Gamma-aminobutyric acid enhances miR-21-5p loading into adipose-derived stem cell extracellular vesicles to alleviate myocardial ischemia-reperfusion injury via TXNIP regulation

BACKGROUND Myocardial ischemia-reperfusion injury(MIRI)poses a prevalent challenge in current reperfusion therapies,with an absence of efficacious interventions to address the underlying causes.AIM To investigate whether the extracellular vesicles(EVs)secreted by adipose mesenchymal stem cells(ADSCs)derived from subcutaneous inguinal adipose tissue(IAT)underγ-aminobutyric acid(GABA)induction(GABA-EVs^(IAT))demonstrate a more pronounced inhibitory effect on mitochondrial oxidative stress and elucidate the underlying mechanisms.METHODS We investigated the potential protective effects of EVs derived from mouse ADSCs pretreated with GABA.We assessed cardiomyocyte injury using terminal deoxynucleotidyl transferase dUTP nick end-labeling and Annexin V/propidium iodide assays.The integrity of cardiomyocyte mitochondria morphology was assessed using electron microscopy across various intervention backgrounds.To explore the functional RNA diversity between EVs^(IAT)and GABA-EVs^(IAT),we employed microRNA(miR)sequencing.Through a dual-luciferase reporter assay,we confirmed the molecular mechanism by which EVs mediate thioredoxin-interacting protein(TXNIP).Western blotting and immunofluorescence were conducted to determine how TXNIP is involved in mediation of oxidative stress and mitochondrial dysfunction.RESULTS Our study demonstrates that,under the influence of GABA,ADSCs exhibit an increased capacity to encapsulate a higher abundance of miR-21-5p within EVs.Consequently,this leads to a more pronounced inhibitory effect on mitochondrial oxidative stress compared to EVs from ADSCs without GABA intervention,ultimately resulting in myocardial protection.On a molecular mechanism level,EVs regulate the expression of TXNIP and mitigating excessive oxidative stress in mitochondria during MIRI process to rescue cardiomyocytes.CONCLUSION Administration of GABA leads to the specific loading of miR-21-5p into EVs by ADSCs,thereby regulating the expression of TXNIP.The EVs derived from ADSCs treated with GABA effectively ameliorates mitochondrial oxidative stress and mitigates cardiomyocytes damage in the pathological process of MIRI.

Preliminary study on the protective effect of electroacupuncture Neiguan acupoint pretreatment on rats with myocardial ischemia-reperfusion injury:role of the miR-214-3p/NCX1 axis

Background:Ischemia-reperfusion can worsen myocardial damage and increase the risk of death.Studies have revealed that ischemic preconditioning provides the best endogenous protection against myocardial ischemia-reperfusion injury(MIRI),and the principle of electroacupuncture(EA)preconditioning is comparable to that of myocardial ischemic preconditioning adaption.Our earlier research demonstrated that EA pretreatment inhibits the expression of calmodulin-dependent protein kinase IIδ(CaMKIIδ),sodium/calcium exchanger 1(NCX1),and cyclophilin D,hence providing protection against MIRI.However,the exact mechanism is still unknown.The expression of NCX1 mRNA is directly regulated by microRNA-214(miR-214).Moreover,it suppresses the levels of CaMKIIδand cyclophilin D.Whether these variables contribute to EA preconditioning to improve MIRI needs to be investigated,though.This study aimed to preliminarily determine whether EA pretreatment ameliorates MIRI by modulating the miR-214-3p/NCX1 axis.Methods:We used a rat MIRI model to investigate the effect of EA pretreatment on MIRI and the expression of miR-214-3p.In addition,adenovirus injection inhibited miR-214-3p expression in the rat MIRI model,and the influence of EA pretreatment towards MIRI was observed in the context of blocked miR-214-3p expression.Both the myocardial histological abnormalities and the alterations in the ST segment of the rat electrocardiogram were analyzed.NCX1 mRNA,cyclophilin D,and CaMKIIδexpression levels were also analyzed.Results:EA pretreatment improved MIRI.In rats with MIRI,EA administration increased miR-214-3p expression while decreasing NCX1 mRNA,cyclophilin D,and CaMKIIδproteins in cardiac tissues.The beneficial effect of EA pretreatment against MIRI was reversed,coupled with elevated levels of NCX1 mRNA,cyclophilin D,and CaMKIIδprotein expression,when an adenovirus injection disrupted the expression of miR-214-3p.Conclusions:Our findings preliminarily show that EA pretreatment inhibits the expression of NCX1 mRNA,cyclophilin D,and CaMKIIδproteins via miR-214-3p,hence exerting MIRI protection.

Protective Effect of Naringenin on Acute Myocardial Ischemia-reperfusion Injury in Rats

[Objectives]To investigate the protective mechanism of naringenin on acute myocardial ischemia-reperfusion injury(AMI-RI)in Sprague-Dawley(SD)rats.[Methods]A total of 32 SD rats with AMI-RI model construction were randomly divided into AMI-RI model control group and citrus pigment A/B/C groups(n=8).The naringenin A,B,and C groups were administrated 20,40 and 80 mg/(kg•d)for 10 d.The AMI group served as the negative control and was not treated.At the conclusion of the treatment regimen,a sample of intraventricular blood was collected for the purpose of measuring lactate dehydrogenase(LDH),glutathione peroxidase(GLH-PX),nitric oxide(NO),and superoxide dismutase(SOD)levels.Additionally,myocardial tissue was identified within the ischemic region.The content of malondialdehyde(MDA)was determined by inducing nitric oxide synthase(iNOS)and endodermal nitric oxide synthase(eNOS)positive cells in the left anterior descending coronary artery.[Results]Following citrus treatment,the contents of GLH-PX and SOD in ventricular blood of the citrus B group were found to be significantly elevated,while the contents of NO and LDH in myocardial MDA and ventricle were observed to be significantly reduced.The number of eNOS-positive cells was significantly increased,while the number of iNOS-positive cells was significantly decreased.The difference was statistically significant when compared with the AMI-RI group(P<0.05).The changes observed in the above indicators in the citrus C group were more pronounced than those observed in the citrus B group.The difference between the citrus C and the B group was statistically significant(P<0.05),indicating that this effect is concentration dependent.[Conclusions]In addition to its ability to inhibit myocardial lipid peroxidation during AMI-RI by increasing SOD activity,naringenin may also affect the synthesis and release of NO by regulating eNOS and iNOS,thereby achieving protection against AMI-RI.One effect is enhanced as the dose of the drug increases.

Inhibition of SLC26A4 regulated by electroacupuncture suppresses the progression of myocardial ischemia-reperfusion injury

Introduction:Myocardial ischemia-reperfusion(IR)injury has received widespread attention due to its damaging effects.Electroacupuncture(EA)pretreatment has preventive effects on myocardial IR injury.SLC26A4 is a Na+independent anion reverse transporter and has not been reported in myocardial IR injury.Objectives:Tofind potential genes that may be regulated by EA and explore the role of this gene in myocardial IR injury.Methods:RNA sequencing and bioinformatics analysis were performed to obtain the differentially expressed genes in the myocardial tissue of IR rats with EA pretreatment.Myocardial infarction size was detected by TTC staining.Serum CK,creatinine kinase-myocardial band,Cardiac troponin I,and lactate dehydrogenase levels were determined by ELISA.The effect of SLC26A4 on cardiomyocyte apoptosis was explored by TUNEL staining and western blotting.The effects of SLC26A4 on inflammation were determined by HE staining,ELISA,and real-time PCR.The effect of SLC26A4 on the NF-κB pathway was determined by western blotting.Results:SLC26A4 was up-regulated in IR rats but downregulated in IR rats with EA pretreatment.Compared with IR rats,those with SLC26A4 knockdown exhibited improved cardiac function according to decreased myocardial infarction size,reduced serum LDH/CK/CK-MB/cTnI levels,and elevated left ventricular ejection fraction and fractional shortening.SLC26A4 silencing inhibited myocardial inflammation,cell apoptosis,phosphorylation,and nuclear translocation of NF-κB p65.Conclusion:SLC26A4 exhibited promoting effects on myocardial IR injury,while the SLC26A4 knockdown had an inhibitory effect on the NF-κB pathway.These results further unveil the role of SLC26A4 in IR injury.

Long non-coding RNA-AK138945 regulates myocardial ischemia-reperfusion injury via the miR-1-GRP94 signaling pathway

Objective:Myocardial ischemia-reperfusion injury(MIRI)is one of the leading causes of death from cardiovascular disease in humans,especially in individuals exposed to cold environments.Long non-coding RNAs(lncRNAs)regulate MIRI through multiple mechanisms.This study explored the regulatory effect of lncRNA-AK138945 on myocardial ischemia-reperfusion injury and its mechanism.Methods:In vivo,8-to 12-weeks-old C57BL/6 male mice underwent ligation of the left anterior descending coronary artery for 50 minutes followed by reperfusion for 48 hours.In vitro,the primary cultured neonatal mouse ventricular cardiomyocytes(NMVCs)were treated with 100μmol/L hydrogen peroxide(H_(2)O_(2)).The knockdown of lncRNA-AK138945 was evaluated to detect cardiomyocyte apoptosis,and a glucose-regulated,endoplasmic reticulum stress-related protein 94(GRP94)inhibitor was used to detect myocardial injury.Results:We found that the expression level of lncRNA-AK138945 was reduced in MIRI mouse heart tissue and H2O2-treated cardiomyocytes.Moreover,the proportion of apoptosis in cardiomyocytes increased after lncRNA-AK138945 was silenced.The expression level of Bcl2 protein was decreased,and the expression level of Bad,Caspase 9 and Caspase 3 protein was increased.Our further study found that miR-1a-3p is a direct target of lncRNA-AK138945,after lncRNA-AK138945 was silenced in cardiomyocytes,the expression level of miR-1a-3p was increased while the expression level of its downstream protein GRP94 was decreased.Interestingly,treatment with a GRP94 inhibitor(PU-WS13)intensified H2O2-induced cardiomyocyte apoptosis.After overexpression of FOXO3,the expression levels of lncRNA-AK138945 and GRP94 were increased,while the expression levels of miR-1a-3p were decreased.Conclusion:LncRNA-AK138945 inhibits GRP94 expression by regulating miR-1a-3p,leading to cardiomyocyte apoptosis.The transcription factor Forkhead Box Protein O3(FOXO3)participates in cardiomyocyte apoptosis induced by endoplasmic reticulum stress through up-regulation of lncRNA-AK138945.

Liqi Huoxue dripping pill protects against myocardial ischemia-reperfusion injury via the PI3K/Akt/GSK-3β signaling pathway in rats

Background:Liqi Huoxue dripping pill(LQHXDP),a traditional Chinese drug for coronary heart disease,has a protective effect on the heart of rats with myocardial ischemia-reperfusion injury(MIRI)in previous studies;however,its mechanism of action remains unclear.The purpose of this study was to investigate the protective mechanism of LQHXDP on MIRI in rats and its relationship with the PI3K/Akt signaling pathway.Methods:In this study,Sprague-Dawley rats were pre-infused with LQHXDP(175 mg/kg/d)for 10 days.PI3K inhibitor LY294002(0.3 mg/kg)was intravenously injected 15 minutes before ischemia.The rat model of MIRI was established by ligating the left anterior descending coronary artery.Subsequently,cardiac hemodynamics,serum myocardial injury markers,inflammatory factors,myocardial infarct size,antioxidant indexes,myocardial histopathology,and phosphorylation levels of key proteins of PI3K/Akt signaling pathway were assessed in rats.Results:LQHXDP was found to improve cardiac hemodynamic indexes,reduce serum creatine kinase MB isoenzyme activity and cardiac troponin and heart-type fatty acid binding protein levels,lower serum interleukin-1 beta,interleukin-6 and tumour necrosis factorαlevels,reduce the myocardial infarct size and enhance the antioxidant capacity of myocardial tissue in MIRI rats.Pathological analysis revealed that LQHXDP attenuated the extent of myocardial injury and protected mitochondria from damage in MIRI rats.Immunoblot analysis revealed that LQHXDP increased the expression levels of p-Akt and p-GSK-3βin MIRI rat cardiomyocytes.PI3K inhibitor LY294002 could impair these effects of LQHXDP.Conclusion:LQHXDP attenuated myocardial injury,attenuated oxidative stress injury and reduced inflammatory response in MIRI rats,and its protective effects were mediated by activating of PI3K/Akt/GSK-3βsignaling pathway.

Effect of Minocycline Postconditioning and Ischemic Postconditioning on Myocardial Ischemia-reperfusion Injury in Atherosclerosis Rabbits

This study examined the protective effect of ischemic postconditioning(IPoC) and minocycline postconditioning(MT) on myocardial ischemia-reperfusion(I/R) injury in atherosclerosis(AS) animals and the possible mechanism.Forty male healthy rabbits were injected with bovine serum albumin following feeding on a high fat diet for 6 weeks to establish AS model.AS rabbits were randomly divided into 3 groups:(1) I/R group,the rabbits were subjected to myocardial ischemia for 35 min and then reperfusion for 12 h;(2) IPoC group,the myocardial ischemia lasted for 35 min,and then reperfusion for 20 s and ischemia for 20 s [a total of 3 cycles(R20s/I20s×3)],and then reperfusion was sustained for 12 h;(3) MT group,minocycline was intravenously injected 10 min before reperfusion.The blood lipids,malondialdehyde(MDA),superoxide dismutase(SOD),soluble cell adhesion molecule(sICAM),myeloperoxidase(MPO),and cardiac troponin T(cTnT) were biochemically determined.The myocardial infarction size(IS) and apoptosis index(AI) were measured by pathological examination.The expression of bcl-2 and caspase-3 was detected in the myocardial tissue by using reverse transcription-polymerase chain reaction(RT-PCR).The results showed that the AS models were successfully established.The myocardial IS,the plasma levels of MDA,sICAM,MPO and cTnT,and the enzymatic activity of MPO were significantly decreased,and the plasma SOD activity was significantly increased in IPoC group and MT group as compared with I/R group(P<0.05 for all).The myocardial AI and the caspase-3 mRNA expression were lower and the bcl-2 mRNA expression was higher in IPoC and MT groups than those in I/R group(all P<0.05).It is concluded that the IPoC and MT can effectively reduce the I/R injury in the AS rabbits,and the mechanisms involved anti-oxidation,anti-inflammation,up-regulation of bcl-2 expression and down-regulation of caspase-3 expression.Minocycline can be used as an effective pharmacologic postconditioning drug to protect myocardia from I/R injury.

Improved methodology for efficient establishment of the myocardial ischemia-reperfusion model in pigs through the median thoracic incision

To investigate the feasibility and effectiveness of establishing porcine ischemia-reperfusion models by ligating the left anterior descending(LAD)coronary artery,we first randomly divided 16 male Bama pigs into a sham group and a model group.After anesthesia,we separated the arteries and veins.Subsequently,we rapidly located the LAD coronary artery at the beginning of its first diagonal branch through a mid-chest incision.Then,we loosened and released the ligation line after five minutes of pre-occlusion.Finally,we ligated the LAD coronary artery in situ two minutes later and loosened the ligature 60 min after ischemia.Compared with the sham group,electrocardiogram showed multiple continuous lead ST-segment elevations,and ultrasound cardiogram showed significantly lower ejection fraction and left ventricular fractional shortening at one hour and seven days post-operation in the model group.Twenty-four hours after the operation,cardiac troponin T and creatine kinase-MB isoenzyme levels significantly increased in the model group,compared with the sham group.Hematoxylin and eosin staining showed the presence of many inflammatory cells infiltrating the interstitium of the myocardium in the model group but not in the sham group.Masson staining revealed a significant increase in infarct size in the ischemia/reperfusion group.All eight pigs in the model group recovered with normal sinus heart rates,and the survival rate was 100%.In conclusion,the method can provide an accurate and stable large animal model for preclinical research on ischemia/reperfusion with a high success rate and homogeneity of the myocardial infarction area.

The therapeutic effect of Jiawei Danshen Decoction on myocardial ischemia-reperfusion injury by inhibiting H_(2)S-mediated autophagy signaling pathway

Objective To investigate the protective effects of Jiawei Danshen Decoction(加味丹参饮,JWDSD)on myocardial ischemia-reperfusion injury(MIRI)via the regulation of serum Hydrogen sulfide(H2S)and cardiac Beclin1,light Chain 3 A/B(LC3 A/B),p62,and autophagy protein5(ATG5).Methods Seventy specific pathogen free(SPF)Sprague-Dawley(SD)rats were randomly assigned to seven groups(n=10 in each group),including normal control,sham operation,MIRI model(model),ischemic preconditioning,Na HS,JWDSD,and JWDSD+CSE inhibitor(JWDSD+PPG)groups,and orally administered the indicated drugs for 14 d.Two hours after the last administration,the left anterior decreased branch of the coronary artery of each rat in model,Na HS,JWDSD,and JWDSD+PPG groups was ligated for 30 min and subsequently reperfused for 90 min to establish the MIRI model,and the rats in the sham operation group were only exposed to the thorax after surgery without coronary ligation.Blood samples were collected to detect H2S levels using an enzyme-linked immunosorbent assay(ELISA).Heart tissues were harvested for histopathological and immunohistochemical examination and quantitative reverse transcription polymerase chain reaction analysis of Beclin1 and ATG5 m RNA expression and Western blot analysis of Beclin1,LC3 A/B,and p62 protein expression.Results(1)The serum H2S content in model group rats was significantly reduced(P<0.01),JWDSD significantly increased the serum H2S content of model group rats(P<0.01),and the CSE inhibitor(PPG)significantly reduced H2S levels in the JWDSD group rats(P<0.01).(2)Compared with the normal control group,the myocardial tissue necrosis and cell destruction occurred in the MIRI model group,and JWDSD could alleviate the myocardial tissue necrosis of model rats,but the ameliorative effect of JWDSD could be reversed by PPG.(3)Beclin1,LC3 A/B,and p62 expression levels in the heart tissues of the model group were significantly increased(P<0.001),whereas decreased by JWDSD(P<0.05,P<0.01,and P<0.001,respectively),and the inhibitory effects of JWDSD on Beclin1,LC3 A/B,and p62 expression were partially reversed by PPG(P<0.01,P<0.05,and P<0.01,respectively).(4)The expression levels of autophagy-related genes Beclin1 and ATG5 were significantly increased in the model group(P<0.001).JWDSD clearly downregulated the expression levels of Beclin1 and ATG5(P<0.05 and P<0.001,respectively),which were reversed by PPG(P<0.001).Conclusion Our experimental data show that JWDSD can exhibit an anti-MIRI role by increasing endogenous H2S generation,and downregulating the expression of Beclin1,LC3 A/B,p62 and ATG5,which are related to inhibiting autophagy signaling.

Experimental study of miRNA-210 modified MSCs in the treatment of myocardial ischemia-reperfusion injury in rats

Objective:To investigate the therapeutic effect of microRNA210(miRNA-210)modified mesenchymal stem cells(MSCs)on myocardial ischemia-reperfusion injury(MIRI)model rats.Methods:One SD rat was sacrificed,and the lower extremity tibia and femur were isolated.MSCs were cultured by whole bone marrow adherence method to construct miRNA-210 modified MSCs.40 SD rats were divided into the sham operation group,model group,MSCs group,and miRNA-210+MSCs group,with 10 rats in each group.The left anterior descending coronary artery was ligated to prepare a model of myocardial ischemia and reperfusion.After successful modeling,50μl of MSCs suspension was injected into the tail vein of the MSCs group,and 50μl of miRNA-210 modified MSCs suspension was injected into the tail vein of the miRNA-210+MSCs group.The sham operation group and the model group were injected with the same amount of normal saline.On the 10th day after modeling,the area of myocardial infarction,morphological changes of myocardial tissue,myocardial cell apoptosis rate,and miRNA-210 expression were compared in each group.Results:The area of myocardial infarction and the rate of myocardial cell apoptosis in the model group were significantly higher than those in the sham operation group(<0.05);The area of myocardial infarction and the rate of myocardial cell apoptosis in the MSCs group were significantly lower than those in the sham operation group(P<0.05);The area of myocardial infarction and the rate of myocardial cell apoptosis in the miRNA-210+MSCs group were significantly higher than those in the MSCs group(P<0.05);The area of myocardial infarction and the rate of myocardial cell apoptosis in the miRNA-210+MSCs group were significantly lower than those in the sham operation group(P<0.05).The expression level of miRNA-210 in the myocardial tissue of the model group was significantly higher than that in the sham operation group(P<0.05);There were no significantly different in the expression level of miRNA-210 in the myocardial tissue between the MSCs group and model group(P>0.05);The expression level of miRNA-210 in the myocardial tissue of MSCs group was significantly higher than in the MSCs group,model group and sham operation group(P<0.05).HE staining showed that the miRNA-210+MSCs group had normal morphology of myocardial tissues,more uniform cytoplasmic staining,and arranged neatly myocardial fibers.The inflammatory cell infiltration and interstitial edema of the miRNA-210+MSCs group were significantly improved compared with the model group and MSCs group.Conclusion:MiRNA-210 modified MSCs can inhibit myocardial cell apoptosis in myocardial ischemia-reperfusion injury model rats,reduce the area of myocardial infarction,and improve pathological damage of myocardial tissue in rats,which has a certain therapeutic effect on myocardial ischemia-reperfusion injury.

Effect of salvianolic acid B-loaded mesoporous silica nanoparticles on myocardial ischemia-reperfusion injury

Background:Currently,no drugs can specifically improve clinical cardiac ischemia-reperfusion injury or the prognosis of hemodialysis.Salvianolic acid B(SalB)is a widely used cardiac protectant;however,its clinical application is limited by its low oral bioavailability and poor intestinal absorption.The exploration of its preparation and clinical applications has become a research hotspot in recent years.Methods:To determine whether mesoporous silica nanoparticles(MSNs)efficiently delivered SalB to the heart and SalB@MSNs-RhB reduced myocardial ischemia-reperfusion injury,we constructed a myocardial ischemia-reperfusion male rat model,hypoxia/reoxygenation cardiomyocytes,and treated them with SalB@MSNs-RhB.Results:SalB@MSNs-RhB showed improved bioavailability,therapeutic effect,heightened JAK2/STAT3-dependent pro-survival signaling,and antioxidant responses,thereby protecting cardiomyocytes from ischemia-reperfusion injury-induced oxidative stress and apoptosis.Conclusion:This use of SalB-loaded nanoparticles and investigation of their mechanism of action may provide a new strategy for treating cardiomyocytes.Thus,hypoxia/reoxygenation promotes the clinical application of SalB.

Atorvastatin Alleviates Myocardial Ischemia-Reperfusion Injury via miR-26a-5p/FOXO1

Purpose: Ischemia-reperfusion (I/R) injury exacerbates myocardial cell death (including apoptosis and necrosis), leading to complications such as arrhythmias, myocardial stenosis, microvascular obstruction and heart failure, and it is particularly important to seek new strategies to mitigate reperfusion injury. In this paper, we will investigate whether atorvastatin can alleviate myocardial ischemia-reperfusion injury and verify its molecular mechanism. Methods: We successfully constructed a hypoxia-reperfusion (H/R) H9c2 cell model and transfected miR-26a-5p mimic, miR-26a-5p inhibitor and its negative control NC-mimic or NC-inhibitor into H9c2 cells using a transfection kit. The expression of miR-26a-5p and FOXO1 were detected by RT-qPCR assay, the expression of related proteins by Western blot assay, the cell viability of H9c2 cells by CCK-8 assay, the apoptosis rate of H9c2 cells by flow cytometry, the CK and LDH activity in cells by CK and LDH assay kits. The targeting relationship between miR-26a-5p and FOXO1 was verified by dual luciferase reporter gene assay. Results: MiR-26a-5p expression was decreased in H/R-induced cells and FOXO1 expression was increased in H/R-induced cells. Atorvastatin alleviated H/R injury in cardiomyocytes and was most effective at a concentration of 1 μM. Atorvastatin alleviated H/R injury in cardiomyocytes by upregulating miR-26a-5p expression, miR-26a-5p and FOXO1 were negatively regulated by targeting. Conclusion: Atorvastatin can alleviate H/R injury in cardiomyocytes by regulating miR-26a-5p/FOXO1.

Myocardial ischemia-reperfusion injury:Possible role of melatonin

Our knowledge and understanding of the pathophysiology of coronary atherosclerosis has increased enormously over the last 20 years.Reperfusion through thrombolysis or percutaneous coronary angioplasty is the standard treatment for preventing acute myocardial infarction.Early reperfusion is an absolute prerequisite for survival of the ischemic myocardium,but reperfusion itself may lead to accelerated and additional myocardial injury beyond that generated by ischemia alone.These outcomes,in a range of reperfusion-associated pathologies,are collectively termed "reperfusion injuries".Reactive oxygen species are known to be produced in large quantities in the first few minutes of the post-ischemia reperfusion process.Similarly,scientific evidence from the last 15 years has suggested that melatonin has beneficial effects on the cardiovascular system.The presence of vascular melatoninergic receptor binding sites has been demonstrated;these receptors are functionally linked to vasoconstrictor or vasodilatory effects of melatonin.It has been shown that patients with coronary heart disease have a low melatonin production rate,especially those with higher risk of cardiac infarction and/or sudden death.Melatonin attenuates molecular and cellular damage resulting from cardiac ischemia-reperfusion in which destructive free radicals are involved.

The role and modulation of autophagy in experimental models of myocardial ischemia-reperfusion injury

A physiological sequence called autophagy qualitatively determines cellular viability by removing protein aggregates and damaged cyto-plasmic constituents, and contributes significantly to the degree of myocardial ischemia-reperfusion （I/R） injury. This tightly orchestrated cata-bolic cellular‘housekeeping’ process provides cells with a new source of energy to adapt to stressful conditions. This process was first described as a pro-survival mechanism, but increasing evidence suggests that it can also lead to the demise of the cell. Autophagy has been implicated in the pathogenesis of multiple cardiac conditions including myocardial I/R injury. However, a debate persists as to whether autophagy acts as a protec-tive mechanism or contributes to the injurious effects of I/R injury in the heart. This controversy may stem from several factors including the va-riability in the experimental models and species, and the methodology used to assess autophagy. This review provides updated knowledge on the modulation and role of autophagy in isolated cardiac cells subjected to I/R, and the growing interest towards manipulating autophagy to increase the survival of cardiac myocytes under conditions of stress-most notably being I/R injury. Perturbation of this evolutionarily conserved intracellular cleansing autophagy mechanism, by targeted modulation through, among others, mammalian target of rapamycin （mTOR） inhibitors, adenosine monophosphate-activated protein kinase （AMPK） modulators, calcium lowering agents, resveratrol, longevinex, sirtuin activators, the proapoptotic gene Bnip3, IP3 and lysosome inhibitors, may confer resistance to heart cells against I/R induced cell death. Thus, therapeutic ma-nipulation of autophagy in the challenged myocardium may benefit post-infarction cardiac healing and remodeling.

Effect of rosiglitazone on rabbit model of myocardial ischemia-reperfusion injury

To explore mechanism and protective effect of rosiglitazone on myocardial ischemia reperfusion(I/R) injury.Methods:A total of 48 male Japanese white big-ear rabbits were randomly divided into control group(A),I/R group(B),low dose of rosiglitazone group(C),high dose of rosiglitazone group(D).Plasma concentration of and also reduced the concentration of plasma serum creatine kinase(CK),CK-MB.high-sensitivity C-reactive protein(hsCRP).ultrasuperoxide dismutase(SOD),malondialdehyde(MD.A).lactic acid glutathione skin peroxidase (C-SH-PX).nitric oxide(NO)and endothelin(ET) were measured 1 h later after I/R.Twenty-four hours after I/R the hearts were harvested for pathological and ultrastructural analysis.Area of myocardial infarction were tested.Results:Plasma concentration of CK,Ck-MB.hsCRP,NO. MDA and ET were decreased in C,D group compared with group B.Plasma concentration of T-SOD and GSH-Px were increased significantly in C.D group compared with group B.Compared with group B.pathological and ullraslructural changes in C and D group were slightly.There was significant difference in myocardial infarction area between group C.D and group B(P【0.05). Myocardial infarction area and arrhythmia rate were lower in group C,D compare with group B. Rosiglitazone may protect myocardium from I/R injury by enhancing T-SOD and GSH-Px concentration,inhibit inflammatory reaction,and improve endothelial function.

Protective effect and mechanism of lithium chloride pretreatment on myocardial ischemia-reperfusion injury in rats

Objective:To investigate the protective effect and mechanism of lithium chloride pretreatment on myocardial ischemia-reperfusion injury(I-RI)in rats.Methods:A total of 60 SD rats were randomly divided into control group,model group,lithium chloride intervention group and L-arginine methyl ester+lithium chloride intervention group with 15 in each.The I-RI model was established in model group,the Utliium chloride intervention group and L-arginine methyl ester+lithium chloride intervention group by method of seaming along left anterior descending coronary artery myocardial,control group was only opened the chest without seaming,STelevation within 2 min was regarded as modeling success.Model group did not adopted any intervention,lithium chloride intervention group was treated with lithium chloride injection15 mg/kg by jugular venipuncture preoperatively,L-arginine methyl ester+lithium chloride intervention group was treated with intraperitoneal injection of 30mg·kg～(-1)·d～(-1)(L—arginine methyl ester 7 d before the test,and intravenous catheter of 15 mg/kg lithium chloride preoperatively.The hydroxybulyric acid dehydrogenase(HBDH),creatine kinase isoenzyme(CK-MB),superoxide dismutase(SOD),malondialdehyde(MDA)level and nitric oxide synthase(NOS)activites were tested.Each large area of myocardial ischemia tissue was extracted for determination of the MDA content,SOD activity in tissue and serum,and morphological changes of myocardial tissue.Results:SOD activity was highest in lithium chloride intervention group,followed by L-arginine methyl ester+lithium chloride intervention group,control group and model group(P<0.05);SOD activity was highest in L-arginine methyl ester+lithium chloride intervention group intervention group,followed by lithium chloride intervention group,control group and model group(P<0.05).MDA content of myocardial tissue was highest in model group,followed by L-arginine methyl ester+lithium chloride intervention group,the lithium chloride intervention group and control group(P<0.05);serum MDA content was highest in L-arginine methyl ester+lithium chloride intervention group,followed by model group,lithium chloride intervention group and control group(P<0.05).Compared with the control group,serum NOS was significantly higher in model group,lithium chloride intervention group and L-arginine methyl ester+lithium chloride intervention group(P<0.05),there was no statistical difference of serum NOS activity between the three groups(P>0.05);HBDH and CK-MB of plasma were highest in model group,followed by L-arginine methyl ester+lithium chloride intervention group,lithium chloride intervention group and control group(P<0.05).A significantly lighter myocardial damage was observed microscopically in lithium chloride intervention group than that in L-arginine methyl ester+lithium chloride intervention group and model group.Conclusions:lithium chloride pretreatment can significandy reduce the myocardial I-RI,maintain structure and function of myocardial cells,improve the antioxidant ability of myocardial tissue,play an effective role on protecting myocardial I-RI.

Effect of shenfu injection on gastrointestinal microcirculation in rabbits after myocardial ischemia-reperfusion injury

AIM： To investigate the effect of shenfu injection on gastrointestinal microcirculation after myocardial ischemic-reperfusion （IR） injury in rabbits and probe into the mechanism. METHODS： Forty healthy flap-eared white rabbits were randomly divided into 4 groups： IR injury control group （group Ⅰ ）, shenfu injection 5 mL/kg per h group （group Ⅱ）, shenfu injection 10 mL/kg per h group （group Ⅲ） and shenfu injection 20 mL/kg per h group （group Ⅳ）. The four groups were treated with Lactated Ringer＇s solution, shenfu injection 5, 10, and 20 mL/ kg per h were infused intravenously 30 min before experiment respectively. The values of hemodynamics [mean arterial pressure （MAP）, heart rate （HR）, gastric intramucosal partial pressure of carbon dioxide （PCO2）, blood gas analysis and pH] were measured and compared with those before myocardial ischemia, 60 min after myocardial ischemia and 60, 90, and 180 rain after reperfusion. RESULTS： The MAP, HR and gastric intramucosal pH were （70.50 ± 4.50） kPa, （165 ± 14） beats per rain, 7.032 ± 0.024 in group Ⅰ 60 min after myocardial ischemia, which were significantly decreased compared with those before myocardial ischemia （88.50 ± 9.75 kPa, 217 ± 18 beats per rain, 7.112 ± 0.035, P 〈 0.05）. The MAP, HR and gastric intramucosal pH were significantly decreased in group Ⅰ 60, 90, and 180 min after reperfusion （61.50 ± 5.25 kPa, 133 ± 31 beats per rain, 6.997 ± 0.025） compared with those before reperfusion respectively （P 〈 0.05）, whereas the values were insignificantly different in groups Ⅱ, Ⅲ or Ⅳ after reperfusion, compared with those before reperfusion, and there were no significant differences between groups Ⅱ, Ⅲ, and Ⅳ after reperfusion. CONCLUSION： Pre-infusion of shenfu injection has a protective effect on gastrointestinal microcirculation after myocardial IR injury in rabbits, in a dose independent manner.

Protective effects of bifunctional platelet GPIIIa49-66 ligand on myocardial ischemia-reperfusion injury in rats

Current antiplatelet drugs mainly focus on prevention rather than the more clinically relevant issue of clearance of an existing thrombus. We recently described a novel and effective therapeutic strategy for dissolution of preexisting platelet thrombus in a murine ischemic stroke model with a bifunctional platelet GPIIIa49-66 ligand (Single-chain antibody Linked first Kringle 1 of plasminogen, named SLK), which homes to newly deposited fibrin strands tangled of platelet thrombus and induces aggregated platelet fragmentation. In this study, we perform in-depth analysis of the effect of SLK on myocardial ischemia-reperfusion (IR) injury in rats. We show that SLK dose-dependently reduces lactate dehydrogenase (LDH) release as well as mean infarction size of left ventricle. Histological observation demonstrates that the arterial thrombi in coronary arteries of rat almost disappear after SLK injection. Optimal dose of SLK (37.5 μg/ individual) provides the myocardial protection at 2 hours post-infusion. However, there are no significant protective effects if SLK was given at 4 or 8 hours post-infusion. The combined application of SLK and urokinase (UK) demonstrates greater myocardial protection than UK alone at 2 hours post-infusion. Thus, SLK could be used as a thrombolytic alternative in other arterial vascular beds associated with thrombosis to enhance fibrinolysis.

Effect of dexmedetomidine on monophasic action potential amplitude in myocardial ischemia-reperfusion and its correlation with myocardial injury

Objective: To study the effect of dexmedetomidine on monophasic action potential amplitude (MAPA) in myocardial ischemia-reperfusion and its correlation with myocardial injury. Methods: SD rats were selected as the experimental animals and randomly divided into control group, ischemia reperfusion group (I/R group) and dexmedetomidine group (Dex group);I/R group and Dex group were made into myocardial ischemia-reperfusion injury models, and Dex group were given exmedetomidine intervention;the MAPA of myocardial tunica intima layer, tunica media layer and tunica externa layer were measured in Langendorff perfusion system;myocardial tissue was collected to determine the contents of oxidative stress molecules and the expression of apoptosis genes. Results: The MAPA levels of myocardial tunica intima layer, tunica media layer and tunica externa layer as well as Klotho and SOD contents in myocardial tissue of I/R group were significantly lower than those of control group whereas CaMKII, NOX2, NOX4 and MDA contents as well as CaSR, USP14, JNK, Bax, Fas and Caspase-3 mRNA expression in myocardial tissue were significantly higher than those of control group;the MAPA levels of myocardial tunica intima layer, tunica media layer and tunica externa layer as well as Klotho and SOD contents in myocardial tissue of Dex group were significantly higher than those of I/R group whereas CaMKII, NOX2, NOX4 and MDA contents as well as CaSR, USP14, JNK, Bax, Fas and Caspase-3 mRNA expression in myocardial tissue were significantly lower than those of I/R group;Pearson test showed that the MAPA levels of myocardial tunica intima layer, tunica media layer and tunica externa layer were negatively correlated with CaMKII, NOX2, NOX4 and MDA contents as well as CaSR, USP14, JNK, Bax, Fas and Caspase-3 mRNA expression in myocardial tissue, and positively correlated with Klotho and SOD contents. Conclusion: Dexmedetomidine can increase the MAPA in myocardial ischemia-reperfusion process, and is closely related to the inhibition of oxidative stress response and apoptosis.

Effects of At2 Receptor Agonist Novokinin on Oxidative Stress, Inflammation and Infarct Size Due to Myocardial Ischemia-Reperfusion

Aim: Ischemia and reperfusion (IR) injury is a serious problem that is occured during thrombolytic therapy, organ transplantation, coronary angioplasty, and cardiopulmonary bypass. There is an increase in the number of AT2 receptors in some pathological conditions such as cardiac hypertrophy, myocardial infarction, congestive heart failure. This study was designed to investigate the effects AT2 receptor agonist Novokinin on infarct size, caveolin-1 (CAV-1), HSP90, ADMA, NADPH oxidase and Rhokinase associated to endothelial dysfunction and oxidative stress, and NFκB and TLR-4 levels induced by inflammation on myocardial IR. Methods: The experimental groups: Sham (C), Novokinin (N), IR and IRN. Novokinin was performed with infusion pump before ischemia, and during IR. The left main coronary artery was occluded for 30 minutes ischemia followed by 120 minutes reperfusion in anesthetized rats. CAV-1, HSP90, and NFκB levels were measured by the quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), ADMA, TLR-4, NADPH oxidase, and Rhokinase levels were measured by ELISA, infarct size was measured by ImageJ, an image analysis software, in the heart tissue. Results: NFκB, HSP90, NADPH oxidase and TLR-4 levels increased with IR and significantly decreased with Novokinin. CAV-1 levels were not different between the groups. ADMA and Rhokinase levels were increased due to IR but decreased with Novokinin. Novokinin reduced infarct size due to IR. Conclusion: Our results showed that, ADMA, HSP90, NFκB, TLR-4, Rhokinase, and NADPH oxidase levels play important roles on IR injury. AT2 receptor agonist Novokinin may affect positively oxidative changes, inflammation, and endothelial function in myocardial IR injury.