[Hesperetin Alleviates Doxorubicin-Induced Cytotoxicity in H9c2 Cells by Activating SIRT1/NRF2 Signaling].

Objective: To investigate whether hesperetin (Hes) alleviates doxorubicin (DOX)-induced cardiomyocytotoxicity by reducing oxidative stress via regulating silent information regulator 1 (SIRT1)/nuclear transcription factor E2-related factor 2 (NRF2) signaling in H9c2 cells. Methods: H9c2 cells were treated with DOX to establish the cardiotoxicity model and were randomly assigned to four groups, a control group (Control) and three treatment groups, receiving respectively DOX (the DOX group), Hes+DOX (the DOX+Hes group), and Hes+SIRT1 inhibitor EX527+DOX (the DOX+Hes+EX527 group). Cellular morphology was observed by the light microscope. Cell viability was evaluated by CCK-8. DOX-induced apoptosis in H9c2 cells was examined by flow cytometry. The levels of reactive oxygen species (ROS) in the H9c2 cells of the four groups were determied with 2'-7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. The activities of lactate dehydrogenase (LDH), superoxide dismutase (SOD), catalase (CAT), and SIRT1 as well as the malondialdehyde (MDA) content were measured using ELISA kits. The expressions of cleaved caspase-3, cytochrome c, SIRT1, Ac-FOXO1, NRF2, and heme oxygenase 1 (HO-1) were determined by Western blot. Results: Compared with the Control group, the DOX group showed swollen cellular morphology, decreased cell density and viability, and increased LDH activity in the medium ( P<0.01); both apoptosis and the expression of cleaved caspase-3 and cytochrome c increased ( P<0.01); the activities of CAT and SOD decreased while the contents of MDA and ROS increased ( P<0.01); the expression of SIRT1, NRF2, and HO-1 decreased, the activity of SIRT1 decreased, and the expression of Ac-FOXO1 increased ( P<0.01). Compared with the DOX group, the DOX+Hes group showed improved cellular morphology, increased cell density and viability, and decreased LDH activity in the medium ( P<0.01); the apoptosis and the expression of cleaved caspase-3 and cytochrome c decreased ( P<0.01); the activities of CAT and SOD increased while the levels of MDA and ROS decreased ( P<0.01); the expression of SIRT1, NRF2, and HO-1 increased, the activity of SIRT1 increased, and the expression of Ac-FOXO1 decreased ( P<0.01). Comparison of the findings for the DOX+Hes group and the DOX+Hes+EX527 group showed that EX527 could block the protective effects of Hes against DOX-induced cell injury, oxidative stress, and SIRT1/NRF2 signaling. Conclusion: Hes inhibits oxidative stress and apoptosis via regulating SIRT1/NRF2 signaling, thereby reducing DOX-induced cardiotoxicity in H9c2 cells.

Pyruvate Upregulates Hepatic FGF21 Expression by Activating PDE and Inhibiting cAMP-Epac-CREB Signaling Pathway.

Fibroblast growth factor 21 (FGF21) functions as a polypeptide hormone to regulate glucose and lipid metabolism, and its expression is regulated by cellular metabolic stress. Pyruvate is an important intermediate metabolite that acts as a key hub for cellular fuel metabolism. However, the effect of pyruvate on hepatic FGF21 expression and secretion remains unknown. Herein, we examined the gene expression and protein levels of FGF21 in human hepatoma HepG2 cells and mouse AML12 hepatocytes in vitro, as well as in mice in vivo. In HepG2 and AML12 cells, pyruvate at concentrations above 0.1 mM significantly increased FGF21 expression and secretion. The increase in cellular cAMP levels by adenylyl cyclase activation, phosphodiesterase (PDE) inhibition and 8-Bromo-cAMP administration significantly restrained pyruvate-stimulated FGF21 expression. Pyruvate significantly increased PDE activities, reduced cAMP levels and decreased CREB phosphorylation. The inhibition of exchange protein directed activated by cAMP (Epac) and cAMP response element binding protein (CREB) upregulated FGF21 expression, upon which pyruvate no longer increased FGF21 expression. The increase in plasma pyruvate levels in mice induced by the intraperitoneal injection of pyruvate significantly increased FGF21 gene expression and PDE activity with a reduction in cAMP levels and CREB phosphorylation in the mouse liver compared with the control. In conclusion, pyruvate activates PDEs to reduce cAMP and then inhibits the cAMP-Epac-CREB signaling pathway to upregulate FGF21 expression in hepatocytes.

The OPG/RANKL/RANK system modulates calcification of common carotid artery in simulated microgravity rats by regulating NF-κB pathway.

Functional and structural adaptation of common carotid artery could be one of the important causes of postflight orthostatic intolerance after microgravity exposure, the mechanisms of which remain unclear. Recent evidence indicates that long-term spaceflight increases carotid artery stiffness, which might present a high risk to astronaut health and postflight working ability. Studies have suggested that vascular calcification is a common pathological change in cardiovascular diseases that is mainly manifested as an increase in vascular stiffness. Therefore, this study investigated whether simulated microgravity induces calcification of common carotid artery and to elucidate the underlying mechanisms. Four-week-old hindlimb-unweighted (HU) rats were used to simulate the deconditioning effects of microgravity on cardiovascular system. We found that simulated microgravity induced vascular smooth muscle cell (VSMC) osteogenic differentiation and medial calcification, increased receptor activator of nuclear factor κB (NF-κB) ligand (RANKL) and RANK expression, and enhanced NF-κB activation in rat common carotid artery. In vitro activation of the RANK pathway with exogenous RANKL, a RANK ligand, increased RANK and osteoprotegerin (OPG) expression in HU rats. Moreover, the expression of osteogenic markers and activation of NF-κB in HU rats were further enhanced by exogenous RANKL but suppressed by the RANK inhibitor osteoprotegerin fusion protein (OPG-Fc). These results indicated that the OPG/RANKL/RANK system modulates VSMC osteogenic differentiation and medial calcification of common carotid artery in simulated microgravity rats by regulating the NF-kB pathway.

Mitochondrial-Derived Peptide MOTS-c Attenuates Vascular Calcification and Secondary Myocardial Remodeling via Adenosine Monophosphate-Activated Protein Kinase Signaling Pathway.

INTRODUCTION: Vascular calcification (VC) is a complex, regulated process involved in many disease entities. So far, there are no treatments to reverse it. Exploring novel strategies to prevent VC is important and necessary for VC-related disease intervention. OBJECTIVE: In this study, we evaluated whether MOTS-c, a novel mitochondria-related 16-aa peptide, can reduce vitamin D3 and nicotine-induced VC in rats. METHODS: Vitamin D3 plus nicotine-treated rats were injected with MOTS-c at a dose of 5 mg/kg once a day for 4 weeks. Blood pressure, heart rate, and body weight were measured, and echocardiography was performed. The expression of phosphorylated adenosine monophosphate-activated protein kinase (AMPK) and the angiotensin II type 1 (AT-1) and endothelin B (ET-B) receptors was determined by Western blot analysis. RESULTS: Our results showed that MOTS-c treatment significantly attenuated VC. Furthermore, we found that the level of phosphorylated AMPK was increased and the expression levels of the AT-1 and ET-B receptors were decreased after MOTS-c treatment. CONCLUSIONS: Our findings provide evidence that MOTS-c may act as an inhibitor of VC by activating the AMPK signaling pathway and suppressing the expression of the AT-1 and ET-B receptors.

Erythropoietin attenuates vascular calcification by inhibiting endoplasmic reticulum stress in rats with chronic kidney disease.

Previous studies suggested that endoplasmic reticulum (ER) stress induced-apoptosis promoted vascular calcification (VC). Interestingly, erythropoietin (EPO), an endogenous glycoprotein, exerts multiple tissue protective effects by inhibiting ER stress and apoptosis. We investigated the role and potential mechanism of EPO on VC in chronic kidney disease (CKD) rats and cultured vascular smooth muscle cells (VSMCs). The calcification model was established by subtotal nephrectomy in vivo or phosphate overload in vitro. The protein level of EPO receptor (EPOR) was increased in the calcified aortas of CKD rats. EPO prevented the reduction of VSMC phenotypic markers, and reversed the increased calcium content and calcium salt deposition in the aortas of CKD rats and cultured calcified VSMCs. The protein levels of activating transcription factor 4 (ATF4) and glucose-regulated protein 94 (GRP94) were upregulated in aortas and VSMCs under calcifying conditions, indicating ER stress activation. EPO treatment of CKD rats or calcified VSMCs downregulated the protein levels of ATF4 and GRP94. Furthermore, ER stress-mediated apoptosis, determined by the protein levels of CCAAT/enhancer-binding protein-homologous protein and cleaved caspase 12, was increased in tunicamycin or calcification media-treated VSMCs, but the increased effect was reversed in EPO-treated groups. The increased apoptotic cells in calcified VSMCs, as indicated by Hoechst staining and flow cytometry, were downregulated by the co-administration of EPO or 4-phenyl butyric acid. In conclusion, EPO might attenuate VC by inhibiting ER stress mediated apoptosis through EPOR signaling.

The basolateral amygdala regulation of complex cognitive behaviours in the five-choice serial reaction time task.

RATIONALE: The basolateral amygdala (BLA) plays important roles in the cognitive control in human and non-human animals. However, inconsistent findings between species have been observed and there have been relatively few detailed investigations of the cognitive properties of BLA, especially in mice. OBJECTIVE: Our aim was to determine the role of BLA in cognition by using optogenetic manipulations. METHODS: Male C57BL/six mice were trained and tested on the five-choice serial reaction time task (5-CSRTT), open-field test (OFT), elevated plus maze (EPM), Y-maze, and novel object recognition (NOR) test during optogenetic stimulation and inhibition of the BLA. RESULTS: Optogenetic activation of the BLA decreased the impulsivity and increased the compulsivity of mice, whereas optogenetic inhibition of BLA had the opposite effect. Similarly, anxiety-like behaviours and spatial working memory were increased in BLA activation mice, whereas BLA inhibition decreased these behaviours. However, both BLA activation and inhibition decreased the motivation of the mice. CONCLUSIONS: These data demonstrate that the BLA regulates impulsive action and spatial working memory, and plays a critical role in anxiety-like behaviours.

[Capsaicin Alleviate Myocardial Ischemia Reperfusion Injury Through Attenuating Mitochondrial Oxidative Stress].

OBJECTIVE: To investigate the role of capsaicin (CAP) in myocardial ischemia reperfusion injury and its underlying mechanisms. METHODS: Twentyfour adult male SD rats were randomized into 4 groups,namely the control group,ischemia reperfusion group,ischemia reperfusion with CAP group,and ischemia reperfusion with CAPZ and CAP group. Isolated rat hearts underwent Langendorff perfusion. Left ventricular enddiastolic pressure (LVEDP) andleft ventricular developed pressure (LVDP) was calculated to evaluate myocardial performance at 30 min of reperfusion.Triphenyltetrazolium chloride staining was used to measure the infarct size of myocardium at 120 min reperfusion. The morphological changes in myocardial fiber was analyzed by HE staining at the end of reperfusion. Lactate dehydrogenase (LDH) content in the coronary flow was determined during the first 5 min reperfusion. The myocardial mitochondria was isolated and extracted for measuring a series of indicators of mitochondrial oxidative stress,including superoxide dismutase (SOD),methane dicarboxylic aldehyde (MDA) at the end of reperfusion. Western blot was used to determine the expression of caspase3 and cytochrome c at 10 min reperfusion. RESULTS: Compared with the control group,IR group significantly decreased in cardiac function,the level of LVDP and SOD activity and induced an enlarged infarct size ( P<0.01),accompanied by the disordered arrangement of myocardial cells,the content of MDA was increased ( P<0.01),the content of caspase3 and cytochrome c were also upregulated ( P<0.01).10 µmol/L CAP significantly attenuated these effects induced by ischemia reperfusion injury,levels of LVDP and infarct size at the end of reperfusion were significantly improved( P<0.01),nevertheless levels of LVEDP and MDA at the end of reperfusion and LDH were down-regulated markedly ( P<0.01),the content of caspase-3 and cytochrome c were also decreased ( P<0.01). CONCLUSION: These results demonstrate that CAP can suppresses cell apoptosis and necrosis,and alleviate heart function and cell survival from ischemia reperfusion injury through attenuating mitochondrial oxidative stress.

Positive association between musclin and insulin resistance in obesity: evidence of a human study and an animal experiment.

BACKGROUND: Musclin is a novel skeletal muscle-derived secretory factor considered to be a potent regulator of the glucose metabolism and therefore may contribute to the pathogenesis of obesity and insulin resistance (IR). METHODS: To test this hypothesis, we examined the plasma musclin levels in overweight/obese subjects and lean controls. Rats on a high fat diet (HFD) were used as the annimal model of obesity. Radioimmunoassay and western blot were used to determine musclin levels in plasma and skeletal muscle. RESULTS: According to radioimmunoassays,the overweight/obese subjects exhibited elevated musclin plasma levels compared with the lean controls (89.49 ± 19.00 ng/L vs 80.39 ± 16.35 ng/L, P < 0.01). The musclin levels were positively correlated with triglyceride, fasting plasma glucose, and homeostasis model assessment of IR levels. These observations were confirmed with a high-fat diet(HFD) rat model. HFD rats also exhibited increased musclin immunoreactivity in plasma (P < 0.01) and in skeletal muscle (P < 0.05), as well as increased musclin mRNA levels in skeletal muscle (P < 0.01). Musclin incubation significantly inhibited muscles 3H-2-DG uptake in the normal diet(ND) group (P < 0.01). The protein expression of glucose transporter type 4 was significantly down regulated by 30% (P < 0.05) in the ND group after soleusmuscle was incubated with musclin compared with the control. Musclin incubation also increased the protein levels of glucose-regulated protein (GRP)78 and GRP94 by 146.8 and 54% (both P < 0.05), respectively, in ND rats. CONCLUSIONS: Our data support the hypothesis that musclin has a strong relationship with obesity-associated IR by impairing the glucose metabolism and, at least in part, through causing endoplasmic reticulum stress.

Intermedin1-53 Attenuates Abdominal Aortic Aneurysm by Inhibiting Oxidative Stress.

OBJECTIVE: Oxidative stress plays a critical role in the development of abdominal aortic aneurysm (AAA). Intermedin (IMD) is a regulator of oxidative stress. Here, we investigated whether IMD reduces AAA by inhibiting oxidative stress. APPROACH AND RESULTS: In angiotensin II-induced ApoE-/- mouse and CaCl2-induced C57BL/6J mouse model of AAA, IMD1-53 significantly reduced the incidence of AAA and maximal aortic diameter. Ultrasonography, hematoxylin, and eosin staining and Verhoeff-van Gieson staining showed that IMD1-53 significantly decreased the enlarged aortas and elastic lamina degradation induced by angiotensin II or CaCl2. Mechanistically, IMD1-53 attenuated oxidative stress, inflammation, vascular smooth muscle cell apoptosis, and matrix metalloproteinase activation. IMD1-53 inhibited the activation of redox-sensitive signaling pathways, decreased the mRNA and protein expression of nicotinamide adenine dinucleotide phosphate oxidase subunits, and reduced the activity of nicotinamide adenine dinucleotide phosphate oxidase in AAA mice. Expression of Nox4 was upregulated in human AAA segments and in angiotensin II-treated mouse aortas and was markedly decreased by IMD1-53. In vitro, vascular smooth muscle cells with small-interfering RNA knockdown of IMD showed significantly increased angiotensin II-induced reactive oxygen species, and small-interfering RNA knockdown of Nox4 markedly inhibited the reactive oxygen species. IMD knockdown further increased the apoptosis of vascular smooth muscle cells and inflammation, which was reversed by Nox4 knockdown. Preincubation with IMD17-47 and protein kinase A inhibitor H89 inhibited the effect of IMD1-53, reducing Nox4 protein levels. CONCLUSIONS: IMD1-53 could have a protective effect on AAA by inhibiting oxidative stress.

[Research Progress of Klotho].

Klotho, a newly identified anti-aging gene, can be regulated by many factors, such as calcitonin gene-related peptide, fibroblast growth factor 2 could up-regulate Klotho expression; whereas renin-angiotensin system, urinary toxins, inflammation and oxidative stress could reduce expression of Klotho. There are two forms of Klotho protein: membrane-bound Klotho and secreted Klotho. Existing studies showed that Klotho was involved in the development of many diseases, including vascular calcification, atherosclerosis, hypertension, kidney damage, hyperparathyroidism, diabetes and tumors. In this paper, the regulation of Klotho expression and its role in diseases are reviewed briefly.

Metabolic changes of H2S in smokers and patients of COPD which might involve in inflammation, oxidative stress and steroid sensitivity.

Oxidative stress and inflammation play crucial role in the pathogenesis of chronic obstructive pulmonary disease (COPD). Most patients with COPD show a poor response to corticosteroids. Hydrogen sulfide (H2S ) has been implicated in the pathogenesis of COPD, but its expression and effects in lung tissue from COPD patients are not clear. In peripheral lung tissue samples from 24 patients, we found that compared with nonsmokers, the protein level of cystathionine-γ-lyase (CSE) was decreased in smokers and COPD patients. CSE mRNA increased but cystathionine-ß-synthase (CBS) mRNA decreased in COPD patients. H2S donors increased glutathione and superoxide dismutase in CS exposed U937 cells and inhibited CS-induced TNF-α and IL-8 secretion. Dexamethasone alone had no effect on lipopolysaccharide (LPS) induced TNF-α release by alveolar macrophages from CS exposed rats, however the combination of dexamethasone and H2S donor significantly inhibited TNF-α release. Thus, H2S metabolism is altered in lung tissue of smokers and COPD patients. Supplementation of H2S protects against CS-induced oxidative stress and inflammation in macrophages and H2S on steroid sensitivity deserves further investigation.

Possible role of fibroblast growth factor 21 on atherosclerosis via amelioration of endoplasmic reticulum stress-mediated apoptosis in apoE(-/-) mice.

Fibroblast growth factor 21 (FGF-21) is an endocrine factor that can be secreted into circulation by the liver. FGF-21 takes part in metabolic actions and is thought to be a promising candidate for the treatment of diabetes. However, the role of FGF-21 in atherosclerosis is unknown. In this study, apoE(-/-) mice were fed an atherogenic diet for 4 weeks with and without subcutaneous injections of FGF-21. ApoE(-/-) mice fed an atherogenic diet showed hyperlipidemia, a large plaque area in aortas and increased vessel wall thickness. Plasma FGF-21 content and protein level of FGF receptor 1 (FGFR1) in aortas was greater in apoE(-/-) than C57BL/6J mice. Exogenous FGF-21 treatment significantly ameliorated dyslipidemia in apoE(-/-) mice. FGF-21-treated apoE(-/-) mice showed reduced number of aortic plaques and plaque area as well as reduced number of TUNEL-positive cells. Protein levels of the endoplasmic reticulum stress markers glucose-regulated protein 94, caspase-12 and C/EBP homologous protein were reduced by 34.5, 31.4 and 26.5 %, respectively, in apoE(-/-) mice. Endogenous expression of FGF-21 and its receptor FGFR1 were upregulated in apoE(-/-) mice, and exogenous administration of FGF-21 ameliorated the atherogenic-induced dyslipidemia and vascular atherosclerotic lesions. FGF-21 protecting against atherosclerosis might be in part by its inhibitory effects on endoplasmic reticulum stress-mediated apoptosis.

Thyroid hormone attenuates vascular calcification induced by vitamin D3 plus nicotine in rats.

Thyroid hormones (THs) including thyroxine (T4) and triiodothyronine (T3) play critical roles in bone remodeling. However, the role and mechanism of THs in vascular calcification (VC) have been unclear. To explore the pathophysiological roles of T3 on VC, we investigated the changes in plasma and aortas of THs concentrations and the effect of T3 on rat VC induced by vitamin D3 plus nicotine (VDN). VDN-treated rat showed decreased plasma T3 content, increased vascular calcium deposition, and alkaline phosphatase (ALP) activity. Administration of T3 (0.2 mg/kg body weight IP) for 10 days greatly reduced vascular calcium deposition and ALP activity in calcified rat aortas when compared with controls. Concurrently, the loss of smooth muscle lineage markers α-actin and SM22a was restored, and the increased bone-associated molecules, such as runt-related transcription factor2 (Runx2), Osterix, and osteopontin (OPN) levels in calcified aorta, were reduced by administration of T3. The suppression of klotho in calcified rat aorta was restored by T3. Methimazole (400 mg/L) blocked the beneficial effect of T3 on VC. These results suggested that T3 can inhibit VC development.

Cardiac sympathetic afferent reflex response to intermedin microinjection into paraventricular nucleus is mediated by nitric oxide and γ-amino butyric acid in hypertensive rats.

Intermedin (IMD) is a member of calcitonin/calcitonin gene-related peptide (CGRP) and involves in the regulation of cardiovascular function in both peripheral tissues and central nervous system (CNS). Paraventricular nucleus (PVN) of hypothalamus is an important site in the control of cardiac sympathetic afferent reflex (CSAR) which participates in sympathetic over-excitation of hypertension. The aim of this study is to investigate whether IMD in the PVN is involved in the inhibition of CSAR and its related mechanism in hypertension. Rats were subjected to two-kidney one-clip (2K1C) surgery to induce renovascular hypertension or sham-operation (Sham). Acute experiments were carried out four weeks later under anesthesia. The CSAR was evaluated with the renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) responses to the epicardial application of capsaicin. The RSNA and MAP were recorded in sinoaortic-denervated, cervical-vagotomized and anesthetized rats. Bilateral PVN microinjection of IMD (25 pmol) caused greater decrease in the CSAR in 2K1C rats than in Sham rats, which was prevented by pretreatment with adrenomedullin (AM) receptor antagonist AM22-52, non-selective nitric oxide (NO) synthase (NOS) inhibitor L-NAME or γ-amino butyric acid (GABA)B receptor blocker CGP-35348. PVN pretreatment with CGRP receptor antagonist CGRP8-37 or GABA(A) receptor blocker gabazine had no significant effect on the CSAR response to IMD. AM22-52, L-NAME and CGP-35348 in the PVN could increase CSAR in Sham and 2K1C rats. These data indicate that IMD in the PVN inhibits CSAR via AM receptor, and both NO and GABA in the PVN involve in the effect of IMD on CSAR in Sham and renovascular hypertensive rats.

Metformin protects the myocardium against isoproterenol-induced injury in rats through alleviating endoplasmic reticulum stress.

Clinical studies have suggested that metformin, a widely used antidiabetic agent, exerts a direct cardioprotective effect on cardiovascular disease in addition to its blood glucose-lowering activity. This study was designed to identify the role of metformin in rats with isoproterenol (ISO)-induced myocardial injury and to investigate its underlying mechanism. A rat model of myocardial ischemic injury was established by the subcutaneous injection of a high dose of ISO, a beta-adrenergic agonist. The results showed that pretreatment of metformin significantly reduced rat mortality induced by ISO, attenuated the increased plasma lactate dehydrogenase activity and myocardium malondialdehyde level, alleviated the hemodynamic disturbance, inhibited the upregulated gene expression of myocardial probrain natriuretic peptide and alleviated the myocardial morphological injury and apoptosis induced by ISO. Furthermore, western blot analysis showed that metformin suppressed the overexpression of the endoplasmic reticulum stress (ERS) markers cleaved caspase-12 and CEBP-homologous protein induced by ISO and increased the phosphorylation of AMP-activated protein kinase (AMPK). In conclusion, these data suggest that metformin might protect the myocardium against acute ischemic injury in rats at least partially by activating AMPK and alleviating aberrant ERS. These findings might provide further experimental evidence for treating patients at risk of ischemic heart disease with metformin.

Intermedin1-53 attenuates vascular smooth muscle cell calcification by inhibiting endoplasmic reticulum stress via cyclic adenosine monophosphate/protein kinase A pathway.

We previously reported that endoplasmic reticulum (ER) stress-mediated apoptosis participated in vascular calcification. Importantly, a novel paracrine/autocrine peptide intermedin1-53 (IMD1-53) in the vasculature inhibited vascular calcification in rats. But the mechanisms needed to be fully elucidated. Vascular smooth muscle cells (VSMCs) calcification was induced by CaCl2 and ß-glycerophosphate. Tunicamycin (Tm) or dithiothreitol (DTT) was used to induce ER stress. We found that IMD1-53 (10(-7)mol/L) treatment significantly alleviated the protein expression of ER stress hallmarks activating transcription factor 4 (ATF4), ATF6, glucose-regulated protein 78 (GRP78) and GRP94 induced by Tm or DTT. ER stress occurred in early and late calcification of VSMCs but was inhibited by IMD1-53. These inhibitory effects of IMD1-53 were abolished by treatment with the protein kinase A (PKA) inhibitor H89. Pretreatment with IMD1-53 decreased the number of apoptotic VSMCs and downregulated protein expression of cleaved caspase 12 and C/EBP homologous protein (CHOP) in calcified VSMCs. Concurrently, IMD1-53 restored the loss of VSMC lineage markers and ameliorated calcium deposition and alkaline phosphatase activity in calcified VSMCs as well. The observation was further verified by Alizarin Red S staining, which showed that IMD1-53 reduced positive red nodules among calcified VSMCs. In conclusion, IMD1-53 attenuated VSMC calcification by inhibiting ER stress through cAMP/PKA signalling.

Ghrelin protects heart against ERS-induced injury and apoptosis by activating AMP-activated protein kinase.

Ghrelin, the endogenous ligand of growth hormone secretagogue receptor (GHS-R), is a cardioprotective peptide. In our previous work, we have revealed that ghrelin could protect heart against ischemia/reperfusion (I/R) injury by inhibiting endoplasmic reticulum stress (ERS), which contributes to many heart diseases. In current study, using both in vivo and in vitro models, we investigated how ghrelin inhibits myocardial ERS. In the in vivo rat heart injury model induced by isoproterenol (ISO), we found that exogenous ghrelin could alleviate heart dysfunction, reduce myocardial injury and apoptosis and inhibit the excessive myocardial ERS induced by ISO. More importantly, the activation of AMP-activated protein kinase (AMPK) was observed. To explore the role of AMPK activation in ERS inhibition by ghrelin, we set up two in vitro ERS models by exposing cultured rat cardiomyocytes to tunicamycin(Tm) or dithiothreitol (DTT). In both models, compared with Tm or DTT treatment alone, pre-incubation cardiomyocytes with ghrelin significantly activated AMPK, reversed the upregulation of the ERS markers, C/EBP-homologous protein (CHOP) and cleaved caspase-12, and reduced apoptosis of cardiomyocytes. Further, we found that the ERS inhibitory and anti-apoptotic actions induced by ghrelin were blocked by an AMPK inhibitor. To investigate how ghrelin activates AMPK, selective antagonist of GHS-R1a and inhibitor of Ca(2+)/Calmodulin-dependent protein kinase kinase (CaMKK) were added, respectively, before ghrelin pre-incubation, and we found that AMPK activation was prevented and the ERS inhibitory and anti-apoptotic actions of ghrelin were blocked. In conclusion, ghrelin could protect heart against ERS-induced injury and apoptosis, at least partially through a GHS-R1a/CaMKK/AMPK pathway.

Activating transcription factor 4 is involved in endoplasmic reticulum stress-mediated apoptosis contributing to vascular calcification.

Our previous work reported that endoplasmic reticulum stress (ERS)-mediated apoptosis was activated during vascular calcification (VC). Activating transcription factor 4 (ATF4) is a critical transcription factor in osteoblastogenesis and ERS-induced apoptosis. However, whether ATF4 is involved in ERS-mediated apoptosis contributing to VC remains unclear. In the present study, in vivo VC was induced in rats by administering vitamin D3 plus nicotine. Vascular smooth muscle cell (VSMC) calcification in vitro was induced by incubation in calcifying media containing ß-glycerophosphate and CaCl2. ERS inhibitors taurine or 4-phenylbutyric acid attenuated ERS and VSMC apoptosis in calcified rat arteries, reduced calcification and retarded the VSMC contractile phenotype transforming into an osteoblast-like phenotype in vivo. Inhibition of ERS retarded the VSMC phenotypic transition into an osteoblast-like cell phenotype and reduced VSMC calcification and apoptosis in vitro. Interestingly, ATF4 was activated in calcified aortas and calcified VSMCs in vitro. ATF4 knockdown attenuated ERS-induced apoptosis in calcified VSMCs. ATF4 deficiency blocked VSMC calcification and negatively regulated the osteoblast phenotypic transition of VSMCs in vitro. Our results demonstrate that ATF4 was involved at least in part in the process of ERS-mediated apoptosis contributing to VC.

Angiotensin-(1-7) inhibits vascular calcification in rats.

Angiotensin-(1-7) [Ang-(1-7)] is a new bioactive heptapeptide in the renin-angiotensin-aldosterone system (RAAS) with potent protective effects in cardiovascular diseases, opposing many actions of angiotensin II (Ang II) mediated by Ang II type 1 (AT1) receptor. It is produced mainly by the activity of angiotensin-converting enzyme 2 (ACE2) and acts through the Mas receptor. However, the role of Ang-(1-7) in vascular calcification (VC) is still unclear. In this study, we investigated the protective effects of Ang-(1-7) on VC in an in vivo rat VC model induced by vitamin D3 plus nicotine. The levels of ACE2 and the Mas receptor, as well as ACE, AT1 receptor, Ang II type 2 receptor and angiotensinogen, were significantly increased in calcified aortas, and Ang-(1-7) reversed the increased levels. Ang-(1-7) restored the reduced expression of lineage markers, including smooth muscle (SM) α-actin, SM22α, calponin and smoothelin, in vascular smooth muscle cells (VSMCs) and retarded the osteogenic transition of VSMCs by decreasing the expression of bone-associated proteins. It reduced alkaline phosphatase activity and calcium deposition in VC and alleviated the hemodynamic disorders of rats with VC. We provide the first in vivo evidence that Ang-(1-7) can inhibit the development of VC by inhibiting the osteogenic transition of VSMCs, at least in part by decreasing levels of the ACE/Ang II/AT1 axis. The increased expression of ACE2 and the Mas receptor in calcified aortas suggests the involvement of the ACE2/Ang-(1-7)/Mas axis during VC. Ang-(1-7) might be an efficient endogenous vasoprotective factor for VC.