Canstatin inhibits hypoxia-induced apoptosis through activation of integrin/focal adhesion kinase/Akt signaling pathway in H9c2 cardiomyoblasts

Humanin activates integrin αV-TGFβ axis and leads to glioblastoma progression

The role of mitochondria peptides in the spreading of glioblastoma remains poorly understood. In this study, we investigated the mechanism underlying intracranial glioblastoma progression. Our findings demonstrate that the mitochondria-derived peptide, humanin, plays a significant role in enhancing glioblastoma progression through the intratumoral activation of the integrin alpha V (ITGAV)-TGF beta (TGFβ) signaling axis. In glioblastoma tissues, humanin showed a significant upregulation in the tumor area compared to the corresponding normal region. Utilizing multiple in vitro pharmacological and genetic approaches, we observed that humanin activates the ITGAV pathway, leading to cellular attachment and filopodia formation. This process aids the subsequent migration and invasion of attached glioblastoma cells through intracellular TGFβR signaling activation. In addition, our in vivo orthotopic glioblastoma model provides further support for the pro-tumoral function of humanin. We observed a correlation between poor survival and aggressive invasiveness in the humanin-treated group, with noticeable tumor protrusions and induced angiogenesis compared to the control. Intriguingly, the in vivo effect of humanin on glioblastoma was significantly reduced by the treatment of TGFBR1 inhibitor. To strengthen these findings, public database analysis revealed a significant association between genes in the ITGAV-TGFβR axis and poor prognosis in glioblastoma patients. These results collectively highlight humanin as a pro-tumoral factor, making it a promising biological target for treating glioblastoma.

Inhibition of integrin alpha v/beta 5 mitigates the protective effect induced by irisin in hemorrhage

INTRODUCTION

Irisin plays an important role in regulating tissue stress, cardiac function, and inflammation. Integrin αvβ5 was recently identified as a receptor for irisin to elicit its physiologic function. It remains unknown whether integrin αvβ5 is required for irisin's function in modulating the physiologic response to hemorrhage. The objective of this study is to examine if integrin αvβ5 contributes to the effects of irisin during the hemorrhagic response.

METHODS

Hemorrhage was induced in mice by achieving a mean arterial blood pressure of 35-45 mmHg for one hour, followed by two hours of resuscitation. Irisin (0.5  μg/kg) was administrated to assess its pharmacologic effects in hemorrhage. Cilengitide, a cyclic Arg-Gly-Asp peptide (cRGDyK) which is an inhibitor of integrin αvβ5, or control RGDS (1 mg/kg) was administered with irisin. In another cohort of mice, the irisin-induced protective effect was examined after knocking down integrin β5 with nanoparticle delivery of integrin β5 sgRNA using CRSIPR/Cas-9 gene editing. Cardiac function and hemodynamics were measured using echocardiography and femoral artery catheterization, respectively. Systemic cytokine releases were measured using Enzyme-linked immunosorbent assay (ELISA). Histological analyses were used to determine tissue damage in myocardium, skeletal muscles, and lung tissues. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was carried out to assess apoptosis in tissues.

RESULTS

Hemorrhage induced reduction of integrin αvβ5 in skeletal muscles and repressed recovery of cardiac performance and hemodynamics. Irisin treatment led to significantly improved cardiac function, which was abrogated by treatment with Cilengitide or knockdown of integrin β5. Furthermore, irisin resulted in a marked suppression of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1), muscle edema, and inflammatory cells infiltration in myocardium and skeletal muscles, which was attenuated by Cilengitide or knockdown of integrin β5. Irisin-induced reduction of apoptosis in the myocardium, skeletal muscles, and lung, which were attenuated by either the inhibition of integrin αvβ5, or knockdown of integrin β5.

CONCLUSION

Integrin αvβ5 plays an important role for irisin in modulating the protective effect during hemorrhage.

Matrikines in kidney ageing and age-related disease

PURPOSE OF REVIEW

Matrikines are cell-signalling extracellular matrix fragments and they have attracted recent attention from basic and translational scientists, due to their diverse roles in age-related disease and their potential as therapeutic agents. In kidney, the matrix undergoes remodelling by proteolytic fragmentation, so matrikines are likely to play a substantial, yet understudied, role in ageing and pathogenesis of age-related diseases.

RECENT FINDINGS

This review presents an up-to-date description of known matrikines with either a confirmed or highly anticipated role in kidney ageing and disease, including their point of origin, mechanism of cleavage, a summary of known biological actions and the current knowledge which links them to kidney health. We also highlight areas of interest, such as the prospect of matrikine cross-tissue communication, and gaps in knowledge, such as the unexplored signalling potential of many kidney disease-specific matrix fragments.

SUMMARY

We anticipate that knowledge of specific matrikines, and their roles in controlling processes of kidney pathology, could be leveraged for the development of exciting new future therapies through inhibition or even with their supplementation.

Recombinant Human Arresten and Canstatin Inhibit Angiogenic Behaviors of HUVECs via Inhibiting the PI3K/Akt Signaling Pathway

Angiogenetic inhibitors are crucial in tumor therapy, and endogenous angiogenesis inhibitors have attracted considerable attention due to their effectiveness, safety, and multi-targeting ability. Arresten and canstatin, which have anti-angiogenesis effects, are the c-terminal fragments of the α1 and α2 chains of type IV collagen, respectively. In this study, human arresten and canstatin were recombinantly expressed in Escherichia coli (E. coli), and their effects on the proliferation, migration and tube formation of human umbilical vein endothelial cells (HUVECs) were evaluated. Regarding the cell cycle distribution test and 5-ethynyl-2′-deoxyuridine (EdU) assays, arresten and canstatin could repress the proliferation of HUVECs at a range of concentrations. Transwell assay indicated that the migration of HUVECs was significantly decreased in the presence of arresten and canstatin, while tube formation assays suggested that the total tube length and junction number of HUVECs were significantly inhibited by these two proteins; moreover, they could also reduce the expression of vascular endothelial growth factor (VEGF) and the phosphorylation levels of PI3K and Akt, which indicated that the activation of the 3-kinase/serine/threonine-kinase (PI3K/Akt) signaling pathway was inhibited. These findings may have important implications for the soluble recombinant expression of human arresten and canstatin, and for the related therapy of cancer.

Identification of circRNA–miRNA–mRNA Regulatory Network and Crucial Signaling Pathway Axis Involved in Tetralogy of Fallot

Tetralogy of Fallot (TOF) is one of the most common cyanotic congenital heart diseases (CHD) worldwide; however, its pathogenesis remains unclear. Recent studies have shown that circular RNAs (circRNAs) act as “sponges” for microRNAs (miRNAs) to compete for endogenous RNA (ceRNA) and play important roles in regulating gene transcription and biological processes. However, the mechanism of ceRNA in TOF remains unclear. To explore the crucial regulatory connections and pathways of TOF, we obtained the human TOF gene, miRNA, and circRNA expression profiling datasets from the Gene Expression Omnibus (GEO) database. After data pretreatment, differentially expressed mRNAs (DEmRNAs), microRNAs (DEmiRNAs), and circRNAs (DEcircRNAs) were identified between the TOF and healthy groups, and a global triple ceRNA regulatory network, including circRNAs, miRNAs, and mRNAs based on the integrated data, was constructed. A functional enrichment analysis was performed on the Metascape website to explore the biological functions of the selected genes. Then, we constructed a protein-protein interaction (PPI) network and identified seven hub genes using the cytoHubba and MCODE plug-ins in the Cytoscape software, including BCL2L11, PIK3R1, SOCS3, OSMR, STAT3, RUNX3, and IL6R. Additionally, a circRNA–miRNA–hub gene subnetwork was established, and its enrichment analysis results indicated that the extrinsic apoptotic signaling pathway, JAK-STAT signaling pathway and PI3K-Akt signaling pathway may be involved in the pathogenesis of TOF. We further identified the hsa_circ_000601/hsa-miR-148a/BCL2L11 axis as a crucial signaling pathway axis from the subnetwork. This study provides a novel regulatory network for the pathogenesis of TOF, revealing the possible molecular mechanisms and crucial regulatory pathways that may provide new strategies for candidate diagnostic biomarkers or potential therapeutic targets for TOF.

Protective Effect of Brassica rapa Polysaccharide against Acute High-Altitude Hypoxia-Induced Brain Injury and Its Metabolomics

Brassica rapa L., a traditional Tibetan medicine, has been wildly used for treating plateau disease. Polysaccharide is an important chemical component in B. rapa. The present study aimed to evaluate the effect of B. rapa polysaccharide (BRP) against acute high-altitude hypoxia (AHH) induced brain injury and its metabolic mechanism. The rats were randomly divided into six groups: control group, AHH group, Hongjingtian oral liquid group, and three BRP groups (38, 75, and 150 mg/kg/d). Serum levels of superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), oxidized glutathione (GSSG), and lactate dehydrogenase (LDH) were detected by commercial biochemical kits. Hippocampus and cortex histopathological changes were observed by H&E staining and Nissl staining. Neuronal apoptosis was observed by TUNEL staining. The protein and gene expression of Caspase-3, Bax, Bcl-2, p-PI3K, PI3K, p-Akt, Akt, HIF-1α, microRNA 210, ISCU1/2, and COX10 were detected by western blotting and qRT-PCR. Then, a brain metabolomics method based on UPLC-Q-Exactive-MS was performed to discover potential biomarkers and analyze metabolic pathways. It was found that BRP decreased levels of MDA, LDH, and GSSG, increased GSH and SOD, reduced the pathological changes, inhibited apoptosis, and activated the PI3K/Akt/HIF-1α signaling pathway as evidenced by increased phosphorylation of PI3K and Akt, enhanced protein expression of HIF-1α and gene levels of microRNA210, ISCU1/2, and COX10. Furthermore, 15 endogenous potential biomarkers were identified in the brain through metabolomics analysis. BRP can regulate 7 potential biomarkers and the corresponding metabolic pathways were mainly associated with pyruvate metabolism and glycolysis/gluconeogenesis. Collectively, BRP has a clear protective effect on AHH-induced brain injury and its mechanisms may be related to ameliorate oxidative stress injury, inhibit apoptosis by activating PI3K/Akt/HIF-1α signaling pathway, and reverse metabolic pathway disturbances.

New insights into short peptides derived from the collagen NC1 α1, α2, and α3 (IV) domains: An experimental and MD simulations study

Proteolytically cleavage of the collagen NC1 α1 to α3 (IV) domains leads to antiangiogenic proteins called Arresten, Canstatin, and Tumstatin, respectively. The research identified that the two overlapping peptides derived from Tumstatin are more effective than other fragments and amino acids L78, V82, and D84 are essential for their activity. In the present study, the efficacy of a nine amino acid peptide derived from Tumstatin (Tum), containing amino acids L78, V82, and D84 was compared to the corresponding sequence in Arresten (Ars) and Canstatin (Can) in vitro and in vivo. Moreover, CD spectroscopy, MD, and docking simulations were performed to evaluate the structure and the interaction of peptides to integrin αvβ3, respectively. Results demonstrated that peptides inhibit viability, migration, and tube formation in vitro, as well as the growth of tumor in vivo and Canstatin-derived peptide was more potent than others. CD measurement and DSSP calculation revealed that Can had more coil conformation. According to MD simulations, Can had more fluctuation, less intramolecular interactions, and less structural compactness compared to Tum and Ars. It can be assumed that amino acid variations lead to a more flexible and loose structure compared to the other peptides. The Canstatin-derived peptide interacts with the integrin αvβ3 extremely close to RGD binding site by the most negative binding energy and more interactions. In conclusion, we for the first time identified an active peptide derived from Canstatin and showed that the sequence affected structure and thereby interaction of peptide to its receptor.

Integrinβ3 mediates the protective effects of soluble receptor for advanced glycation end-products during myocardial ischemia/reperfusion through AKT/STAT3 signaling pathway

Soluble receptor for advanced glycation end-product (sRAGE) was reported to protect myocardial ischemia/reperfusion (I/R) injuries via directly interacting with cardiomyocytes besides competing with RAGE for AGEs. However, the specific molecule for the interaction between sRAGE and cardiomyocytes are not clearly defined. Integrins which were reported to interact with RAGE on leukocytes were also expressed on myocardial cells, therefore it was supposed that sRAGE might interact with integrins on cardiomyocytes to protect hearts from ischemia/reperfusion injuries. The results showed that sRAGE increased the expression of integrinβ3 but not integrinβ1, β2, β4 or β5 in cardiomyocytes during I/R injuries. Meanwhile, the suppressive effects of sRAGE on cardiac function, cardiac infraction size and apoptosis in mice were cancelled by inhibition of integrinβ3 with cilengitide (CLG, 75 mg/kg). The results from cultured cardiomyocytes also proved that sRAGE attenuated myocardial apoptosis and autophagy through interacting with integrinβ3 to activate Akt and STAT3 pathway during oxygen and glucose deprivation/reperfusion (OGD/R) treatment. Furthermore, the phosphorylation of STAT3 was significantly downregulated by the inhibition of Akt (LY294002, 10 μM) in OGD/R and sRAGE treated cardiomyocytes, which suggested that STAT3 pathway was induced by Akt in I/R and sRAGE treated cardiomyocytes. The present study contributes to the understanding of myocardial I/R pathogenesis and provided a novel integrinβ3-dependent therapy strategy for sRAGE ameliorating I/R injuries.

Angiotensin-converting enzyme 2 alleviates pulmonary artery hypertension through inhibition of focal adhesion kinase expression

Focal adhesion kinase (FAK) is an important therapeutic target in pulmonary artery hypertension (PAH); however, the mechanism of its activation remains unknown. The present study aimed to investigate whether angiotensin-converting enzyme 2 (ACE2) could regulate FAK and alleviate PAH in a rat model of PAH established with a single administration of monocrotaline followed by continuous hypoxia treatment. In the current study, right ventricular pressure, body weight and the right ventricular hypertrophy index were measured, and hematoxylin-eosin staining was performed on lung tissues to determine whether the modeling was successful. Changes in the serum levels of FAK were measured using an ELISA kit to evaluate the association between ACE2 and FAK. The mRNA expression levels of ACE2, FAK, caspase-3 and survivin were determined using reverse transcription-quantitative PCR (RT-qPCR). The protein expression levels of ACE2, phosphorylated FAK/FAK, cleaved caspase-3/pro-caspase-3 and survivin were determined via western blotting. Immunohistochemistry was applied to detect the expression of FAK around the pulmonary arterioles. Apoptosis of smooth muscle cells around pulmonary arterioles was observed by TUNEL staining. After treatment with the ACE2 activator DIZE or inhibitor DX-600, the results demonstrated that ACE2 reduced PAH-induced changes in arteriole morphology compared with the control. It also inhibited FAK expression in serum. WB and RT-qPCR results suggested that ACE2 inhibited the expression of FAK and pathway-related proteins, and promoted caspase-3 expression. Additionally, ACE2 reduced FAK expression around the pulmonary arterioles and promoted smooth muscle cell apoptosis. The results indicated that ACE2 activation inhibited FAK expression, leading to alleviation of the symptoms of PAH.

Long-Term Hypoxia Maintains a State of Dedifferentiation and Enhanced Stemness in Fetal Cardiovascular Progenitor Cells

Early-stage mammalian embryos survive within a low oxygen tension environment and develop into fully functional, healthy organisms despite this hypoxic stress. This suggests that hypoxia plays a regulative role in fetal development that influences cell mobilization, differentiation, proliferation, and survival. The long-term hypoxic environment is sustained throughout gestation. Elucidation of the mechanisms by which cardiovascular stem cells survive and thrive under hypoxic conditions would benefit cell-based therapies where stem cell survival is limited in the hypoxic environment of the infarcted heart. The current study addressed the impact of long-term hypoxia on fetal Islet-1+ cardiovascular progenitor cell clones, which were isolated from sheep housed at high altitude. The cells were then cultured in vitro in 1% oxygen and compared with control Islet-1+ cardiovascular progenitor cells maintained at 21% oxygen. RT-PCR, western blotting, flow cytometry, and migration assays evaluated adaptation to long term hypoxia in terms of survival, proliferation, and signaling. Non-canonical Wnt, Notch, AKT, HIF-2α and Yap1 transcripts were induced by hypoxia. The hypoxic niche environment regulates these signaling pathways to sustain the dedifferentiation and survival of fetal cardiovascular progenitor cells.

Basement Membrane Extracellular Matrix Proteins in Pulmonary Vascular and Right Ventricular Remodeling in Pulmonary Hypertension

The extracellular matrix (ECM), a highly organized network of structural and non-structural proteins, plays a pivotal role in cellular and tissue homeostasis. Changes in the ECM are critical for normal tissue repair, while dysregulation contributes to aberrant tissue remodeling. Pulmonary arterial hypertension (PAH) is a severe disorder of the pulmonary vasculature characterized by pathologic remodeling of the pulmonary vasculature and right ventricle (RV), increased production and deposition of structural and non-structural proteins, and altered expression of ECM growth factors and proteases. Furthermore, ECM remodeling plays a significant role in disease progression as several dynamic changes in its composition, quantity, and organization are documented in both humans and animal models of disease. These ECM changes impact upon vascular cell biology and affect proliferation of resident cells. Further, ECM components determine the tissue architecture of the pulmonary and myocardial vasculature as well as the myocardium itself, and provide mechanical stability crucial for tissue homeostasis. However, little is known about the basement membrane (BM), a specialized, self-assembled conglomerate of ECM proteins, during remodeling. In the vasculature, the BM is in close physical association with the vascular endothelium and smooth muscle cells. While in the myocardium, each cardiomyocyte is enclosed by a BM that serves as the interface between cardiomyocytes and the surrounding interstitial matrix. In this review, we provide a brief overview on the current state of knowledge of the BM and its ECM composition and their impact on pulmonary vascular remodeling and RV dysfunction and failure in PAH.

HIF-1/AKT Signaling-Activated PFKFB2 Alleviates Cardiac Dysfunction and Cardiomyocyte Apoptosis in Response to Hypoxia

Myocardial infarction (MI) is the most prevalent disease with severe mortality, and hypoxia-induced cardiac injury and cardiomyocyte apoptosis are the significant and harmful consequences of this disease. The cross talk between hypoxia signaling and glycolysis energy flux plays a critical role in modulating MI-related heart disorder. However, the underlying mechanism remains unclear. Here, we aimed to explore the effect of a key glycolytic enzyme of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase 2 (PFKFB2) on cardiac dysfunction and apoptosis in response to hypoxia. Our data demonstrated that the mRNA and protein expression of PFKFB2 were significantly elevated in the MI mice. The MI treatment promoted the activation of PFKFB2 in vivo, as presented by the remarkably increased phosphorylation levels of PFKFB2. PFKFB2 depletion enhanced MI-induced cardiac dysfunction and cardiomyocyte apoptosis in the MI mouse model. Moreover, hypoxia treatment dramatically upregulated the expression and activation of PFKFB2 in a time-dependent manner in cardiomyocytes. Hypoxia-stimulated PFKFB2 relieved hypoxia-induced cardiomyocyte apoptosis in vitro. PFKFB2 activated the fructose-2, 6-bisphosphate (Fru-2, 6-p2) /PFK/anaerobic adenosine triphosphate (ATP) glycolysis energy flux in response to hypoxia in cardiomyocytes. Mechanically, hypoxia-activated PFKFB2 by stimulating the hypoxia-inducible factor 1 (HIF-1) /ATK signaling. Thus, we conclude that HIF-1/AKT axis-activated PFKFB2 alleviates cardiac dysfunction and cardiomyocyte apoptosis in response to hypoxia. Our finding presents a new insight into the mechanism by which HIF-1/AKT/PFKFB2 signaling modulates MI-related heart disorder under the hypoxia condition, providing potential therapeutic targets and strategy for hypoxia-related myocardial injury.

Preventive Effect of Canstatin against Ventricular Arrhythmia Induced by Ischemia/Reperfusion Injury: A Pilot Study

Ventricular arrhythmia induced by ischemia/reperfusion (I/R) injury is a clinical problem in reperfusion therapies for acute myocardial infarction. Ca2+ overload through reactive oxygen species (ROS) production is a major cause for I/R-induced arrhythmia. We previously demonstrated that canstatin, a C-terminal fragment of type IV collagen α2 chain, regulated Ca2+ handling in rat heart. In this study, we aimed to clarify the effects of canstatin on I/R-induced ventricular arrhythmia in rats. Male Wistar rats were subjected to I/R injury by ligating the left anterior descending artery followed by reperfusion. Ventricular arrhythmia (ventricular tachycardia and ventricular fibrillation) was recorded by electrocardiogram. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity and ROS production in neonatal rat cardiomyocytes (NRCMs) stimulated with oxygen glucose deprivation/reperfusion (OGD/R) were measured by lucigenin assay and 2',7'-dichlorodihydrofluorescein diacetate staining, respectively. The H2O2-induced intracellular Ca2+ ([Ca2+]i) rise in NRCMs was measured by a fluorescent Ca2+ indicator. Canstatin (20 µg/kg) inhibited I/R-induced ventricular arrhythmia in rats. Canstatin (250 ng/mL) inhibited OGD/R-induced NOX activation and ROS production and suppressed the H2O2-induced [Ca2+]i rise in NRCMs. We for the first time demonstrated that canstatin exerts a preventive effect against I/R-induced ventricular arrhythmia, perhaps in part through the suppression of ROS production and the subsequent [Ca2+]i rise.

[Development of basic research toward clinical application of cleaved fragment of type IV collagen]

Basement membrane is a dense sheet-like extracellular matrix (ECM), which separates cells from surrounding interstitium. Type IV collagen is a major component of basement membrane and three of six α chains (namely α1-α6 chains) form a triple-helix structure. Recently, endogenous bioactive factors called "matricryptins" or "matrikines", which are produced by degrading and cleaving C-terminal domain of type IV collagen, attract attentions as a novel therapeutic target or a candidate for biomarkers. In all type IV collagens, matricryptins called arresten (α1 chain), canstatin (α2), tumstatin (α3), tetrastatin (α4), pentastatin (α5), and hexastatin (α6), have been identified. The type IV collagen-derived matricryptins have been previously studied as new therapeutic targets for neoplastic diseases since they exert anti-angiogenic and/or anti-tumor effects. On the other hand, we have recently demonstrated the cardioprotective effects of matricryptins in addition to the altered expression levels in cardiac diseases. In this review, we introduce the results of fundamental studies for the type IV collagen-derived matricryptins in various diseases, such as neoplastic diseases and cardiac diseases, and discuss the potential clinical application as novel therapeutic agents and biomarkers.

Bidirectional regulation of genistein on the proliferation and differentiation of C2C12 myoblasts

Genistein is a widely studied phytoestrogen. The effects of genistein on myoblasts were reported long ago, but the conclusions are controversial. In this study, we evaluated the effects of different concentrations of genistein on C2C12 myoblasts. Genistein treatment promoted myoblast proliferation in a dose-dependent manner in the concentration range of 0-2 µM/L, reaching its maximum effect at 2 µM/L. Proliferation then declined, and a concentration higher than 20 µM/L showed significant inhibition. In addition, genistein treatment promoted myoblast differentiation at a dose of 10 µM/L. However, at treatment concentrations higher than 10 µM/L, the effect on myoblast differentiation was rapidly inhibited as the concentration increased. Genistein treatment also down-regulated the expression of miR-222, resulting in increased expression of its target genes, MyoG, MyoD, and ERα and thereby promoting myoblast differentiation. Our results suggest that genistein has a dose-dependent and bidirectional regulation effect on myoblast proliferation and differentiation. We also found that genistein is a miRNA inducer, and it specifically affects the expression of miR-222 to regulate myoblast differentiation.

Long-term administration of recombinant canstatin prevents adverse cardiac remodeling after myocardial infarction

Myocardial infarction (MI) still remains a leading cause of mortality throughout the world. An adverse cardiac remodeling, such as hypertrophy and fibrosis, in non-infarcted area leads to uncompensated heart failure with cardiac dysfunction. We previously demonstrated that canstatin, a C-terminus fragment of type IV collagen α2 chain, exerted anti-remodeling effect against isoproterenol-induced cardiac hypertrophy model rats. In the present study, we examined whether a long-term administration of recombinant canstatin exhibits a cardioprotective effect against the adverse cardiac remodeling in MI model rats. Left anterior descending artery of male Wistar rats was ligated and recombinant mouse canstatin (20 μg/kg/day) was intraperitoneally injected for 28 days. Long-term administration of canstatin improved survival rate and significantly inhibited left ventricular dilatation and dysfunction after MI. Canstatin significantly inhibited scar thinning in the infarcted area and significantly suppressed cardiac hypertrophy, nuclear translocation of nuclear factor of activated T-cells, interstitial fibrosis and increase of myofibroblasts in the non-infarcted area. Canstatin significantly inhibited transforming growth factor-β1-induced differentiation of rat cardiac fibroblasts into myofibroblasts. The present study for the first time demonstrated that long-term administration of recombinant canstatin exerts cardioprotective effects against adverse cardiac remodeling in MI model rats.

Diosmetin alleviates hypoxia‑induced myocardial apoptosis by inducing autophagy through AMPK activation

Diosmetin has shown great potential in the control of several diseases. The aim of the present study was to evaluate the role of diosmetin as a candidate agent for the treatment of myocardial infarction which was mainly caused by hypoxia. The model of hypoxia‑injured myocardial cells was established using the H9c2 cell line. Cell viability was determined using Cell Counting Kit‑8, cell apoptosis was determined by Annexin V‑FITC Apoptosis Detection Kit and cleaved caspase‑3 level was assessed by western blot analysis. Autophagy was monitored using a commercial kit, and a well‑established reporter system was used to confirm the role of diosmetin in autophagy. The activity of adenosine 5'‑monophosphate‑activated protein kinase (AMPK) signaling was detected by western blot analysis. Cell viability assay indicated that diosmetin alleviated hypoxia‑induced cell death of H9c2 cells in a dose‑dependent manner. Data of the apoptosis assay revealed that diosmetin reduced the proportion of apoptotic cells in the hypoxia‑injured H9c2 cells. It was also found that the occurrence of autophagy was promoted when hypoxia‑injured cells were treated with diosmetin alone, and results of the western blot analysis revealed that AMPK signaling was activated by diosmetin. Administration of diosmetin together with an inhibitor of autophagy (3‑methyladenine, 3‑MA) or AMPK (Compound C) was able to decrease the diosmetin‑induced autophagy as well as the cytoprotective effects in the hypoxia‑injured cells. Our study concluded that diosmetin exhibits a cytoprotective effect on hypoxia‑injured myocardial cells by inducing autophagy and alleviating apoptosis. AMPK was demonstrated to regulate the observed effects caused by diosmetin. This investigation confirmed diosmetin as a promising drug candidate for myocardial infarction treatment. The present findings regarding the inherent molecular mechanisms involved in the protective effects of diosmetin promote the clinical application of diosmetin.

Euscaphic acid and Tormentic acid protect vascular endothelial cells against hypoxia-induced apoptosis via PI3K/AKT or ERK 1/2 signaling pathway

AIMS

Euscaphic acid and Tormentic acid are aglycones of Kaji-ichigoside F1 and Rosamultin, respectively. These four compounds are pentacyclic triterpenoid, isolated from the subterranean root of the Potentilla anserina L. Based on the protective roles against hypoxia-induced apoptosis of Euscaphic acid and Tormentic acid in vascular endothelial cells, this study was designed to determine the mechanisms.

MAIN METHODS

The model of hypoxic injuries in EA. hy926 cells was established. Through applications of PI3K/AKT inhibitor, LY294002 and ERK1/2 inhibitor, PD98059, we explored the relationships between pharmacodynamic mechanisms and PI3K/AKT or ERK 1/2 signaling pathway. The anti-hypoxic effects were studied by methyl-thiazolyl-tetrazolium (MTT) assay, Hematoxylin-Eosin (HE) staining, DAPI staining, and flow cytometry. The mechanisms of anti-mitochondrial apoptosis were explored by western blot. The expressions of p-ERK 1/2, ERK 1/2, p-AKT, AKT, p-NF-κB, NF-κB, Bcl-2, Bax, Cyt C, cleaved caspase-9 and cleaved caspase-3 were detected.

KEY FINDINGS

Euscaphic acid protected vascular endothelial cells against hypoxia-induced apoptosis via ERK1/2 signaling pathway, and Tormentic acid brought its efficacy into full play via PI3K/AKT and ERK1/2 signaling pathways. In addition, PI3K/AKT signaling pathway positively regulated ERK1/2 pathway, and ERK1/2 pathway negatively regulated PI3K/AKT pathway.

SIGNIFICANCE

This evidence provides theoretical and experimental basis for the following research on anti-hypoxic drugs of Potentilla anserina L.

Kaji-Ichigoside F1 and Rosamultin Protect Vascular Endothelial Cells against Hypoxia-Induced Apoptosis via the PI3K/AKT or ERK1/2 Signaling Pathway

As a pair of differential isomers, Kaji-ichigoside F1 and Rosamultin are both pentacyclic triterpenoids isolated from the subterranean root of Potentilla anserina L., a plant used in folk medicine in western China as antihypoxia and anti-inflammatory treatments. We demonstrated that Kaji-ichigoside F1 and Rosamultin effectively prevented hypoxia-induced apoptosis in vascular endothelial cells. We established a hypoxia model, using EA.hy926 cells, to further explore the mechanisms. Hypoxia promoted the phosphorylation of AKT, ERK1/2, and NF-κB. In hypoxic cells treated with Kaji-ichigoside F1, p-ERK1/2 and p-NF-κB levels were increased, while the level of p-AKT was decreased. Treatment with Rosamultin promoted phosphorylation of ERK1/2, NF-κB, and AKT in hypoxic cells. Following the addition of LY294002, the levels of p-AKT, p-ERK1/2, and p-NF-κB decreased significantly. Addition of PD98059 resulted in reduced levels of p-ERK1/2 and p-NF-κB, while p-AKT levels were increased. Pharmacodynamic analysis demonstrated that both LY294002 and PD98059 significantly inhibited the positive effects of Kaji-ichigoside F1 on cell viability during hypoxia, consistent with the results of hematoxylin-eosin (H&E) staining, DAPI staining, and flow cytometry. The antihypoxia effects of Rosamultin were remarkably inhibited by LY294002 but promoted by PD98059. In Kaji-ichigoside F1- and Rosamultin-treated cells, Bcl2 expression was significantly upregulated, while expression of Bax and cytochrome C and levels of cleaved caspase-9 and cleaved caspase-3 were reduced. Corresponding to pharmacodynamic analysis, LY294002 inhibited the regulatory effects of Kaji-ichigoside F1 and Rosamultin on the above molecules, while PD98059 inhibited the regulatory effects of Kaji-ichigoside F1 but enhanced the regulatory effects of Rosamultin. In conclusion, Kaji-ichigoside F1 protected vascular endothelial cells against hypoxia-induced apoptosis by activating the ERK1/2 signaling pathway, which positively regulated the NF-κB signaling pathway and negatively regulated the PI3K/AKT signaling pathway. Rosamultin protected vascular endothelial cells against hypoxia-induced apoptosis by activating the PI3K/AKT signaling pathway and positively regulating ERK1/2 and NF-κB signaling pathways.

Eukaryotic elongation factor 2 (eEF2) kinase/eEF2 plays protective roles against glucose deprivation-induced cell death in H9c2 cardiomyoblasts

During the development of cardiac hypertrophy, glucose deprivation (GD) associated with coronary microvascular rarefaction is caused, leading to cardiomyocyte death. Phosphorylation (inactivation) of eukaryotic elongation factor 2 (eEF2) by eEF2 kinase (eEF2K) inhibits protein translation, a highly energy consuming process, which plays protective roles against nutrient deprivation-induced cell death. We previously showed that eEF2 phosphorylation was increased in isolated heart from several cardiac hypertrophy models. In this study, we investigated whether eEF2K/eEF2 mediates the inhibition of cardiomyocyte death under GD condition. In H9c2 rat cardiomyoblasts cultured with serum-free medium, GD significantly augmented eEF2 phosphorylation and signals related to autophagy [increase of microtubule-associated protein 1 light chain 3 (LC3)-II to LC3-I ratio] and apoptosis (cleavage of caspase-3) as determined by Western blotting. GD induced cell death, which was augmented by eEF2K gene knockdown using a small interfering RNA. eEF2K gene knockdown significantly augmented GD-induced cleavage of caspase-3 and apoptotic nuclear condensation as determined by 4', 6-diamidino-2-phenylindole staining. In contrast, eEF2K gene knockdown significantly inhibited GD-induced increase of LC3-II to LC3-I ratio and autophagosome formation as determined by an immunofluorescence staining. An inhibitor of autophagy, 3-methyladenine or bafilomycin A1 significantly augmented GD-induced cleavage of caspase-3. Further, eEF2K gene knockdown significantly inhibited GD-induced phosphorylation of adenosine monophosphate-activated protein kinase (AMPK)α and its downstream substrate, unc-51 like autophagy activating kinase (ULK)1. An inhibitor of AMPK, dorsomorphin significantly inhibited GD-induced increase of LC3-II to LC3-I ratio. In conclusion, we for the first time revealed that eEF2K/eEF2 axis under GD condition mediates the inhibition of apoptotic H9c2 cell death at least in part via promotion of autophagy through AMPKα/ULK1 signaling pathway.

Downregulation of miR-483-5p decreases hypoxia-induced injury in human cardiomyocytes by targeting MAPK3

Background

MiR-483-5p was recently identified as a risk factor in the early stages of acute myocardial infarction (AMI) patients. Here, we further investigated how miR-483-5p affects cardiomyocyte apoptosis and oxidative stress under hypoxic conditions.

Methods

Plasma samples were collected from AMI patients and healthy volunteers. The expression of miR-483-5p was determined using quantitative real-time PCR. An in vitro hypoxic model was constructed to mimic AMI in AC16 cells. Cell viability, apoptosis and oxidative stress biomarker levels (MDA, SOD and CAT) were respectively determined using CCK-8, flow cytometry and commercial assay kits.

Results

The expression levels of miR-483-5p were significantly higher in AMI patients than in control subjects. Circulating levels of miR-483-5p positively correlated with creatine kinase MB isoform (CK-MB) and cardiac troponin I (cTnI) levels. The in vitro experiments showed that the expression levels of miR-483-5p were also upregulated in hypoxia-induced AC16 cell injury. MiR-483-5p overexpression significantly increased hypoxia-induced cardiomyocyte apoptosis and oxidative stress, while knockdown attenuated these effects. Mechanistically, miR-483-5p directly targets MAPK3 in AC16 cells. Furthermore, the protective effects of miR-483-5p knockdown against hypoxia-induced cardiomyocyte injury are partially dependent on MAPK3.

Conclusions

MiR-483-5p, which targets MAPK3, might be a potential therapeutic target for the diagnosis and prevention of hypoxia-induced myocardial injury.

Canstatin suppresses isoproterenol-induced cardiac hypertrophy through inhibition of calcineurin/nuclear factor of activated T-cells pathway in rats

Pathological cardiac hypertrophy associated with cardiac dysfunction is an independent risk factor for arrhythmia, myocardial infarction and sudden death. Canstatin, a C-terminal fragment of type IV collagen α2 chain, is abundantly expressed in normal heart tissue. We previously demonstrated that canstatin inhibits isoproterenol (ISO)-induced dephosphorylation of nuclear factor of activated T-cells (NFAT)c4, which plays an important role in cardiac hypertrophy, in differentiated H9c2 cardiomyoblasts. Thus, we investigated whether in vivo canstatin administration prevents ISO-induced cardiac hypertrophy through the inhibition of NFATc4 pathway. Rats were subcutaneously injected with ISO (5 mg/kg) or saline (Cont) for 7 days. Simultaneously, recombinant mouse canstatin (20 μg/kg) or vehicle was intraperitoneally administered. After left ventricular wall thickness and cardiac function were measured by echocardiography, the hearts were isolated and left ventricular weight (LVW) was weighed. Azan staining was performed to measure cross-sectional diameter of cardiomyocytes. Activity of calcineurin, which dephosphorylates NFATc4, was measured by calcineurin phosphatase activity assay. Immunohistochemical staining was performed to evaluate nuclear translocation of NFATc4. Intracellular Ca²⁺ concentration in neonatal rat cardiomyocytes (NRCMs) was measured by using a calcium indicator. Canstatin significantly inhibited ISO-induced increase of LVW, left ventricular posterior wall thickness at end-diastole and diameter of cardiomyocytes. Canstatin significantly inhibited ISO-induced activation of calcineurin, nuclear translocation of NFATc4, increased mRNA expression of β-myosin heavy chain and α-skeletal actin, and intracellular Ca²⁺ rise in NRCMs. In summary, we for the first time demonstrated that canstatin administration suppresses ISO-induced cardiac hypertrophy possibly through the blockade of calcineurin/NFATc4 pathway in rats.

Extracorporeal shock waves protect cardiomyocytes from doxorubicin-induced cardiomyopathy by upregulating survivin via the integrin-ILK-Akt-Sp1/p53 axis

Doxorubicin (DOX) is a widely used anti-cancer drug; however, it has limited application due to cardiotoxicity. Extracorporeal shock waves (ESW) have been suggested to treat inflammatory and ischemic diseases, but the concrete effect of ESW in DOX-induced cardiomyopathy remain obscure. After H9c2 cells were subjected to ESW (0.04 mJ/cm²), they were treated with 1 μM DOX. As a result, ESW protected cardiomyocytes from DOX-induced cell death. H9c2 cells treated with DOX downregulated p-Akt and survivin expression, whereas the ESW treatment recovered both, suggesting its anti-apoptotic effect. ESW activated integrin α_vβ₃ and α_vβ₅, cardiomyocyte mechanosensors, followed by upregulation of ILK, p-Akt and survivin levels. Further, Sp1 and p53 were determined as key transcriptional factors mediating survivin expression via Akt phosphorylation by ESW. In in vivo acute DOX-induced cardiomyopathy model, the echocardiographic results showed that group subjected to ESW recovered from acute DOX-induced cardiomyopathy; left ventricular function was improved. The immunohistochemical staining results showed increased survivin and Bcl2 expression in ESW + DOX group compared to those in the DOX-injected group. In conclusion, non-invasive shockwaves protect cardiomyocytes from DOX-induced cardiomyopathy by upregulating survivin via integrin-ILK-Akt-Sp1/p53 pathway. In vivo study proposed ESW as a new kind of specific and safe therapy against acute DOX-induced cardiomyopathy.

Neutrophil Gelatinase-Associated Lipocalin2 Exaggerates Cardiomyocyte Hypoxia Injury by Inhibiting Integrin β3 Signaling

Background

The neutrophil inflammatory protein, lipocalin-2 (NGAL), is elevated in certain forms of cardiac hypertrophy and acute heart failure. However, the specific role of NGAL in cardiac hypoxia injury is unclear. This study aimed to elucidate the functional role of NGAL in cardiomyocyte hypoxia injury.

Material/Methods

Neonatal rat cardiomyocytes were transfected with adenovirus [(Ad-NGAL] to overexpress human-NGAL and then were exposed to hypoxia for 24 h to establish a hypoxia model. Cell inflammation was detected by RT-PCT and ELISA assay. Cell apoptosis was detected by TUNEL assay. Oxidative stress was also detected by commercial kits.

Results

An increased inflammatory response, apoptosis, and augmented oxidative stress were observed after exposure to hypoxia, while NGAL overexpression in cells increased the expression and release of inflammatory cytokines. NGAL overexpression also increased the number of apoptotic cells and the imbalance of Bax/Bcl-2 protein expression. Moreover, NGAL overexpression increased the levels of reactive oxygen species and oxidase activity, but reduced anti-oxidase activity. Mechanistically, we found that NGAL decreased the expression of integrin β3, but not the expression of integrin avβ3 and avβ5, thus inhibiting the downstream protein AKT. When we used the constitutively activated AKT overexpression adenovirus to activate AKT, the deteriorated phenotype by NGAL was counteracted.

Conclusions

NGAL can directly affect cardiomyocytes and cause cardiomyocyte deteriorated hypoxia injury through inhibiting integrin β3 signaling.

Cathepsin S degrades arresten and canstatin in infarcted area after myocardial infarction in rats

The basement membrane surrounding cardiomyocytes is mainly composed of α1 and α2 chain of type IV collagen. Arresten and canstatin are fragments of non-collagenous C-terminal domain of α1 and α2 chain, respectively. We previously reported that the expression of canstatin was decreased in infarcted area 2 weeks after myocardial infarction in rats. In the present study, we investigated the regulatory mechanism for expression of arresten and canstatin. Myocardial infarction model rats were produced by ligating left anterior descending artery. Western blotting and immunohistochemical staining were performed to determine the protein expression and distribution. Arresten and canstatin were highly expressed in the heart. One day and three days after myocardial infarction, the expression of arresten and canstatin in infarcted area was lower than that in non-infarcted area. The expression of cathepsin S, which is known to degrade arresten and canstatin, was increased in the infarcted area. A knockdown of cathepsin S gene using small interference RNA suppressed the decline of arresten and canstatin in the infarcted area 3 days after myocardial infarction. This study for the first time revealed that arresten and canstatin are immediately degraded by cathepsin S in the infarcted area after myocardial infarction. These findings present a novel fundamental insight into the pathogenesis of myocardial infarction through the turnover of basement membrane-derived endogenous factors.

β-Integrin mediates LPS-induced coelomocyte apoptosis in sea cucumber Apostichopus japonicus via the integrin/FAK/caspase-3 signaling pathway

Lipopolysaccharides (LPS) can induce the apoptosis of coelomocytes in Apostichopus japonicus (A. japonicus), and β-integrin serves as an apoptotic inhibitor during this process. However, the underlying mechanism in invertebrates is largely unknown. Integrin/focal adhesion kinase (FAK) signaling pathway modulates the apoptosis in vertebrates. In this study, a novel FAK was identified from A. japonicus (designated as AjFAK) by β-integrin (designated as AjITGB) -mediated GST-pull down assay. This interaction was further validated in the LPS-exposed coelomocytes through co-immunoprecipitation and immunofluorescence analyses. To investigate the functional role of AjFAK in AjITGB-mediated coelomocyte apoptosis, we cloned the full-length cDNA of AjFAK and characterized its relationship with AjITGB through real-time PCR. The mRNA expression levels of AjFAK exhibited consistent expression patterns with those of AjITGB in our previous work with 0.48- and 0.22-fold decreases at 12 and 96 h in LPS-exposed coelomocytes and in Vibrio splendidus challenged sea cucumber, respectively. Moreover, the expression level of AjFAK decreased to 0.35-fold in AjITGB knockdown treatment by specific small interference RNA (siRNA). We further performed an assay for the apoptotic rate of coelomocytes in AjITGB, AjFAK, and AjITGB/AjFAK silencing conditions and found that their apoptotic percentages increased to 26%, 25%, and 30%, respectively, compared with those of the control. Finally, the expression levels of four caspases from A. japonicus were also investigated to determine the apoptotic effector. After AjITGB or AjFAK was silenced, the mRNA levels of caspase-3 were 6.6-fold and 2.5-fold higher than those of the control, respectively. In addition, the enzymatic activity of caspase-3 was enhanced to 1.82- and 1.79-fold that of the control in the two groups. However, no significant changes were detected in caspase-2/6/8. All our results supported that β-integrin mediated the LPS-induced coelomocyte apoptosis in sea cucumber via the integrin/FAK/caspase-3 signaling pathway.

A current perspective of canstatin, a fragment of type IV collagen alpha 2 chain

Type IV collagen is a main component of basement membrane extracellular matrix. Canstatin, a non-collagenous C-terminal fragment of type IV collagen α2 chain, was firstly identified as an endogenous anti-angiogenic and anti-tumor factor, which also has an anti-lymphangiogenic effect. Then, canstatin has been widely investigated as a novel target molecule for cancer therapy. The anti-angiogenic effect of canstatin may be also useful for the treatment of ocular neovascularization. Recently, we have demonstrated that canstatin, which is abundantly expressed in the heart tissue, exerts various biological activities in cardiac cells. In rat H9c2 cardiomyoblasts, canstatin inhibits isoproterenol- or hypoxia-induced apoptosis. Canstatin plays an important role in modulating voltage-dependent calcium channel activity in rat cardiomyocytes. Canstatin also regulates various biological functions in rat cardiac fibroblasts and myofibroblasts. The expression of canstatin decreases in the infarcted area after myocardial infarction. This review focuses on a current perspective for the roles of canstatin in tumorigenesis, ocular neovascularization and cardiac pathology.

Melatonin alleviates hypoxia-induced cardiac apoptosis through PI3K/Akt pathway

Hypoxia-induced apoptosis is an inevitable problem in cyanotic congenital heart disease. In the present study, we investigated effects of melatonin on hypoxic cardiomyocytes in vitro and in vivo, and explored its underlying mechanism. H9C2 cells were subjected to hypoxia for 48 hours. Mice were subjected to hypoxia treatment (10% O₂) for 4 weeks. Cell viability was detected by the cell counting kit-8 assay. Cellular apoptosis was assessed by Annexin V/7 AAD assay. Western blotting was employed to determine the expression of Bcl-2, Bax, cleaved caspase 3, phosphorylation of PI3K, and AKT. Melatonin increased cell viability and alleviated apoptosis in hypoxic H9C2 cells and cardiomyocytes of hypoxia-treated mice. Melatonin pretreatment increased Bcl-2 and decreased cleaved caspase 3 and Bax levels. Moreover, melatonin activated the PI3K/Akt pathway. The protective effects of melatonin were abolished by a PI3K/Akt-inhibitor, LY294002. Our results demonstrated that melatonin confers cardioprotection by inhibiting apoptosis through the activation of PI3K/Akt signaling pathway in hypoxic cardiomyocytes.

Absence of miR-223-3p ameliorates hypoxia-induced injury through repressing cardiomyocyte apoptosis and oxidative stress by targeting KLF15

Apoptosis of cardiomyocytes and oxidant stress are considered essential processes in the progression of cardiovascular diseases. A hypoxic stress which causes apoptosis of cardiomyocytes is the main problem in ischemic heart disease. The aim of the present study was to explore the functional role and potential mechanisms of miR-223-3p in hypoxia-induced cardiomyocyte apoptosis and oxidative stress. Here, we observed a increment of miR-223-3p level accompanied by the decrease of Krüppel-like zinc-finger transcription factor 15 (KLF15) expression in response to hypoxia. Additionally, absence of miR-223-3p manifestly dampened hypoxia-induced cardiomyocyte injury in H9c2 cells, including improving cell viability, attenuating the LDH leakage and preventing cardiomyocyte apoptosis accompanied by an increase in the expression of Bcl-2 and a decrease in the expression of Bax and C-caspase 3 in the setting of hypoxia. Moreover, depletion of miR-223-3p evidently retarded oxidant stress by inhibiting reactive oxygen species generation and lipid peroxidation, as well as enhancing antioxidant enzyme activity in H9c2 cells following exposure to hypoxia. More importantly, KLF15 was a direct and functional target of miR-223-3p. Further data validated that miR-223-3p negatively regulated the expression of KLF15. Mechanistically, deletion of KLF15 partly abrogated the suppressive effects of miR-223-3p deletion on hypoxia-induced cardiomyocyte apoptosis and oxidative stress. Taken all data together, our findings established that our study defines a novel mechanism by which miR-223-3p protects against cardiomyocyte apoptosis and oxidative stress by targeting KLF15, suggesting that the miR-223-3p/KLF15 may be a potential therapeutic target for ischemic heart conditions.

Trichosanthis Pericarpium Aqueous Extract Protects H9c2 Cardiomyocytes from Hypoxia/Reoxygenation Injury by Regulating PI3K/Akt/NO Pathway

Trichosanthis Pericarpium (TP) is a traditional Chinese medicine for treating cardiovascular diseases. In this study, we investigated the effects of TP aqueous extract (TPAE) on hypoxia/reoxygenation (H/R) induced injury in H9c2 cardiomyocytes and explored the underlying mechanisms. H9c2 cells were cultured under the hypoxia condition induced by sodium hydrosulfite for 30 min and reoxygenated for 4 h. Cell viability was measured by MTT assay. The amounts of LDH, NO, eNOS, and iNOS were tested by ELISA kits. Apoptotic rate was detected by Annexin V-FITC/PI staining. QRT-PCR was performed to analyze the relative mRNA expression of Akt, Bcl-2, Bax, eNOS, and iNOS. Western blotting was used to detect the expression of key members in the PI3K/Akt pathway. Results showed that the pretreatment of TPAE remarkably enhanced cell viability and decreased apoptosis induced by H/R. Moreover, TPAE decreased the release of LDH and expression of iNOS. In addition, TPAE increased NO production and Bcl-2/Bax ratio. Furthermore, the mRNA and protein expression of p-Akt and eNOS were activated by TPAE pretreatment. On the contrary, a specific inhibitor of PI3K, LY294002 not only inhibited TPAE-induced p-Akt/eNOS upregulation but alleviated its anti-apoptotic effects. In conclusion, results indicated that TPAE protected against H/R injury in cardiomyocytes, which consequently activated the PI3K/Akt/NO signaling pathway.

New Insights into the Role of Basement Membrane-Derived Matricryptins in the Heart

The extracellular matrix (ECM), which contributes to structural homeostasis as well as to the regulation of cellular function, is enzymatically cleaved by proteases, such as matrix metalloproteinases and cathepsins, in the normal and diseased heart. During the past two decades, matricryptins have been defined as fragments of ECM with a biologically active cryptic site, namely the 'matricryptic site,' and their biological activities have been initially identified and clarified, including anti-angiogenic and anti-tumor effects. Thus, matricryptins are expected to be novel anti-tumor drugs, and thus widely investigated. Although there are a smaller number of studies on the expression and function of matricryptins in fields other than cancer research, some matricryptins have been recently clarified to have biological functions beyond an anti-angiogenic effect in heart. This review particularly focuses on the expression and function of basement membrane-derived matricryptins, including arresten, canstatin, tumstatin, endostatin and endorepellin, during cardiac diseases leading to heart failure such as cardiac hypertrophy and myocardial infarction.

miR-140-5p aggravates hypoxia-induced cell injury via regulating MLK3 in H9c2 cells

Myocardial infarction (MI) is an important cause of cardiovascular disease. microRNAs (miRNAs) have been indicated as pivotal regulators in the physiological and pathological processes of heart diseases. The purpose of this study was to investigate the role of miR-140-5p in hypoxia-induced cell injury in H9c2 cells and its underlying mechanism. H9c2 cells were subjected to hypoxia, before which the expression levels of miR-140-5p and MLK3 were overexpressed or knocked down through transient transfection. The efficiency of transfection was verified by qRT-PCR and Western blotting. Cell viability, apoptotic cell rate, and the expression changes of apoptosis-related proteins were determined by trypan blue exclusion, flow cytometry, and Western blotting, respectively. Furthermore, Western blotting was performed to assess the expression levels of core factors related with p38MAPK and JNK signaling pathways. As a result, hypoxia significantly reduced cell viability and increased cell apoptosis in H9c2 cells. miR-140-5p inhibition attenuated cell injury induced by hypoxia in H9c2 cells, while miR-140-5p overexpression expedited the cell injury, as evidenced by the decreased cell viability and enhanced cell apoptosis. Moreover, miR-140-5p promoted the activation of p38MAPK and JNK pathways. miR-140-5p positively modulated the expression of MLK3. ML3 overexpression reversed the regulatory effects of miR-140-5p inhibition on hypoxia-injured H9c2 cells. In conclusion, this study demonstrated that miR-140-5p aggravated hypoxia-induced cell injury partially through up-regulation of MLK3.

Canstatin modulates L-type calcium channel activity in rat ventricular cardiomyocytes

Excessive increase of cytosolic Ca²⁺ through the activation of L-type Ca²⁺ channels (LTCCs) via β adrenergic receptor induces apoptosis of cardiomyocytes. Canstatin, a cleaved fragment of collagen type IV α2 chain, is abundantly expressed in normal heart tissue. We previously reported that canstatin inhibits β adrenergic receptor-stimulated apoptosis in cardiomyoblasts. Here, we tested the hypothesis that canstatin regulates LTCCs activity in ventricular cardiomyocytes. Collagen type IV α2 chain (COL4A2) small interfering (si) RNA (for canstatin suppression) or control siRNA was injected via jugular vein in Wistar rats. Two days after the injection, electrocardiogram (ECG) was recorded and the left ventricular tissue was isolated using Langendorff apparatus. Immunofluorescence staining was performed to clarify the distribution of canstatin in cardiomyocytes. The knockdown efficiency was confirmed by Western blotting. The L-type Ca²⁺ channel current (I_CaL) of ventricular cardiomyocyte was measured by a whole-cell patch clamp technique. In immunofluorescence staining, colocalization of canstatin and α_v integrin was observed in the isolated ventricular cardiomyocytes. The I_CaL of ventricular cardiomyocyte isolated from COL4A2 siRNA-injected rats was significantly enhanced compared with control siRNA-injected rats. Recombinant canstatin (250 ng/ml) significantly reversed it. ECG analysis showed that QT interval tended to be shortened and amplitude of T wave was significantly increased in the COL4A2 siRNA-injected rats. In summary, we for the first time clarified that suppressing canstatin expression increases the basal I_CaL in ventricular cardiomyocytes. It is proposed that canstatin might play a role in the stabilization of cardiac function through the modulation of LTCC activity in cardiomyocytes.

The impact of microRNA-122 and its target gene Sestrin-2 on the protective effect of ghrelin in angiotensin II-induced cardiomyocyte apoptosis

Ghrelin with n-octanoylated serine 3 residue is a peptide hormone with well-known cardioprotective properties. MicroRNA-122 is associated with the pathogenesis of many cardiovascular diseases, including apoptosis and was found highly increased in our previous rat model of post-myocardial infarction heart failure. In this study, we aimed to identify the target gene of microRNA-122 and to evaluate their impacts on the protective effect of acylated ghrelin in angiotensin II-induced apoptosis. The results showed that microRNA-122 was upregulated in the angiotensin II administration group accompanied by increased cell apoptosis, which were both reversed by ghrelin. Furthermore, microRNA-122 mimics upregulated numerous pro-apoptotic genes and increased apoptosis. The luciferase activity assay revealed Sestrin-2 as a direct target of microRNA-122. The expression of Sestrin-2 was downregulated by angiotensin II and upregulated by co-treatment with ghrelin. Inhibition of microRNA-122 and overexpression of Sestrin-2 alleviated apoptosis which was further reduced upon administered of ghrelin. Together, these results indicated that Sestrin-2 expression is inhibited by microRNA-122 and that this inhibition is involved in the protective effect of ghrelin and angiotensin II-induced apoptosis. We also found that microRNA-122 influenced several apoptosis pathways including the caspase cascade reaction and death receptor-mediated pathways. Collectively, our data reveal that microRNA-122 and its target gene Sestrin-2, under the regulation of angiotensin II and ghrelin, are important players in cardiomyocyte apoptosis. We therefore believe that microRNA-122 and Sestrin-2 can be developed as potential therapeutic targets against apoptosis in cardiovascular diseases.

Inhibition of microRNA-122 and overexpression of Sestrin-2 alleviated angiotensin II-induced cardiomyocyte apoptosis and enhanced the protective effect of ghrelin.

T3 peptide, an active fragment of tumstatin, inhibits H2O2-induced apoptosis in H9c2 cardiomyoblasts

Tumstatin, a cleaved fragment of α3 chain of type IV collagen, is an endogenous anti-angiogenetic peptide. Although the expression level of tumstatin changes in the heart tissues of certain experimental cardiac disease models, its effect on cardiomyocytes has not been clarified. In this study, we examined the effects of T3 peptide, an active subfragment of tumstatin, on hydrogen peroxide (H₂O₂)-induced cell death in H9c2 cardiomyoblasts. Cell viability was examined by a cell counting assay. Staining using 4', 6-diamidino-2-phenylindole was performed to observe nuclear morphology. Western blotting was performed to examine cleaved caspase-3 expression. Mitochondrial membrane potential and morphology were detected by a Mito Tracker Red staining. Intracellular reactive oxygen species production was examined by 2', 7'-dichlorodihydrofluorescein diacetate staining. T3 peptide (300, 1000ng/ml) suppressed H₂O₂ (1mM)-induced cell death, apoptotic changes of nuclei and cleaved caspas-3 expression in a concentration-dependent manner. T3 peptide also inhibited H₂O₂-induced loss of mitochondrial membrane potential, mitochondrial fission and reactive oxygen species production. Cilengitide, an integrin α_vβ₃/α_vβ₅ inhibitor, prevents the inhibitory effect of T3 peptide on H₂O₂-induced reactive oxygen species production. In conclusion, T3 peptide inhibits H₂O₂-induced apoptosis at least partly via the inhibition of intracellular reactive oxygen species production through the action on integrin.

Pathophysiological roles of canstatin on myofibroblasts after myocardial infarction in rats

Myofibroblasts play an important role during remodeling process after myocardial infarction through proliferation, migration, production and degradation of extracellular matrix (ECM) and contraction. Canstatin, a 24kDa polypeptide, is cleaved from α2 chain of type IV collagen, which is a major component of basement membrane around cardiomyocytes. We examined the effects of canstatin on myofibroblasts isolated from the areas of myocardial infarction. Myocardial infarction model was made by ligating left anterior descending artery of Wistar rats. Two weeks after the operation, the cells were isolated by an explant method and identified as myofibroblasts with immunofluorescence staining. Cell counting assay was performed to examine cell proliferation. Boyden chamber assay was performed to examine cell migration. Expression and phosphorylation of proteins were detected by Western blotting. Collagen gel contraction assay was performed to measure cell contractility. Canstatin stimulated proliferation, secretion of matrix metalloproteinases, expression of cyclooxygenase (COX)-2, and inhibited collagen gel contraction in myofibroblasts. Canstatin increased Akt phosphorylation. LY294002, a phosphoinositide-3-kinase/Akt inhibitor, inhibited the canstatin-induced proliferation. NS-398, a COX-2 inhibitor, suppressed the inhibitory effect of canstatin on collagen gel contraction. Canstatin expression in areas of myocardial infarction 2 weeks after surgery decreased. We for the first time demonstrate that canstatin is an endogenous bioactive molecule regulating the various functions of myofibroblasts after myocardial infarction. The decrease of canstatin expression in the maturated areas of myocardial infarction might lead to stabilization of scar tissues perhaps in part through the reduction of proliferation and ECM degradation as well as the stimulation of contractility in myofibroblasts.