scholarly journals Activation of Autophagic Flux Blunts Cardiac Ischemia/Reperfusion Injury

2021 ◽  
Author(s):  
Min Xie ◽  
Geoffrey W Cho ◽  
Yongli Kong ◽  
Dan L Li ◽  
Francisco Altamirano ◽  
...  
Keyword(s):  
Cell Death ◽  
Infarct Size ◽  
Reperfusion Injury ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Neonatal Rat ◽  
Border Zone ◽  
Relative Reduction ◽  
Autophagic Flux ◽  
Hdac Inhibition

Rationale: Reperfusion injury accounts for up to half of myocardial infarct size, and meaningful clinical therapies targeting it do not exist. We have reported previously that autophagy is reduced during reperfusion and that HDAC inhibition enhances cardiomyocyte autophagy and blunts ischemia/reperfusion (I/R) injury when administered at the time of reperfusion. However, whether inducing autophagy per se, as opposed to other effects triggered by HDAC inhibition, is sufficent to protect against reperfusion injury is not clear. Objective: We set out to test whether augmentation of autophagy using a specific autophagy-inducing peptide, Tat-Beclin, protects the myocardium through reduction of reactive oxygen species (ROS) during reperfusion injury. Methods and Results: Eight to twelve-week-old, wild-type, C57BL6 mice and drug-inducible cardiomyocyte-specific ATG7 knockout mice (to test the dependency on autophagy) were randomized into two groups: exposed to a control Tat-Scrambled (TS) peptide or a Tat-Beclin (TB) peptide. Each group was subjected to I/R surgery (45min coronary ligation, 24h reperfusion). Infarct size, systolic function, autophagic flux, and ROS were assayed. Cultured neonatal rat ventricular myocytes (NRVMs) were exposed to TB during simulated ischemia/reperfusion injury. ATG7 knockdown by siRNA in NRVMs was used to evaluate the role of autophagy. TB treatment at reperfusion reduced infarct size by 20% (absolute reduction; 50% relative reduction) and improved contractile function. Improvement correlated with increased autophagic flux in the border zone with less oxidative stress. ATG7 KO mice did not manifest TB-promoted cardioprotection during I/R. In NRVMs subjected to I/R, TB reduced cell death by 41% and reduced I/R-induced ROS generation. Conversely, ATG7 knockdown in NRVMs abolished these beneficial effects of TB on cell death and ROS reduction. Conclusions: Induction of autophagy at the time of reperfusion is sufficient to mitigate myocardial reperfusion injury by reducing ROS and cell death. Maintenance of appropriate autophagic flux may emerge as a viable clinical therapy to reduce reperfusion injury in acute myocardial infarction.

Abstract 14412: Activation of Autophagic Flux Maintains Mitochondrial Homeostasis During Cardiac Ischemia/reperfusion Injury

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Jing Yang ◽  
Geoffrey W CHO ◽  
Lihao He ◽  
Yuxin Chu ◽  
Jin He ◽  
...  
Keyword(s):  
Infarct Size ◽  
Reperfusion Injury ◽  
Mitochondrial Dynamics ◽  
Systolic Function ◽  
Ischemia Reperfusion ◽  
Border Zone ◽  
Autophagic Flux ◽  
Hdac Inhibition ◽  
Infarct Border Zone ◽  
Infarct Border

Background and Hypothesis: Reperfusion injury accounts for ~50% of myocardial infarct size, and clinically efficacious therapies are lacking. Histone deacetylase (HDAC) inhibition enhances cardiomyocyte autophagic activity, mitochondria biogenesis, and blunts ischemia/reperfusion (I/R) injury when given at the time of reperfusion. However, as HDAC inhibition has pleiotropic effects, we will test whether augmentation of autophagic flux using a specific autophagy-inducing peptide, Tat-Beclin (TB), is cardioprotective. Methods: 8-12-week-old, wild-type, C57BL6 mice were randomized into three groups: vehicle control, Tat-Scrambled (TS) peptide, or Tat-Beclin (TB) peptide. Each group was subjected to I/R surgery (45min ischemia, 24h reperfusion). Infarct size, systolic function, and mitochondrial dynamics were assayed. Cultured neonatal rat ventricular myocytes (NRVMs) were used to test for cardiomyocyte specificity. Conditional cardiomyocyte ATG7 knockout (ATG7 KO) mice and ATG7 knockdown by siRNA in NRVMs were used to evaluate the role of autophagy. Results: TB treatment at reperfusion reduced infarct size by 20.1±6.3% (n=23, p<0.02) and improved systolic function. Increased autophagic flux and reduced reactive oxygen species (ROS) were observed in the infarct border zone. The cardioprotective effects of TB were abolished in ATG7 KO mice. TB increased mtDNA content in the border zone significantly. In NRVMs subjected to I/R, TB reduced cell death by 41±6% (n=12, p<0.001), decreased ROS, and increased mtDNA content significantly by ~50%. Moreover, TB promoted expression of PGC1α (a major driver of mitochondrial biogenesis) both in the infarct border zone and NRVMs subjected to I/R by ~40%, and increased levels of mitochondrial dynamics gene transcripts Drp1, Fis1, and MFN1 / 2. Conversely, ATG7 knockdown in NRVMs and cardiac ATG7 KO abolished the beneficial effects of TB on mitochondria DNA content. Conclusions: Autophagic flux is an essential process to mitigate myocardial reperfusion injury acting, at least in part, by inducing PGC1α-mediated mitochondrial biogenesis. Augmentation of autophagic flux may emerge as a viable clinical therapy to reduce reperfusion injury in myocardial infarction.

Abstract 357: Activation of Autophagic Flux Blunts Cardiac Ischemia/Reperfusion Injury

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Geoffrey W Cho ◽  
Min Xie ◽  
Yongli Kong ◽  
Dan L Li ◽  
Xiang L Luo ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Infarct Size ◽  
Reperfusion Injury ◽  
Molecular Mechanisms ◽  
Contractile Function ◽  
Ischemia Reperfusion ◽  
Neonatal Rat ◽  
Border Zone ◽  
Autophagic Flux ◽  
Cardiomyocyte Autophagy

Background: Reperfusion injury accounts for a significant portion of myocardial damage in acute coronary syndromes. Autophagy, a process of cell catabolism, plays a vital role in the heart’s response to stress. We have reported that re-induction of ischemia/reperfusion (I/R)-suppressed cardiomyocyte autophagy with histone deacetylase (HDAC) inhibitors affords significant cardioprotection. However, as HDACs govern many processes and may have off-target effects, we set out to modulate autophagy in a manner independent of HDAC activity. Here, we hypothesized that induction of autophagy with a novel agent, Tat-Beclin, at the time of reperfusion, will reduce I/R injury and rescue cardiac function. Methods: Wild type and ATG7 (protein required for autophagic flux) knockout mice were randomized among 3 treatment groups prior to surgical I/R injury [45 min LAD artery ligation; 24h reperfusion]: vehicle control (VC), Tat-Scrambled (TS), or Tat-Beclin (TB). Each agent was delivered at coronary reperfusion. To define molecular mechanisms, cultured adult and neonatal rat ventricular cardiomyocytes (ARVMs/NRVMs) were subjected to simulated I/R. Results: Induction of cardiomyocyte autophagy at reperfusion reduced infarct size 20.1% (±6.3%, n=23, p<0.02 vs VC). This treatment was associated with improved systolic function (declines in fractional shortening: 19.8±3.7% VC; 18.7±2.1% TS; 8.5±1.7% TB, n=11, p<0.01 vs VC). In NRVMs subjected to I/R injury, cell death was reduced 41% (±6%, n=12, p<0.001 vs VC). Improvements correlated with increased autophagic flux measured by the marker LC3-II, particularly at the infarct border zone. Additional data suggested that autophagy rescues I/R injury through reduction of oxidative stress. ATG7 KO mice or NRVM depleted of ATG7 (RNAi) manifested significantly less cardioprotection. Conclusion: Direct induction of cardiomyocyte autophagy reduces infarct size and declines in contractile function. Autophagy rescues I/R injury in part through reduction of oxidative stress. Critically, this cardioprotection was observed when intervention occurred at the time of reperfusion, the clinically relevant context.

Necrostatin-1 Analog DIMO Exerts Cardioprotective Effect against Ischemia Reperfusion Injury by Suppressing Necroptosis via Autophagic Pathway in Rats

Pharmacology ◽  
2021 ◽  
Vol 106 (3-4) ◽  
pp. 189-201
Author(s):  
Shigang Qiao ◽  
Wen-jie Zhao ◽  
Huan-qiu Li ◽  
Gui-zhen Ao ◽  
Jian-zhong An ◽  
...  
Keyword(s):  
Cell Death ◽  
Ischemia Reperfusion Injury ◽  
Myocardial Infarct ◽  
Ischemia Reperfusion ◽  
Glucose Deprivation ◽  
Neonatal Rat ◽  
Ligand Docking ◽  
Autophagic Flux ◽  
Myocardial Infarct Size ◽  
Rat Cardiomyocytes

Aim: It has been reported that necrostatin-1 (Nec-1) is a specific necroptosis inhibitor that could attenuate programmed cell death induced by myocardial ischemia/reperfusion (I/R) injury. This study aimed to observe the effect and mechanism of novel Nec-1 analog (Z)-5-(3,5-dimethoxybenzyl)-2-imine-1-methylimidazolin-4-1 (DIMO) on myocardial I/R injury. Methods: Male SD rats underwent I/R injury with or without different doses of DIMO (1, 2, or 4 mg/kg) treatment. Isolated neonatal rat cardiomyocytes were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) treatment with or without DIMO (0.1, 1, 10, or 100 μM). Myocardial infarction was measured by TTC staining. Cardiomyocyte injury was assessed by lactate dehydrogenase assay (LDH) and flow cytometry. Receptor-interacting protein 1 kinase (RIP1K) and autophagic markers were detected by co-immunoprecipitation and Western blotting analysis. Molecular docking of DIMO into the ATP binding site of RIP1K was performed using GLIDE. Results: DIMO at doses of 1 or 2 mg/kg improved myocardial infarct size. However, the DIMO 4 mg/kg dose was ineffective. DIMO at the dose of 0.1 μM decreased LDH leakage and the ratio of PI-positive cells followed by OGD/R treatment. I/R or OGD/R increased RIP1K expression and in its interaction with RIP3K, as well as impaired myocardial autophagic flux evidenced by an increase in LC3-II/I ratio, upregulated P62 and Beclin-1, and activated cathepsin B and L. In contrast, DIMO treatment reduced myocardial cell death and reversed the above mentioned changes in RIP1K and autophagic flux caused by I/R and OGD/R. DIMO binds to RIP1K and inhibits RIP1K expression in a homology modeling and ligand docking. Conclusion: DIMO exerts cardioprotection against I/R- or OGD/R-induced injury, and its mechanisms may be associated with the reduction in RIP1K activation and restoration impaired autophagic flux.

Abstract P451: Depletion Of Rbl2 Exacerbates Cardiomyocyte Apoptosis And Ischemia-reperfusion Injury By Augmenting E2f1-mediated Bnip3 Expression

2021 ◽  
Vol 129 (Suppl_1) ◽  
Author(s):  
Jingrui Chen ◽  
Yuening Liu ◽  
Peng Xia ◽  
Zhaokang Cheng
Keyword(s):  
Infarct Size ◽  
Reperfusion Injury ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Cardiomyocyte Apoptosis ◽  
Neonatal Rat ◽  
Mouse Heart ◽  
Wild Type ◽  
Rat Cardiomyocytes

Background: Reperfusion therapy, an effective treatment for myocardial infarction, triggers ischemia-reperfusion (I/R) injury and eventually may result in heart failure. Retinoblastoma-like 2 (Rbl2), a major retinoblastoma family member expressed in the heart, maintains the postmitotic state of adult cardiac myocytes. However, the role of Rbl2 in myocardial I/R injury remains unclear. We hypothesize that Rbl2 deficiency exacerbates myocardial injury following I/R. Methods and results: Wild type C57BL/6 (8–10-week, male) mice were subjected to 30 min of ischemia followed reperfusion. I/R induced phosphorylation of Rbl2 at Ser952, which has been associated with Rbl2 protein inactivation. To determine the role of Rbl2 in vivo, Rbl2-deficient mice and wild-type littermates were subjected to I/R and infarct size was evaluated by Evans blue/TTC staining. Rbl2 deficiency significantly increased infarct size at 24 h post I/R when compared with wild-type littermate controls. Echocardiography and Masson’s trichrome staining revealed that Rbl2 deficiency exacerbated I/R-induced cardiac dysfunction and fibrosis. Moreover, ablation of Rbl2 exacerbated I/R-induced cardiomyocyte apoptosis, as evidenced by the increased TUNEL positive signal. Consistently, knockdown of Rbl2 augmented H 2 O 2 -induced cleavage of PARP and caspase 3 in neonatal rat cardiomyocytes , suggesting that depletion of Rbl2 exacerbated oxidative stress-induced cardiomyocyte apoptosis. Mechanistically, both I/R and H 2 O 2 induced expression of the pro-apoptotic protein BNIP3, which was augmented by depletion of Rbl2. Since the BNIP3 promoter contains an E2F-binding site, we further examined the levels of the transcriptional activator E2F1 and the transcriptional repressor E2F4. Western blotting revealed that disruption of Rbl2 reduced E2F4 but increased E2F1 levels in mouse heart both at baseline and following I/R. Conclusion: Our findings suggest that Rbl2 deficiency exacerbates cardiomyocyte apoptosis and ischemia-reperfusion injury by augmenting E2F1-mediated BNIP3 expression.

scholarly journals miR-380-5p facilitates NRF2 and attenuates cerebral ischemia/reperfusion injury-induced neuronal cell death by directly targeting BACH1

2021 ◽  
Vol 12 (1) ◽  
pp. 210-217
Author(s):  
Yibiao Wang ◽  
Min Xu
Keyword(s):  
Cell Death ◽  
Cerebral Ischemia ◽  
Reperfusion Injury ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Luciferase Assay ◽  
Neuroprotective Effects ◽  
Cerebral Ischemia Reperfusion

Abstract Background This study aimed to explore the role of miR-380-5p in cerebral ischemia/reperfusion (CIR) injury-induced neuronal cell death and the potential signaling pathway involved. Methodology Human neuroblastoma cell line SH-SY5Y cells were used in this study. Oxygen and glucose deprivation/reperfusion (OGD/R) model was used to mimic ischemia/reperfusion injury. CCK-8 assay and flow cytometry were used to examine cell survival. Quantitative real time PCR (RT-qPCR) assay and Western blotting were used to measure the change of RNA and protein expression, respectively. TargetScan and Luciferase assay was used to confirm the target of miR-380-5p. Malondialdehyde (MDA) superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) were measured using commercial kits. Results miR-380-5p was downregulated in SH-SY5Y cells after OGD/R. Cell viability was increased by miR-380-5p, while cell apoptosis was reduced by miR-380-5p mimics. MDA was reduced by miR-380-5p mimics, while SOD and GSHPx were increased by miR-380-5p. Results of TargetScan and luciferase assay have showed that BACH1 is the direct target of miR-380-5p. Expression of NRF2 was upregulated after OGD/R, but was not affected by miR-380-5p. mRNA expression of HO-1 and NQO1 and ARE activity were increased by miR-380-5p. Overexpression of BACH1 reversed the antioxidant and neuroprotective effects of miR-380-5p. Conclusion miR-380-5p inhibited cell death induced by CIR injury through target BACH1 which also facilitated the activation of NRF2, indicating the antioxidant and neuroprotective effects of miR-380-5p.

Sign in / Sign up

Export Citation Format

Share Document