Cortistatin Improves Cardiac Function After Acute Myocardial Infarction in Rats by Suppressing Myocardial Apoptosis and Endoplasmic Reticulum Stress

Reduced plasma cortistatin is related to clinical parameters in patients with essential hypertension

BACKGROUND

Cortistatin (CST), an endogenous bioactive polypeptide, has been acknowledged for its protective effect against several cardiovascular diseases, but its relationship with hypertension remains unclear. Therefore, we aimed to investigate changes in plasma CST in hypertensive patients and further analyze correlations with blood pressure, metabolic parameters and left ventricular structure and function.

METHODS

In this hospital-based study, basic information and plasma samples for evaluating clinically relevant indicators such as total cholesterol (TC), triglycerides (TGs), fasting blood glucose (FGB), serum creatinine (Scr) and CST were collected from 81 essential hypertension patients and 75 normotensive subjects. Plasma CST levels were examined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Compared with normotensive subjects, plasma CST was significantly lower in hypertensive patients. Plasma CST levels in hypertensive patients without blood pressure control was significantly lower than those of hypertensive patients with blood pressure control. Plasma CST levels were significantly negatively correlated with SBP and serum creatinine (Scr) in the overall population. Furthermore, multivariate logistic regression analysis showed that the OR of CST for hypertension was 0.64 using the unadjusted model, and there was still statistical significance using the four-adjusted model.

CONCLUSIONS

The circulating concentration of CST was significantly lower in hypertensive patients and was higher after blood pressure control, suggesting that CST may be a new endogenous protective target for hypertension.

Structural basis for activation of somatostatin receptor 5 by cyclic neuropeptide agonists

Somatostatin receptor 5 (SSTR5) is an important G protein-coupled receptor and drug target for neuroendocrine tumors and pituitary disorders. This study presents two high-resolution cryogenicelectron microscope structures of the SSTR5-Gi complexes bound to the cyclic neuropeptide agonists, cortistatin-17 (CST17) and octreotide, with resolutions of 2.7 Å and 2.9 Å, respectively. The structures reveal that binding of these peptides causes rearrangement of a "hydrophobic lock", consisting of residues from transmembrane helices TM3 and TM6. This rearrangement triggers outward movement of TM6, enabling Gαi protein engagement and receptor activation. In addition to hydrophobic interactions, CST17 forms conserved polar contacts similar to somatostatin-14 binding to SSTR2, while further structural and functional analysis shows that extracellular loops differently recognize CST17 and octreotide. These insights elucidate agonist selectivity and activation mechanisms of SSTR5, providing valuable guidance for structure-based drug development targeting this therapeutically relevant receptor.

Identification of necroptosis-related diagnostic biomarkers in coronary heart disease

Background

The implication of necroptosis in cardiovascular disease was already recognized. However, the molecular mechanism of necroptosis has not been extensively studied in coronary heart disease (CHD).

Methods

The differentially expressed genes (DEGs) between CHD and control samples were acquired in the GSE20681 dataset downloaded from the GEO database. Key necroptosis-related DEGs were captured and ascertained by bioinformatics analysis techniques, including weighted gene co-expression network analysis (WGCNA) and two machine learning algorithms, while single-gene gene set enrichment analysis (GSEA) revealed their molecular mechanisms. The diagnostic biomarkers were selected via receiver operating characteristic (ROC) analysis. Moreover, an analysis of immune elements infiltration degree was carried out. Authentication of pivotal gene expression at the mRNA level was investigated in vitro utilizing quantitative real-time PCR (qRT-PCR).

Results

A total of 94 DE-NRGs were recognized here, among which, FAM166B, NEFL, POLDIP3, PRSS37, and ZNF594 were authenticated as necroptosis-related biomarkers, and the linear regression model based on them presented an acceptable ability to different sample types. Following regulatory analysis, the ascertained biomarkers were markedly abundant in functions pertinent to blood circulation, calcium ion homeostasis, and the MAPK/cAMP/Ras signaling pathway. Single-sample GSEA exhibited that APC co-stimulation and CCR were more abundant, and aDCs and B cells were relatively scarce in CHD patients. Consistent findings from bioinformatics and qRT-PCR analyses confirmed the upregulation of NEFL and the downregulation of FAM166B, POLDIP3, and PRSS37 in CHD.

Conclusion

Our current investigation identified 5 necroptosis-related genes that could be diagnostic markers for CHD and brought a novel comprehension of the latent molecular mechanisms of necroptosis in CHD.

Inhibition of cardiomyocyte apoptosis post-acute myocardial infarction through the efficient delivery of microRNA-24 by silica nanoparticles

MicroRNA-24 (miR-24) is an apoptosis suppressor miRNA downregulated in cardiomyocytes after acute myocardial infarction (AMI). However, due to the lack of effective delivery strategies, the role of anti-apoptotic miR-24 in cardiomyocytes post-acute myocardial infarction remains unexplored. Here, we used a silica nanoparticle-based polyelectrolyte (polyethylenimine, PEI) delivery system to study the role of miR-24. These particles with good biocompatibility could be efficiently internalized into cells and release the loaded miR-24 into the cytoplasm. As a result, the overexpression of miR-24 resulted in the inhibition of the pro-apoptotic Bim, thereby inhibiting cardiomyocyte apoptosis in vitro. Furthermore, in vivo experiments revealed that over-expressed miR-24 additionally significantly improves ventricular remodeling and cardiac function in Sprague-Dawley (SD) rats after coronary artery ligation. In summary, our novel delivery system serves as a therapeutic miRNA formulation for cardiovascular disease treatment.

Acute myocardial infarction therapy: in vitro and in vivo evaluation of atrial natriuretic peptide and triphenylphosphonium dual ligands modified, baicalin-loaded nanoparticulate system

Background

Myocardial infarction (MI) is one of the most common ischemic heart diseases. It is very essential to explore new types of cardioprotective drugs delivery systems in this area.

Objective

The aim of the present study was to investigate the protective effect of baicalin (BA) and puerarin (PU) against acute MI rat models. BA and PU co-loaded nanoparticulate system were developed to improve bioavailability of the drugs, to prolong retention time in vivo and to enhance the protective effect.

Methods

In the present study, ANP and TPP contained ligands were synthesized. ANP/TPP-BN-LPNs were prepared and its physico-chemical properties were evaluated. The MI therapy efficiency of ANP/TPP-BN-LPNs was assessed in rats after intravenous injection. Single ligand contained LPNs, no ligand contained LPNs, and BN solution formulations were also prepared and used for the comparison.

Results

ANP/TPP-BN-LPNs were uniform and spheroidal particles. The size of ANP/TPP-BN-LPNs was 98.5 ± 2.9 nm, with a zeta potential of –19.5 ± 1.9 mV. The dual ligands modified LPNs exhibited significantly improved therapeutic efficiency compared with the single ligand modified LPNs and other systems. In vivo infarct therapy studies in rats proved that ANP/TPP-BN-LPNs were a promising system for efficient delivery of cardiovascular drugs for the treatment of cardiovascular diseases.

Conclusions

ANP/TPP-BN-LPNs could be used as a long-circulating and heart-targeting drug delivery system.

The cardioprotective effects of hydrogen sulfide by targeting endoplasmic reticulum stress and the Nrf2 signaling pathway: A review

Cardiac diseases are emerging due to lifestyle, urbanization, and the accelerated aging process. Oxidative stress has been associated with cardiac injury progression through interference with antioxidant strategies and endoplasmic reticulum (ER) function. Hydrogen sulfide (H₂ S) is generated endogenously from l-cysteine in various tissues including heart tissue. Pharmacological evaluation of H₂ S has suggested a potential role for H₂ S against diabetic cardiomyopathy, ischemia/reperfusion injury, myocardial infarction, and cardiotoxicity. Nuclear factor E2-related factor 2 (Nrf2) activity is crucial for cell survival in response to oxidative stress. H₂ S up-regulates Nrf2 expression and its related signaling pathway in myocytes. H₂ S also suppresses the expression and activity of ER stress-related proteins. H₂ S has been reported to improve various cardiac conditions through antioxidant and anti-ER stress-related activities.

GHSR deficiency exacerbates cardiac fibrosis: role in macrophage inflammasome activation and myofibroblast differentiation

AIMS

Sustained activation of β-adrenergic signalling induces cardiac fibrosis, which marks progression to heart failure. GHSR (growth hormone secretagogue receptor) is the receptor for ghrelin, which is an orexigenic gastric hormone with newly defined cardiovascular effects. The present study determined the effects of GHSR deficiency in a mouse model of isoproterenol (ISO)-induced cardiac fibrosis and examined the underlying mechanism.

METHODS AND RESULTS

Histochemical studies showed that GHSR deficiency exacerbated cardiac fibrosis. Quantitative RT-PCR, western blotting, and immunofluorescence staining demonstrated that cardiac fibroblasts isolated from GHSR-/- mice exhibited increased expression of marker genes for myofibroblast trans-differentiation (α-SMA, SM22, and calponin) upon transforming growth factor-β treatment compared to wild-type mice. RNA-sequencing of heart transcriptomes revealed that differentially expressed genes in GHSR-/- hearts were enriched in such biological processes as extracellular matrix organization, inflammatory response, lipid metabolism, cell cycle, migration, and adhesion. Particularly, GHSR deficiency increased Wnt/β-catenin pathway activation in ISO-induced myocardial fibrosis. In addition, loss of GHSR in macrophages instigated inflammasome activation with increased cleavage and release of interleukin-18.

CONCLUSION

These results for the first time demonstrated that GHSR deficiency aggravated ISO-induced cardiac fibrosis, suggesting that GHSR was a potential target for the intervention of cardiac fibrosis.

MiR-448-5p/VEGFA Axis Protects Cardiomyocytes from Hypoxia Through Regulating the FAS/FAS-L Signaling Pathway

Bioinformatics analysis showed that miR-448-5p expression in the myocardial tissue of rats with myocardial infarction significantly increased, suggesting that it may participate in myocardial cell apoptosis in myocardial infarction. This study aimed to explore the protective effects of miR-448-5p on hypoxic myocardial cells.H9C2 cells were cultured and subjected to anoxia for 2, 4, and 8 hours to establish a hypoxia model. MiR-448-5p mimic and inhibitor were transfected into the cells; then, a dual-luciferase experiment was conducted to verify the targeting relationship between miR-448-5p and VEGFA. Cell viability and apoptosis was detected by cell counting kit-8 and flow cytometry, respectively. The expressions of apoptosis-related proteins, miR-448-5p, FAS, and FAS-L were measured using western blotting and quantitative reverse transcription-polymerase chain reaction (qRT-PCR).Hypoxia-reduced H9C2 cell viability and promoted apoptosis. MiR-448-5p expression was increased after H9C2 cell hypoxia. MiR-448-5p mimic significantly inhibited the viability and promoted the apoptosis of hypoxia-induced model cells. Hypoxia promoted the expression of apoptosis-related protein B-cell lymphoma-2 (Bcl-2) and inhibited the expressions of Bcl-2-associated x protein (Bax), cleaved caspase-3, and caspase-3, whereas the effect of inhibitor on hypoxia-reduced H9C2 cell and apoptotic protein expression were opposite to miR-448-5p mimic. MiR-448-5p targeted VEGFA and regulated its expression. Silenced VEGFA expression significantly inhibited inhibitor effect on increasing cell viability and promoted apoptosis. In addition, miR-448-5p mimic inhibited the effect of hypoxia on promoting the expressions of FAS and FAS-L of H9C2 cells. Inhibitors had the opposite effect on cell hypoxia model.The miR-448-5p/VEGFA axis could protect cardiomyocytes from hypoxia through inhibiting the FAS/FAS-L signaling pathway.

Cardioprotective effect exerted by Timosaponin BⅡ through the regulation of endoplasmic stress-induced apoptosis

BACKGROUND

Timosaponin BⅡ (TBⅡ), one of the primary bioactive compounds from Anemarrhena asphodeloides Bunge, possesses potential cardioprotective effects. However, the mechanism underlying TBⅡ-mediated cardioprotection, especially the involvement of endoplasmic reticulum stress, remains largely unknown.

PURPOSE

This study was designed to evaluate the role of TBⅡ in myocardial injury protection and explore its possible mechanisms.

METHODS

In vivo models of isoproterenol-induced myocardial injury and H₂O₂-induced cytotoxicty were established to investigate the effect of anti-myocardial injury of TBⅡ. The potential mechanisms were investigated in vitro and in vivo using multiple detection methods like electrocardiography, histo-pathological examination, JC-1 staining, TUNEL staining, ELISA technology, and western blot analysis.

RESULTS

In vivo study revealed that TBⅡ improved electrocardiography and heart vacuolation, reduced myocyte apoptosis, and improved the antioxidant potential. In vitro investigation demonstrated that TBⅡ pretreatment inhibited ER stress-mediated apoptosis pathways. Further investigation of the underlying mechanisms revealed that TBⅡ prevented H₂O₂-induced H9c2 cardiomyocytes injury by the PI3K/Akt pathways, whereas the addition of LY294002, the pharmacologic antagonist of PI3K, attenuated TBⅡ-induced expression of apoptotic protein and cytoprotective effects.

CONCLUSION

These results suggested that TBⅡ protects against myocardial injury in vitro and enhances cellular defense capacity by inhibiting ER stress-mediated apoptosis pathways in vivo by activating the PI3K/Akt pathways.

Bcl-2-associated athanogene 5 overexpression attenuates catecholamine-induced vascular endothelial cell apoptosis

Bcl-2 associated athanogene 5 (Bag5) is a novel endoplasmic reticulum (ER) regulator. However, its role in catecholamine-induced endothelial cells damage has not been fully understood. In our study, catecholamine was used to mimic hypertension-related endothelial cell damage. Then, western blots, enzyme-linked immunosorbent assay, immunofluorescence, quantitative polymerase chain reaction and pathway analysis were conducted to analyze the role of Bag5 in endothelial cell damage in response to catecholamine. Our results indicated that the endothelial cell viability was impaired by catecholamine. Interestingly, Bag5 overexpression significantly reversed endothelial cell viability. Mechanistically, Bag5 overexpression inhibited ER stress, attenuated oxidative stress and repressed inflammation in catecholamine-treated endothelial cells. These beneficial effects finally contributed to endothelial cell survival under catecholamine treatment. Pathway analysis demonstrated that Bag5 was under the control of the mitogen-activated protein kinase (MAPK)-extracellular-signal-regulated kinase (ERK) signaling pathway. Reactivation of the MAPK-ERK pathway could upregulate Bag5 expression and thus promote endothelial cell survival through inhibiting oxidative stress, ER stress, and inflammation. Altogether, our results illustrate that Bag5 overexpression sustains endothelial cell survival in response to catecholamine treatment. This finding identifies Bag5 downregulation and the inactivated MAPK-ERK pathway as potential mechanisms underlying catecholamine-induced endothelial cell damage.

Statin rosuvastatin inhibits apoptosis of human coronary artery endothelial cells through upregulation of the JAK2/STAT3 signaling pathway

The purpose of the present study was to explore the potential molecular signaling pathway mediated by the statin rosuvastatin in cultured human coronary artery endothelial cells (HCAECs) induced by CoCl2. CoCl2 was used to induce the apoptosis of HCAECs. Myocardial infarction rats were established and received statin or PBS treatment. Reverse transcription‑quantitative PCR, western blotting, ELISA, TUNEL assay and immunohistochemistry were used to analyze the role of statin treatment. The results showed that rosuvastatin treatment decreased apoptosis of HCAECs induced by CoCl2 by increasing anti‑apoptosis Bcl‑xl and Bcl‑2 expression, and decreasing pro‑apoptosis Bax, Bad, caspase‑3 and caspase‑9 expression. The myocardial ischemia rat model demonstrated that rosuvastatin treatment decreased the mitochondrial reactive oxygen species, inflammation, mitochondrial damage, lipid catabolism, heart failure and the myocardial infarction areas, but improved the cardiac function indicators, right and left ventricular ejection fraction and increased expression levels of Janus kinase (JAK) and signal transducer and activator of transcription (STAT)3 in myocardial tissue. In conclusion, the results of the current study revealed that the statin rosuvastatin presents cardioprotective effects by activation of the JAK2/STAT3 signaling pathway.

Mitochondrial Dysfunction Secondary to Endoplasmic Reticulum Stress in Acute Myocardial Ischemic Injury in Rats

Background

The relationship between endoplasmic reticulum and mitochondria during acute myocardial ischemic injury is still unclear. Our study aimed to define the dynamics of endoplasmic reticulum stress and mitochondrial dysfunction during acute ischemic injury.

Material/Methods

A rat model of acute myocardial infarction and hypoxic cardiomyocytes were used in this study. Groups were set at 0 hours, 1 hour, 2 hours, 4 hours, and 6 hours after ischemic injury for both in vivo and in vitro studies. ATF6 and GRP-78 were examined to indicate endoplasmic reticulum stress. Cellular ATP and cytosolic levels of mitochondrial DNA and cytochrome c were detected to evaluate mitochondrial dysfunction. Caspase-3 was used for apoptosis analysis.

Result

Our results showed that both mRNA and protein levels of ATF6 and GRP-78 were elevated from 1 hour after ischemic injury in vivo and in vitro (P<0.05). However, ATP levels were increased at 2 hours after ischemic injury and significantly decreased from 4 hours after ischemic injury in vivo, while ATP level of cultured cardiomyocytes decreased remarkably from 2 hours after ischemic injury (P<0.05). Cytosolic mitochondrial DNA levels began to increase from 2 hours after ischemic injury (P<0.05). Cytosolic levels of cytochrome c increased from 4 hours after ischemic injury. Additionally, both mRNA and protein expressions of caspase-3 started to significantly elevate at 6 hours after ischemic injury (P<0.05).

Conclusions

The present study suggested that mitochondrial dysfunction was secondary to endoplasmic reticulum stress, which provides a novel experimental foundation for further exploration of the detailed mechanism after ischemic injury, especially the interaction between endoplasmic reticulum and mitochondria.

Cortistatin ameliorates Ang II-induced proliferation of vascular smooth muscle cells by inhibiting autophagy through SSTR3 and SSTR5

AIMS

Vascular smooth muscle cell (VSMC) proliferation plays a significant role in the development of various vascular disorders. However, the effect of cortistatin (CST) on VSMC proliferation remains unclear. Therefore, the purpose of our research aimed to study whether CST protected VSMCs from angiotensin II (Ang II)-induced proliferation and which mechanisms participated in the process.

MAIN METHODS

Cultured rat VSMCs were treated with Ang II with or without CST for 24 h. Cell proliferation rate was measured by cell counting kit-8 (CCK8) assay. The expressions of CST and its receptors were assessed by quantitative real-time PCR (qRT-PCR). The protein expression levels were analyzed by western blots. Immunofluorescence and transmission electron microscopy (TEM) were used to observe autophagy.

KEY FINDINGS

Our results showed that different concentrations of CST alleviated the Ang II-induced VSMC proliferation. The autophagy and reactive oxygen species (ROS) stimulated by Ang II were attenuated by CST. Furthermore, when the autophagy inhibitor 3-methyladenine (3-MA) was added, it exerted similar inhibition effects like CST, but didn't augment the protective role of CST on Ang II-induced VSMC autophagy and proliferation. Moreover, blocking somatostatin receptor 3 and 5 (SSTR3 and SSTR5) partially abrogated the suppressive effect of CST on Ang II-stimulated VSMC proliferation and autophagy.

SIGNIFICANCE

This study indicated that CST could ameliorate Ang II-stimulated VSMC proliferation by inhibiting autophagy partially through its receptors SSTR3 and SSTR5, providing a reasonable evidence for CST as a novel perspective therapeutic target of vascular diseases.

Overexpression of cortistatin alleviates oxygen/glucose-deprivation-induced ER stress and prompts neural stem cell proliferation via SSTR2

Cerebral infarction (CI), a blood circulatory disorder, causes a high mortality and disability rate worldwide. Intriguingly, a newly discovered neuropeptide, Cortistatin (CST), has been indicated to inhibit the cortical activity. In our research, we aimed to explore the functional relevance of CST in neural stem cells (NSCs) in CI rats. The expression of CST was determined in NSCs induced by oxygen-glucose deprivation (OGD). NSCs isolated from the embryonic rat brain were treated with OGD to establish an in vitro CI model while dithiothreitol (DTT) was introduced to induce endoplasmic reticulum stress (ERS), which were evaluated by assessment of GRP94, caspase-12 and CHOP expression. Then CST expression was restored by transfection of oe-CST, followed by assessment of NSC proliferation ability and cytotoxicity. Finally, the expression of CST and its receptor Somatostatin receptor subtype 2 (SSTR2) was quantified for mechanism exploration. CST was downregulated in CI, which was further confirmed in NSCs under OGD treatment. Overexpressed CST was found to promote cell activity and attenuate OGD-induced cytotoxicity of NSCs. Meanwhile, it was observed that the injured proliferation ability of NSCs was restored by CST overexpression. Besides, lower expression of GRP94, caspase-12 and CHOP was indicative of suppressed occurrence of ERS by CST. Mechanically, CST inhibited ERS through SSTR2. CST could facilitate the proliferation of NSCs in CI induced by OGD, ultimately highlighting a novel therapeutic target for CI treatment.

Cardioprotection of cortistatin against isoproterenol-induced myocardial injury in rats

Background

The present study was designed to examine whether cortistatin (CORT) could protect rats from myocardial injury induced by subcutaneously injecting isoproterenol (ISO) and to clarify the possible mechanisms.

Methods

Male Sprague-Dawley (SD) rats were placed at random into four groups: the control group, the ISO group, the ISO + CORT 25 µg/(kg·d) group, and the ISO + CORT 50 µg/(kg·d) group. Rat models of myocardial injury were established with the subcutaneous (s.c.) injections of 85 mg/kg ISO for 2 days. In the ISO+ CORT 25 µg/(kg·d) group and ISO+ CORT 50 µg/(kg·d) group, rats were given s.c. injections of CORT 25 µg/(kg·d) and CORT 50 µg/(kg·d) on the day before ISO, 3 days, respectively. Serum malondialdehyde (MDA) content, lactate dehydrogenase (LDH) activity, and creatine kinase isoenzyme (CK-MB) activity were measured by corresponding test kits. Western blot was applied to evaluate the expression of endoplasmic reticulum stress-related protein glucose regulatory protein 78 (GRP78), enhancer-binding protein homologous protein (CHOP), cysteinyl aspartate specific proteinase-12 (caspase-12), LC3-II, Beclin-1, and p62 in the rat myocardium.

Results

CORT alleviated the increased enzyme activities of serum LDH and CK-MB, and content of MDA (a typical marker of lipid peroxidation) in rats induced by ISO. CORT also prevented pathological myocardial injury in rats induced by ISO. Moreover, CORT attenuated the increased protein levels of GRP78, CHOP, and caspase-12, and reduced the increase of LC3-II, LC3-II/I, Beclin-1, and p62 in rats induced by ISO.

Conclusions

These data demonstrate that CORT can attenuate ISO-induced acute myocardial injury in rats likely by reducing lipid peroxidation, and inhibiting endoplasmic reticulum stress and autophagy. This supports CORT as a potentially being a new target for preventing and treating myocardial injury and its related disease.

Cortistatin exerts antiproliferation and antimigration effects in vascular smooth muscle cells stimulated by Ang II through suppressing ERK1/2, p38 MAPK, JNK and ERK5 signaling pathways

Background

Vascular remodeling, that contributes to cardiovascular diseases such as hypertension develops by anomalous proliferation and migration of vascular smooth muscle cells (VSMCs). Cortistatin (CST), a newly discovered biological peptide, has been acknowledged for its protective effects against cardiovascular diseases. Whether CST has an inhibitory regulation role in angiotensin II (Ang II)-induced proliferation and migration of VSMCs and what molecular mechanisms may participate in the CST inhibition process are still unknown.

Methods

VSMCs were divided into control group, Ang II (10^-7 M) group, Ang II + PD98059 (5×10^-5 M) group, Ang II + SB203580 (10^-5 M) group, Ang II + SP600125 (10^-5 M) group, Ang II + XMD17-109 (10^-6 M) group, Ang II + CST (10^-8 M) group and Ang II + CST (10^-7 M) group. Cell proliferation was detected by western blotting and cell counting kit-8 (CCK8) analysis. Migration of VSMCs was measured by Transwell assay.

Results

Compared with control group, Ang II upregulated the expression levels of proliferating cell nuclear antigen (PCNA) and osteopontin (OPN) and downregulated that of α-smooth muscle actin (α-SMA), increased the proliferation rate as shown by CCK8 and VSMC migration as shown by Transwell assay in cultured VSMCs of the Ang II group. Meanwhile, in Ang II-cultured VSMCs, we found activation of extracellular signal-regulated kinase (ERK) 1/2, p38 MAP kinase (p38 MAPK), c-Jun N-terminal kinase (JNK), and ERK5 pathways by western blotting at different time points. However, the proliferation and migration stimulated by Ang II were partly reversed by drug inhibitors of the four pathways, namely, PD98059, SB203580, SP600125 and XMD17-109. When Ang II-stimulated VSMCs were cultured with CST pretreatment, we found that proliferation and migration were greatly suppressed as well as that the ERK1/2, p38 MAPK, JNK and ERK5 pathways were deactivated by CST.

Conclusions

The accumulated data suggest that CST may play a protective role in Ang II-promoted proliferation and migration of VSMCs via inhibiting the mitogen-activated protein kinase (MAPK) family pathways, providing a new orientation of CST in protecting against cardiovascular diseases.

Cortistatin, a novel cardiovascular protective peptide

Cortistatin (CST) is a small molecule bioactive peptide containing an FWKT tetramer. It is widely distributed in nervous, immune and endocrine systems. Many studies have shown that CST can exert many biological effects, for example: regulating sleep, learning and memory processes, inducing immune tolerance, inhibiting inflammatory responses, and regulating endocrine metabolism. Notably, it is found that CST and its receptors are also widely distributed in the cardiovascular system, such as the aorta, coronary arteries and heart. In recent years, increasing studies have shown that CST played an important role in the development of cardiovascular diseases, such as reducing myocardial damage, inhibiting autoimmune myocarditis, alleviating vascular smooth muscle cell (VSMC) proliferation and migration, reducing vascular calcification (VC), and inhibiting atherosclerosis and aneurysm formation. Therefore, we reviewed the cardiovascular effects of CST in the heart and blood vessels, which will help to understand the role of CST and its receptors in the pathogenesis of cardiovascular diseases, and highlight novel strategies and targets for the prevention and treatment of cardiovascular diseases.

ZYZ-803 Mitigates Endoplasmic Reticulum Stress-Related Necroptosis after Acute Myocardial Infarction through Downregulating the RIP3-CaMKII Signaling Pathway

Acute myocardial infarction (AMI) is a leading cause of morbidity and mortality worldwide, and both cardiac necroptosis and endoplasmic reticulum stress (ERS) have been involved in the pathophysiology of AMI. ZYZ-803 is a hybrid molecule of a dual donor for gasotransmitters H₂S and NO. The aim of the present study is to investigate the antinecroptosis role and potential mechanisms of ZYZ-803 in the setting of ERS during AMI injury. In vivo, ZYZ-803 preserves cardiac function and reduces infarct size significantly after 24-hour left coronary artery ligation through revising H₂S and NO imbalance. In addition, ZYZ-803 relieves ERS and necroptosis in an AMI heart. In vitro, ZYZ-803 ameliorates ERS-related necroptosis induced by tunicamycin, and such effect has been depending on the receptor-interacting protein 3- (RIP3-) Ca²⁺-calmodulin-dependent protein kinase (CaMKII) signaling pathway. These findings have identified a novel antinecroptosis potential of ZYZ-803, providing a valuable candidate for cardioprotection in acute myocardial ischemia.

Endothelial stem cells attenuate cardiac apoptosis via downregulating cardiac microRNA-146a in a rat model of coronary heart disease

Coronary artery disease (CAD) is one of the main causes of hospitalization worldwide and has high morbidity. It has previously been demonstrated that stem cells serve an important role in improving myocardial function. MicroRNA (miRNA)-146a downregulation has been reported to inhibit vascular smooth muscle cell apoptosis in a rat model of coronary heart disease. The aim of the present study was to investigate the mechanisms underlying the effects of endothelial stem cell (ESC)-derived paracrine factors and cardiac miRNAs in CAD. Acute myocardial infarction was induced in 20 rats. Autologous ESCs (n=10; experimental group) or PBS (n=10; control group) were injected in the border zone. Reverse transcription-quantitative polymerase chain reaction, ELISA and immunohistochemistry assays were performed to analyze the therapeutic effects of ESCs in rats with coronary heart disease rats. Serum interleukin (IL)-1, IL-17 and tumor necrosis factor-α were reduced in the experimental group compared with control rats, as was the number of circulating proatherogenic cells. The results demonstrated that ESC transplantation markedly downregulated miRNA-146a expression and decreased apoptosis in the myocardium compared with the control group. Rats in the experimental group also had higher levels of vascular endothelial growth factor compared with the control group. In addition, it was demonstrated that miRNA-146 knockdown reduced cardiac apoptosis and increased VEGF expression. Furthermore, the infarct area in the border zone or rats with CAD was reduced in the experimental group compared with the control group. In conclusion, these results suggest that ESC transplantation may improve cardiac function via downregulating miR-146a, which may be have potential as a treatment for CAD.

The role of the unfolded protein response in arrhythmias

Human heart failure is characterized by arrhythmogenic electrical remodeling consisting mostly of ion channel downregulations. Reversing these downregulations is a logical approach to antiarrhythmic therapy, but understanding the pathophysiological mechanisms of the reduced currents is crucial for finding the proper treatments. The unfolded protein response (UPR) is activated by endoplasmic reticulum (ER) stress and has been found to play pivotal roles in different diseases including neurodegenerative diseases, diabetes mellitus, and heart disease. Recently, the UPR is reported to regulate multiple cardiac ion channels, contributing to arrhythmias in heart disease. In this review, we will discuss which UPR modulators and effectors could be involved in regulation of cardiac ion channels in heart disease, and how the understanding of these regulating mechanisms may lead to new antiarrhythmic therapeutics that lack the proarrhythmic risk of current ion channel blocking therapies.

Co-exposure of silica nanoparticles and methylmercury induced cardiac toxicity in vitro and in vivo

The released nanoparticles into environment can potentially interact with pre-existing pollution, maybe causing higher toxicity. As such, assessment of their joint toxic effects is necessary. This study was to investigate the co-exposure cardiac toxicity of silica nanoparticles (SiNPs) and methylmercury (MeHg). Factorial design was used to determine the potential joint action type. In vitro study, human cardiomyocytes (AC16) were exposed to SiNPs and MeHg alone or the combination. Higher toxicity was observed on cell viability, cell membrane damage in co-exposure compared with single exposure and control. The co-exposure enhanced the ROS, MDA generation and reduced the activity of SOD and GSH-Px. In addition, the co-exposure induced much higher cellular apoptotic rate in AC16. In vivo study, after SD rats exposed to SiNPs and MeHg and their mixture by intratracheal instillation for 30days, pathological changes (myocardial interstitial edema) of heart were occurred in co-exposure compared with single exposure and control. Moreover obvious ultra-structural changes, including myofibril disorder, myocardial gap expansion, and mitochondrial damage were observed in co-exposure group. The activity of myocardial enzymes, including CK-MB, ANP, BNP and cTnT, were significantly elevated in co-exposure group of rat serum. Meanwhile, the cardiac injury-linked proteins expression showed an increase in SERCA2 and decreased levels of cTnT, ANP and BNP in co-exposure group. Factorial design analysis demonstrated that additive and synergistic interactions were responsible for the co-exposure cardiac toxicity in vitro and vivo. In summary, our results showed severe cardiac toxicity induced by co-exposure of SiNPs and MeHg in both cardiomycytes and heart. It will help to clarify the potential cardiovascular toxicity in regards to combined exposure pollutions.

CCAAT/enhancer binding protein homologous protein knockdown alleviates hypoxia-induced myocardial injury in rat cardiomyocytes exposed to high glucose

Diabetic patients are more sensitive to ischemic injury than non-diabetics. Endoplasmic reticulum (ER) stress has been reported to be closely associated with the pathophysiology of ischemic injury in diabetes. The aim of the present study was to investigate the mechanisms involved in the progression of diabetes complicated by myocardial infarction (MI) and further verify the role of CCAAT/enhancer binding protein (C/EBP)-homologous protein (CHOP) using an in vitro model of diabetes/MI. The rats were exposed to 65 mg/kg streptozotocin (STZ) and left anterior descending (LAD) coronary artery ligation. ST-segment elevation, heart rate, left ventricular systolic pressure (LVSP) and LV end-diastolic pressure (LVEDP) were measured. Serum creatinine kinase-MB (CK-MB) and cardiac troponin T (cTnT) levels were examined by ELISA. Infarct size and apoptosis were measured by triphenyltetrazolium chloride staining and terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling assay. Pathological changes were evaluated by hematoxylin and eosin staining. H9c2 cells were used to establish an in vitro model of diabetes complicated by MI. Following CHOP knockdown, cell viability, cell cycle distribution and apoptosis were examined by Cell Counting Kit-8 assay, flow cytometry and Hoechst staining. Glucose-regulated protein 78 (GRP78), CHOP, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), endoplasmic reticulum oxidoreductase 1 (Ero1)-α, Ero1β and protein disulfide isomerase (PDI) levels in both myocardial tissues and H9c2 cells were determined by western blotting. In the present study, diabetes complicated by MI promoted ST-segment elevation and myocardial apoptosis, increased infarct size, induced pathological changes and elevated LVEDP, CK-MB, cTnT, GRP78, CHOP, Bax, Ero1α, Ero1β and PDI; however, it decreased heart rate, LVSP and Bcl-2. Additionally, high glucose combined with hypoxic treatment reduced cell viability, induced cell cycle arrest at G1 phase, promoted cell apoptosis, and activated the GRP78/CHOP and Ero1/PDI signaling pathways, which were reversed by CHOP knockdown. Thus, CHOP may be an effective therapeutic target for the treatment of diabetes complicated by MI.

Activation of the unfolded protein response downregulates cardiac ion channels in human induced pluripotent stem cell-derived cardiomyocytes

RATIONALE

Heart failure is characterized by electrical remodeling that contributes to arrhythmic risk. The unfolded protein response (UPR) is active in heart failure and can decrease protein levels by increasing mRNA decay, accelerating protein degradation, and inhibiting protein translation.

OBJECTIVE

Therefore, we investigated whether the UPR downregulated cardiac ion channels that may contribute to arrhythmogenic electrical remodeling.

METHODS

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) were used to study cardiac ion channels. Action potentials (APs) and ion channel currents were measured by patch clamp recording. The mRNA and protein levels of channels and the UPR effectors were determined by quantitative RT-PCR and Western blotting. Tunicamycin (TM, 50 ng/mL and 5 μg/mL), GSK2606414 (GSK, 300 nmol/L), and 4μ8C (5 μmol/L) were utilized to activate the UPR, inhibit protein kinase-like ER kinase (PERK) and inositol-requiring protein-1 (IRE1), respectively.

RESULTS

TM-induced activation of the UPR caused significant prolongation of the AP duration (APD) and a reduction of the maximum upstroke velocity (dV/dt_max) of the AP phase 0 in both acute (20-24 h) and chronic treatment (6 days). These changes were explained by reductions in the sodium, L-type calcium, the transient outward and rapidly/slowly activating delayed rectifier potassium currents. Na_v1.5, Ca_v1.2, K_v4.3, and K_vLQT1 channels showed concomitant reductions in mRNA and protein levels under activated UPR. Inhibition of PERK or IRE1 shortened the APD and reinstated dV/dt_max. The PERK branch regulated Na_v1.5, K_v4.3, hERG, and K_vLQT1. The IRE1 branch regulated Na_v1.5, hERG, K_vLQT1, and Ca_v1.2.

CONCLUSIONS

Activated UPR downregulates all major cardiac ion currents and results in electrical remodeling in hiPSC-CMs. Both PERK and IRE1 branches downregulate Na_v1.5, hERG, and K_vLQT1. The PERK branch specifically downregulates K_v4.3, while the IRE1 branch downregulates Ca_v1.2. Therefore, the UPR contributed to electrical remodeling, and targeting the UPR might be anti-arrhythmic.

Overexpressing microRNA-150 attenuates hypoxia-induced human cardiomyocyte cell apoptosis by targeting glucose-regulated protein-94

MicroRNA (miR)-150 has been demonstrated to protect the heart from ischemic injury. However, the protective effect of miR-150 in hypoxia-injured cardiomyocytes remains unclear. The present study aimed to investigate the target gene of miR-150 and the underlying molecular mechanisms of miR-150 in hypoxia-induced cardiomyocyte apoptosis. Using the hypoxia model of human cardiomyocytes (HCMs) in vitro, it was demonstrated that miR-150 was markedly inhibited in HCMs after hypoxia treatment. Overexpressing miR-150 significantly decreased hypoxia-induced HCM death and apoptosis. In addition, GRP94 was revealed to be a direct target of miR-150. Additionally, GRP94 was demonstrated to be involved in hypoxia-induced HCM apoptosis, and the protein expression levels of GRP94 were increased in HCMs in the presence of hypoxia. These findings demonstrated that miR-150 is involved in hypoxia-mediated gene regulation and apoptosis in HCMs. Furthermore, GRP94 knockout increased the cell viability of hypoxia-impaired HCMs with miR-150 mimic or miR-150 inhibitor transfection. In conclusion, miR-150 may serve a protective role in cardiomyocyte hypoxia injury, and the underlying mechanism was mediated, at least partially, by inhibiting GRP94 expression. These findings may provide a novel insight for the therapy of hypoxia-induced myocardial I/R injury.

Preventive effect of Agnucastoside C against Isoproterenol-induced myocardial injury

An iridoid glycoside, agnucastoside C (ACC) was isolated from the leaves of Moringa oliefera and its cardio protective potential was investigated in adult rats by examining the effects of this test compound, ACC at 30 mg/kg for 14 days in isoproterenol (100 mg/kg)-induced myocardial injury. Isoproterenol (ISO) administration induced the myocardial injury as evidenced by the altered ECG pattern with ST-segment elevation and an increase in the levels of cardiac injury markers including troponin-I, creatine kinase-MB, alanine transaminase, aspartate transaminase, lactate dehydrogenase; inflammatory markers, interleukine-6 and tumor necrosis factor. In this group, there was also an increase in cardiac lipid peroxidation and a decrease in cellular antioxidants. However, pretreatment with ACC maintained the normal ECG pattern and nearly normal levels of all the cardiac markers in ISO-induced animals. Electron microscopic and histological studies also showed marked reduction in ISO-induced cardiac damages including infarct size by ACC. Analysis by 2-DE revealed the involvement of 19 different cardiac proteins, associated with energy metabolism, oxidative stress and maintenance of cytoskeleton. The expression of those proteins were altered by ISO, but maintained in ACC pretreated rats. Our findings reveal the potential of isolated ACC in the prevention of myocardial damage.