Insight into Cardioprotective Effects and Mechanisms of Dexmedetomidine.

PURPOSE: Cardiovascular disease remains the leading cause of death worldwide. Dexmedetomidine is a highly selective α2 adrenergic receptor agonist with sedative, analgesic, anxiolytic, and sympatholytic properties, and several studies have shown its possible protective effects in cardiac injury. The aim of this review is to further elucidate the underlying cardioprotective mechanisms of dexmedetomidine, thus suggesting its potential in the clinical management of cardiac injury. RESULTS AND CONCLUSION: Our review summarizes the findings related to the involvement of dexmedetomidine in cardiac injury and discusses the results in the light of different mechanisms. We found that numerous mechanisms may contribute to the cardioprotective effects of dexmedetomidine, including the regulation of programmed cell death, autophagy and fibrosis, alleviation of inflammatory response, endothelial dysfunction and microcirculatory derangements, improvement of mitochondrial dysregulation, hemodynamics, and arrhythmias. Dexmedetomidine may play a promising and beneficial role in the treatment of cardiovascular disease.

Dexmedetomidine alleviates H2O2-induced oxidative stress and cell necroptosis through activating of α2-adrenoceptor in H9C2 cells.

Oxidative stress induced necroptosis is important in myocardial ischemia/reperfusion injury. Dexmedetomidine (Dex), an α2-adrenoceptor (α2-AR) agonist, has protective effect on oxidative stress induced cell apoptosis, but effects of Dex and Dex-mediated α2-AR activation on oxidant induced necroptosis was unclear. H9C2 cardiomyocytes were pre-treated with or without Dex and α2-AR antagonist yohimbine hydrochloride (YOH) before being exposed to H2O2 to induce oxidative cellular damage. Cell viability and lactate dehydrogenase (LDH) were detected by ELISA kits, protein expressions of Heme Oxygenase 1(HO-1), receptor interacting protein kinase 1 (RIPK1) and receptor interacting protein kinase 3 (RIPK3) were observed by WB, and TUNEL was used to detected cell apoptosis. H2O2 significantly decreased cell viability and increased LDH release and necroptotic and apoptotic cell deaths (all p < 0.05, H2O2 vs. Control). Dex preconditioning alleviated these injuries induced by H2O2. Dex preconditioning significantly increased expression of protein HO-1 and decreased expressions of proteins RIPK1 and RIPK3 induced by H2O2, while all these protective effects of Dex were reversed by YOH (all p < 0.05, Dex + H2O2 vs. H2O2; and YOH + Dex + H2O2 vs. Dex + H2O2). However, YOH did not prevent this protective effect of Dex against H2O2 induced apoptosis (YOH + Dex + H2O2 vs. Dex + H2O2, p > 0.05). These findings indicated that Dex attenuates H2O2 induced cardiomyocyte necroptotic and apoptotic cell death respectively dependently and independently of α2-AR activation.

Circulating miRNA Expression Profiling and Target Prediction in Patients Receiving Dexmedetomidine.

BACKGROUND/AIMS: Circulating miRNAs could serve as biomarkers for diagnosis or prognosis of heart diseases and cerebrovascular diseases. Dexmedetomidine has protective effects in various organs. The effects of dexmedetomidine on circulating miRNAs remain unknown. Here, we investigated differentially expressed miRNA and to predict the target genes of the miRNA in patients receiving dexmedetomidine. METHODS: The expression levels of circulating miRNAs of 3 patients were determined through high through-put miRNA sequencing technology. Target genes of the identified differentially expressed miRNAs were predicted using TargetScan 7.1 and miRDB v.5. Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to conduct functional annotation and pathway enrichment analysis of target genes respectively. RESULTS: Twelve differentially expressed miRNAs were identified. Five miRNAs were upregulated (hsa-miR-4508, hsa-miR-novel-chr8_87373, hsa-miR-30a-3p, hsa-miR-novel-chr16_26099, hsa-miR-4306) and seven miRNAs (hsa-miR-744-5p, hsa-miR-320a, hsa-miR-novel-chr9_90035, hsa-miR-101-3p, hsa-miR-150-5p, hsa-miR-342-3p, and hsa-miR-140-3p) were downregulated after administration of dexmedetomidine in the subjects. The target genes and pathways related to the differentially expressed miRNAs were predicted and analyzed. CONCLUSION: The differentially expressed miRNAs may be involved in the mechanisms of action of dexmedetomidine. Specific miRNAs, such as hsa-miR-101-3p, hsa-miR-150-5p and hsa-miR-140-3p, are new potential targets for further functional studies of dexmedetomidine.

Expression Profiling of Circular RNAs and Micrornas in Heart Tissue of Mice with Alcoholic Cardiomyopathy.

BACKGROUND/AIMS: Chronic heavy alcohol consumption may result in alcoholic cardiomyopathy. This study was designed to screen differentially expressed microRNAs and circular RNAs in heart tissue of mice with alcoholic cardiomyopathy to reveal the underlying molecular mechanism. METHODS: Having established a murine alcoholic cardiomyopathy model, we screened differentially expressed microRNAs and circular RNAs in three heart samples from the alcohol-treated and control groups by high-throughput microarray analysis. We analyzed the function and biological signaling pathways of differentially expressed non-coding RNAs closely related to alcoholic cardiomyopathy using bioinformatics software to identify some mRNAs and their biological signaling pathways closely related to alcoholic cardiomyopathy. RESULTS: Nineteen microRNAs and 265 circular RNAs were differentially expressed in the alcohol-treated group compared with the control group. After analyzing gene function and signaling pathways by bioinformatics software, we found that the differentially expressed mRNAs were associated with carbohydrate metabolism. CONCLUSIONS: Chronic alcohol consumption can change the non-coding RNA profile of heart tissue, which is closely related to the pathological mechanisms of alcoholic cardiomyopathy.

Aleglitazar, a Balanced Dual PPARα and -γ Agonist, Protects the Heart Against Ischemia-Reperfusion Injury.

PURPOSE: To evaluate whether aleglitazar (Ale), a dual PPARα/γ agonist, has additive effects on myocardial protection against ischemia-reperfusion injury. METHODS: Human cardiomyocytes (HCMs), cardiomyocytes from cardiac-specific PPARγ knockout (MCM-PPARγ (CKO) ) or wild type (MCM-WT) mice were incubated with different concentrations of Ale, and subjected to simulated ischemia-reperfusion (SIR) or normoxic conditions (NSIR). Cell viability, apoptosis and caspase-3 activity were determined. HCMs were transfected with siRNA against PPARα (siPPARα) or PPARγ (siPPARγ) followed by incubation with Ale. PPARα/γ DNA binding capacity was measured. Cell viability, apoptosis and levels of P-AKT and P-eNOS were assessed. Infarct size following 30 min coronary artery occlusion and 24 h reperfusion were assessed in WT and db/db diabetic mice following 3-day pretreatment with vehicle, Ale or glimeperide. RESULTS: Ale (at concentrations of 150-600 nM) increased cell viability and reduced apoptosis in HCMs, MCM-WT and MCM-PPAR (CKO) exposed to SIR. In HCM, the protective effect was partially blocked by siPPARα alone or siPPARγ alone, and completely blocked by siPPARα+siPPARγ. Ale increased P-Akt/P-eNOS in HCMs. P-Akt or P-eNOS levels were decreased when PPARα alone, PPARγ alone and especially when both were knocked down. Peritoneal GTTs revealed that db/db mice had developed impaired glucose tolerance and insulin sensitivity, which were normalized by Ale or glimepiride treatment. Ale, but not glimepiride, limited infarct size in both WT and diabetic mice after ischemia-reperfusion. CONCLUSIONS: Ale protects against myocardial apoptosis caused by hypoxia-reoxygenation in vitro and reduces infarct size in vivo.

Modulation of microRNAs in hypertension-induced arterial remodeling through the ß1 and ß3-adrenoreceptor pathways.

BACKGROUND: Dysregulation of microRNAs (miRNAs) in arterial dysfunction and hypertension has not been extensively investigated yet. This project determined the effects of two anti-hypertensive ß1 adrenergic selective blockers on miRNA expression in the Dahl Salt Sensitive (DSS) hypertensive rat model. METHODS AND RESULTS: Microarray analysis showed that a set of miRNAs is differently expressed in the aorta of high salt (HS) treated rats with miR-320 increased and miR-26b and -21 decreased. All of these changes were reverted to normal by nebivolol (NEB, a ß1 selective-blocker and ß3 activator). The selective ß3-adrenoceptor antagonist S-(-)-cyanopindolol (Syc) counteracted the effect of NEB on these miRNAs. Atenolol (ATN, a pure ß1-blocker) combined with specific ß3 agonist BRL37344 restored the expression of all three miRNAs, similar to NEB, while ATN alone had only a partial effect on miR-320 expression. Computational analysis found Insulin Growth Factor-1 Receptor (IGF1R) as a putative target of miR-320, and Phosphatase and tensin homolog on chromosome ten (PTEN) as a putative target of miR-26b and -21. The targets were verified by luciferase reporter assays. Inhibition of miR-320 by an antisense inhibitor or NEB increased IGF1R expression, while miR-320 overexpression reversed the effect of NEB. Overexpression of miR-26b or -21 or NEB decreased PTEN levels, while inhibition of miR-26b or -21 attenuated the effect of NEB. HS diet induced downregulation of IGF1R and upregulation of PTEN in the aorta. NEB normalized the aberrant expression of IGF1R and PTEN and also improved the impairment of vascular AKT/eNOS signaling. Moreover, both NEB and ATN showed to have protective effects on salt-induced hypertension, oxidative stress, and vascular remodeling. NEB had a greater effect than ATN. CONCLUSIONS: Our data supports a differential miRNA expression profile in salt-induced hypertension. Manipulation of dysregulated miRNAs by ß-blockers may substantially induce alterations of gene expression and prevent arterial dysfunction and remodeling.

Phosphodiesterase-3 inhibition augments the myocardial infarct size-limiting effects of exenatide in mice with type 2 diabetes.

Glucagon-like peptide (GLP)-1 receptor activation increases intracellular cAMP with downstream activation of PKA. Cilostazol (CIL), a phosphodiesterase-3 inhibitor, prevents cAMP degradation. We assessed whether CIL amplifies the exenatide (EX)-induced increase in myocardial cAMP levels and PKA activity and augments the infarct size (IS)-limiting effects of EX in db/db mice. Mice fed a Western diet received oral CIL (10 mg/kg) or vehicle by oral gavage 24 h before surgery. One hour before surgery, mice received EX (1 µg/kg sc) or vehicle. Additional mice received H-89, a PKA inhibitor, alone or with CIL + EX. Mice underwent 30 min of coronary artery occlusion and 24 h of reperfusion. Both EX and CIL increased myocardial cAMP levels and PKA activity. Levels were significantly higher in the EX + CIL group. Both EX and CIL reduced IS. IS was the smallest in the CIL + EX group. H-89 completely blocked the IS-limiting effects of EX + CIL. EX + CIL decreased phosphatase and tensin homolog on chromosome 10 upregulation and increased Akt and ERK1/2 phosphorylation after ischemia-reperfusion. These effects were blocked by H-89. In conclusion, EX and CIL have additive effects on IS limitation in diabetic mice. The additive effects are related to cAMP-induced PKA activation, as H-89 blocked the protective effect of CIL + EX.

Dexmedetomidine abates myocardial ischemia reperfusion injury through inhibition of pyroptosis via regulation of miR-665/MEF2D/Nrf2 axis.

The current study intended to delve into the mechanisms of dexmedetomidine (Dex) in regulating myocardial pyroptosis against myocardial ischemia/reperfusion injury (MIRI). The rat MIRI models were induced by ligation/release of the coronary artery in vivo and Langendorff perfusion ex vivo. Hemodynamic parameters, infarction sizes, and histopathological changes were assessed to understand the effects of Dex on MIRI. We explored the mechanisms through functional experiments on an H9c2 cell hypoxia/reoxygenation (H/R) model. Cell viability and apoptosis were evaluated using cell counting kit 8 (CCK-8) and AV/PI dual staining respectively. The expressions of miR-665 and MEF2D mRNA were detected by qRT-PCR. Western blot was employed to determine the expression levels of pyroptosis- and signaling pathway- related proteins. The interplays between miR-665 and MEF2D were validated by Dual-luciferase reporter assays. Our findings indicated that Dex preconditioning dramatically attenuated hemodynamic derangements, infarct size, and histopathological damage in rats undergoing MIRI. Dex markedly augmented cell viability, while suppressing cell apoptosis and expressions of NLRP3, cleaved-caspase-1, ASC, GSDMD, IL-1ß, and IL-18 in H9c2 cells subjected to H/R injury. MiR-665 was significantly upregulated, MEF2D and Nrf2 downregulated following H/R, whereas Dex preconditioning reversed these changes. MEF2D was validated to be a target gene of miR-665. Overexpression of miR-665 decreased the expression of MEF2D and blunted the protective effects of Dex in H9c2 cells. Moreover, the functional rescue experiment further verified that Dex regulated MEF2D/Nrf2 pathway via miR-665. In conclusion, Dex mitigates MIRI through inhibiting pyroptosis via regulating miR-665/MEF2D/Nrf2 axis.

Regulation of phosphatase and tensin homolog on chromosome 10 in response to hypoxia.

Phosphatase and tensin homolog on chromosome 10 (PTEN) is downregulated during hypertrophic and cancerous cell growth, leading to activation of the prosurvival Akt pathway. However, PTEN regulation in cardiac myocytes upon exposure to hypoxia remains unclear. We explored the role of PTEN in response to hypoxia/ischemia in the myocardium. We validated that PTEN is a transcriptional target of activating transcription factor 2 (ATF-2) and is positively regulated via a p38/ATF-2 signaling pathway. Accordingly, hypoxia-induced upregulation of phosphorylation of ATF-2 and PTEN were reversed by a dominant negative mutant p38. Inhibition of PTEN in cardiomyocytes attenuated hypoxia-induced cell death and apoptosis. Cardiac-specific knockout of PTEN resulted in increased phosphorylation of Akt and forkhead box O 1 (forkhead transcription factors), limited infarct size in animals exposed to ischemia-reperfusion injury, and ameliorated deterioration of left ventricular function and remodeling following permanent coronary artery occlusion. In addition, the activation of Bim, FASL, and caspase was coupled with PTEN activation, all of which were attenuated by PTEN inhibition. In conclusion, cardiomyocyte-specific conditional PTEN deletion limited myocardial infarct size in an in vivo model of ischemia-reperfusion injury and attenuated adverse remodeling in a model of chronic permanent coronary artery ligation.

Phosphodiesterase III inhibition increases cAMP levels and augments the infarct size limiting effect of a DPP-4 inhibitor in mice with type-2 diabetes mellitus.

PURPOSE: We assessed whether phosphodiesterase-III inhibition with cilostazol (Cil) augments the infarct size (IS)-limiting effects of MK0626 (MK), a dipeptidyl-peptidase-4 (DPP4) inhibitor, by increasing intracellular cAMP in mice with type-2 diabetes. METHODS: Db/Db mice received 3-day MK (0, 1, 2 or 3 mg/kg/d) with or without Cil (15 mg/kg/d) by oral gavage and were subjected to 30 min coronary artery occlusion and 24 h reperfusion. RESULTS: Cil and MK at 2 and 3 mg/kg/d significantly reduced IS. Cil and MK had additive effects at all three MK doses. IS was the smallest in the MK-3+Cil. MK in a dose dependent manner and Cil increased cAMP levels (p < 0.001). cAMP levels were higher in the combination groups at all MK doses. MK-2 and Cil increased PKA activity when given alone; however, PKA activity was significantly higher in the MK-2+Cil group than in the other groups. Both MK-2 and Cil increased myocardial levels of Ser(133) P-CREB, Ser(523) P-5-lipoxygenase, Ser(473)P-Akt and Ser(633) P-eNOS. These levels were significantly higher in the MK-2+Cil group. Myocardial PTEN (Phosphatase and tensin homolog on chromosome ten) levels were significantly higher in the Db/Db mice compared to nondiabetic mice. MK-2 and Cil normalized PTEN levels. PTEN levels tended to be lower in the combination group than in the MK and Cil alone groups. CONCLUSION: MK and Cil have additive IS-limiting effects in diabetic mice. The additive effects are associated with an increase in myocardial cAMP levels and PKA activity with downstream phosphorylation of Akt, eNOS, 5-lipoxygenase and CREB and downregulation of PTEN expression.

Dexmedetomidine attenuates myocardial ischemia/reperfusion-induced ferroptosis via AMPK/GSK-3ß/Nrf2 axis.

The present study aimed to investigate whether dexmedetomidine (Dex) exerts cardioprotection effect through inhibiting ferroptosis. Myocardial ischemia/reperfusion injury (MIRI) was induced in Sprague-Dawley rats in Langendorff preparation. The hemodynamic parameters were recorded. Triphenyltetrazolium chloride (TTC) staining was used to determine infarct size. In the in vitro study, the model of hypoxia/reoxygenation (HR) was established in H9c2 cells. Cell viability and apoptosis were detected using cell counting kit 8 (CCK-8), and AV/PI dual staining respectively. Lipid peroxidation as measured by the fluorescence of the fatty acid analog C11-BODIPY581/591 probe and intracellular ferrous iron levels were measured by fluorescence of Phen Green SK (PGSK) probe, whereas immunofluorescence and transmission electron microscopy were also used to examine ferroptosis. Protein levels were investigated by Western blot. The interactions of AMPK/GSK-3ß signaling with Nrf2 were also assessed through AMPK inhibition and GSK-3ß overexpression. Our findings indicated that Dex significantly alleviated myocardial infarction, improved heart function, and decreased HR-induced accumulation of Fe2+ and lipid peroxidation in cardiomyocytes. Dex significantly increased the expression levels of Nrf2, SLC7A11, and GPX4. However, inhibition of Nrf2 by ML385 blunted the protective effect of Dex in HR-treated H9c2 cells. Inhibition of AMPK with a specific inhibitor or siRNA decreased the expression levels of phosphorylation of GSK-3ß and Nrf2 induced by Dex. Overexpression of GSK-3ß resulted in lower levels of nuclear Nrf2, whereas depression of GSK-3ß enhanced expressions of nuclear Nrf2. In conclusion, Dex protects hearts against MIRI-induced ferroptosis via activation of Nrf2 through AMPK/GSK-3ß signaling pathway.

Oxytocin ameliorates high glucose- and ischemia/reperfusion-induced myocardial injury by suppressing pyroptosis via AMPK signaling pathway.

The present study aimed to explore the role of oxytocin (OT) in myocardial injury induced by ischemia/reperfusion (I/R) and hyperglycemia and its underlying mechanisms. In this study, the isolated rat hearts underwent I/R in Langendorff perfusion model and H9c2 cells were subjected to hypoxia/reoxygenation (H/R) to establish an in vitro model. I/R injury was induced by exposing the rat hearts to 40 min of global ischemia followed by 60 min of reperfusion. H9c2 cells were cultured under the normoglycemic or hyperglycemic condition with or without pretreatment of OT, and then exposed to 4 h of hypoxia and 2 h of reoxygenation. Measurement indicators included myocardial infarct size assessed by triphenyltetrazolium chloride (TTC) staining and hemodynamic parameters in the ex vivo model as well as cell viability detected by cell counting kit 8 (CCK-8), apoptotic rate evaluated by flow cytometry, and the protein expressions by Western blot. The findings demonstrated that OT attenuated myocardial I/R injury. First, OT preconditioning significantly reduced hemodynamic disorders and myocardial infarct sizes. In addition, OT increased cell viability, decreased cell apoptosis and the expressions of IL-18, IL-1ß, cleaved-caspase-1, NLRP3, and GSDMD following H/R. NLRP3 activator nigericin eliminated the beneficial effects of OT in H9c2 cells. Furthermore, OT also activated AMPK and decreased the expressions of pyroptosis-related proteins. Administration of AMPK inhibitor compound C blunted OT-induced AMPK phosphorylation and elevated the expressions of pyroptosis-related proteins in H9c2 cells subjected to H/R with hyperglycemia. OT alleviates myocardial I/R injury with hyperglycemia by inhibiting pyroptosis via AMPK/NLRP3 signaling pathway.

The role of microRNA in modulating myocardial ischemia-reperfusion injury.

MicroRNAs (miRNAs) are small (∼22 nt) noncoding single-stranded RNA molecules that downregulate gene expression. Studies have shown that miRNAs control diverse aspects of heart disease, including hypertrophy, remodeling, heart failure, and arrhythmia. Recently, several studies have suggested that miRNAs contribute to ischemia-reperfusion injury by altering key signaling elements, thus making them potential therapeutic targets. By altering the expression of various key elements in cell survival and apoptosis [such as phosphoinositide 3-kinase (PI3K), phosphatase and tensin homolog deleted on chromosome 10 (PTEN), Bcl-2, Mcl-1, heat shock protein (HSP)60, HSP70, HSP20, programmed cell death 4 (Pdcd4), LRRFIP1, Fas ligand (FasL), Sirt-1, etc.], miRNAs alter the response to ischemia-reperfusion injury. Studies using various in vivo, ex vivo, and in vitro models have suggested the possible involvement of miR-1, miR-21, miR-29, miR-92a, miR-133, miR-199a, and miR-320 in ischemia-reperfusion injury and/or remodeling after myocardial infarction. Thus miRNAs could be potential therapeutic targets for the treatment of heart disease. Inhibiting miRNAs by antisense strategies or pharmacological approaches is likely to emerge as an alternative and safe method for conferring short- and intermediate-term protection against ischemia-reperfusion injury.

Impact of HMG-CoA reductase inhibition on oxidant-induced injury in human retinal pigment epithelium cells.

In addition to cholesterol-lowering effect, HMG-CoA reductase inhibition by statins has been shown to have protective effect in many cells type. The loss of vision in retinal degeneration disease associates with oxidative stress and apoptosis in retinal pigment epithelium (RPE) cell. This study was designed to examine the effect of statins on oxidant-induced damage in human RPE cells. Cultured human ARPE-19 (ARPE) cells were challenged with hydrogen peroxide (H(2) O(2) ) plus tumor necrosis factor alpha (TNFα) in the presence or absence of statins or various stress signaling inhibitors, including anti-oxidants N-acetyl cysteine (NAC), the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium (DPI), and the p38 mitogen-activated protein kinase (p38 MAPK) inhibitor SB203580. Apoptosis was evaluated by TUNEL analysis and cell viability was determined by MTT assay. Reactive oxygen species (ROS) were detected by 2',7'-dichlorodihydrofluorescein diacetate (H(2) DCFH-DA). Expression of p-p38 MAPK protein was measured by Western blot analysis. Our findings indicate that statins treatment significantly suppressed oxidant-induced ROS accumulation and RPE apoptosis. Statins increased cell viability in a dose-dependent manner. In addition, statins treatment prevented the activation of NADPH oxidase and p38 MAPK signaling induced by oxidative stress. These results suggest that statins protects ARPE cells from oxidative stress via an NADPH oxidase and/or p38 MAPK-dependent mechanisms, which may contribute to statins-induced beneficial effects on RPE function.

Pioglitazone limits myocardial infarct size, activates Akt, and upregulates cPLA2 and COX-2 in a PPAR-γ-independent manner.

Pioglitazone (PIO), a PPAR-γ agonist, limits myocardial infarct size by activating Akt and upregulating cytosolic phospholipase A(2) (cPLA(2)) and cyclooxygenase (COX)-2. However, PIO has several PPAR-γ-independent effects. We assessed whether PIO limits myocardial infarct size in PPAR-γ-knockout mice, attenuates hypoxia-reoxygenation injury and upregulates P-Akt, cPLA(2), and COX-2 expression in PPAR-γ-knockout cardiomyocytes. Cardiac-specific inducible PPAR-γ knockout mice were generated by crossing αMHC-Cre mice to PPAR-γ(loxp/loxp) mice. PPAR-γ deletion was achieved after 7 days of intraperitoneal tamoxifen (20 mg/kg/day) administration. Mice received PIO (10 mg/kg/day), or vehicle, for 3 days and underwent coronary occlusion (30 min) followed by reperfusion (4 h). We assessed the area at risk by blue dye and infarct size by TTC. Cultured adult cardiomyocytes of PPAR-γ(loxp/loxp/cre) mice without or with pretreatment with tamoxifen were incubated with or without PIO and subjected to 2 h hypoxia/2 h reoxygenation. Cardiac-specific PPAR-γ knockout significantly increased infarct size. PIO reduced infarct size by 51% in PPAR-γ knockout mice and by 55% in mice with intact PPAR-γ. Deleting the PPAR-γ gene increased cell death in vitro. PIO reduced cell death in cells with and without intact PPAR-γ. PIO similarly increased myocardial Ser-473 P-Akt, cPLA(2), and COX-2 levels after hypoxia/reoxygenation in cells with and without intact PPAR-γ. PIO limited infarct size in mice in a PPAR-γ-independent manner. PIO activated Akt, increased the expression of cPLA(2) and COX-2, and protected adult cardiomyocytes against the effects of hypoxia/reoxygenation independent of PPAR-γ activation.

Aliskiren and Valsartan reduce myocardial AT1 receptor expression and limit myocardial infarct size in diabetic mice.

PURPOSE: We assessed the ability of Aliskiren (AL), a direct renin inhibitor, and Valsartan (VA), an angiotensin receptor blocker, to limit myocardial infarct size (IS) in mice with type-2 diabetes mellitus. METHODS: Db/Db mice, fed Western Diet, received 15-day pretreatment with: 1) vehicle; 2) AL 25 mg/kg/d; 3) AL 50 mg/kg/d; 4) VA 8 mg/kg/d; 5) VA 16 mg/kg/d; 6) AL 25+VA 16 mg/kg/d; or 7) AL 50+VA 16 mg/kg/d. Mice underwent 30 min coronary artery occlusion and 24 h reperfusion. Area at risk (AR) was assessed by blue dye and IS by TTC staining. Protein expression was assessed by immunobloting. RESULTS: IS in the control group was 42.9 ± 2.1% of the AR. AL at 25 (21.9 ± 2.9%) and 50 mg/kg/d (15.5 ± 1.3%) reduced IS. VA at 16 mg/kg/d (18.8 ± 1.2%), but not at 8 mg/kg/d (35.2 ± 4.0%), limited IS. IS was the smallest in the AL50+VA16 group (6.3 ± 0.9%). Both AL and VA reduced myocardial AT1R levels, without affecting AT2R levels, and increased the expression of Sirt1 and PGC-1α with increased phosphorylation of Akt and eNOS. CONCLUSIONS: AL, dose dependently limited myocardial IS in mice with type-2 diabetes mellitus. At doses shown to limit IS in non-diabetic animals, VA failed to reduce IS in Db/Db mice. However, at higher dose (16 mg/kg/d), VA reduced IS. Both drugs reduced the expression of AT1R and increased myocardial levels of the longevity genes Sirt1 and PGC-1α along with increased Akt and eNOS phosphorylation.

Dexmedetomidine exerts cardioprotective effect through miR-146a-3p targeting IRAK1 and TRAF6 via inhibition of the NF-κB pathway.

BACKGROUND: Myocardial ischemia/reperfusion (I/R) injury is a common cause of mortality. Cardiac miR-146a is emerging as a potent regulator of myocardial function. Dexmedetomidine preconditioning provides cardioprotective effects, of which mechanisms related to miR-146a-3p are unclear. METHODS: A myocardial I/R model in rats and a cellular anoxia/reoxygenation (A/R) model in H9C2 cells were established and preconditioned with dexmedetomidine or not. H9C2 cells were transfected with mimics, inhibitor, or negative controls of miR-146a-3p, and siRNAs of IRAK1 or TRAF6. Relative expressions of miR-146a-3p were determined by quantitative real-time polymerase chain reaction. The apoptosis rates and reactive oxygen species (ROS) levels in H9C2 cells were examined by flow cytometry. Protein expressions of IRAK1, TRAF6, cleaved Caspase-3, BAX, BCL-2, NF-κB p65, phosphorylated NF-κB p65 (p-NF-κB p65), IκBα, and phosphorylated IκBα (p-IκBα) in H9C2 cells were detected by Western blot. RESULTS: Dexmedetomidine decreased myocardial infarction size and apoptosis rates of H9C2 cells. Dexmedetomidine upregulated expression of miR-146a-3p. Dexmedetomidine significantly decreased protein expressions of IRAK1, TRAF6, cleaved Caspase-3, BAX, and NF-κB p65, but increased expressions of BCL-2 in H9C2 cells. miR-146a-3p overexpression strengthened the anti-apoptotic effect induced by dexmedetomidine in H9C2 cells via decreasing protein levels of IRAK1, TRAF6, cleaved Caspase-3, BAX, NF-κB p65, p-NF-κB p65, and p-IκBα and increasing protein level of BCL-2. Downregulation of miR-146a-3p reversed the changes in these proteins in H9C2 cells. Expressions of NF-κB p65 and p-NF-κB p65 were further decreased following knockdown of IRAK1 or TRAF6. ROS emission was significantly increased after A/R, while significantly decreased following dexmedetomidine preconditioning in H9C2 cells transfected with siIRAK1 or siTRAF6. CONCLUSION: miR-146a-3p targeting IRAK1 and TRAF6 through inhibition of NF-κB signaling pathway and ROS emission is involved in cardioprotection induced by dexmedetomidine pretreatment.

Dexmedetomidine preconditioning mitigates myocardial ischemia/reperfusion injury via inhibition of mast cell degranulation.

The degranulation of cardiac mast cells is associated with occurrence and development of myocardial ischemia/reperfusion (I/R) injury. Dexmedetomidine has a cardioprotective effect from I/R injury. The purpose of this study was to investigate whether dexmedetomidine preconditioning induced cardioprotection is related to suppression of degranulation of cardiac mast cell. Both in vivo and in vitro experimental results revealed that hemodynamic disorder, arrhythmia, infarct size, histopathological score, and mast cell degranulation were dramatically increased in I/R injury groups compared with non-I/R groups, and mastocyte secretagogue compound 48/80 aggravated these damages, but it can be improved by dexmedetomidine preconditioning. Similarly, compound 48/80 increased levels of cardiac troponin I (cTnI) and tryptase, cardiomyocytes apoptosis, and expression of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), and nuclear factor-kappa B p65 (NF-κB p65) in cardiac tissues induced by I/R injury, but it can be partially decreased by dexmedetomidine pretreatment. Compound 48/80 inhibited proliferation of H9C2(2-1) and RBL-2H3, exacerbated apoptosis of H9C2(2-1), and elevated levels of cTnI and tryptase, while both of which were abolished by dexmedetomidine pretreatment. Our data suggest that dexmedetomidine preconditioning alleviates the degranulation of mast cells and the apoptosis of cardiomyocytes caused by I/R injury, and inhibits the activation of inflammatory related factors HMGB1, TLR4, and NF-κB p65.

Oxytocin Protects Against Isoproterenol-Induced Cardiac Hypertrophy by Inhibiting PI3K/AKT Pathway via a lncRNA GAS5/miR-375-3p/KLF4-Dependent Mechanism.

Cardiac hypertrophy is caused by cardiac volume or pressure overload conditions and ultimately leads to contractile dysfunction and heart failure. Oxytocin (OT), an endocrine nonapeptide, has been identified as a cardiovascular homeostatic hormone with anti-hypertrophic effects. However, the underlying mechanism remains elusive. In this study, we aimed to investigate the role and mechanism of OT in cardiac hypertrophy. The rats with cardiac hypertrophy induced by isoproterenol (ISO) were treated with or without oxytocin. Cardiac functional parameters were analyzed by echocardiography. The changes in cell surface area were observed using wheat germ agglutinin (WGA) or immunofluorescence staining. The expressions of cardiac hypertrophy markers (B-Natriuretic Peptide, BNP and ß-myosin heavy chain, ß-MHC), long non-coding RNA Growth (LcRNA) Arrest-Specific transcript 5 (lncRNA GAS5), miR-375-3p, and Kruppel-like factor 4 (Klf4) were detected by qRT-PCR. KLF4 protein and PI3K/AKT pathway related proteins were detected by Western blot. The interactions among lncRNA GAS5, miR-375-3p, and Klf4 were verified by dual-luciferase reporter assays. The findings showed that OT significantly attenuated cardiac hypertrophy, increased expressions of lncRNA GAS5 and KLF4, and decreased miR-375-3p expression. In vitro studies demonstrated that either knock-down of lncRNA GAS5 or Klf4, or over-expression of miR-375-3p blunted the anti-hypertrophic effects of OT. Moreover, down-regulation of lncRNA GAS5 promoted the expression of miR-375-3p and inhibited KLF4 expression. Similarly, over-expression of miR-375-3p decreased the expression of KLF4. Dual-luciferase reporter assays validated that lncRNA GAS5 could sponge miR-375-3p and Klf4 was a direct target gene of miR-375-3p. In addition, OT could inactivate PI3K/AKT pathway. The functional rescue experiments further identified OT regulated PI3K/AKT pathway through lncRNA GAS5/miR-375-3p/KLF4 axis. In summary, our study demonstrates that OT ameliorates cardiac hypertrophy by inhibiting PI3K/AKT pathway via lncRNA GAS5/miR-375-3p/KLF4 axis.