PPARδ signaling mediates the cytotoxicity of DHA in H9c2 cells

Docosahexaenoic acid (22:6n3, DHA) is an n-3 polyunsaturated fatty acid (PUFA) known to affect numerous biological functions. While DHA possesses many properties that impact cell survival such as suppressing cell growth and inducing apoptosis, the exact molecular and cellular mechanism(s) remain unknown. Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors that regulate many cell pathways including cell death. As DHA acts as a ligand to PPARs the aim of this study was to examine the involvement of PPARδ in DHA-mediated cytotoxicity toward H9c2 cells. Treatment with DHA (100 μM) resulted in a significant decline in cell viability, cellular metabolic activity and total antioxidant capacity coinciding with increased total proteasome activities and activity of released lactate dehydrogenase (LDH). No changes in reactive oxygen species (ROS) production or accumulation of lipid peroxidation products were observed but DHA promoted apoptotic cell death as detected by flow cytometry, increased caspase-3 activity and decreased phosphorylation of Akt. Importantly, DHA enhanced PPARδ DNA binding activity in H9c2 cells strongly signifying that the cytotoxic effect of DHA might be mediated via PPARδ signaling. Co-treatment with the selective PPARδ antagonist GSK 3787 (1 μM) abolished the cytotoxic effects of DHA in H9c2 cells. Cytotoxic effects of DHA were attenuated by co-treatment with myriocin, a selective inhibitor of serine palmitoyl transferase (SPT), preventing de novo ceramide biosynthesis. LC/MS analysis revealed that treatment with DHA resulted in the accumulation of ceramide, which was blocked by GSK 3787. Interestingly, inhibition of cytochrome P450 (CYP) oxidase with MS-PPOH (50 μM) abolished DHA-mediated cytotoxicity suggesting downstream metabolites as the active mediators. We further demonstrate that CYP oxidase metabolites of DHA, methyl epoxy docosapentaenoate (EDP methyl esters, 1 μM) (mix 1:1:1:1:1:1; 4,5-, 7,8-, 10,11-, 13,14-, 16,17- and 19,20-EDP methyl esters) and 19,20-EDP cause cytotoxicity via activation of PPARδ signaling leading to increased levels of intracellular ceramide. These results illustrate novel pathways for DHA-induced cytotoxicity that suggest an important role for CYP-derived metabolites, EDPs.     

高糖应激对H9c2细胞凋亡作用

目的 探讨高糖应激早期对H9c2细胞存活的影响及其可能的信号转导通路.方法 高糖培养H9c2细胞24 h后,收集细胞进行细胞活力和凋亡的测定,用Western blot方法 测定蛋白激酶(Akt)的磷酸化水平和内皮细胞一氧化氮合酶(eNOS)的表达.结果 与对照(NG)组相比,高糖培养(HG)组H9c2细胞活力改善,凋亡减少,而P13K抑制剂LY294002预处理和NOS抑制剂L-NAME处理均抑制短期高糖培养对H9c2细胞的保护作用.与NG组相比,HG组早期Akt磷酸化水平升高,eNOS蛋白表达增加,结论 在高糖应激早期(24 h内),高糖通过活化P13K/Akt/eNOS信号通路,改善H9c2细胞的活力,减少其凋亡.     

Ghrelin protects H9c2 cells from hydrogen peroxide-induced apoptosis through NF-κB and mitochondria-mediated signaling

Oxidative stress is a major mechanism underlying the pathogenesis of cardiovascular disease. Herein we investigate the protective effects of ghrelin in H₂O₂-induced apoptosis of H9c2 cells, as well as the possible molecular mechanisms involved. To study apoptosis, the cells were assessed by morphologic examination, MTS assay, Annexin V–propidium iodide dual staining and TUNEL analysis. Intracellular reactive oxygen species (ROS) production and mitochondrial membrane potential were also measured. To investigate the underlying molecular mechanisms, the expression of Bcl-2, Bax, active caspase-9 and NF-κB were assessed by Western blotting, and caspase-3 activity was determined by a colorimetric activity assay kit. After stimulation with H₂O₂ for 18 h, H9c2 cells viability decreased significantly; a large fraction of cells underwent apoptosis. We observed a dose-dependent rescue of H9c2 cells from H₂O₂-induced apoptosis in the presence of different ghrelin concentrations. Preincubation with ghrelin also restored the ROS and mitochondrial membrane potential levels that had been altered by H₂O₂ treatment. Moreover, ghrelin decreased H₂O₂-induced Bax production and caspase-9 activation, and increased Bcl-2 levels. NF-κB phosphorylation was also significantly inhibited by ghrelin in H₂O₂-treated cells. Caspase-3 activation was suppressed by ghrelin in H₂O₂-treated H9c2 cells in a dose-dependent manner. In summary, ghrelin protects H9c2 cells from oxidative stress-induced apoptosis through downregulation of Bax expression, caspase-9 activation and NF-κB phosphorylation, and upregulation of Bcl-2 expression. Caspase-3 activation was also reduced in a dose-dependent manner. These data suggest that ghrelin might protect against cardiovascular disease by protecting the mitochondria.     

Curcumin potentiates doxorubicin-induced apoptosis in H9c2 cardiac muscle cells through generation of reactive oxygen species

Doxorubicin (DOX) is a widely used chemotherapy agent. The major adverse effect of DOX treatment in cancer patients is the onset of cardiomyopathy and heart failure. Reactive oxygen species (ROS) are proposed to be responsible for DOX cardiotoxicity. Curcumin, a natural compound extracted from Curcuma Longa L., is known for its anti-oxidant properties. It has been identified as increased apoptosis in several cancer cell lines in combination with doxorubicin, but there are few studies about the effect of curcumin and doxorubicin on normal cardiac cells. Therefore, we evaluated the effects of curcumin on apoptosis induced by DOX in cardiac muscle cells. Preteatment with curcumin significantly increased DOX-induced apoptosis of cardiac muscle cells through down regulation of Bcl-2, up-regulation of caspase-8 and caspase-9. The Bax/Bcl-2 ratio increased significantly after 1 h pretreatment with curcumin. As well, curcumin increases ROS generation by DOX. In response to DOX, NF-κB was activated. However, curcumin was able to inhibit NF-κB activation. In conclusion, our results indicated that pretreatment with nontoxic concentrations of curcumin sensitized H9c2 cells to DOX-mediated apoptosis by generation of ROS.     

Ubiquitin-protein ligase E3a (UBE3A) as a new biomarker of cardiac hypertrophy in cell models

Cardiac hypertrophy is widely diagnosed in clinical cardiac disorders. The pathophysiology of hypertrophy is complex and multifactorial, a series of molecular and cellular changes are participated, such as activation of different signaling pathways, a switch of fetal gene program in the myocardium, and apoptosis. Some biomarkers have been applied to assess cardiac hypertrophy including atrial natriuretic peptides (ANP), brain/B-type natriuretic peptides (BNP), and α- or β- Myosin Heavy Chain (MHC) in addition to others. Recently, ubiquitin-protein ligase E3A (UBE3A) has been observed to increase in cardiac hypertrophy. Therefore, UBE3A as a new biomarker seems valuable in the clinic. The cardiac hypertrophy is induced in rat-derived heart cell line H9c2 cells by potassium bromate (KBrO3), high glucose (HG), or isoproterenol (Iso), respectively. As an oxidizing agent, KBrO3 increased cell size at concentrations less than 250 μM. Similarly, HG and Iso also induced cardiac hypertrophy in H9c2 cells. Interestingly, each kind of the cell models promoted the gene expression of the well-known biomarkers of cardiac hypertrophy including atrial natriuretic peptides (ANP) and brain/B-type natriuretic peptides (BNP). Additionally, UBE3A is also raised with the signals involved in cardiac hypertrophy such as calcineurin and nuclear factor of activated T-cells (NFAT) determined using Western blots. KBrO3 increased the protein levels of these signals and the specific inhibitor, such as cyclosporine A and tacrolimus, attenuated the signaling in H9c2 cells at concentrations sufficient to inhibit calcineurin in addition to the reduction of mRNA levels of UBE3A, similar to ANP or BNP. Moreover, HG or Iso also significantly increased protein levels of UBE3A in H9c2 cells. Taken together, we provided a new view that UBE3A is markedly raised in cardiac hypertrophy using various cell models, mainly through the activation of the calcineurin/NFAT signaling pathway in H9c2 cells. Therefore, UBE3A could be developed as a new biomarker in the diagnosis of cardiac hypertrophy.     

Overproduction of reactive oxygen species and activation of MAPKs are involved in apoptosis induced by PM2.5 in rat cardiac H9c2 cells

Epidemiological studies show a positive correlation between the air levels of fine particulate matter (PM_2.5) and cardiovascular disorders, but how PM_2.5 affects cardiomyocytes has not been studied in great deal. The aim of the present study was to obtain an insight into the links among intracellular levels of reactive oxygen species (ROS), apoptosis and mitogen‐activated protein kinases (MAPKs) in rat cardiac H9c2 cells exposed to PM_2.5. H9c2 cells were incubated with PM_2.5 at 100–800 µg ml^–1 to evaluate the effects of PM_2.5 on cell viability, cell apoptosis, intracellular levels of ROS and expression of apoptosis‐related proteins as well as activation of MAPKs. PM_2.5 decreased cell viability, increased the cell apoptosis rate and intracellular ROS production in a concentration‐dependent manner. PM_2.5 decreased the Bcl‐2/Bax ratio and increased cleaved caspase‐3 levels. A Western blots study showed up‐regulation of phosphorylated MAPKs including extracellular signal‐regulated protein kinases (ERKs), c‐Jun NH₂‐terminal kinases (JNKs) and p38 MAPK in the PM_2.5‐treated cells. The p38 MAPK inhibitor SB239063 attenuated whereas the ERKs inhibitor PD98059 augmented the effects of PM_2.5 on apoptosis and the expression of related proteins. In conclusion, PM_2.5 decreases cell viability and increases apoptosis by enhancing intracellular ROS production and activating the MAPKs signaling pathway in H9c2 cells. The MAPKs signaling pathway could be a new promising target for clinical therapeutic strategies against PM_2.5‐induced cardiac injury. Copyright © 2015 John Wiley & Sons, Ltd.     

A role for lipid rafts in the protection afforded by docosahexaenoic acid against ethanol toxicity in primary rat hepatocytes

Previously, we demonstrated that eicosapentaenoic acid enhanced ethanol-induced oxidative stress and cell death in primary rat hepatocytes via an increase in membrane fluidity and lipid raft clustering. In this context, another n-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA), was tested with a special emphasis on physical and chemical alteration of lipid rafts. Pretreatment of hepatocytes with DHA reduced significantly ethanol-induced oxidative stress and cell death. DHA protection could be related to an alteration of lipid rafts. Indeed, rafts exhibited a marked increase in membrane fluidity and packing defects leading to the exclusion of a raft protein marker, flotillin. Furthermore, DHA strongly inhibited disulfide bridge formation, even in control cells, thus suggesting a disruption of protein–protein interactions inside lipid rafts. This particular spatial organization of lipid rafts due to DHA subsequently prevented the ethanol-induced lipid raft clustering. Such a prevention was then responsible for the inhibition of phospholipase C-γ translocation into rafts, and consequently of both lysosome accumulation and elevation in cellular low-molecular-weight iron content, a prooxidant factor. In total, the present study suggests that DHA supplementation could represent a new preventive approach for patients with alcoholic liver disease based upon modulation of the membrane structures.     

20-Hydroxyeicosatetraenoic acid inhibits the apoptotic responses in pulmonary artery smooth muscle cells

20-Hydroxyeicosatetraenoic acid (20-HETE), a omega-hydroxylation product of arachidonic acid catalyzed by cytochrome P450 4A (CYP4A), plays a role in vascular smooth muscle remodeling. Although its effects on angiogenic responses are known, it remains unclear whether 20-HETE acts on apoptosis of pulmonary arterial smooth muscle cells (PASMC), an important step in PASMC remodeling, and what pathways are involved in the process. Here we show evidence for the missing information. The effect of 20-HETE on PASMC apoptosis and the apoptosis-associated signaling pathways were determined with cell viability assay, Annexin V and propidium idodide binding, terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL), mitochondrial potentials assay, caspase activity assay and Western blots. We found that exogenous 20-HETE suppressed the serum deprivation-induced loss of bovine PASMCs and prevented Annexin V binding, DNA nick end labeling and chromatin condensation. The effect was worsened by 17-octadecynoic acid (17-ODYA), which inhibited the production of endogenous 20-HETE. Furthermore, 20-HETE induced the expression of bcl-2, maintained the stability of mitochondria membrane, and relieved the activation of caspase-9 and caspase-3. Such effects were reversed in the presence of 17-ODYA. Thus, these findings indicate that 20-HETE protects PASMCs against apoptosis by acting on, at least in part, the intrinsic apoptotic pathway.     

Relative bioavailability and pharmacokinetics of two oral formulations of docosahexaenoic acid/eicosapentaenoic acid after multiple-dose administration in healthy volunteers

Objectives  To assess the comparative pharmacokinetic profile and bioavailability of docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) after multiple-dose administration of a new oral formulation (test formulation) and a commercially available reference formulation in healthy subjects. Methods  Forty-eight healthy subjects received a 28-day oral treatment with DHA/EPA in the form of either the test or the reference product according to an open-label, randomized, parallel-group design. Both formulations were given t.i.d. at 8-h intervals at a dose of 3.0 g/day. Steady-state DHA and EPA concentrations in plasma and lysed whole blood were measured by gas-liquid chromatography at baseline and after 7, 14, 21 and 28 days of treatment. Kinetic parameters were compared both after subtraction of baseline concentrations and by using baseline concentrations as a covariate. Results  For both DHA and EPA, plasma and RBC concentrations measured from day 7 to day 28 were significantly higher than at baseline and did not differ significantly between the two products. On day 28 the plasma DHA concentration on average doubled the baseline level after administration of test and reference product, while there was a 10-fold increase in EPA plasma concentration. When the assessment was performed using baseline values as covariate, test-to-reference ratios for area under the curve (AUCss_0–8) and for peak concentration (Css_max) after the last administration on day 28 met bioequivalence criteria (i.e., 90% confidence intervals within 0.80–1.25 for AUCss_0–8 ratios, and within 0.75–1.33 for Css_max ratios). When the assessment was conducted after subtraction of baseline values, the 90% confidence intervals for Css_max ratios were within the bioequivalence range, whereas the intervals for AUCss_0–8 ratio were borderline for bioequivalence. Conclusion  The two formulations tested were similarly effective in increasing DHA and EPA concentrations in plasma and lysed whole blood, and showed comparable bioavailability for both active components.     

A 3-week dietary bioequivalence study in preweaning farm piglets of two sources of docosahexaenoic acid produced from two different organisms

Docosahexaenoic acid (DHA) and arachidonic acid (ARA) are components of human breast milk and commonly added to infant formula. The first DHA-containing algal oil for infant formulas was DHASCO® produced from the microalgae Crypthecodinium cohnii. Recently, new DHA-rich oil was obtained from the microalgae Schizochytrium sp., herein named DHASCO-B. The objectives of this study were to evaluate the bioequivalence of DHASCO-B to DHASCO when administered in a blend with ARA oil and the potential effects after 3 weeks’ administration in milk replacer formula to preweaning farm piglets. DHASCO-B and DHASCO were added to formula at concentrations 0.32% and 0.96% DHA (% of total fatty acids). There were no test article-related effects of any diet on piglet growth and development (clinical observations, body weight, food consumption), or clinical pathology parameters (hematology, clinical chemistry, coagulation and urinalysis). In addition, there were no adverse effects at terminal necropsy (macro- and microscopic pathology evaluations). DHA content in plasma, RBC, heart, liver and brain showed dose-related accumulation and confirmed no differences between corresponding DHASCO-B and DHASCO groups. Therefore, dietary exposure to DHASCO-B and DHASCO was well tolerated by the preweaning piglets during the 3-week dosing period right after birth and DHASCO-B and DHASCO were bioequivalent.     

甘油醛-3-磷酸脱氢酶核转位与高糖应激诱导的H9c2细胞凋亡密切相关

目的:探讨高糖应激是否引起心肌细胞中甘油醛-3-磷酸脱氢酶(GAPDH)核转位以及GAPDH核转位是否与细胞凋亡有关。方法:高糖培养H9c2细胞48 h后,收集细胞进行细胞凋亡的测定,用DCFH-DA荧光探针测定细胞中活性氧簇(ROS)的水平,用Western Blotting方法测定细胞质和细胞核中GAPDH以及细胞中诱导型一氧化氮合酶(iNOS)的表达,用细胞免疫荧光的方法测定GAPDH的核转位情况。结果:与低糖培养组相比,高糖培养组H9c2细胞凋亡率增高,ROS生成和iNOS表达增多,GAPDH由细胞质向细胞核转位;而线粒体呼吸链复合体I抑制剂鱼藤酮和iNOS抑制剂1400W均阻断GAP-DH的转位,并减少高糖诱导的H9c2细胞的凋亡。结论:高糖诱导H9c2细胞中GAPDH由细胞质向细胞核转位;鱼藤酮和1400W可抑制高糖Flavonoids诱导的细胞凋亡,这一作用与抑制GAPDH核转位有关。     

Herba Cistanche Extract Enhances Mitochondrial ATP Generation in Rat Hearts and H9c2 Cells

Abstract

To investigate the pharmacological basis of the “Yang-invigorating” action of Herbal Cistanche [the dried whole plant of Cistanche deserticola. Y.C. Ma (Orobanchaceae)], in Chinese medicine, the effects of the methanol extract of Herba Cistanche on mitochondrial ATP generation capacity were examined using an ex vivo rat heart model and an in situ H9c2 cell assay. Treatment with Herba Cistanche extract increased the myocardial mitochondrial ATP generation capacity in a dose-dependent manner in rats, as assessed by in vitro measurement. The stimulation of ATP generation capacity was associated with a parallel enhancement in mitochondrial electron transport supported by pyruvate but not succinate. Herba Cistanche treatment also increased the myocardial mitochondrial complex I and complex III activities, with the extent of stimulation on complex I activity being larger. Herba Cistanche treatment produced a dose-and time-dependent increase in mitochondrial ATP generation capacity in H9c2 cells. The results indicate that Herba Cistanche treatment can increase mitochondrial ATP generation in rat hearts ex vivo. and H9c2 cells in situ., possibly through enhancing the oxidative phosphorylation.     

Safety of docosahexaenoic acid (DHA) administered as DHA ethyl ester in a 9-month toxicity study in dogs

DHA Ethyl Ester (DHA-EE) is a 90% concentrated ethyl ester of docosahexaenoic acid manufactured from the microalgal oil. The objective of the 9-month study was to evaluate safety of DHA-EE administered to beagle dogs at dose levels 150, 1000 and 2000 mg/kg bw/day by oral gavage and to determine reversibility of any findings after a 2-month recovery period. DHA-EE was well tolerated at all doses. There were observations of dry flaky skin with occasional reddened areas at doses ≥1000 mg/kg bw/day. These findings lacked any microscopic correlate and were no longer present after the recovery period. There were no toxicologically relevant findings in body weights, body weight gains, food consumption, ophthalmological examinations, and ECG measurements. Test article-related changes in hematology parameters were limited to decreases in reticulocyte count in the high-dose males and considered non-adverse. In clinical chemistry parameters, dose-related decreases in cholesterol and triglycerides levels were observed at all doses in males and females and attributed to the known lipid-lowering effects of DHA. There were no effects on other clinical chemistry, urinalysis or coagulation parameters. There were no abnormal histopathology findings attributed to test article. The No-Observable-Adverse-Effect Level of DHA-EE was established at 2000 mg/kg bw/day for both genders.     

Docosahexaenoic acid enhances the toxic effect of imatinib on Bcr-Abl expressing HL-60 cells

The effect of docosahexaenoic acid (DHA) on the killing efficacy of imatinib on HL-60 cells expressing the Bcr-Abl protein was investigated. Imatinib is an Abl tyrosine kinase inhibitor used in the treatment of patients with chronic myeloid leukemia. The pre-treatment with DHA for 24 h raised the effect of imatinib at 100 μM concentration only. On the other hand, after 72 h pre-treatment, all concentrations of DHA tested (25, 50 and 100 μM) enhanced the toxic effect of imatinib. These results indicate that long-term pre-treatment with DHA makes Bcr-Abl HL-60 cells more susceptible to the toxic effect of imatinib.     

Pheretima aspergillum extract attenuates high‐KCl‐induced mitochondrial injury and pro‐fibrotic events in cardiomyoblast cells

Hyperkalemia is often associated with cardiac dysfunction. In this study an earthworm extract (dilong) was prepared from dried Pheretima aspergillum powder and its effect against high‐KCl challenge was determined in H9c2 cardiomyoblast cells. H9c2 cells pre‐treated with dilong (31.25, 62.5, 125, and 250 mg/mL) for 24 hours, where challenged with different doses of KCl treatment for 3 hours to determine the protective mechanisms of dilong against cardiac fibrosis. High‐KCl administration induced mitochondrial injury and elevated the levels of pro‐apoptotic proteins. The mediators of fibrosis such as ERK, uPA, SP1, and CTGF were also found to be upregulated in high‐KCl condition. However, dilong treatment enhanced IGF1R/PI3k/Akt activation which is associated with cell survival. In addition, dilong also reversed high‐KCl induced cardiac fibrosis related events in H9c2 cells and displayed a strong cardio‐protective effect. Therefore, dilong is a potential agent to overcome cardiac events associated with high‐KCl toxicity.     

丹酚酸B对H_2O_2引起H9c2细胞氧化损伤的保护作用及可能靶点蛋白寻找

观察丹酚酸B对H2O2引起H9c2细胞氧化损伤的影响,在分子水平上探讨丹酚酸B对H2O2诱导氧化损伤保护作用的可能机制。用H2O2刺激H9c2建立体外心肌细胞氧化损伤模型,MTT测定心肌细胞的存活率,Hochest33342染色观察细胞凋亡,并用蛋白质组学技术寻找丹酚酸B在心肌细胞中的可能蛋白质靶点。丹酚酸B可以提高心肌细胞在H2O2处理下的存活率,减少H2O2导致的细胞凋亡,丹酚酸B预处理组与单用H2O2组相比有8个差异表达蛋白,其中Heat shock 27 kua protein蛋白下调,cytochrome C oxidase、myo-sinlight polypeptide 6、myosin、myosin regulatory light chain 2、myosin regulatory light chain 9、tropomyosin和secreted acidic cysteine rich glycoprotein蛋白上调,差异表达的蛋白可能在丹酚酸B的保护机制中发挥重要作用。     

依达拉奉保护H9c2心肌细胞对抗异丙肾上腺素诱导的氧化应激及内质网应激反应

目的探讨依达拉奉(EDA)能否保护H9c2心肌细胞对抗异丙肾上腺素(ISO)诱导的氧化应激和内质网应激(ERS)。方法用ISO处理H9c2心肌细胞,建立β1肾上腺素受体持续兴奋诱导心肌细胞毒性的体外模型。EDA在ISO处理心肌细胞前1 h加入培养基中作为预处理。CCK-8比色法检测细胞存活率;双氯荧光素(DCFH-DA)染色/荧光显微镜照相检测细胞内活性氧(ROS)的含量;罗丹明123(Rh123)染色/荧光显微镜照相检测线粒体膜电位(MMP);Western blot法检测葡萄糖调节蛋白78(GRP78)的表达。结果 ISO在20～100μmol.L-1浓度范围内处理H9c2心肌细胞48 h,呈剂量依赖性地降低细胞存活率;80μmol.L-1ISO处理H9c2心肌细胞可使细胞内ROS含量明显增多及MMP明显降低;80μmol.L-1 ISO处理H9c2心肌细胞0～24 h,可时间依赖性地上调内质网应激蛋白GRP78的表达,其中12 h达到高峰。分别用10、20和40μmol.L-1 EDA预处理1 h可以减弱80μmol.L-1 ISO处理H9c2心肌细胞48h引起的细胞存活率降低,500、1 000和2 000μmol.L-1氧自由基清除剂NAC分别预处理1 h也可减轻ISO诱导的心肌细胞毒性反应;40μmol.L-1的EDA预处理1 h可明显减轻ISO诱导的胞内ROS堆积及MMP降低,并明显抑制ISO引起的GRP78的表达上调。结论 EDA可保护H9c2心肌细胞对抗ISO诱导的损伤作用,其机制可能与抗氧化及抑制内质网应激反应有关。