Mitochondrial adenine nucleotide transport and cardioprotection

Isoquercitrin alleviates pirarubicin-induced cardiotoxicity in vivo and in vitro by inhibiting apoptosis through Phlpp1/AKT/Bcl-2 signaling pathway

Introduction: Due to the cardiotoxicity of pirarubicin (THP), it is necessary to investigate new compounds for the treatment of THP-induced cardiotoxicity. Isoquercitrin (IQC) is a natural flavonoid with anti-oxidant and anti-apoptosis properties. Thus, the present study aimed to investigate the influence of IQC on preventing the THP-induced cardiotoxicity in vivo and in vitro. Methods: The optimal concentration and time required for IQC to prevent THP-induced cardiomyocyte damage were determined by an MTT assay. The protective effect was further verified in H9c2 and HCM cells using dichlorodihydrofluorescein diacetate fluorescent probes, MitoTracker Red probe, enzyme-linked immunosorbent assay, JC-1 probe, and real time-quantitative polymerase chain reaction (RT-qPCR). Rats were administered THP to establish cardiotoxicity. An electrocardiogram (ECG) was performed, and cardiac hemodynamics, myocardial enzymes, oxidative stress indicators, and hematoxylin-eosin staining were studied. Voltage-dependent anion channel 1 (VDAC1), adenine nucleotide translocase 1 (ANT1), and cyclophilin D (CYPD) were detected by qRT-PCR, and the Phlpp1/AKT/Bcl-2 axis proteins were detected by western blot, confirming that IQC markedly increased cell viability and superoxide dismutase (SOD) levels, diminished the levels of ROS and MDA, and elevated mitochondrial function and apoptosis in vivo and in vitro. Results: Results showed that IQC reduced THP-induced myocardial histopathological injury, electrocardiogram (ECG) abnormalities, and cardiac dysfunction in vivo. IQC also decreased serum levels of MDA, BNP, CK-MB, c-TnT, and LDH, while increasing levels of SOD and GSH. We also found that IQC significantly reduced VDAC1, ANT1, and CYPD mRNA expression. In addition, IQC controlled apoptosis by modulating Phlpp1/AKT/Bcl-2 signaling pathways. IQC markedly increased H9c2 and HCM cell viability and SOD levels, diminished the levels of ROS and MDA, and elevated mitochondrial function in H9c2 and HCM cells to defend against THP-induced cardiomyocyte apoptosis in vitro. The AKT inhibitor IMQ demonstrated that IQC lacked antioxidant and anti-apoptotic properties. Moreover, our data showed that IQC regulates Phlpp1 expression, thereby influencing the expression levels of p-AKT, cytochrome c, caspase-3, caspase-9, Bcl-2, and Bax. Discussion: In conclusion, our results indicate that IQC protects the changes in mitochondrial membrane permeability in cardiomyocytes by regulating the Phlpp1/AKT/Bcl-2 signaling pathway, inhibits the release of cytc from the mitochondrial inner membrane to the cytoplasm, forms apoptotic bodies, induces cell apoptosis, and reduces THP induced cardiotoxicity.

Ginsenoside F1 attenuates pirarubicin-induced cardiotoxicity by modulating Nrf2 and AKT/Bcl-2 signaling pathways

Background

Pirarubicin (THP) is an anthracycline antibiotic used to treat various malignancies in humans. The clinical usefulness of THP is unfortunately limited by its dose-related cardiotoxicity. Ginsenoside F1 (GF1) is a metabolite formed when the ginsenosides Re and Rg1 are hydrolyzed. However, the protective effects and underlying mechanisms of GF1 on THP-induced cardiotoxicity remain unclear.

Methods

We investigated the anti-apoptotic and anti-oxidative stress effects of GF1 on an in vitro model, using H9c2 cells stimulated by THP, plus trigonelline or AKT inhibitor imidazoquinoxaline (IMQ), as well as an in vivo model using THP-induced cardiotoxicity in rats. Using an enzyme-linked immunosorbent test, the levels of malondialdehyde (MDA), brain natriuretic peptide (BNP), creatine kinase (CK-MB), cardiac troponin (c-TnT), lactate dehydrogenase (LDH), superoxide dismutase (SOD) and glutathione (GSH) were determined. Nuclear factor (erythroid-derived2)-like 2 (Nrf2) and the expression of Nrf2 target genes, including heme oxygenase-1 (HO-1), glutathione-S-transferase (Gst), glutamate-cysteine ligase modifier subunit (GCLM), and expression levels of AKT/Bcl-2 signaling pathway proteins were detected using Western blot analysis.

Results

THP-induced myocardial histopathological damage, electrocardiogram (ECG) abnormalities, and cardiac dysfunction were reduced in vivo by GF1. GF1 also decreased MDA, BNP, CK-MB, c-TnT, and LDH levels in the serum, while raising SOD and GSH levels. GF1 boosted Nrf2 nuclear translocation and Nrf2 target gene expression, including HO-1, Gst, and GCLM. Furthermore, GF1 regulated apoptosis by activating AKT/Bcl-2 signaling pathways. Employing Nrf2 inhibitor trigonelline and AKT inhibitor IMQ revealed that GF1 lacked antioxidant and anti-apoptotic effects.

Conclusion

In conclusion, GF1 was found to alleviate THP-induced cardiotoxicity via modulating Nrf2 and AKT/Bcl-2 signaling pathways, ultimately alleviating myocardial oxidative stress and apoptosis.

Idarubicin-induced oxidative stress and apoptosis in cardiomyocytes: An in vitro molecular approach

Idarubicin (IDA) is an anthracycline antibiotic, frequently used for the treatment of various human cancers. In vivo rodent model studies have identified a variety of possible adverse outcomes from IDA including heart effects like increased heart weights, myocardial histopathological injury, electrocardiogram abnormalities, and cardiac dysfunction. Despite significant investigations, the molecular mechanisms responsible for the cardiotoxicity of IDA have not been fully clarified. The aim of the current study was to investigate the effects of IDA on the HL-1 cardiac muscle cell. Different concentrations of IDA (10^-6, 10^-5, 10^-4, and 10^-3 M) were used at different time (6, 12, 24, and 48 h) periods, and the Cell Counting Kit-8 (CCK-8); 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) probe method; and enzyme-linked immunosorbent assay (ELISA) were used to detect the oxidative stress level. In addition, we used network analysis to predict IDA-induced cardiotoxicity. The TUNEL assay, qRT-PCR, ELISA assay, and Western blotting detection of related apoptotic factors including caspase family, Bax, and Bcl-2. Overall, we found that IDA was generally more toxic at high concentrations or extended durations of exposure. At the same time, IDA can increase the content of reactive oxygen species (ROS), malondialdehyde (MDA), and decrease the level of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) in cells, and increase the content of lactate dehydrogenase (LDH) and nitric oxide synthase (NOS) in the medium. Network analysis showed that the apoptosis signaling pathway was activated; specifically, the caspase family was involved in the signal pathway. The results of the TUNEL assay, qRT-PCR, ELISA, and Western blot found that IDA can activate apoptotic factors. The mechanism may be related to the activation of apoptosis signaling pathway. These results indicate that the cardiotoxic effects of IDA are most likely associated with oxidative stress and ROS formation, which finally ends in apoptotic factors' activation and induction of cell apoptosis.

Nuclear-mitochondrial communication involving miR-181c plays an important role in cardiac dysfunction during obesity

AIMS

In cardiomyocytes, there is microRNA (miR) in the mitochondria that originates from the nuclear genome and matures in the cytoplasm before translocating into the mitochondria. Overexpression of one such miR, miR-181c, can lead to heart failure by stimulating reactive oxygen species (ROS) production and increasing mitochondrial calcium level ([Ca²⁺]_m). Mitochondrial calcium uptake 1 protein (MICU1), a regulatory protein in the mitochondrial calcium uniporter complex, plays an important role in regulating [Ca²⁺]_m. Obesity results in miR-181c overexpression and a decrease in MICU1. We hypothesize that lowering miR-181c would protect against obesity-induced cardiac dysfunction.

METHODS AND RESULTS

We used an in vivo mouse model of high-fat diet (HFD) for 18 weeks and induced high lipid load in H9c2 cells with oleate-conjugated bovine serum albumin in vitro. We tested the cardioprotective role of lowering miR-181c by using miR-181c/d^-/- mice (in vivo) and AntagomiR against miR-181c (in vitro). HFD significantly upregulated heart levels of miR-181c and led to cardiac hypertrophy in wild-type mice, but not in miR-181c/d^-/- mice. HFD also increased ROS production and pyruvate dehydrogenase activity (a surrogate for [Ca²⁺]_m), but the increases were alleviated in miR-181c/d^-/- mice. Moreover, miR-181c/d^-/- mice fed a HFD had higher levels of MICU1 than did wild-type mice fed a HFD, attenuating the rise in [Ca²⁺]_m. Overexpression of miR-181c in neonatal ventricular cardiomyocytes (NMVM) caused increased ROS production, which oxidized transcription factor Sp1 and led to a loss of Sp1, thereby slowing MICU1 transcription. Hence, miR-181c increases [Ca²⁺]_m through Sp1 oxidation and downregulation of MICU1, suggesting that the cardioprotective effect of miR-181c/d^-/- results from inhibition of Sp1 oxidation.

CONCLUSION

This study has identified a unique nuclear-mitochondrial communication mechanism in the heart orchestrated by miR-181c. Obesity-induced overexpression of miR-181c increases [Ca²⁺]_m via downregulation of MICU1 and leads to cardiac injury. A strategy to inhibit miR-181c in cardiomyocytes can preserve cardiac function during obesity by improving mitochondrial function. Altering miR-181c expression may provide a pharmacologic approach to improve cardiomyopathy in individuals with obesity/type 2 diabetes.

Luteolin Suppresses the Proliferation of Gastric Cancer Cells and Acts in Synergy with Oxaliplatin

Objective. Gastric cancer, one of the most common malignant tumors worldwide, arises from the gastric mucosal epithelium and severely affects patient health and quality of life. Luteolin (LUT) is a flavonoid found in vegetables and fruits with diverse functions. A large number of studies have confirmed that LUT has an antitumor effect. Therefore, this study is aimed at verifying whether LUT can exert antitumor effects in synergy with oxaliplatin (OXA). As such, we examined the effects of LUT, OXA, and their coadministration in a gastric adenocarcinoma cell line (SGC-7901). We used the MTT assay to quantify the proliferation of SGC-7901 cells, flow cytometry to detect the cell cycle and apoptosis, ELISA to detect the expression of cell-cycle-related proteins, and western blot to detect the expression of related apoptotic factors. The results of this study show that the combination of LUT and OXA inhibited SGC-7901 cell proliferation and induced apoptosis by altering cell-cycle proportions. In addition, the combination also activated Cyt c/caspase signaling in SGC-7901 cells. In summary, LUT synergy with OXA inhibited the proliferation of gastric cancer cells in vitro. The present study also elucidated the mechanism by which LUT potentiated the sensitivity of SGC-7901 cells to OXA through the Cyt c/caspase pathway.

Protective Effects of Apocynum venetum Against Pirarubicin-Induced Cardiotoxicity

Pirarubicin (THP) is an anthracycline antibiotic, frequently used for the treatment of various human cancers. Unfortunately, the clinical effectiveness of THP is limited by its dose-related cardiotoxicity. Apocynum leaf extract is an extract of the dried leaves of Apocynum venetum L. (a member of the Apocynaceae family, AVLE) that has many positive effects on the cardiovascular system and is widely consumed as tea in China. In this study we established a cardiactoxicity rat model, which showed that pretreatment with AVLE attenuated THP-induced myocardial histopathological injury, electrocardiogram abnormalities, and cardiac dysfunction. AVLE also significantly reduced serum levels of malondialdehyde (MDA), brain natriuretic peptide (BNP), creatine kinase (CK-MB), cardiac troponin (CTnT), and lactate dehydrogenase (LDH); and increased serum superoxide dismutase (SOD) levels. Treatment with AVLE or dexrazoxane (DZR) resulted in an increase Cytochrome C (cytc) in the mitochondria and reduced Cytc and cleaved-caspase-3 levels (p<0.05) in cytoplasm. We also found that AVLE significantly reduced voltage-dependent anion channel 1 (VDAC1), adenosine nucleotide transporter 1 (ANT1), and cyclophilin D (CYPD) mRNA expression (p<0.05). Furthermore, AVLE appeared to exert therapeutic effects in a dose-dependent manner. Our study suggests the anti-oxidant and anti-apoptotic properties of AVLE may be responsible for the observed cardioprotective effects.

Xeroderma Pigmentosum Group D (XPD) Inhibits the Proliferation Cycle of Vascular Smooth Muscle Cell (VSMC) by Activating Glycogen Synthase Kinase 3β (GSK3β)

BACKGROUND VSMC proliferation plays a key role in atherosclerosis, but the role of XPD in VSMC proliferation remains unknown. We investigated the expression of XPD, which is involved in cell cycle regulation, and its role in VSMC proliferation response to atherogenic stimuli. MATERIAL AND METHODS Human umbilical vein VSMCs were transfected with recombinant plasmid pEGFP-N2/XPD and pEGFP-N2 and incubated with PDGF-BB in vitro. Cell viability was determined by MTT assay. The expressions of XPD, GSK3β, p-GSK3β, CDK4, and cyclin D1 protein were detected by Western blot analysis. Cell cycle was examined by flow cytometry. RESULTS PDGF inhibited the expression of XPD in VSMCs and promoted VSMC proliferation. Overexpression of XPD significantly augmented cell cycle arrest, and attenuated protein expression levels of CDK4 and cyclin D1 in VSMCs. XPD overexpression suppressed the effects of PDGF-BB in promoting G1/S transition and accelerating protein expression levels of CDK4 and cyclin D1. XPD diminished the phosphorylation of GSK3β, and SB216763 inhibited the reduction effect of XPD on CDK4 and cyclin D1. CONCLUSIONS XPD induces VSMC cell cycle arrest, and the activation of GSK3β plays a crucial role in inhibitory effect of XPD on VSMC proliferation.

A microRNA’s journey to the center of the mitochondria

MicroRNAs (miRNAs) are known as the master regulators of gene expression, and for the last two decades our knowledge of their functional reach keeps expanding. Recent studies have shown that a miRNA’s role in regulation extends to extracellular and intracellular organelles. Several studies have shown a role for miRNA in regulating the mitochondrial genome in normal and disease conditions. Mitochondrial dysfunction occurs in many human pathologies, such as cardiovascular disease, diabetes, cancer, and neurological diseases. These studies have shed some light on regulation of the mitochondrial genome as well as helped to explain the role of miRNA in altering mitochondrial function and the ensuing effects on cells. Although the field has grown in recent years, many questions still remain. For example, little is known about how nuclear-encoded miRNAs translocate to the mitochondrial matrix. Knowledge of the mechanisms of miRNA transport into the mitochondrial matrix is likely to provide important insights into our understanding of disease pathophysiology and could represent new targets for therapeutic intervention. For this review, our focus will be on the role of a subset of miRNAs, known as MitomiR, in mitochondrial function. We also discuss the potential mechanisms used by these nuclear-encoded miRNAs for import into the mitochondrial compartment.

Listen to this article’s corresponding podcast at http://ajpheart.podbean.com/e/microrna-translocation-into-the-mitochondria/ .

Cardioprotective effects of rutin in rats exposed to pirarubicin toxicity

We established both an acute and chronic cardiac toxicity rat model, which showed pretreatment with rutin attenuated pirarubicin-induced myocardial histopathological injury, electrocardiogram abnormalities, and cardiac dysfunction. Rutin also significantly reduced serum levels of MDA, BNP, CK-MB, CTnT, and LDH and increased serum SOD levels. Treatment with rutin and dexrazoxane resulted in an increase in Bcl-2/Bax ratio (p < 0.05) and reduction in JNK and Caspase-3 protein levels, compared to the pirarubicin group (all p < 0.05). Furthermore, rutin at a dose of 50 mg/kg significantly attenuated the above-mentioned alterations. Our study suggests the antioxidant and anti-apoptotic properties of rutin may be responsible for the cardioprotective effects observed.

Codelivery of doxorubicin and sodium tanshinone IIA sulfonate using multicompartmentalized vesosomes to enhance synergism and prevent doxorubicin-induced cardiomyocyte apoptosis

Doxorubicin, one of the most effective antitumor drugs, causes serious adverse cardiac effects.

Divergent Effects of miR-181 Family Members on Myocardial Function Through Protective Cytosolic and Detrimental Mitochondrial microRNA Targets

Background

MicroRNA (miRNA) is a type of noncoding RNA that can repress the expression of target genes through posttranscriptional regulation. In addition to numerous physiologic roles for miRNAs, they play an important role in pathophysiologic processes affecting cardiovascular health. Previously, we reported that nuclear encoded microRNA (miR‐181c) is present in heart mitochondria, and importantly, its overexpression affects mitochondrial function by regulating mitochondrial gene expression.

Methods and Results

To investigate further how the miR‐181 family affects the heart, we suppressed miR‐181 using a miR‐181‐sponge containing 10 repeated complementary miR‐181 “seed” sequences and generated a set of H9c2 cells, a cell line derived from rat myoblast, by stably expressing either a scrambled or miR‐181‐sponge sequence. Sponge‐H9c2 cells showed a decrease in reactive oxygen species production and reduced basal mitochondrial respiration and protection against doxorubicin‐induced oxidative stress. We also found that miR‐181a/b targets phosphatase and tensin homolog (PTEN), and the sponge‐expressing stable cells had increased PTEN activity and decreased PI3K signaling. In addition, we have used miR‐181a/b^−/− and miR‐181c/d^−/− knockout mice and subjected them to ischemia‐reperfusion injury. Our results suggest divergent effects of different miR‐181 family members: miR‐181a/b targets PTEN in the cytosol, resulting in an increase in infarct size in miR‐181a/b^−/− mice due to increased PTEN signaling, whereas miR‐181c targets mt‐COX1 in the mitochondria, resulting in decreased infarct size in miR‐181c/d^−/− mice.

Conclusions

The miR‐181 family alters the myocardial response to oxidative stress, notably with detrimental effects by targeting mt‐COX1 (miR‐181c) or with protection by targeting PTEN (miR‐181a/b).

Mitochondrial miRNA (MitomiR): a new player in cardiovascular health

Cardiovascular disease is one of the major causes of human morbidity and mortality in the world. MicroRNAs (miRNAs) are small RNAs that regulate gene expression and are known to be involved in the pathogenesis of heart diseases, but the translocation phenomenon and the mode of action in mitochondria are largely unknown. Recent mitochondrial proteome analysis unveiled at least 2000 proteins, of which only 13 are made by the mitochondrial genome. There are numerous studies demonstrating the translocation of proteins into the mitochondria and also translocation of ribosomal RNA (viz., 5S rRNA) into mitochondria. Recent studies have suggested that miRNAs contain sequence elements that affect their subcellular localization, particularly nuclear localization. If there are sequence elements that direct miRNAs to the nucleus, it is also possible that similar sequence elements exist to direct miRNAs to the mitochondria. In this review we have summarized most of the miRNAs that have been shown to play an important role in mitochondrial function, either by regulating mitochondrial genes or by regulating nuclear genes that are known to influence mitochondrial function. While the focus of this review is cardiovascular diseases, we also illustrate the role of mitochondrial miRNA (MitomiR) in the initiation and progression of various diseases, including cardiovascular diseases, metabolic diseases, and cancer. Our goal here is to summarize the miRNAs that are localized to the mitochondrial fraction of cells, and how these miRNAs modulate cardiovascular health.

Nitrite Confers Preconditioning and Cytoprotection After Ischemia/Reperfusion Injury Through the Modulation of Mitochondrial Function

SIGNIFICANCE

Nitrite is now recognized as an intrinsic signaling molecule that mediates a number of biological processes. One of the most reproducible effects of nitrite is its ability to mediate cytoprotection after ischemia/reperfusion (I/R). This robust phenomenon has been reproduced by a number of investigators in varying animal models focusing on different target organs. Furthermore, nitrite's cytoprotective versatility is highlighted by its ability to mediate delayed preconditioning and remote conditioning in addition to acute protection.

RECENT ADVANCES

In the last 10 years, significant progress has been made in elucidating the mechanisms underlying nitrite-mediated ischemic tolerance.

CRITICAL ISSUES

The mitochondrion, which is essential to both the progression of I/R injury and the protection afforded by preconditioning, has emerged as a major subcellular target for nitrite. This review will outline the role of the mitochondrion in I/R injury and preconditioning, review the accumulated preclinical studies demonstrating nitrite-mediated cytoprotection, and finally focus on the known interactions of nitrite with mitochondria and their role in the mechanism of nitrite-mediated ischemic tolerance.

FUTURE DIRECTIONS

These studies set the stage for current clinical trials testing the efficacy of nitrite to prevent warm and cold I/R injury.

miR-181c regulates the mitochondrial genome, bioenergetics, and propensity for heart failure in vivo

MicroRNAs (miRNAs) are small non-coding RNAs, which inhibit the stability and/or translation of a mRNA. miRNAs have been found to play a powerful role in various cardiovascular diseases. Recently, we have demonstrated that a microRNA (miR-181c) can be encoded in the nucleus, processed to the mature form in the cytosol, translocated into the mitochondria, and ultimately can regulate mitochondrial gene expression. However the in vivo impact of miR-181c is unknown. Here we report an in-vivo method for administration of miR-181c in rats, which leads to reduced exercise capacity and signs of heart failure, by targeting the 3′-end of mt-COX1 (cytochrome c oxidase subunit 1). We cloned miR-181c and packaged it in lipid-based nanoparticles for systemic delivery. The plasmid DNA complexed nanovector shows no apparent toxicity. We find that the mRNA levels of mitochondrial complex IV genes in the heart, but not any other mitochondrial genes, are significantly altered with miR-181c overexpression, suggesting selective mitochondrial complex IV remodeling due to miR-181c targeting mt-COX1. Isolated heart mitochondrial studies showed significantly altered O₂-consumption, ROS production, matrix calcium, and mitochondrial membrane potential in miR-181c-treated animals. For the first time, this study shows that miRNA delivered to the heart in-vivo can lead to cardiac dysfunction by regulating mitochondrial genes.

The bizarre pharmacology of the ATP release channel pannexin1

Pannexins were originally thought to represent a second and redundant family of gap junction proteins in addition to the well characterized connexins. However, it is now evident that pannexins function as unapposed membrane channels and the major role of Panx1 is that of an ATP release channel. Despite the contrasting functional roles, connexins, innexins and pannexins share pharmacological properties. Most gap junction blockers also attenuate the function of Panx1, including carbenoxolone, mefloquine and flufenamic acid. However, in contrast to connexin based gap junction channels, Panx1 channel activity can be attenuated by several groups of drugs hitherto considered very specific for other proteins. The drugs affecting Panx1 channels include several transport inhibitors, chloride channel blockers, mitochondrial inhibitors, P2X7 receptor ligands, inflammasome inhibitors and malaria drugs. These observations indicate that Panx1 may play an extended role in a wider spectrum of physiological functions. Alternatively, Panx1 may share structural domains with other proteins, not readily revealed by sequence alignments. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.