Intake of hot water–extracted apple protects against myocardial injury by inhibiting apoptosis in an ischemia/reperfusion rat model

Mechanism in bradycardia induced by Trimethyltin chloride: Inhibition activity and expression of Na+/K+-ATPase and apoptosis in myocardia

Trimethyltin chloride (TMT) is a stabilizer by-product in the process of manufacturing plastic, which is a kind of very strong toxic substance, and has acute, cumulative and chronic toxicity. TMT may cause bradycardia in patients with occupational poisoning, the mechanism of which has not been reported. This study explored the mechanism of TMT resulting in bradycardia of C57BL/6 mice. TMT was administered to mice to measure heart rate, serum succinate dehydrogenase (SDH) level, and myocardial Na⁺/K⁺-ATPase activity and expression. The effects of TMT on myocardial apoptosis were observed by changing the expressions of caspase-3, Bax and Bcl-2 in myocardium. It was found that the heart rate and SDH activity in serum of mice gradually decreased with the increase of TMT dose compared with the control group. The activity and the expression of Na⁺/K⁺-ATPase in the heart tissue of mice exposed to TMT was measured and gradually decreased with the increase of dose and time. We measured the expression of Bcl-2, Bax, caspase-3 and cleaved caspase-3 in the heart tissues of TMT exposed mice and found that the expressions of Bax, caspase-3 and cleaved caspase-3 increased and the expressions of Bcl-2 decreased in the heart tissues of the TMT-exposed mice at different doses. With the extension of TMT exposure time, the expression of Bax and caspase-3 increased and the expression of Bcl-2 decreased in the heart tissues of TMT exposed mice. Our findings suggest the mechanisms of TMT resulting in bradycardia may be associated with the inhibited activity and decreased content of Na⁺/K⁺-ATPase, thus further leading to the changes of Bcl-2, Bax, caspase-3 and cleaved caspase-3 in the mice's ventricular tissues.

Supplementation with psyllium seed husk reduces myocardial damage in a rat model of ischemia/reperfusion

BACKGROUND/OBJECTIVES

Myocardial infarction (MI) is caused by extensive myocardial damage attributed to the occlusion of coronary arteries. Our previous study in a rat model of ischemia/reperfusion (I/R) demonstrated that administration of arabinoxylan (AX), comprising arabinose and xylose, protects against myocardial injury. In this study, we undertook to investigate whether psyllium seed husk (PSH), a safe dietary fiber containing a high level of AX (> 50%), also imparts protection against myocardial injury in the same rat model.

MATERIALS/METHODS

Rats were fed diets supplemented with PSH (1, 10, or 100 mg/kg/d) for 3 d. The rats were then subjected to 30 min ischemia through ligation of the left anterior descending coronary artery, followed by 3 h reperfusion through release of the ligation. The hearts were harvested and cut into four slices. To assess infarct size (IS), an index representing heart damage, the slices were stained with 2,3,5-triphenyltetrazolium chloride (TTC). To elucidate underlying mechanisms, Western blotting was performed for the slices.

RESULTS

Supplementation with 10 or 100 mg/kg/d of PSH significantly reduces the IS. PSH supplementation (100 mg/kg/d) tends to reduce caspase-3 generation and increase BCL-2/BAX ratio. PSH supplementation also upregulates the expression of nuclear factor erythroid 2-related factor 2 (NRF2), and its target genes including antioxidant enzymes such as glutathione S-transferase mu 2 (GSTM2) and superoxide dismutase 2 (SOD2). PSH supplementation upregulates some sirtuins (NAD⁺-dependent deacetylases) including SIRT5 (a mitochondrial sirtuin) and SIRT6 and SIRT7 (nuclear sirtuins). Finally, PSH supplementation upregulates the expression of protein kinase A (PKA), and increases phosphorylated cAMP response element-binding protein (CREB) (pCREB), a target protein of PKA.

CONCLUSIONS

The results from this study indicate that PSH consumption reduces myocardial I/R injury in rats by inhibiting the apoptotic cascades through modulation of gene expression of several genes located upstream of apoptosis. Therefore, we believe that PSH can be developed as a functional food that would be beneficial in the prevention of MI.

Protective Effects of Arabinogalactan-Peptide Isolated from Wheat Flour against Myocardial Injury in an Ischemia/Reperfusion Rat Model

We have previously shown that supplementation of wheat with hot-water extract reduces myocardial injury by inhibiting apoptosis in a rat model of myocardial infarction (MI). Arabinogalactan-peptide (AGP), a cell wall polysaccharide of wheat, was also responsible for the protection. However, the underlying mechanisms were not elucidated. In this study, we investigated the underlying mechanisms for how AGP supplementation reduces myocardial injury. First, we isolated highly pure AGP from all-purpose wheat flour. We supplemented rats with AGP at a dose of 100 mg/kg/d for 3 days, and subjected the rats to ischemia (30 min) through ligation of the left anterior descending coronary artery followed by reperfusion (3 h) through a release of the ligation. Supplementation with AGP significantly reduced the infarct size in the heart. In addition, AGP intake inhibited the apoptotic cascade, determined through decreased mitogen-activated protein kinases (p38 and c-Jun N-terminal kinase) phosphorylation, decreased Bcl-2-associated X protein/B-cell lymphoma ratios, and decreased generation of nicked DNA, which was confirmed through western blotting and terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling staining. These findings indicate that AGP intake can protect against myocardial injury. Traditionally, consumption of dietary fiber such as AGP has been shown to reduce MI risk by inhibiting preocclusion steps through reducing risk factors. Our findings suggest that AGP intake can also reduce MI risk by inhibiting postocclusion steps. This study describes a better dietary recommendation and new prevention strategy for reducing MI risk through regular consumption of wheat rich in AGP.

RP105 alleviates myocardial ischemia reperfusion injury via inhibiting TLR4/TRIF signaling pathways

The Toll-like receptor 4 (TLR4) signal pathway- induced inflammation is considered to be a crucial link to myocardial ischemia reperfusion injury (MIRI). Our previous study proved that radioprotective 105 kDa protein (RP105), a negative regulator of TLR4, performed a protective role in MIRI by anti-apoptosis approach. However, the mechanism of RP105 cardioprotection of anti-inflammation is still unclear. This study aimed to explore the underlying mechanism of RP105 anti-inflammation effect in MIRI. We established a rat model of MIRI induced by ligation of the left anterior descending coronary artery for 30 min followed by 2 h reperfusion. Animals were pre-infected with Ad-EGFP-RP105, Ad-EGFP or saline at the apex of the heart. All rats were sacrificed to collect blood samples and myocardial tissue and assessed by immunofluorescence, blood biochemical analysis, Evans blue/triphenyltetrazolium chloride (TTC), hematoxylin and eosin (H&E) staining, enzyme-linked immuno sorbent assay (ELISA), western blot analysis, quantitative PCR and electrophoretic mobility shift assay (EMSA). RP105 overexpression with adenovirus vectors reduced serum myocardial enzyme (CK-MB and LDH) activities, decreased myocardial infarct size, mitigated inflammatory factors interferon-β and tumor necrosis factor-α during MIRI. We also found that Ad-RP105 group exerted distinct repression of TLR4/TRIF signal pathway related proteins and mRNAs (TRIF, TBK-1, IRF3 and p-IRF3) with a low transcriptional activity of IRF3. These findings first expounded that RP105 could alleviate the ischemia reperfusion induced inflammatory status in heart via inhibiting TLR4/TRIF signaling pathway and provided a theoretical foundation of RP105 gene in MIRI.

Plant-based foods containing cell wall polysaccharides rich in specific active monosaccharides protect against myocardial injury in rat myocardial infarction models

Many cohort studies have shown that consumption of diets containing a higher composition of foods derived from plants reduces mortality from coronary heart disease (CHD). Here, we examined the active components of a plant-based diet and the underlying mechanisms that reduce the risk of CHD using three rat models and a quantitative proteomics approach. In a short-term myocardial infarction (MI) model, intake of wheat extract (WE), the representative cardioprotectant identified by screening approximately 4,000 samples, reduced myocardial injury by inhibiting apoptosis, enhancing ATP production, and maintaining protein homeostasis. In long-term post-MI models, this myocardial protection resulted in ameliorating adverse left-ventricular remodelling, which is a predictor of heart failure. Among the wheat components, arabinose and xylose were identified as active components responsible for the observed efficacy of WE, which was administered via ingestion and tail-vein injections. Finally, the food components of plant-based diets that contained cell wall polysaccharides rich in arabinose, xylose, and possibly fucose were found to confer protection against myocardial injury. These results show for the first time that specific monosaccharides found in the cell wall polysaccharides in plant-based diets can act as active ingredients that reduce CHD by inhibiting postocclusion steps, including MI and heart failure.

Activating transcription factor 3--an endogenous inhibitor of myocardial ischemia-reperfusion injury (Review)

Coronary heart diseases, particularly acute coronary syndrome, have increased in morbidity and mortality in recent decades. Percutaneous coronary intervention, coronary artery bypass grafting and thrombolytic agents are effective strategies to rescue the infarcted myocardium. In addition to acute myocardial infarction, the resulting myocardial ischemia‑reperfusion injury (MIRI) leads to serious secondary injury of the heart. Studies have demonstrated that activating transcription factor (ATF)/cyclic adenosine monophosphate response element binding family member ATF3 had a negative regulatory role in IRI, particularly in the kidney, cerebrum and liver. The present review expounded the expression characteristics of ATF3 and its protective effects against MIRI, providing a theoretical basis for the overexpression of ATF3 in the myocardium as a promising gene-therapeutic strategy for MIRI.