Chronic stress dysregulates the Hippo/YAP/14-3-3η pathway and induces mitochondrial damage in basolateral amygdala in a mouse model of depression.

Rationale: Recent evidence highlights the pivotal role of mitochondrial dysfunction in mood disorders, but the mechanism involved remains unclear. We studied whether the Hippo/YAP/14-3-3η signaling pathway mediates mitochondrial abnormalities that result in the onset of major depressive disorder (MDD) in a mouse model. Methods: The ROC algorithm was used to identify a subpopulation of mice that were exposed to chronic unpredictable mild stress (CUMS) and exhibited the most prominent depressive phenotype (Dep). Electron microscopy, biochemical assays, quantitative PCR, and immunoblotting were used to evaluate synaptic and mitochondrial changes in the basolateral amygdala (BLA). RNA sequencing was used to explore changes in the Hippo pathway and downstream target genes. In vitro pharmacological inhibition and immunoprecipitation was used to confirm YAP/14-3-3η interaction and its role in neuronal mitochondrial dysfunction. We used virus-mediated gene overexpression and knockout in YAP transgenic mice to verify the regulatory effect of the Hippo/YAP/14-3-3η pathway on depressive-like behavior. Results: Transcriptomic data identified a large number of genes and signaling pathways that were specifically altered from the BLA of Dep mice. Dep mice showed notable synaptic impairment in BLA neurons, as well as mitochondrial damage characterized by abnormal mitochondrial morphology, compromised function, impaired biogenesis, and alterations in mitochondrial marker proteins. The Hippo signaling pathway was activated in Dep mice during CUMS, and the transcriptional regulatory activity of YAP was suppressed by phosphorylation of its Ser127 site. 14-3-3η was identified as an important co-regulatory factor of the Hippo/YAP pathway, as it can respond to chronic stress and regulate cytoplasmic retention of YAP. Importantly, the integrated Hippo/YAP/14-3-3η pathway mediated neuronal mitochondrial dysfunction and depressive behavior in Dep mice. Conclusion: The integrated Hippo/YAP/14-3-3η pathway in the BLA neuron is critical in mediating depressive-like behaviors in mice, suggesting a causal role for this pathway in susceptibility to chronic stress-induced depression. This pathway therefore may present a therapeutic target against mitochondrial dysfunction and synaptic impairment in MDD.

Tetrahydroxystilbene glucoside attenuated homocysteine-upregulated endothelin receptors in vascular smooth muscle cells via the ERK1 /2 /NF-κB signaling pathway.

2,3,5,4'-Tetrahydrostilbene-2-o-ß-d-glucoside (TSG) is the main active component of Polygonum multiflorum Thunb. It has effects on hypertension. However, the mechanism is unclear. Current research is devoted to exploring the mechanism of TSG improving HHcy-induced hypertension. The mice received a subcutaneous injection of Hcy in the presence or absence of TSG for 4 weeks. Blood pressure (BP) was measured using a noninvasive tail-cuff plethysmography method. Levels of plasma Hcy and endothelin-1 were measured using ELISA. Rat SMA without endothelium was cultured in a serum-free medium in the presence or absence of TSG with or without Hcy. The contractile response to sarafotoxin 6c or endothein-1 was studied using a sensitive myography. The levels of protein were detected using Western blotting. The results showed that TSG lowered HHcy-elevated BP and decreased levels of plasma Hcy and endothelin-1 in mice. Furthermore, the results showed that TSG inhibited Hcy-upregulated ET receptor expression and ET receptor-mediated contractile responses as well as the levels of p-ERK1/2 and p-p65 in SMA. In vivo results further validate the in vitro results. In conclusion, TSG can decrease the levels of plasma Hcy and ET-1 and downregulate Hcy-upregulated ET receptors in VSMCs by inhibiting the ERK1/2 /NF-κB/ETB2 pathway to lower the BP.

New paeonol derivative C302 reduces hypertension in spontaneously hypertensive rats through endothelium-dependent and endothelium-independent vasodilation.

Hypertension is a major risk factor for cardiovascular disease and Chinese herb monomers could provide new structural skeletons for anti-hypertension new drug development. Paeonol is a Chinese herbal monomer extracted from Cortex moutan, exhibited some anti-hypertensive activity. The study focused on the structural optimization of paeonol to provide promising lead compounds for anti-hypertension new drug development. Herein, twelve new paeonol derivatives (PD) were designed and synthesized and their vasodilation activity was evaluated by in vitro vasodilation drug screening platform based on Myograph. Its anti-hypertension activity, PD-C302 (2-hydroxy-4-methoxyvalerophenone) as a representative with the optimal vasodilation activity, was determined by its response to blood pressure in spontaneously hypertensive rats (SHR) in vivo. Moreover, its molecular mechanism was probed by the vasodilation activity of rat superior mesenteric artery rings with or without endothelium pre-contracted by potassium chloride (KCl) or phenylephrine hydrochloride (PE). It was indicated that PD-C302 significantly reduced the blood pressure in SHR, which would involve in PD-C302-induced vasodilation. Furthermore, endothelium-dependent pathways and endothelium-independent pathways both contributed importantly to PD-C302-induced vasodilation at low concentration of PD-C302. Endothelium-independent pathways (vascular smooth muscle cell-mediated vasodilation), were mainly responsible for the PD-C302-induced vasodilation at high concentration of PD-C302, which involved in opening multiple K+ channels to restrain Ca2+ channels, and then triggered vasodilation to reduce blood pressure. PD-C302 has a simple structure and favorable anti-hypertensive activity in vivo, which could be a promising lead compound for anti-hypertension new drug development.

Inhibitors of the MAPK/ NF-κB pathway attenuate the upregulation of the ETB receptor mediated by high glucose in vascular smooth muscle cells.

BACKGROUND: Increased vascular smooth muscle cell (VSMC) endothelin type B (ETB) receptor expression is involved in cardiovascular diseases. High glucose (HG) in diabetes is closely related to cardiovascular complications. Although diabetes upregulates VSMC endothelin subtype B (ETB) receptors, its mechanism is still unclear. Our aim is to investigate the mechanism of HG-induced ETB receptors in VSMCs. METHODS: Rat superior mesenteric arteries (SMAs) without endothelium were cultured in medium without serum for 24 h. HG with or without mitogen-activated protein kinase (MAPK) signaling pathway inhibitors and downstream nuclear factor-kappaB (NF-κB) inhibitors was coincubated with SMAs. A sensitive myograph detected the contractile responses to sarafotoxin 6c. Western blotting and immunofluorescence staining were used to determine protein expression. RESULTS: HG promoted the expression of VSMC ETB receptors in rat SMAs and enhanced the ETB receptor-induced contractile response. The results showed that HG increased vascular smooth muscle cell (VSMC) ETB receptor expression and ETB receptor-induced contractile responses in rat SMAs. Both extracellular signal-related kinase 1 and 2 (ERK1/2) inhibitors (U0126) and P38 inhibitors (SB203580) significantly inhibited HG-increased VSMC ETB receptors. However, a C-jun terminal kinase (p-JNK) inhibitor (SP600125) did not affect HG- upregulated VSMC ETB receptors. Further study showed that NF-κB using an IκB kinase inhibitor (wedelolactone) also significantly inhibited HG-increased VSMC ETB receptors. CONCLUSION: In conclusion, HG upregulated the VSMC ETB receptor by activating the ERK1/2- or P38- NF-κB signaling pathway.

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.

Angiotensin II upregulates endothelin receptors through the adenosine monophosphate-activated protein kinase/sirtuin 1 pathway in vascular smooth muscle cells.

OBJECTIVES: This study was designed to test our hypothesis that angiotensin II (Ang II) upregulates endothelin (ET) receptors in vascular smooth muscle cells (VSMCs). METHODS: Rat superior mesenteric artery (SMA) without endothelium was cultured in serum-free medium for 24 h in the presence of Ang II with or without metformin or nicotinamide. In vivo, rats were implanted subcutaneously with a mini-osmotic pump infusing AngII (500 ng/kg/min) for 4 weeks. The level of protein expression was determined using Western blotting. The contractile response to ET receptor agonists was studied using sensitive myography. Caudal artery blood pressure (BP) was measured using non-invasive tail-cuff plethysmography. KEY FINDINGS: The results showed that Ang II significantly increased ET receptors and decreased phosphorylated-adenosine monophosphate-activated protein kinase α (p-AMPKα) in SMA. Furthermore, metformin significantly inhibited Ang II-upregulated ET receptors and upregulated Ang II-decreased sirtuin 1 (Sirt1). However, this effect was reversed by nicotinamide. Moreover, the in-vivo results showed that metformin not only inhibited Ang II-induced upregulation of ET receptors but also recovered Ang II-decreased p-AMPKα and Sirt1. In addition, metformin significantly inhibited Ang II-elevated BP. However, the effect was reversed by nicotinamide, except for p-AMPKα. CONCLUSIONS: Ang II upregulated ET receptors in VSMCs to elevate BP by inhibiting AMPK, thereby inhibiting Sirt1.

Identification of 14-3-3 epsilon as a regulator of the neural apoptotic pathway for chronic-stress-induced depression.

Major depression is a prevalent and long-lasting psychiatric illness with severe functional impairment and high suicide rate. We have previously shown that the ventrolateral orbital cortex (VLO) plays a key role in the stress responses in mice, but the underlying mechanisms remains unclear. Here, we used proteomic method to identify differentially expressed proteins in VLO of chronic unpredictable mild stress (CUMS) mice. Of 4,953 quantified proteins, 45 proteins were differentially expressed following CUMS. The integrated pathway analyses identified 14-3-3ε and TrkB signaling as differentially downregulated in association with stress-induced depressive-like behaviors. 14-3-3ε overexpression in VLO relieved the depressive-like behaviors by rescue of Bad-mediated apoptosis. Moreover, treatment with the 14-3-3ε stabilizer FC-A precluded neuronal apoptotic signaling in VLO of depressed mice. Because 14-3-3ε provides significant protection against chronic stress, boosting 14-3-3ε expression, pharmacological stabilization of 14-3-3s (e.g. with FC-A) is identified as an exciting therapeutic target for major depression.

CaMKIIδ inhibition protects against myocardial ischemia/reperfusion injury: Role of Beclin-1-dependent autophagy.

Ca2+/calmodulin-dependent protein kinase II δ (CaMKIIδ) has been shown to play a vital role in pathological events in myocardial ischemia/reperfusion (IR) injury. Dysregulation of autophagy in cardiomyocytes is implicated in myocardial IR injury. Here, we examined whether CaMKIIδ inhibition could protect against myocardial IR injury through alleviating autophagy dysfunction and evaluated the potential role of CaMKIIδ in Beclin-1-dependent autophagy in ischemia/reperfused hearts. This study was performed using isolated perfused rat hearts and H9c2 cardiac myoblasts. KN-93, but not KN-92, inhibited the phosphorylation of CaMKIIδ at Thr286 and its substrate phospholamban at Thr17 besides the CaMKIIδ activity in myocardial IR. KN-93, but not KN-92 significantly improved post-ischemic cardiac function and reduced cell death. In cultured H9c2 cardiac myoblasts, KN-93 or CaMKIIδ siRNA, but not KN-92, attenuated simulated IR (SIR)-induced cell death. Moreover, CaMKIIδ inhibition could alleviate IR-induced autophagic dysfunction as evidenced in reduced levels of Atg5, p62, and LC3BII in isolated rat hearts and H9c2 cardiac myoblasts. Furthermore, co-treatment with bafilomycin A1, a lysosomal inhibitor, in CaMKII inhibition-treated cells suggested that CaMKII inhibition alleviated autophagic flux. CaMKIIδ inhibition mitigated the phosphorylation of Beclin-1 at Ser90. As expected, Beclin-1 siRNA significantly decreased the levels of Beclin-1 and Beclin-1 phosphorylation accompanied by partial reductions in Atg5, LC3BII, p62, cleaved caspase-3 and cytochrome c. However, Beclin-1 siRNA had little effect on CaMKIIδ phosphorylation. Taken together, these results demonstrated that CaMKIIδ inhibition reduced myocardial IR injury by improving autophagy dysfunction, and that CaMKIIδ-induced autophagy dysfunction partially depended on the phosphorylation of Beclin-1.

[Melatonin protects against myocardial ischemia-reperfusion injury by inhibiting contracture in isolated rat hearts].

OBJECTIVE: To investigate the protective effect of melatonin against myocardial ischemia reperfusion (IR) injury in isolated rat hearts and explore the underlying mechanisms. METHODS: The isolated hearts from 40 male SD rats were randomly divided into 4 groups (n=10): the control group, where the hearts were perfused with KH solution for 175 min; IR group, where the hearts were subjected to global ischemia for 45 min followed by reperfusion for 120 min; IR+melatonin (Mel+IR) group, where melatonin (5 µmol/L) was administered to the hearts 1 min before ischemia and during the first 5 min of reperfusion, followed by 115 min of reperfusion; and IR+2, 3-butanedione monoxime (IR+BDM) group, where the hearts were treated with BDM (20 mmol/L) in the same manner as melatonin treatment. Myocardial injury in the isolated hearts was assessed based on myocardial injury area, caspase-3 activity, and expressions of cytochrome C and cleaved caspase-3 proteins. Cardiac contracture was assessed using HE staining and by detecting lactate dehydrogenase (LDH) activity and the content of cardiac troponin I (cTnI) in the coronary outflow, measurement of left ventricular end-diastolic pressure (LVEDP) and electron microscopy. The content of ATP in the cardiac tissue was also determined. RESULTS: Compared with those in the control group, the isolated hearts in IR group showed significantly larger myocardial injury area and higher caspase-3 activity and the protein expressions of cytochrome C and cleaved caspase-3 with significantly increased LDH activity and cTnI content in the coronary outflow and elevated LVEDP at the end of reperfusion; HE staining showed obvious fractures of the myocardial fibers and the content of ATP was significantly decreased in the cardiac tissue; electron microscopy revealed the development of contraction bands. In the isolated hearts with IR, treatment with Mel or BDM significantly reduced the myocardial injury area, caspase-3 activity, and protein expressions of cytochrome C and cleaved caspase-3, obviously inhibited LDH activity, lowered the content of cTnI and LVEDP, reduced myocardial fiber fracture, and increased ATP content in the cardiac tissue. Both Mel and BDM inhibited the formation of contraction bands in the isolated hearts with IR injury. CONCLUSIONS: Mel can alleviate myocardial IR injury in isolated rat hearts by inhibiting cardiac contracture, the mechanism of which may involve the upregulation of ATP in the cardiac myocytes to lessen the tear of membrane and reduce cell content leakage.

Yes-associated protein and transcriptional coactivator with PDZ-binding motif as new targets in cardiovascular diseases.

As transcriptional co-activators, Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) can regulate cell proliferation, migration, differentiation, and apoptosis by interacting with the transcription factors [e.g., transcriptional enhancer associate domain (TEAD) family members]. Polarity and junctional proteins, mechanical stress, and G protein-coupled receptors (GPCRs) are Hippo pathway-dependent upstream regulatory pathways of YAP and TAZ activity. In addition, posttranslational modifications (such as phosphorylation, O-GlcNAcylation, acetylation, methylation, geranylgeranylation, and palmitoylation) also participate in the regulation of YAP and TAZ activity. YAP and TAZ have recently been implicated in the pathological process of vascular and heart diseases. The activation of YAP and TAZ promotes atherosclerosis, angiogenesis, restenosis, pulmonary hypertension, myocardial hypertrophy, and myocardial fibrosis, whereas the inhibition of YAP and TAZ is involved in aortic aneurysms, aortic dissection, myocardial ischemia-reperfusion injury, and myocardial infarction. Thus, both YAP and TAZ may be potential targets for treating cardiovascular diseases. In this review, we discuss the latest findings regarding YAP and TAZ and the potential drugs that target these compounds to treat cardiovascular diseases. This review lays the foundation for a future direction of cardiovascular disease research.

[The molecular mechanism of fibroblast growth factor 21-inhibited leptin expression in adipocytes].

The present study was aimed to clarify the signaling molecular mechanism by which fibroblast growth factor 21 (FGF21) regulates leptin gene expression in adipocytes. Differentiated 3T3-F442A adipocytes were used as study object. The mRNA expression level of leptin was detected by fluorescence quantitative RT-PCR. The phosphorylation levels of proteins of signal transduction pathways were detected by Western blot. The results showed that FGF21 significantly down-regulated the mRNA expression level of leptin in adipocytes, and FGF21 receptor inhibitor BGJ-398 could completely block this effect. FGF21 up-regulated the phosphorylation levels of ERK1/2 and AMPK in adipocytes. Either ERK1/2 inhibitor SCH772984 or AMPK inhibitor Compound C could partially block the inhibitory effect of FGF21, and the combined application of these two inhibitors completely blocked the effect of FGF21. Neither PI3K inhibitor LY294002 nor Akt inhibitor AZD5363 affected the inhibitory effect of FGF21 on leptin gene expression. These results suggest that FGF21 may inhibit leptin gene expression by activating ERK1/2 and AMPK signaling pathways in adipocytes.

The GPR120 Agonist TUG-891 Inhibits the Motility and Phagocytosis of Mouse Alveolar Macrophages.

Movement and phagocytosis characterize the fundamental actions of macrophages. Although it is known that the free fatty acid receptor GPR120 is expressed in macrophages and regulates cytokine expression to exert anti-inflammatory activities, the effects of GPR120 activation on the motility and phagocytosis of macrophages are not clear. In this study, mouse alveolar macrophages (AM) were stimulated with the GPR120 agonist TUG-891, and the changes in cell motility, intracellular Ca2+ concentration ([Ca2+]i), and the ability of phagocytosis were measured. Mouse AM in controls exhibited active movement in vitro, and TUG-891 significantly restrained AM movement. Meanwhile, TUG-891 stimulated a quick increase in [Ca2+]i in AM, which was blocked separately by the Gq protein inhibitor YM-254890, the phospholipase C (PLC) inhibitor U73122, or depletion of endoplasmic reticulum (ER) Ca2+ store by thapsigargin. The inhibition of AM movement by TUG-891 was eliminated by YM-254890, U73122, thapsigargin, and chelation of cytosolic Ca2+ by BAPTA. Moreover, TUG-891 inhibited AM phagocytosis of fluorescent microspheres, which was also blocked by YM-254890, U73122, thapsigargin, and BAPTA. In conclusion, GPR120 activation in mouse AM increases [Ca2+]i but inhibits the motility and phagocytosis via Gq protein/PLC-mediated Ca2+ release from ER Ca2+ store.

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.

New insights into phenotypic switching of VSMCs induced by hyperhomocysteinemia: Role of endothelin-1 signaling.

Phenotypic switching of vascular smooth muscle cells (VSMCs) plays a key role in atherosclerosis. Hyperhomocysteinemia (HHcy) is an independent risk factor for atherosclerosis. HHcy induces phenotypic switching of VSMCs, but the mechanism is unclear. Endothelin-1 (ET-1) promotes proliferation and migration of VSMCs by inducing phenotypic switching during atherosclerosis. This review examined recent findings on the relationship between HHcy or the ET-1 system (including ET-1 and its receptors) and phenotypic switching of VSMCs as well as the molecular mechanism of HHcy-regulated ET-1 signaling. In particular, we focused on the potential mechanisms and pharmacological targets of phenotypic switching of VSMCs regulated by HHcy through ET-1 signaling.

Metformin inhibited homocysteine-induced upregulation of endothelin receptors through the Sirt1/NF-κB signaling pathway in vascular smooth muscle cells.

Metformin (Met) can improve atherosclerosis (As). Abnormal endothelin receptors [including endothelin type A (ETA) or type B (ETB) receptor] in vascular smooth muscle cells (VSMCs) are involved in As. Hyperhomocysteinemia (HHcy) is an independent risk factor for As. The present study was designed to test our hypothesis that Met inhibits the upregulation of endothelin receptors induced by homocysteine (Hcy) in VSMCs. Rat superior mesenteric artery (SMA) without endothelium, as an in vitro model, was cultured in serum-free medium for 24 h in the presence of Hcy with or without Met or nicotinamide (Nic). In vivo, rats received subcutaneous injections of Hcy in the presence or absence of Met or Nic for 3 weeks. Levels of protein expression were determined by Western blotting. The contractile responses to sarafotoxin 6c (an ETB receptor agonist) or ET-1 (an ETA/ ETB receptor agonist) were studied using a sensitive myograph. The blood pressure of rats was measured using a noninvasive tail-cuff plethysmography method. The results showed that Met could significantly inhibit the Hcy-induced upregulation of endothelin receptors (including ETA and ETB receptor) protein expression and endothelin receptor-mediated vasoconstriction, and it recovered the Hcy-induced decrease in silent information regulator 1 (Sirt1) in a dosage-dependent manner in SMA. However, Nic (a Sirt1 inhibitor) recovered the levels of Met-inhibited endothelin receptors and acetylated p65. Furthermore, the in vivo results showed that Met not only significantly the inhibited HHcy-induced upregulation of endothelin receptors and acetylated p65 but also recovered the HHcy-induced decrease in Sirt1 in a dosage-dependent manner in SMA. In addition, Met significantly inhibited the HHcy-induced blood pressure elevation. However, these effects were reverted by Nic. In conclusion, these data demonstrated that Met inhibited the Hcy-induced increase in endothelin receptor expression by activating Sirt1 and then inhibiting NF-κB in VSMCs. These findings may provide insights into the mechanism underlying of Met-treated cardiovascular diseases induced by Hcy.

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.

CaMKII mediates myocardial ischemia/reperfusion injury­induced contracture in isolated rat heart.

Contracture or diastolic dysfunction is a primary cause of injury following ischemia/reperfusion (IR). The present study examined whether Ca2+/calmodulin­dependent kinase II (CaMKII) is involved in contracture. Isolated rat hearts were subjected to either global IR or Ca2+ paradox (CaP), which is characterized by contracture. Left ventricular end­diastolic pressure, electron microscopy and troponin I  TnI) in coronary effluent were examined to indicate the extent of contracture. Compared with control hearts, both the IR and CaP groups exhibited an increase in necrosis and apoptosis, and a marked depression in contractile function. Western blot analysis showed that IR stimulated the phosphorylation (Thr287) and oxidation (Met281/282) of CaMKII, and the phosphorylation of phospholamban (PLN), a substrate of CaMKII. By contrast, only the phosphorylation of CaMKII was increased in the CaP group. Treatment with either 3 µM KN­62, an inhibitor of CaMKII, or 5 µM KB­R7943, an inhibitor of the Na+/Ca2+ exchanger, mitigated the damage and the post­translational modification of both CaMKII and PLN. Similar to the effect of the negative inotropic agent 2,3­butanedione­monoxime, the increased cell survival after treatment with KN­62 was associated with improved diastolic function. Examination using electron microscopy and a biochemical test showed the development of contraction bands, disruption of the sarcolemmal membrane and an increase in the release of TnI in both IR and CaP hearts; these results indicated the occurrence of contracture. Furthermore, these changes were inhibited by either KN­62 or KB­R7943. Taken together, these data provided evidence that CaMKII mediates reperfusion­elicited contracture, and that the activation of CaMKII via phosphorylation is involved in this process.

[Na+/Ca2+ exchanger mediates ischemia-reperfusion injury by activation of CaMKII in isolated rat heart].

OBJECTIVE: To investigate the role of Na+/Ca2+ exchanger (NCX) in myocardial ischemia-reperfusion injury and the underlying mechanisms.
 Methods: Forty Sprague-Dawley rats were divided into 4 groups randomly: a control group, a KB-R7943 group, an ischemia-reperfusion group (IR group), and an IR plus KB-R7943 group (KB-R7943+IR group). Isolated Sprague Dawley male rat hearts underwent Langendorff perfusion. The ratio of left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), the infarct size of myocardium, and the lactate dehydrogenase (LDH) activity in the coronary flow was determined. HE staining was used to assess the change of myocardial morphology. Western blot was used to determine the levels of cleaved caspase-3, cytochrome c and the phosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and the Thr17 site of phospholamban.
 Results: Compared with the control group, IR group significantly induced an enlarged infarct size, reduction of the ratio of LVDP, up-regulation of cytochrome c, cleaved caspase-3, p-CaMKII and p-phospholamban, and increased in the activity of LDH, the level of LVEDP (P<0.01) and the disordered myocardial morphology. These effects were significantly attenuated in the presence of KB-R7943 treatment (10 µmol/L).
 Conclusion: NCX mediates myocardial ischemia-reperfusion-induced cell apoptosis and necrosis through activation of CaMKII.

Establishment of a novel non­alcoholic fatty liver disease model using cholesterol­fed rabbits with reference to the potential role of endoplasmic reticulum stress.

The aim of the present study was to establish a non­alcoholic fatty liver disease (NAFLD) model using cholesterol­fed rabbits and to investigate whether endoplasmic reticulum stress (ERS) serves a role in the pathogenesis of NAFLD. A total of 20 male rabbits were randomly divided into 3 groups: Those fed a normal chow diet, a high cholesterol diet (HCD) or a high fat and high cholesterol diet (HFCD) for 12 weeks. Total cholesterol, triglycerides and free fatty acids of plasma and the liver were measured. At 12 weeks, a glucose tolerance test was performed. The steatosis of the liver was evaluated using hematoxylin and eosin and Oil Red O staining. Expression levels of glucose regulation protein 78, CCAAT/enhancer­binding protein homologous protein, c­Jun N­terminal kinase (JNK) and caspase­12 mRNA was analyzed by reverse transcription­quantitative polymerase chain reaction. Plasma levels of total cholesterol, triglycerides and free fatty acids in the HCD and HFCD groups were significantly higher when compared with those in the control group (P<0.05 or P<0.01). Histological analysis revealed that HCD and HFCD groups demonstrated marked differences in the fatty liver compared with the control group, while there was no significant difference between the HCD and HFCD groups. JNK and caspase­12 expression were significantly increased in the HCD and HFCD groups when compared with the control. The HCD and HFCD groups exhibited prominent fatty livers, a typical pathological feature of NAFLD. However, the addition of high fat levels in the cholesterol diet did not increase the severity of hepatic steatosis in HFCD when compared with the HCD group. Thus, the ERS pathway may participate in the pathogenesis of NAFLD, and cholesterol­fed rabbits may become a novel model for the study of NAFLD.

High Glucose Upregulated Vascular Smooth Muscle Endothelin Subtype B Receptors via Inhibition of Autophagy in Rat Superior Mesenteric Arteries.

Autophagy plays an important role in cardiovascular diseases. High glucose (HG) upregulates endothelin subtype B (ETB) receptors in vascular smooth muscle cells (VSMCs). However, it is unclear as to whether autophagy is involved in HG-induced upregulation of ETB receptors in VSMCs. The present study was designed to examine the hypothesis that HG upregulates ETB receptors by inhibiting autophagy in VSMCs. We studied HG-treated rat superior mesenteric artery (SMA) without endothelium in the presence and absence of 5-aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside (AICAR), rapamycin, or MHY1485 for 24 hr. We measured contractile responses to sarafotoxin 6c (S6c) (an ETB receptor agonist) using a sensitive myograph. Levels of protein expression were determined using Western blotting. HG impaired autophagy and increased the levels of ETB receptor protein expression and ETB receptor-mediated contractile responses to S6c in SMA. However, these effects were reversed by AICAR (an agonist of adenosine monophosphate [AMP]-activated protein kinase [AMPK]) and rapamycin (an inhibitor of mammalian target of rapamycin [mTOR]). However, MHY1485 (an agonist of mTOR) did not upregulate the AICAR-inhibited ETB receptor-mediated contractile responses or ETB receptor protein expression in the presence of HG. These data suggest that HG upregulated ETB receptors by inhibiting autophagy in VSMCs via AMPK and mTOR signaling pathways.