scholarly journals A Novel Molecular Mechanism of IKKε-Mediated Akt/mTOR Inhibition in the Cardiomyocyte Autophagy after Myocardial Infarction

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Shuai He ◽  
Jian Shen ◽  
Liangpeng Li ◽  
Yueyue Xu ◽  
Yide Cao ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Coronary Artery Ligation ◽  
H9c2 Cells ◽  
Wild Type ◽  
Artery Ligation ◽  
Mtor Inhibition ◽  
Cardiomyocyte Autophagy ◽  
The Impact ◽  
Cardiomyocyte Survival

Autophagy of cardiomyocytes after myocardial infarction (MI) is an important factor affecting the prognosis of MI. Excessive autophagy can lead to massive death of cardiomyocytes, which will seriously affect cardiac function. IKKε plays a crucial role in the occurrence of autophagy, but the functional role in MI remains largely unknown. To evaluate the impact of IKKε on the autophagy of cardiomyocytes after MI, MI was induced by surgical left anterior descending coronary artery ligation in IKKε knockout (KO) mice and wild-type (WT) mice. Starvation of H9c2 cells with IKKε siRNA and rescued with IKKε overexpressed afterwards to test the mechanism of IKKε in autophagy in vitro. Our results demonstrated that the expression of IKKε was upregulated in mice myocardial tissues which were consistent with cardiomyocyte autophagy after MI. Significantly, the IKKε KO mice showed increased infarct size, decreased viable cardiomyocytes, and exacerbated cardiac dysfunction when compared with the wild-type mice. Western blot and electron micrography analysis also revealed that loss of IKKε induces excessive cardiomyocyte autophagy and reduced the expression of p-Akt and p-mTOR. Similar results were observed in IKKε siRNA H9c2 cells in vitro which were under starvation injury. Notably, the levels of p-Akt and p-mTOR can restore in IKKε rescued cells. In conclusion, our results indicated that IKKε protects cardiomyocyte survival by reduced autophagy following MI via regulation of the Akt/mTOR signaling pathway. Thus, our study suggests that IKKε might represent a potential therapeutic target for the treatment of MI.

scholarly journals LRRK2 Deficiency Protects Hearts from Myocardial Infarction Injury in Mice via the P53/HMGB1 Pathway

2021 ◽  
Author(s):  
Yuan Liu ◽  
Changgui Chen ◽  
Lu Chen ◽  
Xiaoxin Pei ◽  
Zekai Tao ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Coronary Artery Ligation ◽  
Wild Type ◽  
Artery Ligation ◽  
Rat Cardiomyocytes ◽  
Ventricular Fibrosis ◽  
Deficient Mice

Abstract Purpose: LRRK2 is a Ser/Thr kinase with multiple functional domains. Current studies have shown that its mutations are closely related to hereditary Parkinson's disease. However, its role in cardiovascular disease, especially in myocardial infarction, is unclear. The aim of this study was to explore the functional role of LRRK2 in myocardial infarction. Methods: Wild-type and LRRK2 knockout mice were subjected to coronary artery ligation (left anterior descent) to establish a myocardial infarction mouse model. Neonatal rat cardiomyocytes were subjected to hypoxia to induce hypoxia injury in vitro. Results: We found increased LRRK2 expression levels in the infarct periphery of mouse hearts and hypoxic cardiomyocytes. LRRK2-deficient mice exhibited a decreased death rate and reduced infarction area compared to the wild-type controls 14 days after infarction. LRRK2-deficient mice showed reduced left ventricular fibrosis and inflammatory response, as well as improved cardiac function. In the in vitro study, LRRK2 silencing decreased the cleaved-caspase3 activity, reduced cardiomyocyte apoptosis, and diminished hypoxia-induced inflammation. However, LRRK2 overexpression enhanced the cleaved-caspase3 activity, increased the number of apoptotic cardiomyocytes, and caused remarkable hypoxia-induced inflammation. When exploring the related underlying mechanisms, we found that hypoxia induced an increase in HIFα expression, which enhanced LRRK2 expression. LRRK2 induced high expression of HMGB1 via P53. When blocking HMGB1 using the anti-HMGB1 antibody, the deteriorating effects caused by LRRK2 overexpression following hypoxia were inhibited in cardiomyocytes.Conclusions: In summary, LRRK2 deficiency protects hearts from myocardial infarction injury. The mechanism underlying this phenomenon involves the P53-HMGB1 pathway.

Abstract 12648: Deletion of 12/15 Lipoxygenase Improves Left Ventricle Function and Survival by Resolving Inflammation Post Myocardial Infarction

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Vasundhara Kain ◽  
Kevin A Ingle ◽  
Janusz Kabarowski ◽  
Sumanth D Prabhu ◽  
Ganesh V Halade
Keyword(s):  
Myocardial Infarction ◽  
Left Ventricle ◽  
Survival Rates ◽  
Coronary Artery Ligation ◽  
Artery Ligation ◽  
Lv Remodeling ◽  
Early Expression ◽  
Cox 2

12/15 lipoxygenase (LOX) is crucial in the inflammatory process leading to diabetes and atherosclerosis. However, the role of 12/15 LOX in myocardial infarction (MI) and left ventricle (LV) remodeling is unclear. We assessed the role of 12/15 LOX in resolving inflammation in post-MI LV remodeling. 8-12 weeks old C57BL/6J wild-type (WT; n=67) and 12/15 LOX (LOX –/– ; n=78) male mice were subjected to permanent coronary artery ligation surgery and monitored through day (d)1 and d5. No MI surgery mice were maintained as d0 naïve controls. LOX -/- mice showed higher survival rate, improved fractional shortening with reduced remodeling and edema index than WT at d1 and d5 post-MI (all p<0.05). LOX -/- mice showed increased Cxcl5 expression at d1 post-MI, consistent with stimulated neutrophil recruitment in the infarct region that was decreased at d5 compared to WT. LOX -/- mice infarct had increased expression of Ccl2 and Cxcl1, that stimulated an earlier recruitment of monocytes with increased macrophages population at d5 (all p<0.05) compared to WT. The altered kinetics of immune cells post-MI indicates a rapid resolving phase, through increase in alternative macrophage phenotypes with reduced collagen density in LOX -/- mice compared to WT mice at d5 post-MI. LOX -/- mice showed a coordinated COX-1 and COX-2 response at d1 post MI, leading to an evident increase in 5-LOX and hemoxygenase-1 (HO-1) at d5 post-MI. 12/15 LOX deletion enhanced the recruitment of alternative macrophages with secretion of HO-1 to resolve inflammation. In-vitro addition of LOX metabolite 12 hydroxyeicosatetraenoic acid to LOX -/- fibroblast induced early expression of COX-2 and 5-LOX compared to WT, indicating 5LOX role in resolution of inflammation. Post-MI increased expression of TIMP-1 and decrease in MMP-9 at d1 and α-SMA at d5 in LOX -/- mice suggested controlled differentiation of fibroblast-to-myofibroblast which is key event during ventricular tissue repair and resolving phase. This change is supported by increased expression of tgf-βi, ctgf and admats-2 (all P<0.05) at d5 post MI. In conclusion, absence of 12/15 LOX improves post-MI survival rates and attenuates LV dysfunction by resolving inflammation through coordination of 5-LOX and HO-1 as key inflammation resolving enzymes.

Abstract 866: Secreted Frizzled Related Protein 2 Modulates Post Myocardial Infarct Remodeling by Inhibiting Collagen Maturation through the Inhibition of Bone Morphogenetic Protein 1 Activity

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Wei He ◽  
Lunan Zhang ◽  
Richard E Pratt ◽  
Victor J Dzau
Keyword(s):  
Myocardial Infarction ◽  
Molecular Mechanisms ◽  
Cardiac Fibrosis ◽  
Myocardial Infarct ◽  
Primary Cultures ◽  
The United States ◽  
Coronary Artery Ligation ◽  
Related Protein ◽  
Artery Ligation

Myocardial infarction and post-infarction remodeling with heart failure are the major cause of mortality and morbidity in the United States. We recently reported that intracardiac implantation of genetically engineered mesenchymal stem cell (MSC) overexpressing the Akt gene dramatically reduced the infarct size and restored cardiac functions in rodent hearts after coronary artery ligation. Further, we identified Secreted Frizzled Related Protein 2 (sfrp2) as a key factor released by Akt-MSC mediating myocardial survival and repair. However, the underlying mechanism remains elusive. Bone Morphogenetic Protein1 (BMP1)/Tolloid (TLD)-like metalloproteinases belong to a subgroup of astacin family and play key roles in the regulation of extracelluar matrix (ECM) formation and cardiac fibrosis. These proteases have procollagen C-proteinase (PCP) activities which are responsible for the cleavage of C-propeptides from procollagen precursors to produce mature collagen fibrils. In this report, we showed that three days following myocardial infarction in rats, both BMP1 protein expression and activity were upregulated in the infarcted left ventricle. Interestingly, we found recombinant sfrp2 could inhibit BMP1 activity in MI tissue samples as measured by an in vitro PCP activity assay. Furthermore, using purified recombinant proteins, we demonstrated that sfrp2, but not sfrp1 or sfrp3, inhibited BMP-1 activity in vitro. Moreover, purified sfrp2 could physically interact with BMP1 protein as shown by the co-immunoprecipitation assay. To provide further evidence that sfrp2 can interfere with collagen processing, we demonstrated that exogenously added sfrp2 interfered with procollagen processing in primary cultures of cardiac fibroblast culture medium. Similar results were obtained when these cells were transiently transfected with sfrp2 expressing plasmids. In summary, our data suggest that one of the molecular mechanisms underlying the cardioprotective and repair effects of sfrp2 protein on myocardial infarction is through the inhibition of BMP-1 activity. Therefore, sfrp2 has the potential clinical application as a novel anti-fibrotic reagent for the modulation of cardiac remodeling after acute myocardial infarction.

Abstract 15058: Disruption of Extracellular Cytotoxic Chromatin by Acute DNase1 Administration Improves Left Ventricular Remodeling after Myocardial Infarction

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Benjamin Vogel ◽  
Hisahito Shinagawa ◽  
Ullrich Hofmann ◽  
Georg Ertl ◽  
Stefan Frantz
Keyword(s):  
Myocardial Infarction ◽  
Ventricular Remodeling ◽  
Left Ventricular Remodeling ◽  
Left Ventricular ◽  
Pcr Analysis ◽  
Coronary Artery Ligation ◽  
Protective Effects ◽  
Artery Ligation ◽  
High Concentrations

Rationale: Myocardial infarction (MI) leads to necrosis of multinucleated and polyploid myocytes. This causes uncontrolled release of cellular content like chromatin to the infarct area. Chromatin is mainly comprised of histones which are essential for controlling and packing of DNA but paradoxically are also known to be cytotoxic. This makes free chromatin a toxic DNA polymer creating local high concentrations of hazardous histones. Objective: We hypothesized that chromatin from necrotic cells accumulates in ischemic myocardium, creates local high concentrations of cytotoxic histones, and thereby potentiates ischemic damage to the heart after MI. The endonuclease DNase1 is capable of dispersing extracellular chromatin through linker DNA digestion and could decrease local histone concentrations and cytotoxicity. Methods and Results: After permanent coronary artery ligation in mice we found extracellular histones accumulated within the infarcted myocardium. Histone cytotoxicity towards isolated myocytes was confirmed in vitro. To reduce histone related cytotoxicity in vivo DNase1 was injected within the first 6 hours after induction of MI. DNase1 accumulated in the infarcted region of the heart, effectively disrupted extracellular cytotoxic chromatin and thereby reduced high local histone concentration. Animals acutely treated with DNase1 revealed significantly improved left ventricular remodeling as measured by serial echocardiography up to 28 days after MI (e.g. NaCl vs DNase1, papillary end diastolic area [mm 2 ]: 23.26 ± 2.06 vs 18.90 ± 1.24, n=9 vs 10, p<0,05). Treatment did not influence mortality, infarct size or inflammatory parameters as determined by neutrophil infiltration and RTQ-PCR analysis of characteristic cytokines. However improved myocyte survival was discovered within the infarct region which might account for the protective effects in DNase1 treated animals (NaCl vs DNase1: 3.0 ± 0.7% vs 8.3 ± 2.3%; p<0.05; n=7 vs 8). Conclusions: Targeting extracellular cytotoxic chromatin within the infarcted heart by DNase1 is a promising approach to preserve myocytes from histone induced cell death and to conserve left ventricular function after MI. The efficacy of other chromatin degrading agents is now under investigation.

scholarly journals Ghrelin Prevents Incidence of Malignant Arrhythmia after Acute Myocardial Infarction through Vagal Afferent Nerves

Endocrinology ◽  
2012 ◽  
Vol 153 (7) ◽  
pp. 3426-3434 ◽  
Author(s):  
Yuanjie Mao ◽  
Takeshi Tokudome ◽  
Kentaro Otani ◽  
Ichiro Kishimoto ◽  
Michio Nakanishi ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Low Frequency ◽  
Coronary Artery Ligation ◽  
Wild Type ◽  
Artery Ligation ◽  
Afferent Nerves ◽  
Malignant Arrhythmia ◽  
Acute Mi ◽  
Vagal Afferent

Ghrelin is a GH-releasing peptide mainly excreted from the stomach. Ghrelin administration has been shown to inhibit cardiac sympathetic nerve activity (CSNA), reduce malignant arrhythmia, and improve prognosis after acute myocardial infarction (MI). We therefore investigated the effects and potential mechanisms of the action of endogenous ghrelin on survival rate and CSNA after MI by using ghrelin-knockout (KO) mice. MI was induced by left coronary artery ligation in 46 KO mice and 41 wild-type mice. On the first day, malignant arrhythmia-induced mortality was observed within 30 min of the ligation and had an incidence of 2.4% in wild-type and 17.4% in KO mice (P &lt; 0.05). We next evaluated CSNA by spectral analysis of heart rate variability. CSNA, represented by the low frequency/high frequency ratio, was higher in KO mice at baseline (2.18 ± 0.43 vs. 0.98 ± 0.09; P &lt; 0.05), and especially after MI (25.5 ± 11.8 vs. 1.4 ± 0.3; P &lt; 0.05), than in wild-type mice. Ghrelin (150 μg/kg, sc) 15 min before ligation suppressed the activation of CSNA and reduced mortality in KO mice. Further, this effect of ghrelin was inhibited by methylatropine bromide (1 mg/kg, ip) or by perineural treatment of both cervical vagal trunks with capsaicin (a specific afferent neurotoxin). Our data demonstrated that both exogenous and endogenous ghrelin suppressed CSNA, prevented the incidence of malignant arrhythmia, and improved the prognosis after acute MI. These effects are likely to be via the vagal afferent nerves.

scholarly journals Aucubin Protects against Myocardial Infarction-Induced Cardiac Remodeling via nNOS/NO-Regulated Oxidative Stress

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Zheng Yang ◽  
Qing-Qing Wu ◽  
Yang Xiao ◽  
Ming Xia Duan ◽  
Chen Liu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Myocardial Infarction ◽  
Cardiac Remodeling ◽  
Coronary Artery Ligation ◽  
No Production ◽  
Protective Effects ◽  
Artery Ligation ◽  
Nos Inhibitors

Whether aucubin could protect myocardial infarction- (MI-) induced cardiac remodeling is not clear. In this study, in a mouse model, cardiac remodeling was induced by left anterior descending coronary artery ligation surgery. Mice were intraperitoneally injected with aucubin (10 mg/kg) 3 days post-MI. Two weeks post-MI, mice in the aucubin treatment group showed decreased mortality, decreased infarct size, and improved cardiac function. Aucubin also decreased cardiac remodeling post-MI. Consistently, aucubin protected cardiomyocytes against hypoxic injury in vitro. Mechanistically, we found that aucubin inhibited the ASK1/JNK signaling. These effects were abolished by the JNK activator. Moreover, we found that the oxidative stress was attenuated in both in vivo aucubin-treated mice heart and in vitro-treated cardiomyocytes, which caused decreased thioredoxin (Trx) consumption, leading to ASK1 forming the inactive complex with Trx. Aucubin increased nNOS-derived NO production in vivo and vitro. The protective effects of aucubin were reversed by the NOS inhibitors L-NAME and L-VINO in vitro. Furthermore, nNOS knockout mice also reversed the protective effects of aucubin on cardiac remodeling. Taken together, aucubin protects against cardiac remodeling post-MI through activation of the nNOS/NO pathway, which subsequently attenuates the ROS production, increases Trx preservation, and leads to inhibition of the ASK1/JNK pathway.

scholarly journals Inhibition of Notch signaling pathway attenuates sympathetic hyperinnervation together with the augmentation of M2 macrophages in rats post-myocardial infarction

2016 ◽  
Vol 310 (1) ◽  
pp. C41-C53 ◽  
Author(s):  
Jie Yin ◽  
Hesheng Hu ◽  
Xiaolu Li ◽  
Mei Xue ◽  
Wenjuan Cheng ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Butyl Ester ◽  
Surface Expression ◽  
Notch Signaling Pathway ◽  
M2 Macrophage ◽  
Coronary Artery Ligation ◽  
Dependent Manner ◽  
Artery Ligation ◽  
High Level

Inflammation-dominated sympathetic sprouting adjacent to the necrotic region following myocardial infarction (MI) has been implicated in the etiology of arrhythmias resulting in sudden cardiac death; however, the mechanisms responsible remain to be elucidated. Although being a key immune mediator, the role of Notch has yet to be explored. We investigated whether Notch regulates macrophage responses to inflammation and affects cardiac sympathetic reinnervation in rats undergoing MI. MI was induced by coronary artery ligation. A high level of Notch intracellular domain was observed in the macrophages that infiltrated the infarct area at 3 days post-MI. The administration of the Notch inhibitor N-N-(3,5-difluorophenacetyl-l-alanyl)-S-phenylglycine-t-butyl ester (DAPT) (intravenously 30 min before MI and then daily until death) decreased the number of macrophages and significantly increased the M2 macrophage activation profile in the early stages and attenuated the expression of nerve growth factor (NGF). Eventually, NGF-induced sympathetic hyperinnervation was blunted, as assessed by the immunofluorescence of tyrosine hydroxylase. At 7 days post-MI, the arrhythmia score of programmed electric stimulation in the vehicle-treated infarcted rats was higher than that in rats treated with DAPT. Further deterioration in cardiac function and decreases in the plasma levels of TNF-α and IL-1β were also detected. In vitro studies revealed that LPS/IFN-γ upregulated the surface expression of NGF in M1 macrophages in a Notch-dependent manner. We concluded that Notch inhibition during the acute inflammatory response phase is associated with the downregulation of NGF, probably through a macrophage-dependent pathway, thus preventing the process of sympathetic hyperinnervation.

Enhanced constrictor responses of skeletal muscle arterioles during chronic myocardial infarction

1997 ◽  
Vol 273 (3) ◽  
pp. H1502-H1508 ◽  
Author(s):  
S. P. Didion ◽  
P. K. Carmines ◽  
H. Ikenaga ◽  
W. G. Mayhan
Keyword(s):  
Myocardial Infarction ◽  
Skeletal Muscle ◽  
Coronary Artery Ligation ◽  
Chronic Myocardial Infarction ◽  
Ang Ii ◽  
Third Order ◽  
Artery Ligation ◽  
Arteriolar Tone ◽  
The Impact

The goal of this study was to test the hypothesis that chronic myocardial infarction potentiates agonist-induced constrictor responses of rat skeletal muscle arterioles in vivo. Eight weeks after we performed coronary artery ligation or sham (control) surgery, the spinotrapezius muscle was prepared for direct visualization of the microcirculation. Diameter of third-order arterioles (40.7 +/- 0.5 microns) to topical suffusion of angiotensin II (ANG II; 0.1-10 nM), arginine vasopressin (AVP; 0.1-10 nM), endothelin-1 (ET-1; 1.0-100 pM), and the thromboxane analog U-46619 (1.0-100 nM) was measured in both groups. Myocardial-infarcted rats exhibited enhanced arteriolar constrictor responses to ANG II and AVP compared with the responses in controls. In contrast, ET-1- and U-46619-induced constrictor responses were similar in control and myocardial-infarcted rats. Additional experiments explored the impact of NG-monomethyl-L-arginine (L-NMMA; 0.1 mM) on arteriolar reactivity. In control animals, L-NMMA potentiated ANG II- and AVP-induced vasoconstriction, achieving values similar to those observed in myocardial-infarcted rats. L-NMMA did not alter vasoconstrictor responses in rats with chronic myocardial infarction. These observations suggest that enhanced agonist-induced vasoconstriction during heart failure may reflect a loss of nitric oxide-mediated modulation of arteriolar tone.

scholarly journals Exosomal miR-218-5p/miR-363-3p from Endothelial Progenitor Cells Ameliorate Myocardial Infarction by Targeting the p53/JMY Signaling Pathway

2021 ◽  
Vol 2021 ◽  
pp. 1-23
Author(s):  
Xiao Ke ◽  
Rongfeng Yang ◽  
Fang Wu ◽  
Xing Wang ◽  
Jiawen Liang ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Signaling Pathway ◽  
Myocardial Fibrosis ◽  
Regulatory Protein ◽  
Luciferase Reporter ◽  
Coronary Artery Ligation ◽  
Endothelial Progenitor ◽  
Artery Ligation ◽  
Qrt Pcr

Accumulating evidence has shown that endothelial progenitor cell-derived exosomes (EPC-Exos) can ameliorate myocardial fibrosis. The purpose of the present study was to investigate the effects of EPC-Exos-derived microRNAs (miRNAs) on myocardial infarction (MI). A miRNA-Seq dataset of miRNAs differentially expressed between EPCs and exosomes was collected. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to validate the miRNA expression indicated by miRNA-Seq. Immunofluorescence, cell proliferation, and angiogenesis assays were employed to investigate the effects of miRNAs on cardiac fibroblasts (CFs) in vitro. Interactions between miRNAs and their respective targets were examined via immunoblotting, qRT-PCR, and luciferase reporter assays. An MI rat model was constructed, and various staining and immunohistochemical assays were performed to explore the mechanisms underlying the miRNA-mediated effects on MI. miR-363-3p and miR-218-5p were enriched in EPC-Exos, and miR-218-5p and miR-363-3p mimic or inhibitor enhanced or suppressed CF proliferation and angiogenesis, respectively. miR-218-5p and miR-363-3p regulated p53 and junction-mediating and regulatory protein (JMY) by binding to the promoter region of p53 and the 3 ′ untranslated region of JMY. Additionally, treatment of CFs with Exo-miR-218-5p or Exo-miR-363-3p upregulated p53 and downregulated JMY expression, promoted mesenchymal-endothelial transition, and inhibited myocardial fibrosis. Administration of exosomes containing miR-218-5p mimic or miR-363-3p mimic ameliorated left coronary artery ligation-induced MI and restored myocardial tissue integrity in the MI model rats. In summary, these results show that the protective ability of EPC-Exos against MI was mediated by the shuttled miR-218-5p or miR-363-3p via targeting of the p53/JMY signaling pathway.

scholarly journals Sphingolipid signaling and treatment during remodeling of the uninfarcted ventricular wall after myocardial infarction

2009 ◽  
Vol 296 (4) ◽  
pp. H1193-H1199 ◽  
Author(s):  
Che-Chung Yeh ◽  
Hongzhe Li ◽  
Deepak Malhotra ◽  
Mei-Chuan Huang ◽  
Bo-Qing Zhu ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Cardiac Myocyte ◽  
Ex Vivo ◽  
Cell Types ◽  
Coronary Artery Ligation ◽  
Artery Ligation ◽  
Echocardiographic Measurement ◽  
Sphingosine 1 Phosphate ◽  
S1p Receptor

The sphingosine kinase (SphK)/sphingosine 1-phosphate (S1P) pathway, known to determine the fate and growth of various cell types, can enhance cardiac myocyte survival in vitro and provide cardioprotection in acute ex vivo heart preparations. However, the relevance of these findings to chronic cardiac pathology has never been demonstrated. We hypothesized that S1P signaling is impaired during chronic remodeling of the uninfarcted ventricle during the evolution of post-myocardial infarction (MI) cardiomyopathy and that a therapeutic enhancement of S1P signaling would ameliorate ventricular dysfunction. SphK expression and activity were measured in the remote, uninfarcted myocardium (RM) of C57Bl/6 mice subjected to coronary artery ligation. The mRNA expression of S1P receptor isoforms was also measured, as was the activation of the downstream S1P receptor mediators. A cardioprotective role for S1P1 receptor agonism was tested via the administration of the S1P1-selective agonist SEW2871 during and after MI. As a result, the expression data suggested that a dramatic reduction in SphK activity in the RM early after MI may reflect a combination of posttranscriptional and posttranslational modulation. SphK activity continued to decline gradually during chronic post-MI remodeling, when S1P1 receptor mRNA also fell below baseline. The S1P1-specific agonism with oral SEW2871 during the first 2-wk after MI reduced apoptosis in the RM and resulted in improved myocardial function, as reflected in the echocardiographic measurement of fractional shortening. In conclusion, these results provide the first documentation of alterations in S1P-mediated signaling during the in situ development of cardiomyopathy and suggest a possible therapeutic role for the pharmacological S1P receptor agonism in the post-MI heart.

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