Hapln1 promotes dedifferentiation and proliferation of iPSC-derived cardiomyocytes by promoting versican-based GDF11 trapping

Hyaluronan and proteoglycan link protein 1(Hapln1)supports active cardiomyogenesis in zebrafish hearts,but its regulation in mammal cardiomyocytes is unclear.This study aimed to explore the potential regulation of Hapln1 in the dedifferentiation and proliferation of cardiomyocytes and its therapeutic value in myocardial infarction with human induced pluripotent stem cell(hiPSC)-derived cardiomyocytes(CMs)and an adult mouse model of myocardial infarction.HiPSC-CMs and adult mice with myocardial infarction were used as in vitro and in vivo models,respectively.Previous single-cell RNA sequencing data were retrieved for bioinformatic exploration.The results showed that recombinant human Hapln1(rhHapln1)promotes the proliferation of hiPSC-CMs in a dose-dependent manner.As a physical binding protein of Hapln1,versican interacted with Nodal growth differentiation factor(NODAL)and growth differentiation factor 11(GDF11).GDF11,but not NODAL,was expressed by hiPSC-CMs.GDF11 expression was unaffected by rhHapln1 treatment.However,this molecule was required for rhHapln1-mediated activation of the transforming growth factor(TGF)-β/Drosophila mothers against decapentaplegic protein(SMAD)2/3 signaling in hiPSC-CMs,which stimulates cell dedifferentiation and proliferation.Recombinant mouse Hapln1(rmHapln1)could induce cardiac regeneration in the adult mouse model of myocardial infarction.In addition,rmHapln1 induced hiPSC-CM proliferation.In conclusion,Hapln1 can stimulate the dedifferentiation and proliferation of iPSC-derived cardiomyocytes by promoting versican-based GDF11 trapping and subsequent activation of the TGF-β/SMAD2/3 signaling pathway.Hapln1 might be an effective hiPSC-CM dedifferentiation and proliferation agent and a potential reagent for repairing damaged hearts.

Effects of docosahexaenoic acid or arachidonic acid supplementation on the behavior of cardiomyocytes derived from human pluripotent stem cells

Background:Human heart changes its energetic substrates from lactate and glucose to fatty acids during the neonatal period.Noticing the lack of fatty acids in media for the culture of cardiomyocytes derived from human pluripotent stem cells(hiPS-CM),researchers have supplemented mixtures of fatty acids to hiPS-CM and reported the enhancement in the maturation of hiPS-CM.In our previous studies,we separately supplemented two polyunsaturated fatty acids(PUFAs),docosahexaenoic acid(DHA)or arachidonic acid(AA),to rat fetal cardiomyocytes and found that the supplementations upregulated the expressions of mRNAs for cardiomyocyte differentiation,fatty acid metabolism,and cellular adhesion.The enhancement in cellular contractility was attributed to the improvement in intercellular connection rather than a direct enhancement of the contractile force.Methods:This study reports the successive results of the effects of DHA or AA supplementation on hiPS-CM.In addition to the contractile force and mRNA measurements used in the previous study,we further investigated the effect of different cellular aggregations on the contractile force output by means of finite element analysis,measured glucose and fatty acids metabolites,and assessed cTNT and MLC2v expressions through immunofluorecsence evaluation.Results:It showed that the sole supplementation of albumin-conjugated DHA or AA can be taken up by hiPS-CM without other uptake-enhancing factors,and the supplementations may activate the CD36_ERRγmetabolic pathway.DHA or AA supplementation increased the cellular contractile ratio on collagen gels and AA supplementation stimulated hiPS-CM aggregation to form cellular clusters.The enhancement effect on the hiPS-CM contractile force was modest since the increase in contractile force was not significant.AA supplementation was more effective than DHA supplementation because it significantly upregulated mRNA expressions of P300 and CD36.However,finite element analysis showed that the formation of clusters on a collagen gel attenuated the contractile force exerted by the gel on its surroundings.Conclusion:DHA and AA,as having been supplemented in infant formulas,have no direct and significant enhancement effect on the performance of the hiPS-CM when they were supplemented individually,although they were able to enter the cellular metabolic system.The AA supplementation showed some auxiliary effect on the maturation of hiPS-CM,which is worthy of further investigation under the consideration of membrane composition alteration and remodeling of membrane molecules.

Disease modeling of desmosome-related cardiomyopathy using induced pluripotent stem cell-derived cardiomyocytes

Cardiomyopathy is a pathological condition characterized by cardiac pump failure due to myocardial dysfunction and the major cause of advanced heart failure requiring heart transplantation.Although optimized medical therapies have been developed for heart failure during the last few decades,some patients with cardiomyopathy exhibit advanced heart failure and are refractory to medical therapies.Desmosome,which is a dynamic cell-to-cell junctional component,maintains the structural integrity of heart tissues.Genetic mutations in desmo-somal genes cause arrhythmogenic cardiomyopathy(AC),a rare inheritable disease,and predispose patients to sudden cardiac death and heart failure.Recent advances in sequencing technologies have elucidated the genetic basis of cardiomyopathies and revealed that desmosome-related cardiomyopathy is concealed in broad cardiomyopathies.Among desmosomal genes,mutations in PKP2(which encodes PKP2)are most frequently identified in patients with AC.PKP2 deficiency causes various pathological cardiac phenotypes.Human cardiomyocytes differentiated from patient-derived induced pluripotent stem cells(iPSCs)in combination with genome editing,which allows the precise arrangement of the targeted genome,are powerful experimental tools for studying disease.This review summarizes the current issues associated with practical medicine for advanced heart failure and the recent advances in disease modeling using iPSC-derived cardiomyocytes targeting desmosome-related cardiomyopathy caused by PKP2 deficiency.

Effect of emulsified isoflurane on apoptosis of anoxia-reoxygenation neonatal rat cardiomyocytes

Objective:To explore the effect of emulsified isoflurane(EI)on apoptosis of anoxia-reoxygenation neonatal rat cardiomyocytea and relevant protein expression.Methods:Cardiac muscle anoxiareoxygenation damage model was established with culture in vitro neonatal rat cardiomyocytes.The cardiomyocytes were divided into control group,model group,fat emulsion group and EI group.The cardiomyocytes apoptosis rates and lactic dehydrogenase(LDH),superoxide dismutase(SOD)and malondialdehyde(MDA)index standardization were detected after relevant treatment The expression of apoptosis-related proteins Bel-2,Bax and Caspase-3 were detected with Western blot approach.Results:After hypoxia/reoxygenation(H/R)model was treated by EI,the cells apoptosis rate decreased and was dramatically below the fat emulsion group(P<0.05),Cardiomyocytes biochemical index detection presented that,compared with the control group that the LDH activity and MDA content dramatically increased(P<0.05),while the SOD activity notably decreased(P<0.05);compared with the H/R group,the SOD activity of the fat emulsion group and EI group increased(P<0.05);while the LDH activity and MDA content decreased(P<0.05).And the change of the EI group was more remarkable than the fat emulsion group(P<0.05).The Western blot analysis presented that,compared with the control group,the Bcl-2 protein expression of the other groups significantly decreased(P<0.05),the expressions of Bax protein and Caspase-3protein increased significantly(P<0.05);compared with H/R group,cardiomyocytes Bc1-2protein expression of EI group increased significantly(P<0.05),the expressions of Bax protein and Caspase-3 protein decreased significantly(P<0.05),and the change of EI group was more remarkable than the fat emulsion group(P<0.05).Conclusions:EI can inhabit the apoptosis of anoxia-reoxygenation damage model cardiomyocytes,and may he related to the up-regulation of expression of Bcl-2 and down-regulation of expression of Caspase-3 protein.

Current methods for the maturation of induced pluripotent stem cellderived cardiomyocytes

Induced pluripotent stem cells(iPSCs) were first generated by Yamanaka and colleagues over a decade ago. Since then, iPSCs have been successfully differentiated into many distinct cell types, enabling tissue-, disease-, and patientspecific in vitro modelling. Cardiovascular disease is the greatest cause of mortality worldwide but encompasses rarer disorders of conduction and myocardial function for which a cellular model of study is ideal. Although methods to differentiate iPSCs into beating cardiomyocytes(iPSC-CMs) have recently been adequately optimized and commercialized, the resulting cells remain largely immature with regards to their structure and function,demonstrating fetal gene expression, disorganized morphology, reliance on predominantly glycolytic metabolism and contractile characteristics that differ from those of adult cardiomyocytes. As such, disease modelling using iPSC-CMs may be inaccurate and of limited utility. However, this limitation is widely recognized, and numerous groups have made substantial progress in addressing this problem. This review highlights successful methods that have been developed for the maturation of human iPSC-CMs using small molecules,environmental manipulation and 3-dimensional(3 D) growth approaches.

Real-time Microwave Exposure Induces Calcium Efflux in Primary Hippocampal Neurons and Primary Cardiomyocytes

Objective To detect the effects of microwave on calcium levels in primary hippocampal neurons and primary cardiomyocytes by the real-time microwave exposure combined with laser scanning confocal microscopy. Methods The primary hippocampal neurons and primary cardiomyocytes were cultured and labeled with probes, including Fluo-4 AM, Mag-Fluo-AM, and Rhod-2, to reflect the levels of whole calcium [Ca], endoplasmic reticulum calcium [Ca]ER, and mitochondrial calcium [Ca]MIT, respectively. Then, the cells were exposed to a pulsed microwave of 2.856 GHz with specific absorption rate(SAR) values of 0, 4, and 40 W/kg for 6 min to observe the changes in calcium levels. Results The results showed that the 4 and 40 W/kg microwave radiation caused a significant decrease in the levels of [Ca], [Ca]ER, and [Ca]MIT in primary hippocampal neurons. In the primary cardiomyocytes, only the 40 W/kg microwave radiation caused the decrease in the levels of [Ca], [Ca]ER, and [Ca]MIT. Primary hippocampal neurons were more sensitive to microwave exposure than primary cardiomyocytes. The mitochondria were more sensitive to microwave exposure than the endoplasmic reticulum. Conclusion The calcium efflux was occurred during microwave exposure in primary hippocampal neurons and primary cardiomyocytes. Additionally, neurons and mitochondria were sensitive cells and organelle respectively.

Panax notogiseng saponin inhibits ischemia-induced apoptosis by activating PI3K/Akt signal pathway in cardiomyocytes

The panax notoginseng saponin(PNS) had been clinically used for the treatment of cardiovascular diseases and stroke in China.It had been demonstrated that PNS could protect cardiomyocytes from injury induced by ischemi- a,but the underlying molecular mechanisms of this protective effect were still unclear.This study was aimed to investigate the protective effect and molecular mechanisms of PNS on apoptosis in H9c2 cells in vitro and rat myocardial ischemia injury model in vivo.Annexin-V/PI assay shew that PNS could protect H9c2 cells from apoptosis induced by serum, glucose and oxygen deprivation(SGOD) in a dose-dependent manner.However,the anti-apoptotic effect of PNS was reversed by LY294002,a specific PI3K inhibitor.This antiapoptotic effect of PNS was confirmed by JC-1,a specific probe of mitochondrial membrane potential staining.PNS could significantly increase phos-Akt in H9c2 cells by Western blot assays and its effect could be inhibited by LY294002.Furthermore,PNS could improve ischemic-induced left ventricular function as reflected by EF,LVDd and LVDs.PNS could also inhibited cellular apoptosis in myocardial tissues in ischemic rats by TUNEL assay.PNS administration also increased the expression of phos-Akt in rat ischemic myocardial tissues.These results suggested that PNS could protect myocardial cells from apoptosis induced by ischemia in vitro model and in vivo model through activating-PI3K/Akt signal pathway which may be meaningful for further understanding the molecular mechanisms of cardiac protection of PNS.And the results might be useful in treatment of myocardial ischemia in future.

Effect of microRNA-208a on mitochondrial apoptosis of cardiomyocytes of neonatal rats

Objective: To explore the effect and mechanism of microRNA-208a(mi R-208a) in the mitochondrial apoptosis of cardiomyocytes of neonatal rats. Methods: The primary cultured cardiomyocytes of neonatal rats were added into the hypoxia incubator for the hypoxia induction. The overexpression system for mi R-208 a of cardiomyocytes of neonatal rats was built. The l ow cytometry assay was employed to detect the incidence of apoptosis in the overexpressed mi R-208 a. The mitochondrial staining technique was used to detect the change in the mitochondrial morphology of over-expressed mi R-208 a. The bioinformatic analysis was chosen to analyze and predict the target gene of mi R-208 a. Results: Firstly, the primary culture system of cardiomyocytes of neonatal rats was successfully built. The mi R-208 a was over-expressed in cardiomyocytes of neonatal rats by mi R-208 a Mimics. Results of flow cytometry assay showed that the over-expressed mi R-208 a could signii cantly reduce the incidence of apoptosis; while results of mitochondrial staining indicated the change in the mitochondrial morphology of over-expressed mi R-208 a and the mitochondrialfission process was inhibited. In conclusion, it was supposed that mi R-208 a could inhibit the activation of mitochondrialfission process to keep the cardiomyocytes from apoptosis. Conclusions: The over-expressed mi R-208 a can reduce the incidence of apoptosis in the cardiomyocytes of neonatal rats, signii cantly change the mitochondrial morphology and inhibit the mitochondrial fission process.

MiR-301a promotes embryonic stem cell differentiation to cardiomyocytes

BACKGROUND Cardiovascular disease is the leading cause of death worldwide.Tissue repair after pathological injury in the heart remains a major challenge due to the limited regenerative ability of cardiomyocytes in adults.Stem cell-derived cardiomyocytes provide a promising source for the cell transplantation-based treatment of injured hearts.AIM To explore the function and mechanisms of miR-301a in regulating cardiomyocyte differentiation of mouse embryonic stem(mES)cells,and provide experimental evidence for applying miR-301a to the cardiomyocyte differentiation induction from stem cells.METHODS mES cells with or without overexpression of miR-301a were applied for all functional assays.The hanging drop technique was applied to form embryoid bodies from mES cells.Cardiac markers including GATA-4,TBX5,MEF2C,andα-actinin were used to determine cardiomyocyte differentiation from mES cells.RESULTS High expression of miR-301a was detected in the heart from late embryonic to neonatal mice.Overexpression of miR-301a in mES cells significantly induced the expression of cardiac transcription factors,thereby promoting cardiomyocyte differentiation and beating cardiomyocyte clone formation.PTEN is a target gene of miR-301a in cardiomyocytes.PTEN-regulated PI3K-AKT-mTOR-Stat3 signaling showed involvement in regulating miR-301a-promoted cardiomyocyte differentiation from mES cells.CONCLUSION MiR-301a is capable of promoting embryonic stem cell differentiation to cardiomyocytes.

Protective role of retinoid X receptor in H9c2 cardiomyocytes from hypoxia/reoxygenation injury in rats

BACKGROUND: Retinoid X receptor(RXR) plays a central role in the regulation of intracellular receptor signaling pathways. The activation of RXR has protective effect on H2O2-induced apoptosis of H9c2 ventricular cells in rats. But the protective effect and mechanism of activating RXR in cardiomyocytes against hypoxia/reoxygenation(H/R)-induced oxidative iniury are still unclear.METHODS: The model of H/R injury was established through hypoxia for 2 hours and reoxygenation for 4 hours in H9c2 cardiomyocytes of rats. 9-cis-retinoic acid(9-cis RA) was obtained as an RXR agonist, and HX531 as an RXR antagonist. Cultured cardiomyocytes were randomly divided into four groups: sham group, H/R group, H/R+9-cis RA-pretreated group(100 nmol/L 9-cis RA), and H/R+9-cis RA+HX531-pretreated group(2.5 μmol/L HX531). The cell viability was measured by MTT, apoptosis rate of cardiomyocytes by flow cytometry analysis, and mitochondrial membrane potential(ΔΨm) by JC-1 fluorescent probe, and protein expressions of Bcl-2, Bax and cleaved caspase-9 with Western blotting. All measurement data were expressed as mean±standard deviation, and analyzed using one-way ANOVA and the Dunnett test. Differences were considered signif icant when P was <0.05.RESULTS: Pretreatment with RXR agonist enhanced cell viability, reduced apoptosis ratio, and stabled ΔΨm. Dot blotting experiments showed that under H/R stress conditions, Bcl-2 protein level decreased, while Bax and cleaved caspase-9 were increased. 9-cis RA administration before H/R stress prevented these effects, but the protective effects of activating RXR on cardiomyocytes against H/R induced oxidative injury were abolished when pretreated with RXR pan-antagonist HX531.CONCLUSION: The activation of RXR has protective effects against H/R injury in H9c2 cardiomyocytes of rats through attenuating signaling pathway of mitochondria apoptosis.

Antiapoptotic Mechanism of Insulin in Reoxygenation-induced Injury in Cultured Cardiomyocytes of Neonatal Rats

To examine the protective effect of insulin on reoxygenation-induced injury and explore the underlying mechanisms, the model of anoxia/reoxygenation （A/R） injury was established by inducing anoxia for 2 h and reoxygenation for 4 h in cultured cardiomyocytes of neonatal rats. The rats were randomized to four groups receiving vehicle, insulin, LY294002, insulin plus LY294002 at the onset of reoxygenation after 2 h of anoxia. At the end of reoxygenation of 4 h, activity of lactate dehydrogenase （LDH） and content of malondialdehyde （MDA） were spectrophotometrically determined, apoptosis of cardiomyocytes were detected by using TUNEL and DNA Ladder, and Western blotting was employed to examine the expression of phosphorylated Akt in all groups. Our results showed that compared with vehicle-treated group, activities of LDH, contents of MDA, apoptosis index （AI） were significantly decreased, and expression of phosphorylated Akt was increased significantly in insulin-treated group. However, changes in LDH, MDA, AI and phosphorylated Akt resulting from insulin were attenuated or abolished by LY294002 （PI3K inhibitor）. These data strongly suggest that early administration of insulin at reoxygenation protects cardiomyocytes from reoxygenation-induced apoptosis through PI3K/Akt signaling pathway.

Cardiac disease modeling using induced pluripotent stem cell-derived human cardiomyocytes

Causative mutations and variants associated with cardiac diseases have been found in genes encoding cardiac ion channels, accessory proteins, cytoskeletal components, junctional proteins, and signaling molecules. In most cases the functional evaluation of the genetic alterationhas been carried out by expressing the mutated proteins in in-vitro heterologous systems. While these studies have provided a wealth of functional details that have greatly enhanced the understanding of the pathological mechanisms, it has always been clear that heterologous expression of the mutant protein bears the intrinsic limitation of the lack of a proper intracellular environment and the lack of pathological remodeling. The results obtained from the application of the next generation sequencing technique to patients suffering from cardiac diseases have identified several loci, mostly in non-coding DNA regions, which still await functional analysis. The isolation and culture of human embryonic stem cells has initially provided a constant source of cells from which cardiomyocytes(CMs) can be obtained by differentiation. Furthermore, the possibility to reprogram cellular fate to a pluripotent state, has opened this process to the study of genetic diseases. Thus induced pluripotent stem cells(i PSCs) represent a completely new cellular model that overcomes the limitations of heterologous studies. Importantly, due to the possibility to keep spontaneously beating CMs in culture for several months, during which they show a certain degree of maturation/aging, this approach will also provide a system in which to address the effect of long-term expression of the mutated proteins or any other DNA mutation, in terms of electrophysiological remodeling. Moreover, since i PSC preserve the entire patients' genetic context, the system will help the physicians in identifying the most appropriate pharmacological intervention to correct the functional alteration. This article summarizes the current knowledge of cardiac genetic diseases modelled with i PSC.

Effects of Crocin on Nox2 Expression and ROS Level of Hypoxia/Reoxygenation-induced Injury of Cardiomyocytes

[Objectives]To explore the protection mechanism of crocin against ischemia-reperfusion injury of myocardial cells.[Methods]Newborn male SD rats were selected,left ventricular cardiomyocytes(CMs)were isolated,and a hypoxia/reoxygenation model of CMs was established to simulate the process of ischemia/reperfusion injury.The cells were randomly divided into four groups:normal cell group(control group),crocin group),hypoxia/reoxygenation group(H/R group),hypoxia/reoxygenation+crocin group(H/R+crocin group).H/R+crocin group selected the concentration of crocin 1,10,and 100μmol/L,and determined the optimal concentration of crocin by detecting the cell proliferation ability.After the cells were pretreated using the optimal concentration of crocin,the levels of superoxide anion,cell proliferation,apoptosis and Nox2 levels in each group of cells were detected.[Results]Compared with the control group,the proliferation ability of CMs after hypoxia-reoxygenation injury was reduced(P<0.05),while cell apoptosis and intracellular superoxide anion levels were significantly increased(P<0.01);the CMs pretreated with crocin can reduce the level of Nox2(P<0.01),increase the cell proliferation ability of CMs,reduce cell apoptosis,and accordingly reduce the level of superoxide anion in the cell(P<0.05).[Conclusions]Crocin protects CMs from hypoxia/reoxygenation injury through down-regulating the level of Nox2 and reducing oxidative stress injury.

Effects of epinephrine on angiogenesis-related gene expressions in cultured rat cardiomyocytes

Epinephrine is often used for the treatment of patients with heart failure, low cardiac output and cardiac arrest. It can acutely improve hemodynamic parameters; however, it does not seem to improve longer term clinical outcomes. Therefore, we hypothesized that epinephrine may induce unfavorable changes in gene expression of cardiomyocyte. Thus, we investigated effects of epinephrine exposure on the mediation or modulation of gene expression of cultured cardiomyocytes at a genome-wide scale. Our investigation revealed that exposure of cardiomyocytes to epinephrine in an in vitro environment can up-regulate the expression ofangiopoietin-2 gene （~ 2.1 times）, and down-regulate the gene expression of neuregulin 1 （-3.7 times）, plasminogen activator inhibitor-1 （-2.4 times） and SPARC-related modular calcium-binding protein-2 （-4.5 times）. These changes suggest that epinephrine exposure may induce inhibition of angiogenesis-related gene expressions in cultured rat cardiomyocytes. The precise clinical significance of these changes in gene expression, which was induced by epinephrine exposure, warrants further experimental and clinical investigations.

Nonhematopoietic erythropoietin derivative protects cardiomyocytes from hypoxia/reoxygenation-induced apoptosis

Objective：Carbamylated EPO（CEPO） is a derivative of erythropoietin（EPO） by subjecting it to carbamylation. It does not stimulate erythropoiesis, but effectively protects tissue from injury. The present study was to investigate the effect of CEPO treatment using in vitro models of hypoxia/reoxygenation（H/R）. Methods：Cardiomyocytes were exposed to hypoxia（95% N2 and 5% CO2） for 1 hour followed by 4 hours of reoxygenation（95% O2 and 5% CO2）. CEPO was administered after hypoxia, just before reoxygenation. The apoptotic cardiomyocytes were determined by flow cytometry. The level of protein was assessed by western blot analysis. Results： CEPO treatment significantly decreased the apoptotic cardiomyocytes by 54.20% compared with H/R group. Western blot analysis showed that CEPO administration increased the level of Bcl-2（an antiapoptotic protein） by 62.22% compared with H/R group. Conclusion： Acute administration of CEPO protected cardiomyocytes from H/R-induced apoptosis. CEPO protected cardiomyocytes with a concomitant upregulation of Bcl-2 after H/R injury.

‘Yang-Invigorating’ Chinese Tonic Herbs Enhance Mitochondrial ATP Generation in H9c2 Cardiomyocytes

‘Yang-invigorating’ Chinese tonic herbs have been shown to enhance the myocardial mitochondrial ATP generation capacity in mice ex vivo. In the present study, we examined the effect of treatment with the methanol extract of ‘Yang-invigorating’ herbs on mitochondrial ATP generation capacity in H9c2 cardio-myocytes. The effect of ‘Yin-nourishing’ herbs was also investigated for comparison. The results indicated that all ‘Yang-invigorating’ Chinese tonic herbs dose-dependently enhanced the mitochondrial ATP genera-tion capacity in H9c2 cardiomyocytes. Three out of nine ‘Yin-nourishing’ herbs produced a dose-dependent stimulatory effect on ATP generation, but to lesser extents than those of Yang herbs. Results obtained from activity-directed fractionation of the three most potent ‘Yang-invigorating’ herbs suggested that the ATP-stimulating ingredients were rather water insoluble and largely resided in the butanol fraction. In con-clusion, ‘Yang-invigorating’ herbs invariably stimulated mitochondrial ATP generation capacity in H9c2 cardiomyocytes. The cell-based assay of ATP generation capacity may be used as pharmacological test for ‘Yang-invigorating’ Chinese tonic herbs.

“Qi-Invigorating” Chinese Tonic Herbs (<i>Shens</i>) Stimulate Mitochondrial ATP Generation Capacity in H9c2 Cardiomyocytes <i>in Situ</i>and Rat Hearts <i>ex Vivo</i>

In the study, using ethanol extracts of Renshen (Panax ginseng C A Meyer), Xiyangshen (Panax quinquefolius L.) and Dangshen (Codonopsis pilosulae), we investigated the effect of these “Qi-invigorating” Chinese tonic herbs on mitochondrial ATP generation capacity (ATP-GC) in H9c2 cardiomyocytes in situ and rat hearts ex vivo. All three types of “Shens” stimulated mitochondrial ATP-GC, with Renshen being most potent. While a parallel enhancement in mitochondrial ATP-GC was observed in Renshen- and Xiyangshen-pretreated rats, Dangshen treatment did not produce detectable effect ex vivo. The discrepancy between in situ and ex vivo assays for Dangshen may be attributed by its limited oral-bioavailability to the heart. The tissue specific activity of Shens on mitochondrial ATP-GC may be explained by the “Meridian Theory” in traditional Chinese medicine.

Yiqi Huoxue Decoction attenuates ischemia/hypoxia-induced oxidative stress injury in H9c2 cardiomyocytes

Objective:Yiqi Huoxue Decoction (YQHX) has been widely used for clinical treatment of ischemic heart disease.While oxidative stress plays a key role in the pathogenesis of ischemic heart disease,the function and molecular mechanism underlying antioxidative protective effects of YQHX on H9c2 cardiomyocytes against ischemia/hypoxia (I/H) have yet to be well clarified.Methods:H9c2 cells were subjected to 12 h of hypoxia with serum-free conditions and then treated with or without YQHX (100-400 μg/mL).Cell viability was examined using a CCK-8 assay.Maleic dialdehyde (MDA) and superoxide dismutase (SOD) activity were detected using commercial kits.Intracellular reactive oxygen species (ROS) levels and mitochondrial membrane potential were measured using fluorescence microscopy and confocal laser-scanning microscopy,respectively.Ultrastructural details of mitochondria in H9c2 cells were observed using transmission electron microscopy.The antioxidative protective pathway was assessed by measuring mRNA and protein expression of Nrf2 and HO-1,as well as AMPK activation.Results:I/H injury gradually induced oxidative stress.Treatment with YQHX significantly increased cell viability and reversed I/H-induced oxidative stress,including reducing the production of oxidative stress products (ROS and MDA),increasing SOD levels,improving mitochondrial morphology,and increasing mitochondrial membrane potential.YQHX was also observed to increase I/H-induced expression of Nrf2 and HO-1,and the activation effects of YQHX were blocked by an AMPK inhibitor.In addition,HPLC analysis showed that YQHX contained two active antioxidative constituents (calycosin and ferulic acid).Conclusion:The results suggest that anti-oxidative effects exerted by YQHX in H9c2 cardiomyocytes may be linked to upregulation of the AMPK-mediated Nrf2/HO-1 pathway.

β3-adrenoceptor Impacts Apoptosis in Cultured Cardiomyocytes via Activation of PI3K/Akt and p38MAPK

β3-adrenoceptor（β3-AR） has been shown to promote myocardial apoptosis. However, the exact physiological role and importance of this receptor in the human myocardium, and its underlying mode of action, have not been fully elucidated. The present study aimed to determine the effects of β3-AR on the promotion of myocardial apoptosis and on norepinephrine（NE） injury. We analyzed NE-induced cardiomyocyte（CM） apoptosis by using a TUNEL and an annexin V/propidium iodide apoptosis assay. Furthermore, we investigated the NE-induced expression of the apoptosis marker genes Akt and p38 MAPK, their phosphorylated counterparts p-Akt and p-p38 MAPK, caspase-3, Bcl-2, and Bax. In addition, we determined the effect of a 48-h treatment with a β3-AR agonist and antagonist on expression of these marker genes. β3-AR overexpression was found to increase CM apoptosis, accompanied by an increased expression of caspase-3, bax/bcl-2, and p-p38 MAPK. In contrast, the β3-blocker reduced apoptosis of CMs and the associated elevated Akt expression. We identified a novel and potent anti-apoptosis mechanism via the PI3K/Akt pathway and a pro-apoptosis pathway mediated by p38 MAPK.

Ginkgolide K protects cardiomyocytes against ER stress through stimulating ER-associated degradation （ERAD） and autophagy

Aim Endoplasmic reticulum （ER） stress is increasingly recognized as an important contributor to the pathophysiology of many diseases, and therapeutic interventions that target ER stress response emerge as new thera- peutic modalities to treat cardiovascular diseases driven by prolonged ER stress. Ginkgolides K （GK） is a diterpene lactone constituent isolated from the leaves of Ginkgo biloba and has been found to possess potent neuroprotective properties. This study is aimed to investigate the cytoprotective effect of GK in cultured cardiomyocytes subjected to ER stress injury. Neonatal rat cardiomyocytes （NRCMs） were treated with ER stress inducer tunicamycin to mimic the ER stress injury. We demonstrated that GK pre-treatment mitigated ER stress-induced apoptosis in tunicamycin treated NRCMs. We observed that the activation of ER-associated degradation （ERAD） and autophagy were in- volved in the ER stress inhibition exerted by GK. These beneficial effects of GK were nearly abolished by the addi- tion of specific short interfering RNA （siRNA） for IRElα and XBP-1. Therefore, we conclude that GK might be a promising therapeutic agent for ER stress-mediated cardiovascular diseases, and ER-associated degradation （ERAD） and autophagy play a vital role in GK mediated cytoprotection.