Mibefradil Alleviates High-Glucose-induced Cardiac Hypertrophy by Inhibiting PI3K/Akt/mTOR-mediated Autophagy

Ovarian Tumor Domain-Containing 7B Attenuates Pathological Cardiac Hypertrophy by Inhibiting Ubiquitination and Degradation of Krüppel-Like Factor 4

BACKGROUND

Cardiac hypertrophy (CH) is a well-established risk factor for many cardiovascular diseases and a primary cause of mortality and morbidity among older adults. Currently, no pharmacological interventions have been specifically tailored to treat CH. OTUD7B (ovarian tumor domain-containing 7B) is a member of the ovarian tumor-related protease (OTU) family that regulates many important cell signaling pathways. However, the role of OTUD7B in the development of CH is unclear. Therefore, we investigated the role of OTUD7B in CH.

METHODS AND RESULTS

OTUD7B knockout mice were used to assay the role of OTUD7B in CH after transverse aortic coarctation surgery. We further assayed the specific functions of OTUD7B in isolated neonatal rat cardiomyocytes. We found that OTUD7B expression decreased in hypertrophic mice hearts and phenylephrine-stimulated neonatal rat cardiomyocytes. Furthermore, OTUD7B deficiency exacerbated transverse aortic coarctation surgery-induced myocardial hypertrophy, abnormal cardiac function, and fibrosis. In cardiac myocytes, OTUD7B knockdown promoted phenylephrine stimulation-induced myocardial hypertrophy, whereas OTUD7B overexpression had the opposite effect. An immunoprecipitation-mass spectrometry analysis showed that OTUD7B directly binds to KLF4 (Krüppel-like factor 4). Additional molecular experiments showed that OTUD7B impedes KLF4 degradation by inhibiting lysine residue at 48 site-linked ubiquitination and suppressing myocardial hypertrophy by activating the serine/threonine kinase pathway.

CONCLUSIONS

These results demonstrate that the OTUD7B-KLF4 axis is a novel molecular target for CH treatment.

1,8-Cineole ameliorates endothelial injury and hypertension induced by L-NAME through regulation of autophagy via PI3K/mTOR signaling pathway

Our previous data confirmed that 1,8-Cineole had an antihypertensive effect in animal models. However, it is unclear whether antihypertension is dependent on the protective effect of 1,8-Cinceole on endothelial function and structure. At present, the purpose was to investigate the protective effects of 1,8-Cineole on vascular endothelial tissue in hypertensive rats and human umbilical vein endothelial cells (HUVECs). Our results showed that 1,8-Cineole significantly reduced the blood pressure and improved the vascular endothelial lesion, attenuated vascular oxidative stress and inflammation induced by L-nitroarginine methyl ester hydrochloride (L-NAME) in rats. Pretreatment with 1,8-Cineole was able to inhibit the increase in malondialdehyde (MDA) and reactive oxygen species (ROS) induced by L-NAME, and increased the release and expression of superoxide dismutase (SOD) and nitric oxide (NO). In addition, 1,8-Cineole also reversed the increase of autophagy-associated protein LC3Ⅱ/LC3Ⅰ and the decrease of P62 in vivo and in vitro respectively. There was a synergistic effect between PI3K agonists and drugs, while PI3K inhibitors blocked the efficacy of 1,8-Cineole. The addition of autophagy inhibitor CQ increases the expression of eNOS. Taken together, our results indicate that 1,8-Cineole has potential beneficial promising antihypertension depending on the integrity of vascular endothelial structure and function induced by L-NAME, and the mechanism involves ameliorating autophagy by regulatiing of PI3K/mTOR.

The role of autophagy in cardiovascular disease: Cross-interference of signaling pathways and underlying therapeutic targets

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic proteins and organelles, which realizes the metabolic needs of cells and the renewal of organelles. Autophagy-related genes (ATGs) are the main molecular mechanisms controlling autophagy, and their functions can coordinate the whole autophagic process. Autophagy can also play a role in cardiovascular disease through several key signaling pathways, including PI3K/Akt/mTOR, IGF/EGF, AMPK/mTOR, MAPKs, p53, Nrf2/p62, Wnt/β-catenin and NF-κB pathways. In this paper, we reviewed the signaling pathway of cross-interference between autophagy and cardiovascular diseases, and analyzed the development status of novel cardiovascular disease treatment by targeting the core molecular mechanism of autophagy as well as the critical signaling pathway. Induction or inhibition of autophagy through molecular mechanisms and signaling pathways can provide therapeutic benefits for patients. Meanwhile, we hope to provide a unique insight into cardiovascular treatment strategies by understanding the molecular mechanism and signaling pathway of crosstalk between autophagy and cardiovascular diseases.

Daidzein ameliorates doxorubicin-induced cardiac injury by inhibiting autophagy and apoptosis in rats

Backgrounds: Doxorubicin (Dox) is a classical antitumor antibiotic widely restricted for use due to its cardiotoxicity. Daidzein (Daid) is a soy isoflavone that enhances antioxidant enzyme systems and inhibits apoptosis to prevent cardiovascular diseases. In this study, we intended to assess whether Daid protects against Dox-induced cardiotoxicity and explored its underlying mechanisms. Methods: Male Sprague-Dawley (SD) rats were divided into five groups: control (Ctrl), 40 mg per kg per day Daidzein (Daid), 3 mg per kg per week doxorubicin (Dox), 20 mg per kg per day Daidzein + 3 mg per kg per week doxorubicin (Daid20 + Dox) and 40 mg per kg per day Daidzein + 3 mg per kg per week doxorubicin (Daid40 + Dox) groups. Cardiac function assessments, immunohistochemistry (IHC) and immunofluorescence (IF) analyses were initially performed in each group of rats. Secondly, the cell proliferative capacity analysis, AO staining, and LC3 puncta analysis were employed to evaluate the cellular response to Dox in H9c2 cells. Ultimately, the protein expressions of cleaved caspase3, LC3 II, Bcl-2, Bax, Akt, p-Akt, and cyclin D1 were examined by western blotting. Results: Pretreatment with a low dose of Daid rather than a high dose significantly enhanced cardiac function and alleviated histopathological deterioration of cardiomyocytes induced by Dox. Daid downregulated the protein levels of Bax, LC3 II, cleaved caspase3 and p-Akt, while up-regulating Bcl-2 and cyclin D1. The Akt agonist SC79 could invalidate all the protective effects of Daid both in vivo and in vitro. Conclusions: Daid reduced autophagy and apoptosis by inhibiting the PI3K/Akt pathway, thereby protecting the hearts from Dox-induced cardiac damage.

Antioxidant Phytochemicals as Potential Therapy for Diabetic Complications

The global prevalence of diabetes continues to increase partly due to rapid urbanization and an increase in the aging population. Consequently, this is associated with a parallel increase in the prevalence of diabetic vascular complications which significantly worsen the burden of diabetes. For these diabetic vascular complications, there is still an unmet need for safe and effective alternative/adjuvant therapeutic interventions. There is also an increasing urge for therapeutic options to come from natural products such as plants. Hyperglycemia-induced oxidative stress is central to the development of diabetes and diabetic complications. Furthermore, oxidative stress-induced inflammation and insulin resistance are central to endothelial damage and the progression of diabetic complications. Human and animal studies have shown that polyphenols could reduce oxidative stress, hyperglycemia, and prevent diabetic complications including diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy. Part of the therapeutic effects of polyphenols is attributed to their modulatory effect on endogenous antioxidant systems. This review attempts to summarize the established effects of polyphenols on endogenous antioxidant systems from the literature. Moreover, potential therapeutic strategies for harnessing the potential benefits of polyphenols for diabetic vascular complications are also discussed.

The combination of high glucose and LPS induces autophagy in bovine kidney epithelial cells via the Notch3/mTOR signaling pathway

BACKGROUND

Aside respiratory diseases, beef cattle may also suffer from serious kidney diseases after transportation. Hyperglycemia and gram-negative bacterial infection may be the main reasons why bovine is prone to severe kidney disease during transportation stress, however, the precise mechanism is still unclear. The purpose of the current study is to explore whether the combined treatment of high glucose (HG) and lipopolysaccharide (LPS) could induce madin-darby bovine kidney (MDBK) cells injury and autophagy, as well as investigate the potential molecular mechanisms involved.

RESULTS

As we discovered, the combined effect of HG and LPS decreased MDBK cells viability. And, HG and LPS combination also induced autophagy in MDBK cells, which was characterized by increasing the expression of LC3-II/I and Beclin1 and decreasing p62 expression. LC3 fluorescence signal formation was also significantly increased by HG and LPS combination treatment. Furthermore, we measured whether the mammalian target of rapamycin (mTOR) and the Notch3 signaling pathways were involved in HG and LPS-induced autophagy. The results showed that the combination of HG and LPS significantly increased the protein expression of Notch3 and decreased protein expression of p-mTOR, indicating that Notch3 and mTOR signaling pathways were activated. However, co-treatment with the Notch3 inhibitor (DAPT) could reverse the induction of autophagy, and increased the protein expression of p-mTOR.

CONCLUSIONS

This study demonstrated that the combination effect of HG and LPS could induce autophagy in MDBK cells, and the Notch3/mTOR signaling pathway was involved in HG and LPS-induced autophagy.

Notch3-Mediated mTOR Signaling Pathway Is Involved in High Glucose-Induced Autophagy in Bovine Kidney Epithelial Cells

It is reported that Notch3 and mTOR signaling pathways are involved in autophagy, and both can be activated by high glucose (HG). However, the relationship between Notch3 and mTOR and how Notch3 affects mTOR to regulate HG-induced autophagy in bovine kidney epithelial cells is still unclear. The purpose of this study is to explore how Notch3 affects mTOR to modulate HG-induced autophagy in bovine kidney cells. Our results showed that HG treatment significantly decreased the cell viability of MDBK cells in a dose-dependent manner. HG treatment significantly increased the expression of LC3-II/I ratio and Beclin1 protein and significantly decreased the expression of p62 protein. Consistently, LC3 fluorescence signal formation was detected by immunofluorescence in both dose and time-dependent manners. In addition, HG treatment significantly increased the expression of Notch3 protein and decreased the expression of the p-mTOR protein in both dose and time-dependent manners. Inhibition of Notch3 upregulated the expression of p-mTOR and p62 protein, and downregulated the expression of LC3-II/I ratio and Beclin1 protein. Besides, the function of Notch3 was investigated. In this study, inhibition of Notch3 activity significantly increased the viability of HG-stimulated MDBK cells. In summary, our results revealed that the Notch3-mediated mTOR signaling pathway was involved in HG-induced autophagy in MDBK cells.

Protein kinases in cardiovascular diseases

ABSTRACT

Cardiovascular disease (CVD) remains the leading cause of death worldwide. Therefore, exploring the mechanism of CVDs and critical regulatory factors is of great significance for promoting heart repair, reversing cardiac remodeling, and reducing adverse cardiovascular events. Recently, significant progress has been made in understanding the function of protein kinases and their interactions with other regulatory proteins in myocardial biology. Protein kinases are positioned as critical regulators at the intersection of multiple signals and coordinate nearly every aspect of myocardial responses, regulating contractility, metabolism, transcription, and cellular death. Equally, reconstructing the disrupted protein kinases regulatory network will help reverse pathological progress and stimulate cardiac repair. This review summarizes recent researches concerning the function of protein kinases in CVDs, discusses their promising clinical applications, and explores potential targets for future treatments.

The Diabetic Cardiomyopathy: The Contributing Pathophysiological Mechanisms

Individuals with diabetes mellitus (DM) disclose a higher incidence and a poorer prognosis of heart failure (HF) than non-diabetic people, even in the absence of other HF risk factors. The adverse impact of diabetes on HF likely reflects an underlying “diabetic cardiomyopathy” (DM–CMP), which may by exacerbated by left ventricular hypertrophy and coronary artery disease (CAD). The pathogenesis of DM-CMP has been a hot topic of research since its first description and is still under active investigation, as a complex interplay among multiple mechanisms may play a role at systemic, myocardial, and cellular/molecular levels. Among these, metabolic abnormalities such as lipotoxicity and glucotoxicity, mitochondrial damage and dysfunction, oxidative stress, abnormal calcium signaling, inflammation, epigenetic factors, and others. These disturbances predispose the diabetic heart to extracellular remodeling and hypertrophy, thus leading to left ventricular diastolic and systolic dysfunction. This Review aims to outline the major pathophysiological changes and the underlying mechanisms leading to myocardial remodeling and cardiac functional derangement in DM-CMP.

High glucose suppresses autophagy through the AMPK pathway while it induces autophagy via oxidative stress in chondrocytes

Diabetes (DB) is a risk factor for osteoarthritis progression. High glucose (HG) is one of the key pathological features of DB and has been demonstrated to induce apoptosis and senescence in chondrocytes. Autophagy is an endogenous mechanism that can protect cells against apoptosis and senescence. The effects of HG on autophagy in cells including chondrocytes have been studied; however, the results have been inconsistent. The current study aimed to elucidate the underlying mechanisms, which could be associated with the contrasting outcomes. The present study revealed that HG can induce apoptosis and senescence in chondrocytes, in addition to regulating autophagy dynamically. The present study demonstrated that HG can cause oxidative stress in chondrocytes and suppress the AMPK pathway in a dose-dependent manner. Elimination of oxidative stress by Acetylcysteine, also called N-acetyl cysteine (NAC), downregulated autophagy and alleviated HG-stimulated apoptosis and senescence, while activation of the AMPK signaling pathway by AICAR not only upregulated autophagy but also alleviated HG-stimulated apoptosis and senescence. A combined treatment of NAC and AICAR was superior to treatment with either NAC or AICAR. The study has demonstrated that HG can suppress autophagy through the AMPK pathway and induce autophagy via oxidative stress in chondrocytes.

Creation of a new class of radiosensitizers for glioblastoma based on the mibefradil pharmacophore

Glioblastoma (GBM) is the most common primary malignant tumor of the central nervous system with a dismal prognosis. Locoregional failure is common despite high doses of radiation therapy, which has prompted great interest in developing novel strategies to radiosensitize these cancers. Our group previously identified a calcium channel blocker (CCB), mibefradil, as a potential GBM radiosensitizer. We discovered that mibefradil selectively inhibits a key DNA repair pathway, alternative non-homologous end joining. We then initiated a phase I clinical trial that revealed promising initial efficacy of mibefradil, but further development was hampered by dose-limiting toxicities, including CCB-related cardiotoxicity, off-target hERG channel and cytochrome P450 enzymes (CYPs) interactions. Here, we show that mibefradil inhibits DNA repair independent of its CCB activity, and report a series of mibefradil analogues which lack CCB activity and demonstrate reduced hERG and CYP activity while retaining potency as DNA repair inhibitors. We present in vivo pharmacokinetic studies of the top analogues with evidence of brain penetration. We also report a targeted siRNA-based screen which suggests a possible role for mTOR and Akt in DNA repair inhibition by this class of drugs. Taken together, these data reveal a new class of mibefradil-based DNA repair inhibitors which can be further advanced into pre-clinical testing and eventually clinical trials, as potential GBM radiosensitizers.

TXNIP positively regulates the autophagy and apoptosis in the rat müller cell of diabetic retinopathy

AIMS

Diabetic retinopathy (DR) can cause vision loss in patients with diabetes. The present study evaluated the expression of thioredoxin interacting protein (TXNIP) and investigated the role of TXNIP in autophagy and apoptosis of DR.

MAIN METHODS

Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to measure the expression level of the targets. Clustered regularly interspaced short palindromic repeats/CRISPR-associated 9 (CRISPR/cas9) method was applied for knockout of TXNIP. TdT-mediated dUTP Nick-End Labeling (TUNEL) assay and flow cytometry were utilized to detect the apoptosis. Cell Counting Kit-8 (CCK-8) assay was used to evaluate the cell viability. EdU assay was carried out to measure the cell proliferation ability. Retinal immunohistochemistry, retinal frozen section immunofluorescence as well as the electroretinogram (ERG) recording were implemented to detect the function of the retina.

KEY FINDINGS

TXNIP was up-regulated under hyperglycemic condition both in vivo and in vitro. Overexpression of TXNIP activated the autophagy and apoptosis in the rat müller cell. Knockout of TXNIP reduced the autophagy and apoptosis in the rat müller cell under high glucose condition. TXNIP positively regulates autophagy via inhibition of the PI3K/AKT/mTOR signaling pathway. Knockdown of TXNIP improved the visual response to light stimulus of DR.

SIGNIFICANCE

Our study unraveled for the first time that TXNIP positively regulates the autophagy in rat müller cell under high glucose condition by inhibiting the PI3K/AKT/mTOR signaling pathway, providing a novel understanding in the pathogenesis of DR and suggesting a potential new therapeutic target of DR.