MADE: Multicurvature Adaptive Embedding for Temporal Knowledge Graph Completion.

Temporal knowledge graphs (TKGs) are receiving increased attention due to their time-dependent properties and the evolving nature of knowledge over time. TKGs typically contain complex geometric structures, such as hierarchical, ring, and chain structures, which can often be mixed together. However, embedding TKGs into Euclidean space, as is typically done with TKG completion (TKGC) models, presents a challenge when dealing with high-dimensional nonlinear data and complex geometric structures. To address this issue, we propose a novel TKGC model called multicurvature adaptive embedding (MADE). MADE models TKGs in multicurvature spaces, including flat Euclidean space (zero curvature), hyperbolic space (negative curvature), and hyperspherical space (positive curvature), to handle multiple geometric structures. We assign different weights to different curvature spaces in a data-driven manner to strengthen the ideal curvature spaces for modeling and weaken the inappropriate ones. Additionally, we introduce the quadruplet distributor (QD) to assist the information interaction in each geometric space. Ultimately, we develop an innovative temporal regularization to enhance the smoothness of timestamp embeddings by strengthening the correlation of neighboring timestamps. Experimental results show that MADE outperforms the existing state-of-the-art TKGC models.

Multi-modal long document classification based on Hierarchical Prompt and Multi-modal Transformer.

In the realm of long document classification (LDC), previous research has predominantly focused on modeling unimodal texts, overlooking the potential of multi-modal documents incorporating images. To address this gap, we introduce an innovative approach for multi-modal long document classification based on the Hierarchical Prompt and Multi-modal Transformer (HPMT). The proposed HPMT method facilitates multi-modal interactions at both the section and sentence levels, enabling a comprehensive capture of hierarchical structural features and complex multi-modal associations of long documents. Specifically, a Multi-scale Multi-modal Transformer (MsMMT) is tailored to capture the multi-granularity correlations between sentences and images. This is achieved through the incorporation of multi-scale convolutional kernels on sentence features, enhancing the model's ability to discern intricate patterns. Furthermore, to facilitate cross-level information interaction and promote learning of specific features at different levels, we introduce a Hierarchical Prompt (HierPrompt) block. This block incorporates section-level prompts and sentence-level prompts, both derived from a global prompt via distinct projection networks. Extensive experiments are conducted on four challenging multi-modal long document datasets. The results conclusively demonstrate the superiority of our proposed method, showcasing its performance advantages over existing techniques.

NADPH oxidase 2 mediates cardiac sympathetic denervation and myocyte autophagy, resulting in cardiac atrophy and dysfunction in doxorubicin-induced cardiomyopathy.

Doxorubicin has been used extensively as a potent anticancer agent, but its clinical use is limited by its cardiotoxicity. However, the underlying mechanisms remain to be fully elucidated. In this study, we tested whether NADPH oxidase 2 (Nox2) mediates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, resulting in cardiac atrophy and dysfunction in doxorubicin-induced heart failure. Nox2 knockout (KO) and wild-type (WT) mice were randomly assigned to receive a single injection of doxorubicin (15 mg/kg, i.p.) or saline. WT doxorubicin mice exhibited the decreases in survival rate, left ventricular (LV) wall thickness and LV fractional shortening and the increase in the lung wet-to-dry weight ratio 1 week after the injections. These alterations were attenuated in Nox2 KO doxorubicin mice. In WT doxorubicin mice, myocardial oxidative stress was increased, myocardial noradrenergic nerve fibers were reduced, myocardial expression of PGP9.5, GAP43, tyrosine hydroxylase and norepinephrine transporter was decreased, and these changes were prevented in Nox2 KO doxorubicin mice. Myocyte autophagy was increased and myocyte size was decreased in WT doxorubicin mice, but not in Nox2 KO doxorubicin mice. Nox2 mediates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy-both of which contribute to cardiac atrophy and failure after doxorubicin treatment.

NADPH oxidase 2 inhibitor GSK2795039 prevents doxorubicin-induced cardiac atrophy by attenuating cardiac sympathetic nerve terminal abnormalities and myocyte autophagy.

Doxorubicin is widely used for the treatment of human cancer, but its clinical use is limited by a cumulative dose-dependent cardiotoxicity. However, the mechanism of doxorubicin-induced cardiac atrophy and failure remains to be fully understood. In this study, we tested whether the specific NADPH oxidase 2 (Nox2) inhibitor GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, leading to the amelioration of cardiac atrophy and dysfunction in chronic doxorubicin-induced cardiomyopathy. Mice were randomized to receive saline, doxorubicin (2.5 mg/kg, every other day, 6 times) or doxorubicin plus GSK2795039 (2.5 mg/kg, twice a day, 9 weeks). Left ventricular (LV) total wall thickness and LV ejection fraction were decreased in doxorubicin-treated mice compared with saline-treated mice and the decreases were prevented by the treatment of the specific Nox2 inhibitor GSK2795039. The ratio of total heart weight to tibia length and myocyte cross-sectional area were decreased in doxorubicin-treated mice, and the decreases were attenuated by the GSK2795039 treatment. In doxorubicin-treated mice, myocardial Nox2 and 4-hydroxynonenal levels were increased, myocardial expression of GAP43, tyrosine hydroxylase and norepinephrine transporter, markers of sympathetic nerve terminals, was decreased, and these changes were prevented by the GSK2795039 treatment. The ratio of LC3 II/I, a marker of autophagy, and Atg5, Atg12 and Atg12-Atg5 conjugate proteins were increased in doxorubicin-treated mice, and the increases were attenuated by the GSK2795039 treatment. These findings suggest that inhibition of Nox2 by GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, thereby ameliorating cardiac atrophy and dysfunction after chronic doxorubicin treatment.

A versatile LTF-GO/gel hydrogel with antibacterial and antioxidative attributes for skin wound healing.

Skin wound healing will become a pressing and difficult problem following injury to the skin structure. Persistent wounds, in particular, become more vulnerable to bacterial infections, which can contribute to persistent skin inflammation. Therefore, it is critical to create a wound dressing that promotes wound healing while also being antimicrobial. In the present work, a multifunctional biological activity hydrogel formed by enzymatic cross-linking was developed by introducing graphene oxide (GO) and lactoferrin to gelatin hydrogel. Furthermore, by incorporating lactoferrin, the composite hydrogels exhibit excellent in vitro antibacterial and biocompatibility. According to cell experiments, the LTF-GO/Gel hydrogel can improve wound healing by enhancing L929 cell migration. Interestingly, under near-infrared light, LTF-GO/Gel hydrogel increases the generation of singlet oxygen (1O2) and hydroxyl radical (-OH), making the hydrogel system excellent antioxidant and antibacterial capabilities, these results demonstrate that the LTF-GO/Gel hydrogel has clinical promise as a wound dressing for wound healing. In vivo experiments unequivocally establish the capacity of the LTF-GO/Gel hydrogel to expedite wound healing and mitigate inflammation. This hydrogel, therefore, harbors immense potential for applications in wound healing.

MicroRNA-154-5p suppresses cervical carcinoma growth and metastasis by silencing Cullin2 in vitro and in vivo.

Background: MicroRNA-154-5p (miR-154-5p) plays a role in tumorigenesis in diverse human malignancies. Nevertheless, little is known about the mechanism by which miR-154-5p alters the growth and metastasis of cervical cancer. This research aimed to analyze the role of miR-154-5p in the pathology of cervical cancer in vitro and in vivo. Methods: The level of miR-154-5p in human papillomavirus 16 positive cervical cancer cells was examined by real-time quantitative polymerase chain reaction. Bioinformatics predicted the downstream targets and potential functions of miR-154-5p. Furthermore, lentiviral technology was used to construct SiHa cell lines with stable up- and down-expression levels of miR-154-5p. Its differential expression effects on the progress and metastasis of cervical cancer were analyzed using cell culture and animal models. Results: MiR-154-5p showed low expression in cervical cancer cells. Overexpression of miR-154-5p could markedly inhibit the proliferation, migration, and colony formation ability of SiHa cells, concomitantly leading to G1 arrest of the cell cycle, while silencing miR-154-5p triggered the opposite results. Meanwhile, overexpression of miR-154-5p restrained the growth and metastasis of cervical cancer by silencing CUL2 in vivo. Additionally, miR-154-5p reduced CUL2 level, and overexpression of CUL2 influenced the effect of miR-154-5p in cervical cancer. In conclusion, miR-154-5p restrained the growth and metastasis of cervical cancer by directly silencing CUL2.

Injectable antibacterial Ag-HA/ GelMA hydrogel for bone tissue engineering.

Background: Fracture or bone defect caused by accidental trauma or disease is a growing medical problem that threats to human health.Currently, most orthopedic implant materials must be removed via follow-up surgery, which requires a lengthy recovery period and may result in bacterial infection. Building bone tissue engineering scaffolds with hydrogel as a an efficient therapeutic strategy has outstanding bionic efficiency.By combining some bionic inorganic particles and hydrogels to imitate the organic-inorganic characteristics of natural bone extracellular matrix, developing injectable multifunctional hydrogels with bone tissue repair effects and also displaying excellent antibacterial activity possesses attractive advantages in the field of minimally invasive therapy in clinical. Methods: In the present work, a multifunctional injectable hydrogel formed by photocrosslinking was developed by introducing hydroxyapatite (HA) microspheres to Gelatin Methacryloyl (GelMA) hydrogel. Results: The composite hydrogels exhibited good adhesion and bending resistance properties due to the existence of HA. In addition, when the concentration of GelMA is 10% and the concentration of HA microspheres is 3%, HA/GelMA hydrogel system displayed increased microstructure stability, lower swelling rate, increased viscosity, and improved mechanical properties. Furthermore, the Ag-HA/GelMA demonstrated good antibacterial activity against Staphylococcus aureus and Escherichia coli, which could signifificantly lower the risk of bacterial infection following implantation. According to cell experiment, the Ag-HA/GelMA hydrogel is capable of cytocompatibility and has low toxicity to MC3T3 cell. Conclusion: Therefore, the new photothermal injectable antibacterial hydrogel materials proposed in this study will provide a promising clinical bone repair strategy and is expected to as a minimally invasive treatment biomaterial in bone repair fields.

QDN: A Quadruplet Distributor Network for Temporal Knowledge Graph Completion.

Temporal knowledge graph completion (TKGC) is an extension of the traditional static knowledge graph completion (SKGC) by introducing the timestamp. The existing TKGC methods generally translate the original quadruplet to the form of the triplet by integrating the timestamp into the entity/relation, and then use SKGC methods to infer the missing item. However, such an integrating operation largely limits the expressive ability of temporal information and ignores the semantic loss problem due to the fact that entities, relations, and timestamps are located in different spaces. In this article, we propose a novel TKGC method called the quadruplet distributor network (QDN), which independently models the embeddings of entities, relations, and timestamps in their specific spaces to fully capture the semantics and builds the QD to facilitate the information aggregation and distribution among them. Furthermore, the interaction among entities, relations, and timestamps is integrated using a novel quadruplet-specific decoder, which stretches the third-order tensor to the fourth-order to satisfy the TKGC criterion. Equally important, we design a novel temporal regularization that imposes a smoothness constraint on temporal embeddings. Experimental results show that the proposed method outperforms the existing state-of-the-art TKGC methods. The source codes of this article are available at https://github.com/QDN for Temporal Knowledge Graph Completion.git.

Multifunctional Fe3O4-PEI@HA nanoparticles in the ferroptosis treatment of hepatocellular carcinoma through modulating reactive oxygen species.

Ferroptosis is a novel form of regulated cell death induced by iron-dependent lipid peroxidation imbalance. It has emerged as a promising antitumor therapeutic strategy in recent years. In this work, we successfully synthesized a complex magnetic nanocube Fe3O4 modified with PEI and HA by the thermal decomposition method. While loading a ferroptosis inducer RSL3 inhibited cancer cells through the ferroptosis signal transduction pathway. The drug delivery system could actively target tumor cells through an external magnetic field and HA-CD44 binding. Zeta potential analysis showed that Fe3O4-PEI@HA-RSL3 nanoparticles were more stable and uniformly dispersed in tumor acidic environment. Moreover, cellular experiments demonstrated that Fe3O4-PEI@HA-RSL3 nanoparticles could significantly inhibit the proliferation of hepatoma cells without a cytotoxic effect on normal hepatic cells. In addition, Fe3O4-PEI@HA-RSL3 played a vital role in ferroptosis by accelerating ROS production. The expression of ferroptosis-related genes Lactoferrin, FACL 4, GPX 4 and Ferritin was significantly suppressed with increasing treatment of Fe3O4-PEI@HA-RSL3 nanocubes. Therefore, this ferroptosis nanomaterial has great potential in Hepatocellular carcinoma (HCC) therapy.

GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis in doxorubicin-induced heart failure through inhibition of NADPH oxidase-derived oxidative stress.

Doxorubicin (DOX), which is widely used for the treatment of cancer, induces cardiomyopathy associated with NADPH oxidase-derived reactive oxygen species. GSK2795039 is a novel small molecular NADPH oxidase 2 (Nox2) inhibitor. In this study, we investigated whether GSK2795039 prevents receptor-interacting protein kinase 1 (RIP1)-RIP3-mixed lineage kinase domain-like protein (MLKL)-mediated cardiomyocyte necroptosis in DOX-induced heart failure through NADPH oxidase inhibition. Eight-week old mice were randomly divided into 4 groups: control, GSK2795039, DOX and DOX plus GSK2795039. H9C2 cardiomyocytes were treated with DOX and GSK2795039. In DOX-treated mice, the survival rate was reduced, left ventricular (LV) end-systolic dimension was increased and LV fractional shortening was decreased, and these alterations were attenuated by the GSK2795039 treatment. GSK2795039 inhibited not only myocardial NADPH oxidase subunit gp91phox (Nox2) protein, but also p22phox, p47phox and p67phox proteins and prevented oxidative stress 8-hydroxy-2'-deoxyguanosine levels in DOX-treated mice. RIP3 protein and phosphorylated RIP1 (p-RIP1), p-RIP3 and p-MLKL proteins, reflective of their respective kinase activities, markers of necroptosis, were markedly increased in DOX-treated mice, and the increases were prevented by GSK2795039. GSK2795039 prevented the increases in serum lactate dehydrogenase and myocardial fibrosis in DOX-treated mice. Similarly, in DOX-treated cardiomyocytes, GSK2795039 improved cell viability, attenuated apoptosis and necrosis and prevented the increases in p-RIP1, p-RIP3 and p-MLKL expression. In conclusion, GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis through inhibition of NADPH oxidase-derived oxidative stress, leading to the improvement of myocardial remodeling and function in DOX-induced heart failure. These findings suggest that GSK2795039 may have implications for the treatment of DOX-induced cardiomyopathy.

Research progress on transcranial magnetic stimulation for post-stroke dysphagia.

Dysphagia is one of the most common manifestations of stroke, which can affect as many as 50-81% of acute stroke patients. Despite the development of diverse treatment approaches, the precise mechanisms underlying therapeutic efficacy remain controversial. Earlier studies have revealed that the onset of dysphagia is associated with neurological damage. Neuroplasticity-based transcranial magnetic stimulation (TMS), a recently introduced technique, is widely used in the treatment of post-stroke dysphagia (PSD) by increasing changes in neurological pathways through synaptogenesis, reorganization, network strengthening, and inhibition. The main objective of this review is to discuss the effectiveness, mechanisms, potential limitations, and prospects of TMS for clinical application in PSD rehabilitation, with a view to provide a reference for future research and clinical practice.

Sphingosine-1-phosphate induces myocyte autophagy after myocardial infarction through mTOR inhibition.

Sphingosine-1-phosphate (S1P)/S1P receptor 1 signaling exerts cardioprotective effects including inhibition of myocyte apoptosis. However, little is known about the effect of S1P treatment on myocyte autophagy after myocardial infarction (MI). In the present study, we tested the hypothesis that S1P induces myocyte autophagy through inhibition of the mammalian target of rapamycin (mTOR), leading to improvement of left ventricular (LV) function after MI. Sprague-Dawley rats underwent MI or sham operation. The animals were randomized to receive S1P (50 µg/kg/day, i.p.) or placebo for one week. H9C2 cardiomyocytes cultured in serum- and glucose-deficient medium were treated with or without S1P for 3 h. MI rats exhibited an increase in LV end-diastolic dimension (EDD) and decreases in LV fractional shortening (FS) and the maximal rate of LV pressure rise (+dP/dt). S1P treatment attenuated the increase in LV EDD and decreases in LV FS and +dP/dt. In the MI placebo group, the LC3 II/I ratio, a marker of autophagy, was increased, and increased further by S1P treatment. S1P also enhanced the autophagy-related proteins Atg4b and Atg5 after MI. Similarly, in cultured cardiomyocytes, autophagy was increased under glucose and serum deprivation, and increased further by S1P treatment. The effect of S1P on myocyte autophagy was associated with mTOR inhibition after MI or in cultured cardiomyocytes under glucose and serum deprivation. S1P treatment prevents LV remodeling, enhances myocyte autophagy and inhibits mTOR activity after MI. These findings suggest that S1P treatment induces myocyte autophagy through mTOR inhibition, leading to the attenuation of LV dysfunction after MI.

Apocynin prevents reduced myocardial nerve growth factor, contributing to amelioration of myocardial apoptosis and failure.

Reduced nerve growth factor (NGF) is associated with cardiac sympathetic nerve denervation in heart failure (HF) which is characterized by increased oxidative stress. Apocynin is considered an antioxidant agent which inhibits NADPH oxidase activity and improves reactive oxygen species scavenging. However, it is unclear whether apocynin prevents reduced myocardial NGF, leading to improvement of cardiac function in HF. In this study, we tested the hypothesis that apocynin prevents reduced myocardial NGF, contributing to amelioration of myocardial apoptosis and failure. Rabbits with myocardial infarction (MI) or sham operation were randomly assigned to receive apocynin or placebo for 4 weeks. MI rabbits exhibited left ventricular (LV) dysfunction, and elevation in oxidative stress, as evidenced by a decreased reduced-to-oxidized glutathione ratio and an increased 4-hydroxynonenal expression, and reduction in NGF and NGF receptor tyrosine kinase A (TrKA) expression in the remote non-infarcted myocardium. Apocynin treatment ameliorated LV dysfunction, reduced oxidative stress, prevented decreases in NGF and TrKA expression and reduced cardiomyocyte apoptosis after MI. In cultured H9C2 cardiomyocytes, hypoxia or hydrogen peroxide decreased NGF expression, and apocynin normalized hypoxia-induced reduction of NGF. Recombinant NGF attenuated hypoxia-induced apoptosis. Apocynin prevented hypoxia-induced apoptosis, and the suppressive effect of apocynin on apoptosis was abolished by NGF receptor TrKA inhibitor K252a. We concluded that apocynin prevented reduced myocardial NGF, leading to attenuation of cardiomyocyte apoptosis and LV remodelling and dysfunction in HF after MI. These findings suggest that strategies to prevent NGF reduction by inhibition of oxidative stress may be of value in amelioration of LV dysfunction in HF.

The NADPH oxidase inhibitor apocynin improves cardiac sympathetic nerve terminal innervation and function in heart failure.

NEW FINDINGS: What is the central question of this study? Does NADPH oxidase activation mediate cardiac sympathetic nerve denervation and dysfunction in heart failure. What is the main findings and its importance? Cardiac sympathetic nerve terminal density and function were reduced in heart failure after myocardial infarction in rabbits. The NADPH oxidase inhibitor apocynin prevented the reduction in cardiac sympathetic nerve terminal density and function in heart failure. This suggest that NADPH oxidase activation mediates cardiac sympathetic nerve terminal abnormalities in heart failure. NADPH oxidase may be a potential therapeutic target for cardiac sympathetic denervation and dysfunction in heart failure. ABSTRACT: Congestive heart failure (CHF) is characterized by cardiac sympathetic nerve terminal abnormalities, as evidenced by decreased noradrenaline transporter (NAT) density and cardiac catecholaminergic and tyrosine hydroxylase (TH) profiles. These alterations are associated with increased reactive oxygen species (ROS). NADPH oxidase is a major source of ROS in CHF. In this study, we tested the hypothesis that NADPH oxidase activation mediates cardiac sympathetic nerve terminal abnormalities in CHF. CHF was produced by myocardial infarction (MI) in rabbits. Rabbits with MI or a sham operation were randomized to orally receive an NADPH oxidase inhibitor, apocynin (6 mg kg-1  day-1 ), or placebo for 30 days. MI rabbits exhibited left ventricular dilatation, systolic dysfunction, and increases in NADPH oxidase activity and 4-hydroxynonenal expression in the remote non-infarcted myocardium, all of which were prevented by treatment with apocynin. Cardiac catecholaminergic histofluorescence profiles and immunostained TH and PGP9.5 expression were decreased, and the decreases were ameliorated by apocynin treatment. NAT, TH and PGP9.5 protein and mRNA expression were reduced and the reduction was mitigated by apocynin treatment. The effects of apocynin were confirmed by utilizing the NADPH oxidase inhibitor diphenyleneiodonium in a separate experiment. In conclusion, the NADPH oxidase inhibitor apocynin attenuated increased myocardial oxidative stress and decreased cardiac sympathetic nerve terminals in CHF after MI in rabbits. These findings suggest that the activation of NADPH oxidase mediates cardiac sympathetic nerve terminal abnormalities in CHF, and the inhibition of NADPH oxidase may be beneficial for the treatment of heart failure.

Antioxidant N-acetylcysteine inhibits maladaptive myocyte autophagy in pressure overload induced cardiac remodeling in rats.

Increased oxidative stress and myocyte autophagy co-exist in cardiac remodeling. However, it is unclear whether oxidative stress mediates maladaptive myocyte autophagy in pathological ventricular remodeling. In this study, we tested the hypothesis that antioxidants prevent maladaptive myocyte autophagy in pressure overload-induced left ventricular (LV) remodeling. Sprague-Dawley rats underwent abdominal aortic constriction (AAC) or sham operation. The animals were randomized to receive an antioxidant N-acetylcysteine (NAC), an autophagy inhibitor 3-methyladenine (3-MA) or placebo treatment for 2 weeks. We measured LV structure and function by echocardiography and hemodynamics, myocyte autophagy and oxidative stress assessed by 8-hydroxy-2-deoxyguanosine (8-OHdG). AAC rats exhibited increased LV hypertrophy assessed by LV wall thickness and myocyte cross-sectional area. NAC prevented LV hypertrophy in AAC rats. There were no significant differences in LV fractional shortening, end-diastolic dimension and the maximal rate of LV pressure rise among the groups. AAC rats showed an increase in myocardial 8-OHdG that was prevented by NAC. The expression of LC3 II protein, a marker of autophagy, was increased at 2 weeks after AAC. Immunohistochemical scores further confirmed the increase in LC3 expression in AAC rats. The expression of autophagic proteins Beclin1 and Atg12 and ERK activity were also increased in AAC rats. NAC prevented the increases in LC3 II protein, LC3 scores, Beclin1, Atg12 and ERK activity in AAC rats. Inhibition of autophagy by 3-MA prevented LV hypertrophy after pressure overload. These findings suggest that antioxidants may be of value to prevent pressure overload-induced cardiac remodeling through inhibition of maladaptive myocyte autophagy.

Oxidative stress impairs myocyte autophagy, resulting in myocyte hypertrophy.

NEW FINDINGS: What is the central question of this study? Does oxidative stress induce impairment of autophagy that results in myocyte hypertrophy early after pressure overload? What is the main finding and its importance? In cultured myocytes, hydrogen peroxide decreased autophagy and increased hypertrophy, and inhibition of autophagy enhanced myocyte hypertrophy. In rats with early myocardial hypertrophy after pressure overload, myocyte autophagy was progressively decreased. The antioxidant N-acetyl-cysteine or the superoxide dismutase mimic tempol prevented the decrease of myocyte autophagy and attenuated myocyte hypertrophy early after pressure overload. These findings suggest that oxidative stress impairs myocyte autophagy that results in myocyte hypertrophy. ABSTRACT: Insufficient or excessive myocyte autophagy is associated with left ventricular (LV) hypertrophy. Reactive oxygen species mediate myocyte hypertrophy in vitro and pressure overload-induced LV hypertrophy in vivo. In the present study, we tested the hypothesis that oxidative stress induces an impairment of autophagy that results in myocyte hypertrophy. H9C2 cardiomyocytes pretreated with the autophagy inhibitor 3-methyladenine were exposed to 10 and 50 µm hydrogen peroxide (H2 O2 ) for 48 h. Male Sprague-Dawley rats underwent abdominal aortic constriction (AAC) or sham operation. The animals were killed 24, 48 or 72 h after surgery. In a separate group, the AAC and sham-operated rats randomly received the antioxidant N-acetyl-cysteine or the superoxide dismutase mimic tempol for 72 h. In H9C2 cardiomyocytes, H2 O2 decreased the ratio of microtubule-associated protein light chain 3 (LC3) II to LC3 I and increased P62 and phosphorylated ERK (p-ERK) proteins and myocyte surface area. 3-Methyladenine further increased H2 O2 -induced p-ERK expression. In rats after AAC, the heart to body weight ratio was progressively increased, the LC3 II/I ratio was progressively decreased, p62 and p-ERK expression was increased, and expression of Beclin1, Atg5 and Atg12 was decreased. N-Acetyl-cysteine or tempol prevented the decreases in the LC3 II/I ratio and Beclin1 and Atg5 expression and attenuated the increases in LV wall thickness, myocyte diameter and brain natriuretic peptide expression in AAC rats. In conclusion, oxidative stress decreases Beclin1 and Atg5 expression that results in impairment of autophagy, leading to myocyte hypertrophy. These findings suggest that antioxidants or restoration of autophagy might be of value in the prevention of early myocardial hypertrophy after pressure overload.

The role of endogenous reactive oxygen species in cardiac myocyte autophagy.

Autophagy is implicated in the maintenance of cardiac homeostasis. Autophagy is activated in heart failure, in which reactive oxygen species (ROS) are increased. Exogenous ROS have been shown to induce cardiomyocyte autophagy alterations. However, little is known about the influences of physiological levels of endogenous ROS on cardiomyocyte autophagy. In the present study, we tested the hypothesis that endogenous ROS in cardiomyocytes play an important role in inducing autophagy. Cultured H9C2 cardiomyocytes or Sprague-Dawley rats were treated with the antioxidant N-acetyl-cysteine (NAC) or the superoxide dismutase mimic tempol under the basal or nutrient deprivation conditions. The autophagic flux was assessed by the lysosomal inhibitor chloroquine. In H9C2 cardiomyocytes, under a basal condition, NAC or tempol increased the ratio of LC3 II/I proteins and reduced LC3 II autophagic flux. Under nutrient deprivation, NAC increased the LC3 II/I ratio and reduced LC3 II autophagic flux. In vivo studies in rats, NAC treatment increased the LC3 II/I ratio and p-Akt protein expression in myocardium. We concluded that the antioxidants reduced autophagic flux in cardiomyocytes under the basal or nutrient deprivation conditions, suggesting that endogenous ROS promote autophagy flux under physiological conditions, and this effect is mediated, at least in part, through Akt inhibition.

Progressive Reduction in Myocyte Autophagy After Myocardial Infarction in Rabbits: Association with Oxidative Stress and Left Ventricular Remodeling.

BACKGROUND/AIMS: The alterations in myocyte autophagy after myocardial infarction (MI) and the underlying mechanisms have not been fully understood. In this study, we investigated the temporal changes of myocyte autophagy in the remote non-infarcted myocardium in rabbits after MI and the relationships between alterations of myocyte autophagy and left ventricular (LV) remodeling and myocardial oxidative stress. METHODS: Rabbits were assigned to MI or sham operation. Rabbits with MI or sham were randomly assigned to receive chloroquine, an autophagy inhibitor, antioxidant vitamins C and E or placebo for 4 weeks. H9C2 cardiomyocytes were subjected to hypoxia or hydrogen peroxide (H2O2) treatment. RESULTS: MI rabbits exhibited progressive increases of LV end-diastolic dimension (EDD), and decreases of LV fractional shortening (FS) and dP/dt over 8 weeks. Myocyte autophagy assessed by the scores of LC3 and Beclin1 expression was progressively decreased at 1, 4 and 8 weeks after MI. The ratio of LC3 II/I and Beclin1 and Atg5 proteins were also decreased at 4 weeks after MI. There was a negative correlation between autophagy and LV EDD and a positive correlation between autophagy and LV FS and dP/dt. The autophagy inhibitor chloroquine worsened LV remodeling after MI. Decreased myocyte autophagy was associated with increased myocardial 4-hydroxynonenal. Antioxidant vitamins C and E prevented the decrease in myocyte autophagy after MI. In cultured H9C2 cardiomyocytes, the LC3 II/I ratio was decreased at 4 and 8 h after exposure to hypoxia, and the change was associated with increased 8-hydroxy-2-deoxyguanosine. A low concentration of H2O2 decreased the LC3 II/I ratio. CONCLUSION: Progressive reduction in myocyte autophagy in the remote non-infarcted myocardium was associated with myocardial oxidative stress and LV remodeling after MI. Antioxidants prevented the reduction in myocyte autophagy after MI, suggesting that oxidative stress mediates reduction in myocyte autophagy that contributes to post-MI remodeling.

Globular adiponectin reduces vascular calcification via inhibition of ER-stress-mediated smooth muscle cell apoptosis.

OBJECTIVE: This study aims to explore the mechanism of globular adiponectin inhibiting vascular calcification. METHODS: We established drug-induced rat vascular calcification model, globular adiponectin was given to observe the effect of globular Adiponectin on the degree of calcification. The markers of vascular calcification and apoptosis were also investigated. Meanwhile, the in vitro effect of globular Adiponectin on vascular calcification was also evaluated using primary cultured rat vascular smooth muscle cells. RESULTS: We found that globular adiponectin could inhibit drug-induced rat vascular calcification significantly in vivo. The apoptosis of vascular smooth muscle cells was also reduced. The possible mechanism could be the down-regulation of endoplasmic reticulum stress by globular adiponectin. Experiments in primary cultured vascular smooth muscle cells also confirmed that globular adiponectin could reduce cell apoptosis to suppress vascular calcification via inhibition of endoplasmic reticulum stress. CONCLUSIONS: This study confirmed that globular adiponectin could suppress vascular calcification; one of the mechanisms could be inhibition of endoplasmic reticulum stress to reduce cell apoptosis. It could provide an effective method in the therapy of vascular calcification-associated diseases.