Cardioprotective effect of KR-33889, a novel PARP inhibitor, against oxidative stress-induced apoptosis in H9c2 cells and isolated rat hearts

Macrod1 suppresses diabetic cardiomyopathy via regulating PARP1-NAD+-SIRT3 pathway

Diabetic cardiomyopathy (DCM), one of the most serious long-term consequences of diabetes, is closely associated with oxidative stress, inflammation and apoptosis in the heart. MACRO domain containing 1 (Macrod1) is an ADP-ribosylhydrolase 1 that is highly enriched in mitochondria, participating in the pathogenesis of cardiovascular diseases. In this study, we investigated the role of Macrod1 in DCM. A mice model was established by feeding a high-fat diet (HFD) and intraperitoneal injection of streptozotocin (STZ). We showed that Macrod1 expression levels were significantly downregulated in cardiac tissue of DCM mice. Reduced expression of Macrod1 was also observed in neonatal rat cardiomyocytes (NRCMs) treated with palmitic acid (PA, 400 μM) in vitro. Knockout of Macrod1 in DCM mice not only worsened glycemic control, but also aggravated cardiac remodeling, mitochondrial dysfunction, NAD+ consumption and oxidative stress, whereas cardiac-specific overexpression of Macrod1 partially reversed these pathological processes. In PA-treated NRCMs, overexpression of Macrod1 significantly inhibited PARP1 expression and restored NAD+ levels, activating SIRT3 to resist oxidative stress. Supplementation with the NAD+ precursor Niacin (50 μM) alleviated oxidative stress in PA-stimulated cardiomyocytes. We revealed that Macrod1 reduced NAD+ consumption by inhibiting PARP1 expression, thereby activating SIRT3 and anti-oxidative stress signaling. This study identifies Macrod1 as a novel target for DCM treatment. Targeting the PARP1-NAD+-SIRT3 axis may open a novel avenue to development of new intervention strategies in DCM. Schematic illustration of macrod1 ameliorating diabetic cardiomyopathy oxidative stress via PARP1-NAD+-SIRT3 axis.

Exploring the role and mechanism of hyperoside against cardiomyocyte injury in mice with myocardial infarction based on JAK2/STAT3 signaling pathway

BACKGROUND

Myocardial infarction (MI) is one of the most deadly diseases in the world. Hyperoside (Hyp) has been shown to have a protective effect on cardiovascular function through various signaling pathways, but whether it can protect myocardial infarction by regulating JAK2/STAT3 signaling pathway is unknown.

AIM OF THE STUDY

To investigate whether Hyp could protect the heart against myocardial infarction injury in mice by modulating JAK2/STAT3 signaling pathway and its potential mechanism.

METHODS

In vivo experiments, the myocardial infarction model was established by ligating the left anterior descending coronary artery (LAD) of male C57BL/6 mice permanently. The mice were divided into seven groups: sham group, MI group, MI+Hyp (9 mg/kg), MI+Hyp (18 mg/kg) group, MI+Hyp (36 mg/kg) group, MI+Captopril group (15 mg/kg) group and MI+Hyp (36 mg/kg)+AG490 (7.5 mg/kg) group. Each group of animals were given different concentrations of hyperoside, positive control drug or inhibitor of JAK2/STAT3 singaling. After 14 days of administration, the electrocardiogram (ECG), echocardiography and serum myocardial injury markers were examined; Slices of mouse myocardial tissue were assessed for histopathological changes by HE, Masson and Sirius Red staining. TTC and TUNEL staining were used to evaluate the myocardial infarction area and cardiomyocytes apoptosis respectively. The expression of JAK2/STAT3 signaling pathway, apoptosis and autophagy-related proteins were detected by western blot. In vitro experiments, rat H9c2 cardiomyocytes were deprived of oxygen and glucose (OGD) to stimulate myocardial ischemia. The experiment was divided into seven groups: Control group, OGD group, OGD+Hyp (20 μM) group, OGD+Hyp (40 μM) group, OGD+Hyp (80 μM), OGD+Captopril (10 μM) group and OGD+Hyp (80 μM)+AG490 (100 μM) group. Myocardial cell damage and redox index were measured 12 h after OGD treatment. ROS content in cardiomyocytes was detected by immunofluorescence. Cardiomyocytes apoptosis was detected by flow cytometry. The expressions of JAK2/STAT3 signaling pathway-related proteins, apoptosis and autophagy related proteins were detected by western blot.

RESULTS

In vivo, hyperoside could ameolirate ECG abnormality, increase cardiac function, reduce myocardial infarction size and significantly reduce myocardial fibrosis level and oxidation level. The experimental results in vitro showed that Hyp could reduce the ROS content in cardiomyocytes, decrease the level of oxidative stress and counteract the apoptosis induced by OGD injury . Both in vivo and in vitro experiments showed that hyperoside could increase phosphorylated JAK2 and STAT3, indicating that hyperoside could play a cardioprotective role by activating JAK2/STAT3 signaling pathway. It was also shown that hyperoside could increase the autophagy level of cardiomyocytes in vivo and in vitro. However the cardiomyocyte-protective effect of Hyp was abolished in combination with JAK2/ STAT3 signaling pathway inhibitor AG490. These results indicated that the protective effect of Hyp on cardiomyocyte injury was at least partially achieved through the activation of the JAK2/STAT3 signaling pathway.

CONCLUSION

Hyp can significantly improve cardiac function, ameliorate myocardial hypertrophy and myocardial remodeling in MI mice. The mechanism may be related to improving mitochondrial autophagy of cardiomyocytes to maintain the advantage of autophagy, and blocking apoptosis pathway through phagocytosis, thus suppressing apoptosis level of cardiomyocytes. These effects of Hyp are achieved, at least in part, by activating the JAK2/STAT3 signaling pathway.

Cardio-protective effect of tetrahydrocurcumin, the primary hydrogenated metabolite of curcumin in vivo and in vitro: Induction of apoptosis and autophagy via PI3K/AKT/mTOR pathways

Tetrahydrocurcumin (THC) is an essential metabolite of curcumin, a major active component of the Curcuma species, which have been used traditionally for the treatment of cardiovascular diseases. The PI3K/AKT/mTOR signaling pathways serve a vital role during myocardial ischemia-reperfusion (MI/R) injury. The aim of the present study was to investigate the cardioprotective potential and mechanism of THC. In the in vivo study, an animal model of MI/R was induced by coronary occlusion. Results indicated that THC (50 mg/kg/day) protected the rat hearts from MI/R-induced heart failure by increasing ejection fraction (EF) and fractional shortening (FS) and decreasing left ventricular end systolic diameter (LVESD) and left ventricular end systolic volume (LVESV). THC also reduced myocardial infarct size and apoptosis. Furthermore, H9c2 cells were incubated with THC (20 μM) to explore its potential effect following exposure to hypoxia and reoxygenation (H/R). THC post-treatment significantly augmented cell viability and prevented lactate dehydrogenase (LDH) release after H/R exposure. THC effectively improved antioxidant activity by increasing SOD and CAT activities and decreasing MDA level. THC also enhanced mitochondrial membrane potential, inhibited apoptotic cell death, diminished the Bax/Bcl-2 ratio and cleaved caspase-3 level relative to the H/R model. In addition, THC effectively decreased Beclin1 expression and LC3 II/LC3 I ratio, but increased p62 expression, compared with the H/R model group, and decreased the formation of H/R-induced autophagosomes and autolysosomes. Furthermore, THC promoted the phosphorylation of PI3K/AKT/mTOR and induced the expression of hypoxia-inducible factor 1α (HIF-1α) after H/R. However, these effects on H9c2 cells were notably abolished by the PI3K inhibitor LY294002 and mTOR inhibitor rapamycin. In conclusion, THC effectively inhibited H/R-induced autophagy and apoptosis via, at least partially, activating the PI3K/AKT/mTOR pathways. THC might have the potential to be further developed into a potential candidate for the treatment of MI/R injury.

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.

Fluzoparib increases radiation sensitivity of non-small cell lung cancer (NSCLC) cells without BRCA1/2 mutation, a novel PARP1 inhibitor undergoing clinical trials

PROPOSE

Poly (ADP-ribose) polymerase 1 inhibitors were originally investigated as anti-cancer therapeutics with BRCA1/2 genes mutation. Here, we investigate the effectiveness of a novel PARP1 inhibitor fluzoparib, for enhancing the radiation sensitivity of NSCLC cells lacking BRCA1/2 mutation.

METHODS

We used MTS assays, western blotting, colony formation assays, immunofluorescence staining, and flow cytometry to evaluate the radiosensitization of NSCLC cells to fluzoparib and explore the underlying mechanisms in vitro. Through BRCA1 and RAD50 genes knockdown, we established dysfunctional homologous recombination (HR) DNA repair pathway models in NSCLC cells. We next investigated the radiosensitization effect of fluzoparib in vivo using human NSCLC xenograft models in mice. The expression of PARP1 and BRCA1 in human NSCLC tumor samples was measured by immunohistochemistry. Furthermore, we sequenced HR-related gene mutations and analyzed their frequencies in advanced NSCLC.

RESULTS

In vitro experiments in NSCLC cell lines along with in vivo experiments using an NSCLC xenograft mouse model demonstrated the radiosensitization effect of fluzoparib. The underlying mechanisms involved increased apoptosis, cell-cycle arrest, enhanced irradiation-induced DNA damage, and delayed DNA-damage repair. Immunohistochemical staining showed no correlation between the expression of PARP1 and BRCA1. Moreover, our sequencing results revealed high mutation frequencies for the BRCA1/2, CHEK2, ATR, and RAD50 genes.

CONCLUSION

The potential therapeutic value of fluzoparib for increasing the radiation sensitivity of NSCLC is well confirmed. Moreover, our findings of high mutation frequencies among HR genes suggest that PARP1 inhibition may be an effective treatment strategy for advanced non-small cell lung cancer patients.

Role of Akt Activation in PARP Inhibitor Resistance in Cancer

Poly(ADP-ribose) polymerase (PARP) inhibitors have recently been introduced in the therapy of several types of cancers not responding to conventional treatments. However, de novo and acquired PARP inhibitor resistance is a significant limiting factor in the clinical therapy, and the underlying mechanisms are not fully understood. Activity of the cytoprotective phosphatidylinositol-3 kinase (PI3K)-Akt pathway is often increased in human cancer that could result from mutation, expressional change, or amplification of upstream growth-related factor signaling elements or elements of the Akt pathway itself. However, PARP-inhibitor-induced activation of the cytoprotective PI3K-Akt pathway is overlooked, although it likely contributes to the development of PARP inhibitor resistance. Here, we briefly summarize the biological role of the PI3K-Akt pathway. Next, we overview the significance of the PARP-Akt interplay in shock, inflammation, cardiac and cerebral reperfusion, and cancer. We also discuss a recently discovered molecular mechanism that explains how PARP inhibition induces Akt activation and may account for apoptosis resistance and mitochondrial protection in oxidative stress and in cancer.

Reactive oxygen/nitrogen species contribute substantially to the antileukemia effect of APO866, a NAD lowering agent

APO866 is a small molecule drug that specifically inhibits nicotinamide phosphoribosyltransferase (NAMPT), a key enzyme involved in nicotinamide adenine dinucleotide (NAD) biosynthesis from the natural precursor nicotinamide. Although, the antitumor activity of APO866 on various types of cancer models has been reported, information regarding mechanisms by which APO866 exerts its cytotoxic effects is not well defined. Here we show that APO866 induces a strong, time-dependent increase in highly reactive ROS, nitric oxide, cytosolic/mitochondrial superoxide anions and hydrogen peroxide. We provide evidence that APO866-mediated ROS production is modulated by PARP1 and triggers cell death through mitochondria depolarization and ATP loss. Genetic or pharmacologic inhibition of PARP1 prevented hydrogen peroxide accumulation, caspase activation, mitochondria depolarization, ATP loss and abrogates APO866-induced cell death, suggesting that the integrity of PARP1 status is required for cell death. Conversely, PARP1 activating drugs enhanced the anti-leukemia activity of APO866 Collectively, our studies show that APO866 induces ROS/RNS productions, which mediate its anti-leukemia effect. These results support testing new combinatorial strategies to enhance the antitumor activities of APO866.

Poly (ADP-ribose) polymerase inhibition protects against myocardial ischaemia/reperfusion injury via suppressing mitophagy

Myocardial ischaemia/reperfusion (I/R) injury attenuates the beneficial effects of reperfusion therapy. Poly(ADP-ribose) polymerase (PARP) is overactivated during myocardial I/R injury. Mitophagy plays a critical role in the development of myocardial I/R injury. However, the effect of PARP activation on mitophagy in cardiomyocytes is unknown. In this study, we found that I/R induced PARP activation and mitophagy in mouse hearts. Poly(ADP-ribose) polymerase inhibition reduced the infarct size and suppressed mitophagy after myocardial I/R injury. In vitro, hypoxia/reoxygenation (H/R) activated PARP, promoted mitophagy and induced cell apoptosis in cardiomyocytes. Poly(ADP-ribose) polymerase inhibition suppressed H/R-induced mitophagy and cell apoptosis. Parkin knockdown with lentivirus vectors inhibited mitophagy and prevented cell apoptosis in H/R-treated cells. Poly(ADP-ribose) polymerase inhibition prevented the loss of the mitochondrial membrane potential (ΔΨm). Cyclosporin A maintained ΔΨm and suppressed mitophagy but FCCP reduced the effect of PARP inhibition on ΔΨm and promoted mitophagy, indicating the critical role of ΔΨm in H/R-induced mitophagy. Furthermore, reactive oxygen species (ROS) and poly(ADP-ribosylation) of CypD and TSPO might contribute to the regulation of ΔΨm by PARP. Our findings thus suggest that PARP inhibition protects against I/R-induced cell apoptosis by suppressing excessive mitophagy via the ΔΨm/Parkin pathway.

Loss of GCN5L1 in cardiac cells disrupts glucose metabolism and promotes cell death via reduced Akt/mTORC2 signaling

GCN5L1 regulates protein acetylation and mitochondrial energy metabolism in diverse cell types. In the heart, loss of GCN5L1 sensitizes the myocardium to injury from exposure to nutritional excess and ischemia/reperfusion injury. This phenotype is associated with the reduced acetylation of metabolic enzymes and elevated mitochondrial reactive oxygen species (ROS) generation, although the direct molecular targets of GCN5L1 remain largely unknown. In this study, we sought to determine the mechanism by which GCN5L1 impacts energy substrate utilization and mitochondrial health. We find that hypoxia and reoxygenation (H/R) leads to a reduction in cell viability and Akt phosphorylation in GCN5L1 knockdown AC16 cardiomyocytes, in parallel with elevated glucose utilization and impaired fatty acid use. We demonstrate that glycolysis is uncoupled from glucose oxidation under normoxic conditions in GCN5L1-depleted cells. We show that GCN5L1 directly binds to the Akt-activating mTORC2 component Rictor, and that loss of Rictor acetylation is evident in GCN5L1 knockdown cells. Finally, we show that restoring Rictor acetylation in GCN5L1-depleted cells reduces mitochondrial ROS generation and increases cell survival in response to H/R. These studies suggest that GCN5L1 may play a central role in energy substrate metabolism and cell survival via the regulation of Akt/mTORC2 signaling.

Cardioprotective Effect of Resveratrol in a Postinfarction Heart Failure Model

Despite great advances in therapies observed during the last decades, heart failure (HF) remained a major health problem in western countries. In order to further improve symptoms and survival in patients with heart failure, novel therapeutic strategies are needed. In some animal models of HF resveratrol (RES), it was able to prevent cardiac hypertrophy, contractile dysfunction, and remodeling. Several molecular mechanisms are thought to be involved in its protective effects, such as inhibition of prohypertrophic signaling molecules, improvement of myocardial Ca²⁺ handling, regulation of autophagy, and the reduction of oxidative stress and inflammation. In our present study, we wished to further examine the effects of RES on prosurvival (Akt-1, GSK-3β) and stress signaling (p38-MAPK, ERK 1/2, and MKP-1) pathways, on oxidative stress (iNOS, COX-2 activity, and ROS formation), and ultimately on left ventricular function, hypertrophy and fibrosis in a murine, and isoproterenol- (ISO-) induced postinfarction heart failure model. RES treatment improved left ventricle function, decreased interstitial fibrosis, cardiac hypertrophy, and the level of plasma BNP induced by ISO treatment. ISO also increased the activation of P38-MAPK, ERK1/2^{Thr183-Tyr185}, COX-2, iNOS, and ROS formation and decreased the phosphorylation of Akt-1, GSK-3β, and MKP-1, which were favorably influenced by RES. According to our results, regulation of these pathways may also contribute to the beneficial effects of RES in HF.

Hesperetin post-treatment prevents rat cardiomyocytes from hypoxia/reoxygenation injury in vitro via activating PI3K/Akt signaling pathway

Hesperidin (HES), a citrus fruit extract, has beneficial effects on various ischemia/reperfusion (I/R) models. Here, we investigated the possible positive effect of hesperetin (HPT), an active metabolite of HES, and identified the potential molecular mechanisms involved in cardiomyocytes H/R-induced injury. To construct the cardiomyocyte model of hypoxia/reoxygenation (H/R) injury, cultured neonatal rat cardiomyocytes were subjected to 3h of hypoxia followed by 3h of reoxygenation. Cell viability and apoptosis were detected. The levels of Apoptosis-related proteins and PI3K/Akt proteins were detected by western blot. Our results showed that HPT post-treatment significantly inhibited apoptosis by elevating the expression of Bcl-2, decreasing the expression of Bax and cleaved caspase-3, and diminished the apoptotic cardiomyocytes ratio. Mechanism studies demonstrated that HPT post-treatment up-regulated the expression levels of p-PI3K, and p-Akt. Co-treatment of the cardiomyocytes with the PI3K/Akt-specific inhibitor LY294002 blocked the HPT-induced cardioprotective effects. Taken together, these data suggested that HPT post-treatment prevented cardiomyocytes from H/R injury in vitro most likely through the activation of PI3K/Akt signaling pathway.