrial calcium in cardiac ischemia/reperfusion injury and cardioprotection

Mitochondrial calcium (Ca2+) signals play a central role in cardiac homeostasis and disease. In the healthy heart, mitochondrial Ca2+ levels modulate the rate of oxidative metabolism to match the rate of adenosine triphosphate consumption in the cytosol. During ischemia/reperfusion (I/R) injury, pathologically high levels of Ca2+ in the mitochondrial matrix trigger the opening of the mitochondrial permeability transition pore, which releases solutes and small proteins from the matrix, causing mitochondrial swelling and ultimately leading to cell death. Pharmacological and genetic approaches to tune mitochondrial Ca2+ handling by regulating the activity of the main Ca2+ influx and efflux pathways, i.e., the mitochondrial Ca2+ uniporter and sodium/Ca2+ exchanger, represent promising therapeutic strategies to protect the heart from I/R injury.

Effect of humanine on the Notch signaling pathway in myocardial infarction

Background/aim

By applying humanin (HN) before myocardial infarction (MI), its protection in myocardial injury and the possible roles of its cellular mechanism in the Notch pathway were investigated.

Materials and methods

The study was carried out at Fırat University Experimental Research Center (12/24/2018-12/23/2019). Spraque-Dawley rats were divided into 10 groups: I (control) (n = 6), II (HN 6 h) (n = 6), III (HN 24 h) (n = 6), IV (HN day 7) (n = 6), V (MI 6 h) (n = 7), VI (MI 24 h) (n = 7), VII (MI day 7) (n = 7), VIII (MI+HN 6 h) (n = 7), IX (MI+HN 24 h) (n = 7), and X (MI+HN day 7) (n = 7). To create MI, 200 mg/kg of isoproterenol (ISO) was administered to the rats subcutaneously. Moreover, 252 μg/kg of HN was given intraperitoneally (ip) to the rats on its own and before MI. Molecular parameters Notch1, Notch2, Hes1, Hes2, Jagged1, Jagged2, DLL1, and DLL4 were examined using polymerase chain reaction in the heart tissue, Notch1, Hes1, and DLL4 were examined using western blot, while heart tissue was taken for histochemical examinations.

Results

The mRNA expression levels of the Notch signaling members (Notch1, Notch2, Hes1, Hes2, Jagged1, Jagged2, DLL1, and DLL4) tended to decrease after MI. The Notch signaling members increased more significantly, especially toward day 7 after HN application before MI. In the western blot anylyses, the Notch1, Hes1, and DLL4 protein levels increased significantly toward day 7 in the groups given HN before MI. Moreover, the serum AST, LDH, CK-MB, and troponin I levels tended to decrease with the application of HN before MI and there was a significant decrease in edema, hemorrhage, and mononuclear cells in the heart tissue at 24 h post-MI and fibrosis on day 7 post-MI.

Conclusion

HN administration before MI has a cardioprotective effect on rats via the Notch signaling pathway.

Perspective: mitochondrial STAT3 in cardioprotection

Activation of signal transducer and activator of transcription 3 (STAT3) has been identified as a key cardioprotective signal not only in animal studies but also in humans-in animals, STAT3 is causally involved in cardioprotection. In response to late ischemic conditioning, canonical function of STAT3 activation upregulates the expression of cardioprotective and anti-apoptotic proteins. In its non-canonical function, STAT3 is activated during ischemic conditioning and is part of the cardioprotective cytosolic survival activating factor enhancement pathway. Activated STAT3 is imported and localized to the mitochondria. Mitochondrial STAT3 stimulates the activity of mitochondrial electron transport chain complex I, reduces mitochondrial reactive oxygen species production and mitochondrial permeability transition pore opening. Finally, two novel aspects of STAT activation in cardioprotection are discussed: a genetic variance of the STAT encoding region as a potential primordial confounding variable for cardioprotection, and the cardioprotective potential of sodium-glucose cotransporter 2 inhibitors through STAT3 activation.

Apoptotic cell death in disease-Current understanding of the NCCD 2023

Apoptosis is a form of regulated cell death (RCD) that involves proteases of the caspase family. Pharmacological and genetic strategies that experimentally inhibit or delay apoptosis in mammalian systems have elucidated the key contribution of this process not only to (post-)embryonic development and adult tissue homeostasis, but also to the etiology of multiple human disorders. Consistent with this notion, while defects in the molecular machinery for apoptotic cell death impair organismal development and promote oncogenesis, the unwarranted activation of apoptosis promotes cell loss and tissue damage in the context of various neurological, cardiovascular, renal, hepatic, infectious, neoplastic and inflammatory conditions. Here, the Nomenclature Committee on Cell Death (NCCD) gathered to critically summarize an abundant pre-clinical literature mechanistically linking the core apoptotic apparatus to organismal homeostasis in the context of disease.

The protective effects of Clerodendranthus spicatus (Thunb.) C. Y. Wu extract on oxidative stress induced by 2,2'-azo (2-methylpropamidine) dihydrochloride in HL-1 mouse cardiomyocytes

To investigate the protective effects of Clerodendranthus spicatus (Thunb.) C. Y. Wu extract (CSTE) on oxidative stress injury in HL-1 mouse cardiomyocytes induced by 2,2'-azo (2-methylpropamidine) dihydrochloride (AAPH, 1 mmol/L), HL-1 cells were co-cultured with different concentrations (10–100 μg/mL) of the CSTE for 24 h. A cell damage model was established by continuously culturing the cells in Dulbecco's Modified Eagle Medium plus AAPH for 4 h. Cell survival rates were measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay, and by measuring intracellular malondialdehyde (MDA) content. MDA and total reactive oxygen species (ROS) levels were determined by thiobarbituric acid colorimetry and the 2',7'-dihydrodichlorofluorescent sodium yellow diacetate probe, respectively. Apoptosis was measured by flow cytometry. The intracellular catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), glutathione s-transferase (GST), γ-glutamylcysteine synthetase (γ-GCS), and glutathione (GSH) contents were determined by colorimetric methods. CSTE content was determined by high performance liquid chromatography. The CSTE pretreatment improved survival rates in damaged HL-1 cells, reduced total intracellular ROS and MDA levels, and reduced apoptosis. The CSTE also increased the activities of the antioxidant enzymes (CAT, SOD, GSH-Px, and GST), as well as the γ-GCS and GSH levels in damaged cells. Real-time fluorescence quantitative polymerase chain reaction analysis indicated that the CSTE upregulated CAT, SOD1, and GSH-Px mRNA expression levels. Additionally, the CSTE reduced MDA and ROS levels in HL-1 cells by improving the endogenous antioxidant system; thus, alleviating the oxidative stress damage caused by AAPH. Our compositional analyses revealed that the CSTE contained caffeic acid, isoquercetin, rosmarinic acid, luteolin, and baicalin. The CSTE demonstrates antioxidant and protective effects in myocardial cells.

Angiotensin-converting enzyme 2 inhibits inflammation and apoptosis in high glucose-stimulated microvascular endothelial cell damage by regulating the JAK2/STAT3 signaling pathway

Mounting evidence supports that angiotensin-converting enzyme 2 (ACE2) may exert a vital function in multiple complications induced by diabetes. The aim of this research was to verify the function of ACE2 in diabetic angiopathy (DA). In our study, it was revealed that high glucose (HG) treatment impeded cell proliferation and induced cell apoptosis. Moreover, ACE2 level was reduced in HG-stimulated HMEC-1 cells. Functional assays demonstrated that ACE2 addition promoted cell viability, suppressed apoptosis, oxidative stress, ROS generation, and inflammation in HG-stimulated HMEC-1 cells. Furthermore, the activation of the JAK2/STAT3 pathway induced by HG was impeded by overexpression of ACE2. Besides, JAK2/STAT3 pathway inhibitor AG490 reversed the changes of cell viability, apoptosis, oxidative stress, and inflammation caused by ACE2 deletion in HG-treated HMEC-1 cells. In sum, our findings highlighted that ACE2 promoted the viability and restrained the oxidative stress, inflammation, and apoptosis in HG-induced microvascular endothelial cells (VECs) injury via regulating the JAK2/STAT3 pathway, suggesting ACE2 might be a potential therapeutic target for DA treatment.

Upregulation of p67phox in response to ischemia/reperfusion is cardioprotective by increasing ZIP2 expression via STAT3

While the zinc transporter ZIP2 (Slc39a2) is upregulated via STAT3 as an adaptive response to protect the heart from ischemia/reperfusion (I/R) injury, the precise mechanism underlying its upregulation remains unclear. The purpose of this study was to investigate the role of NADPH oxidase (NOX) isoform NOX2-derived ROS in the regulation of ZIP2 expression, focusing on the role of the NOX2 cytosolic factor p67^phox. Mouse hearts or H9c2 cells were subjected to I/R. Protein expression was detected with Western blotting. Infarct size was measured with TTC staining. The cardiac-specific p67^phox conditional knockout mice (p67^phox cKO) were generated by adopting the CRISPR/Cas9 system. I/R-induced upregulation of STAT3 phosphorylation and ZIP2 expression was reversed by the ROS scavenger N-acetylcysteine (NAC) and the NOX inhibitor diphenyleneiodonium (DPI). p67^phox but not NOX2 expression was increased 30 min after the onset of reperfusion, and downregulation of p67^phox by siRNA or cKO invalidated I/R-induced upregulation of STAT3 phosphorylation and ZIP2 expression. Both NAC and DPI prevented upregulation of STAT3 phosphorylation and ZIP2 expression induced by overexpression of p67^phox, whereas the STAT3 inhibitor stattic abrogated upregulation ZIP2 expression, indicating that the increase of p67^phox at reperfusion is an upstream signaling event responsible for ZIP2 upregulation via STAT3. Experiments also showed that chelation of Zn²⁺ markedly enhanced p67^phox and ZIP2 expression as well as STAT3 phosphorylation, whereas supplementation of Zn²⁺ had the opposite effects, indicating that cardiac Zn²⁺ loss upon reperfusion triggers p67^phox upregulation. Furthermore, ischemic preconditioning (IPC) upregulated ZIP2 via p67^phox, and cKO of p67^phox aggravated cardiac injury after I/R, indicating that p67^phox upregulation is cardioprotective against I/R injury. In conclusion, an increase of p67^phox expression in response to Zn²⁺ is an intrinsic adaptive response to I/R and leads to cardioprotection against I/R by upregulating ZIP2 via STAT3.

Impact of High Altitude on Cardiovascular Health: Current Perspectives

Globally, about 400 million people reside at terrestrial altitudes above 1500 m, and more than 100 million lowlanders visit mountainous areas above 2500 m annually. The interactions between the low barometric pressure and partial pressure of O2, climate, individual genetic, lifestyle and socio-economic factors, as well as adaptation and acclimatization processes at high elevations are extremely complex. It is challenging to decipher the effects of these myriad factors on the cardiovascular health in high altitude residents, and even more so in those ascending to high altitudes with or without preexisting diseases. This review aims to interpret epidemiological observations in high-altitude populations; present and discuss cardiovascular responses to acute and subacute high-altitude exposure in general and more specifically in people with preexisting cardiovascular diseases; the relations between cardiovascular pathologies and neurodegenerative diseases at altitude; the effects of high-altitude exercise; and the putative cardioprotective mechanisms of hypobaric hypoxia.

Neurotrophin-3 contributes to benefits of human embryonic stem cell-derived cardiovascular progenitor cells against reperfused myocardial infarction

Acute myocardial infarction (MI) resulting from coronary ischemia is a major cause of disability and death worldwide. Transplantation of human embryonic stem cell (hESC)‐derived cardiovascular progenitor cells (hCVPCs) promotes the healing of infarcted hearts by secreted factors. However, the hCVPC‐secreted proteins contributing to cardiac repair remain largely unidentified. In this study, we investigated protective effects of neurotrophin (NT)‐3 secreted from hCVPCs in hearts against myocardial ischemia/reperfusion (I/R) injury and explored the underlying mechanisms to determine the potential of using hCVPC products as a new therapeutic strategy. The implantation of hCVPCs into infarcted myocardium at the beginning of reperfusion following 1 hour of ischemia improved cardiac function and scar formation of mouse hearts. These beneficial effects were concomitant with reduced cardiomyocyte death and increased angiogenesis. Moreover, hCVPCs secreted a rich abundance of NT‐3. The cardioreparative effect of hCVPCs in the I/R hearts was mimicked by human recombinant NT‐3 (hNT‐3) but canceled by NT‐3 neutralizing antibody (NT‐3‐Ab). Furthermore, endogenous NT‐3 was detected in mouse adult cardiomyocytes and its level was enhanced in I/R hearts. Adenovirus‐mediated NT‐3 knockdown exacerbated myocardial I/R injury. Mechanistically, hNT‐3 and endogenous NT‐3 inhibited I/R‐induced cardiomyocyte apoptosis through activating the extracellular signal‐regulated kinase (ERK) and reducing the Bim level, resulting in the cardioreparative effects of infarcted hearts together with their effects in the improvement of angiogenesis. These results demonstrate for the first time that NT‐3 is a cardioprotective factor secreted by hCVPCs and exists in adult cardiomyocytes that reduces I/R‐induced cardiomyocyte apoptosis via the ERK‐Bim signaling pathway and promotes angiogenesis. As a cell product, NT‐3 may represent as a noncell approach for the treatment of myocardial I/R injury.

Moderate Hydrogen Peroxide Postconditioning Ameliorates Ischemia/Reperfusion Injury in Cardiomyocytes via STAT3-Induced Calcium, ROS, and ATP Homeostasis

INTRODUCTION

Moderate hydrogen peroxide postconditioning (H2O2PoC) activates signal transducer and activator of transcription 3 (STAT3) to alleviate mitochondrial calcium overload during cardiac ischemia/reperfusion (I/R). However, the initial time window of STAT3-induced calcium hemostasis, the production of reactive oxygen species (ROS) and adenosine triphosphate (ATP) in H2O2PoC, and its regulated mechanism remain unknown. This study aimed to investigate H2O2PoC-induced homeostasis of calcium, ROS and ATP, and the role of STAT3 in the regulation.

METHODS

Isolated rat cardiomyocytes were exposed to H2O2PoC and Janus kinase 2 (JAK2)/STAT3 inhibitor AG490 during I/R. Ca2+ transients, cell contraction, intracellular calcium concentration, ROS production, ATP contents, phosphorylation of STAT3, gene and protein expression of manganese superoxide dismutase (MnSOD), metallothionein 1 (MT1) and metallothionein 2 (MT2), as well as activities of mitochondrial complex I and complex II were detected.

RESULTS

Moderate H2O2PoC improved post-ischemic Ca2+ transients and cell contraction recovery as well as alleviated cytosolic and mitochondrial calcium overload, which were abrogated by AG490 in rat cardiomyocytes. Moderate H2O2PoC increased ROS production and rate of ROS production at early reperfusion in rat I/R cardiomyocytes, and this phenomenon was also abrogated by AG490. Notably, the expression of phosphorylated nuclear STAT3; gene and protein expression of MnSOD, MT1, and MT2; and activities of mitochondrial complex I and complex II were upregulated by moderate H2O2PoC but downregulated by AG490.

CONCLUSION

These findings indicated that the cardioprotection of moderate H2O2PoC against cardiac I/R could be associated with activated STAT3 at early reperfusion to maintain calcium, ROS, and ATP homeostasis in rat cardiomyocytes.

Folic Acid Deficiency Enhances the Tyr705 and Ser727 Phosphorylation of Mitochondrial STAT3 in In Vivo and In Vitro Models of Ischemic Stroke

Ischemic stroke remains one of the most common causes of death and disability worldwide. The stroke patients with an inadequate intake of folic acid tend to have increased brain injury and poorer prognosis. However, the precise mechanisms underlying the harmful effects of folic acid deficiency (FD) in ischemic stroke is still elusive. Here, we aimed to test the hypothesis that mitochondrial localized STAT3 (mitoSTAT3) expression may be involved in the process of neuronal damage induced by FD in in vivo and in vitro models of ischemic stroke. Our results exhibited that FD increased infarct size and aggravated the damage of mitochondrial ultrastructure in ischemic brains. Meanwhile, FD upregulated the phosphorylation levels of mitoSTAT3 at Tyr705 (Y705) and Ser727 (S727) sites in the rat middle cerebral artery occlusion/reperfusion (MCAO/R) model and oxygen-glucose deprivation followed by reperfusion (OGD/R) N2a cells. Furthermore, the inhibition of JAK2 by AG490 led to a significant decrease in FD-induced phosphorylation of Y705, while S727 phosphorylation was unaffected. Conversely, U0126 and LY294002, which respectively inhibited phosphorylation of ERK1/2 and Akt, partially prevented S727 phosphorylation, but had limited effects on the level of pY705, suggesting that phosphorylation of Y705 and S727 is regulated via independent mechanisms in FD-treated brains.

Inactivated pseudomonas aeruginosa protects against myocardial ischemia reperfusion injury via Nrf2 and HO-1

The current study investigated the protective effects of inactivated pseudomonas aeruginosa (IPA) on myocardial ischemia reperfusion injury (MIR/I) and the mechanisms governing this interaction. Left anterior descending coronary artery ligation was performed on rats for 30 min and reperfusion was performed for a subsequent 2 h. Rat hearts were obtained and the myocardial infarction area was determined using nitroblue tetrazolium. Myocardial cell apoptosis was determined using flow cytometry. Malondialdehyde (MDA) content, lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity and catalase (CAT) activities were assayed using the corresponding kits. Additionally, nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) were assayed using western blot and immunofluorescence analysis. When compared with the model group, the results of IPA treatment revealed improved heart function, reduced myocardial infarction area and reduced endothelial cell apoptosis, which led to decreased LDH and MDA levels, and increased SOD and CAT levels in serum, and decreased LDH and MDA levels and increased SOD and CAT in myocardial tissues. Moreover, increased Nrf2 and HO-1 expression levels in the myocardial tissues were also observed at all concentrations of IPA. It was concluded that IPA pretreatment ameliorated MIR/I and reduced endothelial apoptosis and oxidative stress via the Nrf2/HO-1 pathway.

Role of TG2-Mediated SERCA2 Serotonylation on Hypoxic Pulmonary Vein Remodeling

Sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) pumps take up Ca2+ from the cytoplasm to maintain the balance of intracellular Ca2+. A decline in expression or activity of SERCA results in persistent store-operated calcium entry (SOCE). In cardiomyocytes as well as vascular smooth muscle cells (SMCs), SERCA2 acts as an important regulator of calcium cycling. The purpose of this study is to identify and better understand the role of transglutaminases2 (TG2) as a key factor involved in SERCA2 serotonination (s-SERCA2) and to elucidate the underlying mechanism of action. Human pulmonary venous smooth muscle cell in normal pulmonary lobe were isolated and cultured in vitro. Establishment of hypoxic pulmonary hypertension model in wild type and TG2 knockout mice. SERCA2 serotonylation was analyzed by co-(immunoprecipitation) IP when the TG2 gene silenced or overexpressed under normoxia and hypoxia in vivo and in vitro. Intracellular calcium ion was measured by using Fluo-4AM probe under normoxia and hypoxia. Real-time (RT)-PCR and Western blot analyzed expression of TG2, TRPC1, and TRPC6 under normoxia and hypoxia. Bioactivity of cells were analyzed by using Cell Counting Kit (CCK)-8, flow cytometry, wound healing, RT-PCR, and Western blot under PST-2744 and cyclopiazonic acid. We confirmed that 1) hypoxia enhanced the expression and activity of TG2, and 2) hypoxia increased the basal intracellular Ca2+ concentration ([Ca2+]i) and SOCE through activating TRPC6 on human pulmonary vein smooth muscle cells (hPVSMC). Then, we investigated the effects of overexpression and downregulation of the TG2 gene on the activity of SERCA2, s-SERCA2, basal [Ca2+]i, and SOCE under normoxia and hypoxia in vitro, and investigated the activity of SERCA2 and s-SERCA2 in vivo, respectively. We confirmed that SERCA2 serotonylation inhibited the activity of SERCA2 and increased the Ca2+ influx, and that hypoxia induced TG2-mediated SERCA2 serotonylation both in vivo and in vitro. Furthermore, we investigated the effect of TG2 activity on the biological behavior of hPVSMC by using an inhibitor and agonist of SERCA2, respectively. Finally, we confirmed that chronic hypoxia cannot increase vessel wall thickness, the right ventricular systolic pressure (RVSP), and right ventricular hypertrophy index (RVHI) of vascular smooth muscle-specific Tgm2−/− mice. These results indicated that hypoxia promoted TG2-mediated SERCA2 serotonylation, thereby leading to inhibition of SERCA2 activity, which further increased the calcium influx through the TRPC6 channel. Furthermore, tissue-specific conditional TG2 knockout mice prevents the development of pulmonary hypertension caused by hypoxia. In summary, we uncovered a new target (TG2) for treatment of chronic hypoxic pulmonary hypertension (CHPH).

Chronic intermittent hypobaric hypoxia attenuates skeletal muscle ischemia-reperfusion injury in mice

AIM

The aim of this study was to investigate the protective effect of chronic intermittent hypobaric hypoxia (CIHH) against skeletal muscle ischemia-reperfusion (IR) injury and to determine the underlying mechanism.

MAIN METHODS

C57BL/6 mice were randomly divided into 3 groups: skeletal muscle IR injury group (IR), CIHH pretreatment following IR group (IR + CIHH), and sham operation group (Sham). The skeletal muscle IR injury model was induced by the unilateral application of a tourniquet on a hind limb for 3 h and then releasing it for 24 h. CIHH pretreatment simulating a 5000-m altitude was applied 6 h per day for 28 days. The functional and morphological performance of IR-injured gastrocnemius muscle was evaluated using contraction force, H&E staining, and transmission electron microscopy. IR injury-induced CD68⁺ macrophage infiltration was assessed by immunofluorescence. TNFα levels in serum and muscle were measured by ELISA and western blotting, respectively. Apoptosis was examined by TUNEL staining and Cleaved Caspase-3 protein expression.

KEY FINDINGS

Acute IR injury resulted in reduced contraction tension, morphological destruction, macrophage infiltration, increased TNFα levels, and apoptosis in gastrocnemius muscle. CIHH pretreatment significantly ameliorated contraction function and morphological performance in IR-injured skeletal muscle. In addition, CIHH pretreatment resulted in marked decreases in CD68⁺ macrophage infiltration, TNFα levels, and apoptosis.

SIGNIFICANCE

These data demonstrated that CIHH has a protective effect against acute IR injury in skeletal muscle via inhibition of inflammation and apoptosis.

N-n-Butyl Haloperidol Iodide Ameliorates Oxidative Stress in Mitochondria Induced by Hypoxia/Reoxygenation through the Mitochondrial c-Jun N-Terminal Kinase/Sab/Src/Reactive Oxygen Species Pathway in H9c2 Cells

Both c-Jun N-terminal kinase (JNK) and reactive oxygen species (ROS) play important roles in myocardial ischemia/reperfusion (I/R) injury. Our previous studies suggest that N-n-butyl haloperidol iodide (F2) exerts cardioprotection by reducing ROS production and JNK activation caused by I/R. In this study, we hypothesized that there is a JNK/Sab/Src/ROS pathway in the mitochondria in H9c2 cells following hypoxia/reoxygenation (H/R) that induces oxidative stress in the mitochondria and that F2 exerts mitochondrial protective effects during H/R injury by modulating this pathway. The results showed that H/R induced higher-level ROS in the cytoplasm on the one hand and JNK activation and translocation to the mitochondria by colocalization with Sab on the other. Moreover, H/R resulted in mitochondrial Src dephosphorylation, and subsequently, oxidative stress evidenced by the increase in ROS generation and oxidized cardiolipin in the mitochondrial membranes and by the decrease in mitochondrial superoxide dismutase activity and membrane potential. Furthermore, treatment with a JNK inhibitor or Sab small interfering RNA inhibited the mitochondrial translocation of p-JNK, decreased colocalization of p-JNK and Sab on the mitochondria, and reduced Src dephosphorylation and mitochondrial oxidative stress during H/R. In addition, Src dephosphorylation by inhibitor PP2 increased mitochondrial ROS production. F2, like inhibitors of the JNK/Sab/Src/ROS pathway, downregulated the H/R-induced mitochondrial translocation of p-JNK and the colocalization of p-JNK and Sab on the mitochondria, increased Src phosphorylation, and alleviated the above-mentioned mitochondrial oxidative stress. In conclusion, F2 could ameliorate H/R-associated oxidative stress in mitochondria in H9c2 cells through the mitochondrial JNK/Sab/Src/ROS pathway.

Exercise and Cardioprotection: A Natural Defense Against Lethal Myocardial Ischemia-Reperfusion Injury and Potential Guide to Cardiovascular Prophylaxis

Similar to ischemic preconditioning, high-intensity exercise has been shown to decrease infarct size following myocardial infarction. In this article, we review the literature on beneficial effects of exercise, exercise requirements for cardioprotection, common methods utilized in laboratories to study this phenomenon, and discuss possible mechanisms for exercise-mediated cardioprotection.

Characterizations of mitochondrial uncoupling induced by chemical mitochondrial uncouplers in cardiomyocytes

Induction of mild mitochondrial uncoupling is protective in a variety of disorders; however, it is unclear how to recognize the mild mitochondrial uncoupling induced by chemical mitochondrial uncouplers. The aim of the present study is to identify the pharmacological properties of mitochondrial uncoupling induced by mitochondrial uncouplers in cardiomyocytes. Neonatal rat cardiomyocytes were cultured. Protein levels were measured by using western blot technique. The whole cell respiratory function was determined by using high-resolution respirometry. The typical types of chemical mitochondrial uncouplers, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), niclosamide, and BAM15, induced biphasic change of STAT3 activity in cardiomyocytes, activating STAT3 at low dose and inhibiting STAT3 at high dose, though the dose range of these drugs was distinct. Low-dose uncouplers induced STAT3 activation through the mild increase of mitochondrial ROS (mitoROS) generation and the subsequent JAK/STAT3 activation in cardiomyocytes. However, high-dose uncouplers induced inhibition of STAT3, decrease of ATP production, and cardiomyocyte death. High-dose uncouplers induced STAT3 inhibition through the excessive mitoROS generation and the decreased ATP -induced AMPK activation. Low-dose mitochondrial uncouplers attenuated doxorubicin (DOX)-induced STAT3 inhibition and cardiomyocyte death, and activated STAT3 contributed to the cardioprotection of low-dose mitochondrial uncouplers. Uncoupler-induced mild mitochondrial uncoupling in cardiomyocytes is characterized by STAT3 activation and ATP increase whereas excessive mitochondrial uncoupling is characterized by STAT3 inhibition, ATP decrease and cell injury. Development of mitochondrial uncoupler with optimal dose window of inducing mild uncoupling is a promising strategy for heart protection.

Mitochondria "THE" target of myocardial conditioning

Several interventions, such as ischemic preconditioning, remote pre/perconditioning, or postconditioning, are known to decrease lethal myocardial ischemia-reperfusion injury. While several signal transduction pathways become activated by such maneuvers, they all have a common end point, namely, the mitochondria. These organelles represent an essential target of the cardioprotective strategies, and the preservation of mitochondrial function is central for the reduction of ischemia-reperfusion injury. In the present review, we address the role of mitochondria in the different conditioning strategies; in particular, we focus on alterations of mitochondrial function in terms of energy production, formation of reactive oxygen species, opening of the mitochondrial permeability transition pore, and mitochondrial dynamics induced by ischemia-reperfusion.

Hydrogen-rich solution attenuates myocardial injury caused by cardiopulmonary bypass in rats via the Janus-activated kinase 2/signal transducer and activator of transcription 3 signaling pathway

The incidence of complications and mortality following open-heart surgery with cardiopulmonary bypass (CPB) is associated with the severity of the myocardial injury that occurs during surgery. Hydrogen-rich solution (HRS) may prevent antioxidant stress and inhibit apoptosis and inflammation. The present study was designed to investigate the effects of HRS on CPB-induced myocardial injury, and to investigate its potential regulation of the Janus-activated kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway. The HRS treatment resulted in the significant upregulation of malonyl dialdehyde (MDA) and myeloperoxidase (MPO), whilesuperoxide dismutase (SOD) levels were significantly downregulated, compared with the Sham group (P<0.05). Additionally, HRS treatment improved myocardial injury, and decreased the expression levels of cardiac troponins, heart-type fatty acid binding protein, interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, MDA and MPO, and increased SOD release in CPB rats (P<0.05). Additionally, in the CPB group without the HRS treatment, the expression levels of B-cell lymphoma (Bcl)-2, JAK2, phospho-JAK2 (p-JAK2), STAT3 and phospho-STAT3 (p-STAT3) were significantly decreased, and Bax was significantly increased, compared with the Sham group (P<0.05). By contrast, compared with the CPB group, the expression levels of B-cell lymphoma 2 (Bcl-2), JAK2, phosphorylated (p)-JAK2, STAT3 and p-STAT3 in the HRS group were significantly increased, and Bcl-2-associated X protein expression was significantly decreased (P<0.05). In JAK2 knockdown experiments using siRNA, HRS treatment following hypoxia/reoxygenation also significantly increased the viability of myocardial cells, decreased the rate of myocardial cell apoptosis, elevated the levels of SOD and suppressed the release of MDA and lactate dehydrogenase in the control siRNA and CPB groups (P<0.05). Furthermore, JAK2 siRNA attenuated these protective effects of HRS (P<0.05 vs. control siRNA, HRS and CPB groups). Additionally, the results demonstrated that the HRS treatment significantly increased the expression levels of p-JAK2, p-STAT3 and Bcl-2 in myocardial cells following hypoxia and decreased Bax expression in the control siRNA and CPB groups (P<0.05). In addition, JAK2 siRNA was determined to attenuate these effects of HRS (P<0.05 vs. control siRNA, HRS and CPB groups). Taken together, these results indicated that HRS may alleviate CPB-induced myocardial injury, inhibit myocardial cell apoptosis and protect myocardial cells through regulation of the JAK2/STAT3 signaling pathway.

Protective effect and mechanism of Lactobacillus on cerebral ischemia reperfusion injury in rats

The present study was designed to investigate the protective effects and mechanism of inactivated lactobacillus (ILA) on cerebral ischemia reperfusion injury (CIRI) in rats. In this experiment, 30 male Sprague Dawley rats were randomly divided into control group, IRI groups, and ILA group. A middle cerebral artery occlusion and reperfusion model was prepared. The rats were killed after 24 hours of recovery of blood flow of cerebral ischemia resulting from 60-min occlusion. The cerebral infarction volume and neurological scores were assayed by staining and behavioral observation. Malondialdehyde (MDA) and superoxide dismutase (SOD) levels were assayed by biochemical kits. Cell apoptosis was assayed by Tunnel and the Toll-like receptor (TLR)-4, IkB, and A20 were assayed by western blot. The neurobehavioral scores in IRI rats were significantly lower compared to the control group while ILA improved the neurobehavioral scores of the ILA groups. The cerebral infarction volume and neural cell apoptosis of rats in the ILA groups decreased significantly compared with those in the IRI group. In addition, MDA level in the ILA groups decreased whereas SOD activity increased compared to the IRI group. Moreover, ILA also inhibited the expression of TLR-4 and promoted the expression of IkB and A20. ILA inhibited the apoptosis of neural cells, decreased cerebral infarction volume, and reduced oxidative stress through inhibition of TLR-4/NF-kappa B signaling, improving neurobehavioral scores. Thus from the present study it was concluded that ILA has protective effect on CIRI.

Folic acid supplementation repressed hypoxia-induced inflammatory response via ROS and JAK2/STAT3 pathway in human promyelomonocytic cells

Hypoxia is associated with inflammation and various chronic diseases. Folic acid is known to ameliorate inflammatory reactions, but the metabolism of folic acid protecting against hypoxia-induced injury is still unclear. In our study, we examined the inflammatory signal transduction pathway in human promyelomonocytic cells (THP-1 cells) with or without treatment with folic acid under hypoxic culture conditions. Our results indicated that supplementation with folic acid significantly reduced the levels of interleukin-1β and tumor necrosis factor-α in hypoxic conditions. Treating THP-1 cells with folic acid suppressed oxidative stress and hypoxia-inducible factor-1α in a dose-dependent manner. Folic acid targeted the activation of Janus kinase 2, downregulated the phosphorylation of signal transducer and activator of transcription 3, and decreased the expression of nuclear factor-κB p65 protein in cells. However, the absence of folic acid did not make cells more vulnerable under hypoxic conditions. In conclusion, folic acid efficiently inhibited the inflammatory response of THP-1 cells under hypoxic conditions by inhibiting reactive oxygen species production and the Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway. Our study supports a basis for treatment with folic acid for chronic inflammation, which correlated with hypoxia.

Ang-(1-7) protects HUVECs from high glucose-induced injury and inflammation via inhibition of the JAK2/STAT3 pathway

Angiotensin (Ang)‑1‑7, which is catalyzed by angiotensin‑converting enzyme 2 (ACE2) from angiotensin‑II (Ang‑II), exerts multiple biological and pharmacological effects, including cardioprotective effects and endothelial protection. The Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway has been demonstrated to be involved in diabetes‑associated cardiovascular complications. The present study hypothesized that Ang‑(1‑7) protects against high glucose (HG)‑induced endothelial cell injury and inflammation by inhibiting the JAK2/STAT3 pathway in human umbilical vein endothelial cells (HUVECs). HUVECs were treated with 40 mmol/l glucose (HG) for 24 h to establish a model of HG‑induced endothelial cell injury and inflammation. Protein expression levels of p‑JAK2, t‑JAK2, p‑STAT3, t‑STAT3, NOX‑4, eNOS and cleaved caspase‑3 were tested by western blotting. CCK‑8 assay was performed to assess cell viability of HUVECs. Apoptotic cell death was analyzed by Hoechst 33258 staining. Mitochondrial membrane potential (MMP) was obtained using JC‑1. Superoxide dismutase (SOD) activity was tested by SOD assay kit. Interleukin (IL)‑1β, IL‑10, IL‑12 and TNF‑α levels in culture media were tested by ELISA. The findings demonstrated that exposure of HUVECs to HG for 24 h induced injury and inflammation. This injury and inflammation were significantly ameliorated by pre‑treatment of cells with either Ang‑(1‑7) or AG490, an inhibitor of the JAK2/STAT3 pathway, prior to exposure of the cells to HG. Exposure of the cells to HG also increased the phosphorylation of JAK2/STAT3 (p‑JAK2 and p‑STAT3). Increased activation of the JAK2/STAT3 pathway was attenuated by pre‑treatment with Ang‑(1‑7). To the best of our knowledge, the findings from the present study provided the first evidence that Ang‑(1‑7) protects against HG‑induced injury and inflammation by inhibiting activation of the JAK2/STAT3 pathway in HUVECs.

Hepatoma-Derived Growth Factor Secreted from Mesenchymal Stem Cells Reduces Myocardial Ischemia-Reperfusion Injury

Objectives

The present study aimed to explore the major factors that account for the beneficial effects of mesenchymal stem cells (MSCs).

Methods

Using isobaric tags for relative and absolute quantitation method, hepatoma-derived growth factor (HDGF) was identified as an important factor secreted by MSCs, but not by cardiac fibroblasts (CFs). The protective effects of conditioned medium (CdM) from MSCs or CFs were tested by using either H9C2 cells that were exposed by hypoxia-reoxygenation (H/R) insult or an in vivo mouse model of myocardial ischemia-reperfusion.

Results

Compared to CF-CdM, MSC-CdM conferred protection against reperfusion injury. CdM obtained from MSCs that were treated with HDGF-targeted shRNA failed to offer any protection in vitro. In addition, administration of recombinant HDGF alone recapitulated the beneficial effects of MSC-CdM, which was associated with increased protein kinase C epsilon (PKCε) phosphorylation, enhanced mitochondria aldehyde dehydrogenase family 2 activity, and decreased 4-hydroxy-2-nonenal accumulation. A significant decrease in infarct size and ameliorated cardiac dysfunction was achieved by administration of HDGF in wild-type mice, which was absent in PKCε dominant negative mice, indicating the essential roles of PKCε in HDGF-mediated protection.

Conclusions

HDGF secreted from MSCs plays a key role in the protection against reperfusion injury through PKCε activation.

Phosphorylation of signal transducer and activator of transcription 3 induced by hyperglycemia is different with that induced by lipopolysaccharide or erythropoietin via receptor‑coupled signaling in cardiac cells

The signal transducer and activator of transcription 3 (STAT3) is known to be involved in hypertrophy and fibrosis in cardiac dysfunction. The activation of STAT3 via the phosphorylation of STAT3 is required for the production of functional activity. It has been established that lipopolysaccharide (LPS)‑induced phosphorylation of STAT3 in cardiomyocytes primarily occurs through a direct receptor‑mediated action. This effect is demonstrated to be produced rapidly. STAT3 in cardiac fibrosis of diabetes is induced by high glucose through promotion of the STAT3‑associated signaling pathway. However, the time schedule for STAT3 activation between LPS and high glucose appears to be different. Therefore, the difference in STAT3 activation between LPS and hyperglycemia in cardiomyocytes requires elucidation. The present study investigated the phosphorylation of STAT3 induced by LPS and hyperglycemia in the rat cardiac cell line H9c2. Additionally, phosphorylation of STAT3 induced by erythropoietin (EPO) via receptor activation was compared. Then, the downstream signals for fibrosis, including the connective tissue growth factor (CTGF) and matrix metalloproteinase (MMP)‑9, were determined using western blotting, while the mRNA levels were quantified. LPS induced a rapid elevation of STAT3 phosphorylation in H9c2 cells within 30 min, similar to that produced by EPO. However, LPS or EPO failed to modify the mRNA level of STAT3, and/or the downstream signals for fibrosis. High glucose increased STAT3 phosphorylation to be stable after a long period of incubation. Glucose incubation for 24 h may augment the STAT3 expression in a dose‑dependent manner. Consequently, fibrosis‑associated signals, including CTGF and MMP‑9 protein, were raised in parallel. In the presence of tiron, an antioxidant, these changes by hyperglycemia were markedly reduced, demonstrating the mediation of oxidative stress. Therefore, LPS‑ or EPO‑induced STAT3 phosphorylation is different compared with that caused by high glucose in H9c2 cells. Sustained activation of STAT3 by hyperglycemia may promote the expression of fibrosis‑associated signals, including CTGF and MMP‑9, in H9c2 cells. Therefore, regarding the cardiac dysfunctions associated with diabetes and/or hyperglycemia, the identification of nuclear STAT3 may be more reliable compared with the assay of phosphorylated STAT3 in cardiac cells.

Ghrelin protects the heart against ischemia/reperfusion injury via inhibition of TLR4/NLRP3 inflammasome pathway

AIMS

The aim of this study was to investigate the cardioprotective effects of ghrelin against myocardial ischemia/reperfusion (I/R) injury and the underlying mechanism.

MAIN METHODS

Sprague-Dawley rats were randomized into Sham, I/R and I/R+ghrelin groups. After 30 minutes ischemia, ghrelin (8nmol/kg) was injected intraperitoneally at the time of reperfusion in the I/R+ghrelin group. Then hemodynamic parameters were observed at 24h after reperfusion.

KEY FINDINGS

Ghrelin exhibited dramatic improvement in cardiac functions, as manifested by increased LVSP and ±dP/dt_max and decreased LVDP. At 24h after reperfusion, ghrelin significantly attenuated the myocardial infarction area and apoptosis, accompanied with a decrease in the levels of the myocyte injury marker enzymes. Oxidative stress injury and inflammatory response were also relieved by ghrelin. Western blot showed that the expression of TLR4, NLRP3, and caspase-1 were obviously increased in I/R group, while ghrelin significantly inhibited the I/R-induced TLR4, NLRP3, and caspase-1 expression. Ghrelin could inhibit the increased protein levels of NLRP3, caspase-1, and IL-1β induced by lipopolysacharide in primary cultured cardiomyocytes of neonatal rats.

SIGNIFICANCE

Ghrelin protected the heart against I/R injury by inhibiting oxidative stress and inflammation via TLR4/NLRP3 signaling pathway. Our results might provide new strategy and target for treatment of myocardial ischemia/reperfusion injury.

Berbamine postconditioning protects the heart from ischemia/reperfusion injury through modulation of autophagy

Pretreatment of berbamine protects the heart from ischemia/reperfusion (I/R) injury. However it is unknown whether it has cardioprotection when given at the onset of reperfusion (postconditioning (PoC)), a protocol with more clinical impact. Autophagy is upregulated in I/R myocardium and exacerbates cardiomyocyte death during reperfusion. However, it is unknown whether the autophagy during reperfusion is regulated by berbamine. Here we investigated whether berbamine PoC (BMPoC) protects the heart through regulation of autophagy by analyzing the effects of BMPoC on infarct size and/or cell death, functional recovery and autophagy in perfused rat hearts and isolated cardiomyocytes subjected to I/R. Berbamine from 10 to 100 nM given during the first 5 min of reperfusion concentration-dependently improved post-ischemic myocardial function and attenuated cell death. Similar protections were observed in cardiomyocytes subjected to simulated I/R. Meanwhile, BMPoC prevented I/R-induced impairment of autophagosome processing in cardiomyocytes, characterized by increased LC3-II level and GFP-LC3 puncta, and decreased p62 degradation. Besides, lysosomal inhibitor chloroquine did not induce additional increase of LC3-II and P62 abundance after I/R but it reversed the effects of BMPoC in those parameters in cardiomyocytes, suggesting that I/R-impaired autophagic flux is restored by BMPoC. Moreover, I/R injury was accompanied by enhanced expression of Beclin 1, which was significantly inhibited by BMPoC. In vitro and in vivo adenovirus-mediated knockdown of Beclin 1 in myocardium and cardiomyocytes restored I/R-impaired autophagosome processing, associated with an improvement of post-ischemic recovery of myocardial contractile function and a reduction of cell death, but it did not have additive effects to BMPoC. Conversely, overexpression of Beclin 1 abolished the cardioprotection of BMPoC as did by overexpression of an essential autophagy gene Atg5. Furthermore, BMPoC-mediated cardioprotection was abolished by a specific Akt1/2 inhibitor A6730. Our results demonstrate that BMPoC confers cardioprotection by modulating autophagy during reperfusion through the activation of PI3K/Akt signaling pathway.

Spinosad induces programmed cell death involves mitochondrial dysfunction and cytochrome C release in Spodoptera frugiperda Sf9 cells

Spinosad, a reduced-risk insecticide, acts on the nicotinic acetylcholine receptors and the gamma-aminobutyric acid receptor in the nervous system of target insects. However, its mechanism of action in non-neural insect cells is unclear. This study aimed to evaluate mitochondrial functional changes associated with spinosad in Spodoptera frugiperda (Sf9) insect cells. Our results indicate that in Sf9 cells, spinosad induces programmed cell death and mitochondrial dysfunction through enhanced reactive oxygen species production, mitochondrial permeability transition pore (mPTP) opening, and mitochondrial membrane potential collapse, eventually leading to cytochrome C release and apoptosis. The cytochrome C release induced by spinosad treatment was partly inhibited by the mPTP inhibitors cyclosporin A and bongkrekic acid. Subsequently, we found that spinosad downregulated Bcl-2 expression and upregulated p53 and Bax expressions, activated caspase-9 and caspase-3, and triggered PARP cleavage in Sf9 cells. These findings suggested that spinosad-induced programmed cell death was modulated by mitochondrial dysfunction and cytochrome C release.

Sodium orthovanadate suppresses palmitate-induced cardiomyocyte apoptosis by regulation of the JAK2/STAT3 signaling pathway

Elevated circulatory free fatty acids (FFAs) especially saturated FFAs, such as palmitate (PA), are detrimental to the heart. However, mechanisms responsible for this phenomenon remain unknown. Here, the role of JAK2/STAT3 in PA-induced cytotoxicity was investigated in cardiomyocytes. We demonstrate that PA suppressed the JAK2/STAT3 pathway by dephosphorylation of JAK2 (Y1007/1008) and STAT3 (Y705), and thus blocked the translocation of STAT3 into the nucleus. Conversely, phosphorylation of S727, another phosphorylated site of STAT3, was increased in response to PA treatment. Pretreatment of JNK inhibitor, but not p38 MAPK inhibitor, inhibited STAT3 (S727) activation induced by PA and rescued the phosphorylation of STAT3 (Y705). The data suggested that JNK may be another upstream factor regulating STAT3, and verified the important function of P-STAT3 (Y705) in PA-induced cardiomyocyte apoptosis. Sodium orthovanadate (SOV), a protein tyrosine phosphatase inhibitor, obviously inhibited PA-induced apoptosis by restoring JAK2/STAT3 pathways. This effect was diminished by STAT3 inhibitor Stattic. Collectively, our data suggested a novel mechanism that the inhibition of JAK2/STAT3 activation was responsible for palmitic lipotoxicity and SOV may act as a potential therapeutic agent by targeting JAK2/STAT3 in lipotoxic cardiomyopathy treatment.

Oxygen cycling to improve survival of stem cells for myocardial repair: A review

Heart disease represents the leading cause of death among Americans. There is currently no clinical treatment to regenerate viable myocardium following myocardial infarction, and patients may suffer progressive deterioration and decreased myocardial function from the effects of remodeling of the necrotic myocardium. New therapeutic strategies hold promise for patients who suffer from ischemic heart disease by directly addressing the restoration of functional myocardium following death of cardiomyocytes. Therapeutic stem cell transplantation has shown modest benefit in clinical human trials with decreased fibrosis and increased functional myocardium. Moreover, autologous transplantation holds the potential to implement these therapies while avoiding the immunomodulation concerns of heart transplantation. Despite these benefits, stem cell therapy has been characterized by poor survival and low engraftment of injected stem cells. The hypoxic tissue environment of the ischemic/infracting myocardium impedes stem cell survival and engraftment in myocardial tissue. Hypoxic preconditioning has been suggested as a viable strategy to increase hypoxic tolerance of stem cells. A number of in vivo and in vitro studies have demonstrated improved stem cell viability by altering stem cell secretion of protein signals and up-regulation of numerous paracrine signaling pathways that affect inflammatory, survival, and angiogenic signaling pathways. This review will discuss both the mechanisms of hypoxic preconditioning as well as the effects of hypoxic preconditioning in different cell and animal models, examining the pitfalls in current research and the next steps into potentially implementing this methodology in clinical research trials.

Understanding STAT3 signaling in cardiac ischemia

Cardiovascular disease is the leading cause of death worldwide. It remains one of the greatest challenges to global health and will continue to dominate mortality trends in the future. Acute myocardial infarction results in 7.4 million deaths globally per annum. Current management strategies are centered on restoration of coronary blood flow via percutaneous coronary intervention, coronary artery bypass grafting and administration of anti-platelet agents. Such myocardial reperfusion accounts for 40-50 % of the final infarct size in most cases. Signaling transducer and activator of transcription 3 (STAT3) has been shown to have cardioprotective effects via canonical and non-canonical activation and modulation of mitochondrial and transcriptional responses. A significant body of in vitro and in vivo evidence suggests that activation of the STAT3 signal transduction pathway results in a cardio protective response to ischemia and attempts have been made to modulate this with therapeutic effect. Not only is STAT3 important for cardiomyocyte function, but it also modulates the cardiac microenvironment and communicates with cardiac fibroblasts. To this end, we here review the current evidence supporting the manipulation of STAT3 for therapeutic benefit in cardiac ischemia and identify areas for future research.

Notch1 Pathway Protects against Burn-Induced Myocardial Injury by Repressing Reactive Oxygen Species Production through JAK2/STAT3 Signaling

Oxidative stress plays an important role in burn-induced myocardial injury, but the cellular mechanisms that control reactive oxygen species (ROS) production and scavenging are not fully understood. This study demonstrated that blockade of Notch signaling via knockout of the transcription factor RBP-J or a pharmacological inhibitor aggravated postburn myocardial injury, which manifested as deteriorated serum CK, CK-MB, and LDH levels and increased apoptosis in vitro and in vivo. Interruption of Notch signaling increased intracellular ROS production, and a ROS scavenger reversed the exacerbated myocardial injury after Notch signaling blockade. These results suggest that Notch signaling deficiency aggravated postburn myocardial injury through increased ROS levels. Notch signaling blockade also decreased MnSOD expression in vitro and in vivo. Notably, Notch signaling blockade downregulated p-JAK2 and p-STAT3 expression. Inhibition of JAK2/STAT3 signaling with AG490 markedly decreased MnSOD expression, increased ROS production, and aggravated myocardial injury. AG490 plus GSI exerted no additional effects. These results demonstrate that Notch signaling protects against burn-induced myocardial injury through JAK2/STAT3 signaling, which activates the expression of MnSOD and leads to decreased ROS levels.

Hypoxic Conditioning as a New Therapeutic Modality

Preconditioning refers to a procedure by which a single noxious stimulus below the threshold of damage is applied to the tissue in order to increase resistance to the same or even different noxious stimuli given above the threshold of damage. Hypoxic preconditioning relies on complex and active defenses that organisms have developed to counter the adverse consequences of oxygen deprivation. The protection it confers against ischemic attack for instance as well as the underlying biological mechanisms have been extensively investigated in animal models. Based on these data, hypoxic conditioning (consisting in recurrent exposure to hypoxia) has been suggested a potential non-pharmacological therapeutic intervention to enhance some physiological functions in individuals in whom acute or chronic pathological events are anticipated or existing. In addition to healthy subjects, some benefits have been reported in patients with cardiovascular and pulmonary diseases as well as in overweight and obese individuals. Hypoxic conditioning consisting in sessions of intermittent exposure to moderate hypoxia repeated over several weeks may induce hematological, vascular, metabolic, and neurological effects. This review addresses the existing evidence regarding the use of hypoxic conditioning as a potential therapeutic modality, and emphasizes on many remaining issues to clarify and future researches to be performed in the field.